Single-Stage Arthroscopic Cartilage Repair With Gel Scaffold and BMAC

Abstract

Background:

Injectable scaffold augmentation has been gaining traction as a promising modality for single-stage cartilage repair. It involves the use of a biological scaffold that augments microfracture techniques by aiding in clot stabilization and maturation. The scaffold provides a matrix that helps with mesenchymal stem cell (MSC) retention and encourages differentiation along a chondrogenic lineage. Bone marrow aspirate concentrate (BMAC) has also been proposed as an alternative source of MSCs to microfracture, and it can potentially avoid the pitfalls of microfracture techniques.

Indications:

Injectable scaffold augmentation to microfracture techniques are recommended in lesions >4 cm, as long-term follow-up has shown increasing failure over time with microfracture alone.

Technique Description:

We describe a technique of autologous matrix-induced chondrogenesis using CartiFill, a porcine-derived type 1 collagen scaffold, combined with BMAC as a source of MSCs (avoiding the use of microfracture).

Results:

Injectable scaffold augmentation has been shown in recent studies to lead to better radiological fill, higher quality of histological repair, and better clinical outcomes as compared with microfracture alone. These injectable scaffolds have the versatility to be used on lesions which have traditionally been considered difficult to address, such as vertical or inverted lesions. Moreover, the use of scaffolds allows the repair to be further augmented with BMAC which provides a source of MSCs without the need to perform microfracture and perforate the subchondral bone.

Discussion/Conclusion:

Scaffold augmentation is a promising technique that improves upon the results of conventional microfracture repair by allowing augmentation with BMAC, as well as giving surgeons the versatility to apply the scaffold on vertical/inverted lesions. BMAC is also a viable alternative source of MSCs for cartilage repair.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

In this video, we demonstrate the use of single-stage arthroscopic cartilage repair with an injectable collagen scaffold and bone marrow aspirate concentrate (BMAC) in the management of a patient with a kissing lesion cartilage defect in the patellofemoral joint. We present an overview of the technique and the patient’s clinical presentation and share how the repair is performed, as well as summarize the tips of this technique and postsurgery rehabilitation.

Single-stage cartilage repair with injectable scaffold utilizes a biological scaffold to augment current microfracture repair techniques. The scaffold is made from porcine collagen and traps the blood clot from microfracture, helping to improve clot stabilization and maturation. It also promotes differentiation of the mesenchymal stem cells (MSCs) along a chondrogenic lineage.

This type of scaffold repair is indicated in chondral defect lesions of >1.5 cm². Studies have shown that scaffold augmentation leads to better radiological fill, histological repair, and clinical outcomes. An injectable gel-like scaffold has the added benefit of allowing surgeons to apply the scaffold in more difficult-to-treat lesions.

The use of BMAC as a source of MSCs allows us to avoid microfracture. This avoids penetrating the subchondral plate, and the properties of BMAC with scaffold have been shown to be comparable to techniques utilizing microfracture. In this patient, we harvest BMAC from the ipsilateral iliac crest. Once the bone marrow aspirate is obtained, it is concentrated in a centrifuge and added to the gel scaffold mixture.

Our patient is a 41-year-old male in an elite unit of the police force. He presents with left anterior knee pain for 2 years, which was worse on physical activity and walking on uneven terrain, affecting his ability to train with his unit. The pain was worse on descending stairs as well. The physical examination was unremarkable, except for pain with grinding of the patella. There was minimal patellar maltracking noted on physical examination.

The magnetic resonance imaging (MRI) of his left knee showed a full thickness chondral defect in the patellar apex with delamination into the lateral facet. There was also a chondral irregularity in the central trochlea.

He had been managed with nonsurgical modalities for 2 years with limited benefit under a sports physician and a physiotherapist. During this time, he has had anti-inflammatory medications, physiotherapy, and an intra-articular hyaluronic acid injection. He was then referred for surgical management, as nonsurgical therapy did not improve his situation.

He was offered knee arthroscopic debridement and cartilage repair with scaffold and BMAC, in view of persistent symptoms which were affecting his work. He was advised of the subsequent rehabilitation timeframe after surgery. As he had minimal patellar maltracking, had normal patella height and TT-TG distance measured on MRI was 12 mm, he did not require corrective osteotomy. In such cases, we perform suprapatellar scar release and limited lateral release during surgery to improve patella tracking and cartilage visualization as well as access during arthroscopy.

The patient is positioned supine on the operating table, with a thigh tourniquet secured. The operated leg hangs free over the table and a side support is placed. The other leg is placed in a stirrup leg holder and brought away from the surgical field. The ipsilateral iliac crest is cleaned and draped as well.

