Aims. The aim of this study was to assess the ability of morphological spinal parameters to predict the outcome of bracing in patients with adolescent idiopathic scoliosis (AIS) and to establish a novel supine correction index (SCI) for guiding bracing treatment. Methods. Patients with AIS to be treated by bracing were prospectively recruited between December 2016 and 2018, and were followed until brace removal. In all, 207 patients with a mean age at recruitment of 12.8 years (SD 1.2) were enrolled. Cobb angles, supine flexibility, and the rate of in-brace correction were measured and used to predict curve progression at the end of follow-up. The SCI was defined as the ratio between correction rate and flexibility. Receiver operating characteristic (ROC) curve analysis was carried out to assess the optimal thresholds for flexibility, correction rate, and SCI in predicting a higher risk of progression, defined by a change in Cobb angle of ≥ 5° or the need for surgery. Results. The baseline Cobb angles were similar (p = 0.374) in patients whose curves progressed (32.7° (SD 10.7)) and in those whose curves remained stable (31.4° (SD 6.1)). High supine flexibility (odds ratio (OR) 0.947 (95% CI 0.910 to 0.984); p = 0.006) and correction rate (OR 0.926 (95% CI 0.890 to 0.964); p < 0.001) predicted a lower incidence of progression after adjusting for Cobb angle, Risser sign, curve type, menarche status, distal radius and ulna grading, and brace compliance. ROC curve analysis identified a cut-off of 18.1% for flexibility (sensitivity 0.682, specificity 0.704) and a cut-off of 28.8% for correction rate (sensitivity 0.773, specificity 0.691) in predicting a lower risk of curve progression. A SCI of greater than 1.21 predicted a lower risk of progression (OR 0.4 (95% CI 0.251 to 0.955); sensitivity 0.583, specificity 0.591; p = 0.036). Conclusion. A higher supine flexibility (18.1%) and correction rate (28.8%), and a SCI of greater than 1.21 predicted a lower risk of progression. These novel parameters can be used as a guide to optimize the outcome of bracing. Cite this article: Bone Joint J 2022;104-B(4):495–503

Acetabular retroversion is a recognised cause of hip impingement. Pelvic tilt influences acetabular orientation and is known to change in different functional positions. While previously reported in patients with developmental dysplasia of the hip, positional changes in pelvic tilt have not been studied in patients with acetabular retroversion. We retrospectively analysed supine and standing AP pelvic radiographs in 22 patients with preoperative radiographs and 47 with post-operative radiographs treated for symptomatic acetabular retroversion. Measurements were made for acetabular index (AI), lateral centre-edge angle (LCEA), crossover index, ischial spine sign, and posterior wall sign. The change in pelvic tilt angle was measured both by the Sacro-Femoral-Pubic (SFP) angle and the Pubic Symphysis to Sacro-iliac (PS-SI) Index. In the supine position, the mean calculated pelvic tilt angle (by SFP) was 1.05° which changed on standing to a pelvic tilt of 8.64°. A significant increase in posterior pelvic tilt angle from supine to standing of 7.59° (SFP angle) and 5.89° (PS –SI index) was calculated (p<0.001;paired t-test). There was a good correlation in pelvic tilt change between measurements using SFP angle and PS-SI index (rho .901 in pre-op group, rho .815 in post-op group). Signs of retroversion were significantly reduced in standing x-rays compared to supine: Crossover index (0.16 vs 0.38; p<0.001) crossover sign (19/28 vs 28/28 hips; p<0.001), ischial spine sign (10/28 hips vs 26/28 hips; p<0.001) and posterior wall sign (12/28 vs 24/28 hips; p<0.001). Posterior pelvic tilt increased from supine to standing in patients with symptomatic acetabular retroversion, in keeping with previous studies of pelvic tilt change in patients with hip dysplasia. The features of acetabular retroversion were much less evident on standing radiographs. The low pelvic tilt angle in the supine position is implicated in the appearance of acetabular retroversion in the supine position. Patients presenting with symptoms of hip impingement should be assessed by supine and standing pelvic radiographs so as not to miss signs of retroversion and to assist with optimising acetabular correction at the time of surgery

Acetabular component positioning is commonly referenced with the pelvis in the supine position in direct anterior approach THA. Changes in pelvic tilt (PT) from the pre-operative supine to the post-operative standing positions have not been well investigated and may have relevance to optimal acetabular component targeting for reduced risk of impingement and instability. The aims of this study were therefore to determine the change in PT that occurs from pre-operative supine to post-operative standing, and whether any factors are associated with significant changes in tilt ≥13° in posterior direction. 13° in a posterior direction was chosen as that amount of posterior rotation creates an increase in functional anteversion of the acetabular component of 10°. 1097 THA patients with pre-operative supine CT and standing lateral radiographic imaging and 1 year post-operative standing lateral radiographs (interquartile range 12–13 months) were reviewed. Pre-operative supine PT was measured from CT as the angle between the anterior pelvic plane (APP) and the horizontal plane of the CT device. Standing PT was measured on standing lateral x-rays as the angle between the APP and the vertical line. Patients with ≥13° change from supine pre-op to standing post-op (corresponding to a 10° change in cup anteversion) were grouped and compared to those with a <13° change using unpaired student's t-tests. Mean pre-operative supine PT (3.8±6.0°) was significantly different from mean post-operative standing PT (−3.5±7.1°, p<0.001), ie mean change of −7.3±4.6°. 10.4% (114/1097) of patients had posterior PT changes ≥13° supine pre-op to standing post-op. A significant number of patients, ie 1 in 10, undergo a clinically significant change in PT and functional anteversion from supine pre-op to standing post-op. Surgeons should be aware of these changes when planning component placement in THA

