Prone Position | Sural Nerve at Risk | Posterior Malleolus and Pilon Access
Surgical Imaging
The posterolateral approach to the ankle requires prone positioning. Supine positioning does not allow direct access to the posterior malleolus or posterior tibial plafond. Patient must be stable for prone (no cervical spine injury, cardiovascular stability). Allows true posterior visualisation and buttress plating.
The sural nerve courses with the short saphenous vein in the subcutaneous plane midway between the lateral malleolus and Achilles tendon. It must be identified and protected. Injury causes lateral foot numbness and painful neuroma. Use gentle retraction and vessel loop if needed.
The flexor hallucis longus tendon and muscle belly are the key deep landmarks. The posterior tibial neurovascular bundle lies medial to FHL. All dissection stays lateral to FHL to avoid the bundle. The muscle belly of FHL indicates the safe plane.
Posterior malleolar fragments greater than 25 percent of the plafond or with greater than 2 mm step-off require fixation. Buttress plating from posterior prevents posterior talar subluxation. Indirect reduction via ligamentotaxis is often possible but direct visualisation improves accuracy.
High-energy pilon fractures may have large posterior fragments extending into the metaphysis. The posterolateral approach allows access to these fragments for reduction and buttress plating. Combined approaches are frequently required for complete reconstruction.
Trimalleolar fractures often require combined posterolateral and lateral approaches. The posterolateral incision can be used for both posterior malleolus and fibular plating through the same interval or with slight modification. Plan skin bridges carefully.
At a Glance
The posterolateral approach to the ankle provides direct access to the posterior malleolus, posterior tibial plafond and distal fibula in the prone position. It is indicated for posterior malleolar fractures involving greater than 25 percent of the articular surface, posterior pilon fragments, and combined fibular and posterior fixation in trimalleolar injuries. The incision is placed midway between the lateral malleolus and the Achilles tendon. Superficially the sural nerve and short saphenous vein are at risk. The deep interval lies between the peroneal tendons laterally and the flexor hallucis longus medially. The posterior tibial neurovascular bundle lies medial to FHL and must be protected by staying lateral to the FHL tendon. This approach allows direct buttress plating of the posterior malleolus, which is critical for maintaining ankle stability and preventing posterior talar subluxation. The approach is extensile proximally for posterior pilon variants and can be combined with lateral fibular plating without repositioning.
POSTEROLATPOSTEROLATERAL ANKLE - Surgical Steps
Hook:POSTEROLAT approach - always PRONE with sural and FHL protection!
DANGERDANGER STRUCTURES - Layer by Layer
Hook:Remember DANGER structures layer by layer to avoid complications!
FHL SAFEFHL - The Critical Deep Landmark
Hook:FHL is your friend - stay lateral to it and the bundle is safe!
Surgical Technique
Patient Positioning
Position: Prone on Radiolucent Table
Pre-positioning Checklist:
- Confirm patient stable for prone position (anesthetic assessment, no cervical spine injury, cardiovascular stability)
- Padding for all pressure points including face, chest, pelvis, patellae, ankles and toes
- Arms positioned safely with shoulders abducted less than 90 degrees and elbows flexed
- Radiolucent table confirmed with full C-arm access from both medial and lateral sides
- Tourniquet applied high on the thigh if planned - consider tourniquet-free surgery to assess vascular status
Positioning Details:
- Prone position with chest rolls or Wilson frame for thoracic support
- Affected ankle positioned with slight plantarflexion over a padded bolster to relax the posterior structures
- Foot overhanging the end of the table to allow free dorsiflexion and plantarflexion during reduction maneuvers
- Contralateral leg well padded and supported to prevent pressure injury
- Consider slight knee flexion to relax the gastrocnemius-soleus complex and improve posterior access
Prone positioning is mandatory for direct posterior access to the ankle. Some surgeons prefer lateral decubitus with the affected side up when combining with anterolateral approaches, but true prone gives the best visualisation of the posterior malleolus and tibial plafond. Always document positioning and all protective measures taken.
Alternative Positioning:
- Lateral decubitus with affected side up allows combined posterolateral and anterolateral access without repositioning
- Some exposure is sacrificed compared with true prone but may be appropriate for selected trimalleolar patterns
Exam Viva Scenarios
Practise clinical reasoning and management decisions out loud
“A 42-year-old presents with a trimalleolar ankle fracture after a fall from height. CT shows a posterior malleolar fragment involving 35 percent of the plafond with 3 mm step-off. How would you approach the posterior fragment?”
“A 35-year-old polytrauma patient has a high-energy pilon fracture with a large posterior fragment extending into the metaphysis. CT shows the fragment involves 40 percent of the plafond. How would you plan surgical access?”
“Following a posterolateral approach for posterior malleolar fixation, the patient reports numbness on the lateral border of the foot and a painful tingling sensation. What is your assessment and management?”