Comprehensive guide to the posterolateral approach to the tibia for posterolateral tibial plateau fractures - prone positioning, CPN protection, fibular head anatomy, and buttress plating for Orthopaedic exam
Reviewed by OrthoVellum Editorial Team
Orthopaedic clinicians and medical editors • Published by OrthoVellum Medical Education Team
Prone Position | CPN at Risk | Buttress Plating for PL Fragments
The posterolateral approach requires prone positioning. Cannot be done supine. Patient must be stable for prone position (no spinal injury, cardiovascular stability). Allows excellent visualization of the posterolateral tibial plateau.
The common peroneal nerve (CPN) wraps around the fibular neck 1-2cm distal to fibular head. Must be identified early and protected. Injury causes foot drop and severe permanent disability. Use gentle retraction, no metal retractors on nerve.
The posterolateral fragment displaces posteriorly under axial load. A buttress plate must be placed on the posterior surface to prevent re-displacement. Use contoured 3.5mm or locking plate. Screws directed anteriorly.
Bicondylar fractures (Schatzker V/VI) often require combined approaches. PL approach for posterolateral fragment, anterolateral or posteromedial for other columns. Plan for two-stage positioning if needed.
The posterolateral approach to the tibia provides access to posterolateral tibial plateau fragments, which occur in 15-20% of tibial plateau fractures and cannot be adequately visualized or stabilized through standard anterolateral approaches. Prone positioning is mandatory for true posterolateral access, with the incision placed lateral to the fibular head between peroneus longus and soleus. The common peroneal nerve (CPN) is the critical at-risk structure, wrapping around the fibular neck 1-2cm distal to the fibular head—it must be identified early and protected throughout. A buttress plate placed on the posterolateral tibial surface prevents posterior displacement under axial loading. Bicondylar fractures (Schatzker V/VI) often require combined approaches with staged positioning.
Memory Hook:POSTEROLAT approach - always PRONE with CPN protection!
Memory Hook:The CPN is the most important structure at risk - keep it SAFE!
Primary Indications:
Why This Approach is Chosen: The posterolateral tibial plateau is inaccessible from standard anterolateral approaches. The tibial plateau slopes posteriorly approximately 10 degrees, and posterolateral fragments displace posteriorly under axial load. Only a posterolateral approach allows direct buttress plating of this fragment.
Contraindications:
Alternative Approaches:
Posterolateral Approach to the Tibia provides direct access to the posterolateral tibial plateau for fractures that cannot be adequately visualized or fixed through standard anterolateral approaches.
Key Characteristics:
Why This Approach Matters:
Exam Relevance:
Bony Anatomy: The posterolateral tibial plateau forms part of the lateral tibial condyle. The tibial plateau has an inherent 7-10 degree posterior slope. The posterolateral corner is the least supported region, making it vulnerable to split-depression fractures with axial loading combined with valgus stress.
Muscular Layers:
| Layer | Muscle | Nerve Supply | Action |
|---|---|---|---|
| Superficial | Biceps femoris | Sciatic (tibial + CPN) | Knee flexion, lateral rotation |
| Lateral compartment | Peroneus longus | Superficial peroneal | Plantar flexion, eversion |
| Lateral compartment | Peroneus brevis | Superficial peroneal | Eversion |
| Posterior superficial | Gastrocnemius (lateral head) | Tibial | Knee flexion, plantarflexion |
| Posterior deep | Soleus | Tibial | Plantarflexion |
Neurovascular Anatomy:
| Structure | Location | Clinical Significance |
|---|---|---|
| Common peroneal nerve | Wraps around fibular neck 1-2cm distal to head | MOST IMPORTANT - injury causes foot drop |
| Superficial peroneal nerve | Between peroneus longus and brevis | Supplies lateral compartment muscles |
| Deep peroneal nerve | Deep in anterior compartment | Not at risk in this approach |
| Peroneal artery | Deep in posterior compartment | May be encountered with deep dissection |
| Anterior tibial artery | Through interosseous membrane | Protected by anterior compartment |
Three-Column Classification of Tibial Plateau: Understanding which column is fractured guides approach selection:
Deep Internervous Plane:
Superficial Dissection: There is no true internervous plane in the superficial dissection. The approach passes through the lateral compartment which is supplied entirely by the superficial peroneal nerve. However, the muscles are retracted rather than divided, minimizing denervation risk.
Internervous Plane Nuance
Unlike hip approaches where the internervous plane is between two major muscles, the tibial posterolateral approach relies on inter-compartmental dissection between the lateral and posterior compartments. The key is to stay anterior to the soleus while protecting the CPN which runs between the two heads of peroneus longus.
