Achieving acetabular cup stability following revision total hip arthroplasty (rTHA) involving acetabular defects is challenging. Current computational modeling approaches to investigate implant stability under physiological loading are time consuming to implement and, to date, have been based on low sample sizes across limited defect classifications. This study had two aims. First, to develop an automated rTHA simulation framework to estimate postoperative implant response to physiological loading across the range of Paprosky acetabular defects; and second, to use this framework to estimate regional implant stability and osseointegration potential of rTHA implants augmented with four different screw configurations: (i) superior fixation only (ii) superior and infero-posterior fixation (iii) superior and infero-anterior fixation, and (iv) superior, infero-posterior, and infero-anterior fixation. A modeling pipeline employing artificial neural networks and statistical shape modeling was developed to convert patient computed tomography (CT) images to finite element models for automated surgical planning and simulation of rTHA involving acetabular defects. Computed tomography images from sixty subjects were used as input to the framework resulting in 214 completed simulations. An infero-posterior screw when used with a superior screw was associated with a significant reduction in posterior acetabular micromotion compared to using a superior screw alone (mean reduction: 129 μm, p  < 0.001). Use of an infero-posterior screw improved overall implant stability more than that of an infero-anterior screw. The results suggest that screw holes allowing inferior fixation ought to be made standard in revision acetabular components. The findings of this study may be useful in surgical planning for rTHA.

Background: The contribution of specific nutritional biomarkers to skeletal fragility remains poorly understood, in part because most studies include participants with metabolic conditions that obscure nutrient-specific effects. We aimed to examine incremental contribution of six pathway-specific nutritional biomarkers. Methods: In a prospective cross-sectional case-control design, 108 patients undergoing arthroplasty were enrolled (hip-fracture, n = 63; non-fracture, n = 45), and bone biopsies and blood specimens were collected intraoperatively. Circulating biomarkers reflecting vitamin K, one-carbon metabolism, antioxidant nutrients (vitamins E and C), protein and zinc status were measured. Bone outcomes included remodelling markers, trabecular microarchitecture and bone strength. Hierarchical regression was used to quantify the incremental contribution of nutritional biomarkers beyond clinical covariates with a priori outcome selection. Results: Bone remodelling markers did not differ between groups after covariate adjustment, indicating that fractures in this cohort were characterised by deficits in bone strength and quality rather than elevated systemic remodelling activity. Among six nutritional pathways tested, only vitamin K-dependent biomarkers showed consistent independent associations with bone outcomes, suggesting a degree of pathway specificity. Critically, carboxylated (cOC), undercarboxylated (ucOC) and fully uncarboxylated (unOC) osteocalcin fractions showed differential associations reflecting their distinct biological roles: cOC was independently associated with greater bone strength (section modulus, femoral neck width and cortical shaft thickness; p < 0.05) and lower trabecular separation (Tb.Sp); ucOC was associated with higher Tb.Sp (p = 0.004); and unOC was positively associated with cortical bone instability (buckling ratio, p = 0.003) and explained 17% of the variance in the bone resorption marker (p < 0.001), consistent with a shift towards bone loss. Vitamin K2-7 was negatively associated with hip axis length (p = 0.021). Conclusions: These findings identify vitamin K-dependent carboxylation as a mechanistically specific and modifiable factor associated with skeletal fragility beyond bone mineral density, with distinct skeletal consequences across osteocalcin carboxylation states.

