• Osteochondritis dissecans (OCD) is a disorder primarily affecting subchondral bone, leading to osseous collapse and destabilization of overlying articular cartilage (Fig. 58-1).¹,²

• OCD may be present in many joints but most commonly affects the medial femoral condyle of the knee (70% of cases).³,⁴

• While OCD may affect both pediatric and adult populations, the incidence of disease is higher in children and adolescents (9.5 per 100,000 persons age 6 to 19 per year).⁵

• Osteochondral allograft (OCA) transplantation has been shown to be an effective knee joint preservation procedure for OCD of the knee,⁶ with high patient satisfaction and low rates of graft failure.⁷

• Isolated, unipolar symptomatic chondral or osteochondral lesions of the femoral condyle, trochlea, or patella

• Bipolar lesions of the patellofemoral compartment also can be treated with OCA, though outcomes are less predictable.

• Young (chronologically <50 years of age), high physical demand patients

• Lesion area is typically >10 mm².

• Body mass index (BMI) < 35, neutral alignment, and meniscal status are modifiable risk factors that should be considered when deciding if OCA is appropriate.

• OCA can be successfully performed concomitantly with osteotomy, meniscal procedure, or ligament repair/reconstruction.⁶

• Many patients with symptomatic lesions can be successfully treated with nonoperative measures including injections, physical therapy, and activity modification.

• OCA can be used as a primary option for patients who remain or become symptomatic and in whom conservative measures have failed. In addition, OCA is a viable option for patients who have failed prior surgical intervention such as arthroscopic debridement, OCA fixation, or fragment excision.⁸,⁹

• Well-padded tourniquet

• A press-fit technique is commonly used for most contained defects of the femoral condyles by the senior author using commercially available systems (Allograft OATS, Arthrex, Naples, FL) (Fig. 58-2).

• Instrument and implant considerations (many of the following may not be required and decisionmaking is based on surgeon experience and defect-specific variables)

• Cannulated cylindrical sizing guides (15, 18, 20, 25, 30, and 35 mm)

• Cannulated cutting bore

• Allograft workstation

• Donor harvester

• Arthroscopy tower and arthroscope

• Arthroscopic shaver may be necessary.

• Z retractors (2), large rakes (2), and/or Hohmann retractors (2)

• No. 15 blade scalpel

• Small ruler

• Sterile marking pen

• Hemostat

• Room temperature saline

• Guidewire

• Pulsatile lavage of combination saline and CO2 (CarboJet, Kinamed, Camarillo, CA)

• Oscillating saw

• Rongeur

• Hand tamp and mallet

• Metallic headless screws (Acutrak 2 mini screws, Acumed, Hillsboro, OR), Bio-Compression screws (Arthrex, Naples, FL), Orthosorb pins (Depuy, Inc., Warsaw, IN)

• The patient can be positioned supine, or the limb can be placed in a standard anterior cruciate ligament (ACL) leg holder (Fig. 58-3).

• For simple OCA transplantation, the patient is supine with the leg placed straight on the bed.

• For complex OCA transplantation with concomitant procedures, we may use the ACL leg positioner such that the knee is draped free at 90 degrees of flexion allowing circumferential access.

• A well-padded thigh tourniquet is used for the duration of the case and deflated at the end of the case before closure to ensure hemostasis.

• The operative extremity is prepared and draped for a standard anterior approach to the knee.

• This procedure typically is performed through a small parapatellar arthrotomy using a central incision.

• In general, the arthrotomy is made on the ipsilateral side to the pathology, though this may vary based on the optimal angle to allow a perpendicular approach to the osteochondral lesion.

• On the medial side, a vastus-sparing approach is preferred.

• On the lateral side, we prefer to release the lateral retinaculum for exposure, which can largely be left open at the conclusion of the case.

• The arthrotomy can be extended proximally or distally to improve exposure depending on lesion size and location.

• The arthrotomy can be extended distally to accommodate a high tibial osteotomy (HTO) when indicated for a medial femoral condyle OCA.

• Z retractors or Hohmann retractors are used to (a) retract soft tissue and (b) retract the patella by placing a retractor in the notch (Fig. 58-4).

• The knee can then be flexed to optimally expose the lesion.

• A lateral approach is preferred for patellofemoral lesions with eversion of the patella to ˜90 degrees or more when needed. When concomitant tibial tubercle osteotomy is performed, we do this first to improve visualization but do not elevate the entire shingle of bone or disrupt the fat pad in an effort to minimize morbidity.

• For the remainder of the procedure, the flexion angle is kept the same by the leg positioner.