Introduction and Epidemiology

Osteochondritis dissecans (OCD) was first described by König in 1887 as a possible explanation for the presence of loose bodies within a joint. Initially, he postulated that inflammation led to the atraumatic formation of loose bodies, hence the designation of “osteochondritis.” Although the exact cause of OCD remains elusive, we recognize it to be acquired, focal lesions of subchondral bone with varying degrees of osseous resorption, fragmentation, and sclerosis that risk possible disruption of superficial articular cartilage.

OCD lesions remain a disease of maturing joints. The overall incidence of OCD across all joints declines to 2.52 (female) and 4.41 (male) per 100,000 person-years in patients aged 20–45 years. Several authors have noted an increasing incidence of OCD in the elbow with time and decreasing age at presentation ^, and suggest that it may correlate with the increasing popularity of competitive sports among young athletes.

Of all the OCD lesions diagnosed in adolescent athletes, the elbow represents only 12% of lesions. The reported incidence of elbow OCD lesions in patients aged 6–19 years is 2.2 per 100,000, with 3.8 per 100,000 in males and 0.6 per 100,000 in females. This represents a 6.8 times greater odds ratio in males than females. Additionally, the same study found that the odds ratio was 21.7 times higher in patients aged 12–19 years when compared with those aged 6–11 years. The vast majority of elbow OCD lesions (97.5%) are found in the capitellum, with rare lesions seen on the trochlea (2.5%) and radial head ^, ( Fig. 19.1 ).

(A and B) Osteochondritis dissecans of the capitellum. Arrow indicates OCD lesion capitellum.

Capitellar OCD lesions are typically seen in adolescent athletes engaging in repetitive overhead activities such as baseball, gymnastics, football, javelin, or overhead weight lifting. Kida et al. describe a prevalence of 3.4% among adolescent baseball players (14.5 ± 1.5 years), as detected by ultrasound. The authors also found that players with elbow OCD had played for longer periods, started playing at an earlier age, and experienced more elbow pain. Furthermore, patients who had continued to pitch despite having elbow pain demonstrated more advanced lesions. This was additionally confirmed by Matsuura et al. who found a prevalence of 3.2% among baseball players aged 10–12 years using ultrasound.

Although no large-scale studies have been undertaken with female athletes, several reports note an elevated risk of capitellar OCD in female gymnasts. Although Kessler et al. noted a 6.8 times greater odds ratio of having elbow OCD in adolescent males as opposed to females, these findings are likely biased by sport popularity in Southern California. A similar, but much smaller, cohort out of Boston noted similar rates of OCD among male and female athletes. Interestingly, in the cohort out of Boston, female gymnasts were noted to be more likely to present at a younger physical and skeletal age and to have an injury to their nondominant arm compared to the group of largely male baseball players.

Mechanism of Injury

Although the initial description by König in 1887 suggested a central role for inflammation in the formation of osteochondral fragments, this has since been disproven by multiple histologic studies. Currently, the most widely accepted cause for OCD formation across joints is repetitive microtrauma. Within the elbow, this theory is supported by the relatively high prevalence of capitellar OCD in adolescent baseball players and gymnasts, where the elbow is subjected to repetitive valgus loading. For baseball players, the elbow is subjected to high valgus stress during the late cocking and early acceleration phases of throwing, which generates both compressive and shear forces across the radiocapitellar joint. In contrast, the stress experienced during gymnastics appears to be an axial load, 60% of which is born by the radiocapitellar joint. ^, Interestingly, female gymnasts’ events result in increased axial loading and adduction moment, potentially placing them at higher risk of elbow injury than their male counterparts. ^, The variation in loading pattern between baseball and gymnastics translates into different locations for capitellar OCD between baseball players, who have more anterior lesions, and gymnasts, who have more distal lesions.

However, repetitive microtrauma may only be part of the elbow OCD story. The European Pediatric Orthopedic Society conducted a large multicenter study, which demonstrated that only 55% of patients with knee OCD regularly participated in sports or strenuous physical activity. Importantly, OCD may also result from obesity or anatomic variations. Kessler et al. found that extreme childhood obesity, as defined by body mass index >35 kg/m ² or weight 1.2× the 95th percentile, increases the risk of OCD formation across all joints by 86%. Interestingly, the highest risk joints in this study were the elbow and ankle, where extreme obesity conferred 3.1 and 3.0 times increased risk of OCD formation, respectively.

