Getting it Right with Navigation   |    
Imageless Navigation in Hip Resurfacing: Avoiding Component Malposition During the Surgeon Learning Curve
James R. Romanowski, MD1; Michael L. Swank, MD2
1 Department of Orthopaedic Surgery, University of Cincinnati, 224 Leather Leaf Lane, Lebanon, OH 45036
2 Cincinnati Orthopaedic Research Institute, 9825 Kenwood Road, Suite 200, Cincinnati, OH 45242. E-mail address: mswank2789@aol.com
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Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. A commercial entity (BrainLAB) paid or directed in any one year, or agreed to pay or direct, benefits of less than $10,000 to a research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which one or more of the authors, or a member of his or her immediate family, is affiliated or associated.

The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2008 Aug 01;90(Supplement 3):65-70. doi: 10.2106/JBJS.H.00462
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Background: Studies suggest that hip arthroplasty procedures performed in specialty hospitals or by physicians in practices with a high surgical volume are associated with a decreased rate of adverse outcomes related to component malpositioning. Little is known, however, about the influence of imageless computer navigation systems on the procedural experience of the surgeon and the subsequent alignment of implants in the setting of hip resurfacing arthroplasty.

Methods: Seventy-one consecutive hip resurfacing arthroplasties in which the components were placed with use of computer-assisted navigation were reviewed retrospectively. Intraoperative femoral and acetabular component parameters were compared with postoperative radiographic alignment values. Within this single surgeon series, operative time, intraoperative cup inclination and femoral stem-shaft angles, and postoperative cup inclination and femoral stem-shaft angles were measured and compared over the course of three discrete, sequential operative time periods. Patient demographic data and surgical parameters, including blood loss, surgical approach, and anesthesia time, were recorded.

Results: No significant difference was seen between the intraoperative and postoperative cup inclination angles. A significant difference was noted between the intraoperative and postoperative femoral stem-shaft angles; however, the mean angles in all groups had a valgus orientation when compared with the mean native neck angles. Over three sequential operative time periods, computer-assisted navigation produced consistent values with regard to intraoperative cup inclination (43°, 44°, and 40°) and postoperative radiographic alignment of the cup (46°, 44°, and 43°) and femoral stem (148°, 147°, and 144°), despite different levels of surgeon experience. Operative times significantly decreased with surgeon experience, showing the largest decrease after the first sequence interval (110, ninety-eight, and ninety-five minutes, respectively). There was a significant difference with evolving surgeon experience concerning intraoperative stem placement (144°, 142°, and 138°, respectively) despite the mean values remaining well-clustered. No femoral notching occurred throughout the series.

Conclusions: Computer-assisted navigation is a dependable and accurate method of positioning hip resurfacing components during arthroplasty, as measured by cup inclination, and a reliable technique for valgus stem placement and avoidance of notching. Furthermore, computer navigation allows for consistency of component alignment independent of procedural experience.

Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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