Osteochondritis dissecans (OCD) is a condition described in 1870 by König as an idiopathic focal lesion affecting the subchondral bone with possible compromise of the stability of the adjacent cartilage. The condition can cause arthrosis at a young age¹⁾. The spectrum of lesions is broad and ranges from the superficial compromise of the cartilage to osteochondral collapse and the formation of intra-articular loose bodies²⁾.

There has yet to be a consensus about the aetiology, and it has been associated with avascular necrosis of the subchondral bone, genetic causes, abnormal calcification patterns, and endocrine abnormalities²⁾. Genetic studies have associated specific alterations with OCD, such as the ACAN gene; however, a pattern has not yet been identified³⁾.

The most commonly affected joint is the knee, specifically the medial femoral condyle. OCD mainly affects men (2:1 compared to women) in the adolescent stage between the second and third decades⁴⁾. The most frequent clinical presentation is knee pain of increasing intensity during daily and sports activities that may be accompanied by a sensation of locking knee^2,5).

Many classifications for OCD has been proposed. According to the review performed by Jacobs et al.¹⁾ the first classification proposed for OCD was the one proposed by Guhl y cols in 1979. This classification consisted of 4 stages: grade 1, lesion is present yet intact; grade 2, superficial fissure of the cartilage; grade 3, partial detachment of the cartilage; and grade 4, complete detachment of the cartilage, loose bodies and the presence of a crater in the subchondral bone. Classification systems have been modified and adapted for magnetic resonance imaging (MRI)¹⁾. The treatment of grade 4 OCD lesions depends on the size, cartilage stability, and the physeal status⁶⁾.

This case report aims to present a novel technique to treat grade 4 OCD with good functional outcomes at one-year follow-up.

An 18-year-old patient with no prior trauma history sought a medical consultation after suffering knee pain for ten months. A physical examination revealed medial knee pain, joint effusion, and a full knee range of motion. An MRI was requested, which revealed a lesion in the medial condyle compatible with grade 4 OCD (Fig. 1). The patient-reported outcome before surgery was level 2 on the Tegner scale and 36 points on the Lysholm scale.

The patient underwent surgery under spinal anesthesia and sedation. First, diagnostic arthroscopy was conducted by an anterolateral portal and an anteromedial portal and no other lesions were found. The defect in the medial condyle was confirmed and measured 2 cm in length and 1 cm in width.

Then, the contralateral anterior iliac crest (AIC) was addressed by an open approach performed parallel to the AIC. The anterior-superior iliac spine was identified, and the harvest was performed 2 cm posterior to avoid an injury to the lateral femoral cutaneous nerve. Bone harvesting was performed with the trapdoor technique as described by Cooper and Coughlin⁷⁾.

Finally, a medial parapatellar arthrotomy was performed to expose the medial condyle. The knee was flexed and the patella was gently pulled laterally by a retractor to obtain full exposure. Curettage of the lesion was performed with removal of all the devitalized tissue under the cartilage defect until healthy tissue was visualized, and then the 1-cm deep defect was noted (Fig. 2). The defect was filled with the cancellous bone graft obtained from the AIC up to the level of the adjacent subchondral bone; then it was sealed with Hyalofast^® (Cimed Healthcare, Kuala Lumpur, Malaysia) biodegradable hyaluronic acid scaffold. This scaffold was sutured with four stitches of 2-0 Ethibond^® (Ethicon, Somerville, NJ, USA). Full range of motion and no weight bearing were encouraged for six weeks after hospital discharge.

At one-year follow-up, the patient was asymptomatic without joint pain and had a full range of motion. An MRI was performed, which showed complete healing of the subcondral bone and a continuous signal of the cartilage in the medial femoral condyle (Fig. 3). The patient was authorized to resume sports. Patient-reported outcomes at one-year follow-up were level 4 on the Tegner scale and 90 points on the Lysholm scale.

OCD is a disabling pathology in adolescent athletes, representing an important challenge for the knee surgeon, especially in grade 4 lesions⁸⁾. Standard treatment for grade 4 OCD is to perform an osteochondral autologous transfer (OATS), which consists of obtaining an osteochondral cylinder from a knee region with low contact pressure, most commonly, the lateral trochlea, and to transfer it to the site of the defect⁹⁾. This procedure has the disadvantage of leaving a defect in another area of the knee; nevertheless, reports show a favorable outcome in 82% of patients¹⁰⁾.

In our case, the size of the lesion was so large that it was at the upper size limit of the traditional OATS indication; two 10 mm plugs would have to be used for OATS in the patient, which means a large donor area in the trochlea^11,12). Taking this into account, it was decided to use an iliac crest autograft to fill the defect and seal it with a biodegradable hyaluronic acid membrane. With this, a structural and biological environment for fibrocartilage formation was provided. A disadvantage of this technique is the risk of iliac crest pain and paresthesia of the lateral femoral cutaneous nerve; nevertheless, the patient had no complaints after the first postoperative month.

The size of the lesion is critical in the treatment decision making of OCD²⁾. For a large lesion, several techniques are described. Hohmann and Tetsworth¹³⁾ described in patients with OCD over 2.5 cm², the use of a fresh-frozen irradiated allograft provided good results; nevertheless, this type of graft is expensive and unavailable worldwide. Zellner et al.¹⁴⁾ reported good outcomes were achieved with use of bone autograft from either the iliac crest or the distal femur, combined with autologous chondrocyte transplantation in large and deep osteochondral defects; however, this also raises costs and is not widely available.

Development of cell-free scaffolds (chondrocytes) has arisen with the purpose of inducing tissue regeneration through the proliferation and migration of mesenchyme cells¹⁵⁾. Also, scaffolds would be able to sustain the clot created after microfractures or nanofractures and increase the success rate in medial condyle lesions¹⁶⁾. Focusing on patients with OCD, Berruto et al.¹⁵⁾ reported a multicenter study with 2 years of follow-up where good functional outcomes were achieved in large OCD lesions treated with scaffolds without chondrocytes.

The result of the treatment we proposed in this report is comparable to the good results obtained with other types of treatment^{10,13,14,17,18)}. It also has the advantage of not requiring an intra-articular donor site and allografts in cases with deep and large defects greater than 2 cm². Besides, the hyaluronic acid scaffold, despite the high cost, is more affordable than autologous chondrocyte transplants and fresh-frozen allografts. Significant clinical and functional improvements were observed in this case, considering that the treated lesion was large, 2 cm² in size and 1 cm in depth.

In conclusion, treatment of large (2 cm²) and deep grade 4 OCD lesions with autologous iliac crest bone grafts and hyaluronic acid scaffolds seems to be a good alternative for this challenging condition. Further studies must be conducted with longer follow-ups.

No potential conflict of interest relevant to this article was reported.