Aims. The purpose of this study was to compare the clinical, radiological, and patient-reported outcome measures (PROMs) in the first 100 consecutive patients undergoing total hip arthroplasty (THA) via a direct superior approach (DSA) with a matched group of patients undergoing THA by the same surgeon, using a posterolateral approach (PLA). Methods. This was a retrospective single surgeon study comparing the first 100 consecutive DSA THA patients with a matched group of patients using a standard PLA. Case notes were examined for patient demographics, length of hospital stay, operating time, intra- and postoperative complications, pain score, satisfaction score, and Oxford Hip Score (OHS). Leg length discrepancy and component positioning were measured from postoperative plain radiographs. Results. The DSA patients had a shorter length of hospital stay (mean 2.09 days (SD 1.20) DSA vs 2.74 days (SD 1.17) PLA; p < 0.001) and shorter time to discharge from the inpatient physiotherapy teams (mean 1.44 days (SD 1.17) DSA vs 1.93 days (SD 0.96) PLA; p < 0.001). There were no differences in operating time (p = 0.505), pain levels up to postoperative day 1 (p = 0.106 to p =0.242), OHS (p = 0.594 to p = 0.815), satisfaction levels (p = 0.066 to p = 0.299), stem alignment (p = 0.240), acetabular component inclination (p < 0.001) and anteversion (p < 0.001), or leg length discrepancy (p = 0.134). Conclusion. While the DSA appears safe and was not associated with a significant difference in PROMs, radiological findings, or intraoperative or postoperative complications, a randomized controlled trial with functional outcomes in the postoperative phase is needed to evaluate this surgical approach formally. Cite this article: Bone Joint J 2021;103-B(3):500–506

Aims. Spinopelvic mobility plays an important role in functional acetabular component position following total hip arthroplasty (THA). The primary aim of this study was to determine if spinopelvic hypermobility persists or resolves following THA. Our second aim was to identify patient demographic or radiological factors associated with hypermobility and resolution of hypermobility after THA. Methods. This study investigated patients with preoperative posterior hypermobility, defined as a change in sacral slope (SS) from standing to sitting (ΔSS. stand-sit. ) ≥ 30°. Radiological spinopelvic parameters, including SS, pelvic incidence (PI), lumbar lordosis (LL), PI-LL mismatch, anterior pelvic plane tilt (APPt), and spinopelvic tilt (SPT), were measured on preoperative imaging, and at six weeks and a minimum of one year postoperatively. The severity of bilateral hip osteoarthritis (OA) was graded using Kellgren-Lawrence criteria. Results. A total of 136 patients were identified as having preoperative spinopelvic hypermobility. At one year after THA, 95% (129/136) of patients were no longer categorized as hypermobile on standing and sitting radiographs (ΔSS. stand-sit. < 30°). Mean ΔSS. stand-sit. decreased from 36.4° (SD 5.1°) at baseline to 21.4° (SD 6.6°) at one year (p < 0.001). Mean SS. seated. increased from baseline (11.4° (SD 8.8°)) to one year after THA by 11.5° (SD 7.4°) (p < 0.001), which correlates to an 8.5° (SD 5.5°) mean decrease in seated functional cup anteversion. Contralateral hip OA was the only radiological predictor of hypermobility persisting at one year after surgery. The overall reoperation rate was 1.5%. Conclusion. Spinopelvic hypermobility was found to resolve in the majority (95%) of patients one year after THA. The increase in SS. seated. was clinically significant, suggesting that current target recommendations for the hypermobile patient (decreased anteversion and inclination) should be revisited. Cite this article: Bone Joint J 2021;103-B(12):1766–1773

