Instability is a common indication for revision total hip arthroplasty (THA). However, even after the initial revision, some patients continue to have recurrent dislocations. This study investigates those at risk for recurrent dislocation after revision THA for instability at a single institution. Between 2009 and 2019, 163 patients underwent revision THA for instability at a single institution. Thirty-three of these patients required re-revision THA due to recurrent dislocation. Cox proportional hazard models with death as a competing event were used to analyze risk factors, including prosthesis sizing and alignment. Paired t-tests or Wilcoxon signed rank tests were used to assess patient outcomes (Veterans RAND 12 (VR-12) physical score, VR-12 mental score, Harris Hip Score, and hip disability and osteoarthritis outcome score for joint replacement). Duration of follow-up until either re-revision or final follow-up was a mean of 45.3 ± 38.2 months. The 1-year cumulative incidence for recurrent dislocation after revision was 8.7%, which increased to 19.6% at 5 years and 32.9% at 10 years postoperatively. In the multivariable analysis, high ASA score [HR 2.71], being underweight (BMI<18 kg/m. 2. ) [HR 36.26] or overweight/obese (BMI>25 kg/m. 2. ) [HR 4.31], use of specialized liners [HR 5.51–10.71], lumbopelvic stiffness [HR 6.29], and postoperative abductor weakness [HR 7.20] were significant risk factors for recurrent dislocation. Increasing the cup size decreased the dislocation risk [HR 0.89]. The dual mobility construct did not affect the risk for recurrent dislocation in univariate or multivariable analyses. VR-12 physical and HHS (pain and function) scores improved postoperatively at midterm. Patients requiring revision THA for instability are at risk for recurrent dislocation. Higher ASA scores, abnormal BMI, use of special liners, lumbopelvic stiffness, and postoperative abductor weakness are significant risk factors for re-dislocation

Aims. To determine if primary cemented acetabular component geometry (long posterior wall (LPW), hooded, or offset reorientating) influences the risk of revision total hip arthroplasty (THA) for instability or loosening. Methods. The National Joint Registry (NJR) dataset was analyzed for primary THAs performed between 2003 and 2017. A cohort of 224,874 cemented acetabular components were included. The effect of acetabular component geometry on the risk of revision for instability or for loosening was investigated using log-binomial regression adjusting for age, sex, American Society of Anesthesiologists grade, indication, side, institution type, operating surgeon grade, surgical approach, polyethylene crosslinking, and prosthetic head size. A competing risk survival analysis was performed with the competing risks being revision for other indications or death. Results. The distribution of acetabular component geometries was: LPW 81.2%; hooded 18.7%; and offset reorientating 0.1%. There were 3,313 (1.5%) revision THAs performed, of which 815 (0.4%) were for instability and 838 (0.4%) were for loosening. Compared to the LPW group, the adjusted subhazard ratio of revision for instability in the hooded group was 2.31 (p < 0.001) and 4.12 (p = 0.047) in the offset reorientating group. Likewise, the subhazard ratio of revision for loosening was 2.65 (p < 0.001) in the hooded group and 13.61 (p < 0.001) in the offset reorientating group. A time-varying subhazard ratio of revision for instability (hooded vs LPW) was found, being greatest within the first three months. Conclusion. This registry-based study confirms a significantly higher risk of revision after cemented THA for instability and for loosening when a hooded or offset reorientating acetabular component is used, compared to a LPW component. Further research is required to clarify if certain patients benefit from the use of hooded or offset reorientating components, but we recommend caution when using such components in routine clinical practice. Cite this article: Bone Joint J 2021;103-B(11):1669–1677

