How to perform a posterolateral ankle approach
Source
Surgeon:
Lasse Rämö (orthopedic surgeon)
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Summary
Focus: Posterolateral ankle approach for access to the posterior tibia, Volkmann fragment, posterior malleolus, and distal fibula.
Key elements: Patient positioning, landmark-based incision, careful protection of the sural nerve, exposure through the peroneal muscles and flexor hallucis longus, fracture reduction and fixation, closure, aftercare, pitfalls, and complications.
Indications and Clinical Context
General
Medical experts: Lasse Rämö (orthopedic surgeon), Thomas Schlenzka (orthopedic surgeon), Mikael Åkerback (orthopedic surgeon)
Name of Procedure: Posterolateral ankle approach
Goal of Operation
To ensure safe and adequate access to the fracture site, as well as to restore the anatomy of the ankle mortise and the function of the ankle joint by fixating the fracture.
Problem
A fracture leading to a deformed or unstable ankle joint.
Diagnosis
Bi- or trimalleolar fracture (ICD-10: S82.8)
Short Pathophysiological Description
The malleoli of tibia and fibula hold the talus stable against the distal surface of tibia, at the talocrural joint. These three structures—the malleoli and the distal articular surface of tibia (=the tibial plafond)—form the ankle mortise. Ankle syndesmosis is a ligament complex binding distal tibia and fibula together, ensuring the stability of the ankle mortise, crucial for its function. Some ankle fractures deform the ankle mortise, or destabilize it, compromising joint functionality. In addition, fracture displacements at the joint surfaces may lead to post-traumatic arthritis. These types of fractures often require surgical treatment.
Presented on our platform are three approaches that should provide adequate exposure for the majority of common malleolar fractures, either isolated medial/lateral, bimalleolar, or trimalleolar. The “third” malleolus stands for the posterior aspect of the tibial plafond, referred to as the posterior malleolus.
Generally, isolated fractures of the lateral malleolus and distal fibula can be approached via the lateral approach, fractures of the posterior malleolus via the posterolateral approach, which also allows exposure of distal fibula, and fractures of the medial malleolus via the medial approach.
Key Anatomical Structures
Tibia
Fibula
Talus
Syndesmosis
Flexor hallucis longus muscle (FHL)
Peroneal muscles
Sural nerve
Tibial nerve
Small saphenous vein
Posterior tibial artery
Step-by-Step Technique
Patient Positioning, Anesthesia, and Preparation
For the posterolateral approach, the patient can be either in prone or lateral position. Prone position allows access to the lateral, medial, and posterior aspects of the ankle simultaneously, without the need to turn the patient.
When choosing the posterolateral approach and a fracture of the medial malleolus also needs fixation, keep in mind that flexion of the knee is necessary in order to gain an adequate view of the anteromedial joint surface. Optionally, the patient can be turned into supine position once you have addressed the posterior and lateral fractures.
Both spinal and general anesthesia are applicable.
Landmarks
Locate, visualize, and palpate the lateral edge of the Achilles tendon and the posterior margin of the distal and palpable segment of fibula.
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Skin Incision
Make a 10 cm long skin incision halfway between these landmarks. Some surgeons prefer to incise slightly closer to the Achilles (calcaneal) tendon.
Advance Through Subcutis
With this approach, you can expose both the posterolateral aspect of tibia (the Volkmann fragment) and the fibula.
First, address the posterior tibia. Hardware material used in the fixation of other associated fractures could disturb evaluating the reduction of a Volkmann fragment on lateral X-rays. Therefore, it is recommendable to start here.
Advance through the subcutaneous tissue carefully. The sural nerve and the small saphenous vein come close to the operation site here, and there could be potential variations of the sural nerve. Look out for any nerve structures and avoid damaging them.
Expose the Fracture Site
Under subcutis, cut through the crural fascia in line with the skin incision to reveal the peroneal muscles laterally and the flexor hallucis longus muscle (FHL) beneath the deep posterior compartment fascia.
Similarly, cut open the deeper fascial layer and carefully retract the peroneal muscles laterally, in order to reveal FHL.
Detach the distal portion of FHL from fibula and retract it medially to expose the posterior aspect of tibia.
During fracture surgery, you would now reduce and fix the posterior tibial fragment, described below, and only then advance to exposing a potential fibular fracture, which can also be fixed from this incision.
Access the Fibula
Accessing the fibula from the posterolateral incision should be straightforward. Retracting the peroneal muscles, longus and brevis, medially should expose the posterior aspect of the fibula.
Fracture Reduction and Fixation
In fracture surgery, you would ideally start with reduction and fixation of the Volkmann fragment. However, sometimes proceeding in this order is not possible.
Operating at the posterior aspect of the tibial plafond, the posterior malleolus, keep in mind the tibial nerve, the posterior tibial artery, the flexor digitorum tendons, and the tibialis posterior tendon are all running at the medial aspect of the area.
As for other fractures, start with removing any debris interfering with correct fracture reduction, while keeping periosteal stripping to a minimum.
