High Yield Overview

POSTEROLATERAL APPROACH TO THE TIBIA

Prone Position | CPN at Risk | Buttress Plating for PL Fragments

Critical Posterolateral Approach Exam Points

Prone Position Essential

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.

CPN Protection Critical

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.

Buttress Plate Biomechanics

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.

Combined Approach Often Needed

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.

At a Glance

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.

Mnemonic

POSTEROLATPRONE POSTEROLATERAL - Surgical Steps

Memory Hook:POSTEROLAT approach - always PRONE with CPN protection!

Mnemonic

CPN SAFECPN - Protection Principles

Memory Hook:The CPN is the most important structure at risk - keep it SAFE!

Indications and Approach Selection

Primary Indications:

Posterolateral tibial plateau fractures (isolated PL column)
Schatzker II fractures with significant posterolateral split-depression
Bicondylar fractures (V/VI) requiring posterolateral column fixation
Revision surgery for posterolateral fragment malunion

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:

Medical unfitness for prone position (spinal cord injury, recent MI)
Active infection of skin over approach
Severe soft tissue compromise posteriorly (may need delay)
Isolated anterior/medial fractures (use appropriate alternative approach)

Alternative Approaches:

Anterolateral approach: For lateral plateau split/depression without PL fragment
Posteromedial approach: For medial plateau or posteromedial fragments
Extended lateral with fibular osteotomy: When combined AL and PL access needed
Anteromedial approach: For medial plateau fractures

Overview

Definition

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:

Requires prone or lateral decubitus positioning
Common peroneal nerve (CPN) is the critical at-risk structure
Enables buttress plating of posteriorly displacing fragments
Often used in combination with other approaches for complex fractures

Clinical Significance

Why This Approach Matters:

15-20% of tibial plateau fractures involve posterolateral fragments
PL fragments missed on plain radiographs in up to 20% of cases
Cannot buttress PL fragments from anterolateral approach
Malreduction leads to posterior subluxation and early arthritis

Exam Relevance:

High-yield surgical approach for Operative Surgery station
CPN protection is a classic examiner question

Anatomy

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:

Lateral column: Anterolateral approach
Medial column: Anteromedial or posteromedial approach
Posterior column (PL + PM): Posterolateral and/or posteromedial approach

Internervous Plane

Deep Internervous Plane:

Between: Peroneus longus (superficial peroneal nerve) laterally and Soleus (tibial nerve) medially/posteriorly
Clinical relevance: This is the safe interval between the two muscle groups innervated by different nerves

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

Positioning and Patient Setup

Position: Prone on Radiolucent Table

Pre-positioning Checklist:

Confirm patient stable for prone position (anesthetic assessment)
Padding for all pressure points (face, chest, pelvis, patella, ankles)
Arms positioned safely (abducted less than 90 degrees, padded)
Radiolucent table confirmed
C-arm access verified from lateral aspect

Positioning Details:

Prone position with chest rolls or Wilson frame
Affected knee slightly flexed over a bolster (relaxes CPN)
Foot overhanging end of table or supported
Tourniquet applied high on thigh if planned (consider tourniquet-free surgery)

Prone Position Risks

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:

Lateral decubitus can be used with the affected side UP
Allows combination with anteromedial or anterolateral approaches without repositioning
Some exposure is sacrificed compared to true prone positioning

Surface Anatomy and Landmarks

Key Bony Landmarks:

Fibular head - palpable prominence lateral to knee
Biceps femoris tendon - inserts onto fibular head
Lateral tibial plateau - can palpate lateral joint line
Gerdy's tubercle - anterolateral tibial insertion of ITB

Key Soft Tissue Landmarks:

Common peroneal nerve - can often be palpated wrapping around fibular neck
Popliteal fossa - defines posterior boundary
Lateral gastrocnemius head - marks posterior musculature

Incision Planning:

Longitudinal incision behind the fibular head extending distally
Length: 8-12cm depending on exposure required
Stays anterior to the biceps tendon proximally
Curves around fibular head following the lateral fibular border

Classification

Three-Column Classification (Luo)