Aims. The aim of this study was to evaluate the accuracy of implant placement when using robotic assistance during total hip arthroplasty (THA). Patients and Methods. A total of 20 patients underwent a planned THA using preoperative CT scans and robotic-assisted software. There were nine men and 11 women (n = 20 hips) with a mean age of 60.8 years (. sd. 6.0). Pelvic and femoral bone models were constructed by segmenting both preoperative and postoperative CT scan images. The preoperative anatomical landmarks using the robotic-assisted system were matched to the postoperative 3D reconstructions of the pelvis. Acetabular and femoral component positions as measured intraoperatively and postoperatively were evaluated and compared. Results. The system reported accurate values for reconstruction of the hip when compared to those measured postoperatively using CT. The mean deviation from the executed overall hip length and offset were 1.6 mm (. sd. 2.9) and 0.5 mm (. sd. 3.0), respectively. Mean combined anteversion was similar and correlated between intraoperative measurements and postoperative CT measurements (32.5°, . sd. 5.9° versus 32.2°, . sd. 6.4°; respectively; R. 2. = 0.65; p < 0.001). There was a significant correlation between mean intraoperative (40.4°, . sd. 2.1°) acetabular component inclination and mean measured postoperative inclination (40.12°, . sd. 3.0°, R. 2. = 0.62; p < 0.001). There was a significant correlation between mean intraoperative version (23.2°, . sd. 2.3°), and postoperatively measured version (23.0°, . sd. 2.4°; R. 2. = 0.76; p < 0.001). Preoperative and postoperative femoral component anteversion were significantly correlated with one another (R. 2. = 0.64; p < 0.001). Three patients had CT scan measurements that differed substantially from the intraoperative robotic measurements when evaluating stem anteversion. Conclusion. This is the first study to evaluate the success of hip reconstruction overall using robotic-assisted THA. The overall hip reconstruction obtained in the operating theatre using robotic assistance accurately correlated with the postoperative component position assessed independently using CT based 3D modelling. Clinical correlation during surgery should continue to be practiced and compared with observed intraoperative robotic values. Cite this article: Bone Joint J 2018;100-B:1303–9

Aims. Posterior tilt of the pelvis with sitting provides biological acetabular opening. Our goal was to study the post-operative interaction of skeletal mobility and sagittal acetabular component position. Materials and Methods. This was a radiographic study of 160 hips (151 patients) who prospectively had lateral spinopelvic hip radiographs for skeletal and implant measurements. Intra-operative acetabular component position was determined according to the pre-operative spinal mobility. Sagittal implant measurements of ante-inclination and sacral acetabular angle were used as surrogate measurements for the risk of impingement, and intra-operative acetabular component angles were compared with these. Results. Post-operatively, ante-inclination and sacral acetabular angles were within normal range in 133 hips (83.1%). A total of seven hips (4.4%) had pathological imbalance and were biologically or surgically fused hips. In all, 23 of 24 hips had pre-operative dangerous spinal imbalance corrected. Conclusions. In all, 145 of 160 hips (90%) were considered safe from impingement. Patients with highest risk are those with biological or surgical spinal fusion; patients with dangerous spinal imbalance can be safe with correct acetabular component position. The clinical relevance of the study is that it correlates acetabular component position to spinal pelvic mobility which provides guidelines for total hip arthroplasty. Cite this article: Bone Joint J 2017;99-B(1 Supple A):37–45

There remains confusion in the literature with regard to the spinopelvic relationship, and its contribution to ideal acetabular component position. Critical assessment of the literature has been limited by use of conflicting terminology and definitions of new concepts that further confuse the topic. In 2017, the concept of a Hip-Spine Workgroup was created with the first meeting held at the American Academy of Orthopedic Surgeons Annual Meeting in 2018. The goal of this workgroup was to first help standardize terminology across the literature so that as a topic, multiple groups could produce literature that is immediately understandable and applicable. This consensus review from the Hip-Spine Workgroup aims to simplify the spinopelvic relationship, offer hip surgeons a concise summary of available literature, and select common terminology approved by both hip surgeons and spine surgeons for future research. Cite this article: Bone Joint J 2019;101-B:808–816

Aims. Patients with abnormal spinopelvic mobility are at increased risk for instability. Measuring the change in sacral slope (ΔSS) can help determine spinopelvic mobility preoperatively. Sacral slope (SS) should decrease at least 10° to demonstrate adequate posterior pelvic tilt. There is potential for different ΔSS measurements in the same patient based on sitting posture. The purpose of this study was to determine the effect of sitting posture on the ΔSS in patients undergoing total hip arthroplasty (THA). Methods. In total, 51 patients undergoing THA were reviewed to quantify the variability in preoperative spinopelvic mobility when measuring two different sitting positions using SS for planning. Results. A total of 32 patients had standardized relaxed sitting radiographs, while 35 patients had standardized flexed sitting images. Of the 32 patients with relaxed sitting views, the mean ΔSS was 20.7° (SD 8.9°). No patients exhibited an increase in SS during relaxed sitting (i.e. anterior pelvic tilt or so-called reverse accommodation). Of the 35 patients with flexed sitting radiographs, the mean ΔSS was only 2.1° (SD 9.7°) with 16/35 (45.71%) showing anterior pelvic tilt, or so-called reverse accommodation, unexpectedly increasing the sitting SS compared to the standing SS. Overall, 18 patients had both relaxed sitting and flexed sitting radiographs. In patients with both types of sitting radiographs, the mean relaxed sit to stand ΔSS was 18.06° (SD 6.07°), while only a 3.00° (SD 10.53°) ΔSS was noted when flexed sitting. There was a mean ΔSS difference of 15.06° (SD 7.67°) noted in the same patient cohort depending on sitting posture (p < 0.001). Conclusion. A 15° mean difference was noted depending on the sitting posture of the patient. Since decisions on component position can be made on preoperative lateral sit-stand radiographs, postural standardization is crucial. If using ΔSS for preoperative planning, the relaxed sitting radiograph is preferred. Cite this article: Bone Joint J 2020;102-B(7 Supple B):41–46

