Peroneal Tendon Dysfunction: Why Peroneal Tendon Tears Should Be Treated Like Posterior Tibial Tendon Tears

About 20 years ago, I spent the three years of my residency in Pittsburgh working on treatments and ideas for posterior tibial tendon dysfunction (PTTD). Over the course of three years, we performed numerous procedures ranging from pure tendon repairs to full hindfoot fusions.  In my first five years of practice, I saw many patient referrals for PTTD and began to dial in my own thoughts. I learned what worked for me and how to treat different levels of PTTD with different procedures for each patient. 

What was and still is paramount for proper patient care is understanding the underlying cause of the PTTD and tendon tear. Was it equinus? Was it flatfoot? Was it an injury? Furthermore, it is also paramount to treat the underlying cause, correcting the acquired flatfoot to ideally reposition the foot in order to protect the now repaired tendon and tendon transfer.

In the past five years, I began to think of peroneal tendon tears in a similar manner to PTTD. This approach has helped me understand the cause of the tear, the underlying damage and what it means for the patient, his or her foot alignment, and the surgical repair requirements. I now refer to peroneal tendon tears as peroneal tendon dysfunction and treat it with the same aggressive mindset as the posterior tibial tendon. As a result, my surgical outcomes have improved dramatically and I would like to share my experiences.

Understanding The Mechanisms And Etiologies Of Peroneal Tendon Tears

The peroneal tendons are primarily abductors  of the foot. The peroneus longus can also stabilize and plantarflex the first ray. Collectively, the peroneus brevis and peroneus longus also help to stabilize the ankle against lateral sprain. The tendons are fairly large and strong. Furthermore, since there are two tendons, they seem to assist each other which, I believe, helps to protect both tendons against injury more so than the solo posterior tibial tendon.

In my experience, injury to the peroneal tendons comes in three forms. The first is traumatic injury, commonly a severe sprain. In such a case, the ankle sprain is very severe and the peroneal tendons, most commonly the peroneus brevis, go through a severe strain and tears. Unlike the Achilles tendon, the peroneal tendons uncoil with a longitudinal tear and do not snap in half. 

The second type of injury is chronic overuse from a previous insult. In such cases, there is an instability of the ankle, which results in a failed anterior drawer test with or without a talar tilt. In such cases, the peroneal tendons begin to strain in trying to stabilize the ankle joint. That strain then slowly causes fraying of the tendon and an eventual tear. In some rare cases, there may be a chronic issue instability from an ankle sprain that results in a subluxing peroneal tendon, which can tear against the posterior fibular groove through a fraying mechanism. 

Finally, there is chronic overload of the peroneal tendons due to an abnormal foot position, in this case a cavus foot type. With the chronic cavus foot position, there is strain on the posterior tibial tendon, resulting in overuse of the peroneal tendons and potentially a subsequent tear. This last category of peroneal tendon dysfunction is undertreated and, similar to PTTD, requires more aggressive treatment in order to have better outcomes. 

A second point to consider in the treatment of peroneal tendon tears, similar to PTTD, is what happens to the foot, which has an untreated tendon tear for an extended period of time. With PTTD, the foot begins to lose its arch. Slowly, there is flattening of the foot, progressing from flexible to rigid. Over time, if it is left untreated, there can be dislocations of the midfoot and even partial dislocation of the ankle joint with severe collapse. 

In PTTD, as the deformity and pathology progresses, the procedure requirements and surgical complexities increase. There are similar challenges with peroneal tendon tears. The posterior tibial tendon is working without the opposing peroneal tendon pull, resulting in elevation of the arch. Furthermore, the peroneus brevis is more commonly torn than the peroneus longus in my experience. Therefore, the continued pull of the peroneus longus causes plantarflexion of the first ray and also contributes to an increased cavus foot position. Over time, the foot goes from a flexible cavus to a rigid cavus and, in rare cases, the ankle joint can also exhibit a partial lateral dislocation. Much like PTTD, with more severe cases, a repair of the peroneal tendon does nothing to realign the foot and the tendon is at high risk for repeat tear.

Essential Considerations In Treating Peroneal Tendon Tears

The initial examination is critical for proper preoperative evaluation of peroneal tendon tears. Which tendon is torn? Again, in my experience, the brevis tendon is far more commonly torn and more symptomatic than the longus tendon. Is the ankle unstable? If this is the case, combining an ankle ligament repair with the peroneal tendon repair can decrease the strain on the tendon and stabilize the ankle. 

What is the foot position and how does it compare to the contralateral foot? It is essential to compare one foot to the other. What if the patient has a natural and asymptomatic cavus foot that is mild to moderate in severity, and bilateral in presentation? If the injury to the affected foot is from an ankle sprain, it may not be necessary to realign the foot.

However, if there is a dramatic difference in the cavus deformity from one foot to the other and there is a tendon tear, realignment of the foot is more important to consider as part of the overall procedure. Realignment of a cavus foot usually requires two procedures. The two most common procedures are a Dwyer calcaneal osteotomy and an elevation osteotomy of the first metatarsal. A third procedure may also be necessary in cases involving  a very strong and enlarged longus tendon along with a weak brevis tendon. In these cases, a longus to brevis tendon transfer or a longus to cuboid tendon transfer may be indicated. With this approach, the peroneus longus tendon is more of an abductor of the foot than a plantarflexor of the first ray, which is perhaps a better use of the tendon as part of the realignment.  

The actual tendon repair is a tubularization procedure. This involves debriding the tendon of the torn regions and repairing it with a thin, non-absorbable suture of the surgeon’s choice. I prefer a 4-0 nylon suture with a running locking suturing technique. If the patient is a large athletic male, I may use 2-0 FiberWire^® (Arthrex^®) but I find this material can be a bit more irritating to the other peroneal tendon than the nylon.  

Many cases of peroneal repair include a modified Brostrum ankle stabilization. It is very rare to perform a secondary ankle ligament repair with a free tendon graft unless there have been several ankle injuries with prior repair attempts and hypermobility conditions such as Ehlers-Danlos Syndrome. 

Finally, in cases of one or both tendons having severe damage or being of poor quality, a pure tubularization is not enough as the tendon(s) may not have adequate quality to work well. In such cases, an end-to-end tenodesis of the longus and brevis tendon to each other is the preferred technique, and can create one good, fully functioning tendon. 

Final Thoughts

With proper planning, one can employ a systematic algorithm to treating peroneal tendon dysfunction, which requires a more comprehensive and diligent approach than just a simple tendon repair. Much like PTTD, which requires multiple procedures to correct the tendon tear and possibly reposition the foot, peroneal tendon tears also require consideration of multiple causes and symptoms in order to have exceptional outcomes. 

Dr. Baravarian is an Assistant Clinical Professor at the UCLA School of Medicine. He is the Director and Fellowship Director at the University Foot and Ankle Institute in Los Angeles (https://www.footankleinstitute.com/podiatrist/dr-bob-baravarian). Dr. Baravarian has disclosed that he is a consultant for CrossRoads Extremity Systems and OSSIO.