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Section Editor: Darren L. Johnson, MD

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Cartilage Lesions of the Patella: Management After Acute Patellar DislocationAdam V. Metzler, MD; Christian Lattermann, MD; Darren L. Johnson, MD

Patellar dislocations are common knee injuries,

and in patients younger than 16 years, the annual incidence is 43/100,000.1 Risk factors for patellar dislocation include patella alta, family history, previous dislocation, troch-lear dysplasia, and high Q-angle.2 Fithian et al3 reported a 17% redislocation rate after a first-time patellar dislocation

and a 50% rate after a second dislocation. The main concern with each dislocation is the re-petitive trauma to the articular cartilage of the patellofemo-ral joint potentially leading to early osteoarthritis.

In the setting of an acute patellar dislocation, most au-thors would suggest nonsur-gical treatment for first-time dislocations. Exceptions to

this include osteochondral fracture, substantial disruption of the medial patellar stabiliz-ers, a laterally subluxed patella with normal alignment of the contralateral patella, a second dislocation, or a patient who is not improving with appropri-ate rehabilitation.4 When com-paring medial patellofemoral ligament (MPFL) reconstruc-tion with repair, a recent sys-tematic review showed that there was a statistically sig-nificantly higher failure rate among those who underwent MPFL repair (26.9%) than those who underwent recon-struction (6.6%) or medial retinacular repair/plication (16.5%).5

Common sequelae of acute patellar dislocations are chon-dral and osteochondral inju-ries to the patella or the lateral femoral condyle. The reported rate of chondral injury after patellar dislocation has been reported to be as high as 95%.6,7 Nomura et al7 reported that, after acute patellar dislo-cations in 39 patients, 17% of

patellar lesions had chondral or osteochondral fracturing, 23% had cracks (fissures), and 54% had lesions with both frac-turing and cracks (fissures).7 These chondral lesions may cause swelling, pain, mechani-cal symptoms, and functional impairment. The complexity of the patellofemoral joint and high shear forces, in addition to the avascularity of articu-lar cartilage, makes treatment challenging.8,9 This article discusses the challenges faced when attempting to treat acute chondral/osteochondral inju-ries after acute patellar dislo-cations.

Case RepoRtA 16-year-old starting

high school football player sustained a valgus load to his left knee from another player’s helmet. He had no previous history of patellar instability or knee injury. He presented with a diffusely swollen knee and significant lateral patellar apprehension. Radiographs showed a well-centered pa-

The authors are from Commonwealth Orthopaedic Centers (AVM), Edge-wood; and the Department of Orthopaedic Surgery (CL, DLJ), University of Kentucky School of Medicine, Lexington, Kentucky.

The authors have no relevant financial relationships to disclose.Correspondence should be addressed to: Darren L. Johnson, MD, De-

partment of Orthopaedic Surgery, University of Kentucky School of Medi-cine, 740 S Limestone St, K-415 Kentucky Clinic, Lexington, KY 40536-0284 (dljohns@uky.edu).

doi: 10.3928/01477447-20150504-05

Abstract: Articular cartilage injuries to the patella are fre-quent after patellar dislocation. The management of these acute cartilage injuries in the acute setting can be challenging. It is well documented that acute fixation is the optimal choice for treatment of osteochondral injuries. This article discuss-es the challenges and potential treatment options for acute chondral/osteochondral injuries to the patella after acute pa-tellar dislocation. [Orthopedics. 2015; 38(5):310-314.]

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tella in the trochlea (Figure 1). Lateral radiographs showed a Caton ratio of 1.05 (Figure 2). Emergent magnetic reso-nance imaging (MRI) showed a significant chondral injury to the medial patellar facet con-sistent with an acute patellar dislocation and multiple loose chondral fragments (Figure 3). It appeared that the MPFL was torn in multiple locations. The tibial tubercle-trochlear groove distance was 16 mm. The patient was scheduled for emergent MPFL reconstruc-tion and possible chondral fix-ation. Arthroscopic evaluation showed multiple macerated and ground-up loose bodies, with the largest piece being approximately 2×1.5 cm, in addition to multiple smaller fragments (Figure 4). The full extent of the cartilage injury was not fully appreciated un-til the patella was everted via a medial parapatellar arthroto-my (Figure 5). There was no bone on the backside of any of the cartilaginous pieces, and the larger pieces were macer-ated.

