Muscle fiber conduction velocity and muscle strength impairments 12 months after repaired Achilles tendon rupture: a cross-sectional study

Background

Clinically, muscle strength and neuromuscular function are expected to return toward normal levels within 12 months after surgical repair of Achilles tendon rupture (rATR). However, the recovery of muscle fiber conduc-tion velocity (MFCV) as a muscle fiber property remains unclear. Thus, we aimed to determine whether MFCV and maximal voluntary isometric contraction (MVIC) of the plantar-flexors are restored 12 months after rATR compared with healthy individuals.

Aim

Thus, we aimed to determine whether MFCV and MVIC of the plantar-flexors are restored 12 months after rATR compared with healthy individuals.

Methods

A total of 20 participants (10 men with rATR and 10 healthy controls) were included in this cross-sectional study. Medial gastrocnemius MFCV at 40% and 60% of MVIC was measured using a 16-channel linear electro-myography array to be compared between groups using mixed-model repeated-measures ANOVA. Plantar-flexion MVIC was compared using a one-tailed Mann-Whitney U test. Alpha error was set to 0.05.

Results

The Achilles group showed higher MFCV at 60% compared to 40% of MVIC (4.7±1.2 vs 4.2±1.1 ms-1; p=0.020), whereas the control group did not (4.0±0.3 vs 3.6±0.7 ms-1; p=0.120). The Achilles group exhibited higher MFCV than controls at both 40% (4.2±1.1 vs 3.6±0.7 ms-1; p=0.040) and 60% MVIC (4.7±1.2 vs 4.0±0.3 ms-1; p=0.010). The Achilles group exhibited lower MVIC than controls (1.5±0.6 vs 2.1±0.5 Nmkg-1; p=0.033).

Interpretation

Neuromuscular function and strength are not normalized one-year after rATR. Patients generate plantar-flexion strength with higher MFCV than healthy individuals.