BACKGROUND:The influence of femoral offset on the survival of cementless femoral stems in total hip arthroplasty (THA) remains unclear. This study aimed to evaluate the influence of total femoral offset (TFO - stem plus head) on the risk of revision for early aseptic femoral loosening (AFL) and all-cause revision (ACR). METHODS:A retrospective cohort study was conducted using data from a national registry for all primary, cementless THAs performed for osteoarthritis between 2012 and 2024 with the five most common stem designs. The final cohort consisted of 93,027 hips, and a total of 419 revisions for AFL and 2,592 for ACR were observed. The primary exposure was TFO, analyzed as both a continuous variable and as three categories (less than 42 mm, 42 to 48 mm, and greater than 48 mm). The primary endpoint was revision surgery for AFL, and the secondary endpoint was ACR. Kaplan-Meier survival analyses and multivariable Cox proportional hazards models were used to estimate survival and hazard ratios (HRs) while adjusting for confounders. RESULTS:The 10-years implant survival for AFL was significantly lower in the high-offset group (98.9%, 95% confidence interval (CI) 98.6 to 99.1) compared to the standard (99.3%, 95% CI 99.2 to 99.4) and low-offset groups (99.5%, 95% CI 99.4 to 99.6; P < 0.001). After adjusting for confounders, the risk of revision for AFL increased by 4.1% for every 1-mm increase in TFO (HR 1.04, 95% CI 1.02 to 1.06). The high-offset group (greater than 48 mm) had a significantly increased risk of revision for AFL (HR 1.83, 95% CI 1.28 to 2.63) and ACR (HR 1.20, 95% CI 1.04 to 1.38). CONCLUSIONS:In this registry population, higher TFO combinations are associated with an 83 and 20% increased risk of revision for aseptic femoral loosening and a risk of all-cause revision following cementless THA. Collars were associated with a 50% reduction in revision risk.

Background The influence of collar design on femoral stem survival in total hip arthroplasty (THA) remains debated despite its potential biomechanical advantages. This registry analysis investigated whether collared stems demonstrate superior survival compared to non-collared designs in primary THA. Methods A retrospective cohort study using national database data from 2012 to 2024 was conducted. A total of 168,493 primary THAs performed for osteoarthritis in patients aged ≥ 50 years, were analyzed, comprising 143,427 (85.1%) non-collared and 25,066 (14.9%) collared cementless femoral stems. The primary outcome was revision for aseptic femoral loosening (AFL), with all-cause revision as a secondary outcome. Kaplan-Meier survival analysis and multivariable Cox proportional hazards models were used to assess outcomes up to a 10-year follow-up period, adjusting for age, body mass index, sex, American Society of Anesthesiologists score, and surgical approach. Results At 10 years, collared stems demonstrated significantly higher survival rates for both AFL (99.3%, 95% confidence interval (CI) 99.1 to 99.6 versus 98.9, 95% CI 98.9 to 99.0, P < 0.001) and all-cause revision (96.8%, 95% CI 96.4 to 97.3 versus 95.3%, 95% CI 95.2 to 95.5, P < 0.001). After adjusting for confounders, collared stems were associated with a 42% reduced risk of revision for aseptic loosening (hazard ratio (HR) 0.58, 95% CI 0.43 to 0.78) and a 35% reduced risk of all-cause revision (HR 0.65, 95% CI 0.59 to 0.73) compared to non-collared stems. Conclusion This large-scale registry analysis provides compelling evidence that collared femoral stems are associated with significantly lower rates of both aseptic loosening and all-cause revision risk in THA. These findings suggest that collared stems may represent a favorable option for improving outcomes in primary THA for osteoarthritis, though future research incorporating radiological assessment and patient-reported outcomes would further enhance our understanding of this design feature's clinical impact.

