Ten-Year Outcomes of MobilityTM Total Ankle Replacement Confirms Radiological Loosening is Not Conclusive or Reliable for Long Term Survival Analysis

Abstract

Category: Ankle; Ankle Arthritis Introduction/Purpose: Different designs of Ankle replacement are being performed nowadays, long-term outcome data is the better way to understand these implants behaviour and survival. We compared the differences in demographic data, clinical, Radiological, and patient-reported outcomes among patients who underwent total ankle replacement performed with use of the uncemented stemmed mobile bearing (MOBILITY) Total Ankle System with 10 year follow up. Methods: We analysed 156 (15 bilateral ankles (3 non-mobility) Mobility TAR (of which 41, 45, 22 for OA, PTOA, Inflammatory arthritis respectively). Mean age 61.7 (SD 11.4) (Range 33-90). 70 Ankles had 10 years of follow up, 115 had 5 years follow up,. 96 were males, with 30 patients deceased before 10 years follow up covering 33 ankles. All from our local registry looking at the patient's demographic data, and patient-reported outcomes as measured with use of WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index), the Foot and Ankle Outcome Score (FAOS), the 36-item Short-Form (SF-36) Health Survey, clinical and radiological outcomes and patient-satisfaction scores, collected preoperatively and at 1,3,5 and 10 years postoperatively. Results: Of the 156 ankles18 had wound complications after surgery two only needed surgical debridement. 5 CRPS,16 stress fractures 2 only requiring surgical fixation,11 had subsequent STJ fusion.77 had no signs of radiolucency. The rest had some degree of radiolucency on x-ray (55% on the tibia side) only 11 where symptomatic to require further surgery (6 revised to another TAR, 2 fused, and3 required bone grafting). 11 needed osteotomies after surgery. Aseptic loosening and infection are the least common complications requiring revision. There was significant improvement in WOMAC for pain (35.9 to 67.9), function (40.6 to 66.9) and stiffness (39.4 to 62.5) from pre-op to 1 year (p<0.05), this was maintained for 10 years. Although improvement noted in the composite physical component of SF=36 (28.3 to 34.5) there was no significant increase for composite mental component score. 77.5% reported satisfaction from pain relief,72.4% with return to ADL, 40% were dissatisfied with return to recreational activities and15.5% reported dissatisfaction with overall results of surgery. Mobility TAR shown about 86% survival in our 10 years cohort. Conclusion: With improved PROMS at 1,3,5,10 years showing Patient satisfaction score at 10 years indicates that uncemented mobile bearing implants have good long-term results, osteolysis and aseptic loosening as the least common cause of revision. It is pertinent that reporting of radiological loosening in an uncemented ankle is not conclusive or reliable for long term survival analysis.