RF: Paper 01: Tendon Transection Healing can be improved with Tenogenically Differentiated Adipose Derived Stem Cells Category: Tendon Basic Science Level of Evidence: N/A Michael J. Fitzgerald, MD Taylor Mustapich, BA Haixiang Liang, MD Christopher G. Larsen, MD Kate W. Nellans, MD, MPH Daniel A. Grande HYPOTHESIS Prior investigations have demonstrated the ability of adipose derived stem cells (ADSCs) to aid in Achilles’ tendon healing after a puncture defect is made to the tendon. We hypothesized that tenogenically differentiated ADSCs would improve tendon healing when a transection injury is sustained, a common problem faced by hand surgeons. METHODS Rat Achilles’ tendons were transected and then either left unrepaired or repaired with a Nicoladoni technique. Both groups were treated with either a hydrogel alone, a hydrogel with ADSCs harvested from rat inguinal tissue, or a hydrogel with ADSCs that were treated with growth differentiation factor 5 (GDF-5) and platelet derived growth factor. GDF-5/PDGF has been shown to play a role in promoting ADSCs to differentiate towards a tenogenic lineage and in enhancing cellular proliferation. At three weeks the tendons were observed under light microscopy and evaluated based on blood vessel formation and structure, tendon fiber organization, and any gaps that remained. The tendons were also evaluated in vitro for gene expression of several genes known to play an important role in successful tendon healing (SOX9, SCX (scleraxis), TNMD (tenomodulin), Collagen I, PCNA (cell proliferation), and HIF-1a (angiogenesis induction)). RESULTS In both unrepaired and repaired tendons in vivo, groups treated with no ADSCs exhibited the largest blood vessels, largest gaps, and most tendon fiber disorganization. Groups treated with both ADSCs and GDF-5/PDGF showed the smallest blood vessels, smallest gaps, and best tendon fiber organization. Repaired tendons had better tendon connections in all groups. In vitro GDF-5/PDGF did not stimulate tenocyte differentiation but did increase expression of the pro-tenogenesis gene SOX9 at 7 days. GDF-5/PDGF treatment increased cell-cell connections, improved cellular proliferation, promoted extracellular metabolism, and reduced reactive oxygen species (ROS) production. Implanted ADSCs differentiated into either tendon cells or blood vessel cells. These findings suggest that addition of ADSCs with GDF-5/PDGF to repaired

tendon injuries can augment healing by promoting both tenocyte differentiation and a more organized vascular infiltration. SUMMARY ADSCs cultured with GDF-5/PDGF promote tenogenesis and expression of genes associated with tendon repair When added to tendon repair, ADSCs cultured with GDF-5/PDGF resulted in the greatest degree of organized tendon healing. Future goals are to apply this model specifically to tendons of the hand and to biomechanically test the strength of these repairs REFERENCES: Norelli JB, Plaza DP, Stal DN, Varghese AM, Liang H, Grande DA. Tenogenically differentiated adipose-derived stem cells are effective in Achilles tendon repair in vivo. J Tissue Eng. 2018;9:2041731418811183.

RF: Paper 02: Wrist Arthroscopy Using the 2-3 Radiocarpal Portal. Is It Safer Than the 1-2 Portal? Category: Bone and Joint;Nerve;Skin and Soft Tissue Surgical Technique; Anatomy Level of Evidence: N/A Katharine Moss Hinchcliff, MD Sanjeev Kakar, MD Taghi Ramazanian, MD Lauren Dutton, MD HYPOTHESIS The 1-2 radiocarpal portal has been described as an important working portal for the treatment of radial sided wrist pathology. However, it’s use places the dorsal sensory branch of the radial nerve and the radial artery at risk for injury. This cadaveric study describes the 2-3 portal and evaluates the proximity of this portal to surrounding structures. METHODS Wrist arthroscopy was performed on 8 cadaver specimens via the 1-2 and 2-3 radiocarpal portals. Subsequently, the limbs were dissected under 3.5mm loupe magnification and the superficial branches of the radial nerve and the radial artery in the anatomic snuffbox identified. Two surgeons then independently used digital calipers to measure the closest distance from the structures to each portal, with trocars in place. The mean of these values was recorded. Two-tail T-tests for correlated samples were performed to evaluate the difference in distances between the portals and the critical neurovascular structures. RESULTS The mean distance from the nearest radial nerve branch to the 1-2 portal was 3.04mm (range 0.01-8.45mm). For the 2-3 portal, the mean distance was 7.60mm (Range 0.01-14.09). This difference was significant, p = 0.027. The mean distance between the radial artery in the snuffbox and the 1-2 portal was 1.43 mm (rage 0.01 – 2.59mm); for the 2-3 portal, this mean was 14.25 mm (range 10.08-18.58mm), p < 0.0001. SUMMARY - The 2-3 portal is significantly farther away from the radial artery than the 1-2 portal. - The 2-3 portal is also significantly farther away from the superficial radial nerve branches than the 1-2 portal, although both portals are in close proximity to these nerve branches. - Based on our findings, we advocate using the 2-3 portal preferentially when treating radial sided wrist pathology, to decrease the risk of iatrogenic neurovascular injury.

RF: Paper 03: Risk Factors for Failed Nonoperative Treatment in Patients with Thumb Carpometacarpal Arthritis Category: Bone and Joint Evaluation/Diagnosis; Treatment; Prognosis/Outcomes Level of Evidence: 3 Derek T. Schloemann, MD, MPHS Serena E. B. Liu, MD, MSc Joshua R. Atkinson David N. Bernstein, MBA, MA Warren C. Hammert, DDS, MD Ryan P. Calfee, MD, MSc HYPOTHESIS Our hypothesis was that factors present at the time of initial evaluation by a hand surgeon would be associated with failure of nonoperative treatment, defined as eventual surgical treatment of thumb carpometacarpal joint (CMC) arthritis. METHODS This retrospective cohort study analyzed 1,994 patients with thumb CMC arthritis treated at two institutions between February 2015 and November 2018. Patient demographic and clinical information were obtained from medical records to characterize treatment modalities prior to hand surgeon evaluation, mental and physical comorbidities, and PROMIS assessments. After bivariate analysis, a multivariable logic regression model evaluated factors associated with failure of nonoperative treatment. RESULTS This cohort was predominately female (70%) and white (91%) with a mean age at first appointment of 62±10 years. One hundred and seventy (9%) patients underwent surgery for thumb CMC arthritis at a median of 114 days (IQR 27-328). PROMIS Depression scores correlated with Pain Interference scores and a history of diagnosed depression or anxiety were associated with less perceived Physical Function at presentation. However, only prior contralateral thumb CMC surgery, CMC injection prior to surgeon evaluation, younger age, and treating institution were associated with failure of nonoperative treatment in regression modeling. SUMMARY • Pain and functional limitations associated with thumb CMC arthritis are influenced by mental health comorbidit • Mental health comorbidities do not predict surgical treatment • The odds of thumb CMC surgery vary according to patient demographic and treatment factors but also are influenced by treatment location

REFERENCES: Wilder F V., Barrett JP, Farina EJ. Joint-specific prevalence of osteoarthritis of the hand. Osteoarthr Cartil. 2006;14(9):953-957. doi:10.1016/j.joca.2006.04.013 Weiss A-PC, Goodman AD. Thumb Basal Joint Arthritis. J Am Acad Orthop Surg. 2018;26(16):562-571. doi:10.5435/JAAOS-D-17-00374 Spaans AJ, Van Minnen LP, Kon M, Schuurman AH, Schreuders AR, Vermeulen GM. Conservative treatment of thumb base osteoarthritis: A systematic review. J Hand Surg Am. 2015;40(1):16-21.e5. doi:10.1016/j.jhsa.2014.08.047 Fowler A, Swindells MG, Burke FD. Intra-articular corticosteroid injections to manage trapeziometacarpal osteoarthritis—a systematic review. Hand. 2015;10(4):583-592. doi:10.1007/s11552-015-9778-3 Meenagh GK, Patton J, Kynes C, Wright GD. A randomised controlled trial of intra-articular corticosteroid injection of the carpometacarpal joint of the thumb in osteoarthritis. Ann Rheum Dis. 2004;63(10):1260-1263. doi:10.1136/ard.2003.015438

