Osteochondral Allograft Transplantation for Osteochondral Defects of the Knee
A 20-year-old collegiate basketball player presents with a 1-year history of left knee pain accompanied by clicking, catching, and effusions. Will OCA transplantation relieve his symptoms and allow him to return to play?
Anant Dixit, MD, and Kevin B Freedman, MD, MSCE
Chondral lesions of the knee are common, with a prevalence of more than 60% in those undergoing knee arthroscopy.  These cartilaginous injuries often occur in athletes and may significantly limit elite performance if left unaddressed. [2,3] Unfortunately, the poor healing potential of hyaline cartilage limits injury management. 
Chondral lesions are often localized, full-thickness, and amenable to a joint-preservation procedure. [5,6] They can have a significant impact on quality of life, ranging from pain while performing activities of daily living to inability to return to high-level sport. 
Treatment options for chondral injuries include:
- Conservative management
- Bone marrow stimulation
- Mosaicplasty/osteochondral autograft transfer system
- Autologous chondrocyte implantation (ACI)
- Osteochondral allograft (OCA) transplantation
Treatment should be tailored to the characteristics of the pathology, including size, multifocal involvement, location, subchondral bone involvement, and presence of bony malalignment.
Fresh OCA transplantation describes a single-stage transplantation of a size-matched allograft of cartilage and underlying subchondral bone into a defect of a recipient knee. Large defects (more than 2 cm x 2 cm) are often treated with ACI or OCA, both yielding significantly improved functional outcomes and patient satisfaction rates. [8-10] However, OCA transplantation may be preferred in the setting of unshouldered lesions, subchondral bone edema, and/or subchondral bone loss. 
The following case presentation illustrates the use of OCA transplantation in the treatment of an osteochondral lesion, outlining the surgical technique and postoperative protocol.
A 20-year-old collegiate basketball player presented with a 1-year history of left knee pain. The patient complained of pain localized to the medial side of his knee, which worsened with weight-bearing. He reported mechanical symptoms of clicking and catching and complains of recurrent effusions. He denied any instability.
The patient had attempted extensive conservative management with his athletic trainer – including the use of non-steroidal anti-inflammatory drugs and physical therapy – but it was unsuccessful and the patient still had significant knee pain.
- Antalgic gait, which favored the left side
- Mild effusion
- Full, painless active range of motion
- Tenderness to palpation over the medial femoral condyle; no tenderness along the medial or lateral joint lines
- No demonstrable ligamentous laxity
- Neurovascularly intact
- Weight-bearing anteroposterior (AP), lateral, and Merchant view radiographs show osteochondritis dessicans lesion on the medial femoral condyle, with no joint space narrowing (Figure 1).
- MRI shows an osteochondral loose body and unstable osteochondritis dessicans lesion on the medial femoral condyle with underlying signal intensity (Figure 2).
Figure 1. AP, lateral, and Merchant view radiographs of the left knee demonstrate an osteochondral lesion on the medial femoral condyle.
Figure 2. T1- and T2-weighted MRI images demonstrate an osteochondral loose body and unstable osteochondritis dessicans lesion, respectively.
- Unstable osteochondritis dissecans of the medial femoral condyle with loose body
Diagnostic arthroscopy was initially undertaken to better characterize the size of the osteochondral defect, as well as to identify any concomitant intra-articular pathology. Loose bodies were removed, and the defect was measured. The defect in this case example was measured to be 2.5 cm x 2.5 cm (Figure 3).
Figure 3. Arthroscopic views of the lesion. Diagnostic arthroscopy allowed for confirmation of lesion size, location, subchondral bone loss, and concomitant intra–articular pathology.
Preoperative AP and lateral radiographs with a standard marker were used to obtain a size-matched medial femoral condyle osteochondral allograft. The graft was cultured for bacterial growth and tested for disease transmission. Grafts are typically implanted between day 18 and 28 after harvesting to ensure chondrocyte viability.
Once the graft was available, the patient was scheduled for the OCA transplantation procedure:
- The patient was placed in the supine position with appropriate padding of all bony prominences. A well-padded high-thigh tourniquet was applied to the operative extremity, and a leg positioner was used to ease extremity positioning during exposure and closure.
- A parapatellar arthrotomy was performed to allow for visualization of the entire chondral/osteochondral defect, with careful attention to avoiding damage to the surrounding compartment and meniscus (Figure 4).
- An appropriate sizer was identified to allow for excision of the entire chondral lesion. A guide pin was placed perpendicular to the center of the lesion.
- A scoring device was used to mark the outer boundary of the lesion. This helps prevent potentiation and thermal necrosis during recipient site preparation.
- A reamer was used to prepare the recipient site to an approximate depth of 6 mm to 8 mm (Figure 5). The depth of each quadrant was measured with a depth gauge and recorded.