Acetabular retroversion is a recognised cause of hip impingement. Pelvic tilt influences acetabular orientation and is known to change in different functional positions. While previously reported in patients with developmental dysplasia of the hip, positional changes in pelvic tilt have not been studied in patients with acetabular retroversion. We retrospectively analysed supine and standing AP pelvic radiographs in 22 patients with preoperative radiographs and 47 with post-operative radiographs treated for symptomatic acetabular retroversion. Measurements were made for acetabular index (AI), lateral centre-edge angle (LCEA), crossover index, ischial spine sign, and posterior wall sign. The change in pelvic tilt angle was measured both by the Sacro-Femoral-Pubic (SFP) angle and the Pubic Symphysis to Sacro-iliac (PS-SI) Index. In the supine position, the mean calculated pelvic tilt angle (by SFP) was 1.05° which changed on standing to a pelvic tilt of 8.64°. A significant increase in posterior pelvic tilt angle from supine to standing of 7.59° (SFP angle) and 5.89° (PS –SI index) was calculated (p<0.001;paired t-test). The mean pelvic tilt change of 6.51° measured on post-operative Xrays was not significantly different (p=.650). There was a good correlation in pelvic tilt change between measurements using SFP angle and PS-SI index (rho .901 in pre-op group, rho .815 in post-op group). Signs of retroversion were significantly reduced in standing x-rays compared to supine: Crossover index (0.16 vs 0.38; p<0.001) crossover sign (19/28 vs 28/28 hips; p<0.001), ischial spine sign (10/28 hips vs 26/28 hips; p<0.001) and posterior wall sign (12/28 vs 24/28 hips; p<0.001). Posterior pelvic tilt increased from supine to standing in patients with symptomatic acetabular retroversion, in keeping with previous studies of pelvic tilt change in patients with hip dysplasia. The features of acetabular retroversion were much less evident on standing radiographs. The low pelvic tilt angle in the supine position is implicated in the appearance of acetabular retroversion in the supine position. Patients presenting with symptoms of hip impingement should be assessed by supine and standing pelvic radiographs so as not to miss signs of retroversion and to assist with optimising acetabular correction at the time of surgery

Introduction. Assessment of the humeral head translation with respect to the glenoid joint, termed humeral head migration (HHM), is crucial in total shoulder arthroplasty pre-operative planning. Its assessment informs current classification systems for shoulder osteoarthritis as well as the evaluation of surgical correction. In current clinical practice, HHM assessment relies on computed-tomography (CT) imaging. However, the associated supine position might undermine its functional relevance as it does not reflect the weight-bearing condition with active muscle engagement associated with the upright standing position of most daily activities. Therefore, we assessed to what extent HHM in a supine position is associated with HHM in a range of functional arm positions. Method. 26 shoulder osteoarthritis patients and 12 healthy volunteers were recruited. 3D shapes of the humerus and scapula were reconstructed from their respective CT scans using an image processing software. 3. , and their CT-scan-based HHMs were measured. Furthermore, all subjects underwent low-dose biplanar radiography . 4. in four quasi-static functional arm positions while standing: relaxed standing, followed by 45 degrees of shoulder extension, flexion, and abduction. Using a previously validated method implemented in the programming platforms. 5. , 3D shapes were registered to the pairs of biplanar images for each arm position and the corresponding functional HHM was measured. Bivariate correlations were assessed between the CT-based HHM and each functional arm position. Result. HHM in 45 degrees of flexion and extension both showed significant and strong correlations (r>0.66 and P<0.01) with HHM assessed in the supine position. However, such a high correlation was not found for relaxed standing and 45 abduction. Conclusion. Although HHM in a supine position correlates with HHM in 45-degree extension and flexion, it is poorly associated with the HHM in abduction and relaxed standing. These results may suggest the inclusion of more functionally-relevant patient positioning toward better-informed shoulder arthroplasty planning. Acknowledgement. Funding from PRosPERos-II Project

