Aims

Research on hip biomechanics has analyzed femoroacetabular contact pressures and forces in distinct hip conditions, with different procedures, and used diverse loading and testing conditions. The aim of this scoping review was to identify and summarize the available evidence in the literature for hip contact pressures and force in cadaver and in vivo studies, and how joint loading, labral status, and femoral and acetabular morphology can affect these biomechanical parameters.

Removal of bullets retained within joints is indicated to prevent mechanical blockade, 3rd body wear and resultant arthritis, plus lead arthropathy and systemic lead poisoning. The literature is sparse on this subject, with mostly sporadic case reports utilizing hip arthroscopy. We report on the largest series of removal of bullets from the hip joints using open surgical. We reviewed prospectively collected data of patients who presented to a single institution with civilian gunshot injuries that breached the hip joint between 01 January 2009 and 31 December 2022. We included all cases where the bullet was retained within the hip joint area. Exclusion criteria: cases where the hip joint was not breached, bullets were not retained around the hip area or cases with isolated acetabulum involvement. One hundred and eighteen (118) patients were identified. One patient was excluded as the bullet embedded in the femur neck was sustained 10 years earlier. Of the remaining 117 patients, 70 had retained bullets around the hip joint. In 44 patients we undertook bullet removal using the followingsurgical hip dislocation (n = 18), hip arthrotomy (n = 18), removal at site of fracture fixation/replacement (n = 2), posterior wall osteotomy (n = 1), direct removal without capsulotomy (tractotomy) (n = 5). In 26 patients we did not remove bullets for the following reasons: final location was extra-capsular embedded in the soft tissues (n=17), clinical decision to not remove (n=4), patients’ clinical condition did not allow for further surgery (n= 4) and patient refusal (n=1). No patients underwent hip arthroscopy. With adequate pre-operative imaging and surgical planning, safe surgical removal of retained bullets in the hip joint can be achieved without the use of hip arthroscopy; using the traditional open surgical approaches of arthrotomy, tractotomy and surgical hip dislocation

Aims. Developmental dysplasia of the hip (DDH) is a complex musculoskeletal disease that occurs mostly in children. This study aimed to investigate the molecular changes in the hip joint capsule of patients with DDH. Methods. High-throughput sequencing was used to identify genes that were differentially expressed in hip joint capsules between healthy controls and DDH patients. Biological assays including cell cycle, viability, apoptosis, immunofluorescence, reverse transcription polymerase chain reaction (RT-PCR), and western blotting were performed to determine the roles of the differentially expressed genes in DDH pathology. Results. More than 1,000 genes were differentially expressed in hip joint capsules between healthy controls and DDH. Both gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that extracellular matrix (ECM) modifications, muscle system processes, and cell proliferation were markedly influenced by the differentially expressed genes. Expression of Collagen Type I Alpha 1 Chain (COL1A1), COL3A1, matrix metalloproteinase-1 (MMP1), MMP3, MMP9, and MMP13 was downregulated in DDH, with the loss of collagen fibres in the joint capsule. Expression of transforming growth factor beta 1 (TGF-β1) was downregulated, while that of TGF-β2, Mothers against decapentaplegic homolog 3 (SMAD3), and WNT11 were upregulated in DDH, and alpha smooth muscle actin (αSMA), a key myofibroblast marker, showed marginal increase. In vitro studies showed that fibroblast proliferation was suppressed in DDH, which was associated with cell cycle arrest in G0/G1 and G2/M phases. Cell cycle regulators including Cyclin B1 (CCNB1), Cyclin E2 (CCNE2), Cyclin A2 (CCNA2), Cyclin-dependent kinase 1 (CDK1), E2F1, cell division cycle 6 (CDC6), and CDC7 were downregulated in DDH. Conclusion. DDH is associated with the loss of collagen fibres and fibroblasts, which may cause loose joint capsule formation. However, the degree of differentiation of fibroblasts to myofibroblasts needs further study. Cite this article: Bone Joint Res 2021;10(9):558–570

Abstract. OBJECTIVES. Abnormal joint mechanics have been proposed as adversely affecting natural hip joint tribology, whereby increased stress on the articular cartilage from abnormal loading leads to joint degeneration. The aim of this project was to assess the damage caused by different loading conditions on the articular surfaces of the porcine hip joint in an experimental simulator. METHODS. Porcine hip joints were dissected and mounted in a single station hip simulator (SimSol, UK) and tested under loading scenarios (that corresponded to equivalent of different body mass index's’ (BMI) in humans), as follows:“Normal” (n=4), the loading cycle consisted of a simplified gait cycle based on a scaled version of a simplified twin-peak human gait cycle, the peak load was 900N (representative of a healthy BMI). Representative of an “Overweight” BMI (n=3), as the normal cycle with a peak load of 1,130N Representative of an “Obese” BMI (n=1), as the normal cycle with a peak load of 1,340N Tests were conducted at 1Hz for 14,400 cycles in Ringers solution; photogrammetry was used to characterise the appearance of the cartilage and labrum pre, during and post simulation. the appearance and location of damage was recorded. RESULTS. No significant damage was observed for samples tested under normal conditions. Following “overweight” condition testing, tears and detachment of the labrum were observed during testing in two (of three) samples. In addition to damaged observed in “overweight” tested samples the “obese” showed similar damage and also cartilage bruising and wear tracks on the articular surface of the acetabulum. DISCUSSION. The absence of damage in “normal” loading provides evidence that this is an appropriate methodology and loading regime for porcine hips. Increased damage with increasing loads demonstrates the potential to develop further this experimental simulation to assess adverse loading in natural hip joints. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Aims. Surgical approaches that claim to be minimally invasive, such as the direct anterior approach (DAA), are reported to have a clinical advantage, but are technically challenging and may create more injury to the soft-tissues during joint exposure. Our aim was to quantify the effect of soft-tissue releases on the joint torque and femoral mobility during joint exposure for hip resurfacing performed via the DAA. Methods. Nine fresh-frozen hip joints from five pelvis to mid-tibia cadaveric specimens were approached using the DAA. A custom fixture consisting of a six-axis force/torque sensor and motion sensor was attached to tibial diaphysis to measure manually applied torques and joint angles by the surgeon. Following dislocation, the torques generated to visualize the acetabulum and proximal femur were assessed after sequential release of the joint capsule and short external rotators. Results. Following initial exposure, the ischiofemoral ligament (7 to 8 o’clock) was the largest restrictor of exposure of the acetabulum, contributing to a mean 25% of overall external rotational restraint. The ischiofemoral ligament (10 to 12 o’clock) was the largest restrictor of exposure of the proximal femur, contributing to 25% of overall extension restraint. Releasing the short external rotators had minimal contribution in torque generated during joint exposure (≤ 5%). Conclusion. Adequate exposure of both proximal femur and acetabulum may be achieved with minimal torque by performing a full proximal circumferential capsulotomy while preserving short external rotators. The joint torque generated and exposure achieved is dependent on patient factors; therefore, some cases may necessitate further releases. Cite this article: Bone Joint J 2024;106-B(3 Supple A):59–66

Aims. Osteoporosis is common in total hip arthroplasty (THA) patients. It plays a substantial factor in the surgery’s outcome, and previous studies have revealed that pharmacological treatment for osteoporosis influences implant survival rate. The purpose of this study was to examine the prevalence of and treatment rates for osteoporosis prior to THA, and to explore differences in osteoporosis-related biomarkers between patients treated and untreated for osteoporosis. Methods. This single-centre retrospective study included 398 hip joints of patients who underwent THA. Using medical records, we examined preoperative bone mineral density measures of the hip and lumbar spine using dual energy X-ray absorptiometry (DXA) scans and the medications used to treat osteoporosis at the time of admission. We also assessed the following osteoporosis-related biomarkers: tartrate-resistant acid phosphatase 5b (TRACP-5b); total procollagen type 1 amino-terminal propeptide (total P1NP); intact parathyroid hormone; and homocysteine. Results. The prevalence of DXA-proven hip osteoporosis (T-score ≤ -2.5) among THA patients was 8.8% (35 of 398). The spinal osteoporosis prevalence rate was 4.5% (18 of 398), and 244 patients (61.3%; 244 of 398) had osteopenia (-2.5 < T-score ≤ -1) or osteoporosis of either the hip or spine. The rate of pharmacological osteoporosis treatment was 22.1% (88 of 398). TRACP-5b was significantly lower in the osteoporosis-treated group than in the untreated group (p < 0.001). Conclusion. Osteoporosis is common in patients undergoing THA, but the diagnosis and treatment for osteoporosis were insufficient. The lower TRACP-5b levels in the osteoporosis-treated group — that is, osteoclast suppression — may contribute to the reduction of the postoperative revision rate after THA. Cite this article: Bone Joint Res 2022;11(12):873–880

The interleukin-6/gp130-associated Janus Kinases/STAT3 axis is known to play an important role in mediating inflammatory signals, resulting in production of matrix metalloproteinase-3 (MMP-3). The hip joints with rapidly destructive coxopathy (RDC) demonstrate rapid chondrolysis, probably by increased production of MMP-3 observed in the early stage of RDC. In the recent study, no apparent activation of STAT3 has been shown in the synovial tissues obtained from the osteoarthritic joint at operation. However, no data are currently available on STAT3 activation in the synovial tissues in the early stage of RDC. This study aimed to elucidate STAT3 activation in the synovial tissues in the early stage of RDC. Synovial tissues within 7 months from the disease onset were obtained from four RDC patients with femoral head destruction and high serum levels of MMP-3. RDC synovial tissues showed the synovial lining hyperplasia with an increase of CD68-positive macrophages and CD3-positive T lymphocytes. STAT3 phosphorylation was found in the synovial tissues by immunohistochemistry using anti-phospho-STAT3 antibody. The majority of phospho-STAT3-positive cells were the synovial lining cells and exhibited negative expression of macrophage or T cell marker. Treatment with tofacitinib, a Janus Kinase inhibitor, resulted in a decrease in phospho-STAT3-positive cells, especially with high intensity, indicating effective suppression of STAT3 activation in RDC synovial tissues. Inhibitory effect of tofacitinib could act through the Janus Kinase/STAT3 axis in the synovial tissues in the early stage of RDC. Therefore, STAT3 may be a potential therapeutic target for prevention of joint structural damage in RDC. Acknowledgements: This study was supported by Katakami Foundation for Clinical Research

