Predicting the Potential Complications of Lateral Column Lengthening: A Cadaveric Biomechanical Study

Abstract

Category: Hindfoot; Other Introduction/ Purpose: Lateral column lengthening calcaneus osteotomy is a common procedure used to treat flatfoot deformity. However, the incidence of subtalar joint impingement and sinus tarsi pain presents a concern related to this treatment. The hypothesis of this study was with opening of the osteotomy, the anterior fragment of the calcaneus anterior process moves anteriorly, while the posterior fragment simultaneously moves posteriorly which can compromise the outcome as well as cause subtalar joint impingement. The goal of this study was to observe movements of the anterior and posterior fragments with an osteotomy of different sizes. Methods: Eight fresh frozen cadaveric feet were used. A vertical calcaneus osteotomy was designed 1.5cm posterior to the calcaneocuboid joint. Optical markers were attached on each side of the osteotomy to measure movements of the anterior and posterior segments during the lengthening procedure. Three more markers were placed for reference purposes with one on the lateral process of the talus, one on the table, and one on the base of the 3rd metatarsal (Figure 1). Following the osteotomy 4mm, 6mm, 8mm, 10mm and 12mm of lengthening was obtained for each specimen using a lamina spreader. The exact lengthening achieved was measured with a micro-caliper. Movements of the anterior and posterior fragments were recorded using a Sentech model STC-MBCM401U3V camera and calculated with MaxTRAQ motion analysis software. Mixed linear regression analyses were performed using R Studio. Results: With the open osteotomy, the anterior fragment moved anteriorly, while the posterior fragment moved posteriorly (Table 1, 2). The anterior movement was larger than the posterior one. There was no difference in the amount of anterior movements during each attempted 2mm lengthening, however, the amount of the posterior movement peaked at 6mm-8 mm and went down at 8mm-10mm and 10mm-12mm, which was caused by subtalar joint impingement and limited the posterior excursion. Starting at 6mm lengthening there was a linear regression relationship between the anterior & posterior movement and the lengthening (anterior movement = -4.80 + 1.06 × Lengthening of the Lateral Column, posterior Movement = -1.26 + 0.22 × Lengthening of the Lateral Column) (Figure 2,3). 1mm lengthening induced 1.06mm anterior (p < 0.05), and 0.22mm posterior shift (p < 0.05). Conclusion: Lateral lengthening causes the calcaneus to move both anteriorly and posteriorly which not only compromises the power of the procedure, but also can cause subtalar impingement. The findings of this study provide our colleagues with more insight into the correlation between the size of the lengthening, results, and potential complications.