Peroneal Sheath Volumes Are Greater in Patients With Peroneal Pathology Compared With Controls

Peroneal tendon pathology is common. Several factors have been implicated, including low-lying muscles and accessory tendons. Studies have reported on the presence and length measurements of these structures. This study evaluates volume measurements within the sheath using magnetic resonance images for patients with operatively treated peroneal tendon pathology and control patients without peroneal disease.

Fifty-one patients with peroneal tendon pathology and 15 controls were included. The volumes of the peroneal sheath, peroneal tendons, peroneal muscle, and accessory peroneus tendons were measured. The distal extent of the peroneus brevis (PB) muscle was measured. Volume and length measurements were then compared.

The mean PB muscle length from the tip of the fibula was 5.55 ± 2.5 mm (peroneal group) and 11.79 ± 4.07 mm (control) (P = .017). The mean peroneal sheath volume was 7.06 versus 5.12 mL, respectively (P = .001). The major contributors to this increased volume was the tenosynovitis (3.58 vs 2.56 mL, respectively; P = .019), the peroneal tendons (2.17 vs 1.7 mL, P = .004), and the accessory peroneus tendon + PB muscle (1.31 vs 0.86 mL, P = .023).

The current study supports that the PB muscle belly is more distal in patients with peroneal tendon pathology. The study also demonstrates increased total volume within the peroneal sheath among the same patients. We propose that increased volume within the sheath, regardless of what structure is enlarged, is associated with peroneal tendon pathology. Further studies are needed to determine if debridement and decompression of the sheath will result in improved functional outcomes for these patients.

Level III: Case control imaging study.