Introduction

Beyond common fractures and their attendant complications, elbow problems are relatively uncommon in the young. Nevertheless, there are a number of conditions that can result in elbow symptoms, especially in young athletes. Osteochondritis dissecans (OCD) is but one of these conditions. It is important to identify OCD promptly because the prognosis is often poor and appropriate management can prevent deterioration and improve the outcome.

Background/aetiology

Sporting activities that require the upper limb to repeatedly bear abnormal loads are most commonly responsible for elbow pain in the skeletally immature. Activities include gymnastics, weightlifting and, most frequently, baseball. Baseball pitching imparts repeated valgus stress to the elbow joint. This tensions the medial structures and compresses the lateral structures, leading to a variety of elbow symptoms which have been termed ‘little leaguer’s elbow’. Experience is greatest in the USA and Japan, where baseball is a popular youth sport, but relatively limited in the UK.

The most common ‘little leaguer elbow’ symptoms are on the medial side of the joint and are related to traction injury and inflammation of the medial collateral structures, especially the vulnerable medial epicondyle. Less frequently, symptoms are lateral and related to compressive overloading of the lateral bony structures, including the radial head and especially the capitellum. OCD and Panner’s disease are both seen in the capitellum and it is therefore important to define and distinguish these conditions (Table 14.1).

Table 14.1 Panner’s disease and osteochondritis dissecans

Panner’s disease is considered to be an avascular necrosis of the developing capitellar ossification centre. It is characterized initially by radiological sclerosis and then fragmentation of the capitellum (Fig. 14.1), followed by gradual restoration. It is not necessarily associated with trauma.^1,2 The process is very similar to the series of changes seen in the femoral epiphysis in Perthes’ disease. Panner’s disease occurs in the relatively young (under 10 years). Management is usually non-operative and primarily involves avoidance of the causative stress together with range-of-movement therapy to maintain extension. Although it may take some time for the radiological lesion to resolve, the prognosis is relatively good. As in Perthes’ disease, the capitellar cartilaginous anlagen, devoid of its supporting bony nucleus, can deform and sometimes reossifies into a flattened oval in the sagittal plane, ultimately limiting full extension.

Figure 14.1 Panner’s disease. Sclerosis and fragmentation of the entire ossific nucleus of the capitellum.

From J Bone Joint Surg Am, April 1960; 42:513–516. Avascular necrosis of the capitellum humeri (Panner’s disease): a report of a case. Charles J. Heller and Leon L. Wiltse.

By contrast, OCD occurs most commonly in the adolescent age range. It is usually a more discreet condition, affecting a section of the subchondral bone and the overlying articular cartilage (Fig. 14.2). The pathology and radiology are similar to OCD seen in other joints such as the knee and ankle and there is potential for loose body formation. Management is sometimes operative and depends on the stability of the OCD lesion. Prognosis is accordingly variable and generally worse than Panner’s disease. Early recognition is important because appropriate early management can influence the prognosis.

Figure 14.2 Radiographic classification of OCD. Grade I (A) is localized flattening or radiolucency. Grade II (B) is a non-displaced fragment. Grade III (C) is a displaced or detached fragment with an empty defect.

From J Bone Joint Surg Am, June 2007; 89:1205–1214. Classification, treatment, and outcome of osteochondritis dissecans of the humeral capitellum. Masatoshi Takahara, Nariyuki Mura, Junya Sasaki, Mikio Harada, and Toshihiko Ogino.

The capitellum of the immature elbow has a tenuous vascular supply consisting of one or two posterior vessels that traverse the capitellar cartilage before entering the epiphysis. There is no metaphyseal blood supply until the physis closes at maturity.³ This tenuous circulation makes the capitellum vulnerable to avascular necrosis following lateral condyle fractures and it is postulated that it may also play a role in the genesis of Panner’s disease and OCD. Some reports suggest a genetic predisposition in some families but most evidence supports the hypothesis of repeated shear and compressive trauma, particularly in relation to OCD.

Presentation

Although the articular surface of any joint can be affected by OCD, there is a predilection for the convex surfaces of load-bearing joints, especially the knee and ankle. At the elbow any surface can be affected but the anterolateral convex surface of the capitellum is most frequently involved when the upper limb is subjected to supra-physiological load-bearing activities.

The patient usually presents with focal pain on the lateral side of the elbow. There is often a history of athletic activity. The condition most frequently affects male throwing athletes and female gymnasts. The dominant (throwing) elbow is predominantly affected. Symptoms are usually worse with activity and improve with rest, although there can be a prolonged ache following activity. There may be mechanical symptoms such as clicking or locking, especially if the lesion is unstable or if loose bodies are present. Clinical examination identifies tenderness over the capitellum. Full extension is often limited. Pain can be provoked by valgus stress of the elbow or by active pronation and supination of the extended elbow, which generates dynamic compression of the lateral structures.

Investigation and classification

Evaluation should not overlook other potential explanations for pain. Investigation usually commences with standard anteroposterior and lateral plain radiography. The typical early appearance of OCD is anterolateral radiolucency within the capitellum, with flattening progressing to irregularity of the central or anterolateral articular surface. A separated fragment can subsequently form and either remain in its bed or become detached, forming a loose body. Radiographic findings can be classified into three grades (Fig. 14.2).⁴ Grade I is localized flattening or radiolucency. Grade II is an undisplaced fragment and grade III a displaced or detached fragment. Reliable grading is, however, difficult and subject to inter-observer variation.

Furthermore, plain radiography lacks sensitivity. Early grade I changes are difficult to visualize and early lesions can be easily overlooked. One study has shown that only 7 of 15 known cases of early OCD were identified with plain radiographs.⁵ As a result, some authors recommend supplementing the standard films with an anteroposterior view of the elbow when it is flexed to 45° to give a tangential view of the anterolateral capitellum, where the lesion is most typically located.⁶ Magnetic resonance imaging (MRI) is more sensitive than plain radiography and should therefore be utilized if the history and examination suggest OCD as a possible differential diagnosis.

The primary purpose of investigation is to both identify and classify the extent of the lesion. However, before discussing the relative merits of MRI it is worthwhile reviewing the current arthroscopic classification of OCD.