RF: Paper 04: Impact of Pregnancy on Development of Thumb Carpometacarpal Osteoarthritis Category: Bone and Joint;Other Clinical Topics Evaluation/Diagnosis Level of Evidence: 4 Taylor Shackleford Layla Nasr Sam Schick Sherri Davis Jennifer Koay Shafic Sraj HYPOTHESIS Previous literature identified Relaxin, a pregnancy hormone, as a factor linked to the development of osteoarthritis in women. We hypothesize that females experiencing more pregnancies, and thus more exposure to high levels of relaxin, are more likely to have thumb carpometacarpal osteoarthritis, and will have worse disease at younger age than females with fewer pregnancies. METHODS After receiving IRB approval, a retrospective chart review was performed on females over age 45 at one institution. Those patients with documented gravidity and parity along with radiographs with visualization of the thumb carpometacarpal joint were eligible. Patients with previous thumb trauma, thumb surgery, or inflammatory arthritis were excluded. Radiographic analysis of the thumb carpometacarpal joint was performed to group patients into 3 groups: no arthritis, carpometacarpal arthritis, and pantrapezial arthritis. ANOVA was conducted on age, gravidity, and radiographic osteoarthritis level. RESULTS 690 females met inclusion criteria (61.9 ± 9 years of age). Age was found to be highly correlated to more severe osteoarthritis. ANOVA analysis of the coefficients of our model resulted in a p-value of 0.0062 for age. After correcting for age, ANOVA revealed no significant influence of gravidity on the level of osteoarthritis developed (p-value of 0.84). SUMMARY • While studies have shown a link between hormones of pregnancy and thumb carpometacarpal osteoarthritis, this study found no correlation between the number of pregnancies a female experiences and the radiographic level of arthritis. •Further work needs to be done to evaluate if exposure to pregnancies impacts the development of clinically significant thumb carpometacarpal osteoarthritis or to identify a confounder that better explains this relationship.

REFERENCES: Wolf, J. M., Scher, D. L., Etchill, E. W., Scott, F., Williams, A. E., Delaronde, S., & King, K. B. (2014, April). Relationship of relaxin hormone and thumb carpometacarpal joint arthritis.

RF: Paper 05: Development of a Murine Model of Pyogenic Flexor Tenosynovitis Category: Skin and Soft Tissue;Tendon Basic Science Level of Evidence: N/A Bowen Qiu MD Justin Cobb BA Alayna Loiselle PhD Constantinos Ketonis HYPOTHESIS Pyogenic flexor tenosynovitis (PFTS) is a devastating infection involving the flexor tendon sheath of the fingers. However, despite the current gold standard empiric treatment with antibiotics and surgical debridement, outcomes remain poor in part due to the lack of scalable in-vivo model. The purpose of this study is to demonstrate the plausibility of a murine model of pyogenic flexor tenosynovitis and to histologically characterize the effects of PFTS on tendons. METHODS Two mL of sterile phosphate buffered saline or 1x107 CFU bioluminescent Xen29 Staphylococcus aureus was injected into the tendon sheath of thirty-six 6-week-old male C57BL/6J mice. Experimental endpoint was set at 14 days. The infectious course was monitored by bioluminescence (BLI) signal via IVIS imaging, recording of weight and gross anatomic examination. Infected hind paws were harvested at four time points: 24 hours, 72 hours, 7 days, and 14 days for histopathology using Alcian Blue hematoxylin staining. Two-way ANOVA with Sidak’s multiple comparison test was used for statistical analysis. RESULTS The infected cohort displayed significantly elevated bioluminescent values during the early days of infection. By day 7 most infected mice saw a substantial decrease in BLI signal intensity, however two infected mice exhibited persistent BLI intensity through day 14. (fig. 1) Clinical features of infection were present throughout the infection course: reductions in weight and fusiform swelling of the infected digit. (fig 2a). Histopathology of hindpaw of the infected cohort showed tissue disorganization and the presence of a cellular infiltrate in the flexor tendon sheath at all time points. (fig. 2b) SUMMARY • We describe a murine model of pyogenic flexor tenosynovitis. • This animal model offers a platform for investigation of the pathophysiology of pyogenic flexor tenosynovitis. • It can aid in elucidating the basic molecular/cellular mechanisms that lead to scarring and long-term sequelae while also being utilized to evaluate novel therapeutic strategies.

RF: Paper 06: Defining Features of Hand Anomalies in Severe Thumb Hypoplasia: A Classification Modification Category: Bone and Joint;Pediatric Trauma and Congenital Conditions Evaluation/Diagnosis; Treatment Level of Evidence: 4 Peter Chang Charles A. Goldfarb Summer Roberts Lindley B. Wall HYPOTHESIS Not all morphologic hand anomalies in children with thumb hypoplasia and radial sided hand deficiency will be classifiable by the Blauth classification. METHODS Fifteen extremities in 13 patients with severe thumb hypoplasia and associated absent radial sided digits were identified through the Congenital Upper Limb Differences (CoULD) registry. All patients had forearm involvement. Medical records, clinical photographs, and radiographs were evaluated. RLD and thumb hypoplasia was classified according to the Bayne and Klug classification and Blauth classification respectively. Unusual or defining associated hand characteristics were identified and categorized. RESULLTS The most common type of forearm abnormality was a complete absence of the radius (Bayne and Klug Type IV) which was present in 10/15 extremities in the cohort. All 15 extremities had a complete thumb absence and associated absent digits. Six of the patients had an associated identified syndrome (46%). SUMMARY · Severe forms of thumb hypoplasia in RLD are uncommon and are not able to be classified by the Blauth classification system. · Proposed modification of the Blauth classification of thumb hypoplasia, a Type VI with multiple patterns of presentation. REFERENCES: Blauth W. The hypoplastic thumb. Arch Orthop Unfallchir. 1967;62:225-246. James MA, McCarroll HR Jr, Manske PR. The spectrum of radial longitudinal deficiency: a modified classification. J Hand Surg Am. 1999;24:1145-1155. Goldfarb CA, Manske PR, Busa R, Mills J, Carter P, Ezaki M. Upper-Extremity Phocomelia Reexamined: A Longitudinal Dyslasia. J Bone and Joint Surg Am. 2005;87:2639-2648. James MA, Green H, Relton M, Manske P. The association of radial deficiency with thumb hypoplasia. J Bone and Joint Surg Am. 2004;86:2196-2205.

