Selective tarsal arthrodesis: an in vitro analysis of the effect on foot motion.

Five different intertarsal arthrodeses were simulated in 15 fresh cadaver feet/ankles utilizing external fixation. Pin placement was verified radiographically. Range of motion measurements were performed before pin placement, after pin placement, and after simulated arthrodesis. The deficit in foot motion created by selected limited intertarsal fusions was then measured. The prearthrodesis range of motion measurements were found to be dorsiflexion (DF), 27 degrees; plantarflexion (PF), 57 degrees; total inversion (INVT), 29 degrees; eversion total (EVT), 22 degrees; hindfoot varus (VRH), 16 degrees; hindfoot valgus (VLH), 12 degrees. The deficits in motion after arthrodesis were as follows. Ankle (tibiotalar): DF, 50.7%; PF, 70.3%; INVT, 8.7%; EVT, 9.4%; VRH, 34.6%; VLH, 27.8%. Hindfoot arthrodesis (Tibiotalar calcaneal): DF, 53%; PF, 71.3%; INVT, 49.5%; EVT, 47.6%, VRH, 100%; VLH, 100%. Pantalar (Tibotalar calcaneal cuboid navicular): DF, 62.8%; PF, 82.2%; INVT, 71.7%; EVT, 67.4%; VRH, 100%; VLH, 100%. Triple (Talocalcaneal cuboid navicular): DF, 12.5%; PF, 15.5%; INVT, 50%; EVT, 51.4%; VRH, 60.5%; VLH, 60.5%. Total tarsal arthrodesis: DF, 78.5%; PF, 90.2%, INVT, 87.5%; EVT, 83.6%; VRH, 100%; VLH, 100%.