Posttraumatic arthrodesis of the subtalar joint--outcome in workers compensation and rates of non-union.

BACKGROUND: Regardless of the simple surgical technique, the success of the subtalar arthrodesis is limited by the rate of non-unions of the arthrodesis. The functional outcome of workers compensation is known to be poorer compared to patients without pending litigation. The aim of this study was to quantify the rate of non-unions and to determine risk factors leading to failure of the osseous consolidation after arthrodesis of the subtalar joint. The outcome assessed is a general health assessment with the SF-36 questionnaire and more illness specific with the AOFAS hindfoot score. Secondly, the influence of the health insurance status of the patients with or without worker's compensation on the outcome was tested.

METHODS AND RESULTS: The inclusive criterion was an arthrodesis of the subtalar joint with and without autologous cancellous bone grafting and screw osteosynthesis. This cohort study included the clinical course of 115 patients with posttraumatic osteoarthritis from 2000 to 2006. The average age of the patients (n=115) was 47±11.0 years, 83% of the treated patients were men. 68% of the patients suffered of secondary osteoarthritis after calcaneal fracture. The time interval from trauma to presenting at the physician due to therapy resistant pain was in the average 5.5±9.9 years. After primary arthrodesis (n=101) of the subtalar joint osseous consolidation was proved in 55% cases, consolidation was questionable in 21% and the rate of no consolidation with revision was remarkable high with 24%. The duration of osseous consolidation was proved by plain projection radiography or computer tomography and clinical reduction of pain. For primary arthrodesis osseous consolidation was reached after 6.4±6.3 month, after secondary arthrodesis osseous consolidation was reached after 9.4±13.1 month. After revision surgery 57% of the arthrodesis healed, 12% the osseous consolidation was questionable, and the failure rate was still 12%.

CONCLUSION: The outcome measures of the patients with SF-36 and the more functional related AOFAS hindfoot score showed poor outcome rates after subtalar fusion in posttraumatic osteoarthritis. The AOFAS hindfoot score was 47±24 points after primary arthrodesis and 46±17 points after secondary arthrodesis of the subtalar joint. The patients regained their former ability to work only in 30% after fusion of the subtalar joint. If revision surgery was necessary 8% of the patients got back to their work prior to the injury.