RF: Paper 07: A Novel Physical Exam Test for Trigger Finger: The Independent Flexion Test Category: Tendon Evaluation/Diagnosis Level of Evidence: 3 Robert Matthew Zbeda Daniel B. Polatsch, MD Daniel P. Murray, MD Steven Beldner HYPOTHESIS The purpose of our study is to describe a novel physical exam test for trigger finger – the Independent Flexion Test (IFT). We hypothesize that the IFT is more sensitive in diagnosing trigger finger compared to triggering with active range of motion (ROM). METHODS From January to May 2019, we performed a prospective review of 118 consecutive cases of trigger fingers in 85 patients. Patients who reported stiffness or triggering in digits 2-5 with a complete physical exam were included. Physical evaluation included tenderness over the A1 pulley, triggering with active ROM, and IFT. The IFT test is administered by asking the patient to make a full composite fist and extend each of the unaffected digits in a sequential manner. The patient is then asked to fully extend the digit in question and test is considered positive if there is active triggering or locking. A two-proportion test was performed to determine if IFT was more sensitive than triggering with active ROM. RESULTS Among 118 cases of trigger finger, the average age was 63.0 years (range, 25.3 to 93.4 years) and 50.8% (60/118) were female. The long and ring fingers were involved 84.0% of the time. In 118 trigger fingers, 108 (92%) had a history of catching or locking and 110 (93%) had A1 tenderness to palpation. The IFT was found to be more sensitive (91%) than triggering with active ROM (44%) in diagnosing trigger finger (p<.001). SUMMARY • Patients who report a history of triggering or stiffness are not always able to trigger on physical exam testing • IFT is a novel physical exam test for trigger finger that reliably reproduces symptoms of triggering and is more sensitive than triggering with active ROM • IFT can be performed in the office to confirm diagnosis of trigger finger and in the operating room during wide awake surgery to confirm that the digit is no longer triggering

RF: Paper 08: Recurrence Rates of Dorsal Wrist Ganglion Cysts Following Arthroscopic Versus Open Surgical Excision: A Retrospective Comparison Category: Skin and Soft Tissue;Other Clinical Topics Treatment; Surgical Technique; Prognosis/Outcomes Level of Evidence: 3 Matthew W. Konigsberg Liana Tedesco John Mueller R. Kumar Kadiyala Robert Strauch Melvin Rosenwasser HYPOTHESIS This study directly compares the recurrence rates of dorsal wrist ganglion cysts in patients treated via open surgical excision versus arthroscopic surgical excision. We hypothesized that there would be no difference between recurrence rates with these two surgical options. METHODS We retrospectively reviewed the charts of all patients with a dorsal ganglion cyst undergoing either open or arthroscopic surgical excision at a single academic center with three fellowship-trained attending hand surgeons from 2012-2017. Charts were reviewed using postoperative office notes for preoperative and postoperative symptoms, episodes of recurrence, time at which recurrence occurred, subsequent operations, and outcome at final follow up. RESULTS The charts of 172 patients undergoing either arthroscopic or open dorsal ganglion excision were reviewed. 9/54 (16.7%) arthroscopic excisions resulted in cyst recurrence while 8/118 (6.8%) open excisions resulted in cyst recurrence (p=0.044). 2/9 (22%) recurrences after arthroscopic ganglion excision versus 2/8 (25%) recurrences after open ganglion excision underwent repeat surgical intervention. Time to recurrence, as well as final follow up, was not statistically different between groups. SUMMARY · Dorsal wrist ganglion cysts are the most common benign soft tissue mass of the upper extremity, but it remains unknown whether arthroscopic or open surgical excision leads to lower recurrence rate · Scant literature exists directly comparing these two methods of surgical excision; this study includes the largest cohort of patients, to our knowledge · This study suggests that open excision leads to a lower recurrence rate of dorsal wrist ganglia than does arthroscopic excision

REFERENCES: Kang L, Akelman E, Weiss APC. Arthroscopic Versus Open Dorsal Ganglion Excision: A Prospective, Randomized Comparison of Rates of Recurrence and of Residual Pain. J Hand Surg Am. 2008;33(4):471-475. doi:10.1016/j.jhsa.2008.01.009 Crawford C, Keswani A, Lovy AJ, et al. Arthroscopic versus open excision of dorsal ganglion cysts: a systematic review. J Hand Surg Eur Vol. 2018;43(6):659-664. doi:10.1177/1753193417734428 Rizzo M, Berger RA, Steinmann SP, Bishop AT. Arthroscopic Resection in the Management of Dorsal Wrist Ganglions: Results with a Minimum 2-Year Follow-Up Period. J Hand Surg Am. 2004;29(1):59-62. doi:10.1016/j.jhsa.2003.10.018 Gallego S, Mathoulin C. Arthroscopic resection of dorsal wrist ganglia: 114 cases with minimum follow-up of 2 years. Arthrosc - J Arthrosc Relat Surg. 2010;26(12). doi:10.1016/j.arthro.2010.05.008

RF: Paper 09: Supinator to anterior interosseous nerve transfer for lower brachial plexus injuries: an anatomical study Category: Nerve Surgical Technique; Anatomy Level of Evidence: N/A Zvi Steinberger Erin L Weber Francesco Amendola Jonathan Lundy L Scott Levin David Steinberg HYPOTHESIS Brachialis, Brachioradialis and ECRB have been described as potential donors for nerve transfer to the anterior interosseous nerve (AIN, C8-T1) to restore finger flexion in lower brachial plexus injury (C8-T1)1,2,3. When these donors are not available, the supinator (C5-6) may be an alternative donor that is easy to acquire and a good match in size and fascicle number. METHODS Ten cadaveric upper limbs were dissected under loupe magnification through an anterior lazy-S incision at the antecubital fossa to gain access to both median and radial nerves. The median nerve was first identified proximally and traced distally to the AIN. Internal neurolysis of the AIN was performed proximally until the fascicles became inseparable from the median nerve. The AIN was transected at this location. The superficial radial nerve was identified beneath the brachioradialis muscle and traced proximally to the deep branch of the radial nerve, which was then followed as it passed deep to the supinator muscle. Here, the branches to the supinator muscle were transected just proximal to entry into the muscle. The diameter, number of fascicles, and the location of the branching point with respect to distance from the medial epicondyle were measured for both the AIN and supinator nerves. The supinator branches were then coapted to the AIN in a tension-free manner, superficial to the vasculature in the proximal forearm with the elbow in full extension and supination. For statistical analysis, measurements are presented as mean values with standard errors. The number of fascicles and branches are reported as median values. RESULTS The AIN branched from the median nerve 2.8 +/- 0.4 cm distal to medial epicondyle. The average AIN diameter was 1.3 +/- 0.3 mm with a median of 2 fascicles. Internal neurolysis achieved an additional 0.9 +/- 0.5 cm of AIN length. The supinator nerve branches arose from the posterior interosseous nerve 4.7 +/- 0.8 cm distal to medial epicondyle. The supinator nerve diameter, measured collectively, was 1 mm and a median of 2 branches were identified, with each branch containing a single fascicle. The distance between AIN and supinator nerves was

3.3 +/- 0.2 cm and there was an excess nerve overlap of 1.8 +/- 0.4 cm after transposition over the forearm vasculature. SUMMARY • The AIN and supinator nerves are similar in size and fascicle number. • Supinator to AIN transfer is a reproducible and anatomically feasible alternative for the restoration of finger flexion in lower brachial plexus palsy. REFERENCES: Bertelli JA. Transfer of the Radial Nerve Branch to the Extensor Carpi Radialis Brevis to the Anterior Interosseous Nerve to Reconstruct Thumb and Finger Flexion. J Hand Surg Am. (2015) Feb;40(2):323-328. Bertelli JA, Ghizoni MF. Nerve transfers for restoration of finger flexion in patients with tetraplegia. J Neurosurg Spine (2017) 26:55–61. Emamhadi M, Andalib S. Double nerve transfer for restoration of hand grasp and release in C7 tetraplegia following complete cervical spinal cord injury. Acta Neurochir. (2018) Nov;160(11):2219-2224.

