Aims. The benefit of a dual-mobility acetabular component (DMC) for primary total hip arthroplasties (THAs) is controversial. This study aimed to compare the dislocation and complication rates when using a DMC compared to single-mobility (SM) acetabular component in primary elective THA using data collected at a single centre, and compare the revision rates and survival outcomes in these two groups. Methods. Between 2010 and 2019, 2,075 primary THAs using either a cementless DM or SM acetabular component were included. Indications for DMC were patients aged older than 70 years or with high risk of dislocation. All other patients received a SM acetabular component. Exclusion criteria were cemented implants, patients treated for femoral neck fracture, and follow-up of less than one year. In total, 1,940 THAs were analyzed: 1,149 DMC (59.2%) and 791 SM (40.8%). The mean age was 73 years (SD 9.2) in the DMC group and 57 years (SD 12) in the SM group. Complications and revisions have been analyzed retrospectively. Results. The mean follow-up was 41.9 months (SD 14; 12 to 134). There were significantly fewer dislocations in the DMC group (n = 2; 0.17%) compared to the SM group (n = 8; 1%) (p = 0.019). The femoral head size did not influence the dislocation rate in the SM group (p = 0.702). The overall complication rate in the DMC group was 5.1% (n = 59) and in the SM group was 6.7% (n = 53); these were not statistically different (p = 0.214). No specific complications were attributed to the use of DMCs. In the DMC group, 18 THAs (1.6%) were revised versus 15 THAs in the SM group (1.9%) (p = 0.709). There was no statistical difference for any cause of revisions in both groups. The acetabular component aseptic revision-free survival rates at five years were 98% in the DMC group and 97.3% in the SM group (p = 0.780). Conclusion. The use of a monobloc DMC had a lower risk of dislocation in a high-risk population than SM component in a low-risk population at the mid-term follow-up. There was no significant risk of component-specific complications or revisions with DMCs in this large cohort. Cite this article: Bone Joint J 2024;106-B(3 Supple A):81–88

Background. The current orthopaedic literature demonstrates a clear relationship between acetabular component positioning, polyethylene wear and risk of dislocation following Total Hip Arthroplasty (THA). Problems with edge loading, stripe wear and squeaking are also associated with higher acetabular inclination angles, particularly in hard-on-hard bearing implants. The important parameters of acetabular component positioning are depth, height, version and inclination. Acetabular component depth, height and version can be controlled with intra-operative reference to the transverse acetabular ligament. Control of acetabular component inclination, particularly in the lateral decubitus position, is more difficult and remains a challenge for the Orthopaedic Surgeon. Lewinnek et al described a ‘safe zone’ of acetabular component orientation: Radiological acetabular inclination of 40 ± 10° and radiological anteversion of 15 ± 10°. Accurate implantation of the acetabular component within the ‘safe zone’ of radiological inclination is dependent on operative inclination, operative version and pelvic position. Traditionally during surgery, the acetabular component has been inserted with an operative inclination of 45°. This assumes that patient positioning is correct and does not take into account the impact of operative anteversion or patient malpositioning. However, precise patient positioning in order to orientate acetabular components using this method cannot always be relied upon. Hill et al demonstrated a mean 6.9° difference between photographically simulated radiological inclination and the post-operative radiological inclination. The most likely explanation was felt to be adduction of the uppermost hemipelvis in the lateral decubitus position. The study changed the practice of the senior author, with target operative inclination now 35° rather than 40° as before, aiming to achieve a post-operative radiological inclination of 42° ± 5°. Aim. To determine which of the following three techniques of acetabular component implantation most accurately obtains a desired operative inclination of 35 degrees:. Freehand. Modified (35°) Mechanical Alignment Guide, or. Digital inclinometer assisted. Methods. 270 patients undergoing primary uncemented THA were randomised to one of the three methods of acetabular component implantation. Target operative inclination for all three techniques was 35°. Operative inclination was measured intra-operatively using both a digital inclinometer and stereophotogrammetric system. For both the freehand and Mechanical Alignment Guide implantation techniques, the surgeon was blinded to intra-operative digital inclinometer readings. Results. The freehand implantation technique had an operative inclination range of 25.2 – 43.2° (Mean 32.9°, SD 2.90°). The modified (35°) Mechanical Alignment Guide implantation technique had an operative inclination range of 29.3 – 39.3° (Mean 33.7°, SD 1.89°). The digital inclinometer assisted technique had an operative inclination range of 27.5 – 37.5° (Mean 34.0°, SD 1.57°). Mean unsigned deviation from target 35° operative inclination was 2.92° (SD 2.03) for the freehand implantation technique, 1.83° (SD 1.41) for the modified (35°) Mechanical Alignment Guide implantation technique and 1.28° (SD 1.33) for the digital inclinometer assisted technique. Conclusions. When aiming for 35° of operative inclination, the digital inclinometer technique appears more accurate than either the freehand or Mechanical Alignment Guide techniques. In order to improve accuracy of acetabular component orientation during Total Hip Arthroplasty, the surgeon should consider using such a technique

