Osteochondral Allograft Transplantation

Abstract

Background:

Articular cartilage lesions are a significant cause of morbidity and impaired knee function, and attempts to surgically repair damaged cartilage have failed to reliably reproduce native cartilage. Thus, osteochondral allograft transplantation is an effective one-step procedure to repair large cartilage defects.

Indications:

Osteochondral allograft transplantation is indicated for young active patients with large focal defects, those with a history of previous cartilage repair, and those with cartilage-related degenerative disorders such as osteonecrosis, osteochondritis dissecans, and/or post-traumatic osteochondral defects.

Technique Description:

In short, after the focal chondral defect is identified, a socket is created with specific dimensions in depth and diameter. The donor cartilage is then secured in a graft station, and a sizing guide is placed through a bushing to confirm the allograft harvest location. Using stabilization from the graft station arm, a coring reamer is then advanced through the donor cartilage, and a saw is used to allow for easy removal of the graft from the donor condyle. The plug is then fashioned to fit the exact dimensions of the socket created earlier in the procedure. A cut on the donor plug is made to fashion the plug to the appropriate depth. A rongeur is used to make the plug more bullet shaped at the end to allow the plug to enter the socket more easily. Small holes are then drilled into the base of the socket to help promote incorporation of the plug into the socket during the healing process. After the socket is irrigated, the plug is then placed into the socket, and a tamp is used to gently tap the cartilage until it is flush with the surrounding surface.

Results:

After an appropriate rehabilitation protocol is followed for up to 10 months postoperatively, osteochondral allograft transplantation allows for near-to-complete restoration of patient functionality and strength, with return to full activity possible within 1 year.

Conclusion:

Acute repair of large focal chondral defects is effective in restoring knee strength and functionality and is associated with high patient satisfaction.

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

Osteochondral allograft transplantation as presented by John Belk, Drs Jonathan Bravman, Rachel Frank, Jason Dragoo, and Eric McCarty.

The knee has 3 primary compartments with cartilage surfaces that are susceptible to injury, including the patellofemoral, medial, and lateral compartments.

There are 2 types of cartilage in the knee joint, and one of these types is articular cartilage, which is the smooth white cartilage that coats the ends of the bones in the knee to provide a smooth gliding surface so the bones in the joint can move fluidly against one another. Articular cartilage can be damaged through traumatic injury, degenerative tears, or a genetic profile that predisposes cartilage to early deterioration. Generally, problems with the type of cartilage are caused by poor genetics or by trauma like anterior cruciate ligament (ACL) injury or patellar dislocation.

Active men and women can develop a focal or localized defect in the cartilage coating, which can occur behind the kneecap, in the groove that the kneecap sits in, or on the outside or inside of the knee. This becomes very much like a pothole in a road and makes joint movement very painful.

About two-thirds of patients undergoing standard knee arthroscopy have been shown to have articular cartilage pathology, with approximately 20% having a localized cartilage defect. In a study evaluating nearly 1000 patients undergoing knee arthroscopy, 11% had grade 3 or 4 cartilage lesions, and over half of these were larger than 20’mm.

These defects commonly result from traumatic incidents that alter the biomechanics of the knee. Associated injuries include ACL or other knee ligament ruptures, meniscal disruption, or general malalignment of the knee joint. These defects occur often in sports-related environments, where a shearing force creates enough stress to penetrate through the entirety of the cartilage matrix. It is important to note that osteochondral injuries can also be iatrogenic or genetic and can also be caused by vascular abnormalities.

One of the leading causes of osteochondral lesions in the knee is patellar dislocations, which are responsible for 40% to 50% of defects around the medial and lateral femoral condyles. As mentioned earlier, this kind of acute, large cartilage disruption is most common in active patients aged 20 to 40 years old and can also be caused by recurrent microtrauma, which is exacerbated in the malaligned patient.

