A simple method for restoring the femoral head center in hip arthroplasty: a 3-dimensional analysis in the Chinese population.

BACKGROUND: Various authors have successfully demonstrated that the distance from the greater trochanter to the femoral head center (GTFHC) and the distance from the lesser trochanter to the femoral head center (LTFHC) can be used as parameters to determine the recovery of the femoral head center (FHC) during hip arthroplasty. It is necessary to undertake an anatomical study concerning the correlations between the greater trochanter (GT), the lesser trochanter (LT), and the FHC using data obtained from the 3D-CT reconstruction method. METHODS: The study comprised 293 patients (151 males and 142 females), with an average age of 65.06 years. The femoral head diameter(FHD), the linear distance from FHC to GT (GTFHC), and the linear distance from FHC to LT(LTFHC) were all measured and recorded data. The correlation between FHD with LTFHC and GTFHC was assessed using Pearson correlation coefficients, and the ratio of LTFHC and GTFHC to FHD was calculated from this ratio. All measured parameters were compared between the left and right sides and the sexes of the participants. RESULTS: The average ratios of GTFHC/FHD and LTFHC/FHD were 0.99 and 0.95, respectively .96% of the LTFHC had absolute lateral differences of < 4 mm . 92% of the GTFHC had absolute lateral differences of < 4 mm. CONCLUSION: LTFHC and GTFHC are reliable reference parameters for preoperative planning and reconstruction of FHC of hip arthroplasty. The ratio displayed in this research may yield insight into a practical and straightforward method for orthopedic surgeons to perform hip arthroplasty in patients with femoral neck fractures. Ratios from studies based on the same race may be desirable for future work.

Measurement of the relative position of the femoral head center, greater trochanter, and lesser trochanter.

BACKGROUND: Understanding the relationship between the greater trochanter, the lesser trochanter, and the femoral head center is helpful to achieve satisfactory lower limb length in hip arthroplasty, and it may be more important when the contralateral side of the surgical hip cannot be referenced. This work aims to measure the relative position of the femoral head center, the greater trochanter, and the lesser trochanter, and analyze the relationship between these anatomical landmarks. METHODS: The femoral head diameter (D), the linear distance (G) from the femoral head center (C) to the greater trochanter, and the linear distance (L) from the femoral head center to the lesser trochanter were measured by pelvic X-ray. The basic information of the data was analyzed, the ratios of G to D and L to D were calculated, the functional relationship between the data was analyzed after the factors of gender and age were included, and the 95% reference intervals of the basic data and ratio data were calculated. RESULTS: A total of 97 patients with 194 hips were enrolled in this study. The diameter D was 5.08±0.43 cm, the distance G was 4.68±0.45 cm, and the distance L was 4.28±0.49 cm. The G/D ratio was 0.92±0.07, and the 95% reference range was 0.78-1.06. The L/D ratio was 0.84±0.08, and the 95% reference range was 0.68-1.00. Gender (g) was included in the regression analysis, and the regression equations G =1.890+0.536*D and L =1.129+0.620*D were obtained. Age was not related to the distances G and L. CONCLUSIONS: The basic data of G, D, and L was measured, and the relationship between these anatomical landmarks was analyzed.

Estimating soft tissue artifact of the thigh in high knee flexion tasks using optical motion Capture: Implications for marker cluster placement.

Soft tissue artifact in motion capture is widely accepted as a significant source of error in kinematic and kinetic measurements. Non-invasive methods of estimating soft tissue artifact, those requiring only motion capture, provide a feasible method to evaluate marker placement on a segment and enable recommendations for marker configurations which can minimize soft tissue artifact. The purpose of this study was to investigate the effect of thigh marker cluster location on soft tissue artifact during high knee flexion (>120 deg) as unique deformation of soft tissue occurs in this range (e.g. thigh-calf contact). Motion of the pelvis and lower limbs were recorded during squatting and kneeling in fifty participants. Six rigid marker clusters were affixed to the skin on the anterior, lateral, and anterolateral aspect, at the distal and middle third of the thighs. To estimate soft tissue artifact, the functional hip joint center was reconstructed relative to the pelvis cluster and each of the six thigh clusters throughout motion. The difference in the position of these two points was input into Bland-Altman analyses and compared between the thigh clusters. Across the tasks, the total mean difference ranged from 2.81 to 8.95 cm while the lower and upper limits of agreement ranged from -0.79 to 2.54 cm and 5.04 to 17.65 cm, respectively. Using this non-invasive method, the mid-anterolateral cluster was least susceptible to soft tissue artifact and thus would be recommended, while the lateral clusters were most susceptible and should avoided in high knee flexion and similar tasks.

MRI-based 3D models of the hip joint enables radiation-free computer-assisted planning of periacetabular osteotomy for treatment of hip dysplasia using deep learning for automatic segmentation.