Aims. The purpose of this multicentre observational study was to investigate the association between intraoperative component positioning and soft-tissue balancing on short-term clinical outcomes in patients undergoing robotic-arm assisted unicompartmental knee arthroplasty (UKA). Patients and Methods. Between 2013 and 2016, 363 patients (395 knees) underwent robotic-arm assisted UKAs at two centres. Pre- and postoperatively, patients were administered Knee Injury and Osteoarthritis Score (KOOS) and Forgotten Joint Score-12 (FJS-12). Results were stratified as “good” and “bad” if KOOS/FJS-12 were more than or equal to 80. Intraoperative, post-implantation robotic data relative to CT-based components placement were collected and classified. Postoperative complications were recorded. Results. Following exclusions and losses to follow-up, 334 medial robotic-arm assisted UKAs were assessed at a mean follow-up of 30.0 months (8.0 to 54.9). None of the measured parameters were associated with overall KOOS outcome. Correlations were described between specific KOOS subscales and intraoperative, post-implantation robotic data, and between FJS-12 and femoral component sagittal alignment. Three UKAs were revised, resulting in 99.0% survival at two years (95% confidence interval (CI) 97.9 to 100.0). Conclusion. Although little correlation was found between intraoperative robotic data and overall clinical outcome, surgeons should consider information regarding 3D component placement and soft-tissue balancing to improve patient satisfaction. Reproducible and precise placement of components has been confirmed as essential for satisfactory clinical outcome. Cite this article: Bone Joint J 2019;101-B:435–442

Objectives. The primary objective of this study was to compare accuracy in restoring the native centre of hip rotation in patients undergoing conventional manual total hip arthroplasty (THA) versus robotic-arm assisted THA. Secondary objectives were to determine differences between these treatment techniques for THA in achieving the planned combined offset, component inclination, component version, and leg-length correction. Materials and Methods. This prospective cohort study included 50 patients undergoing conventional manual THA and 25 patients receiving robotic-arm assisted THA. Patients undergoing conventional manual THA and robotic-arm assisted THA were well matched for age (mean age, 69.4 years (. sd. 5.2) vs 67.5 years (. sd. 5.8) (p = 0.25); body mass index (27.4 kg/m. 2. (. sd. 2.1) vs 26.9 kg/m. 2. (. sd. 2.2); p = 0.39); and laterality of surgery (right = 28, left = 22 vs right = 12, left = 13; p = 0.78). All operative procedures were undertaken by a single surgeon using the posterior approach. Two independent blinded observers recorded all radiological outcomes of interest using plain radiographs. Results. The correlation coefficient was 0.92 (95% confidence interval (CI) 0.88 to 0.95) for intraobserver agreement and 0.88 (95% CI 0.82 to 0.94) for interobserver agreement in all study outcomes. Robotic THA was associated with improved accuracy in restoring the native horizontal (p < 0.001) and vertical (p < 0.001) centres of rotation, and improved preservation of the patient’s native combined offset (p < 0.001) compared with conventional THA. Robotic THA improved accuracy in positioning of the acetabular component within the combined safe zones of inclination and anteversion described by Lewinnek et al (p = 0.02) and Callanan et al (p = 0.01) compared with conventional THA. There was no difference between the two treatment groups in achieving the planned leg-length correction (p = 0.10). Conclusion. Robotic-arm assisted THA was associated with improved accuracy in restoring the native centre of rotation, better preservation of the combined offset, and more precise acetabular component positioning within the safe zones of inclination and anteversion compared with conventional manual THA

