Clinical Impact of Pelvic Malrotation on X-ray based Preoperative Planning for Total Hip Arthroplasty: A Proof-of-concept and Prudent Prediction of Acceptable Rotation

IntroductionPelvic rotation (PR) on preoperative X-ray templating can affect various critical measured acetabular angles and potentially outcomes of successful total hip arthroplasty (THA). Optimising anatomical reconstruction of the joint is essential to achieve function, longevity and prevention of complications following surgery. There is limited literature that standardises the degree of acceptable PR on X-ray or its effects on the fitting of acetabular prostheses. ObjectiveThis study aimed to develop a proof-of-concept that quantifies how PR can affect various acetabular angles used in pre-operative THA templating and to formulate a practicable method of determining if the preoperative PR is acceptable. Materials and MethodsComputerised tomography (CT) models from three control and two THA patients were generated and manipulated in various degrees of PR. CT slices were thickened to simulate X-rays and acetabular angles measured. ResultsThe acetabular anteversion distance (AAD) and lateral opening angle (LOA) demonstrated a linear and quadratic relationship with good correlation (R2=0.923, R2=0.710 respectively, p<0.0001) in relation to PR. Change in area of prosthesis (AOP) demonstrated a good linear correlation (r2=0.774 and r2=0.875, p<0.0001) with PR. Two novel measurements were used to estimate the degree of PR from a pelvic X-ray; the horizontal distance between pubic symphysis and middle of sacrococcygeal joint (PSSC) and the simplified pelvic rotation ratio (SPRR). A strong correlation between PSSC and SPRR with change in PR was observed (R2=0.970, R2=0.953, p<0.001). ConclusionPreliminary results suggests that an SPRR >2.0 correlates to PR>20° with potential to have a clinical impact on preoperative measurements.

Analysis of Measurement Changes in the Pelvic Incidence According to Pelvic Rotation using a 3-dimensional Model

Background: Pelvic incidence (PI) is used as a key parameter in surgical correction of adult spinal deformity (ASD) patients. However, there is a limitation to reflecting the exact center or inclination of 3-dimentional anatomical structures in a 2-dimensional (2D) sagittal radiographs, and these can lead to the measurement errors. Therefore, we evaluated whether there is a change in PI measurement according to the actual rotation of the pelvis, and conducted a study on a more accurate method of measuring PI in a 2D sagittal radiograph.Methods: From 2014 to 2015, 30 patients who visited our outpatient clinic were analyzed retrospectively. CT scan images including the lower lumbar spine, pelvis, and both femurs in DICOM format were imported to Mimics Research 17.0 (Materialise NV, Belgium), Solidworks (Dassault systems, France), and AutoCAD 2014 (AUTODESK, US), and the changes in PI according to vertical and horizontal pelvic rotations were evaluated.Results: The average PI according to the horizontal pelvic rotations measured on AutoCAD with 0º, 5º, 10º, 15º, 20º, 25º, 30º, 35º, and 40º was 48.8º, 48.7º, 48.3º, 47.8º, 46.9º, 45.6º, 44.0º, 42.2º, and 39.9º, respectively. The PI of an acceptable error of 6º on radiographs was 35º in the horizontal pelvic rotation. The average PI according to the vertical pelvic rotations measured on AutoCAD with 0º, 5º, 10º, 15º, 20º, 25º, 30º, 35º, and 40º was 48.8º, 49.0º, 49.5º, 50.2º, 51.3º, 52.7º, 54.4º, 56.6º, and 59.4º, respectively. The PI of an acceptable error of 6º on radiographs was 30º in the vertical pelvic rotation. Conclusions: This study revealed that the PI value could differ from the actual anatomical value due to the horizontal and vertical rotation of the pelvis while acquiring the radiograph. In whole-spine lateral radiographs, errors in PI measurement may occur due to rotation of the pelvis or nonvertical projection of X-rays. In the standing pelvic lateral radiographs, placing the overlapping femoral heads at the center and obtaining the straight sacral endplate as much as possible by referring to CT or magnetic resonance imaging would be a more accurate measurement method to define the PI.

Increased Shoulder Distraction Force and Shoulder Horizontal Abduction in Professional Baseball Pitchers With Discordant Torso Rotation Order

