Aims

Reimers migration percentage (MP) is a key measure to inform decision-making around the management of hip displacement in cerebral palsy (CP). The aim of this study is to assess validity and inter- and intra-rater reliability of a novel method of measuring MP using a smart phone app (HipScreen (HS) app).

Aims

Hip disease is common in children with cerebral palsy (CP) and can decrease quality of life and function. Surveillance programmes exist to improve outcomes by treating hip disease at an early stage using radiological surveillance. However, studies and surveillance programmes report different radiological outcomes, making it difficult to compare. We aimed to identify the most important radiological measurements and develop a core measurement set (CMS) for clinical practice, research, and surveillance programmes.

Background

Migration analysis after total joint arthroplasty are performed using EBRA analysis (Krismer et al., 1997) or - more accurate but also much more cost-intensive and time-consuming – via radiostereometric analysis (RSA). For the latter, additional radiographs from two inclined perspectives are needed in regular intervals in order to define the position of the implant relative to tantalum bone markers which have been implanted during surgery of the artificial joint (Fig. 1). Modern analysis software promises a migration precision along the stem axis of a hip implant of less than 100 μm (Witvoet-Brahm et al., 2007). However, as the analysis is performed semi-automatically, the results are still dependent on the subjective evaluation of the X-rays by the observer. Thus, the present phantom study aims at evaluating the inter- and intra-observer reliability, the repeatability as well as the precision and gives insight into the potential and limits of the RSA method.

Introduction: The aims of this paper are to compare the results of Measuring migration rates on radiographs manually and by computer assisted analysis of digitised images.

Methods: Standardised anteroposterior standing hip radiographs taken post operatively and then yearly following hip replacement were used. The radiographs were then scanned at 150 dpi (gray scale) and saved as tif files. The migration was measured manually by drawing a line along the long axis of the femoral component connecting the distal tip, to the notch, which is used to impact the stem proximally. This gives us the length of the hip replacement and an axis along which migration can be measured. The tip of the greater trochanter was selected as a bony landmark. On the plain radiographs two sets of readings were made by one observer. The digitized images were then analysed in the same way using a software package (designed in-house at the University of Dundee). Two sets of readings were performed by observer one and a second set by an independent observer. Statistics: Inter and Intra observer rates were calculated using a paired sample t test.

Results: For the manual readings intra observer mean difference was 0.53mm (Cl 0.31–0.74mm). Comparing manual vs computer readings for observer one there was a correlation of 0.89. For the computer readings intra observer mean difference was 0.36mm (CI 0.64–0.8mm) and inter observer mean difference 0.16 mm, both non-significant differences. This evidence shows that the readings made manually and by computer were not significantly different and that there was no significant inter and intra observer variation. The advantage of computer storage and reading being the faster analysis, the ability to store and access large numbers of radiographs. The disadvantages being the need to scan the radiographs to allow measurement.

Introduction: The aims of this paper are to compare the results of measuring migration rates on radiographs manually and by computer assisted analysis of digitised images.

Methods: Standardised anteroposterior standing hip radiographs taken post operatively and then yearly following hip replacement were used. The radiographs were then scanned at 150 dpi (gray scale) and saved as tif files. The migration was measured manually by drawing a line along the long axis of the femoral component connecting the distal tip, to the notch which is used to impact the stem proximally. This gives us the length of the hip replacement and an axis along which migration can be measured. The tip of the greater trochanter was selected as a bony landmark. On the plain radiographs two sets of readings were made by one observer. The digitised images were then analysed in the same way using a software package (designed in house at the University of Dundee). Two sets of readings were performed by observer one and a second set by an independent observer.

Statistics: Inter and Intra observer rates were calculated using a paired sample t test.

Results: For the manual readings intra observer mean difference was 0.53 mm (CI 0.31–0.74 mm). Comparing manual vs computer readings for observer one there was a correlation of 0.89. For the computer readings intra observer mean difference was 0.36 mm (CI 0.64–0.8 mm) and inter observer mean difference 0.16 mm. Both non significant differences. This evidence shows that the readings made manually and by computer were not significantly different and that there was no significant inter and intra observer variation. The advantage of computer storage and reading being the faster analysis, the ability to store and access large numbers of radiographs. The disadvantages being the need to scan the radiographs to allow measurement.

Accurate detection of migration of hip arthroplasty stems without the burden of bone markers and stereo-radiographic equipment is of interest. This would facilitate the study of stem migration in an experimental setting, but more importantly, it would allow assessing stem loosening in patients with a painful hip outside a study protocol. We developed and validated a marker-free automated CT-based spatial analysis method (CTSA) to quantify stem-bone migration in successive CT scan acquisitions. First, we segmented the bone and stem within both three-dimensional images, then we pairwise registered those elements (Fig. 1). By comparing the rigid transformations of stem and bone, we calculated the migration of the stem with reference to the bone and transferred the three translation and three rotation parameters to an anatomic coordinate system. Based on the rigid transformation, we also calculated the point of the stem that presented the maximal migration (PMM). Accuracy was assessed in a stem-bone model (Fig. 2) by imposing 39 predefined stem rotations and translations, and by comparing those with values calculated with the CTSA tool. In all cases, differences were below 0.20 mm for translations and 0.19° for rotations (95% tolerance interval (95% TI) below 0.22 mm and 0.20°, largest standard deviation of the signed error (SDSE) 0.081 mm and 0.057°). Precision was defined as stem migration calculated in eight clinical relevant zero-migration scenarios. In all cases, precision was below 0.05 mm and 0.08° (95% TI below 0.06 mm and 0.08°, largest SDSE 0.012 mm and 0.020°). The largest displacement of the PMM on the stem was 0.169mm. The precision estimated in five patients was very dependent on the CT scan resolution and was below 0.48 mm and 0.37° (95% TI below 0.59 mm and 0.61°, largest SDSE 0.202 mm and 0.279°, largest displacement of the PMM 0.972 mm). In optimized conditions, the precision in patients improved largely and was below 0.040 mm and 0.111° (largest SDSE 0.202 mm and 0.279°, largest displacement of the PMM 0.156 mm). Our marker-free automated CT-based spatial analysis can detect hip stem migration with an accuracy and precision comparable to that of radiostereometric analysis (RSA), but without the burden of bone markers and the cost of stereo-radiographic equipment. As such, we believe our tool could make accurate measurement of stem migration available to departments without access to RSA and boost this type of research. Moreover, as CTSA does not rely on bone makers, it is applicable to all-comers with a painful hip arthroplasty. Indeed, in those patients with a reference CT scan after hip replacement, a new CT scan could demonstrate stem migration. If no initial CT scan is available, a reference scan could be taken during a first visit and repeated later. Additionally, a “stress test” of the hip could be performed. During such test, comparing CT images acquired during forced maximal intern and external rotation could demonstrate stem loosening

Purpose. This study re-examined the influence of the head shaft angle (HSA) on hip dislocation in a large cohort of children with cerebral palsy (CP). Method. The radiographs of GMFCS Level III – V children from a surveillance programme database were analysed and migration percentage (MP) and HSA measured. The first radiograph of each patient was taken to remove the effect of the surveillance programme. The most displaced hip in each child, by MP, was used for analysis and the corresponding HSA measured. Hip displacement was defined as MP > 40% and logistic regression was used to adjust for HSA, GMFCS, age and sex. Results. 640 children were eligible (271 female (42.3% ), 369 male (57.7% ), mean age 8.2 years, GMFCS III: 160 (25% ), GMFCS IV: 184 (28.75% ), GMFCS V: 296 (46.25% ). 118 children (18.44% ) had a MP > 40% and mean HSA was 160° (range 111 – 180°). Statistical analysis showed that an increasing HSA was associated with hip displacement (odds ratio of 1.02 for a 1° change). A 10° difference in HSA between two patients of the same age, sex and GMFCS gave odds of 1.26 of the patient with the higher HSA having hip displacement. Age and sex had no influence in this model, while a high GMFCS-level was a strong risk factor. Conclusion. Chougule et al found no correlation between HSA and hip migration in children with CP using linear regression analysis. However, the relationship between these variables is not linear. The present study independently confirms an earlier study that HSA is a risk factor for hip displacement in GMFCS III-V children

Purpose. The purpose of this paper is to describe the outcomes of major hip surgery for children with cerebral palsy and communication difficulties using a validated health related quality of life measure and a validated pain score. Method. Children with hypertonic bilateral cerebral palsy (CP) GMFCS levels IV and V, 2–15 years old, having femoral + /- acetabular osteotomies for hip displacement were included if their ability to communicate necessitated the use of the CPCHILD (Caregiver Priorities and Child Health Index of Life with Disabilities) and PPP (Paediatric Pain Profile). The underlying indication for surgery was a hip migration index of more than 40% . CPCHILD and PPP questionnaires were completed face-to-face with the parents or carers at baseline, at 3 months after surgery and at 6 months after surgery. Results. There were 54 patients with a mean age of 8.8 years (SD 3.6). At baseline the mean CPCHILD was 52.1 (SD 11.8). At 3 months it was 58.5 (SD 13.1; p< 0.001). At 6 months it was 59.4 (SD 12.4; p< 0.001). This paper also describes the changes within each domain of the CPCHILD. At baseline the PPP was 12.7 (SD 7.2); at 3 months the PPP was 9.8 (SD 7.2; p< 0.01); at 6 months the PPP was 9.2 (SD 6.4; p< 0.001). Conclusion. Hip reconstruction for displacement is a major intervention for an often asymptomatic condition. This paper confirms that health related quality of life (measured by the CPCHILD) and pain (measured by the PPP) return to baseline or better than baseline within 3 months of surgery and that this is maintained at 6 months. These results should be reassuring for families and healthcare workers looking after children with severe disability undergoing surgery of this sort

Though over ten-year follow-up results of impaction bone grafting for acetabular reconstruction from European countries are available in literatures, clinical reports from Asian countries are rare. The purpose of the present study is to assess mid-term clinical and radiographic follow-up results at least three years after acetabular reconstruction with impaction bone grafting technique by single surgeon in Japanese cohort. The senior author performed 24 acetabular revisions with impaction bone grafting technique in 24 patients from February 2001 to June 2005. The average age of the patients at the revision was 67.5 years (36–82 years). The average follow-up period was 5 years and 5 months (3–7.3 years). The reasons for the operation were aseptic loosening of sockets in 17 hips and migration of bipolar heads in seven. The acetabular bone defects were classified as cavitary in 3 hips and as combined segmental-cavitary in 21 hips according to AAOS classification. For clinical assessment, Merle d’Aubigné and Postel hip score was assessed. Peri-operative complications were recorded. For radiological assessment, antero-posterior hip radiograph was analyzed pre-operatively, and post-operatively at one month, 6 months and every 6 months thereafter. Clear lines more than 2 mm around the sockets using DeLee and Charnley zone classification, and migration of the sockets were assessed. Hodgikinson’s type 3 (complete demarcation line) and type 4 (migration more than 5 mm or change of the angle more than 5 degrees) were classified as “loosening”. Kaplan-Meier survival analysis was performed with radiographic loosening and any re-operation (including recommendation for the re-operation) for the sockets as the end point, respectively. The mean Merle d’Aubigné and Postel hip score improved from 11.5 points before operation to 15.7 points at the final follow-up. Though, intra-operative blow-out fracture of the acetabular floor was detected in 3 hips, re-containment had been achieved by adding metal mesh or bone graft. Clear lines at cement-bone interface were detected at zone 3 in 2 hips. Migration more than 5 mm was detected in 2 hips of type III defect at 2 years and 6 months. Re-revision was recommended for one migrated hip at 3 years and 6 months after the operation, and the other hip was stable with no clinical symptom without progressive migration at the final follow-up of 5 years. The Kaplan-Meier survival analysis, with loosening and re-operation as the end point, predicted a rate of survival of the socket of 91.7% and 95.2% at 5 years, respectively. In conclusion, acetabular reconstruction with impaction bone grafting is attractive, but technical demanding procedure. The survival rate of the present series was compatible with the results of previous literatures. However, careful follow-up is essential, especially for the cases with massive bone defect

Background. Dislocation is a common complication after proximal and total femur prosthesis reconstruction for primary bone sarcoma patients. Expandable prosthesis in children puts an additional challenge due to the lengthening process. Hip stability is impaired due to multiple factors: Resection of the hip stabilizers as part of the sarcoma resection: forces acts on the hip during the lengthening; and mismatch of native growing acetabulum to the metal femoral head. Surgical solutions described in literature are various with reported low rates of success. Objective. Assess a novel 3D surgical planning technology by use of 3D models (computerized and physical), 3D planning, and Patient Specific Instruments (PSI) in supporting correction of young children suffering from hip instability after expandable prosthesis reconstruction following proximal femur resection. This innovative technology creates a new dimension of visualization and customization, and could improve understanding of this complex problem and facilitate the surgical decision making and procedure. Method. Two children, both patients with Ewing Sarcoma of the left proximal femur stage-IIB, ages 3/5 years at diagnosis, were treated with conventional chemotherapy followed by proximal femur resection. Both were reconstructed with expandable prosthesis (one at resection and other 4 years after resection). Hip migration developed gradually during lengthening process in the 24m follow up period. 3D software (Mimics, Materialise, Belgium) were used to make computerized 3D models of patients' pelvises. These were used to 3D print 1:1 physical models. Custom 3D planning software (MSk Lab, Imperial College London) allowed surgeons visualizing the anatomical status and assess of problem severity. Thereafter, osteotomies planes and the desired position of acetabular roof after reduction of hip joint were planned by the surgeons. These plans were used to generate 3D printed PSIs to guide the osteotomies during shelf and triple osteotomy surgeries. Accuracy of planning and PSIs were verified with fluoroscopy and post-op X-rays, by comparing cutting planes and post-op position of the acetabulum. Results. Surgeons reported excellent experience with the 3D models (computerized and physical). It helped them in the decision process with an improved understanding of the relationship between prosthesis head and acetabulum, a clear view of the osteophytes and bone formation surrounding the pseudoacetabulum, and osteophytes inside the native acetabulum. These osteophytes were not immediately visible on 2D CT imaging slices. Surgeons reported a good fit and PSIs' simplicity of use. The hip stability was satisfactory during surgery and in the immediate post-op period. X-ray showed a good and centered position of the hip and good levels of the osteotomies. Conclusions. 3D surgical planning and 3D printing was found to be very effective in assisting surgeons facing complex problems. In these particular cases neither CT nor MRI were able to visualize all bony formation and entrapment of prosthesis in the pseudoacetabulum. 3D visualisation can be very helpful for surgical treatment decisions, and by planning and executing surgery with the guidance of PSIs, surgeons can improve their surgical results. We believe that 3D technology and its advantages, can improve success rates of hip stability in this unique cohort of patients

Introduction. Acetabular reconstruction of a total hip arthroplasty (THA) for a case with severe bone loss is most challenging for surgeon. Relatively high rate of failure after the reconstruction surgery have been reported. We have used Kerboull-type acetabular reinforcement devices with morsellised or bulk bone allografts for these cases. The purpose of this study was to examine the midterm results of revision THA using Kerboull-type acetabular reinforcement devices. Patients and methods. We retrospectively reviewed 20 hips of revision THA (20 patients) between February 2002 and August 2010. The mean age of the patients at the time of surgery was 67.4 years (range 45–78). All of the cases were female. The mean duration of follow-up was 6.5 years (range 2.1–10.4). The reasons of revision surgeries were aseptic loosening in 10 hips, migration of bipolar hemiarthroplasty in 8 hips, and rheumatoid arthritis in 2 hips. We classified acetabular bone defects according to the American Academy of Orthopaedic Surgeons (AAOS) classification; we found two cases of Type II and eighteen cases of Type III. In terms of bone graft, we performed both bulk and morsellised bone grafts in 6 hips and morsellised bone grafts only in 14 hips. We assessed cup alignment using postoperative computed tomography (CT) and The post-operative and final follow-up radiographs were compared to assess migration of the implant. We measured the following three parameters: the angle of inclination of the acetabular device (Fig. 1); the horizontal migration (Fig. 2a); and vertical migration (Fig. 2b). Substantial migration was defined as a change in the angle of inclination of more than 3 degrees or migration of more than 3 mm. The pre- and postoperative hip functions were evaluated using the Japanese Orthopaedic Association (JOA) hip score. Results. The mean cup inclination and anteversion were 38.4 degrees and 10.6 degrees, respectively. The mean change in the angle was 1.9 degrees in inclination of the device. The average horizontal migration was 1.0 mm, and the vertical migration was 2.0 mm. Only one hip showed substantial migration with breakage of the device. This failure case represented a large amount of posterior pelvic tilt in standing position postoperatively. The mean JOA hip score was increased from 46.7 to 74.8. Discussion. Poor outcome using Kerboull-type reinforcement plate with morsellised bone graft only has been demonstrated by many reports. In these literatures, bulk bone graft was recommended particularly in the case of large bone defect such as larger than half of the rounded plate of the device or more than 2 cm of thickness. In our case series, acetabular reconstruction using a Kerboull- type acetabular reinforcement device and bone graft gives satisfactory mid-term results even with morsellized bone graft only. One possible interpretation is that most of our cases had relatively small bone defect according to the staging of severity of the superior segmental bone loss made by Kawanabe et al. We suggest that the progressive posterior pelvic tilt should be considered to be a risk of poor outcome of the acetabular reconstruction using this device. To view tables/figures, please contact authors directly

This study evaluates outcomes of hip adductor surgery in children with cerebral palsy in preventing hip displacement. This review is from the perspective of an extended follow-up (beyond 3 years in contrast to currently available literature) and the Gross Motor Function Classification System (GMFCS). A retrospective audit was performed of children with cerebral palsy aged 2 to 10 years who had primary adductor surgery at the Royal Children’s Hospital Melbourne between January 1994 and December 2004. These children had hip migration percentages (MP) greater than 30% and been followed up for a minimum 12 months post-operatively

Scoliosis and hip subluxation/dislocation are common and often coexistent problems encountered in patients with cerebral palsy (CP). The underlying mechanism may be related to muscle imbalance. Surgical correction may become necessary in severe symptomatic cases. The effect of surgical correction of one deformity on the other is not well understood. We retrospectively reviewed a series of 17 patients with total body cerebral palsy with diagnoses of both scoliosis and hip subluxation who had undergone either surgical correction of their scoliosis (9 patients) or a hip reconstruction to correct hip deformity (8 patients). In all patients, the degree of progression of both deformities was measured, radiographically, using the Cobb angle for the spine and the percentage migration index for hip centre of rotation at intervals before and at least 18 months post surgery. All patients who underwent scoliosis correction had a progressive increase in the percentage of hip migration at a rate greater than that prior to scoliosis surgery. Similarly, patients who underwent a hip reconstruction procedure demonstrated a more rapid increase in their spine Cobb angles post surgery. There may be a relationship between hip subluxation/dislocation and scoliosis in CP patients. Surgery for either scoliosis or hip dysplasia may in the presence of both conditions lead to a significant and rapid worsening of the other. The possible negative implications on the overall functional outcome of the surgical procedure warrants careful consideration to both hip and the spine before and after surgical correction of either deformity. In selected cases there may be an indication for one procedure to follow soon after the other

Introduction: The aims of this study are:. To report and validate the early migration rates of the collarless polished tapered hip replacement using manual and computer measurements. To report early clinical results of the CPT hip. Patients and methods: 80 patients undergoing primary total hip replacement in a single centre were prospectively recruited into the trial. There were 59 females and 21 males: age range 31–84 years, (mean 68 years sd 9.86). Surgery was performed through an anterolateral approach in all cases. A standard cementing technique using a cement gun and cement restrictor was employed. The patients had standardised anteroposterior standing hip radiographs taken post operatively, then yearly. The migration was measured along the long axis of the femoral component In the anteroposterior plane, using the tip of the greater trochanter as a bony landmark. Measurements were made by two independent observers (specialist registrars). Plain radiographs were measured manually using a ruler and set square and digitised images using a software package designed in-house at Dundee University. Correction for magnification was incorporated. Hip assessments were performed at each review by an independent reviewer. Results: The mean migration rates and 95% confidence intervals (Cl) and mean Harris pain and Harris hip scores and Std Deviations were:. There was no significant difference between inter or intra observer measurements for hip migration. This is the first study to date that we are aware of that describes the subsidence rates of the CPT hip which includes validation by inter and intra observer readings

Purpose: We report the clinical and radiological outcome of revision of cemented hip arthroplasties using Hydroxyapatite ceramic (HAC) coated femoral and acetabular components. Patients and Methods: 66-revision hip arthroplasties were performed in 64 patients with JRI Furlong HAC coated femoral and acetabular components. The patients were followed for a mean 10.6 years (7–15). The femoral component was revised in all hips and the acetabular cup was revised in 52 hips (79%). The clinical outcome was measured using Harris, Charnley and Oxford hip scores. Anterior thigh pain was quantified on a visual analogue scale (VAS). The quality of life was assessed using EuroQol EQ-5D. All pre op, immediate post op and last follow up radiographs were analysed for ace-tabular and femoral component loosening. Results:The mean age was 78.2yrs (58–89yrs). The mean time to revision of the primary hip replacement was 96 months (24 to 161). 11 patients died due to causes unrelated to the index revision. At last follow up, the mean Harris and Oxford hip scores were 82 (59 – 100) and 24.4 (12-52) respectively. The Charnley score was 5.0 (3-6) for pain, 4.9 (3-6) for movement and 4.4 (3-6) for mobility. Acetabular bone grafting was performed in 26 (50%) hips. Migration > 4mm of the acetabular component was seen in 2 (4%) hips. Acetabular radiolucen-cies were present in 26 hips (55%). The mean linear polythene wear was 0.05mm/year. The mean stem subsidence was 1.6mm (0.30- 2.4mm). Radiolucencies were present around 21 (33%) stems. Stress shielding was seen in 40 of the 56 stems. Calcar resorption was seen in 11 stems (16%). Endosteal cavitation was seen around 2 stems. Ectopic calcification was seen in 12 (19%) hips. Of the 3 hips re- revised, 2 were for deep sepsis and 1 for recurrent dislocation. The mean EQ- 5D description scores and health thermometer scores were 0.69 (0.51-0.89) and 79 (54-95) respectively (p> 0.05 for both scores compared to average UK population scores). With failure defined as repeat revision because of aseptic loosening, the rate of survival at 12 years was 100% for the acetabular and femoral components. Overall survival at 12 years with removal or repeat revision of either component for any reason as the end point was 93% (95% CI ± 2.3). Conclusion:The results of this study support the continued use of this prosthesis and document the durability of the HAC coated components. Our study had fewer cases of loosening of the components and had a better survival than bipolar implants or cemented acetabular components. As loosening can occur as a late phenomenon, a longer follow up is needed to determine the longevity and durability of the HAC coated prosthesis

Aims

Hip displacement, common in patients with cerebral palsy (CP), causes pain and hinders adequate care. Hip reconstructive surgery (HRS) is performed to treat hip displacement; however, only a few studies have quantitatively assessed femoral head sphericity after HRS. The aim of this study was to quantitatively assess improvement in hip sphericity after HRS in patients with CP.

Aims

Complex total hip arthroplasty (THA) with subtrochanteric shortening osteotomy is necessary in conditions other than developmental dysplasia of the hip (DDH) and septic arthritis sequelae with significant proximal femur migration. Our aim was to evaluate the hip centre restoration with THAs in these hips.

Purpose. A Trabecular Metal Modular Acetabular System (Zimmer, Warsaw, Indiana, USA) is a peripheral rim expansion (elliptical) cup, i.e. a non-hemispherical cup. Radiologically a non-hemispherical cup may be deferent from other conventional hemispherical cups. We reviewed radiological findings of a Trabecular Metal Modular Acetabular System chronologically. Methods. Twenty six patients with osteoarthritis underwent primary total hip arthroplasty (THA) using a Trabecular Metal Modular Acetabular System from 2011 to April 2013. Twenty five patients (follow-up rate: 96.2%) 31 hips could be followed-up over a year were registered. In common, the diameter of every femoral head was 32 mm. We planned the acetabular cup inclination angle to be 45-degree, the cup coverage with host-bone (cup-CE angle) to be over 10-degree, and high hip center was allowed up to 20mm. In case of the cup-CE angle under 10-degree, an acetabular cup was placed medially using Dorr's medial protrusio technique. We established the medial protrusion angle indicating the degree of medial protrusion of an acetabular cup over the pelvic internal wall. The medial protrusion angle was defined by the center point of THA (C) and the 2 cross-points (X. 1. , X. 2. ) which the outline of an acetabular cup crosses the Kohler's line (Figure 1). The cup anteversion angle was measured by the method of Lewinnek, and the cup fixation was evaluated according to the Tompkin's classification. Results. The average follow-up period was 1 year and 3 months (1y1m to 2y8m). The mean diameter of the cup was 54 (48 to 56) mm. Seven high-hip center joints were recognized (2 to 11 mm). The average of cup inclination angle was 42 (32 to 52) degree, of cup anteversion angle was 14 (5 to 36) degree, and of cup CE angle was 25 (−14 to 45) degree. Dorr's medial protrusio technique was necessary in 18 hips. In these 18 hips, the average of medial protrusion angle was 57 (24 to 70) degree. In 4 hips of cup-CE angle less than 10 degree, acetabular bulky bone graft was added. All 31 hips showed the stable fixation, even in 18 hips undergone medial protrusio technique. There was none of hips with migration and/or rotation of an acetabular cup. Radiolucent zone was found in the zone-C of 8 hips. The width of radiolucent zone of all 8 hips was less than 2mm. In these 8 hips, medial protrusio technique was done in 5 hips, and high hip center was found in 3 hips. The radiolucency appeared at postoperatively 2–3 months and disappeared by postoperatively 12 months. Conclusions. All hips showed rigid fixation of a Trabecular Metal Modular Acetabular System in short-term observation. Even in the hips performed Dorr's medial protrusio technique, a Trabecular Metal Modular Acetabular System reached the stable fixation. Radiolucent zone was found transiently in the zone-C of 8 hips (25.8%) and disappeared by postoperatively 12 months. However our series was small and the observation period was short, our results implied that the fixation of a Trabecular Metal Modular Acetabular System was not affected adversely from Dorr's medial protrusio technique

Introduction: The C-stem (DePuy, Leeds, UK) is triple tapered, polished and collarless. These features can facilitate distal stem migration within the cement mantle, a phenomenon first noticed on radiographs and later confirmed by radiostrereometric analysis (RSA) for the double tapered polished Exeter stem (Stryker, Mahwah, NJ). Low revision rates are reported for the Exeter stem and the view that early migration predicts later failure has not been confirmed with double tapered designs. If a triple tapered stem has any advantages is however not known. Patients and methods: 33 primary hip arthroplasties with a median age of 66 (46–74) years were followed for 2 years with radiostereometric analysis (RSA) at 3 months, 6 months, 1, 2 and 3 years. The diagnosis was primary osteoarthrosis in all hips. Both migration and rotation were studied. Results: All the stems migrated distally and posteriorly within the cement mantle. The median distal migration was 1.47 mm at 3 years and the median posterior migration was 1.56 mm at 3 years. All the stems rotated towards retroversion and median rotation at 3 years was 2.0°. For all the other directions the prosthesis was stable up to 3 years. Discussion: The C-stem migrates and rotates more than cemented prostheses of other designs. Compared with other tapered prostheses the distal migration is at the same level but posterior rotation is higher and furthermore it migrates posteriorly, which the other tapered stems do not. If this migration/rotation pattern is tolerable without risk of prosthetic failure needs to be studied further, but at present there is no indication from the available clinical results for the C-Stem that this pattern is deleterious

Hip resurfacing preserves proximal femoral bone stock, optimises stress transfer to the proximal femur and offers inherent stability and optimal range of movement. The early results of metal–on-polyethylene resurfacing designs were poor and the resurfacing concept was largely abandoned. Modern metal-on-metal articulations enabled the introduction of a new generation of hip resurfacings with encouraging early results. In 1997 two of the authors developed a hip resurfacing system utilizing a metal-on-metal bearing. Our study reports on the clinical and radiological outcomes of the first 200 hips that were treated with the Durom hip resurfacing at an average follow up of 4.6 years (range 3.5–6). Between May 2001 and December 2003, 200 consecutive hip resurfacings were performed on 189 patients, using the Durom hybrid metal-on-metal system. The average age of the patients was 50 years (range 22.5 – 72.3) and 119 were male. Patients were seen at 6 weeks and at 3, 6 and 12 months and annually thereafter for clinical and radiological evaluation. Clinical results were evaluated using the Harris Hip Score. A subjective assessment of patient satisfaction was obtained and patient activity was assessed using the UCLA activity score. No patient was lost to follow up. There were no dislocations and no femoral neck fractures. One femoral component was revised due to aseptic loosening 3.9 years postoperatively. There was one late acute haematogenous infection that was successfully treated elsewhere by debridement and retention of the prosthesis. The mean Harris Hip Score improved significantly from 46.7 preoperatively to 94.4 postoperatively. The mean HHS constituents for pain, function and motion all were significantly improved from the preoperative values of 11.9, 25.7 and 4.2 to 41.8, 43.4 and 4.8 respectively following the resurfacing procedure. The mean UCLA activity score was 7.2 indicating a relatively active patient population and 179 hips were rated as excellent by the patients. No cup was considered radiographically loose. Extensive radiologic changes were observed around the femoral stem in 2.5% of the hips, with migration of the femoral component in one case and stem demarcation in 4 cases. All 5 patients maintained excellent function and had no hip pain. Pelvic osteolysis was observed in 2 cases. Neck remodelling changes were observed in 35 hips (17.5%). Kaplan-Mayer survivorship analysis demonstrated the rate of survival of the resurfacing components to be 99.5% (95% confidence interval 98.5 to 100) with revision for any reason as the endpoint. Early results with the Durom resurfacing system appear encouraging. Although these should be regarded with caution, modern metal-on-metal hip resurfacing potentially offers the ultimate bone preservation and restoration of function in appropriately selected young patients