RF: Paper 10: Evaluation of the Role of Dynamic Elbow Stabilizers on Radiocapitellar Joint Alignment Category: Bone and Joint;Tendon;Other Clinical Topics Evaluation/Diagnosis; Anatomy; Basic Science Level of Evidence: 2 Austin Roebke, MD Richard Samade, MD, PhD Perry Altman MD Sonu Jain, MD Kanu S. Goyal, MD, FAAOS Amy Speeckaert, MD HYPOTHESIS To determine the effect of the dynamic stabilizers of the radiocapitellar (RC) joint by comparing the radiocapitellar ratio (RCR) of the elbow in patients before and after the administration of regional anesthetic. METHODS A prospective within-subject study of 14 patients was performed in a single institution between 1/1/2019 – 7/1/2019, with each patient presenting for elective surgery in the studied extremity. Inclusion criteria included age > 18 years and able to receive a supraclavicular regional anesthetic block. Exclusion criteria included history of prior surgery or trauma to the studied elbow. In each patient, 1 anteroposterior (AP) and 9 lateral fluoroscopic images were obtained. The lateral images were obtained with maximal forearm pronation, neutral rotation, and supination with the elbow (1) fully extended, (2) flexed to 90 degrees with 0 degrees of shoulder internal rotation (IR), and (3) flexed to 90 degrees with 90 degrees of shoulder IR. After obtaining 10 initial images, the block was performed to achieve less than 3/5 motor strength of the imaged elbow. Then, the same 10 images were again obtained in each patient. RCRs were then calculated with a negative RCR indicating posterior subluxation of the radial head in relation to the capitellum. The paired t-test was used to compare carrying angles and RCRs between groups (significance level 0.05). RESULTS The 14 patients had a mean age of 47.8±15.7 years and 10 (71.4%) were female. A significant difference between RCRs measured prior to and after regional block administration was seen were seen with forearm maximally supinated / elbow flexed to 90 degrees / shoulder at 90 degrees of IR (-1.89%±6.22% to -6.88%±8.13%, P = 0.0035). Furthermore, a trend toward significance was seen with the forearm maximally supinated / elbow flexed to 90 degrees / shoulder at 0 degrees of IR (1.77%±9.54% to -1.72%±6.00%, P = 0.0551. No significant difference was seen in carrying angles (15.5±4.09 to 16.6±4.25, P = 0.314).

SUMMARY • The dynamic stabilizers of the elbow play a role in certain positions of the arm, notably with maximal forearm supination, elbow flexion to 90 degrees, and 90 degrees of shoulder internal rotation • The best way to examine elbow stability intra-operatively after supraclavicular regional anesthetic block is take lateral fluoroscopic images with the forearm in maximum pronation REFERENCES: Rouleau, D.M., et al., Radial head translation measurement in healthy individuals: the radiocapitellar ratio. J Shoulder Elbow Surg. 2012. 21(5): p. 574-9. Sandman, E., et al. Effect of elbow position on radiographic measurements of radio-capitellar alignment. World J Orthop. 2016. 7(2): p. 117-22. Kaufmann, R.A., et al. Elbow Biomechanics: Soft Tissue Stabilizers. J Hand Surg Am. 2020. 45(2): p. 140-147.

RF: Paper 13: Reducing Overuse of Prophylactic Antibiotics in Carpel Tunnel Release Category: Bone and Joint;Skin and Soft Tissue;Other Clinical Topics Prognosis/Outcomes; Residents/Fellow/Educator Resources Level of Evidence: 4 Kevin M. McKay Neil G. Harness HYPOTHESIS An educational outreach program directed to reduce the use of antibiotics in clean hand surgeries will lead to a reduction in antibiotic prophylaxis. METHODS A surgeon leader assembled a group of surgeon champions at 10 service areas within Kaiser Permanente Southern California (KPSC) and implemented a program in 2018 to reduce the use of antibiotics for carpal tunnel release (CTR) performed in the surgery center or inpatient surgery setting. The program consisted of 1) an evidence based educational session for all participating Orthopedic and Plastics hand surgeons during which the elimination of use of antibiotics in CTR was requested, and 2) a year long, monthly antibiotic use audit and feedback cycle for individual surgeons. Rate of antibiotic use in CTR the year during the intervention was compared to the rate prior to the intervention using non-parametric tests. A survey was distributed among participating surgeons to elucidate reasons for continued usage. RESULTS Combined rate of antibiotic usage for CTR decreased from 51.41 to 20.91%, and the average rate of decrease per center was 25.39%, (95% CI 7.02-43.74). A one-sided Wilcoxon Signed rank test was performed to further characterize the decrease in use of antibiotics at participating centers. Median rates for 2017-2018 and 2018-2019 were 37.6% and 22.0% respectively. Decrease in median rate of antibiotic use was confirmed to be statistically significant (W=0, z = -2.8, p = 0.002, α level < 0.05). Two-sided Wilcoxon Signed rank test for change in total number of CTR cases between years was performed. Medians for 2017-2018 and 2018-2019 were 166 and 160.5 respectively and the difference was not significant (W = 25.5, z = -0.2039, p = 0.842, α level < 0.05). The follow up surgeon survey elicited 34 responses (out of 39 surgeons; 87.18% response rate). Notably, it revealed that 97% of respondent surgeons agreed with the evidence that prophylactic antibiotics show no benefit in clean hand surgery. However, relating to patient factors, respondents answered that antibiotics should be used as HgA1c level increased from 6 (21%) to 12 (65%), and that antibiotics should be used for patients who are immunosuppressed (65%).

SUMMARY · Rate of antibiotic usage in CTR decreased from 51.41% the year prior, to 20.91% the year of implementing a surgeon led program to reduce unnecessary antibiotic prophylaxis in CTR. · Multiple barriers were identified in the follow up cross sectional survey which may limit implementation of this best practice. REFERENCES: Murphy, G. R. F., Gardiner, M. D., Glass, G. E., Kreis, I. A., Jain, A., & Hettiaratchy, S. (2016, April 1). Meta-analysis of antibiotics for simple hand injuries requiring surgery. British Journal of Surgery. John Wiley and Sons Ltd. https://doi.org/10.1 Johnson, S. P., Zhong, L., Chung, K. C., & Waljee, J. F. (2018). Perioperative Antibiotics for Clean Hand Surgery: A National Study. Journal of Hand Surgery, 43(5), 407-416.e1. https://doi.org/10.1016/j.jhsa.2017.11.018 Tosti, R., Fowler, J., Dwyer, J., Maltenfort, M., Thoder, J. J., & Ilyas, A. M. (2012). Is antibiotic prophylaxis necessary in elective soft tissue hand surgery? Orthopedics, 35(6). https://doi.org/10.3928/01477447-20120525-20 Li, K., Sambare, T. D., Jiang, S. Y., Shearer, E. J., Douglass, N. P., & Kamal, R. N. (2018). Effectiveness of preoperative antibiotics in preventing surgical site infection after common soft tissue procedures of the hand. Clinical Orthopaedics and Relate

RF: Paper 14: Clinical Presentation and Epidemiology of Hand and Wrist Ganglion Cysts in Children Category: Bone and Joint;Skin and Soft Tissue;Tendon Evaluation/Diagnosis Level of Evidence: 4 Joshua Bram, BS David P. Falk, MD Benjamin Chang, MD Jennifer Ty, MD Ines Lin, MD Apurva Shah, MD, MBA HYPOTHESIS Ganglion cysts are the most common mass in the hand and wrist. However, the epidemiology in children is not well-reported. Our study sought to illustrate the epidemiology of pediatric ganglion cysts in a large, prospective cohort. We hypothesized that dorsal wrist ganglions would occur in older patients and would be larger. METHODS A multicenter prospective investigation of children (<18 years) who presented for ganglion cysts of the hand or wrist was conducted between 2017-2019. Data collected included age, sex, cyst location, hand dominance, pain (Wong-Baker), and PROMIS scores for upper extremity (UE) function. Patients were divided into cohorts based on age, cyst location, and cyst size. Chi-squared, Fisher’s exact, and Mann-Whitney U tests were used to compare cohorts. RESULTS 173 patients were enrolled with mean age of 10.1±5.3 years and female: male ratio of 1.4 (p=0.018). The dorsal wrist was most commonly affected (49.7%) followed by the volar wrist (26.6%) and flexor retinaculum (18.5%). Dorsal wrist ganglions occurred in older patients (Table 1) compared to retinacular cysts (11.9±4.1 versus 6.2±5.8 years, p<0.001) and were also larger (86.7% >1cm) than cysts in other locations (34.5% >1cm, p<0.001). Patients >10 years of age reported higher pain scores (2.3±2.9 versus 0.9±1.6, p=0.005), with 21.5% of older patients reporting moderate/severe pain scores versus 5.0% in younger children (p=0.021). Ultrasound (34.7% vs 10.9%, p<0.001) was more often used to diagnose cysts in children <10 years. Cysts >1 cm (Table 2) occurred more frequently in older patients (11.7±4.4 versus 7.5±5.6 years, p<0.001) and presented to clinic 2.4 months later (p=0.047) than cysts <1cm. Compared to the average pediatric population, patients with ganglions had lower PROMIS UE function scores (47.4 versus 50.0, p=0.020). In multivariate analysis, younger age (B=0.552, 95% CI 0.033-1.070, p=0.037) and higher pain scores (B=1.177, 95% CI 0.540-1.815, p<0.001) predicted worse upper extremity function. Only older age predicted a pain score ³5 (moderate/severe pain).