- The donor plug was harvested from the fresh condyle to match the curvature of the recipient site. Each quadrant of the donor plug was then cut to match the depth of the recipient site.
- The donor plug was thoroughly cleansed using pulsatile lavage to remove antigenic elements, transplanted into the recipient site, and then gently impacted (Figure 6).
- The donor plug was implanted using a press-fit technique; however, the donor plug can be secured with bioresorbable screws as necessary.
- The knee was cycled to ensure graft stability.
- The parapatellar arthrotomy was then closed in the standard fashion.
Figure 4. A limited medial parapatellar arthrotomy allows for visualization of the entire lesion.
Figure 5. The recipient site is fully prepared with a depth of 6 mm to 8 mm.
Figure 6. The donor plug is transplanted into the recipient site, restoring the articular contour.
0 to 6 Weeks Postop
- The patient was made non-weight-bearing, with a hinged knee brace locked in extension.
- A continuous passive motion machine was used when the patient was not ambulating.
- The patient began isometric strengthening of the quadriceps and hamstring muscles.
6 to 8 Weeks Postop
- Partial weight-bearing was allowed and the hinged knee brace was progressively unlocked during ambulation.
- The patient continued quadriceps and hamstring muscle strengthening.
8 to 12 Weeks Postop
- Weight-bearing was progressed to allow for full weight-bearing.
- The pateint started closed chain exercises.
6 to 10 Months Postop
- An MRI at 6 months after surgery revealed marrow infiltration of the graft and intact articular cartilage (Figure 7).
- The patient was allowed to return to jogging. Sport-specific training was also initiated.
- A full return to sports was allowed at 10 months postoperatively.
Figure 7. T1- and T2-weighted MRI images, respectively, demonstrating an intact graft and restoration of the articular contour.
Osteochondral allograft transplantation has yielded positive results in the treatment of chondral and osteochondral defects in the knee. [12,13] More specifically, OCA transplantation has proven to be beneficial in large chondral lesions with or without involvement of the underlying subchondral bone. This technique has been found to restore the geometry of the articular contour, provide bony structural support, and result in improved patient outcomes. [14-16]
These results have been successfully translated into treatment of the elite athlete with chondral pathology. Krych et al  reviewed a case series of 43 athletes treated with OCA transplantation with an average follow-up of 2.5 years. They found a 79% return to preinjury levels of play.
A retrospective review of 13 collegiate and high school athletes treated with OCA transplantation yielded a 77% adjusted return to competitive play or a belief of return to competitive play if not precluded by graduation.  These findings were echoed in a case series examining 11 collegiate and professional basketball players undergoing OCA transplantation (14 treated lesions), which resulted in an 80% return to preinjury levels of play. 
OCA transplantation can be used with success in settings beyond isolated lesions of a femoral condyle. In a systematic review, Chahla et al  demonstrated 5- and 10-year satisfaction rates of 87.9% and 77.2%, respectively, with OCA transplantation in the uniquely challenging patellofemoral compartment. Cotter et al  demonstrated improved outcomes in active patients undergoing multifocal OCA transplantation.
Favorable outcomes have been demonstrated in OCA graft survivorship in the setting of concomitant meniscal transplantation, despite the complexity of the procedure.  Finally, OCA has been successfully used in revision chondral surgery: In a prospective cohort, Merkely et al  demonstrated successful revision of failed ACI with OCA transplantation in terms of survivorship, clinical outcomes, and reoperation rates.
Despite the wide application of OCA transplantation, patient and chondral lesion characteristics can limit the outcome. A case series of 52 knees demonstrated an increased failure rate in patients over age 40 compared with patients under age 40.  However, a study of 115 patients under age 40 and 55 patients age 40 and older yielded higher postoperative KOOS scores in the latter cohort, possibly attributable to a difference in expectations between the groups. Finally, Familiari et al  performed a systematic review that identified revision procedures, patellar chondral lesions, and bipolar lesions as having lower survival rates.
OCA transplantation serves as a versatile tool in joint preservation. The specific characteristics of the chondral lesion should be considered when determining the appropriate joint preservation technique. Osteochondral allograft transplantation yields high rates of return to competitive play and high rates of patient satisfaction.
At the time this article was written, Anant Dixit, MD, was a sports medicine fellow at The Rothman Institute, Philadelphia, Pennsylvania. He is now a sports medicine surgeon with the Southern California Permanente Medical Group at Fontana Medical Center in Fontana, California. Kevin B Freedman, MD, MSCE, is an attending surgeon with The Rothman Institute, focusing on sports medicine injuries to the knee and shoulder. He is an Associate Professor at Thomas Jefferson Medical College, Philadelphia, Pennsylvania, and Medical Director of the Bryn Mawr Hospital Cartilage Restoration Program, Bryn Mawr, Pennsylvania.
Sports Medicine Editor, Rothman Institute Grand Rounds
Disclosures: The authors have no disclosures relevant to this article.
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