First Tarsometatarsal Fusion Using Saw Preparation vs. Standard Preparation of the Joint: A Cadaver Study

Abstract

Category: Basic Sciences/Biologics, Midfoot/Forefoot Introduction/Purpose: First tarsometatarsal (TMT) joint fusion is indicated for several underlying causes of first ray dysfunction and pain, including arthritis, traumatic injury, and recurrent hallux valgus. Preparation of the joint surface by denuding the articular cartilage is a key step for arthrodesis, as inadequate preparation may result in poor fixation and non-union. However, excessive removal of cartilage and bone may result in excessive shortening of the ray. Despite the importance of joint preparation on the outcomes of fusion, the effects of using a bone saw versus osteotome on ray length is poorly documented in the literature. The purpose of this study was to investigate whether utilization of an osteotome or saw would minimize shortening of the first ray in TMT arthrodesis. Methods: Ten fresh-frozen cadaver specimens without evidence of musculoskeletal abnormalities were used for this anatomic dissection study. A medial incision was made along the first ray from the medial aspect of the medial cuneiform to the base of the first metatarsal. The first TMT joint was exposed through transverse capsulotomy. The soft tissues surrounding the joint were not removed from the bone. The specimens were randomly assigned to undergo cartilage removal and joint preparation using either an osteotome (n=5) or saw (n=5). Care was taken to reach the plantar-most aspect of the joint. Fusion was then performed using a cross-screw construct through the dorsal aspect of the proximal phalanx and the medial cuneiform. Pre- and post-operative x- rays were taken with a radiopaque ruler in the field, and length changes were compared between osteotome and sawblade groups. Results: The average change in metatarsal length was significantly smaller in the osteotome group (1.6 mm) as compared to the saw group (4.4 mm) (p=0.031). The average percent change in metatarsal length was also significantly smaller in the osteotome group (3.0%) compared to the saw group (8.4%) (p=0.025). There was no significant difference between the two groups with respect to change in cuneiform length. The osteotome group demonstrated a significantly smaller average measured change (3.0 mm vs. 6.9 mm, p=0.001) and percent change (4.1% vs. 9.3%, p<0.001) in total length (cuneiform plus metatarsal) in comparison to the saw group. Conclusion: The results of this study demonstrate that first TMT joint preparation with an osteotome may prevent over- shortening of the first ray, thereby theoretically decreasing the risk of metatarsalgia and the need for additional procedures when compared to utilization of a bone saw. Judicious use of the bone saw for joint preparation may still be beneficial in some cases. This information can be used clinically to implement evidence-based standardization of operative techniques to improve the outcomes of these cases.