Preoperatively, an exten-sive conversation was had with the family regarding treatment plans. The goal was to acutely repair the chondral injury (if able) and perform an MPFL reconstruction. The fam-ily was made aware that the chondral fragments may not be repairable and were given options for this scenario. In the setting of the inability to repair the chondral fragments, the following options were discussed: (1) microfracture with allograft cartilage aug-mentation (BioCartilage; Ar-

threx, Naples, Florida) and MPFL reconstruction as a single-stage procedure; (2) osteochondral autograft plus MPFL reconstruction as a single-stage procedure; (3) autologous chondrocyte im-plantation (ACI) with MPFL reconstruction in 2 stages; and (4) minced juvenile cartilage implantation (DeNovo NT; Zimmer, Warsaw, Indiana) in addition to MPFL reconstruc-tion in 2 stages. The literature was discussed with the family in detail, and in this case the family elected for a single-stage procedure. The athlete was entering into his senior year of football.

Once it was determined that the chondral injury was unable to be fixed with screw/pin fixation due to the extent of the chondral injury, the family was notified, and they wished to proceed with microfracture with supplemental BioCarti-lage in a single-stage proce-dure. A medial parapatellar ar-throtomy was performed; the patella was everted (Figure 5) and extensive chondral fis-sure was noted with significant instability of the surrounding fissured cartilage. The un-stable cartilage was debrided back to a stable base, creating vertical walls, and the basic principles of a microfracture were followed (Figures 6-7). To augment the microfracture, a novel composite graft con-sisting of platelet-rich plasma and micronized allogenous cartilage fragments (BioCarti-lage) was used (Figures 8-9). The MPFL reconstruction was performed using a gracilis ten-don allograft, and the patient

was placed in a continuous passive motion machine post-operatively.

Therapy included weight bearing as tolerated in a hinged brace locked at 0°, with range of motion from 0° to 45° for the first 4 weeks. After 4 weeks, the brace was unlocked for ambulation, and range of motion was progressed as tol-erated. The patient returned to full competitive sports at 7 months postoperatively in a patella J brace. He had no pain with running, cutting, or foot-ball drills. Range of motion was 0° to 135°, and the patella was stable with no crepitance or apprehension on examina-tion.

DisCussionThe management of acute

focal chondral/osteochondral

injuries after patellar disloca-tions can be challenging. Giv-en its prevalence, these inju-ries should be suspected in all patellar dislocations, especial-ly if the patient presents with a knee effusion. Radiographs, including a sunrise view or a Merchant view, should be ob-tained; however, chondral in-juries may be missed, and an MRI should be considered if the patient has any signs of an intra-articular effusion or me-chanical symptoms.10,11

In the setting of a repair-able chondral/osteochondral fragment, anatomic repair is advised using the most ap-propriate fixation principles, including the options of both absorbable and nonabsorb-able implants that provide compression of the fragment.

Figure 1: Sunrise radiograph of the patella.

Figure 2: Lateral radiograph of the knee.

Figure 3: Axial magnetic resonance image showing a large chondral in-jury to the patella (orange arrow) and large loose body (red arrow).

Figure 4: Loose bodies removed from the knee.

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Nonabsorbable screws may re-quire removal and potentially takedown of the MPFL recon-struction to gain access to the hardware. Therefore, appro-priate planning for removal is imperative before placement of nonabsorbable implants in the patellofemoral joint. Small defects (<1 cm2) may be asymptomatic and may be appropriate for loose body removal and limited chondro-plasty.12,13 Microfracture may also be performed; however, the literature reports less fa-vorable outcomes for larger lesions in the weight-bearing aspect of the patella.12,13

Off-the-shelf augmenta-tions such as BioCartilage may be a novel option to sup-plement a microfracture in dif-ficult environments such as the patella; however, no clinical data exist on this technology to date.14-19

