Lateral Position | Perforator Ligation | Linea Aspera Exposure
Surgical Imaging
The perforating branches of the profunda femoris artery pierce the lateral intermuscular septum to reach the vastus lateralis. There are typically six to eight perforators. Each must be identified, ligated or cauterised before division. Uncontrolled bleeding from a retracted perforator is difficult to control and can cause significant blood loss. Always ligate in continuity before cutting.
In the proximal third of the femur the sciatic nerve lies immediately medial to the linea aspera, deep to the gluteus maximus and adductor magnus. The nerve must be identified and protected with a medial retractor or Langenbeck before any posterior femoral exposure. Injury causes foot drop and is a devastating complication.
The lateral intermuscular septum is the key fascial plane. Vastus lateralis attaches to its anterior surface; the approach develops the plane immediately posterior to the septum. The septum is continuous with the linea aspera and must be incised longitudinally to allow subperiosteal elevation of the vastus lateralis origin.
Lateral decubitus with the affected side up allows gravity to retract the vastus lateralis anteriorly once the septum is divided. Prone positioning is an alternative but requires more assistant retraction. Supine positioning is rarely used because the vastus lateralis falls posteriorly into the wound.
The linea aspera is the posterior ridge of the femur where all three vasti and the adductors attach. Subperiosteal dissection begins here and proceeds circumferentially around the posterior, medial and lateral cortices. The nutrient artery enters the femur near the linea aspera in the middle third - control bleeding from this vessel.
The posterolateral approach can be extended proximally to the greater trochanter and distally to the lateral femoral condyle, providing exposure of almost the entire femur. Proximal extension requires identification of the sciatic nerve and protection of the gluteal vessels. Distal extension crosses the knee joint capsule carefully.
At a Glance
The posterolateral approach to the femur is the standard extensile exposure for femoral shaft fractures requiring plate fixation, nonunion surgery, and bone grafting. The patient is positioned in lateral decubitus or prone. The skin incision runs along the posterior border of the iliotibial tract. The deep interval lies posterior to vastus lateralis, which is reflected anteriorly off the lateral intermuscular septum. All perforating branches of the profunda femoris that pierce the septum are ligated to prevent haemorrhage. Subperiosteal elevation exposes the linea aspera and posterior femoral cortex. In the proximal third the sciatic nerve lies immediately medial and must be protected. The approach is extensile from the greater trochanter to the lateral femoral condyle.
FEMUR PLATEPOSTEROLATERAL FEMUR - Key Steps
LIGATEPERFORATORS - Ligation Sequence
DANGERDANGER ZONES - Layer by Layer
Indications and Approach Selection
Primary Indications:
- Femoral shaft fractures requiring plate fixation (transverse, short oblique, or comminuted patterns unsuitable for nailing)
- Femoral nonunion or malunion requiring open reduction, bone grafting and plate stabilisation
- Infected nonunion requiring debridement, sequestrectomy and antibiotic delivery
- Tumour resection or biopsy of femoral shaft lesions
- Revision surgery after failed intramedullary nailing when nail removal and plating is planned
Why This Approach is Chosen: The posterolateral approach provides direct access to the posterior, lateral and medial femoral cortex through a single incision. The linea aspera is the ideal site for plate placement because of its biomechanical strength. The approach avoids the quadriceps mechanism anteriorly and the medial neurovascular bundle. It is extensile and can be combined with other approaches if needed.
Contraindications:
- Active infection in the surgical field (relative - may proceed with debridement)
- Severe soft-tissue loss or scarring that precludes closure
- Patient unable to tolerate lateral or prone positioning (severe cardiopulmonary disease)
- Isolated anterior femoral lesions better approached anterolaterally
Alternative Approaches:
- Anterolateral approach: For proximal femoral fractures or when anterior plating is planned
- Direct lateral approach: Limited exposure, insufficient for long-plate constructs
- Medial approach: Rarely used, risks femoral artery and vein
- Posterior approach (Kocher-Langenbeck): For acetabular or proximal femoral pathology, not shaft
Overview
Posterolateral Approach to the Femur provides extensile exposure of the femoral shaft from the greater trochanter to the lateral femoral condyle. The approach utilises the interval posterior to vastus lateralis and anterior to the lateral intermuscular septum, allowing subperiosteal access to the linea aspera and posterior femoral cortex.
