Abstract
Background:
Bipolar osteochondral allograft (OCA) transplantation is a durable option for patients with symptomatic chondral defects involving the patellofemoral joint. When due to patellar instability, treatment of bipolar lesions in the patellofemoral joint requires concomitant medial patellofemoral ligament (MPFL) reconstruction (MPFLR), and often tibial tubercle osteotomy (TTO).
Indications:
OCA transplantation with concomitant anteromedializing TTO and MPFLR is indicated in the setting of symptomatic Outerbridge grade 3 or 4 lesions involving both the trochlea and patella due to patellar instability.
Technique Description:
The tibial tubercle is osteotomized at 45°. The patellofemoral joint is exposed via a laterally based arthrotomy. Fresh OCA plugs are press-fit into the trochlea and then the patella. The MPFL is reconstructed with a hamstring allograft. The lateral retinaculum is lengthened. The tibial tubercle is medialized, anteriorized, and fixed with cannulated screws.
Results:
We represent a 27-year-old with symptomatic bipolar chondral defects involving the patellofemoral joint due to recurrent patellar instability. Bipolar OCA transplantation to the patellofemoral joint yields significant improvements in patient-reported outcomes, and graft survival rates are high for at least 10 years after surgery. The results of bipolar OCA transplantation are improved by concomitantly correcting any underlying anatomical pathology with TTO and MPFLR, the order of which requires thoughtful consideration.
Discussion/Conclusion:
OCA transplantation can be safely performed in the same surgical setting as MPFLR and TTO for patients with symptomatic patellar-instability-related bipolar patellofemoral joint chondral defects.
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.
This is a visual representation of the abstract.
Keywords
Video Transcript Background
The purpose of this presentation is to review indications for bipolar patellofemoral osteochondral allograft (OCA) transplantation with concomitant tibial tubercle osteotomy (TTO) and medial patellofemoral ligament reconstruction (MPFLR), present a case report of the above, and review the surgical technique and postoperative outcomes. The indications for this include patellar instability, symptomatic Outerbridge grade 3 or 4 chondral defects involving both the patella and trochlea, and an elevated tibial tubercle–trochlear groove distance or predominantly lateral patellar facet arthropathy. Contraindications to this procedure include significant chondral pathology in either tibiofemoral compartment that cannot be addressed at the same time, inflammatory arthropathy, or skeletal immaturity.
Indications
Our indications for adding cartilage reconstruction to patellar stabilization surgery include focal Outerbridge grade 3 or 4 chondral defects in the setting of concordant symptoms. Specifically, retropatellar pain that occurs in the absence of instability episodes and or activity-related knee effusions. Our preferred method for addressing focal chondral defects is with OCA plugs, but surface restoration procedures such as matrix-induced autologous chondrocyte implantation are viable options if the underlying subchondral bone is healthy.
The patient presented is a healthy 28-year-old woman who sustained her first patellar dislocation 5 years before her initial 3 subsequent dislocations, all of which spontaneously reduced. In addition to complaints of subjective patellar instability, she also endorsed retro patellar knee pain that limited her ability to participate in hobbies, such as recreational marathon running. She had no pertinent surgical history involving her left knee. Previous treatments at presentation included only as-needed nonsteroidal anti-inflammatory agents and physical therapy. Her plain films were largely unremarkable and demonstrated maintained tricompartmental joint spaces with du jour d trochlear dysplasia and a Caton Deschamps index of 0.94.
Mechanical axis films demonstrated neutral alignment. Noncontrast-enhanced magnetic resonance image (MRI) of the knee shows Outerbridge grade 3 changes along the central aspect of the lateral patellar facet with underlying subchondral edema, along with focal grade 4 changes along the lateral aspect of the trochlea. On the physical examination, there was no evidence of an intra-articular effusion. Her range of motion was full. The patient experienced pain with the patellofemoral grind.
Technique Description
She had a one-and-a-half-quadrant gradual J sign with open-chain knee extension. Patellar translation in full extension was 2 quadrants medially and laterally. Given the patient’s treatment naivety, she underwent a diagnostic arthroscopy and patellofemoral chondroplasty. At the time of surgery, her examination under anesthesia revealed a lateral patellar translation of 3 compared with 1 on the unaffected side. As demonstrated on her preoperative MRI, she had a grade 4 defect along the central patella measuring 25 ×15 mm and a kissing lesion along the lateral aspect of the trochlea measuring 15 ×15 mm.
Following diagnostic arthroscopy, her medial and lateral compartments were intact; however, she continued to endorse subjective patellar instability and retropatellar pain with increasing activity levels. Ultimately, she elected to undergo bipolar patellofemoral OCA transplantation with concomitant anteromedializing TTO and MPFLR. A 5-cm incision was made centered over the patella, and a separate 7-cm incision was made centered over the tibial tubercle. The anterior compartment fascia was released from the tibia using electrocautery. A large cob was used to sweep the anterior compartment musculature away from the underlying bone.
The Arthrex T3 anteromedialization system cutting guide was utilized to make a 45° osteotomy. A curved osteotome was used to free the proximal portion of the tubercle, allowing it to be translated anteriorly and medially while leaving the distal hinge intact. Attention was then turned back to the patellofemoral joint. The trochlear was exposed using a pair of zebra tractors. A sizing guide was placed on the trochlear defect.
A skin marker was used to color the rim of the sizing guide to better determine the appropriateness of the proposed plug size. Once the appropriate diameter plug was determined, the bulk allograft was brought onto the surgical field and marked with the same guide. A guide pin was placed in the center of the trochlear defect. The cartilage was then scored. The diseased cartilage, a thin layer of underlying subchondral bone, was reamed away.
