Showing papers by "Anthony M. DiGioia published in 2005"

Cup alignment error model for total hip arthroplasty.

Abstract: Almost all computer-assisted orthopaedic surgery systems that rely on the anterior pelvic plane definition, such as in computed tomography and magnetic resonance image-based, fluoroscopy-based, and nonimage total hip replacement approaches, are derived from identifying two pairs of pelvic bony landmarks: anterior superior iliac spines and the pubic tubercles. Although these systems strive to achieve cup alignment accuracy of approximately 1 degree, even a minor failure to correctly identify these anatomic landmarks can lead to higher inaccuracies in the final cup alignment. This study shows how to examine the effects of these inaccuracies on the final acetabular cup implant orientation during total hip replacement by generating a kinematic model, which then is simulated. Simulation results indicate that, for example, a total error of 4 mm in measuring the anterior superior iliac spine and the pubic tubercles would result in a final cup orientation of 47 degrees and 27 degrees in abduction and version respectively, resulting in a 2 degrees abduction error and 7 degrees error in version when targeting 45 degrees abduction and 20 degrees version results. These calculations can be repeated for any error values.

MBARS: mini bone-attached robotic system for joint arthroplasty

Abstract: A report on a new active, miniature bone-attached, robotic system including its design, high level and low level control, is given together with a description of the system implementation and first experimental use. The system is capable of preparing the bone cavity for an implant during joint arthroplasty procedures. Without loss of generality, the report describes the implementation of the system for a Patellofemoral Joint Replacement procedure. The system is image-free and all planning is performed intra-operatively in the robot coordinate system, eliminating the need for external tracking systems in the operating room. Experiments were conducted using the first robot prototype and the results supported the feasibility of the concept. The methodology which is presented can be modified to other orthopaedic procedures and could improve the results in terms of accuracy and operational time. Moreover, it enables minimally invasive procedures and use of the next generation of more anatomically shaped implants.

Measurements of acetabular cup position and pelvic spatial orientation after total hip arthroplasty using computed tomography/radiography matching

Abstract: This study presents a clinical validation of postoperative measurements of acetabular cup alignment following total hip arthroplasty (THA) The methodology was based on concurrent anatomic three-dimensional (3D) measurements of both the acetabular cup alignment and pelvic orientation, using an original CT/X-ray matching algorithm named Xalign The subjects were 19 patients who had undergone bilateral THA using CT-based surgical navigation All patients had postoperative pelvic CT scans and multiple antero-posterior (AP) pelvic X-rays Using a proprietary software algorithm, the X-rays included in the study were matched with the corresponding postoperative CT scans The goal of this method was to allow 3D anatomic pelvic and acetabular measurements on two-dimensional AP X-rays The postoperative cup abduction, version and pelvic flexion angles were determined in three different ways: using CT images directly, applying the Xalign method, and finally by performing conventional (abduction only) measurements on AP pelvic X-rays The cup orientation measured on CT images was taken as the ground truth The Xalign measurement errors were defined as the difference between the CT cup values and those obtained by applying the matching method The mean cup abduction error was 085 degrees +/- 13 degrees (+/- standard deviation) and the mean version error was 001 degrees +/- 199 degrees Conventionally measured cup abduction ranged from 44 degrees to 62 degrees and correlated significantly (p = 0001, r = -05) with pelvic flexion angle, proving the linear negative correlation between pelvic flexion and the error in conventional radiographic cup measurements The Xalign method offered reasonable accuracy for cup orientation, and allowed cup and pelvic 3D anatomic measurements at different times