ABSTRACT
BACKGROUND: Insertional Achilles tendinopathy (IAT) is a common pathology with multiple surgical interventions available for treatment. The Zadek, dorsal closing wedge calcaneal osteotomy (ZO) has been demonstrated to be effective treatment of IAT. There have been various recommendations in the literature as to what measurement of wedge removal should be considered ideal to produce greatest postoperative range of motion (ROM), thus postoperative biomechanical potential. Accordingly, the purpose of this cadaveric study was to assess the range of motion achieved after various measurements of wedge removal by ZO. METHODS: The ZO was performed on six cadaveric specimens. A 7.5 mm and 15 mm wedge osteotomy was marked and sequentially completed on each specimen. Lateral fluoroscopic imaging was utilized to take preoperative and postoperative ROM measurements for each osteotomy. Dorsiflexion (DF) and plantarflexion (PF) ROM arcs were measured for each wedge size and compared by t-test. Effect sizes were calculated by Cohen's d analysis. RESULTS: Maximal DF was 110.87 ± 12.97 deg in the pre-osteotomy state. Removal of a 7.5 mm wedge improved DF by 8 deg to a mean 102.93 ± 13.81 deg (p = 0.08). Removal of a 15 mm wedge improved DF by 16 deg to a mean 95.96 ± 11.41 deg (p = 0.003). Cohen's d and effect size calculation demonstrated a 7.5 mm wedge to have a small effect on DF, while a 15 mm wedge had a medium effect (0.29, 0.52 respectively). Maximal PF did not change significantly amongst the pre-osteotomy, 7.5 mm wedge, or 15 mm wedge positions. ICC was 0.96. CONCLUSION: Based on the results presented in this study, removal of a 15 mm wedge with ZO yields significant and greater improvement in ROM than a 7.5 mm wedge. We hope the current study will better inform preoperative planning for ZO. STUDY TYPE: Prospective Cadaver Study. LEVEL OF EVIDENCE: V.