The resisted torsional stress test in diagnosis of femoral stem loosening in uncemented total hip arthroplasty - first description and retrospective study.

INTRODUCTION: Aseptic femoral stem loosening is among the most common causes for revision in total hip arthroplasty (THA). We describe a simple clinical test that triggers pain in the proximal femur in patients with a loose stem. A previously described passive rotation test was associated with a poor sensitivity. The resisted torsional stress test (RTST) was used for several years in our hospital, and this is the first description of its reliability. METHODS: We retrospectively reviewed our database of uncemented stem revisions. Preoperative clinical reports were searched for data on the RTST. A positive RTST was defined as sharp pain felt at the stem level with active internal rotation against a passive external rotation impulse in 90° hip flexion. The definition of stem fixation (fixed vs. loose) was made by readout of the surgery reports. RESULTS: The RTST was reported in 83 cases and was positive in 32 of the 43 stems, which were found loose intraoperatively and in 9 of the 40 stems, which were well integrated. This leads to an accuracy of classification of 79.5%. The sensitivity was 80% and the specificity was 79.1%. PPV and NPV were 78% and 81%, respectively. CONCLUSION: The RTST provides a helpful tool in the clinical assessment of femoral stem fixation in THA with good accuracy and should be included in standard follow-up examinations and in the assessment of painful THAs.

Physiological stretching induces a differential extracellular matrix gene expression response in acetabular labrum cells.

The acetabular labrum is a fibrocartilaginous ring surrounding the acetabulum and is important for hip stability and contact pressure dissipation through a sealing function. Injury of the labrum may contribute to hip-joint degeneration and development of secondary osteoarthritis. Understanding how extracellular matrix (ECM) production and remodelling is regulated is of key importance for successful tissue restoration. The present study hypothesised that physiological stretching enhanced the metabolic activity and altered the ECM gene expression in labrum cells. Primary bovine labrum cells were physiologically stretched for up to 5 d. 24 h after the last stretch cycle, changes in metabolic activity were measured using the PrestoBlue™ HS Cell Viability Reagent and ECM gene expression was examined using the quantitative polymerase chain reaction method. Targets of interest were further investigated using immunofluorescence and enzyme-linked immunosorbent assay. Metabolic activity was not affected by the stretching (0.9746 ± 0.0614, p > 0.05). Physiological stretching upregulated decorin (DCN) (1.8548 ± 0.4883, p = 0.002) as well as proteoglycan 4 (PRG4) (1.7714 ± 0.6600, p = 0.029) and downregulated biglycan (BGN) (0.7018 + 0.1567, p = 0.008), cartilage oligomeric matrix protein (COMP) (0.5747 ± 0.2650, p = 0.029), fibronectin (FN1) (0.5832 ± 0.0996, p < 0.001) and spondin 1 (SPON1) (0.6282 ± 0.3624, p = 0.044) gene expression. No difference in PRG4 and DCN abundance or release could be measured. The here identified mechanosensitive targets are known to play relevant roles in tissue organisation. Therefore, physiological stretching might play a role in labrum tissue homeostasis and regeneration.

Is hip morphology a risk factor for developing hip osteoarthritis? A systematic review with meta-analysis.

OBJECTIVE: To appraise the highest evidence on hip morphology as a risk factor for developing hip osteoarthritis (OA). DESIGN: We searched for studies evaluating the association between radiological hip morphology parameters and the prevalence, incidence or progression of hip OA (based on different radiographic and clinical criteria) in the MEDLINE, EMBASE, Web of Science, Scopus, Cochrane Library and PEDro databases from inception until June 2020. Prospective and cross-sectional studies were separately evaluated. Data are presented as odds ratios (OR) with 95% confidence intervals (CI). RESULTS: We included 9 prospective and 21 cross-sectional studies in the meta-analysis, and evaluated 42,831 hips from 25,898 individuals (mean age: 59 years). Prospective studies showed that, compared with control hips, hips with cam morphology (alpha angle >60°; OR = 2.52, 95% CI: 1.83 to 3.46, P < 0.001) or hip dysplasia (lateral center-edge angle (LCEA) <25°; OR = 2.38, 95% CI: 1.84 to 3.07, P < 0.001), but not hips with pincer morphology (LCEA >39°; OR = 1.08, 95% CI: 0.57 to 2.07, P = 0.810), were more likely to develop hip OA than hips without these morphologies. Cross-sectional studies showed a greater prevalence of pincer morphology (LCEA >39°, OR = 3.71, 95% CI: 2.98 to 4.61, P < 0.001) and acetabular retroversion (crossover sign; OR = 2.65, 95% CI: 1.17 to 6.03, P = 0.020) in hips with OA than in control hips. CONCLUSION: Cam morphology and hip dysplasia were consistently associated with the development of hip OA. Pincer morphology was associated with hip OA in cross-sectional but not in prospective studies. The heterogeneous quantification of pincer morphology on radiographs limits a clear conclusion on its association with hip OA.

Computer-assisted femoral head reduction osteotomies: an approach for anatomic reconstruction of severely deformed Legg-Calvé-Perthes hips. A pilot study of six patients.

BACKGROUND: Legg-Calvé-Perthes (LCP) is a common orthopedic childhood disease that causes a deformity of the femoral head and to an adaptive deformity of the acetabulum. The altered joint biomechanics can result in early joint degeneration that requires total hip arthroplasty. In 2002, Ganz et al. introduced the femoral head reduction osteotomy (FHRO) as a direct joint-preserving treatment. The procedure remains one of the most challenging in hip surgery. Computer-based 3D preoperative planning and patient-specific navigation instruments have been successfully used to reduce technical complexity in other anatomies. The purpose of this study was to report the first results in the treatment of 6 patients to investigate whether our approach is feasible and safe. METHODS: In this retrospective pilot study, 6 LCP patients were treated with FHRO in multiple centers between May 2017 and June 2019. Based on patient-specific 3D-models of the hips, the surgeries were simulated in a step-wise fashion. Patient-specific instruments tailored for FHRO were designed, 3D-printed and used in the surgeries for navigating the osteotomies. The results were assessed radiographically [diameter index, sphericity index, Stulberg classification, extrusion index, LCE-, Tönnis-, CCD-angle and Shenton line] and the time and costs were recorded. Radiologic values were tested for normal distribution using the Shapiro-Wilk test and for significance using Wilcoxon signed-rank test. RESULTS: The sphericity index improved postoperatively by 20% (p = 0.028). The postoperative diameter of the femoral head differed by only 1.8% (p = 0.043) from the contralateral side and Stulberg grading improved from poor coxarthrosis outcome to good outcome (p = 0.026). All patients underwent acetabular reorientation by periacetabular osteotomy. The average time (in minutes) for preliminary analysis, computer simulation and patient-specific instrument design was 63 (±48), 156 (±64) and 105 (±68.5), respectively. CONCLUSION: The clinical feasibility of our approach to FHRO has been demonstrated. The results showed significant improvement compared to the preoperative situation. All operations were performed by experienced surgeons; nevertheless, three complications occurred, showing that FHRO remains one of the most complex hip surgeries even with computer assistance. However, none of the complications were directly related to the simulation or the navigation technique.

Findings and Management of the Rare Caput Flexum Deformity of the Hip: A Case Report.

CASE: A 10-year-old girl presented after possible occult hip trauma, with shortening of the leg being the initial clinical symptom, followed by motion-dependent pain. She had limited external rotation in extension with anterior apprehension. Radiographically, the deformity was an anterior tilt of the epiphysis with coxa vara. Surgery included surgical dislocation using a retinacular flap for the anterior open wedge femoral neck osteotomy for extension and posterior translation, with an excellent 4.5-year clinical outcome. CONCLUSIONS: Caput flexum is a rare deformity with localized premature closure of the anterior growth plate of the hip. To avoid secondary impingement, an osteotomy was successfully placed close to the deformity.

Skin crease 'bikini' incision for the direct anterior approach in total hip arthroplasty: a two- to four-year comparative study in 964 patients.

Aims: The classical longitudinal incision used for the direct anterior approach (DAA) to the hip does not follow the tension lines of the skin and can lead to impaired wound healing and poor cosmesis. The purpose of this retrospective study was to determine the satisfaction with the scar, and functional and radiographic outcomes comparing the classic longitudinal incision with a modified skin crease 'bikini' when the DAA is used for total hip arthroplasty (THA). Patients and Methods: A total of 964 patients (51% female; 59% longitudinal, 41% 'bikini') completed a follow-up questionnaire between two and four years postoperatively, including the Oxford Hip Score (OHS), the University of North Carolina '4P' scar scale (UNC4P) and two items for assessing the aesthetic appearance of the scar and symptoms of numbness. The positioning of the components, rates of heterotopic ossification (HO) and rates of revision were assessed. Results: The mean OHS was similar in both groups (p = 0.41). The mean UNC4P total score was slightly better (p = 0.01) and the proportion of patients who were very satisfied with the cosmetic aspects of the scar was higher in the 'bikini' group (p < 0.001). The proportion of patients reporting numbness in the scar was higher in the longitudinal group (14.5% vs 7.5%, respectively, p < 0.001). The abduction angle of the acetabular component, the position of the stem and rates of HO did not differ between the groups. There were no differences in the revision rates of both groups, being 2.3% in the longitudinal and 1.5% in the 'bikini' group (p = 0.911). Conclusion: We found that a short oblique 'bikini' skin crease incision is safe when used for the DAA at THA, without compromising the positioning of the components or increasing the rate of lateral femoral cutaneous nerve dysaesthesia. Although it leads to a superior scar satisfaction, as it is less extensile, it should be used after having gained experience with the classic longitudinal incision. Cite this article: Bone Joint J 2018;100-B:853-61.

Femoral and acetabular re-alignment in slipped capital femoral epiphysis.

NEW PATHOPHYSIOLOGICAL INSIGHTS: Based on improved knowledge of the vascular supply of the proximal femur, a safe surgical dislocation of the hip joint was established allowing direct insights to the pathomorphological malfunctioning of the joint. One insight was that slipped capital femoral epiphysis (SCFE) impingement leads to substantial damage of the chondrolabral rim area, even in the presence of minor slips. A further surgical development was the extended retinacular flap allowing for correction of the deformity with calculable risk for iatrogenic necrosis. CONSECUTIVE SURGICAL CONCEPT: In 20 years of experience, a treatment concept for SCFE could be established which replaces classic pinning in situ and indirect correction of the deformity with subcapital re-alignment when the physis is still open, with true femoral neck osteotomy for hips with closed physis. Pinning in situ still has a place in minor slips but should be combined with open or arthroscopic recreation of an anterior metaphyseal waisting. UNEXPECTED COMPLICATION: Loss of joint stability is a rare complication of anatomic re-alignment. It can be disease-related when the impingement has induced severe destruction of acetabular cartilage. It can be related to the surgical procedure, especially when the neck was excessively shortened and refixation of the trochanter was not advanced. Finally, in cases with severe and long-lasting deformity, the acetabulum may undergo adaptive flattening, being the cause of joint destabilisation with the correction of the deformity. Advancement of the greater trochanter and/or peri-acetabular osteotomy may be discussed to restabilise the joint.

Instability of the hip after anatomical re-alignment in patients with a slipped capital femoral epiphysis.

AIMS: Several studies have reported the safety and efficacy of subcapital re-alignment for patients with slipped capital femoral epiphysis (SCFE) using surgical dislocation of the hip and an extended retinacular flap. Instability of the hip and dislocation as a consequence of this surgery has only recently gained attention. We discuss this problem with some illustrative cases. MATERIALS AND METHODS: We explored the literature on the possible pathophysiological causes and surgical steps associated with the risk of post-operative instability and articular damage. In addition, we describe supplementary steps that could be used to avoid these problems. RESULTS: The causes of instability may be divided into three main groups: the first includes causes directly related to SCFE (acetabular labral damage, severe abrasion of the acetabular cartilage, flattening of the acetabular roof and a bell-shaped deformity of the epiphysis); the second, causes not related to the SCFE (acetabular orientation and poor quality of the soft tissues); the third, causes directly related to the surgery (capsulotomy, division of the ligamentum teres, shortening of the femoral neck, pelvi-trochanteric impingement, previous proximal femoral osteotomy and post-operative positioning of the leg). CONCLUSION: We present examples drawn from our clinical practice, as well as possible ways of reducing the risks of these complications, and of correcting them if they happen. Cite this article: Bone Joint J 2017;99-B:16-21.

Simultaneous versus staged bilateral direct anterior Total Hip Arthroplasty: Are early patient-centered outcomes equivalent?

While accumulating data on the direct anterior approach to total hip arthroplasty (THA) have demonstrated clinical benefit and durable results, there is little data that exists on patient-centered outcomes and satisfaction when comparing simultaneous bilateral procedures with staged arthroplasty. The aim of this study was to determine whether simultaneous bilateral THA and staged arthroplasty result in equivalent early (1) patient-centered outcomes and patient satisfaction; while maintaining acceptable rates of (2) objective clinical outcome scores, (2) complication rates; and (3) radiographic results. In retrospective review, 41 patients who underwent bilateral one-stage THA were compared to 44 patients who underwent staged bilateral THA during the same time period. The minimum clinical follow up was two years. Generic (EQ-VAS and EuroQoL-5D index) and condition-specific (Oxford Hip Score) instruments were used to assess patient-reported outcomes. Other variables included length of hospital stay (LOS), operative and anesthetic times, blood loss, intra- and post-operative (local and systemic) complications, and radiographic analysis. No significant differences between the two groups were found for patient-reported outcomes, complications, or radiographic assessment. The simultaneous THA group had shorter LOS and operative and anesthetic times, as well as less blood loss.

The evolution and concepts of joint-preserving surgery of the hip.

The use of joint-preserving surgery of the hip has been largely abandoned since the introduction of total hip replacement. However, with the modification of such techniques as pelvic osteotomy, and the introduction of intracapsular procedures such as surgical hip dislocation and arthroscopy, previously unexpected options for the surgical treatment of sequelae of childhood conditions, including developmental dysplasia of the hip, slipped upper femoral epiphysis and Perthes' disease, have become available. Moreover, femoroacetabular impingement has been identified as a significant aetiological factor in the development of osteoarthritis in many hips previously considered to suffer from primary osteoarthritis. As mechanical causes of degenerative joint disease are now recognised earlier in the disease process, these techniques may be used to decelerate or even prevent progression to osteoarthritis. We review the recent development of these concepts and the associated surgical techniques.

Prevalence of cam and pincer-type deformities on hip MRI in an asymptomatic young Swiss female population: a cross-sectional study.

OBJECTIVES: Femoroacetabular impingement is proposed to cause early osteoarthritis (OA) in the non-dysplastic hip. We previously reported on the prevalence of femoral deformities in a young asymptomatic male population. The aim of this study was to determine the prevalence of both femoral and acetabular types of impingement in young females. METHODS: We conducted a population-based cross-sectional study of asymptomatic young females. All participants completed a set of questionnaires and underwent clinical examination of the hip. A random sample was subsequently invited to obtain magnetic resonance images (MRI) of the hip. All MRIs were read for cam-type deformities, increased acetabular depths, labral lesions, and impingement pits. Prevalence estimates of cam-type deformities and increased acetabular depths were estimated, and relationships between deformities and signs of joint damage were examined using logistic regression models. RESULTS: The study included 283 subjects, and 80 asymptomatic females with a mean age of 19.3 years attended MRI. Fifteen showed some evidence of cam-type deformities, but none were scored to be definite. The overall prevalence was therefore 0% [95% confidence interval (95% CI) 0-5%]. The prevalence of increased acetabular depth was 10% (95% CI 5-19). No association was found between increased acetabular depth and decreased internal rotation of the hip. Increased acetabular depth was not associated with signs of labral damage. CONCLUSIONS: Definite cam-type deformities in women are rare compared to men, whereas the prevalence of increased acetabular depth is higher, suggesting that femoroacetabular impingement has different gender-related biomechanical mechanisms.

Fulfilment of patient-rated expectations predicts the outcome of surgery for femoroacetabular impingement.

OBJECTIVE: The aim of this study was to explore the role of expectations in relation to patient-rated global treatment outcome in patients undergoing hip preservation surgery for femoroacetabular impingement (FAI). METHOD: Pre-operatively, 86 patients completed the Oxford Hip Score (OHS), a question about the motivation for undergoing surgery, and Likert-scales rating the improvement expected in various domains (pain, general function, sport, walking capacity, independence, social function, mental well-being). 12-months post-operatively, they rated the actual perceived improvement in each domain and the global outcome of surgery (GTO, 5-point Likert-scale: operation "helped a lot" through to "made things worse"), and completed the OHS again. RESULTS: The most frequent "top reason" for surgery was "alleviation of pain", being indicated by 33% patients; 20% patients chose "fear of worsening", 16% "improvement in everyday activities", 11% "other therapies failed", 10% "improvement in sporting activities" and 10% other. The 12-month data revealed prior expectations had been overly optimistic in more than 50% patients for hip pain, sport, and general physical capacity, and in 33-45% patients for independence, mental well-being, and walking capacity. Multiple regression revealed significant (P<0.05) unique associations between GTO and "fulfilled expectations" for pain and sport (explaining 47% and 12% variance, respectively). CONCLUSION: Expectations of surgery were overly optimistic. Having one's expectations fulfilled, especially in relation to pain, was important for a good outcome. The results emphasise the benefit of assessing patient-orientated outcome in routine practice and the factors that might influence it, such that realistic expectations can be established for patients prior to surgery.

The early outcome of surgical treatment for femoroacetabular impingement: success depends on how you measure it.

OBJECTIVE: To evaluate the proportion of "successes" after surgery for femoroacetabular impingement (FAI) using different external criteria, "feeling better" and "feeling good", and to determine the corresponding cut-off scores indicating "success" for the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) (0-10-point response scale), Oxford Hip Score (OHS) and EuroQoL-5D (EQ-5D and EQ-VAS). DESIGN: Prospective, observational study based in an orthopaedic hospital. Ninety-nine consecutive patients with FAI completed the questionnaires before and 6 months after surgery (arthroscopy or mini-open surgical dislocation). Patient-ratings of change in state ("feeling better") were assessed using a global treatment outcome (GTO) item. Acceptability of the current health state was assessed using the symptom-specific well-being (SSWB) item. Cut-off (threshold) scores for the different instruments indicating the minimal clinically important change (MCIC) and acceptable symptom state were calculated using Receiver Operating Characteristics (ROC) analyses. RESULTS: Significant improvements in all scores (P < 0.001) were recorded 6 months after surgery. The proportion of good outcomes measured with GTO was 60%; 55% of patients reported having achieved an acceptable symptom state. The MCIC scores for improvement were ≥6 for the OHS (0-48 total score range), ≥15 for EQ-VAS, ≥0.16 for EQ-5D index, and ≥22 for the WOMAC-total score (0-100 total score range); absolute scores of ≥40, ≥80, ≥0.682 and ≤8, respectively, were associated with an acceptable symptom state. CONCLUSIONS: The results show that feeling better does not always equate to feeling good, and that improvements in outcome scores, even large, do not necessarily indicate acceptability of the current state. The cut-off values may help in the interpretation of trial results and individual change-scores recorded in clinical practice.

Use of multimodal intra-operative monitoring in averting nerve injury during complex hip surgery.

Peripheral nerve injury is an uncommon but serious complication of hip surgery that can adversely affect the outcome. Several studies have described the use of electromyography and intra-operative sensory evoked potentials for early warning of nerve injury. We assessed the results of multimodal intra-operative monitoring during complex hip surgery. We retrospectively analysed data collected between 2001 and 2010 from 69 patients who underwent complex hip surgery by a single surgeon using multimodal intra-operative monitoring from a total pool of 7894 patients who underwent hip surgery during this period. In 24 (35%) procedures the surgeon was alerted to a possible lesion to the sciatic and/or femoral nerve. Alerts were observed most frequently during peri-acetabular osteotomy. The surgeon adapted his approach based on interpretation of the neurophysiological changes. From 69 monitored surgical procedures, there was only one true positive case of post-operative nerve injury. There were no false positives or false negatives, and the remaining 68 cases were all true negative. The sensitivity for predicting post-operative nerve injury was 100% and the specificity 100%. We conclude that it is possible and appropriate to use this method during complex hip surgery and it is effective for alerting the surgeon to the possibility of nerve injury.

The pathoanatomy and arthroscopic management of femoroacetabular impingement.

Femoroacetabular impingement (FAI) causes pain and chondrolabral damage via mechanical overload during movement of the hip. It is caused by many different types of pathoanatomy, including the cam 'bump', decreased head-neck offset, acetabular retroversion, global acetabular overcoverage, prominent anterior-inferior iliac spine, slipped capital femoral epiphysis, and the sequelae of childhood Perthes' disease. Both evolutionary and developmental factors may cause FAI. Prevalence studies show that anatomic variations that cause FAI are common in the asymptomatic population. Young athletes may be predisposed to FAI because of the stress on the physis during development. Other factors, including the soft tissues, may also influence symptoms and chondrolabral damage. FAI and the resultant chondrolabral pathology are often treated arthroscopically. Although the results are favourable, morphologies can be complex, patient expectations are high and the surgery is challenging. The long-term outcomes of hip arthroscopy are still forthcoming and it is unknown if treatment of FAI will prevent arthrosis.

Survivorship of second-generation metal-on-metal primary total hip replacement.

BACKGROUND: Second generation metal-on-metal total hip replacements (THR) were introduced in the late 1980s and various studies reported conflicting data on their outcome. METHODS: Implant survival of 1,270 second-generation 28 mm metal-on-metal primary THR in 1,121 patients followed prospectively at a mean of 6.8 years postoperatively was evaluated retrospectively. The probability of survival at 10 years was estimated using the method of Kaplan and Meier, and relative risk factors including age, gender, BMI, type of implant fixation and component size were calculated using the Cox proportional-hazards model. RESULTS: Sixty-three (5%) THRs were revised, these being 28 hips for aseptic loosening and 35 for reasons other than aseptic loosening. The probability of survival at 10 years, with revision for any reason as the endpoint, was 0.90 (95% confidence interval (CI) 0.86-0.94) for the THR as a whole, 0.91 (95% CI 0.87-0.95) for the cup, and 0.96 (95% CI 0.94-0.98) for the stem. No demographic factors or covariates were found to significantly affect the implant survivorship. DISCUSSION: As there was no superior probability of survival, and there have been concerns on putative local and systemic toxicity of metal debris, the use of second-generation metal-on-metal articulations for primary THR remains moot.

Hip flexor muscle fatigue in patients with symptomatic femoroacetabular impingement.

PURPOSE: Patients with symptomatic femoroacetabular impingement (FAI) have considerable hip muscle weakness, in particular, hip flexion and hip adduction. In addition, they experience disabilities while performing prolonged dynamic tasks. It was therefore postulated that, besides hip flexor muscle weakness, patients with symptomatic FAI would show greater hip flexor fatigue compared with healthy controls. METHODS: Hip flexor fatigue was evaluated in two different experiments. Fifteen patients with symptomatic FAI and 15 age-matched healthy controls were tested in each experiment. In the first one, changes in hip flexor torque fluctuations and electromyographic (EMG) activity were measured during a sustained submaximal isometric contraction. In the second experiment, hip flexor torque decline was measured during a series of 20 maximal dynamic contractions. RESULTS: Patients with FAI exhibited hip flexor weakness under both isometric (P = 0.02) and isokinetic conditions (P = 0.03). Fatigue-induced changes in isometric hip flexor torque fluctuations, EMG root mean square and median frequency did not differ significantly between patients and controls (P > 0.05). Similarly, isokinetic hip flexor torque decline was comparable in patients with FAI and controls (P > 0.05). CONCLUSIONS: None of the hip flexor fatigue outcomes considered here differed between patients with symptomatic FAI and controls. Therefore, the disabilities that patients experience while performing prolonged dynamic tasks do not seem to be caused by exaggerated hip flexor muscle fatigue.

Hip muscle weakness in patients with symptomatic femoroacetabular impingement.

OBJECTIVE: Femoroacetabular impingement (FAI) is a pathomechanical process, which may cause hip pain, disability and early development of hip osteoarthritis (OA) in young and active adults. Patients with FAI experience functional disability during dynamic weight-bearing activities, which could originate from weakness of the hip muscles. The objective of this study was to compare hip muscle strength between patients with symptomatic FAI and healthy controls. It was hypothesized that patients would present overall hip muscle weakness compared to controls. METHODS: A total of 22 FAI patients and 22 controls matched for gender, age, and body mass participated in the study. We evaluated isometric maximal voluntary contraction (MVC) strength of all hip muscle groups using hand-held and isokinetic dynamometry, and electromyographic (EMG) activity of the rectus femoris (RF) and tensor fasciae latae (TFL) muscles during active flexion of the hip. RESULTS: FAI patients had significantly lower MVC strength than controls for hip adduction (28%), flexion (26%), external rotation (18%) and abduction (11%). TFL EMG activity was significantly lower in FAI patients compared with controls (P=0.048), while RF EMG activity did not differ significantly between the two groups (P=0.056). CONCLUSIONS: Patients with symptomatic FAI presented muscle weakness for all hip muscle groups, except for internal rotators and extensors. Based on EMG recordings, it was demonstrated that patients with symptomatic FAI have a reduced ability to activate TFL muscle during hip flexion. These findings provide orthopedic surgeons with objective information about the amount and specificity of hip muscle weakness in patients with FAI. Future research should investigate the relationship between hip muscle weakness, functional disability and overuse injury risks, as well as the effects of hip muscle strengthening on clinical outcomes in individuals with symptomatic FAI.

Hip resurfacing arthroplasty: current status and future perspectives.

Hip resurfacing arthroplasty (HRA) is a concept of hip replacement that allows treating young active patients with a femoral bone preserving procedure. The proposed advantages of resuming an active lifestyle with increased frequency and duration of sports activities have been shown to be realistic. The 30-year cost-effectiveness in young male patients has been shown to be higher in resurfacing compared to conventional total hip replacement (THA). However, prognosticators of an inferior outcome have also been identified. The most important patient related factors are secondary osteoarthritis as the indication for surgery such as post-childhood hip disorders or AVN, female gender, smaller component sizes and older age (>65 years for males and >55 years for females). In addition, surgical technique (approach and cementing technique) and component design are also important determinant factors for the risk of failure. Moreover, concerns have surfaced with respect to high metal ion concentrations and metal ion hypersensitivities. In addition, the presumed ease of revising HRA has not reflected in improved or equal survivorship in comparison to a primary THA. This highlights the importance of identifying patient-, surgery-, and implant-related prognosticators for success or failure of HRA. Rather than vilifying the concept of hip resurfacing, detailed in depth analysis should be used to specify indications and improve implant design and surgical techniques.