Osteochondral autograft offers another intraoperative option that can be used in the acute setting; however, this de-pends on the size and location of the defect. With any osteo-chondral autograft, donor-site morbidity remains a concern. An osteochondral autograft transplantation to the patella is technically challenging given the contour of the pa-tella and the depth that can be drilled.20-22

For larger lesions (2-10 cm2), ACI has the most sup-portive literature for chronic patellar cartilage defects.23-28 Gillogly et al27 reported an 83% good-to-excellent result after ACI with anteromedial-ization of the tibial tubercle

for isolated patellar cartilage defects with 5- to 11-year follow-up. However, the study had an overall reoperation rate of 40%.27 Gomoll et al28 per-formed a multicenter study looking at 110 patients with a minimum of 4 years’ follow-up who underwent ACI to the patella; they reported an 86% good-to-excellent result.

In addition to ACI, matrix-assisted autologous chondro-cyte implantation (MACI) has also shown promise in the lit-erature.29 However, although the results show good or very good results in 70% to 86% of patients treated with MACI or ACI to the patella, the results are still not as promising as the 90% good-to-excellent results seen with ACI to the femoral condyles.30-33 At the time of publication, ACI remains an off-label use in the patella, and prospective patients must be informed of this during the consent process.

Particulated juvenile car-tilage implantation (DeNovo NT) can also be an option with the possibility of a single-stage procedure.34-38 Thomp-kins et al36 performed a case series of 15 knee surgeries for grade 4 lesions of the patella treated with DeNovo NT. At an average follow-up of 28 months, mean fill was 89% and the International Cartilage Repair Society cartilage repair assessment score on MRI was nearly normal for all patients. Clinical outcomes scores for International Knee Documen-tation Committee and Knee Injury and Osteoarthritis Out-come Score scales were com-parable with those published

for ACI.36 One limitation is in the acute setting in which a pa-tient is taken to the operating room for possible fixation of a chondral/osteochondral frag-ment; DeNovo NT is often not available acutely. In ad-dition, if the MRI under- or overestimates the size of the defect compared with the in-traoperative findings, then too little or too much implant may be ordered. The lack of long-term literature on DeNovo NT makes insurance approval a major obstacle. Currently in the authors’ practice, if De-Novo NT is used, it is done in a staged procedure so the chondral injury can be appro-priately sized intraoperatively and the appropriate amount of DeNovo NT graft is ordered.

ConClusionOsteochondral injuries to

the patella are relatively com-mon after lateral patellar dis-locations. However, most of these defects are small and can simply be debrided. Manage-ment of acute, large cartilage injuries in the setting of an acute patellar dislocation can present many challenges to the surgeon. Accurate and quick diagnosis of patellar chondral injuries is imperative because the ideal situation is to directly fix all chondral injuries that are unstable. In some cases, the chondral injures are not fixable, and other cartilage restoration techniques must be performed. The case presented in this article shows the com-plex decision making needed for such cases and the impor-tance of shared decision mak-ing with the patient and fam-

Figure 8: BioCartilage (Arthrex, Na-ples, Florida) filled in the cartilage void.

Figure 7: Microfracture was per-formed.

Figure 5: Everted patella showing significant cartilage injury with fis-suring and cracks.

Figure 6: Unstable cartilage was de-brided.

Figure 9: Fibrin glue was placed over BioCartilage (Arthrex, Naples, Florida).

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ily. The surgeon should make every option available and should be comfortable with different cartilage restoration techniques.

Clinical data are available to support ACI or DeNovo NT for chronic patellar car-tilage injuries; however, this cannot be done in an acute setting. There is a paucity of higher-level data for the acute management of chondral in-juries associated with patel-lar dislocations. The literature currently supports nonsurgi-cal management of first-time patellar dislocations, except in the setting of chondral in-juries.4 Microfracture may be a viable option in the acute setting for smaller lesions but may have limited success with larger defects. The addition of graft substitutes to the micro-fracture, such as platelet-rich plasma or BioCartilage, may improve outcomes, as early basic science research shows. However, this still needs to be proven in clinical studies.

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