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. Methods. Between 2012 and 2020, across two centres, 94 patients underwent revision of Birmingham MoM hip arthroplasties or resurfacings. Mean age was 65.5 years (33 to 87). In 53 patients (56.4%), the acetabular component was retained and dual-mobility bearings were used (DM); in 41 (43.6%) the acetabulum was revised (AR). Patients underwent follow-up of minimum two-years (mean 4.6 (2.1 to 8.5) years). Results. In the DM group, two (3.8%) patients underwent further surgery: one (1.9%) for dislocation and one (1.9%) for infection. In the AR group, four (9.8%) underwent further procedures: two (4.9%) for loosening of the acetabular component and two (4.9%) following dislocations. There were no other dislocations in either group. In the DM group, operating time (68.4 vs 101.5 mins, p < 0.001), postoperative drop in haemoglobin (16.6 vs 27.8 g/L, p < 0.001), and length of stay (1.8 vs 2.4 days, p < 0.001) were significantly lower. There was a significant reduction in serum metal ions postoperatively in both groups (p < 0.001), although there was no difference between groups for this reduction (p = 0.674 (cobalt); p = 0.186 (chromium)). Conclusion. In selected patients with Birmingham MoM hips, where the acetabular component is well-fixed and in a satisfactory position with no surface damage, the metal head can be exchanged for polyethylene ADM/MDM bearings with retention of the acetabular prosthesis. This presents significant benefits, with a shorter procedure and a lower risk of complications. Cite this article: Bone Jt Open 2024;5(6):514–523

Aims. Isolated acetabular liner exchange with a highly crosslinked polyethylene (HXLPE) component is an option to address polyethylene wear and osteolysis following total hip arthroplasty (THA) in the presence of a well-fixed acetabular shell. The liner can be fixed either with the original locking mechanism or by being cemented within the acetabular component. Whether the method used for fixation of the HXLPE liner has any bearing on the long-term outcomes is still unclear. Methods. Data were retrieved for all patients who underwent isolated acetabular component liner exchange surgery with a HXLPE component in our institute between August 2000 and January 2015. Patients were classified according to the fixation method used (original locking mechanism (n = 36) or cemented (n = 50)). Survival and revision rates were compared. A total of 86 revisions were performed and the mean duration of follow-up was 13 years. Results. A total of 20 patients (23.3%) had complications, with dislocation alone being the most common (8.1%; 7/86). Ten patients (11.6%) required re-revision surgery. Cementing the HXLPE liner (8.0%; 4/50) had a higher incidence of re-revision due to acetabular component liner-related complications than using the original locking mechanism (0%; 0/36; p = 0.082). Fixation using the original locking mechanism was associated with re-revision due to acetabular component loosening (8.3%; 3/36), compared to cementing (0%; 0/50; p = 0.038). Overall estimated mean survival was 19.2 years. There was no significant difference in the re-revision rate between the original locking mechanism (11.1%; 4/36) and cementing (12.0%; 6/50; p = 0.899). Using Kaplan-Meier survival analysis, the revision-free survival of HXLPE fixed with the original locking mechanism and cementing was 94.1% and 93.2%, respectively, at ten years, and 84.7% and 81.3%, respectively, at 20 years (p = 0.840). Conclusion. The re-revision rate and the revision-free survival following acetabular component liner exchange revision surgery using the HXLPE liner were not influenced by the fixation technique used. Both techniques were associated with good survival at a mean follow-up of 13 years. Careful patient selection is necessary for isolated acetabular component liner exchange revision surgery in order to achieve the best outcomes. Cite this article: Bone Joint J 2024;106-B(5 Supple B):59–65

