Analysis of Shortening and Elevation of the First Ray With Instrumented Triplane First Tarsometatarsal Arthrodesis.

BACKGROUND

The Lapidus procedure using planar saw resection has often been criticized for complications related to excessive shortening and elevation of the first ray. The goal of this study was to assess the amount of shortening that occurs when using a cutting guide for controlled saw resection of the first tarsometatarsal (TMT) joint surfaces, along with assessment of deformity correction in all 3 anatomic planes.

METHODS

A prospective multicenter study with IRB approval included 35 hallux valgus subjects evaluated at baseline and 6 months following instrumented triplane first TMT arthrodesis without lesser metatarsal osteotomies.

RESULTS

The average first ray bone segment length loss was 3.1 mm (95% confidence interval [CI] 2.4-3.7) in the anteroposterior (AP) radiographic assessment and 2.4 mm (95% CI 1.7-3.1) in the sagittal plane. The mean preoperative radiographic measurements were 1.7 degrees (dorsiflexion) for sagittal plane angle, 13.8 degrees for intermetatarsal angle (IMA), and 5.1 for tibial sesamoid position (TSP). Improvements were seen postoperatively for all measures with a mean difference of -0.2 degrees (95% CI -1.0 to 0.6) for sagittal plane angle, -9.2 degrees (95% CI -10.1 to -8.3 degrees) for IMA, and -3.5 (95% CI -4.0 to -3.1) for TSP. Five of the patients reported lesser metatarsal pain preoperatively, and no patients complained of lesser metatarsalgia at 6-month follow-up.

CONCLUSIONS

Minimal length loss of the first ray can be expected following instrumented triplane TMT arthrodesis while achieving full 3-dimensional deformity correction and reducing the risk of lesser metatarsalgia.

LEVEL OF EVIDENCE

Level II, prospective comparative study.