SUMMARY Ganglion cysts most commonly afflicted the dorsal wrist in pediatric patients >10 years Cysts >1 cm were more common in older children and were associated with longer delays to presentation For children <10 years, volar wrist and flexor retinaculum cysts were more frequent and ultrasound was more often used for diagnostic confirmation of a ganglion Ganglion cyst patients had significantly worse upper extremity function compared to the average pediatric population Younger age and higher Wong-Baker pain predicted lower upper extremity function

RF: Paper 15: Incidence, Timing, and Risk Factors for Tendon Rupture After Surgical Fixation of Distal Radius Fractures Category: Tendon Treatment; Prognosis/Outcomes Level of evidence: 2 Catphuong Vu Sara Cook Jerry I. Huang HYPOTHESIS Flexor and extensor tendon ruptures are both known complications that can occur with plate fixation of distal radius fractures. However, timing and true incidence of tendon rupture after distal radius repair have not been well characterized. We hypothesize that the incidence of tendon ruptures following surgical fixation of distal radius fractures is low and most commonly occurs in the first year after surgery. METHODS The Marketscan database was used to establish a cohort who underwent surgical fixation of distal radius fractures (CPT codes 25606-25609) from 2007-2015. Records were analyzed for tendon rupture based on ICD9/ICD10 diagnosis codes and CPT codes indicating surgical reconstruction or tendon transfers following tendon ruptures. Kaplan-Meier survival analysis was used for time to event analysis and Cox regression was used to determine risk factors associated with tendon rupture. RESULTS From 2007-2015, 46,403 cases of distal radius fractures with mean age of 52 underwent operative fixation. Tendon ruptures occurred in 299 (0.64%) cases, with 241 (76.0%) involving extensor tendons and 76 cases of flexor tendon ruptures. Eighteen patients had both flexor and extensor tendon ruptures. Median time to extensor tendon rupture was significantly earlier than flexor tendon ruptures (108 vs. 243 days). There is an increased risk of tendon rupture with age but no increased risk with obesity or diabetes. A twofold increased risk of extensor tendon rupture occurred with open treatment compared with closed reduction with percutaneous pinning. SUMMARY · Open reduction internal fixation of distal radius fractures is a common procedure with a low incidence of tendon ruptures. · Extensor tendon ruptures are more common than flexor tendon ruptures. · Most tendon rupture injuries occurred within one year postop. · Flexor tendon rupture occurred at a later time than extensor tendon rupture.

RF: Paper 16: The Safety and Efficacy of Bier Blocks For Distal Radius Fracture Reduction Performed by Orthopedic Residents Category: Bone and Joint;Other Clinical Topics Treatment; Prognosis/Outcomes; Residents/Fellow/Educator Resources Level of Evidence: 4 Michelle Zeidan Megan Campbell Justin M. Haller, MD David L. Rothberg Thomas F. Higgins Lucas S. Marchand, MD HYPOTHESIS The use of intravenous regional anesthesia (IVRA or Bier Block) can be a controversial method of emergency department (ED) analgesia due to its potential life-threatening complications [1]. It is also unknown if there is an effect on the rate of complex regional pain syndrome (CRPS). We hypothesized that Bier block anesthesia used in the emergency department for closed reduction of distal radius fractures is safe and effective and does not affect rates of CRPS. METHODS Retrospective chart review was performed on patients who presented to our institution’s emergency department or clinic with a distal radius fracture between November 2009 to December 2019. Demographics, type of anesthesia (conscious sedation, hematoma block, IVRA), complications, neurologic exam including CRPS diagnosis at final follow up, and need for operative fixation were recorded. Descriptive statistics were used to interpret our results. RESULTS A total of 899 patients underwent closed reduction of a distal radius fracture. Of the 899 patients, 82 (9.1%) received conscious sedation, 169 (18.8%) received a hematoma block, and 648 (72.1%) received IVRA. Of the 648 patients, 63% were female with an average age of 54 ± 18.6 years. There were no major complications and 7 (1.1%) patients experienced minor complications. These included chest pain without sequelae (n=1), transient tinnitus and peri-oral numbness (n=3), unbearable tourniquet pain with severe anxiety (n=2), and acute carpal tunnel syndrome resolving after re-splinting (n=1). Of the 648 patients, 550 had at least 30 days of follow-up (average follow up=113 days). Of those patients, 229 (41.6%) underwent open reduction and internal fixation (ORIF) and 11 patients (2%) developed CRPS. SUMMARY • Bier blocks are used in the majority of reductions at our institution and only minor complications have occurred. • The rate of CRPS in our large series is less than reported rates for distal radius fractures [2-4]. • When performed properly, Bier blocks are a safe method to

perform distal radius reductions, and can be performed by orthopedic residents without the presence of an anesthesia provider. REFERENCES: Guay J. Adverse events associated with intravenous regional anesthesia (Bier block): a systematic review of complications. Journal of Clinical Anesthesia. 2009;21(8):585-594. Field, J. and R. Atkins (1997). "Algodystrophy is an early complication of Colles' fracture. What are the implications?" Journal of Hand Surgery (British and European Volume, 22)(2): 178-182. Dijkstra PU, Groothoff JW, Duis HJ, Geertzen JHB. Incidence of complex regional pain syndrome type I after fractures of the distal radius. European Journal of Pain. 2003;7(5):457-462. Crijns TJ, van der Gronde B, Ring D, Leung N. Complex Regional Pain Syndrome After Distal Radius Fracture Is Uncommon and Is Often Associated With Fibromyalgia. Clin Orthop Relat Res. 2018;476(4):744-750.

RF: Paper 17: Hand Surgery Transfers to a Level 1 Center: Cost Effectiveness and Variables Affecting Transfer Method Category: Other Clinical Topics Evaluation/Diagnosis Level of Evidence: 4 Rachel Pedreira Jill Putnam Paige Fox HYPOTHESIS Patient transfers to a level 1 trauma center for management by a hand specialist may be unnecessary and costly. The purpose of this analysis is to evaluate whether or not time of consult, transfer distance, and involved provider level influence the pre-transfer diagnostic accuracy and method of transport for higher level of care. Further, the authors wish to evaluate the cost effectiveness of transfers. METHODS Our facility’s transfer center provided data for 265 patients transferred between 2014 and 2019. Each transfer record was evaluated for patient and injury characteristics, time of consult, transfer distance, involved provider level, method of transport, accuracy of diagnosis at time of transport, and management of injury. RESULTS The average age of the patient population analyzed was 36.9 years and 80.3% of patients were male. 16% of patients required translation services due to a language barrier. As expected, increasing interfacility distance and specific diagnoses were associated with an increased likelihood of utilizing air transport (p < 0.05). Mean transfer distance for air transport was 166 miles, versus 63 miles for ground transport. 21% of transfers were diagnosed inaccurately by the transferring facility, and certain diagnoses correlated with an increased likelihood of diagnostic inaccuracy. In particular, partial amputations and flexor tenosynovitis (FTS) were diagnosed incorrectly in a statistically significant number of transferred patients (p < .01). Of all transfers, 14 (5%) of patients were discharged from our emergency department with no further treatment. 9 patients (3%) were admitted for observation without surgical intervention. 73 patients (27%) had a procedure in the emergency department prior to discharge home from the emergency department. Finally, 166 cases (62%) were managed acutely in the operating room. SUMMARY At our facility, many transfers involved care that likely could have been provided at the transferring facility without incurring the cost of transportation and additional work up. Certain diagnoses are associated with increased risk for diagnostic error and unnecessarily urgent transport methods. These include FTS and partial amputations. Providers at accepting

