Hip Center Research Articles

Long-term results of medial open reduction surgery on pelvic and hip kinematics in children with developmental hip dislocation:A pilot study

Total hip arthroplasty in severe dysplasia is challenging due to diminished periacetabular bone stock and the highly placed femoral head. Although anatomical reconstruction of the hip, with required interventions such as subtrochanteric osteotomy and graft usage, is the main aim of the procedure, good long-term clinical outcomes of the high hip center technique have also been reported. Information regarding the effect of hip center placement on gait characteristics is limited; therefore, the aim of this study is to analyze the differences in gait parameters between the high hip center technique and anatomical reconstruction of the hip.Twenty patients (40 hips) with bilateral Crowe type III-IV developmental dysplasia of the hip who underwent bilateral total hip arthroplasty and completed at least 2 years of follow-up were included. Group 1 comprised 10 patients (20 hips) who underwent anatomical hip center reconstruction, while group 2 comprised 10 patients (20 hips) who underwent high hip center reconstruction. The gait characteristics of patients were examined through markers placed in certain anatomical regions, the cameras placed around, and the force plates embedded in the walking platform.There was no significant difference in the gait characteristics according to the location of the hip rotation center. The mean temporospatial, kinematic, and kinetic values were similar between the groups. The most prominent difference was in the peak dynamic hip extension, which was lower in group 2 (−9.71° ± 7.46°) compared to group 1 (−6.80° ± 11.44°), although it was not statistically significant (P = .09).The bilateral high hip center technique can provide similar gait characteristics as anatomical reconstruction and may be preferred in particularly difficult cases based on the surgeon’s decision.

Objective visualization of the effect of different knee flexion angles on medial-lateral displacement of the knee center in frontal plane during single-Leg Squat

Introduction:The subjective single-leg squat (SLS) test can be used as a functional diagnostic agent to prevent knee injuries. [1] However, there are missing objective data about its functional rating, performance, squat depth and medio-lateral knee displacement in the frontal plane. [2] There-fore, the purpose of this pilot study was to evaluate the medio-lateral knee displacement in the frontal plane with a 3D motion capture system at different knee flexion angles during the SLS in healthy patients.Hypotheses:The hypothesis was that according to different knee flexion angles, there is a variability of medial knee displacement (= valgus positions) in healthy patients.Methods:17 healthy and sporty subjects (9 ♀/ 8 ♂, age 25±4 years, BMI 24±2 kg/m2) participated in this study. Exclusion criteria were balance disorders, hip knee and/ or ankle complaints, sur-gery history, high deviation in lower extremity axis (i.e. Genu varum/ Genu valgus). Knee dis-placement was measured by 3D motion analysis system (Vicon Motion Systems, Oxford, UK) using a modified method of Krosshaug et al. [3] Thus, knee displacement was defined as distance between knee joint center and reference plane including the calculated hip and ankle joint center and the fixed toe marker on the second metatarsal head. A positive knee dis-placement was associated with a knee valgus, a knee varus was described as negative knee displacement. Every participant did 12 single-leg squats on each side.Results:The following knee flexion angles of all SLSs were captured (°, mean and standard deviation (±)): start position at 11 ± 6; downward phase at 40 ± 0 and 60 ± 0; maximum at 86 ± 16; up-ward phase at 60 ± 0 and 40 ± 0; end position at 8 ± 6. The medio-lateral knee displacement of all SLSs showed at the mentioned knee flexion an-gles the following values respectively (mm, median, interquartile range (25th - 75th quartile)): -12 (-19 to -5); 0 (-9 to 7); 13 (-2 to 28); 38 (8 to 61); 17 (0 to 36); 4 (-6 to 16); -15 (-22 to -7).Conclusion:According to different knee flexion angles, there is a variability of medio-lateral knee dis-placements in healthy patients. This variability should be included in the functional rating of a SLS as well as in the interpretation of different knee pathologies. Moreover, it provides an objective basis in the prediction of knee injuries.