On this image here, you can clearly see the disruption to the medial femoral condyle, which would then be confirmed and more specifically identified upon magnetic resonance imaging (MRI) visualization.

X-rays are typically used to evaluate bony avulsions or any bony abnormalities, while MRIs are used to differentiate between grade 1, 2, 3, and 4 type lesions and further specify lesion location.

Articular cartilage lesions can be treated both nonoperatively and with surgical management depending on the case. Nonoperative management has been indicated for inactive patients, patients with stable, asymptomatic lesions, and those who wish to avoid surgery in general. These patients are often recommended to employ activity modification, bracing, physical therapy, and non steroidal anti-inflammatories.

Surgically, there are a number of procedures that can be used for different types of lesions, including autologous chondrocyte implantation, subchondral marrow stimulation, osteochondral autograft transplantation, and osteochondral allograft transplantation.

Osteochondral allograft transplantation is often used in the setting of larger defects to avoid harvesting significant amounts of tissue from the patient’s own body. Advantages include the introduction of metabolically active chondrocytes and immunoprivileged allografts that are avascular and aneural in nature. This procedure provides full resurfacing of full-thickness lesions while avoiding donor-site morbidity.

A 2017 systematic review evaluating over a thousand patients undergoing osteochondral allograft transplantation demonstrated an 86.7% survival rate at the 5-year follow-up and a 78.7% survival rate at the 10-year follow-up.’Subjective International Knee Documentation Committee (IKDC) scores increased from 39.6 preoperatively to 69.7 at the 10-year follow-up.

Similarly, another systematic review from 2017 showed the same kind of improvements in patients undergoing osteochondral allograft (OCA). In almost 100 athletes, 88% of patients returned to sport at a mean of 9.6 months, and Knee Injury and Osteoarthritis Outcome Score (KOOS) sport scores improved more than 250% from preoperatively to postoperatively.

There are 2 primary techniques used in OCA procedures. The Shell technique uses allografts of various shapes and sizes that are built free hand by the surgeon to match the recipient’s defect. With the dowel technique, allografts are prepared by cylindrically coring out the defect and inserting a matched dowel into the recipient site using commercially available series of cutting guides.

Due to the reproducibility and ease of specimen and defect preparation, the dowel technique has become more common for larger defects involving the central weight-bearing portions of the femoral condyles, trochlea, and patella.

For this case, we will discuss a 28-year-old man recreational athlete who presents with pain along the lateral aspect of his left knee. He has a history of a left knee arthroscopy, ACL reconstruction, partial medial and lateral meniscectomy, and microfracture of a grade 4 defect on the medial femoral condyle.

He reports an increase in pain with lateral cutting movements or when walking on uneven surfaces and feelings of instability when his knee swells. He is 2 months status post partial lateral meniscectomy and debridement of the lateral femoral condyle, during which a 25 to 30 mm articular cartilage defect was identified.

Shown here is the surgical diagram that was filled out 2 months ago in his last arthroscopy, which more clearly identifies that defect on the lateral femoral condyle.

Upon examination, he has moderate quadriceps atrophy, slightly limited range of motion, mild effusion, and good quadriceps strength. He reports pain with flexion movements and his left lower extremity is neurovascularly intact.

X-rays of the left knee showed mild osteoarthritis of the’medial and lateral compartments without evidence of’osteophytic changes. There are no other obvious abnormalities.

An MRI of the left knee demonstrates diffuse moderate chondral thinning of the posterior aspect of the lateral compartment, both on the femoral and tibial sides with the coronal view, which is noted by the red circle.

On the sagittal view, you can see the same type of chondral thinning of the lateral femoral condyle with associated bony edema.

Based on these results, the patient is indicated for an osteochondral allograft transplantation.

A vertical incision is made just lateral to the patellar tendon, and the tissue is retracted to allow for visualization of the femoral condyle. The articular cartilage defect is identified in the lateral compartment of the femoral condyle, and a sizing guide is placed perpendicular to the articular surface of the condyle and is held in place while a guide pin is drilled through the guide into the center of the defect.

