Biomedical subjects

Timothy J Levison

Publications and source records attributed to Timothy J Levison.

6 recordsLinked to original sources

PubMed2006

Accuracy of pelvic flexion measurements from lateral radiographs.

Variations in pelvic orientation affect preoperative planning decisions, intraoperative navigation, and postoperative measurements. By providing the means to measure pelvic flexion at low cost and reporting pelvic flexion using the standard reference system, a lateral radiograph technique based on the pubic tubercles and anterior superior iliac spines may be useful for studying functional pelvic orientation and functional alignment and for improving accuracy of postoperative measurement. We evaluated the accuracy of this method by synthesizing 50 lateral pelvic radiographs. Six observers performed manual landmark-based pelvic flexion measurements on the resultant radiographs. Pelvic flexion measurement errors were small (0.004 masculine +/- 1.38 masculine). Apart from one outlier with an error of 12.4 masculine, the errors ranged from -4.0 masculine to 3.0 masculine. The data suggest that accurate measurements of pelvic flexion can be made from lateral radiographs with respect to the standard anatomic reference system. However, failure to correctly observe a landmark can introduce large errors. Therefore, the clarity of the relevant landmarks should be considered carefully before applying this technique. Lateral radiographs can be easily acquired and analyzed, making this technique convenient and inexpensive.

Body Weights and Measures↗

PubMed2006

Functional pelvic orientation measured from lateral standing and sitting radiographs.

We prospectively obtained preoperative and 3-month postoperative lateral pelvic radiographs in the standing and sitting positions from 84 patients who underwent total hip arthroplasty. We measured pelvic orientation (flexion extension) using the anterior pelvic plane as defined by the anterior superior iliac spines and pubic tubercles as references. There was a trend towards upright pelvic alignment when standing, with a mean anterior pelvic plane angle of 1.2 degrees (range, -22 degrees - +27 degrees). In the sitting position the pelvis tended to extend posteriorly, with a mean anterior pelvic plane angle of -36.2 degrees (range, -64 degrees - +4 degrees). There was a wide variation in the arc of pelvic flexion extension as patients moved from standing to sitting, with are of pelvic motion in some patients as mobile as 70 degrees and in others as stiff as 5 degrees. There was no significant variation between males and females or between preoperative and postoperative pelvic flexion extension. There were substantial variations in pelvic orientation when comparing standing and sitting for an individual patient and between different patients. This variation can be unpredictable, and may influence implant alignment and stability after total hip arthroplasty.

Adult↗

PubMed2005

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

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 0.85 degrees +/- 1.3 degrees (+/- standard deviation) and the mean version error was 0.01 degrees +/- 1.99 degrees . Conventionally measured cup abduction ranged from 44 degrees to 62 degrees and correlated significantly (p = 0.001, r = -0.5) 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.

Acetabulum↗

PubMed2004

Less invasive total hip arthroplasty using navigational tools.

Although traditional total hip arthroplasty offers good visualization of bony landmarks and allows for the accurate orientation and fixation of implants, these benefits are achieved at the expense of extensive soft-tissue dissection and can result in postoperative complications and a delayed return to full function. To address these disadvantages, navigational tools were coupled with a mini-incision technique that allowed accurate bone preparation and orientation of the implant components without direct visualization of the bony landmarks. Additionally, image-guided systems provide three-dimensional information before and during surgery, making it possible to know, in real time, the orientation of implants and to visualize the full bony anatomy. This "computer-enhanced vision" allows surgeons to perform less invasive and eventually minimally invasive total hip arthroplasty with improved accuracy.

Arthroplasty, Replacement, Hip↗

PubMed2003

Mini-incision technique for total hip arthroplasty with navigation.

This prospective study compares a mini-incision technique and traditional posterior approach for total hip arthroplasty (THA). Thirty-three patients who had undergone a mini-incision THA were matched by diagnosis, gender, average age, and preoperative Harris Hip Score (HHS) to 33 patients who had undergone THA using the traditional posterior approach. The average length of the incision for group 1 was 11.7 cm (range, 7.3-13.0) and for group 2 was 20.2 cm (range, 14.8-26.0). At the 3-month follow-up, patients in the mini-incision group had significant improvement in limp (P<.05) and ability to climb stairs (P <.01) compared with the traditional group. At the 6 month follow-up, the mini-incision group was significantly better in terms of limp (P <.05), distance walked (P<.001), and stairs (P < 0.001). There was no significant difference between groups for pain, function, or range of motion at the 1-year follow-up examination.

Aged↗

PubMed2002

Comparison of a mechanical acetabular alignment guide with computer placement of the socket.

We hypothesized that use of mechanical acetabular guides for intraoperative alignment leads to variations between the actual and desired implant orientation. Acetabular implant orientation using only the mechanical guide was studied in 78 patients (82 hips) undergoing primary total hip arthroplasty. A computer-assisted navigation system was used to measure alignment and to monitor the orientation of the pelvis during surgery. When using the mechanical guide, there was significant variation in cup alignment from the desired goal of 45 degrees of abduction and 20 degrees of flexion, and this would have resulted in unacceptable acetabular alignment in 78% of hips. With the support system used, there was significant variability in pelvic orientation during surgery. The mean anteversion of the pelvis was an average of 18 degrees from the optimal orientation. These results show a clear need to develop more reliable tools than were used or anatomically based alignment strategies to provide reproducible and accurate acetabular alignment.

Acetabulum↗