Abstract Purpose This study aims to investigate the relationship between anterosuperior labral hypertrophy and other morphological parameters in hips with radiographically sufficient lateral coverage. Our hypothesis is that anterior undercoverage or combined high values of femoral torsion and acetabulaer version, represented as an increased McKibbin Index, would be associated with localized anterior labral hypertrophy. Methods This was a retrospective case‐control study at a single institution. A consecutive cohort was screened between January 2014 and September 2024 that received either magnetic resonance imaging (MRI) or MR‐arthrography of the hip. Only hips with normal lateral centre edge angle values (between 25° and 40°) were included. Previously described radiographic parameters were evaluated: femoral torsion, acetabular version, Tönnis angle, anterior wall index (AWI), posterior wall index (PWI), McKibbin Index and labral height‐to‐length ratio on axial planes as a measure of anterior labral hypertrophy. Statistical analysis included χ2 test, Fisher's exact test, Pearson and partial Pearson correlation analysis, as well as univariate and multiple regression analysis. A total of 132 patients were included in the study, of whom 51 (39%) exhibited anterosuperior labral hypertrophy (labral height‐to‐length ratio of less than 1:2). Results The McKibbin Index demonstrated a significant negative correlation with the labral height‐to‐length ratio on the axial plane (r = –0.182, p = 0.018), indicating greater labral hypertrophy with increased combined femoral and acetabular anteversion. Femoral torsion showed a similar association (r = –0.167, p = 0.028). Using the multiple regression analysis, the McKibbin Index remained significant in variable exclusion testing (p = 0.037), supporting its relevance to labral morphology. Conclusion Our findings highlight the correlation of the increased McKibbin index with anterosuperior labral hypertrophy and suggest relevant implications of the global rotational alignment, including both the acetabular version and femoral torsion on joint and labral biomechanics. Level of Evidence Level IV.

Background: Acetabular impaction bone grafting (IBG) is used to address bone loss in revision total hip arthroplasty (rTHA). We evaluated graft incorporation and cup migration after acetabular IBG in rTHA. Methods: Systematic search of MEDLINE, EMBASE, and Scopus from inception to June 30, 2024 (PROSPERO CRD42024557047). Studies of acetabular IBG in rTHA with ≥12-month follow-up were included. Outcomes were graft incorporation and horizontal (i.e., lateral to medial axis) and vertical cup migration. Prespecified subgroup analyses assessed bone-loss severity, graft type, additional fixation, and age. Random-effects meta-analyses were used; heterogeneity was quantified with I2. Risk of bias was assessed with the Methodological Index for Non-Randomized Studies. Results: Nineteen studies (1093 hips) were included; weighted follow-up was 8.0 years (range 2.0-16.9). Pooled graft incorporation was 89% (95% CI [confidence interval] 79-96; I2 85%). Mean lateral migration was 2.4 mm (95% CI 0.53-4.27) and mean superior migration 4.2 mm (95% CI 1.61-6.75); heterogeneity was high (I2 100% for both). Lateral migration was greater in cohorts with ≥5 years’ follow-up than <5 years (3.65 vs 1.16 mm; P = .018). No significant differences in incorporation were detected by bone-loss severity, graft type, or age; however, subgroup analyses were frequently underpowered and exploratory. Conclusions: Acetabular IBG can achieve mid- to long-term graft incorporation of 89%, but estimates are imprecise due to heterogeneous (I2 = 85%), predominantly retrospective evidence. Migration occurs—most commonly cranial—and may accrue over time; values often remain within commonly accepted surveillance thresholds but warrant structured radiographic follow-up. Given high heterogeneity, variable outcome definitions, and potential small-study/publication bias, recommendations should be interpreted cautiously.