Influence of step width on the hip adduction moment during gait

Compensatory mechanisms for hip pain, pathology, and weakness include excessive trunk lean towards the stance limb, counteracting pelvic drop to maintain stability during single leg stance. Trunk lean shifts the center of mass towards the hip joint center to decrease the moment arm and reduce hip abductor demand. The purpose of this study was to evaluate whether adolescent patients with symptomatic hip pain demonstrate excessive trunk lean and the effect on the hip abductor moment impulse.Self-selected speed walking data collected through an approved study were reviewed on pre-operative patients clinically diagnosed with a hip deformity. Instrumented motion analysis was performed to analyze trunk kinematics and the hip abductor moment impulse.There was a weak, but significant correlation between hip abductor moment impulse and trunk lean. Patients diagnosed with Acetabular Dysplasia demonstrated an increased trunk lean and a decreased hip abductor moment impulse (r = − 0.311, p = 0.001). Of those who presented with excessive trunk lean, 62% of these patients had a normal hip abductor moment impulse. There was no correlation between hip abductor moment impulse and hip abductor strength.Excessive trunk lean was not seen uniformly across adolescent patients with symptomatic hip deformities, despite pain being reported in 80% of patients. Furthermore, a majority of those that presented with excessive trunk lean did not present with a reduced moment, suggesting that although the amount of lean was greater than normal, it was not enough to significantly reduce the demand on the hip musculature.

Simple method for correcting hip joint center position in overweight subjects

Simple method for correcting hip joint center position in overweight subjects

Estimation of the hip joint centre in children with cerebral palsy

Estimation of the hip joint centre in children with cerebral palsy

Cup-on-cup technique: a reliable management solution for severe acetabular bone loss in revision total hip replacement.

The management of acetabular bone loss is a challenging problem in revision total hip arthroplasty (rTHA). The goals of treatment are a stable acetabular fixation, implant stability, and restoration of hip centre of rotation.This study aims to report clinical, radiological outcomes and complications at short-term to mid-term follow-up of the cup-on-cup technique in the management of severe acetabular bone loss in rTHA. We retrospectively reviewed the records of patient receiving rTHA performed with double porous tantalum cup technique in a single Joint Replacement Unit from 2014 to 2017. Objective and subjective clinical scores (Harris Hip Score, Oxford Hip Score, and visual analogue scale), radiological parameters (centre of rotation, leg-length discrepancy, heterotopic ossification, osseointegration, loosening and radiolucencies) and complications were recorded. We analysed the implant survival rate and periprosthetic joint infection rate. We included 9 patients (9 hips) with a mean follow-up of 35.3 ± 10.8 months. Functional scores showed a statistically significant improvement at the final follow-up (p < 0.01). All patients rated their surgery as satisfactory. The cup-on-cup construct demonstrated radiological osseointegration with the centre of rotation restoration and leg length discrepancy improvement. In 1 patient, periprosthetic joint infection was diagnosed and treated with suppressive antibiotic therapy. No patients underwent acetabular components revision surgery for any reason. Cup-on-cup technique is a valid and safe solution for reconstruction of selected Paprosky type IIIA and IIIB bone defects with satisfactory clinical and radiographic results at short-term and mid-term follow-up.

Evaluation of Dislocation Risk Factors With Total Hip Arthroplasty in Developmental Hip Dysplasia Patients: A Multivariate Analysis

BackgroundThis study aimed to investigate the risk factors for dislocation in patients diagnosed with developmental dysplasia of the hip (DDH) who underwent total hip arthroplasty. MethodsWe retrospectively reviewed 40 patients who developed dislocation and compared them with 400 patients in the control group without hip instability. Patients-, surgery-, and implant-related factors were investigated. Risk factors were evaluated using multivariate logistic regression. ResultsThe mean follow-up period was 32.3 months. The mean time to dislocation was 4.4 months. There were 7 men (17.5%) and 33 women (82.5%) in the dislocation group and 83 men (20.7%) and 317 women (79.3%) in the control group (P = .627). Diabetes mellitus (DM; P = .032) and history of previous hip surgery for DDH were associated with dislocation (P < .001). The subtrochanteric shortening osteotomy (P = .001), acetabular inclination (P = .037), acetabular anteversion (P < .001), femoral head size (P < .001), and postoperative infection (P = .003) were associated with dislocation. Major predictors of hip dislocation after total hip arthroplasty in patients with DDH were previous hip surgery (odds ratio [OR], 6.76; 95% confidence interval [CI], 1.86-24.6; P = .004), high hip center (OR, 2.90; 95% CI, 1.31-6.38; P = .008), DM (OR, 2.68; 95% CI, 1.06-6.80; P = .037), and acetabular inclination (OR, 2.62; 95% CI, 1.09-6.26; P = .03). ConclusionPatients with DM and previous hip surgery should be informed about increased dislocation rates. Using a larger head diameter and restoration of the true hip rotation center are essential to prevent hip dislocation in these patients. Furthermore, accurate positioning of the acetabular inclination and anteversion are also important.

