Fresh Osteochondral Allograft to Medial Femoral Condyle With Proximal Tibial Opening Wedge Osteotomy

Abstract

Background:

Contributors to knee degeneration include mechanical axis malalignment, patellar maltracking, meniscal deficiency, and tibiofemoral instability. Full-thickness osteochondral defects in young, active patients can lead to significant pain and instability. The gold standard treatment for large (>2 cm²) osteochondral defects is an osteochondral allograft (OCA) which addresses the pathologic articular cartilage loss and underlying bone deficiency. While biologic failure of fresh OCAs is reported, the majority of early failures are attributed to unaddressed mechanical malalignment in the coronal plane. Proximal tibial osteotomy (PTO) corrects malalignment thereby unloading the affected medial compartment and the newly placed OCA, improving long-term survivability.

Indications:

OCAs are indicated for isolated osteochondral defects and lesions in active young patients. PTO is indicated for patients with varus malalignment who risk potential graft failure of the affected medial compartment.

Technique Description:

The articular cartilage defect is identified, and a guide pin is drilled in the center. The defect is templated and scored around the margins. A reamer is used to drill to a total depth of 7 to 8 mm. The recipient site is then dilated for graft insertion. On the donor graft, the harvest site is outlined and drilled to the proper diameter. Careful measurement is utilized to ensure graft depth measurements match the recipient site. Once sized, the graft is tapped into place obtaining an anatomic fit along its entire periphery. The osteotomy is performed by using guide pins to delineate the plane cutting the tibia. Fluoroscopy confirmed the osteotomy site and angle. A spacing plate was securely inserted with screws, with placement confirmed by fluoroscopy.

Results:

Fresh OCAs can restore osteochondral defects. PTO corrects malalignment and unloads the affected medial compartment, decreasing the risk of revision graft failure or total knee arthroplasty.

Discussion:

Clinical and biomechanical studies that compared isolated and concomitant procedures demonstrated that OCA with PTOs had significantly greater survival rates. Significant malalignment increases the risk of graft failure. It remains unclear whether concomitant osteotomy with osteoarticular allografts leads to increased complication risk; inherent risks remain associated with individual procedures. In adolescents, simultaneous corrective osteotomy along with fresh OCA may delay arthroplasty and associated ambulatory restrictions.

Patient Consent Disclosure Statement:

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

This is a video presentation depicting a fresh osteochondral allograft (OCA) to the medial femoral condyle with proximal tibial opening wedge osteotomy to treat a young patient with a dislodged osteochondritis dissecans (OCD) lesion.

Shown here are the authors’ disclosures.

Osteochondral lesions, specifically OCD, are multifactorial in etiology. An idiopathic process can occur from childhood into adulthood, with a majority of affected patients in their adolescence. The severity of OCD ranges from asymptomatic/mild discomfort to severe pain, joint instability, and locking. Lesions can progress to the fragmentation of superficial cartilage with formation of loose bodies in the synovial capsule. ¹⁰ Contributors include mechanical malalignment, patellar maltracking and instability, meniscal deficiency, and instability of the tibiofemoral articulation. ⁶ Treatment options for OCD lesions include microfracture, osteochondral autografting, osteochondral allografting, or autologous chondrocyte implantation. ⁹ Osteochondral allografting redistributes metabolically active chondrocytes without concurrent donor-site morbidity. ³ Grafts include both hyaline cartilage and viable structural bone. Biomechanical and clinical studies have demonstrated that the most common reason for graft failure was untreated malalignment. While graft and biologic failure are expected to occur, the vast majority of failures were attributed to untreated background anatomic and biomechanical issues such as meniscal deficiency, instability, and malalignment. ⁶ Proximal tibial osteotomy (PTO) redistributes weightbearing from diseased compartments. In conjunction, restoration of alignment via an opening wedge PTO increases the long-term procedural viability of the graft by reduced overloading.^2,4,5

A 16-year-old otherwise healthy male presented to our office in November 2022 after reporting right knee pain. He reported that the pain has been ongoing for about 6 months but had significantly worsened a couple weeks ago. He reported persistent pain, swelling, and mild mechanical symptoms worsening with activity. He had no significant history of prior knee injuries or surgeries.

Examination of the patient's right knee revealed moderate effusion. Range of motion was −2 cm heel height to 120° flexion, compared with 2 cm heel height and 140° flexion on the contralateral side. Minimal quad atrophy noted and compared bilaterally. Right lower extremity is warm and appears well perfused and sensory-motor function is intact.

Radiographs revealed the patient in varus weightbearing alignment bilaterally. In addition, there is an OCD lesion noted at the lateral aspect of the medial femoral condyle of the right knee. All joint spaces were preserved with no signs of collapse.

Magnetic resonance imaging (MRI) revealed a large unstable OCD lesion of the medial femoral condyle. The fragment is nondisplaced, though there was fluid underlying suggesting that it is unstable. The defect appears to be in at least 2 pieces.

The final diagnosis was a full-thickness osteochondral defect of the lateral aspect of the medial femoral condyle with genus varus alignment. The patient's conditions were discussed, and the risks and benefits of surgery were provided. A 2-stage surgery was indicated to first remove the unstable osteochondral defect to improve patient function and pain and measure the size of the defect for an osteoarticular allograft. The second stage would be performed once the patient's growth plates were closed and would include an OCA transplantation with a proximal tibial opening wedge osteotomy to correct genus varus alignment. The OCA and osteotomy were performed at the same time due to the need to determine the size of the defect for the donor allograft at the first surgery and due to both second surgeries requiring the same rehabilitation protocol in which the patient was nonweightbearing for 8 weeks. OCA was chosen instead of other techniques due to the size and depth of the defect.