Aims. Pelvic incidence (PI) is a position-independent spinopelvic parameter traditionally used by spinal surgeons to determine spinal alignment. Its relevance to the arthroplasty surgeon in assessing patient risk for total hip arthroplasty (THA) instability preoperatively is unclear. This study was undertaken to investigate the significance of PI relative to other spinopelvic parameter risk factors for instability to help guide its clinical application. Methods. Retrospective analysis was performed of a multicentre THA database of 9,414 patients with preoperative imaging (dynamic spinopelvic radiographs and pelvic CT scans). Several spinopelvic parameter measurements were made by engineers using advanced software including sacral slope (SS), standing anterior pelvic plane tilt (APPT), spinopelvic tilt (SPT), lumbar lordosis (LL), and PI. Lumbar flexion (LF) was determined by change in LL between standing and flexed-seated lateral radiographs. Abnormal pelvic mobility was defined as ∆SPT ≥ 20° between standing and flexed-forward positions. Sagittal spinal deformity (SSD) was defined as PI-LL mismatch > 10°. Results. PI showed a positive correlation with parameters of SS, SPT, and LL (r-value range 0.468 to 0.661). Patients with a higher PI value showed higher degrees of standing LL, likely as a compensatory measure to maintain sagittal spine balance. There was a positive correlation between LL and LF such that patients with less standing LL had decreased LF (r = 0.49). Similarly, there was a positive correlation between increased SSD and decreased LF (r = 0.54). PI in isolation did not show any significant correlation with lumbar (r = 0.04) or pelvic mobility (r = 0.02). The majority of patients (range 89.4% to 94.2%) had normal lumbar and pelvic mobility regardless of the PI value. Conclusion. The PI value alone is not indicative of either spinal or pelvic mobility, and thus in isolation may not be a risk factor for THA instability. Patients with SSD had higher rates of spinopelvic stiffness, which may be the mechanism by which PI relates to THA instability risk, but further clinical studies are required. Cite this article: Bone Joint J 2022;104-B(3):352–358

Aims. The aim of this study was to determine if uncemented acetabular polyethylene (PE) liner geometry, and lip size, influenced the risk of revision for instability or loosening. Methods. A total of 202,511 primary total hip arthroplasties (THAs) with uncemented acetabular components were identified from the National Joint Registry (NJR) dataset between 2003 and 2017. The effect of liner geometry on the risk of revision for instability or loosening was investigated using competing risk regression analyses adjusting for age, sex, American Society of Anesthesiologists grade, indication, side, institution type, surgeon grade, surgical approach, head size, and polyethylene crosslinking. Stratified analyses by surgical approach were performed, including pairwise comparisons of liner geometries. Results. The distribution of liner geometries were neutral (39.4%; 79,822), 10° (34.5%; 69,894), 15° (21.6%; 43,722), offset reorientating (2.8%; 5705), offset neutral (0.9%; 1,767), and 20° (0.8%; 1,601). There were 690 (0.34%) revisions for instability. Compared to neutral liners, the adjusted subhazard ratios of revision for instability were: 10°, 0.64 (p < 0.001); 15°, 0.48 (p < 0.001); and offset reorientating, 1.6 (p = 0.010). No association was found with other geometries. 10° and 15° liners had a time-dependent lower risk of revision for instability within the first 1.2 years. In posterior approaches, 10° and 15° liners had a lower risk of revision for instability, with no significant difference between them. The protective effect of lipped over neutral liners was not observed in laterally approached THAs. There were 604 (0.3%) revisions for loosening, but no association between liner geometry and revision for loosening was found. Conclusion. This registry-based study confirms a lower risk of revision for instability in posterior approach THAs with 10° or 15° lipped liners compared to neutral liners, but no significant difference between these lip sizes. A higher revision risk is seen with offset reorientating liners. The benefit of lipped geometries against revision for instability was not seen in laterally approached THAs. Liner geometry does not seem to influence the risk of revision for loosening. Cite this article: Bone Joint J 2021;103-B(12):1774–1782

Large ceramic femoral heads offer several advantages that are potentially advantageous to patients undergoing both primary and revision total hip replacement. Many high-quality studies have demonstrated the benefit of large femoral heads in reducing post-operative instability. Ceramic femoral heads may also offer an advantage in reducing polyethylene wear that has been reported in vitro and is starting to become clinically apparent in mid-term clinical outcome studies. Additionally, the risk of taper corrosion at a ceramic femoral head–neck junction is clearly lower than when using a metal femoral head. With improvements in the material properties of both modern ceramic femoral heads and polyethylene acetabular liners that have reduced the risk of mechanical complications, large ceramic heads have gained popularity in recent years. Cite this article: Bone Joint J 2013;95-B, Supple A:63–6