Structures at Risk in Each Layer:
| Layer | Structure | Protection Strategy |
|---|---|---|
| Superficial | Common peroneal nerve | Identify early, tape sling, no metal retractors |
| Deep | Peroneal vessels | Ligate small branches, preserve major vessels |
| Deep | Popliteal vessels | Should not be encountered if dissection plane correct |
| Articular | Lateral meniscus | Incise capsule carefully, protect during reduction |
Position: Prone on Radiolucent Table
Pre-positioning Checklist:
Positioning Details:
Prone positioning carries risks including facial swelling, brachial plexus injury, and compartment syndrome of the thigh. Limit operative time, ensure adequate padding, and document all protective measures taken.
Alternative Positioning:
Key Bony Landmarks:
Key Soft Tissue Landmarks:
Incision Planning:
| Column | Location | Approach Required | Key Structure at Risk |
|---|---|---|---|
| Lateral | Anterolateral plateau | Anterolateral approach | Peroneal nerve branches |
| Medial | Anteromedial plateau | Anteromedial approach | Saphenous nerve/vein |
| Posterolateral | Posterior-lateral plateau | POSTEROLATERAL approach | Common Peroneal Nerve |
| Posteromedial | Posterior-medial plateau | Posteromedial approach | Saphenous nerve |
Neurovascular Assessment (Critical):
Soft Tissue Assessment:
Plain Radiographs (Initial):
CT Scan (Essential for ALL tibial plateau fractures):
CT is Mandatory
Every tibial plateau fracture being considered for operative treatment requires CT scanning. Posterolateral fragments are commonly missed on plain radiographs and change the surgical approach.
Indications (Rare for PL fragments):
Protocol:
Surgical Indications:
Approach Selection Based on CT:
Step 1: Incision
Make a longitudinal incision starting at lateral joint line and extending distally along posterior border of fibula. Length 8-12cm depending on fracture extent.
Step 2: Superficial Dissection
Incise skin and subcutaneous tissue. Identify and protect the lateral sural cutaneous nerve if encountered. Incise fascia over lateral compartment.
Step 3: CPN Identification (CRITICAL)
The CPN emerges from behind the biceps femoris tendon. It wraps around the fibular neck 1-2cm distal to the fibular head. Identify it early before any retraction. Carefully trace its course. Place vessel loop or tape sling for gentle retraction.
Step 4: Deep Dissection
Develop plane between peroneus longus (anterior) and soleus (posterior). Retract peroneus longus anteriorly (CPN goes with it - protected). Retract soleus and gastrocnemius posteriorly. Subperiosteal dissection exposes posterolateral tibial plateau.
THE most important structure at risk. Wraps around fibular neck 1-2cm distal to fibular head. Injury causes foot drop (loss of ankle dorsiflexion and toe extension). Prevention: early identification, gentle handling, vessel loop protection, no metal retractors.
The peroneal artery and veins run deep in the posterior compartment. Usually not encountered with correct dissection plane. If damaged, ligate small branches; major vessel injury requires repair.
Branch of popliteal artery at the joint line. May be encountered during capsular incision. Ligate if bleeding - does not require repair.
At risk during capsular incision and articular surface visualization. Protect during reduction maneuvers. Peripheral tears can be repaired; body tears may need partial meniscectomy.
CPN Injury Management:
Fibular Osteotomy:
Proximal Extension:
Distal Extension:
Combined Approaches: For bicondylar fractures (Schatzker V/VI), often need:
Intra-operative Complications:
| Complication | Prevention | Management |
|---|---|---|
| CPN injury | Early ID, gentle retraction, no metal retractors | Document, EMG at 3 weeks, explore if no recovery |
| Articular malreduction | Good visualization, fluoroscopy, CT if concern | Accept less than 2mm step-off; redo if more |
| Peroneal vessel injury | Stay in correct plane | Ligate small branches, repair major vessels |
| Intra-articular hardware | Careful screw length measurement, fluoroscopy | Remove and replace with shorter screw |
Post-operative Complications:
| Complication | Incidence | Prevention | Treatment |
|---|---|---|---|
| CPN palsy | 3-5% | Careful technique | Observe, AFO, explore if no recovery 3 months |
| Infection | 2-5% | Antibiotics, soft tissue rest | Irrigation and debridement, antibiotic suppression or removal |
| Post-traumatic OA | 20-40% | Anatomic reduction | Weight loss, analgesia, eventual TKA |
| Nonunion/malunion | Under 5% | Bone graft, stable fixation | Revision ORIF or TKA |
| DVT/PE | 2-5% | Chemoprophylaxis, early mobilization | Anticoagulation |
CPN Injury Statistics
CPN injury in tibial plateau surgery ranges from 3-20% depending on approach and complexity. Posterolateral approaches have higher risk than anterolateral. Most injuries are neurapraxia that recover, but permanent foot drop occurs in 1-3% and is a devastating complication.