facilities might use this information to consider transfer patterns at their own facilities, and to educate transferring providers. The high percentage of inaccurate diagnoses presents an opportunity for investigation into how modalities like telemedicine may be applied as a means of preventing unnecessary transfer for hand specialist evaluation. REFERENCES: Bauer AS, Blazar PE, Earp BE, Louie DL, Pallin DJ. Characteristics of emergency department transfers for hand surgery consultation. Hand N Y N. 2013;8(1):12-16. doi:10.1007/s11552-012-9466-5 Hartzell TL, Kuo P, Eberlin KR, Winograd JM, Day CS. The overutilization of resources in patients with acute upper extremity trauma and infection. J Hand Surg. 2013;38(4):766-773. doi:10.1016/j.jhsa.2012.12.016 Koval KJ, Tingey CW, Spratt KF. Are patients being transferred to level-I trauma centers for reasons other than medical necessity? J Bone Joint Surg Am. 2006;88(10):2124-2132. doi:10.2106/JBJS.F.00245 Friebe I, Isaacs J, Mallu S, Kurdin A, Mounasamy V, Dhindsa H. Evaluation of appropriateness of patient transfers for hand and microsurgery to a level I trauma center. Hand N Y N. 2013;8(4):417-421. doi:10.1007/s11552-013-9538-1 Kuo P, Hartzell TL, Eberlin KR, et al. The characteristics of referring facilities and transferred hand surgery patients: factors associated with emergency patient transfers. J Bone Joint Surg Am. 2014;96(6):e48. doi:10.2106/JBJS.L.01213

RF: Paper 18: Differences in Long-Term Outcomes Between Proximal Row Carpectomy and 4-Corner Arthrodesis: Mean Follow-up of 11 Years Category: Bone and Joint Prognosis/Outcomes Level of Evidence: 4 Neill Yun Li Andrew M Hresko Kalpit N. Shah Janine D. Molino Arnold-Peter C Weiss HYPOTHESIS Few studies have compared long-term outcomes between proximal row carpectomy (PRC) and 4-corner arthrodesis (FCA). This study aimed to assess differences in patient reported and functional outcomes as well as radiographic changes for patients more than 5 years from their index procedure. METHODS Following IRB approval, patients who received a PRC or FCA by the senior author (APCW) at least 5 years prior were contacted. Participants were assessed for grip strength, wrist range of motion, visual analog scale for pain (VAS), and Patient Rated Wrist Evaluation (PRWE) for pain and disability. Fluoroscopic images assessed post-operative joint degeneration using a scale by Culp and Jepson on Radiocarpal Arthritis. Linear regression models compared grip strength and range of motion between procedure types while generalized linear models were used to compare PRWE and VAS scores between procedure types. Due to the small number of women in the study and the known differences in grip strength between men and women, the grip strength analyses were restricted to male participants only. Statistical significance was established at the P<0.05 level and all interval estimates were calculated for 95% confidence. RESULTS A total of 11 PRCs and 10 FCAs were enrolled. Mean follow-up was 11.0 years with 9.6 years after PRC, and 12.6 years after FCA. There were no significant differences between the PRC and FCA cohorts for flexion (25.3° vs. 27.1°, p=0.79), extension (36.0° vs. 45.6°, p=0.07), radial deviation (7.4° vs. 8.9°, p=0.47), ulnar deviation (26.7° vs. 26.8°, p=0.99), VAS (0.6 vs. 1.3, p=0.23), PRWE (19.3 vs. 23.3, p=0.67), or joint degeneration grade (1.4 vs. 0.9, p=0.08. However, for male patients, grip strength was significantly stronger following FCA than PRC (27.7 kg vs. 37.9 kg, p<0.01) (figure 2). Furthermore, the increase in years post-op was associated with significantly decreased grip strength in the PRC group (p<0.0001), but years post-op was not associated with grip strength in the FCA group (p=0.75).

SUMMARY • At a mean follow-up of 11 years, patients undergoing FCA or PRC demonstrated no differences in PRWE • FCA was associated with higher grip strength compared to PRC with PRC significantly decreasing in grip strength over time. • No significant difference was seen in joint degeneration following PRC or FCA. REFERENCES: Williams J, Weiner H, Tyser A. Long-Term Outcome and Secondary Operations after Proximal Row Carpectomy or Four-Corner Arthrodesis. J Wrist Surg. 2017;07(01):051-056. doi:10.1055/s-0037-1604395 Wagner ER, Werthel JD, Elhassan BT, Moran SL. Proximal Row Carpectomy and 4-Corner Arthrodesis in Patients Younger Than Age 45 Years. J Hand Surg Am. 2017;42(6):428-435. doi:10.1016/j.jhsa.2017.03.015 Berkhout MJL, Bachour Y, Zheng KH, Mullender MG, Strackee SD, Ritt MJPF. Four-corner arthrodesis versus proximal row carpectomy: A retrospective study with a mean follow-up of 17 years. J Hand Surg Am. 2015;40(7):1349-1354. doi:10.1016/j.jhsa.2014.12.035 Jebson PJL, Hayes EP, Engber WD. Proximal Row Carpectomy: a minimum 10-year follow-up study. J Hand Surg Am. 2003;28(4):561-569. Culp RW, McGuigan FX, Turner MA, Lichtman DM, Osterman AL, McCarroll HR. Proximal row carpectomy: a multicenter study. J Hand Surg Am. 1993;18(1):19-25.

RF: Paper 20: Radiographic changes in Alignment of the Thumb Carpometacarpal Joint over a 6-year period: A Prospective Study Category: Bone and Joint Evaluation/Diagnosis; Prognosis/Outcomes Level of Evidence: 4 Kalpit N. Shah Edgar Garcia-Lopez Amy M. Morton Matthew Navarro Douglas C. Moore Amy Ladd, Arnold-Peter C. Weiss, Joseph J. Crisco HYPOTHESIS Limited literature exists regarding the radiographic changes in alignment with time in patients with thumb carpometacarpal (CMC) osteoarthritis (OA). We assumed the null hypothesis that radiographic alignment will not change significantly over a 6-year period. Our secondary hypothesis is that there will be no difference between men and women. METHODS Patients with nascent thumb CMC OA (pain and positive clinical signs with no or minor radiographic changes) were enrolled prospectively. Two radiographic parameters (radial subluxation of the thumb metacarpal on stress view1 and dorsal subluxation of the thumb metacarpal on a lateral view) were measured at 5 time points (year 0, 1.5, 3, 4.5 and 6) over the course of the 6-year longitudinal study of thumb CMC OA. Clinical staging based on the Eaton-Glickel classification was recorded for all patients. Linear mixed-effects model was used to compare changes in the radiographic alignment parameters over time. RESULTS Ninety-two patients (47F and 43M between the ages of 45 and 75 yrs) were enrolled in the study. The radial subluxation was noted to have a 10.9% decrease over time (R2 = 0.55, P < 0.05) while no difference was noted in the dorsal subluxation (R2 = 0.45, P < 0.05) (Fig. 1a-b). Males and female both showed you a significant decrease in the radial subluxation but not dorsal subluxation (p<0.05 and p>0.05, respectively) (Fig. 2a-b). The changes in radial subluxation did not correlate with changes in the modified Eaton score of thumb CMC OA. SUMMARY • Radial subluxation on the stress radiographic decreased by 10.9% over the 6-year study period, for men and women • Dorsal subluxation on the thumb lateral radiographs did not change over time • The changes seen in the radial subluxation did not differ significantly between men and women with thumb CMC OA

