Abstract
Background:
Cartilage injury in the setting of acute patellar dislocation is a devastating condition that can lead to decreased quality of life and can progress to early osteoarthritis of the knee if not treated adequately.
Indications:
Matric-associated chondrocyte implantation (MACI) with concomitant medial patellofemoral ligament reconstruction (MPFLR) is indicated for young, high-demand patients with a symptomatic, full-thickness chondral lesions >2 cm2 that have failed an initial trial of conservative management or are found to have evidence of extensive cartilage damage or loose body that is not amenable to fixation.
Technique Description:
The MACI technique requires a 2-stage procedure. An initial diagnostic arthroscopy aids in characterization of the chondral lesion with regard to lesion size, depth, and morphology. Hyaline cartilage was harvested and autologous chondrocytes are seeded onto a MACI scaffold to grow. At the second stage, an MPFLR is planned alongside MACI. First a midline incision is made. Notably, instead of performing the capsulotomy at this stage, we proceed with the dissection for the MPFLR first creating a plane between layer #2 and #3 for easier graft retrieval later. The defect site is prepared, and the MACI graft is seated in the defect and secured. Medial patellofemoral ligament reconstruction is then begun by fixing the preloaded semitendinosus allograft to the patella. Shottle point is confirmed via fluoroscopy and dissection down to the femoral condyle is performed. The graft is retrieved between the 2 layers that were dissected earlier in the procedure and fixed within the femoral tunnel. Finally, the synovial layer is closed deep to the MPFL graft and the vastus medialis oblique (VMO) layer is closed superficial to it before closing the wound in the standard fashion.
Results:
The MACI procedure demonstrates high rates of satisfaction for relief of pain and significant improvements in clinical outcomes with generally low incidence of complications. Matric-associated chondrocyte implantation has been shown to be superior to microfracture in the treatment of larger (>3 cm2) symptomatic articular defects at 5 years.
Discussion/Conclusion:
Matric-associated chondrocyte implantation procedure with concomitant MPFLR should be considered in indicated patients with full thickness cartilage defects that are not amenable to fixation.
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
In this video, we will demonstrate the surgical approach for full thickness cartilage defects with patellar instability utilizing a matrix-associated chondrocyte implantation (MACI) technique with medial patellofemoral ligament reconstruction (MPFLR).
The author disclosures are listed here.
As an overview, we will review the pertinent history, physical examination, and imaging findings. We will discuss preoperative planning pearls and demonstrate the surgical approaches as dictated by the patient’s pathology.
We will then briefly discuss the postoperative management and rehabilitation protocol, as well as postoperative outcomes and complications from the available literature. Our patient is a 24-year-old man who presented 3 weeks following a twisting injury while playing spike ball on the beach. He had no history of previous injury to the knee.
On examination of the left knee, there was a moderate effusion and positive patellar apprehension. He was unable to ambulate without support and had limited knee flexion to 80°, the knee was otherwise stable.
Plain radiographs were obtained and were suspicious for a large chondral defect in the medial patellar facet. He was indicated for an MRI, which demonstrated tearing of the MPFL and a large chondral defect of the medial patellar facet with subjacent marrow edema and multiple loose articular cartilage fragments. The tibial tuberosity-trochlear groove distance was 14.5 mm.
Preoperative planning for patellar instability cases include careful evaluation of cartilage injuries and the presence and characteristics of any loose fragments. Successful management of chondral injuries includes reducing and fixing the fragment if amenable while being prepared to change course if intraoperative findings do not support fixation due to the fragment quality or size.
The bony anatomy and the lower extremity alignment are also closely scrutinized to determine the need for adjunct procedures. Consideration of the physeal status is critically important in younger patients. Although numerous graft options are available for MPFL reconstruction, allograft reconstruction has demonstrated reliably good outcomes while avoiding the morbidity associated with autograft. Semitendinosus allografts were utilized in the case presented here.
For full thickness cartilage defects, a variety of options are available such as microfracture, osteochondral allograft, or autologous chondrocyte implantation. The donor site fragment was not amenable to fixation in this case; therefore, a MACI was determined to be the most appropriate course of treatment due to its durability, ease of contouring to the patellar surface, and lack of a bony defect requiring repair. Third-generation autologous chondrocyte implantation techniques, including MACI, use cell-loaded membranes to avoid graft-related complications and simplify the surgical technique. The MACI scaffold (Vericel; Cambridge, MA) specifically uses a porcine type I/III collagen membrane seeded with autologous chondrocytes.7,8
The MACI technique requires a 2-stage procedure. First, an arthroscopic evaluation is conducted by positioning the patient supine on an operating table with the foot of bed lowered to allow for a standard knee arthroscopy.
Arthroscopy revealed an acute medial patellar facet full thickness defect, and the decision to repair in addition to performing MPFL reconstruction was made. The defect was not amenable to fixation due to fragmentation and lack of bone attachment. The loose body was harvested and sent for MACI biopsy. The patient was brought back to the operating room approximately 8 weeks later for MACI implantation, at which time we proceeded directly with an open surgical approach.
For the surgical approach, bony landmarks are identified and a skin incision is marked in the midline. The knee is placed in a sliding knee positioner at 45° of flexion and the skin and subcutaneous tissue are incised and flaps are raised both medially and laterally. The dissection proceeds down to the vastus medialis oblique fascia and medial retinaculum.
Instead of performing the capsulotomy at this stage, we proceed with the dissection for the MPFL reconstruction first. This becomes more difficult once the capsulotomy is performed. A new 15 blade is used to incise along the medial border of the patella, leaving a cuff of tissue to allow later closure. This is carried through the vastus medialis oblique (VMO) down to layer #2 with tunneling to the epicondyle, which facilitates identifying the plane between the first 2 layers and the capsular tissue. This plane is then developed using sharp and blunt dissection. A Metzenbaum scissors is then used to open the space superficial to the capsule to create a plane for the MPFL allograft.