Aims. While previously underappreciated, factors related to the spine contribute substantially to the risk of dislocation following total hip arthroplasty (THA). These factors must be taken into consideration during preoperative planning for revision THA due to recurrent instability. We developed a protocol to assess the functional position of the spine, the significance of these findings, and how to address different pathologies at the time of revision THA. Patients and Methods. Prospectively collected data on 111 patients undergoing revision THA for recurrent instability from January 2014 to January 2017 at two institutions were included (protocol group) and matched 1:1 to 111 revisions specifically performed for instability not using this protocol (control group). Mean follow-up was 2.8 years. Protocol patients underwent standardized preoperative imaging including supine and standing anteroposterior (AP) pelvis and lateral radiographs. Each case was scored according to the Hip-Spine Classification in Revision THA. Results. Survival free of dislocation at two years was 97% in the protocol group (three dislocations, all within three months of surgery) versus 84% in the control group (18 patients). Furthermore, 77% of the inappropriately positioned acetabular components would have been unrecognized by supine AP pelvis imaging alone. Conclusion. Using the Hip-Spine Classification System in revision THA, we demonstrated a significant decrease in the risk of recurrent instability compared with a control group. Without the use of this algorithm, 77% of inappropriately positioned acetabular components would have been unrecognized and incorrect treatment may have been instituted. Cite this article: Bone Joint J 2019;101-B:817–823

Cemented acetabular components commonly have a long posterior wall (LPW). Alternative components have a hooded or offset reorientating geometry, theoretically to reduce the risk of THR instability. We aimed to determine if cemented acetabular component geometry influences the risk of revision surgery for instability or loosening. The National Joint Registry for England, Wales and Northern Ireland (NJR) dataset was analysed for primary THAs performed between 2003 – 2017. A cohort of 224,874 cemented acetabular components were identified. The effect of acetabular component geometry on the risk of revision for instability or for loosening was investigated using binomial regression adjusting for age, gender, ASA grade, diagnosis, side, institution type, operating surgeon grade, surgical approach, polyethylene crosslinking and head size. A competing risk survival analysis was performed with the competing risks being revision for other indications or death. Among the cohort of subjects included, the distribution of acetabular component geometries was: LPW – 81.2%, hooded – 18.7% and offset reorientating – 0.1%. There were 3,313 (1.47%) revision THAs performed, of which 815 (0.36%) were for instability and 838 (0.37%) were for loosening. Compared to the LPW group, the adjusted subhazard ratio of revision for instability in the hooded group was 2.29 (p<0.001) and 4.12 (p=0.047) in the offset reorientating group. Likewise, the subhazard ratio of revision for loosening was 2.43 (p<0.001) in the hooded group and 11.47 (p<0.001) in the offset reorientating group. A time-varying subhazard ratio of revision for instability (hooded vs LPW) was found, being greatest within the first 6 months. This Registry based study confirms a significantly higher risk of revision THA for instability and for loosening when a cemented hooded or offset reorientating acetabular component is used, compared to an LPW component. Further research is required to clarify if certain patients benefit from the use of hooded or offset reorientating components, but we recommend caution when using such components in routine clinical practice

