Prof. Vladimir BobićMD FRCSEd, Consultant Orthopaedic Knee Surgeon
Chester Knee Clinic at Nuffield Health, The Grosvenor Hospital Chester, United Kingdomwww.kneeclinic.info [email protected] @ChesterKnee
BioPoly®RS Knee System The partial resurfacing implant
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Relevant Disclosures
1: Royalties received from Schwartz Biomedical3b: Paid Consultant for intellectual property (implant
and instrument design), Schwartz Biomedical
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Mr Mike McNicholasBSc, MD, FRCSEd(Tr&Orth), FFSEM RSCI
Consultant, University Hospital Aintree, LiverpoolHon Prof, Directorate of Sport, University of Salford
Hon Senior Lecturer, Department of Musculoskeletal Biology, University of Liverpool
BioPoly®RS Knee System
The partial resurfacing implant
Cardiff, 3rd February 2017
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@BioKneeSociety
Articular Cartilage Repair: Surgical Options
ACI/MACI
BioPoly: Filling the Void?
OATSMicrofracture
Allografts UKR & TKR4
• BioPoly® Material– “Microcomposite” (UHMWPE and Hyaluronic Acid)– Hydrophilic (water attracting) polymer
• Hyaluronic Acid within BioPoly®– Attracts synovial fluid for lubrication– Allows for articulation with cartilage
• No damage to opposing cartilage surfaces• No damage to implant surface
• Resurfacing Applications
BioPoly® Technology Overview
Hyaluronic Acid
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Material properties
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Material Density Modulus Poisson’s ratio Hyperelastic
Trabecular bone 1.8 g/cc1 1.15 GPa 0.22 NA
Cartilage 1 g/cc 10 MPa 0.495 (incompressible)
Neo HookeC10 = 1.672 MPa,
D1 = 0.0
Titanium 4.5 g/cc3 103 GPa 0.343 NA
Co-Cr 8.41 g/cc3 233 GPa 0.3 NA
UHMWPE (unhydrated) 0.945 g/cc4 830 MPa 0.464 NA
1 http://silver.neep.wisc.edu/~lakes/BoneTrab.html2 van Rietbergen B, Majumdar S, Pistoia W, et al. Assessment of cancellous bone mechanical properties from micro-FE models based on micro-CT, pQCT and MR images. Technol Health Care. 1998;6:413–420.3 http://www.fwmetals.com/titanium-wire-alloys.php4 http://www.goodfellow.com/E/Polyethylene-UHMW.html
FEA Comparison of Partial Resurfacing Femoral Implants: BioPoly RS and a metallic implant
• Contact biomechanics between femoral condyle focal defect implant and the opposing tibial articulating surface.
• Resulting biomechanical interface: Reduced contact stresses and strains
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Results: Compressive Strains
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Metallic Implant Compressive Log strains at the tibial
surface below implant apex
Peak -0.3
BioPoly Compressive Log Strains at the tibial
surface below implant apexPeak -0.100
Additional load sharing zones
Results in lower opposing cartilage contact pressure (2.5x body weight load)
BioPoly Tibial Cartilage
Contact Pressure
Peak = 3.46 MPa
Active Contact Zone Loaded Area ~ 471
mm2
Metal Implant Tibial Cartilage
Contact Pressure
Peak = 7.24 MPa
Active Contact Zone Loaded Area ~ 314 mm2
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®Confidential
BioPoly RS Knee and Patella System
• CE Marked• Suitable for cartilage defects in the distal
femur and patella up to 3.1 cm2
• Femoral Condyle and Trochlear Facet Implants
– Ti64 grit blasted stems. Press fit or cemented• Patella implants
– All BioPoly construction for cementation• Simple surgical instrument set and
technique• Existing reimbursement codes
Femoral Condyles and Trochlear Facets
Patella15mm 20mm 15x24mm
15mm/0 15mm/1 20mm/0 20mm/1
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Current BioPoly® RS Partial Resurfacing3 Families of Products
BioPoly® RS KNEECE Marked
BioPoly® RS PATELLACE Marked
BioPoly® RS SHOULDERCE Marked
Patella HumeralheadDistal Femur
