High Yield Overview
PROXIMAL HAMSTRING INJURIES
Avulsions | Tendinopathy | Sciatic Nerve
ClassificationWood Classification
NerveSciatic Nerve (1-2 cm lateral)
RetractionSurgery if greater than 2cm
MechanismEccentric contraction (Water skiing)
Wood Classification (MRI)
Type 1
PatternOsteo-apophyseal avulsion (Adolescent)
TreatmentConservative
Type 2
PatternMusculotendinous junction tear
TreatmentConservative
Type 3
PatternIncomplete Tendon Avulsion
TreatmentConservative
Type 4
PatternComplete Tendon Avulsion (Bone)
TreatmentSurgery (if retracted)
Type 5
PatternComplete Avulsion + Symptomatic Sciatic Nerve
TreatmentSurgery
Critical Must-Knows
- Anatomy: Semimembranosus (Lateral), Semitendinosus/Biceps (Medial/Conjoint). Wait, Semimembranosus is superolateral on tuberosity.
- Mechanism: Forced hip flexion with knee extension (e.g. Waterskiing, doing the splits).
- Sciatic Nerve: Runs 1.2cm lateral to the ischial tuberosity. At risk during repair.
- Surgery Indications: 2-tendon avulsion with retraction greater than 2cm in active patients.
- Rehab: Avoid tension (hip flex + knee ext) for 6 weeks post-op.
Examiner's Pearls
- "Bowstring Sign: Active knee flexion at 90 deg hip flexion - absent cord.
- "Ecchymosis in posterior thigh is a pathognomic delayed sign.
- "MRI is gold standard for grading retraction.
- "Chronic repairs (greater than 4 weeks) often need allograft or lysis of adhesions.
Clinical Imaging
Imaging Gallery
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Critical Concepts
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Sciatic Nerve
The Peril. The sciatic nerve is intimately related to the proximal hamstring origin (approx 1.2cm lateral). In chronic cases, it is scarred to the stump. Neurolysis is mandatory during repair.
Acute vs Chronic
The 4 Week Window. Prognosis drops significantly after 4 weeks due to tendon retraction and scarring. Acute repair (less than 4 weeks) is much easier than chronic reconstruction.
Hamstring Injury Types
| Feature | Proximal Avulsion | Mid-substance Strain | Distal Avulsion |
|---|---|---|---|
| Mechanism | Forced Hip Flexion (Waterski) | Running/Sprinting | Direct Blow/Cut |
| Location | Ischial Tuberosity | Musculotendinous Junction | Pes Anserinus/Fibula |
| Bruising | Massive Posterior Thigh | Localised | Knee region |
| Management | Surgery (if retracted) | Conservative | Depends on ligament |
Mnemonic
Semi-MembranousHamstring Muscles
Semi
Semitendinosus
Conjoint with Biceps (Posteromedial)
Mem
Membranous
Semimembranosus (Anterolateral on tuberosity)
Bi
Biceps Femoris
Long head (Conjoint with Semi-T)
Memory Hook:Semi-T and Biceps are joined at the hip.
Mnemonic
RAWSurgical Indications
R
Retraction
Greater than 2cm
A
Avulsion
Complete bony or tendinous avulsion (all 3)
W
Weakness
Professional athlete / High demand
Memory Hook:Repair Raw hamstrings.
Mnemonic
Flex-ExtRehab Danger Zone
Flex
Hip Flexion
Avoid greater than 90 degrees
Ext
Knee Extension
Avoid full extension
Memory Hook:Don't combine Flexion and Extension.
Overview and Epidemiology
Proximal hamstring injuries range from minor strains to complete avulsions. Complete avulsions are devastating injuries in athletes, leading to significant weakness and loss of function if missed.
- Mechanism: Rapid eccentric contraction. Forced hip flexion with knee extension.
- Water skiing (getting up).
- Bull riding.
- Gymnastics (splits).
- Slipping on wet floor (splits).
- Demographics:
- Young Athletes: Epiphyseal avulsions (ischial apophysis).
- Middle-aged: Tendinous avulsions (degeneration).
Pathophysiology and Mechanisms
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Hamstring Origin
All originate from Ischial Tuberosity.
- Semimembranosus: Originates from the superolateral impression. It has the largest footprint.
