Key Insights On Treating Os Peroneum Syndrome

This author details the surgical treatment, following failed conservative care, of a 63-year-old patient who presented with chronic pain in the right lateral foot. 

The os peroneum is small sesamoid located in the peroneal longus tendon at the level of the lateral cuboid groove. The os peroneum is present in 20 percent of the population and 60 percent of the time, it is present bilaterally.¹

A painful os peroneum is known as os peroneum syndrome and radiologists can mischaracterize this finding.² Os peroneus syndrome can be of a chronic nature or result from acute trauma such as an inversion injury. Pain is present at the area and there is often tearing or damage to the surrounding peroneus longus tendon.

Treatment involves a robust effort at conservative care and ultimately, in recalcitrant cases, surgical intervention can relieve the pain. What follows is a case presentation of os peroneum syndrome.

What You Should Know About The Patient Presentation

A 63-year-old woman presented for a second opinion regarding a painful right lateral foot of three months in duration. This pain was precipitated by a two-year successful effort in treating classic plantar medial plantar fasciitis with her previous provider. The patient had no inciting acute event but noted pain that she characterized as significant and present daily at the lateral midfoot. She wore a boot for five weeks under treatment by her previous provider and used non-steroidal anti-inflammatory drugs (NSAIDs) prior to her arrival at my office.

The patient’s radiographs showed an os perineum with an irregular, multipartite appearance. We decided on a cortisone injection followed by two weeks of boot protection and physical therapy. We gave the patient instructions to return if symptoms did not improve.

The patient returned two months later. She said the injection helped for 10 days but the pain subsequently returned. Magnetic resonance imaging (MRI) showed a partial thickness tear/tendinopathy and mild tenosynovitis of the peroneal longus at the interim from the calcaneus to the cuboid. The MRI report did not mention the os peroneum. We planned surgery for peroneal longus repair with excision of the os peroneum.

A Closer Look At The Os Peroneum Syndrome Surgery

The patient went to the operating room and received general anesthesia in a lateral position with the surgical limb in a superior position. The incision followed the course of the peroneus longus from the distal peroneal trochlea to the plantar lateral cuboid. Identifying and protecting the sural nerve prior to deep dissection is necessary.

I identified the peroneal tendon tear and placed retractors to expose the os peroneum. I meticulously shelled out the os peroneum with a #15 blade. I prefer to start by using the cartilaginous deep surface, preserving as much of the surrounding peroneal tendon as possible. This process is tedious and often difficult due to the depth one is working within the incision. In this patient, the os peroneum had sharp borders and was in three distinct pieces.

After excision of the os peroneum, I reinforced the weakened area of the peroneal tendon with a contoured strip of acellular graft and incorporated it to normal appearing tendon on either side of the weakened excision site with a 0 vicryl suture. I repaired the more proximal peroneal tendon longitudinal tear with a retubularization running suture. Range of motion testing showed no tendon entrapments or failures. I flushed the area and closed it in layers.

The patient wore a non-weightbearing splint for two weeks and a non-weightbearing cast for two further weeks. She was subsequently weightbearing in a boot for two more weeks and then transitioned to a brace and physical therapy thereafter.

The patient has returned to regular activities without pain. I believe the plantar fasciitis and the subsequent lateral column weightbearing she encountered for years leading up this os peroneum syndrome caused the os peroneum to become symptomatic and perhaps lead to peroneal tearing.

In Conclusion

When conservative management fails to relieve symptoms, surgical intervention can relieve os peroneum syndrome. One may improve surgical success with meticulous dissection and shelling out of the os peroneum, and reinforcement of the peroneal tendon with an acellular graft.

Dr. Bussewitz is a fellowship-trained foot and ankle surgeon, who is in private practice at Steindler Orthopedic Clinic in Iowa City, Iowa.

References

1. Sobel M, Pavlov H, Geppert MJ, Thompson FM, DiCarla EF, Davis WH. Painful os peroneum syndrome: a spectrum of conditions responsible for plantar lateral foot pain. Foot Ankle Int. 1994; 15(3):112-24.

2. Dombek MF, Lamm BM, Saltrick K, Mendicino RW, Catanzariti AR. Peroneal tendon tears: a retrospective review. J Foot Ankle Surg. 2003; 42(5):250-8.