Introduction:Calcium sulfate (CS) has emerged as a local antibiotic delivery system, offering biodegradability, osteoconductive properties and sustained antibiotic release. The aim was to evaluate the clinical outcomes and safety of antibiotic-loaded CS beads as an adjunct in the management and prevention of orthopaedic infections. Methods:The systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies reporting outcomes on the use of antibiotic-loaded CS beads in orthopaedics were considered eligible. Risk of bias assessment was performed using the methodological index for non-randomized studies (MINORS) criteria. Evaluated outcomes included rates of infection eradication or incidence, bone union, CS resorption, complications and reinterventions. Exploratory meta-analyses used a random-effects model, with heterogeneity assessed via the I2 statistic. Results:The systematic search included 41 studies. No randomized controlled trials were identified. Twenty-three studies examined patients with osteomyelitis, yielding a pooled infection eradication rate of 88% (95% CI: 85 to 90%; I2 = 19%). Among patients with infected nonunion, the pooled bone union rate was 93% (95% CI: 85 to 97%; I2 = 36%). In patients with periprosthetic joint infections (PJI), the pooled infection eradication rate reached 88% (95% CI: 76 to 95%; I2 = 87%). Wound-related complications were documented in 17% (189/1086) of osteomyelitis cases, compared to 8% (23/277) of PJI cases. PJI treatment was associated with minimal complications, including 12 cases of hypercalcemia (12/277, 4%) and nine cases of heterotopic ossification (9/262, 3%). Conclusion:Current evidence describes favorable infection eradication rates when antibiotic-loaded CS beads are used as an adjunct in orthopaedic infection management and prevention, but the absence of comparative trials precludes conclusions regarding independent efficacy. All studies showed complete CS resorption. Wound-related complications were substantial in osteomyelitis cases, while other adverse events were rare. Higher-quality comparative studies are required before routine adoption.

To evaluate the incidence of surgical complications, particularly periprosthetic fractures, following femoral impaction bone grafting (fIBG) in revision total hip arthroplasty (rTHA). This systematic review followed PRISMA guidelines. Studies reporting on fIBG in rTHA with a minimum follow-up of 12 months were included. Risk of bias was assessed using the Methodological Index for Non-Randomised Studies (MINORS). A random-effects meta-analysis with inverse-variance weighting was performed. Heterogeneity was assessed using Higgins and Thompson’s I2 statistic and Cochran’s Q test. Subgroup analyses were conducted based on patient characteristics, revision indication, follow-up period, bone loss severity, stem length, and cementation. Complications requiring intervention, as well as nerve lesions with partial or no recovery, were classified as major. Forty-five studies including 4,686 hips (4,409 patients) were analyzed. The pooled incidence of major complications was 21

BACKGROUND:The Trendelenburg and Duchenne signs are commonly used to clinically assess hip abductor function. Previous studies, however, have shown only a partial reduction of functional abduction force after paralyzing the gluteus medius and minimus. This study aimed to investigate the effects of experimentally induced sequential paralysis of the tensor fasciae latae, gluteus medius and minimus, and gluteus maximus on the Trendelenburg and Duchenne signs. METHODS:Ten healthy adults received sequential nerve blocks of the branch of the superior gluteal nerve to the tensor fasciae latae, the branch of the superior gluteal nerve to the gluteus medius and minimus, and the inferior gluteal nerve supplying the gluteus maximus. After each block, participants performed a ten-second single-leg stance recorded with 56 skin markers and 27 cameras. Pelvic drop and spinal obliquity were analyzed to determine the presence of a Trendelenburg or Duchenne sign. FINDINGS:Paralysis of the tensor fasciae latae resulted in compensatory mechanisms in 2 of 10 participants. Following paralysis of the gluteus medius and minimus, 5 of 10 could not maintain single-leg stance for ten seconds and one exhibited a Trendelenburg sign. Gluteus maximus paralysis led to failure in 5 of 10 participants, with two showing a Duchenne sign. INTERPRETATION:Our study demonstrates that the Trendelenburg and Duchenne signs lack both sensitivity and specificity and should not be solely attributed to gluteus medius and minimus weakness. Importantly, impairment of the gluteus maximus may also produce similar compensatory patterns or mask abductor deficits.