We analysed the results of different strategies in the revision of primary uncemented acetabular components reported to the Norwegian Arthroplasty Register. The aim was to compare the risk of further acetabular revision after isolated liner exchange and complete component revision. The results of exchanging well-fixed components were also compared with those of exchanging loose acetabular components. The period studied was between September 1987 and April 2005. The following groups were compared: group 1, exchange of liner only in 318 hips; group 2, exchange of well-fixed components in 398; and group 3, exchange of loose components in 933. We found that the risk of a further cup revision was lower after revision of well-fixed components (relative risk from a Cox model (RR) = 0.56, 95% confidence interval 0.37% to 0.87%) and loose components (RR = 0.56, 95% confidence interval 0.39% to 0.80%), compared with exchange of the liner in isolation. The most frequent reason for a further acetabular revision was dislocation, accounting for 61 (28%) of the re-revisions. Other reasons for further revision included pain in 27 (12%), loosening in 24 (11%) and infection in 20 (9%). Re-revisions because of pain were less frequent when complete component (fixed or loose) revision was undertaken compared with isolated exchange of the liner (RR = 0.20 (95% confidence interval 0.06% to 0.65%) and RR = 0.10 (95% confidence interval 0.03% to 0.30%), respectively). The risk of further acetabular revision for infection, however, did not differ between the groups. In this study, exchange of the liner only had a higher risk of further cup revision than revision of the complete acetabular component. Our results suggest that the threshold for revising well-fixed components in the case of liner wear and osteolysis should be lowered

Aims. Dislocation remains a leading cause of failure following revision total hip arthroplasty (THA). While dual-mobility (DM) bearings have been shown to mitigate this risk, options are limited when retaining or implanting an uncemented shell without modular DM options. In these circumstances, a monoblock DM cup, designed for cementing, can be cemented into an uncemented acetabular shell. The goal of this study was to describe the implant survival, complications, and radiological outcomes of this construct. Methods. We identified 64 patients (65 hips) who had a single-design cemented DM cup cemented into an uncemented acetabular shell during revision THA between 2018 and 2020 at our institution. Cups were cemented into either uncemented cups designed for liner cementing (n = 48; 74%) or retained (n = 17; 26%) acetabular components. Median outer head diameter was 42 mm. Mean age was 69 years (SD 11), mean BMI was 32 kg/m. 2. (SD 8), and 52% (n = 34) were female. Survival was assessed using Kaplan-Meier methods. Mean follow-up was two years (SD 0.97). Results. There were nine cemented DM cup revisions: three for periprosthetic joint infection, three for acetabular aseptic loosening from bone, two for dislocation, and one for a broken cup-cage construct. The two-year survivals free of aseptic DM revision and dislocation were both 92%. There were five postoperative dislocations, all in patients with prior dislocation or abductor deficiency. On radiological review, the DM cup remained well-fixed at the cemented interface in all but one case. Conclusion. While dislocation was not eliminated in this series of complex revision THAs, this technique allowed for maximization of femoral head diameter and optimization of effective acetabular component position during cementing. Of note, there was only one failure at the cemented interface. Cite this article: Bone Joint J 2024;106-B(4):352–358

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

In metal-on-metal (MoM) hip replacements or resurfacings, mechanical induced corrosion can lead to a local inflammatory response, pseudo tumours and elevated serum metal ions, requiring revision surgery. The size and diametral clearance of Anatomic (ADM) and Modular (MDM) Dual Mobility bearings matches that of certain MOM components. Presenting the opportunity for revision with exchange of the metal head for ADM/MDM bearings without removal of the acetabular component if it is well-fixed and appropriately positioned. Between 2012 and 2020, across two centres, 94 patients underwent revision of a MoM hip replacement or resurfacing. The mean age was 65.5 (33–87) years. In 53 patients (56.4%), the acetabular component was retained, and dual mobility bearings were used (DM); in 41 (43.6%) the acetabulum was revised (AR). DM was only considered where the acetabular component was satisfactorily positioned and well-integrated into bone, with no surface damage. Patients underwent clinical and radiographic follow-up to at least one-year (mean 42.4 (12–96) months). One (1.1%) patient died before one-year, for reasons unrelated to the surgery. In the DM group, two (3.8%) patients underwent further surgery; one (1.9%) for dislocation and one (1.9%) for infection. In the AR group, four (12.2%) underwent further procedures; two (4.9%) for loosening of the acetabular component and two (4.9%) following dislocations. There were no other dislocations in either group. In the DM group, operative time (68.4 v 101.5 mins, p<0.001), postoperative drop in haemoglobin (16.6 v 27.8 g/L, p<0.001), and length of stay (1.8 v 2.4 days, p<0.001) were significantly lower. There was a significant reduction in serum metal ions postoperatively in both groups (p<0.001 both Cobalt and Chromium) although there was no difference between groups for this reduction (p=0.674 Cobalt; p=0.186 Chromium). In selected patients with MoM hip arthroplasty, where the acetabular component is well-fixed, in a satisfactory position and there is no surface damage, the metal head can be exchanged for ADM/MDM bearings with retention of the acetabular prosthesis. Presenting significant benefits through a less invasive procedure, and a low risk of complications, including dislocation

