Biomedical subjects

Ulrich Langlotz

Publications and source records attributed to Ulrich Langlotz.

3 recordsLinked to original sources

PubMed2004

C-arm based navigation in total hip arthroplasty-background and clinical experience.

After experimental and preclinical evaluation of a CT-free image guided surgical navigation system for acetabular cup placement, the system was introduced into clinical routine. The computation of the angular orientation of the cup is based on reference coordinates from the anterior pelvic plane concept. A hybrid strategy for pelvic landmark acquisition has been introduced, involving percutaneous pointer-based digitization with the noninvasive bi-planar landmark reconstruction using multiple registered fluoroscopy images. From January 2001 to October 2003, a total of 236 consecutive patients (mean age 66 years, 144 male, 92 female, 124 left and 112 right hip joints) were operated on with the hybrid CT-free navigation system. During each operation, the angular orientation of the inserted implant was recorded. To determine the placement accuracy of the acetabular components, the first 50 consecutive patients underwent a CT scan 7-10 days postoperatively to analyze the cup position relative to the anterior pelvic plane. This procedure was done blinded and with commercial planning software. There was no significant learning curve observed for the use of the system. Mean values for postoperative inclination read 42 degrees (SD 3.6, range (37-49)) and anteversion 21 degrees (SD 3.9, range (10-28)). The resulting system accuracy, ie, the difference between intraoperatively calculated cup orientation and postoperatively measured implant position shows a maximum error of 5 degrees for the inclination (mean 1.5 degrees, SD 1.1) and 6 degrees for the anteversion (mean 2.4 degrees, SD 1.3). An accuracy of better than 5 degrees inclination and 6 degrees anteversion was achieved under clinical conditions, which implies that there is no significant difference in performance from the established CT-based navigation methods. Image-guided CT-free cup navigation provides a reliable solution for future total hip arthroplasty (THA).

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PubMed2003

Image-based hip navigation.

After experimental and preclinical evaluation (HAP Paul Award 2001) of a CT-free image-guided surgical navigation system for acetabular cup placement, the system was introduced into clinical routine. The computation of the angular orientation of the cup is based on reference coordinates from the anterior pelvic plane (APP) concept. A hybrid strategy for pelvic landmark acquisition has been introduced involving percutaneous pointer-based digitization with the noninvasive biplanar landmark reconstruction using multiple registered fluoroscopy images. From January 2001 to May 2002, 118 consecutive patients (mean age 68 years, 82 male, 36 female, and 62 left and 56 right hip joints) were operated on with the hybrid CT-free navigation system. During each operation, the angular orientation of the inserted implant was recorded. To determine the placement accuracy of the acetabular components, the first 50 consecutive patients underwent a CT scan 7-10 days postoperatively to analyze the cup position relative to the APP. This was done blinded with commercial planning software. There was no significant learning curve observed for the use of the system. Mean values for postoperative inclination read 43 degrees (SD 3.0, range 37-49) and anteversion 19 degrees (SD 3.9, range 10-28). The resulting system accuracy, i.e., the difference between intraoperatively calculated cup orientation and postoperatively measured implant position, shows a maximum error of 5 degrees for the inclination (mean 1.5 degrees, SD 1.1) and 6 degrees for the anteversion (mean 2.4 degrees, SD 1.3). An accuracy of better than 5 degrees inclination and 6 degrees anteversion was achieved under clinical conditions, which implies that there is no significant difference in performance from the established CT-based navigation methods. Image-guided CT-free cup navigation provides a reliable solution for future total hip arthroplasty (THA).

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PubMed2002

A hybrid CT-free navigation system for total hip arthroplasty.

OBJECTIVE: To design and evaluate a novel CT-free image-guided surgical navigation system for assisting placement of both acetabular and femoral components in total hip arthroplasty (THA). MATERIALS AND METHODS: The methodology in this paper is conceptually based on our previous work on CT-free cup placement. For femoral component placement, two patient-specific reference coordinate systems are first defined: One for the pelvis, based on the so-called anterior pelvic plane (APP) concept, and one for the femur, using the center of the femoral head, the posterior condylar tangential line, and the medullary canal axis of the proximal femur. A hybrid method is used for the associated landmark acquisition, which involves percutaneous point-based digitization and bi-planar landmark reconstruction using multiple registered fluoroscopy images. The following clinical parameters are computed in real time: cup inclination and anteversion, antetorsion and varus/valgus of the stem, lateralization, and change in leg length for complete THA. In addition, instrument actions such as reaming, impaction, and rasping are visualized for the surgeon by superimposing virtual instrument representations onto the fluoroscopic images. RESULTS: A laboratory study of computer-assisted measurement of antetorsion and varus/valgus, change in leg length, and lateralization for femoral stem placement demonstrated the high precision of the proposed navigation system. Compared with CT-based measurement, mean deviations of 1.0 degrees, 0.6 degrees, 0.7 mm, and 1.7 mm were found for antetorsion, varus/valgus, change in leg length, and lateralization, respectively, with standard deviations of 0.5 degrees, 0.5 degrees, 0.6 mm, and 0.7 mm, respectively. A pilot clinical evaluation showed that THA could benefit from this newly developed CT-free hybrid system. CONCLUSIONS: The proposed CT-free hybrid system promises to increase the accuracy and reliability of THA surgery.

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