INTRODUCTION: Both Hip Dysplasia(DDH) and Femoro-acetabular-Impingement(FAI) are complex three-dimensional hip pathologies causing hip pain and osteoarthritis in young patients. 3D-MRI-based models were used for radiation-free computer-assisted surgical planning. Automatic segmentation of MRI-based 3D-models are preferred because manual segmentation is time-consuming.To investigate(1) the difference and(2) the correlation for femoral head coverage(FHC) between automatic MR-based and manual CT-based 3D-models and (3) feasibility of preoperative planning in symptomatic patients with hip diseases. METHODS: We performed an IRB-approved comparative, retrospective study of 31 hips(26 symptomatic patients with hip dysplasia or FAI). 3D MRI sequences and CT scans of the hip were acquired. Preoperative MRI included axial-oblique T1 VIBE sequence(0.8 mm3 isovoxel) of the hip joint. Manual segmentation of MRI and CT scans were performed. Automatic segmentation of MRI-based 3D-models was performed using deep learning. RESULTS: (1)The difference between automatic and manual segmentation of MRI-based 3D hip joint models was below 1 mm(proximal femur 0.2 ±â€¯0.1 mm and acetabulum 0.3 ±â€¯0.5 mm). Dice coefficients of the proximal femur and the acetabulum were 98 % and 97 %, respectively. (2)The correlation for total FHC was excellent and significant(r = 0.975, p < 0.001) between automatic MRI-based and manual CT-based 3D-models. Correlation for total FHC (r = 0.979, p < 0.001) between automatic and manual MR-based 3D models was excellent.(3)Preoperative planning and simulation of periacetabular osteotomy was feasible in all patients(100 %) with hip dysplasia or acetabular retroversion. CONCLUSIONS: Automatic segmentation of MRI-based 3D-models using deep learning is as accurate as CT-based 3D-models for patients with hip diseases of childbearing age. This allows radiation-free and patient-specific preoperative simulation and surgical planning of periacetabular osteotomy for patients with DDH.

Identification of femoral head center of bipolar hemiarthroplasy in radiostereometric analysis with elementary geometrical shape models.

Elementary geometrical shape (EGS) models are useful in radiostereometric analysis (RSA) on hip stems because tantalum markers attached to the stems can be omitted. In order to create an EGS model of a femoral stem, the center of the femoral head has to be identified. The contour of the femoral head is recommended to be used. However, the contour of the femoral head cannot be detected exclusively by computer if it is combined with a bipolar head or a metal cup. We therefore hypothesized that the contour of the outer head of bipolar hemiarthroplasty can be included in the EGS model as well as the femoral head contour. We calculated the time required for the detection of the contour, the precision of analysis and the stem micromotion at 2 years using the two different methods in the same picture set and compared the results. The detection of the bipolar head contour was 10 times faster than that of the femoral head contour. The precision for subsidence was 0.16 mm in EGS RSA with the femoral head contour, and 0.15 mm with the bipolar head contour (p=0.68). The precisions were comparable and clinically acceptable. There was no significant difference between the results of the 2-year micromotion with the two different methods. We conclude that this new method is applicable to measure stem micromotion of hemi-arthroplasty with EGS RSA and the method facilitates the Radiostereometric analysis.

Easy identification of mechanical axis during total knee arthroplasty.

PURPOSE: We devised an intraoperatively identifiable mechanical axis (IIMA) as a reference of alignment in total knee arthroplasty (TKA). MATERIALS AND METHODS: Between February 2010 and January 2011, primary TKAs were consecutively performed on 672 patients (1007 knees) using an IIMA as a reference in the coronal plane. RESULTS: The alignment of the lower extremity improved from a mean of 11.4±6.7° (-10.3-34.4°) of varus preop. to 0.7±3.5° (-5.2-8.6°) immediately after surgery. Mean alignment of the femoral component in the coronal plane was 89.3±2.3° (83.4-97.2°) postop. and mean alignment of the tibial component was 90.4±2.2° (85.1-94.2°) postop. CONCLUSION: This study showed that IIMA could be of considerable value as a new guider of alignment that is easily accessible and highly effective during total knee arthroplasty.

Easy Identification of Mechanical Axis during Total Knee Arthroplasty

PURPOSE: We devised an intraoperatively identifiable mechanical axis (IIMA) as a reference of alignment in total knee arthroplasty (TKA). MATERIALS AND METHODS: Between February 2010 and January 2011, primary TKAs were consecutively performed on 672 patients (1007 knees) using an IIMA as a reference in the coronal plane. RESULTS: The alignment of the lower extremity improved from a mean of 11.4+/-6.7degrees (-10.3-34.4degrees) of varus preop. to 0.7+/-3.5degrees (-5.2-8.6degrees) immediately after surgery. Mean alignment of the femoral component in the coronal plane was 89.3+/-2.3degrees (83.4-97.2degrees) postop. and mean alignment of the tibial component was 90.4+/-2.2degrees (85.1-94.2degrees) postop. CONCLUSION: This study showed that IIMA could be of considerable value as a new guider of alignment that is easily accessible and highly effective during total knee arthroplasty.