Aims. Various surgical techniques have been described for total hip arthroplasty (THA) in patients with Crowe type III dislocated hips, who have a large acetabular bone defect. The aim of this study was to evaluate the long-term clinical results of patients in whom anatomical reconstruction of the acetabulum was performed using a cemented acetabular component and autologous bone graft from the femoral neck. Methods. A total of 22 patients with Crowe type III dislocated hips underwent 28 THAs using bone graft from the femoral neck between 1979 and 2000. A Charnley cemented acetabular component was placed at the level of the true acetabulum after preparation with bone grafting. All patients were female with a mean age at the time of surgery of 54 years (35 to 68). A total of 18 patients (21 THAs) were followed for a mean of 27.2 years (20 to 33) after the operation. Results. Radiographs immediately after surgery showed a mean vertical distance from the centre of the hip to the teardrop line of 21.5 mm (SD 3.3; 14.5 to 30.7) and a mean cover of the acetabular component by bone graft of 46% (SD 6%; 32% to 60%). All bone grafts united without collapse, and only three acetabular components loosened. The rate of survival of the acetabular component with mechanical loosening or revision as the endpoint was 86.4% at 25 years after surgery. Conclusion. The technique of using autologous bone graft from the femoral neck and placing a cemented acetabular component in the true acetabulum can provide good long-term outcomes in patients with Crowe type III dislocated hips. Cite this article: Bone Joint J 2021;103-B(2):299–304

Aims. Uncemented metal acetabular components show good osseointegration, but material stiffness causes stress shielding and retroacetabular bone loss. Cemented monoblock polyethylene components load more physiologically; however, the cement bone interface can suffer fibrous encapsulation and loosening. It was hypothesized that an uncemented titanium-sintered monoblock polyethylene component may offer the optimum combination of osseointegration and anatomical loading. Methods. A total of 38 patients were prospectively enrolled and received an uncemented monoblock polyethylene acetabular (pressfit) component. This single cohort was then retrospectively compared with previously reported randomized cohorts of cemented monoblock (cemented) and trabecular metal (trabecular) acetabular implants. The primary outcome measure was periprosthetic bone density using dual-energy x-ray absorptiometry over two years. Secondary outcomes included radiological and clinical analysis. Results. Although there were differences in the number of males and females in each group, no significant sex bias was noted (p = 0.080). Furthermore, there was no significant difference in age (p = 0.910) or baseline lumbar bone mineral density (BMD) (p = 0.998) found between any of the groups (pressfit, cemented, or trabecular). The pressfit implant initially behaved like the trabecular component with an immediate fall in BMD in the inferior and medial regions, with preserved BMD laterally, suggesting lateral rim loading. However, the pressfit component subsequently showed a reversal in BMD medially with recovery back towards baseline, and a continued rise in lateral BMD. This would suggest that the pressfit component begins to reload the medial bone over time, more akin to the cemented component. Analysis of postoperative radiographs revealed no pressfit component subsidence or movement up to two years postoperatively (100% interobserver reliability). Medial defects seen immediately postoperatively in five cases had completely resolved by two years in four patients. Conclusion. Initially, the uncemented monoblock component behaved similarly to the rigid trabecular metal component with lateral rim loading; however, over two years this changed to more closely resemble the loading pattern of a cemented polyethylene component with increasing medial pelvic loading. This indicates that the uncemented monoblock acetabular component may result in optimized fixation and preservation of retroacetabular bone stock. Cite this article: Bone Joint J 2021;103-B(5):872–880

