A Pilot Study of Musculoskeletal Abnormalities in Patients in Recovery from a Unilateral Rupture-Repaired Achilles Tendon

Abstract

The purpose of this study was to compare the inter-limb joint kinematics, joint moments, muscle forces, and joint reaction forces in patients after an Achilles tendon rupture (ATR) via subject-specific musculoskeletal modeling. Six patients recovering from a surgically repaired unilateral ATR were included in this study. The bilateral Achilles tendon (AT) lengths were evaluated using ultrasound imaging. The three-dimensional marker trajectories, ground reaction forces, and surface electromyography (sEMG) were collected on both sides during self-selected speed during walking, jogging and running. Subject-specific musculoskeletal models were developed to compute joint kinematics, joint moments, muscle forces and joint reaction forces. AT lengths were significantly longer in the involved side. The side-to-side triceps surae muscle strength deficits were combined with decreased plantarflexion angles and moments in the injured leg during walking, jogging and running. However, the increased knee extensor femur muscle forces were associated with greater knee extension degrees and moments in the involved limb during all tasks. Greater knee joint moments and joint reaction forces versus decreased ankle joint moments and joint reaction forces in the involved side indicate elevated knee joint loads compared with reduced ankle joint loads that are present during normal activities after an ATR. In the frontal plane, increased subtalar eversion angles and eversion moments in the involved side were demonstrated only during jogging and running, which were regarded as an indicator for greater medial knee joint loading. It seems after an ATR, the elongated AT accompanied by decreased plantarflexion degrees and calf muscle strength deficits indicates ankle joint function impairment in the injured leg. In addition, increased knee extensor muscle strength and knee joint loads may be a possible compensatory mechanism for decreased ankle function. These data suggest patients after an ATR may suffer from increased knee overuse injury risk.

Keywords: Achilles tendon rupture; ankle; gait; knee; musculoskeletal modeling.

Figure 1

Data processing flow chart, from experimental testing to OpenSim simulation. Note. GRF: ground reaction force; sEMG: surface electromyography.

Figure 2

Schematic depiction of the subject-specific musculoskeletal modeling used in this study. (a) The generic musculoskeletal model is scaled for each subject using experimental markers placed on anatomical landmarks. (b) The slack Achilles tendon length of the involved side was measured with an ultrasound of each subject to obtain subject-specific parameters. (c) Graphic depiction of modifying gas_med, gas_lat and soleus muscle-tendon parameters. Note. Gas Med: gastrocnemius medialis, Gas Lat: gastrocnemius lateralis.

Figure 3

Comparison of muscle activations from static optimization estimated (blue line) and filtered electromyography (EMG) signals measured from one subject during the same trial of normal walking, jogging and running. (a): Rectus femoris muscle activation during stance phase of walking; (b): Biceps femoris lh (long head) muscle activation during stance phase of walking; (c): Gastrocnemius medialis (Gas_med) muscle activation during stance phase of walking; (d): Gastrocnemius lateralis (Gas_lat) muscle activation during stance phase of walking; (e) Rectus femoris muscle activation during stance phase of jogging; (f) Biceps femoris lh (long head) muscle activation during stance phase of jogging; (g) Gastrocnemius medialis (Gas_med) muscle activation during stance phase of jogging; (h): Gastrocnemius lateralis (Gas_lat) muscle activation during stance phase of jogging; (i): Rectus femoris muscle activation during stance phase of running; (j): Biceps femoris lh (long head) muscle activation during stance phase of running; (k): Gastrocnemius medialis (Gas_med) muscle activation during stance phase of running; (l): Gastrocnemius lateralis (Gas_lat) muscle activation during stance phase of running. Note. EMG and activations were normalized from zero to one for each subject based upon the minimum and maximum values over the stance phase.

Figure 4

Mean and standard deviation lower extremity joint angle waveforms over stance phase (100%) for the uninvolved side (yellow) and involved side (blue) during self-selected speed walking, jogging and running. (a): Hip joint flexion/extension (FLX/EXT) during stance phase of walking; (b): Knee joint flexion/extension (FLX/EXT) during stance phase of walking; (c) Ankle joint dorsiflexion/plantarflexion (DF/PF) during stance phase of walking; (d) Subtalar joint inversion/eversion (INV/EVE) during stance phase of walking; (e): Hip joint flexion/extension (FLX/EXT) during stance phase of jogging; (f): Knee joint flexion/extension (FLX/EXT) during stance phase of jogging; (g) Ankle joint dorsiflexion/plantarflexion (DF/PF) during stance phase of jogging; (h) Subtalar joint inversion/eversion (INV/EVE) during stance phase of jogging; (i): Hip joint flexion/extension (FLX/EXT) during stance phase of running; (j): Knee joint flexion/extension (FLX/EXT) during stance phase of running; (k) Ankle joint dorsiflexion/plantarflexion (DF/PF) during stance phase of running (l) Subtalar joint inversion/eversion (INV/EVE) during stance phase of running. Grey shaded regions on graphs indicate a significant difference between the two sides (p < 0.05) from SPM1d (one-dimensional Statistical Parametric Mapping) analyses.

