Abstract
Aim
To determine the effects of knee and ankle position on tendo Achilles (TA) gap distance in patients with acute rupture using ultrasound.
Methods
Twenty seven patients with twenty-eight acute complete TA ruptures confirmed on ultrasound were recruited within a week of injury. The mean age at presentation was 42 years (range 23-80 years). Ultrasound measurements included location of the rupture and the gap distance between the superficial tendon edges with the ankle in neutral and knee extended. The gap distance was sequentially measured with the foot in maximum equinus and 0°, 30°, 60° and 90° of knee flexion.
Results
The mean distance of the rupture from the enthesis was 52mm (range: 40-76mm). The mean gap distance with the ankle in neutral and knee extended was 11.4mm (95%CI: 9.9, 12.9). This reduced to 4.8mm (95%CI: 3.3, 6.4) when the foot was in maximum equinus, 3.8mm (95%CI: 2.5, 5.1) with 30° knee flexion, 2.6mm (95%CI: 1.7, 3.6) with 60° knee flexion and 1.5mm (95% CI: 0.8, 2.2) with 90° knee flexion. Expressing the reduction in gap distance with each successive position as a percentage of the gap distance with the knee extended and ankle in neutral revealed a mean reduction of 58.9%, 66.9%, 77.1% and 85.9% with maximum equinus and 0°, 30°, 60° and 90° of knee flexion respectively. The difference in gap distance between each of these positions was statistically significant (p<0.05).
Discussion
Maximum equinus alone significantly reduces the gap distance in acute TA rupture. Increasing knee flexion demonstrates a lesser effect throughout the initial 90° arc suggesting apposition is encouraged by use of a below knee maximum equinus cast permitting full knee flexion.