Aims. Appropriate acetabular component placement has been proposed for prevention of postoperative dislocation in total hip arthroplasty (THA). Manual placements often cause outliers in spite of attempts to insert the component within the intended safe zone; therefore, some surgeons routinely evaluate intraoperative pelvic radiographs to exclude excessive acetabular component malposition. However, their evaluation is often ambiguous in case of the tilted or rotated pelvic position. The purpose of this study was to develop the computational analysis to digitalize the acetabular component orientation regardless of the pelvic tilt or rotation. Methods. Intraoperative pelvic radiographs of 50 patients who underwent THA were collected retrospectively. The 3D pelvic bone model and the acetabular component were image-matched to the intraoperative pelvic radiograph. The radiological anteversion (RA) and radiological inclination (RI) of the acetabular component were calculated and those measurement errors from the postoperative CT data were compared relative to those of the 2D measurements. In addition, the intra- and interobserver differences of the image-matching analysis were evaluated. Results. Mean measurement errors of the image-matching analyses were significantly small (2.5° (SD 1.4°) and 0.1° (SD 0.9°) in the RA and RI, respectively) relative to those of the 2D measurements. Intra- and interobserver differences were similarly small from the clinical perspective. Conclusion. We have developed a computational analysis of acetabular component orientation using an image-matching technique with small measurement errors compared to visual evaluations regardless of the pelvic tilt or rotation. Cite this article: Bone Joint Res 2020;9(7):360–367

Aims. Mechanical impingement of the iliopsoas (IP) tendon accounts for 2% to 6% of persistent postoperative pain after total hip arthroplasty (THA). The most common initiator is anterior acetabular component protrusion, where the anterior margin is not covered by anterior acetabular wall. A CT scan can be used to identify and measure this overhang; however, no threshold exists for determining symptomatic anterior IP impingement due to overhang. A case-control study was conducted in which CT scan measurements were used to define a threshold that differentiates patients with IP impingement from asymptomatic patients after THA. Methods. We analyzed the CT scans of 622 patients (758 THAs) between May 2011 and May 2020. From this population, we identified 136 patients with symptoms suggestive of IP impingement. Among them, six were subsequently excluded: three because the diagnosis was refuted intraoperatively, and three because they had another obvious cause of impingement, leaving 130 hips (130 patients) in the study (impingement) group. They were matched to a control group of 138 asymptomatic hips (138 patients) after THA. The anterior acetabular component overhang was measured on an axial CT slice based on anatomical landmarks (orthogonal to the pelvic axis). Results. The impingement group had a median overhang of 8 mm (interquartile range (IQR) 5 to 11) versus 0 mm (IQR 0 to 4) for the control group (p < 0.001). Using receiver operating characteristic curves, an overhang threshold of 4 mm was best correlated with a diagnosis of impingement (sensitivity 79%, specificity 85%; positive predictive value 75%, negative predictive value 85%). Conclusion. Pain after THA related to IP impingement can be reasonably linked to acetabular overhang if it exceeds 4 mm on a CT scan. Below this threshold, it seems logical to look for another cause of IP irritation or another reason for the pain after THA before concluding that impingement is present. Cite this article: Bone Joint J 2024;106-B(3 Supple A):97–103

Aims. Modular dual mobility (MDM) acetabular components are often used with the aim of reducing the risk of dislocation in revision total hip arthroplasty (THA). There is, however, little information in the literature about its use in this context. The aim of this study, therefore, was to evaluate the outcomes in a cohort of patients in whom MDM components were used at revision THA, with a mean follow-up of more than five years. Methods. Using the database of a single academic centre, 126 revision THAs in 117 patients using a single design of an MDM acetabular component were retrospectively reviewed. A total of 94 revision THAs in 88 patients with a mean follow-up of 5.5 years were included in the study. Survivorship was analyzed with the endpoints of dislocation, reoperation for dislocation, acetabular revision for aseptic loosening, and acetabular revision for any reason. The secondary endpoints were surgical complications and the radiological outcome. Results. The overall rate of dislocation was 11%, with a six-year survival of 91%. Reoperation for dislocation was performed in seven patients (7%), with a six-year survival of 94%. The dislocations were early (at a mean of 33 days) in six patients, and late (at a mean of 4.3 years) in four patients. There were three intraprosthetic dissociations. An outer head diameter of ≥ 48 mm was associated with a lower risk of dislocation (p = 0.013). Lumbrosacral fusion was associated with increased dislocation (p = 0.004). Four revision THAs (4%) were further revised for aseptic acetabular loosening, and severe bone loss (Paprosky III) at the time of the initial revision was significantly associated with further revision for aseptic acetabular loosening (p = 0.008). Fourteen acetabular components (15%) were re-revised for infection, and a pre-revision diagnosis of reimplantation after periprosthetic joint infection (PJI) was associated with subsequent PJI (p < 0.001). Two THAs had visible metallic changes on the backside of the cobalt chromium liner. Conclusion. When using this MDM component in revision THA, at a mean follow-up of 5.5 years, there was a higher rate of dislocation (11%) than previously reported. The size of the outer bearing was related to the risk of dislocation. There was a low rate of aseptic acetabular loosening. Longer follow-up of this MDM component and evaluation of other designs are warranted. Cite this article: Bone Joint J 2021;103-B(7 Supple B):66–72

