title: High rate of implant loosening for uncemented resurfacing-type medial unicompartmental knee arthroplasty.
abstract: OBJECTIVE
  To determine the medium-term implant survivorship, the clinical results and the failure mechanisms of a novel unicompartmental arthroplasty for uncemented resurfacing of the medial tibio-femoral compartment.
  
  
  METHODS
  Seventy-six consecutive patients were prospectively evaluated with a mean final follow-up of 6 years (SD 5.3 months). In 44 patients, the diagnosis was osteoarthritis, and in 32 patients, it was avascular necrosis of the medial femoral condyle. The Hospital for Special Surgery Score was used for objective clinical evaluation, and a self-administered visual analogue scale was used to quantify residual pain at each observation point. Implant survivorship was determined assuming revision for any reason as endpoint.
  
  
  RESULTS
  Nineteen patients were revised (6 with osteoarthritis and 13 with avascular necrosis of the medial femoral condyle). The mean interval time from index surgery to revision was 11.2 months (SD 4.66 months). Implant survivorship was higher in patients with osteoarthritis with respect to those with avascular necrosis of the medial femoral condyle (p = 0.018). Aseptic loosening was the most frequent failure mechanism. Femoral component loosening was reported in five patients and tibial component loosening was reported in other six patients. Assuming revision for any reason as endpoint, an implant survivorship of 74.3 % at 6-year follow-up was determined. In the remaining 57 patients, satisfactory clinical results were obtained. Hospital for Special Surgery Score and visual analogue scale for residual pain showed significant improvements (p < 0.03 and p < 0.045, respectively).
  
  
  CONCLUSIONS
  At the present time, the standard cemented implants and the conventional designs for unicompartmental knee replacement still represent the optimal solution. The authors do not recommend the widespread use of this technique.
  
  
  METHODS
  IV.
authors.affiliation: 2nd Orthopaedics and Traumatologic Clinic, Rizzoli Orthopaedic Institute, Via Pupilli 1, 40136, Bologna, Italy. d.bruni@biomec.ior.it.|Biomechanics and Technologic Innovation Laboratory, Codivilla-Putti Research Center, Via di Barbiano 1/10, 40136, Bologna, Italy. d.bruni@biomec.ior.it.|Bologna University, Bologna, Italy. d.bruni@biomec.ior.it.
authors.forename: Danilo
authors.initials: D
authors.lastname: Bruni
authors.affiliation: 2nd Orthopaedics and Traumatologic Clinic, Rizzoli Orthopaedic Institute, Via Pupilli 1, 40136, Bologna, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Zaffagnini
authors.affiliation: 2nd Orthopaedics and Traumatologic Clinic, Rizzoli Orthopaedic Institute, Via Pupilli 1, 40136, Bologna, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Iacono
authors.affiliation: Biomechanics and Technologic Innovation Laboratory, Codivilla-Putti Research Center, Via di Barbiano 1/10, 40136, Bologna, Italy.|Bologna University, Bologna, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Bragonzoni
authors.affiliation: 2nd Orthopaedics and Traumatologic Clinic, Rizzoli Orthopaedic Institute, Via Pupilli 1, 40136, Bologna, Italy.
authors.forename: Mirco
authors.initials: M
authors.lastname: Lo Presti
authors.affiliation: 2nd Orthopaedics and Traumatologic Clinic, Rizzoli Orthopaedic Institute, Via Pupilli 1, 40136, Bologna, Italy.
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Neri
authors.affiliation: 2nd Orthopaedics and Traumatologic Clinic, Rizzoli Orthopaedic Institute, Via Pupilli 1, 40136, Bologna, Italy.
authors.forename: Giulio Maria Marcheggiani
authors.initials: GM
authors.lastname: Muccioli
authors.affiliation: 2nd Orthopaedics and Traumatologic Clinic, Rizzoli Orthopaedic Institute, Via Pupilli 1, 40136, Bologna, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Nitri
authors.affiliation: 2nd Orthopaedics and Traumatologic Clinic, Rizzoli Orthopaedic Institute, Via Pupilli 1, 40136, Bologna, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Raspugli
authors.affiliation: 2nd Orthopaedics and Traumatologic Clinic, Rizzoli Orthopaedic Institute, Via Pupilli 1, 40136, Bologna, Italy.|Biomechanics and Technologic Innovation Laboratory, Codivilla-Putti Research Center, Via di Barbiano 1/10, 40136, Bologna, Italy.|Bologna University, Bologna, Italy.
authors.forename: Maurilio
authors.initials: M
authors.lastname: Marcacci
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D005271:Femur Head Necrosis / Q000601:surgery; D005500:Follow-Up Studies; D006801:Humans; D007719:Knee Joint / Q000601:surgery; D007720:Knee Prosthesis / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery; D011446:Prospective Studies; D011475:Prosthesis Failure; D012086:Reoperation; D064232:Visual Analog Scale
keywords: Aseptic loosening; Cementless fixation; Focal resurfacing; Minimal bone resection; Minimally invasive surgery; Unicompartmental knee replacement