Addressing Posterior Malleolar Ankle Fractures

Posterior malleolar ankle fractures can be a challenge to reduce and fixate. Accordingly, these authors provide compelling case examples and emphasize the use of computed tomography and a posterior approach to facilitate optimal outcomes.

The on-call foot and ankle surgeon is likely to see a variety of fractures at the local emergency room. Due to different mechanisms of ankle injury/fracture variability, our management varies from immobilization to complex reconstruction. Posterior malleolar fractures have always provided a more difficult reduction than their medial and lateral counterparts because of the location. Over the years, many surgeons have shied away from the open approach and have opted for indirect fixation due to concern for neurovascular compromise and difficult dissection.

   In addition to reviewing current trends, such as indirect visualization, which we believe are often inappropriate, we will take a closer look at the posterior approach as well as effective imaging to assist the surgeon.

   There is no true consensus in the foot and ankle literature on whether to fixate posterior malleolar fractures. Numerous papers have quoted displacement of 20 to 30 percent of the joint surface as justifying fixation with these percentages being based on the lateral radiograph. We believe there are many morphologies of posterior malleolar fractures that can have a tremendous impact on joint kinematics.

   Due to a large variety of fracture patterns, we advocate the use of computed tomography (CT). This imaging modality not only allows the surgeon to clearly see how many fragments are present but helps determine where the major fragment is located. The major fracture fragment will allow the surgeon to decide between a posterior medial or posterior lateral approach.

Pertinent Pearls On Technique

We favor using radiographs after obtaining reduction and putting the patient in a splint (no need to keep the ankle dislocated for imaging). If there is a suspicion of a posterior malleolar fracture, order a CT scan to evaluate the size and location of the main fracture fragments. This will help determine the surgical approach. In most circumstances, we favor immediate operative management. Surgery may be delayed if the patient needs further medical evaluation.

   Regardless of fracture fragment positioning, as long as a posterior malleolar fracture is present, we ensure that the patient is in a prone position. This allows for proper visualization of the fracture.

   Medial approach. With the main fracture fragment medially located, as determined with radiographs and CT, place the incision just posterior to the medial malleolus. Although the medial aspect of the ankle contains many vital structures, there are “safe zones” that allow clear visualization into the ankle joint. Carry dissection down to the posterior tibial tendon. This creates an anatomic plane that allows one to retract the posterior tibial tendon anteriorly and ensures that one can retract the neurovascular bundle posteriorly. With these structures protected, the surgeon can carry the incision directly to the distal tibia. You can clearly visualize the fracture fragment at this point.

   Lateral approach. When the main fracture fragment is laterally based, center the incision at the interval between the peroneal tendons and Achilles tendon. Within the superficial dissection, one must locate and carefully retract the sural nerve. Visualize the flexor hallucis muscle belly and elevate it from the interosseous membrane. This will allow the surgeon to visualize the posterior malleolar fracture.

What You Should Know About Reduction And Fixation

Surgeons can most often achieve reduction utilizing a simplified technique by dorsiflexing the ankle. Many times, this will push the fragment out to length. With regard to fixation, the surgeon can utilize a variety of options.

   Our fixation method relies on AO principles. After reducing the fracture, place temporary fixation utilizing K-wires. One can achieve permanent fixation with an under-contoured, one-third tubular plate in an antiglide fashion. The reason for utilizing an antiglide, under-contoured plate is that it will push the posterior malleolar fracture into the body of the tibia at the fracture apex. In past reductions, we have noted that bulkier plates, although pre-contoured, do not provide the reduction and have been “bulkier” than a simple one-third tubular plate.

   The one caveat to posterior reduction is that the surgeon must be aware that an under-contoured plate can cause the fragment to displace distally if one does not temporarily fixate it.

   Most posterior malleolar fractures have concomitant injuries such as lateral or medial malleolar fractures. We have found that fixating these fractures with the patient in the prone position enables the surgeon to achieve excellent reduction. With regard to distal fibular fractures, posterior plating (the anti-glide technique) has been far superior biomechanically to lateral plating in our experience. After fixating the posterior malleolus, surgeons can turn their attention to the fibula through the posterior lateral incision. With regard to the medial malleolus, one can easily use the posteromedial incision to fixate the malleolus utilizing screws or plating techniques.

Key Insights On Effective Postoperative Care

With a majority of ankle fractures, the treating physician can allow protective weightbearing once the skin has healed. Unlike medial and lateral malleolar fractures, posterior malleolar fractures can be displaced with direct axial compression. That is why our postoperative protocol includes six weeks of non-weightbearing. Once we feel the skin has healed, we begin open kinetic chain range of motion.