Immediate Post-operative:
Weight Bearing Protocol:
Range of Motion:
Follow-up Schedule:
DVT Prophylaxis:
Critical Monitoring:
Positioning and Immobilization:
Good Prognostic Factors:
Poor Prognostic Factors:
Position Question
Q: What position is required for the posterolateral approach to the tibia? A: Prone position is required. The posterolateral tibial plateau cannot be adequately exposed in the supine position. Lateral decubitus (affected side up) is an alternative that allows combination with other approaches.
Nerve at Risk Question
Q: What is the most important structure at risk during the posterolateral approach? A: The common peroneal nerve (CPN) is the most critical structure. It wraps around the fibular neck 1-2cm distal to the fibular head and is at risk during retraction. Injury causes foot drop.
Internervous Plane Question
Q: What is the deep internervous plane in the posterolateral approach? A: Between peroneus longus (superficial peroneal nerve) and soleus (tibial nerve). This inter-compartmental plane allows access to the posterolateral tibia without denervating muscle.
Buttress Plate Question
Q: Why is a buttress plate required for posterolateral tibial plateau fractures? A: The posterolateral fragment displaces posteriorly under axial load. A buttress plate on the posterior tibial surface prevents this displacement. An anterolateral plate cannot provide this buttress function.
CT Importance Question
Q: Why is CT scanning essential for tibial plateau fractures? A: Posterolateral fragments are commonly missed on plain radiographs. CT defines the fracture morphology, identifies all fragments, and allows preoperative planning of approach selection. Up to 20% of tibial plateau fractures have posterolateral fragments requiring direct fixation.
Combined Approach Question
Q: When would you use combined approaches for tibial plateau fractures? A: Bicondylar fractures (Schatzker V/VI) often require combined approaches. Use posterolateral approach for PL fragments plus anteromedial or anterolateral for other columns. May require staged positioning.
Tibial plateau fractures are commonly managed at major trauma centers throughout Australia. The three-column concept is widely adopted, and CT scanning is now standard for operative planning. Australian trauma surgeons increasingly utilize posterior approaches when posterolateral or posteromedial fragments are identified.
The Royal Australasian College of Surgeons (RACS) trauma committees emphasize the importance of preoperative planning and approach selection based on CT findings. Early soft tissue assessment is critical given the high-energy mechanism in many Australian cases (motor vehicle accidents, agricultural injuries).
Consent in Australia should include discussion of CPN injury risk (3-5%), infection risk (2-5%), post-traumatic arthritis (20-40%), and the possibility of requiring total knee replacement in the future if significant articular cartilage damage has occurred.
Orthopaedic Relevance
For the Orthopaedic Operative Surgery station, you must be able to describe the posterolateral approach systematically: prone positioning, CPN identification and protection, the internervous plane, and buttress plate placement. Know the evidence for CT scanning of all tibial plateau fractures and when combined approaches are needed.
Practice these scenarios to excel in your viva examination
"A 45-year-old presents after a motorcycle accident with a tibial plateau fracture. CT shows a posterolateral split-depression fragment. How would you approach this?"
Assessment: Full trauma assessment following ATLS principles. Detailed history of mechanism. Clinical examination for knee stability, neurovascular status (especially ankle dorsiflexion), and soft tissue condition. Imaging with plain radiographs (AP, lateral, oblique) followed by CT with 3D reconstruction.
Surgical Planning: CT confirms posterolateral fragment - requires posterolateral approach as cannot buttress from anterolateral. Patient must be suitable for prone positioning. Assess soft tissue - wait for wrinkle test if blistering present.
Surgical Approach: Prone position on radiolucent table. Longitudinal incision posterior to fibula. Identify and protect CPN early - vessel loop. Develop plane between peroneus longus (anteriorly) and soleus (posteriorly). Expose posterolateral tibial plateau.
Reduction and Fixation: Elevate depressed fragments with bone tamp. Reduce split component with clamps. Bone graft metaphyseal void. Apply buttress plate to posterior tibial surface with screws directed anteriorly. Confirm reduction on fluoroscopy - accept less than 2mm step-off.
Post-operative: Document CPN function. NWB for 6-12 weeks. Early ROM. DVT prophylaxis.
"During a posterolateral approach, you notice the patient develops weak ankle dorsiflexion post-operatively. What is your assessment and management?"
Immediate Assessment: Full motor examination - test ankle dorsiflexion (deep peroneal nerve), toe extension (deep peroneal), and foot eversion (superficial peroneal). Sensory examination - first web space (deep peroneal) and lateral leg/dorsum of foot (superficial peroneal). Document findings accurately.