- Conjoint Tendon: Semitendinosus and Biceps Femoris (Long Head). Originates from the posteromedial impression.
Note: Biceps Short Head originates from the Linea Aspera (Femur), not the ischium, so it is spared in avulsions.
The Ischial Tuberosity is divide into upper and lower facets.
Classification Systems
Wood Classification (MRI based)
- Type 1: Osteo-apophyseal avulsion (Adolescent).
- Type 2: Musculotendinous junction tear.
- Type 3: Incomplete Tendon Avulsion.
- Type 4: Complete Tendon Avulsion (from Bone).
- Type 5: Complete Avulsion with Sciatic Nerve symptoms.
Cohen and Bradley (2007) simplified this to Number of Tendons (1, 2, or 3) and Retraction (less than 2cm vs greater than 2cm).
Type 5 is the most severe (Sciatic nerve).
Clinical Assessment
History
- "Pop" or "tearing" sensation in the buttock.
- Falls while doing splits.
- Immediate pain, inability to walk without limp.
- Sciatic symptoms: Numbness, foot drop (rare but urgent).
Physical Examination
- Inspection: "Hamstring Droop" (loss of proximal contour). Extensive ecchymosis (bruising) tracking down to knee (appears days later).
- Palpation: Defect at ischial tuberosity. Tender.
- Strength: Weakness in Knee Flexion and Hip Extension.
- Note: Knee flexion may still be present due to intact Biceps Short Head, Gracilis, and Sartorius.
- Bowstring Sign: Patient prone, knee flexed to 90. Palpate distal tendons. If "bowstringing" is absent or asymmetrical, suggests avulsion.
Investigations
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X-Ray
- AP Pelvis: Rule out bony avulsion (Ischial tuberosity fracture).
- Particularly important in adolescents (apophysis).
MRI
- Gold Standard.
- Determines:
- Number of tendons involved (1, 2, or 3).
- Amount of retraction (cm).
- Sciatic nerve involvement.
- Chronicity (fatty atrophy).
Ideally obtained within 2 weeks of injury.
Management Algorithm
Treatment Strategy
Non-OperativeIndications
- Single tendon tears.
- Low retraction (less than 2cm).
- Sedentary patients.
- Partial tears.
Operative (Acute)Indications (less than 4 wks)
- 2 or 3 tendon avulsion.
- Retraction greater than 2cm.
- Active patients / Athletes.
- Sciatic nerve symptoms.
Operative (Chronic)Indications (greater than 4 wks)
- Persistent pain/weakness.
- Requires Allograft usually.
- Neurolysis required.
Surgical Technique
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Open Proximal Hamstring Repair
Position: Prone. Jack-knife position (flex hips to relax hamstrings). Incision: Transverse gluteal fold incision or Longitudinal posterior incision. Exposure:
- Identify Gluteus Maximus inferior border. Retract superiorly.
- FIND SCIATIC NERVE: First step. Identify and protect.
- Identify Ischial Tuberosity (debride to bleeding bone).
- Find tendon stump (often retracted distally).
Fixation:
- Suture anchors (titatium or PEEK) into ischial tuberosity (usually 2-4 anchors).
- Locking stitch (Krackow) in tendon.
- Reduce tendon to bone (Flex knee to 90 if needed).
- Tie sutures.
Care must be taken to avoid over-tensioning.
Complications
| Complication | Risk | Note |
|---|---|---|
| Sciatic Nerve Palsy | Unknown | Stretch or direct injury. Most resolve. |
| Recurrence | low | If rehab is too aggressive |
| Sitting Pain | Common | Scar tissue at ischium (Ischial bursitis) |
| Wound Breakdown | Common | Gluteal fold is high tension/moisture area |
Postoperative Care
Rehabilitation Protocol
- Phase 1 (0-6 weeks):
- Brace: Hip extension brace or Knee flexion brace? Usually Knee brace locked at 30-90 deg?
- Typically: Hip orthosis preventing flexion greater than 45, or simply crutches and cautious movement.
- Weight Bearing: Toe touch / PWB for 4-6 weeks.
- Avoid: Hip Flexion + Knee Extension (The stretch).
- Phase 2 (6-12 weeks):
- Wean crutches.
- Active hamstring curls (no resistance).
- stationary bike.
- Phase 3 (3-6 months):
- Strengthening. Nordic curls.