The protective effect of lipped polyethylene uncemented acetabular liners against revision THA for instability has been reported. However, the effect of lip size has not been explored, nor has the effect on revision THA for loosening. We aimed to determine if uncemented acetabular liner geometry, and lip size, influences the risk of revision THA for instability or loosening. 202511 primary THAs with uncemented polyethylene acetabular components were identified from the NJR dataset (2003 – 2017). The effect of acetabular liner geometry and lip size on the risk of revision THA for instability or loosening was investigated using binomial regression and competing risks survival analyses (competing risks were revision for other causes or death) adjusting for age, gender, ASA grade, diagnosis, side, institution type, surgeon grade, surgical approach, head size and polyethylene crosslinking. The distribution of acetabular liners was: neutral – 39.4%, offset neutral – 0.9%, 10-degree – 34.5%, 15-degree – 21.6%, 20-degree – 0.8%, offset reorientating – 2.82%. There were 690 (0.34%) revision THAs for instability and 604 (0.3%) for loosening. Significant subhazard risk ratios were found in revision THA for instability with 10-degree (0.63), 15-degree (0.48) and offset reorientating (1.6) liners, compared to neutral liners. There was no association found between liner geometry and risk of revision THA for loosening. This Registry based study confirms a significantly lower risk of revision THA for instability when a lipped liner is used, compared to neutral liners, and a higher risk with the use of offset reorientating liners. Furthermore, 15degree liners seem to have a lower risk than 10degree liners. We did not find an association between acetabular liner geometry and revision THA for loosening. 10- and 15-degree lipped polyethylene liners seem to offer a lower revision risk over neutral liners, at least at medium term followup. Further studies are required to confirm if this benefit continues into the long-term

Topic. Utilizing radiographic, physical exam and history findings, we developed a novel clinical score to aid in the surgical decision making process for hips with borderline/ transitional dysplastic hips. Background. Treatment of borderline acetabular dysplasia (BD) is controversial with some patients having primarily instability-based symptoms while others have impingement-based symptoms. The purpose of this study was to identify the most important patient characteristics influencing the diagnosis of instability vs. non-instability, develop a clinical score (Borderline Hip Instability Score, BHIS) to collectively characterize these factors and to externally validate BHIS in a multicenter cohort BD patients. Methods. First a retrospective cohort of 186 hips undergoing surgical treatment of BD (LCEA 20°-25°) from a single surgeon experienced in arthroscopic and open techniques was used. Multivariate analysis determined characteristics associated with presence of instability (PAO+/−hip arthroscopy) or absence of instability (isolated hip arthroscopy) based on clinical diagnosis. During the study period, 39.8% of the cohort underwent PAO. Multivariate analysis with bootstrapping was performed and results were transformed into a BHIS nomogram (higher score representing more instability). Then, BHIS was externally validated in 114 BD patients enrolled in a multicenter prospective cohort study across 10 surgeons (with varied treatment approaches from arthroscopy to open procedures). Results. The most parsimonious, best fit model included 4 variables associated with the diagnosis of instability: acetabular inclination (AI), anterior center edge angle (ACEA), maximum alpha angle, and internal rotation in 90 degrees of flexion (IRF). Sex and LCEA were not significant predictors. Mean BHIS in the population was 50.0 (instability 57.7 ±7.9; non-instability 44.8±7.3, p<0.001). BHIS demonstrated excellent predictive (discriminatory) ability with c-statistic=0.89. In Part 2, BHIS maintained excellent c-statistic=0.92 in external validation. Mean BHIS in the external cohort was 53.9 (instability 66.5±11.5; non-instability 43.0±10.8, p<0.001). Discussion. In patients with BD, key factors in diagnosing significant instability treated with PAO were AI, ACEA, maximum alpha-angle, and IRF. The BHIS score allowed for differentiation of patients with and without instability in the development and external validation cohort. For any tables or figures, please contact the authors directly

Dislocation after total hip replacement (THR) is a devastating complication. Risk factors include patient and surgical factors. Mitigation of this complication has proven partially effective. This study investigated a new innovating technique to decrease this problem using rare earth magnets.

Computer simulations with design and magnetic finite element analysis software were used to analyze and quantitate the forces around hip implants with embedded magnets into the components during hip range of motion. N52 Neodymium-Iron-Boron rare earth magnets were sized to fit within the existing acetabular shells and the taper of a hip system. Additionally, magnets placed within the existing screw holes were studied. A 50mm titanium acetabular shell and a 36mm ceramic liner utilizing a taper sleeve adapter were modeled which allowed for the use of a 12mm × 5mm magnet placed in the center hole, an 18mm × 15mm magnet within the femoral head, and 10mm × 5mm magnets in the screw holes.

Biomechanical testing was also performed using in-vitro bone and implant models to determine retention forces through a range of hip motion.

