Long-term follow-up of mobile-bearing total ankle replacement in patients with inflammatory joint disease.

Little is known about the long-term outcome of mobile-bearing total ankle replacement (TAR) in the treatment of end-stage arthritis of the ankle, and in particular for patients with inflammatory joint disease. The aim of this study was to assess the minimum ten-year outcome of TAR in this group of patients. We prospectively followed 76 patients (93 TARs) who underwent surgery between 1988 and 1999. No patients were lost to follow-up. At latest follow-up at a mean of 14.8 years (10.7 to 22.8), 30 patients (39 TARs) had died and the original TAR remained in situ in 28 patients (31 TARs). The cumulative incidence of failure at 15 years was 20% (95% confidence interval (CI) 11 to 28). The mean American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score of the surviving patients at latest follow-up was 80.4 (95% CI 72 to 88). In total, 21 patients (23 TARs) underwent subsequent surgery: three implant exchanges, three bearing exchanges and 17 arthrodeses. Neither design of TAR described in this study, the LCS and the Buechel-Pappas, remains currently available. However, based both on this study and on other reports, we believe that TAR using current mobile-bearing designs for patients with end-stage arthritis of the ankle due to inflammatory joint disease remains justified.

Metabolic cost and mechanical work during walking after tibiotalar arthrodesis and the influence of footwear.

BACKGROUND: This study examined metabolic energy cost and external mechanical work for step-to-step transitions after tibiotalar arthrodesis, and the effect of MBT rocker bottom shoes. METHODS: Oxygen uptake, forceplate and kinematic data were recorded in 18 controls and 15 patients while walking at a fixed speed of 1.25 m/s in three walking conditions: barefoot, normal walking shoes and MBT rocker bottom shoes. Metabolic energy cost, external mechanical work, and the roll-over shape of the ankle-foot complex were analyzed. FINDINGS: Tibiotalar arthrodesis leads to higher metabolic energy cost during walking. During step-to-step transitions positive work during push-off with the impaired ankle was decreased but negative work during collision was not affected. The roll-over shape of the ankle-foot complex did not differ between groups and shoe conditions. However, both in patients and controls rocker bottom shoes did lead to decreased positive work at push-off and increased negative work at collision and consequently higher metabolic energy cost of walking. INTERPRETATION: External mechanical work for step-to-step transitions is not different between patients and controls and could not account for the higher metabolic energy cost in patients. Apparently, patients adopt a different walking strategy that limits step-to-step transition cost but nevertheless induces a higher metabolic energy cost. Despite restricted ankle movement, patients retain a normal roll-over shape of the ankle-foot complex. MBT shoes do not affect roll-over shape and appear to have a counterproductive effect on step-to-step transition cost and walking economy.

Computational assessment of press-fit acetabular implant fixation: the effect of implant design, interference fit, bone quality, and frictional properties.

Patients suffering from rheumatoid arthritis typically have a poor subchondral bone quality, endangering implant fixation. Using finite element analysis (FEA) an investigation was made to find whether a press-fit acetabular implant with a polar clearance would reduce interfacial micromotions and improve fixation compared with a standard hemispherical design. In addition, the effects of interference fit, friction, and implant material were analysed. Cups were introduced into an FEA model of a human pelvis with simulated subchondral bone plasticity. The models were loaded with a loading configuration simulating two cycles of normal walking, during which contact stresses and interfacial micromotions were monitored. Subsequently, a lever-out simulation was performed to assess the fixation strength of the various cases. A flattened cup with good bone quality produced the lowest interfacial micromotions. Poor bone decreased the fixation strength regardless of the geometry of the cup. Increasing the interference fit of the flattened cup compensated for the loss of fixation strength caused by poor bone quality. In conclusion, a flattened cup did not significantly improve implant fixation over a hemispherical cup in the case of poor bone quality. However, implant fixation can be optimized by increasing interference fit and avoiding inferior frictional properties and low-stiffness implants.

Radiolunate arthrodesis: A procedure for stabilising and preserving mobility in the arthritic wrist.

We carried out arthrodesis of the radiolunate joint in 46 wrists (38 patients) for pain and ulnar translation of the carpus because of rheumatoid (42) or psoriatic arthritis (4). At follow-up, three patients had died and in three (1 bilateral) an additional midcarpal arthrodesis had been undertaken. The remaining 32 patients (39 wrists) were evaluated after a mean of five years. The clinical results were good with a mean visual analogue score of 8.3 for pain, 7.2 for hand function and 9 for overall satisfaction. Except for palmar flexion, mobility was equal to or better than before operation. Radiologically, there was deterioration of the midcarpal joint with an increase in the Larsen score from 1.8 to 2.7 (p < 0.001), some decrease in carpal height and recurrence of carpal translation. Radiolunate arthrodesis gives good clinical results at five years although there is some deterioration radiologically.

Synovectomy of the rheumatoid knee does not prevent deterioration. 7-year follow-up of 83 cases.

Eighty-three knees in 65 patients were studied retrospectively 7 (3-11) years after synovectomy for rheumatoid arthritis. Half of all the knees had an osteotomy or prosthesis operation after a median interval of 4 years. Early synovectomy had been performed in 67 knees; half of these had a satisfactory result. Most of the late synovectomies were unsatisfactory. Our results support the opinion that deterioration of the rheumatoid knee cannot be prevented by early synovectomy. Late synovectomy is discouraged.