Closing the gap on Achilles tendon rupture: a cadaveric study quantifying the tendon apposition achieved with commonly used immobilisation practices

R. Collins, C. Loizou, A. Sudlow, G. Smith

Introduction: Operative and non-operative treatment regimens for Achilles tendon ruptures vary greatly but commonly involve rigid casting or functional bracing. The aim of our study was to investigate the extent of tendon apposition following such treatments.

Methods: Twelve fresh-frozen, adult below knee lower-extremity cadaveric specimens with intact proximal tibiofibular joints were used. Each was prepared by excising a 10cm x 5cm skin and soft tissue window exposing the Achilles tendon. With the ankle in neutral position, the tendon was transfixed with a 2mm k-wire into the tibia, 8cm from its calcaneal insertion. A typical post-rupture gap was created by excising a 2.5cm portion of tendon between 3.5cm and 6cm from its calcaneal insertion. The specimens were then placed into a low profile walker boot (SideKICK^TM, Procare) without wedges and a window cut into the back. The distance between the proximal and distal Achilles tendon cut edges was measured and repeated with 1, 2 and 3 (10mm) wedges. Subsequently the specimens were placed into a complete below knee cast in full equinus which was also windowed.

Results: The Achilles tendon gap (mean +/- SD) measured: 2.7cm (0.5) with no wedge, 2.3cm (0.4) with 1, 2.0cm (0.4) with 2, 1.5cm (0.4) with 3 wedges and 0.4cm (0.3) in full equinus cast. The choice of treatment had a significant effect on tendon gap (p< 0.0001 - repeated measures ANOVA), and all pairwise comparisons were significantly different (Bonferroni), with all p< 0.001, apart from 0 wedge vs. 1 wedge (p< 0.01) and 1 wedge vs. 2 wedges (p< 0.05).

Conclusions: Our results showed that each wedge apposed the tendon edges by approximately 0.5cm with the equinus cast achieving the best apposition. Surgeons should consider this when planning appropriate immobilisation regimes for Achilles tendon ruptures.