Key Characteristics:
- Lateral decubitus or prone positioning
- Six to eight perforating arteries require ligation
- Sciatic nerve protection essential in proximal third
- Extensile proximally and distally
Why This Approach Matters:
- Gold-standard exposure for femoral shaft plating and nonunion surgery
- Avoids anterior quadriceps scarring that impairs knee function
- Allows circumferential access to the femur for long-plate constructs
- Critical for revision cases after failed nailing
Exam Relevance:
- High-yield surgical approach for Operative Surgery station
- Perforator ligation and sciatic nerve protection are classic questions
Anatomy
Bony Anatomy: The femoral shaft is triangular in cross-section in the middle third, with the linea aspera forming the posterior apex. The linea aspera gives origin to vastus lateralis, vastus medialis, vastus intermedius and the adductors. The nutrient foramen lies near the linea aspera in the middle third and enters the femur from posterior. The femur bows anteriorly with an average anterior bow of 10-15 degrees.
Muscular Layers: The vastus lateralis originates from the linea aspera and the lateral intermuscular septum. It is the only quadriceps muscle encountered in this approach. The lateral intermuscular septum separates the anterior compartment (vastus lateralis) from the posterior compartment (biceps femoris short head and adductor magnus). The short head of biceps femoris originates from the linea aspera just medial to the vastus lateralis insertion.
Neurovascular Anatomy: The perforating arteries (usually six to eight) arise from the profunda femoris, pierce the adductor magnus and the lateral intermuscular septum, and supply the vastus lateralis. Each perforator must be ligated. The sciatic nerve lies in the posterior compartment, medial to the linea aspera in the proximal third, and is at risk during medial retraction. The femoral artery lies anteromedially and is protected by the vastus medialis unless aggressive medial dissection is performed.
Lateral Intermuscular Septum: This thick fascial sheet runs from the iliac crest to the lateral femoral condyle. Vastus lateralis attaches to its anterior surface. The posterolateral approach develops the plane immediately behind the septum. Incising the septum longitudinally allows the vastus lateralis to be reflected anteriorly, exposing the linea aspera.
Internervous Plane
Deep Internervous Plane:
- Between: Vastus lateralis (femoral nerve) anteriorly and the short head of biceps femoris (sciatic nerve - tibial division) posteriorly
- Clinical relevance: This is a true internervous plane. No muscle is denervated by developing this interval. The lateral intermuscular septum is incised longitudinally to enter the plane.
Superficial Dissection: There is no true internervous plane superficially. The iliotibial tract is incised longitudinally. The fascia lata is continuous with the lateral intermuscular septum. Branches of the lateral cutaneous nerve of the thigh may be encountered in the subcutaneous tissue and should be preserved if possible.
The posterolateral approach to the femur is one of the few true internervous approaches in the lower limb. The femoral nerve (vastus lateralis) and the sciatic nerve (short head of biceps femoris) supply the muscles on either side of the interval. Because the short head of biceps femoris is a small muscle and the approach stays lateral to it, there is minimal functional deficit even if some fibres are divided. The key technical point is to stay immediately posterior to the lateral intermuscular septum and to ligate every perforating vessel before it retracts into the posterior compartment.
Structures at Risk in Each Layer:
- Structure
- Lateral cutaneous nerve of thigh
- Protection Strategy
- Identify and preserve branches if possible
- Structure
- Lateral intermuscular septum
- Protection Strategy
- Incise longitudinally, protect underlying muscle
- Structure
- Vastus lateralis
- Protection Strategy
- Reflect anteriorly, protect muscle belly with retractors
- Structure
- Perforating arteries (6-8)
- Protection Strategy
- Ligate in continuity before division
- Structure
- Sciatic nerve (proximal third)
- Protection Strategy
- Identify medial to linea aspera, protect with retractor
- Structure
- Nutrient artery
- Protection Strategy
- Control bleeding at mid-shaft linea aspera
Positioning and Patient Setup
Position: Lateral Decubitus (Preferred) or Prone
Pre-positioning Checklist:
- Confirm patient can tolerate lateral or prone positioning (cardiopulmonary assessment)
- Padding for all pressure points (greater trochanter, fibular head, malleoli, axilla)
- Arms positioned safely (upper arm supported, lower arm padded)
- Radiolucent table confirmed with full fluoroscopic access
- C-arm positioned for AP and lateral views of entire femur
Positioning Details:
- Lateral decubitus with affected side up, torso stabilised with beanbag or supports
- Affected hip slightly extended and knee flexed 30-40 degrees (relaxes sciatic nerve)
- Tourniquet applied high on thigh if planned (rarely used for femoral shaft)
- Prep and drape to include the iliac crest proximally and the knee distally for extensile exposure
Lateral decubitus positioning risks include brachial plexus injury from axillary roll malposition, compartment syndrome of the dependent leg, and sciatic nerve stretch if the hip is over-flexed. Document all protective measures and check the dependent leg pulses and compartments regularly.