Despite improvements in techniques and materials, aseptic loosening of artificial hip joints remains as the most serious problem. This study investigated mechanical and biological effects of biocompatible 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer on prevention of aseptic loosening. To examine mechanical effects of MPC grafting, we performed hip simulator tests (3million cycles) using cross-linked polyethylene (CL-PE) liners with or without nano-grafting of MPC onto articulating surface (MPC liner/CL-PE liner) and PE liner against CoCrMo heads. To examine biological responses of macrophages and osteoblasts, we prepared MPC nanoparticles (500nm). Using in vitro/vivo murine particle-induced osteolysis model, we examined biological effects of MPC nanoparticles on osteoclastogenesis. The friction torque was about 90% lower in MPC liners than control liners. Total amounts of wear produced from MPC liner was about 1/5and 1/30 of those from CL-PE and PE liners, respectively. Three-dimensional analysis and SEM analysis of MPC liners revealed no or little wear. The effect of MPC nanografting was maintained even after the test, because XPS analysis confirmed the remainder of specific spectra of MPC on the liner surface. When nanoparticles were exposed to cultured mouse macrophages, MPC nano particles were hardly phagocytosed by macrophages and did not enhance the concentration of bone resorptive cytokines and PGE2. Furthermore, culture medium of macrophages exposed to MPC nanoparticles did not induce RANKL expression in osteoblasts and osteoclastogenesis from bone marrow cells. In vivo murine osteolysis model, particle-induced bone resorption was hardly observed in mice implanted MPC nanoparticles. Some medical devices grafted MPC onto itssurface have been already used under authorization of the FDA. This study demonstrated that MPC grafting markedly decreases wear production. In addition, even if wear particles are produced, they are biologically inert in respect to phagocytosis by macrophages and subsequent resorptive actions, suggesting an epochal improvement of artificial hip joints preventing aseptic loosening

Aims. Acetabular edge-loading was a cause of increased wear rates in metal-on-metal hip arthroplasties, ultimately contributing to their failure. Although such wear patterns have been regularly reported in retrieval analyses, this study aimed to determine their in vivo location and investigate their relationship with acetabular component positioning. Methods. 3D CT imaging was combined with a recently validated method of mapping bearing surface wear in retrieved hip implants. The asymmetrical stabilizing fins of Birmingham hip replacements (BHRs) allowed the co-registration of their acetabular wear maps and their computational models, segmented from CT scans. The in vivo location of edge-wear was measured within a standardized coordinate system, defined using the anterior pelvic plane. Results. Edge-wear was found predominantly along the superior acetabular edge in all cases, while its median location was 8° (interquartile range (IQR) -59° to 25°) within the anterosuperior quadrant. The deepest point of these scars had a median location of 16° (IQR -58° to 26°), which was statistically comparable to their centres (p = 0.496). Edge-wear was in closer proximity to the superior apex of the cups with greater angles of acetabular inclination, while a greater degree of anteversion influenced a more anteriorly centred scar. Conclusion. The anterosuperior location of edge-wear was comparable to the degradation patterns observed in acetabular cartilage, supporting previous findings that hip joint forces are directed anteriorly during a greater portion of walking gait. The further application of this novel method could improve the current definition of optimal and safe acetabular component positioning. Cite this article: Bone Joint Res 2021;10(10):639–649

Abstract. Objectives. Hip joint laxity after total hip arthroplasty (THA) has been considered to cause microseparation and lead to complications, including wear and dislocation. In the native hip, the hip capsular ligaments may tighten at the limits of range of hip motion and provide a passive stabilising force preventing edge loading and reduce the risk of dislocation. Previous attempts to characterise mechanical properties of hip capsular ligaments have been largely variable and there are no cadaveric studies quantifying the force contributions of each ligament in different hip positions. In this study we quantify the passive force contribution of the hip capsular ligaments throughout a complete range of motion (ROM). Methods. Nine human cadaveric hip specimens (6 males and 3 females) with mean age of (76.4 ± 9.0 years) were skeletonised, preserving the capsular ligaments. Prepared specimens were tested in a 6 degree of freedom system to assess ROM with 5 Nm torque applied in external and internal rotation throughout hip flexion and extension. Capsular ligaments were resected in a stepwise fashion to assess internal force contributions of the iliofemoral (superior and inferior), pubofemoral, and ischiofemoral ligaments during ROM. Results. In external rotation, the superior and inferior iliofemoral ligament minimum force contributions were (136.52 ± 27.15 N) in flexion and (82.40 ± 27.85 N) in extension, respectively. In internal rotation, the ischiofemoral ligament force contributions were dominant in adducted-flexion positions and abducted-extension positions. Conclusions. These findings provide insights into the primary capsular structures that stabilise the hip joint in different manoeuvres. This data allows for an improved understanding of which capsular ligaments contribute the most to hip stability and has important implications for choosing surgical approaches and repair strategies to minimise complications related to joint instability. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Objectives. To validate the precision of digitally reconstructed radiograph (DRR) radiostereometric analysis (RSA) and the model-based method (MBM) RSA with respect to benchmark marker-based (MM) RSA for evaluation of kinematics in the native hip joint. Methods. Seven human cadaveric hemipelves were CT scanned and bone models were segmented. Tantalum beads were placed in the pelvis and proximal femoral bone. RSA recordings of the hips were performed during flexion, adduction and internal rotation. Stereoradiographic recordings were all analyzed with DRR, MBM and MM. Migration results for the MBM and DRR with respect to MM were compared. Precision was assessed as systematic bias (mean difference) and random variation (Pitman’s test for equal variance). Results. A total of 288 dynamic RSA images were analyzed. Systematic bias for DRR and MBM with respect to MM in translations (p < 0.018 mm) and rotations (p < 0.009°) were approximately 0. Pitman’s test showed lower random variation in all degrees of freedom for DRR compared with MBM (p < 0.001). Conclusion. Systematic error was approximately 0 for both DRR or MBM. However, precision of DRR was statistically significantly better than MBM. Since DRR does not require marker insertion it can be used for investigation of preoperative hip kinematics in comparison with the postoperative results after joint preserving hip surgery. . Cite this article: L. Hansen, S. De Raedt, P. B. Jørgensen, B. Mygind-Klavsen, B. Kaptein, M. Stilling. Marker free model-based radiostereometric analysis for evaluation of hip joint kinematics: A validation study. Bone Joint Res 2018;7:379–387. DOI: 10.1302/2046-3758.76.BJR-2017-0268.R1

Hip osteoarthritis (OA) is a disorder of high socio-economic relevance. The causes of hip osteoarthritis are multifactorial; however, the epidemiological literature regularly cites occupational tasks, such as heavy lifting and carrying, as a risk factor for the development of hip OA. The level of mechanical stresses upon the hip joint caused by occupational tasks remain largely unclear, however. This project sought to quantify the levels of stresses upon the hip joint during occupational tasks. In particular we were interested in comparing load as well as stress levels from everyday activities with occupational tasks typically performed by blue collar workers. Sectors and occupational activities presenting a high potential for stress upon the hip joint were identified by means of a survey conducted among accident insurance institutions. Lifting, carrying and load transfer (25 to 50 kg), ladder climbing and stair climbing (without additional load and with an additional load of 25 kg) were selected from among these sectors and activities for the purpose of the study. Laboratory measurements were performed in which motion capturing and a range of force measurement apparatus were used to record and evaluate the performance of the selected tasks by 12 skilled workers from a number of sectors. multi-body simulation was used to calculate the stress in the form of hip-joint contact forces. The contact pressures and their geometric distribution on the cartilage surfaces of the hip joint were then calculated from these results by means of finite-element analysis. This produced an indicator for the strain upon the hip joint. The highest hip-joint forces, at (637±148)% of the body weight, occurred during handling of the 50 kg load. This corresponded to 1.7 times the stress arising during walking, at (368±78)% of the body weight. Significantly higher hip-joint forces compared to those arising during walking were observed for the carrying of loads of 40 kg and 50 kg, the handling of loads of 25 kg, 40 kg and 50 kg, and stair climbing with an additional load of 25 kg. Maximum contact pressures of 24.1 MPa were computed during the finite-element analysis (lifting of 50 kg); only very small regions of the joint surface were however affected by these high pressures. During walking, the maximum pressure reached 15 MPa. The results obtained provide a quantitative overview of the strains upon the hip joint during occupational and everyday tasks. They constitute an aid to future quantitative exposure assessments in a range of sectors and occupational fields, and thus contribute to improving estimation of the relevance of stresses of occupational origin to the incidence of hip OA

Introduction. Soft tissue artefact (STA) affects the kinematics retrieved with skin marker-based motion capture, and thus influences the outcomes of biomechanical models that rely on such kinematics. To date, compensation for STA remains an unsolved challenge due to its complexity. Factors include its dependency on subject, on motion activity and on skin-marker configuration, its non-linearity over the movement cycle, and the scarcity of reference in-vivo estimations. The objective of this study was extending the existing knowledge of the effects of STA on the kinematics of the hip joint and on the hip joint center location, by quantifying them for a sample total hip arthroplasty (THA) population, for a broader range of activities of daily living (ADLs). Methods. Four activities of daily living (overground gait, stairs descent, chair rise and putting on socks) were measured simultaneously with optical motion capture (MC) at 100 Hz and with a movable single-plane video-fluoroscopy system (VF) at 25 Hz, for fifteen patients with successful total hip arthroplasty (THA). The joint segment positions were computed by least-square fitting for MC and by semi-automatic 2D/3D registration for VF. Anatomical coordinate systems were defined for each joint segment based on skin markers location at a reference standing position. Errors induced by STA on the retrieved joint motion were computed as the difference between MC-based kinematics and the reference VF-based kinematics. Statistical analysis was carried out to determine the whether the differences between the kinematics obtained with the two methods were significant. Results. MC underestimated the ROM of the hip joint for all activities. The ROM for the flexion-extension was underestimated by on average 4.1°, 6.5°, 8.0° and 6.9° for gait, stair decent, chair rise and putting on socks respectively. Overall, during dynamic activities the hip joint was less flexed, more adducted and more internally rotated as retrieved using MC, compared to VF. The flexion angle was underestimated by MC during late stance phase and early swing phase for both gait and stairs descent. The internal rotation of the hip was overestimated by MC throughout the whole cycle of each activity. MC error for the thigh was larger than the MC error for the pelvis. MC errors above 1 cm were observed for the location of the hip joint center, with higher values for the cranial-caudal direction. Discussion. Reduced ROM supports the notion that skin-sliding is a major contributor to STA. The underestimation of hip flexion appeared to be positively correlated to the degree of flexion. Larger skin deformation and sliding occurring for the thigh at higher hip flexion angles may produce the observed patterns of MC error for FE. The CC error was possibly due to inertial effects, and was more pronounced for the stair descent due to larger vertical movement and acceleration. This study led further bases for the activity-dependent correction of STA. This has the potential of improving the accuracy of motion capture and boosting its use for motion analysis as opposite to video-fluoroscopy techniques, which deliver radiation dose to the subjects