Background: Inefficient energy transfer from the pelvis and trunk has been shown to increase compensation at the level of the shoulder. Kinetic chain sequencing of the core segments is underexamined in professional baseball pitchers, especially as it relates to changes in upper extremity kinetics. Purpose: To evaluate elbow and shoulder kinetics in a cohort of professional pitchers differentiated by instances of discordant pelvic to upper torso sequencing during the pitch. Study Design: Descriptive laboratory study. Methods: 285 professional baseball pitchers were evaluated using 3D motion capture (480 Hz). Pitchers were divided into “chronological” and “discordant” groups based on whether maximum pelvic rotation velocity occurred before (chronological) or after (discordant) maximum upper torso rotation velocity during the pitch motion. Pelvic, upper torso, and shoulder kinematic parameters, shoulder distraction force, shoulder internal rotation torque, and pitch efficiency (PE) were compared between groups. Results: Pitchers with discordant torso sequencing (n = 30; 110 pitches) had greater shoulder horizontal adduction at maximum external rotation (mean difference, 3.6°; 95% CI, −5.2° to −2.0°; t = −4.5; P < .001) and greater maximum shoulder external rotation (mean difference, 3.7°; 95% CI, 5.7° to 1.5°; t = −3.5; P < .001) than chronological pitchers (n = 255; 2974 pitches). PE did not differ between groups ( P = .856), whereas ball velocity was significantly faster in the discordant group (mean difference, 0.6 m/s; 95% CI, −1.1 to −0.3 m/s; t = −3.3; P = .0012). Chronological pitchers had significantly reduced shoulder distraction force (mean difference, −4.7% body weight (BW); 95% CI, −7.9% to −1.5% BW; t = −2.9; P = .004) with no difference in shoulder internal rotation torque ( P = .160). These kinematic and kinetic differences were not observed when accounting for interpitcher variability. Conclusion: Between pitchers, those who had a discordant pelvic to upper torso sequence experienced significantly greater shoulder distraction forces, potentially compensating by increasing maximum shoulder external rotation and horizontal abduction. Achieving maximal pelvic rotation velocity before maximal rotation velocity may be advantageous in preventing compensation at the upper extremity and excessive throwing arm loading. Clinical Relevance: Identifying risk factors for increased upper extremity forces has potential implications in injury prevention. Specifically, mitigating shoulder distraction forces may be beneficial in reducing risk of injury.

The Accuracy And Influencing Factors of An Accelerometer-Based Portable Navigation System For Total Hip Arthroplasty In The Supine Position : A Prospective Multicenter Study Using 3D CT Measurement

This multicenter prospective study aimed to evaluate the accuracy of a newly introduced accelerometer-based portable navigation system for total hip arthroplasty (THA) in the supine position. Three hundred twenty-four THAs using supine position in 9 hospitals were prospectively enrolled in the study. An accelerometer-based portable navigation system was used for cup fixation and the intraoperative navigation data (cup alignment, pelvic tilt, and pelvic rotation) were recorded. Postoperative cup alignment was measured on 3D-CT images. The accuracy (absolute difference in cup alignment between the intraoperative navigation record and postoperative 3D-CT measurements) was 3 ± 3° (mean ± standard deviation) for cup inclination and 3 ± 3° for cup anteversion. The pelvis tilted anteriorly in 148 hips (46%) and posteriorly in 162 hips (50%), and did not tilt in 14 hips (4%). The pelvis rotated toward the operating side in 179 hips (55%), toward the contralateral side in 112 hips (35%), and did not rotate in 33 hips (10%). Multiple regression analysis showed that the patients’ characteristics, pelvic tilt, and pelvic rotation did not affect the accuracy of the navigation system. The accuracy was 3 ± 3° and not affected by patient characteristics, surgical factors, or substantial pelvic movement during cup fixation.

The loss of the ‘pelvic step’ in human evolution

ABSTRACT Human bipedalism entails relatively short strides compared with facultatively bipedal primates. Unique non-sagittal-plane motions associated with bipedalism may account for part of this discrepancy. Pelvic rotation anteriorly translates the hip, contributing to bipedal stride length (i.e. the ‘pelvic step’). Facultative bipedalism in non-human primates entails much larger pelvic rotation than in humans, suggesting that a larger pelvic step may contribute to their relatively longer strides. We collected data on the pelvic step in bipedal chimpanzees and over a wide speed range of human walking. At matched dimensionless speeds, humans have 26.7% shorter dimensionless strides, and a pelvic step 5.4 times smaller than bipedal chimpanzees. Differences in pelvic rotation explain 31.8% of the difference in dimensionless stride length between the two species. We suggest that relative stride lengths and the pelvic step have been significantly reduced throughout the course of hominin evolution.

Effects of the abdominal drawing-in maneuver on hamstring rotational activity and pelvic stability in females

BACKGROUND: The medial hamstring (MH) and lateral hamstring (LH) can be selectively trained through tibial internal and external rotation during prone knee flexion. However, no study has identified how a combined tibial rotation and lumbo-pelvic stability strategy influences MH and LH muscle activities. OBJECTIVE: To investigate the combined effects of tibial rotation and the abdominal drawing-in maneuver (ADIM) on MH and LH muscle activities as well as pelvic rotation during prone knee flexion. METHODS: Fifteen female volunteers performed prone knee flexion with tibial internal and external rotation, with and without the ADIM. Under each condition, MH and LH muscle activities were measured by surface electromyography (EMG), and the pelvic rotation angle by a smartphone inclinometer application. RESULTS: The results showed increased MH (without the ADIM: p< 0.001, effect size (d) = 2.05; with the ADIM: p< 0.001, d= 1.71) and LH (without the ADIM: p< 0.001, d= 1.64; with the ADIM: p= 0.001, d= 1.58) muscle activities under internal and external tibial rotation, respectively. However, addition of the ADIM led to increased MH (internal tibial rotation: p= 0.001, d= 0.67; external tibial rotation: p= 0.019, d= 0.45) and LH (internal tibial rotation: p= 0.003, d= 0.79; external tibial rotation: p< 0.001, d= 1.05) muscle activities combined with reduced pelvic rotation (internal tibial rotation: p< 0.001, d= 3.45; external tibial rotation: p< 0.001, d= 3.01) during prone knee flexion. CONCLUSIONS: These findings suggest that the ADIM could be useful for reducing compensatory pelvic rotation and enhancing selective muscle activation in the MH and LH, according to the direction of tibial rotation, during prone knee flexion.