REFERENCES: Wolf JM, Oren TW, Ferguson B, Williams A, Petersen B. The carpometacarpal stress view radiograph in the evaluation of trapeziometacarpal joint laxity. J Hand Surg Am. 2009 Oct;34(8):1402-6

RF: Paper 21: Prosthetic Use in Upper Extremity Amputees after Targeted Muscle Reinnervation: A Case Series Category: Nerve;Skin and Soft Tissue Treatment; Prognosis/Outcomes Level of Evidence: 4 Ryan Jefferson Andrew O'Brien Julie West Ian Valerio Amy Moore Steven Schulz HYPOTHESIS Targeted Muscle Reinnervation [TMR] performed after upper extremity amputation improves the rate of prosthetic use and influences the type of prosthetic chosen by patients. METHODS All cases of upper extremity TMR performed by our group between 2016-2020 were reviewed. Both acute [within 30 days of amputation] and secondary [performed beyond 30 days of index amputation] were included. Data was obtained during pre-operative and post-operative office visits and from direct patient phone calls. Medical records were reviewed to collect patient demographics, amputation indication, level of amputation [trans-radial, trans-humeral, or shoulder disarticulation], number of TMR nerve coaptations, rate of prosthetic use, and type of prosthetic selected [cosmetic, body-powered, or myoelectric]. RESULTS Nineteen patients were identified in our retrospective review. Thirteen patients underwent acute TMR, while six had TMR performed secondary to painful neuroma formation and/or phantom limb pain that developed after index amputation. The most common indication for amputation was cancer [42.1%], followed by non-military trauma [36.8%], congenital deformity [10.5%], and vascular insult [10.5%]. The most common level of amputation was trans-humeral [42.1%], followed by trans-radial [36.8%], and shoulder disarticulation [21.1%]. The mean number of nerve coaptations performed was 4.1 [2-6]. The mean follow up was 14.1 months [0.63-38.4 months]. Eleven of the patients reported using a prosthetic after TMR [57.9%]. Of note, three of the eight patients not using a prosthetic currently are planning to use one in the near future. Of 11 patients currently using a prosthetic, 10 use a myoelectric [90.1%]; the remaining patient uses a body-powered prosthetic. Among the six secondary TMR patients, four did not use any prosthetic prior to TMR. Two of these patients now use a prosthetic after TMR [one myoelectric, one body powered], and all who used a prosthetic before TMR continued to use one

SUMMARY · TMR patients in this series demonstrate a high rate of prosthetic use compared to commonly accepted rates of use after upper extremity amputation. · TMR patients using a prosthetic demonstrate a strong predilection for myoelectic prostheses compared to cosmetic or body powered. · Secondary TMR improved the rate of prosthetic use among amputees previously not using a prosthetic.

RF: Paper 22: Motion at the Thumb Carpometacarpal Joint during Functional Tasks in Early OA patients: A Prospective Study Category: Bone and Joint Evaluation/Diagnosis; Prognosis/Outcomes Level of Evidence: 4 Kalpit Nimish Shah Edgar Garcia-Lopez Amy M. Morton Douglas C. Moore Amy Ladd Arnold-Peter C. Weiss, Joseph J. Crisco PhD HYPOTHESIS Changes in the position of the thumb carpometacarpal (CMC) joint during functional tasks has not been studied in patients with early thumb CMC osteoarthritis (OA). We hypothesized that the changes in the position of the thumb CMC joint will not differ significantly between early OA patients and controls. METHODS Patients with early modified Eaton score of 0 or 1 thumb CMC OA and controls with no known thumb pathology were evaluated at enrollment with CT scans with the thumb CMC joint in neutral and during 3 functional tasks (loaded pinch, grasp and jar-holding position).1,2 Digital thumb metacarpal (MC) and trapezium bone surface models were segmented from the patient CT scans, articular surfaces identified, and coordinate systems (CS) were calculated for each bone.3 Displacement was described by the dorsal-volar and radial-ulnar components of the 3D vector characterizing the thumb MC displacement from trapezium for each position. Displacement values were normalized by the square root of the trapezial facet area to control for differences in bone size. The displacement for each functional task was compared to neutral thumb pose, as well as between subjects and control, using student t-test. Linear mixed-effects model was used to compare changes in the thumb metacarpal position during the different tasks over time. RESULTS Ninety patients (47F and 43M; range: 45 and 75 years) and 46 controls (25F and 21M; range:18-75 years) were enrolled in the study. Almost all tasks led to a change in the position the thumb CMC joint that was statistically different when compared to the position of the thumb CMC joint at neutral, in both the early OA group and the controls. The thumb MC moved in a radial and dorsal direction during pinch, mostly ulnar direction during grasp and radial and dorsal direction during jar holding position compared to the trapezium. (Table 1) When comparing the motion seen in early OA patients to that of controls, there was almost no difference between the two groups in terms of radial displacement. However, the early OA patients tended to

displace dorsally more than controls during the neutral, grasp and jar-holding positions (Table 2). SUMMARY • Almost all tasks led to a change in the position the thumb CMC joint that was statistically different when compared to the position of the thumb CMC joint at neutral • The thumb MC moved in a radial and dorsal direction during pinch, mostly ulnar direction during grasp and radial and dorsal direction during jar holding position • When comparing early OA patients in comparison to that of controls, there was almost no difference in radial displacement, but early OA patients tended to displace dorsally more than controls during the neutral, grasp and jar-holding positions REFERENCES: Ladd AL, Messana JM, Berger AJ, Weiss A-PC. Correlation of clinical disease severity to radiographic thumb osteoarthritis index. J Hand Surg. 2015;40(3):474-482. doi:10.1016/j.jhsa.2014.11.021 Crisco JJ, Patel T, Halilaj E, Moore DC. The Envelope of Physiological Motion of the First Carpometacarpal Joint. J Biomech Eng. 2015;137(10):101002. doi:10.1115/1.4031117 Halilaj E, Rainbow MJ, Got CJ, Moore DC, Crisco JJ. A thumb carpometacarpal joint coordinate system based on articular surface geometry. J Biomech. 2013;46(5):1031-1034. doi:10.1016/j.jbiomech.2012.12.002

RF: Paper 23: Impact of Tendon Transfers on Shoulder Motion in Children with Brachial Plexus Injuries Category: Nerve;Pediatric Trauma and Congenital Conditions;Tendon Treatment; Prognosis/Outcomes; Basic Science Level of Evidence: 4 Stephanie Russo James Richards Ross Chafetz Spencer Warshauer Dan Zlotolow Scott Kozin HYPOTHESIS Tendon transfers are frequently utilized to improve external rotation and overhead motion in children with brachial plexus birth injuries (BPBI); while, the theory is that these tendon transfers increase glenohumeral (GH) motion, the impact of these procedures on the scapulothoracic (ST) versus GH joints remains unknown. We hypothesized that transfer of teres major and latissimus dorsi or teres major only would increase shoulder external rotation and elevation, decrease internal rotation, and reorient the same total arc of motion. METHODS Motion capture analysis of the ST, GH, and humerothoracic (HT) joints was performed on ten children before and after transfer of teres major or teres major and latissimus dorsi. Scapular markers were re-palpated while children held their arms in 12 positions, including the modified Mallet positions. The internal/external rotation arc of motion was calculated from the maximal internal and external rotation angles measured across the tested positions. Joint angles in the abduction, external rotation, and internal rotation positions and the internal/external rotation arcs of motion were compared before and after surgery using paired t-tests. RESULTS There were no differences in ST, GH, or HT motion in the abduction position after surgery (Table). In the external rotation position, GH and HT external rotation were significantly increased (p=0.019 and p=0.006, respectively) postoperatively. In the internal rotation position, GH internal rotation was significantly decreased (p=0.021), while ST internal rotation was significantly increased (p=0.027). There was no difference (p=0.146) in the total HT internal/external rotation arc after surgery. However, the ST arc was significantly increased (p=0.031), while the GH arc was significantly decreased (p=0.028). SUMMARY · Although tendon transfer surgery is traditionally thought to increase GH motion, the GH arc of motion was significantly decreased postoperatively in this cohort. The GH arc of motion was