Tantalum Augments Combined with Antiprotrusio Cages for Massive Acetabular Defects in Revision Arthroplasty

BackgroundTantalum components have gained popularity for the management of Paprosky type IIIA and IIIB defects during revision total hip arthroplasty. Although the use of antiprotrusio cages solely shows suboptimal results, there are certain defects that still require their use. We hypothesized that combining tantalum augments and an antiprotrusio cage would (1) improve radiographic stability, (2) enhance survivorship, (3) decrease complications, and (4) improve clinical outcomes. MethodsWe retrospectively reviewed 20 patients with Paprosky type IIIA or IIIB defects who underwent revision of the acetabular component with a highly porous tantalum augment and an antiprotrusio cage combination. Preoperative and postoperative radiographs, survivorship free from aseptic component revision, and the Harris Hip Score, Western Ontario and McMaster Universities Osteoarthritis Index, and Short Form-36 scores were analyzed. The mean follow-up was 2.8 years. ResultsAt the most recent follow-up, no antiprotrusio cages had migrated and all tantalum augments had radiographic evidence of osseointegration. In addition, only 2 components were revised for aseptic etiologies and only 1 was loose. Both were revised secondary to failures of the inferior flange of the antiprotrusio cage. All clinical outcome scores significantly improved postoperatively. Finally, the risk of major postoperative complications was noted to be 10%. ConclusionsIn summary, a tantalum augment combined with an antiprotrusio cage in Paprosky IIIA and IIIB defects with divergent anatomy not amenable to a hemispherical socket provides a reliable technique to restore the anatomic hip center and prevent superior migration and provides a bony ingrowth surface. Longer term follow-up is required before the technique is widely adapted. Level of EvidenceLevel IV, therapeutic studies.

Sagittal Spinopelvic Translation Is Combined With Pelvic Tilt During the Standing to Sitting Position: Pelvic Incidence Is a Key Factor in Patients Who Underwent THA

BackgroundSagittal spinopelvic translation (SSPT) is the horizontal distance from the hip center to the C7 plumb line (C7PL). SSPT is an important variable showing the overall patient balance in different functional positions which could affect the rate of hip instability. This study investigates the SSPT modification in patients who underwent total hip arthroplasty (THA). MethodsA total of 120 patients were assessed preoperatively and postoperatively on standing and sitting acquisitions (primary unilateral THA without complication). SSPT is zero when the C7PL goes through the center of the femoral heads and positive when the C7PL is posterior to the hips’ center (negative if anterior). Three subgroups were defined based on the pelvic incidence (PI): low PI <45°, 45°< normal PI <65°, or high PI >65°. ResultsThe overall mean preoperative SSPT change from standing to sitting was 2.2 cm ([-7.2 to 17.4]) (P < .05). The overall mean postoperative SSPT change from standing to sitting was 1.2 cm ([-14.2 to 22.4]) (P < .05). In low- and normal-PI groups, standing to sitting SSPT and preoperative to postoperative changes in standing SSPT were increased significantly after surgery with the C7PL behind the hips’ center (P < .05). In the high-PI group, standing to sitting SSPT was increased postoperatively (P = .034) (no significant changes from preoperative to postoperative status in standing and sitting). ConclusionsAdaptation from standing to sitting positions combines pelvic tilt and anteroposterior pelvic translation. THA implantation induces significant changes in SSPT mainly for low- and standard-PI patients. This is an important variable to consider when investigating the causes of THA subluxation or dislocation.