Purpose:3D bone surface model reconstructions of CT exams are used for surgical planning. However, the accuracy of these models in tin-filtered ultra-low-dose CT examinations is unknown. Thus, we evaluated the accuracy of 3D-reconstructed bone models obtained from tin-filtered ultra-low-dose CT (tfCT) compared to standard CT (sCT) and calculated the radiation dose reduction. Materials and Methods:IRB-approved prospective study with informed consent. Patients undergoing a pelvic sCT examination were scanned additionally with tfCT. 3D surface model reconstructions (left and right hemipelvis, and left and right proximal femur) of both scans were created, for each patient independently by two readers. The average error between the surface models of both methods was obtained using root mean square error (RMSE). The dose parameters that were used were volume CT dose index (CTDIvol) and dose length product (DLP). Radiation dose differences of both scans were evaluated using the Wilcoxon signed-rank test. Results:23 subjects (9 males and 14 females; mean age 31±8 years) were included. The mean RMSE was 0.47-0.48 mm for the right hemipelvis (left hemipelvis: 0.48-0.5 mm) and 0.52-0.56 for the proximal right femur (left femur: 0.5-0.57 mm). The average CTDIvol was 8.19±4.45 mGy for sCT examinations and 1.09±0.02 mGy for tfCT exams. The mean DLP was 220.45±124.36 mGy*cm for sCT examinations, and 29.12±1.54 mGy*cm for tfCT exams. The average CTDIvol and DLP were substantially lower (-87%) for tfCT compared to sCT (p<0.001). Conclusion:3D surface model reconstruction from tfCT is feasible and has similar accuracy to that of sCT but with a substantially lower radiation dose. Key Points:· Pelvic 3D bone surface model reconstructions are feasible with tin-filtered ultra-low-dose CT.. · Reconstructions from tin-filtered ultra-low-dose CT have a similar accuracy as standard CT.. · Tin-filtered ultra-low-dose CT has a significantly lower radiation dose than standard CT.. Citation Format:· Falkowski AL, Carrillo F, Novina D et al. 3D bone reconstruction of the pelvis and hip through segmentation of tin-filtered ultra-low-dose CT compared with standard CT - a feasibility study. Rofo 2026; DOI 10.1055/a-2811-9609.

The acetabular cup version in patients with total hip arthroplasty (THA) is a key parameter influencing hip stability and functional outcomes. Although CT remains the reference standard for assessing cup orientation, MRI with metal artifact reduction techniques is increasingly used for evaluating postoperative pain. This study compared MRI- and CT-based measurements of acetabular cup version regarding agreement, reproducibility, and reliability. Patients who underwent THA between 2015 and 2025 with postoperative CT and MRI were retrospectively analyzed. MRI was performed using optimized metal artifact reduction sequences. Acetabular cup version was measured on axial high-bandwidth T1-weighted turbo spin-echo sequences and on corresponding CT scans by two musculoskeletal radiologists. Inter- and intra-reader, as well as inter-modality agreement, were assessed using intraclass correlation coefficients (ICC). Bland-Altman plots evaluated systematic bias. Thirty patients were included (mean age, 64.1 years; 14 women). Mean acetabular version was 31.2° (standard deviation (SD), 9.4–10.3) for CT and 30.1–30.2° (SD, 8.9–9.3) for MRI for both readers. Inter-reader agreement was almost perfect for CT (ICC, 0.96) and substantial for MRI (ICC, 0.76). Intra-reader agreement was almost perfect for both modalities (ICC, CT, 0.99; MRI, 0.94). Bland-Altman analysis showed no statistically significant differences between CT and MRI measurements with a slight positive bias for MRI (mean pooled difference, 1.1°; p = 0.058; limits of agreement, −4.7 to 6.8°) and almost perfect agreement for both readers (ICC, 0.86–0.90). MRI measures acetabular cup version with excellent reliability and close agreement with CT, reinforcing MRI’s role in postoperative THA evaluation.

Background:The anteroposterior radiograph of the pelvis is essential for diagnosing hip pathologies. Radiograph-like projections reconstructed as cone-beam images from CT data correlate strongly with conventional radiographs. However, CT inherently uses parallel x-rays rather than a cone-beam geometry. This study aims to determine whether parallel-beam radiograph-like projections from CT provide comparable reference values to cone-beam reconstructions. Methods:63 patients (126 hips) undergoing CT for symptomatic hip pathologies without prior hip surgery were included. From the same CT data, cone-beam and parallel-beam radiograph-like images were reconstructed using a standardized algorithm. Reference values, including lateral center-edge angle (LCEA), medial center-edge angle (MCEA), acetabular index (AI), acetabular arc (AA), extrusion index (EI), crossover sign, and posterior wall sign, were measured on both projection types, eliminating technical bias. Two observers performed all measurements twice to assess inter- and intra-observer reliability, and intraclass correlation coefficients (ICCs) were calculated. Results:126 hips were analyzed: 52 with LCEA <22° ("acetabular undercoverage"), 49 with LCEA 22°-33° ("normal coverage"), and 25 with LCEA >33° ("acetabular overcoverage"). ICCs between observers and between projection types demonstrated good to excellent reliability for all reference values (0.89-0.99). Conclusion:Parallel-beam radiograph-like projections demonstrate good to excellent reliability (ICCs: 0.89-0.99) for key reference values of hip pathologies compared to cone-beam radiograph-like projections from the same CT data. These findings suggest parallel beam projections can be reliably used with established reference values for conventional radiographs.

