Jianlin Xiao

Acetate templating on calibrated standing digital radiograph improves accuracy of preoperative templating for total hip arthroplasty

BACKGROUND The accuracy of preoperative templating with respect to leg length, femoral offset, and the size of femoral and acetabular components is essential to the success of total hip arthroplasty (THA). Traditionally, templating has been performed using printed film with acetate templates. However, preoperative templating designed by different prosthetic manufacturers cannot be used directly on the film due to varying acetate template amplification ratios. Computer-based templating needs specialized digital templating software, which has cost implications. To address these shortcomings, we bring forward several questions: (1) the accuracy of traditional manual templating combined with the calibrated digital radiograph for preoperative templating, (2) the inter- and intraobserver reliability of this method. HYPOTHESIS Using calibrated digital radiograph with traditional manual templating improves the accuracy and reproducibility of preoperative templating for THA. PATIENTS AND METHODS We designed a stepwise method that combines the traditional manual templating with standing digital radiograph calibrated by a scaling ball. Two separate observers (XJL, QYG) analyzed data of 82 patients (109 THAs) who had undergone THA with preoperative templating using the calibrated digital templating. The intra- and interobserver reliability was assessed by intraclass correlation coefficient. RESULTS The size of the acetate template acetabular based on our method was identical to the actual implanted acetabular size in 55.0% (XJL 110/218 [50.5%]; QYG 130/218 [59.6%]) of the cases indicating moderate accuracy. The intraclass correlation coefficient (ICC) for acetabular templating indicated almost perfect interobserver (ICC=0.918 [95% CI, 0.893-0.937]) and intraobserver agreement (ICC=0.932 [95% CI, 0.912-0.947]). While the exact implanted femoral size was predicted in 55.3% (XJL 122/218 [56.0%]; QYG 119/218 [54.6%]) of the cases. The ICC for femoral component templating indicated almost perfect interobserver (ICC=0.944 [95% CI, 0.927-0.957]) and intraobserver agreement (ICC=0.909 [95% CI, 0.883-0.930]). DISCUSSION This new stepwise method may prove to be a more reliable preoperative design choice to accurately calibrate magnification with radiograph, and could solve the incompatibility of the preoperative template designed by different prosthetic companies for direct use with the x-ray film. The method described is practical, convenient, cost-effective and does not require specialized equipment or software, thus making it particularly suitable for use in underdeveloped settings. LEVEL OF EVIDENCE Level IV, case series without controls.

Cross-sectional Anatomy of Ilium for Guiding Acetabular Component Placement Using High Hip Center Technique in Asian Population.

Background:Many clinical studies have been published involving the use of a high hip center (HHC), achieved good follow-up. However, there is a little anatomic guidance in the literature regarding the amount of bone stock available for initial implant coverage in this area of the ilium. The purpose of this study was to evaluate the thickness and width of the human ilium and related acetabular cup coverage for guiding acetabular component placement in HHC. Methods:A total of 120 normal hips in 60 cases of adult patients from lower extremities computer tomographic angiography Digital Imaging and Communications in Medicine data were chosen for the study. After importing the data to the mimics software, we chose the cross sections every 5-mm increments from the rotational center of the hip to the cephalic of the ilium according the body sagittal axis, then we measured the thickness and width of the ilium for each cross section in axial plane, calculated the cup coverage at each chosen section. Results:At the acetabular dome, the mean thickness and width of the ilium were 49.71 ± 4.88 mm and 38.92 ± 3.67 mm, respectively, whereas at 1 cm above the dome, decreased to 41.35 ± 5.13 and 31.13 ± 3.37 respectively, and 2 cm above the dome, decreased to 31.25 ± 4.04 and 26.65 ± 3.43, respectively. Acetabular cup averaged coverage for 40-, 50-, and 60-mm hemispheric shells, was 100%, 89%, and 44% at the acetabular dome, 100%, 43.7%, and 27.5% for 1 cm above the dome, and 37.5%, 21.9%, and 14.2% for 2 cm above the dome. Conclusions:HHC reconstructions within 1 cm above the acetabular dome will be an acceptable and smaller diameter prosthesis would be better.

Three-dimensional reconstruction method for measuring the knee valgus angle of the femur in northern Chinese adults.

The purpose of this study was to establish a method for measuring the knee valgus angle from the anatomical and mechanical axes on three-dimensional reconstruction imaging models, and to use this method for estimating an average knee valgus angle value for northern Chinese adults. Computed tomographic angiography data in DICOM format for 128 normal femurs from 64 adult subjects were chosen for analysis. After the femur images were subjected to three-dimensional reconstruction, the deepest point in the intercondylar notch (point A), the midpoint of the medullary cavity 20 cm above the knee-joint line (point B), and the landmark of the femoral head rotation center (point C) were identified on each three-dimensional model. The knee valgus angle was defined as the angle enclosed by the distal femoral anatomical axis (line AB) and the femoral mechanical axis (line AC). The average (mean±SD) of knee valgus angle for the 128 femurs was 6.20°±1.20° (range, 3.05° to 10.64°). Significant positive correlations were found between the knee valgus angles of the right and left sides and between the knee valgus angle and age. During total knee arthroplasty, choosing a valgus cut angle of approximately 6° may achieve a good result in reestablishing the natural mechanical alignment of the lower extremity for patients of northern Chinese ethnicity. Larger valgus cut angles should be chosen for older patients.概要研究目的利用三维重建影像模型获取膝外翻角, 并通过使用这种方法来测量中国北方成人膝外翻角的平均估计值。创新要点本研究所获取的膝外翻角平均值对于在中国北方人群进行膝关节置换术时有着重要的参考意义, 新的三维重建测量法使得膝外翻角的术前个体化测量更加精确。研究方法利用64 名患者的CT 血管造影(CTA)的DICOM数据获取共128 件股骨三维重建模型。 在重建的股骨模型上分别定位髁间凹最高点(点A)、 膝关节线上20 cm 截面的髓腔中点(点B)和股骨头旋转中心(点C)。 之后膝关节外翻角即由股骨远端解剖轴(线AB)与股骨机械轴(线AC)所围成(上述定位过程详见图5)。 经统计分析后, 128 件股骨的平均外翻角值为6.20°±1.20°。 统计分析还发现, 膝外翻角与个体年龄呈显著性正相关, 同一个体的左右侧外翻角呈显著性正相关。重要结论在对北方成年人群进行膝关节置换术时, 选取外翻角为6°可会在重建人体下肢力线上获得更好的术后效果。 在对年长患者进行手术时应选用更大的外翻角。