Prosthetic joint infection (PJI) is a devastating complication that affects up to 1.7% of patients within 2 years following total hip arthroplasty (THA) or total knee arthroplasty (TKA). PJI is associated with significant patient morbidity, reduction in quality of life, prolonged hospitalisation, and healthcare expenditure. With a 5-year mortality reported as high as 21%, PJI is one of the most feared complications of joint arthroplasty. Identification of PJI is of critical importance to ensure successful and definitive treatment. However, diagnosis remains challenging due to the lack of a gold standard, culture-negative infection, and varying sensitivity and specificity of diagnostic tests. The rapid expansion of machine learning (ML) in the literature has led to the emergence of models that utilise patient demographics, clinical features, serological studies, synovial fluid biomarkers, and imaging to improve PJI diagnostics. The purpose of this study was to describe the literature on using ML to diagnose PJI. A systematic review of the literature for original studies describing ML use in PJI diagnostics following THA or TKA was conducted. This review identified 12 studies applying ML to diagnose or predict PJI, through patient demographics, clinical features, and imaging. Most models demonstrated good predictive performance, with Area Under the Curve (AUC) from 0.68 to 0.993. However, few studies validated their models externally. In conclusion, ML presents a promising approach to enhance PJI diagnostic accuracy, which may reduce diagnostic delays and ensure appropriate treatment. Further studies are needed to assess the model's generalisability and validate these models in external cohorts. Statement of Clinical Significance: The diagnosis of PJI remains a challenge due to limitations in current diagnostic criteria. ML offers a data-driven approach to improve diagnostic accuracy, potentially allowing earlier and more accurate identification to ensure appropriate treatment in a timely manner.

Background and purpose: 2-year proximal migration thresholds for acetabular cups used at primary total hip arthroplasty were first established in 2012 by matching radiostereometric analysis (RSA) measurements of cup migration with long-term survivorship from cohort studies. Subsequently, there have been new RSA studies reporting migration of contemporary cup designs whose survivorships are available from long-term registry data. The primary aim of this study was to re-evaluate the 2-year postoperative RSA migration thresholds and investigate whether thresholds at time points earlier than 2 years were possible. Methods: The mean 6-month, 1-, and 2-year proximal migration of each RSA cohort was matched to the pooled 10-year proportion of acetabular cup revision due to aseptic loosening in the Australian Orthopaedic Association National Joint Replacement Registry and the Dutch Arthroplasty Registry in 2023. Revision rates were pooled according to these classifications using a random effects model. Results: 164 implant-survival combinations (228,053 cups), involving 27 cup designs, were identified with RSA migration data to 2 years. At 1 year, mean cup migration of ≤ 0.1 mm was considered acceptable, while migration > 0.8 mm was unacceptable. The pooled proportions of acetabular cup revision in the acceptable, at-risk, and unacceptable threshold categories were 0.36% (95% confidence interval [CI] 0.26–0.47), 1.05% (CI 0.80–1.31), and 5.07% (CI 1.41–8.73) respectively. At 2 years, mean cup migration ≤ 0.2 mm was considered acceptable while mean migration > 1.0 mm had unacceptable survivorship. The pooled proportions of acetabular cup revision in the acceptable, at-risk, and unacceptable threshold categories were 0.55% (CI 0.48–0.62), 1.27% (CI 0.87–1.67), and 21.6% (CI 0.0–54.7), respectively, meaning that acetabular cups with high migration can be identified at both 1 and 2 years. Conclusion: This study confirmed the existing 2-year migration thresholds and established a new threshold at 1 year. We found no association between continuous migration between 1 and 2 years and 10-year revision rates. The 1-year migration threshold is the earliest surrogate measure for assessing late loosening of the acetabular cup and may identify underperforming implants.

BACKGROUND:In public hospitals the number of complex urgent and semi-urgent revision joint replacements has increased over time, conversely the number of primary joint replacements has decreased. This study aimed to investigate the effect of this change on service delivery of elective surgery and training in one large metropolitan hospital. METHODS:We retrospectively reviewed changes in staffing, workload and all hip and knee joint replacements performed at the Royal Adelaide Hospital over a 20-year period, between January 2003 to December 2023. RESULTS:The number of primary total hip replacements (THR) and total knee replacements (TKR) performed on elective lists has decreased from 210/year to 140/year. The number of revisions THR and TKR increased from 76/year to 219/year (135 septic). The number of patients awaiting elective surgery has increased from 220 in 1999 (THR 18) to 597 in 2024 (THR 69). CONCLUSIONS:There is an urgent need of decisions by local policy makers to plan for the continual increase in THR and TKR as well as revision joint replacements. The significant change in pathology requires consideration of staffing, training and funding to account for the increased number of complex septic revisions.