37+ BioPoly® RS Femoral Trochlea and Talar Dome in the pipeline
BioPoly® RS Partial Resurfacing Knee SystemTypical Resurfacing Patient
▪ 21+ year old active adult▪ Knee pain▪ Too young for TKR▪ Often failed Debridement, Microfracture,
OATS or ACI▪ Patients wanting to regain active lifestyle
▪ Focal defects ▪ Femoral condyles
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Indications : Lesion Characteristics• Medial or Lateral femoral condyle, NOT tibial condyles
• Focal 2cm2 or (2.4 x 1.5) cm2 ≤3.1cm2 (Entire lesion visualized in static knee through static arthroscope)
• ICRS grade 2, 3, or 4
• Contained ICRS 0/1
• Depth from articular surface < 4mm
• Good subchondral bone (MRI)
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Contradictions Lesion characteristics:
• Uncontained• Very large• >1 implant required• Kissing lesion
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Contradictions Other joint pathology
• Malalignment
• Laxity
• Major meniscal deficiency
• Subchondral sclerosis
• Advanced degenerative changes43
Study Investigators and Collaborators:Prof Vladimir Bobic - Chester Knee Clinic, Chester, UKProf Mike McNicholas – Aintree, Liverpool, UKMr Dinesh Nathwani - Imperial College, London, UKProf Alister Hart - RNOH Stanmore, London, UKMr Jonathan Miles - RNOH Stanmore, London, UKMatt Hill - Schwartz Biomedical, USAHerb Schwartz - Schwartz Biomedical, USA
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Registry Study Design• Study Type: Post-market registry• 35 patients & 4 UK Centres• Control: Historical microfracture outcomes• Outcome measures: KOOS, VAS, Tegner, SF-36
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Major Inclusion and Exclusion CriteriaInclusion Criteria Exclusion Criteria• Age 21 years and older • Body Mass Index (BMI) ≥ 30• Symptomatic lesions classified as ICRS grade 2, 3, or 4 • Generalized degenerative or autoimmune arthritis
• Lesion size ≤ 3.1cm2 circumscribed by normal or nearly normal (ICRS grade 0 or 1) cartilage with an overall depth ≤ 4mm from the articulating surface
• Uncorrected chronic malalignment of the knee*• Uncorrected ligamentous instability*• Uncorrected mechanically symptomatic meniscal tear or total meniscectomy*
• Sufficient subchondral bone quality to support implant • Kissing lesion on tibia• More than one implant required to accommodate lesion• Use with opposing articulating tibial components*Can be corrected during surgery
Registry Study Results
• Interim results after 2 years indicate:– Significant improvement in
all clinical outcomes– One revision (2.9%) due to
subchondral bone disorder– No differences between
younger and older patients
• Mean Defect size = 2.7cm2
• Over half of patient population (54.3%) failed previous cartilage repair procedures
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Failed BioPoly Implant• Why? No structural or technical problems identified. No infection. Patient selection? Surgical technique?• Very difficult to remove! Revised successfully with deep subchondral drilling + ChondroTissue patch.• Possible reasons: inadequate osseous support (previous microfractures + failed MACI = failure of implant
to bone integration)
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Patient Adverse Events
• 1 Wound infection reported after 1/12– Resolved quickly with medication
• 1 Patient began experiencing pain at 3/12– Arthroscopy revealed implant intact, and loose
cartilage body as source of pain– Removal of loose cartilage body resolved
2symptoms
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Registry Study Results
• BioPoly compared to historical microfracture outcomes– BioPoly patients on average 7 – 9 years older
• Significantly superior KOOS QoL and Sport after 2 years52
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