A 20-year-old male collegiate track athlete presented with 8 months of right posterolateral leg pain and paresthesia. The symptoms had begun shortly after starting to use a new pair of orthotics during his season. The symptoms were initially described as a sharp pain, present usually only with activity, rarely symptomatic at rest, and notably worse with going up stairs or from sitting to standing. He was initially treated for shin splints, and after a period of rest, placement in a walking boot, and physical therapy, the symptoms did improve slightly. He continued to have persistent tingling and intermittent shooting pains with long runs, sprints, playing basketball, and with lifting, most notably with squats. Physical exam was remarkable for numbness around the right fibular head with percussion or after exercise.
He was referred to orthopedics where X-rays of the knee were normal (Figures 1 and 2). There was concern for a possible lumbar radiculopathy, so imaging of his lumber spine was obtained. He was started on a course of prednisone and was referred to a physical medicine and rehabilitation specialist for further evaluation. There, his symptoms were localized around his fibular head and peroneal nerve, with no spinal involvement. He was sent to neurology for peripheral nerve testing. He underwent EMG and had an ultrasound of his peroneal nerve, which did show bilateral nerve enlargement, but with normal conduction. He was then referred to a primary care sports medicine specialist that performs compartment syndrome testing. These tests were mildly positive, but his symptoms were felt to be somewhat inconsistent with that diagnosis. The athlete was then sent to another primary care sports medicine physician that specializes in musculoskeletal ultrasound so that a dynamic evaluation of the posterior knee could be performed.
The dynamic ultrasound evaluation was performed using a GE S8 ultrasound machine with a 6-15 MHz transducer (General Electric, Chicago, Illinois, USA). The dynamic ultrasound showed a moderate-sized fabella in the posterior knee adjacent to the peroneal nerve, with a dynamic compression of the nerve on knee flexion and nerve enlargement distally (see Figure 3 and ultrasound videos 1 and 2). The patient underwent peroneal nerve hydrodissection with corticosteroid injection 8cc of 1% lidocaine and 1 mg dexamethasone under ultrasound guidance. The patient returned to rehabilitation and physical therapy in the school's training room, with improvement in symptoms with plans to return to compete in the spring season. A month later, he started training for his spring season and the symptoms returned. A repeat hydrodissection with a corticosteroid injection was tried again to get him through the season, but it failed.
Preoperatively, we were able to palpate and mark the fabella with the patient (Figure 4). A tourniquet is used throughout the case to limit bleeding. We used a longitudinal incision directly over the fabella. The common peroneal nerve was identified, decompressed, and retracted laterally. The lateral gastrocnemius tendon was incised longitudinally directly over the fabella (Figure 5). The fabella itself was then removed as a single unit and measured 13 mm in length by 10 mm in width (Figure 6). There was an articulation of the fragment with the posterior femur, which was exposed. Great care is taken to protect the nerve while the exposure is closed in layers.
Postoperatively, the patient reported that the numbness had resolved from before surgery. He was kept touchdown weight bearing to allow the gastrocnemius tendon to heal. Physical therapy was started immediately after surgery to work on a knee range of motion. At 6 weeks, he was allowed to progress with a return to sport protocol and he returned symptom-free to track activities at 12 weeks. He remains asymptomatic over 2 years since his surgery.