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Hamstrings and psoas lengths during normal and crouch gait: implications for muscle-tendon surgery
S L Delp1, A S Arnold, R A Speers
1Rehabilitation Institute of Chicago, IL 60611, USA.
Summary
Crouch gait in children with cerebral palsy is often treated by hamstring surgery. However, this study found most patients have normal or long hamstrings, suggesting psoas muscle length is a key factor, not hamstring length.
Area of Science:
- Orthopedics
- Pediatric Rehabilitation
- Biomechanics
Background:
- Crouch gait, a common cerebral palsy (CP) movement disorder, involves persistent knee flexion during stance.
- Hamstring muscle shortening is traditionally believed to cause crouch gait, leading to surgical hamstring lengthening.
- This approach may not address the underlying biomechanical issues in all CP patients.
Purpose of the Study:
- To investigate the actual in-vivo muscle lengths of hamstrings and psoas during gait in children with crouch gait.
- To challenge the conventional understanding of crouch gait etiology and surgical treatment.
- To provide a more accurate basis for surgical decision-making in CP.
Main Methods:
- Utilized a graphics-based lower extremity model.
- Incorporated three-dimensional kinematic data from gait analysis.
- Estimated hamstring and psoas muscle lengths during normal and crouch gaits.
Main Results:
- Only 3 of 14 subjects (20% of limbs) with crouch gait had significantly short hamstrings.
- 80% of subjects exhibited normal or longer hamstring lengths despite knee flexion.
- All subjects with crouch gait demonstrated a shorter-than-normal psoas muscle length.
Conclusions:
- Hamstring length is not the primary cause of crouch gait in most children with CP.
- Shortened psoas muscles appear to be a significant contributing factor.
- Surgical interventions should consider multi-joint kinematics and muscle lengths, not solely hamstrings.