Changes in Tarsal Tunnel Volume and Pressure After Minimally Invasive Lateral Sliding Calcaneal Osteotomy: A Cadaveric Study

Background: Hindfoot varus deformity is often corrected using lateral sliding calcaneal osteotomies, which may compress the tarsal tunnel and risk tibial nerve entrapment. Minimally invasive surgery (MIS) techniques may mitigate soft tissue disruption, but their impact on tarsal tunnel biomechanics remains unclear. Purpose is to evaluate the effect of calcaneal lateralization using a 3-mm MIS burr on tarsal tunnel volume and pressure in a cadaveric model. Methods: Ten matched pairs of fresh frozen cadaveric lower limbs underwent lateral-to-medial calcaneal osteotomy using a 3-mm MIS burr. Computed tomography (CT) scans measured tarsal tunnel volume pre- and post-osteotomy. Intra-compartmental pressure within the tarsal tunnel was assessed using an ultrasound-guided pressure monitor. Volumes were calculated using CT-derived cross-sectional reconstructions, and pressures were compared before and after lateralization. Results: Calcaneal lateralization led to significantly decreased tarsal tunnel volume (mean Δ = −3.06 ± 1.50 cm³, P < .0001) and significantly increased tunnel pressure (mean Δ = +11.18 ± 6.19 mm Hg, P < .0001). There was a significant inverse relationship between lateralization distance and volume change ( R 2 = 0.184, P < .0001), and a direct relationship between lateralization and pressure increase ( R 2 = 0.129, P = .026). Percentage volume change was negatively correlated with percentage pressure change ( R 2 = 0.042, P = .009). The average lateralization achieved was 6.33 mm. Conclusion: MIS calcaneal lateralization significantly reduces tarsal tunnel volume and increases intratunnel pressure, which may theoretically contribute to tibial nerve compression. However, the magnitude of pressure increase observed was generally below levels associated with neural dysfunction. Although MIS approaches offer soft tissue advantages, this study suggests that tarsal tunnel decompression and flexor retinaculum release may still be warranted if symptoms develop postoperatively. In cases where greater lateralization is required, the flexor retinaculum release performed during a tarsal tunnel decompression allows for greater translation without the concomitant rise in tarsal tunnel pressure. Clinical Relevance: This model demonstrates the volume and pressure changes and lateralization distance that occur during an MIS lateral slide calcaneal osteotomy.