***This is an ongoing study. 31/40 patients have completed the protocol are included in this preliminary abstract.

Abstract Title A Comparison of Push-off and Gait Strength following Open Haglund’s Resection vs. Percutaneous Zadek Osteotomy for Insertional Achilles Tendinopathy

Background The gold standard for surgical treatment of insertional Achilles tendinopathy (IAT) is the open midline Achilles tendon splitting Haglund’s resection (OH). However, the percutaneous Zadek osteotomy (ZO) is a safe and effective alternative intervention. Retrospective studies have compared patient-reported outcomes and radiographic findings between ZO and OH; however, data on post-operative strength remain limited. Accordingly, the current prospective study evaluated the postoperative push-off and gait strength following OH vs ZO for IAT. Methods Thirty-one patients >18 years of age who underwent unilateral OH (N=17) or ZO (N=14) for IAT with ≥1-year follow-up met the inclusion criteria; patients with prior midfoot/hindfoot surgery, recent lower extremity surgery, neuromuscular conditions were excluded. Static plantarflexion/dorsiflexion strength were assessed in seated and supine positions. Standing strength was evaluated by unilateral and bilateral calf raises performed on pressure plates. Single-leg balancing was timed. Finally, vertical and anterior ground reaction forces at toe off were captured during gait. The mean difference between operative/non-operative limbs was calculated for each measurement and reported as percentage of body weight (%BW). Results In patients who underwent OH, a significant decrease in lower anterior ground reaction force of the operative limb was observed (0.00950.013, p=0.007). Also, following OH, patients demonstrated a decrease in unilateral vertical ground reaction force when compared to the non-operative limb (0.0210.035, p=0.02). Interestingly, following OH patients balanced on their operative limb a mean 8.311.7 seconds longer in comparison to their non-operative limb (p=0.01). No significant differences were observed in the ZO cohort. Conclusion Statistically significant decreases in operative limb strength during unilateral calf raise and forward propulsion was observed following OH for IAT. Meanwhile, no such loss of strength was observed following ZO. While both procedures are safe and effective surgical options for managing IAT, these preliminary findings suggest ZO may allow for preserved post-operative strength relative to OH.