Aims. The conventionally described mechanism of distal biceps tendon rupture (DBTR) is of a ‘considerable extension force suddenly applied to a resisting, actively flexed forearm’. This has been commonly paraphrased as an ‘eccentric contracture to a flexed elbow’. Both definitions have been frequently used in the literature with little objective analysis or citation. The aim of the present study was to use video footage of real time distal biceps ruptures to revisit and objectively define the mechanism of injury. Methods. An online search identified 61 videos reporting a DBTR. Videos were independently reviewed by three surgeons to assess forearm rotation, elbow flexion, shoulder position, and type of muscle contraction being exerted at the time of rupture. Prospective data on mechanism of injury and arm position was also collected concurrently for 22 consecutive patients diagnosed with an acute DBTR in order to corroborate the video analysis. Results. Four videos were excluded, leaving 57 for final analysis. Mechanisms of injury included deadlift, bicep curls, calisthenics, arm wrestling, heavy lifting, and boxing. In all, 98% of ruptures occurred with the arm in supination and 89% occurred at 0° to 10° of elbow flexion. Regarding muscle activity, 88% occurred during isometric contraction, 7% during eccentric contraction, and 5% during concentric contraction. Interobserver correlation scores were calculated as 0.66 to 0.89 using the free-marginal Fleiss Kappa tool. The prospectively collected patient data was consistent with the video analysis, with 82% of injuries occurring in supination and 95% in relative elbow extension. Conclusion. Contrary to the classically described injury mechanism, in this study the usual arm position during DBTR was forearm supination and elbow extension, and the muscle contraction was typically isometric. This was demonstrated for both video analysis and ‘real’ patients across a range of activities leading to rupture. Cite this article: Bone Jt Open 2022;3(10):826–831

Imageless computer navigation systems have the potential to improve acetabular cup position in total hip arthroplasty (THA), thereby reducing the risk of revision surgery. This study aimed to evaluate the accuracy of three alternate registration planes in the supine surgical position generated using imageless navigation for patients undergoing THA via the direct anterior approach (DAA). Fifty-one participants who underwent a primary THA for osteoarthritis were assessed in the supine position using both optical and inertial sensor imageless navigation systems. Three registration planes were recorded: the anterior pelvic plane (APP) method, the anterior superior iliac spines (ASIS) functional method, and the Table Tilt (TT) functional method. Post-operative acetabular cup position was assessed using CT scans and converted to radiographic inclination and anteversion. Two repeated measures analysis of variance (ANOVA) and Bland-Altman plots were used to assess errors and agreement of the final cup position. For inclination, the mean absolute error was lower using the TT functional method (2.4°±1.7°) than the ASIS functional method (2.8°±1.7°, ρ = .17), and the ASIS anatomic method (3.7°±2.1, ρ < .001). For anteversion, the mean absolute error was significantly lower for the TT functional method (2.4°±1.8°) than the ASIS functional method (3.9°±3.2°, ρ = .005), and the ASIS anatomic method (9.1°±6.2°, ρ < .001). All measurements were within ± 10° for the TT method, but not the ASIS functional or APP methods. A functional registration plane is preferable to an anatomic reference plane to measure intra-operative acetabular cup inclination and anteversion accurately. Accuracy may be further improved by registering patient location using their position on the operating table rather than anatomic landmarks, particularly if a tighter target window of ± 5° is desired

Introduction. The pelvis is not a static structure. It rotates in the sagittal plane depending upon the activity being performed. These dynamic changes in pelvic tilt have a substantial effect on the functional orientation of the acetabulum. The aim of this study was to quantify the changes in sagittal pelvic position between three functional postures. Methodology. Pre-operatively, 90 total hip replacement patients had their pelvic tilt measured in 3 functional positions – standing, supine and flexed seated (posture at “seat-off” from a standard chair), Fig 1. Lateral radiographs were used to define the pelvic tilt in the standing and flexed seated positions. Pelvic tilt was defined as the angle between a vertical reference line and the anterior pelvic plane (defined by the line joining both anterior superior iliac spines and the pubic symphysis). In the supine position pelvic tilt was defined as the angle between a horizontal reference line and the anterior pelvic plane. Supine pelvic tilt was measured from computed tomography, Fig 2. Results. The mean standing pelvic tilt was −2.1° ± 7.4°, with a range of −15.2° – 15.3°. Mean supine pelvic tilt was 4.1° ± 5.5°, with a range of −9.7° – 17.9°. Mean pelvic tilt in the flexed seated position was −1.8° ± 14.1°, with a range of −31.8° – 29.1°, Fig 3. The mean absolute change from supine to stand, and stand to flexed seated was 6.9° ± 4.1° and 11.9° ± 7.9° respectively. 86.6% of patients had a more anteriorly tilted pelvis when supine than standing. 52.2% of patients had a more anteriorly tilted pelvis when seated than standing. Conclusions. The position of the pelvis in the sagittal plane changes significantly between functional activities. The extent of change is specific to each patient. Planning and measurement of cup placement in the supine position can lead to large discrepancies in orientation during more functionally relevant postures. As a result of the functional changes in pelvic position, cup orientations during dislocation and edge-loading events are likely to be significantly different to that measured from standard CT and radiographs. Optimal cup orientation is likely patient-specific and requires an evaluation of functional pelvic dynamics to pre-operatively determine the target angles

