Abstract
Background:
Patellofemoral cartilage defects can be caused by patellar instability, maltracking, trauma, or osteochondritis dissecans. Although cartilage restoration techniques, such as matrix-associated autologous chondrocyte implantation (MACI), are well-established, reducing contact pressures and shear forces on the graft remains critical for improving outcomes. This video demonstrates the surgical technique of patellofemoral offloading through tibial tubercle osteotomy (TTO) and lateral retinacular lengthening (LRL), combined with MACI, to optimize biomechanical alignment and enhance clinical results.
Indications:
This case presents a 34-year-old woman with anterior knee pain, effusions, and a history of patellar instability, which failed to resolve with conservative treatment. Imaging revealed patella alta, trochlear dysplasia, and a full-thickness cartilage defect of the lateral patellar facet, which was confirmed during diagnostic arthroscopy as a 1.5 × 1.5 cm lesion. Due to persistent clinical symptoms in the setting of structural abnormalities, the patient was indicated for TTO with MACI and LRL.
Technique Description:
The extensor mechanism is exposed through a midline incision slightly lateral to the patella. The tibial tubercle is identified, and an anteromedial osteotomy is performed using a saw and osteotome. The angle of osteotomy determines the degree of anteriorization, medialization, and distalization. Next, the lateral retinaculum is dissected, cut 1 to 2 cm from the patellar attachment, and lifted from the underlying capsule. A lateral and partial medial arthrotomy is performed to expose the patella. The patellar chondral lesion is debrided, and the prepared MACI membrane is placed on the recipient site and secured with fibrin glue. The patella is reduced, and the tubercle is repositioned and fixed with 6.5-mm cancellous screws. The lateral retinaculum is reapproximated with appropriate length and tension.
Results:
Combining MACI with TTO improves clinical outcomes compared with isolated MACI, with high rates of return to activity. TTO significantly reduces patellofemoral contact pressure, protecting the graft, while LRL enhances patellofemoral biomechanics, reducing instability and preserving vastus lateralis integrity.
Discussion/Conclusion:
Cartilage restoration techniques, when combined with patellofemoral offloading, offer an effective strategy for addressing complex patellofemoral defects, especially in cases of malalignment and soft tissue imbalance.
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
In this video, we present our technique for tibial tubercle osteotomy (TTO) with matrix-associated autologous chondrocyte implantation (MACI) and lateral retinacular lengthening (LRL) for a patellar chondral defect in a 34-year-old woman.
The patient is a 34-year-old woman presenting with chronic right anterior knee pain and persistent effusions. She has a remote history of patellar instability.
She did not improve after a trial of conservative treatment, and she has no pertinent past medical or surgical history.
On physical examination, she has a full range of motion of the knee with mild effusion and anterior knee pain. She has no patellar apprehension or J-sign. She has no cruciate or collateral ligamentous instability. Clinically, she has normal coronal alignment.
Imaging—XR
Radiographic evaluation demonstrates well-maintained medial, lateral, and patellofemoral joint spaces. She has patella alta, measured with a Caton-Deschamps Index (CDI) of 1.46. She does not have significant trochlear dysplasia on plain radiographs.
Imaging—MRI
Magnetic resonance imaging (MRI) of the knee demonstrates a full-thickness cartilage defect on the lateral facet of the patella.
On the axial MRI views, the patient has a shallow trochlea, and she can be classified as having Dejour A trochlear dysplasia.
She has a tibial tubercle–trochlear groove distance of 12 mm.
Her patellofemoral engagement (also called the patellotrochlear index) is 0.3. Normal is generally >0.28 but <0.5.
Diagnostic Arthroscopy and Cartilage Biopsy
The patient did not improve after a trial of conservative treatment. She underwent a diagnostic arthroscopy of the right knee to assess her lesion seen on MRI and to assess her patellofemoral tracking.
She was found to have a 1.5 × 1.5 cm articular defect with soft, abnormal surrounding cartilage. A cartilage biopsy was performed.
Indications
The patient presented was indicated for surgery due to persistent anterior knee pain and effusions in the setting of patella alta and a lateral patellar chondral defect. While she had a remote history of patellar instability, she had no recent instability episodes and had no patellar apprehension or J-sign clinically.
Essential to successful patellofemoral joint preservation is correction of the underlying pathoanatomy based on preoperative planning and confirmed by intraoperative assessments. Ultimately, the goal is to normalize tubercle–trochlear groove distance (TT-TG), CDI, patellotrochlear index, or other measures that were the basis for indicating surgery.