Acetabular depth, an early predictive factor of acetabular development: MRI in patients with developmental dysplasia of the hip after open reduction.

Early prediction of future acetabular development is important to determine an additional surgery for developmental dysplasia of the hip (DDH). The purpose of this study was to investigate the predictive factors of acetabular development using MRI. We retrospectively investigated dislocated 40 hips and 34 normal hips in 37 pediatric patients (9 males and 28 females) with DDH who underwent open reduction after walking age. We evaluated the cartilaginous acetabulum and labrum of the patients using coronal MRI T2*-weighted images at 5 years of age. The mean age at the time of surgery was 22 months, and the mean age at the final survey was 19 years. We divided patients into two groups in accordance with the Severin classification at the final follow-up. Groups with good outcomes (affected 26 hips and unaffected 27 hips) and poor outcomes (14 hips and 7 hips) were compared using the MRI parameters on each side. Predictive factors of acetabular development were identified using univariate and multiple logistic regression analyses. Using multiple logistic regression analysis, labral acetabular roof depth and labral hip center distance at 5 years of age represented predictors after open reduction (odds ratio 0.27, P = 0.035; odds ratio 3.4, P = 0.028, respectively) on the affected side, and bony hip center distance represented a predictor on the unaffected side (odds ratio 2.6, P = 0.049). Acetabular development in the unaffected side could be predicted by bony assessment, while acetabular development in the affected side had to be assessed by labrum using MRI.

Mid-term results of revision surgery using double-trabecular metal cups alone or combined with impaction bone grafting for complex acetabular defects

BackgroundRevision surgery for complex acetabular defects is still technically challenging. In this study, we discussed and compared the clinical and radiological outcomes of revision surgery between two methods using double-trabecular metal (TM) cups alone or combined with impacting bone grafting (IBG).MethodsThe records of 18 patients (18 hips) who underwent revision surgery using double-trabecular metal (double-TM) cups between 2008 and 2016 were retrospectively reviewed. All the patients were diagnosed with Paprosky III acetabular defects. The acetabular defects were reconstructed by double-TM cups alone or in combination with IBG. We used the modified Harris Hip Score (mHHS), University of California, Los Angeles (UCLA), and Short Form 36 (SF-36) to evaluate the clinical outcomes. Pelvis plain X-ray was used to assess hip center of rotation (COR), abduction angle and anteversion angle of acetabular cup, and incorporation of the bone graft to host bone.ResultsThe median follow-up time was 61.0 (IQR 56.0 to 65.8) months. No patients underwent re-revision for loosening or any other reasons. Complications included 3 patients (16.7%) with early dislocation and 3 patients (16.7%) with delayed wound healing. The average mHHS and UCLA preoperatively were 44.1 ± 4.0 (range 35 to 50) and 2.6 ± 0.7 (range 2 to 4), respectively and at the last follow-up were 73.7 ± 4.2 (range 68 to 85) and 7.3 ± 0.5 (range 7 to 8), respectively. The mean SF-36 scores at the last follow-up were improved significantly than preoperative scores, especially in bodily pain category (P < 0.05). The average limb-length discrepancy (LLD) decreased significantly from 24.2 ± 2.6 (range 20 to 32) mm preoperatively to 5.8 ± 1.8 (range 3 to 9) mm at the last follow-up, respectively. However, there was no significant difference between two methods at the last follow-up in terms of mHHS, UCLA, SF-36, LLD, and hip COR (P > 0.05). Radiographic evaluation demonstrated bone graft incorporation in all hips in the follow-up.ConclusionsDefect reconstruction using double-TM cups alone or combined with IBG are practical and reliable treatment options for Paprosky III acetabular defects without pelvic discontinuity. Nevertheless, high postoperative complication rate, especially in terms of dislocation, remains a challenge.

High Hip Center Technique in Total Hip Arthroplasty for Crowe Type II-III Developmental Dysplasia: Results of Midterm Follow-up.

