At NewYork-Presbyterian and Columbia, the regenerative power of particulated juvenile articular cartilage (PJAC) allograft transplantation is being harnessed to restore the knees of athletes with patellofemoral articular cartilage defects, a common cause of knee pain and a challenging condition to treat. Although several preclinical studies have demonstrated articular growth and graft remodeling after PJAC allograft transplantation in animal models, few studies have examined the short- and long-term efficacy of this innovative technique in humans.
To bridge this information gap, David P. Trofa, MD, an orthopedic surgeon at NewYork-Presbyterian and Columbia, and his colleagues performed a single-center retrospective review of athletes with patellofemoral articular cartilage defects who underwent PJAC allograft transplantation. They found PJAC effectively treats patellofemoral articular cartilage defects in many patients, including those with coexisting knee pathologies, enabling them to return to their sports.
“Cartilage preservation to prevent early arthritis is at the heart of everything we do in sports medicine, whether its repairing a meniscus tear or stabilizing a knee with an ACL reconstruction,” explains Dr. Trofa, who specializes in advanced knee disorders and complex knee pathologies. “With cartilage transplantation we are specifically filling in a focal cartilage defect to prevent further knee degeneration that could lead to debilitating pain. A cell-based cartilage transplantation technique, such as PJAC, is one option we currently have in our armamentarium to treat this complex pathology, and our published results are quite promising.”
Cartilage preservation to prevent early arthritis is at the heart of everything we do in sports medicine, whether its repairing a meniscus tear or stabilizing a knee with an ACL reconstruction.
— Dr. David Trofa
Affecting roughly one out of three athletes, focal cartilage lesions result from repetitive activities, age-related degeneration, or traumatic events to the knee such as a patellar dislocation. Cartilage defects rarely heal on their own because chondrocytes are poorly vascularized and have limited capacity to regenerate after injury. If left untreated, focal cartilage defects can cause pain and lead to knee osteoarthritis.
Patellofemoral articular cartilage defects are difficult entities to treat due to the unique triangular shape of the patella that articulates with the underlying trochlea. “The topography of the patella and trochlea make more traditional cartilage transplant techniques, such as osteochondral plugs which are more commonly used in medial and lateral compartment defects, difficult to implant,” says Dr. Trofa. Moreover, patients with patellofemoral articular cartilage defects often present with concomitant knee pathologies that are, in many instances, the root cause of the defect.
“We often see patients who dislocated their patella and the sheer force of the injury resulted in a loose body originating from an osteochondral injury of the patella,” explains Dr. Trofa. “As a result, we often need to perform a surgical procedure to correct the patella instability and any underlying alignment pathology as well as the cartilage restoration procedure, whether through repair or transplantation.”
Different Approaches to Treating Patellofemoral Articular Cartilage Defects
Several different approaches are used to address patellofemoral articular cartilage defects, including chondroplasty, microfracture, osteochondral transplantation, and cell based techniques such as autologous cultured chondrocytes on a porcine collagen membrane and PJAC, which harnesses the power of juvenile cartilage tissue from donors ages 13 and younger to repair and restore cartilage.
In the PJAC technique, the patient’s cartilage defect is filled with juvenile allograft chondrocytes that generate neocartilage alongside the patient’s own chondrocytes. Compared to adult allograft cartilage cells, juvenile allograft cartilage cells produce more collagen and have superior cell density and proliferation rates, improving its ability to restore native cartilage. Furthermore, unlike other cell-based techniques which requires a biopsy to harvest the patients chondrocytes first, this procedure can be performed in a single setting.
“PJAC is a promising treatment, and reports on its efficacy continue to be generated,” says Dr. Trofa. “Prior to our study, published data had only been reported on 157 patients who received a PJAC transplantation. Our study, which is the largest series to date, added another 38 patients for analysis and helps cartilage surgeons better understand the short- and long-term efficacy of PJAC in this patient group.”
Our study, which is the largest series to date, added another 38 patients for analysis and helps cartilage surgeons better understand the short- and long-term efficacy of PJAC in this patient group.
— Dr. David Trofa
Results of The Retrospective Study
For the study, the authors analyzed reported return-to-sport rates, postoperative patient-reported outcomes (PROs), complication rates, and reoperation rates of a cohort of patients who underwent PJAC allograft transplantation for patellofemoral articular cartilage defects from 2014 to 2022. The study included 41 knees with a mean age of 23 years, plus or minus 9.7 years, and a mean follow-up period of roughly 30 months.
“The younger age range of patients in the study reflects patient eligibility for the procedure,” says Dr. Trofa. “Older patients tend to have more advanced articular cartilage pathology, like arthritis, making them less appropriate candidates for cartilage transplantation. However, age is just one factor we evaluate when indicating patients for cartilage restoration and even our aging patients are looking for solutions to help them continue being active.”
The study found that among patients playing organized sports at the high school and collegiate levels, the overall return-to-sport rate was 100% (17 of 17). During follow-up, complications developed in 12 knees (29.3%), the most common of which was anterior-based knee pain, and 6 knees (14.6%) required a total of 8 reoperations, which occurred from 6 to 32 months postoperatively. “The study’s 100% return-to-sport rate is pretty remarkable,” says Dr. Trofa. “This means that active patients who require a PJAC transplantation have a good chance of returning to their desired activities.”
The study’s 100% return-to-sport rate is pretty remarkable. This means that active patients who require a PJAC transplantation have a good chance of returning to their desired activities.
— Dr. David Trofa
The complication and reoperation rates of 29.3% and 14.6%, respectively, reflect the complex etiology and treatment of patellofemoral articular defects. “This is a very challenging patient population,” says Dr. Trofa. “Many patients who undergo this operation also have concomitant knee pathology, such as patella instability or maltracking, and may have some form of residual anterior knee pain after the procedure.”
“While more research is needed to explore the efficacy of PJAC allograft transplantation, this study reaffirms that the approach is an acceptable treatment for these types of lesions.,” says Dr. Trofa. “It's particularly helpful to have an option that allows us to address all concomitant pathology of the patellofemoral joint in a single surgical procedure, which is one reason the technique is so desirable.”
Collaborative and Multidisciplinary Approach to Treating Sports Injuries
The collaborative and multidisciplinary approach to evaluating and treating sports injuries at NewYork-Presbyterian fuels Dr. Trofa’s passion to pursue research to improve the PJAC technique. “One of the great benefits of being at NewYork-Presbyterian is my ability to partner with basic scientists in the biomedical engineering department at Columbia,” says Dr. Trofa. “One of my mentors, Dr. Clark Hung, is a basic scientist who explores multiple facets of cartilage preservation and restoration with efforts to improve patient clinical outcomes.”