Column-Based Approach Selection

Schatzker Classification Relevance

Type II: Lateral split-depression - may have PL component
Type V: Bicondylar - often requires combined approaches
Type VI: Bicondylar with metaphyseal-diaphyseal dissociation - frequently has posterior fragments

Clinical Assessment

History

Mechanism: High-energy (MVA, fall from height) vs low-energy (elderly, osteoporotic)
Timing of injury: Affects soft tissue planning
Associated injuries: Polytrauma assessment
Medical fitness: Suitability for prone positioning

Examination

Neurovascular Assessment (Critical):

Dorsalis pedis and posterior tibial pulses: Document bilateral comparison
Ankle dorsiflexion: Tests CPN function pre-operatively (baseline)
Toe extension: Deep peroneal nerve function
First web space sensation: Deep peroneal sensory

Soft Tissue Assessment:

Swelling: Degree and circumference
Blistering: Serous vs hemorrhagic (hemorrhagic = deeper injury)
Wrinkle test: Positive indicates safe for surgery
Skin condition: Abrasions, lacerations, degloving

Investigations

Imaging Algorithm

Plain Radiographs (Initial):

AP knee - assess overall alignment, fracture pattern
Lateral knee - identify posterior fragment displacement
Oblique views (internal and external rotation) - improve fragment visualization

CT Scan (Essential for ALL tibial plateau fractures):

Axial, coronal, sagittal reconstructions
3D reconstruction for surgical planning
Identifies posterolateral fragments missed in up to 20% on plain films
Quantifies articular depression and fragment size

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.

Management

Non-Operative Management

Indications (Rare for PL fragments):

Non-displaced or minimally displaced (less than 2mm step-off)
Low functional demand patient
Medical contraindications to surgery

Protocol:

Hinged knee brace
Non-weight bearing 6-8 weeks
Early ROM exercises
Serial radiographs to monitor displacement

Operative Management (Standard for PL Fragments)

Surgical Indications:

Articular step-off greater than 2mm
Condylar widening greater than 5mm
Any instability in extension
Associated ligamentous injury requiring repair

Approach Selection Based on CT:

Isolated PL fragment → Posterolateral approach
PL + PM fragments → Combined posterior approaches (prone)
PL + lateral column → Extended lateral or staged approaches
Bicondylar (Schatzker V/VI) → Multiple approaches, staged positioning

Surgical Technique

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.

Structures at Risk

Common Peroneal Nerve

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.

Peroneal Vessels

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.

Lateral Inferior Geniculate Artery

Branch of popliteal artery at the joint line. May be encountered during capsular incision. Ligate if bleeding - does not require repair.

Lateral Meniscus

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:

If nerve identified as damaged intra-operatively: primary repair if transected
If neurapraxia suspected: observe, document, follow up closely
Post-operative foot drop: urgent EMG/NCS at 3 weeks, consider exploration if no recovery by 3 months

Extensile Modifications

Fibular Osteotomy:

Indication: When standard PL approach does not provide adequate exposure
Technique: Oblique osteotomy of fibular neck from posterolateral to anteromedial
CPN protection: Must identify and protect nerve BEFORE osteotomy
Fixation: Repair with small plate or tension band at end of case
Complication: Fibular nonunion (5%), CPN injury (higher risk)

Proximal Extension:

Can extend incision proximally along biceps femoris
Allows access to the posterolateral femoral condyle if needed
CPN becomes more superficial proximally - increased risk

Distal Extension:

Extend distally along fibula for access to tibial diaphysis
Useful for fractures extending into shaft
Stay in same intermuscular plane

Combined Approaches: For bicondylar fractures (Schatzker V/VI), often need:

Posterolateral approach (for PL fragment)
Plus anteromedial approach (for PM fragment)
Or anterolateral (for lateral plateau split)

Complications

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.