The purpose of this study was to examine the influence of weight-bearing on the measurement of in vivo wear of total knee replacements using model-based RSA at 1 and 2 years following surgery. Model-based RSA radiographs were collected for 106 patients who underwent primary TKR at a single institution. Supine RSA radiographs were obtained post-operatively and at 6-, 12-, and 24-months. Standing (weight-bearing) RSA radiographs were obtained at 12-months (n=45) and 24-months (n=48). All patients received the same knee design with a fixed, conventional PE insert of either a cruciate retaining or posterior stabilized design. Ethics approval for this study was obtained. In order to assess in vivo wear, a highly accurate 3-dimensional virtual model of each in vivo TKA was developed. Coordinate data from RSA radiographs (mbRSA v3.41, RSACore) were applied to digital implant models to reconstruct each patient's replaced knee joint in a virtual environment (Geomagic Studio, 3D Systems). Wear was assessed volumetrically (digital model overlap) on medial and lateral condyles separately, across each follow-up. Annual rate of wear was calculated for each patient as the slope of the linear best fit between wear and time-point. The influence of weight-bearing was assessed as the difference in annual wear rate between standing and supine exams. Age, BMI, and Oxford-12 knee improvement were measured against wear rates to determine correlations. Weight bearing wear measurement was most consistent and prevalent in the medial condyle with 35% negative wear rates for the lateral condyle. For the medial condyle, standing exams revealed higher mean wear rates at 1 and 2 years, supine, 16.3 mm3/yr (SD: 27.8) and 11.2 mm3/yr (SD: 18.5) versus standing, 51.3 mm3/yr (SD: 55.9) and 32.7 mm3/yr (SD: 31.7). The addition of weight-bearing increased the measured volume of wear for 78% of patients at 1 year (Avg: 32.4 mm3/yr) and 71% of patients at 2 years (Avg: 48.9 mm3/yr). There were no significant (95% CI) correlations between patient demographics and wear rates. Volumetric, weight-bearing wear measurement of TKR using model-based RSA determined an average of 33 mm3/yr at 2 years post-surgery for a modern, non-cross-linked polyethylene bearing. This value is comparable to wear rates obtained from retrieved TKRs. Weight-bearing exams produced better wear data with fewer negative wear rates and reduced variance. Limitations of this study include: supine patient imaging performed at post-op, no knee flexion performed, unknown patient activity level, and inability to distinguish wear from plastic creep or deformation under load. Strengths of this study include: large sample size of a single TKR system, linear regression of wear measurements and no requirement for implanted RSA beads with this method. Based on these results, in vivo volumetric wear of total knee replacement polyethylene can be reliably measured using model-based RSA and weight-bearing examinations in the short- to mid–term. Further work is needed to validate the accuracy of the measurements in vivo

Purpose. The purpose of this study was to examine the influence of weight-bearing on the measurement of in vivo wear of total knee replacements using model-based RSA at 1 and 2 years following surgery. Methods. Model-based RSA radiographs were collected for 106 patients who underwent primary TKR at a single institution. Supine RSA radiographs were obtained post-operatively and at 6-, 12-, and 24-months. Standing (weight-bearing) RSA radiographs were obtained at 12-months (n=45) and 24-months (n=48). All patients received the same knee design with a fixed, conventional PE insert of either a cruciate retaining or posterior stabilized design. Ethics approval for this study was obtained. In order to assess in vivo wear, a highly accurate 3-dimensional virtual model of each in vivoTKA was developed. Coordinate data from RSA radiographs (mbRSA v3.41, RSACore) were applied to digital implant models to reconstruct each patient's replaced knee joint in a virtual environment (Geomagic Studio, 3D Systems). Wear was assessed volumetrically (digital model overlap) on medial and lateral condyles separately, across each follow-up. Annual rate of wear was calculated for each patient as the slope of the linear best fit between wear and time-point. The influence of weight-bearing was assessed as the difference in annual wear rate between standing and supine exams. Age, BMI, and Oxford-12 knee improvement were measured against wear rates to determine correlations. Results. Weight bearing wear measurement was most consistent and prevalent in the medial condyle with 0–4% of calculated wear rates being negative compared to 29–39% negative wear rates for the lateral condyle. For the medial condyle, standing exams revealed higher mean wear rates at 1 and 2 years; supine, 16.3 mm. 3. /yr (SD: 27.8) and 11.2 mm. 3. /yr (SD: 18.5) versus standing, 51.3 mm. 3. /yr (SD: 55.9) and 32.7 mm. 3. /yr (SD: 31.7). The addition of weight-bearing increased the measured volume of wear for 78% of patients at 1 year (Avg: 32.4 mm. 3. /yr) and 71% of patients at 2 years (Avg: 48.9 mm. 3. /yr). There were no significant (95% CI) correlations between patient demographics and wear rates. Discussion and Conclusion. This study demonstrated TKA wear to occur at a rate of approximately 10 mm. 3. /year and 39 mm. 3. /year in patients imaged supine versus standing, respectively, averaged over 2 years of clinical follow-up. In an effort to eliminate the effect of PE creep and deformation, wear was also calculated between 12 and 24 months as 9.3 mm. 3. (standing examinations), This value is comparable to wear rates obtained from retrieved TKRs. Weight-bearing exams produced better wear data with fewer negative wear rates and reduced variance. Limitations of this study include: supine patient imaging performed at post-op, no knee flexion performed, and unknown patient activity level. Strengths of this study include: large sample size of a single TKR system, linear regression of wear measurements and no requirement for implanted RSA beads with this method. Based on these results, in vivo volumetric wear of total knee replacement polyethylene can be reliably measured using model-based RSA and weight-bearing examinations in the short- to mid–term. For any figures or tables, please contact authors directly