- Jogging.
- Return to sport at 6 months.
Surgical Complications Detail
- Sciatic Nerve Palsy: Can be neuropraxia from retraction or direct injury.
- Management: Observation for 3 months. EMG at 3 months if no recovery.
- Wound Dehiscence: Transverse gluteal crease incisions are high risk due to moisture and sitting pressure.
- Prevention: meticulous closure, avoiding prolonged sitting in early phase.
- Deep Infection: Rare but devastating. Requires debridement and often anchor removal.
- Rerupture: Occurs in 1-3% of repairs.
- Risk factors: Early return to sport, non-compliance with brace.
Outcomes and Prognosis
Acute Surgical Repair Outcomes
Return to Sport:
- Overall return rate: 80-90%
- Return to pre-injury level: 70-80%
- Mean time to return: 6 months
Functional Outcomes:
- Isokinetic strength testing shows 85-95% recovery vs contralateral
- Endurance activities recover well
- Sprinting and explosive movements may have persistent deficit
| Measure | Acute Repair | Chronic Repair | Conservative |
|---|---|---|---|
| Return to Sport | 82-90% | 65-75% | 50-60% |
| Pre-injury Level | 72% | 55% | 30% |
| Strength Recovery | 85-95% | 70-80% | 60-70% |
| Patient Satisfaction | High | Moderate | Low-Moderate |
Acute repair consistently outperforms delayed treatment.
Evidence Base
Surgical vs Conservative
Harris et al • Int J Sports Med (2011)
Key Findings:
- Surgery superior for complete tears
- High, return to sport
- Low complication rate
Clinical Implication: Offer surgery for complete avulsions.
Chronic Repair
Folsom AND Hennessey • Am J Sports Med (2008)
Key Findings:
- Outcomes still good in chronic
- Requires neurolysis
- Technically difficult
Clinical Implication: It is not too late to fix relative chronic tears.
Anatomy and MRI
Koulouris et al • Skeletal Radiol (2008)
Key Findings:
- Conjoined tendon is posteromedial
- Semimembranosus is anterolateral
- MRI accurate for grading
Clinical Implication: Know your anatomy.
Retraction Distance and Outcomes
Sallay et al • Am J Sports Med (1996)
Key Findings:
- Retraction over 2cm associated with poorer conservative outcomes
- Early repair (within 4 weeks) had better results
- Complete 3-tendon avulsion has worst prognosis without surgery
- Athletes with retraction should undergo early surgical repair
Clinical Implication: Use 2cm retraction as threshold for surgical decision-making
Return to Sport After Surgical Repair
Bodendorfer et al • Am J Sports Med (2018)
Key Findings:
- Systematic review of 792 patients
- Return to sport rate 82% overall
- Return to pre-injury level 72%
- Mean return time 6 months
- Sciatic nerve symptoms resolve in 90% post-repair
Clinical Implication: Counsel athletes that majority return to sport but full recovery takes 6 months
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
VIVA SCENARIOStandard
Scenario 1: Waterskiing Wipeout
EXAMINER
"A 45-year-old male water-skier felt a pop in his buttock when the boat accelerated. He has a massive bruise down his posterior thigh and cannot run. MRI shows a 3-tendon avulsion with 4cm retraction."
EXCEPTIONAL ANSWER
This is a complete proximal hamstring avulsion (Type 4/5). Diagnosis: Validated by MRI showing 3 tendons and significant retraction (greater than 2cm). Management: This requires Surgical Repair. Rationale: In an active patient, conservative management of retracted complete tears leads to significant weakness, cramping, and functional deficit. Technique: Open repair with suture anchors, protecting the sciatic nerve. Timing: Ideally within 2-3 weeks (Acute) to avoid scarring/retraction difficulties.
KEY POINTS TO SCORE
3 tendon + greater than 2cm = Surgery
Acute repair is standard
Protect sciatic nerve
Water skiing is classic mechanism
COMMON TRAPS
✗Treating conservatively (will develop functional deficit)
✗Missing sciatic nerve symptoms
✗Waiting too long (greater than 4 weeks)
LIKELY FOLLOW-UPS
"What nerves are at risk?"
"How do you rehab him?"
"What if he presents at 6 months?"