Aims. The results of kinematic total knee arthroplasty (KTKA) have been reported in terms of limb and component alignment parameters but not in terms of gap laxities and differentials. In kinematic alignment (KA), balance should reflect the asymmetrical balance of the normal knee, not the classic rectangular flexion and extension gaps sought with gap-balanced mechanical axis total knee arthroplasty (MATKA). This paper aims to address the following questions: 1) what factors determine coronal joint congruence as measured on standing radiographs?; 2) is flexion gap asymmetry produced with KA?; 3) does lateral flexion gap laxity affect outcomes?; 4) is lateral flexion gap laxity associated with lateral extension gap laxity?; and 5) can consistent ligament balance be produced without releases?. Patients and Methods. A total of 192 KTKAs completed by a single surgeon using a computer-assisted technique were followed for a mean of 3.5 years (2 to 5). There were 116 male patients (60%) and 76 female patients (40%) with a mean age of 65 years (48 to 88). Outcome measures included intraoperative gap laxity measurements and component positions, as well as joint angles from postoperative three-foot standing radiographs. Patient-reported outcome measures (PROMs) were analyzed in terms of alignment and balance: EuroQol (EQ)-5D visual analogue scale (VAS), Knee Injury and Osteoarthritis Outcome Score (KOOS), KOOS Joint Replacement (JR), and Oxford Knee Score (OKS). Results. Postoperative limb alignment did not affect outcomes. The standing hip-knee-ankle (HKA) angle was the sole positive predictor of the joint line convergence angle (JLCA) (p < 0.001). Increasing lateral flexion gap laxity was consistently associated with better outcomes. Lateral flexion gap laxity did not correlate with HKA angle, the JLCA, or lateral extension gap laxity. Minor releases were required in one third of cases. Conclusion. The standing HKA angle is the primary determinant of the JLCA in KTKA. A rectangular flexion gap is produced in only 11% of cases. Lateral flexion gap laxity is consistently associated with better outcomes and does not affect balance in extension. Minor releases are sometimes required as well, particularly in limbs with larger preoperative deformities. Cite this article: Bone Joint J 2019;101-B:331–339

Aims. The aim of this study was to determine whether there is a difference in the rate of wear between acetabular components positioned within and outside the ‘safe zones’ of anteversion and inclination angle. Patients and Methods. We reviewed 100 hips in 94 patients who had undergone primary total hip arthroplasty (THA) at least ten years previously. Patients all had the same type of acetabular component with a bearing couple which consisted of a 28 mm cobalt-chromium head on a highly crosslinked polyethylene (HXLPE) liner. A supine radiostereometric analysis (RSA) examination was carried out which acquired anteroposterior (AP) and lateral paired images. Acetabular component anteversion and inclination angles were measured as well as total femoral head penetration, which was divided by the length of implantation to determine the rate of polyethylene wear. Results. The mean anteversion angle was 19.4° (-15.2° to 48°, . sd. 11.4°), the mean inclination angle 43.4° (27.3° to 60.5°, . sd. 6.6°), and the mean wear rate 0.055 mm/year (. sd. 0.060). Exactly half of the hips were positioned inside the ‘safe zone’. There was no difference (median difference, 0.012 mm/year; p = 0.091) in the rate of wear between acetabular components located within or outside the ‘safe zone’. When compared to acetabular components located inside the ‘safe zone’, the wear rate was no different for acetabular components that only achieved the target anteversion angle (median difference, 0.012 mm/year; p = 0.138), target inclination angle (median difference, 0.013 mm/year; p = 0.354), or neither target (median difference, 0.012 mm/year; p = 0.322). Conclusion. Placing the acetabular component within or outside the ‘safe zone’ did not alter the wear rate of HXLPE at long-term follow-up to a level that risked osteolysis. HXLPE appears to be a forgiving bearing material in terms of articular surface wear, but care must still be taken to position the acetabular component correctly so that the implant is stable. Cite this article: Bone Joint J 2018;100-B:891-7

Aims

The primary objective of this study was to develop a validated classification system for assessing iatrogenic bone trauma and soft-tissue injury during total hip arthroplasty (THA). The secondary objective was to compare macroscopic bone trauma and soft-tissues injury in conventional THA (CO THA) versus robotic arm-assisted THA (RO THA) using this classification system.

Aims

Although CT is considered the benchmark to measure femoral version, 3D biplanar radiography (hipEOS) has recently emerged as a possible alternative with reduced exposure to ionizing radiation and shorter examination time. The aim of our study was to evaluate femoral stem version in postoperative total hip arthroplasty (THA) patients and compare the accuracy of hipEOS to CT. We hypothesize that there will be no significant difference in calculated femoral stem version measurements between the two imaging methods.

