POPS - Painful Os Peroneum Syndrome


Sagittal T1: Low signal within the OP	Sagittal IR: Low signal within the OP with surrounding edema-like changes. May signify sclerosis within the OP


Coronal T1: Low signal within OP	Coronal T2: Surrounding edematous changes

Background Information:

There are 4 soft tissue attachments/tethers of the os peroneum: 1) plantar fascia 2) 5th met base 3) cuboid 4) the peroneus brevis. This is why we do not see much migration of the os peroneum in cases with PL rupture/tear
The synovial sheath of the PL begins 2.5-3.5cm proximal to the tip of the lateral malleolus and ends 1.5 cm distal to the calcaneocuboid joint.
Presenting symptoms include pain with ascending stairs (pain with resisted plantarflexion of the first ray), sural nerve dysesthesia, and a feeling of “stepping on a pebble”-
Physical exam findings include acute point tenderness along the PL tendon, lateral foot pain upon heel rise along the course of the PL tendon, Tinel’s sign-
Etiology includes:

1. enlarged peroneal tubercle which entraps the os peroneum during excursion

2. callus formation from old healed fx of os peroneum causing a stenosing tenosynovitis of PL

3. diastasis of old fracture fragments due to progressing partially ruptured peroneus longus

MR findings- (you would know best!)

-tenosynovitis of PL

-partial/complete rupture of PL

-marrow edema in cuboid and/or calcaneus

Comments

The PL tendon often possesses a small cartilaginous sesamoid fragment as it curves medially under the cuboid tunnel. Perhaps as a way of negotiating a biomechanically challenging anatomic situation, this sesamoid fragment or os peroneum may contain an articular facet for the adjacent undersurface of the cuboid. Radiographically, only when these cartilaginous nuclei are calcified, do they become apparent.

POPS is a good illustration of the principle that many 'normal variants' may be symptomatic. POPS encompasses clinical manifestations due to changes in the os peroneum itself or secondary to peroneus longus tendinopathy. So in one extreme, there are cases of edema-like changes in the PL, fragmentation, AVN or fractures; whereas other cases present with associated tendinosis, tenosynovitis or tendon ruptures.

Apropos of the rule of thumb that even in cases of rupture, there is no significant proximal retraction, check out the following case. This patient ruptured the os peroneum in the course of one month.

December 2004	January 2005

Courtesy Marina Liem, MD