Post-operative Care

Immediate Post-operative:

Neurovascular check documenting ankle dorsiflexion (CPN function)
Wound inspection
Knee immobilizer or hinged brace for comfort
Elevate limb above heart level

Weight Bearing Protocol:

Non-weight bearing or touch weight bearing for 6-12 weeks
Progression based on fracture healing and surgeon preference
Crutches or walker required

Range of Motion:

CPM or early ROM exercises as pain allows
Goal: 0-90 degrees by 6 weeks
No resistance exercises until fracture healed

Follow-up Schedule:

2 weeks: Wound check, suture/staple removal
6 weeks: Radiographs, assess healing, progress WB if appropriate
12 weeks: Radiographs, confirm union, progress to full WB
6 months: Final radiographs, functional assessment
1 year: Clinical and radiographic review

DVT Prophylaxis:

LMWH or aspirin per institutional protocol
Duration: Until mobile (minimum 2 weeks, often 4-6 weeks)

Postoperative Care Protocol

Immediate Post-Operative (0-48 hours)

Critical Monitoring:

Neurovascular check every 2 hours for first 24 hours
Document ankle dorsiflexion (CPN function) - compare to pre-op baseline
Monitor for compartment syndrome (pain, pallor, pulselessness, paresthesia)
Wound inspection at 24-48 hours

Positioning and Immobilization:

Elevate limb above heart level
Knee immobilizer or hinged brace locked in extension
Ice packs around knee (not directly on surgical site)

Weight Bearing Protocol

Weeks 0-6: Non-weight bearing or touch weight bearing
Weeks 6-10: Partial weight bearing (25-50%)
Weeks 10-12: Progressive to full weight bearing
Progression criteria: Radiographic evidence of healing, no pain with weight bearing

Outcomes

Functional Outcomes

Good Prognostic Factors:

Anatomic articular reduction (less than 2mm step-off)
Young age and low energy mechanism
Isolated PL fragment (not bicondylar)
No associated ligament injury
Early ROM and rehabilitation

Poor Prognostic Factors:

Articular step-off greater than 2mm
Bicondylar fractures (Schatzker V/VI)
Associated ligament/meniscal injury
High-energy mechanism
Delayed surgery due to soft tissue compromise

Evidence Base

Posterolateral Approach Without Fibular Osteotomy

Frosch et al • Archives of Orthopaedic and Trauma Surgery (2010)

Clinical Implication: Supports the non-osteotomy approach as primary technique for most posterolateral tibial plateau fractures

Articular Reduction Quality and Outcomes

Rademakers et al • Journal of Bone and Joint Surgery (2007)

Clinical Implication: Emphasizes importance of anatomic reduction - less than 2mm step-off is the goal for optimal outcomes

Three-Column Classification

Luo et al • Bone and Joint Journal (2010)

Clinical Implication: Foundation for understanding which approach or approaches are needed for each fracture pattern

CT Detection of Posterolateral Fragments

Bhattacharyya et al • Journal of Orthopaedic Trauma (2006)

Clinical Implication: CT scanning mandatory for preoperative planning of all tibial plateau fractures to avoid missed fragments

CPN Injury in Tibial Plateau Surgery

Elsoe et al • Injury (2015)

Clinical Implication: Consent must include discussion of CPN injury risk - examiners will ask about this complication

MCQ Practice Points

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.

Australian Context

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.

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Posterolateral Tibial Plateau Fracture

EXAMINER

"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?"

VIVA SCENARIOChallenging

Scenario 2: Post-operative CPN Palsy

EXAMINER

"During a posterolateral approach, you notice the patient develops weak ankle dorsiflexion post-operatively. What is your assessment and management?"

VIVA SCENARIOChallenging

Scenario 3: Bicondylar Tibial Plateau Fracture Planning

EXAMINER

"You are planning surgery for a Schatzker VI tibial plateau fracture with significant posteromedial and posterolateral fragments. How would you approach this?"

VIVA SCENARIOStandard

Scenario 4: Posterolateral vs Posteromedial Approach

EXAMINER

"What are the key differences between the posterolateral and posteromedial approaches to the tibia?"

VIVA SCENARIOChallenging

Scenario 5: Soft Tissue Compromise

EXAMINER

"A patient has a posterolateral tibial plateau fragment but significant anterior soft tissue swelling and blistering. How does this affect your surgical planning?"