title: Lateral unicompartmental knee arthroplasty through a lateral parapatellar approach has high early survivorship.
abstract: BACKGROUND
  The literature suggests lateral unicompartmental knee arthroplasties are associated with low revision rates. However, there are fewer reports describing techniques for lateral unicompartmental arthroplasty and whether technique influences ROM and function compared to reports for medial unicompartmental arthroplasty.
  
  
  OBJECTIVE
  We report our indications for lateral unicompartmental arthroplasty, how we perform this procedure, and the subsequent Knee Society scores, ROM, and revision and reoperation rates.
  
  
  METHODS
  From a retrospective review of electronic records from 2004 through 2008, we identified 93 patients who had 100 lateral unicompartmental arthroplasties. Indications were complete lateral bone-on-bone arthrosis with a correctible deformity and maintenance of the medial joint space on varus stress radiographs or isolated lateral disease by diagnostic arthroscopy. Average age was 68 years. Seventy percent of patients were women. At followup, we obtained Knee Society scores and ROM. Minimum followup was 24 months (average, 39 months; range, 24-81 months).
  
  
  RESULTS
  At followup, Knee Society scores averaged 46 for pain, 94 for clinical, and 89 for function, and ROM averaged 124°. Three patients had reoperations: one an open reduction and internal fixation for fracture at 2 years postoperatively, one an arthroscopy for a medial meniscal tear, and one a revision for pain.
  
  
  CONCLUSIONS
  Based on our observations, we believe complete cartilage loss laterally and correctible deformity with maintenance of the medial joint on varus stress radiographs are reasonable indications for lateral unicompartmental arthroplasty. We recommend a lateral parapatellar approach can be utilized. The early reoperation and revision rates were low.
authors.affiliation: Department of Orthopaedics, Ohio State University, Columbus, OH, USA. berendkr@joint-surgeons.com
authors.forename: Keith R
authors.initials: KR
authors.lastname: Berend
authors.forename: Michael C
authors.initials: MC
authors.lastname: Kolczun
authors.forename: Joseph W
authors.initials: JW
authors.lastname: George
authors.forename: Adolph V
authors.initials: AV
authors.lastname: Lombardi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D001182:Arthroscopy / Q000379:methods; D016208:Databases, Factual; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000175:diagnosis / Q000601:surgery*; D010147:Pain Measurement; D017847:Patellar Ligament / Q000601:surgery*; D011183:Postoperative Complications / Q000503:physiopathology; D011475:Prosthesis Failure; D016059:Range of Motion, Articular / Q000502:physiology*; D020127:Recovery of Function; D012086:Reoperation / Q000706:statistics & numerical data; D012189:Retrospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D013997:Time Factors; D016896:Treatment Outcome