Abstract
Background:
There are several techniques to treat chondral defects. Osteochondral allograft transplantation is an excellent option, and for elongated lesions, there are 2 techniques—the Snowman technique and the BioUni technique.
Indications:
Osteochondral allograft transplantation is indicated for active individuals with isolated, symptomatic full-thickness chondral defects without concomitant ligamentous injury or malalignment.
Technique Description:
The lesion on the native condyle is sized. A plug is then harvested from the allograft using a cutting block and sagittal saw. The recipient site is then prepared with an overlapping reamer system with a cutting block. Graft is then implanted in a press-fit manner.
Results:
Osteochondral allograft transplantation leads to improved patient-reported outcomes. The literature has demonstrated survival rates between 70% and 80% at 10 years.
Discussion/Conclusion:
Osteochondral allograft transplantation is a restorative cartilage treatment that has good clinical outcomes. The BioUni system is a good option for irregular or elongated lesions.
This is a visual representation of the abstract.
Keywords
Video Transcript
Today, we will be discussing osteochondral allograft transplantation for a full-thickness chondral lesion of the medial femoral condyle utilizing the BioUni technique. The authors are Michael Campbell, Hayden Sonnier, and Kevin Freedman.
Our disclosures are listed here.
We will present the patient’s history and physical examination, preoperative imaging, and arthroscopic findings. We will discuss preoperative planning. We will discuss the surgical technique, including the pearls and pitfalls to avoid. We will touch on our postoperative management and rehabilitation protocol. Finally, we will briefly discuss clinical outcomes.
There are several methods to treat articular cartilage defects in the knee, including autologous chondrocyte implantation, subchondral marrow stimulation, osteochondral autograft, and osteochondral allograft. Matrix-associated autologous chondrocyte implantation (MACI) can be used for ovoid lesions and can be used with bone defects up to 6 to 8 mm. In the setting of underlying bone edema or bone loss, there is a preference for osteochondral allograft. An advantage of osteochondral allograft is that it can resurface large, full-thickness osteochondral defects and restore the defect to an architecturally stable articular surface with mature chondrocytes. Not all defects are perfectly circular, so there are broadly 2 options for irregular or ovoid lesions: the Snowman technique, which utilizes 2 overlapping plugs, or the BioUni technique, which is a single plug technique. Inferior outcomes in the literature have been shown for unicondylar multiplug osteochondral allograft transplantation as compared with single-graft transplantation. To our knowledge, there have been no clinical outcome studies comparing the Snowman and BioUni technique. Here, we will discuss our technique for BioUni osteochondral allograft transplantation.
Our patient is a 50-year-old woman who presented with 6 weeks of medial and anterior knee pain. Her initial injury occurred while exercising and performing a deep squat. Subsequently, she noted swelling and pain with ambulation. On examination, she had a mildly antalgic gait with a 1+ effusion. She had flexion to 130°. There was medial joint line tenderness, especially along medial femoral condyle. She had no ligamentous laxity. She was neurovascularly intact distally.
Her radiographs demonstrated preservation of her medial, lateral, and patellofemoral compartment joint space.
A magnetic resonance imaging (MRI) was obtained, which showed a full-thickness cartilage defect to the medial femoral condyle, with otherwise preserved lateral and patellofemoral compartments. There was no meniscus pathology.
At this point, the decision was made with the patient to perform a diagnostic arthroscopy to evaluate the lesion for potential cartilage restoration. She was found to have an ovoid full-thickness cartilage defect of the medial femoral condyle measuring 20 mm anterior to posterior and 14 mm wide with a preserved tibial articular surface. In addition, she had a circular full-thickness defect of the trochlea measuring 18 mm in diameter with preserved patellar articular cartilage.
Based on her arthroscopic findings, we felt that she would benefit from a cartilage restoration procedure. Decision was made to proceed with osteochondral allograft to restore her articular surface, utilizing the BioUni technique for the ovoid medial femoral condyle lesion, as a circular restoration technique would not adequately incorporate the full extent of her diseased cartilage.