Figure 5

Mean and standard deviation of lower extremity joint moment waveforms over stance for the uninvolved side (yellow) and involved side (blue) during self-selected speed walking, jogging and running. (a): Hip joint flexion/extension (FLX/EXT) moment during stance phase of walking; (b): Knee joint flexion/extension (FLX/EXT) moment during stance phase of walking; (c) Ankle joint dorsiflexion/plantarflexion (DF/PF) moment during stance phase of walking; (d) Subtalar joint inversion/eversion (INV/EVE) moment during stance phase of walking; (e): Hip joint flexion/extension (FLX/EXT) moment during stance phase of jogging; (f): Knee joint flexion/extension (FLX/EXT) moment during stance phase of jogging; (g) Ankle joint dorsiflexion/plantarflexion (DF/PF) moment during stance phase of jogging; (h) Subtalar joint inversion/eversion (INV/EVE) moment during stance phase of jogging; (i): Hip joint flexion/extension (FLX/EXT) moment during stance phase of running; (j): Knee joint flexion/extension (FLX/EXT) moment during stance phase of running; (k) Ankle joint dorsiflexion/plantarflexion (DF/PF) moment during stance phase of running (l) Subtalar joint inversion/eversion (INV/EVE) moment during stance phase of running. Grey shaded regions on graphs indicate a significant difference between the two sides (p < 0.05) from SPM1d analyses.

Figure 6

Mean and standard deviation of estimated vas_med (vastus medialis), vas_lat (vastus lateralis), vas_inter (vastus intermedius) and rectus femoris muscle-tendon forces waveforms over stance between the uninvolved side (yellow) and involved side (blue) during walking, jogging and running. (a): vas_med muscle-tendon forces during stance phase of walking; (b): vas_lat muscle-tendon forces during stance phase of walking; (c) vas_inter muscle-tendon force during stance phase of walking; (d) rectus femoris muscle-tendon force during stance phase of walking; (e): vas_med muscle-tendon forces during stance phase of jogging; (f): vas_lat muscle-tendon forces during stance phase of jogging; (g) vas_inter muscle-tendon force during stance phase of jogging; (h) rectus femoris muscle-tendon force during stance phase of jogging; (i): vas_med muscle-tendon forces during stance phase of running; (j): vas_lat muscle-tendon forces during stance phase of running; (k) vas_inter muscle-tendon force during stance phase of running; (l) rectus femoris muscle-tendon force during stance phase of running. Grey shaded regions on graphs indicate a significant difference between the two sides (p < 0.05) from SPM1d analyses.

Figure 7

Mean and standard deviation of estimated gas_med (gastrocnemius medialis), gas_lat (gastrocnemius lateralis) and soleus muscle-tendon forces waveforms over stance between the uninvolved side (yellow) and involved side (blue) during walking, jogging and running. (a): gas_med muscle-tendon forces during stance phase of walking; (b) gas_lat muscle-tendon forces during stance phase of walking; (c) soleus muscle-tendon forces during stance phase of walking; (d): gas_med muscle-tendon forces during stance phase of jogging; (e) gas_lat muscle-tendon forces during stance phase of jogging; (f) soleus muscle-tendon forces during stance phase of jogging; (g): gas_med muscle-tendon forces during stance phase of running; (h) gas_lat muscle-tendon forces during stance phase of running; (i) soleus muscle-tendon forces during stance phase of running. Grey shaded regions on graphs indicate a significant difference between the two sides (p < 0.05) from SPM1d analyses.

Figure 8

Mean and standard deviation of estimated joint reaction forces waveforms over stance at the hip, knee and ankle joints for uninvolved side (yellow) and involved side (blue) during walking, jogging and running. (a): Hip joint reaction forces during stance phase of walking; (b) Knee joint reaction forces during stance phase of walking; (c) Ankle joint reaction forces during stance phase of walking; (d): Hip joint reaction forces during stance phase of jogging; (e) Knee joint reaction forces during stance phase of jogging; (f) Ankle joint reaction forces during stance phase of jogging; (g): Hip joint reaction forces during stance phase of running; (h) Knee joint reaction forces during stance phase of running; (i) Ankle joint reaction forces during stance phase of running. Grey shaded regions on graphs indicate a significant difference between the two sides (p < 0.05) from SPM1d analyses.