title: Experimental validation of a pinless femoral reference array for computer-assisted hip arthroplasty.
abstract: The use of computer navigation systems during total hip arthroplasty requires the femoral fixation of a reflective dynamic reference base (DRB), which theoretically involves the risk of bony fracture, infection, and pin loosening. The first objective of this study was to evaluate the relative movements between a novel, noninvasive external femoral DRB system and the femur. Secondly, the maximum effects of these 3D movements on intraoperative, computer-assisted leg length and offset measures were evaluated. An imageless navigation system was used to track the positions of the soft tissue attached, pinless DRB relative to an invasive reference marker on the femur during a less-invasive, anterior surgical hip approach. Relative translatory movements up to 8.2 mm mediolaterally and up to 8.8 degrees in rotation were measured. Using a measurement technique in which the calculation of leg length and offset changes is primarily based on a specific realignment of the leg, maximum differences of 1.3 mm for leg length and 1.2 mm for offset were found when comparing the pin-based and pinless methods. Thus, invasive fixation techniques with screws or pins are still the method of choice when standard measurement algorithms for intraoperative leg length and offset measures are used. Though direct translatory and rotational variations between the pinless array and the femoral bone were detected, the pinless array can be used to assess leg length and offset when used with a specific measurement technique that compensates for such variations.
authors: Department of Orthopaedic Surgery, Regensburg University Medical Center, Asklepios Klinikum Bad Abbach, Kaiser-Karl V.-Allee 3, 93077 Bad Abbach, Germany. tobias.renkawitz@web.de
authors: Tobias
authors: T
authors: Renkawitz
authors: Melanie
authors: M
authors: Wegner
authors: Sabine
authors: S
authors: Gneiting
authors: Martin
authors: M
authors: Haimerl
authors: Ernst
authors: E
authors: Sendtner
authors: Thomas
authors: T
authors: Kalteis
authors: Joachim
authors: J
authors: Grifka
mesh_terms: D000465:Algorithms; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation / Q000592:standards*; D002102:Cadaver; D005260:Female; D005269:Femur; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000592:standards*; D007866:Leg; D008297:Male; D012015:Reference Standards; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000592:standards*