Background and purpose: National joint arthroplasty registries are the gold standard for monitoring long-term acetabular implant survivorship. Sensitive radiographic surveillance (SRS) has been recommended as a complementary surveillance approach, but no study has investigated whether implants introduced with no sensitive radiographic surveillance (NSRS) are associated with higher revision rates. Therefore, we investigated whether acetabular implants with NSRS are associated with higher revision rates than those with SRS. Methods: Acetabular implants with SRS were defined as those with published evidence of stability measurements assessed using either radiostereometric analysis or “Ein Bild Röntgen Analyse.” Evidence of SRS of acetabular implant designs was sourced from 2 literature reviews. A mixed-effects model was used to pool and compare the revision rate of acetabular implants with SRS and NSRS at 5 and 10 years from 5 arthroplasty registries. Results: There were 29 unique acetabular implant designs with SRS and 86 designs with NSRS that had matching 5- and 10-year revision rates. At 5 years, there was a mean difference of 0.8% (95% confidence interval [CI] 0.5–1.1) in mean all-cause revision rates favoring implants with SRS. Mean all-cause revision rates at 10 years for acetabular implants with SRS and NSRS were 5.2% (CI 4.9–5.5) and 7.4% (CI 7.0–7.9) respectively, with a mean difference of 1.8% (CI 1.2–2.3) favoring implants with SRS. Conclusion: Acetabular implants with NSRS were associated with 1.8% higher pooled revision rates than those with SRS at 10 years, which represents a relative increase in acetabular revision burden of approximately 36%.

Background:Knee replacements are among the most common orthopedic surgeries. Periprosthetic joint infection (PJI) is a devastating complication that can occur after total knee replacement, and a 2-stage approach is considered the gold standard for managing it. Static spacers are often used for patients with medical comorbidities that affect wound healing. This study introduces a new technique that employs a static spacer with threaded rods for a 2-stage revision.Methods:Between July 2022 and June 2024, 7 patients with knee PJI were treated using a static spacer made with threaded Ilizarov rods. The average age of the patients was 70 years (range: 64 to 79). All patients had significant medical comorbidities, and 6 out of 7 were culture-positive for PJI. Patient outcomes were assessed based on wound healing, weight-bearing capacity, and the success of second-stage revision.Results:All wounds healed successfully after the static spacer was inserted. Five patients were able to weight-bear with protection after the first-stage revision. All patients underwent second-stage revision successfully. One patient was converted to a non-articulated spacer with a gastrocnemius flap for soft tissue cover.Conclusion:The static spacer with threaded rods is a cost-effective and efficient interim prosthesis for the first stage of a 2-stage revision for PJI. This technique minimizes impact during insertion and allows for easy rod removal in the second stage, making it a practical option for medically complex patients.

Carboxylated osteocalcin (cOC), produced during post-translational modification of osteocalcin (OC) in a vitamin K-dependent pathway, has a high affinity for calcium and hydroxyapatite. Despite the observed link between vitamin K deficiency and fracture risk, supplementation studies have not consistently demonstrated improvements in bone mineral density (BMD) or bone microarchitecture, though studies have reported improvement in cOC status. We hypothesise that these inconsistent findings are due to the lack of knowledge on the mechanisms by which cOC affects bone health. Hence, the aim of this study was to investigate the relationship between cOC and bone turnover markers, cortical and trabecular bone microarchitecture and strength. Forty-five patients who underwent hip arthroplasty for hip osteoarthritis were prospectively recruited. Patients with conditions or medications that could affect bone outcomes were excluded and intra-operative bloods and bone biopsies were collected. Cortical thickness and hip strength was measured with dual-energy X-ray absorptiometry and micro-computed tomography was used to determine trabecular bone microarchitecture. Cortical thickness, cross-sectional area, cross-sectional moment of inertia, femoral neck width and section modulus correlated positively with cOC (p < 0.05, all). There was no association between partially or fully un-carboxylated fractions and hip strength variables. Further, cOC was found to be an independent predictor of bone alkaline phosphastase while the partially or fully un-carboxylated OC predicted c-terminal telopeptide of type 1 collagen. In conclusion, higher cOC concentrations were associated with improved femoral bone strength, and the effect is possibly mediated through higher bone mineralisation, independent of age, parathyroid hormone, kidney function, BMD and physical activity.

