A 38-year-old semiprofessional football player complained of pain in the lateral aspect of the left leg of 8-month duration. Initially, he had pain only for few minutes at the beginning of games. In the last 4 months, pain lasted for progressively longer periods of time until he had to stop playing. In the nonsporting activities there was no pain. After a period of rest, he returned to play but had to stop again due to persistent discomfort.
The patient had undergone excision of a left-sided L4-L5 disc herniation 4 years before, with no residual symptoms except for occasional episodes of back pain. When first seen, he reported having had an episode of back pain 1 month before. Physical examination showed no evidence of L5 radiculopathy. However, magnetic resonance imaging (MRI) of the lumbar spine was carried out on the suspicion of a recurrent L4-L5 disc herniation. MRI showed mild bulging at the operated on disc, which led to prescribing nonsteroidal anti-inflammatory medication for 3 weeks. Electromyography of the lower limbs was negative.
When evaluated again, deep palpation on the middle third of the left peroneal muscles elicited moderate local pain. Both ipsilateral hip and knee appeared to be normal at clinical examination. Radiographs showed a heterotopic ossification in the middle third of the leg (Figure 1). The patient denied having sustained any severe trauma to the left leg. Computerized tomography (CT), performed to better determine the site and extension of the ossification, revealed that the lesion was located in the interosseous membrane and started from the left fibula but did not reach the lateral aspect of the tibia (Figure 2). MRI of the leg showed, on T2-weighted cross-sectional fat saturation sequences, a hyperintense signal on both the lateral aspect of the periosteum and lateral part of the tibial diaphysis at the level of the ossification (Figure 3). These findings indicated edematous changes, suggestive of a local inflammatory process that might be related to mechanical stress. The patient refused to undergo bone scan. Excision of the ossification was thus scheduled.
At operation, a posterolateral incision was carried out at the level of ossification. After longitudinal dissection and posterior retraction of the peroneus longus muscle, the fibular shaft was freed of muscle insertions. The tibialis anterior muscle was retracted anteriorly paying attention not to injure the interosseous artery and nerve. The lamina of heterotopic bone was cut from the fibula, elevated anteriorly to detach the insertions of the tibialis posterior muscle from its posterior aspect, and then excised. Postoperative radiographs confirmed complete removal of the lesion. Two months after surgery the patient returned to sporting activity with no discomfort. At 1-year follow-up, radiographs showed no recurrence of the ossification (Figure 4).
The excised specimen consisted of cortical bone arranged in slightly sclerotic trabeculae, focally in continuity with fibrous connective tissue. The bone marrow exhibited expanded adipose involution and mild fibrosis (Figure 5), as it may occur in some cases of myositis ossificans.
An informed consent was obtained from the patient for publication of the data.