Acetabular morphology and orientation differs from ethnic group to another. Thus, investigating the normal range of the parameters that are used to assess both was a matter of essence. Nevertheless, the main aim of this study was clarification the relationship between acetabular inclination (AI) and acetabular and femoral head arcs’ radii (AAR and FHAR). A cross-sectional retrospective study that had been done in a tertiary center where Computed tomography abdomen scouts’ radiographs of non-orthopedics patients were included. They had no history of pelvic or hips’ related symptoms or fractures in femur or pelvis. A total of 84 patients was included with 52% of them were females. The mean of age was 30.38± 5.48. Also, Means of AI were 38.02±3.89 and 40.15±4.40 (P 0.02, significant gender difference) for males and females, respectively. Nonetheless, Head neck shaft angle (HNSA) means were 129.90±5.55 and 130.72±6.62 for males and females, respectively. However, AAR and FHAR means for males and females were 21.3±3.1mm, 19.9±3.1mm, P 0.04 and 19.7±3.1mm, 18.1±2.7mm, P 0.019, respectively. In addition, negative significant correlations were detected between AI against AAR, FHAR, HNSA and body mass index (BMI) (r 0.529, P ≤0.0001, r 0.445, P ≤0.0001, r 0.238, P 0.029, r 0.329, P ≤0.007, respectively). On the other hand, high BMI was associated with AAR and FHAR (r 0.577, P 0.0001 and r 0.266, p 0.031, respectively). This study shows that high AI is correlated with lower AAR, FHAR. Each ethnic group has its own normal values that must be studied to tailor the path for future implications in clinical setting

Background

Positioning of the acetabular component in total hip arthroplasty has profound effects on the biomechanics, stability and wear of the prosthesis. Normal anatomical position in females is 57 degrees (50 – 67 degrees) inclination with 19 degrees (9 – 32 degrees) of anteversion, whilst in males 56 degrees of inclination (48 – 66 degrees) with 19 degrees (9 – 32 degrees) is normal. In total hip arthroplasty, inclination recommendation ranges from 30 – 50 degrees. The aim of this study was to radiographically measure acetabular component position in total hip arthroplasty and compare to normal values.

The angle of acetabular inclination is an important measurement in total hip replacement (THR) procedures. Determining the acetabular component orientation intra-operatively remains a challenge. An increasing number of innovators have described techniques and devices to achieve it. This paper describes a mechanical inclinometer design to measure intra-operative acetabular cup inclination. Then, the mechanical device is tested to determine its accuracy. The aim was to design an inclinometer to measure inclination without existing instrumentation modification. The device was designed to meet the following criteria: 1. measure inclination with acceptable accuracy (+/− 5o); 2. easy to use intra-operatively (handling & visualization); 3. adaptable and useable with majority of instrumentation kits without modification; 4. sterilizable by all methods; 5. robust/reusable. The prototype device was drafted by computer aided design (CAD) software. Then a prototype was constructed using a 3D printer to establish the final format. The final device was CNC machined from SAE 304 stainless steel. The design uses an eccentrically weighted flywheel mounted on two W16002-2RS ball bearings pressed into symmetrical housing components. The weighted wheel is engraved with calibrated markings relative to its mass centre. Device functioning is dependent on gravity maintaining the weighted wheel in a fixed orientation while the housing can adapt to the calibration allowing for determining the corresponding measurement. The prototype device accuracy was compared to a digital device. A digital protractor was used to create an angle. The mechanical inclinometer (user blinded to digital reading) was used to determine the angle and compared to the digital reading. The accuracy of the device compared to the standard freehand technique was assessed using a saw bone pelvis fixed in a lateral decubitus position. 18 surgeons (6 expert, 6 intermediate, 6 novice) were asked to place an uncemented acetabular cup in a saw bone pelvis to a target of 40 degrees. First freehand then using the inclinometer. The inclination was determined using a custom-built inertial measurement unit with the user blinded to the result. Comparison between the mechanical and digital devices showed that the mechanical device had an average error of −0.2, a standard deviation of 1.5, and range −3.3 to 2.6. The average root mean square error was 1.1 with a standard deviation of 0.9. Comparison of the inclinometer to the freehand technique showed that with the freehand component placement 50% of the surgeons were outside the acceptable range of 35–45 degrees. The use of the inclinometer resulted all participants to achieve placement within the acceptable range. It was noted that expert surgeons were more accurate at achieving the target inclination when compared to less experienced surgeons. This work demonstrates that the design and initial testing of a mechanical inclinometer is suitable for use in determining the acetabular cup inclination in THR. Experimental testing showed that the device is accurate to within acceptable limits and reliably improved the accuracy of uncemented cup implantation in all surgeons

Objectives. Acetabular component orientation in total hip arthroplasty (THA) influences results. Intra-operatively, the natural arthritic acetabulum is often used as a reference to position the acetabular component. Detailed information regarding its orientation is therefore essential. The aim of this study was to identify the acetabular inclination and anteversion in arthritic hips. Methods. Acetabular inclination and anteversion in 65 symptomatic arthritic hips requiring THA were measured using a computer navigation system. All patients were Caucasian with primary osteoarthritis (29 men, 36 women). The mean age was 68 years (SD 8). Mean inclination was 50.5° (SD 7.8) in men and 52.1° (SD 6.7) in women. Mean anteversion was 8.3° (SD 8.7) in men and 14.4° (SD 11.6) in women. . Results. The difference between men and women in terms of anteversion was significant (p = 0.022). In 75% of hips, the natural orientation was outside the safe zone described by Lewinnek et al (anteversion 15° ± 10°; inclination 40° ± 10°). Conclusion. When using the natural acetabular orientation to guide component placement, it is important to be aware of the differences between men and women, and that in up to 75% of hips natural orientation may be out of what many consider to be a safe zone. Cite this article: Bone Joint Res 2015;4:6–10

Native anatomy of the arthritic hip is an important consideration in hip replacement surgery and implant design. Acetabular component orientation in total hip replacement (THR) is the single greatest factor that influences dislocation rate. Detailed knowledge regarding orientation of the native acetabulum is therefore essential. Native acetabular orientation in healthy hips is well documented but we could not find any papers detailing native acetabular orientation in the arthritic hip. A commercially available computer navigation system (Orthopilot BBraun Aesculap, Tuttlingen, Germany) was used to assess acetabular inclination and anteversion in 65 hips with symptomatic arthritis requiring THR. Acetabular inclination in all hips was also measured on pre op anteroposterior pelvic radiographs. Patients with DDH were excluded. All patients were Caucasian and had primary osteoarthritis, 29 males and 35 females. Average age 68(SD 8). Mean values as recorded by computer navigation were: inclination 51.4°(SD 7.1); anteversion 11.7°(SD 10.7). As recorded from radiographs mean acetabular inclination was 58.8°(SD 5.7). There was a difference between males and females. Mean navigated inclination: male 50.5°(SD 7.8); female 52.1°(SD 6.7). Mean navigated anteversion: male 8.3°(SD 8.7); female 14.39°(SD 11.6) Mean radiographic inclination: male 57.4°(SD 5.1) and female 59.8°(SD 6). Natural acetabular orientation in arthritic hips falls out with the safe zones defined by Lewinnek. When compared with healthy hips, as described in current literature, the arthritic hip appears to have a smaller angle of inclination and anteversion, by approximately 5° and 10° respectively, in both males and females. This is useful when positioning the cup during surgery. The difference between males and females, particularly in terms of anteversion, should also be considered

Abstract. Objectives. Accurate orientation of the acetabular component during a total hip replacement is critical for optimising patient function, increasing the longevity of components, and reducing the risk of complications. This study aimed to determine the validity of a novel VR platform (AescularVR) in assessing acetabular component orientation in a simulated model used in surgical training. Methods. The AescularVR platform was developed using the HTC Vive® VR system hardware, including wireless trackers attached to the surgical instruments and pelvic sawbone. Following calibration, data on the relative position of both trackers are used to determine the acetabular cup orientation (version and inclination). The acetabular cup was manually implanted across a range of orientations representative of those expected intra-operatively. Simultaneous readings from the Vicon® optical motion capture system were used as the ‘gold standard’ for comparison. Correlation and agreement between these two methods was determined using Bland-Altman plots, Pearson's correlation co-efficient, and linear regression modelling. Results. A total of 55 separate orientation readings were obtained. The mean average difference in acetabular cup version and inclination between the Vicon and VR systems was 3.4° (95% CI: −3–9.9°), and −0.005° (95% CI: −4.5–4.5°) respectively. Strong positive correlations were demonstrated between the Vicon and VR systems in both acetabular cup version (Pearson's R = 0.92, 99% CI: 0.84–0.96, p<0.001), and inclination (Pearson's R = 0.94, 99% CI: 0.88–0.97, p<0.001). Using linear regression modelling, the adjusted R. 2. for acetabular version was 0.84, and 0.88 for acetabular inclination. Conclusion. The results of this study indicate that the AescularVR platform is highly accurate and reliable in determining acetabular component orientation in a simulated environment. The AescularVR platform is an adaptable tracking system, which may be modified for use in a range of simulated surgical training and educational purposes, particularly in orthopaedic surgery. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Reorientating pelvic osteotomies are performed to improve femoral head coverage and secondary degenerative arthritis. A rectangular triple pelvic innominate osteotomy (3PIO) is performed in symptomatic cases. However, deciding optimal screw fixation type to avoid complications is questionable. Therefore, this study aimed to investigate the biomechanical behavior of two different acetabular screw configurations used for rectangular 3PIO osteosynthesis. It was hypothesized that bi-directional screw fixation would be biomechanically superior to mono-axial screw fixation technique. A rectangular 3PIO was performed in twelve right-side artificial Hemi-pelvises. Group 1 (G1) had two axial and one transversal screw in a bi-directional orientation. Group 2 (G2) had three screws in the axial direction through the iliac crest. Acetabular fragment was reoriented to 10.5° inclination in coronal plane, and 10.0° increased anteversion along axial plane. Specimens were biomechanically tested until failure under progressively increasing cyclic loading at 2Hz, starting at 50N peak compression, increasing 0.05N/cycle. Stiffness was calculated from machine data. Acetabular anteversion, inclination and medialization were evaluated from motion tracking data from 250-2500 at 250 cycle increments. Failure cycles and load were evaluated for 5° change in anteversion. Stiffness was higher in G1 (56.46±19.45N/mm) versus G2 (39.02±10.93N/mm) but not significantly, p=0.31. Acetabular fragment anteversion, inclination and medialization increased significantly each group (p≤0.02) and remained non-significantly different between the groups (p≥0.69). Cycles to failure and failure load were not significantly different between G1 (4406±882, 270.30±44.10N) and G2 (5059±682, 302.95±34.10N), p=0.78. From a biomechanical perspective, the present study demonstrates that a bi-directional screw orientation does not necessarily advantageous versus mono-axial alignment when the latter has all three screws evenly distributed over the osteotomy geometry. Moreover, the 3PIO fixation is susceptible to changes in anteversion, inclination and medialization of the acetabular fragment until the bone is healed. Therefore, cautious rehabilitation with partial weight-bearing is recommended

The aim of this study was to characterise noise associated with ceramic-on-ceramic total hip arthroplasty (THA). A questionnaire was constructed to assess noise associated with THA. 116 patients responded. All had ceramic-on-ceramic hybrid THA at Glasgow Royal Infirmary between 2005 and 2007 using a Trident prosthesis and Exeter stem. Oxford Hip Questionnaires (OHS) were also completed by the patients. 16.4% of respondents reported noise associated with their ceramic hip. The vast majority reported onset at least 1 year after implantation. The most common noise types were ‘clicking’ (47%) or ‘grinding’ (42%), while ‘squeaking’ was least frequently reported (11%). Noise was most commonly brought on by bending and during sit to stand movements. No correlation was identified between the incidence of noise and any patient specific factor or demographic variable. The mean OHS at questionnaire follow-up was 39 and there was no significant difference in OHS when comparing noisy and silent hips (p=0.65). Only 1 patient limited social or recreational activities and overall patients felt the noise had minimal effect on their quality of life. Acetabular component inclination angles were compared on post-operative x-rays. There was no significant difference (p=0.51) in inclination angles of the noisy (47.1°±6.3°, range 30–57°) and silent hips (47.8°±6.1°, range 35–68°). The groups were further analysed for deviation out with the desirable inclination range of 40–45°. Of the noisy hips, a total of 73% were out with this range compared to 63% in the silent hip group. The incidence of noise within this ceramic-on-ceramic THA group did not appear to be related to patient specific factors, patient reported outcome (OHS) or acetabular inclination angles. Subjective appraisal of the noise revealed that ‘squeaking’ was not common but patients tended to report ‘clicking’ and ‘grinding’ more. The precipitation of noise with bending activities reinforces a possible mechanical cause

Background. The position of the hip-joint centre of rotation (HJC) within the pelvis is known to influence functional outcome of total hip replacement (THR). Superior, lateral and posterior relocations of the HJC from anatomical position have been shown to be associated with greater joint reaction forces and a higher incidence of aseptic loosening. In biomechanical models, the maximum force, moment-generating capacity and the range of motion of the major hip muscle groups have been shown to be sensitive to HJC displacement. This clinical study investigated the effect of HJC displacement and acetabular cup inclination angle on functional performance in patients undergoing primary THR. Methods. Retrospective study of primary THR patients at the RNOH. HJC displacement from anatomical position in horizontal and vertical planes was measured relative to radiological landmarks using post-operative, calibrated, anterior-posterior pelvic radiographs. Acetabular cup inclination angle was measured relative to the inter-teardrop line. Maximum range of passive hip flexion, abduction, adduction, external and internal rotation were measured in clinic. Patient reported functional outcome was assessed by Oxford Hip Score (OHS) and WOMAC questionnaires. Data analysed using a linear regression model. Results. 109 THRs were studied in 104 patients (69 Female). Mean age at THR=63 years (22-88). Mean follow-up=17 months (11-39 months). Median OHS=16, WOMAC=8. Increasing vertical HJC displacement (in either superior or inferior direction) from anatomical position was associated with worsening OHS (p<0.05) and WOMAC scores (p<0.05) and a reduced range of passive hip flexion (p<0.05). No relationship was found between either horizontal HJC displacement or acetabular cup inclination angle and patient functional outcome. Conclusion. A significant relationship was identified between increasing vertical displacement of the HJC and worsening patient functional outcome. This supports current opinion regarding the disadvantageous consequences of a superiorly displaced HJC in terms of survivorship and function. We therefore advocate an anatomical restoration of HJC position wherever possible

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

The link between squeaking and ceramic on ceramic (CoC) bearings has been widely reported in orthopaedic literature and is described as a hard bearing phenomenon. We aim to look at the incidence of noise in CoC bearings compared to Metal on Polyethylene (MoP) bearing, which have yet to be linked to squeaking. We developed a noise characterizing hip questionnaire and sent that along with the Oxford Hip Score (OHS) to 1000 patients; 3:2 ratio of CoC to MoP. 282 CoC patients and 227 MoP patients returned the questions: 509 patients in total. Our patient database provided details on femoral head size and the acetabular inclination angle, for each respondent. 47 (17%) of the CoC hip patients reported noise compared to 19 (8%) of the MoP hip patients (P=0.054). 9 CoC patients and 4 MoP patients reported squeaking, while clicking was the most frequent answer in both groups. 27% patients with noise reported avoiding recreational activities because of it. Patient's with noisy hips scored on average, 5 points worse in the OHS (CoC: P = 0.04 and MoP: P = 0.007) and were on average 5 years younger (CoC: P<0.001 and MoP: P=0.007). No correlation was found between noisy hips and femoral head size or inclination angle. The squeaking hip phenomenon is not exclusive to hard bearing THA. Noise from patient's hips may have social implications and this should be highlighted when consenting a patient for either of these hip procedures. In both implants, we showed there to be a correlation between noise production and a lower OHS. However, longer follow up studies are needed to link noise to a poorly functioning implant

Metal-on-metal (MOM) hip arthroplasty, including resurfacing, has become the subject of recent research and debate. There is the perceived benefit of improved wear rates of bearing surfaces leading to superior durability and performance of these types of implant. An associated feature of MOM bearing surfaces is the generation of metal ions. These can have local and systemic cytotoxic effects. An immunoloigical response has been suggested, however, metal wear debris may cause direct damage to cellular DNA. Studies have shown that release of these ions is related to bearing diameter and component alignment. However, little is known about the relationship between metal ion levels and implant survivorship. The MHRA has published guidelines on the follow-up of patients with MOM implants including measurement of serum ion levels and cross sectional imaging. Between February 2001 and November 2009, 135 patients (164 hips) had MOM resurfacing arthroplasty at our institution. We report a retrospective analysis of the data generated by review of these patients. Of the 135 patients, 91 were identified for clinical review. Each patient had serum metal ion levels measured, plain AP radiographs of the pelvis examined and, in the presence of raised metal ions, a Metal Artefact Reduction Sequence (MARS) MRI performed. 27 patients (35 hips) had raised metal ion levels (Cobalt and Chromium). Patients with raised metal ion levels had a mean acetabular cup inclination of 52.7 degrees compared with a mean inclination of 48.6 degrees in patients with normal ion levels (p<0.05). MARS MRI in the raised ion group revealed 9 patients with appearances suggestive of ALVAL. A number of these patients had hip revision surgery with the remainder awaiting potential revision. These findings reflect current evidence suggesting a relationship between sub-optimal component position and raised metal ion levels and an increased rate of ALVAL

Introduction. Total hip prostheses which use a ceramic head within a metal liner are a relatively recent introduction. As such, survivorship rates from independent centres alongside explant analysis are rare. The early experience with this novel ceramic-on-metal (CoM) bearing couple is reported. Methods and Materials. All CoM hips implanted between 2008 and 2009 at a single hospital by a single surgeon were reviewed. Radiographs were analysed using EBRA software to determine acetabular cup inclination and anteversion angles. Blood metal ion concentrations were measured using inductively coupled plasma mass spectroscopy (ICPMS). Explants were measured for bearing surface and taper wear using a high precision co-ordinate measuring machine. The roughness of the articulating surfaces was measured with a non-contact profilometer. Results. In 54 patients 56 CoM hips were implanted. Mean (range) age was 64 years (34-87). There were 41 females and 15 males. Patients were followed-up for a mean of 1.5 years. Three hips were revised at mean of 1.2 years (2 female, 1 male) with a further 3 listed for revision under 1.5 years giving an overall failure rate of 10.7%. All these patients reported with pain. X-rays of failed devices showed a characteristic pattern of femoral stem loosening. Serum cobalt and chromium were less than 2 micrograms/L. Explant analysis of the three revised hips showed wear at the liner rim in each case. In two of these cases the wear extended completely around the circumference. The wear volumes were 4.1, 2.0 and 2.3mm3 respectively. The ceramic heads were unworn but some transfer of metal could be seen visually. There was no significant wear or deformation at the taper junctions. Typical ceramic head roughness values were 3nm Ra and so most of the surface area of the heads remained in a pristine condition. Discussion. The very high early failure rate using COM is concerning. Explant analysis suggests equatorial contacts with propagation of high frictional forces distally. These forces may have caused early loosening of the femoral stems. Orthopaedic surgeons need to be aware of this new mechanism of failure which is associated with low metal ions

Objectives

Mechanical wear and corrosion at the head-stem junction of total hip arthroplasties (THAs) (trunnionosis) have been implicated in their early revision, most commonly in metal-on-metal (MOM) hips. We can isolate the role of the head-stem junction as the predominant source of metal release by investigating non-MOM hips; this can help to identify clinically significant volumes of material loss and corrosion from these surfaces.

In order to evaluate the relationship between acetabular and proximal femoral alignment in the initiation and evolution of osteoarthritis of the dysplastic hip, the acetabular and femoral angles were calculated geometrically from radiographs of 62 patients with pre-arthrosis and early osteoarthritis. The sum of the lateral opening angle of the acetabulum and the neck-shaft angle was defined as the lateral instability index (LII), and the sum of the anterior opening angle of the acetabulum and the anteversion angle of the femoral neck as the anterior instability index (AII). These two indices were compared in dysplastic and unaffected hips. A total of 22 unilateral hips with pre-arthrosis were followed for at least 15 years to determine whether the two indices were associated with the progression of osteoarthritis.

The LII of the affected hips (197.4 (sd 6.0)) was significantly greater than that of the unaffected hips (1830 (sd 6.9)). A follow-up study of 22 hips with pre-arthrosis showed that only the LII was associated with progression of the disease, and an LII of 196 was the threshold value for this progression.