ObjectivesWe aimed to show the utility of high hip center technique used in patients with Crowe II–III developmental dysplasia of the hip at the midterm follow‐up and evaluated the clinical and radiographic results between different heights of hip center.MethodsFrom December 2003 to November 2013, we retrospectively evaluated 69 patients (85 hips) with Crowe II–III dysplasia who underwent a high hip center cementless total hip arthroplasty. The patients were divided into two groups according to the height of hip center, respectively group A (≥ 22 mm and < 28 mm) and group B (≥28 mm). The survivorship outcomes and radiographic and clinical results, including the vertical and horizontal distances of hip center, femoral offset, abductor lever arm, cup inclination, leg length discrepancy, Trendelenburg sign, and limp were evaluated.ResultsThe mean follow‐up time was 8.9 ± 1.8 years. The mean location of the hip center from the inter‐teardrop was 25.1 ± 1.6 mm vertically and 30.0 ± 3.8 mm horizontally in group A, and 33.1 ± 4.8 mm vertically and 31.4 ± 6.1 mm horizontally in group B. Eleven hips of group B showed a lateralization over 10 mm, and the same was shown in one hip in group A (P = 0.012). There were no statistically significant differences between two groups in postoperative femoral offset, abductor lever arm, leg length discrepancy and cup inclination. At the final follow up, the mean WOMAC and Harris hip score were significantly improved in both groups. Of the 85 hips, four hips in group A and three hips in group B showed a positive Trendelenburg sign. Additionally, four patients in group A and two patients in group B presented with a limp. No significant differences were shown regarding the Harris hip score, WOMAC score, Trendelenburg sign, and limp between two groups. One hip of group A was revised by reason of dislocation at 8.3 years after surgery. One hip of group B was diagnosed with osteolysis and underwent a revision at 8.1 years after surgery. The Kaplan–Meier implants survivorship rates at the final follow‐up for all‐causes revisions in group A and group B were similar (96.7% [95% confidence interval, 90.5%–100%] and 96.2% [95% confidence interval, 89.0%–100%], respectively).ConclusionsThe high hip center technique is a valuable alternative to achieve excellent midterm results for Crowe II–III developmental dysplasia of the hip. Further, between the groups with differing degrees of HHC, there were no significant differences in outcomes or survivorship in our study.

Hip Arthroplasty in Patients with Hip Dysplasia by Individual Augments: Early Results

Relevance. The altered hip anatomy makes total hip arthroplasty in patients with hip dysplasia a difficult and non-standard task. The acetabulum is deformed with femoral head in subluxation or dislocation. The most important task of surgery is to restore the anatomical position of the hip center of rotation.The study purpose — to evaluate the early results of hip arthroplasty with individual augments in the patients with hip dysplasia.Materials and Methods. Since 2017, nine patients with hip dysplasia have undergone surgery using individually printed augments. All patients were women with average age 51.3±14.5 years (23 to 67). The mean follow-up was 14.3±5.2 months (8 to 20). Patients were evaluated using follow-up X-rays, a visual analogue scale (VAS), Harris Hip Score (HHS), and Western Ontario and McMaster Universities Arthritis Index (WOMAC).Results. There was no a single case of endoprosthesis dislocation, loosening of components, prosthetic infection or revision surgery in the analyzed group of patients. The planned sizes of the acetabular components were equal to the placed in 7 cases (77.8%). In two cases (22.2%), the acetabular components were 2 mm larger because the surgeon wanted a greater degree of press-fit fixation. The restoration of the anatomical position of the acetabular component was noted. Before the surgery, the femoral head was on average 22.7±11.7 mm (10 to 43 mm) higher. After the surgery, the level of the acetabular component was on average only 0.75±2.1 mm (1.7 to 5 mm), p = 0.008. Also, there were a decrease in pain and quality of life improvement by VAS from 6.78±1.39 before surgery to 2.22±1.09 at follow-up (p = 0.007), HHS increase from 30.5±18. 1 to 77.59±14.26 (p = 0.008), and WOMAC decrease from 73.3±14.1 to 18.22±8.2 (p = 0.008).Conclusion. The individually printed augments have shown high efficacy for restoration of the anatomical center of rotation and good early results in the patients with hip dysplasia undergone hip arthroplasty.