The novel system incorporating magnets generated retentive forces between the acetabular cup and femoral head of between 10 to 20 N through a range of hip motion. Retentive forces were stronger at the extreme position hip range of motion when additional magnets were placed in the acetabular screw holes. Greater retentive forces can be obtained with specially designed femoral head bores and acetabular shells specifically designed to incorporate larger magnets. Mechanical testing validated the loads obtained and demonstrated the feasibility of the magnet system to provide joint stability and prevent dislocations.

Rare earth magnets provide exceptional attractive strength and can be used to impart stability and prevent dislocation in THR without the complications and limitations of conventional methods.

Aims. Several studies have reported the safety and efficacy of subcapital re-alignment for patients with slipped capital femoral epiphysis (SCFE) using surgical dislocation of the hip and an extended retinacular flap. Instability of the hip and dislocation as a consequence of this surgery has only recently gained attention. We discuss this problem with some illustrative cases. Materials and Methods. We explored the literature on the possible pathophysiological causes and surgical steps associated with the risk of post-operative instability and articular damage. In addition, we describe supplementary steps that could be used to avoid these problems. Results. The causes of instability may be divided into three main groups: the first includes causes directly related to SCFE (acetabular labral damage, severe abrasion of the acetabular cartilage, flattening of the acetabular roof and a bell-shaped deformity of the epiphysis); the second, causes not related to the SCFE (acetabular orientation and poor quality of the soft tissues); the third, causes directly related to the surgery (capsulotomy, division of the ligamentum teres, shortening of the femoral neck, pelvi-trochanteric impingement, previous proximal femoral osteotomy and post-operative positioning of the leg). Conclusion. We present examples drawn from our clinical practice, as well as possible ways of reducing the risks of these complications, and of correcting them if they happen. Cite this article: Bone Joint J 2017;99-B:16–21

Aims. A borderline dysplastic hip can behave as either stable or unstable and this makes surgical decision making challenging. While an unstable hip may be best treated by acetabular reorientation, stable hips can be treated arthroscopically. Several imaging parameters can help to identify the appropriate treatment, including the Femoro-Epiphyseal Acetabular Roof (FEAR) index, measured on plain radiographs. The aim of this study was to assess the reliability and the sensitivity of FEAR index on MRI compared with its radiological measurement. Patients and Methods. The technique of measuring the FEAR index on MRI was defined and its reliability validated. A retrospective study assessed three groups of 20 patients: an unstable group of ‘borderline dysplastic hips’ with lateral centre edge angle (LCEA) less than 25° treated successfully by periacetabular osteotomy; a stable group of ‘borderline dysplastic hips’ with LCEA less than 25° treated successfully by impingement surgery; and an asymptomatic control group with LCEA between 25° and 35°. The following measurements were performed on both standardized radiographs and on MRI: LCEA, acetabular index, femoral anteversion, and FEAR index. Results. The FEAR index showed excellent intraobserver and interobserver reliability on both MRI and radiographs. The FEAR index was more reliable on radiographs than on MRI. The FEAR index on MRI was lower in the stable borderline group (mean -4.2° (. sd. 9.1°)) compared with the unstable borderline group (mean 7.9° (. sd. 6.8°)). With a FEAR index cut-off value of 2°, 90% of patients were correctly identified as stable or unstable using the radiological FEAR index, compared with 82.5% using the FEAR index on MRI. The FEAR index was a better predictor of instability on plain radiographs than on MRI. Conclusion. The FEAR index measured on MRI is less reliable and less sensitive than the FEAR index measured on radiographs. The cut-off value of 2° for radiological FEAR index predicted hip stability with 90% probability. Cite this article: Bone Joint J 2019;101-B:1578–1584

We compared the dynamic instability of 25 dysplastic hips in 25 patients using triaxial accelerometry before and one year after periacetabular osteotomy. We also evaluated the hips clinically using the Harris hip score and assessed acetabular orientation by radiography before surgery and after one year. The mean overall magnitude of acceleration was significantly reduced from 2.30 m/s. 2. (. sd. 0.57) before operation to 1.55 m/s. 2. (. sd. 0.31) afterwards. The mean Harris hip score improved from 78.08 (47 to 96) to 95.36 points (88 to 100). The radiographic parameters all showed significant improvements. This study suggests that periacetabular osteotomy provides pain relief, improves acetabular cover and reduces the dynamic instability in patients with dysplastic hips

