Accuracy of Patient-Specific Instruments for Supramalleolar Osteotomies.

BACKGROUND: Supramalleolar osteotomy (SMO) enables deformity correction of the distal tibia, but the procedure remains technically demanding. Patient-specific instruments (PSIs) have the potential to mitigate the technical drawbacks associated with SMO that are performed free-hand, but their accuracy has not been investigated. Therefore, we aimed to perform a pre- vs post-operative comparison to assess the accuracy of PSI in the setting of SMO correction. METHODS: Eighteen patients (mean age = 47 ± 13.5 years) who underwent SMO with a PSI were prospectively recruited in a pre-post comparative study design. Inclusion criteria were correction of supramalleolar ankle varus or valgus deformity by a closing wedge SMO. Exclusion criteria consisted of biplanar SMO that required associated free-hand osteotomies. Clinical outcomes were collected by the American Orthopaedic Foot & Ankle Society (AOFAS), European Foot and Ankle Society (EFAS), and visual analogue scale (VAS) scores. Apart from the standard weightbearing radiographs, a weightbearing CT was performed to generate corresponding 3-dimensional (3D) bone models and measure the lateral distal tibia angle (LDTA) as main radiographic parameter. The mean simulated correction differed from the mean post-operative achieved correction within 1° (mean = 0.4°; range 0.1°-0.8°). CONCLUSION: This study demonstrated an accurate correction of distal tibia deformities by SMO using PSIs. The achieved post-operative correction differed within the range of 1° from the pre-operatively simulated correction. This indicates that PSIs provide a precise execution of the pre-operative planning. Future studies should assess the added value of performing an SMO with PSI compared with former free-hand techniques towards clinical and radiographical outcomes.