Femoral impaction bone grafting (IBG) is an established technique for managing severe bone loss during revision total hip arthroplasty (rTHA). Despite its widespread use, the extent of graft incorporation and the degree of stem subsidence remain incompletely characterized. This systematic review evaluates graft incorporation and stem subsidence outcomes in femoral IBG for rTHA. A systematic review was conducted following the PRISMA (Preferred Reporting Items for Systematic reviews and Meta–Analyses) guidelines. Three databases were searched from inception to December 31, 2024, for studies involving rTHA with femoral IBG and a minimum follow–up of 12 months. Meta–analyses focused on graft incorporation rates and stem subsidence. Subgroup analysis examined age, pre–operative bone loss, graft type, follow–up duration and other predictors. Heterogeneity was assessed using the I2 statistic under a random–effects model. A total of 33 studies (2395 patients; 2514 hips) met inclusion criteria. The mean patient age was 66 years (range 22–95 years), with a male–to–female distribution of 48

Background: Identifying hip instability in symptomatic patients with borderline dysplasia of the hip (BDH) is of paramount importance, as it can influence both surgical decision-making and surgical outcomes. The femoroepiphyseal acetabular roof (FEAR) index is strongly affected by the hip adduction/abduction angle during the pelvic radiograph, which has not yet been considered in the recommended threshold values. Purpose: To compare the corrected FEAR index in symptomatic patients with BDH treated with pelvic periacetabular osteotomy (PAO) or hip arthroscopy. Study Design: Cohort study; Level of evidence, 3. Methods: Patients with symptomatic hips and radiographical BDH were categorized into 2 cohorts. The first cohort included patients treated with PAO (n = 42) and the second cohort consisted of patients treated with hip arthroscopy due to symptomatic femoroacetabular impingement (n = 50). All patients presented with good patient-reported outcomes at the final follow-up. The FEAR index was measured on the pelvic radiograph at the initial hip adduction/abduction angle (uncorrected FEAR index) and after correcting the hip abduction angle to 0° (corrected FEAR index). Negative values of the FEAR index represent a lateral closing angle, whereas positive values represent a lateral opening angle. As for the hip adduction/abduction angle, negative values represent adduction, whereas positive values represent abduction. Results: The corrected FEAR index varied significantly from the uncorrected FEAR index in both groups with a mean difference of 6°± 4° in patients treated with PAO and 5°± 5° in patients treated with hip arthroscopy. The corrected FEAR index in patients with BDH treated with hip arthroscopy (−11°± 8°) was significantly lower ( P < .001) compared with the patients with BDH treated with PAO (−7°± 7°) (Table 1). The optimal threshold for the corrected FEAR index was −13° (odds ratio, 7.8 [95% CI, 2.6-23.1]; P < .001), which yielded a sensitivity of 85% and a specificity of 52%, distinguishing the 2 surgical cohorts. Conclusion: The corrected FEAR index might vary significantly from the uncorrected FEAR index, which is highly dependent on the hip adduction/abduction angle during the pelvic radiograph. Symptomatic patients with BDH treated with PAO exhibit a corrected FEAR index of ≥–13° compared with those with BDH treated with hip arthroscopy for impingement symptomatology.