Alternative Positioning:
- Prone position on radiolucent table with chest rolls and knee flexion
- Useful when bilateral femoral surgery is planned or when posterior exposure is needed for both femurs
- Requires more assistant retraction because gravity does not assist vastus lateralis retraction
Surface Anatomy and Landmarks
Key Bony Landmarks:
- Greater trochanter - palpable laterally, marks proximal extent
- Lateral femoral condyle - palpable at knee, marks distal extent
- Linea aspera - not directly palpable but corresponds to the posterior midline of the thigh
- Gerdy's tubercle - lateral tibial flare, useful for distal extension orientation
Key Soft Tissue Landmarks:
- Iliotibial tract - palpable as a tight band along the lateral thigh when the knee is extended
- Biceps femoris tendon - palpable posteriorly at the knee, marks the posterior boundary
- Vastus lateralis - the muscle belly can be palpated and defines the anterior extent of dissection
Incision Planning:
- Longitudinal incision along the posterior border of the iliotibial tract
- Length: 15-25 cm depending on fracture location and plate length required
- Centred over the fracture site for direct access
- Can be extended proximally along the posterior border of the greater trochanter
- Can be extended distally along the lateral femoral condyle, staying anterior to the biceps femoris tendon
Surgical Technique
Step 1: Incision Make a longitudinal skin incision along the posterior border of the iliotibial tract, centred over the fracture or pathology. The length is determined by the required plate length, typically allowing three to four screw holes proximal and distal to the pathology. Extend the incision proximally or distally as needed for extensile exposure.
Step 2: Superficial Dissection Incise skin and subcutaneous tissue. Identify and preserve branches of the lateral cutaneous nerve of the thigh if encountered. Incise the fascia lata in line with the skin incision, exposing the iliotibial tract. The ITB is incised longitudinally along its posterior border, revealing the vastus lateralis muscle belly.
Step 3: Identify the Lateral Intermuscular Septum Palpate the firm fascial plane posterior to the vastus lateralis. This is the lateral intermuscular septum. Develop the plane between the posterior surface of vastus lateralis and the anterior surface of the septum using blunt dissection. The septum is continuous with the linea aspera.
Step 4: Reflect Vastus Lateralis Anteriorly Incise the lateral intermuscular septum longitudinally with scissors or diathermy. Reflect the vastus lateralis anteriorly using a Cobb elevator or periosteal elevator. The muscle is reflected off the septum and the linea aspera. Multiple perforating arteries will be encountered piercing the septum from posterior to anterior. Each must be ligated or clipped before division.
Step 5: Ligate Perforating Arteries Identify each perforating branch as it emerges through the septum. Isolate the vessel with a right-angled clamp, apply two ligatures or vascular clips, and divide between them. There are typically six to eight perforators along the length of the femur. Failure to ligate each vessel in continuity allows the vessel to retract into the posterior compartment, causing difficult-to-control haemorrhage.
Step 6: Subperiosteal Exposure of the Femur Once all perforators are controlled, continue subperiosteal elevation around the posterior, medial and lateral femoral cortex using a Cobb or periosteal elevator. Expose the linea aspera fully. The nutrient artery may cause bleeding at the mid-shaft - control with bone wax or diathermy. Circumferential exposure allows plate placement on the posterior or lateral surface as biomechanically indicated.
Structures at Risk
Six to eight perforating branches pierce the lateral intermuscular septum. Each must be ligated in continuity before division. If a vessel retracts into the posterior compartment, bleeding can be profuse and difficult to control. Always identify, isolate, and ligate each perforator before cutting.
Lies medial to the linea aspera in the proximal third. Must be identified and protected with a retractor before any medial or posterior femoral exposure. Injury causes foot drop, loss of knee flexion (if tibial division also affected), and sensory loss below the knee. Most injuries are from traction or compression rather than transection.
Enters the femur near the linea aspera in the middle third from posterior. Can cause brisk bleeding during subperiosteal elevation. Control with bone wax, diathermy, or ligation. The nutrient artery is a branch of the second perforating artery in most individuals.
Branches may cross the incision in the subcutaneous tissue. Injury causes numbness or dysaesthesia over the lateral thigh. Preserve if possible by careful subcutaneous dissection; most patients tolerate division without significant morbidity.
Originates from the linea aspera just medial to vastus lateralis. The muscle belly lies posterior to the intermuscular septum and is retracted posteriorly during the approach. Excessive medial retraction can injure the muscle or its sciatic nerve supply.
Lies anteromedially, protected by vastus medialis. Aggressive medial dissection around the femur can place the artery at risk. The artery is more vulnerable in the proximal and distal thirds where it lies closer to the femur.
