Achilles tendon

The Achilles tendon does not have a sheath associated with it; therefore tenosynovitis does not occur. Tendinosis and partial tears are commonly seen in the Achilles tendon. Complete disruption is commonly seen in athletes and in males around the age of 40; however, it is such an easy clinical diagnosis that MRI examination is usually not necessary. Complete tears are also commonly associated with other systemic disorders that cause tendon weakening, such as rheumatoid arthritis, collagen vascular diseases, crystal deposition diseases, and hyperparathyroidism.

Achilles tendon disruption can be treated surgically or by placing the patient in a cast with equinus positioning (marked plantar flexion) for several months. It is very controversial as to which treatment is superior, with both methods of treatment seemingly working well. I have known two surgeons who were dogmatic in their approach to always recommending surgery for torn Achilles tendons until they ruptured their own and opted for nonsurgical treatment.

MRI scanning is being used by some surgeons to help decide if surgery should be performed. If a large gap is present (Figure 12-1), some surgeons believe surgery should be performed to reappose the torn ends of the tendon, whereas if the ends of the tendon are not retracted, nonsurgical treatment is preferred. No papers have been published to show that this is, in fact, scientifically valid.

Posterior tibial tendon

The flexor tendons are easily remembered and identified by using the mnemonic “Tom, Dick, and Harry,” with Tom representing the posterior tibial tendon (PTT); Dick, the flexor digitorum longus; and Harry, the flexor hallucis longus (FHL) (Figure 12-2). The PTT is the most medial and the largest, with the exception of the Achilles, of the flexor tendons. The PTT inserts onto the navicular, second to fourth cuneiforms, and the bases of the second to fourth metatarsals. As it sweeps under the foot, it provides some support for the longitudinal arch; hence, problems in the arch or plantar fascia can sometimes lead to stress on the PTT with resulting tendinosis or even rupture. Posterior tibial tendinosis and rupture are commonly encountered in patients with rheumatoid arthritis.

Rupture of the PTT results clinically in a flat foot as a result of the loss of arch support given by this tendon. The spring ligament runs just deep to the PTT and then goes underneath the neck of the talus, which it supports in a slinglike fashion. When the PTT tears, the stress is then placed on the spring ligament to support the talus and the arch. The spring ligament has a high incidence of disruption when the PTT tears. Once the PTT and the spring ligament tear, the next structure to fail is the subtalar joint ligaments: the sinus tarsi. We looked at 20 patients with PTT tears and found that 92% of them had abnormal spring ligaments (thickened or torn) and 75% had an abnormal sinus tarsi.² It’s clear that these structures are linked and injury or stress to one can affect the others.

Differentiation of partial tears from tendon rupture can be difficult clinically, and MRI examination has become very valuable for making this distinction.³ Most surgeons will operate on a disrupted PTT, whereas nonoperative therapy is usually preferred for partial tears.

Posterior tibial tendinosis is seen on axial T1- or T2-weighted images as swelling and/or signal within the normally low-signal tendon on one or more images (Figure 12-3). The increased signal should not be fluid bright on the T2-weighted images. Tendon disruption is diagnosed by noting the absence of low-signal tendon on one or more axial image (Figure 12-4). This typically occurs just at or above the level of the tibiotalar joint.

The spring ligament is identified on axial and coronal images just deep to the PTT. When it is stressed, it typically gets scarred and thickened (Figure 12-5). A tear can be diagnosed by noting a gap in the ligament.

Flexor hallucis longus

The FHL tendon is easily identified near the tibiotalar joint because it is usually the only tendon at that distal level that has muscle still attached. In the foot the FHL is easily identified beneath the sustentaculum talus, which it uses as a pulley to plantar flex the foot.

The FHL is known as the Achilles tendon of the foot in ballet dancers because of the extreme flexion position they frequently employ. Ballet dancers often have tenosynovitis of the FHL, seen on MRI scans as fluid in the sheath surrounding the tendon. Care must be taken to have clinical correlation, because up to 20% of healthy people have a communication between the ankle joint and the FHL tendon sheath; therefore fluid can be seen in the FHL tendon sheath from a connection to an ankle joint, which has an effusion. Rupture of the FHL is rare.

Peroneal tendons

The peroneus longus and brevis tendons can be seen posterior to the distal fibula, to which they are bound by a thin fibrous structure, the superior retinaculum. The fibula serves as a pulley for the tendons to work as the principal evertor of the foot. The tendons course close together adjacent to the lateral aspect of the calcaneus until a few centimeters below the lateral malleolus where they separate, with the peroneus brevis inserting onto the base of the fifth metatarsal and the peroneus longus crossing under the foot to the base of the first metatarsal. Avulsion of the base of the fifth metatarsal from a pull by the peroneus brevis is known as a dancer’s fracture or a Jones fracture.

Disruption of the superior retinaculum, often seen in skiing accidents, can result in displacement of the peroneal tendons (Figure 12-6), which must be surgically corrected. It often occurs with a small bony avulsion, called a flake fracture, off of the fibula caused by the avulsed superior retinaculum.

Related posts:

Lumbar spine: Disc disease and stenosis Miscellaneous conditions Metabolic bone disease Don t touch lesions Arthritis Trauma

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