BACKGROUND:Femoral impaction bone grafting (IBG) is widely used in revision total hip arthroplasty for cases with severe bone loss. The purpose of this systematic review and meta-analysis was to assess survivorship and patient-reported outcome measures (PROMs) following femoral IBG. METHODS:The systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies reporting on femoral IBG in revision total hip arthroplasty with a minimum follow-up of 12 months were included. A random-effects model and the inverse-variance weighting method were used for meta-analysis. Heterogeneity was assessed using Higgins and Thompson's I2 statistic and Cochran's Q test. RESULTS:The systematic search included a total of 45 studies, comprising 4,102 hips in 3,805 patients. The overall 10-year survivorship for femoral IBG was 95% (confidence interval 92 to 97), with significant data heterogeneity (I2 = 79%, P < 0.01). Patients who had higher Endo-Klinik (EK) grades of femoral bone loss (III and IV) had significantly lower 10-year survival rates (90.9 versus 97.4% for EK grades I and II, P = 0.048). Neither patient age (≥ 65 years: 94.5 versus < 65 years: 96.6%, P = 0.23) nor stem length (short stems: 95.5 versus long stems: 94.8%, P = 0.86) significantly affected 10-year survival outcomes. PROMs included the Harris Hip Score, which notably improved postsurgery (standardized mean difference: 10.7, 95% confidence interval: 8.26 to 13.05, I2 = 99%). CONCLUSIONS:Hip revision arthroplasty with femoral IBG demonstrates high long-term (10-year) survivorship rates (95%, 92 to 97%, I2 = 79%) and significant improvements in PROMs, specifically the Harris Hip Score (I2 = 92%), especially in cases with moderate bone loss (EK stages I and II). There was a lower survivorship (90%) in hips with severe bone defects (EK stages III and IV), regardless of additional fixation.

Introduction Lunges are commonly used in resistance training and rehabilitation as functional closed kinetic chain exercises. The gluteal muscles play a critical role in stabilizing the hip and pelvis during such movements. Research question How does selective experimentally-induced gluteal muscle paralysis affect joint kinematics, joint reaction forces (JRFs), and dynamic balance during lunge performance? Methods Ten healthy adults underwent sequential blocks of 1) branch of the superior gluteal nerve to the tensor fasciae latae (SGNtfl) muscle, 2) superior gluteal nerve (SGN), and 3) inferior gluteal nerve (IGN) on the dominant right leg. Participants performed forward lunges under control and post-block conditions. Kinematic data were recorded using a 3D motion capture system, ground reaction forces were collected via dual force plates, and joint reaction forces were estimated using musculoskeletal modeling. Results For the affected right leg leading the lunge, SGN and IGN blocks resulted in a significantly higher lunge position (SGN: + 45 mm; IGN: + 33 mm), driven by reduced right knee and ankle flexion and diminished left hip extension. Following the SGN block, pelvic flexion and rotation toward the affected (right) side were observed. JRFs were significantly reduced in the right hip, knee, and ankle (average maximum difference hip: 100 % BW, knee: 200 % BW, ankle: 50 % BW). Conclusion Despite altered mechanics and reduced joint loading following selective gluteal paralysis, participants were able to complete the lunge task, even if the lunge position was higher, and compensatory pelvic flexion and rotation towards the affected side occurred.

Purpose:Previous studies have shown that rotational osteotomy of the femur reliably corrects anatomical torsion but may result in a ±1 cm antero-posterior shift of the greater trochanter (GT) per 10° of torsional correction. It is unclear whether an inadvertent displacement of the GT following surgical treatment of femoral maltorsion affects the hip abductors in a clinically relevant manner and needs to be addressed by compensatory digastric trochanteric osteotomy. The aim of this study was to investigate the influence of rotational subtrochanteric osteotomy on hip abductor force generation using three-dimensional (3D) surface models. Methods:A 3D statistical shape model (SSM) of a hip/femur was used. From a baseline value of 12°, the SSM was derotated/rotated in 10° increments, creating five different scenarios of anatomical femoral torsion: 32°, 22°, 12° (baseline), 2°, -8° (corresponding to 8° of retro torsion). The origins and insertions of the gluteus medius (GMed) and minimus (GMin) muscles were created. The hip abductor moment was defined as the muscle force (of the hip abductor muscles) multiplied by the force ratio in the direction of abduction (FRDA) multiplied by the lever arm. All values were measured, whereas muscle strength was defined as the length of the muscle fibres in relation to their optimal length. Results:Results indicated minimal changes in muscle length (±1.2%) and FRDA (1.7% to -7%) for GMed und GMin across all scenarios. However, lever arm demonstrated variations (21% to -10%), with an increase observed for derotational osteotomies and a decrease for rotational osteotomies. Conclusion:Subtrochanteric osteotomy in the management of femoral maltorsion affects the hip abduction moment solely through the altered lever arm. A 20° derotation for increased femoral torsion (FT) corresponds to a 20% increase in abduction force of the GMed (improved lever arm), whereas a 20° rotation for decreased FT reduces the abduction force by 10%. Level of Evidence:Level III, diagnostic.

