Tears
Peroneus brevis tear caused by abrasion on the edge of the labrum as an unstable tendon subluxes laterally.
Other tears are probably caused by compression of brevis against the fibula by longus.
Peroneus brevis tears are
- about three times commoner than those of peroneus longus
- often associated with laxity of the SPR
- also associated with a low musculotendonous junction or an accessory peroneus quartus muscle – these may make the tendon stiffer or stretch the SPR. Freccero et al (2006) found that the musculotendinous junction was 8mm more distal in patients with peroneus brevis tears than in patients with normal tendons; however, Saupe et al (2007) reported that the men distance from the musculotendinous junction in asymptomatic volunteers was 0mm - 33mm more distal than Freccero et al's proven tears. Saupe et al also found peroneus quartus in 17% of normals
- commonly associated with lateral ligament injuries of the ankle – about 50% also have ankle instability; peroneal tenosynovitis, tears and instability may be present in up to 70% of patients with ankle instability
- usually longitudinal, partial tears – only about 10% are complete tears
- normally centred on the level of the superior peroneal retinaculum
- probably caused by compression of the brevis tendon between the longus tendon and the fibula, especially if the tendon can be squeezed over the edge of the groove because the retinaculum is lax, or if there is a sharp ridge at the edge of the groove (Sobel et al 1991)
Peroneus longus tears are:
- Strongly associated with pes cavus – 80% in the study by Brandes and Smith (2000) – the plantarflexed first ray may increase the stresses in the tendon
- Usually at the level of the inferior peroneal retinaculum or the point where the tendon turns under the cuboid
- Usually partial longitudinal tears
About 10% of patients have combined tears of both tendons.
Pain at the point where the peroneus longus tendon turns into the cuboid groove is sometimes known as “painful os peroneum syndrome” (POPS) (Sobel et al 1994). This may be due to:
- Acute stress fracture of the os peroneum
- Chronic fracture of the os perineum, with or without peroneus longus tendonopathy or tear
- Peroneal tendonopathy or tear at the level of the inferior peroneal retinaculum, often of a stenosing type
Instability
Tearing or detachment of the SPR may allow the tendons to prolapse laterally, with pain, swelling and weakness of eversion. The brevis tendon is often torn – it is thought it may be lacerated by the sharp edge of the fibular groove. A shallow fibular groove is commoner in patients with instability, as is an abnormally distal origin of the peroneus brevis muscle belly. There is a strong association with ankle instability.
Eckert and Davis (1976) described three types of retinacular deficiency. In practice almost all instability is type 2.
Normal peroneal tendons in cross-section behind the lateral malleolus
R - retinaculum
L - labrum
B - brevis
L - longus
Type 1
Retinaculum and labrum are completely avulsed from the fibula. The tendons sublux subcutaneously. A tear of brevis is often present.
Type 2
Retinaculum and labrum are avulsed in continuity with a flap of fibular periosteum, forming a sub-periosteal pocket into which the tendons sublux. Das De pointed out the similarity to the Bankhart lesion in the shoulder
Type 3
Similar to type 2 but the labrum is avulsed with a small flake of bone