Isolated subtalar osteoarthritis (OA) is a debilitating condition usually occurring after trauma and particularly in the setting of an intraarticular calcaneal fracture. Currently, subtalar (talo-calcaneal joint) fusion surgery is the treatment of choice in managing subtalar OA after failure of conservative treatment. Unfortunately, subtalar fusion eliminates joint motion and increases the load over the adjacent midfoot and ankle joints, which affects the outcome of the surgery over time. Popular in the ankle, distraction arthroplasty offers another joint-preserving option, particularly important for active patients. In contrast to fusion as a salvage procedure, subtalar distraction arthroplasty allows the possibility of maintaining the function of the arthritic subtalar joint while reducing pain and improving the overall function of the foot and ankle.
We performed subtalar distraction arthroplasty using a circular external fixator combined with BMAC on seven patients with symptomatic and refractory subtalar OA. All these patients were interested in an alternative to fusion. We obtained clinical and radiographic data before and after surgery. Ankle Osteoarthritis Score (AOS) and the Marijnissen Distraction Clinical Score (MDCS) were obtained before surgery, after one year, and at latest follow-up.
The average age was 56 years (range 45-69). The mean duration of post-operative follow-up was 35.4 months (range 15.2-53.5). The inversion of the ankle joint changed from 16.9° (10°-25°) pre-operatively to 14.3° (10°-20°) post-operatively (P = 0.28), and the eversion from 5.6° (0°-10°) to 10.0° (0°-20°) (P = 0.17). We found an increase in subtalar joint space from 1.4 mm (0-3) to 2.6 mm (2-4) before and after surgery (P = 0.01), respectively. Finally, Pixel Density Ratio (PDR) increased from 0.87 (0.66-1.30) to 1.01 (0.89-1.18) (P = 0.19). Compared to pre-operative conditions, we observed a decrease in subchondral sclerosis on X-ray in all cases post-operatively. The AOS score for ankle pain improved from 58.8 (47-74) to 15.1 (0-31) (p < 0.01). The AOS score for ankle disability improved from 68.2 (57-81) to 16.1 (0-43.5) (p < 0.001). We found improvement in the MDCS over time for all measured parameters. The clinical condition improved from 1.4 (0-2) to 0.8 (0-2) after one year and to 0.3 (0-2) at the latest follow-up (p < 0.001). Mobility was measured as ROM in the treated ankle relative to each patient's contralateral ankle. This increased from 35% (0-100) to 66% (15-120) to 76% (15-100) (p = 0.059). Function improved from 2.3 (0-3) to 1.3 (0-3) to 0.6 (0-3) (p < 0.001). Pain decreased from 7.4 (2-10) to 4.4 (2-8) to 2.1 (0-7) (p < 0.01). Complications include one patient with sensory neuralgia.
Preliminarily, results of subtalar distraction arthroplasty as a new joint preservation technique are encouraging. Our research suggests the possibility of subtalar distraction arthroplasty as an effective treatment for symptomatic subtalar OA. Furthermore, this new operation does not eliminate the possibility of a future surgery like fusion. Subtalar distraction arthroplasty can be helpful in the management of subtalar OA in active patients who desire preservation of foot and ankle motion.