Does Isolated Ankle Arthrodesis Affect Medial Column Alignment in Patients With Progressive Collapsing Foot Deformity and End-stage Ankle Osteoarthritis?

Background Progressive collapsing foot deformity (PCFD) is characterized by multiplanar talar malalignment, including medial arch collapse. Although ankle arthrodesis is a well-established treatment for end-stage ankle osteoarthritis, its effect on concomitant PCFD-related parameters remains unclear. We observed that ankle arthrodesis appeared to result in radiographic changes in the medial column alignment, raising questions about whether talar stabilization might influence PCFD-related deformity. Questions/purposes (1) Do patients with severe medial column collapse achieve greater radiographic correction after ankle arthrodesis compared with those with mild collapse? (2) Do patients with severe medial column collapse experience greater functional gains than patients with mild collapse after isolated ankle arthrodesis? (3) Do pedobarographic parameters change after ankle arthrodesis in patients with PCFD? Methods Between January 2015 and June 2024, one surgeon performed ankle arthrodesis in 171 patients with end-stage ankle osteoarthritis. Of these, 58% (99) had radiographic evidence of medial column collapse (lateral Meary angle > 4°). After excluding patients 15°; n = 40). The mean ± SD age and follow-up time were 70 ± 6 years and 36 ± 21 months in the mild group and 72 ± 6 years and 34 ± 19 months in the severe group, respectively. We compared preoperative and postoperative PCFD-related radiographic parameters and functional outcomes using the Foot and Ankle Outcome Score (FAOS), the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot scale, and a VAS for pain. Pedobarographic analysis was performed in 10 consecutive patients preoperatively and postoperatively from the severe group who had equipment available during their follow-up visits. Results Patients with severe medial column collapse achieved greater radiographic correction than those with mild collapse; for example, the lateral Meary angle improved by mean ± SD 12° ± 7° in the severe group versus 6° ± 4° in the mild group (mean difference 6° 95% confidence interval (CI) 3° to 9°; p < 0.001). Patients with severe collapse did not experience larger functional gains than those with mild collapse; the improvement in AOFAS score was no different between groups (22 ± 22 points versus 26 ± 26 points, mean difference -5 points 95% CI -16 to 6 points; p = 0.36). Pedobarographic analysis in 10 patients from the severe group showed pressure redistribution from preoperative to final follow-up, with medial midfoot pressure remaining stable (13 versus 14 kPa; p = 0.44), while lateral forefoot pressure increased most prominently (17 versus 32 kPa; p = 0.01). Conclusion Patients with severe PCFD achieved greater radiographic correction than those with mild collapse after isolated ankle arthrodesis, yet functional improvements did not differ between groups. Surgeons can consider isolated ankle arthrodesis for end-stage ankle osteoarthritis with concomitant PCFD, even in severe cases, expecting substantial deformity correction without additional procedures. Future studies should determine the threshold beyond which adjunctive procedures become necessary and assess long-term adjacent joint degeneration. Level of Evidence Level III, therapeutic study.