Background. Cup anteversion and inclination are important to avoid implant impingement and dislocation in total hip arthroplasty (THA). However, it is well known that functional cup anteversion and cup inclination also change as the pelvic sagittal inclination (PSI) changes, and many reports have been made to investigate the PSI in supine and standing positions. However, the maximum numbers of subjects studied are around 150 due to the requirement of considerable manual input in measuring the PSIs. Therefore, PSI in supine and standing positions were measured fully automatically with a computational method in a large cohort, and the factors which relate to the PSI change from supine to standing were analyzed in this study. Methods. A total of 422 patients who underwent THA from 2011 to 2015 were the subjects of this study. There were 83 patients with primary OA, 274 patients with DDH derived secondary OA (DDH-OA), 48 patients with osteonecrosis, and 17 patients with rapidly destructive coxopathy (RDC). The median age of the patient was 61 (range; 15–87). Preoperative PSI in supine and standing positions were measured and the number of cases in which PSI changed more than 10° posteriorly were calculated. PSI in supine was measured as the angle between the anterior pelvic plane (APP) and the horizontal line of the body on the sagittal plane of APP, and PSI in standing was measured as the angle between the APP and the line perpendicular to the horizontal surface on the sagittal plane of APP (Fig. 1). The value was set positive if the pelvis was tilted anteriorly and was set negative if the pelvis tilted posteriorly. Type of hip disease, sex, and age were analyzed with multiple logistic regression analysis if they were related to PSI change of more than 10°. For accuracy verification, PSI in supine and standing were measured manually with the previous manual method in 100 cases and were compared with the automated system used in this study. Results. The median PSI in the supine position was 5.1° (interquartile range [IQR]: 0.4 to 9.4°), and the median PSI in the standing position was −1.3° (IQR: −6.5 to 4.2°). There were 79 cases (19%) in which the PSI changed more than 10° posteriorly from supine to standing with a maximum change of 36.9° (Fig. 2). In the analysis of the factors, type of hip disease (p = 0.015) and age (p = 0.006, Odds Ratio [OR] = 1.035) were the significant factors. The OR of primary OA (p = 0.005, OR: 2.365) and RDC (p = 0.03, OR: 3.146) were significantly higher than DDH-OA. In accuracy verification, the automated PSI measurement showed ICC of 0.992 (95% CI: 0.988 to 0.955) for supine measurement and 0.978 (95% CI: 0.952 to 0.988) for standing measurement. Conclusions. PSI changed more than 10° posteriorly from supine to standing in 19% of the cases. Age and diagnosis of primary OA and RDC were related to having their pelvis recline more than 10° posteriorly. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Imageless computer navigation systems in total hip arthroplasty (THA) improve acetabular cup position, thereby reducing the risk of revision surgery for all causes as well as dislocation. We aimed to evaluate the registration accuracy of 3 alternate registration planes. A prospective, observational study was conducted with 45 THA in the supine position using two imageless navigation systems and 3 registration planes. Patient position was registered sequentially using an optical system (Stryker OrthoMap) and an inertial sensor-based system (Navbit Sprint) with 3 planes of reference: (Plane 1) an anatomical plane using the anterior superior iliac spines (ASISs) and the pubic symphysis; (Plane 2) a functional plane parallel to the line between the ASISs and the table plane; and, (Plane 3) a functional plane that was perpendicular to the gravity vector and aligned with the longitudinal axis of the patient. The 3 measurements of acetabular cup inclination and anteversion were compared with the measurements from postoperative computed tomography (CT) scans. For inclination, the mean absolute error was significantly lower for Plane 3 (1.80°) than for Plane 2 (2.74°), p = .038 and was lower for both functional planes than for the anatomical plane (3.75°), p < .001. For anteversion, the mean absolute error was significantly lower for Plane 3 (2.00°) than for Plane 2 (3.69°), p = .004 and was lower for both functional planes than for the anatomical plane (8.58°), p < .001. Patient registration using functional planes more accurately measured the acetabular cup position than registration using anatomic planes

