Osteochondral Allograft Transplant of the Patella Using Femoral Condylar Allografts: Magnetic Resonance Imaging and Clinical Outcomes at Minimum 2-Year Follow-up

Abstract

Background: Fresh osteochondral allograft transplant (OCA) has good outcomes in the knee. However, donor tissue for patellar OCA is limited. Outcomes after nonorthotopic OCA of the patella using more readily available femoral condylar allograft (FCA) tissue have not been previously reported. Purpose: To assess short-term magnetic resonance imaging (MRI) and minimum 2-year clinical outcomes of nonorthotopic patellar OCA using an FCA donor. Study Design: Case series; Level of evidence, 4. Methods: A prospective institutional cartilage registry was reviewed to identify patients treated with patellar OCA using an FCA donor between August 2009 and June 2016. OCA plugs were obtained from the FCA at its trochlear-condylar junction and implanted into the recipient patellar lesion. Early postoperative MRI scans were graded by a blinded musculoskeletal radiologist using the Osteochondral Allograft MRI Scoring System (OCAMRISS). International Knee Documentation Committee Subjective Knee Evaluation Form (IKDC), Knee Outcomes Survey–Activities of Daily Living (KOS-ADL), and pain visual analog scale (VAS) scores were collected preoperatively and at minimum 2 years postoperatively, and outcomes were compared using the paired t test. Results: A total of 25 patients were included for clinical outcome analysis and 20 patients for MRI analysis. MRI scans obtained at a mean of 11.4 months (range, 6-22 months) postoperatively showed a mean total OCAMRISS score of 9.0 (range, 7-11); mean bone, cartilage, and ancillary subscores were 2.6, 3.7, and 2.6, respectively. At the latest follow-up (mean, 46.5 months; range, 24-85 months), postoperative improvements were noted in IKDC (from 45.0 to 66.2; P = .0002), KOS-ADL (from 64.3 to 80.4; P = .0012), and VAS (from 5.1 to 3.4; P = .001) scores, with IKDC and KOS-ADL scores above the corresponding previously reported minimal clinically important difference. Conclusion: In this study, patellar OCA using nonorthotopic FCA led to significant short-term improvements in pain and patient-reported outcomes. The majority of nonorthotopic patellar grafts demonstrated full osseous incorporation and good restoration of the articular surface on MRI at short-term follow-up.

No Difference in Outcomes Following Osteochondral Allograft with Fresh Precut Cores Compared to Hemi-Condylar Allografts

“…20,21 Although the literature comparing imaging assessments between orthotropic and nonorthotopic OCA is exceedingly limited, the existing studies have displayed comparable scores between the two. 20,22-25 This aligns with the findings in our study demonstrating no difference in the imaging analysis of fresh precut OCA cores compared to size matched condylar grafts.…”

Osteochondral Allograft Transplant of the Patella Using Femoral Condylar Allografts: Letter to the Editor

“…Maintenance of native surface topography is equally important in the patella, and the differences in radius of curvature between the patella and femoral condyle are much greater than any differences between femoral condyles. In the study by Lin et al, 10 the authors reported that the graft was always harvested at the same location, the trochlear-condylar junction, and although no explanation was provided as to why this graft harvest location was selected, we surmise that this location was chosen in an effort to match patellar topography. The authors likely had a variety of locations on the patella which required grafting, and we question whether the radius of curvature differences can be reliably matched using this harvest site.…”

“…We congratulate Lin et al 10 on their recent study entitled “Osteochondral Allograft Transplant of the Patella Using Femoral Condylar Allografts: Magnetic Resonance Imaging and Clinical Outcomes at Minimum 2-Year Follow-up.” In this case series, minimum 2-year follow-up PROs and minimum 6-month postoperative magnetic resonance imaging (MRI) findings were assessed in 25 and 20 patients, respectively, who underwent OCA to the patella or patella and trochlea using a femoral condyle allograft (FCA). The rationale for this approach is based on the scarcity of patellar grafts compared to that of the femoral condyle.…”

“…The study by Lin et al 10 strives to solve an underlying problem plaguing this procedure: the lack of patellar graft availability. The larger concern that this paper raises is the paucity of literature describing how to appropriately match donor grafts and what is the ultimate clinical effect of cartilage and/or osseous mismatch.…”

Arthroscopic Patellar Osteochondral Transplantation

“… 3 However, osteochondral grafting to the patella is still performed with an open approach, with arthrotomy and patellar eversion, to provide the necessary perpendicular access. 4 , 5 …”