Prone Position | Two Intervals | Posterior Malleolus Buttress
Surgical Imaging
The posterior approaches to the distal tibia require prone positioning. Supine positioning does not allow direct visualization or buttress plate application on the posterior surface. Patient must be medically stable for prone position with appropriate padding of all pressure points including face, chest, pelvis and knees.
The posterior tibial neurovascular bundle (artery, veins and tibial nerve) travels in the deep posterior compartment between the tibialis posterior and flexor digitorum longus. It is the primary structure at risk in the posteromedial interval and must be identified and protected with vessel loops before deep dissection proceeds.
Posterior malleolar and pilon fragments displace posteriorly and proximally under the pull of the Achilles and plantarflexion forces. A buttress (antiglide) plate placed on the posterior tibial surface is required to resist this displacement. Screws are directed anteriorly from the plate.
The posterolateral interval (between peroneal tendons and flexor hallucis longus) provides access to posterolateral fragments and the fibula without directly crossing the neurovascular bundle. The posteromedial interval (between TP/FDL and the NV bundle) is used for posteromedial fragments but requires careful protection of the posterior tibial vessels and nerve.
Fragments involving greater than 25 percent of the articular surface or with greater than 2 mm step-off or gap generally require direct reduction and buttress fixation. Smaller fragments may be treated with percutaneous anterior-to-posterior screws but carry higher risk of malreduction.
Complex pilon fractures (AO 43-C) and trimalleolar ankle fractures with large posterior malleolar fragments frequently require combined approaches. Posterior approaches are performed first in the prone position, followed by anterior or lateral approaches after repositioning if needed.
At a Glance
The posterior approach to the distal tibia provides direct access to the posterior malleolus and posterior distal tibial plafond for fractures that cannot be adequately reduced or stabilized through standard lateral or anteromedial approaches. Approximately 7-44 percent of ankle fractures involve the posterior malleolus, with higher rates in pilon fractures. The approach is performed in the prone position to allow gravity-assisted retraction of the posterior compartment muscles and direct visualization of the posterior surface. Two primary intervals are used: the posterolateral interval between the peroneal tendons and flexor hallucis longus (FHL) for posterolateral fragments, and the posteromedial interval between the tibialis posterior/flexor digitorum longus and the posterior tibial neurovascular bundle for posteromedial fragments. The posterior tibial neurovascular bundle is the critical deep structure at risk. A buttress plate applied to the posterior tibial surface prevents posterior displacement of the fragment under axial and plantarflexion loading. This approach is essential for anatomic reduction of large posterior malleolar fragments in trimalleolar ankle fractures and pilon fractures.
POSTLATPOSTEROLATERAL INTERVAL - Key Steps
Hook:POSTLAT - Prone, Oblique incision, Sural protection, Then lateral to FHL, Artery ligation, Tibial exposure, NV protection, Apply plate
PTNV SAFEPOSTEROMEDIAL INTERVAL - Danger Structures
Hook:PTNV SAFE - Posterior Tibial NeuroVascular protection is essential in posteromedial work
BUTTRESSBUTTRESS PLATE PRINCIPLES
Hook:BUTTRESS - Buttress plate, Under-contour, Three screws, Trajectory anterior, Reconstruction plate, Ensure joint safe, Reduction check, Supplement graft
Surgical Technique and Approach Details
Position: Prone on Radiolucent Table
Pre-positioning Checklist:
- Confirm patient stable for prone position (no cervical spine injury, cardiovascular stability)
- Padding for face, chest rolls, pelvis, patellae, and ankles
- Arms abducted less than 90 degrees with padding
- Radiolucent table verified for C-arm access
- Tourniquet applied high on thigh if planned
Positioning Details:
- Prone with chest rolls or Wilson frame
- Affected knee flexed 20-30 degrees over a radiolucent bolster (relaxes gastrocnemius-Achilles complex)
- Foot overhanging end of table or supported on a padded rest
- Contralateral hip slightly elevated if needed for C-arm clearance
Surface Landmarks:
- Medial and lateral malleoli
- Achilles tendon midline posteriorly
- Fibular tip and posterior border of fibula (for posterolateral interval)
- Posteromedial border of distal tibia (for posteromedial interval)
- Course of posterior tibial artery palpable behind medial malleolus
Additional Positioning Notes: The prone flexed-knee position relaxes the posterior compartment musculature and allows gravity to assist with retraction. This position also facilitates fluoroscopic imaging in the lateral and mortise projections without interference from the contralateral limb. Ensure the C-arm can rotate freely from the lateral side of the table. If the patient cannot tolerate prone positioning due to pulmonary or spinal concerns, a lateral decubitus position with the affected side up can be used as an alternative, although visualization is slightly compromised.
Viva Scenarios - Posterior Distal Tibia Approach
Practise clinical reasoning and management decisions out loud
“A 35-year-old male sustains a trimalleolar ankle fracture after a fall from height. CT shows a posterior malleolar fragment involving 35 percent of the articular surface with 3 mm of step-off. What approach would you use and why?”
“A 42-year-old female has an AO 43-C3 pilon fracture with a large posterolateral and posteromedial fragment after a motor vehicle collision. CT confirms both posterior columns involved. How do you plan the surgical approach and positioning?”
“During a posteromedial approach for a posteromedial pilon fragment, you encounter brisk bleeding and loss of palpable posterior tibial pulse after placing a retractor. What is your immediate management?”