Copious amounts of irrigation were used while reaming to protect the adjacent healthy cartilage from thermal necrosis. A dilator was used to expand the defect diameter enough to accommodate a press-fit donor plug. A cut ruler was then placed inside the defect, and the depth was measured at 12, 3, 6, and 9 o’clock positions. These were verbalized in a diagram formed on the back table for later donor plug preparation. Having prepared the recipient site on the trochlea, attention was turned to harvesting the OCA plug from the donor trochlea.
The plug was oriented to match the recipient site. The 12:00 position was marked on the articular surface with a marking pen. The measurements of the depth of the recipient site were then marked onto the donor plug. The deep surface of the plug was then cut so that the thickness of the donor plug matches as closely as possible with the depth of the recipient site, then scored with a saw.
The plug was then thoroughly irrigated with pulsatile lavage in an attempt to remove as many donor marrow elements as possible. After irrigation, the deep surface of the plug was dried using high-pressure carbon dioxide. The osseous portion of the plug was then soaked with bone marrow aspirate concentrate. The donor plug was then brought to the surgical field. A suture tape was laid into the recipient site, and the donor plug was pressed into place.
The suture tape allows for easy removal of the plug if the orientation needs to be adjusted or if the plug and or donor site needs to be modified. Attention was then turned to preparing the patella. Two tower clips were used to hold the patella in an inverted position. A similar sizing guide was used to determine the diameter of the defect. The same process for preparing the trochlear recipient site was utilized to prepare the patella.
With the patella recipient site prepared, attention was turned to the MPFLR. Roughly 5 mm off the medial border of the patella, a fresh knife was used to dissect through the medial layers of the knee. A 1.6-mm wire was placed in the mid-portion of the patella. A second wire was then placed at the superomedial corner of the patella, aiming distally. With both wires in place, the patella recipient site was checked to confirm that neither anchor would violate the OCA plug.
The superomedial wire was then overdrilled, and the 3.9-mm PEEK knotless anchor was placed. This was then repeated over the distal wire. Once both anchors were placed, a small rongeur was used to create a bony trough between the anchors in which the allograft would lie. With the patella fully prepared for MPFLR and placement of the OCA plug, attention was turned to preparing the patellar donor plug. This was done in the same way as the trochlear donor plug.
Using a patellar clamp, the donor plug was pressed into place, and the underlying suture tape was removed. Next, attention was turned back to the tibial tubercle, which was manually translated in an anteromedial direction, aiming for about a 15 mm correction. Two 4.5-mm fully threaded screws were placed in lag by technique fashion. Attention was then turned to establishing the femoral socket for the MPFLR. The Schottle point was identified, and a beath pin was driven across the femur.
A blind socket was reamed over the beath pin and advanced to the lateral cortex. The allograft was secured to the patella using the knotless mechanism. The free limbs of the allograft were then passed through the previously developed plane between the native MPFL and the capsule, and then docked into the femoral socket. The graft was then secured with a tenodesis screw.
Results
Postoperatively, our patients are placed into a hinged knee brace, which is unlocked to allow for range of motion as tolerated immediately. They are toe-touch weightbearing for the first 6 weeks, during which time they are advised to use a continuous passive motion machine for 6 to 8 hours per day, as able. At 6 weeks, they discontinue bracing and transition to full weightbearing. They are allowed to strength train and do non-impact cardio beginning at 12 weeks. They are cleared to engage in all activities without restrictions 1 year after surgery.
In young patients, bipolar patellofemoral chondral defects severe enough to warrant OCA typically occur due to underlying pathoanatomy that predisposes the patient to patellar maltracking or frank patellar instability. In either case, a recent expert consensus statement concluded that the suspected underlying anatomical causes for the patellofemoral lesions should be addressed either before or at the time of OCA transplantation (Chahla et al). 1 Although the use of allograft plugs in the patellofemoral joint is more technically demanding and occasionally results in incomplete lesion treatment due to shape, size, or contour limitations, these are preferred over shell allografts due to a much lower rate of midterm graft failure as demonstrated by a retrospective cohort study by Cotter et al. 2 While most individual studies involving bipolar patellofemoral OCAs are small case series in which patellofemoral OCA is included with tibiofemoral OCA transplants, a systematic review and meta-analysis of the literature by Gowd et al 3 focusing exclusively on bipolar OCA in the patellofemoral joint has concluded that bipolar patellofemoral OCA transplantation provides significant improvements in patient-reported outcomes with low failure rates over the course of the first postoperative decade.
Discussion/Conclusion
Bipolar OCA transplantation to the patellofemoral joint is a viable option for patients with symptomatic chondral lesions involving both the patella and trochlea. Any underlying pathoanatomy should be addressed before or during the patellofemoral OCA transplantation.
We have demonstrated a safe and efficient technique for performing concomitant TTO and MPFLR at the time of OCA transplantation. When properly indicated and executed, bipolar patellofemoral OCA transplantation with concomitant anteromedializing TTO and MPFLR yields good and durable outcomes.
Footnotes
Submitted February 10, 2025; accepted June 30, 2025.
One or more of the authors has declared the following potential conflict of interest or source of funding: A.Y. is a paid consultant for AlloSource, JRF Ortho, and Stryker; an unpaid consultant for Patient IQ and Sparta Biomedical; and holds stock or stock options in Patient IQ, Icarus, and Sparta Biomedical. 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.