Introduction. The resultant cup orientation depends upon the orientation of the pelvis at impaction. No studies to date have assessed whether patient-position during total hip arthroplasty (THA) has an effect on cup orientation. This study aims to 1) Determine the difference in pelvic position that occurs between surgery and radiographic, supine, post-operative assessment; 2) Examine how the difference in pelvic position influences subsequent cup orientation and 3) Establish whether pelvic orientation, and thereafter cup orientation, differences exist between THAs performed in the supine versus the lateral decubitus positions. Patients/Materials & Methods. This is a retrospective, multi-surgeon, single-centre, consecutive series. 321 THAs who had intra-operative, post-cup impaction, AP pelvic radiograph, in the operative position were included; 167 were performed with the patient supine (anterior approach), whilst 154 were performed in the lateral decubitus (posterior approach). Cup inclination/anteversion was measured from intra- and post-operative radiographs and the difference (Δ) was determined. Change in pelvic position (tilt, rotation, obliquity) between surgery and post-operatively was calculated from Δinclination/anteversion using the Levenberg-Marquardt algorithm. Results. The mean post-operative inclination and anteversion were 40°±8 and 23°±9 respectively. 74 had either Δ. inclination. and/or Δ. anteversion. ±10° (21%). Intra-operatively (compared to post-operative), the pelvis was on average 4°±10 anteriorly tilted; 1°±10 internally rotated and 1°±5 adducted. Having a Δ. inclination. and/or Δ. anteversion. ±10° was associated with an odds ratio of 3.5 in having a cup orientation outside the target. A greater proportion of cases had Δ. inclination. and/or Δ. anteversion. > ±10° amongst the hips operated in the lateral decubitus (54/153) compared to the supine position (8/167) (p<0.001). The pelvis was significantly more anteriorly tilted (p<0.001) and the hemi-pelvis was significantly more internally rotated intra-operatively in the lateral position (p=0.04) compared to supine. Discussion. Pelvic movement is significantly less in supine position, which leads to more consistent cup orientation. Significant differences in pelvic tilt and rotation were seen in the lateral position, illustrating the difficulties for surgeons to consistently position the pelvis

Introduction: A good cup positioning requires reliable anatomical landmarks expecially for navigation. The anterior pelvic plane (APP) seems to be a good reference for navigation because it is in relation with pelvic tilt which do affect the position of the cotyle and consequently the position of the cup. The value of this plane is not well known according to gender, age, weight… The aim of the study is to assess radiologically the APP in standing and supine position before and after total hip arthroplasty. MATERIALS AND Methods: 92 Patients (32 males, 60 females, mean age 65 years) underwent strict lateral X-rays in standing and supine standardized position. Uninterpretable or unsatisfying X rays were withdrawn. 45 patients underwent a standing X-ray, 24 a supine X-ray, 21 a supine and standing X ray. Statistical analysis used a Student t-test. Results: Non matched values showed a retroversion of the pelvis of 6.4° (+/− 6.9) in supine position, 0.3° (+/− 7.4) in standing position. Matches values showed an retroversion of the pelvic of 6.9° (+/− 5.3) in supine position, 0.3° (+/− 5.03) in standing position (significant difference). Extreme values varied from −15° to + 18° (3 patients showed no variation, 2 patients a retroversion from supine to standing position). There was no statistical difference between male and female but a statistical differences in females. Discussion: The APP is easily assessable by X rays in standing as in supine position. Bony landmarks of the plane are also assessable by navigation tools and to can be a good plane as reference. Several authors showed the repercussion of the pelvic tilt on the cotyle position. The difference between standing and supine position is about 6°. But for some patients the difference is may be of 20°and that could explain some impigment and instability. A cup well positioned in supine position may be not so good in standing position because of the pelvic tilt. Conclusion: The value of the APP is important to know before THA and seems to be a good plane as reference for navigation

Aims: For planning of Total Hip Arthroplasties (THA) plain X-rays of the pelvis in anterior posterior orientation are used. New methods such as CT scans and intraoperative digitization with navigation devices introduce the third dimension into orthopaedic planning. In order to compare measurements derived from three-dimensional data-acquisition with standard pelvic measurements it is important to estimate the underlying variances of those standards. Methods: 120 patients were investigated and subdivided in 4 groups depending of their age or the condition of their hip joints. The patients were positioned in a supine position on a table and in a standing position. Three landmarks at the patientñs pelvis (left and right anterior superior iliac spine (ASIS) and the pubic tubercle (PT)) were percutaneously digitized with a digitizing arm (Micro-Scribe-3DX, Vizion, Glendale, CA). The pelvic positions in space were calculated in relation to the horizontal and the vertical plane. Results: Despite the anatomical deþnition (0¡), we found an inclination of 4-6¡. There is no signiþcant difference between supine and standing position and no signiþcant difference between the groups and no diffenrence between genders. All patients lyed ßat in supine position without special positioning effort Conclusions: The pelvis orientation ist very stable in standing as well in supine position no matter if the patient is old or young, has coxarthrosis ore none or a THA. Therefore it can be concluded that our knowledge derived from measurements of planar a.-p.x-rays is not inßuenced by a massive variance in pelvic positions