Background: Despite the popularity of the modified Harris Hip Score (mHHS) to monitor patient-reported outcome measures (PROMs) following Total Hip Arthroplasty (THA) over the last 5 decades, International Joint Registries have recently favoured the Hip disability and Osteoarthritis Outcome Score (HOOS). The ability to convert mHHS collected in historical and ongoing studies would be beneficial to benchmark more recent HOOS reports. Hence, this study aimed to create multi-directional crosswalks between mHHS and HOOS. Methods: Forty-nine patients undergoing primary THA prospectively completed both HHS and HOOS forms pre-operatively and at either 3, 6 and/or 12 months postoperatively. The Equipercentile (EQ) and Linear Regression (LR) crosswalk methodology were used. The Mean Absolute Error (MAE) of the crosswalk-derived scores was established against patient-derived (PD) scores. Results: There was a strong correlation between PD mHHS and HOOS (0.90) and HOOS-12 (0.90). The MAE of mHHS-to-HOOS-12 crosswalk was 10.4 (EQ) and 10.1 (LR). Subcategory activity had a larger contribution towards the error in the crosswalks than pain. Conclusions: This is the first crosswalk to facilitate conversion of mHHS and HOOS scores, which are required in long-term THA quality-assurance and research studies, which often span 2 decades of expected implant survivorship.

BACKGROUND:This systematic review and meta-analysis aimed to synthesize the hospital costs of revision total hip arthroplasty (rTHA) by periprosthetic joint infection, periprosthetic fracture (PPF), aseptic loosening, and recurrent dislocation diagnoses. In addition, as several surgical options are available within some diagnoses, this study aimed to synthesize the evidence on hospital costs for septic rTHA between debridement, antibiotics, and implant retention and one-stage and two-stage rTHA, and for PPF, the cost between rTHA and open reduction and internal fixation treatment. METHODS:A systematic search of PubMed, Embase, and Scopus identified all studies reporting the hospital costs of rTHA. Screening, data extraction, and risk of bias assessment were conducted. Hospital costs of each study cohort by main diagnosis and treatment were adjusted to 2024 United States Dollar and pooled using a random-effects model. RESULTS:Of 866 publications identified, 24 studies were included in the meta-analysis. Mean pooled costs of rTHA for dislocation, aseptic loosening, PPF, and septic rTHA were $25,256, $34,533, $35,904, and $55,707, respectively. The mean cost of septic rTHA (16 study cohorts) at $57,264 was 87% higher than aseptic rTHA (22 cohorts) at $30,224. A two-stage septic rTHA ($70,311) cost 77% more than one-stage septic rTHAs ($39,676). The cost of rTHA for PPF ($35,904) was 26% more than open reduction and internal fixation for PPF ($28,410). CONCLUSIONS:The cost of rTHA is progressively higher by diagnosis in the order of dislocation, aseptic loosening, PPF, and infection. Future studies should separately report rTHA costs by diagnosis and treatment type and longitudinally examine the hospital costs of this patient cohort, particularly for septic cases, beyond initial treatment to better understand the burden of rTHA.