   We have also started to employ postoperative CT scans to ensure that the articular surface of the tibia has healed. Once the patient has achieved radiographic healing, he or she can begin weightbearing and continue physical therapy for approximately three months.

Case Study One: When A Patient Presents With A Dislocated Trimalleolar Ankle Fracture

A 29-year-old female presented to the emergency room with a dislocated trimalleolar ankle fracture. There was a visible tenting in the anterior skin of her ankle. The treating physician performed an immediate reduction of the fracture and the lateral radiograph revealed what appeared to be a small posterior malleolar fracture. A CT scan exposed a large posterior fragment with bony fragments interlocking on the lateral aspect.

   The patient went to the OR that night. With the patient in the prone position, surgeons reduced the posterior malleolar fracture from a posterior lateral approach. Surgeons fixated the lateral malleolus fracture with an anti-glide plate and fixated the medial side with standard screw fixation. The ankle was stressed and there was noted syndesmotic instability. The surgeon made a small stab incision over the lateral malleolus and the use of a lateral plate allowed for syndesmosis reduction with two screws.

   Postoperative care involved immobilization for four weeks followed by two more weeks in a non-weightbearing protective boot. This allowed the patient to begin range of motion. At six weeks, a follow-up CT scan showed that the posterior malleolus was healed and helped ensure the patient could bear weight without disastrous consequences. The patient returned to physical activities at six months.

Case Study Two: When The CT Reveals A Large Posterior Medial Fragment And Associated Distal Fibular Comminution

A female in her 30s suffered a slip in a rural area. She presented to an outpatient clinic where she learned that she suffered an ankle fracture and would need operative treatment. The patient presented at our clinic 36 hours later with the ankle still dislocated. In the clinic setting, surgeons reduced the fracture and splinted her. Her X-rays showed a dislocated trimalleolar fracture. A CT determined the best operative approach. The CT revealed a large posterior medial fragment with associated distal fibular comminution. Physicians delayed surgery for five days in order to allow for the swelling to diminish.

   When the patient went to surgery, there were no associated fracture blisters and the skin was intact. Due to the presence of the large posterior medial fragment, surgeons decided to utilize a posterior medial approach in conjunction with a standard lateral approach.

   For surgery, the patient was in the prone position with a thigh tourniquet. Surgeons fixated the fibula first, utilizing a contoured posterior plate because of the significant comminution. After obtaining anatomic length, they created a posterior medial incision. Creating exposure through a surgical plane between the posterior tibial tendon and flexor digitorum longus allowed for direct visualization of the distal tibia. Throughout the medial exposure, one should take care to retract the neurovascular bundle. A two-hole plate (utilized in antiglide fashion) secured the main posterior fragment. Once the main posterior fragment was stable, the surgeons stabilized the posterior medial fragments utilizing a combination of screws and plates. They admitted the patient for pain control and therapy for 48 hours.

   The patient was discharged on low molecular weight heparin for deep vein thrombosis prophylaxis and oxycodone for pain control. The patient was in a non-weightbearing cast for five weeks. At week six, the patient started wearing a walking boot and got instructions on range of motion exercises. At week eight, the patient transitioned to regular shoes with an ankle brace. At the 12-week mark, the patient was able to ambulate in a standard shoe and resume activities.

Case Study Three: When A Patient’s Fall Leads To A Posterior Malleolar Fracture With A Distal Fibular Fracture

A police officer in her early 40s fell down the stairs while at work. The patient immediately went to the emergency room where X-rays revealed a posterior malleolar fracture along with a distal fibular fracture. On the lateral radiograph, the posterior malleolar fracture appeared to comprise 20 percent of the articular surface. A CT scan revealed a fracture fragment that involved a large posterior fracture including a significant portion of the tibial plafond. The main fracture fragment was lateral in relation to the tibial plafond.

   The patient went to surgery five hours following the injury. Utilizing the CT imaging, the surgeons decided to use a posterior lateral approach. The patient was in the prone position for the surgical exposure. The surgeons made the incision within the interval between the Achilles tendon and the peroneal tendons. During the exposure, they encountered the sural nerve and carefully retracted it. They mobilized and fixated the posterior malleolar fracture with a one-third tubular plate in an antiglide fashion and two 3.5 mm interfragmentary screws. Surgeons provided fixation of the fibular fracture through the same incision with a solitary plate in antiglide fashion. (It should be noted that fixation for the posterior malleolus occurred first with this posterior lateral approach. If the surgeon fixes the fibular first, it can be difficult to reduce the posterior fracture fragment.)