The aim of this study is to assess the discrepancy between weight bearing long leg radiographs and supine MRI alignment. There is currently increasing interest in the use of MRI to assess knee alignment and develop custom made cutting blocks utilising this data. However in almost all units MRI scans are performed supine and it is recognised that knee alignment can alter with weight bearing. 46 patients underwent MRI scans as pre-operative planning for Biomet signature total knee replacement and the measure of varus or valgus deformity on MRI was obtained from the plan produced by Biomet Signature software system. 41 of these patients had long leg weight bearing radiographs performed. 33 of these radiographs were amenable to measuring the knee alignment on the picture archiving and communication system (PACS). These measurements were performed by two assessors and inter-observer reliability was satisfactory. There was a significant difference between the alignment as measured on supine MRI compared with weight bearing long leg films. In knee arthroplasty one of the aims is to correct the biomechanical axis of the knee and one of the appeals of custom made cutting blocks is that this can be achieved more easily. However it is important to realise that alignment is not a static value and thus correcting supine alignment may not necessarily result in correction of weight bearing alignment

Introduction:. External rotation (ER) of the shoulder is a commonly used clinical measurement to assess the glenohumeral joint; however, the position in which these measurements are obtained varies between clinicians. The purpose of this study was to compare the following: ER in the upright & supine positions, motion capture & goniometric values of ER, active & passive ER, ER in the right & left shoulders, and ER in male & female subjects. Methods:. Eighteen subjects (mean age 25.4 yrs) with ‘normal’ shoulders (by screening questionnaire) were enrolled in the study and subject to triplicate measurements of active and passive ER of both shoulders with a goniometer and a 12 camera, high speed optical motion analysis system in both the upright and supine positions. ANOVA was used to compare variables and linear regression used to correlate the goniometer & optical motion capture measurements. Results:. On average, shoulder ER in the supine position was 10.0° greater than in the upright position (p < 0.001) using the motion capture data and 5.8° greater using the goniometer (p = 0.025). There was a strong correlation between the goniometer and optical motion capture measurements with an R. 2. value of 0.6573 (p = 2.39E-13); on average, the goniometer readings were 11.0° greater than the corresponding optical measurements. External rotation of the right shoulder was 7.2° greater than the left using the optical measurements (p = 0.02) and 4.4° greater with the goniometer (p = 0.039). In addition, females did have significantly greater external rotation than males using the optical measurements (p < 0.001), averaging 16.7° more external rotation; findings were similar for the goniometric measurements with 18.5° greater average external rotation seen in female subjects (p < 0.001). There was no significant difference between measured active and passive external rotation (p = 0.589). Conclusion:. Significant differences do exist between measured values of external rotation depending on the position of measurement (upright vs supine), hand dominance, and gender. It does not appear that there is a difference between active and passive external rotation. Our recommendations are for the musculoskeletal clinician to be meticulous when documenting the position of measured external rotation, as values vary depending on the position of measurement. One should also be cautious of comparing external rotation of one shoulder to the contralateral side, as well as comparing values between genders, as these measurements appear to be different as well