Objectives. The high revision rates of the DePuy Articular Surface Replacement (ASR) and the DePuy ASR XL (the total hip arthroplasty (THA) version) have led to questions over the viability of metal-on-metal (MoM) hip joints. Some designs of MoM hip joint do, however, have reasonable mid-term performance when implanted in appropriate patients. Investigations into the reasons for implant failure are important to offer help with the choice of implants and direction for future implant designs. One way to assess the performance of explanted hip prostheses is to measure the wear (in terms of material loss) on the joint surfaces. Methods. In this study, a coordinate measuring machine (CMM) was used to measure the wear on five failed cementless Biomet Magnum/ReCap/ Taperloc large head MoM THAs, along with one Biomet ReCap resurfacing joint. Surface roughness measurements were also taken. The reason for revision of these implants was pain and/or adverse reaction to metal debris (ARMD) and/or elevated blood metal ion levels. Results. The mean wear rate of the articulating surfaces of the heads and acetabular components of all six joints tested was found to be 6.1 mm. 3. /year (4.1 to 7.6). The mean wear rate of the femoral head tapers of the five THAs was 0.054 mm. 3. /year (0.021 to 0.128) with a mean maximum wear depth of 5.7 µm (4.3 to 8.5). Conclusion. Although the taper wear was relatively low, the wear from the articulating surfaces was sufficient to provide concern and was potentially large enough to have been the cause of failure of these joints. The authors believe that patients implanted with the ReCap system, whether the resurfacing prosthesis or the THA, should be closely monitored. Cite this article: S. C. Scholes, B. J. Hunt, V. M. Richardson, D. J. Langton, E. Smith, T. J. Joyce. Explant analysis of the Biomet Magnum/ReCap metal-on-metal hip joint. Bone Joint Res 2017;6:113–122. DOI: 10.1302/2046-3758.62.BJR-2016-0130.R2

Background. In vivo fluoroscopic studies have proven that femoral head sliding and separation from within the acetabular cup during gait frequently occur for subjects implanted with a total hip arthroplasty. It is hypothesized that these atypical kinematic patterns are due to component malalignments that yield uncharacteristically higher forces on the hip joint that are not present in the native hip. This in vivo joint instability can lead to edge loading, increased stresses, and premature wear on the acetabular component. Objective. The objective of this study was to use forward solution mathematical modeling to theoretically analyze the causes and effects of hip joint instability and edge loading during both swing and stance phase of gait. Methods. The model used for this study simulates the quadriceps muscles, hamstring muscles, gluteus muscles, iliopsoas group, tensor fasciae latae, and an adductor muscle group. Other soft tissues include the patellar ligament and the ischiofemoral, iliofemoral, and pubofemoral hip capsular ligaments. The model was previously validated using telemetric implants and fluoroscopic results from existing implant designs. The model was used to simulate theoretical surgeries where various surgical alignments were implemented and to determine the hip joint stability. Parameters of interest in this study are joint instability and femoral head sliding within the acetabular cup, along with contact area, contact forces, contact stresses, and ligament tension. Results. During swing phase, it was determined that femoral head pistoning is caused by hip capsule laxity resulting from improperly positioned components and reduced joint tension. At the point of maximum velocity of the foot (approximately halfway through), the momentum of the lower leg becomes too great for a lax capsule to properly constrain the hip, leading to the femoral component pistoning outwards. This pistoning motion, leading to separation, is coupled with a decrease in contact area and an impulse-like spike in contact stress (Figure 1). During stance phase, it was determined that femoral head sliding within the acetabular cup is caused by the proprioceptive notion that the human hip wants to rotate about its native, anatomical center. Thus, component shifting yields abnormal forces and torques on the joint, leading to the femoral component sliding within the cup. This phenomenon of sliding yields acetabular edge-loading on the supero-lateral aspect of the cup (Figure 2). It is also clear that joint sliding yields a decreased contact area, in this case over half of the stable contact area, corresponding to a predicted increase in contact stress, in this case over double (Figure 2). Discussion. From our current analysis, the causes and effects of hip joint instability are clearly demonstrated. The increased stress that accompanies the pistoning/impulse loading scenarios during swing phase and the supero-lateral edge-loading scenarios during stance phase provide clear explanations for premature component wear on the cup, and thus the importance of proper alignment of the THA components is essential for a maximum THA lifetime. For any figures or tables, please contact authors directly

Introduction. Native hip joint infection can result in hip arthrosis as a complication requiring the need for subsequent arthroplasty. There is little evidence to support single or staged THA. We present the results of patients who have undergone total hip arthroplasty (THA) following hip joint sepsis in our institution. Methods. Patients receiving a THA following previous hip joint sepsis between 2003 and 2015 were identified from the operative records database. Further clinical information was collected from the medical records, including timing of infection and surgery, as well as culture results. Functional outcome (Oxford Hip Score, OHS) and patient satisfaction scores (PSS) were recorded. Results. There were 21 males and 12 females with a mean age of 54 (21–82) at a mean follow up of 6.4 years (2–12) following definitive implantation. Thirteen patients underwent a single stage THA and 20 patients had a 2 stage procedure, two of whom required a repeat 1. st. stage prior to implantation. The mean time from native hip infection to operation was 17.2 years (3–59). At implantation, positive cultures were present in 19 cases, 13 of which were S. aureus. Two patients required revision due to a periprosthetic fracture and one patient required debridement, antibiotics and implant retention (DAIR). Therefore, the implant survivorship was 94% and infection rate was 3% at 6.4 years. Discussion. Both single and staged arthroplasty provide good results in patients who have developed septic arthritis. THA as a single stage was performed predominately in patients with a long remission between their initial infection and presentation. Positive culture at implantation does not confer a bad outcome as long as a thorough debridement is performed as routine in this patient group. Patient comorbidities are an important factor as both cases requiring reoperation were in IV drug users with Hepatitis C

INTRODUCTION. The purpose of this study is to elucidate longitudinal kinematic changes of the hip joint during heels-down squatting after THA. METHODS. 66 patients with 76 primary cementless THAs using a CT-based navigation system were investigated using fluoroscopy. An acetabular component and an anatomical femoral component were used through the mini-posterior approach with repair of the short rotators. The femoral head size was 28mm (9 hips), 32mm (12 hips), 36mm (42 hips), and 40mm (12 hips). Longitudinal evaluation was performed at 3 months, 1 year, and 2≤ years postoperatively. Successive hip motion during heels-down squatting was recorded as serial digital radiographic images in a DICOM format using a flat panel detector. The coordinate system of the acetabular and femoral components based on the neutral standing position was defined. The images of the hip joint were matched to 3D-CAD models of the components using a2D/3D registration technique. In this system, the root mean square errors of rotation was less than 1.3°, and that of translation was less than 2.3 mm. We estimated changes in the relative angle of the femoral component to the acetabular component, which represented the hip ROM, and investigated the incidence of bony and/or prosthetic impingement during squatting (Fig.1). We also estimated changes in the pelvic posterior tilting angle (PA) using the acetabular component position change. In addition, when both components were positioned most closely during squatting, we estimated the minimum angle (MA) up to theoretical prosthetic impingement as the safety margin (Fig.2). RESULTS. No prosthetic or bony impingement and no dislocation occurred in any hips. The mean maximum hip flexion ROM was 92.4° (range, 76.6° – 107.9°) at 3 months, 103.4° (range, 81.5° – 115.2°) at 1 year, and 102.4° (range, 87.1° – 120.6°) at 2≤ years (3 months vs 1 year, p<0.05; 1 year vs 2≤ years, p>0.05, paired t-test). The mean PA was 26.7° (range, 0.9° – 49.8°) at 3 months, 21.7° (range, 3.4° – 43.8°) at 1 year, and 21.2° (range, −0.7° – 40.4°) at 2≤ years (3 months vs 1 year, p<0.05; 1 year vs 2≤ years, p>0.05). The mean flexion ROM and MA at 2≤ years were 98.4±20.8° and 14.3±7.3° in 28 mm heads, 102.3±10.7° and 15.6±4.8° in 32 mm heads, 102.8±14.5° and 20.3±9.6° in 36 mm heads, and 103.2±16.9° and 23.4±10.9° in 40 mm heads, respectively. There were no significant differences in the hip flexion ROM between 28, 32, 36, and 40 mm head cases, whereas MA significantly increased as the femoral head diameter was larger (p<0.05, unpaired t-test). DISCUSSION AND CONCLUSION. Three-dimensional assessment of dynamic squatting motion after THA using the 2D/3D registration technique enabled us to elucidate longitudinal kinematic change of the hip joint. Longitudinal kinematic analysis indicated that hip flexion ROM and posterior tilt during squatting changed significantly by 1 year postoperatively, and there were no significant changes after 1 year while safety margin kept > 10°. For figures/tables, please contact authors directly.

Aims

Studies of infant hip development to date have been limited by considering only the changes in appearance of a single ultrasound slice (Graf’s standard plane). We used 3D ultrasound (3DUS) to establish maturation curves of normal infant hip development, quantifying variation by age, sex, side, and anteroposterior location in the hip.

