Does Unilateral Lower Limb Amputation Influence Ankle Joint Torque in the Intact Leg?

Comparison of thicknesses of talar cartilage, tibialis anterior, and gastrocnemius muscles between high-activity patients with unilateral traumatic transtibial amputation and nonamputated individuals: A clinical and sonographic study

BACKGROUND

The aim of this study was to compare the thicknesses of intact talar cartilage, tibialis anterior (TA), gastrocnemius medialis (GCM), and gastrocnemius lateralis (GCL) muscles of traumatic unilateral transtibial amputees with that of nonamputated individuals by ultrasound and to investigate the relationship between cartilage and muscle thickness measurements with clinical parameters.

METHODS

Thirty-six patients with unilateral traumatic transtibial amputation, and 36 age-matched, sex-matched, and body mass index-matched nonamputated controls were included in this cross-sectional study. Subjects' talar cartilage, TA, GCM, and GCL muscle thickness measurements were performed using musculoskeletal ultrasound. Other outcome measures were 6-minute walking test, the Foot and Ankle Outcome Score, and Short Form-36.

RESULTS

TA and GCM muscles were thicker on the intact limbs of the patients than those of the controls (p = 0.015 and p = 0.014, respectively). There was no statistically significant difference in talar cartilage and GCL muscle thicknesses when patients were compared with control subjects. Talar cartilage thickness was positively correlated with body mass index, 6-minute walking test, and sport and recreation subscale score of the Foot and Ankle Outcome Score. TA and GCM muscle thicknesses were positively correlated with the duration of prosthesis use and role limitations because of the physical health subscale score of Short Form-36.

CONCLUSIONS

TA and GCM muscles were found to be thickened on the intact sides of traumatic unilateral transtibial amputees. The correlations between lower leg muscle thicknesses and clinical parameters suggest that the observed thickness change is not necessarily pathological and has potential impact on function at least in our young cohort.

Contribution of Achilles tendon mechanical properties to torque steadiness in persons with transfemoral amputation

BACKGROUND

How Achilles tendon mechanics and plantar flexion strength and torque steadiness are altered in the intact leg of persons with trauma-related amputation is unknown. Understanding Achilles tendon mechanics following amputation will further inform rehabilitation approaches to enhance posture, balance, and force control.

OBJECTIVE

Conduct a pilot study to quantify plantar flexion maximal voluntary contraction torque, torque steadiness, and Achilles tendon mechanics in persons with unilateral trauma-related transfemoral amputation and controls without amputation.

STUDY DESIGN

Cross-sectional study.

METHODS

Isometric plantar flexion maximal voluntary contractions were performed with the intact leg of ten males with transfemoral amputation (48 ± 14 years) and the dominant leg of age-matched male controls without amputation. Torque steadiness was calculated as the coefficient of variation in torque over 6 s during submaximal tracking tasks (5%, 10%, 25%, 50%, and 75% maximal voluntary contraction). Achilles tendon elongation and cross-sectional area were recorded with ultrasound to calculate strain, stress, and stiffness.

RESULTS

Maximal voluntary contraction and torque steadiness did not differ between persons with amputation (90.6 ± 31.6 N m, 3.7 ± 2.0%) and controls (95.8 ± 26.8 N m, 2.9 ± 1.2%; p > 0.05). Tendon stiffness (21.1 ± 18.2 N/mm) and strain (5.2 ± 1.3%) did not differ between groups (p > 0.05). Tendon cross-sectional area was 10% greater in persons with amputation leading to 29% lower stress (p = 0.021). Maximal voluntary contraction was a predictor of a lower coefficient of variation in torque (R2 = 0.11, p < 0.05).

CONCLUSION

Persons with trauma-related transfemoral amputation do not differ in plantar flexion maximal voluntary contraction and torque steadiness of the intact leg compared with controls without amputation. Larger tendon cross-sectional area reduces stress and enables distribution of force across a greater area.