Acetabular Inclination Angle Research Articles

Effect of Acetabular Position on Polyethylene Liner Wear Measured Using Simultaneous Biplanar Acquisition

BackgroundStudies that have previously examined the relationship between acetabular component inclination angle and polyethylene wear have shown increased wear of conventional polyethylene with high inclination angles. To date, there are no long-term in vivo studies examining the correlation between cup position and polyethylene wear with highly crosslinked polyethylene. MethodsAn institutional arthroplasty database was used to identify patients who had metal-on-highly crosslinked polyethylene primary total hip arthroplasty using the same component design with a minimum follow-up of 10 years. A modified radiostereometric analysis examination setup was utilized, recreating standard anteroposterior and cross-table lateral examinations in a single stereo radiostereometric analysis acquisition. The same radiographs were used to measure inclination angle and anteversion. ResultsA total of 43 hips were included for analysis in this study. Average follow-up was 12.3 ± 1.2 years. The average linear wear rate was calculated to be 0.066 ± 0.066 mm/y. Inclination angle was not correlated with polyethylene wear rate (P = .82). Anteversion was also not correlated with polyethylene wear rate (P = .11). ConclusionAt long-term follow-up of >10 years, highly crosslinked polyethylene has a very low wear rate. This excellent tribology is independent of acetabular position. The low wear rate highlights the excellent results of metal on highly crosslinked polyethylene, and supports its use in total hip arthroplasty.

Magnetic resonance imaging evaluation of acetabular orientation in normal Chinese children.

There are no data regarding the acetabular orientation on magnetic resonance imaging (MRI); this study investigates the changes of acetabular orientation with age in normal Chinese children.We retrospectively analyzed the medical records of children who underwent hip MRI examination at our hospital from January 2009 to December 2015. A total of 180 patients with normal MRI reading of the hip joints were included and were divided into 14 groups according to age: from 6 months of age and then for each year from 1 to 16 years. The bony and cartilage acetabular anteversion angle (AAA), acetabular inclination angle (AIA), and acetabular index (AI) were measured. Total bony and cartilage femoral head coverage angles were measured on axial section total femoral head coverage angle (a-TCA) and coronal section total femoral head coverage angle (c-TCA).The mean bony AAA and AIA were 12.2 ± 2.5° and 50.9 ± 2.5°, respectively; both of them stayed constant from the age of 6 months to 16 years. Similar results were found in cartilage AAA (12.1 ± 2.5°) and AIA (41.2 ± 3.0°). There was no difference between bony and cartilage AAA, but bony AIA was significantly larger than cartilage AIA. Bony AI was 24.1 ± 2.4° at the age of 6 months, decreasing to 12.5 ± 2.3° by 12 to 13 years of age; cartilage AI (5.9 ± 1.7°) maintained a steady value with age. The mean bony a-TCA and c-TCA at 6 months were 117.0 ± 5.8° and 127.5 ± 5.1°, increasing to 144.5 ± 4.6° and 140.7 ± 2.5° at the age of 16 years. However, the cartilage a-TCA (145.2 ± 7.2°) and c-TCA (154.1 ± 5.7°) did not change significantly with age.Both bony and cartilage AAA and AIA remain constant up to the age of 16 years in normal Chinese pediatric population. Although the cartilage coverage of femoral head by the acetabulum remains unchanged with age, the bony coverage of femoral head increases.

A Comparison of Radiographic Outcomes After Total Hip Arthroplasty Between the Posterior Approach and Direct Anterior Approach With Intraoperative Fluoroscopy

BackgroundRadiographic outcomes after total hip arthroplasty (THA) have been linked to clinical outcomes. The direct anterior approach (DAA) for THA has been criticized by some for providing limited exposure and compromised implant position but allows for routine use of intraoperative fluoroscopy. We sought to determine whether radiographic measurements differed by THA approach using prospective cohorts. MethodsTwo reviewers blinded to surgical approach examined 194 radiographs, obtained 4-6 weeks after primary THA, and obtained measurements for acetabular inclination angle, acetabular anteversion, radiographic limb length discrepancy (LLD), and femoral offset. All surgeries were performed at a tertiary academic medical center in rural New England by an experienced fellowship-trained arthroplasty surgeon. Measurements for inclination angle, anteversion, LLD, and offset were made into binary yes/no responses based on whether the mean measurement (between the 2 reviewers) was acceptable or not based on established criteria. Multivariate logistic regression analyses were performed using preoperative and intraoperative characteristics to identify predictors of acceptability for each measurement. ResultsThe DAA group had higher rates of acceptable acetabular angle (96 vs 85%, P = .005) and was protective against an unacceptable angle in an adjusted predictive model (odds ratios 0.16, P = .005). There were no significant differences between approaches for acceptable anteversion, LLD, or offset. Body mass index of 30-34 was associated with higher odds of unacceptable inclination angle compared to the nonobese group (adjusted odds ratio, 6.82, P = .013). ConclusionDAA for THA was associated with lower odds of unacceptable inclination angle compared to the posterior approach, with no differences in anteversion, LLD, or offset.

Cobalt serum levels differ in well functioning Birmingham resurfacing and Birmingham modular THA.

Metal-on-metal (MoM) bearings are known to release metal ions secondary to wear and corrosion. This may cause local reactions (adverse soft tissue reactions and osteolysis) and systemic effects. Little is known about the exact pattern and the differences between large head MoM total hip replacements (THA) and resurfacings (HR). (1) Is there a difference in metal ion concentrations between HR and MoM-THR using the same bearing design (Birmingham Hip Resurfacing System, Smith & Nephew, Inc. Memphis, TN, USA)? (2) Are metal ion levels changing over time in MoM-THA or HR? (3) Do acetabular inclination angle and femoral component size influence cobalt and chromium levels? Is there a correlation between clinical outcome and metal ion levels? A retrospective analysis was conducted in 77 well functioning unilateral Birmingham HR and 42 well functioning unilateral modular Birmingham MoM-THA (Smith & Nephew, Inc. Memphis, TN, USA) operated on between 2007 and 2012. Blood samples were taken at a minimum of 13months and subsequent during annual follow-ups. (1) Cobalt levels were significantly higher in MoM-THA compared to HR (p<0.001). There was no significant difference in chromium levels (p=0.313). (2) Cobalt is increasing over time in MoM-THA (p=0.030) whereas metal ions remain stable in HR. (3) Metal ion levels were not affected by acetabular inclination angle and femoral component size in MoM-THA. Chromium levels correlate with the femoral component size (r=-0.240; p=0.037), the UCLA activity score (r=-0.344; p=0.003) and the VAS (r=0.263; p=0.38) in HR. Considering that HR and MoM-THA used the same MoM bearing design, increased cobalt levels may be related to trunnion wear or corrosion. Elevated cobalt levels should raise concern for corrosion related failure in MoM-THA.

Does hemipelvis structure and position influence acetabulum orientation?

BackgroundAlthough acetabulum orientation is well established anatomically and radiographically, its relation to the innominate bone has rarely been addressed. If explored, it could open the discussion on patomechanisms of such complex disorders as femoroacetabular impingement (FAI). We therefore evaluated the influence of pelvic bone position and structure on acetabular spatial orientation. We describe this relation and its clinical implications.MethodsThis retrospective study was based on computed tomography scanning of three-dimensional models of 31 consecutive male pelvises (62 acetabulums). All measurements were based on CT spatial reconstruction with the use of highly specialized software (Rhinoceros). Relations between acetabular orientation (inclination, tilt, anteversion angles) and pelvic structure were evaluated. The following parameters were evaluated to assess the pelvic structure: iliac opening angle, iliac tilt angle, interspinous distance (ISD), intertuberous distance (ITD), height of the pelvis (HP), and the ISD/ITD/HP ratio. The linear and nonlinear dependence of the acetabular angles and hemipelvic measurements were examined with Pearson’s product − moment correlation and Spearman’s rank correlation coefficient. Correlations different from 0 with p < 0.05 were considered statistically significant.ResultsComparison of the axis position with pelvis structure with orientation in the horizontal plane revealed a significant positive correlation between the acetabular anteversion angle and the iliac opening angle (p = 0.041 and 0.008, respectively). In the frontal plane, there was a positive correlation between the acetabular inclination angle and the iliac tilt angle (p = 0.025 and 0.014, respectively) and the acetabular inclination angle and the ISD/ITD/HP ratio (both p = 0.048).ConclusionsThere is a significant correlation of the hemipelvic structure and acetabular orientation under anatomic conditions, especially in the frontal and horizontal planes. In the anteroposterior view, the more tilted-down innominate bone causes a more caudally oriented acetabulum axis, whereas in the horizontal view this relation is reversed. This study may serve as a basis for the discussion on the role of the pelvis in common disorders of the hip.

Effect of increased load on the wear of a large diameter metal-on-metal modular hip prosthesis with a high inclination angle of the acetabular cup

In some earlier hip simulator studies of large-diameter metal-on-metal (MoM) hip prostheses high, unexplained variation in wear has been observed. In the present study it was found that high variation occurs when the tribological endurance limit of the MoM device in question is being approached. When the limit is exceeded, high wear takes place uniformly, and the variation is low. Below the limit, both the wear and its variation are low. The endurance limit was exceeded by increasing the peak load from 2kN to 3kN, to simulate obesity. The acetabular cup inclination angle was high, 70°. Potential clinical wear problems can be predicted by hip simulator studies provided that relevant adverse test conditions are included.

A randomised controlled trial of cemented and cementless femoral components for metal-on-metal hip resurfacing: a bone mineral density study.

The primary purpose of this study of metal-on-metal (MoM) hip resurfacing was to compare the effect of using a cementless or cemented femoral component on the subsequent bone mineral density (BMD) of the femoral neck. This was a single-centre, prospective, double-blinded control trial which randomised 120 patients (105 men and 15 women) with a mean age of 49.4 years (21 to 68) to receive either a cemented or cementless femoral component. Follow-up was to two years. Outcome measures included total and six-point region-of-interest BMD of the femoral neck, radiological measurements of acetabular inclination, neck-shaft and stem-shaft angles, and functional outcome scores including the Harris hip score, the Western Ontario and McMaster Universities Osteoarthritis Index and the University of California at Los Angeles activity scale. In total, 17 patients were lost to follow-up leaving 103 patients at two years. There were no revisions in the cementless group and three revisions (5%) in the cemented group (two because of hip pain and one for pseudotumour). The total BMD was significantly higher in the cementless group at six months (p < 0.001) and one year (p = 0.01) than in the cemented group, although there was a loss of statistical significance in the difference at two years (p = 0.155). All patient outcomes improved significantly: there were no significant differences between the two groups. The results show better preservation of femoral neck BMD with a cementless femoral component after two years of follow-up. Further investigation is needed to establish whether this translates into improved survivorship.

MULTIPLANAR RECONSTRUCTED CT STUDY OF NORMAL ACETABULUM – INCLINATION ANGLE, ANTEVERSION ANGLE AND ACETABULAR DEPTH

Knowledge of acetabular morphometry parameters namely acetabular inclination and anteversion angles beside acetabular depth aid surgeons to accurately plan hip replacement procedure. The current hip implants designed based on Caucasian population which may not accurately match morphologic features of our population. Our objective is to determine normal acetabular morphometric parameters from CT scans of Malay patients in Hospital Universiti Sains Malaysia and compare gender and age group differences. A cross-sectional study was done within 18 months duration from November 2010 till May 2012. A total of 133 samples collected and divided into four age groups. Mean and standard deviations for all parameters were determined. No significant difference between acetabular parameters among males and females (p&gt;0.001). Significant difference between age groups noted, mainly in group 1 (18 to 30 years) with group 4 (51 to 60 years) in all parameters. As for conclusion, no significant parameter differences between genders, hence no indication for gender or population specific hip implants. Significant differences noted when parameters compared between age groups, especially between the two extremes of age groups.

Abductor Biomechanics Clinically Impact the Total Hip Arthroplasty Dislocation Rate: A Prospective Long-Term Study

BackgroundFactors related to the patient, implant, and surgery have been associated to the rate of dislocation for total hip arthroplasty (THA). We ask if the position of the cup and the reconstruction of the abductor mechanism actually lower the THA dislocation rate. MethodsWe evaluated 1318 patients (1414 hips) undergoing cementless THA between 1992 and 2012. All THAs had a 28- or a 32-mm femoral head size. Hip reconstruction was radiologically assessed evaluating cup position and the hip rotation center according to Ranawat. The reconstruction of the abductor mechanism was measured using 2 variables: the lever arm distance and the height of the greater trochanter. ResultsThere were 38 dislocations (2.7%). After controlling the relevant confounding variables, such as demographic and implant data, multivariate regression analysis showed that the most important factors associated with dislocation were a greater distance to the anatomic hip rotation center and hips outside 2 safe windows for cup position (acetabular inclination and version angles) and abductor mechanism (lever arm distance and height of the greater trochanter). ConclusionA proper reconstruction of the hip is essential to decrease the risk of dislocation after primary THA. The weakness of the abductor muscles of the hip may be one of the most important causes for dislocation.

Risk Factors for Early Conversion to Total Hip Arthroplasty following Hip Arthroscopy

Objectives:The most common reason for reoperation following arthroscopic hip surgery is conversion to total hip arthroplasty (THA). The purpose of this study was to identify clinical and radiographic risk factors for early conversion to THA.Methods:Data were prospectively collected on all hip arthroscopy patients from January 2009 through December 2011. Inclusion criteria for the study group were patients undergoing hip arthroscopy for a labral tear who eventually converted to THA. Patients were then compared to a control group of patients who underwent hip arthroscopy for a labral tear and did not convert to THA during the same period. Exclusion criteria were patients with previous hip conditions such as Legg-Calves-Perthes, slipped capital femoral epiphysis, pigmented villonodular synovitis, and avascular necrosis. A bivariate analysis of 41 preoperative and intraoperative variables was performed.Results:A total of 792 patients met inclusion and exclusion criteria. A total of 72 (9%) converted to THA. The control group consisted of 720 patients who did not convert to THA. Bivariate analysis demonstrated that the study group had significantly higher means or frequencies than the control group for the following variables: male gender, age at time of surgery, BMI, back pain, previous back surgery, Tönnis grade above 0, acetabular inclination angle, alpha angle, Seldes combined-type labral tear, labral tear size, chondral injury, traction time, labral debridement (versus repair), number of anchors used repair or reconstruction, and capsular release (versus repair). The study group had significantly lower means or frequencies than the control group for the following variables: preoperative patient reported outcome scores, crossover sign, lateral center edge angle, and psoas release. A statistically significant difference in average joint space was not observed.Conclusion:Multiple risk factors are possible preoperative and intraoperative risk factors for conversion to THA following hip arthroscopy. The clinician and patient should be aware of these variables.

How does pelvic rotation or tilt affect radiographic measurement of acetabular component inclination angle during THA?

BackgroundIt is unclear how radiographic measurements of cup position are sensitive to deviations from a perfect AP pelvis image. PurposeTo quantify changes in radiographic measurements of cup abduction angle due to pelvic tilt or obliquity. MethodsPart A, a retrospective comparison of radiographic cup abduction angle measurements from intraoperative and post-operative radiographs of 23 patients undergoing THA. Part B, a pelvic sawbones model was used to quantify changes in radiographic measurement of cup abduction angle due to known changes in pelvic tilt or obliquity. ResultsPart A, a perfect AP pelvis was obtained in just 30% of intraoperative radiographs. The mean intraoperative cup angle measurement was underestimated by 3.4° compared to post-operative standard radiographs. In Part B, pelvic tilt caused cup abduction angle measurement to decrease on inlet view and increase on outlet view. Pelvic obliquity caused cup abduction angle measurement to decrease on obturator oblique view and increase on iliac oblique view. ConclusionsA trend exists toward slight underestimation of cup abduction angle measurement using intraoperative radiographs. Pelvic tilt or obliquity alters the measured cup abduction angle in known directions.

Acetabular Version Measurement in Total Hip Arthroplasty: the Impact of Inclination and the Value of Multi-Planar CT Reformation.

The orientation of the acetabular cup component of a total hip arthroplasty can be evaluated in a number of ways, utilizing a myriad of imaging techniques and measurement parameters, including intraoperative surgical estimates, postoperative radiographs, and cross-sectional imaging such as computed tomography (CT) and magnetic resonance imaging (MRI). How do traditional versus corrected measurements of acetabular version vary from one another based on the inclination of the cup? What is the reliability of the corrected acetabular version measurements based on interobserver and intraobserver consistency? Two fellowship-trained musculoskeletal radiologists reviewed CT scans on 60 total hip arthroplasties. Acetabular inclination, traditional CT acetabular version, and CT acetabular version corrected for inclination (by utilizing multi-planar reformations to measure in the plane of the cup face) were each measured. The difference was then calculated between the "traditional" axial CT and "corrected" acetabular version measurements, and the association between this difference and the acetabular inclination was assessed. The "traditional" axial CT and "corrected" acetabular version measurements differed from one another in every case, with the traditional method yielding a version measurement that was on average 9.5° higher than the corrected technique. However, as the acetabular cup inclination angle decreased, the "traditional" measurement became more variable and increasingly discordant with the "corrected" version measurement. There is inherent variability between the many methods utilized for defining and measuring acetabular version, with axial CT measurements often used as an accepted proxy for true cup anteversion. However, the variability between different measurement techniques is correlated with acetabular inclination, and this variability is most pronounced when acetabular inclination is low, ultimately leading to potential confusion in measurement terminology. The increasingly widespread availability of multi-planar CT reformations provides an opportunity to standardize methodology, eliminate the impact of inclination on acetabular version measurements, and potentially provide a more reliable comparison of the impact of cup orientation on surgical outcomes.

To Compare Time-Weighted Graphs to Evaluate the Inclination of the Acetabular Component of Patients Who Had Total Hip Replacement Surgery.

Time-weighted graphs are used to detect small shifts in statistical process control. The aim of this study is to evaluate the inclination of the acetabular component with CUmulative SUM (CUSUM) chart, Moving Average (MA) chart, and Exponentially Weighted Moving Average (EWMA) chart. The data were obtained directly from thirty patients who had undergone total hip replacement surgery at Ondokuz Mayis University, Faculty of Medicine. The inclination of the acetabular component of these people, after total hip replacement, was evaluated. CUSUM chart, Moving Average chart, and Exponentially Weighted Moving Average were used to evaluate the quality control process of acetabular component inclination. MINITAB Statistical Software 15.0 was used to generate these control charts. The assessment done with time-weighted charts revealed that the acetabular inclination angles were settled within control limits and the process was under control. It was determined that the change within the control limits had a random pattern. As a result of this study it has been obtained that time-weighted quality control charts which are used mostly in the field of industry can also be used in the field of medicine. It has provided us with a faster visual decision.

Does intraoperative fluoroscopy improve component positioning in total hip arthroplasty?

Accurate placement of components is imperative for successful outcomes after total hip arthroplasty (THA). Although technology-assisted techniques offer the potential for greater accuracy in prosthesis positioning, the need for additional resources prevents their widespread use. The goal of this study was to compare primary THA procedures performed with and without intraoperative fluoroscopic guidance with regard to accuracy of prosthesis placement, operative time, and postoperative complications. The authors reviewed 341 consecutive cases (330 patients) undergoing primary THA at the authors' institution from September 2007 to January 2010. Postoperative anteroposterior radiographs were used to measure acetabular inclination angle, leg length discrepancy, and femoral offset discrepancy. Operative time and postoperative complications related to implant positioning were recorded. Mean acetabular inclination angle, leg length discrepancy, and offset discrepancy for control vs study groups were 43.0° (range, 32.2°-61.4°) vs 43.8° (range, 29.0°-55.1°), 4.75 mm (range, 0-25) vs 4.24 mm (range, 0-27), and 8.47 mm (range, 0-9.7) vs 7.70 mm (range, 0-31), respectively. Complication rates were not significantly different between the control (8.1%) and study (5.3%) groups. Mean operative time was significantly higher in the study group compared with the control group (59.8 vs 52.8 minutes) (P<.0001). The findings showed that intraoperative fluoroscopy may not improve prosthesis accuracy or decrease postoperative complication rates compared with a freehand technique. Because of significantly increased operative time and cost associated with fluoroscopic guidance, the authors discourage the use of this technique in uncomplicated primary THA performed at high-volume arthroplasty institutions.

Total hip replacement using a highly crosslinked polyethylene liner in Asians with small acetabulum.

To evaluate the medium-term outcomes of total hip replacement (THR) using a thin highly cross-linked polyethylene (HXLPE) liner in an Asian population. Medical records of 20 men and 44 women aged 26 to 80 (mean, 59) years who underwent 80 THRs using a thin HXLPE liner by a single surgeon were reviewed. Indications for THR included dysplasia (n = 26), avascular necrosis (n=26), osteoarthritis (n = 22), rheumatoid arthritis (n = 4), and ankylosing spondylitis (n = 2). The surgical technique, implant used, and rehabilitation protocol were standardised. Radiographs were evaluated for cup migration and peri-implant radiolucency. Femoral head penetration was assessed at day 1 and last follow-up using the Kang modification of the Dorr and Wan method and the PowerPoint method. After a mean follow-up of 7.5 (range, 5.0-11.9) years, no patient had undergone acetabular revision. Two hips were revised for the femoral stem. Femoral head penetration did not correlate with sex, age at surgery, hip pathology, acetabular inclination angle, cup size, or liner thickness. The maximum femoral head penetration was 0.09 mm/year, which was below the osteolysis threshold of 0.1 mm/year. The mean ± standard deviation femoral head penetration was 0.29 ± 0.12 mm (or 0.04 ± 0.02 mm/year) by the PowerPoint method and 0.17 ± 0.22 mm (or 0.02 ± 0.03 mm/year) by the Kang modification of the Dorr and Wan method. Femoral head penetration correlated with the number of years of follow-up (p = 0.012). The use of a thin HXLPE liner in primary THR for patients with small acetabulum achieved good outcomes after a mean of 7.5 years.

The impact of surgeon handedness in total hip replacement.

Total hip replacement (THR) is successful and performed commonly. Component placement is a determinant of outcome. Influence of surgeon handedness on component placement has not been considered previously. This study was a radiographic assessment of component positioning with respect to handedness. Early data from 160 patients are reported. Overall, 160 primary THRs for osteoarthritis were included. Equal numbers of left and right THRs were performed by four surgeons, two right-handed and two left-handed. Postoperative radiography was assessed for THR component position by measurement of leg length inequality, acetabular inclination and centre of rotation. Surgeons' handedness was assessed using the Edinburgh inventory. For leg length inequality, no significant interaction was seen between hip side and surgeon handedness. Acetabular inclination angles showed a statistically significant difference, however, depending on hand dominance, with higher inclination angles recorded when operating on the dominant side. There was a trend towards greater medialisation of the centre of rotation on the non-dominant side although this did not reach statistical significance. Surgeon handedness appears to influence acetabular component position during THR but it is one factor of many that interact to achieve a successful outcome.

The Bernese periacetabular osteotomy: is transection of the rectus femoris tendon essential?

The Bernese periacetabular osteotomy (PAO) traditionally is performed using the iliofemoral or the ilioinguinal approach with transection of the rectus femoris tendon attachments. Although a rectus-preserving approach has been developed, there is limited direct comparison data regarding the surgical safety, radiographic correction, and improvement in hip pain and function between the rectus-preserving and the classic approaches. The purposes of this study were to determine whether preserving the rectus femoris tendon attachment would (1) reduce intraoperative blood loss and length of surgery; (2) improve Harris hip scores (HHS); (3) decrease the rate of complications; and (4) affect the radiographic correction when compared with the classic approach. A retrospective matched cohort study was used to compare the endpoints listed above after PAO using a rectus-preserving approach versus the classic approach. Operative blood loss, preoperative and postoperative hematocrit, duration of surgery, HHS, and postoperative complications were recorded for the two groups. Pelvic radiographs were reviewed for measurement of the lateral center-edge angle, anterior center-edge angle, and Tönnis acetabular inclination angle. A total of 64 patients were included (32 in each group). Followup was at a minimum of 1 year (mean, 20 months; range, 13-44 months). Blood loss (p = 0.2405), hematocrit change (p = 0.3277), and operative time (p = 0.3960) were similar between groups. At latest followup, the HHS improved in the rectus-preserving (mean improvement, 25; 95% CI, 21-29; p < 0.0001) and control groups (mean improvement, 21; 95% CI, 17-25; p < 0.0001) with no difference in HHS improvement between the groups (mean difference, 4.3; 95% CI, -1.6 to 10.1; p = 0.1523). The complication rate was 12.5% (four of 32) in the rectus-preserving group and 25% (eight of 32) in the classic approach groups, respectively (p = 0.2002). The rectus-preserving approach allowed for similar lateral center-edge angle (p = 0.4463), anterior center-edge angle (p = 0.0936), and Tönnis angle (p = 0.7953) improvement when compared with the classic approach. The rectus-preserving approach for PAO is as safe and effective as the classic approach to achieve radiographic correction and HHS improvement at minimum 1 year. Additional investigation is needed to determine whether the rectus-preserving approach allows for improvement in functional recovery including hip flexion strength.

Functional anthropometric measurements of Indian pelvis.

To determine the normal values of several radiographic measurements of hip and pelvis in individuals of Indian population. We conducted a cross-sectional study of Indian population and calculated mean and variation seen in different parameters in Indian pelvis. We took the plain X-ray of randomly selected hundred patients in identical position with 20% magnification factor. Different parameters including acetabular inclination angle, cup size, tear drop position, neck shaft angle, neck offset, abductor lever arm and head size were drawn on the X-rays and values measured. 100 subjects were taken (63 male and 37 female). The mean of acetabular inclination angle was 37.70±3.82° (30-47°). The mean neck shaft angle was131.53±7.70°(114-158) the most commonly occurring value was 131°. The mean abductor lever arm was 38.48mm±5.77 (23-54) with the mode of 40. The mean cup size was 48.9±3.67mm (34-58) with the most commonly occurring value as 50. The mean angle from tip of trochanter to center of head was 80.2±9.1 (62-110). Among all the seven parameters correlations were drawn. There were in all 22 correlations out of which 14 were statistically significant. Since there is significant difference between the neck shaft angles and other measurements of Indian population than to the European population, an evaluation in the design of the implant by the Indian manufacturers is recommended. Also this study proposes that the normal values of our own population be used as reference values in interpreting standard radiographs of pelvis with both hips.

Predictivity and Fate of Metal Ion Release From Metal-On-Metal Total Hip Prostheses

Blood metal ion levels in 72 patients with large head metal-on-metal hip arthroplasty were studied to determine the correlation between the values measured in whole blood and urine. Urinary cobalt and chromium levels of 30μg and 21μg, respectively, adjusted to creatinine were found to correspond to the 7μg/l cut-off value that has been accepted in whole blood. Cobalt and chromium levels in whole blood and urine both significantly correlated with increased acetabular component inclination angle over 50 degrees and pain scores. There was no correlation with socket anteversion angle or femoral head diameter. The data support the use of urinary measurement of metal ions adjusted to creatinine to monitor patients with large head metal-on-metal total hip arthroplasty.

MRI Findings Following Metal on Metal Hip Arthroplasty and Their Relationship With Metal Ion Levels and Acetabular Inclination Angles

Following the global recall of all ASR metal on metal hip products, our aim was to correlate MRI findings with acetabular inclination angles and metal ion levels in patients with these implants. Both cobalt and chromium levels were significantly higher in the presence of a periprosthetic fluid collection. There was no association between the presence of a periprosthetic mass, bone marrow oedema, trochanteric bursitis or greater levels of abductor muscle destruction for cobalt or chromium. There was no association between the level of periprosthetic tissue reaction and the acetabular inclination angle with any of the pathologies identified on MRI. The relationship between MRI pathology, metal ion levels and acetabular inclination angles in patients with ASR implants remains unclear adding to the complexity of managing patients.