We are viewing the left knee from the anterolateral portal with instruments from the anteromedial portal and the knee held in extension. Portals are created 1 cm medial and lateral to the patella tendon. In the treatment of patellofemoral lesions, we avoid placing the portals too high as this makes visualization of the patella difficult. A limited lateral release has been performed to improve access to and visualization of the undersurface of the patella for the cartilage repair. Here, we demonstrate the preparation of the lesion without microfracture performed. We will utilize BMAC to obtain MSCs for the repair. There is a 2 cm by 1.5 cm Outerbridge grade 4 lesion on the femoral trochlea, and there is a 1 cm by 1 cm Outerbridge grade 4 inverted lesion on the patella. Arthroscopic ring curettes are used to create a cartilage defect with stable margins and a vertical shoulder. Arthroscopic shavers are used to remove loose flaps of cartilage and freshen the defect base. Care must be taken to avoid injuring the healthy surrounding cartilage. Here you can see the prepared inverted patella and femoral trochlea lesions.

We harvest the bone marrow aspirate from the ipsilateral iliac crest. This is done after confirmation that we will proceed with cartilage repair and after lesion preparation.

By placing a thumb and index finger, we locate the width of the iliac crest. Using a trocar, we aim for the middle of our thumb and index finger and introduce the needle using the trocar into the iliac crest bone. We rotate the trocar needle slowly to go through the outer table. Once the needle passes through the outer table into the region of the cancellous bone, the BMAC can then be aspirated. We remove the central trocar and attach a VacLok syringe (Merit Medical) and begin aspiration. The syringe can be locked by turning the plunger clockwise to maintain the negative pressure; 30 mL of bone marrow is aspirated. The bone marrow aspirate is then spun down in a centrifuge to obtain 3 mL of BMAC. This BMAC is then mixed into the Cartifill (Sewon Cellontech) collagen scaffold in a 1 mL BMAC:1 mL gel scaffold ratio and is ready for application.

The fluid from the knee joint is drained, and dry arthroscopy is performed. Dry arthroscopy is necessary to improve adherence of the gel scaffold/BMAC mixture onto the cartilage lesion site. Suction tips are used to drain excess fluid from the joint. Neuropatties are repeatedly used to ensure that the defect bed is kept dry from fluid and blood to facilitate application of the scaffold. The trochlea defect is tackled first. Here, you can see the injection of the gel scaffold into the trochlea defect using a blunt needle. The more viscous gel mixture is then applied to the inverted roof lesion on the patella. Similarly, here you can see injection of the gel scaffold into the inverted roof lesion on the patella. This is a view of the completed cartilage repair. Irrigation is turned on, and wet arthroscopy is performed. This clip shows a clear view of the trochlea and the patella lesions which have been repaired with the injectable gel scaffold and BMAC mixture. The repair is stable on wet arthroscopy. Here, we bring the knee joint through its full range of motion to demonstrate that the repair remains stable during joint movement.

We share some surgical tips. First, the repair site should be dried before application of the scaffold. Tools can be used to retract the soft tissue from the field during application. The knee should be supported with a side table to allow optimal flexion. Lateral release will help to improve lesion visualization and access. A probe can be used to mold the scaffold to the desired shape.

We discuss ways to prevent potential complications. Inadvertent damage to surrounding cartilage can be avoided by careful use of curettes and shavers as well as good lesion visualization and access during arthroscopy. Loosening of the scaffold can be avoided by ensuring a dry defect bed during application. BMAC donor site complications can be avoided with good harvesting technique.

At our institution, we have specific patellofemoral joint cartilage repair rehabilitation protocol. For weightbearing, patients are allowed 50% partial weightbearing for 6 weeks and then progressed to full weightbearing after 6 weeks. All patients are issued a postoperative knee brace to limit range of motion and to lock the knee in full extension when weightbearing for 6 weeks. The range of motion in the brace is increased by 30° every consecutive 2 weeks, and at 6 weeks, the patient is allowed full range of motion. Strengthening exercises are commenced after 6 weeks, focusing on quadriceps and gluteal strengthening.

Cycling and elliptical machine training is commenced 6 weeks from surgery, in conjunction with strengthening. Running is permitted only after the strength of the operated leg has recovered to within 80% of the unoperated leg using Biodex testing. Cutting and sports drills are commenced only after the patient has symmetrical running gait and remains pain free. Return to sports is permitted after 9 months if patient fulfills the following criteria: the strength of the recovery of the operated limb is symmetrical to the contralateral limb and there is no pain or knee swelling, and the patient has completed agility and sports drills.

This patient recovered and remained pain free with no knee swelling. He recovered his strength and agility and was able to return to active duty at 12 months after surgery. The senior author has used this technique as single-stage cartilage repair in the last 3 years with good postsurgery functional outcomes. At an average follow-up of 42 months, both the Lysholm and the Knee injury and Osteoarthritis Outcome scores improved from baseline. In a multicenter randomized controlled trial, CartiFill has been shown to result in improved outcomes when compared to microfracture alone.

In summary, cartilage repair of kissing lesions in the patellofemoral joint can be performed with single-stage arthroscopic repair with gel scaffold and BMAC. The addition of BMAC to the scaffold mixture can avoid the need to perform microfracture, hence avoiding its purported pitfalls. The lesions in the patella can be repaired with arthroscopy and visualized in an inverted position using injectable gel scaffold and BMAC.