The definition of osseous instability in radiographic borderline dysplastic hips is difficult. A reliable radiographic tool that aids decision-making specifically, a tool that might be associated with instability-therefore would be very helpful for this group of patients. The aims of this study were:. (1) To compare a new radiographic measurement, which we call the Femoro-Epiphyseal Acetabular Roof (FEAR) index, with the lateral centre-edge angle (LCEA) and acetabular index (AI), with respect to intra- and interobserver reliability; (2) to correlate AI, neck-shaft angle, LCEA, iliocapsularis volume, femoral antetorsion, and FEAR index with the surgical treatment received instable and unstable borderline dysplastic hips; and (3) to assess whether the FEAR index is associated clinical instability in borderline dysplastic hips. We defined and validated the FEAR index in 10 standardized radiographs of asymptomatic controls using two blinded independent observers. Interrater and intrarater coefficients were calculated, supplemented by Bland-Altman plots. We compared its reliability with LCEA and AI. We performed a case-control study using standardized radiographs of 39 surgically treated symptomatic borderline radiographically dysplastic hips and 20 age-matched controls with asymptomatic hips (a 2:1 ratio), the latter were patients attending our institution for trauma unrelated to their hips but who had standardized pelvic radiographs between January 1, 2016 and March 1, 2016. Patient demographics were assessed using univariate Wilcoxon two-sample tests. There was no difference in mean age (overall: 31.5 ± 11.8 years [95% CI, 27.7–35.4 years]; stable borderline group: mean, 32.1± 13.3 years [95%CI, 25.5–38.7 years]; unstable borderline group: mean, 31.1 ± 10.7 years [95% CI, 26.2–35.9 years]; p = 0.96) among study groups. Treatment received was either a periacetabular osteotomy (if the hip was unstable) or, for patients with femoroacetabular impingement, either an open or arthroscopic femoroacetabular impingement procedure. The association of received treatment categories with the variables AI, neck-shaft angle, LCEA, iliocapsularis volume, femoral antetorsion, and FEAR index were evaluated first using Wilcoxon two-sample tests (two-sided) followed by stepwise multiple logistic regression analysis to identify the potential associated variables in a combined setting. Sensitivity, specificity, and receiver operator curves were calculated. The primary endpoint was the association between the FEAR index and instability, which we defined as migration of the femoral head either already visible on conventional radiographs or recentering of the head on AP abduction views, a break of Shenton's line, or the appearance of a crescent-shaped accumulation of gadolinium in the posteroinferior joint space at MR arthrography. The FEAR index showed excellent intra- and interobserver reliability, superior to the AI and LCEA. The FEAR index was lower in the stable borderline group (mean, −2.1 ± 8.4; 95% CI, −6.3 to 2.0) compared with the unstable borderline group (mean, 13.3 ± 15.2; 95% CI, 6.2–20.4) (p < 0.001) and had the highest association with treatment received. A FEAR index less than 5° had a 79% probability of correctly assigning hips as stable and unstable, respectively (sensitivity 78%; specificity 80%). A painful hip with a LCEA of 25° or less and FEAR index less than 5° is likely to be stable, and in such a situation, the diagnostic focus might more productively be directed toward femoroacetabular impingement

We compared the rate of revision for instability after total hip replacement (THR) when lipped and non-lipped acetabular liners were used. We hypothesised that the use of a lipped liner in a modular uncemented acetabular component reduces the risk of revision for instability after primary THR. Using data from the New Zealand Joint Registry, we found that the use of a lipped liner was associated with a significantly decreased rate of revision for instability and for all other indications. Adjusting for the size of the femoral head, the surgical approach and the age and gender of the patient, this difference remained strongly significant (p < 0.001). We conclude that evidence from the New Zealand registry suggests that the use of lipped liners with modular uncemented acetabular components is associated with a decreased rate of revision for instability after primary THR. Cite this article: Bone Joint J 2014;96-B:884–8

