Fixation Of Posterior Malleolus Fractures: Literature Review And Technical Tips
Ankle fractures are one of the most common lower extremity injuries with an incidence of approximately 179 per 100,000 people a year.1 As life expectancy continues to rise and adults continue to remain active, there is an expectation that ankle fracture incidence will increase over the next few decades.2,3 The distal fibula is the most commonly injured segment (67 percent) of ankle fractures, followed by bimalleolar ankle fractures (25 percent), and trimalleolar ankle fractures (seven percent).1,4 However, posterior malleolus involvement may not be as uncommon as historically described.1,4 Literature shows the incidence of posterior malleolar fractures to be as high as 44 percent, often necessitating additional strategic planning for fixation of displaced articular fracture patterns.5,6 Though adequate posterior malleolar fracture reduction is critical for ankle biomechanical stability, controversy remains on the indications and methods of optimal fixation. Historically, the standard of care advocated for fixating posterior malleolar fractures if the injury involved approximately 25 percent of the articular surface. Recent studies challenge this paradigm, advocating for standardizing fixation of most posterior malleolar fractures.7,8,9
When And Why Is Fixation Necessary?
The recent push towards direct anatomic reduction of posterior malleolar fractures is secondary to the recognition of the intimate association between anatomic reduction of the posterior malleolus and stability of the syndesmosis. The syndesmotic joint is composed of the anterior inferior tibiofibular ligament, interosseous ligament and posterior inferior tibiofibular ligament (PITFL). The PITFL provides 42 percent of the strength of the syndesmosis.10 This ligament courses from the distal and lateral aspects of the posterior tibia to the posterior and distal aspects of the fibula. In a study by Haraguchi and colleagues, avulsion of the PITFL off the posterolateral aspect of the tibia was the most common (67 percent) morphology of posterior malleolus fractures.11 They also described a medial extension pattern (19 percent) and a small posterior shell pattern (14 percent).11 Reduction of the fibula may result in anatomic reduction of the posterior malleolus through ligamentotaxis, but without fixation of the fragment, the syndesmosis may be at greater risk of malreduction.12
Recent reports advocate for posterior fixation regardless of the amount of articular involvement, finding better outcomes in patients treated with either screw or plate fixation.13 As more attention and research is focused on the treatment of posterior malleolus fractures, we agree with Solan and team14 “fixation of the posterior malleolus therefore has several advantages: restoration of the articular surface of the tibia; accurate restoration of length of the fibula, helping to avoid malunion; and restoration of stability of the syndesmosis with fewer patients requiring its fixation.”14
Understanding The Direct Versus Indirect Approaches To Fixation
Approaches to reduction and fixation of posterior malleolar fractures include indirect reduction with percutaneous fixation or direct reduction via open posterolateral, posteromedial or lateral transmalleolar visualization. Indirect reduction is most commonly utilized with the patient in a supine position. Surgeons can obtain reduction via ligamentotaxis, usually following reduction of the fibula. Additionally, one can apply a large clamp, placed through the lateral fibular fracture incision on the posterior tibial fragment, to reduce the posterior malleolus fracture prior to temporary fixation. The senior author places a guidewire for a partially-threaded cannulated screw from the anterior tibia, perpendicular to the fracture fragment. He then drives the wire out the posterolateral ankle between the Achilles tendon and the peroneal tendons. This allows percutaneous placement of a screw from posterior to anterior in order to ensure unipolar thread purchase (blunt dissection ensures safe placement of the screw, avoiding soft tissue injury). Conversely, if the fracture fragment is large enough the screw can be placed from the anterior tibia to the posterior malleolus.
Direct reduction is preferrable for larger fragments, grossly unstable ankle fractures, comminuted fragments or for management of fragments that do not reduce with ligamentotaxis.15 The direct approach allows for direct visualization of the posterior fragment. However, fixating the medial malleolus through prone positioning is a challenge. The senior author prefers this approach in dislocation injuries that required prior closed reduction or external fixation. The direct approach allows the surgeon to have options for either screw or plate constructs. Shi and colleagues compared functional and radiographic outcomes for patients treated by direct reduction utilizing the posterolateral approach or indirect reduction utilizing percutaneous screw placement.6 They found that patients had higher functional outcomes and better-quality reduction when treated through direct reduction utilizing a posterolateral approach.6 Since joint congruency is critical to successful long term outcomes, direct visualization allows for better reduction and can provide superior results.
Determining The Best Fixation Construct
Surgeons can apply various fixation constructs for posterior malleolar fractures. Anterior to posterior (AP) screws are utilized with the indirect approach, whereas plates or screws are used for the direct approach. Posterolateral plating has shown superior scores on short musculoskeletal function assessment (SFMA-36) when compared to anterior to posterior screws.8 Anwar and colleagues compared biomechanical efficacy of anterior to posterior lag screws, posterior to anterior (PA) lag screws and a buttress plate for fixation in 3D posterior malleoli models through progressive loading.16 The AP screw group demonstrated the most displacement, followed by the PA screw group, with the posterior plate group having the least displacement.16 It demonstrated the biomechanical superiority of posterior plate construct fixation for posterior malleoli fractures. When performing the posterolateral approach, Erdem and colleagues found no difference in ankle range of motion or American Orthopaedic Foot and Ankle Society (AOFAS) scores when comparing fixation with lag screws to fixation with buttress plates.17 Overall, the posterior approach demonstrates better subjective outcomes and biomechanical stability compared to the anterior approach, highlighting its superior utility in posterior malleolus fracture patterns.