Exclude Other Causes: Remove dressings - check for constriction. Assess for compartment syndrome (pain with passive stretch, tense compartments). Review intra-operative events - was nerve visualized, any inadvertent injury noted?
Most Likely Diagnosis: Common peroneal nerve neurapraxia from traction or compression during retraction. CPN is particularly vulnerable as it wraps around the fibular neck with limited mobility.
Initial Management: Provide ankle-foot orthosis (AFO) to maintain ankle in neutral and prevent equinus contracture. Counsel patient about prognosis - most neurapraxias recover within 3-6 months. Document thoroughly including discussion with patient.
Follow-up Plan: EMG/NCS at 3 weeks post-injury (allows time for Wallerian degeneration if axonal injury). If no clinical or EMG recovery by 3 months, consider nerve exploration. Tendon transfers (tibialis posterior to dorsum) are an option for permanent foot drop.
"You are planning surgery for a Schatzker VI tibial plateau fracture with significant posteromedial and posterolateral fragments. How would you approach this?"
CT Analysis: Use three-column concept to analyze fracture. Identify: lateral column involvement, medial column involvement, and posterior column (subdivided into posteromedial and posterolateral). This Schatzker VI with PM and PL fragments requires at least two approaches.
Approach Selection: Posterolateral approach for PL fragment (prone, lateral to fibula, buttress plate posteriorly). Posteromedial approach for PM fragment (prone or supine with leg externally rotated, medial to gastrocnemius, buttress plate posteromedially). If significant anterior column involvement, add anterolateral approach.
Positioning Strategy - Option 1: Start prone - allows access to both PL and PM fragments through separate incisions. Can address both posterior columns in one position. May need to flip to supine if anterolateral approach required.
Positioning Strategy - Option 2: Lateral decubitus with affected side up - allows access to PM and PL without repositioning, and can also access anterolateral. Some surgeons prefer this for combined approaches.
Sequence: Generally fix posterior columns first as they are more difficult to access. Then flip to supine for anterior work if needed. Bone graft all metaphyseal voids. Aim for less than 2mm articular step-off on all columns.
"What are the key differences between the posterolateral and posteromedial approaches to the tibia?"
Posterolateral Approach: Targets the posterolateral tibial plateau. Positioning: prone or lateral decubitus with affected side up. Incision: posterior to fibula. Internervous plane: between peroneus longus (superficial peroneal nerve) and soleus (tibial nerve). Key structure at risk: COMMON PERONEAL NERVE - injury causes foot drop (motor loss).
Posteromedial Approach: Targets the posteromedial tibial plateau. Positioning: prone, lateral, or supine with leg externally rotated (knee flexed). Incision: posteromedial leg, along medial border of gastrocnemius. Internervous plane: between medial gastrocnemius (tibial nerve) and semimembranosus/pes anserinus (tibial nerve branches). Key structure at risk: SAPHENOUS NERVE - sensory only.
Safety Comparison: The posteromedial approach is generally considered safer because the nerve at risk (saphenous) is sensory only, whereas the posterolateral approach risks the CPN which causes significant motor deficit (foot drop) if injured.
Common Principle: Both approaches require buttress plate placement on the posterior tibial surface to prevent posterior fragment displacement under axial loading.
When to Use Both: Bicondylar fractures (Schatzker V/VI) often have both PM and PL fragments requiring both approaches for complete fixation.
"A patient has a posterolateral tibial plateau fragment but significant anterior soft tissue swelling and blistering. How does this affect your surgical planning?"
Significance of Soft Tissue Injury: Blistering and significant swelling indicate high-energy injury mechanism. The anteromedial tibial skin is at highest risk (subcutaneous bone, poor vascularity). Operating through compromised skin dramatically increases infection risk (up to 20-30% with poor soft tissue timing).
Soft Tissue Assessment: Examine the entire circumference of the knee and proximal tibia. Differentiate serous blisters (intact epidermis) from hemorrhagic blisters (deeper injury). The posterolateral skin over the fibula may be spared even with significant anteromedial swelling.
Timing Decision: Apply the wrinkle test - gently compress skin to assess for wrinkling which indicates adequate dermal blood flow for healing. Typically need to wait 7-14 days for soft tissue recovery. Wait until swelling resolved, blisters re-epithelialized, and wrinkle test positive.
Interim Management: If fracture unstable, apply spanning external fixator (temporary knee-spanning construct). Elevate limb above heart level. Splint for comfort. Serial neurovascular checks. Counsel patient about delayed definitive surgery and reasons.
Staged Surgery Option: If posterolateral skin is healthy but anterior skin compromised, may proceed with posterolateral approach first to address PL fragment, then delay anterolateral approach until anterior soft tissue recovery. This allows partial stabilization while awaiting optimal conditions for complete fixation.
High-Yield Exam Summary