A scoring device is then inserted over the guidewire and used to score the lesion. The scoring device is then removed, and a triple reamer is placed over the guide pin and reamed to a depth between 5 and 8 mm. The reamer is removed from the guidewire, and a dilator is used again to ensure the shape and general dimensions of the socket are as desired.

The dilator is hammered down until it sits flush with the bottom of the socket. The dilator and guide pin are then removed, the socket is irrigated, and the exact depth of the socket is measured. 8 mm; 3 o’clock is 8 mm; 6 o’clock is 7 mm; and 9 o’clock is 7 mm. This is then reaffirmed by a clock diagram drawn for later reference.

A sizing guide is then used to confirm the location of the graft from the donor cartilage. A graft station is used to hold the allograft with 4 securing pins, which are positioned away from the harvest site to avoid penetrating the cartilage of the graft. A sizing guide is placed through the bushing to confirm the allograft harvest location. Using stabilization from the graft station arm, a coring reamer is then advanced through the donor cartilage.

Using a saw, a cross cut is made to facilitate removal of the graft from the condyle. A 12 o’clock line is drawn on the plug for orientation, and based on previous measurements, the plug is then fashioned to fit the exact dimensions of the socket. As demonstrated before, 12 o’clock is 8 mm; 3 o’clock is 8 mm; 6 o’clock is 7 mm; and 9 o’clock is 7 mm. Graft holding forceps are then used to hold the plug in place, and ensure that the markings at each position on the plug are flush with the superior edge of the forceps. A cut is made to fashion the plug to the appropriate depth, and the depth of each position on the plug is then confirmed with a ruler. A rongeur is used to bevel the edges, or make the plug more bullet shaped at the end to allow the plug to enter the socket more easily.

Small holes are then drilled into the base of the socket to help promote incorporation of the plug into the socket during the healing process.

After the socket is irrigated, suture tape is placed in the plug to allow for easy removal of the plug in the event that the plug does not fit appropriately into the socket. The plug is then placed into the socket, the suture tape is removed, and a tamp is used to gently tap the cartilage until it is flush with the surrounding surface.

Now let’s discuss a few tips for this procedure.

First, make sure to take all of your measurements twice. This includes measuring all 4 o’clock positions twice in the defect and then twice again on the allograft plug. Healing holes are also an underrated part of this procedure. Drilling small holes in the base of the defect really helps the plug incorporate and promotes a lot of good healing.

Finally, laying suture tape in the bottom of the defect site before you insert the plug for the first time is a pro move. This way, if the plug doesn’t fit perfectly, you can easily remove it without altering the dimensions of the graft.

The postoperative rehabilitation protocol is really important to ensure proper healing and incorporation of the allograft into the donor site. The primary goals of rehabilitation are to protect the postsurgical knee and restore normal range of motion and knee biomechanics.

In the first 1 to 6 weeks of rehabilitation, the patient will concentrate on healing and passive range of motion in physical therapy, but will remain locked in full extension in a splint brace outside of physical therapy. This is followed by progressive weight-bearing period, which should focus on normalizing gait and maintaining good control with functional movements. All impact activities should be avoided until 12 weeks postoperatively, with a goal to return to sport at 10 months postoperatively.

The most commonly encountered complications of OCA procedures are failure of the graft to properly incorporate into the donor site and the necessity for reoperation. Other complications include arthrofibrosis, formation of osteophytes, loose bodies, and infection.

In summary, nonoperative management should be considered in the low demand, older patient, or in patients with stable, asymptomatic lesions. Nonoperative management is not recommended for athletes, patients with lesions >20 mm, or in young patients. If proceeding with osteochondral allograft transplantation, the dowel technique should be used to ensure the entire lesion is replaced by new, healthy cartilage.