Introduction. Advantages of ceramic materials for hip joint prosthesis are recognized to be high hardness, scratch resistance, improved wettability, lower friction and lower wear than CoCr surfaces. Recent studies suggest the use of ceramic femoral head reduce fretting corrosion at stem taper junction compared to metal-on-metal taper junction[1]. Continuous improvement of ceramic materials for orthopedic lead to the development of a resurfacing ceramic-on-ceramic hip joint prosthesis. The main differences of resurfacing heads respect to standard heads are their anatomical dimension and the empty shape suitable to cover the femoral bone and to connect with the resurfacing stem. Ceramic is essentially a brittle material and its strength is influenced by the minimum thickness in the stressed area. Ceramic resurfacing head minimum thickness is comparable with ceramic revision head already on the market. The aim of this study is to develop a mechanical pre-clinical analysis verification process for the newly developed system. Materials and methods. The empty shape of the ceramic resurfacing head may influence its strength in a crush loading scenario. Although this is not a physiological condition this test represents the most severe loading for a resurfacing head. Also comparative analysis can be done considering the yield point of conventional metal resurfacing heads reported by the FDA Center for Devices and Radiological Health. For this reason a static unsupported head strength test is performed by applying a compressive load perpendicular to the head axis along the equatorial plane[2](Fig.1). Resurfacing ceramic head made in ZTA is suitable both for a resurfacing stem and an adaptor to be coupled with a standard stem. Mechanical test was performed on worst case resurfacing head size both with resurfacing stem and standard stem based and on FE non linear analysis performed in ANSYS 17.2 according the following material properties: ZTA ceramic (modulus of elasticity E, Poisson ratio ν and density ρ of 348GPa, 0.23 and 4.25g/cm. 3. respectively), and Ti6Al4V (E=114GPa, ν=0.33 and ρ=4.43g/cm. 3. ). For comparison purposes unsupported test was performed on standard head Ø28#S both in Biolox®Delta and Biolox®Forte ceramic. At least three components were used for each test and the average values was compared with predicates[2]. Static compressive load was applied with MTS hydraulic actuators with load cell of 100kN. Results. FE analysis indicated the larger resurfacing head as the worst case size in the size range(Fig.2). Static unsupported head strength test was performed on resurfacing ceramic head Ø57 coupled both with resurfacing stem and standard stem, Biolox®Delta head Ø28#S, Biolox®Forte head Ø28#S and respectively reached a strength value of 53±7kN, 90±3kN, 78±27kN, 49±1kN. Equivalent test were reported in literature for DeltaSurf® Ø58 and BHR. TM. , and respectively reached a strength of 26kN and 5.6kN. Discussion and Conclusion. LIMA ceramic resurfacing head and Biolox Forte Ø28#S showed equivalent unsupported head burst strength. LIMA ceramic resurfacing head showed higher unsupported head burst strength respect to DeltaSurf® and BHR. TM. highlighting its potential in clinical use. For any figures or tables, please contact the authors directly

To confirm whether developmental dysplasia of the hip has a risk of hip impingement, we analysed maximum ranges of movement to the point of bony impingement, and impingement location using three-dimensional (3D) surface models of the pelvis and femur in combination with 3D morphology of the hip joint using computer-assisted methods. Results of computed tomography were examined for 52 hip joints with DDH and 73 normal healthy hip joints. DDH shows larger maximum extension (p = 0.001) and internal rotation at 90° flexion (p < 0.001). Similar maximum flexion (p = 0.835) and external rotation (p = 0.713) were observed between groups, while high rates of extra-articular impingement were noticed in these directions in DDH (p < 0.001). Smaller cranial acetabular anteversion (p = 0.048), centre-edge angles (p < 0.001), a circumferentially shallower acetabulum, larger femoral neck anteversion (p < 0.001), and larger alpha angle were identified in DDH. Risk of anterior impingement in retroverted DDH hips is similar to that in retroverted normal hips in excessive adduction but minimal in less adduction. These findings might be borne in mind when considering the possibility of extra-articular posterior impingement in DDH being a source of pain, particularly for patients with a highly anteverted femoral neck. Cite this article: Bone Joint J 2014;96-B:580–9

Pre-operative definitive diagnosis of infection in painful total hip arthroplasty (THA) is not always easy to be established, making the intra-operative decision-making process crucial in management of revision hip surgery. Calprotectin is a promising point-of-care novel biomarker that has displayed high accuracy in detecting PJIs.

From November 2020 to December 2022, 105 patients with painful primary THA were treated with revision THA in 3 orthopaedic departments. Pre-operatively, 23 were considered infected and treated with two-stage revision THA. The remaining 82 were likely infected according to the 2019 EBJIS criteria. The suspicion of low-grade infection was based on clinical (rest and/or night pain), laboratory (CRP, ESR, WBC – normal or slightly elevated) and radiological evaluation (loosening). Hip aspiration under CT imaging was performed in these cases and 34 of them yielded positive culture and were treated with two-stage revision. Aspiration was ineffective in the remaining 48 cases (33 negative, 15 unsuccessful attempts). Intra-operatively, calprotectin was measured with lateral flow immunoassay test in these patients. Cases with calprotectin levels ≥ 50 mg/L were treated with 2-stage revision THA; otherwise, they were considered not-infected and one-stage revision was performed. Synovial fluid and tissue samples were collected for analysis. Implants were sent for sonication fluid cultures.

Calprotectin was positive (≥ 50 mg/L) in 27 cases and negative in 21 cases. There was 1 false negative case with positive tissue cultures. Out of the 27 positive cases, 25 had positive tissue cultures and sonication. However, 2 cases with high calprotectin levels (>200 mg/L) were not infected. The false positive result was attributed to severe metallosis. Calprotectin sensitivity was 96.2%, specificity 90.9%, PPV 92.6%, NPV 95.2%, AUC 0.935.

The results of this ongoing study indicate that calprotectin seems to be a valuable tool in facilitating the intra-operative decision-making process in cases that low-grade infection is suspected and diagnosis cannot be established pre-operatively.

We have utilized arthroscopic arthroplasty of the hip joint (arthroscopic partial resection of the acetabular edge) for the treatment of advanced osteoarthritis of hip joint. We have utilized arthroscopic Arthroplasty to widen the joint space and tried to improve the outcome of joint preserving operation. We have treated advanced osteoarthritis of nine hip joints of eight patients (age from 41 to 56, averaged 44.3 years old) by arthroscopic arthroplasty in the past six years. The patient was put on the surgical traction table in the supine position. Arthroscope was inserted into the hip joint from antero-medial approach under fluoroscopic control and the acetabular edge was shaved until bleeding from subchondral bone was seen. In eight joints of seven patients, additional surgical procedures were applied later. Acetabular edge resection alone might resulted in the lateral-proximal displacement of the femoral head and to acquire good result in the long term, some additional procedure should be considered. However, in one case of this series showed good roof osteophyte formation after arthroscopic arthroplasty with improved JOA score. This might be a result of improved blood supply at the edge of acetablum. We believe that arthroscopic arthroplasty for advanced osteoarthritis in combination with other procedures may avoid total hip arthroplasty

Introduction: Septic arthritis of the hip joint in the pediatric age group is considered as an indication for surgical drainage of the joint. The commonly accepted treatment is arthrotomy of the hip joint, and continuous lavage and drainage. The child is treated with intravenous antibiotic therapy and is sometimes placed in a cast. Because of repeated technical problems with the drains, the senior author developed a method of treatment by repeated aspirations of the hip joint under ultra-sound guidance. We report the results of the first group of these patients, followed up for at least 2 years. Methods: Hip aspiration is performed when a child is suspected to have septic arthritis of the hip joint based on clinical, radiographic, ultrasonic and laboratory examinations. When hip effusion is found, aspiration is performed under ultrasound guidance, using topical anesthesia and strict sterile technique. If the aspirated fluid is visibly purulent, the joins is irrigated with sterile saline until clear fluid is aspirated. The patient is admitted to the hospital and intravenous antibiotic therapy is initiated. Repeated ultrasound examinations are performed daily, and the joint is decompressed and irrigated again. The procedure is continued until no effusion is demonstrated. Results: Twenty-four patients were treated for septic arthritis of the hip joint at our institution between January 1st 1990 and December 31st 1998. The first 3 patients were operated and then aspirated when the drains were clogged during the first post operative day. Twenty-one patients were treated by repeated aspirations. Four of those patients were operated when the aspiration failed or when the clinical course did not improve, all of them during the first 4 years of the study. Seventeen patients were treated by repeated aspirations only. The mean number of aspirations was 4, and the children tolerated them well. No complications were seen on follow-up, and all patients went back to full activities. No cases of avascular necrosis of the femoral head were identified. Discussion and Conclusions: Arthrotomy and drainage of hip joint is an emergency procedure for the treatment of septic arthritis of the hip joint. Possible complications of the procedure are dislocation of the hip joint, avascu-lar necrosis of the hip joint and technical problems with drains. We describe a reliable and safe procedure, that does not necessitate general anesthesia and surgery. The 4 patients who did have to undergo surgery represent a learning curve, and were all treated during the first four years. No complications or late sequelae were seen in our patients

1. One hundred patients with dislocation of the hip joint have been reviewed, many having been re-examined at intervals ranging from two to five years after injury. 2. There were forty-six simple dislocations, forty-three dislocations with fracture of the acetabular rim, seven dislocations with fracture of the acetabular floor, and five dislocations with fracture of the femoral head. 3. Complete recovery, as judged by clinical and radiographic examination, was observed in 76 per cent. of simple dislocations, 63 per cent. of dislocations with fracture of the acetabular rim, and 40 per cent. of dislocations with fracture of the femoral head; in no case of dislocation with fracture of the acetabular floor was recovery complete. 4. Only in one case did myositis ossificans develop, and that was the only case treated by "massage and movements" throughout the first ten weeks after injury. 5. Avascular necrosis of the femoral head was recognised in a smaller proportion of patients than had been expected, but since the follow-up review extended only to four years after injury the results, in this respect, are unreliable. The incidence of this complication after injury to the hip joint cannot be assessed unless the follow-up period is at least five to ten years. 6. Early traumatic arthritis developed in 26 per cent. of patients—in 15 per cent. of simple dislocations, 25 per cent. of dislocations with fracture of the acetabular margin, 60 per cent. of dislocations with fracture of the femoral head, and 100 per cent. of dislocations with fracture of the acetabular floor. 7. When central or posterior dislocations are accompanied by fracture of the acetabular floor, early arthrodesis is the treatment of choice. 8. Displacement of marginal acetabular fragments is usually corrected by manipulative reduction or by traction. 9. Sciatic paralysis in dislocation of the hip joint is nearly always due to damage of the nerve by a displaced acetabular fragment. In such cases, if the fragment is not replaced accurately by manipulation or traction, operative reduction is urgently indicated

