title: Minimally invasive unicompartmental knee arthroplasty for spontaneous osteonecrosis of the knee.
abstract: OBJECTIVE
  To explore the outcome and surgical technique of minimally invasive unicompartmental knee arthroplasty (UKA) for spontaneous osteonecrosis of the knee.
  
  
  METHODS
  Twenty-seven patients with medial compartmental spontaneous osteonecrosis treated by minimally invasive Oxford phase 3 UKA from January 2009 to June 2013 were reviewed retrospectively. Twelve subjects were men and 15 women, with an average age of 64.6 ± 8.6 years (52-82 years). At the time of diagnosis, 11 patients had with grade III necrosis and 16 grade IV according to Mont's classification. Pain, range of motion (ROM) and Hospital for Special Surgery (HSS) knee scores were evaluated before and after UKA. Pre-and postoperative alignment of the lower limbs was measured and compared. Postoperative radiographic assessments were made according to the guidelines proposed by the Oxford group at the final follow-up.
  
  
  RESULTS
  All patients were followed for a mean time of 27.8 ± 15.9 months (6-59 months). There were no serious adverse events, such as infection, bearing dislocation, aseptic loosening, pulmonary embolism, deep venous thrombosis, cardio-cerebral vascular incident or psychological problems. One revision was required for unrelated causes (fracture of tibia plateau) 3 years after arthroplasty. One femoral component was tilted with a postoperative radiographic angle >10°. One radiolucent line was observed in a patient with spontaneous osteonecrosis of the knee. The two patients with implant failure had no symptoms at last follow-up. Visual analogue scale scores decreased from 6.9 ± 0.9 to 2.0 ± 1.1 (t = 19.27, P = 0.00). Pain was relieved in 96.3% of subjects (26/27). The mean post-operative ROM and femorotibial angle were 125.7° ± 9.6° and 177.7° ± 3.1°, respectively. HSS scores increased from 61.3 ± 9.7 to 93.0 ± 4.8 (t = 14.46, P = 0.00). Of the 27 patients, 26 (96.3%) were satisfied with the outcome of this surgical procedure.
  
  
  CONCLUSIONS
  Minimally invasive UKA is an effective means of managing spontaneous osteonecrosis of the knee. The short-term outcome of UKA is encouraging.
authors.affiliation: Department of Joint Surgery, China-Japan Friendship Hospital, Beijing, China.
authors.forename: Wan-shou
authors.initials: WS
authors.lastname: Guo
authors.affiliation: Department of Joint Surgery, China-Japan Friendship Hospital, Beijing, China.
authors.forename: Qi-dong
authors.initials: QD
authors.lastname: Zhang
authors.affiliation: Department of Joint Surgery, China-Japan Friendship Hospital, Beijing, China.
authors.forename: Zhao-hui
authors.initials: ZH
authors.lastname: Liu
authors.affiliation: Department of Joint Surgery, China-Japan Friendship Hospital, Beijing, China.
authors.forename: Li-ming
authors.initials: LM
authors.lastname: Cheng
authors.affiliation: Department of Joint Surgery, China-Japan Friendship Hospital, Beijing, China.
authors.forename: De-bo
authors.initials: DB
authors.lastname: Yue
authors.affiliation: Department of Joint Surgery, China-Japan Friendship Hospital, Beijing, China.
authors.forename: Wei-guo
authors.initials: WG
authors.lastname: Wang
authors.affiliation: Department of Joint Surgery, China-Japan Friendship Hospital, Beijing, China.
authors.forename: Nian-fei
authors.initials: NF
authors.lastname: Zhang
authors.affiliation: Department of Joint Surgery, China-Japan Friendship Hospital, Beijing, China.
authors.forename: Zi-rong
authors.initials: ZR
authors.lastname: Li
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D062785:Hemiarthroplasty / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000379:methods*; D010020:Osteonecrosis / Q000601:surgery*; D012189:Retrospective Studies; D016896:Treatment Outcome
keywords: Knee arthroplasty; Minimally invasive; Osteoarthritis; Spontaneous osteonecrosis of the knee