Aims. Periprosthetic fracture and implant loosening are two of the major reasons for revision surgery of cementless implants. Optimal implant fixation with minimal bone damage is challenging in this procedure. This pilot study investigates whether vibratory implant insertion is gentler compared to consecutive single blows for acetabular component implantation in a surrogate polyurethane (PU) model. Methods. Acetabular components (cups) were implanted into 1 mm nominal under-sized cavities in PU foams (15 and 30 per cubic foot (PCF)) using a vibratory implant insertion device and an automated impaction device for single blows. The impaction force, remaining polar gap, and lever-out moment were measured and compared between the impaction methods. Results. Impaction force was reduced by 89% and 53% for vibratory insertion in 15 and 30 PCF foams, respectively. Both methods positioned the component with polar gaps under 2 mm in 15 PCF foam. However, in 30 PCF foam, the vibratory insertion resulted in a clinically undesirable polar gap of over 2 mm. A higher lever-out moment was achieved with the consecutive single blow insertion by 42% in 15 PCF and 2.7 times higher in 30 PCF foam. Conclusion. Vibratory implant insertion may lower periprosthetic fracture risk by reducing impaction forces, particularly in low-quality bone. Achieving implant seating using vibratory insertion requires adjustment of the nominal press-fit, especially in denser bone. Further preclinical testing on real bone tissue is necessary to assess whether its viscoelasticity in combination with an adjusted press-fit can compensate for the reduced primary stability after vibratory insertion observed in this study. Cite this article: Bone Joint Res 2024;13(6):272–278

Abstract. Optimal acetabular component position in Total Hip Arthroplasty is vital for avoiding complications such as dislocation and impingement, Transverse acetabular ligament (TAL) have been shown to be a reliable landmark to guide optimum acetabular cup position. Reports of iliopsoas impingement caused by acetabular components exist. The Psoas fossa (PF) is not a well-regarded landmark for Component positioning. Our aim was to assess the relationship of the TAL and PF in relation to Acetabular Component positioning. A total of 22 cadavers were implanted on 4 occasions with the an uncemented acetabular component. Measurements were taken between the inner edge of TAL and the base of the acetabular component and the distance between the lower end of the PF and the most medial end of TAL. The distance between the edge of the acetabular component and TAL was a mean of 1.6cm (range 1.4–18cm). The distance between the medial end of TAL and the lowest part of PF was a mean of 1.cm (range 1,3–1.8cm) It was evident that the edge of PF was not aligned with TAL. Optimal acetabular component position is vital to the longevity and outcome following THA. TAL provides a landmark to guide acetabular component position. However we feel the PF is a better landmark to allow appropriate positioning of the acetabular component inside edge of the acetabulum inside the bone without exposure of the component rim and thus preventing iliopsoas impingement at the psoas notch and resultant groin pain

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

Introduction. Re-revision due to instability and dislocation can occur in up to 1 in 4 cases following revision total hip arthroplasty (THA). Optimal placement of components during revision surgery is thus critical in avoiding re-revision. Computer-assisted navigation has been shown to improve the accuracy and precision of component placement in primary THA; however, its role in revision surgery is less well documented. The purpose of our study was to evaluate the effect of computer-assisted navigation on component placement in revision total hip arthroplasty, as compared with conventional surgery. Methods. To examine the effect of navigation on acetabular component placement in revision THA, we retrospectively reviewed data from a multi-centre cohort of 128 patients having undergone revision THA between March 2017 and January 2019. An imageless computer navigation device (Intellijoint HIP®, Intellijoint Surgical, Kitchener, ON, Canada) was utilized in 69 surgeries and conventional methods were used in 59 surgeries. Acetabular component placement (anteversion, inclination) and the proportion of acetabular components placed in a functional safe zone (40° inclination/20° anteversion) were compared between navigation assisted and conventional THA groups. Results. Mean inclination decreased post-operatively versus baseline in both the navigation (44.9°±12.1° vs. 43.0°±6.8°, p=0.65) and control (45.8°±19.4° vs. 42.8°±7.1°, p=0.08) groups. Mean anteversion increased in both study groups, with a significant increase noted in the navigation group (18.6°±8.5° vs. 21.6°±7.8°, p=0.04) but not in the control group (19.4°±9.6° vs. 21.2°±9.8°, p=0.33). Post-operatively, a greater proportion of acetabular components were within ±10° of a functional target (40° inclination, 20° anteversion) in the navigation group (inclination: 59/67 (88%), anteversion: 56/67 (84%)) than in the control group (49/59 (83%) and 41/59, (69%), respectively). Acetabular component precision in both study groups improved post-operatively versus baseline. Variance in inclination improved significantly in both control (50.6° vs. 112.4°, p=0.002) and navigation (46.2° vs. 141.1°, p<0.001) groups. Anteversion variance worsened in the control group (96.3° vs. 87.6°, p=0.36) but the navigation group showed improvement (61.2° vs. 72.7°, p=0.25). Post-operative variance amongst cup orientations in the navigation group (IN: 46.2°; AV: 61.2°) indicated significantly better precision than that observed in the control group (IN: 50.6°, p=0.36; AV: 96.3°, p=0.04). Discussion. Re-revision is required in up to 25% of revision THA cases, of which 36% are caused by instability. This places a significant burden on the health care system and highlights the importance of accurate component placement. Our data indicate that the use of imageless navigation in revision THA – by minimizing the likelihood of outliers – may contribute to lower rates of re-revision by improving component orientation in revision THA. Conclusion. Utilizing imageless navigation in revision THAs results in more consistent placement of the acetabular component as compared to non-navigated revision surgeries