   Postoperative care included six weeks of non-weightbearing. She began active range of motion at week four (only dorsiflexion and plantarflexion). At week six, we obtained a CT scan to ensure union. At four months, the patient began light jogging and was back to full active duty at six months. There was some residual numbness along the course of the sural nerve for eight months following surgery. These symptoms began to resolve after a year.

In Conclusion

Ankle fractures are a common injury and present in a variety of forms. The common mistake made by foot and ankle surgeons is treating these injuries in a dogmatic fashion. Posterior malleolar fractures are challenging. Even within this fracture group, there are a variety of subclasses. Surgeons have established loose criteria for fixing these fractures and it is likely that many of these fractures are left untreated.

   Historically, surgeons have employed radiographic imaging to help determine treatment for posterior malleolar fractures. It is no longer acceptable to treat these fractures subjectively. In an era of evidence-based medicine, we feel that posterior malleolar fractures require a new “standard of care.”

   Similar to how we approach calcaneal fractures, we conclude that CT imaging is a necessity in surgical planning for the reduction of these fractures. Too often, the surgeon will fixate the posterior malleolar fracture with an indirect anterior to posterior technique. Although this reduction technique is easier, it leads to poor alignment. Surgeons can achieve anatomic reduction of these complicated fractures if they employ basic principles: proper imaging, complete understanding of surgical anatomy and a solid understanding of internal fixation principles.

   Surgeons will always debate different approaches for fracture reduction. One thing that is not debatable is the importance of proper anatomic reduction with regard to intra-articular fractures. We believe this cannot occur consistently in posterior malleolar fractures without a well planned out posterior approach.

   Dr. Todd is an Associate of the American College of Foot and Ankle Surgeons. He is affiliated with the Department of Podiatry at the Palo Alto Medical Foundation in Mountain View, Calif.

   Dr. Jennings is affiliated with the Department of Orthopedics and Podiatry at the Palo Alto Medical Foundation in Mountain View, Calif. She is a Fellow of the American College of Foot and Ankle Surgeons.

   Dr. Rush is affiliated with the Department of Orthopedics at the Palo Alto Medical Foundation in Mountain View, Calif. He is a Fellow of the American College of Foot and Ankle Surgeons.

   Dr. Wood is affiliated with the Department of Podiatry at the Palo Alto Medical Foundation in Mountain View, Calif.

   Dr. Jensen is affiliated with the Department of Podiatry at the Palo Alto Medical Foundation in Mountain View, Calif. He is a Fellow of the American College of Foot and Ankle Surgeons.

Suggested Reading
1. Buchler L, Tannast M, Bonel H, Weber M. Reliability of radiologic assessment of the fracture anatomy at the posterior tibial plafond in malleolar fractures. J Orthop Trauma. 2009; 23(3):208-212.
2. DeCoster TA. External rotation-lateral view of the ankle in the assessment of the posterior malleolus. Foot Ankle Int. 2000; 21(2):158.
3. Ferries JS, DeCoster TA, Firoozbakhsh KK, Garcia JF, Miller RA. Plain radiographic interpretation in trimalleolar ankle fractures poorly assesses posterior fragment size. J Orthop Trauma. 1994; 8(4):328-331.
4. Fitzpatrick DC, Otto JK, McKinley TO, Marsh L, Brown TD. Kinematic and contact stress analysis of posterior malleolus fractures of the ankle. J Orthop Trauma. 2004; 18(5):271-278.
5. Forberger J, Sabandal PV, Dietrich M, et al. Posterolateral approach to the displaced posterior malleolus: functional outcome and local morbidity. Foot Ankle Int. 2009; 30(4):309-314.
6. Haraguchi N, Haruyama H, Toga H, Kato F. Pathoanatomy of posterior malleolar fractures of the ankle. J Bone Joint Surg. 2006; 88(5):1085-1092.
7. Raasch WG, Larkin JJ, Draganich LF. Assessment of the posterior malleolus as a restraint to posterior subluxation of the ankle. J Bone Joint Surgery. 1992; 74(8):1201-1206.
8. Tornetta III P, Ricci W, Nork S, et al. The posteriorlateral approach to the tibia for posterior malleolar injuries. J Orthopedic Trauma. 2011; 25(2):123-126.

   For further reading, see the DPM Blog “Fixation Of The Medial Malleolus Fracture: What You Should Know” by Neal Blitz, DPM, FACFAS at https://tinyurl.com/lqsxelz .