An anterior incision was made extending over the vastus medialis oblique (VMO), incorporating his previous medial portal, and then continuing over the tibia about midway between the anterior tibial crest and the posterior medial border of the tibia. We then dissected down on the tibia and elevated up the periosteum and elevated posteriorly under the medial collateral ligament and anteriorly under the patellar tendon and deep infrapatellar bursa.

We now proceeded with arthrotomy. The patella was then retracted laterally with Z retractors. We proceeded to identify the defect. It was 2.25 cm in size and was clearly discernible from the surrounding articular cartilage. The defect was marked with a surgical marker. We then proceeded to place a guide pin in the center of it, confirming that we were in the desired location and then used the scoring device.

We now used the 22.5-mm reamer to ream to a depth of between 7 and 8 mm of total depth with very copious irrigation. This removed all the subchondral cysts that were present as we encountered them in the reaming. The defect was now dilated with a 22.5-mm dilator.

We now brought the fresh graft up and outlined on the graft where we would like to harvest, noting the shape of the native medial femoral condyle and the graft to ensure an anatomic fit.

We now harvested the graft on the back table. First, the graft was cut to a 22.5-mm diameter to ensure a press fit into the recipient site. Then, we measured the points of the compass at the recipient site and then made the graft the same depth.

Pulsatile lavage was now used to remove all the subchondral bone products while the articular cartilage is protected with a sponge.

We now inserted the graft and gently tapped it into place to obtain an anatomic fit around the entire periphery.

We now brought in fluoroscopic imaging and proceeded with the osteotomy. Using a guide, we started by placing 2 guide pins aiming toward the fibular head and the desired location of the osteotomy. We confirmed this with anteroposterior (AP) and lateral fluoroscopic imaging. We then inserted another stabilizing pin and proceeded to use an oscillating saw to cut to the depth of about 4 to 5 mm on the medial cortex.

The osteotomy proceeded with using a small osteotome anteriorly, a medium osteotome in the mid portion, and a small osteotome posteriorly.

The opening spreader device was now placed and held in place until 6 mm of opening was obtained. This was then held in place for 5 minutes to allow for stress relaxation of his lateral cortical hinge.

We now placed in the opening tine device and then placed in the 6-mm anterior sloped Puddu plate.

We then placed two 6.5 mm fully threaded cancellous screws proximally and two 4.5 mm cortical screws distally. Each tunnel for the screws was pre-drilled and measured to obtain the proper screw length. We were pleased with this position.

We finished with closing the arthrotomy, and the deep and superficial tissues.

The patient will be nonweightbearing on his right lower extremity for 8 weeks. He will start with a continuous passive motion (CPM) machine 2 hours a time up to 4 times a day starting at 0° to 60° of knee flexion, increasing range of motion based on tolerance due to his arthrotomy incision. Radiographs are repeated at the 8-week point to assess for healing. If this shows evidence of healing, we will plan to initiate a partial protected weightbearing program, advancing a quarter body weight per week, until he is fully weightbearing at 3 months. We will then repeat the radiograph at the 3-month point. If that shows further evidence of healing, we will plan to have him wean off of crutches. Radiographs will be repeated at the 6-month, 1-year, and 2-year intervals. Impact activities will be avoided for the first year.

This is a complex procedure with a number of potential complications. One such complication is iatrogenic meniscal or chondral injury when creating the arthrotomy for exposure of the osteochondral defect. This can be avoided by starting the arthrotomy proximally to the patella. Then you can either use scissors as you move distally, or place a retractor into the beginning of your arthrotomy and pull the tissue toward you and cut onto the retractor to ensure you do not plunge deep and damage the cartilage. As you work distally, continued mobilization of the tissue toward you and ensuring visualization of the anterior horn of the medial meniscus can help to prevent iatrogenic damage.

Inappropriate fit of the OCA is another common complication, specifically if the graft is too proud upon placement. A graft that is too proud will lead to overload of the OCA and early failure. This can be avoided by taking multiple depth measurements around the “clock face” or “compass position” of the defect and then using those depth measurements to contour the OCA graft to those identical dimensions. If a perfect fit is not possible, slight undersizing is better biomechanically than slight oversizing.

The last complication to avoid is subchondral cyst formation following implantation. Subchondral cyst formation following OCA implantation can lead to continued symptoms and OCA failure. A couple of steps can be taken to help avoid this complication. First, the size of the graft is important; previous literature suggests that the grafts with bone portions greater than 10 mm in depth are at risk of forming subchondral cysts following implantation. ¹ Second, pulsatile lavage should be performed on the bone surface of the OCA to ensure removal of all blood products prior to implantation as that too can increase the risk of cyst formation. Additionally, refrigeration of fresh OCAs is considered to allot time for serologic and microbiologic testing to mitigate infection risk. ⁸

A clinical study by Hsu et al ⁶ with 17 patients who underwent simultaneous OCA transplantation and proximal tibial opening wedge osteotomy reported that 15 out of 17 patients had intact grafts with a survival rate of 8.1 years. In addition, patient-reported outcomes from the International Knee Documentation Committee reported significantly improved outcomes.

A clinical study by Krych et al ⁷ with 59 total cases also concluded that the most commonly recognized reason for failure in cartilage repair surgeries was malalignment. While biologic and graft failures are expected at times, the majority of the failures were attributed to untreated anatomic background issues. Thorough preoperative consideration and identification of malalignment, meniscal volume, and joint stability is critically important to postoperative outcomes.

Plain films were obtained and received in the clinic at postoperative day 1. There is no evidence of acute fracture or soft tissue abnormalities appreciated. All joint spaces appear preserved compared with prior imaging. Hardware is intact and nondisplaced with improved alignment.