Calcaneal "Z" osteotomy effect on hindfoot varus after triple arthrodesis in a cadaver model.

Background: Triple arthrodesis involves subtalar, talonavicular, and calcaneocuboid joint fusion and is performed to relieve pain and correct deformity. Complications include malunion resulting in equinovarus and lateral column overload, which can lead to painful callosities and stress fractures. This study quantified the effectiveness of a closing-wedge calcaneal "Z" osteotomy for correction of the varus condition and reduction of abnormal loading of the lateral border of the foot.

Methods: Ten fresh-frozen feet were used. Angle meters were attached to the calcaneus and second cuneiform to measure hindfoot and midfoot varus, and pressure sensors were placed under the first and fifth metatarsal heads to document loading of the borders of the foot. Tensile loads were applied to ten extrinsic tendons and the Achilles tendon while an 1187 N axial foot load was applied. Calcaneus and second cuneiform coronal plane angles and medial and lateral plantar pressures were measured initially, after triple fusion-induced varus, and after "Z" osteotomy.

Results: The calcaneal "Z" osteotomy had no significant corrective effect, with hindfoot alignment virtually identical before and after the procedure under the described foot loading conditions. Similarly, second cuneiform inclination, representative of midfoot alignment, showed no change from the osteotomy. Medial and lateral peak plantar pressures after calcaneal "Z" osteotomy did not differ from those measured after varus triple fusion.

Conclusion: In this cadaver model of varus malunited triple arthrodesis, the closing-wedge calcaneal "Z" osteotomy was ineffective for correction of bone alignment and lateral forefoot overloading under the tested conditions.

Clinical Relevance: The results provide additional information on which to base treatment after triple arthrodesis with varus malunion.