Reliability Of Quantitative Kinematics From A Portable Hand-held Device

The current gold standard for assessing kinematics is three-dimensional (3D) motion analysis. However, the equipment required to accomplish this is not generally available in sport or clinical settings. Portable handheld devices (PD) are available that synchronize multiple two-dimensional video views to qualitatively evaluate complex sport skills. However, the use of quantitative kinematic analysis on PD compared to standard computer software (CS) has not been investigated. PURPOSE: To investigate the intra- and inter-rater reliability of PD compared to an open source CS. METHODS: Twenty-seven collegiate male soccer players (height:179.8±5.6cm, mass: 75.9±6.9kg) were analyzed (120 Hz) during a drop vertical jump from a 30-cm box. PD and CS were separately used to 1) select a single frame from the frontal plane view when both knees were visually the most medial during landing and 2) digitize and record the frontal plane knee angle from hip, knee and ankle joint centers to estimate lower extremity valgus. Reliability between systems and reliability between testers were established with intraclass correlations (ICC2,k, ICC3,k, respectively). Precision was calculated with standard error of measurement (SEM). RESULTS: Intra-rater reliability was 0.993 [95% CI 0.985, 0.997] with SEM of 1.09 on the right, and 0.971 [95% CI 0.938, 0.987] SEM of 2.69 on the left limb. Inter-rater reliability on the right side was 0.979 [95% CI 0.954, 0.990] with SEM of 1.97 for the right limb and 0.978 [95% CI 0.943, 0.990] with SEM of 2.37 on the left, respectively. CONCLUSION: In collegiate male soccer players, PD exhibited excellent intra- and inter-rater reliability. The data indicates that it might be a useful tool to integrate into a screening protocol to quickly estimate lower extremity valgus. However, future analyses should compare traditional 3D motion analysis to determine validity.

Safety of a 'swing room' surgery model at a high-volume hip and knee arthroplasty centre.

The practice of overlapping surgery has been increasing in the delivery of orthopaedic surgery, aiming to provide efficient, high-quality care. However, there are concerns about the safety of this practice. The purpose of this study was to examine the safety and efficacy of a model of partially overlapping surgery that we termed 'swing room' in the practice of primary total hip (THA) and knee arthroplasty (TKA). A retrospective review of prospectively collected data was carried out on patients who underwent primary THA and TKA between 2006 and 2017 in two academic centres. Cases were stratified as partially overlapping (swing room), in which the surgeon is in one operating room (OR) while the next patient is being prepared in another, or nonoverlapping surgery. The demographic details of the patients which were collected included operating time, length of stay (LOS), postoperative complications within six weeks of the procedure, unplanned hospital readmissions, and unplanned reoperations. Fisher's exact, Wilcoxon rank-sum tests, chi-squared tests, and logistic regression analysis were used for statistical analysis. A total of 12,225 cases performed at our institution were included in the study, of which 10,596 (86.6%) were partially overlapping (swing room) and 1,629 (13.3%) were nonoverlapping. There was no significant difference in the mean age, sex, body mass index (BMI), side, and LOS between the two groups. The mean operating time was significantly shorter in the swing room group (58.2 minutes) compared with the nonoverlapping group (62.8 minutes; p < 0.001). There was no significant difference in the rates of complications, readmission and reoperations (p = 0.801 and p = 0.300, respectively) after adjusting for baseline American Society of Anesthesiologists scores. The new 'swing room' model yields similar short-term outcomes without an increase in complication rates compared with routine single OR surgery in patients undergoing primary THA or TKA. Cite this article: Bone Joint J 2020;102-B(7 Supple B):112-115.

