Anatomical Structures at Risk and Joint Preparation Effectiveness in Percutaneous First Metatarsophalangeal Fusion with the Shannon Burr: A Cadaveric Study

Abstract

Background: This cadaveric study aims to evaluate the anatomical structures at risk and the amount of joint preparation achieved during percutaneous first metatarsophalangeal joint preparation with a Shannon burr using a direct medial and dorsal-lateral approach.

Methods: Eleven fresh-frozen cadaver foot and ankle specimens underwent first metatarsophalangeal joint preparation with a Shannon burr under fluoroscopy. Following joint preparation, dissection was carried out to locate and evaluate critical soft tissue structures in the vicinity of the first metatarsophalangeal joint, including the extensor hallucis longus tendon, medial dorsal cutaneous nerve, and lateral dorsal digital artery. Measurements from the surgical site to these critical structures were recorded. Image analysis using ImageJ software was conducted to measure the joint surface area prepared on both the distal metatarsal and proximal phalanx articular surfaces.

Results: Contact with the lateral dorsal digital artery and extensor hallucis longus tendon occurred three times each out of the 11 procedures (27%) through the dorsal-lateral approach without macroscopic laceration. The medial dorsal cutaneous nerve was contacted three times (27%) via the medial approach without macroscopic laceration and transected once (9%). The average percentage of joint preparation for the distal first metatarsal was 71.8% (+/- 24.0%), and for the proximal first phalanx was 78.2% (+/- 19.8%). There was no statistically significant difference in joint preparation percentage between both surfaces (p = 0.507). The raw joint surface area prepared on the metatarsal and phalangeal surfaces was 215.24 mm³and 187.98 mm³, respectively.

Conclusion: This study emphasizes the importance of understanding local anatomy and maintaining surgical precision during percutaneous first metatarsophalangeal joint fusion using a Shannon burr. Additionally, this technique offers comparable joint surface preparation to other minimally invasive techniques, however, inferior joint preparation compared to open techniques. Future studies with larger in vivo sample sizes are warranted to further refine the percutaneous approach and enhance patient outcomes. Level of Evidence: V.

Keywords: foot and ankle surgery; hallux rigidus; hallux valgus; minimally invasive surgery.

Figure 1A to 1B.

Landmarks (1A) and radiographs (1B) for dorsallateral approach.

Figure 2A to 2B.

Landmarks (2A) and radiographs (2B) for medial approach.

Figure 3.

Dissection of the dorsal aspect of the foot. Lateral dorsal digital artery (red), medial dorsal cutaneous nerve (green), and extensor hallicus longus (pink).

Figure 4.

Transected medial dorsal cutaneous nerve.

Figure 5.

Instance of contact of the lateral dorsal digital artery (B) Instance of contact of extensor hallucis longus (A) (arrow indicates medial portal). Instances of contact did not reveal any macroscopic damage to the structure of interest.