Aims. 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. Methods. A multicentre database with preoperative imaging for 15,830 THA patients was reviewed. Spinopelvic parameter measurements were made by experienced engineers, including anterior pelvic plane tilt (APPT), spinopelvic tilt (SPT), sacral slope (SS), lumbar lordosis (LL), and pelvic incidence (PI). Lumbar flexion (LF), sagittal spinal deformity, and hip user index (HUI) were calculated using parameter measurements. Results. With advancing age, patients demonstrate increased posterior APPT, decreased standing LL, decreased LF, higher pelvic incidence minus lumbar lordosis (PI-LL) mismatch, higher prevalence of abnormal spinopelvic mobility, and higher HUI percentage. With each decade, APPT progressed posteriorly 2.1°, LF declined 6.0°, PI-LL mismatch increased 2.9°, and spinopelvic mobility increased 3.8°. Significant differences were found between the sexes for APPT, SPT, SS, LL, and LF, but were not felt to be clinically relevant. Conclusion. With advancing age, spinopelvic biomechanics demonstrate decreased spinal mobility and increased pelvic/hip mobility. Surgeons should consider the higher prevalence of instability risk factors in elderly patients and anticipate changes evolving in spinopelvic biomechanics for young patients. Cite this article: Bone Joint J 2024;106-B(8):792–801

Previous reports on the outcomes of isolated head and liner exchange in revision total hip arthroplasty have found high rates of instability following these surgeries. Most reports have studied constructs using ≤28mm femoral heads. The purpose of this study was to determine if modern techniques with the use of larger head sizes can improve the rate of instability after head and liner exchange. We identified 138 hips in 132 patients who underwent isolated head and liner exchange for polyethylene wear/osteolysis (57%), acute infection (27%), metallosis (13%), or other (2%). All patients underwent revision with either 32mm (23%), 36mm (62%), or 40mm (15%) diameter heads. Crosslinked polyethylene was used in all revisions. Lipped and/or offset liners were used in 104 (75%) hips. Average follow up was 3.5 (1.0–9.1) years. Statistical analyses were performed with significance set at p<0.05. Revision-free survivorship for any cause was 94.6% and for aseptic causes was 98.2% at 5 years. 11 (8%) hips experienced a complication with 7 (5%) hips requiring additional revision surgery. Following revision, 4 (3%) hips experienced dislocation, 5 (4%) hips experienced infection, and 1 (1%) hip was revised for trunnionosis. No demographic or surgical factors significantly affected outcomes. Our study shows that isolated head and liner exchange using large femoral heads and modern liners provides for better stability than previous reports. The most common complication was infection. We did not identify specific patient, surgical or implant factors that reduced the risk of instability or other complication

Aims. The aim of our study was to investigate the effect of asymmetric crosslinked polyethylene liner use on the risk of revision of cementless and hybrid total hip arthroplasties (THAs). Methods. We undertook a registry study combining the National Joint Registry dataset with polyethylene manufacturing characteristics as supplied by the manufacturers. The primary endpoint was revision for any reason. We performed further analyses on other reasons including instability, aseptic loosening, wear, and liner dissociation. The primary analytic approach was Cox proportional hazard regression. Results. A total of 213,146 THAs were included in the analysis. Overall, 2,997 revisions were recorded, 1,569 in THAs with a flat liner and 1,428 in THAs using an asymmetric liner. Flat liner THAs had a higher risk of revision for any reason than asymmetric liner THAs when implanted through a Hardinge/anterolateral approach (hazard ratio (HR) 1.169, 95% confidence interval (CI) 1.022 to 1.337) and through a posterior approach (HR 1.122, 95% CI 1.108 to 1.346). There was no increased risk of revision for aseptic loosening when asymmetric liners were used for any surgical approach. A separate analysis of the three most frequently used crosslinked polyethylene liners was in agreement with this finding. When analyzing THAs with flat liners only, THAs implanted through a Hardinge/anterolateral approach were associated with a reduced risk of revision for instability compared to posterior approach THAs (HR 0.561 (95% CI 0.446 to 0.706)). When analyzing THAs with an asymmetric liner, there was no significant difference in the risk of revision for instability between the two approaches (HR 0.838 (95% CI 0.633 to 1.110)). Conclusion. For THAs implanted through the posterior approach, the use of asymmetric liners reduces the risk of revision for instability and revision for any reason. In THAs implanted through a Hardinge/anterolateral approach, the use of an asymmetric liner was associated with a reduced risk of revision. The effect on revision for instability was less pronounced than in the posterior approach. Cite this article: Bone Joint J 2021;103-B(9):1479–1487

