Accuracy of Percutaneous Lateral Release for Hallux Valgus: An Anatomic Study

Abstract

Category: Bunion; Other Introduction/Purpose: Minimally Invasive Chevron and Akin (MICA) surgery is growing in popularity. There are now multiple studies comparing minimally invasive bunion correction to traditional open techniques. Many of these studies include percutaneous lateral soft tissue release using a specific blade, while others use an open technique. To our knowledge, there is no prior study confirming the accuracy of soft tissue release via percutaneous technique. Our objective was to evaluate the precision of the percutaneous release, both the structures released and percent release. Additionally, we identified adjacent nerves potentially at risk with a lateral soft tissue release, measuring their proximity to the incision and if they were damaged. Methods: Sixteen fresh frozen cadaveric foot specimens (8 paired limbs) underwent percutaneous lateral release utilizing a beaver blade under fluoroscopic guidance by two Foot and Ankle Fellowship Faculty who regularly perform the procedure. As described in early MICA technique papers by Redfern and Vernois, the blade was inserted into the plantar plate between the lateral sesamoid and the proximal phalanx. Then the blade was rotated laterally while the hallux was directed into varus. The goal was to release the lateral head of the Flexor Hallucis Brevis (FHB) without violating the Lateral Collateral Ligament (LCL). During our experiment the sesamoids were able to be successfully reduced after each release. The specimens were then dissected to reveal the extent of release of the FHB and LCL. Distance was measured between the blade path and the dorsal digital branch of the deep peroneal nerve, as well as the plantar digital nerve. Results: The FHB was at least partially released in 15/16 specimens. It was completely released in two specimens. 5/16 specimens had greater than 50% but less than 100% release and 8/16 specimens had <50% release. The LCL was completely intact in 8/16 specimens. It was partially released in 8/16 specimens (5 less than 50% released and 3 greater than 50% released). There was no correlation between percent of FHB release and the likelihood of LCL release. The dorsal cutaneous nerve was consistently near the path of the beaver blade, with a median distance of 2mm (range 1-8mm). However, the nerve was never found to be incised or transected. Likewise, the plantar nerve was never injured. Conclusion: This study sought to verify the effectiveness of percutaneous lateral release. We found the FHB to be at least partially released in all but one case, resulting in adequate clinical correction of sesamoid position. Full FHB release may not be necessary to achieve the clinical objective of sesamoid reduction. There was no correlation between percent of FHB release and concomitant release of the LCL, which demonstrates the challenge of an isolated FHB release. The dorsal cutaneous nerve was consistently near the blade path but was never injured, suggesting patients should be counseled regarding the risk.