Monday, August 9, 2010

OLT (Osteochondral lesions of the talus)


O.L.T. (Otherwise known as OCD of the talus)


This is a relatively common pathology that is seen at the Family Foot and Leg Center. We are not referring to an obsessive compulsive disorder of the foot, we are referring to cartilage damage within the ankle joint.


Pathology

Anterolateral lesions on the talar dome result from inversion and dorsiflexion forces, which cause the anterolateral aspect of the talar dome to impact the fibula. These lesions are usually shallower and more wafer-shaped than medial lesions, possibly because of a more tangential force vector that results in shearing-type forces.
Posttraumatic medial lesions are deeper and cup-shaped. They result from a combination of inversion, plantarflexion, and external rotation forces that cause the posteromedial talar dome to impact the tibial articular surface with a relatively more perpendicular force vector.
A study of the contact pressures on the talus with varying degrees of lateral ligament transections and ankle positions showed that the medial rim of the talus was subjected to high pressures, even without ligamentous transection. Results of another study implicated the difference in cartilage stiffness; the tibial cartilage is 18-37% stiffer than the corresponding sites on the talus.

The results of other studies indicated that the mean cartilage thickness is inversely related to the mean compressive modulus. These findings may lend credence to the clinically observed etiology of osteochondral lesions of the talus (OLTs) (ie, repetitive overuse syndrome in medial lesions and an acute traumatic event in lateral lesions).
Observations from biomechanical studies suggest that the size of the lesion may alter the contact stresses in the ankle. Statistically significant changes in contact characteristics occur with lesions larger than 7.5 mm × 15 mm; this finding indicates that lesion size may play a role in predicting long-term outcome.


Presentation


In most cases, the mechanism of injury is an inversion injury to the lateral ligamentous complex. Patients typically present with chronic ankle pain along with intermittent swelling and, possibly, weakness, stiffness, instability, and giving way.
Upon physical examination, assess joint laxity with the anterior drawer test and assess strength by comparison with the contralateral ankle. Physical examination findings of joint laxity are uncommon. Palpation may reveal tenderness behind the medial malleolus when the ankle is dorsiflexed, indicating a posteromedial lesion. Anterolateral lesions may be tender when the anterolateral ankle joint is palpated with the joint in maximal plantarflexion.
Treatment
Medical Therapy
Conservative management of osteochondral lesions of the talus (OLTs) should be attempted first. Symptomatic patients with negative findings on plain radiographs should undergo an initial period of immobilization, followed by physical therapy. Studies have shown that a trial of conservative therapy does not adversely affect surgery performed after conservative therapy has failed. Patients whose plain images indicate OLTs and those who remain symptomatic after 6 weeks should undergo additional evaluation with MRI.
Surgical Therapy
Surgical treatment depends on a variety of factors, including patient characteristics (eg, activity level, age, degenerative changes) and lesions (eg, location, size, chronicity). However, surgical treatment adheres to 1 of the following 3 principles:
1) Loose-body removal with or without stimulation of fibrocartilage growth (microfracture, curettage, abrasion, or transarticular drilling)
2) Securing OLTs to the talar dome through retrograde drilling, bone grafting, or internal fixation
3) Stimulating the development of hyaline cartilage through osteochondral autografts (osteochondral autograft transfer system [OATS], mosaicplasty), allografts, or cell culture (Carticel, Genzyme Biosurgery, Cambridge, Mass)
Arthroscopic intervention is associated with less surgical morbidity and joint stiffness, decreased rehabilitation time, and an increased functional outcome.
Postoperative Details
A postoperative rehabilitation program should be tailored to each patient's individual circumstances and goals by a licensed physical therapist. Rehabilitation can generally begin after healing is demonstrated, which may occur after 6-7 weeks of non–weightbearing status if drilling or internal fixation was performed. With the goal of attaining full ankle range of motion, physical rehabilitation includes active and passive range-of-motion exercises and a home program, edema control, and strength and proprioceptive training.
Follow-up

Pain following operative treatment of OLTs is common for up to a year. MRI changes, including edema, are slow to resolve and often match the patient's report of an achy feeling in the joint. After 6 months, a persistent effusion, a catching sensation, or severe pain signifies that healing is not progressing as intended, and further investigation with CT or MRI is appropriate.
For excellent patient education resources, visit eMedicine's Foot, Ankle, Knee, and Hip Center and Imaging Center. Also, see eMedicine's patient education articles Ankle Arthroscopy, Understanding X-rays, and Magnetic Resonance Imaging (MRI).