BACKGROUND AND AIMS:Patients with elevated homocysteine (Hcy) levels are associated with an increased risk of fracture. B-vitamin supplementation studies have consistently shown an ability to reduce Hcy levels but have had no or marginal effect on bone mineral density (BMD), which led us to hypothesize that hyperhomocysteinemia may increase fracture risk by altering bone quality outcome measures beyond BMD. The aim of our systematic review was to investigate the association between Hcy and bone quality outcome measures, i.e. bone turnover, bone microarchitecture, collagen crosslinks and micro damage accumulation, in healthy adults. METHODS:A systematic search was performed on Pubmed, Embase, and Scopus from the date of inception to 30th of September, 2024. Studies were included that had sufficient data to identify the pooled relationship between plasma Hcy and at least one domain of bone quality, such as bone microarchitecture, bone turnover, advanced glycation product (AGE) pentosidine levels, collagen crosslinks, or micro damage accumulation. Studies involving patients who were on medications or had conditions affecting plasma Hcy or bone health were excluded. Osteoporotic patients were included only if they had not been treated. RESULTS:Twenty-seven studies were included in our systematic review. Our meta-analysis found a significant positive correlation between Hcy and osteocalcin [Pearson's coefficient of correlation (r) = 0.39, significance value (p) = 0.023, 95 % Confidence Interval (CI) = 0.36-0.42]. No significant correlation was observed between Hcy and Procollagen type-1 N propeptide (P1NP), C-terminal telopeptide of type 1 collagen (CTX-1), or Bone-specific alkaline phosphatase (Bone ALP). Additionally, we found a strong positive correlation between Hcy and the AGE serum pentosidine [r = 0.72; 95 % CI: 0.67-0.76; p = 0.020], a molecule linked to increased non-enzymatic collagen cross-linkage. Further, two studies measured collagen-crosslinking in the bone, and both reported elevated Hcy to be associated with higher non-enzymatic crosslinks and reduced enzymatic crosslinks. CONCLUSION:Our results suggest that elevated Hcy impacts bone quality outcome measures. The effect is possibly mediated via increased bone turnover and accumulation of non-enzymatic collagen crosslinking, resulting in decreased bone strength. PROSPERO REGISTRATION NO:CRD42024595870.

Revision total hip arthroplasty (rTHA) involving large acetabular defects is associated with high early failure rates, primarily due to cup loosening. Most acetabular defect classification systems used in surgical planning are based on planar radiographs and do not encapsulate three-dimensional geometry and morphology of the acetabular defect. This study aimed to develop an automated computational modeling pipeline for rapid generation of three-dimensional acetabular bone defect geometry. The framework employed artificial neural network segmentation of preoperative pelvic computed tomography (CT) images and statistical shape model generation for defect reconstruction in 60 rTHA patients. Regional acetabular absolute defect volumes (ADV), relative defect volumes (RDV) and defect depths (DD) were calculated and stratified within Paprosky classifications. Defect geometries from the automated modeling pipeline were validated against manually reconstructed models and were found to have a mean dice coefficient of 0.827 and a mean relative volume error of 16.4%. The mean ADV, RDV and DD of classification groups generally increased with defect severity. Except for superior RDV and ADV between 3A and 2A defects, and anterior RDV and DD between 3B and 3A defects, statistically significant differences in ADV, RDV or DD were only found between 3B and 2B-2C defects (p < 0.05). Poor correlations observed between ADV, RDV, and DD within Paprosky classifications suggest that quantitative measures are not unique to each Paprosky grade. The automated modeling tools developed may be useful in surgical planning and computational modeling of rTHA.

Prosthetic joint infection (PJI) is a serious complication of joint replacement surgery. Emerging evidence suggests that gut dysbiosis (characterised by reduced microbial diversity, altered immune responses, and increased intestinal permeability) could facilitate bacterial translocation from the gut to prosthetic joints and contribute to the development of PJI. In this scoping review, we analysed eight studies (three preclinical and five clinical) that investigated the potential link between gut microbiota alteration (dysbiosis) and PJIs. Preclinical models indicated that animals experiencing gut dysbiosis had higher rates of PJI, with a study testing the Trojan horse hypothesis showing that neutrophils carrying viable meticillin-resistant Staphylococcus aureus from the gut seeded the prosthetic joints without detectable bloodstream infection. Clinical research identified higher levels of zonulin (a marker of intestinal barrier integrity) and inflammatory markers, decreased gut microbial diversity, and presence of gut commensals within the joint tissues of patients with PJI. However, few studies used stool sequencing or adhered to microbiome research guidelines, thereby restricting conclusions. This Review highlights the need for future research that includes gut microbiota profiling, tight junction biomarker characterisation, and intervention trials (eg, testing the effect of probiotic use) to elucidate the role of gut dysbiosis in PJI. Investigating the gut microbiota before arthroplasty and incorporating suitable control groups could help to identify any causative relationships. The findings of this Review suggest that gut dysbiosis could be a modifiable risk factor for PJI, warranting the exploration of osteomicrobiology and gut-joint axis mechanisms in arthroplasty outcomes.

