What is an Osteochondral Allograft?
An Osteochondral Allograft is required when knee cartilage damage occurs in several dimensions, locations, and depths. They range from being minor, secluded, superficial lesions to outsized, full-thickness, and multifocal defects. Chondral injury of the knee tends to occur at a young age. It occurs in approximately 60% of individuals with knee arthroscopy.
Defects of the articular cartilage can occur due to acute trauma or repeated overloading, leading to cartilage softening, flap tears, fissuring, or delamination.
Methods of Correcting Cartilage Defects of The Knee
There are several treatment options available for the treatment of cartilage defects, including:
- Abrasion arthroplasty
- Autologous chondrocyte implantation
- Osteochondral autograft transplantation
- Osteochondral allograft transplantation
Each method, as mentioned above, has intrinsic limitations. For example, marrow stimulation leads to the formation of hyaline-like fibrocartilage repair surface, that is believed to be biomechanically and physiologically inferior to innate hyaline cartilage.
Osteochondral autograft transfer (OAT) has donor site morbidity limitation. Debridement, OAT, and marrow stimulation techniques are ineffective for larger lesions (>2 cm). 2.16–18 In addition, staged cell-based cartilage restoration like autologous chondrocyte implantation (ACI) is a practical option for significant knee defects.
However, osteochondral allograft (OCA) transplantation is a one-stage procedure in which full-thickness, effective hyaline cartilage, prevents donor site morbidity, allows resurfacing of large-sized defects, and possibly achieves a more natural, similar form of the innate recipient external anatomy.
A study was done on Osteochondral allograft transplantation for chondral repair of the knee. It reported better patient outcome scores as opposed to scores before surgery. The survival rate of the graft was also found to be 79% to 100% at an average 2 to 4-year follow-up, 78% at 10 years, about 73% at 15 years, and 67% at 20 years. In addition, Osteochondral allograft transplantation is also reported to be desirable in the setting of extensive subchondral oedema, unshouldered lesions, or extensive bone loss, which needs restoration.
Indications and Contraindications for Osteochondral Allograft
The indications of Osteochondral allograft transplantation are as follows:
- Primary surgical management of lesions of the femoral condyles that are:
- Large (>2-3 cm2),
- Full-thickness (grade 3 or 4)
- Chondral or osteochondral lesions.
- Second-line therapy of tibial and patellofemoral and defects in patients who are symptomatic but refractory to nonsurgical management.
- Posttraumatic lesions
- Idiopathic lesions
- Defects associated with osteonecrosis, osteochondritis dissecans (OCD), and unsuccessful previous cartilage repair can be managed through Osteochondral allograft transplantation.
Osteochondral allograft Contraindications
The contraindications of OCA transplantation include the following:
- Current tobacco use
- Body mass index (BMI) greater than 35 kg/m
- Inflammatory conditions
- Diffuse degenerative articular changes
- Uncorrected knee pathologies such as abnormal patellar tracking, knee malalignment, meniscal deficiency, or ligamentous insufficiency.
Osteochondral allograft transplantation surgery is done under general anesthesia. The patient is placed in a supine position during anesthetization. After administration of adequate anesthesia, a comprehensive knee examination is performed. If platelet-rich plasma (PRP) or any other biologic aide is used, blood is drawn from the iliac crest or another site for use later. Application of a well-padded thigh tourniquet is made with or without performing diagnostic arthroscopy.
A lateral or medial parapatellar arthrotomy is done according to the lesion location. Different sized templates are used to measure the size of the chondral defect. The size of the template that completely covers the defect is chosen. The edges of the lesion are scored with the help of a guide pin placed in the centre of the defect.
A socket is created in the defect by reaming for the transfer of the Osteochondral allograft. Meanwhile, irrigation is done in order to avoid heat necrosis of the nearby subchondral bone and articular cartilage. The process of reaming is continued up until healthy bone is met, identified by bleeding. Care is taken not to go beyond a maximum of 7 to 8 mm of the total depth of bone. Next up, the reamed lesion is measured cautiously so that adequate donor plug trimming is ensured.
Preparation of The Allograft
The replacement allograft of 15-28 days is warmed by immersing in saline solution at room temperature. After being warmed, the specimen of the allograft is protected with the help of an allograft workstation. The harvesting of the osteochondral donor plug is carried out using a coring reamer. Irrigation is continually used during this step to prevent heat necrosis. The trimming of the plug is done to match the required dimensions (depth and diameter) of the lesion.
While preparing for the implantation, cleansing of the donor plug is done using saline with the help of pulsed lavage. This is done to eliminate any residual components of the bone marrow from the subchondral bone. This is considered to diminish the risk of immune reaction in the recipient. In cases in which blood was drawn for use as a biologic auxiliary, soaking of the graft may be soaked in platelet-rich plasma (PRP) or any other biologic medium.
Insertion of The Bone Plug
A “press fit” technique is then used to insert the bone plug into the recipient socket. This will match the precise height of the surrounding articular cartilage. For patients in whom the fit is agreeable, copious irrigation of the knee is done, and wound closure is done in a layered fashion.
Cost of Osteochondral allograft Transplantation
The Osteochondral allograft transplantation is a specialized procedure. Its cost is thus high depending upon the cost of the allografts that ranges around $10,000. Your specialist will be better able to give you a precise figure for your surgery.
Side Effects of Osteochondral allograft Transplantation
The advantage of Osteochondral allograft transplantation includes its potential to cater to bigger defects with stable hyaline cartilage short of donor site morbidity. Nonetheless, it also includes the following downsides:
- Greater rejection response of the transplanted bone.
- Graft availability
- High cost
- Risk of disease transmission
- Reduction in chondrocyte viability after harvest
- Significantly small window available for implantation storage of allografts at tissue banks.
- Haber DB, Logan CA, Murphy CP, Sanchez A, LaPrade RF, Provencher MT. OSTEOCHONDRAL ALLOGRAFT TRANSPLANTATION for the KNEE: POST-OPERATIVE REHABILITATION. Int J Sports Phys Ther. 2019;14(3):487-499. doi:10.26603/ijspt20190487
- Mistry H, Metcalfe A, Smith N, et al. The cost-effectiveness of osteochondral allograft transplantation in the knee. Knee Surg Sports Traumatol Arthrosc. 2019;27(6):1739-1753. doi:10.1007/s00167-019-05392-8
- Aleexev M. Autograft or allograft. AAOS. Jan, 2019. https://www.aaos.org/aaosnow/2019/oct/clinical/clinical01