Sciatic Nerve Injury Management:
- If nerve identified as damaged intra-operatively: primary repair if transected, or documentation and referral if neurapraxia suspected
- Post-operative foot drop: urgent EMG/NCS at 3 weeks, consider exploration if no recovery by 3-6 months
- Tendon transfer (tibialis posterior to dorsum) is the reconstructive option for permanent foot drop
Extensile Modifications
Proximal Extension:
- Extend incision along posterior border of greater trochanter
- Split gluteus maximus in line with fibres or retract posteriorly
- Identify and protect sciatic nerve medial to proximal femur
- Expose piriformis fossa and greater trochanter for subtrochanteric pathology
- Risk: superior gluteal vessels and sciatic nerve injury
Distal Extension:
- Extend along lateral femoral condyle anterior to biceps femoris
- Open knee joint capsule if intra-articular extension required
- Protect lateral collateral ligament and popliteus tendon posteriorly
- Can reach the lateral tibial plateau if needed (combined with tibial approaches)
Circumferential Exposure:
- The approach allows full circumferential access to the femur
- Medial cortex can be exposed by continuing subperiosteal elevation medially
- Dual plating (lateral and posterior or medial) is possible through the same incision
Combined Approaches:
- Posterolateral + anterolateral for dual-plating of comminuted fractures
- Posterolateral + medial for complex nonunion with bone loss
- Staged positioning may be required for combined anterior and posterior work
Complications
Intra-operative Complications:
- Prevention
- Ligate each vessel in continuity before division
- Management
- If retracted, pack and ligate at source; consider vascular surgery consult if uncontrolled
- Prevention
- Identify early in proximal third, protect with retractor
- Management
- Document, primary repair if transected, EMG follow-up
- Prevention
- Control with bone wax or diathermy at linea aspera
- Management
- Bone wax, diathermy, or ligation
- Prevention
- Plan incision length and extensile options pre-operatively
- Management
- Extend incision proximally or distally as required
Post-operative Complications:
- Incidence
- 1-3%
- Prevention
- Careful proximal dissection and retraction
- Treatment
- AFO, EMG at 3 weeks, explore if no recovery 3-6 months
- Incidence
- 2-5%
- Prevention
- Prophylactic antibiotics, meticulous haemostasis
- Treatment
- Irrigation and debridement, antibiotics, possible implant removal
- Incidence
- 5-10% (higher in revision cases)
- Prevention
- Bone graft, stable fixation, optimise biology
- Treatment
- Revision plating, bone grafting, consider nail conversion
- Incidence
- 5-10%
- Prevention
- Anatomic reduction, long plate with adequate working length
- Treatment
- Corrective osteotomy if symptomatic
- Incidence
- 3-8%
- Prevention
- Chemoprophylaxis, early mobilisation
- Treatment
- Anticoagulation, IVC filter if recurrent
- Incidence
- 10-20%
- Prevention
- Early ROM exercises
- Treatment
- Physiotherapy, manipulation under anaesthesia if refractory
Missed or inadequately ligated perforating arteries are the most common cause of intraoperative blood loss in this approach. Each perforator can bleed 50-100 mL/min if uncontrolled. Systematic ligation of all six to eight perforators before deep exposure prevents this complication. If a vessel retracts into the posterior compartment, the short head of biceps femoris must be partially detached to gain access for control.
Post-operative Care
Immediate Post-operative (0-48 hours):
- Neurovascular checks every 2 hours for first 24 hours, documenting sciatic nerve function (dorsiflexion, plantarflexion, sensation)
- Monitor drain output and wound for haematoma
- Elevate limb above heart level
- DVT prophylaxis (LMWH or aspirin per protocol)
Weight Bearing Protocol:
- Non-weight bearing or touch weight bearing for 6-12 weeks
- Progression based on radiographic healing and fracture stability
- Full weight bearing typically at 3-6 months for nonunion or comminuted fractures
Range of Motion:
- Early hip and knee ROM exercises as pain allows
- Goal: full knee flexion and extension by 6-8 weeks
- Quadriceps and hamstring strengthening once wound healed
Follow-up Schedule:
- 2 weeks: wound check, suture/staple removal
- 6 weeks: radiographs, assess healing, progress weight bearing if appropriate
- 3 months: radiographs, confirm early union
- 6 months: confirm union, full weight bearing
- 1 year: final clinical and radiographic review
DVT Prophylaxis:
- LMWH or aspirin per institutional protocol
- Duration: until mobile (minimum 4-6 weeks, longer for nonunion cases)
- Mechanical prophylaxis (IPC) while inpatient
Exam Viva Scenarios
Practise clinical reasoning and management decisions out loud
“A 38-year-old male presents with a femoral shaft nonunion 9 months after intramedullary nailing. CT shows a hypertrophic nonunion with broken distal locking screw. How would you approach revision surgery?”
“A 55-year-old female sustains a proximal-third femoral shaft fracture after a fall from standing height. CT shows a short oblique fracture with medial comminution extending to the subtrochanteric region. What approach would you use and what structures are at particular risk?”
“During a posterolateral approach to the femur for shaft plating, you encounter brisk bleeding from a vessel that retracts into the posterior compartment after being divided. How do you manage this situation?”