Published 11/1/2018
Terry Stanton

Study Follows Up on Skeletally Immature Patients with Osteochondritis Dissecans in the Knee

Skeletally immature patients who had osteochondritis dissecans (OCD) in the knee demonstrated “clinically promising outcomes” at 14 years of follow-up, according to a study presented during the American Orthopaedic Society for Sports Medicine Annual Meeting. Patients in the study had persistent knee pain rates at or less than 15 percent, symptomatic osteoarthritis (OA) rates at or less than 8 percent, and conversion to total knee arthroplasty (TKA) rates of less than 5 percent, regardless of initial operative or nonoperative management.

Management of OCD lesions remains controversial, said Aaron J. Krych, MD, of the Mayo Clinic in Rochester, Minn., who presented the study. “While the general treatment algorithm for clinical decisions regarding operative and nonoperative management is fairly well accepted, significant room exists for interpretation on a case-by-case basis,” he said. Current studies recommend complex decision making that considers history, physical exam findings, and MRI. Complicating management, the study authors wrote, is that “the reliability and accuracy of MRI in identifying lesions as stable or unstable, especially in the skeletally immature population, has recently been brought into question in studies correlating imaging and arthroscopic findings. If left untreated, focal OCD can progress to early arthritis, pain, and disability.”

It has been previously estimated that 4 percent of primary knee OA in men is caused by previously undiagnosed OCD lesions. However, few studies have reported the rate of OCD progression to arthritis or compared the long-term effects of operative versus nonoperative management. Additionally, most studies have been limited by small sample size and short duration of follow-up due to the relative rarity of the condition. Considering the risk for knee pain and progression to early TKA, better understanding of the long-term outcomes of operative and nonoperative management of OCD lesions is necessary.

The authors conducted the study for two reasons: (1) to evaluate the rate of persistent knee pain, symptomatic OA, and conversion to TKA in a skeletally immature population with OCD; and (2) to determine factors associated with persistent knee pain at time of final follow-up. They hypothesized that: (1) patients with OCD of the knee would have a clinically significant risk of symptomatic knee pain at final follow-up and undergo TKA at an earlier age than the general population; and (2) previously established short-term risk factors, such as unstable lesions and patellar location, would predict worse outcomes.

Fig. 1 Arthroscopic images of an unstable unsalvageable osteochondritis dissecans progeny fragment (left) with subsequent arthroscopic removal (right)
Courtesy of Aaron J. Krych, MD/Mayo Clinic

Looking at the long term

“OCD of the knee remains an uncommon diagnosis,” Dr. Krych commented. “Therefore, there are no large data sets on these patients, and the natural history remains largely unknown. Particularly, we wanted to evaluate the long-term outcomes of treatment of OCD in skeletally immature patients. Typically, there tends to be a lot of bias toward surgical outcomes in the literature. However, we wanted to evaluate both the long-term nonoperative as well as operative management of OCD of the knee.”

The investigators reviewed a geographic database of more than 500,000 patients to identify those with knee OCD. They identified 95 potential patients, then manually reviewed records for each to verify the accuracy of the diagnosis. They then entered demographics, including age, body mass index, and lesion laterality, and captured details regarding treatment course on a standardized database. Inclusion criteria consisted of symptomatic OCD lesions of the femoral condyle (medial or lateral), trochlea, or patella and skeletally immature patients with open distal femoral and proximal tibial physes on plain radiographs.

For an OCD lesion, a knee radiograph must have demonstrated a radiolucent line separating an osteochondral segment in the femur or patella from the underlying bone, or an MRI must have shown high-signal intensity between an osteochondral segment and the underlying bone. On manual review, all 95 patients were confirmed to have met criteria for inclusion.

Thirty-one males (74 percent) and 11 females (26 percent) with a mean age of 12.0 years (range, 7–15 years) were treated non-
operatively and followed for a mean of 13.0 years (range, 2–38 years). Seven patients were immobilized and asked to avoid weight bearing, 32 patients received a brace, and 13 patients were given an assistive device to walk. At the time of final follow-up, four patients had symptomatic knee pain.

Of the 53 patients treated surgically, at a mean of 33.5 years postoperatively, two patients had developed symptomatic OA. Both patients received TKA: one at 35.0 years after surgery and the other at 38.0 years. Thus, 10-, 20-, and 30-year survival rates free from both OA and TKA were 100 at all time points.

In total, three patients managed operatively or nonoperatively converted to TKA at a mean age of 51.5 ± 2.6 years, which is statistically below (P = 0.004) the latest available institutional average age of 68.0 ± 10.0 years for primary TKA in the 2002–2005 period, the authors noted.

Demographic variables and factors, which differed between the operative and nonoperative groups, such as lesion location, were assessed for predictive value for symptomatic knee pain. Males were at a decreased risk of symptomatic knee pain (P = 0.02), whereas patellar lesion location (P = 0.02) and unstable lesions according to the De Smet criteria (P = 0.03) were associated with an increased risk of symptomatic knee pain at final follow-up. Operative versus nonoperative treatment; patient age; lesion width, depth, and contour; subchondral bone disruption; intra-articular fragment displacement; and adjacent cartilage defects did not predict symptomatic knee pain. In a subanalysis of the individual operative and nonoperative management groups, unstable lesions trended toward predicting knee pain at final follow-up in the operative cohort (P = 0.19), whereas unstable lesions remained highly significant in predicting knee pain in the nonoperative cohort
(P < 0.001).

Fig. 2 Follow-up radiograph of right lateral femoral condyle osteochondritis dissecans lesion following excision
Courtesy of Aaron J. Krych, MD/Mayo Clinic

Better outcomes ahead

“I was surprised that more patients were not treated with cartilage restoration procedures,” said Dr. Krych. “Of the operative procedures, a significant proportion underwent drilling or fixation with salvage of the progeny OCD fragment. However, about half of the operative patients had a lesion that was not able to be salvaged and was excised (Figs. 1 and 2). In a contemporary study, many of these patients would undergo cartilage and bone restoration with an osteochondral allograft or an autologous chondrocyte implantation procedure with bone grafting. Hopefully, future studies will have even better outcomes with these cartilage restoration procedures.”

The clinical takeaways, he said, are that “patients can have a good long-term outcome. The currently developed algorithms for treatment of stable and unstable lesions in the skeletally immature patients seem to work well. The rate of symptoms and arthritis are very low at [a mean] 14-year follow-up.”

In future studies, he reiterated, “it will be very interesting to see the long-term results of these patients with cartilage restoration procedures when the OCD lesion cannot be salvaged. We hope we will see even lower rates of knee symptoms and arthritis.”

Dr. Krych’s coauthors of “Osteochondritis Dissecans in the Knee of Skeletally Immature Patients: Rates of Persistent Pain, Osteoarthritis, and Arthroplasty at Mean 14-Years’ Follow-Up” are Mario Hevesi, MD; Thomas L. Sanders, MD; Ayoosh Pareek, MD; Todd A. Milbrandt, MD; Bruce A. Levy, MD; Michael J. Stuart, MD; and Daniel B.F. Saris, MD, PhD.

Terry Stanton is the senior science writer for AAOS Now. He can be reached at tstanton@aaos.org.