The Volkmann fragment is attached to the posterior joint capsule. Dorsiflexion of the ankle should pull the fragment towards its correct position and facilitate reduction.
To stabilize the reduction before definitive fixation, you can use either large reduction forceps or temporary K-wires.
Using large reduction forceps requires an additional small incision anteriorly, slightly above the joint level, just medial to the tibialis anterior tendon. This positioning of the forceps should be safe with regards to the anterior neurovascular structures.
When the reduction is satisfactory, perform definitive fixation. This may require adjustments to the temporary fixation, e.g. changing the location of the K-wires, in order to allow proper positioning of the hardware used for definitive fixation, commonly performed with plates and screws.
Wound Closure
The peroneal muscles and tendons should cover the plate placed in the fibula.
The flexor hallucis longus (FHL muscle) usually covers the posterior plate. The deep posterior compartment should be closed if possible.
For closure of the peroneal compartment fascia, use absorbable braided sutures, size 0, e.g. Vicryl. Be careful not to take a suture bite of the sural nerve.
For closure of the subcutis, use continuous sutures, e.g. 2-0 Vicryl. Again, beware of the sural nerve.
Skin can be closed with surgical staples or sutures.
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Piftalls and Complications
Pitfalls
A skin incision made too deep or too posterior may cause injury to the sural nerve, the course of which in the posterior ankle may vary. It is advisable to make the skin incision at the midline of the lateral edge of the Achilles tendon and the posterior edge of the fibula.
Inadequate Knowledge of Anatomical Variations
The course of the sural nerve may vary; therefore, it must be noted when advancing through the subcutis. The sural nerve can also appear as two separate branches at ankle level.
Careless Tissue Handling
When performing the skin incision, it should be noted that the sural nerve may run very superficially in the subcutis, so the incision should only be skin-deep.
In the posterior tibial surface region, the course of the tendons running nearby, posterior tibial and long digital flexor, the tibial nerve, and the posterior tibial vessels should be noted, and caution exercised in tissue handling. Usually, however, these structures remain protected medially.
On the lateral side, retractor position should be verified to avoid compression of the peroneal artery, which runs in the deep posterior compartment medial to the peroneal muscle compartment.
Unnecessary tension of the skin or other tissues by retractors, for example, should be avoided.
Complications
Injury to the Sural Nerve
A skin incision made too deep or incautious advancing in the subcutis may result in sural nerve injury. Moreover, when closing the peroneal compartment fascia and the subcutis, caution should be exercised not to take a suture bite of the sural nerve. A sural nerve injury may result in neuralgia or paraesthesia in the lateral foot. Due to anatomical variation, the sural nerve may occur as two separate branches at the ankle level.
Injury to the Peroneal Artery
The peroneal artery runs in the deep posterior compartment, medial to the lateral compartment of the peroneal muscles. When approaching the posterolateral tibial area, retractor position should be verified to avoid compression of the peroneal artery.
When accessing the posterior fibula, the safer route is to approach from the lateral side of the peroneal muscles. If operating without a tourniquet, the vessel can usually be identified by its pulsatile flow, although it may be of small calibre in some patients. In approximately 5% of patients, the peroneal artery is the dominant arterial supply to the foot; this anatomical variant warrants particular consideration when positioning posterior implants.
Injury to the Tibial Nerve and/or the Posterior Tibial Vessels
The tibial nerve and the posterior tibial artery and vein form the neurovascular bundle running in the deep posterior compartment and may be injured if sufficient caution is not exercised when advancing towards the posterior malleolus. For this reason, the FHL muscle is separated from the tibial surface laterally and transferred to the medial side, in which case the tibial nerve and the posterior tibial artery and vein are protected medially.
Injury to the Peroneal Tendons
If injured during the operation, the peroneal tendons should be sutured. The complication should also be noted in the instructions for post-operative mobilization.
Injury to the Small Saphenous Vein
The small saphenous vein runs along the sural nerve. Injury to the small saphenous vein should be avoided but, if injured, it can be ligated without any adverse effects on the patient.
Aftercare
General Guidelines
Casting, weight-bearing, and other rehabilitation guidelines depend largely on the type of fracture treated.
FAQ
What patient positions can be used for the posterolateral ankle approach?
For the posterolateral approach, the patient can be either in prone or lateral position. Prone position allows access to the lateral, medial, and posterior aspects of the ankle simultaneously, without the need to turn the patient.
What structures can be exposed through this approach?
With this approach, both the posterolateral aspect of tibia (the Volkmann fragment) and the fibula can be exposed.
Why is the posterior tibia addressed first in fracture surgery?
Hardware material used in the fixation of other associated fractures could disturb evaluating the reduction of a Volkmann fragment on lateral X-rays. Therefore, it is recommendable to start there.
Which structures are at risk when advancing through the subcutis?
The sural nerve and the small saphenous vein come close to the operation site, and there may be potential variations of the sural nerve.
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