BACKGROUND:Total hip arthroplasty (THA) is recognised to improve patients' quality of life; however revision surgery incurs a substantial burden upon patients, clinicians, hospitals and healthcare systems. This study aimed to investigate (1) the hospital costs of revision THA (rTHA) relative to primary THA (pTHA) by diagnosis and the cost drivers within each episode of care (EoC); and (2) the cumulative costs of rTHA for prosthetic joint infections (PJI) by treatment pathway. METHODS:Median hospital costs of patients undergoing pTHA (n = 1101) or rTHA (n = 396) at a tertiary referral hospital between 2014 and 2022 were calculated by diagnosis, cost drivers and treatment pathways. Admission and procedural data were verified across multiple hospital databases, including a prospective hospital-based arthroplasty register. Costs were adjusted for inflation to 2024 Australian Dollars (AU$). RESULTS:Median cost of rTHA per EoC ($45 165) was significantly more costly than pTHA ($25 615, p < 0.05). Median rTHA cost by diagnosis increased from dislocation ($37 072), loosening ($47 708), periprosthetic fractures ($52 521) to PJI ($65 325). Within each diagnosis of rTHA, the most expensive cost drivers were ward-related and surgical theatre costs. Regarding PJI treatment pathways, median cost was $123 688 for two-stage rTHA, $63 261 for single stage rTHA and $51 760 for debridement and implant retention. CONCLUSION:Median costs of rTHA for dislocation, loosening, periprosthetic fracture and PJI were associated with a 1.5, 1.9, 2.1 and 2.6-fold higher cost relative to pTHA per EoC, respectively. Ongoing surgical treatment and readmission for PJI lead to complex treatment pathways and increased costs.

Aims This study investigated the outcomes of total hip arthroplasty (THA) performed for acute acetabular fractures through a replace-in-situ technique, where no attempt was made at fracture reduction, fixation, or restoration of columns before acetabular component insertion. Methods We report the clinical outcomes at a mean follow-up of five years of 41 acute complex acetabular fractures in 41 patients, with a mean age of 76 years (54 to 97), who underwent THA through a replace-in-situ technique. Results Four patients died during the acute episode of care, and one within 12 months. All fractures healed within six months and all patients who survived the acute episode of care returned to their baseline function. A total of four patients underwent further surgery: one underwent revision for cup loosening at 18 months, one underwent open reduction and internal fixation of a femoral periprosthetic fracture at seven years, and two underwent head-liner exchange at two and four months for recurrent dislocation. One additional cup was radiologically loose but not revised, as this caused no additional symptoms. Conclusion THA using a replace-in-situ technique shows promising results comparable to those reported for fix-and-replace techniques. As clinical outcomes continue to be inferior to those of THA for osteoarthritis, larger multicentre studies are required to investigate possible differences between surgical indications and techniques.