BACKGROUND:The purpose of the present study was to investigate the effects of an experimentally induced weakness of the gluteal muscles on joint kinematics, reactions forces, and dynamic balance performance using the center of mass during stair climbing. METHODS:Ten healthy adult volunteers received sequential blocks of superior gluteal nerve to tensor fascia lata, superior, and inferior gluteal nerve on their dominant right leg. A full-body movement analysis during stair climbing was performed. A two-way repeated measured analysis of variances were applied to compare the average rotational kinematics, joint reaction forces and center of mass. FINDINGS:Following superior gluteal nerve block, 50 % of healthy participants couldn't complete the task. In participants who completed the task, their joint kinematics were significantly different compared to the control condition, demonstrating more hip flexion (average maximum difference at 50 %: 15 ± 14°, p < 0.05) and more internal rotation (average maximum difference at 20 %: 8 ± 5°, p < 0.05) than in the control condition. Significantly lower joint reaction forces were observed following superior und inferior gluteus nerve blocks at the hip compared to the control condition (up 110 % of body weight average maximum difference, p < 0.05). Participants demonstrated also an increased displacement of their center of mass in the mediolateral direction during both stair-ascent and descent under the superior and inferior gluteal nerve block. INTERPRETATION:A weakness in the hip abductors severely affected stair climbing performance. Those who managed to complete the task demonstrated abnormal kinematics, reduced joint reaction forces, and poorer dynamic balance.

Hip abductors are essential for hip function. To understand abduction weakness, it is important to know which muscles contribute to abduction force. Our aim was to investigate the effects of an experimentally induced weakness of the different muscles (tensor fasciae latae [TFL], gluteus medius and minimus (Gmed/min), gluteus maximus [Gmax]) on the abduction force. Ten participants received sequential nerve blocks of the TFL, the Gmed/min, and the Gmax. Subsequently, abduction force was measured in the lateral decubitus position in three sagittal positions of the hip (30° flexion, neutral, 30° extension). In 30° flexion, the average abduction force was 220 N without block, 187 N with block of the TFL, 83 N with block of the Gmed/min, and 97 N with block of the Gmax, respectively. In neutral position, average abduction force was 213 N without block, 200 N with block of the TFL, 82 N with block of the Gmed/min, and 115 N with block of the Gmax, respectively. In 30° extension, average abduction force was 116 N without block, 146 N with block of TFL, 61 N with block of the Gmed/min, and 94 N with block of the Gmax, respectively. An induced weakness of the TFL reduces abduction force only in 30° of hip flexion by 15%. It is not highly relevant as an abductor. An induced weakness of the Gmax reduces abduction force in flexion by 43%-56%, depending on the position. It is, therefore, highly relevant as an abductor of the hip.