Aims. Concurrent hip and spine pathologies can alter the biomechanics of spinopelvic mobility in primary total hip arthroplasty (THA). This study examines how differences in pelvic orientation of patients with spine fusions can increase the risk of dislocation risk after THA. Patients and Methods. We identified 84 patients (97 THAs) between 1998 and 2015 who had undergone spinal fusion prior to primary THA. Patients were stratified into three groups depending on the length of lumbar fusion and whether or not the sacrum was involved. Mean age was 71 years (40 to 87) and 54 patients (56%) were female. The mean body mass index (BMI) was 30 kg/m. 2. (19 to 45). Mean follow-up was six years (2 to 17). Patients were 1:2 matched to patients with primary THAs without spine fusion. Hazard ratios (HR) were calculated. Results. Dislocation in the fusion group was 5.2% at one year versus 1.7% in controls but this did not reach statistical significance (HR 1.9; p = 0.33). Compared with controls, there was no significant difference in rate of dislocation in patients without a sacral fusion. When the sacrum was involved, the rate of dislocation was significantly higher than in controls (HR 4.5; p = 0.03), with a trend to more dislocations in longer lumbosacral fusions. Patient demographics and surgical characteristics of THA (i.e. surgical approach and femoral head diameter) did not significantly impact risk of dislocation (p > 0.05). Significant radiological differences were measured in mean anterior pelvic tilt between the one-level lumbar fusion group (22°), the multiple-level fusion group (27°), and the sacral fusion group (32°; p < 0.01). Ten-year survival was 93% in the fusion group and 95% in controls (HR 1.2; p = 0.8). Conclusion. Lumbosacral spinal fusions prior to THA increase the risk of dislocation within the first six months. Fusions involving the sacrum with multiple levels of lumbar involvement notably increased the risk of postoperative dislocation compared with a control group and other lumbar fusions. Surgeons should take care with component positioning and may consider higher stability implants in this high-risk cohort

Aims

In metal-on-metal (MoM) hip arthroplasties and resurfacings, mechanically induced corrosion can lead to elevated serum metal ions, a local inflammatory response, and formation of pseudotumours, ultimately requiring revision. The size and diametral clearance of anatomical (ADM) and modular (MDM) dual-mobility polyethylene bearings match those of Birmingham hip MoM components. If the acetabular component is satisfactorily positioned, well integrated into the bone, and has no surface damage, this presents the opportunity for revision with exchange of the metal head for ADM/MDM polyethylene bearings without removal of the acetabular component.

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Femoral component anteversion is an important factor in the success of total hip arthroplasty (THA). This retrospective study aimed to investigate the accuracy of femoral component anteversion with the Mako THA system and software using the Exeter cemented femoral component, compared to the Accolade II cementless femoral component.

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The aims of the study were to report for a cohort aged younger than 40 years: 1) indications for HRA; 2) patient-reported outcomes in terms of the modified Harris Hip Score (HHS); 3) dislocation rate; and 4) revision rate.

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Precise implant positioning, tailored to individual spinopelvic biomechanics and phenotype, is paramount for stability in total hip arthroplasty (THA). Despite a few studies on instability prediction, there is a notable gap in research utilizing artificial intelligence (AI). The objective of our pilot study was to evaluate the feasibility of developing an AI algorithm tailored to individual spinopelvic mechanics and patient phenotype for predicting impingement.

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Custom triflange acetabular components (CTACs) play an important role in reconstructive orthopaedic surgery, particularly in revision total hip arthroplasty (rTHA) and pelvic tumour resection procedures. Accurate CTAC positioning is essential to successful surgical outcomes. While prior studies have explored CTAC positioning in rTHA, research focusing on tumour cases and implant flange positioning precision remains limited. Additionally, the impact of intraoperative navigation on positioning accuracy warrants further investigation. This study assesses CTAC positioning accuracy in tumour resection and rTHA cases, focusing on the differences between preoperative planning and postoperative implant positions.

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This study aimed to investigate the optimal sagittal positioning of the uncemented femoral component in total knee arthroplasty to minimize the risk of aseptic loosening and periprosthetic fracture.

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Spinopelvic pathology increases the risk for instability following total hip arthroplasty (THA), yet few studies have evaluated how pathology varies with age or sex. The aims of this study were: 1) to report differences in spinopelvic parameters with advancing age and between the sexes; and 2) to determine variation in the prevalence of THA instability risk factors with advancing age.