Early Results of A Nitinol Dynamic Compression Nail for Subtalar Joint Arthrodesis vs Two-Screw Fixation Construct

Abstract

Category: Hindfoot Introduction/Purpose: Subtalar joint arthrodesis (STJA) for deformity correction and management of arthritis is a common surgery. STJA is a reliable operation with high patient satisfaction scores. Securing the talus to the calcaneus, so as to optimize the physiologic environment for osseous healing, has been achieved with multiple fixation techniques including one, two, and three screw constructs, plates, and staples. The goal of our study is to introduce a nitinol nail system with dynamic compression as a novel fixation method for STJA and compare union rates with a standard 2 screw fixation construct. The secondary goal was to assess union rates for this subtalar fusion nail when performed below a previous ipsilateral ankle arthrodesis (AA), with comparison to results from previously published studies. Methods: From May 2019 through July 2020, 15 consecutive patients treated with a novel nitinol nail for STJA were compared to 27 patients undergoing STJA using a two-screw fixation method. The nail group was subcategorized into cases with (6 patients) or without (9 patients) ipsilateral AA. Concomitant talonavicular joint arthrodesis was also performed in patients from each group when indicated. Arthrodesis sites were augmented with autologous bone graft with or without bone graft substitute in all patients. Standard postoperative protocols were used. Primary outcomes included subtalar joint union rates determined by radiographic and clinical assessment. Perioperative complications were compared between groups. Patient specific risk factors were studied to assess any potential negative effects on STJA union rates. Results: Overall, the union rates between the nitinol nail group and screw group did not demonstrate any significant difference (87% vs 88.9%). The nail group with ipsilateral AA demonstrated a 67% union rate (4/6) whereas the nail group without previous AA achieved a 100% union rate (9/9). All patients in our study who underwent STJA with associated TNJA went on to union. Union rates were similar in both groups despite the average age of patients in the nail cohort (61.3 years) being greater than the screw cohort (55.4 years). The average age of patients in the nail group with previous AA was 71 years. No significant relationship was seen between smoking, diabetes or alcohol consumption and union rates. Conclusion: Our data supports the nitinol dynamic compression nail to have superior union rates to the two-screw fixation group when patients with previous AA were excluded (100% vs 88). Our data also indicate that the nitinol nail may provide at least equivalent or better union rates when performed under previous AA when compared to results from prior studies, despite the patients in our group having a much higher average age at the time of surgery. The early results of this nitinol nail for STJA are encouraging and appear to offer an alternative fixation construct with excellent union rates and minimal complications.