Rockwood Adults CH64

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CHAPTER 64 • Ankle Fractures

of the tip of the malleolus in 20% of patients 163 : Blunt dissec- tion through fat is recommended. The periosteum should be elevated from the fracture margins only enough to allow an anatomical reduction. Strategic perforations may be made in the anterior fascia to allow the placement of reduction clamps without excessive dissection. Occasionally, the incision may be curved anteriorly at its distal extent to allow an arthrotomy and inspection of the articular surface of the ankle joint, or for access to the tubercle of Chaput. Alternatively, for posterior plating of the fibula, the incision is aligned with the poste- rior border of the fibula and the peroneal tendons are retracted away from the posterior surface of the bone. This more poste- rior location of the incision prevents satisfactory access to the AITFL and ankle joint, and will not allow fixation of a Chaput tubercle fracture. POSTEROLATERAL APPROACH This approach allows access to posterior malleolar fractures, and to the posterior aspect of the fibula and is performed with the patient prone. The longitudinal incision is made midway between the posterior border of the lateral malleolus, and the lateral border of the Achilles tendon. Blunt dissection through fat avoids injury to the sural nerve and exposes the deep fas- cia of the leg which is incised sharply. The internervous plane is between the peroneal tendons (superficial peroneal nerve) which are retracted laterally, and the FHL (tibial nerve). The FHL has muscular origins from the fibula and tibia even at this level, and should be elevated and retracted medially to expose the posterior malleolus. Classification of ankle fractures may be undertaken on the basis of anatomy, injury mechanics, or stability. While mul- tiple classification systems have been developed, only a few remain in frequent use. Pott provided the first known detailed description of ankle fractures in 1758, 308 prior to the discovery of medical radiographs in 1895, but the classification system based on the number of fractured malleoli that is commonly attributed to him may have been first described by Cooper. 70 Fractures can be classified as unimalleolar, bimalleolar, or trimalleolar based on the combined fractures of the lateral, medial, and posterior malleoli. As the number of fractured malleoli increases the prognosis worsens. 46 Despite, or per- haps because of, the simplicity of the system it remains in widespread use. Danis–Weber and AO Classifications An alternative classification developed by Danis 82 and modified by Weber, 407 describes the injury based on the location of the lateral malleolar fracture. Fractures may be classified as A, B, ASSESSMENT OF ANKLE FRACTURES CLASSIFICATION OF ANKLE FRACTURES Pott Classification

(which forms the tarsal tunnel) and their constant relationship from anterior to posterior is classically remembered according to the pneumonic Tom, Dick, and very nervous Harry: T ibia- lis posterior, flexor d igitorum, the tibialis posterior a rtery and v ein, tibial n erve, and flexor h allucis longus. Superficially in the subcutaneous plane, the great saphenous vein and nerve pass immediately anterior to the medial malleolus where the vein can be conveniently exposed for emergency vascular access, or more inconveniently damaged during the surgical approach to the medial malleolus.

SURGICAL APPROACHES FOR ANKLE FRACTURES

MEDIAL APPROACH The medial approach allows access to medial malleolar fractures and exploits an internervous interval between the dorsiflexors (deep peroneal nerve) and invertors and plantarflexors (poste- rior tibial nerve) of the ankle. Two variations exist: A straight longitudinal incision directly over the malleolus is often sim- plest and allows easy access to the fracture and the start point for screw insertion at the malleolar tip. Alternatively, a curvilin- ear incision may be made further anteriorly over the front of the medial malleolus to allow visualization of the medial corner of the plafond, curving posteriorly distal to the malleolus to allow screw or plate placement. In either case, the great saphenous vein and nerve are at risk in the subcutaneous fat as they pass just anterior to the malleolus. POSTEROMEDIAL APPROACH Although not frequently used, the posteromedial incision allows access to the posterior malleolus and can be particu- larly helpful where the fracture plane results in a posteromedial distal fragment. The incision is made longitudinally half way between the medial malleolus and the Achilles tendon. Blunt dissection will expose the fascia overlying the flexor tendons and this can be incised longitudinally well away from the back of the medial malleolus. The safest interval is found between the flexor hallicus longus (FHL) tendon (which can be iden- tified by the muscle fibers which insert into it at this level) and the peroneal tendons lateral to it. Retracting FHL medially will expose the back of the ankle joint while protecting the neurovascular bundle. Access to the malleolus more medially requires the identification and careful retraction laterally of the neurovascular bundle. LATERAL APPROACH The line of the incision is made directly over the subcutaneous border of the fibula, the length and center of the incision being dictated by the level and type of fracture present. The principle structure at risk is the superficial peroneal nerve as it pierces the deep fascia and lies in the subcutaneous fat. It is increasingly vulnerable as one moves proximally from the fibular tip, but its course is variable and a substantial branch lies within 5 cm