Total hip arthroplasty (THA) using minimally invasive surgeries (MIS) now become popular operative procedures. It is not easy to understand geometric information of pelvis and femur in the restricted operative fields during MIS-THA. Recently, THA in supine position comes into the limelight again to place acetabular cups in an optimum position because we can minimise the intra-operative pelvic motion during THA in supine position. To verify the usefulness of supine position, we measured the angels of acetabular trial cups intra-operatively using the CT-based navigation system. The trial cup positions were placed according to a conventional acetabular cup alignment guide. We compared the angles of acetabular trial cups between supine and lateral positions through the same MIS antero-lateral (AL) surgical approach. Thirty eight hips underwent THA in lateral position (the AL group; average age: 63.9 years old, female: 29 cases, 33 hips, male: 5 cases, 5 hips) and 40 hips underwent THA in supine position (the AL Supine group; average age: 62.2 years old, female 40 cases, 40 hips) were subjected in this study. The single surgeon (the first author) performed all surgeries. We used the Roettinger's modified Watson-Jones approach in both groups. The pelvic registration for navigation was carried out using the CT-fluoro matching procedure with VectorVision Hip (BrainLAB, Germany). After acetabular reaming, the acetabular trial cups were placed into the reamed acetabulum to be at 45 degrees of operative inclination (OI) and at 20 degrees of operative anteversion (OA) using a conventional acetabular cup alignment guide. These angles of the trial cups were measured intra-operatively using the CT-based navigation system, VectorVision Hip. After removing the acetabular trial cup, the acetabular cups were placed using the navigation system. Trilogy cups (Zimmer, USA) and AMS HA shells (JMM, Japan) were used in this study. The average angles of OI were 45.7 degrees (SD 5.5 degrees) in the AL group and 46.3 degrees (SD 4.6 degrees) in the AL Supine group. The average angles of OA were 30.0 degrees (SD 13.5 degrees) in the AL group and 23.5 degrees (SD 8.2 degrees) in the AL Supine group. The hip numbers whose errors were less than 10 degrees were 13 hips in the AL group and 26 hips in the AL Supine group, respectively. There was significant difference in hip numbers whose errors of angles were less than 10 degrees between the AL and Supine groups. The hip numbers whose errors were less than 5 degrees were 7 hips in the AL group and only 6 hips in the AL Supine group, respectively. There was no significant difference in hip numbers whose errors of angles were less than 5 degrees between the AL and Supine groups. The error values of OI were less than 10 degrees except one hip in both groups. However, the error values of 25 hips in the AL group were more than 10 degrees. In lateral position, the pelvis easily rotated when the affected lower extremity was extended, externally rotated, and adducted during the femoral preparation in the AL group, which resulted in malalignment of acetabular OA. In contrast, most hips could be set with the error values less than 10 degrees in the AL Supine position because the pelvis could be stabilised on the operative table. In addition, landmarks, such as bilateral antero-superior iliac spines and the symphysis pubis, were palpable in supine position. However, the hips with error values less than 5 degrees were only 6 out of 40 hips even though in supine position. Using MIS techniques, we can provide more stable hip joint just after surgery since the muscles surrounding hip joints can be preserved. We have to place acetabular cups in an optimum position to achieve wide range of hip motion to prevent dislocation and to provide limitation-free daily activities for patients. These data suggests that we should use more accurate guide systems for acetabular cup replacement such as navigation systems, patient specific templates, and patient specific mechanical instruments to place acetabular cups in an optimum position

The aim of this study is to assess the discrepancy between weight bearing long leg radiographs and supine MRI alignment. There is currently increasing interest in the use of MRI to assess knee alignment and develop custom made cutting blocks utilising this data. However in almost all units MRI scans are performed supine and it is recognised that knee alignment can alter with weight bearing. 46 patients underwent MRI scans as pre-operative planning for Biomet signature total knee replacement and the measure of varus or valgus deformity on MRI was obtained from the plan produced by Biomet Signature software system. 41 of these patients had long leg weight bearing radiographs performed. 37 of these radiographs were amenable to measuring the knee alignment on the picture archiving and communication system (PACS). These measurements were performed by two assessors and inter-observer reliability was satisfactory. There was a significant difference between the alignment as measured on supine MRI compared with weight bearing long leg films. In knee arthroplasty one of the aims is to correct the biomechanical axis of the knee and one of the appeals of custom made cutting blocks is that this can be achieved more easily. However it is important to realise that alignment is not a static value and thus correcting supine alignment may not necessarily result in correction of weight bearing alignment

Purpose: We report the operative technique and preliminary results for percutaneous osteosynthesis in the supine position with computed tomography guidance for acetabular fractures without joint displacement. Material and methods: This prospective study conducted in a single unit included a consecutive non-randomised series of 55 patients who underwent surgery for an unstable pelvic injury between June 1996 and December 2000 under computed tomography guidance. In ten cases, the radiographic and computed tomographic analysis demonstrated a coronal fracture of one of the columns without joint displacement accessible for anteroposterior screw fixation. There were eight men and two women, mean age 35 years. Surgery: the ten patients were operated on in the supine position, in the scanner room under the same aseptic conditions as in the operation room. The reference computed tomography slice was the Corse slice. The femoral vasculo-nervous bundle was identified. A threaded guide wire was inserted perpendicuallary to the fracture line, anteriorly to posteriorly (Cap Corse technique). A perforated screw with a 7.3 mm diameter was used to fix the fracture. Minimal post-surgical surveillance was 48 hours. Weight bearing was not authorised for six weeks to three months. Al patients were followed prospectively, and mean follow-up ws 16 months (12–36). Results: Traction was lifted immediately after surgery in all cases. All the patients got up the day after surgery. Mean hospital stay was less than five days postoperatively in all cases. There were no complications (vascular, neurologic, infectious) and no secondary displacement. At last follow-up, he Postel Merle d’Aubigné score was 18 for eight patients, 16 for one and 14 for one. Two patients showed radiographic signs of degenerative hip disease. Discussion: This percutaneous osteosynthesis method using computed tomographic guidance is reliable (100% well positioned screws) and avoids the need for traction in bed. Morbidity is low (no complications). Even though these eight patients did not present clinical and radiographic signs of osteoarthritis, this technique did not avoid the risk of degenerative hip disease in two patients. Conclusion: An alternative to traction, percutaneous osteo-synthesis with computed tomographic guidance performed in the supine position for acetabular fractures is a cost-effective procedure