Patellofemoral joint cartilage restoration with particulated juvenile allograft in patients under 21 years old

Published:August 07, 2021DOI:


      • PJAC restoration can be performed safely and effectively in young patients.
      • Young patients treated with PJAC were able to return to sport postoperatively.
      • PJAC can restore defects due to a wide variety of underlying etiologies.



      Patellofemoral joint cartilage defects are difficult to treat due to their unique thickness and topography.


      To report the postoperative outcomes of patients age 21 and younger treated with particulated juvenile allograft cartilage (PJAC) for full-thickness cartilaginous defects of the patellofemoral joint. The primary aim was to report surgical outcomes and complication rates, as well as return to sport activity. A secondary aim was to provide objective scores of defect restoration by magnetic resonance imaging (MRI) assessment.


      A retrospective review of all PJAC cases conducted between 2012 and 2019 at a single tertiary care urban musculoskeletal institution was conducted. Patients 21 years old or younger with minimum clinical follow up of 1 year and postoperative MRI at a minimum of 6 months were included. Cartilage restoration by MRI was independently assessed using the International Cartilage Repair Society’s (ICRS) standardized system.


      Thirty four patients, 36 knees, were included, with mean age 16.1 ± 3.1 years old. Return to sport rate among patients who participated in a sport preoperatively was 100%. On independent MRI assessment, two thirds of defects achieved an overall grade of normal or nearly normal, while 28 patients (78%) had majority defect fill. Primary graft failure occurred in two cases and one patient experienced a surgical complication.


      Restoration of patellofemoral chondral defects in young patients with particulated juvenile allograft results in satisfactory short-term outcomes and postoperative MRI appearance, along with high rates of return to sport and low rate of complications and graft failure.
      What is known about the subject: Patellofemoral joint cartilage defects are difficult to treat due to their unique thickness and topography. Several cartilage restoration techniques are available, but these rarely achieve the same mechanical properties as native hyaline cartilage. PJAC is a cell-based technique that has demonstrated promise since its introduction in 2007.
      What this study adds to existing knowledge: This series of patients adds the largest single cohort of pediatric and adolescent patients who receive PJAC for defects of the patellofemoral joint. Surgeons treating patients in this age group should be aware of every technique, and their respective outcomes.



      JOCD (juvenile osteochondritis dissecans), PJAC (particulated juvenile allograft cartilage), ACI (autologous chondrocyte implantation), MRI (Magnetic resonance imaging study), ICRS (International Cartilage Repair Society), JIA (juvenile idiopathic arthritis), MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue), PFI (Patellofemoral instability)
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