Anthropometric And Kinematic Predictors Of Base Of Gait During Running

A narrow base of gait (BOG) during running, such that the foot crosses contralateral to the body’s line of gravity, has been implicated as a cause of iliotibial band syndrome and patellofemoral pain. BOG has been shown to vary by sex and running speed, but it is unknown if body anthropometric and running kinematic measures predict BOG. Determining predictors of BOG will clarify if BOG is a result of non-modifiable anthropometric factors or biomechanical factors, which could be modified using targeted interventions. PURPOSE: To determine if BOG at midstance during running can be predicted by anthropometric or kinematic measures. METHODS: Whole body kinematics were obtained for 71 Division I cross country runners (30 males) during treadmill running at preferred speed. Athletes were healthy with no history of stress fracture 3 months before testing or any history of lower extremity surgery. Anthropometric measures from each athlete were obtained from whole body dual-energy X-ray absorptiometry scans: greater trochanteric (GTR) and hip joint center width; leg and femur length. Kinematic measures during stance phase included: peak lateral pelvic drop, hip adduction (HADD), knee flexion (KFLEX); vertical excursion of center of mass (vCOM); anterior-posterior distance from heel to COM at initial contact. Correlations between predictors and BOG were calculated, with variables moderately correlated or better (|r| ≥ 0.3) included in subsequent analyses. Data from both limbs were included in a forward, stepwise regression to determine predictors of BOG, controlling for sex and speed. RESULTS: Stride length, vCOM, peak KFLEX and HADD, GTR width, and leg and femur length (|r| = 0.32 - 0.51) were entered into the model. The model with the best overall fit included all predictors except leg length (R2 = 0.383, BIC: -32.1). The strongest predictors were GTR width (β = -0.27), vCOM, (β = -0.18), and peak HADD (β = -0.17). CONCLUSIONS: Biomechanical and anthropometric measures explain less than 40% of the variance in BOG. Given that GTR width is the strongest predictor of BOG and is non-modifiable, BOG appears to be largely influenced by an individual’s anthropometrics. Conversely, vCOM and peak HADD are modifiable through gait retraining strategies such as step rate modification and may be targeted in those where narrow BOG is a concern.

Association between total hip arthroplasty following periacetabular osteotomy and acetabular component overhang.

There is limited understanding of anterior acetabular component overhang, which induces groin pain, in post-periacetabular osteotomy (PAO) hips during conversion to total hip arthroplasty (THA). The aim of the study were to determine the following: (1) the differences in the amount of acetabular component overhang among pre-PAO hips and post-PAO hips in simulating THA; (2) the factors associated with the amount of component overhang in THA following PAO; (3) whether high component placement with elevation of the hip center by 10mm reduces the amount of component overhang compared to the anatomical component position in THA following PAO. Computer-based simulations of acetabular component implantation were performed using preoperative and postoperative CT data from 30 patients undergoing PAO. Implantation was performed thrice in each patient: in pre-PAO hips (anatomical component position) and post-PAO hips (anatomical and high component position). Component overhang was measured on the axial plane, which passes through the component center. Overhang was greater in post-PAO hips [mean (SD) overhang: 5.2 (2.9) mm, pre-PAO hips: 10.2 (4.6) mm, post-PAO hips-mean difference, 5.0mm; p < 0.001]. A smaller distance between the pubic osteotomy and the acetabulum, and greater overhang in pre-PAO hips was independent factors associated with increased overhang in post-PAO hips. Overhang was smaller with the high component position than with the anatomical component position in post-PAO hips [mean (SD) overhang-3.5mm (2.9) with high component position among post-PAO hips; mean difference, 6.6mm; p < 0.001). Ten post-PAO hips with the anatomical component position had overhang of at least 12mm (the likely threshold for groin pain). Of these, 9 hips had reduced overhang (< 12mm) with the high component position. Acetabular component overhang was more severe in THA following PAO than in THA without prior PAO. Pubic osteotomy should be performed closer to the acetabular rim to prevent severe overhang in potential THA conversion cases. A high component position decreased the risk of severe overhang.

Surgical Approach and Reaming Depth Influence the Direction and Magnitude of Acetabular Center of Rotation Changes During Total Hip Arthroplasty.