Aims. To investigate the extent of bone development around the scaffold of custom triflange acetabular components (CTACs) over time. Methods. We performed a single-centre historical prospective cohort study, including all patients with revision THA using the aMace CTAC between January 2017 and March 2021. A total of 18 patients (18 CTACs) were included. Models of the hemipelvis and the scaffold component of the CTACs were created by segmentation of CT scans. The CT scans were performed immediately postoperatively and at least one year after surgery. The amount of bone in contact with the scaffold was analyzed at both times, and the difference was calculated. Results. The mean time between the implantation and the second CT scan was two years (1 to 5). The mean age of the patients during CTAC implantation was 75 years (60 to 92). The mean scaffold-bone contact area increased from 16% (SD 12.6) to 28% (SD 11.9). The mean scaffold-bone distance decreased from a mean of 6.5 mm (SD 2.0) to 5.5 mm (SD 1.6). None of the CTACs were revised or radiologically loose. Conclusion. There was a statistically significant increase of scaffold-bone contact area over time, but the total contact area of the scaffold in relation to the acetabular bone remained relatively low. As all implants remained well fixed, the question remains to what extend the scaffold contributes to the observed stability, in relation to the screws. A future design implication might be an elimination of the bulky scaffold component. This design modification would reduce production costs and may optimize the primary fit of the implant. Cite this article: Bone Joint J 2024;106-B(4):359–364

Aims. The main aims were to identify risk factors predictive of a radiolucent line (RLL) around the acetabular component with an interface bioactive bone cement (IBBC) technique in the first year after THA, and evaluate whether these risk factors influence the development of RLLs at five and ten years after THA. Methods. A retrospective review was undertaken of 980 primary cemented THAs in 876 patients using cemented acetabular components with the IBBC technique. The outcome variable was any RLLs that could be observed around the acetabular component at the first year after THA. Univariate analyses with univariate logistic regression and multivariate analyses with exact logistic regression were performed to identify risk factors for any RLLs based on radiological classification of hip osteoarthritis. Results. RLLs were detected in 27.2% of patients one year postoperatively. In multivariate regression analysis controlling for confounders, atrophic osteoarthritis (odds ratio (OR) 2.17 (95% confidence interval (CI), 1.04 to 4.49); p = 0.038) and 26 mm (OR 3.23 (95% CI 1.85 to 5.66); p < 0.001) or 28 mm head diameter (OR 3.64 (95% CI 2.07 to 6.41); p < 0.001) had a significantly greater risk for any RLLs one year after surgery. Structural bone graft (OR 0.19 (95% CI 0.13 to 0.29) p < 0.001) and location of the hip centre within the true acetabular region (OR 0.15 (95% CI 0.09 to 0.24); p < 0.001) were significantly less prognostic. Improvement of the cement-bone interface including complete disappearance and poorly defined RLLs was identified in 15.1% of patients. Kaplan-Meier survival analysis for the acetabular component at ten years with revision of the acetabular component for aseptic loosening as the end point was 100.0% with a RLL and 99.1% without a RLL (95% CI 97.9 to 100). With revision of the acetabular component for any reason as the end point, the survival rate was 99.2% with a RLL (95% CI 97.6 to 100) and 96.5% without a RLL (95% CI 93.4 to 99.7). Conclusion. This study demonstrates that acetabular bone quality, head diameter, structural bone graft, and hip centre position may influence the presence of the any RLL. Cite this article: Bone Joint Open 2021;2(5):278–292

