Incidence and predictors of valgus tibiotalar tilt after progressive collapsing foot deformity reconstruction using subtalar fusion with concomitant procedures.

Purpose: Development of valgus tibiotalar tilt is a significant complication after subtalar fusion for progressive collapsing foot deformity (PCFD) correction. However, its incidence and etiologic factors have not been extensively studied. The purpose of this study was to define the incidence of valgus tibiotalar tilt after subtalar fusion for PCFD reconstruction, and to determine predictors of this complication.

Methods: This study included 59 patients who underwent PCFD reconstruction with subtalar fusion. Patients with tibiotalar tilt prior to surgery were excluded. On standard weightbearing radiographs, the talonavicular coverage angle, talo-1st metatarsal angle, calcaneal pitch, hindfoot moment arm (HMA), and medial distal tibial angle were measured. Weightbearing computed tomography (WBCT) was used to determine the presence of lateral bony impingement. A radiologist evaluated the superficial and deep deltoid ligaments using magnetic resonance imaging (MRI). Univariate regression analysis was used to identify the factors associated with development of postoperative valgus tibiotalar tilt, defined as tilt > 2 degrees.

Results: Seventeen patients (28.8%) developed postoperative valgus tibiotalar tilt at a mean of 7.7 (range 2-31) months. Eight (47.1%) of these patients developed valgus tibiotalar tilt within 3 months. Univariate logistic regression demonstrated association between preoperative HMA and postoperative valgus tibiotalar tilt (odds ratio 1.06, P = 0.026), with a 6% increase in risk per millimeter of increased HMA. Deltoid ligament status and concomitant procedures on other joints did not correlate with postoperative valgus tilt.

Conclusion: Our findings indicate that surgeons should be cognizant of patients with a greater degree of preoperative hindfoot valgus and their propensity to develop a valgus ankle deformity. Additionally, our relatively high incidence of valgus tibiotalar tilt suggests that weightbearing ankle radiographs should be included in the initial and subsequent follow-up of PCFD patients with hindfoot valgus treated with subtalar fusion.