Background:While porous tantalum components have shown to be advantageous in the revision setting, registry studies have identified tantalum components used in primary total hip arthroplasty (THA) to be associated with an increased risk of revision. The only study to examine the migration of tantalum acetabular components with radiostereometric analysis (RSA) beyond 2 years found continued migration. The aim of this 7-year follow-up RSA study was to determine if the mid-term migration of tantalum acetabular components without ancillary screw fixation is no greater than that of fiber metal titanium components with one ancillary screw fixation. Methods:We prospectively reviewed the mid-term implant stability of patients who underwent primary THA and were randomized intra-operatively to receive either the tantalum or titanium acetabular component. Of the initial 66 patients enrolled, 51 (77.3%) were available at 7-year follow-up; 2 tantalum components were revised due to recurrent dislocation and infection, respectively, and 2 titanium components underwent open reduction internal fixation to treat femoral periprosthetic fracture. Acetabular component migration relative to the surrounding acetabular bone was measured using RSA at 4-6 days post-operatively and at 6 weeks, 3 months, 1, 2, 3, 5, and 7 years following THA. Results:At 7 years, the mean proximal migration of tantalum components was 0.22 mm (95% confidence interval 0.08-0.35) and non-inferior to that of titanium components at 0.19 mm (95% confidence interval 0.07-0.32). In addition, the mean proximal migration of tantalum components was non-inferior to that of titanium at both 3 and 5 years. There were no significant differences noted between cohorts for any other axis of translation and rotation. Conclusions:The continued mid-term stability of tantalum acetabular components without ancillary screw fixation is encouraging for long-term stability. The non-inferiority compared to titanium acetabular components with established excellent long-term survivorship provides reassurance to the operative surgeon using tantalum components in the primary setting. Level of Evidence:I.

Bone biopsies are an important biological tool for investigating bone microarchitecture, which can be non-destructively imaged in 3D via micro-computed tomography (micro-CT). Image thresholding and delineation of a region of interest (ROI) are prerequisites for quantifying bone parameters. Validated automatic protocols enable quantification of biopsies that contain trabecular and cortical bone. However, irregularly shaped trabecular bone biopsies with peripheral and internal debris have required manual ROI delineation, which is time-intensive and subject to inter and intra-observer variance. We hypothesise that an automated workflow will be a suitable alternative to overcome these issues and objectively determine bone microarchitecture in surgical biopsies, at higher throughput suitable for clinical studies. Hence, the aim of this study was to develop an objective, reproducible and automated workflow to analyse microarchitecture of trabecular bone biopsies. To accomplish this aim, we tested six different methods of ROI delineation: a whole biopsy ROI, and both manual (slow) and automatically delineated (fast) reduced ROIs to remove peripheral debris, each with (adaptive thresholding and a set of morphological operations to remove debris) and without (global thresholding) processing in a subset (n = 8) of intertrochanteric femoral biopsies obtained from patients undergoing hip arthroplasty. Number of objects, bone volume to tissue volume (BV/TV), trabecular separation (Tb.Sp), structure model index (SMI) and Euler number and trabecular pattern factor (Tb.Pf) were compared between the six workflows using Friedman's test and post-hoc pairwise comparisons with Bonferroni correction was performed. The two most reproducible techniques were tested for validation in a larger cohort of arthroplasty patients (n = 60) and results were compared with appropriate t-test. Subset analysis indicated that the manual and automated ROI with processing increased the ability to resolve real differences between these groups in parameters BV/TV, Tb.Sp and Euler number compared to with no processing and whole biopsy ROI approach. A validation cohort consisted of thirty osteoarthritis patients with a mean age 68.25 ± 8.64 and thirty neck of femur fracture with a mean age 82.4 ± 8.9. The manual technique failed to detect differences in BV/TV, SMI and Tb.Pf between the two patient groups (p > 0.05, for all) while the automated workflow demonstrated significant differences in these parameters between the OA and the NOF patients (p < 0.05). This is probably due to irregularity in the reference VOI volume introduced by manual ROI delineation reducing morphometric precision, compared to the automated method. In conclusion, our automated workflow performed better than customary practice; it represents a user-independent, high throughput technique to measure bone microarchitecture accurately in surgical biopsies.

