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.

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.

Histological characteristics of the human femoral head in patients with femoral neck fracture.

The reparative reaction including angiogenesis and osteogenesis in human bone after an ischemic event remains unknown. To investigate the reparative reaction in human bone, the distribution of tartrate resistant acid phosphatase (TRAP)-positive cells and the expressions of hypoxia inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), fibroblast growth factor-2 (FGF-2), and CD31 were observed around the fracture site in 101 hips in 100 patients with femoral neck fracture. These 17 men and 83 women had a mean age of 80 years (range, 58-97 years). Of the hips, 17 were Garden stage 3, and 84 were Garden stage 4. The mean duration from fracture to surgery was 6.3 days (range, 1-14 days). Hematoxylin-eosin staining, TRAP staining, and immunohistochemistry using anti-HIF-1α, anti-VEGF anti-FGF-2, and anti-CD31 antibodies were performed for the coronal section of the retrieved whole femoral heads. TRAP-positive cells were detected near the trabecular bone around the fracture site in ten hips (10 %). HIF-1α expression was detected in 41 hips (41 %), mainly in the endothelial cells of the vessels. VEGF showed diffuse cytoplasmic staining of the mononuclear cells in the edematous area in 39 hips (39 %) while FGF-2 was detected in the cytoplasm of mononuclear cells in the bone marrow in 82 hips (82 %). CD31 was expressed in the bone marrow vessels in 35 hips (35 %). There were significant differences in HIF-1α expression relative to the duration between the fracture and the surgery, and in CD31 expression relative to Garden stage. HIF-1α expression was detected around the fracture site in the early period after fracture and CD31 expression was detected more frequently in Garden 3 hips while VEGF and FGF-2 expressions were detected regardless of Garden classification.

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.

Comparison of navigation accuracy in THA between the mini-anterior and -posterior approaches.

BACKGROUND: The accuracy of a CT-based hip navigation might depend on surgical approaches, resulting in varying accuracy of implant alignment. METHODS: We performed primary cementless total hip arthroplasty (THA) with mini-incision surgery (MIS) to 40 well-matched patients (anterior or posterior approaches, 20 hips each), using navigation with surface registration. We investigated cup alignment using postoperative computed tomography (CT) and compared the navigation accuracy between the two approaches, i.e. the difference between intra-operative and postoperative alignments of the cup. RESULTS: There was no significant difference between the two approaches. The mean navigation accuracies in abduction and anteversion were 2.0 degrees (SD 1.4 degrees) and 2.7 degrees (SD 1.9 degrees), respectively, in the anterior approach, and 2.4 degrees (SD 2.0 degrees) and 2.0 degrees (SD 1.4 degrees), respectively, in the posterior approach. All cup alignments were within 10 degrees of the target orientation. CONCLUSIONS: This CT-based navigation for MIS-THA provides navigation accuracy without significant differences between the two approaches and with favourable alignment of the cup.

Proximal bone remodelling differed between two types of titanium long femoral components after cementless revision arthroplasty.

In revision surgery with proximal femoral bone loss, progressive bone atrophy due to stress shielding remains a concern. We compared 2-year radiological results between two types of cementless long titanium stems with different configurations and surface coatings. Of 17 hips implanted with a wholly hydroxyapatite-coated stem, 12 (71%) exhibited stress shielding of the second degree or higher according to Engh's criteria, and the mean relative bone mass index decreased from 22.1% pre-operatively to 14.6% at 2 years post-operatively. In 23 hips implanted with a sand-blasted, conically shaped stem, no hip showed stress shielding of the second degree or higher. The mean relative bone mass index increased from 21.6% to 31.4%. These results indicate that the configuration and surface coating of the stem have a significant influence on proximal bone remodelling after revision surgery.