Ten year comparison of Oxidized Zirconium & Cobalt Chrome Femoral Components in Total Knee Arthroplasty- a randomised controlled trial Justin Roe, Justin Roe, Lucy Salmon, Alison Waller, Mihai Vioreanu, Leo Pinczewski

Disclosures I declare that in the past three years I have: held shares in:Optimized Ortho received royalties from:n/a done consulting work for:Stryker given paid presentations for:Smith and Nephew received institutional support from:Stryker Optimized Ortho Signed: Justin Roe

Introduction PE wear debris is phagocytosed by macrophages Incite an inflammatory response producing cytokines Stimulates osteoclasts Bony resorption and aseptic loosening Ultimately implant failure. Loosening/Lysis accounts for 29.1% of revision TKRs in ANJRR PE wear is a major cause of failure of joint replacements Source: ANJRR 2014 Associate Professor Justin Roe

Introduction Attempts at minimising PE wear Design Quality PE modification Ceramic/PE combinations favourable low wear rates in laboratory studies Monolithic Ceramics ( Koshino ) Oxidising surface metal to ceramic ( OxZr, Smith+Nephew).

Proposed benefits of Oxidized Zirconium When compared to CoCr: Better abrasion resistance and increased lubricity; less friction* Equivalent fatigue strength Reduced polyethylene wear in knee wear simulators** *Walker et al. Wear testing of materials and surfaces for total knee replacements. J.Biomed.Mater. Res., 33(3), 1996, pp **Ezzet et al. CORR 428, 2004, pp Spector et al. JBJS 83A(Supp):80-86,2001

Aim To compare the clinical outcome of OxZr and CoCr femoral components with respect to Clinical and subjective outcomes Incidence of adverse events or complications Clinical signs of wear Associate Professor Justin Roe

Study Design January 2002-December 2003 Double Blind Randomised Controlled Trial Single surgeon Patients undergoing Simultaneous Bilateral TKA Cemented Genesis™ II CR TKA, deep dished tibial PE (not XLPE) Patella selectively resurfaced bilaterally Associate Professor Justin Roe

Inclusion Criteria Bilateral knee osteoarthritis requiring simultaneous bilateral TKR. Informed consent to participate in the study. (ie. one knee to receive OxZr and one to receive CoCr) Associate Professor Justin Roe

Demographics 40 patients consented to the study and met the inclusion criteria 15 Female: 25 Male Mean age 68 years (range 55-85) 11 underwent bilateral patellar resurfacing Associate Professor Justin Roe

Study Design Patients were randomized at the time of consent to receive OxZr Femoral component into L or R knee Concealed from the surgeon until surgery Concealed from the patient Concealed from the 2 clinical examiners. Associate Professor Justin Roe

Outcome Measures Clinical: Examination Subjective: WOMAC, BOA Patient Satisfaction Scale, Knee Society Score, Knee Osteoarthritis Outcome Score (KOOS) Radiographic: Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System, clincial assessment of polyethylene thickness (Collier J Arthrop 2003) Associate Professor Justin Roe

Participant Flow 62 pts requiring Bilateral TKA 40 pts (80 knees) enrolled 34 pts (68 knees) reviewed 38 pts (76 knees) reviewed 1 pt deceased 3 pts deceased 2 pts senile dementia 1 pt unable to attend 22 pts 5yrs 28 pts (56 knees) reviewed 9 pts deceased 1 pt senile dementia 1 rheumatoid arth 1 pt unable to 10 yrs Associate Professor Justin Roe

Results: Subjective Outcome No significant difference in KOOS scores

Results: Clinical Examination Cobalt ChromeOxiniump value Mean Flexion (SD)116 (7)113 (6)0.25 Mean Extension (SD)1.3 (4)1.6 (4)0.81 Effusion (%)14%21%

Results: Radiological Examination Cobalt ChromeOxiniump value Mean Coronal Alignment Mean Femoral Flexion Angle Mean Tibial Sagittal Angle (slope) Knee Society TKA Roentgenographic Score (Ewald 1989)

Results: Radiological Examination Cobalt ChromeOxiniump value Radiolucenies <4 (non progressive and probably not significant) 64%68%0.512 Radiolucenies 5-9 (should be followed for progression) 36%32% Radiolucenies 10 or > (possible or impending failure) 0% Knee Society TKA Roentgenographic Score (Ewald 1989)

Results: Radiological Examination Cobalt ChromeOxiniump value Mean Medial Poly thickness Mean Lateral Poly thickness Tibial Polyethylene Thickness as per Collier et al 2003, expressed as % of tibial stem diameter

Results 89% enthusiastic/satisfied at 10 years IS ONE KNEE BETTER THAN THE OTHER? Right or Left? 10 subjects (36%) preferred CoCr knee 3 subjects (11%) preferred OxZ knee 15 subjects (53%) reported knees the same p=0.023 Associate Professor Justin Roe

Results 2 patients required patellar 5 years PE liner exchange performed at time of resurfacing. allowed subsequent retrieval analysis to be performed 1 patient underwent unilateral patellar resurfacing (OxZ 7 years Associate Professor Justin Roe

5 year Operative Findings at Patellar Resurfacing Cobalt Chrome Femoral Component Obvious surface scratches. Associate Professor Justin Roe

Surfacing scratching less obvious due to surface layer of fluid 5 year Operative Findings at Patellar Resurfacing Oxidised Zirconium Femoral Component Associate Professor Justin Roe

Results: Retrieval Analysis blinded examiners No differences between the retrieved PE liners under Stereo Zoom Microscopy or Environmental Scanning Electron Microscopy. Associate Professor Justin Roe

No difference in clinical, subjective, radiographic or retrieval analysis at short and mid-term follow up to 10 years. Retrieval analysis of two pairs of tibial PE does nothing to support the laboratory findings of lower wear rates. Discussion Associate Professor Justin Roe

This study confirms that no adverse events were associated with the use of cemented OxZr femoral components over ten years Improved in vivo survivorship of OxZr has yet to be established and will require longer term follow-up Discussion Associate Professor Justin Roe

Discussion Source: ANJRR 2014

There has been no evidence to indicate any clinically significant difference between CoCr and OxZr femoral components in the Genesis II TKR apart from the patients’ subjective preference for the CoCr implant at 10 years. Conclusion Associate Professor Justin Roe

Thank you for your attention. Associate Professor Justin Roe

Preferred CoCr knee at 5 years n=13 No preference at 10 years n=5 2/5 patella resurfaced 3/5 female Preferred CoCr knee at 10 years n=6 2/6 patellar resurfaced 3/6 female 1 RIP 1 DNA

Patellar Resurfacing No patellar resurfacing Patellar resurfaced p value N1810 Satisfaction Satisfied or Enthusiastic16 (89%)9 (90%)0.693 Non Comittal1 (6%)0 Disappointed1 (6%) Same surgery again under same circumstances? 18 (100%)9 (90%)0.172 Justin I would interpret this with great caution, there is way too much selection bias present to make meaningful conclusions regarding patellar resurfacing in this group as Leo selectively resurfaced…..