Outlining Our Preferred Technique For The Posterolateral Approach
We position the patient prone with a well-padded pneumatic thigh tourniquet. A standard posterolateral incision is made between the lateral border of the Achilles tendon and the medial border of the peroneal tendons. Next, we perform blunt dissection down through the subcutaneous tissue, taking care to identify and retract the sural nerve and lesser saphenous vein. The sural nerve typically crosses from medial to lateral at a distance of 9.8 cm from the Achilles tendon insertion.18 The authors find that retraction into the posterior medial soft tissue envelope is technically easier, but this varies depending on patient anatomy.
Next, we identify and incise the deep fascia in the interval between the flexor hallucis longus and peroneal muscles, which allows for mobilization of both muscles. Direct visualization of the fibula and posterior malleolus is also possible through this interval. A Cobb elevator bluntly frees the soft tissues about the fracture fragments and distal osseous structures. We then evacuate any hematoma and use a curette to remove any periosteum or debris interposed between the fracture fragments. Sharp periosteal dissection is necessary to expose the end of the fragments, especially on the tibial component as this can be scarred with a thicker periosteal layer than the fibula.
The senior author finds that utilizing large, blunted Hohmann retractors on the medial side of the tibia and lateral side of the fibula allows for adequate visualization. The authors often utilize a Hintermann distractor to distract impacted fibula fracture fragments. This may allow for distraction and reduction of the tibial component, which is then temporarily fixated using a K-wire within the surgical incision or percutaneously to avoid obstructing plate fixation. The Hintermann can also directly assist in reduction of the posterior malleolar fracture. Intraoperative fluoroscopy confirms reduction of both components. We then apply a posterior plate to the tibia and fibula utilizing proper AO technique.
Typically, plating of the posterior malleolus fragment takes place prior to that of the fibula. This allows optimal fluoroscopic visualization without interference from the fibular hardware. We drill the first hole above the superior aspect of the posterior malleolus fracture and insert the screw bicortically to ensure reduction of the fracture fragment and proper plate-to-bone interface. This plate acts in an anti-glide fashion, and we subsequently secure the plate with screws proximally. Screw placement is also possible through the fragment within the plate at the surgeon’s discretion. After confirming fixation with intraoperative fluoroscopy, we then fixate the fibula in the standard fashion with either a buttress or bridge plate. Use of lag screw fixation is per the surgeon’s discretion based on the fracture pattern.
If a medial malleolus fracture is present, the operative team may then transfer the patient from a prone to a supine position. Alternatively, one can simply bend the extremity at the knee while in a prone position before making the standard midline medial malleolus open incision. K-wires are then used reduce and temporarily fixate the fragment. The authors utilize two 4.0 screws or a hook or standard plate in comminuted fracture patterns (the latter placed with the patient in a supine position). It is important to perform a stress examination under intraoperative fluoroscopy to evaluate the syndesmosis. We do not universally employ syndesmotic fixation but may be necessary in many cases after rotation testing. If the syndesmosis is unstable, reduction is performed, and stabilization is accomplished via either screw or suture button fixation. This can be done through a small separate incision on the lateral aspect of the fibula. Layered closure is performed, and a non-weight bearing Jones posterior splint is applied.
In Conclusion
Although ankle fractures are common lower extremity injuries, the management and indications for treatment of posterior malleolus fractures still remains controversial. Recent research and trends shine a light on the need for proper evaluation of posterior malleolus fractures. The paramount importance of joint congruency through direct approaches, anatomic reduction and stable fixation allows for early mobilization and better prognostic outcomes.
Dr. Ali is a third-year resident at the Veteran Affairs Administration/Rubin Institute of Advanced Orthopedics in Baltimore.
Dr. Cates is a fellowship-trained foot and ankle surgeon with Hand and Microsurgery medical group in San Francisco, CA.
Dr. DuBois is a Limb Preservation and Deformity Correction Fellow in the Department of Orthopaedics at the University of Maryland School of Medicine in Baltimore.
Dr. Wynes is an Assistant Professor of Orthopaedics at the University of Maryland School of Medicine and the Director of the Limb Preservation and Deformity Correction Fellowship in Baltimore.
Dr. Brandão is a fellowship-trained foot and ankle surgeon and faculty with the Limb Preservation and Deformity Correction Fellowship in practice at The Centers for Advanced Orthopaedics, Orthopaedic Associates of Central Maryland Division, Catonsville, MD.
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