title: Meniscal Extrusion Does Not Progress During the Midterm Follow-up Period After Lateral Meniscal Transplantation.
abstract: BACKGROUND
  Meniscal extrusion is related to degeneration of the native knee joint. However, the clinical effect of the phenomenon after meniscal allograft transplantation (MAT) has not been clearly identified. Purpose/Hypothesis: The purpose of this study was to evaluate the change in meniscal extrusion in both the coronal and sagittal planes after lateral MAT through the midterm follow-up period. We hypothesized that meniscal extrusion does not progress during the midterm follow-up period.
  
  
  METHODS
  Case series; Level of evidence, 4.
  
  
  METHODS
  A total of 46 patients with a mean follow-up of 51.1 ± 7.1 months were included in the study. The patients underwent lateral MAT using the keyhole technique. Postoperative magnetic resonance imaging (MRI) was performed at 6-week, 1-year, and midterm (3- to 5-year) follow-up. In the coronal plane, the absolute value of meniscal subluxation and the relative percentage of extrusion (RPE) were measured. In the sagittal plane, meniscal subluxation was measured as the absolute and relative anterior cartilage meniscal distance (ACMD) and posterior cartilage meniscal distance (PCMD). The joint-space width (JSW) on weightbearing radiographs with 2 different knee positions was measured preoperatively and at 1-year and midterm follow-up. The Lysholm score was assessed at the same time points.
  
  
  RESULTS
  In the coronal plane, the mean absolute meniscal extrusion at 6-week, 1-year, and final follow-up was 2.90 ± 0.94, 2.85 ± 0.97, and 2.83 ± 0.89 mm, respectively, and the mean RPE was 27.0% ± 9.4%, 27.1% ± 10.1%, and 27.8% ± 9.7%, respectively. There were no statistically significant differences in absolute and relative coronal extrusion among the 3 time periods ( P > .05). The percentage of patients with meniscal extrusion (≥3 mm) was 37.0% at 6-week follow-up and 34.8% at 1-year and final follow-up. In the sagittal plane, the mean absolute ACMD was 2.59 ± 1.75, 2.58 ± 1.85, and 2.37 ± 1.60 mm, respectively, and the mean relative ACMD was 20.7% ± 13.1%, 20.6% ± 13.8%, and 19.0% ± 12.2%, respectively, at the 3 follow-up time points. The mean absolute PCMD was -1.23 ± 3.34, -1.28 ± 3.08, and -1.42 ± 2.77 mm, respectively, and the mean relative PCMD was -10.3% ± 25.9%, -11.0% ± 24.6%, and -12.2% ± 23.2%, respectively, at the same time points. Sagittal extrusion was not significantly different between the time points ( P > .05). The mean JSW at 2 days preoperatively, 1 year postoperatively, and midterm follow-up was 5.40 ± 1.07, 5.44 ± 1.04, and 5.43 ± 0.98 mm, respectively, on anterior-posterior radiographs with full extension, and it was 4.90 ± 0.94, 4.94 ± 0.98, and 4.89 ± 0.96 mm, respectively, on posterior-anterior radiographs with 45° of flexion. The mean JSW values were not significantly different between the 3 different time points ( P > .05). The mean preoperative Lysholm score was 58. 9 ± 8.3; the score increased to 90.4 ± 9.7 at 1 year postoperatively and 90.5 ± 10.1 at final follow-up, which is a significant improvement compared with the preoperative status ( P < .05). There was no statistically significant difference between the scores at the 2 postoperative time points ( P > .05).
  
  
  CONCLUSIONS
  This study demonstrated that extrusion of the meniscal allograft did not significantly progress either in the coronal or sagittal plane after lateral MAT during the midterm follow-up period.
authors.affiliation: Department of Orthopedic Surgery, Medi-Yin Hospital, Paju, Korea.
authors.forename: Nam-Ki
authors.initials: NK
authors.lastname: Kim
authors.affiliation: Department of Orthopedic Surgery, College of Medicine, Asan Medical Center, University of Ulsan, Seoul, Korea.
authors.forename: Seong-Il
authors.initials: SI
authors.lastname: Bin
authors.affiliation: Department of Orthopedic Surgery, College of Medicine, Asan Medical Center, University of Ulsan, Seoul, Korea.
authors.forename: Jong-Min
authors.initials: JM
authors.lastname: Kim
authors.affiliation: Department of Orthopedic Surgery, College of Medicine, Busan Paik Hospital, Inje University, Busan, Korea.
authors.forename: Chang-Rack
authors.initials: CR
authors.lastname: Lee
authors.affiliation: Department of Orthopedic Surgery, College of Medicine, Asan Medical Center, University of Ulsan, Seoul, Korea.
authors.forename: Jae-Hyan
authors.initials: JH
authors.lastname: Kim
mesh_terms: D000328:Adult; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007718:Knee Injuries / Q000473:pathology* / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008592:Menisci, Tibial / Q000000981:diagnostic imaging / Q000473:pathology* / Q000637:transplantation*; D008875:Middle Aged; D011184:Postoperative Period; D011859:Radiography; D000070600:Tibial Meniscus Injuries / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery*; D014184:Transplantation, Homologous
keywords: allograft; extrusion; meniscus; subluxation; transplantation