What are the indications and considerations for hamstring lengthening in patients with extension contracture, particularly those with cerebral palsy, stroke, or spinal cord injury?

Hamstring Lengthening for Extension Contracture

Hamstring lengthening is indicated for patients with knee flexion contractures (not extension contractures) that impair function, positioning, or cause pain, particularly in cerebral palsy patients who are either ambulatory with crouch gait or non-ambulatory with sitting difficulties. 1, 2

Critical Clarification: Extension vs. Flexion Contracture

The hamstrings are knee flexors and hip extensors. Hamstring contracture causes knee flexion contracture (inability to fully extend the knee), not extension contracture. 3, 2 This is a fundamental anatomical distinction that determines surgical candidacy.

Indications for Hamstring Lengthening

For Ambulatory Patients with Cerebral Palsy

• Crouch gait pattern with excessive knee flexion during stance phase that limits walking efficiency and causes progressive deformity 4, 5
• Hamstring contracture with popliteal angle >40-50 degrees that restricts knee extension during gait 6, 5
• Failed conservative management including stretching, serial casting, and spasticity management 1

For Non-Ambulatory Patients

• Severe hamstring contracture preventing proper sitting posture with hip extensor thrust and increased kyphosis 2
• Wheelchair-bound patients with spastic quadriplegic cerebral palsy who cannot achieve functional sitting position 2
• Difficulty with positioning for hygiene and skin care 1

For Stroke and Spinal Cord Injury Patients

• The guidelines prioritize non-surgical approaches first: positioning, range of motion exercises, stretching, splinting, and serial casting 1
• Surgical correction is reserved for contractures that restrict movement, cause pain, or impede rehabilitation after conservative measures fail 1
• Ankle plantarflexion contractures are more common than hamstring contractures post-stroke and should be addressed with AFOs 1, 7

Surgical Technique Considerations

Open vs. Percutaneous Approach

Open hamstring lengthening is superior to percutaneous technique and should be the preferred approach. 6

• Open fractional lengthening achieves significantly greater improvement in popliteal angle (mean 30-degree improvement) compared to percutaneous technique (12-degree improvement, p<0.0001) 6
• Percutaneous technique causes uncontrolled muscle fiber injury in >50% of cases rather than precise fascial lengthening 6
• Critical safety concern: The peroneal nerve physically touches the lateral hamstring tendon in 15.6% of knees, creating high risk of nerve transection with percutaneous lateral hamstring lengthening 8
• Popliteal vessels can be within 3mm of medial hamstring tendons in some patients, particularly those with spastic diplegia 8

However, one recent study found equivalent kinematic outcomes between open and percutaneous techniques when performed by experienced surgeons, with percutaneous allowing faster rehabilitation 5 This represents conflicting evidence, but given the anatomical safety data showing neurovascular proximity 8 and the superior popliteal angle improvement with open technique 6, the open approach remains recommended unless surgeon expertise with percutaneous technique is exceptional.

Specific Technical Recommendations

• For lateral hamstring (biceps femoris): Always use open technique with direct visualization or preoperative ultrasound to identify peroneal nerve location 8
• For medial hamstrings (semimembranosus/semitendinosus): Open fractional lengthening at multiple levels achieves better outcomes than single-level percutaneous cuts 6
• Proximal hamstring lengthening at the ischial origin is effective for non-ambulatory patients focused on sitting improvement 2
• Distal hamstring lengthening is appropriate for ambulatory patients with crouch gait 4

Expected Outcomes

Ambulatory Patients

• Significant reduction in knee flexion at initial contact (12-19 degrees improvement) 5
• Increased maximum knee extension in stance phase (8-14 degrees improvement) 5
• Improved popliteal angle and straight leg raising (p<0.001) 2, 4
• Functional gait improvements require prolonged postoperative physical therapy 4

Non-Ambulatory Patients

• Significant improvement in sitting ability (p<0.01) 2
• Reduced hip extensor thrust and kyphosis during sitting 2
• Improved positioning for care and hygiene 2

Integration with Comprehensive Spasticity Management

Hamstring lengthening should be part of a stepwise approach: 1

1. First-line: Positioning, passive stretching, range of motion exercises several times daily 1
2. Second-line: Serial casting or static adjustable splints for mild-moderate contractures 1, 7
3. Pharmacologic adjuncts: Botulinum toxin or phenol for focal spasticity; oral baclofen, tizanidine, or dantrolene for generalized spasticity 1
4. Surgical correction: Reserved for established contractures that interfere with function after conservative measures fail 1

Critical Pitfalls to Avoid

• Do not perform hamstring lengthening for true knee extension contracture (inability to flex the knee) - this would worsen the problem 3
• Avoid percutaneous lateral hamstring lengthening due to high risk of peroneal nerve injury 8
• Do not rely on muscle relaxants (diazepam, benzodiazepines) as they impair stroke recovery and lack efficacy for contractures 1, 7
• Ensure adequate postoperative rehabilitation - surgical lengthening alone without prolonged physical therapy yields suboptimal functional outcomes 4
• Screen for concomitant ankle equinus contracture which commonly coexists and may require simultaneous Achilles lengthening or AFO management 1, 7