Chronological Changes in Axial Alignment of the Ipsilateral Hip and Knee After Total Hip Arthroplasty.

BACKGROUND: Internal rotation of the hip and lateral patellar tilt increases after total hip arthroplasty (THA). However, it remains unknown whether these parameters change with time after the index THA. METHODS: A total of 91 patients undergoing 2-stage bilateral primary THAs between January 2008 and May 2014 were included to assess the association of chronological changes in internal rotation of the hip or lateral patellar tilt with anthropometric and perioperative parameter and changes in alignment after the index THA. Chronological changes were assessed as changes between postoperative computed tomography on the index surgery and the preoperative computed tomography on the contralateral THA. Internal rotation of the hip was defined as the angle between the posterior intercondylar line and a line passing through the posterior inferior iliac spines. Lateral patellar tilt was defined as the angle between the posterior intercondylar line and a line joining the medial and lateral edges of the patella. RESULTS: Internal rotation of the hip and lateral patellar tilt changed until 2 years after the index surgery by a mean of -2° (range -17.3° to 17.7°) and -2° (range -18.2° to 5.3°), respectively. Adductor tenotomy was associated with increasing internal rotation of the hip with time (adjusted R2 0.076); leg lengthening and larger preoperative femorotibial angle were associated with decreasing lateral patellar tilt with time (adjusted R2 0.159). CONCLUSION: Both internal rotation of the hip at rest and lateral patellar tilt decreased by approximately 2° until 2 years after surgery and there was a large variation in chronological change.

Validation of patient specific surgical guides in total hip arthroplasty.

BACKGROUND: The validation of patient-specific surgical guides (PSGs) by their design and the comparison of planned and actual PSG setting in total hip arthroplasty (THA) have not previously been reported. METHODS: The errors between preoperative planning and computed tomography (CT)-based PSG setting (E1), and between preoperative planning and implantation (E2) were evaluated using CT in 16 fresh cadaveric hips. RESULTS: E2 was significantly smaller with the wide-base-contact resurfacing-THA PSG than with the narrow-base-contact type (P<0.05). E1/E2 of the wide-base-contact neck-cut PSG was 1.6±0.7°/2.4±1.1° for the coronal plane and 1.2±0.8 mm/0.7±0.5mm for the medial neck-cut height. E1/E2 of the wide-base-contact cup-impaction PSG was 1.0±0.9°/3.4±1.9° for inclination and 1.7±1.1°/6.6±4.4° for anteversion. CONCLUSIONS: The wide-base-contact PSG in resurfacing-THA and the PSG for neck-cut in THA could be applied clinically. Although cup-impaction PSG setting was acceptable, errors were made due to the impaction process during cup implantation.

Accuracy of angle and position of the cup using computed tomography-based navigation systems in total hip arthroplasty.

OBJECTIVE: The objectives of this study were to evaluate the accuracy of computed tomography (CT)-based navigation and to investigate whether the level of surgeon experience affects the accuracy of cup positioning under navigation. METHODS: This study investigated 117 hips in 103 patients who underwent primary total hip arthroplasty (THA) by 7 surgeons using a CT-based navigation system. Pre- and postoperative CT images were matched using a volume registration technique. Postoperative cup angles and positions were then measured using the same pelvic coordinates, and results were compared for experienced and inexperienced surgeons. RESULTS: The mean absolute error of the cup angle was 1.8 ± 1.6° for inclination and 1.2 ± 1.1° for anteversion. The mean absolute errors of cup position were 1.9 ± 1.5 mm, 1.4 ± 1.2 mm, and 1.9 ± 1.3 mm on the x-, y- and z-axes, respectively. No significant differences in accuracy were identified between experienced and inexperienced surgeons. CONCLUSIONS: The absolute spatial error of cup position was ≤ 2 mm for each axis, and the angle error was ≤ 2° for the angles of inclination and anteversion. This navigation system could therefore help surgeons perform accurate cup placement irrespective of the surgeon's level of experience.

Validation of the femoral component placement during hip resurfacing: a comparison between the conventional jig, patient-specific template, and CT-based navigation.

BACKGROUND: Appropriate insertion of a femoral guidewire is essential for hip resurfacing. A simulation study was planned using synthetic femoral bone models and the accuracy and precision of femoral guidewire alignment and insertion point were compared between conventional jigs, patient-specific templates, and computed tomography (CT) based navigation techniques. METHODS: Anteversion, stem-shaft angle, and the three-dimensional insertion point were measured postoperative with CT. Errors between planned and postoperative measurement and precision were evaluated. RESULTS: There were no statistically significant differences in error for anteversion or insertion point, although the mechanical jig showed greater error in the stem-shaft angle than the others. Patient-specific template and CT-based navigation showed good precision with high intraclass correlation (ICC) (template, 0.908 to 1.000; navigation, 0.929 to 0.995) and small root mean square error (RMSE) (0.954 to 2.969; 1.468 to 3.213). The mechanical jig group performance was inferior to the others. CONCLUSIONS: Patient-specific templates and CT-based navigation had good accuracy and precision. The mechanical jig technique was inferior to the others.

Application of computed tomography-based navigation for revision total hip arthroplasty.

The usefulness of navigation systems for revision total hip arthroplasty (THA) remains unclear. The purpose of this study was to evaluate the accuracy of cup positioning using a navigation system in revision THA. Cup alignment of thirty revision cases was evaluated. Data were also compared with those of 30 navigated primary THA cases. In the revision THA group, mean difference in postoperative measurement from preoperative plan was 0.5 ± 4° (range, -9° to 8°) for inclination and -0.07° ± 5° (-14° to 13°) for anteversion. Mean difference in postoperative measurement from intraoperative record was 0.7° ± 3° (-5° to 8°) for inclination and -0.7° ± 3° (-12° to 5°) for anteversion. Compared with the primary THA group, none of these parameters were significantly different. This navigation system was useful even in revision THA.

Evaluation of the accuracy of computed tomography-based navigation for femoral stem orientation and leg length discrepancy.

Although there is a great deal in the literature about the clinical accuracy of computed tomography (CT)-based navigation systems for acetabular cup orientation and leg length discrepancy in total hip arthroplasty, there is little analysis of femoral stem orientation. Thirty total hip arthroplasties in which CT-based navigation system had been used had their anteversion, valgus angle of stem, and leg length discrepancy measured on postoperative CT data. Differences in postoperative measurements from intraoperative records were -0.6° ± 4.8° (range, -11° to 10°) for stem anteversion, -0.2° ± 1.8° (range, -4° to 3°) for valgus angle of stem, and 1.3 ± 4.1 mm (range, -6 to 10 mm) for leg length. Although this system may need further improvement for stem orientation, it was helpful for intraoperative leg length adjustment.