Preoperative T1 Slope as a Predictor of Change in Cervical Alignment and Range of Motion After Cervical Disc Arthroplasty

Background This study analyzed the effect of preoperative T1 slope on cervical alignment and range of motion (ROM) after cervical disc arthroplasty (CDA) in patients with cervical degenerative disease. Material/Methods This retrospective study included 32 patients with single-level symptomatic cervical disc disease who underwent CDA with the Mobi-C cervical disc prosthesis and had a mean follow-up of 26.8±6.4 months. Standing lateral, flexion, and extension X-rays of the cervical spine were obtained preoperatively and postoperatively at 24-month follow-up. Simple linear regression analysis was used to assess the impact of preoperative T1 slope on changes from preoperative values in radiologic parameters. Results Compared to preoperative values, at 24-month follow-up, there was a significant increase in mean functional spinal unit (FSU) angle (+7.4°), upper adjacent segment (UAS) angle (+3.1°), and overall cervical alignment (C2–C7 angle) (+6.3°), and a significant decrease in mean lower adjacent segment (LAS) angle (−2.4°). Mean ROM of the FSU (−3.6°), LAS (−3.0°), and overall cervical spine (−11.5°) significantly decreased, and mean ROM of the UAS (+1.6°) significantly increased. There were significant correlations between preoperative T1 slope and mean change from preoperative value in FSU angle, C2–C7 angle, and ROM of the overall cervical spine (C2–C7). Conclusions T1 slope is useful for evaluating changes in the FSU angle, C2–C7 angle, and ROM of the overall cervical spine following CDA with the Mobi-C disc. Patients with a large preoperative T1 slope may be good candidates for CDA with the Mobi-C prosthesis due its motion maintenance and the fact that it has little adverse impact on sagittal alignment. It also could be a good option in terms of sagittal alignment improvement or motion maintenance for patients with kyphosis.

Correcting pelvic obliquity in the lateral position to improve acetabular component orientation during total hip arthroplasty

BACKGROUND The acetabular component orientation during total hip arthroplasty (THA) impacts future hip function and early revision. Correcting pelvic obliquity may improve outcomes. OBJECTIVE To correct pelvic obliquity in the lateral position by applying a gradienter and plumb during THA using fluoroscopy. METHODS Fifty patients undergoing THA were randomized and divided into 2 groups. In controls, acetabular components were placed using traditional methods. In experimental patients, acetabular components were placed after correcting pelvic obliquity. We measured pelvic obliquity and recorded intra-operative and post-operative abduction angles, comparing abduction angle bias between post-operative measurements and intra-operation estimations. RESULTS Before correction, the average pelvic obliquity was -1.647∘± 4.512∘ in experimental patients. The average abduction angle in experimental patients was 42.685∘± 3.355∘ postoperatively, differing by 1.962∘± 1.515∘ from intra-operative estimates, while in control patients, it was 44.534∘± 4.844∘ postoperatively, differing by 4.244∘± 3.042∘ from intra-operative estimates. The bias of the abduction angle was much greater in control than in experimental patients (P< 0.05). CONCLUSION The pelvic obliquity in the lateral position affects surgeon judgment during THA. By correcting pelvic obliquity with a gradienter and plumb, the abduction angle bias can be reduced.

Accuracy of the lesser trochanter for guiding lag screw insertion in hip fracture management.

The goal of this study was to evaluate the accuracy of the lesser trochanter for entry of lag screw placement in the fixation of hip fractures. Radiographs of the pelvis with both hips in 50 Chinese patients were analyzed to determine the accuracy of using the lesser trochanter as a reference landmark for inserting lag screws. The femoral neck was divided into 4 parts, and the second distal part was classified as the safe zone. Cobb angles of 125° and 130° were used as representative lag screw insertion angles, referencing the lateral cortex of the lesser trochanter for measurement, and insertion tracks were drawn on the neck of the femur. The accuracy of lag screw placement in the defined safe zone was evaluated. Accuracy of placement in the safe zone for entry points at the superior tip, apex, and inferior tip of the lesser trochanter were 78%, 39%, and 0%, respectively, for the 125° Cobb angle. Rates for the superior tip, apex, and inferior tip of the lesser trochanter were 31%, 74%, and 6%, respectively, for the 130° Cobb angle. The entry point at the level of the inferior tip of the lesser trochanter had incidence rates of 95% and 71% for cutout for 125° and 130° screws, respectively. The authors found that the superior tip of the lesser trochanter was a good reference point for 125° lag screw insertion and that the apex of the lesser trochanter was a good reference point for 130° lag screw insertion. Entry at the level of the inferior tip of the lesser trochanter has a very high rate of cutout and should be avoided.