When Subluxation of the Peroneal Tendons Occurs After Ankle Sprain

Trauma to the lateral ankle can lead to a myriad of problems for our patients, from acute/chronic ankle laxity and instability to torn peroneal tendons. A commonly misdiagnosed or missed additional problem is peroneal subluxation and dislocation. Dislocation typically results from sequelae of ankle trauma leading to incompetence or tearing of the superior peroneal retinaculum from its fibular insertion. This occurs during a forced dorsiflexion moment of an everted foot on the ankle and is associated with cutting movements seen in skiing, ice skating, soccer, rugby, basketball, and gymnastics.¹ It can also be caused by a shallow fibular groove or a low-lying peroneal muscle belly.

Several treatment methods exist with varying degrees of difficulty and success rates.² In this article, we will share our experience and preferred surgical technique.

A Guide to the Anatomy, Presentation, and Classification

The superior peroneal retinaculum (SPR) originates on the posterolateral surface of the fibula, passes over the peroneal tendons posteriorly and plantarly, and attaches to the lateral calcaneus. The shape of the posterior surface of the lateral malleolus, commonly referred to as the retrofibular or retromalleolar groove, plays a role in the stability of the peroneal tendons during their motion.³ In most patients an actual groove exists in this region. It is formed by the concavity of the fibula and consists mainly of a ridge of collagenous tissue and periosteum extending along the posterolateral lip of the distal fibula. The shape of the groove is determined primarily by the fibrocartilaginous ridge. If this groove is flat or convex, there is an increased risk of tendon instability and dislocation during sport or activity.

Peroneal subluxation can often be misdiagnosed as a high ankle sprain. Patients will often describe a characteristic “popping” or “snapping” sensation to the lateral ankle and hindfoot. Gait analysis is paramount, as is a positive Kleiger test, performed by stabilizing the lower leg just above the ankle with one hand while the other hand dorsiflexes and externally rotates the ankle. The Kleiger test can help differentiate between a peroneal tendon subluxation and tendinopathy. The common forms of peroneal subluxation with true tendon dislocation from posterior to the fibula to anterior or lateral to the fibula are easy to diagnose visually. A less common, but often problematic, finding is an intraretinacular subluxation, which is often noted with a snapping of the peroneal tendons against each other but without dislocation from the posterior fibula.⁴ This less common problem may result in chronic pain and peroneal tendinopathy or tear over a period of months to years.

It is important to keep in mind that oftentimes a patient can suffer from peroneal subluxation in addition to a concomitant ligament sprain or longitudinal split tear (most often of the peroneus brevis) as a result of their ankle trauma.⁵ This is where advanced imaging is necessary, and we will routinely obtain magnetic resonance imaging (MRI) of these ankles. While standard weight-bearing radiographs are important to rule out other pathology, computed tomography (CT) can evaluate the shape and depth of the retromalleolar groove. MRI is our modality of choice for visualization of both soft tissue and morphology of the fibular groove.

Once MRI is obtained, it is important to be prepared to repair any split tears visualized in the tendon(s). One must emphasize the importance of the fibular groove analysis. If the fibular groove is found to be flat or even convex, the repair of the peroneal subluxation/dislocation is more likely to require groove deepening,which is important to consider and discuss in the preoperative workup with the patient.⁵

Eckert and Davis first classified superior peroneal retinaculum injuries and peroneal subluxation in 1976, followed by an additional stage by Oden in 1987.^6,7 Grade I is when the SPR separates from the fibrous lip and lateral malleolus but remains attached to the periosteum, allowing for subluxation of both tendons. This is the most common grade of injury. Grade II reflects separation of the SPR from the fibrocartilaginous ridge of the lateral malleolus and elevation within the retinaculum, allowing the tendons to sublux between the SPR and fibrocartilaginous ridge. Grade III involves a cortical avulsion of the anterior attachment of the SPR off the lateral malleolus, allowing the tendons to move underneath the fragment between the fibrocartilaginous rim and the lateral malleolus. Grade IV is described as an SPR tear from the posterior attachment on the calcaneus and found lying deep to the tendons, often referred to as a “fleck sign.”

Surgical Treatment Considerations

Conservative care largely consists of boot immobilization followed by ankle bracing with a course of physical therapy for 2–8 weeks.⁸ Patients often report improvement of their pain and swelling from the acute trauma, but the “popping” and “clicking” of their lateral ankle persists. This can be debilitating, causing pain and limitation during activity. The literature varies on efficacy of conservative treatment for peroneal subluxation, with a 50–78% failure rate, oftentimes with recurrence.⁸ Surgical intervention is the preferred method of treatment for this pathology, with several studies reporting over 90% “good” or “excellent” results and high patient satisfaction scores with low rates of recurrence.⁹

There are effectively three different surgical intervention methods for treatment of peroneal subluxation in addition to repair of the SPR: drilling and tamping the fibula, groove deepening, or an osteotomy. Bony procedures have the reported highest rate of complications and postoperative recurrent dislocation,⁵ in addition to longer healing times given the nature of the procedure; therefore, we do not consider this as a viable treatment option. Our procedure of choice is a repair of the SPR in addition to groove deepening with a burr.

We typically place an incision over the posterior third of the fibula, which allows visualization of the peroneal tendons along with direct visualization of the posterior fibula to prepare it for SPR repair/advancement and groove deepening. This will also allow adequate exposure of the peroneus brevis to repair any split tears identified on MRI. Once the retinaculum is reflected off the fibula and the peroneal tendons are visualized, stressing the first ray will identify the peroneus longus from the brevis. At this time if we encounter a low-lying muscle belly on the peroneus brevis, we will excise it to reduce bulk. If a split tear exists, we will repair at this time either by excision of nonviable tendon or tubularization.

Next, we will relocate the peroneal tendons to ensure they sit appropriately in the retromalleolar groove. If drilling and tamping is required, we will place 2–3 small anchors along the course of the peroneal tendons into the fibular body to imbricate the SPR. If groove deepening is necessary, we will use a small burr to deepen the groove and create a more concave surface prior to placement of the anchors. The goal is to deepen the central and medial aspect of the posterior fibula without damage to the lateral cortex or wall. The tendons are placed back in the groove and the ankle is rotated during the groove-deepening process until no subluxation is noted while the retinaculum is still open.

Although osteotomy of the fibula can be performed with posterior displacement of the lateral half, it has not been noted to be necessary in our hands with groove deepening. Furthermore, we have not found the need to drill and tamp the fibula for groove deepening and a posterior burr technique has not resulted in stenosis or fibrosis of the peroneal tendons as range of motion is started fairly quickly. To advance the SPR, we will make a series of paired drill holes through the lateral cortex of the fibula and use nonabsorbable suture. In essence this changes the attachment of the retinaculum from the lateral portion of the fibula to within the groove. Any redundant retinaculum we will suture back to the anterior portion.

Postsurgical care includes a period of 3 weeks of non-weight-bearing in a boot. Range of motion is started at 1 week in cases of no peroneal tear and 3 weeks in cases of peroneal tear. Weight-bearing in a boot is allowed from week 3 to week 6 and patients are then advanced to an ankle brace from week 6 to week 12 prior to returning to sports specific training and exercises.

In Conclusion

For active patients, peroneal subluxation can be a painful pathology limiting activity level and return to sport after an ankle injury. Proper evaluation, preoperative imaging, and a detailed surgical technique are essential for effective treatment. We find that patients do well with this procedure and have high satisfaction rates as well as return to activity. 

Dr. Adloo is a Fellow at University Foot and Ankle Institute.

Dr. Baravarian is the Director and Fellowship Director at University Foot and Ankle Institute.

References

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