BackgroundChanges in acetabular or hip center of rotation (HCOR) commonly occur during acetabular component preparation during total hip arthroplasty (THA). HCOR displacement in mediolateral or superoinferior directions is known to influence offset and leg length, but the incidence and range of HCOR change in the anteroposterior direction is less understood as the sagittal plane cannot be measured on standard anteroposterior radiographs. This study assessed the 3-dimensional displacement of HCOR after cup implantation and evaluated for potential factors associated with increased acetabular component translations.MethodsA total of 894 THAs were performed using a posterior, lateral, or direct anterior approach. Only intraoperative data from the navigation device were included in the analysis. All THAs performed between September 2015 and October 2017 were included. Paired t-tests were used to compare native HCOR and new HCOR values.ResultsThe mean HCOR displacement in 3 directions was 4.97mm medially (P < .001), 0.83mm superiorly (P < .001), and 0.64mm posteriorly (P < .001). Subgroup analysis revealed greater posterior HCOR displacement with the anterior approach than the lateral/posterior approach (2.32mm vs 0.44mm; P < .001). Increasing medial HCOR displacement also resulted in increased superior and posterior HCOR displacement across surgical cases (P < .001).ConclusionsHCOR displacement is commonly observed in medial, superior, and posterior directions. HCOR changes are influenced by surgical approach, potentially secondary to patient positioning, with greater posterior HCOR displacement observed in anterior cases. Surgeons should be aware of these factors, particularly in cases with deficient or reduced posterior column bone stock.

A strathclyde cluster model for gait kinematic measurement using functional methods: a study of inter-assessor reliability analysis with comparison to anatomical models

A major source of error in reliability of gait analysis arises from the palpation of anatomical landmarks (ALs). The purpose of this study was to investigate whether less reliance on manually identifying ALs could improve inter-assessor reliability of joint kinematics compared to two anatomical models. It was hypothesised that the Strathclyde functional cluster model (SFCM), in which the hip, knee and ankle joint centres and knee and ankle flexion axes were determined by functional methods, would obtain greater inter-assessor reliability. Ten able-bodied participants and seven assessors were recruited. Each participant completed three trials conducted by different assessors on non-consecutive days. Agreement and inter-assessor reliability between the models were compared and analysed, whilst factor effects of assessor experience and body mass index (BMI) were investigated. The SFCM obtained excellent agreement with anatomical models for all sagittal angles and hip ab/adduction angle, and it showed slightly higher inter-assessor reliability with smaller variations in the knee and ankle. The assessor experience was not a significant factor, but the BMI had a significant effect on the inter-assessor reliability. The results demonstrate that the SFCM may be more beneficial for less experienced assessors.

Surgical Technique and Case Series of Total Hip Arthroplasty with the Hueter Anterior Approach for Crowe Type-IV Dysplasia.

Total hip arthroplasty (THA) is being increasingly performed via the Hueter anterior approach (HAA), which has proven benefits with nondysplastic hips; however, little has been published on its outcomes with dysplastic hips, where it can provide better acetabular exposure. We describe our technique for THA via the HAA in hips with Crowe type-IV developmental dysplasia and report the mid-term outcomes of cases that were performed over 5 consecutive years. We retrospectively evaluated a continuous series of 8 hips (6 patients) with Crowe type-IV dysplasia; the patient ages ranged from 44 ± 20 years (range, 17 to 65 years) at the index THA. All of the patients received uncemented implants via the HAA on a traction table to restore the hip center of rotation to the true acetabulum. Femoral head autografts (FHAs) were used to increase acetabular coverage in 6 hips, and subtrochanteric shortening osteotomies (SSOs) were performed in 5 hips. Patients were assessed clinically and radiographically at a minimum follow-up of 2 years. There were no revisions, deaths, dislocations, or infections. Two hips (25%) had intraoperative complications, and 1 hip (13%) had a postoperative complication that required reoperation without implant removal. All of the hips were assessed clinically and radiographically at 4 ± 1 years (range, 2 to 6 years). The modified Harris hip score (mHHS) improved from 33 ± 7 to 90 ± 7, and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) improved from 53 ± 14 to 89 ± 6; the postoperative leg-length discrepancy was 3.2 mm (range, -10 to 20 mm). None of the hips had osteolysis or radiolucent lines of >2 mm. THA via the HAA on a traction table for hips with Crowe type-IV dysplasia yielded satisfactory mid-term outcomes. Both FHA and SSO can be adequately performed via the HAA to help restore the hip center of rotation to the true acetabulum. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.