Introduction: Chronic hip abductor insufficiency is a rare debilitating condition. In cases refractory to conservative treatment and not amenable to direct repair an augmentation becomes necessary. The preferred salvage method at our institution is augmentation with the anterior third of the gluteus maximus tendon. The aim of this study is to describe the results of 8 patients, treated for painful chronic hip abductor insufficiency with gluteus maximus muscle transfer, after a minimal follow-up of 24 months including a full clinical and MRI evaluation of the hip abductors pre- and postoperatively. Methods: We retrospectively reviewed a consecutive series of 8 patients who were surgically managed for painful chronic hip abductor insufficiency. All patients had a Trendelenburg sign, impaired muscle strength (M <= 3) as well as a complete avulsion of the hip abductors with marked fatty degeneration (>= 3). Pain levels, muscle strength, functional scores as well as a postoperative MRI was obtained after a minimal follow-up of 24 months Results: The mean age of the patients was 69 years, mean follow-up was 35 (26-54) months. Pain was significantly reduced postoperatively to VAS 2.5 from VAS 5 (p = 0.046). Trendelenburg sign remained positive in all patients and hip abductor strength did not improve significantly from 2.4 to 3.1 (p = 0.19). Complete healing of the transferred tendon was confirmed by MRI in all patients at last follow-up. Conclusions: In the setting of painful chronic hip abductor insufficiency refractory to conservative treatment with advanced muscle degeneration without the possibility of a direct reconstruction the gluteus maximus tendon transfer significantly decreased pain. The effect on hip abductor strength and patient-reported functional outcome scores is limited. Despite the modest results it remains our preferred salvage treatment option for lack of better alternatives. Larger studies are necessary to confirm these findings.

Purpose Lateralized stems in primary cementless total hip arthroplasty (THA) showed to be associated with aseptic femoral loosening. However, femoral head length also affects femoral offset but was not considered so far. This study analyzed the impact of high femoral offset (hFO) combinations, formed by lateralized stems or large femoral head lengths, on aseptic femoral component loosening. Methods Retrospective cohort study was performed including all patients that underwent primary cementless THA at our institution between July 2004 and December 2016. Patients were screened for aseptic femoral component loosening and grouped in aseptic loosening (AL) and non-aseptic loosening (nAL) group. Medical records were screened; implant details were noted and classified in hFO and standard femoral offset (sFO) combinations. Supposed risk factors for aseptic loosening were analyzed. Results Two thousand four hundred fifty-nine THA could be included, containing 14 THA (0.6%) with aseptic femoral component loosening. The AL group contained 11 hFO combinations (78.6%), whereas in the nAL group, 1315 hFO combinations (53.8%) were used. Subgroup analysis showed significant difference between two groups for hFO combinations ( p = 0.014), age ( p = 0.002), NSAR ( p = 0.001), and bilateral THA on same day ( p = 0.001). The multiple logistic regression analysis showed that hFO combination was the only variable for increased probability of aseptic loosening (OR, 3.7; p = 0.04). Conclusion High femoral offset combinations, formed by lateralized stems or large femoral head lengths in our collective of standard straight stems implanted by an anterior approach, show a 3.7-fold increased probability for aseptic femoral component loosening. Adjustment of the postoperative protocol may be considered in these cases to ensure proper stem ingrowth.

Symptomatic hips with borderline hip dysplasia (BHD) morphology pose a challenge in differentiating stable from unstable hips. The current study aims to compare indirect radiographic signs of instability in a symptomatic BHD population to those in a healthy cohort. The study group consisted of patients with a lateral centre–edge angle (LCEA) with values 18° ≤ LCEA < 25° who underwent corrective periacetabular osteotomy (PAO) and reported an improvement in patient-reported outcome measures (PROMs). The comparison group consisted of a healthy cohort of athletes who did not complain of any hip-related symptoms and who had normal values of their hip morphological parameters (LCEA, acetabular index (AI°), alpha angle (α°), femoral version, acetabular version). Indirect signs of instability consisting of the femoro-epiphyseal acetabular roof index (FEAR), iliocapsularis-to-rectus-femoris (IC/RF) ratio and labral dimensions (height-to-length ratio) were assessed in both groups. Partial Pearson correlation, logistic multiple regression analysis and Receiver-Operating Characteristic (ROC) curve analysis were performed to determine correlations, as well as the sensitivity and specificity of these signs to differentiate between healthy hips and BHD. On binary logistic multiple regression analysis, the FEAR Index was the only independent predictor to differentiate between BHD and healthy hips (p < 0.001). The IC/RF ratio did not achieve significance. The calculated area under the curve (AUC) was 0.93 (0.87 – 0.99, CI 95