Sensitivity of plantar pressure and talonavicular alignment to lateral column lengthening in flatfoot reconstruction

Lateral column lengthening (LCL) of the calcaneus is commonly performed as part of correction of the adult acquired flatfoot deformity. Increases in postoperative lateral plantar pressure associated with pain in the lateral aspect of the foot have been reported. The aim of this study was to investigate changes in pressures in the lateral aspect of the forefoot with increments of 6, 8, and 10 mm of LCL in a cadaveric flatfoot model. The hypothesis was that increasing the LCL incrementally by 2 mm will linearly increase the plantar pressures in the lateral aspect of the forefoot.

Eight fresh-frozen cadaveric foot specimens were used. A robot compressively loaded the foot to 400 N with a 310-N tensile load applied to the Achilles tendon. A flatfoot model was created by resecting the medial and inferior soft tissues of the midfoot, followed by axial load of 800 N for 100 cycles. Kinematic and plantar pressure data were gathered after the different amounts of LCL (6, 8, and 10 mm) were achieved.

The talonavicular joint demonstrated a median abduction angle of 4.4° in the axial plane and -2.6° in the sagittal plane in the flatfoot condition as compared with the intact condition. The 6, 8, and 10-mm LCLs showed axial correction of talonavicular alignment by -1.4°, -4.9°, and -9.2° beyond that of the intact foot, and sagittal correction of -0.1°, 1.3°, and 2.9°, respectively. LCL of 6, 8, and 10 mm showed consistently increasing lateral forefoot average mean pressure, peak pressure, and contact area.

LCL in 2-mm increments consistently reduced talonavicular abduction and consistently increased plantar pressure in the lateral aspect of the forefoot.

The lateral column should be lengthened judiciously, as a 2-mm difference leads to significant difference not only in angular correction of the talonavicular joint but also with regard to pressure in the lateral aspect of the forefoot.