Lower extremity alignment plays a significant role in the development of OCD in the knee, with varus knees tending to develop medial femoral condyle OCD lesions and valgus knees tending to develop lateral femoral condyle OCD lesions. Anatomic considerations appear to be critical to elbow OCD development as well. First, the converse pattern appears to be true for the elbow, where patients with capitellar OCD are more likely to have a varus carrying angle than matched controls. Second, Schenck et al. demonstrated in cadaveric studies that a stiffness mismatch is present in the radiocapitellar joint, which may lead the lateral capitellum to experience a higher strain environment during valgus load. Third, healing after injury may be compromised by limited vascular supply to the distal/anterior capitellum. The immature capitellum lacks a substantial metaphyseal blood supply and instead relies on branches from the radial recurrent and interosseous recurrent arteries. ^, This leaves the capitellum vulnerable to ischemia, particularly in the setting of repetitive injury.

One potentially unifying theory involves disordered ossification of a portion of the epiphysis. ^, According to this theory, there is an unspecified insult (single or repetitive) to the epiphysis that leads to either temporary or permanent cessation of ossification in one region. The remainder of the epiphysis continues to grow and undergo endochondral ossification, leading to the development of a growing defect. Here, a complete cessation in ossification would generate a completely cartilaginous OCD, whereas a temporary stop would generate a partially ossified fragment. Although Barrie ^, did not provide any direct evidence to support this mechanism, unpublished MRI data out of the Research in Osteochondritis of the Knee (ROCK) group suggest it may be visible on MRI. Regardless, capitellar OCD formation is likely the result of a combination of factors including repetitive stresses across the radiocapitellar joint, tenuous vascular supply to the capitellum, and a mismatch in stiffness between the radial head and lateral capitellum.

Treatment and Outcomes

Operative Management

Multiple surgical procedures have been described for the management of capitellar OCD lesions that have failed conservative management or have radiographic indicators of instability. Surgical treatment options include fragment removal with or without curettage or drilling, ^, direct fragment fixation, reconstruction with autograft, reconstruction with allograft or autologous chondrocytes, and closing wedge osteotomy of the distal humerus. Early surgical treatments consisted of open fragment removal with or without drilling or curettage of the donor site. ^, Although there were short-term improvements in elbow symptoms after surgical treatment, all four studies noted residual symptoms in 42%–65% of patients at long-term follow-up.

An alternative surgical treatment is arthroscopic removal of loose bodies, debridement, and chondroplasty ( Figs. 19.2 and 19.3 ). All studies describing this technique demonstrate improvements in pain postoperatively, with return to preinjury levels of sport ranging from 40% to 92%. When combined in a meta-analysis, the overall return to any level of sport rate was 87%, with 71% returning to their previous level of activity at a mean time of 4 ± 1.5 months after arthroscopy with or without microfracture. These results are supported by the long-term case series in adolescent baseball players by Matsuura et al., which showed an 87% return-to-sport rate and durable symptom relief at a minimum of 10-year follow-up. Importantly, this study notes that although their return to sport rate was high overall, it was much lower for pitchers, where only one of five patients returned to pitching. Of note, poorer results from arthroscopy were seen in patients with lesions that extended to the lateral border of the capitellum, as such lesions may compromise elbow biomechanics. ^,

Osteochondritis dissecans lesion of the capitellum, uncontained lesion. Arrow indicates OCD lesion capitellum.

Large loose body in the posterior compartment of the elbow. Arrow indicates OCD lesion capitellum.

Microfracture has also been described as an option for full-thickness osteochondral lesions of the capitellum. A retrospective review of 23 patients (25 elbows) demonstrated that 77.3% of patients were able to return to sport. In female gymnasts, however, only 50% were able to return to sport. The authors concluded that use of osteochondral allograft should be the preferred treatment for a large osteochondral defect in a gymnast, whereas other sports such as swimming and water polo had greater success with microfracture ( Fig. 19.4A and B ).

(A) Microfracture of osteochondritis dissecans (OCD) defect after debridement. (B) OCD lesion after microfracture. Arrow indicates OCD lesion capitellum.

Multiple studies have also evaluated the utility of OCD fixation using wires, Herbert screws, or dynamic stapling. All methods of fixation provide good short-term improvements in symptoms, with variable return-to-sport rates ranging from 66% to 100%. However, when the data was combined in a meta-analysis completed by Westermann et al., patients who underwent fixation of capitellar OCD lesions had a return-to-sport rate of only 64%. This data is strongly influenced by the studies from Nobuta et al. and Hennrikus et al. which had much lower return-to-sport rates than the other studies included in the analysis. In the level II study completed by Takahara et al., the authors found similar outcomes for fragment fixation and removal with smaller unstable lesions (<50% capitellar articular width). However, with unstable lesions larger than 50% of the capitellar width, the authors reported superior outcomes with either fragment fixation or reconstruction as compared with removal alone.

