Posterior Approach to the Distal Femur and Popliteal Fossa

What it exposes. The posterior approach gives direct access to the posterior aspect of the distal femoral condyles, the posterior capsule of the knee and the posterior cruciate ligament (PCL) tibial insertion, and the contents of the popliteal fossa — the tibial nerve, the common peroneal nerve (CPN) and the popliteal artery and vein. Primary indications. - Posterior coronal (Hoffa) fractures of the distal femoral condyles

• Large bony avulsions of the PCL from the posterior tibia
• Popliteal fossa masses — tumours, Baker cysts and vascular lesions
• Exploration of a tibial nerve or CPN injury, traumatic or iatrogenic
• Popliteal artery injury or aneurysm requiring direct vascular control
• Combined posterior distal femur fractures with posterior column involvement Why this approach is chosen. The posterior distal femur and popliteal fossa cannot be adequately visualised or instrumented from standard anterior or lateral approaches. Hoffa fragments displace posteriorly and need direct buttress plating from behind; anterior-to-posterior lag screws alone are biomechanically inferior. PCL avulsions are best reduced and fixed under direct vision through a posterior window. The popliteal neurovascular bundle lies in a confined space that demands a dedicated posterior exposure for safe exploration and repair. Contraindications. Medical instability precluding prone positioning; active infection in the popliteal region; severe soft-tissue compromise or scarring; and isolated anterior or lateral pathology better addressed by other approaches. Alternative approaches. A lateral approach for a lateral condyle fracture without posterior extension; a medial approach for a medial condyle fracture; a standard anterior approach for most supracondylar and intercondylar fractures; and combined medial and lateral approaches for complex bicondylar patterns. Position and landmarks. Place the patient prone on a radiolucent table after confirming cardiovascular and spinal stability. Pad the face, chest, pelvis, patellae and feet meticulously; position the arms abducted less than 90 degrees; apply a high-thigh tourniquet before turning if planned; and confirm C-arm access from both sides. Flex the knee 20-30 degrees over a radiolucent bolster to relax the neurovascular structures, and let the foot hang freely. Lateral decubitus (affected side up) is an alternative when combined anterior and posterior access is anticipated, but true prone gives superior visualisation of the fossa. Palpable landmarks are the medial and lateral femoral epicondyles, the adductor tubercle, the fibular head (for distal reference) and the joint line. The key soft-tissue landmarks are the biceps femoris tendon laterally (the CPN lies just medial to it), the semitendinosus and gracilis tendons medially, and the popliteal crease. Mark a lazy-S incision (typically 12-18 cm) with the transverse limb crossing the popliteal crease obliquely, the proximal limb along the border of biceps femoris or semitendinosus, and the distal limb following the interval between the two gastrocnemius heads.

The popliteal fossa is a diamond-shaped space: superomedially bounded by semitendinosus and semimembranosus, superolaterally by biceps femoris, and inferomedially and inferolaterally by the two heads of gastrocnemius, with plantaris lying between the medial head and the tibial nerve. The tibial nerve enters from the sciatic bifurcation and courses distally in the midline, giving off the medial sural cutaneous nerve — the surgical landmark. The CPN runs laterally along the medial border of the biceps femoris tendon and winds around the fibular neck. The popliteal artery lies deep and slightly medial to the tibial nerve, with the vein between the artery and nerve. The internervous plane. There is no true internervous plane superficially. The safe deep plane is the interval between the medial and lateral heads of gastrocnemius — both supplied by the tibial nerve, so no nerve crosses it. The popliteal neurovascular bundle lies medial and deep to this interval and is protected by keeping the medial gastrocnemius head between the dissection and the bundle.

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The danger structures live in three layers — subcutaneous, fascial and deep muscular — and each is protected by a specific manoeuvre.

Extensile options. Extend proximally along the lateral or medial intermuscular septum to expose the posterior femur up to the mid-diaphysis, protecting the sciatic nerve in the proximal wound. Extend distally along the chosen gastrocnemius head into the calf to reach the proximal tibia and the soleus and flexor hallucis longus origins for more extensive vascular or nerve work. For complex distal femur fractures, combine a posterior approach for the Hoffa fragment with a lateral approach for the supracondylar component and a medial approach for the medial condyle — this may need staged turning or a lateral decubitus position. Closure. Irrigate copiously and secure meticulous haemostasis, especially around the geniculate vessels. Place a suction drain in the popliteal fossa through a separate stab incision away from the main wound. Close the posterior capsule with absorbable suture if it was opened, allow the gastrocnemius interval to fall together, close the popliteal fascia loosely, and close the subcutaneous tissue and skin in layers — taking particular care at the corners of the transverse lazy-S limb to avoid skin necrosis. Obtain AP and lateral radiographs of the distal femur and knee, and a CT if articular reduction quality is uncertain. Complications. Intra-operative risks are tibial or CPN injury from excessive retraction, popliteal vessel injury during deep dissection, an inadvertent capsular tear or PCL damage, and inadequate exposure leading to malreduction of a Hoffa fragment. Post-operative risks are wound dehiscence or necrosis at the transverse limb, infection (higher risk in popliteal fossa surgery), stiffness or flexion contracture from a poorly designed incision, transient neurovascular deficit, and deep vein thrombosis related to prone positioning and popliteal manipulation. Meticulous padding, early nerve identification with vessel-loop protection, staying in the correct gastrocnemius interval and careful layered closure reduce all of these. Aftercare. Perform neurovascular observations hourly for the first 6 hours then 2-hourly, documenting ankle dorsiflexion, plantarflexion and sensation on the sole and dorsum of the foot. Immobilise the knee in extension in a brace, elevate the limb above heart level and start DVT prophylaxis in theatre. Protect with touch or non-weight-bearing for 6-12 weeks depending on fixation stability, begin early passive range of motion once the wound is stable, and review at 2 weeks (wound check), 6 weeks (radiographs), 3 months (CT if articular healing is uncertain) and 6-12 months (final functional assessment).

• Hoffa fragment fixation — reduce the posterior coronal fragment under direct vision and apply a buttress plate (a 3.5 mm T-plate or anatomic posterior distal femur plate) to the posterior surface with screws directed anteriorly; bone-graft any metaphyseal void.
• Distal femur ORIF — when a Hoffa fragment coexists with supracondylar or intercondylar fractures, fix the posterior fragment through this approach first, then add standard lateral or medial plating through separate incisions.
• PCL bony avulsion — reduce the avulsed tibial fragment anatomically and fix with one or two cannulated screws with washers, a small buttress plate for a large fragment, or suture anchors; repair the posterior capsule afterwards.
• Popliteal fossa exploration — expose and control the popliteal artery proximally and distally for vascular injury; decompress or repair the tibial or CPN under magnification for nerve injury; and dissect a mass free while protecting all neurovascular structures, excising a Baker cyst completely including its joint communication.