Dual mobility (DM) is most often used by surgeons to reduce instability in high risk patients. NJR data on DM has not demonstrated a reduction in all cause revision and has reported an increase in revision for peri-prosthetic fracture (PPF). The aim of our study was:. Report outcome of DM used in high-risk patients including non-revision re-operations (dislocation & PPF). Comparison with conventional bearing THA (cTHA) with local, national and NJR benchmarking data. Retrospective cohort assessment of falls risk for patients receiving DM. Prospective F/U of a DM implant since 2016 and enrolled into Beyond Compliance (BC). Primary outcome measure all-cause revision with secondary outcome including any re-operation and Oxford Hip Score (OHS). All patients were risk stratified and considered high risk for instability. Complications were identified via hospital records, clinical coding linkage, NJR and BC. Benchmarking data for comparison was obtained from same data sources we also considered all B type PPF that occurred with cemented polished taper stem (PTS). 159 implants in 154 patients with a mean age 74.0 years and a maximum F/U of 6.7 years. Survivorship for all-cause revision 99.4% (95% CI 96.2–99.8). One femoral only revision. Mean gain in OHS 27.4. Dislocation rate 0.6% with a single event. Patients with a PTS rate of Type B PPF 2.1% requiring revision/fixation. Compared to cTHA this cohort was significantly older (74.0 vs 68.3 years), more co-morbidity (ASA 3 46.5% vs 14.4%) and more non-OA indications (32.4% vs 8.5%). Relative risks for dislocation 0.57 (95%CI 0.08–4.1) and PPF 1.75 (95%CI 0.54–5.72). Every patient had at least one risk factor for falling and >50% of cohort had 4 or more risk factors using NICE tool. The selective use of DM in high-risk patients can reduce the burden of instability. These individuals are very different to the “average” THA patient. A “perfect storm” is created using a high-risk implant combination (DM & PTS) in high-risk falls risk population. This re-enforces the need to consider all patient and implant factors when deciding bearing selection

There is a paucity of data available for the use of Total Femoral Arthroplasty (TFA) for joint reconstruction in the non-oncological setting. The aim of this study was to evaluate TFA outcomes with minimum 5-year follow-up. This was a retrospective database study of TFAs performed at a UK tertiary referral revision arthroplasty unit. Inclusion criteria were patients undergoing TFA for non-oncological indications. We report demographics, indications for TFA, implant survivorship, clinical outcomes, and indications for re-operation. A total of 39 TFAs were performed in 38 patients between 2015–2018 (median age 68 years, IQR 17, range 46–86), with 5.3 years’ (IQR 1.2, 4.1–18.8) follow-up; 3 patients had died. The most common indication (30/39, 77%) for TFA was periprosthetic joint infection (PJI) or fracture-related infection (FRI); and 23/39 (59%) had a prior periprosthetic fracture (PPF). TFA was performed with dual-mobility or constrained cups in 31/39 (79%) patients. Within the cohort, 12 TFAs (31%) required subsequent revision surgery: infection (7 TFAs, 18%) and instability (5 TFAs, 13%) were the most common indications. 90% of patients were ambulatory post-TFA; 2 patients required disarticulation due to recurrent PJI. While 31/39 (79%) were infection free at last follow-up, the remainder required long-term suppressive antibiotics. This is the largest series of TFA for non-oncological indications. Though TFA has inherent risks of instability and infection, most patients are ambulant after surgery. Patients should be counselled on the risk of life-long antibiotics, or disarticulation when TFA fails