title: A matched-pair comparison of inlay and onlay trochlear designs for patellofemoral arthroplasty: no differences in clinical outcome but less progression of osteoarthritis with inlay designs.
abstract: OBJECTIVE
  To compare clinical and radiographic results after isolated patellofemoral arthroplasty (PFA) using either a second-generation inlay or onlay trochlear design. The hypothesis was that an inlay design will produce better clinical results and less progression of tibiofemoral osteoarthritis (OA) compared to an onlay design.
  
  
  METHODS
  Fifteen consecutive patients undergoing isolated PFA with an onlay design trochlear component (Journey™ PFJ, Smith & Nephew) were matched with 15 patients after isolated PFA with an inlay design trochlear component (HemiCAP®Wave, Arthrosurface). Matching criteria were age, gender, body mass index, and follow-up period. An independent observer evaluated patients prospectively, whereas data were compared retrospectively. Clinical outcome was assessed using WOMAC, Lysholm score, and pain VAS. Kellgren-Lawrence grading was used to assess progression of tibiofemoral OA.
  
  
  RESULTS
  Conversion to total knee arthroplasty was necessary in one patient within each group, leaving 14 patients per group for final evaluation. The mean follow-up was 26 months in the inlay group and 25 months in the onlay group (n.s.). Both groups displayed significant improvements of all clinical scores (p < 0.05). No significant differences were found between the two groups with regard to the clinical outcome and reoperation rate. No significant progression of tibiofemoral OA was observed in the inlay group, whereas 53 % of the onlay group showed progression of medial and/or lateral tibiofemoral OA (p = 0.009).
  
  
  CONCLUSIONS
  Isolated PFA using either a second-generation inlay or onlay trochlear component significantly improves functional outcome scores and pain. The theoretical advantages of an inlay design did not result in better clinical outcome scores; however, progression of tibiofemoral OA was significantly less common in patients with an inlay trochlear component. This implant design may therefore improve long-term results and survival rates after isolated PFA.
  
  
  METHODS
  III.
authors.affiliation: Department of Orthopaedic Sports Medicine, Technical University Munich, Ismaninger Str. 22, 81675, Munich, Germany.|Department of Orthopedic Surgery and Traumatology, Freiburg University Hospital, Freiburg, Germany.
authors.forename: Matthias J
authors.initials: MJ
authors.lastname: Feucht
authors.affiliation: Department of Orthopaedic Sports Medicine, Technical University Munich, Ismaninger Str. 22, 81675, Munich, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Cotic
authors.affiliation: Department of Orthopaedic Sports Medicine, Technical University Munich, Ismaninger Str. 22, 81675, Munich, Germany.
authors.forename: Knut
authors.initials: K
authors.lastname: Beitzel
authors.affiliation: Department of Orthopaedic Sports Medicine, Technical University Munich, Ismaninger Str. 22, 81675, Munich, Germany.
authors.forename: Julia F
authors.initials: JF
authors.lastname: Baldini
authors.affiliation: Department of Orthopaedic Sports Medicine, Technical University Munich, Ismaninger Str. 22, 81675, Munich, Germany.|Department of Trauma and Orthopaedic Surgery, Trauma Center Murnau, Murnau, Germany.
authors.forename: Gebhart
authors.initials: G
authors.lastname: Meidinger
authors.affiliation: Department of Orthopaedic Sports Medicine, Technical University Munich, Ismaninger Str. 22, 81675, Munich, Germany.|Department of Orthopaedics and Trauma Surgery, Isar Medical Center, Munich, Germany.
authors.forename: Philip B
authors.initials: PB
authors.lastname: Schöttle
authors.affiliation: Department of Orthopaedic Sports Medicine, Technical University Munich, Ismaninger Str. 22, 81675, Munich, Germany. a.imhoff@lrz.tum.de.
authors.forename: Andreas B
authors.initials: AB
authors.lastname: Imhoff
mesh_terms: D000328:Adult; D000368:Aged; D001178:Arthroplasty / Q000295:instrumentation* / Q000379:methods; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D016555:Matched-Pair Analysis; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000601:surgery*; D057071:Patellofemoral Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D011859:Radiography; D012086:Reoperation; D012189:Retrospective Studies; D016896:Treatment Outcome
keywords: HemiCAP Wave; Inlay; Journey PFJ; Onlay; Patellofemoral arthritis; Patellofemoral arthroplasty