Once this is achieved, the medial capsulotomy is performed, and the patella is everted to expose the fragment donor site. Here, we see fibrous repair tissue, which lacks the biomechanical characteristics of hyaline cartilage that is necessary to withstand the compressive forces distributed across the knee. Therefore, an 11 blade is used to remove the fibrocartilage and the base of the defect is prepared with curettage to identify the stable rim.
The defect is then measured to be roughly 20 mm×20 mm, and a malleable paper is overlaid onto the defect to mark the borders. The paper is then cut to size and re-assessed for appropriate sizing. This imprint is then used as a guide to create an identical aluminum sizer which will better hold its shape. Once it is reassessed for correct sizing, the MACI graft is placed onto a base aluminum sheet with the original sizer sandwiching it in place. Here, the shape of the MACI graft can be accurately created by cutting along the aluminum sizer with scissors.
Next, fibrin glue is applied to the base and rim of the defect before carefully positioning the MACI graft. Fibrin glue is then applied to the periphery of the implant and although not always necessary, when stability is in question the implant can be tacked in the corners with a mineral-oil-coated 6-0 vicryl. The knee is then cycled and the patella everted slightly to confirm the integrity of the MACI construct.
Attention is then redirected to the MPFL reconstruction. The patella is exposed under the medial tissue sleeve, and fluoroscopy is obtained to confirm positioning of 2 pushlock anchors at the 1 and 3 o’clock positions on the right knee. Care is taken to ensure the drill does not penetrate the patellar cartilage. The semitendinosus allograft, which was prepared by an assistant on the back table, is then introduced to the surgical field preloaded on 2 pushlock anchors. These are sequentially placed, with the graft positioned superficially and sutures exiting on the deep side of the eyelet. Tensioning occurs before and during anchor seating.
A free needle is then used to pass the free ends of the sutures from deep to superficial 3 mm from the graft-bone interface and tied over the graft. This creates a larger graft-bone footprint. The plane that was created at the beginning of the procedure between layers 2 and 3 is identified, which will allow easier passing of the graft for femoral fixation.
Fluoroscopy is obtained to identify Schottle point on the lateral projection, and an incision is made, with blunt and sharp dissection carried out to the medial distal femur. Fluoroscopy is then used to further assess tunnel position. A guide pin is placed at Schottle point. Here, the surgeon demonstrates the plane created previously and a Kelly clamp is passed through to retrieve the graft using a free suture passed through the U-limb of the graft. Care is taken to ensure that the synovial layer remains between the graft and the articular surface thus keeping the graft extra articular.
Before securing graft into place, a simulated fixation while cycling the knee is used to evaluate isometry. The tunnel is drilled to at least 30 mm with a 7-mm reamer. The graft is marked at the entrance of the tunnel, and again 25 mm beyond the insertion point. The 2 limbs are then whipstitched together along this length, and the additional tails of the graft are amputated to avoid bottoming out. The graft is then reduced into the tunnel with a pull through method.
Prior to final fixation, a lateral lengthening was performed by delaminating the lateral soft tissues and closing this with #1 Vicryl.
Once this was complete, the medial sided graft was tensioned at 45° of flexion and a 7 x 23 milagro screw was used to reduce the graft into the tunnel, with good fixation. Tension of the graft is evaluated by palpation, and then the knee is cycled, to confirm full range of motion. The patellar should still have 1 to 2 quadrants of lateral translation. The synovial layer is then closed under the MPFL graft with #1 vicryl vicryl sutures in an interrupted pattern. The VMO and retinacular incision is closed over the graft with #1 vicryl vicryl, and the soft tissue and skin is closed in standard fashion. Postoperatively, the patient is made non-weight bearing for the first 2 weeks in a hinged knee brace that is locked in extension with range of motion from 0 to 30° and continuous passive motion beginning postoperative Day 1.
Then at 2 weeks, motion is allowed to progress to full motion between 2 and 6 weeks. Weight bearing as tolerated is allowed locked in full extension from 2 to 6 weeks, then the brace is unlocked at 6 weeks and discontinued at 8 weeks. At this point, patients should focus on full extension while progressing to full knee flexion. They will also begin to progress through more closed chain strengthening and balance exercises.
At 4 months, they can begin a plyometric program and sport-specific exercises as able, with the goal of returning to full sports by 6 months postoperatively. Clinical and radiographic studies have demonstrated significant improvements in patient-reported outcomes and excellent filling and integration at medium-term follow-up.4,5,10
In a report of the superiority of MACI Implant Versus Microfracture Treatment trial, 3 clinical outcomes following the treatment of chondral defects (≥3 cm2) with MACI were clinically superior at 5 years compared with microfracture treatment.
One of the more significant complications after MPFL reconstruction is redislocation, and recent systematic reviews 9 have noted that about 2% of patients sustain a recurrent dislocation, with a larger number experiencing possible subluxation events.
Finally, complications following MACI are generally low with symptomatic graft hypertrophy, graft failure, infections, and subsequent revision surgeries being the most commonly reported. 2 A recent systematic review found that long-term failures ranged from 10% to 11% at 11 years and increased to 58% in knees with evidence of osteoarthritis at 15 years follow-up.1,3,6,10,11
Our references can be found here.
Thank you.
Footnotes
Submitted January 1, 2023; accepted February 15, 2023.
The author reports the following potential conflict of interest or source of funding: K.B.F. is a consultant for DePuy Synthes and Vericel. 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.