Aims. Our aim in this study was to describe the long-term survival of the native hip joint after open reduction and internal fixation of a displaced fracture of the acetabulum. We also present long-term clinical outcomes and risk factors associated with a poor outcome. Patients and Methods. A total of 285 patients underwent surgery for a displaced acetabular fracture between 1993 and 2005. For the survival analysis 253 were included, there were 197 men and 56 women with a mean age of 42 years (12 to 78). The mean follow-up of 11 years (1 to 20) was identified from our pelvic fracture registry. There were 99 elementary and 154 associated fracture types. For the long-term clinical follow-up, 192 patients with complete data were included. Their mean age was 40 years (13 to 78) with a mean follow-up of 12 years (5 to 20). Injury to the femoral head and acetabular impaction were assessed with CT scans and patients with an ipsilateral fracture of the femoral head were excluded. Results. A total of 36 patients underwent total hip arthroplasty (THA). The overall ten-year survival of the hip joint was 86% (95% confidence interval (CI) 81% to 90%) and the 20-year survival was 82% (95% CI 76% to 87%). Injury to the femoral head and acetabular impaction were the strongest predictors of failure, with the long-term survival rate falling towards 50% in these patients. The survival fell to 0% at three years when both these risk factors were present in patients aged > 60 years. Conclusion. The long-term survival of the native hip joint after acetabular fractures was good, but the presence of injury to the femoral head and acetabular impaction proved to be strong predictors of failure, especially in patients aged > 60 years. These patients may be better treated with a combination of open reduction and internal fixation and primary arthroplasty. Cite this article: Bone Joint J 2017;99-B:834–40

1. This is a simple clinical study of the end-results of arthrodesis of the hip joint in patients followed up and re-examined five to twenty-five years after operation. 2. The study was stimulated by our astonishment at recent reports which suggested that arthrodesis of the hip caused serious operative mortality, a high rate of wound infection, and failure of sound fusion in one of every two cases; and that even when sound fusion was gained there was always pain in the back and usually stiffness of the knee. To say that we were astonished puts it mildly. 3. This review includes 120 patients aged from ten to seventy years, treated for osteoarthritis of the hip joint by intra-articular arthrodesis with the internal fixation of a nail, usually with an iliac graft, and with immobilisation in plaster for not less than four months. 4. Of these 120 patients there was sound fusion of the joint, proved radiographically, in 94 per cent; a mortality of nil; and recovery of free movement of the knee joint to the right angle or far beyond in 91·5 per cent. Almost half of the patients regained normal movement, the heel touching the buttock. Only in eight patients was there less than right-angled flexion. 5. There was no pain in the back—none whatever—in 64 per cent of the patients. In 36 per cent there was some pain or discomfort. One alone said that the low back pain was worse than before the operation. Many others said that pain in the back had been relieved by the operation. 6. It is emphasised that these results were gained only from sound fixation of the joint in the mid-position with neutral rotation, no more abduction than is needed to correct true shortening, and no more flexion of the joint than that with which the patient lies on the table. The limb was immobilised in plaster for at least four months after operation. The stiff knee was mobilised by the patient's own exercise without passive stretching, force or manipulation. 7. Two other groups of patients are considered. There are fourteen treated by fixation of the joint with nail alone, an operation that was never intended to arthrodese the joint and which has long since been abandoned. The other small group is that of patients with old unreduced traumatic dislocation of the hip, a procedure in which the risks of operation are so great and the number of successful results so small as to dissuade us from attempting operative reduction. 8. After successful arthrodesis of the hip joint patients can return to every household activity and every recreation including ski-ing, mountaineering, rock climbing, or whatever else they want

Introduction. A deep squat (DS) is a challenging motion at the level of the hip joint generating substantial reaction forces (HJRF). During DS, the hip flexion angle approximates the functional range of hip motion. In some hip morphologies this femoroacetabular conflict has been shown to occur as early as 80° of hip flexion. So far in-vivo HJRF measurements have been limited to instrumented hip implants in a limited number of older patients performing incomplete squats (< 50° hip flexion and < 80° knee flexion). Clearly, young adults have a different kinetical profile with hip and knee flexion ranges going well over 100 degrees. Since hip loading data on this subgroup of the population is lacking and performing invasive measurements would be unfeasible, this study aimed to report a personalised numerical model solution based on inverse dynamics to calculate realistic in silico HJRF values during DS. M&M. Fifty athletic males (18–25 years old) were prospectively recruited for motion and morphological analysis. DS motion capture (MoCap) acquisitions and MRI scans of the lower extremities with gait lab marker positions were obtained. The AnyBody Modelling System (v6.1.1) was used to implement a novel personalisation workflow of the AnyMoCap template model. Bone geometries, semi-automatically segmented from MRI, and corresponding markers were incorporated into the template human model by an automated nonlinear morphing. Furthermore, a state-of-the-art TLEM 2.0 dataset, included in the Anybody Managed Model Repository (v2.0), was used in the template model. The subject-specific MoCap trials were processed to compute squat motion by resolving an overdeterminate kinematics problem. Inverse dynamics analyses were carried out to compute muscle and joint reaction forces in the entire body. Resulting hip joint loads were validated with measured in-vivo data from Knee bend trials in the OrthoLoad library. Additionally, anterior pelvic tilt, hip and knee joint angles were computed. Results. A preliminary set of results (20 out of 50 subjects) was analysed. The average HJRF was 3.42 times bodyweight at the peak of DS (95% confidence interval: 2.99 – 3.85%BW). Maximal hip and knee flexion angles were 113° (109.7°–116.8°) and 116° (109.4 – 123.0°) respectively. The anterior pelvic tilt demonstrated a biphasic profile with peak value of 33° (28.1° – 38.4°). Discussion. A non-invasive and highly personalised alternative for determining hip loading was presented. Consistently higher HJR forces during DS in young adults were demonstrated as opposed to the Orthoload dataset. Similarly, knee and hip flexion angles were much higher, which could support the increase in HJRF. We can conclude that DS hip kinetics in young adults clearly differ from the typical total hip arthroplasty population

Background and Aims: Concentric pressure of the femoral head on acetabulum is the necessary prerequisite for normal hip development. In the case of diminished hip joint area an elevation of hip joint pressure ensues. If this pressure elevation lasts for a long period of time early degenerative changes are proposed to occur. The aim of our study is to substantiate the connection between hip joint pressure and occurrence of hip osteoarthritis in dysplastic hips. Methods: From 1955 to 1965 112 patients were treated non-operatively for hip dysplasia in developmental dysplasia of the hip in Dept. of Orthopaedic Surgery, Ljubljana. Using mathematical model of the hip, peak joint stress was measured in 27 patients, which met the enrolment criteria consisting of: a.) initial rentgenograph taken at least 20 years ago, b.) closed triradiate cartilage and no rentgenographic signs of osteoarthritis at the time of initial radiograph, c.) no neurological deþcit of lower limbs and no operative procedure during follow up period. All hips were re-examined clinically in year 2000. Results: Mean age at the latest follow up was 47 years (35 years to 61 years). Mean time interval between the rentgenograph from which the hip joint stress was measured and clinical examination was 27 years (20 years to 33 years). Signiþcant correlation was found between peak hip joint stress and Harris hip score (p 0.0013). Discussion and conclusions: Our results indicate that occurrence osteoarthritis of the hip could be related to the degree of hip dysplasia at the end of skeletal growth. The correlation between peak hip joint stress and Harris hip score was one order of magnitude larger than the corresponding correlation between CE angle and Harris hip score, which indicates that hip joint stress represents a valuable parameter describing the status of the hip joint

Introduction and aims: Increasingly the accurate reconstruction of the hip in total hip arthroplasty is planned using pre-operative pelvic radiographs. The accuracy of reconstruction is assessed using post-operative pelvic radiographs. This study defines significant variations in the offset, hip joint centre and femoral head centre-trochanteric height relations in normal radiographs. Method: One hundred standard normal pelvic radiographs were examined based on a defined criterion. The medial offset, the vertical height of hip joint centre with reference to the ischial tuberosity and the femoral head centre-trochanterc height relation were measured for both hips. The differences in measurements were evaluated to determine the normal variation in offset and the hip joint centre. The relationship of the femoral head centre to the tip of the greater trochanter was determined. Results: On average, the right hip and left hip differed by 2.54mm in their offset .The standard deviation of differences was 2.31. Therefore the offset of one hip will predict the offset of the other hip to within 4.62mm, with 95% accuracy. If the reconstructed hip has an offset to within + 4.62 to – 4.62mm of the contra lateral side, then the offset should be considered to be reconstructed as normal. The average difference in height of the hip joint centres of right hip from left hip with reference to bi-ischial line was found to be 3.49mm. The standard deviation of differences was 3.15. Therefore the hip joint centre height measured in one hip will predict the hip joint centre height of the opposite hip to within 6.3mm with 95% accuracy. Thus the hip joint centre height of one hip may differ from the opposite hip by 6.3mm in normal individuals. The tip of greater trochanter was on average 8mm higher than the centre of rotation of the femoral head. The greater trochanter was not at the same level as the femoral head centre as commonly believed. Conclusion: This study demonstrates considerable variation in the medial offset and the hip joint centre location on pelvic wall. The femur head centre is lower than commonly assumed. These factors should be taken into account when pre-operative planning using pelvic radiographs and assessing the quality of the post-operative reconstruction