Normal TT-TG is between 10 and 14 mm. Borderline TT-TG is between 15 and 20 mm, and TT-TG >20 mm is considered abnormal. While the patient's measured TT-TG of 12 mm is within normal limits, she has patella alta with increased CDI and a patellotrochlear index of 0.3.
Therefore, she was indicated for a Fulkerson TTO to distalize and anteriorize her patella, correcting her patella alta and offloading her patellar chondral defect, which was concurrently indicated for MACI. LRL is performed as part of this approach. As a Fulkerson TTO does produce medialization, additional medial-sided stabilization was not deemed necessary in this case. The Fulkerson TTO is modified in this patient to be a more vertical cut (approximately 60°) to increase the anterior translation power of the osteotomy relative to the medialization. With a 60° osteotomy, there is a 2 to 1 ratio of anteriorization to medialization.
In this patient, the goal was to achieve approximately 7 mm of distalization based on her CDI difference, approximately 10 mm of anteriorization to offload her patellar chondral defect, and 5 mm of medialization.
The details of the multiple described TTO techniques and their variations are beyond the scope of this video; however, the indications for cartilage restoration procedures and TTO, as well as contraindications, can be seen in this table.
Indications include lateral or central cartilage defects with a lesion size >3cm2, whereas relative contraindications are increased body mass index or active smoking status.
Technique Description
A longitudinal midline incision is made slightly lateral to the patella. The subcutaneous tissues are dissected, and retractors are placed.
The extensor mechanism is exposed, and the medial and lateral borders of the patellar tendon are identified. Cautery is used to dissect laterally to the patellar tendon down to the anterior proximal tibia. The tendon insertion on the tubercle is identified, and a retractor is used to improve visualization.
Similarly, the medial side is exposed, and the infrapatellar fat pad can be removed to improve visualization of the tendon insertion on the tubercle.
An osteotome is used to make a transverse cut just superior to the tubercle, which is approximately 2 cm distal to the joint line. The medial and lateral margins of the planned osteotomy are scored at a 45° angle proximally on either side of the tubercle.
The anterior compartment is then exposed with cautery and scissors, and the muscle is gently lifted from the bone with an elevator. At this stage, it is important to protect the proximal neurovascular bundle in the anterior compartment.
A retractor is then slid posteriorly to the tibia. The anterior compartment musculature is retracted laterally.
The cutting block is then positioned at the intersection of the medial osteotome cuts. This is the axis of rotation for the osteotomy. The foot should be placed vertically to understand the orientation of the intended osteotomy. The cutting block can be angled to increase or decrease the size of the tubercle fragment. The surgeon must position the cutting block to avoid osteotomy at the proximal isthmic portion of the tibia to avoid fracture propagation.
The osteotomy is begun with a saw, but the superior portion of the cutting block is not cut to avoid the saw trajectory toward the articular surface. The osteotomy is finished superiorly and distally with an osteotome. The soft tissue bridges are removed.
The angle of the osteotomy determines the geometry of tubercle movement. A more transverse osteotomy provides more lateral to medial translation, while a more vertical cut provides more potential for anteriorization.
The tubercle can also be distalized along the cut of the osteotomy. Therefore, this osteotomy technique provides the ability to determine anteriorization, medialization, and distalization.
Attention is then turned proximally to the intended arthrotomy location and LRL. Retinacular vessels are often identified at the proximal and distal borders of the lateral retinaculum. These should be preserved, if possible, to avoid compromising blood supply to the patella and surrounding tissues during the procedure.
The borders of the patella are identified. An incision is made with a 15-blade along the superior two-thirds of the patellar fascia.
The lateral soft tissue complex acts to stabilize the extensor mechanism of the knee and the patellofemoral joint. The complex has superficial longitudinal fibers (superficial fibers of the iliotibial band [ITB] expansion into the patella) and deep transverse fibers (deep fibers of the ITB expansion into the patella), as well as the vastus lateralis, the lateral patellofemoral ligament, the lateral patellotibial ligament, and the lateral meniscal ligament.
The retinaculum can be carefully dissected with Metzenbaum scissors. Once a sufficient length of the retinaculum has been dissected, it is cut 1 to 2 cm from the patellar attachment and lifted from the underlying capsular layer. The lateral retinaculum will be reapproximated at the end of the case. In cases requiring significant medialization, a longer retinacular length is desired for closure.
After sufficient lengthening is achieved, the capsule is incised, and a lateral parapatellar arthrotomy is completed.
A partial medial arthrotomy is then performed for increased access and to evert the patella. The arthrotomy is made to approximately the mid patella, distal to the attachment of the native medial patellofemoral ligament.
The patellar chondral lesion is identified, and the soft surrounding cartilage is removed with a knife and a ring curette. The template is used to outline the final margins of resection. The calcified cartilage layer is debrided until clean subchondral bone is exposed. Debris is irrigated.
