Rigid fixation of pelvic tracker essential for accurate cup placement in CT-based navigation total hip arthroplasty.

Research is lacking on the effect of intraoperative pelvic tracker displacement relative to the pelvis on cup orientation accuracy in computed tomography (CT)-based navigation (CTN) or multivariable analysis to detect factors associated with CTN accuracy. Here, we asked: (1) how pelvic tracker displacement influences the CTN accuracy of cup orientation in total hip arthroplasty (THA)? and (2) what factors are associated with CTN accuracy on multivariable analysis? Regarding cup orientation in 446 THA procedures using CTN, we evaluated clinical error defined as the difference between postoperative measurement and preoperative planning and measurement error defined as the difference between postoperative and intraoperative measurements. Multivariable regression analyses detected the associated factors. Subjects with an intraoperative tracker displacement of < 2 mm were classified in the verified group. Mean absolute clinical and measurement errors were < 1.5° in the verified group, whereas the measurement error of 2.6° for cup inclination and 1.3° for anteversion was larger in the non-verified versus verified group. Tracker displacement and screw fixation were associated with larger clinical errors, while tracker displacement and surgeon inexperience were associated with larger measurement errors. Clinical and measurement accuracies were high for CTN cup placement with rigid pelvic tracker fixation.

Effect of soft-tissue impingement on range of motion during posterior approach Total Hip Arthroplasty: an in vivo measurement study.

PURPOSE: While implant impingement and bony impingement have been recognized as causes of poor outcomes in total hip arthroplasty (THA), reports of soft-tissue impingement are rare. To clarify the issue, the effect of anterior capsule resection on hip range of motion (ROM) was quantitatively measured in vivo during posterior approach THA using a CT-based hip navigation system. MATERIALS AND METHODS: For 47 patients (51 hips), hip ROM was measured intraoperatively before and after resection of the anterior hip capsule, and the difference was compared. RESULTS: Resection of the anterior hip capsule brought about an average 6° increase of ROM in the direction of flexion with internal rotation and did not markedly change ROM in other directions. CONCLUSIONS: During THA through a posterior approach, soft-tissue impingement by the anterior hip capsule can occur. Clinically, we expect that resection of the anterior hip capsule can reduce the risk of posterior instability without increasing the risk of anterior instability.

The Accuracy of a Mechanical Cup Alignment Guide in Total Hip Arthroplasty (THA) Through Direct Anterior and Posterior Approaches Measured with CT-Based Navigation.

The purpose of this study was to compare the accuracy of a mechanical cup alignment guide using CT-based navigation between a direct anterior approach (DAA) in both supine and lateral positions and a posterior approach (PA) in the lateral position. A trial cup was placed with a mechanical guide that aimed at 47° of radiographic inclination and 14° of anteversion. The average cup inclination and anteversion were measured using CT-based navigation. The average radiographic anteversion in the DAA supine and lateral group was larger, and that in the PA group was smaller than the target angle. In conclusion, there are no differences in the accuracy or precision of cup angles among the DAA supine, DAA lateral position, and PA groups using a mechanical guide.

[Genetic basis for skeletal disease. Orthopaedic intervention for bone dysplasias].

The aims of orthopaedic intervention for bone dysplasias are to maintain joint function, to prevent neurological complications, and then to improve the patient's quality of life. Bone lengthening technique can not only increase the body height, but also correct malalignment of the limb at the same treatment session, which is important to prevent early occurrence of the degenerative osteoarthritis. Intramedullary nailing for osteogenesis imperfecta protects long bones from fractures and prevents malunion when fracture takes place. Spinal instrumentation surgery is effective for prevention of the neurological complications and deterioration of the spinal deformities.