Peroneal Tendon Dislocation
When you hear the word dislocation the majority of people will think of some joint; shoulder, hip, etc. They would not be inaccurate in their thinking, but did you know that it is possible to dislocate a tendon? Some are more easily dislocated than others. In the foot and ankle there is one, actually two because they are so closely connected, that can become dislocated: the Peroneus longus and Peroneus brevis.
First, lets define what it means to be dislocated.
Dislocation disruption of an established order. NOTE: this is one of several that you will find in the dictionary. The main medical definition refers to one or more bones of joint, but this does not fit our topic. The best definition then is the one mentioned because the established order of the tendons is altered.
You may now be wondering what the Peroneal tendons are?
The peroneal tendons believe it or not belong to the peroneal muscles which are located on the outside of each of your legs.
- The peroneus longus courses behind fibula towards the base of your 5th metatarsal before making a quick turn and continuing through the plantar central portion of your foot. It inserts on to the lateral side of the 1st metatarsal base. It functions to stabilize the 1st metatarsal to the 2nd and also plantarflexes the 1st metatarsal.
- The peroneus brevis follows the same course as the longus but instead of turning at the base of the 5th metatarsal, it actually inserts on to the base. Its main function is to be the major evertor of your foot, but it also causes some dorsiflexion.
- NOTE: these tendons course beneath a retinaculum which is designed to help keep them in their natural anatomical position.
The next question that should be racing around in your mind is how do these tendons become dislocated?
- Tendon dislocation may occur from a myriad of athletic activities. Snow skiing being the more common cause; 1 in every 200.1 Other athletic activities include: football, rugby, basketball, water skiing, dance, gymnastics, mountain climbing, and combat training. Golf isnt looking like too bad a sport now is it?1
o Indirect causes is much more common than direct; direct being rare.
o Chronic subluxation may often be found in those with recurrent ankle sprains. For you Disney fans, Meg could have peroneal tendon subluxation/dislocation. If you already know which Disney movie Meg is from then Kudos to you. For those who need a little more help Ill drop a hint. HINT: He made Arnold Schwarzenegger look like a girly man.2
o Finally, dislocation may stem from neuromuscular abnormalities such as paralysis and polio.2
- MOI (Mechanism of Injury)
o Results from a sudden and rapid dorsiflexory force across the ankle with subsequent simultaneous, violent, reflex contraction of the peroneal tendons and ankle joint plantarflexors.1,3
o Violent contracture of the peroneal tendons with the foot in a supinated position. The ankle also being dorsiflexed.1,2,3
o Retinacular rupture rarely occurs. In fact, the retinaculum is typically stripped off the fibular insertion or avulsed with a small fleck of fibular cortex.2
Eckert and Davis developed a classification scheme to determine severity of injury as well as incidence of occurrence; based off observations that were noted during surgical repair.1,2,3
- The retinaculum is elevated off the lateral malleolus with the tendons now located between the fibula and retinaculum; Occurrence rate of 51%.
- The fibrocartilaginous ridge is elevated with retinaculum attached and the tendons displaced beneath this ridge; Occurrence rate of 33%.
- A small portion of the lateral malleolus is avulsed off and the tendons now located beneath this fragment of bone; Occurrence rate of 16%.
- NOTE: as you can see, the more severe stage 3 is much less common.
On physical exam pain is more localized to the posterior aspect of the fibula which is opposite of that if this were an injury to the ATFL (anterofibular ligament). Patients may complain of a snapping sensation over the lateral malleolus.4The tendons can be actively subluxed/dislocated in the office with:
- Resisted dorsiflexion and eversion of the foot
- Circumduction of the ankle and foot in a clockwise and counterclockwise fashion.
- NOTE: it is always important for your practitioner to examine the opposite foot.
The peroneus brevis can develop partial tears due to continued dislocation over the lateral malleolus.4
X-ray, CT, and MRI may all be used as adjunct to clinical evaluation in the diagnosis. MRI may help diagnose any underlying injury to the tendon substance itself.
- Conservative: below knee cast for 5-6 weeks. Literature reports a 50% success rate with conservative treatment.1,2 Some studies report a 14-56% success rate.3
- Surgical: often times this is determined by the severity of the injury.1,2,3
o Direct repair of the retinaculum to the periosteum of the fibula is the treatment of choice for acute injuries.
o Chronic injuries may require a little more ingenuity.
– Reattachment of the retinaculum with reinforcement using tendon transfers
– Rerouting the peroneal tendons
– Fibular groove deepening. Whats the fibular groove? The fibular groove is a groove in the posterior aspect of the fibula that the peroneal tendons sit in. If this groove is too shallow, it may aid in the dislocation process.5 By deepening this groove, you alter and increase the stability of the peroneal tendons.2
– Bone block procedures: these are osteotomies (cuts in the bone) that are meant to reform and deepen the fibular groove.
- McGlamry et al. Foot and Ankle Surgery. 3rd Edition. Volume 2.
- Coughlin and Mann. Surgery of the Foot and Ankle. 8th Edition. Volume 2.
- Easley et al. Operative Techniques in Foot and Ankle Surgery.
- Ogawa et al. Peroneal Tendon Subluxation Repair with an Indirect Fibular Groove Deepening Technique. Foot & Ankle International/Vol. 28, No. 11/November 2007.
- Adachi et al. Morphologic Variations of the Fibular Malleolar Groove with Recurrent Dislocation of the Peroneal Tendons. Foot & Ankle International/Vol. 30, No. 6/June 2009.
Photo Credit: sebadelval via pixabay.com
Category: Foot Problems
Tags: Dislocations, Tendon injuries