Surgical dislocation of the hip joint using the technique developed by Rheinhold Ganz, is a relatively new method for surgical exposure of the hip. A review of 8 cases that underwent surgical dislocation of the hip joint was undertaken, to assess the short term outcome, complications associated with the procedure and to identify some of the indications for this technique. This is a retrospective analysis of surgical dislocation in two centers undertaken by the same surgeon with a maximum follow up period of one year. Surgical dislocation of the hip allows access to the hip joint with some associated morbidity due to the surgical exposure but there were no cases of avascular necrosis in the short term follow up. We were able to define specific pathological conditions affecting the hip where there is significant improvement following treatment using this method of exposure of the hip joint. Good exposure of the hip joint is obtained via surgical dislocation so allowing good access for surgical intervention. There is an associated morbidity with the technique but this method of hip exposure allows an alternative to hip arthroscopy and allows easier access to the joint for the treatment of intra articular pathology

Similar to the radiological findings in rapidly destructive arthrosis of the hip joint (RDA), subchondral insufficiency fracture of the femoral head (SIF) can result in progressive femoral head collapse of unknown etiology. We thus examined the osteoclast activity in hip joint fluid in SIF with progressive collapse in comparison to that in RDA. Twenty-nine hip joint fluid samples were obtained intraoperatively with whole femoral heads from 12 SIF patients and 17 RDA patients. SIF cases were classified into subgroups based on the presence of ≥2mm collapse on preoperative radiographs: SIF with progressive collapse (n=5) and SIF without progressive collapse (n=7). The levels of tartrate-resistant acid phosphatase (TRACP)-5b, interleukin-8, vascular endothelial growth factor (VEGF), and matrix metalloproteinase (MMP)-9 were measured. Numbers of multinuclear giant cells at the subchondral region were assessed histopathologically using mid-coronal slices of each femoral head specimen. Median levels of all markers and median numbers of multinuclear giant cells in SIF with progressive collapse were significantly higher than those in SIF without progressive collapse, while there were no significant differences in SIF with progressive collapse versus RDA. Regression analysis showed that the number of multinuclear giant cells correlated positively with the level of TRACP-5b in joint fluid. This study suggests an association of increased osteoclast activity with the existing condition of progressive collapse in SIF, which was quite similar to the findings in RDA. Therefore, high activation of osteoclast cell may reflect the condition of progressive collapse in SIF as well as RDA

The location of the hip joint center (HJC) allows correct prosthesis aligning and positioning in Computer-Assisted Orthopaedic Surgery (CAOS) applications. For the kinematic HJC localisation, the femur is moved around the pelvis with ad hoc motion trials (“pivoting”). The “Pivoting algorithm” [Siston et al., J Biomech 39 (2006) 125–130] is the functional state-of-the-art method for the hip center localisation. A source of systematic error in HJC localisation algorithms is represented by the pelvis motion during the pivoting. In computer assisted total knee arthroplasty applications, the pelvis pose is not acquired during passive movements. In motion capture applications, Kalman Filter (KF) methodology was used to estimate the pose of hidden segment for rigid body pose estimation. The purpose of this study was to validate the accuracy and robustness of a Kalman Filter algorithm, applied to a state space formulation based on two links model of the hip joint, to track the HJC position during passive movements of the articulation in CAOS procedure. The state space model describes femur and pelvis kinematics under the hypothesis of non-laxity of the articulation (ideal spherical joint). The first link models the femoral bone, while the second link models the pelvis. The femur is tracked with a Dynamic Reference Frame (DRF) attached to the distal end, composed by four active markers, while the pelvis is tracked attaching a marker to it. The kinematic relations between the state vector and the observations are non linear function. The state space has been implemented with II order linear dynamics. The position of HJC in the Femur Reference Frame is modeled with non-dynamic state variables. In order to validate the proposed algorithm, a physical model of the hip joint (femur and pelvis) was realised using SawBones models. An active optical localisation system (Certus, NDI, Ontario, Canada) was used in order to track the coordinates of two DRF rigidly connected on each segment and the coordinates of a marker attached to the pelvis segment (on the Anterior Superior Iliac Spine ASIS). The pelvis phantom is locked on a Mass-Spring-Damper platform with 2 DoFs, which mimics soft tissues behaviour. During the pivoting motion, the poses of the femur DRF and the positions of the ASIS marker of the pelvis DRF were collected. The acquired data were the observable outputs to the KF algorithm, which computes an estimation of the state parameters. The accuracy is evaluated as the Euclidean distance between respectively the estimated and Gold Standard HJC positions in FRF. The KF method performances were compared with the “Pivoting” algorithm. The localisation errors computed for both the methodologies were evaluated with respect to the HJC translation, to the Range Of pivoting Motion (ROM) and to the velocity of femur DRF trajectory (Pearson correlation analysis). The positive correlation coefficients between HJC translation and the localization errors result statistically significant (p<0.01) for both “Pivoting” (correlation index equal to 0.838) and KF (correlation index equal to 0.415) algorithms; while a negative (correlation index equal to −0.355) and positive (correlation index equal to 0.263) correlation respectively for ROM and Velocity is computed as statistically significant (p<0.05) only for KF algorithm errors. Statistically significant difference (Kruskal-Wallis, p<0.01) between “Pivoting” [median 26.71 mm and inter-quartile range (24.04, 32.18)mm] and KF [median 11.71mm and inter-quartile range (7.74, 18.82)mm] algorithms was assessed for HJC translation greater than 7 mm. The new method KF proved to be applicable in current CAOS systems. The substantial improvement of KF method is the possibility of reducing the systematical error, caused by pelvis motion during passive movement of the femur, to compute HJC position. On the other hand, tracking the HJC trajectory in real time is a nontrivial task and requires a very accurate filter parameters tuning. Further tests must be made to estimate the in-vivo range of HJC translation during passive pivoting movements and evaluate the performances of KF method with respect to others state-of-the-art methods

Developmental dysplasia of the hip (DDH) is the most common post-natal skeletal abnormality. It is widely acknowledged that conditions which cause or result in reduced movement in utero are contributing factors to the incidence of DDH. However, the hypothesis that prenatal movement plays a role in normal development of the hip joint has not been tested using embryonic model systems. This research investigates the effects of immobilization in chick embryos on hip joint morphogenesis. Embryonic chicks were treated in ovo using a neuromuscular blocking agent from embryonic days 5 to 9. Limbs were stained for cartilage using alcian blue, and were scanned in 3-D. Standardized virtual sections of the femur were taken and a number of virtual sections from age-matched limbs were overlaid in order to compare between control and immobilized limbs. The results show that not all immobilised limbs were equally affected, with some immobilised embryos having almost normal joint shapes, and other immobilised embryos displaying decreased protuberance of the femoral head and decreased indentation at the femoral neck. Our results demonstrate that the mechanobiological response to immobilisation can vary between individuals, but also that preventing movement during embryonic development can lead to abnormal morphogenesis of the developing proximal femur in some individuals, providing evidence that reduced movement during development can lead to features of DDH

Introduction. Nociceptive and neuropathic components both contribute to chronic pain. Since these components require different pain management strategies, correct pain diagnosis before and during treatment is important. Freynhagen et al. (2006) reported that they had developed and validated the pain-DETECT questionnaire (PD-Q) to detect neuropathic components in chronic low back pain patients. They also reported that 37% of unselected cohort of chronic LBP patients had predominantly neuropathic pain. However, the extent to which neuropathic components relate to the pathomechanism of pain deriving from osteoarthritis of hip joint remains unknown. The purpose of this study was to utilize PD-Q to investigate the relationship between neuropathic components and pain deriving from osteoarthritis of the hip joint. Methods. Between March and August 2010, 125 patients with osteoarthritis of hip joint completed PD-Qs about their pain. From this data set, we investigated whether or not the patients’ pain contained neuropathic components. Results. Only 6.4% of the patients had a score 19, indicating that a neuropathic component was likely (90%). Conversely, 79.2 % had a score 12, indicating that a neuropathic component was unlikely (15%). For the remaining 14.4% with an intermediate score (13–18), the presence of a neuropathic component remained uncertain. Conclusion. In this set of patients with osteoarthritis of hip joint, the PD-Q responses indicated that only a small percentage (6.4%) were likely to have a neuropathic component to their hip pain

In this study we used subject-specific finite element analysis to investigate the mechanical effects of rotational acetabular osteotomy (RAO) on the hip joint and analysed the correlation between various radiological measurements and mechanical stress in the hip joint. We evaluated 13 hips in 12 patients (two men and ten women, mean age at surgery 32.0 years; 19 to 46) with developmental dysplasia of the hip (DDH) who were treated by RAO. Subject-specific finite element models were constructed from CT data. The centre–edge (CE) angle, acetabular head index (AHI), acetabular angle and acetabular roof angle (ARA) were measured on anteroposterior pelvic radiographs taken before and after RAO. The relationship between equivalent stress in the hip joint and radiological measurements was analysed. The equivalent stress in the acetabulum decreased from 4.1 MPa (2.7 to 6.5) pre-operatively to 2.8 MPa (1.8 to 3.6) post-operatively (p < 0.01). There was a moderate correlation between equivalent stress in the acetabulum and the radiological measurements: CE angle (R = –0.645, p < 0.01); AHI (R = –0.603, p < 0.01); acetabular angle (R = 0.484, p = 0.02); and ARA (R = 0.572, p < 0.01). The equivalent stress in the acetabulum of patients with DDH decreased after RAO. Correction of the CE angle, AHI and ARA was considered to be important in reducing the mechanical stress in the hip joint. Cite this article: Bone Joint J 2015;97-B:492–7

