Osteochondritis dissecans (OCD) is a pathologic process affecting subchondral bone and the adjacent articular cartilage, which can advance to osteochondral fragment instability and loose body formation.¹ The pathophysiologic basis for the condition has not been definitively established but, in most cases is felt to involve impaired vascular supply and/or healing response in a focal area of subchondral bone. The knee is the most commonly affected joint in the body, with the medial femoral condyle being most frequently affected location in the knee. Although described in adults, OCD most commonly affects skeletally immature patients (which has traditionally been referred to as juvenile OCD, a term most authors now do not favor), which generally have a better prognosis than OCD in adults.

Presenting symptoms of OCD are variable but may include limp, knee pain, mechanical symptoms such as clicking or locking, and/or effusion. Obtaining standard anteroposterior (AP) (Fig. 22.1) and lateral knee radiographs, with the addition of a tunnel or notch view, to allow for better assessment of the commonly affected posterior aspect of the condyle represents the primary initial diagnostic step. However, magnetic resonance imaging (MRI) has emerged as the gold standard for classifying OCD lesions as either stable (Fig. 22.2A,B) or unstable, a distinction that dictates the approach to treatment. Stable lesions are generally characterized by an intact articular cartilage surface overlying the subchondral bone lesion. This chapter focuses on the most commonly used technique of surgical treatment for stable juvenile OCD lesions transarticular drilling.

Drilling of the OCD lesion is considered the gold standard of surgical treatment of stable OCD in skeletally immature knees. Drilling is thought to disrupt the sclerotic margin of the lesion and consequently promote healing via growth factors released from healthy underlying cancellous bone. There are two primary methods of drilling knee OCD lesions: transarticular (or retrograde) and retroarticular (also referred to as anterograde).

Transarticular drilling involves perforation of the articular cartilage under direct visualization of the OCD lesion, whereas retroarticular drilling through the affected condyle spares the articular cartilage and used intraoperative fluoroscopy to perforate the OCD from the backside of the lesion. Theoretical advantages of the transarticular drilling technique include relative technical simplicity and direct visualization and assessment of the OCD lesion and K-wire entry sites during drilling (Fig. 22.3). Consequently, drilling passes can be optimally spaced relative to the lesion’s borders and relative to each other (Fig. 22.4). Finally, intraoperative fluoroscopy is rarely required to localize lesion (in contrast to retroarticular drilling). The theoretical disadvantage of transarticular drilling is the direct articular surface perforation and uncertain long-term implications of these perforations. Also, from a practical standpoint, far posterior condylar lesions may be difficult to access from transarticular approach due to required knee hyperflexion.

Although high-quality studies comparing transarticular and retroarticular drilling are lacking, a recent systematic review concluded no difference in patient outcomes or radiographic healing for skeletally immature patients with stable knee OCD lesions treated with these techniques. In total, 12 studies were
included which demonstrated a 91% radiographic healing rate in average of 4.5 months for transarticular drilling versus 86% in average of 5.6 months for retroarticular drilling with no differences in clinical response.³

A summary of the currently published literature on transarticular drilling in isolation for the treatment of juvenile knee OCD lesions is summarized in Table 22.1.⁴,⁵,⁶,⁷,⁸,⁹ Across all studies, there is agreement on the indications for drilling, in that almost every patient had a stable OCD lesion which had failed at least 3 months of nonoperative management. The clinical and radiographic outcomes reported are excellent overall. Significant variability exists in terms of intraoperative drilling technique and postoperative rehabilitation.