Evaluation of a computed tomography-based navigation system prototype for hip arthroscopy in the treatment of femoroacetabular cam impingement

Arthroscopy. 2009 Apr;25(4):382-91. doi: 10.1016/j.arthro.2008.11.012. Epub 2009 Feb 11.


Purpose: The purpose of this study was to investigate the impact of a new computed tomography-based computer navigation system on the accuracy of arthroscopic offset correction in patients with cam type femoroacetabular impingement (FAI), and to evaluate if the accuracy of offset restoration compromises the early clinical outcome.

Methods: We prospectively treated 50 patients (25 navigated and 25 non-navigated) by hip arthroscopy and arthroscopic offset restoration for cam FAI. The patients were a mean age 42.9 years, and the average follow-up was 26.7 months, with no patients lost to follow-up. Magnetic resonance imaging scans were performed preoperatively and 6 weeks postoperatively. A postoperative alpha angle of less than 50 degrees or a reduction of the alpha angle of more than 20 degrees was considered to be successful offset restoration. Outcomes were measured with a visual analogue scale for pain, range of motion, and the nonarthritic hip score.

Results: The mean alpha angle improved from 76.5 degrees (range, 57 degrees to 110 degrees) to 54.2 degrees (range, 40 degrees to 84 degrees). In both the navigated and the non-navigated groups, 6 patients (24%) showed insufficient offset correction. Range of motion, visual analogue scale for pain scores, and nonarthritic hip scores significantly improved in all subgroups. Statistical analysis showed no significant difference regarding the clinical outcome between patients with sufficient and insufficient correction of the alpha angle.

Conclusions: In this series, a significant percentage of patients (24%) showed an insufficient correction of the alpha angle after hip arthroscopy for cam FAI. This study shows that the presented navigation system could not improve this rate and that the insufficient accuracy of reduction of the alpha angle does not appear to compromise the early clinical outcome.

Level of evidence: Level II, prospective comparative study.

Publication types

  • Comparative Study
  • Evaluation Study

MeSH terms

  • Acetabulum / diagnostic imaging*
  • Acetabulum / surgery*
  • Adolescent
  • Adult
  • Aged
  • Arthroscopy / methods*
  • Female
  • Follow-Up Studies
  • Hip Joint / diagnostic imaging*
  • Hip Joint / physiopathology
  • Hip Joint / surgery*
  • Humans
  • Joint Diseases / diagnostic imaging*
  • Joint Diseases / surgery*
  • Magnetic Resonance Imaging
  • Male
  • Middle Aged
  • Nerve Compression Syndromes / diagnostic imaging
  • Nerve Compression Syndromes / surgery
  • Preoperative Care
  • Prospective Studies
  • Range of Motion, Articular
  • Tomography, X-Ray Computed / methods
  • Treatment Outcome
  • Young Adult