Impact relief ability of Metal-on-Metal artificial hip joint with multi-garter spring using drop impact tester for practical use. Toshiaki Kaneeda, Xinming Zhao and Hiroshi Matsuura. Metal-on-metal (MoM) joints can provide better wear properties than hard-on-polymer joints, leading to reducing osteolysis. However during gait, MoM hip joints have no material to relieve impact. These impacts can cause severe pain in postoperative patients. Kaneeda proposed double-shell MoM artificial hip joints in which multi garter springs were inserted between the inner and outer acetabular shell as an impact relief device. The proposed double-shell metal-on-metal artificial hip joint is composed of two layers, as shown in Fig. 11). A garter spring is usually used when by loading and a compression stress from the outside to the center axis. In the model testing for garter spring, it is demonstrated that garter spring had impact relief ability, then using dual garter springs could lead to better impact relief ability than single one2). In this work, the impact relief ability of model hip joint were investigated by using the Instron CEAST 9340 machine as shown in Fig. 2. The machine is a floor standing impact system designed to deliver 0.30–405J of energy and equipped with precise locating system for height. A holding device of double-shell cup was made to fix the right position. A shape of drop impact weight was modified for this experiment. The model hip joint was applied vertical load over 6000N, which is estimated to be equal to maximum vertical load during jumping. The ability in the case of single garter spring and dual garter springs was evaluated in the model hip joint, comparing with UHMWPE liner in the same size of femur head. Each testing was conducted 10 times. Fig. 3 shows load-time curve detected. From the results, it can be seen that in both case Load L gradually rise with Time T, then reach maximum values, finally L gently drop: maximum impact load as well as maximum impact load arriving time also presented nearly the same values. Much differences in shape of the curve between model hip joint with dual garter springs and UHMWPE liner could not be recognized. The model hip joint with dual garter springs may has enough impact relief ability

The pressure distribution between the cartilaginous surfaces in the human hip joint was measured using pressure-sensitive film. Five cadaveric hip joints (aged between 58 and 87 years) were measured at three positions and loads, representing three instants in the stance phase of the walking cycle. The pressure distribution was not uniform, indicating that the cartilage did not, to any great extent, distribute the applied load. The maximum pressures recorded were about 10 MN/m2. The anterosuperior surface of the cartilage was identified as an area of high pressure

With the growing number of individuals with asymptomatic cam-type deformities, elevated alpha angles alone do not always explain clinical signs of femoroacetabular impingement (FAI). Differences in additional anatomical parameters may affect hip joint mechanics, altering the pathomechanical process resulting in symptomatic FAI. The purpose was to examine the association between anatomical hip joint parameters and kinematics and kinetics variables, during level walking. Fifty participants (m = 46, f = 4; age = 34 ± 7 years; BMI = 26 ± 4 kg/m²) underwent CT imaging and were diagnosed as either: symptomatic (15), if they showed a cam deformity and clinical signs; asymptomatic (19), if they showed a cam deformity, but no clinical signs; or control (16), if they showed no cam deformity and no clinical signs. Each participant's CT data was measured for: axial and radial alpha angles, femoral head-neck offset, femoral neck-shaft angle, medial proximal femoral angle, femoral torsion, acetabular version, and centre-edge angle. Participants performed level walking trials, which were recorded using a ten-camera motion capture system (Vicon MX-13, Oxford, UK) and two force plates (Bertec FP4060–08, Columbus, OH, USA). Peak sagittal and frontal hip joint angles, range of motion, and moments were calculated using a custom programming script (MATLAB R2015b, Natick, MA, USA). A one-way, between groups ANOVA examined differences among kinematics and kinetics variables (α = 0.05), using statistics software (IBM SPSS v.23, Armonk, NY, USA); while a stepwise multiple regression analysis examined associations between anatomical parameters and kinematics and kinetics variables. No significant differences in kinematics were observed between groups. The symptomatic group demonstrated lower peak hip abduction moments (0.12 ± 0.08 Nm/kg) than the control group (0.22 ± 0.10 Nm/kg, p = 0.01). Sagittal hip range of motion showed a moderate, negative correlation with radial alpha angle (r = −0.33, p = 0.02), while peak hip abduction moment correlated with femoral neck-shaft angle (r = 0.36, p = 0.009) and negatively with femoral torsion (r = −0.36, p = 0.009). With peak hip abduction moment in the stepwise regression analysis, femoral torsion accounted for a variance of 13.3% (F(1, 48) = 7.38; p = 0.009), while together with femoral neck-shaft angle accounted for a total variance of 20.4% (R² change = 0.07, F(2, 47) = 6.01; p = 0.047). Although elevated radial alpha angles may have limited sagittal range of motion, the cam deformity parameters did not affect joint moments. Femoral neck-shaft angle and femoral torsion were significantly associated with peak hip abduction moment, suggesting that the insertion location of the abductor affects muscle's length and its resultant force vector. A varus neck angle, combined with severe femoral torsion, may ultimately influence muscle moment arms and hip mechanics in individuals with cam FAI

Hip joint preservation remains a preferred treatment option for hips with mechanically correctable pathologies prior to the development of significant secondary arthrosis. The pathologies most amenable to joint preservation are hip dysplasia and femoroacetabular impingement. These pathologies sometimes overlap. Untreated acetabular dysplasia of modest severity always leads to arthrosis if uncorrected. Acetabular dysplasia is best treated by periacetabular osteotomy, usually combined with arthrotomy for management of labral pathology and associated cam-impingement if present. Pre-operative variables associated with the best long-term outcomes include less secondary arthrosis, younger age, and concentric articular surfaces. The earlier PAO series show 20 year survivorship of 81% and 65% in Tonnis Grade 0 and 1 hips. Femoroacetabular impingement has become progressively recognised as perhaps the most common cause of secondary arthrosis. The etiology of impingement is multifactorial and includes both genetic factors and stresses experienced by the hip prior to cessation of growth. Cam impingement can be quantified by the alpha angle as measured on plain radiographs and radial MR sequences. Cam impingement can be treated by arthroscopic or open femoral head-neck osteochondroplasty. As with hip dysplasia, prognosis following treatment is correlated with the severity of pre-operative secondary arthrosis but unfortunately impinging hips more commonly have some degree of arthrosis pre-operatively whereas dysplastic hips can become symptomatic with instability in the absence of arthrosis. The scientific basis for the treatment of pincer impingement is less strong. Unlike cam impingement and hip dysplasia, pincer impingement pathology in the absence of coxa profunda has not been correlated with arthrosis and so rim trimming with labral refixation is probably performed more often than is clinically indicated. Overall, joint preserving surgery remains the preferred treatment for hips with mechanically correctable problems prior to the development of significant secondary arthrosis

Introduction The consequence of discongrency of the hip joint may be early, secondary osteoarthritis of the hip joint, that leads to important limits in movement abilities of an individual. The deficit of the femoral head coverage can be rather easily corrected, but only until the growth and maturation of the pelvis is completed. Redirection of the acetabular fragment can be performed by use of the periacetabular osteotomy according to Ganz. This type of the osteotomy is mainly used in the treatment of the acetabular displasia in patients with closed Y cartilage, but also in the treatment of the osteoarthritis of the hip joint. The Aim of the study was to present our early results of treatment of the patients with the secondary osteoarthritis of the hip joint by use of the periacetabular osteotomy according to Ganz. Material and Methods. Our material consisted of 64 patients, 72 hip joints, operated on between 1998–2004. 20 patients (24 hip joints) were selected from this group. In these 20 patients the indication for the treatment was not only the acetabular displasia, but also osteoarthritis of the hip joint. Our group consisted of 17 female and 3 male. In 4 cases the both hip joints were affected. The age of the patients was 26–44 years, average 34 years. The observation period was from 4 months to 6 years, average 2,5 years. The most important clinical symptom was the groin pain on the rest or while flexing the hip joint with internal rotation and adduction. The radiological symptoms in patients before the operation were: decentration, narrowing of the articular space, cysts beyond the sclerotic zone, fatigue fractures of the acetabular edge. Results. In all the patients, except of one, the pain disappeared. Abduction and internal rotation in the hip joint increased, but flexion decreased. The Wiberg’s angle increased from 10–15° to 25–40°, and the interior Wiberg’s angle from 10–0° to 15–20°. During follow up we observed remodeling of the cysts. The treatment was subjectively assessed by the patients as very good. Conclusion. The use of the periacetabular osteotomy occording to Ganz is the operation that corrects the hip joint. But in some cases of the osteoarthritis of the hip joint it allows to improve the quality of life and we hope may also delay the arthroplasty in the young age

1. In this series of 150 cases of arthritis of the hip joint treated by vitallium mould arthroplasty (182 arthroplasties), 80 per cent. of late results are satisfactory to both patient and surgeon. 2. Striking features are the relative painlessness, smooth hip joint movement, progressive improvement in function, and reformation of the joint lines as seen radiographically in the post-operative period. 3. Function after arthroplasty for traumatic and degenerative arthritis approaches the normal hip joint much more closely than in cases of infective and rheumatoid arthritis. 4. There is a complete absence of low back symptoms or postural difficulties, and there is no difficulty in preventing stiffness of the knee joint. 5. Different technical procedures are indicated according to the degree of absorption of the femoral head or neck, and the stability of the mould in the acetabulum. 6. The operative mortality rate in this series was nil, and during the six-year follow-up period only one case died as the result of a complication of the arthroplasty. 7. In addition to meticulous operative technique and the use of special instruments, the importance of careful and prolonged after-treatment must be stressed. 8. It must also be emphasised that secondary operative revisions are often necessary, particularly in cases of infective and rheumatoid arthritis

1. Three cases of osteochondromatosis of the hip joint are described. 2. Attention is drawn to the diagnostic importance of erosions at the junction of head and neck of the femur, and the conical shape of the femoral neck. 3. Arthrography is of particular value in diagnosis when the loose bodies are radio-translucent

1. The operation of pseudarthrosis of the hip joint is described and the results are assessed in ninety-three patients. 2. The result was good in eighty-three cases and poor in seven cases. Three patients died as a result of the operation. 3. Pseudarthrosis is the most satisfactory and the most reliable operation: 1) in ankvlosing spondylitis, and 2) in patients over sixty years of age with disabling osteoarthritis. 4. The more formidable operation of cup arthoplasty may prove to be superior in younger patients with osteoarthritis