VIVA SCENARIOChallenging
Scenario 2: The Chronic Pain
EXAMINER
"A 50-year-old runner presents 6 months after a 'pulled hamstring'. He has difficulty sitting and deep buttock pain. He has weakness. MRI shows a chronic rupture with 6cm retraction."
EXCEPTIONAL ANSWER
This is a Chronic Proximal Hamstring Rupture with possible Hamstring Syndrome (Sciatic entrapment). Management: This is a salvage situation. Options: 1. Conservative (if low demand). 2. Surgical Reconstruction. Primary repair is unlikely to be possible without extreme tension. I would plan for an Achilles Tendon Allograft reconstruction and Sciatic Neurolysis. The sitting pain is likely due to the stump scarring to the nerve/ischium.
KEY POINTS TO SCORE
Chronic = Retracted and Scarred
Need Allograft
Neurolysis mandatory
Sitting pain = Ischial pathology
COMMON TRAPS
✗Attempting primary repair under tension
✗Ignoring the nerve entrapment
✗Promising normal function
LIKELY FOLLOW-UPS
"Where do you get the allograft?"
"What position do you operate in?"
"Risks of surgery?"
VIVA SCENARIOStandard
Scenario 3: The Adolescent Sprinter
EXAMINER
"A 14-year-old sprinter feels a pop at the start of a race. X-ray shows a bony fragment displaced 1cm from the ischial tuberosity."
EXCEPTIONAL ANSWER
This is an Ischial Apophysis Avulsion Fracture (Wood Type 1). Diagnosis: Skeletally immature athlete. X-ray confirms bony avulsion. Management: Non-operative management is the standard for displacements less than 2cm. 1. Rest/Crutches. 2. Gradual rehab. 3. Return to sport when bony healing confirmed (usually 3 months). Surgery is reserved for widespread displacement (greater than 2cm) or non-union with symptoms.
KEY POINTS TO SCORE
Adolescent = Bony Avulsion
Displacement less than 2cm = Conservative
Good prognosis
Watch for non-union
COMMON TRAPS
✗Operating on minimally displaced fractures
✗Confusing with soft tissue avulsion
✗Returning to sport too early (re-avulsion)
LIKELY FOLLOW-UPS
"When does the apophysis fuse?"
"What muscle attaches there?"
"Complications of non-op?"
MCQ Practice Points
Nerve Relation
Q: What is the relationship of the Sciatic nerve to the Ischial Tuberosity? A: Lateral. Approximately 1.2cm lateral to the tuberosity.
Blood Supply
Q: What is the main blood supply to the proximal hamstrings? A: Perforating branches of Profunda Femoris and Inferior Gluteal Artery.
Muscle Origin
Q: Which muscle originates most Anterolaterally on the tuberosity? A: Semimembranosus. The Conjoint tendon (Semi-T/Biceps) is Posteromedial.
Most common injury
Q: Which tendon is most commonly involved in avulsions? A: Biceps Femoris. Often as part of the conjoint tendon unit.
Risk Factors
Q: What is a key risk factor for chronic tendon degeneration? A: Fluoroquinolone antibiotics (rare) but more commonly Previous Injury and Age.
Australian Context
Epidemiology
- Common in water skiers (Murray River) and AFL players (kicking/slipping).
- "Hamstring strains" (distal/midsubstance) are #1 injury in AFL, but proximal avulsions are distinct.
Referral
- Orthopaedic referral for any 3-tendon tear or greater than 2cm retraction.
- Acute referral (less than 2 weeks) is critical for easier repair.
PROXIMAL HAMSTRING INJURIES
High-Yield Exam Summary
Classification
- •1 Tendon: Conservative
- •2 Tendons: Gray zone (Retraction?)
- •3 tendon + greater than 2cm = Surgery
- •Bony Avulsion: Conservative (Adolescent)
Diagnosis
- •Waterskiing/Splits mechanism
- •Bruising prone to knee
- •Palpable gap
- •MRI Gold Standard
Management
- •Acute (less than 4 wk): Primary Repair
- •Chronic (greater than 4 wk): Allograft?
- •Neurolysis of Sciatic Nerve
- •Rehab: No tension (flexion) for 6 weeks
Anatomy
- •Ischial Tuberosity Origin
- •Sciatic Nerve 1.2cm Lateral
- •Conjoint Tendon = Medial
- •Semimembranosus = Lateral