also oriented into greater external rotation postoperatively. Scapulothoracic internal rotation increased postoperatively, which helped maintain the same total arc of HT internal/external rotation. The HT arc of rotation was also more externally rotated postoperatively (Figure). · In internal rotation, the scapula was able to compensate for some of the lost internal rotation, but HT internal rotation was still significantly lower than before surgery. · While no difference in GH or HT elevation was identified postoperatively, the more externally rotated position of the humerus lead to improved overhead reach (Figure). · These findings help improve our understanding of shoulder tendon transfer procedures and expected outcomes in the BPBI population. REFERENCES: 1. Kozin SH, Chafetz RS, Barus D, Filipone L. Magnetic resonance imaging and clinical findings before and after tendon transfers about the shoulder in children with residual brachial plexus birth palsy. Journal of shoulder and elbow surgery. 2006;15(5):55 2. Russo SA, Kozin SH, Zlotolow DA, et al. Scapulothoracic and glenohumeral contributions to motion in children with brachial plexus birth palsy. Journal of shoulder and elbow surgery. 2014;23(3):327-338. 3. Waters PM, Bae DS. Effect of tendon transfers and extra-articular soft-tissue balancing on glenohumeral development in brachial plexus birth palsy. The Journal of bone and joint surgery American volume. 2005;87(2):320-325.

RF: Paper 24: Clinical Determination of Mallet Scores Overestimates Shoulder Motion Category: Nerve;Pediatric Trauma and Congenital Conditions;Other Clinical Topics Evaluation/Diagnosis Level of Evidence: 3 Ross Chafetz Stephanie Russo Jamie Landgarten Erica Johnson Scott Kozin Dan Zlotolow HYPOTHESIS Shoulder function in brachial plexus birth injuries (BPBI) is frequently measured using the modified Mallet classification (Figure 1); however, the modified Mallet has been criticized for lack of specificity and large variation within single scores in the ordinal scale. We hypothesized that Mallet scores determined by objectively measured joint angles would substantially differ from Mallet scores determined during clinical exam. METHODS 102 children with BPBI who had a motion capture assessment and Mallet scores determined for clinical purposes on the same date were reviewed retrospectively. The Mallet scores that assess planar measurements with defined joint angles were included (abduction and external rotation). The clinical Mallet scores were obtained from the medical record. Mallet score assessments were performed by a hand surgeon or occupational therapist who specialized in pediatric care and had substantial experience with Mallet scores for BPBI. Motion capture measurements were used to calculated humerothoracic elevation and external rotation in the abduction and external rotation positions, respectively. The Mallet scores determined by the motion capture-measured joint angles were considered the gold standard. The percent of misclassified Mallet scores determined by clinicians was calculated. RESULTS For abduction, 23.5% of Mallet scores were misclassified. Of the misclassified scores, 19 were overestimated by 1 point, and 5 were underestimated by 1 point compared to motion capture. For external rotation, 75.5% of Mallet scores were misclassified. Of the misclassified scores, 43 were overestimated by 1 point, 32 were overestimated by 2 points, and 2 were underestimated by 1 point. SUMMARY · Children with BPBI utilized many compensatory movement strategies to maximize their range of motion. These include altered scapulothoracic movement patterns as well as thoracic

movements, such as leaning, to accomplish greater reach. · In the external rotation position, children with BPBI frequently elevate their arms and extend their wrists, which may falsely increase the appearance external rotation (Figure 2). · These compensatory strategies may be difficult to account for during clinical exams, leading to frequent overestimation of Mallet scores. Prior studies have demonstrated acceptable intra- and inter-rater reliability of the Mallet classification; however, reliability does not imply accuracy. · The inaccuracy of clinically-determined Mallet scores is alarming given that they are frequently utilized to assist with surgical indications and are one of the most common outcome measures utilized in the BPBI literature. Objective measures, such as motion capture, offer an alternative for accurate assessment of shoulder function in children with BPBI. REFERENCES: 1. Al-Qattan, MM and AAF El-Sayed. The outcome of primary brachial plexus reconstruction in extended Erb’s obstetric palsy when only one root is available for intraplexus neurotization. Eur. J Plast Surg. 2017;40:323-328. 2. Russo SA, Kozin SH, Zlotolow DA, Nicholson KF, Richards JG. Motion Necessary to Achieve Mallet Internal Rotation Positions in Children With Brachial Plexus Birth Palsy. J Pediatr Orthop. 2017;39(1):14-21. 3. Abzug JM, Chafetz RS, Gaughan JP, et al. Shoulder function after medial approach and derotational humeral osteotomy in patients with brachial plexus birth palsy. J Pediatr Orthop. 2010;30(5):469-74. 4. Bae DS, Waters PM, Zurakowski D. Reliability of three classification systems measuring active motion in brachial plexus birth palsy. The Journal of bone and joint surgery American volume. 2003;85-A(9):1733-1738. 5. van der Sluijs JA vD-LM, Ritt MJ, Wuisman PI. Interobserver reliaiblity of the Mallet Score. J Pediatr Orthop. 2006;15(5):324-327.

RF: Paper 25: Ectoderm-derived Wnt and Hedgehog signaling drive digit tip regeneration Category: Skin and Soft Tissue;Miscellaneous Nonclinical Topics Basic Science Level of Evidence: N/A Janos Barrera, MD Zeshaan Maan MD, MSd Deshka Foster MD, MA Michael T Longaker MD Irv Weissman PhD Geoffrey C Gurtner MD HYPOTHESIS Reports of “salamander-like” spontaneous regeneration in human fingertips and advances using mouse digit tip regeneration models raise the possibility of regenerative rather than reparative approaches to traumatic hand injuries, which often result in loss of function. Here we hypothesize that these novel murine digit tip regeneration models can be used to elucidate the signaling mechanisms responsible for this regenerative process. METHODS Tissue harvested from murine digit tips 7 days after amputation at the regenerative plane or non-regenerative plane were compared using microarray analysis. Viral knockdown of candidate genes identified by microarray analysis was used to confirm a functional role for these signaling networks in vivo. Tissue specific expression and response patterns of target genes were assessed using gene specific reporter mice. Clonal analysis using Rainbow mice was performed to characterize the behavior of candidate gene-responsive cells. RESULTS Ingenuity pathway analysis of microarray results identified Wnt and Hedgehog (HH) signaling as the top associated gene networks differentially regulated in regenerating digit tips. Suppression of either Wnt signaling or HH signaling significantly impaired digit tip regeneration. HH overexpression impaired epidermal closure, typically driven by Wnt, suggesting crosstalk between these pathways. Reporter mice demonstrated that Wnt expression and responsiveness were restricted to the ectoderm, while Hedgehog expression originated in the ectoderm, but responsiveness occurred in the mesoderm. Clonality of mesodermal cells was confirmed using transgenic rainbow mice. SUMMARY · Unbiased microarray analysis identifies a central role for Wnt and hedgehog signaling in digit tip regeneration. · In vivo studies confirm that both Wnt and hedgehog are critical mediators of this process. · Lineage-tracing with transgenic mice confirms a germ-layer restricted pattern of

expression and responsiveness in Wnt and hedgehog. · Understanding and targeting the crosstalk between these pathways could enable regeneration in normally non-regenerative extremity injuries.