First tarsometatarsal fusion using saw preparation vs. standard preparation of the joint: A cadaver study.

Background: First tarsometatarsal (TMT) joint fusion is effective for treatment of arthritis and some first ray deformities. To prepare the articular surfaces, cartilage should be carefully but completely denuded. Inadequate preparation may result in non-union, while excessive preparation may cause ray shortening and consequential transfer metatarsalgia. Preparation can be performed with an osteotome or a saw. 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 were randomly assigned to undergo joint preparation using either an osteotome (n=5) or saw (n=5). Sample size was determined by cadaver availability. Fusion was 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 changes in length in the first metatarsal and first cuneiform were compared between osteotome and sawblade groups.

Results: The average change in metatarsal length was significantly smaller in the osteotome group (1.6mm) as compared to the saw group (4.4mm) (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 (3.0mm vs. 6.9mm, 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.

Conclusions: In first TMT fusion, joint preparation with an osteotome may prevent over-shortening of the first ray in comparison to preparation with a saw.