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Purpose: Although many factors were suggested to affect acetabular cup positioning during primary total hip arthroplasty, the effect of surgeon handedness was rarely evaluated. We aimed primarily to assess the difference in cup positioning (inclination and anteversion) between the right and left sides during primary THA. Secondly, to check the difference in the percentages of cups positioned in the safe zone for inclination and anteversion and if there will be a difference in cup positioning according to the type of cup fixation (cemented vs. cementless). Methods: Cup inclination and anteversion of 420 THAs were radiographically evaluated retrospectively. THAs were performed by a senior right-handed surgeon, who operated through a direct lateral approach in a lateral decubitus position using manual instruments and freehand technique for cup placement. Patients were assigned to two groups: Group A (right, or dominant side), and Group B (left, or non-dominant side), with equal cases of THAs (n = 210) in each group. Results: No difference was found in patients' basic characteristics, preoperative diagnosis, and cup fixation (54.3% cemented and 45.7% cementless) between the two groups. There was a significant difference in cup inclination between Groups A and Group B (40.1° ± 6.3° vs. 38.2° ± 6.1°) (P = 0.002). No significant difference was revealed in anteversion between the two groups (11.7° ± 4.4° vs. 11.8° ± 4.7°) (P = 0.95). The percentage of cups located within the safe zone in terms of both inclination and anteversion was 85.2% vs. 83.8% and 69% vs. 73.3% for Group A and Group B, according to Lewinnek and Callahan's safe zones, respectively. There existed a significant difference in the cemented cup inclination between Group A and Group B (40.8° ± 6.4° vs. 38.3° ± 6.3°) (P = 0.004). Conclusion: Cup inclination is affected by the surgeon's handedness when operating through a direct lateral approach and using a freehand technique, while anteversion is less affected. Furthermore, the difference is greater with cemented cups. [ABSTRACT FROM AUTHOR]

Purpose: The aim was to investigate the effect of surgeon handedness on acetabular cup positioning, functional outcomes, and dislocation incidence during primary THA. Methods: A systematic review was conducted according to the PRISMA guidelines. Studies published in English were searched in three databases (PubMed, Embase, and Scopus). A dominant side is a right-handed (RHD) or left-handed (LHD) surgeon who operates on the right or left hip, respectively. The opposite is considered to be the non-dominant side. We used odds ratios for dichotomous data and mean differences for continuous data, with 95% confidence intervals for quantitative data synthesis. Heterogeneity was assessed using the I² test, with outcomes graphically represented in a forest plot and a p-value of < 0.05 considered statistically significant; analyses were performed using Review Manager 5.4 (RevMan 5.4.1). >. Result: Four observational studies were included out of 98 articles. Ten experienced surgeons participated (8 RHD and 2 LHD) and operated on 822 patients (1484 hips), divided equally between dominant and non-dominant sides, and the posterolateral approach was utilized in 80.9% of THAs. RHD surgeons operated on 1404 (94.6%) THAs. The pooled synthesis for inclination indicated no significant difference between either side [MD: 0.10 (95% CI -2.10 to 2.30, P = 0.93, I² = 91%)]. While the difference was significant for anteversion [MD: -2.37 (95% CI -3.82 to -0.93, P = 0.001, I² = 31%)]. The functional outcome was better on the dominant side [MD: 1.44 (95% CI 0.41 to 2.48, P = 0.006, I² = 0%)], and the dislocation incidence was significantly higher on the non-dominant side [OR: 0.45 (95% CI 0.25 to 0.81, P = 0.008, I² = 0%)]. Conclusion: Surgeon handedness and whether operating on the dominant or non-dominant side could affect the acetabular cup positioning and outcomes during primary THAs, even in the hands of high-volume surgeons. [ABSTRACT FROM AUTHOR]

Abstract Purpose Although many factors were suggested to affect acetabular cup positioning during primary total hip arthroplasty, the effect of surgeon handedness was rarely evaluated. We aimed primarily to assess the difference in cup positioning (inclination and anteversion) between the right and left sides during primary THA. Secondly, to check the difference in the percentages of cups positioned in the safe zone for inclination and anteversion and if there will be a difference in cup positioning according to the type of cup fixation (cemented vs. cementless). Methods Cup inclination and anteversion of 420 THAs were radiographically evaluated retrospectively. THAs were performed by a senior right-handed surgeon, who operated through a direct lateral approach in a lateral decubitus position using manual instruments and freehand technique for cup placement. Patients were assigned to two groups: Group A (right, or dominant side), and Group B (left, or non-dominant side), with equal cases of THAs (n = 210) in each group. Results No difference was found in patients’ basic characteristics, preoperative diagnosis, and cup fixation (54.3% cemented and 45.7% cementless) between the two groups. There was a significant difference in cup inclination between Groups A and Group B (40.1° ± 6.3° vs. 38.2° ± 6.1°) (P = 0.002). No significant difference was revealed in anteversion between the two groups (11.7° ± 4.4° vs. 11.8° ± 4.7°) (P = 0.95). The percentage of cups located within the safe zone in terms of both inclination and anteversion was 85.2% vs. 83.8% and 69% vs. 73.3% for Group A and Group B, according to Lewinnek and Callahan’s safe zones, respectively. There existed a significant difference in the cemented cup inclination between Group A and Group B (40.8° ± 6.4° vs. 38.3° ± 6.3°) (P = 0.004). Conclusion Cup inclination is affected by the surgeon’s handedness when operating through a direct lateral approach and using a freehand technique, while anteversion is less affected. Furthermore, the difference is greater with cemented cups.

Abstract Purpose The aim was to investigate the effect of surgeon handedness on acetabular cup positioning, functional outcomes, and dislocation incidence during primary THA. Methods A systematic review was conducted according to the PRISMA guidelines. Studies published in English were searched in three databases (PubMed, Embase, and Scopus). A dominant side is a right-handed (RHD) or left-handed (LHD) surgeon who operates on the right or left hip, respectively. The opposite is considered to be the non-dominant side. We used odds ratios for dichotomous data and mean differences for continuous data, with 95% confidence intervals for quantitative data synthesis. Heterogeneity was assessed using the I² test, with outcomes graphically represented in a forest plot and a p-value of . Result Four observational studies were included out of 98 articles. Ten experienced surgeons participated (8 RHD and 2 LHD) and operated on 822 patients (1484 hips), divided equally between dominant and non-dominant sides, and the posterolateral approach was utilized in 80.9% of THAs. RHD surgeons operated on 1404 (94.6%) THAs. The pooled synthesis for inclination indicated no significant difference between either side [MD: 0.10 (95% CI -2.10 to 2.30, P = 0.93, I² = 91%)]. While the difference was significant for anteversion [MD: -2.37 (95% CI -3.82 to -0.93, P = 0.001, I² = 31%)]. The functional outcome was better on the dominant side [MD: 1.44 (95% CI 0.41 to 2.48, P = 0.006, I² = 0%)], and the dislocation incidence was significantly higher on the non-dominant side [OR: 0.45 (95% CI 0.25 to 0.81, P = 0.008, I² = 0%)]. Conclusion Surgeon handedness and whether operating on the dominant or non-dominant side could affect the acetabular cup positioning and outcomes during primary THAs, even in the hands of high-volume surgeons.

Purposes: Due to the morphological diversity of deformities, technical difficulties, improperly designed components, and so on, THA remains a challenging task in dysplastic hips, especially in highly dislocated hips. The purpose of this study was to comprehensively evaluate the clinical outcomes of robot-assisted THA in patients with DDH through a large cohort study, including the precision of acetabular cup positioning, indicators of inflammatory response, indicators of muscle damage, and complications. Methods: We retrospectively analyzed patients with DDH who underwent THA in our prospectively constructed joint registry between August 2018 and August 2022. Finally, 147 manual THAs and 147 robotic-assisted THAs were included in the final analysis. Patient demographics, indicators of inflammation, indicators of muscle damage, operative time, Harris hip scores (HHS), and forgotten joint score (FJS) were recorded for analysis. The precision of the positioning of the acetabular component was assessed with plain radiographs. Results: In the Crowe II/III groups, the reconstructed center of rotation (COR) in the robotic-assisted group was closer to the anatomical COR with less variation than the manual group (absolute horizontal distances of COR 3.5 ± 2.8 vs. 5.4 ± 4.9 mm, p < 0.05; absolute vertical distances of COR 6.4 ± 4.1 vs. 11.7 ± 8.2 mm, p = 0.001). For all Crowe subtypes, the robotic-assisted THA significantly increased the proportion of acetabular cups located in the safety zone within 5° (all p < 0.05). Interleukin-6 and creatine kinase levels were slightly lower and significantly different in the robotic-assisted group at three days postoperatively (all p < 0.05). Conclusions: Compared to the manual technique, the robot-assisted technique improved the precision and reproducibility of acetabular component positioning, particularly in DDH patients with Crowe types II/III. The robotic-assisted technique did not increase operative time, bleeding, complications, or revision rates, and had a slighter early inflammatory response and muscle damage. [ABSTRACT FROM AUTHOR]

Background: Replacement arthroplasty of the hip is one of the common operations in orthopedic practice and the final success depends on the stability of the implant which depends largely on the proper orientation of the cup during sugary, free hand technique is the commonest conventional method used in practice for cup inclination. A more anatomical methods are adapted to seat the cup abduction such as the use of acetabular fossa all aiming at a better patient directed stable cup. Aims of the Study: To compare the results of the use of acetabular fossa against the use of free hand technique for preoperative seating of acetabular cup inclination in primary cement less hip replacement by the use of post-operative antero-posterior pelvic X-ray to measure the angle of cup abduction and the clinical subjective result as described by the patient. Method: This is a comparative study which was done during the period from July 2017 to march 2022 in the Medical City directorate, Baghdad - Iraq by one surgical team, All patients treated with the same type of primary cement less replacement of the hip through a Posterolateral approach during the study period and were divided into two groups; group A of 34 patients where free hand technique used for seating of cup inclination and group B of 36 patients where acetabular fossa used as an anatomical reference for preoperative cup inclination. The results were assessed by the use of antero-posterior pelvic X-ray for measurement of cup abduction and the use of a subjective patient directed clinical outcome for the result of the surgery after two weeks and after three months of operation which was given by the patient as good, fair or bad. Results: The safe zone of abduction angle identified by Lewinnek et al. which is 40°±10° was used as a gold standard for assessment of the cup inclination. The shortest follow up period was three months. All the angles for the 2 groups fell within the safe zone of Lewinnek, 42.03 ± 4.23 for group A and 42.67 ± 3.92 for group B The patient based clinical outcome was assessed according to WOMAC scoring system and regarding pain domain improved from 12.1±0.98, to 3.6±0.8 2 weeks after surgery and 2.9±0.6 3 months postoperatively and physical activity improved from 43.2±8.1 preoperatively to 26.7±2.2 two weeks after surgery and18.4±1.6 3 months postoperatively for group A with statistically significant result P value <0.05. Conclusion: A proper preoperative planning and templating as well as a standardized patient set up are of prime importance in proper cup placement regardless the operative technique used. [ABSTRACT FROM AUTHOR]

Abstract Aims The objective of this study was to evaluate the accuracy of acetabular cup positioning in the obese patients when using robotic-assisted technology during total hip arthroplasty (THA). Methods Data were retrospectively collected from patients who underwent primary (THA) with a body mass index (BMI) ≥ 28 kg/m2 and ≥ 1 year of follow-up between January 2018 and December 2019. Their demographics, diagnosis, acetabular cup positioning, American Society of Anesthesiologists (ASA) score, Harris Hip Score (HHS), and Forgotten Joint Score (FJS) at the final follow-up were recorded for analysis. Results There were no statistically significant differences between the two groups in height, weight, BMI, ASA score, or preoperative Harris Hip Score (HHS). Also, there was no difference in inclination angle between the two groups (R-THA: 41.29° ± 3.04°; manual THA (M-THA): 40.47° ± 5.46°; P = 0.312). However, the mean anteversion angle was greater in the R-THA group (20.71° ± 1.98° vs. 19.08° ± 4.04°; P

Total hip arthroplasty (THA) for fibrous-fused hips is technically demanding. This study aimed to evaluate the precision and accuracy, as well as the rate of conversion of robotic-assisted THA in such difficult patients. We retrospectively analyzed 67 patients (84 hips) who underwent THA with fibrous-fused hips between August 2018 and June 2021 at our institution. Demographics, acetabular cup positioning, leg-length discrepancies, and postoperative Harris hip scores were recorded for all patients. Thirty-six patients (44 hips) who underwent robotic-assisted THA and 31 patients (40 hips) who underwent manual THA were enrolled in this study. The robot accurately executed the preoperative plan, and there were no statistically significant differences between the preoperative planned anteversion, inclination, and postoperative measurements. In the robotic group, the percentage of acetabular cups in the safe zone was significantly higher than in the manual group (87.2 versus 55%, respectively, P =.042). The rate of conversion to manual THA for various reasons in the robotic-assisted THA group was 11.4% (5/44). Compared with manual THA, the mean increase in operative time for conversion from robotic-assisted to manual THA was 24 min (P <.001). In patients who have fibrous-fused hips, preoperative planning can be accurately executed by robotic-assisted technology. Compared with manual THA, robotic-assisted THA had a remarkable advantage in improving the frequency of achieving cup positioning within the target zone. Overall, robotic-assisted technology was helpful in such difficult cases, and the approximately 11.4% of cases converted to manual THA are reminders that surgeons should be thoroughly prepared preoperatively. [ABSTRACT FROM AUTHOR]

Aims: Navigation devices are designed to improve a surgeon’s accuracy in positioning the acetabular and femoral components in total hip arthroplasty (THA). The purpose of this study was to both evaluate the accuracy of an optical computer-assisted surgery (CAS) navigation system and determine whether preoperative spinopelvic mobility (categorized as hypermobile, normal, or stiff) increased the risk of acetabular component placement error. Methods: A total of 356 patients undergoing primary THA were prospectively enrolled from November 2016 to March 2018. Clinically relevant error using the CAS system was defined as a difference of > 5° between CAS and 3D radiological reconstruction measurements for acetabular component inclination and anteversion. Univariate and multiple logistic regression analyses were conducted to determine whether hypermobile (Δsacral slope(SS)stand-sit > 30°), or stiff (ΔSSstand-sit < 10°) spinopelvic mobility contributed to increased error rates. Results: The paired absolute difference between CAS and postoperative imaging measurements was 2.3° (standard deviation (SD) 2.6°) for inclination and 3.1° (SD 4.2°) for anteversion. Using a target zone of 40° (± 10°) (inclination) and 20° (± 10°) (anteversion), postoperative standing radiographs measured 96% of acetabular components within the target zone for both inclination and anteversion. Multiple logistic regression analysis controlling for BMI and sex revealed that hypermobile spinopelvic mobility significantly increased error rates for anteversion (odds ratio (OR) 2.48, p = 0.009) and inclination (OR 2.44, p = 0.016), whereas stiff spinopelvic mobility increased error rates for anteversion (OR 1.97, p = 0.028). There were no dislocations at a minimum three-year follow-up. Conclusion: Despite high reliability in acetabular positioning for inclination in a large patient cohort using an optical CAS system, hypermobile and stiff spinopelvic mobility significantly increased the risk of clinically relevant errors. In patients with abnormal spinopelvic mobility, CAS systems should be adjusted for use to avoid acetabular component misalignment and subsequent risk for long-term dislocation. Cite this article: Bone Jt Open 2022;3(6):475–484.

Patient-specific instrumentation (PSI) has been suggested to reduce improper component positioning, though the effectiveness of PSI in total hip arthroplasty (THA) remains inconclusive. The purpose of this study was to evaluate the radiographic parameters and clinical outcomes comparing PSI and standard instrumentation (SI). This systematic review and meta-analysis was conducted in accordance with the 2020 PRISMA statement and was registered on PROSPERO. PubMed, Embase, Scopus, Google Scholar, and ClinicalTrials.gov were searched for relevant studies pertaining to the use of PSI in THA. Inclusion criteria included PSI used in THA, PSI was directly compared to SI, and publication in English. Exclusion criteria included non-primary THA, review articles, abstracts, book chapters, and animal models. 2,458 studies were initially identified, with 13 studies (677 THAs: 338 controls, 339 PSI) meeting all criteria. PSI was favored for the deviation from the preoperative plan for acetabular cup position for anteversion (p = 0.04) and inclination (p = 0.0002); risk of acetabular cup positioning outside the Lewinnek safe zone for anteversion (p = 0.005) and inclination (p < 0.0001); and postoperative Harris Hip Score (p = 0.0002). No significant differences were found for the deviation from the preoperative plan for femoral stem position for anteversion (p = 0.74) or varus/valgus (p = 0.15); intraoperative time (p = 0.55); or intraoperative blood loss (p = 0.62). The use of PSI in THA is effective in improving acetabular component positioning and postoperative functional outcomes, without increasing intraoperative time or blood loss, compared to SI. [ABSTRACT FROM AUTHOR]

Aims: The objective of this study was to evaluate the accuracy of acetabular cup positioning in the obese patients when using robotic-assisted technology during total hip arthroplasty (THA). Methods: Data were retrospectively collected from patients who underwent primary (THA) with a body mass index (BMI) ≥ 28 kg/m2 and ≥ 1 year of follow-up between January 2018 and December 2019. Their demographics, diagnosis, acetabular cup positioning, American Society of Anesthesiologists (ASA) score, Harris Hip Score (HHS), and Forgotten Joint Score (FJS) at the final follow-up were recorded for analysis. Results: There were no statistically significant differences between the two groups in height, weight, BMI, ASA score, or preoperative Harris Hip Score (HHS). Also, there was no difference in inclination angle between the two groups (R-THA: 41.29° ± 3.04°; manual THA (M-THA): 40.47° ± 5.46°; P = 0.312). However, the mean anteversion angle was greater in the R-THA group (20.71° ± 1.98° vs. 19.08° ± 4.04°; P < 0.001). Compared to M-THA, R-THA more frequently achieved an acetabular cup angle within 5° of the target (anteversion, 98.1% vs. 78.1% P = 0.001; inclination, 88.5% vs. 53.1%, P < 0.001). The R-THA group was more advantageous in restoring the hip center of rotation (COR) and leg length difference (LLD). There was no statistical difference in postoperative HHS (P = 0.404) or FJS (P = 0.497) between the two groups. Conclusions: Compared to manual technique, robotic-assisted technique provided more precise acetabular cup positioning and better leg length restoration for obese patients. The robotic-assisted technique was more advantageous in recovering the center of rotation position and achieved a higher proportion of the acetabular cup placed in the target safety zone. Further studies are needed to confirm the clinical outcomes of surgeries in obese patients using robotic-assisted technology. [ABSTRACT FROM AUTHOR]

Introduction: In total hip arthroplasty (THA), improper cup orientation can result in dislocation, early excessive polyethylene wear, and pain following THA. The supine position during THA provides a more reproducible functional pelvic position than the lateral decubitus position and may allow freehand cup placement as reliable as that obtained by computer navigation. The purpose of this study was to investigate the accuracy of freehand cup placement through a supine direct anterior approach (DAA) compared with computed tomography (CT)-based navigation. Materials and methods: The same surgeon performed primary cementless THA through the DAA in 144 supine patients. Seventy-two patients underwent freehand cup placement with standard mechanical guidance-oriented radiographic target cup positioning, and 72 underwent placement with CT-based navigation guidance. Using three-dimensional templating software, the study group calculated cup inclination and anteversion on postoperative CT scans. Results: The navigation method resulted in a significantly smaller deviation of inclination from the target (p < 0.05); the difference in anteversion was not significant. In addition, the navigation method resulted in significantly fewer cups placed ± 10° outside the target position (0% for inclination, 0% for anteversion) than did the freehand procedure (26% for inclination, 25% for anteversion) (p < 0.0001). Conclusions: Freehand cup placement is less reliable even in the supine position. Use of a CT-based navigation system can significantly improve cup positioning in THA through the DAA by reducing the incidence of outliers. [ABSTRACT FROM AUTHOR]

Purpose: We investigated the accuracy of the acetabular cup position and orientation in robotic-assisted total hip arthroplasty (rTHA) compared to navigated THA (nTHA) using computed tomography (CT) for patients with osteoarthritis secondary to developmental dysplasia of the hip (DDH). Methods: We studied 31 hips of 28 patients who underwent rTHA and 119 hips of 112 patients who underwent nTHA with the same target cup orientation. After propensity score matching, each group comprised 29 hips. Post-operative cup position and orientation were measured from the postoperative CT data. Errors from the target cup position and orientation were compared between the two groups. Results: Post-operatively, the absolute error of the anteroposterior and superoinferior cup positions from the target position was significantly lower in the rTHA group than in the nTHA group. The change in the post-operative radiographic inclination from the target orientation was lower in the rTHA group than in the nTHA group. Screw fixation for cup implantation was required for three hips in the nTHA group but not in the rTHA group. Conclusion: rTHA achieved more precise cup implantation with reduced variation from the target orientation compared to nTHA in patients with osteoarthritis secondary to DDH. [ABSTRACT FROM AUTHOR]

Purpose: To create a patient-specific instrument (PSI) in lowering the surgical experience requirement for junior physicians to perform total hip arthroplasty (THA) on developmental dysplasia of the hip (DDH) patients.Methods: Combined with rapid prototyping technology, we created a PSI and established DDH hip model in vitro. We enrolled 48 junior physicians and randomly assigned them into two groups. After creation of the PSI, they performed simulated THA surgery on a full-scale hip model with or without PSI on DDH models. The planned prothesis orientation, post-operative prothesis orientation, and surgery time were recorded.Results: The final cup inclination was 42.0 ± 0.8° in PSI group and 37.8 ± 2.0° in control group, while final cup anteversion was 16.0 ± 0.7° in PSI group and 24.7 ± 3.5° in control group. The △inclination in PSI group was smaller than that in control group (4.2 ± 0.5° vs 9.5 ± 1.4°, P < 0.01), so does △inclination (2.9 ± 0.4° in PSI group vs 15.2 ± 2.5° in control group, P < 0.01). The outlier percent was 8.3% in PSI group and 70.8% in control group (P < 0.01). At the same time, the PSI group did not prolong the operation time (P = 0.551).Conclusion: The PSI can greatly increase the accuracy of placing the cup orientation and lower the threshold for junior physicians to perform THA on DDH patients. It could be a training tool for them to increase their THA surgical skills. [ABSTRACT FROM AUTHOR]

Purpose of Review: The orientation of the spine relative to the pelvis—particularly that in the sagittal plane—has been shown in both kinematic and radiographic studies to be paramount in governance of acetabular alignment during normal bodily motion. The purpose of this review is to better understand the challenges faced by arthroplasty surgeons in treating patients that have concurrent lumbar disease and are therefore more likely to have poorer clinical outcomes after THA than in patients without disease. Recent Findings: The concept of an "acetabular safe zone" has been well described in the past regarding the appropriate orientation of acetabular component in THA. However, this concept is now under scrutiny, and rising forth is a concept of functional acetabular orientation that is based on clinically evaluable factors that are patient and motion specific. Summary: The interplay between the functional position of the acetabulum and the lumbar spine is complex. The challenges that are thereby faced by arthroplasty surgeons in terms of proper acetabular cup positioning when treating patients with concomitant lumbar disease need to be better understood and studied, so as to prevent catastrophic and costly complications such as periprosthetic joint dislocations and revision surgeries. [ABSTRACT FROM AUTHOR]

Abstract Background The large-scale clinical problem caused by unacceptable tribological behaviour of certain large diameter metal-on-metal prosthetic hips has directed attention to adverse condition testing. High metal-on-metal wear is connected with adverse reaction to metal debris. Friction is important because high friction may be associated with high wear, risk the fixation of the cup, and cause detrimental heating of periprosthetic tissues. Methods A friction measurement system was added to a multidirectional, established hip joint wear simulator, and its functionality was evaluated. In preliminary tests, a 50 mm diameter metal-on-metal prosthesis was tested in an optimal acetabular cup inclination angle (48°) and in a steep angle (70°) using a normal peak load (2 kN) and an increased peak load (3 kN). The test length was 100 h. Long-term adverse condition tests of 3 million cycles were run for three 52 mm metal-on-metal prostheses. The lubricant was diluted calf serum at 37 °C. Findings In the 100 h tests, metal-on-metal frictional torque was not highly sensitive to the angle, load and serum degradation, and it was close to that of a conventional 28 mm prosthesis with a polyethylene cup, mostly below 5 Nm. However, a manyfold higher frictional torque (10 to 20 Nm) was observed in long-term metal-on-metal tests with substantial wear. Interpretation To obtain a realistic prediction of the frictional behaviour of a hip design, long-term, multidirectional wear tests are necessary. The friction should preferably be measured during the wear test. In addition to normal conditions, adverse condition testing is strongly recommended. Highlights • Single-axis friction measurement hip joint simulators cannot produce realistic wear. • Friction should be measured in conditions similar to those of the wear test. • Friction measurement was added to an established, multidirectional hip simulator. • High metal-on-metal wear resulted in friction manyfold to that of unworn prostheses. • For a realistic view of frictional behaviour a multidirectional wear test is needed. [ABSTRACT FROM AUTHOR]

Background: The purpose of this study is to measure acetabular cup position and wear of the highly crosslinked polyethylene liner in the supine and standing position for patients at a minimum of 10 years after the operation.Methods: A total of 38 patients were recruited at a mean of 12.5 years after the operation. All patients received a single acetabular cup design with a highly crosslinked liner and a 28-mm cobalt-chromium femoral head. Patients underwent supine and standing radiostereometric examinations in which the X-ray sources and detectors were positioned to obtain an anterior-posterior and cross-table lateral radiograph. Acetabular cup position and the three-dimensional wear rate were measured from the radiographs, and outcome scores were recorded for each patient.Results: Anteversion significantly increased (P < .0001) a mean of 12° from supine (15.1° ± 10.4°) to standing (27.2° ± 10.5°) position. Inclination also significantly increased (P = .001) a mean of 2° from supine (44.4° ± 6.8°) to standing (46.3° ± 7.7°) position. There was no difference (P = .093) in wear rate between supine (0.067 ± 0.070 mm/y) and standing (0.073 ± 0.074 mm/y) positions. There were no correlations between cup orientation and wear rate in either position.Conclusion: Highly crosslinked polyethylene is a forgiving bearing material. Although adherence to the traditional acetabular position target zone is recommended, ensuring hip stability and consideration of the patient's functional position are also important objectives to consider for the acetabular position. [ABSTRACT FROM AUTHOR]

Being one of the most successful surgeries in the history of medicine, the indications for total hip arthroplasty have widened and are increasingly being offered to younger and fitter patients. This has also led to high expectations for longevity and outcomes. Acetabular cup position has a significant impact on the results of hip arthroplasty as it affects dislocation, abductor muscle strength, gait, limb lengths, impingement, noise generation, range of motion (ROM), wear, loosening, and cup failure. The variables in cup position are depth, height, and angular position (anteversion and inclination). The implications of change in depth of center of rotation (COR) are medialized versus anatomical positioning. As opposed to traditional medialization with beneficial effects on joint reaction force, the advantages of an anatomical position are increasingly recognized. The maintained acetabular offset offers advantages in terms of ROM, impingement, cortical rim press fit, and maintaining medial bone stock. The height of COR influences muscle activity and limb lengths and available bone stock for cup support. On the other hand, ideal angular position remains a matter of much debate and reliably achieving a target angular position remains elusive. This is not helped by variations in the way we describe angular position, with operative, radiologic, or anatomic definitions being used variably to describe anteversion and inclination. Furthermore, pelvic tilt plays a major role in functional positions of the acetabulum. In addition, commonly used techniques of positioning often do not inform us of the real orientation of the pelvis on operating table, with possibility of significant adduction, flexion, and external rotation of the pelvis being possibilities. This review article brings together the evidence on cup positioning and aims to provide a systematic and pragmatic approach in achieving the best position in individual cases. [ABSTRACT FROM AUTHOR]

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 2 kN to 3 kN, 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. [ABSTRACT FROM AUTHOR]

This retrospective study measured the change of the acetabular component orientation between supine and standing radiographs in 113 THA patients and identified the associated anatomical parameters that may help direct pre-operative planning. The mean change of the acetabular component inclination and version from supine to standing was 4.6° and 5.9° respectively ( P < 0.0001), with 49 (43%) hips showing inclination change > 5° and 69 (53%) hips showing version change > 5°. Twelve (43%) of 28 ‘malpositioned’ cups became ‘well-positioned’ and 26 (31%) of 85 ‘well-positioned’ cups became ‘malpositioned’ upon standing. Changes in inclination were associated with leg length discrepancy and pelvic obliquity; and changes in version were associated with pelvic tilt and pelvic incidence. Standing position and patient factors should be considered when defining “optimal” acetabular orientation. [ABSTRACT FROM AUTHOR]

Abstract: After periacetabular osteotomy (PAO), some patients develop osteoarthritis with need of a total hip arthroplasty (THA). We evaluated the outcome of THA following PAO and explored factors associated with inferior cup position and increased polyethylene wear. Follow-up were performed 4 to 10years after THA in 34 patients (38 hips) with previous PAO. Computer analysis evaluated cup position and wear rates. No patient had dislocations or revision surgery. Median scores were: Harris hip 96, Oxford hip 38 and WOMAC 78. Mean cup anteversion and abduction angles were 22o (range 7°–43°) and 45° (range 28°–65°). Outliers of cup abduction were associated with persisting dysplasia (CE <25°). THA after PAO can produce excellent clinical results. Persisting acetabular dysplasia following PAO may lead surgeons to place the acetabular component in excessive cup abduction, and this tendency should be recognized at the time of the PAO. [Copyright &y& Elsevier]

Abstract: Clinically, malposition of the acetabular cup in large-diameter metal-on-metal prosthetic hip designs is associated with high wear, adverse reaction to metal debris and early failure. A steep angle of the cup (>60°) may lead to poor tribological performance. Large-diameter CoCr-on-CoCr prostheses were run in the HUT-4 hip joint simulator so that a steep angle was included. With a correct position, the tribological behaviour was excellent, the wear rate being 0.1mm3/106 cycles. In the steepest position, lubrication failed and the wear rate was two orders of magnitude higher. This study stresses the importance of rigorous pre-clinical testing. [Copyright &y& Elsevier]

Abstract: Proper acetabular cup orientation is essential in total hip arthroplasty. The purpose of this study was to evaluate the accuracy of a particular imageless computer navigation system in determining cup position. Thirty-nine computer-navigated total hip arthroplasty intraoperative measurements of cup abduction and anteversion were compared with those from follow-up radiographs. Sensitivity, specificity, accuracy, prevalence-adjusted positive value (PPV), and negative predictive value were calculated for both navigation and radiographs. Navigation measurements had high specificity and PPV when assessing cup abduction and anteversion (specificity >90%, PPV >94%). In contrast, the system was not very effective in detecting suboptimal cup position (sensitivity abduction, 50%; anteversion, 33%). Intraoperative navigation readings in the safe zone have high probability of indicating correct placement. However, confirmation of suboptimal cup position intraoperatively requires additional diagnostic methods. [Copyright &y& Elsevier]

Purpose: The purpose of this study was to compare different methods of evaluating the version of a metallic acetabular cup from plain radiographs and to compare them regarding their accuracy, inter- and intra-observer reliability. Methods: Conventional anterior-posterior radiographs were taken of a phantom-model at different defined ante- and retroversion angles of the acetabular cup. The version angles of the acetabular cup were derived according to four different established methods from the radiographs by five independent examiners. Results: We were able to determine the radiographic version with the greatest accuracy according to a modified technique of Pettersson et al. Furthermore, we found the highest intra- and inter-observer reliability using this technique. Conclusions: A modified technique of Pettersson et al. broadens the spectrum of applicability for the radiographic evaluation of the version angle of metal-backed acetabular cups in comparison to the originally introduced method. In clinical practice, however, the significance of deriving the cup position from standard radiographs should not be over-estimated and therefore a computed tomography should be performed in certain critical cases. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this study was to evaluate the results of bilateral total hip arthroplasties (THAs) with special regard to angle of cup position in patients with bilaterally ankylosed hips. Twenty-four ankylosed hips were converted to THAs in 12 patients. Their mean age was 36 years and they were followed up for more than 3 years (average, 11 years). The mean Harris hip score increased from 55.4 to 82.3 points. Osteolysis and loosening were found in 3 and 2 hips, respectively. Eleven cups of 24 hips (46%) were outside the safe ranges of Lewinnek. Overall outcome after bilateral conversion of bilaterally ankylosed hips to THA was favorable, but the fused position of the contralateral limb had the tendency to define the direction of the malposition of the acetabular cup. [Copyright &y& Elsevier]

The acetabular cup position after total hip arthroplasty (THA) regarding its inclination and version angles are influential parameters concerning the postoperative range of motion and dislocation stability. Standard anterior-posterior X-rays remain an important diagnostic instrument to observe the postoperative outcome and to secure quality control after THA, where an optimal positioning of the patient is recommended when taking these X-rays. The purpose of this preliminary study was to determine the effect of pelvic tilting regarding the positioning calculation of the acetabular cup from standard radiographs using a modified method according to Pettersson et al. (Acta Radiol Diagn, 23:259–263, ). In our model experiment, we were able to show that pelvic tilting to either side causes a considerable difference between the radiographic and calculated version angles following approximately linear functions. However, pelvic tilting to either side, leads, regarding the calculation of the inclination, to an average deviation between radiographic and calculated inclination angles less than 2°. [ABSTRACT FROM AUTHOR]