Regarding preoperative planning, it is critical to perform a thorough physical examination to rule out concomitant ligamentous injury. Alignment films rule out malalignment that could affect cartilage restoration success. MRI confirms there is no meniscal pathology and is used for allograft size matching based on condylar width. 5 In addition, anteroposterior and lateral x-rays with a sizing marker can be used for confirming a size match for the donor and recipient condyle. There are several widths and lengths available to best match the size and radius of curvature for full coverage of the defect. Diagnostic arthroscopy characterizes the chondral defect and ensures there are no additional lesions not identified on preoperative imaging. Using shared decision making, the best option for cartilage restoration can be decided with the patient.
For patient positioning, supine on an operative table is preferred. We use a foot positioner to stabilize the knee with the appropriate amount of flexion to best visualize the lesion. We prefer to use collateral ligament and Z retractors to assist with exposure.
An incision just medial to midline is made. Dissection is carried out through the subcutaneous tissue down to the retinaculum. A medial parapatellar arthrotomy is made, taking care to avoid injury to the medial meniscus. The lesion is exposed. An appropriate sized guide is used to template the lesion. In this case, it was a 14 L guide. A marker is used to outline the template for later recipient site preparation.
The same template is used to mark the site on the allograft condyle at the same site and trajectory. This is a key step to ensure that the graft will have the same contour as the surrounding native cartilage. The template is outlined with a marker, and the allograft is secured. The oblong cutting guide with inserter is then placed at the same position that was previously marked.
It is pinned into place. Impactor handle is placed onto the cutting guide. The guide is malleted until the third laser line is flush with the cartilage. Insert the distractor tool and advance to remove the cutting guide. The saw depth guide is then placed and malleted until it sits flush on all sides with the allograft condyle. Use a sagittal saw through the saw depth guide and advance it through the allograft to create the graft base. Remove the impactor handle. The graft will be within the saw depth guide. The distractor tool can be used to remove the graft from the guide. The graft is then thoroughly irrigated to remove any preservatives. Of note, the edges of the graft can be bulleted with a rongeur to help with graft impaction later.
The template is then placed on the native condyle overlying the lesion, where it had previously been marked. Two pins are placed 2 to 3 cm in depth. Place the cutting guide over the pins and mallet it 2 to 3 mm in depth. The cutting guide is removed, and the appropriate step guide is placed over the superior pin. Utilize the appropriately sized reamer, and ream over the inferior pin until the reamer bottoms out on the step guide. Repeat this step using the step guide on the inferior pin. This should create 2 circular defects. Place the box cutter over the 2 pins. Mallet until it bottoms out at the base of the recipient site. Remove the box cutter and pins. Remove the remaining bone with a rongeur, curette, and osteotome. Irrigate the recipient site thoroughly.
A suture is placed in the base of the defect to allow for easy removal should the size of the graft need to be adjusted. The graft is then lightly tapped into place, ensuring that is contoured appropriately to the surrounding native cartilage. The suture is then cut and removed. The knee is taken through a range of motion to confirm stability of the graft.
A layered closure is performed.
There are some pearls of this technique. While harvesting the graft, please ensure the cutting guide has been malleted to the third laser line circumferentially. This is critical for the graft to fit appropriately. Bullet the edges of the graft to allow for easier insertion. And utilize a suture for easy graft removal should it be necessary to make some minor adjustments.
Our postoperative rehabilitation is shown below. There are no clearly set guidelines regarding return to sport. Most published series describe return to sport at 6 to 12 months postoperatively. 8 An additional study demonstrated a 79% return to same level of sport in their series of 43 patients, at an average of 9.6 months. 9 In their case series, the average lesion size was 7.25 cm2, and either a single or double circular dowel technique was used. 9 One systematic review reported that return to sport rates ranged from 75% to 82%. 4 Regarding postoperative imaging prior to return to sport, some surgeons advocate MRI at 6 to 12 months postoperatively. This is to evaluate the healing of the allograft prior to return, but this recommendation is expert opinion. We do not routinely obtain postoperative MRIs.
One systematic review found good survival of osteochondral allografts. 6 Decreased survival was found with revision cases, patellar defects, and bipolar lesions.
Our references are listed here.1-3,5-9
Thank you.
Footnotes
Submitted January 7, 2022; accepted April 21, 2022.
One or more of the authors has declared the following potential conflict of interest or source of funding: M.P.C. is a board or committee member of the American Orthopaedic Society for Sports Medicine. K.B.F. has received personal fees outside the submitted work from DePuy, a Johnson & Johnson company, and Vericel; and is a board or committee member of the American Orthopaedic Society for Sports Medicine. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.