title: [Accuracy improvement of acetabular component placement using non-image based surgical navigation system].
abstract: OBJECTIVE
  To improve the accuracy of the acetabular component placement using the non-image based surgical navigation system.
  
  
  METHODS
  Twenty-three patients (14 males, 9 females; age, 28-55 years; 26 hips) with hip disease underwent the total hip arthroplasty (THA) using the non-image based surgical navigation system from February 2004 to April 2006. Rheumatoid arthritis was found in 3 patients (3 hips), necrosis of the femoral head in 6 patients (6 hips), and osteoarthritis in 14 patients (16 hips). All the patients were randomly divided into the following 2 groups: the navigated group (11 patients, 13 hips), treated by THA using the non-image based surgical navigation system; and the control group (12 patients, 13 hips), treated by the traditional THA. According to the design of the study, the acetabular component was placed in the best inclination angle (45 degrees) and the anteversion angle (15 degrees). The postoperative component position was examined.
  
  
  RESULTS
  No fracture, dislocation, infection or injury to the sciatic nerve was found. In the navigated group, the inclination and the anteversion reached 15.4 +/- 1.4 degrees and 45.5 +/- 1.3 degrees, respectively. In the control group, the inclination and the anteversion were 13.9 +/- 7.6 degrees and 43.7 +/- 6.4 degrees, respectively. The inclination difference was considered statistically significant (P < 0.01). All the patients were followed up for 10-40 months,averaged 26 months. In the navigated group, the postoperative average Harris hip score was 95 (range, 85-110), with an excellent result in 11 hips and a good result in 2 hips. In the control group, the postoperative average Harris hip score was 92 (range, 75-110), with an excellent result in 9 hips, a good result in 3 hips, and a fair result in 1 hip. The Harris hip score difference was considered statistically significant (P < 0.05). There was a significantly better result obtained in the navigated group than in the control group.
  
  
  CONCLUSIONS
  The acetabular component can be implanted accurately by the non-image based surgical navigation system, which can reduce the incidence of the loosening of the prostheses and has an important value in clinical practice.
authors.affiliation: Department of Orthopedics, Nanjing First Hospital Affiliated to Nanjing Medical Universty, Nanjing Jiangsu 210006, PR. China. yuzhong19741208@163.com
authors.forename: Zhong
authors.initials: Z
authors.lastname: Yu
authors.forename: Liming
authors.initials: L
authors.lastname: Wang
authors.forename: Jianchao
authors.initials: J
authors.lastname: Gui
mesh_terms: D000077:Acetabulum / Q000601:surgery*; D000328:Adult; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D003625:Data Collection / Q000295:instrumentation; D005260:Female; D005271:Femur Head Necrosis / Q000601:surgery*; D005500:Follow-Up Studies; D006621:Hip Joint / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery*; D016059:Range of Motion, Articular; D025321:Surgery, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D016896:Treatment Outcome