The MACI membrane is placed onto the gray mat for cutting. The cells are facing upward when the cutout portion is located in the bottom left portion of the mat. The template is placed on the membrane and struck with a mallet. The cutout portion is then slid into a petri dish using a no-touch technique with a small amount of saline. It is important to remember the orientation of the chondrocytes in the petri dish at this stage.
The recipient site is prepared with a small layer of fibrin glue. The membrane is placed onto the recipient site with chondrocytes placed directly onto the subchondral bone. The edges are sealed with a small amount of fibrin glue. This is left to seal for approximately 3 minutes.
The patella is reduced, and the tubercle is brought back down to the desired location. In this case, the tubercle was distalized approximately 7 mm, anteriorized 10 mm, and medialized 5 mm based on preoperative surgical planning.
A Steinmann pin is placed to hold the tubercle in the desired location. Two 6.5-mm large fragment cancellous screws are lagged across the osteotomy for fixation, perpendicular to the osteotomy. Screws should be bicortical for best compression. In revision settings, or if the tubercle shingle is thin, a washer can be utilized. Patients are cautioned preoperatively about the high rate of symptomatic hardware, and screws can be removed once the osteotomy has healed if they are symptomatic postoperatively.
The soft tissues are irrigated, and the lateral retinaculum is reapproximated with appropriate length and tension. There should be minimal tension of the retinaculum at the time of closure, and it should not tilt the patella or be overtightened. Due to the angle of osteotomy and minimal medialization in this case, there was excess retinaculum, which only needed approximately 5 mm of length to close the lateral defect. In cases with large corrections, a large remnant of the lateral retinaculum is desired for re-tensioning.
The remaining soft tissues are closed in a layered fashion.
Results
Postoperatively, the patient was given Aspirin 81 mg daily for 28 days for deep vein thrombosis prophylaxis.
She was made nonweightbearing with crutches for 4 weeks. She was instructed to keep the hinged knee brace locked in extension while ambulating.
She began using a continuous passive motion device immediately from 0° to 30° of flexion and increased by 5° per day. Weightbearing was advanced at 4 weeks.
The goal in the first several months is not to overload the graft. The anticipated return to running is around 6 months, with low-impact activities encouraged between months 6 and 9. High-impact activities can be initiated 1 year postoperatively if the patient has met the appropriate milestones.
Discussion
Outcomes
Although a limited number of studies have documented the results of concomitant realignment procedures in patients without malalignment, these procedures may play a role in protecting a fresh graft that would otherwise be susceptible to mechanical overload, even at normal loads, due to shearing forces applied across the joint. 6
Patients undergoing autologous chondrocyte implantation with osteotomy do better clinically than those without osteotomy. 6
In active-duty service members with medium to very heavy occupational demand, autologous chondrocyte implantation with TTO enabled a 78% return rate. 8
Patellar cartilage repair yields good clinical outcomes, with no evidence of worse results in complex cases requiring additional patellofemoral realignment procedures. 2
Patellofemoral Cartilage Defects
First-line treatment is nonoperative management, including anti-inflammatory medications, activity and exercise modification, and physical therapy. When this approach fails, surgical management should be considered with the goals of restoring cartilage surface congruity, reestablishing normal patellofemoral biomechanics, alleviating symptoms, and improving function and quality of life.1,7
The choice of technique is influenced by the individual (eg, age, activity level, body mass index, and patellofemoral alignment) and morphological defect characteristics (eg, location, size, depth, and containment).1,7
Lateral Retinacular Lengthening
The advantages of LRL over lateral retinacular release include controlled elongation of the lateral retinaculum, maintenance of vastus lateralis/quadriceps tendon integrity, and avoidance of lateral void and synovial herniation.3,4
LRL demonstrates less instability, quadriceps atrophy, and better outcomes compared with lateral retinacular release.3,4,5
The lateral retinaculum is a secondary stabilizer of lateral patellar translation. Lengthening is preferred to rebalance the lateral soft tissues without complete disruption.4,5
Footnotes
Submitted April 4, 2025; accepted August 21, 2025.
One or more of the authors has declared the following potential conflict of interest or source of funding: N.S. serves on the editorial board of Arthroscopy: The Journal of Arthroscopic and Related Surgery. C.B.G.L. is a paid consultant for Aesculap, Joint Restoration Foundation, Organogenesis, and Vericel; receives research support from Joint Restoration Foundation; is a board or committee member for the Biologic Association and the International Cartilage Repair Society; and serves on the editorial or governing boards of Cartilage, Journal of Sports Physiology, The Knee, and Orthopaedic Journal of 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.