Introduction. A deep squat (DS) is a challenging motion at the level of the hip joint generating substantial reaction forces (HJRF). As a closed chain exercise, it has great value in rehabilitation and muscle strengthening of hip and knee. During DS, the hip flexion angle approximates the functional range of hip motion risking femoroacetabular impingement in some morphologies. In-vivo HJRF measurements have been limited to instrumented implants in a limited number of older patients performing incomplete squats (< 50° hip flexion and < 80° knee flexion). On the other hand, total hip arthroplasty is being increasingly performed in a younger and higher demanding patient population. These patients clearly have a different kinetical profile with hip and knee flexion ranges going well over 100 degrees. Since measurements of HJRF with instrumented prostheses in healthy subjects would be ethically unfeasible, this study aims to report a personalised numerical solution based on inverse dynamics to calculate realistic in-silico HJRF values during DS. Material and methods. Thirty-five healthy males (18–25 years old) were prospectively recruited for motion and morphological analysis. DS motion capture (MoCap) acquisitions and MRI scans with gait lab marker positions were obtained. The AnyBody Modelling System (v6.1.1) was used to implement a novel personalisation workflow of the AnyMoCap template model. Bone geometries, semi-automatically segmented from MRI, and corresponding markers were incorporated into the template human model by an automated procedure. A state of-the-art TLEM 2.0 dataset, included in the Anybody Managed Model Repository (v2.0), was used in the template model. The subject-specific MoCap trials were processed to compute kinematics of DS, muscle and joint reaction forces in the entire body. Resulting hip joint loads were compared with in-vivo data from OrthoLoad dataset. Additionally, hip and knee joint angles were computed. Results. An average HJRF of 274%BW (251.5 – 297.9%BW; 95% confidence interval) was calculated at the peak of DS. The HJRF on the pelvis was directed superior, medial and posterior throughout the DS. Peak knee and hip flexion angles were 112° (108.1° – 116.5°) and 107° (104.6° – 109.4°) on average. Discussion and conclusions. A comprehensive approach to construct an accurate personalised musculoskeletal model from subject-specific MoCap data, bone geometries, and palpatory landmarks was presented. Consistently higher HJR forces during DS in young adults were demonstrated as opposed to the Orthoload dataset. Similarly, knee and hip flexion angles were much higher, which could cause the increase in HJRF. It can be concluded that DS kinetics in young adults differ from the typical total hip arthroplasty population. These models will enable further in-silico joint biomechanics studies, and could serve the purpose of a virtual test bed for implant design

Surgical invention to preserve the native hip joint remains a preferred treatment option for hips in young patients with mechanically correctable pathologies prior to the development of significant secondary arthrosis. The two most common pathologies most amenable to joint preservation are hip dysplasia and femoroacetabular impingement. These pathologies sometimes overlap. Untreated acetabular dysplasia of modest severity, if left uncorrected, always leads to arthrosis. Acetabular dysplasia is best treated by periacetabular osteotomy, usually combined with arthrotomy for management of labral pathology and associated cam-impingement, if present. Correction of deformities on the femoral side is now less common and reserved for only the more severe combined femoral and acetabular dysplasias or the rare isolated femoral dysplasia. Pre-operative variables associated with the best long-term outcomes include less secondary arthrosis, younger age, and concentric articular surfaces. Femoroacetabular impingement has become progressively recognised as perhaps the most common cause of secondary arthrosis. The etiology of impingement is multifactorial and includes both genetic factors and stresses experienced by the hip prior to cessation of growth. Cam impingement can be quantified by the alpha angle as measured on plain radiographs and radial MR sequences. Further, significant cam impingement is clearly associated with the development of osteoarthrosis. Treatment can be performed either by arthroscopic or open femoral head-neck osteochondroplasty. As with hip dysplasia, prognosis following treatment is correlated with the severity of pre-operative secondary arthrosis but unfortunately impinging hips more commonly have some degree of arthrosis pre-op whereas dysplastic hips can become symptomatic with the onset of instability in the absence of significant secondary arthrosis. The scientific basis for the treatment of pincer impingement is less strong. Unlike cam impingement and hip dysplasia, pincer impingement pathology in the absence of coxa profunda has not been correlated with arthrosis and so rim trimming with labral refixation is probably performed more often than is clinically indicated. Similarly, caution should be exercised when considering rim-trimming for protrusion since high central contact pressures due to an enlarged acetabular notch are not corrected by rim trimming. Overall, joint preserving surgery remains the preferred treatment for hips with mechanically correctable problems prior to the development of significant secondary arthrosis

Aims: The present experiment addressed the question whether lipopolysaccharides (LPS), hip joint tamponade or their combination modulate hip perfusion. Methods: 16 immature Danish Landrace pigs of both genders were treated in 3 groups. 4 animals received LPS from escherichia coli intravenously 4 hours previous to hip joint tamponade. 8 pigs underwent the hip operation without previous medication. 4 animals without treatment served as control group. Blood ßow measurement was done by the Radioactive Tracer Microspheres technique. Results: Femoral head epiphyseal blood ßow decreased signiþcantly during hip joint tamponade. Reperfusion occurred to a level not signiþcantly differing from that before ischemia, whereas epiphyses remained ischemic in 2 pigs. The hip joint capsule showed signiþcant hyperperfusion during and after joint tamponade. No signiþcant difference was revealed comparing the LPS-treated and non-treated groups of pigs in all hip regions (p = 0.79, U-test). In addition, in the LPS-group, none of the femoral head epiphyses remained ischemic. Conclusions: LPS and hip joint tamponade, which have separately been discussed as pathomechanic factors of Non Traumatic Femoral Head Necrosis, have been combined in a bifactorial porcine model. Systemic lipopolysacchrides as bacterial endotoxin have no acute effect on regional hip perfusion which would make a consequent osteonecrosis probable. 6hourly hip joint tamponade alone evoked non reperfusion in 2 out of 8 pigs and a prolongation of the 6 hours ischemia might evoke more cases of non reperfusion

Purpose: The purpose of our study is to estimate the effectiveness of Parecoxib in the post surgical analgesia in the fractures of the hip joint in comparison with the usage of the combination of Diclofenac ant Pethidine. Material and methods: We have carried out a prospective randomized clinical study, during the period January 2003-July 2004, on 90 patients were operated with fractures of the hip joint. We examined two similar groups of patients concerning the age, the type of fracture and the type of anaesthesia. In group A, consisting of 35 patients, we provided 40 mg of Parecoxib i.v., as postsurgical analgesia, twice a day and in Group B, of 55 patients, we provided the combination of Diclofenac 75mg i.m. twice a day and Pethidine i.m. in case of persisting pain. The intensity of pain was estimated by the Pain Intensity Scale ( PIS ). Results: In Group A the PIS was 2.5 ± 0.8, and none of the patients needed supplementary analgesic. In Group B the PIS was 3.2 ± 0.8 and 21 (38.3%) patients needed supplementary analgesics (Pethidine). In the use of Parecoxib no side effects were noticed (decrease BP, vomiting etc). Conclusion: Parecoxib is more effective in the post surgical analgesia than Diclofenac and Pethidine in the fractures of the hip joint. It is easier to administer (i.v) and is also seems to be safe (no side effects were noticed). Therefore, we suggest that it should be the drug of choice in the post surgical analgesia of the fractures of the hip joint

Hip joint preservation remains a preferred treatment option for hips with mechanically correctable pathologies prior to the development of significant secondary arthrosis. The pathologies most amenable to joint preservation are hip dysplasia and femoroacetabular impingement. These pathologies sometimes overlap. Untreated acetabular dysplasia of modest severity always leads to arthrosis if uncorrected. Acetabular dysplasia is best treated by periacetabular osteotomy, usually combined with arthrotomy for management of labral pathology and associated cam-impingement if present. Preoperative variables associated with the best long-term outcomes include less secondary arthrosis, younger age, and concentric articular surfaces. Femoroacetabular impingement has become progressively recognised as perhaps the most common cause of secondary arthrosis. The etiology of impingement is multifactorial and includes both genetic factors and stresses experienced by the hip prior to cessation of growth. Cam impingement can be quantified by the alpha angle as measured on plain radiographs and radial MR sequences. Cam impingement can be treated by arthroscopic or open femoral head-neck osteochondroplasty. As with hip dysplasia, prognosis following treatment is correlated with the severity of preoperative secondary arthrosis but unfortunately impinging hips more commonly have some degree of arthrosis preop whereas dysplastic hips can become symptomic with instability in the absence of arthrosis. The scientific basis for the treatment of pincer impingement is less strong. Unlike cam impingement and hip dysplasia, pincer impingement pathology in the absence of coxa profunda has not been correlated with arthrosis and so rim trimming with labral refixation is probably performed more often than is clinically indicated. Overall, joint preserving surgery remains the preferred treatment for hips with mechanically correctible problems prior to the development of significant secondary arthrosis

Introduction: The aim of the present study was to evaluate the efficacy of the vacuum–assisted closure (V.A.C.) therapy in the treatment of early hip joint infections. Patients and Methods: 28 patients (11 m/17 f; mean age 71 y. [43–84]) with early hip joint infections have been treated by means of the V.A.C.–therapy. At least one surgical procedure [1–7] has been unsuccessfully performed for infection treatment prior to V.A.C. – application. Pathogen organisms could have been isolated in 22/28 wounds. During revision, cup inlay and prosthesis head have been exchanged and 1–3 polyvinylalcohol sponges inserted into the wound cavity/periprosthetically at an initial continuous pressure of 200 mm Hg. Postoperatively, a systemic antibiosis was given according to antibiogram. Results: 48–72 h after surgery an alteration from haemorrhagic to serous fluid was observed in the V.A.C.-canister. Afterwards, the pressure was decreased to 150 mm Hg and remained at this level till sponge removal. After a mean period of 9 [3–16] days the inflammation parameters have been retrogressive and the sponges were removed. An infection eradication could be achieved in 26/28 cases. In the two remaining cases the infected prosthesis had to be explanted and a gentamicin-vancomycin-loaded spacer has been implanted, respectively. At a total mean follow-up of 36 [12–87] months no reinfection or infection persistence was observed. Discussion: The V.A.C.-system can be a valuable contribution in the treatment of early joint infections when properly used. Indications should be early infections with well-maintained soft-tissues for retention of the vacuum