Background: Revision total hip arthroplasty (THA) has been reported to have worse outcomes when compared to primary procedures, which may, in part, be due to the increased exposure required for the procedure. We aimed to investigate the postoperative functional outcomes of 2 groups of primary and revision THA, when revision procedures were performed using a gluteal-sparing extended posterior approach. Methods: Two groups of 51 primary and 21 revision THAs were prospectively recruited from a single center between 2016 and 2019. Both groups were assessed preoperatively using quantitative gait analysis and patient-reported outcomes, and at 3 and 12 months postoperatively. Hip and knee kinematics were computed from motion capture data acquired at the gait analysis. Kinematic and patient-reported outcome measures data were analyzed using linear mixed models. Statistical parametric analysis complemented the main analysis of the kinematics. Results: Patients in the primary group had worse preoperative patient-reported outcome measures when compared to the revision group. There were no between-group differences in walking speed. Hip extension in late stance phase of gait was 9° and 5° lower for the revision group when compared to the primary group at 3 and 12 months, respectively. These differences were not statistically significant, but the magnitude of the effect size was noteworthy suggesting a functional deficit (Cohen’s d = 0.64 and 0.54, respectively). Conclusions: Revision THA using a gluteal-sparing extended posterior approach may be able to achieve similar patient-reported and gait outcomes with those of primary THA within the first 12 postoperative months.

BACKGROUND:Measuring early micromotion using radiostereometric analysis is the gold standard to evaluate new implant performance. The aim of this study was to assess the continued stability of a new cementless Paragon stem at 5 years. Secondary aims were to assess patient reported outcomes and compare the continued stability between 2 and 5 year to an existing gold standard, the Corail stem. METHODS:This is a brief follow-up report of a radiostereometric analysis study. Of the original 46 patients in the 2 year study, four patients were lost to follow-up, three had died, five relocated interstate and seven withdrew from the study. We prospectively reviewed 27 primary total hip arthroplasty patients who underwent radiographic examinations at 5 years for beaded radiostereometric analysis measurements of stem translational and rotation migration. FINDINGS:Median subsidence of the Paragon stem at 5 years was -0.428 mm (range - 0.107 to -1.092) and the median stem subsidence between 2 and 5 years was -0.010 mm (0.115 to -0.269). When compared to the historical Corail stem stability between two and six years, the Paragon stem demonstrated similar subsidence (p = 0.09); and significantly less medial translation (p = 0.0033), anterior translation (p < 0.0001), anterior tilt (p = 0.0004) and anteversion (p = 0.015) between 2 and 5 years. The mean Oxford Hip Score improved substantially within the first year and did not decrease between 2 (44.7, SD 5.9) and 5 years (44.0, SD 8). INTERPRETATION:The Paragon stem showed continued stability up to 5 years follow-up which is encouraging for the further clinical use of this new design.

Revision total hip arthroplasty (rTHA) involving acetabular defects is a complex procedure associated with lower rates of success than primary THA. Computational modeling has played a key role in surgical planning and prediction of postoperative outcomes following primary THA, but modeling applications in rTHA for acetabular defects remain poorly understood. This study aimed to systematically review the use of computational modeling in acetabular defect classification, implant selection and placement, implant design, and postoperative joint functional performance evaluation following rTHA involving acetabular defects. The databases of Web of Science, Scopus, Medline, Embase, Global Health and Central were searched. Fifty-three relevant articles met the inclusion criteria, and their quality were evaluated using a modified Downs and Black evaluation criteria framework. Manual image segmentation from computed tomography scans, which is time consuming, remains the primary method used to generate 3D models of hip bone; however, statistical shape models, once developed, can be used to estimate pre-defect anatomy rapidly. Finite element modeling, which has been used to estimate bone stresses and strains, and implant micromotion postoperatively, has played a key role in custom and off-the-shelf implant design, mitigation of stress shielding, and prediction of bone remodeling and implant stability. However, model validation is challenging and requires rigorous evaluation and comparison with respect to mid- to long-term clinical outcomes. Development of fast, accurate methods to model acetabular defects, including statistical shape models and artificial neural networks, may ultimately improve uptake of and expand applications in modeling and simulation of rTHA for the research setting and clinic.