Advances in imaging for pre-surgical planning in hip resurfacing arthroplasty.

BACKGROUND: Accurate preoperative templating is essential for the success of hip resurfacing arthroplasty (HRA). While digital radiograph is currently considered the gold standard, stereoradiograph and CT converted 3D methods have shown promising results. However, there is no consensus in the literature regarding the preferred modality for HRA templating, and angular measurements are often overlooked. Thus, this study aimed to: (1) compare the performances of different modality in implant sizing and angle measurements, (2) evaluate the measurement reproducibility, (3) assess the impact of severe osteoarthritis on femoral head sizing, and (4) based on the analysis above, explore the optimal imaging and planning strategy for HRA. HYPOTHESIS: An optimal imaging modality exists for HRA planning regarding implant sizing and angular measurements. MATERIALS AND METHODS: Preoperative imaging data from seventy-seven HRA surgeries were collected. Three raters performed templating using digital radiograph, stereoradiograph, and CT converted 3D models. Measurements for femoral head size, neck-shaft angle, and calcar-shaft angle were obtained. The femoral head sizing was compared to the intraoperative clinical decision. The reproducibility of measurements was assessed using the intraclass correlation coefficient (ICC). Correlations were examined between sizing disagreement and osteoarthritis grade (Tonnis Classification). RESULTS: Digital radiograph, stereoradiograph, and 3D techniques predicted one size off target in 27/77 (35%), 49/70 (70%), and 75/77 (97%) of cases, respectively, corresponding to 1.8±1.6 (0 to 5.67), 0.9±0.7 (0 to 2.67), and 0.4±0.4 (0 to 1.67) sizes off target, indicating statistically significant differences among all three modalities, with p-values all below 0.01. There were no statistically significant differences among the different modalities for angular measurements. Measurements showed moderate to excellent reproducibility (ICC=0.628-0.955). High-grade osteoarthritis did not impact image sizing in any modality (r=0.08-0.22, all p>0.05). DISCUSSION: CT converted 3D models were more accurate for implant sizing in HRA, but did not significantly outperform other modalities in angular measurements. Given the high costs and increased radiation exposure associated with CT, the study recommended using CT scans selectively, particularly for precise femoral head sizing, while alternative imaging methods can be effectively used for angular measurements. LEVEL OF EVIDENCE: III; retrospective comparative diagnostic study.

Two-Year Results of Ceramic-on-Ceramic Hip Resurfacing in an International Multicenter Cohort.

BACKGROUND: Hip resurfacing arthroplasty (HRA) is a bone-conserving alternative to total hip arthroplasty. We present the 2-year clinical and radiographic follow-up of a novel ceramic-on-ceramic HRA in an international multicenter cohort. METHODS: Patients undergoing HRA between September 2018 and January 2021 were prospectively included. Patient-reported outcome measures (PROMs) in the form of the Forgotten Joint Score, Hip Disability and Osteoarthritis Outcome Score Jr., Western Ontario and McMaster Universities Arthritis Index, Oxford Hip Score, and University of California, Los Angeles, Activity Score were collected preoperatively, and at 1 and 2 years postoperation. Serial radiographs were assessed for migration, component alignment, evidence of osteolysis or loosening, and heterotopic ossification formation. RESULTS: The study identified 200 patients who reached a minimum 2-year follow-up (mean 3.5 years). Of these, 185 completed PROMs follow-up at 2 years. There was a significant improvement in Hip Disability and Osteoarthritis Outcome Score (P < .001) and Oxford Hip Score (P < .001) between the preoperative, 1-year, and 2-year outcomes. Patients had improved activity scores on the University of California, Los Angeles, Active Score (P < .001), with 45% reporting a return to high-impact activity at 2 years. At 1 and 2 years, the Forgotten Joint Score was not significantly different (P = .38). There was no migration, osteolysis, or loosening of any of the implants. No fractures were reported over the 2-year follow-up, with only 1 patient reporting a sciatic nerve palsy. There were 2 revisions, 1 for unexplained pain at 3 months due to acetabular component malposition and 1 at 33.5 months for acetabular implant failure. CONCLUSIONS: The ceramic-on-ceramic resurfacing at 2 years postoperation demonstrates promising results with satisfactory outcomes in all recorded PROMs. Further long-term data are needed to support the widespread adoption of this prosthesis as an alternative to other HRA bearings.

Evaluating pelvic tilt using the pelvic antero-posterior radiographs: A novel method.

Pelvic tilt (PT) is an important parameter for orthopedic surgeries involving hip and spine, typically determined from sagittal pelvic radiographs. However, various challenges can compromise the feasibility of measurement from sagittal imaging, including obscured landmarks, anatomical variations, hardware interference, and limited medical resources. Addressing these challenges and with the aim of reducing radiation exposure to patients, our study developed a novel method to estimate PT from antero-posterior (AP) radiographs, using vertical distances from the pelvic outlet and obturator foramen. We correlated these measurements with PT, defined both anatomically (anterior pelvic plane, PTa) and mechanically (centers of femoral heads and sacral plate, PTm). The study explored creating linear, exponential, and multivariate regression models based on twelve 3D CT-derived pelvic models (six men, six women), simulating AP radiograph projections with controlled PTs. We then validated these models against 105 pairs of patient stereoradiographs. Statistical analysis revealed that combined exponential-linear models yielded the most accurate results, with Pearson correlation coefficients of 0.75 for PTa and 0.77 for PTm, and mean absolute errors of 3.7° ± 2.6° for PTa and 4.5° ± 3.4° for PTm, showing excellent measurement reliability (all ICCs > 0.9) without significant gender discrepancies. In conclusion, this study presents a validated, simple, and accessible method for estimating PT using AP radiograph parameters, supported by the Supporting Information S1: Excel Tool, showing great potential for clinical application in hip and spine procedures.

Determination of preoperative risk factors for iliopsoas tendonitis after total hip arthroplasty: A simulation study.

This study aims to identify preoperative risk factors for iliopsoas tendonitis after total hip arthroplasty, a complication typically attributed to acetabular cup position and orientation, using a validated iliopsoas impingement detection simulation. Analyzing CT scans and X-rays of 448 patients using a validated preoperative planning protocol, patients were simulated for iliopsoas impingement and categorized into at-risk and not at-risk groups based on a prior validation study, with a 23% at-risk incidence. Implementing a propensity score matching algorithm to reduce covariate imbalance, we identified factors that may exacerbate risk of iliopsoas tendonitis. Parameters that were investigated included standing pelvic tilt, functional femoral rotation, and the difference between the planned acetabular cup diameter and native femoral head diameter (ΔC-NFH). Comparing pelvic tilt, we found a significant difference between the groups (at-risk: -6.0°, not at-risk: -0.7°; p << 0.01). A similar trend was noted for ΔC-NFH (at-risk: +5.7 mm, not at-risk: +5.1 mm; p = 0.01). Additional simulations of at-risk patients indicated increased anteversion of the acetabular cup reduces impingement risk more effectively than medialisation. These findings suggest that spinopelvic parameters may exacerbate iliopsoas irritation risk, underscoring their importance in preoperative planning and patient expectation management. Similar findings of a greater than 6 mm difference between cup size and native femoral head diameter being a significant risk for iliopsoas tendonitis have been observed before, underscoring its potential veracity. These results may provide surgeons with a simple threshold that can be used in determining a cup size to reduce the risk of iliopsoas tendonitis.

Inadequate Annotation and Its Impact on Pelvic Tilt Measurement in Clinical Practice.

BACKGROUND: Accurate pre-surgical templating of the pelvic tilt (PT) angle is essential for hip and spine surgeries, yet the reliability of PT annotations is often compromised by human error, inherent subjectivity, and variations in radiographic quality. This study aims to identify challenges leading to inadequate annotations at a landmark dimension and evaluating their impact on PT. METHODS: We retrospectively collected 115 consecutive sagittal radiographs for the measurement of PT based on two definitions: the anterior pelvic plane and a line connecting the femoral head's centre to the sacral plate's midpoint. Five annotators engaged in the measurement, followed by a secondary review to assess the adequacy of the annotations across all the annotators. RESULTS: The outcomes indicated that over 60% images had at least one landmark considered inadequate by the majority of the reviewers, with poor image quality, outliers, and unrecognized anomalies being the primary causes. Such inadequacies led to discrepancies in the PT measurements, ranging from -2° to 2°. CONCLUSION: This study highlights that landmarks annotated from clear anatomical references were more reliable than those estimated. It also underscores the prevalence of suboptimal annotations in PT measurements, which extends beyond the scope of traditional statistical analysis and could result in significant deviations in individual cases, potentially impacting clinical outcomes.

Comparison of iliopsoas tendonitis after hip resurfacing arthroplasty and total hip arthroplasty: A case-controlled investigation using a validated simulation.

Iliopsoas tendonitis, typically caused by impingement with the acetabular cup, occurs in up to 18% of patients after total hip arthroplasty (THA) and up to 30% of patients after hip resurfacing arthroplasty (HRA). We have developed a simulation for detecting iliopsoas impingement and validated it in a previous study of THA patients. However, due to the difference in incidence between HRA and THA, this study had two aims. First, to validate the simulation in a cohort of HRA patients and, second, to comparethe results of the HRA and THA patients to understand any differences in their etiology. We conducted a retrospective search in an experienced surgeon's database for HRA patients with iliopsoas tendonitisand control patients without iliopsoas tendonitis, resulting in two cohorts of 12 patients. Using CT scans, 3D models of the each patient's prosthetic and bony anatomy were generated, landmarked, and simulated. Regarding validation of the simulation for HRA patients, impingement significantly predicted the probability of iliopsoas tendonitis in logistic regression models and the simulation had a sensitivity of 83%, specificity of 100%, and an AUC ROC curve of 0.95. Unexpectedly, the HRA cohort exhibited less impingement than the THA cohort. Our novel simulation has now been demonstrated to detect iliopsoas impingement and differentiate between the symptomatic and asymptomatic cohorts in investigations of THA and HRA patients. This tool has the potential to be used preoperatively, to guide decisions about optimal cup placement, and postoperatively, to assist in the diagnosis of iliopsoas tendonitis.

Evaluating Pelvic Tilt Using the Pelvic Antero-Posterior Projection Images: A Systematic Review.

BACKGROUND: Pelvic tilt (PT) is a routinely evaluated parameter in hip and spine surgeries, and is usually measured on a sagittal pelvic radiograph. This may not always be feasible due to limitations such as landmark visibility, pelvic anomaly, and hardware presence. Tremendous efforts have been dedicated to using pelvic antero-posterior (AP) radiographs for assessing sagittal PT. Thus, this systematic review aimed to collect these methods and evaluate their performances. METHODS: Two independent reviewers searched the PubMed, Ovid, Cochrane, and Web of Science databases in June 2023 with backward reference trailing (Google Scholar archive). There were 30 studies recruited. Risk of bias was assessed using the prediction model risk of bias assessment tool. The relevant data were tabulated in a standardized form for evaluating either the absolute PT or relative PT. Disagreement was resolved by discussing with the senior author. RESULTS: There were 19 parameters from pelvic AP projection images involved, with 4 studies which used artificial intelligence, eyeball, or statistical shape method not involving a specific parameter. In comparing the PT values from pelvic sagittal images with those extrapolated from antero-posterior projection images, the highest correlation coefficient was found to be 0.91. The mean absolute difference (error) was 2.6°, with a maximum error reaching 10.9°. Most studies supported the feasibility of using AP parameters to calculate changes in PT. CONCLUSIONS: No individual AP parameter was found to precisely estimate absolute PT. However, relative PT can be derived by evaluating serial AP radiographs of a patient in varying postures, employing any AP parameters.

Quadriceps tendon malalignment is an independent anatomical deformity which is the primary abnormality associated with lateral facet patellofemoral joint osteoarthritis.

PURPOSE: The purposes of this study are to, firstly, develop techniques to accurately identify extensor mechanism malalignment by measuring the alignment of the quadriceps tendon (QTA) with computerized tomography (CT) scans. Secondly, to investigate correlations between QTA and lower limb bony anatomical variations within a representative normal population. Lastly, to evaluate the clinical significance of QTA by establishing its potential connection with lateral facet patellofemoral joint osteoarthritis (LFPFJOA). METHOD: CT scans were orientated to a mechanical axis reference frame and three techniques developed to measure the alignment of the quadriceps tendon. Multiple measurement of bony alignment from the hip to the ankle were performed on each scan. A series of 110 cadaveric CT scans were measured to determine normal values, reproducibility, and correlations with bony anatomy. Secondly, a comparison between 2 groups of 25 patients, 1 group with LFPFJOA and 1 group with isolated medial OA and no LFPFJOA. RESULTS: From the cadaveric study, it was determined that the alignment of the quadriceps tendon is on average 4.3° (SD 3.9) varus and the apex of the tendon is 9.1 mm (SD 7.7 mm) lateral to the trochlear groove and externally rotated 1.9° (SD 12.4°) from the centre of the femoral shaft. There was no association between the quadriceps tendon alignment and any other bony measurements including tibial tubercle trochlear groove distance (TTTG), coronal alignment, trochlear groove alignment and femoral neck anteversion. A lateralized QTA was significantly associated with LFPFJOA. QTA in the LFPFJOA group was 9.6° varus (SD 2.8°), 21.3 mm (SD 6.6) lateralised and 17.3° ER (SD 11°) compared to 5.5° (SD 2.3°), 10.7 mm (SD 4.9) and 3.3° (SD 7.2°), respectively, in the control group (p < 0.001). A significant association with LFPFJOA was also found for TTTG (17.2 mm (SD 5.7) vs 12.1 mm (SD 4.3), p < 0.01). Logistic regression analysis confirmed the QTA as having the stronger association with LFPFJOA than TTTG (AUC 0.87 to 0.92 for QTA vs 0.79 for TTTG). CONCLUSION: These studies have confirmed the ability to accurately determine QTA on CT scans. The normal values indicate that the QTA is highly variable and unrelated to bony anatomy. The comparative study has determined that QTA is clinically relevant and a lateralised QTA is the dominant predictor of severe LFPFJOA. This deformity should be considered when assessing patella maltracking associated with patella osteoarthritis, patella instability and arthroplasty. LEVEL OF EVIDENCE: III (retrospective cohort study).

Effect of Aspirin vs Enoxaparin on 90-Day Mortality in Patients Undergoing Hip or Knee Arthroplasty: A Secondary Analysis of the CRISTAL Cluster Randomized Trial.

Importance: Ischemic heart disease remains the leading cause of mortality following hip and knee arthroplasty. Due to its antiplatelet and cardioprotective properties, aspirin has been proposed as an agent that could reduce mortality when used as venous thromboembolism (VTE) prophylaxis following these procedures. Objective: To compare aspirin with enoxaparin in reducing 90-day mortality for patients undergoing hip or knee arthroplasty procedures. Design, Setting, and Participants: This study was a planned secondary analysis of the CRISTAL cluster randomized, crossover, registry-nested trial performed across 31 participating hospitals in Australia between April 20, 2019, and December 18, 2020. The aim of the CRISTAL trial was to determine whether aspirin was noninferior to enoxaparin in preventing symptomatic VTE following hip or knee arthroplasty. The primary study restricted the analysis to patients undergoing total hip or knee arthroplasty for a diagnosis of osteoarthritis only. This study includes all adult patients (aged ≥18 years) undergoing any hip or knee arthroplasty procedure at participating sites during the course of the trial. Data were analyzed from June 1 to September 6, 2021. Interventions: Hospitals were randomized to administer all patients oral aspirin (100 mg daily) or subcutaneous enoxaparin (40 mg daily) for 35 days after hip arthroplasty and 14 days after knee arthroplasty procedures. Main Outcomes and Measures: The primary outcome was mortality within 90 days. The between-group difference in mortality was estimated using cluster summary methods. Results: A total of 23 458 patients from 31 hospitals were included, with 14 156 patients allocated to aspirin (median [IQR] age, 69 [62-77] years; 7984 [56.4%] female) and 9302 patients allocated to enoxaparin (median [IQR] age, 70 [62-77] years; 5277 [56.7%] female). The mortality rate within 90 days of surgery was 1.67% in the aspirin group and 1.53% in the enoxaparin group (estimated difference, 0.04%; 95% CI, -0.05%-0.42%). For the subgroup of 21 148 patients with a nonfracture diagnosis, the mortality rate was 0.49% in the aspirin group and 0.41% in the enoxaparin group (estimated difference, 0.05%; 95% CI, -0.67% to 0.76%). Conclusions and Relevance: In this secondary analysis of a cluster randomized trial comparing aspirin with enoxaparin following hip or knee arthroplasty, there was no significant between-group difference in mortality within 90 days when either drug was used for VTE prophylaxis. Trial Registration: http://anzctr.org.au Identifier: ACTRN12618001879257.

Accuracy of acetabular component alignment with surgical guidance systems during hip arthroplasty.

BACKGROUND: Navigation in total hip arthroplasty has been shown to improve acetabular positioning and can decrease the incidence of mal-positioned acetabular components. This study aimed to assess two surgical guidance systems by comparing intra-operative measurements of acetabular component inclination and anteversion with a post-operative CT scan. METHODS: We prospectively collected intra-operative navigation data from 102 hips receiving conventional THA or hip resurfacing arthroplasty through either a direct anterior or posterior approach. Two guidance systems were used simultaneously: an inertial navigation system (INS) and an optical navigation system (ONS). Acetabular component anteversion and inclination were measured on a post-operative CT. RESULTS: The average age of the patients was 64 years (range: 24-92) and the average BMI was 27 kg/m2 (range 19-38). 52% had hip surgery through an anterior approach. 98% of the INS measurements and 88% of the ONS measurements were within 10° of the CT measurements. The mean (and standard deviation) of the absolute difference between the postoperative CT and the intra-operative measurements for inclination and anteversion were 3.0° (2.8) and 4.5° (3.2) respectively for the ONS, along with 2.1° (2.3) and 2.4° (2.1) respectively for the INS. There was a significantly lower mean absolute difference to CT for the INS when compared to ONS in both anteversions (p < 0.001) and inclination (p = 0.02). CONCLUSIONS: We found that both inertial and optical navigation systems allowed for adequate acetabular positioning as measured on postoperative CT, and thus provide reliable intraoperative feedback for optimal acetabular component placement. LEVEL OF EVIDENCE: Therapeutic Level II.

Correlations Analysis of Different Pelvic Tilt Definitions: A Preliminary Study.

Background: Pelvic tilt (PT) is described as the pelvic orientation along the transverse axis, yet 4 PT definitions were established based on radiographic landmarks: anterior pelvic plane (PTa), the center of femoral heads to sacral plate (PTm), pelvic outlet (PTh), and sacral slope (SS). These landmarks quantify a similar concept, yet understanding of their relationships is lacking, and their differences are sometimes ignored. Purpose: This study aimed to examine the correlations and differences of PT definitions for education and research purposes. Methods: This study reviewed 105 sagittal pelvic radiographs of patients (68 men and 37 women) awaiting hip surgery at a single clinic. Hip hardware and spine pathologies were examined for subgroup analysis. Two observers annotated 4 PTs in a gender-dependent manner and repeated it after 6 months. The linear regression model and intraclass correlation coefficient (ICC) were applied with a 95% confidence interval. Results: The SS showed no correlation to the other 3 PT definitions, except for females in the hip hardware subgroup (n = 17). PTm demonstrated very strong linear correlation to PTh (r > 0.9) under the linear model PTm = 0.951 × PTh - 68.284. Conclusion: The PTm and PTh can be calculated from each other under a simple linear regression equation, which enables comparisons between them. SS presented poor correlations to the other PT parameters, except for the female subgroup with hip implant that required further analysis; PTa-related comparisons showed high anatomical variations between patients.

The Sacro-femoral-pubic Angle Is Unreliable to Estimate Pelvic Tilt: A Meta-analysis.

BACKGROUND: The accurate measurement of pelvic tilt is critical in hip and spine surgery. A sagittal pelvic radiograph is most often used to measure pelvic tilt, but this radiograph is not always routinely obtained and does not always allow the measurement of pelvic tilt because of problems with image quality or patient characteristics (such as high BMI or the presence of a spinal deformity). Although a number of recent studies have explored the correlation between pelvic tilt and the sacro-femoral-pubic angle using AP radiographs (SFP method), which aimed to estimate pelvic tilt without a sagittal radiograph, disagreement remains about whether the SFP method is sufficiently valid and reproducible for clinical use. QUESTIONS/PURPOSES: The purpose of this meta-analysis was to evaluate the correlation between SFP and pelvic tilt in the following groups: (1) overall cohort, (2) male and female cohort, and (3) skeletally mature and immature cohorts (young and adult groups, defined as patients older or younger than 20 years). Additionally, we assessed (4) the errors of SFP-estimated pelvic tilt angles and determined (5) measurement reproducibility using the intraclass correlation coefficient. METHODS: This meta-analysis was reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and registered in PROSPERO (record ID: CRD42022315673). PubMed, Embase, Cochrane, and Web of Science were screened in July 2022. The following keywords were used: sacral femoral pubic, sacro femoral pubic, or SFP. The exclusion criteria were nonresearch articles such as commentaries or letters and studies that only investigated relative pelvic tilt rather than absolute pelvic tilt. Although the included studies had different patient recruitment strategies, study quality-wise, they all used an adequate amount of radiographs for landmark annotation and applied a correlation analysis for the relationship between the SFP angle and pelvic tilt. Thus, no risk of bias was found. Participant differences were mitigated via subgroup and sensitivity analyses to remove outliers. Publication bias was assessed using the p value of a two-tailed Egger regression test for the asymmetry of funnel plots, as well as the Duval and Tweedie trim and fill method for potential missing publications to impute true correlations. The extracted correlation coefficients r were pooled using the Fisher Z transformation with a significance level of 0.05. Nine studies were included in the meta-analysis, totaling 1247 patients. Four studies were used in the sex-controlled subgroup analysis (312 male and 460 female patients), and all nine studies were included in the age-controlled subgroup analysis (627 adults and 620 young patients). Moreover, a sex-controlled subgroup analysis was conducted in two studies with only young cohorts (190 young male patients and 220 young female patients). RESULTS: The overall pooled correlation coefficient between SFP and pelvic tilt was 0.61, with high interstudy heterogeneity (I 2 = 76%); a correlation coefficient of 0.61 is too low for most clinical applications. The subgroup analysis showed that the female group had a higher correlation coefficient than the male group did (0.72 versus 0.65; p = 0.03), and the adult group had a higher correlation coefficient than the young group (0.70 versus 0.56; p < 0.01). Three studies reported erroneous information about the measured pelvic tilt and calculated pelvic tilt from the SFP angle. The mean absolute error was 4.6° ± 4.5°; in one study, 78% of patients (39 of 50) were within 5° of error, and in another study, the median absolute error was 5.8º, with the highest error at 28.8° (50 female Asian patients). The intrarater intraclass correlation coefficients ranged between 0.87 and 0.97 for the SFP angle and between 0.89 and 0.92 for the pelvic tilt angle, and the interrater intraclass correlation coefficients ranged between 0.84 and 1.00 for the SFP angle and 0.76 and 0.98 for the pelvic tilt angle. However, large confidence intervals were identified, suggesting considerable uncertainty in measurement at the individual radiograph level. CONCLUSION: This meta-analysis of the best-available evidence on this topic found the SFP method to be unreliable to extrapolate sagittal pelvic tilt in any patient group, and it was especially unreliable in the young male group (defined as patients younger than age 20 years). Correlation coefficients generally were too low for clinical use, but we remind readers that even a high correlation coefficient does not alone justify clinical application of a metric such as this, unless further subgroup analyses find low error and low heterogeneity, which was not the case here. Further ethnicity-segregated subgroup analyses with age, sex, and diagnosis controls could be useful in the future to determine whether there are some subgroups in which the SFP method is useful. LEVEL OF EVIDENCE: Level III, diagnostic study.

Iliopsoas tendonitis after total hip arthroplasty : an improved detection method with applications to preoperative planning.

AIMS: Iliopsoas impingement occurs in 4% to 30% of patients after undergoing total hip arthroplasty (THA). Despite a relatively high incidence, there are few attempts at modelling impingement between the iliopsoas and acetabular component, and no attempts at modelling this in a representative cohort of subjects. The purpose of this study was to develop a novel computational model for quantifying the impingement between the iliopsoas and acetabular component and validate its utility in a case-controlled investigation. METHODS: This was a retrospective cohort study of patients who underwent THA surgery that included 23 symptomatic patients diagnosed with iliopsoas tendonitis, and 23 patients not diagnosed with iliopsoas tendonitis. All patients received postoperative CT imaging, postoperative standing radiography, and had minimum six months' follow-up. 3D models of each patient's prosthetic and bony anatomy were generated, landmarked, and simulated in a novel iliopsoas impingement detection model in supine and standing pelvic positions. Logistic regression models were implemented to determine if the probability of pain could be significantly predicted. Receiver operating characteristic curves were generated to determine the model's sensitivity, specificity, and area under the curve (AUC). RESULTS: Highly significant differences between the symptomatic and asymptomatic cohorts were observed for iliopsoas impingement. Logistic regression models determined that the impingement values significantly predicted the probability of groin pain. The simulation had a sensitivity of 74%, specificity of 100%, and an AUC of 0.86. CONCLUSION: We developed a computational model that can quantify iliopsoas impingement and verified its accuracy in a case-controlled investigation. This tool has the potential to be used preoperatively, to guide decisions about optimal cup placement, and postoperatively, to assist in the diagnosis of iliopsoas tendonitis.Cite this article: Bone Jt Open 2023;4(1):3-12.

Effect of Aspirin vs Enoxaparin on Symptomatic Venous Thromboembolism in Patients Undergoing Hip or Knee Arthroplasty: The CRISTAL Randomized Trial.

Importance: There remains a lack of randomized trials investigating aspirin monotherapy for symptomatic venous thromboembolism (VTE) prophylaxis following total hip arthroplasty (THA) or total knee arthroplasty (TKA). Objective: To determine whether aspirin was noninferior to enoxaparin in preventing symptomatic VTE after THA or TKA. Design, Setting, and Participants: Cluster-randomized, crossover, registry-nested trial across 31 hospitals in Australia. Clusters were hospitals performing greater than 250 THA or TKA procedures annually. Patients (aged ≥18 years) undergoing hip or knee arthroplasty procedures were enrolled at each hospital. Patients receiving preoperative anticoagulation or who had a medical contraindication to either study drug were excluded. A total of 9711 eligible patients were enrolled (5675 in the aspirin group and 4036 in the enoxaparin group) between April 20, 2019, and December 18, 2020. Final follow-up occurred on August 14, 2021. Interventions: Hospitals were randomized to administer aspirin (100 mg/d) or enoxaparin (40 mg/d) for 35 days after THA and for 14 days after TKA. Crossover occurred after the patient enrollment target had been met for the first group. All 31 hospitals were initially randomized and 16 crossed over prior to trial cessation. Main Outcomes and Measures: The primary outcome was symptomatic VTE within 90 days, including pulmonary embolism and deep venous thrombosis (DVT) (above or below the knee). The noninferiority margin was 1%. Six secondary outcomes are reported, including death and major bleeding within 90 days. Analyses were performed by randomization group. Results: Enrollment was stopped after an interim analysis determined the stopping rule was met, with 9711 patients (median age, 68 years; 56.8% female) of the prespecified 15 562 enrolled (62%). Of these, 9203 (95%) completed the trial. Within 90 days of surgery, symptomatic VTE occurred in 256 patients, including pulmonary embolism (79 cases), above-knee DVT (18 cases), and below-knee DVT (174 cases). The symptomatic VTE rate in the aspirin group was 3.45% and in the enoxaparin group was 1.82% (estimated difference, 1.97%; 95% CI, 0.54%-3.41%). This failed to meet the criterion for noninferiority for aspirin and was significantly superior for enoxaparin (P = .007). Of 6 secondary outcomes, none were significantly better in the enoxaparin group compared with the aspirin group. Conclusions and Relevance: Among patients undergoing hip or knee arthroplasty for osteoarthritis, aspirin compared with enoxaparin resulted in a significantly higher rate of symptomatic VTE within 90 days, defined as below- or above-knee DVT or pulmonary embolism. These findings may be informed by a cost-effectiveness analysis. Trial Registration: ANZCTR Identifier: ACTRN12618001879257.

Improving Acetabular Component Positioning in Total Hip Arthroplasty: A Cadaveric Study of an Inertial Navigation Tool and a Novel Registration Method.

Background: Incorrect acetabular component positioning in total hip arthroplasty (THA) has been associated with poor outcomes. Computer-assisted hip arthroplasty increases accuracy and consistency of cup positioning compared to conventional methods. Traditional navigation units have been associated with problems such as bulkiness of equipment and reproducibility of anatomical landmarks, particularly in obese patients or the lateral position. Purpose: We sought to evaluate the accuracy of a novel miniature inertial measurement system, the Navbit Sprint navigation device (Navbit, Sydney, Australia), to navigate acetabular component positioning in both the supine and lateral decubitus positions. We also aimed to validate a new method of patient registration that does not require acquisition of anatomical landmarks for navigation. Methods: We performed THA in a cadaveric study in supine and lateral positions using Navbit navigation to record cup position and compared mean scores from 3 Navbit devices for each cup position on post-implantation CT scans. Results: A total of 11 cups (5 supine and 6 lateral) were available for comparison. A difference of 2.34° in the supine direct anterior approach when assessing acetabular version was deemed to be statistically but not clinically significant. There was no statistically significant difference between CT and navigation measurements of cup position in the lateral position. Conclusion: This cadaveric study suggests that a novel inertial-based navigation tool is accurate for cup positioning in THA in the supine and lateral positions. Furthermore, it validates a novel registration method that does not require the identification of anatomical landmarks.

Surfing After Hip Resurfacing Surgery.

OBJECTIVE: There is no information about surfing after hip resurfacing arthroplasty (HRA). We did a retrospective study aiming to evaluate the safety and feasibility to resume surfing-an extreme sport with high-impact physical activity-after HRA. DESIGN: Retrospective case series. SETTING: Specialist Orthopaedic Group, Mater Hospital Sydney, NSW, Australia. PATIENTS: We evaluated 45 patients who practiced surfing before the onset of pain and hip surgery. Complete clinical and radiographical follow-up and a completed questionnaire were available for 37 (82%) patients. INTERVENTIONS: Hip resurfacing arthroplasty. MAIN OUTCOME MEASURES: Postel-Merle d'Aubigne score, the Oxford hip score, the Harris hip score, and the University of California at Los Angeles activity score. Radiographical evaluation at 6 weeks, 3, and 12 months after surgery and yearly thereafter. Return to surf rates using a specific questionnaire. Complications and failures during follow-up. RESULTS: All clinical scores improved significantly after HRA. Eight of 37 (22%) patients stopped surfing after their HRA. More than 80% of patients commenced surfing within the first 6 months after surgery. During surfing, 21 patients (72%) were completely pain free. CONCLUSION: No literature exists regarding the return to a high-impact sport as surfing after HRA. Most of our patients (71%) were able to return at least to their preoperative level of surfing after surgery. No complications related to this sport activity were observed during short-term follow-up. We believe that surfing is compatible with HRA, but long-term studies are necessary to assess the influence of this extreme sport on loosening and revision rates.

Novel Measure of Acetabular Cup Inclination and Anteversion During Total Hip Arthroplasty.

PURPOSE: The purposes of the present research were to assess the accuracy and usability of the inertial navigation system (INS). MATERIALS AND METHODS: The accuracy of the device navigation subsystem was assessed using benchtop testing. The usability was assessed through simulated use with surgeons. These results were compared to recent cadaveric results for the same system. RESULTS: The navigation subsystem had an overall mean absolute error of 1.21° and a maximum absolute error across all devices of 4.79°. The device was found to be usable and to add an estimated 7 minutes to surgery time. CONCLUSION: The INS uses a novel approach to provide the surgeon with accurate and fast acetabular cup inclination and anteversion angles during THA.

Long-Term Results of Alumina Ceramic-On-Ceramic Bearings in Cementless Total Hip Arthroplasty: A 20-Year Minimum Follow-Up.

BACKGROUND: Alumina ceramic-on-ceramic bearings are used in total hip arthroplasty (THA) because of their wear-resistant and inert properties. In this study, we assessed the clinical and radiographic outcomes of patients undergoing primary cementless ceramic-on-ceramic THA at a minimum follow-up of 20 years. METHODS: A series of 301 consecutive primary THAs in 283 patients were assessed. Clinically, patients were assessed with the modified Harris Hip Score (HHS) and pain questionnaires. Anteroposterior radiographs of the pelvis and lateral radiographs of the hip were used to radiologically assess the implant. Patients were classified as lost to follow-up if they could not be contacted on multiple occasions or did not wish to participate further in this study. RESULTS: At twenty years after operation, 60 patients had died of a cause unrelated to surgery, 16 had experienced complications requiring reoperation, and 100 hips had both clinical assessments and radiographs at a minimum of 20 years of follow-up. The average HHS improved from 56.1 (range: 17-89) before THA to 92.5 (range: 63-100) at the latest follow-up. The classification of the HHS was good or excellent in 96.4% of patients. Only 1.8% of patients still had moderate residual pain at the thigh or groin. Radiographically, all patients demonstrated bony ingrowth but no clinical symptoms of loosening. The overall survival rate of the implants was 94.2% at 20 years with revision for any reason as the end point. CONCLUSION: Long-Term follow-up in our series showed excellent implant survival, excellent functional outcomes, and minimal late complications. There was no significant radiographic evidence of failure at a minimum of 20 years after THA. LEVEL OF EVIDENCE: Therapeutic Level IV.

The Use of Computer Navigation in Total Hip Arthroplasty Is Associated with a Reduced Rate of Revision for Dislocation: A Study of 6,912 Navigated THA Procedures from the Australian Orthopaedic Association National Joint Replacement Registry.

BACKGROUND: The use of computer navigation has been shown to produce more accurate cup positioning when compared with non-navigated total hip arthroplasty (THA), but so far there is only limited evidence to show its effect on clinical outcomes. The present study analyzed data from the Australian Orthopaedic Association National Joint Replacement Registry to assess the impact of computer navigation on the rates of all-cause revision and revision for dislocation following THA. METHODS: Data for all non-navigated and navigated primary THAs performed for osteoarthritis in Australia from January 1, 2009, to December 31, 2019, were examined to assess the rate of revision. We analyzed the effects of navigation on rate, reason, and type of revision. Hazard ratios (HRs) from Cox proportional hazard models, adjusted for age, sex, and head size, were utilized. Because of known prosthesis-specific differences in outcomes, we performed a further analysis of the 5 acetabular and femoral component combinations most commonly used with navigation. RESULTS: Computer navigation was utilized in 6,912 primary THAs for osteoarthritis, with the use of navigation increasing from 1.9% in 2009 to 4.4% of all primary THAs performed in 2019. There was no difference in the rate of all-cause revision between navigated and non-navigated THAs looking at the entire group. There was a lower rate of revision for dislocation in the navigation THA cohort. The cumulative percent revision for dislocation at 10 years was 0.4% (95% confidence interval [CI], 0.2% to 0.6%) for navigated compared with 0.8% (95% CI, 0.8% to 0.9%) for non-navigated THAs (HR adjusted for age, sex, and head size, 0.46; 95% CI, 0.29 to 0.74; p = 0.002). In the 5 component combinations most commonly used with navigation, the rate of all-cause revision was significantly lower when these components were navigated compared with non-navigated. The cumulative percent revision at 10 years for these 5 prostheses combined was 2.4% (95% CI, 1.6% to 3.4%) for navigated compared with 4.2% (95% CI, 4.0% to 4.5%) for non-navigated THAs (HR, 0.64; 95% CI, 0.48 to 0.86; p = 0.003). CONCLUSIONS: This study showed that the use of computer navigation was associated with a reduced rate of revision for dislocation following THA. Furthermore, in the component combinations most commonly used with navigation there was also a reduction in the rate of all-cause revision. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Minimal important change and minimum clinically important difference values of the KOOS-12 after total knee arthroplasty.

PURPOSE: The minimal important change (minimal amount of change vs. baseline that a patient recognizes as a clinical change) and minimum clinically important difference (smallest difference between two measurements that are deemed important by patients) are important values to evaluate the clinical relevance of changes over time and differences between groups. This study aims to establish these values for the KOOS-12 at 1 year postoperatively. METHODS: KOOS-12 scores were calculated from the full-length KOOS completed by patients undergoing primary TKA preoperatively and at 1 year follow up. Minimal important change (MIC) values were estimated using the anchor-based predictive modeling approach and adjustment for the large proportion of improved patients in the study cohort was performed. The MCID was defined as the difference in the mean change in the KOOS-12 between the 'no improvement' and 'little improvement' groups. RESULTS: A total of 352 patients (161 male:191 female) with an overall mean age of 67.9 years (standard deviation (SD) 8.2) and a mean body mass index of 31.4 kg/m2 (SD 6.3) were included: 97.1% of patients reported an important improvement, 1.1% reported being about the same and 1.7% reported being importantly worse. The MIC improvement values were 11.5 for Pain, 13.7 for Function, 5.5 for Quality of Life (QoL) and 14.9 for the total KOOS-12 score. MCID values were 13.5 for Pain, 15.2 for Function, 8.0 for QoL and 11.1 for the total KOOS-12 score. CONCLUSION: MIC of 14.9 and MCID of 11.1 established in this study can assist clinicians and researchers in the interpretation of within-group changes (MIC) and differences between groups (MCID) at 1 year after TKA.