Another surgical option for large, advanced or irreparable capitellar OCD lesions is osteochondral autograft transfer (OATS), which has been described using autografts from both the rib and the knee. ^{, , , ,} In the previously mentioned meta-analysis by Westermann et al., the authors found a 95% return to any level of sport rate and 94% return to previous level of sport rate at a mean of 5.9 ± 0.9 months following OATS for capitellar OCD. Notably, the authors reported that OATS provided superior return-to-sport rates when compared with debridement and marrow stimulation (71%) and fragment fixation (64%).

Similar to the knee, there are a number of other cartilage restoration and offloading procedures that are currently being investigated in the literature. One technique of interest is autologous chondrocyte implantation, which has long been studied in the knee. ^, Although there are no outcome studies in the elbow published at present, Patzer et al. published a technique paper describing the procedure for arthroscopic autologous chondrocyte implantation for the capitellum. Additionally, Dunn et al. reported on one case with the associated technique for particulated juvenile cartilage transfer. Finally, Mirzayan et al. reported good outcomes and near 100% pain relief with fresh osteochondral allograft transplantation in nine adolescent baseball players.

Another technique of interest is distal humeral osteotomy, originally reported by Yoshizu and colleagues. Similar to the concepts of high tibial osteotomy and distal femoral osteotomy of the knee, the closing wedge distal humeral osteotomy seeks to offload the radiocapitellar joint to allow for OCD healing. Since then, there have been multiple small case series evaluating the utility of the procedure. Kiyoshige et al. reported on the treatment of seven adolescent baseball players, with six of seven players returning to their prior level of sport. Ueki et al. reported on a series of 17 patients treated with distal humeral osteotomy for capitellar OCD with a minimum follow-up of 2 years. The authors reported poor healing in 2 of 17 lesions, and although all patients returned to sport, only 11 of 17 returned to their preinjury sport of choice. Although promising, the reported outcomes are inferior to other cartilage restoration procedures, suggesting that distal humeral osteotomy alone may find utility as an adjunct or salvage procedure.

Outcomes in Female Athletes

Perhaps because of the popularity of baseball in both the United States and Japan, the vast majority of studies on outcomes of OCD treatment have focused on male athletes. Early studies of OCD in female athletes, predominantly gymnasts, suggest that they may have inferior outcomes than their male counterparts. ^, Maffulli et al. looked at a series of 12 gymnasts, 6 males and 6 females, and found that only 1 of 12 athletes was able to continue competing at a high level at skeletal maturity. Jackson et al. reported similarly poor results in a series of seven female gymnasts treated with arthroscopic removal of loose bodies, curettage of loose articular margins, and drilling, with only one of seven athletes continuing to compete at follow-up. These findings are in contrast to the earlier series from Singer and Roy, where they found four of five female gymnasts were able to return to sport. The variability of these studies is unquestionably due to the small sizes of these case series and lack of data on lesion grading.

More recent work has suggested that both gymnasts and female athletes have similar outcomes with both conservative and surgical management of elbow OCD. Niu et al. found that gender and sport had no impact on the healing of stable OCD lesions with conservative management. Jones et al. evaluated outcomes of patients after arthroscopic debridement and loose body removal with or without drilling and bone grafting. This study included return-to-sport data on their subgroups, with 8 of 10 baseball players and 4 of 5 gymnasts returning to their preinjury sporting activities. Brownlow et al. also included return-to-sport information for their subgroups after arthroscopic treatment of capitellar OCD. They reported an overall return-to-sport rate of 85%, with six of seven female gymnasts returning to their prior level of activity. This data is supported by the larger case series presented by Yehyawi et al. at the American Society for Hand Surgery in 2018. The authors evaluated 80 OCD lesions in 64 gymnasts that were managed surgically and reported a return to sport rate of 81%. Unfortunately, they did not specify whether the study patients were male or female. However, overall, the data indicates that lesion stability has a much stronger impact on outcomes than gender or sport.

Summary

OCD is a well-recognized cause of elbow pain and disability in adolescent athletes, both male and female. OCD lesions are most commonly seen in athletes who participate in sports that subject the elbow to high valgus and/or axial loads, such as baseball and gymnastics. Female gymnasts may be at particular risk for capitellar injury than their male counterparts. Although the exact mechanism for OCD formation in the elbow has yet to be determined, it likely involves single or repetitive microtrauma to the capitellar epiphysis, which is vulnerable to disordered ossification and necrosis due to a tenuous blood supply. Good treatment outcomes have been seen in early or stable capitellar OCD managed conservatively, regardless of patient gender or sport. Surgical management of advanced or unstable lesions may consist of removal of loose bodies via an open or arthroscopic technique, fragment fixation, or articular surface reconstruction. Good outcomes have been seen with arthroscopic management of smaller (<50% of capitellar width) lesions, regardless of sport or gender. However, larger, unstable lesions may benefit from articular surface reconstruction with OATS or other reconstructive procedures.