title: Results of hip resurfacing for developmental dysplasia of the hip of Crowe type I and II.
abstract: BACKGROUND
  Recently, the new generation of metal-on-metal total hip resurfacing arthroplasty is well known for preserving the proximal femoral bone stock, minimizing the risk of postoperative dislocation using large femoral heads, and expecting low wear of metal-on-metal articulation for longer prosthesis survival. It also has the advantage in biomechanical loading in the proximal femur. The osteoarthritis secondary to developmental dysplasia of the hip (DDH) has been the most common reason for total hip arthroplasty. Most of the patients are young and active, who require improved range of motion of the hip besides relief of the pain, even expect to resume the ability to run and jump after the joint arthroplasty, thus to be allowed an active lifestyle. The objective of the current study was to evaluate the early outcome of resurfacing arthroplasty for the mild DDH cases (Crowe type I and II).
  
  
  METHODS
  Between September 2005 and May 2007, twenty-one consecutive patients (twenty-six hips) with the diagnosis of osteoarthritis secondary to DDH underwent metal-on-metal resurfacing arthroplasty. The average age at the time of surgery was 46.5 years (range, 37-59 years). Six patients (28.6%) were male and fifteen (71.4%) were female. Clinical and radiographic results were observed. The follow-up was performed at 6 weeks, 3, 6, 9 months and then yearly.
  
  
  RESULTS
  All patients were followed for a mean of 18 months (9-29 months). During the follow-up period no complications, such as dislocation of hip joints, infection or femoral neck fracture occurred. The clinical outcomes, as rated with the Harris hip score, improved significantly compared with the preoperative ratings. The mean postoperative Harris hip score was 90.7, compared to 35.5 preoperatively. The radiographic analysis showed that all prostheses were fixed with no radiolucencies. All of the patients who had equal limb lengths preoperatively had equal lengths postoperatively. Of the nine patients with preoperative limb-length discrepancy of 0.8 to 1.2 cm, all regained equal limb length postoperatively. In addition the pain was nearly completely relieved, the range of motion was remarkably improved and no restriction was needed after operation regarding early exercise.
  
  
  CONCLUSIONS
  The new generation of metal-on-metal resurfacing arthroplasty may be a reasonable option for DDH of the Crowe types I and II.
authors.affiliation: Department of Orthopedics, Changhai Hospital Affiliated to the Second Military Medical University, Shanghai, China. xuwdshanghai@126.com
authors.forename: Wei-Dong
authors.initials: WD
authors.lastname: Xu
authors.forename: Jia
authors.initials: J
authors.lastname: Li
authors.forename: Zhen-Hua
authors.initials: ZH
authors.lastname: Zhou
authors.forename: Yue-Song
authors.initials: YS
authors.lastname: Wu
authors.forename: Ming
authors.initials: M
authors.lastname: Li
mesh_terms: D000328:Adult; D019643:Arthroplasty, Replacement; D005260:Female; D006618:Hip Dislocation, Congenital / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular