Background. We herein report a case of isolated hip pain in a four year old boy. The unique aspect of this case study is the unusual history, presentation, ultrasonography, MRI and blood culture results, which lead to the diagnosis and treatment of adductor pyomyositis with a rare organism (Streptococcus Mitis) in a temperate country. The objectives of this case study is to discuss the key learning outcomes with respect to assessment and management of this case. Methods. The patient presented with a one day history of malaise, fever, left groin pain and inability to weight bear on the left leg. There was no history of any trauma, predisposing infections or recent travel. A working diagnosis of transient synovitis / septic arthritis of the hip was made on clinical examination. Results. Plain radiograph and ultrasound of the hip was normal with no effusion. Two consecutive blood cultures suggested Streptococcus Mitis bacteriaemia and MRI scan confirmed pyomyositis of the left hip adductors that was too small to drain. Streptococcus Mitis is a normal commensal organism of the oral cavity however it can lead to opportunistic infections particularly endocarditis. Echocardiogram revealed no cardiac complications, in particular no endocarditic vegetation. Patient was treated with intravenous benzylpenicillin for a week followed by oral phenoxymethylpenicillin for a week. Conclusion. Adductor pyomyositis must be considered as a differential diagnosis in a child with unusual presentation of hip pain. When an ultrasound is normal, MRI scan is warranted to confirm diagnosis. Septic screen should include blood cultures. The commonest causative organisms are the Staphylococcus family. However if Streptococcus Mitis is isolated, cardiac sources of infection resulting in septic emboli must be investigated. Repeated MRI scans are required particularly if the patient does not respond to medical management. Level of Evidence. IV

Introduction and Objective. Hip osteoarthritis (OA) is the leading cause for total hip arthroplasty (THA). Although, being considered as the surgery of the century up to 23% of the patients report long-term pain and deficits in physical function and muscle strength may persist after THA. Progressive resistance training (PRT) appear to improve several outcomes moderately in patients with hip OA. Current treatment selection is based on low-level evidence as no randomised controlled trials have compared THA to non-surgical treatment. The primary objective of this trial is to determine the effectiveness of THA followed by standard care compared to 12 weeks of supervised PRT followed by 12 weeks of optional unsupervised PRT, on changes in hip pain and function, in patients with severe hip OA after 6 months. Materials and Methods. This is a protocol for a multicentre, parallel-group, assessor blinded, randomised controlled superiority trial. Patients aged ≥50 years with clinical and radiographic hip OA found eligible for THA by an orthopaedic surgeon will be randomised to THA or PRT (allocation 1:1). The primary outcome will be change in patient-reported hip pain and function, measured using the Oxford Hip Score. Key secondary outcomes will be change in the Hip disability and Osteoarthritis Outcome Score subscales, University of California Los Angeles Activity Score, 40-meter fast-paced walk test, 30-second chair stand test, and number of serious adverse events. Results. The trial has been approved by The Regional Committees on Health Research Ethics for Southern Denmark (Project-ID: S-20180158) in February 2019 and registration was performed at . ClinicalTrials.gov. (NCT04070027) in August 2019. Recruitment was initiated on the 2. nd. of September 2019 and the final deadline will be on the 30. th. of June 2021, or when a sample size of 120 patients has been accomplished. Conclusions. The results of the current trial are expected to enable evidence-based recommendations, which may be used to facilitate the shared-decision making process in the discussion of treatment strategy for the individual patient with severe hip OA. All results will be presented in peer-reviewed scientific journals and international conferences

Osteonecrosis of the femoral head is a complex pathologic process with many aetiological factors. Factors most often mentioned in the literature are mechanical disruption (hip trauma or surgery), steroid use, smoking, haemoglobinopathies and hyperlipidaemia. 1. Our case depicts a rare association of crack cocaine related to osteonecrosis of the femoral head which has never been reported in the available literature. Case Report: A 32 year old man was referred to our Orthopaedic clinic with right hip pain. He had a 9 pack-year history of cigarette smoking and had also smoked crack cocaine between ages 20 to 28; shortly after this the hip pain started. He denied antecedent injury. He had undergone a steroid injection into his right ankle abroad for swelling one year before referral, which was after onset of hip pain. MRI of his hip previously performed abroad had been normal. The patient had an indoor job and was otherwise fit and well. On examination he had reduced of movement in his right hip with 5–10 degrees of fixed flexion deformity. Plain radiography demonstrated cyst formation and sclerosis of both femoral heads. Repeat MRI confirmed bilateral osteonecrosis, worse on the right with risk of head collapse. The patient underwent bilateral core decompressions. Subsequent follow-up demonstrated a mobile patient with no need for arthroplasty and he was discharged after two years. Osteonecrosis is caused by the coagulation of the intra-osseous microcirculation leading to thrombosis formation and eventual reduction in osseous blood supply. Steroid use is associated with increased risk of osteonecrosis to the femoral head, however in these cases the patients often undergo either direct local or systemic infiltration of steroid. In this case steroid was administered after symptoms began to a far distant site and therefore cannot be the cause. Cigarette smoking is also known to cause osteonecrosis. Our patient had smoked cigarettes for fourteen years without problems, and it was after he ceased to smoke crack cocaine that his symptoms began. Cocaine blocks voltage-gated sodium-channels causing vasospasm. It is known to cause nasal and facial bone osteonecrosis due to its common intranasal method of delivery. We postulate that in this case crack cocaine was a synergistic factor towards development of femoral head osteonecrosis

Introduction. In osteonecrosis of the femoral head (ONFH), progression of collapse is influenced by a repair reaction, especially bone resorptive activity, around the necrotic bone. Alendronate is a potent inhibitor of bone resorption by inhibiting osteoclast activity. We performed a clinical study to test if systemic alendronate treatment would prevent the development of collapse in patients with ONFH. Methods. Thirty-three hips in 22 ONFH patients with initial ARCO Stage 1 to 3 were included. Fourteen patients (20 hips) received daily administration of oral alendronate 5mg/day (alendronate group) and 8 patients (13 hips) did not receive alendronate administration (Control group). Baseline investigations included anteroposterior and lateral plain radiographs, T1-weighted magnetic resonance imaging (MRI), and biochemical markers (urinary NTX and serum BAP). Examination of the biochemical markers were repeated at 3, 6, and 12 months, and MRI imaging was repeated at 12 months. At 3 years, clinical symptoms and findings on plain radiographs were compared between the 2 groups. Advancement of ARCO stages or increase of collapse by more than 2 mm were considered as development of collapse. Results. At baseline, there were no significant differences regarding patients' age, distribution of gender, etiology, ARCO radiographic stage, and extent of necrosis between the 2 groups. In the alendronate group, there was an early decrease of osteoclast activity (NTX) and osteoblastic activity (BAP) at 3 months, with significantly larger decrease in NTX (43%) than BAP (21%) at 12 months. At 3 years, development of collapse was observed in 7 hips (54%) of the Control group, and in 3 hips (15%) of the alendronate group. Hip pain was noted in 9 hips (69%) of the Control group, and in 6 hips (30%) of the alendronate group. There was a significant difference oncollapse development and occurrence of hip pain between the two groups (p<0.05). Signal change around the necrotic region on serial MRI images during the first 1 year was observed in 54 % of the Control group, and only 11% of the alendronate group. Conclusion. Alendronate therapy decreased biochemical markers, especially osteoclast activity, after an early period from start of administration. Several clinical studies have shown promising short-term results for prevention of collapse in ONFH by administration of bisphosphonates. The present study showed a significant preventing effect of collapse development by administration of alendronate which was maintained for 3 years of treatment. Low incidence of signal change on serial MRI images may also reflect decrease of repair activity in the alendronate group. Further studies with longer follow-up, larger numbers of patients, and randomized administration of the drug among patients are required., However, alendronate administration may become one of the effective conservative treatments which might obviate the need for osteotomy or replacement surgery in some populations of ONFH patients

We report the survival, functional and radiological outcome of a series of Birmingham hip resurfacing procedures performed by a single surgeon at a district general hospital. The aim of this study was to retrospectively report the medium term outcome and survival of our patients. There were 45 hip resurfacings performed in 38 patients between 2004 and 2010. Patients were followed for a mean duration of four years. Mean age of 52.6 years (range 26 to 65). Although no patients were lost to follow up, four did not complete the oxford hip scoring assessment. The median Oxford hip score was 16.25 points (range 12–39 points, standard deviation 5.9) at 48 months follow up (range 11.5–84.2 months). The mean acetabular inclination was 46.9 (range 40.9–59.9) in the 45 hip resurfacings post operatively. There was one patient with varus subsidence of the prosthesis and one patient with persistent hip pain post operatively under investigation currently. There was no definite radiological evidence of loosening or of narrowing of the femoral neck. No cases were revised and no cases developed any other complications. These medium-term results from a district general hospital are comparable to the other studies performed. Few independent studies have reported the outcome of resurfacing arthroplasty of the hip in a district general hospital. Further evaluation and follow up of these patients is required to address the concerns raised by other centers related to fracture and metal debris

We undertook a retrospective cohort study to determine if body mass index (BMI) is an independent factor in determining patient outcome following total hip replacement (THR). Outcomes were determined using the Oxford Hip Score, a questionnaire designed to evaluate self-reported function and pain levels in people with hip pain. We looked at all THRs carried out on patients with a BMI of ≥30 over a 38 month period (220 operations) and compared these with 220 randomly selected THRs carried out on patients with a BMI of <30 within the same 38 month period. For each case we recorded patient BMI, P score and Oxford scores. We calculated the difference between pre-operative and one-year post-operative Oxford hip scores. We used Kendall's rank correlation to assess any potential correlation between BMI and functional change, and the Mann-Whitney U test to establish if functional change between the groups was statistically significant. Our study indicates that BMI is not an independent factor in determining relative subjective functional change following THR. Although it showed that patients with a BMI of ≥30 have worse function both before and after THR, there was no statistically significant difference between the two groups in terms of functional change. We therefore suggest that patients with a higher BMI be considered candidates for THR as they can expect the same degree of functional improvement. Given the trend for increasing numbers of obese patients in the population these findings could have a significant impact on the future of THR operations

Reconstruction of severe acetabular defects during revision hip arthroplasty presents a significant surgical challenge. Such defects are associated with significant loss of host bone stock, which must be addressed in order to achieve stable implant fixation. A number of imaging techniques including CT scanning with 3D image reconstruction are available to assist the surgeon in the pre-operative planning of such procedures. We describe the use of a novel technique to assist the pre-operative planning of severe acetabular defects during revision hip arthroplasty. Patient and Methods – We present the use of this technique in the case of a 78 year old patient who presented 20 years from index procedure with severe hip pain and inability to weight bear due aseptic loosening of a previously revised total hip arthroplasty. A Paprosky 3B defect was noted with intra-pelvic migration of the acetabular component. Pre-operative investigations included: inflammatory markers, pelvic CT scan with 3D reconstruction, pelvic angiography and hip aspiration. Using DICOM images obtained from the CT scan, we used free open source software to carry out a 3D surface render of the bony pelvis. This was processed and converted to a suitable format for 3D printing. Using selective laser sintering, a physical 3D model of the pelvis, acetabular component and proximal femur were produced. Using this model the surgeon was able to gain an accurate representation of both the position of the intra-pelvic cup and more accurately assess the loss of bone stock. This novel technique is particularly useful in the pre-operative planning of such complex acetabular defects in order to determine if/which reconstruction technique is most likely to be successful. 3D printing is a relatively recent technology, which has numerous potential clinical applications. This is the first reported case of this technology being used to assess acetabular defects during revision hip arthroplasty. The use of this technology gives the surgeon a 3D model of the pelvis, quickly (7 days from CT) and at a tenth of the cost (£280) of producing such a model through the traditional commercial routes. The model allowed the surgeon to size potential implant, quantify the amount of bone graft required (if applicable) and to more accurately classify the loss of acetabular bone stock

Introduction. The goal of joint-preserving surgery for the treatment of osteonecrosis of the femoral head (ONFH) is to delay or prevent osteoarthritic development. Bone marrow is a source of osteogenic progenitors that are key elements in the process of bone formation and fracture healing. We established an easy-to-use method using a conventional manual blood bag centrifugation technique traditionally used for extracting buffy coats, for concentration of nucleated cells and platelets from clinical bone marrow aspirates to obtain osteogenic progenitors and growth factors. However, it is unclear whether the surgical goals are really achieved and if so in which patients. The purpose of this study was to identify demographic, clinical, and radiographic factors predicting total hip arthroplasty (THA) conversion after CABMAT for the treatment of idiopathic ONFH. Methods. We retrospectively reviewed 123 patients (213 hips) who had CABMAT between 2003 and 2010. Sixty-five subjects (115 hips) were male and 58 (98 hips) were female with an average age at the time of CABMAT of 40.1 years. Of the 213 hips, 143 hips in 78 patients had corticosteroid-induced ONFH, 46 hips in 27 patients had alcohol-associated, and 24 hips in 18 patients had no etiological factors could be detected. The mean follow-up period was 60.5 months. The endpoint of evaluation was set as the time point which the patient required additional surgery (THA) depending on the spontaneous hip pain, x-ray change, and social back ground. The following factors were investigated: age, sex, body mass index (BMI), unilateral or bilateral, etiological factors, preoperative classification and staging, visual analogue scale (VAS), JOA clinical score. The 213 hips were divided into two groups: a THA conversion (THA) group and a non-THA conversion (non-THA) group. A multivariate analysis was performed using a logistic regression model. Results. In this series, of the 213 hips, 51 hips (23.9%) in 37 patients converted THA. The mean age of patients in THA group was 43.0 years and that of non-THA group was 39.2 years. The mean duration between CABMAT and THA conversion was 26.9 months. Preoperatively, 11 of the 213 hips were classified as type A, 8 hips as type B, 78 hips as type C1, and 116 hips as type C2. 48 hips were classified as stage 1, 65 hips as stage 2, 58 as Stage 3A, 34 as Stage 3B, 8 as stage 4. Postoperatively, no hips in types A and B, 11 hips (14.1%) in type C1, 40 hips (34.5%) in type C2, and 8 hips (16.7%) in stage 1, 13 hips (25.0%) in stage 2, 14 hips (24.1%) in stage 3A, 11 hips (32.4%) in stage 3B, 5 hips (62.5%) in stage 4 were converted THA. Conclusions. The strongest predictors of THA conversion after CABMAT were type, the extent of necrotic area, and age. The results suggest that what factors determine the THA conversion after CABMAT and which patients of idiopathic ONFH are appropriate for CABMAT treatment. Further careful follow-up is needed clinically, and an additional treatment strategy to improve CABMAT is currently in progress

Summary Statement. Pincer deformities are involved in the genesis of femoro-acetabular impingement (FAI). Radiographic patterns suggestive of pincer deformities are common among general population. Prevalence of the pincer deformities among general population may be overestimated if only plain radiographs are considered. Background. Pincer deformities (coxa profunda, protrusio acetabuli, global retroversion, isolated cranial over-coverage) have been advocated as a cause of femoro-acetabular impingement (FAI) and early hip osteoarthritis (OA). Different radiographic patterns may advocate the presence of a pincer deformity. The prevalence of these radiographic patterns among general adult population, as their role in early hip OA, is poorly defined. Methods. From a database of 40.351 pelvic radiograms and CT collected at our institution between 2005 and 2010, we selected 118 caucasian individuals (56 females, 62 males), aged between 15 and 60 years, who underwent both plain radiographs and CT of the pelvis. A series of exclusion criteria were strictly applied to achieve a sample of adult general population as more representative as possible. In particular patients with presence of any disease involving hip joint, including: advanced hip OA (grade II or III of Tonnis scale), head necrosis, fractures, heterotopic ossifications, bone and soft tissue tumors, rheumatic pathologies, classic hip dysplasia with lateral center-edge angle (L-CEA) less than 20°, clinical diagnosis of FAI or hip pain, were excluded from the present study. We also excluded patients in which open growth plates, osteopenia, hardware or evidence of prior surgery were present. Radiographs were investigated for pelvic tilt, signs of retroversion, lateral center-edge angle (L-CEA), presence of coxa profunda or protrusio acetabuli. EAV was measured on CT scans at the equatorial plane of the acetabulum passing by the 3 o'clock position, while CAV was calculated at a more cranial level corresponding to the 1 o'clock position EAV and CAV were obtained in the axial plane by measuring the angle made by a line connecting the anterior and posterior rims of the acetabulum and a line perpendicular to the line connecting the ischial spines. A new parameter, Acetabular torsion (AT), has been introduced in order to discriminate between global retroversion and isolated cranial over-coverage. AT was defined as the difference between EAV and CAV. Cam deformity was assessed by calculating the alpha angle on the femoral side; an alpha angle > 55° was considered abnormal and suggestive of cam deformity. Radiological signs of chondrolabral degeneration were noticed. Results. Mean EAV and mean CAV were higher in females, mean AA was higher in males. L-CEA, EAV and CAV increased with age. Mean AT was 8.8±6.3. AT was inversely related to CAV (r=−0.799; p<0.0005) but independent from EAV (r=−0.076; p=0.244). EAV≤10.2° was defined as the marker of global retroversion, while AT≥21.2° was defined as the marker of isolated cranial over-coverage. Overall prevalence of pincer deformities was 21.6% (> females; p=0.02). Early OA changes were related to age (p<0.0005) and AA (p<0.0005), but not to pincer deformities (p=0.96). Radiological signs of retroversion showed good or excellent negative predictability but poor positive predictability. Conclusions. Radiographic patterns of pincer deformities are common among general population. Relationship with radiological signs of chondrolabral degeneration is poor. CT allows to discriminate between global retroversion and isolated cranial over-coverage. Prevalence of the pincer deformities among general population may be overestimated if only plain radiographs are considered

Introduction. Subchondral insufficiency fracture of the femoral head (SIF) often occurs in osteoporotic elderly patients. Patients usually suffer from acute hip pain without any obvious antecedent trauma. Radiologically, a subchondral fracture is seen mainly in the superolateral portion of the femoral head. The T1-weighted magnetic resonance (MR) images show a low-intensity band in the subchondral area of the femoral head, which tends to be irregular, disconnected, and convex to the articular surface. This low-intensity band in SIF was histologically proven to correspond to the fracture line with associated repair tissue. Some cases of SIF resolve after conservative treatment, while others progress until collapse, thereby requiring surgical treatment. The prognosis of SIF remains unclear. This study investigated the risk factors that influence the prognosis of SIF based on the progression of the collapse. Methods. Between June 2002 and June 2008, seventeen patients diagnosed as SIF were included in this study. Sequential radiographs were evaluated for the presence of progression of the collapse. The clinical profiles, including the age, body mass index (BMI), follow-up period and Singh index were examined. The morphological characteristics of the low intensity band on the T1-weighted magnetic resonance images were also examined, with regard to the band length, band thickness and band length ratio; which is defined as a proportion of the band length to the weight-bearing portion of the femoral head. Results. Radiographically, a progression of the collapse was observed in 8 of 17 (47.1%) patients. The band length in patients with progression of the collapse (mean: 22.6 mm) was significantly larger than that in those without progression of the collapse (mean: 12.3 mm; P < 0.05). The band length ratio in patients with progression of the collapse (mean: 73.3 %) was also significantly higher than that in those without progression of the collapse (mean: 42.3 %; P < 0.01). No significant differences were seen in the other variables (the age, BMI, follow-up period, Singh index, and band thickness). Conclusion. One of the important differential diagnoses in determining SIF may include osteonecrosis. The shape of the low signal intensity band on the T1-weighted MR images is one of the characteristic findings in SIF: namely, it is generally irregular, serpiginous, convex to the articular surface, and often discontinuous. This low-intensity band is generally surrounded by bone marrow edema. Histopathologically the band in SIF represents the fracture line with associated repair tissue. On the other hand, in osteonecrosis, since the low-intensity band represents repair tissue, it is generally smooth and circumscribes all of the necrotic segments. In this study, the prognosis of SIF varied even though all the patients received similar non-operative treatments. If the prognosis for SIF can be predicted at the early stage, it would allow the design of optimal treatments in each patient. In this preliminary investigation, both the band length and band length ratio were demonstrated to be useful when selecting the optimal treatment for SIF

Introduction. Osteonecrosis of the femoral head (ONFH) is one of the most serious complications associated with corticosteroid therapy. In patients with ONFH, collapse of the femoral head often occurs and causes severe hip pain and impaired hip joint function. Despite the widely spread use of corticosteroids for treating various diseases and a known association between prevalence of ONFH and daily dose of corticosteroids, the pathomechanism for the development of ONFH has not been identified. Since hepatic cytochrome P4503A (CYP3A) is a predominant enzyme responsible for metabolizing corticosteroids and its activities varies more than 10-fold, low hepatic CYP3A activity leads to a remarkable increase of corticosteroid levels and its effect. We have previously reported that hepatic CYP3A levels are significantly lower in patients with corticosteroid-induced ONFH than that in control patients and patients with alcohol-related ONFH and that hepatic CYP3A activity inversely correlated with the incidence of osteonecrosis and extent of the necrotic area caused by the same dose of corticosteroids in a rabbit model, suggesting possible prevention of the corticosteroid-induced osteonecrosis by adjusting corticosteroid dose based on the level of individual hepatic CYP3A activity prior to corticosteroid therapy. To examine hepatic CYP3A activity, measuring clearance of administrated midazolam (MDZ) is a reliable method, as shown by the significant correlations between the clearance of midazolam and hepatic CYP3A levels measured by biopsy and the clearance of other CYP3A-specific substrates. However, the method is invasive and time consuming for measuring clearance of administrated MDZ, needing multiple blood samplings over half a day for each subject. The aim of this study was to develop the simple, safe and noninvasive methods for measuring the level of hepatic CYP3A activity, which is applicable to prevent the occurrence of corticosteroid-induced osteonecrosis prior to corticosteroid therapy. Methods. Thirty seven healthy male (n=20) and female (n=17), volunteers who had a mean age of 27 years received single oral administration of a small quantity of midazolam (50 mg/kg) and concentrations of total midazolam and its principal metabolite, 1-hydroxymidazolam (1-OH-midazolam), in each plasma at 15, 30, 45, 60, and 90 minutes and 2, 3, 4, 6, 9 and 12 hours post-drug administration were measured. Secondarily, the assessment of the Observer's Assessment of Alertness/Sedation (OAA/S) Scale was also used during the 12-hour post-administration period. Results. The best correlations between midazolam clearance and the ratio of 1- OH- midazolam/ midazolam plasma concentrations measured at each experimental time were observed at 4 hours (R2 = 0.83) post-dosing, and better correlations were found at 3 hours with a strong correlation (R2 = 0.81). Good correlations between midazolam clearance and OAA/S scale were found at 15 minutes (p = 0.04). Conclusion. A single midazolam plasma measurement taken at 4 hours post-oral administration may represent an accurate marker of CYP3A activity. This simple, safe and noninvasive method for measuring CYP3A activity could be used for patients prior to corticosteroid therapy, and the adjusting dose of corticosteroids, tailor-made medicine, depending on the CYP3A activity of the individual patient could avoid the occurrence of corticosteroid-induced osteonecrosis

Objectives

We have previously investigated an association between the genome copy number variation (CNV) and acetabular dysplasia (AD). Hip osteoarthritis is associated with a genetic polymorphism in the aspartic acid repeat in the N-terminal region of the asporin (ASPN) gene; therefore, the present study aimed to investigate whether the CNV of ASPN is involved in the pathogenesis of AD.

Objectives

The aim of this study was to systematically review the literature on measurement of muscle strength in patients with femoroacetabular impingement (FAI) and other pathologies and to suggest guidelines to standardise protocols for future research in the field.

Using a rat model the characteristics of the sensory neurones of the dorsal-root ganglia (DRG) innervating the hip were investigated by retrograde neurotransport and immunohistochemistry.

Fluoro-Gold solution (FG) was injected into the left hip of ten rats. Seven days later the DRG from both sides between T12 and L6 were harvested. The number of FG-labelled calcitonin gene-related peptide-immunoreactive or isolectin B4-binding neurones were counted.

The FG-labelled neurones were distributed throughout the left DRGs between T13 and L5, primarily at L2, L3, and L4. Few FG-labelled isolectin B4-binding neurones were present in the DRGs of either side between T13 and L5, but calcitonin gene-related peptide-immunoreactive neurones made up 30% of all FG-labelled neurones.

Our findings may explain the referral of pain from the hip to the thigh or lower leg corresponding to the L2, L3 and L4 levels. Since most neurones are calcitonin gene-related peptide-immunoreactive peptide-containing neurones, they may have a more significant role in the perception of pain in the hip as peptidergic DRG neurones.

Studies on the migration of an implant may be the only way of monitoring the early performance of metal-on-metal prostheses. The Ein Bild Roentgen Analyse - femoral component analysis (EBRA-FCA) method was adapted to measure migration of the femoral component in a metal-on-metal surface arthroplasty of the hip using standard antero-posterior radiographs. In order to determine the accuracy and precision of this method a prosthesis was implanted into cadaver bones. Eleven series of radiographs were used to perform a zero-migration study. After adjustment of the femoral component to simulate migration of 3 mm the radiographs were repeated. All were measured independently by three different observers.

The accuracy of the method was found to be ± 1.6 mm for the x-direction and ± 2 mm for the y-direction (95% percentile). The method was validated using 28 hips with a minimum follow-up of 3.5 years after arthroplasty. Seventeen were sound, but 11 had failed because of loosening of the femoral component. The normal (control) group had a different pattern of migration compared with that of the loose group. At 29.2 months, the control group showed a mean migration of 1.62 mm and 1.05 mm compared with 4.39 mm and 4.05 mm in the failed group, for the centre of the head and the tip of the stem, respectively (p = 0.001). In the failed group, the mean time to migration greater than 2 mm was earlier than the onset of clinical symptoms or radiological evidence of failure, 19.1 versus 32.2 months (p = 0.001) and 24.8 months (p = 0.012), respectively.

EBRA-FCA is a reliable and valid tool for measuring migration of the femoral component after surface arthroplasty and can be used to predict early failure of the implant. It may be of value in determining the long-term performance of surface arthroplasty.