The Norwegian Arthroplasty Register has shown that several designs of uncemented femoral stems give good or excellent survivorship. The overall findings for uncemented total hip replacement however, have been disappointing because of poor results with the use of metal-backed acetabular components. In this study, we exclusively investigated the medium-to long-term performance of primary uncemented metal-backed acetabular components. A total of 9113 primary uncemented acetabular components were implanted in 7937 patients between 1987 and 2007. These were included in a prospective, population-based observational study. All the implants were modular and metal-backed with ultra-high-molecular-weight polyethylene liners. The femoral heads were made of stainless steel, cobalt-chrome (CoCr) alloy or alumina ceramic. In all, seven different designs of acetabular component were evaluated by the Kaplan-Meier survivorship method and Cox regression analysis. Most acetabular components performed well up to seven years. When the endpoint was revision of the acetabular component because of aseptic loosening, the survival ranged between 87% and 100% at ten years. However, when the endpoint was revision for any reason, the survival estimates were 81% to 92% for the same implants at ten years. Aseptic loosening, wear, osteolysis and dislocation were the main reasons for the relatively poor overall performance of the acetabular components. Prostheses with alumina heads performed slightly better than those with stainless steel or CoCr alloy in subgroups. Whereas most acetabular components performed well at seven years, the survivorship declined with longer follow-up. Fixation was generally good. None of the metal-backed uncemented acetabular components with ultra-high-molecular-weight polyethylene liners in our study had satisfactory long-term results because of high rates of wear, osteolysis, aseptic loosening and dislocation

We compared the orientation of the acetabular component obtained by a conventional manual technique with that using five different navigation systems. Three surgeons carried out five implantations of an acetabular component with each navigation system, as well as manually, using an anatomical model. The orientation of the acetabular component, including inclination and anteversion, and its position was determined using a co-ordinate measuring machine. The variation of the orientation of the acetabular component was higher in the conventional group compared with the navigated group. One experienced surgeon took significantly less time for the procedure. However, his placement of the component was no better than that of the less experienced surgeons. Significantly better inclination and anteversion (p < 0.001 for both) were obtained using navigation. These parameters were not significantly different between the surgeons when using the conventional technique (p = 0.966). The use of computer navigation helps a surgeon to orientate the acetabular component with less variation regarding inclination and anteversion

Aims. 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. Methods. A multicentre observational cohort study in Australia between February 2017 and March 2021 included consecutive patients undergoing acetabular reconstruction with CTACs in rTHA (Paprosky 3A/3B defects) or tumour resection (including Enneking P2 peri-acetabular area). Of 103 eligible patients (104 hips), 34 patients (35 hips) were analyzed. Results. CTAC positioning was generally accurate, with minor deviations in cup inclination (mean 2.7°; SD 2.84°), anteversion (mean 3.6°; SD 5.04°), and rotation (mean 2.1°; SD 2.47°). Deviation of the hip centre of rotation (COR) showed a mean vector length of 5.9 mm (SD 7.24). Flange positions showed small deviations, with the ischial flange exhibiting the largest deviation (mean vector length of 7.0 mm; SD 8.65). Overall, 83% of the implants were accurately positioned, with 17% exceeding malpositioning thresholds. CTACs used in tumour resections exhibited higher positioning accuracy than rTHA cases, with significant differences in inclination (1.5° for tumour vs 3.4° for rTHA) and rotation (1.3° for tumour vs 2.4° for rTHA). The use of intraoperative navigation appeared to enhance positioning accuracy, but this did not reach statistical significance. Conclusion. This study demonstrates favourable CTAC positioning accuracy, with potential for improved accuracy through intraoperative navigation. Further research is needed to understand the implications of positioning accuracy on implant performance and long-term survival. Cite this article: Bone Jt Open 2024;5(4):260–268

Aims. Registry studies on modified acetabular polyethylene (PE) liner designs are limited. We investigated the influence of standard and modified PE acetabular liner designs on the revision rate for mechanical complications in primary cementless total hip arthroplasty (THA). Methods. We analyzed 151,096 primary cementless THAs from the German Arthroplasty Registry (EPRD) between November 2012 and November 2020. Cumulative incidence of revision for mechanical complications for standard and four modified PE liners (lipped, offset, angulated/offset, and angulated) was determined using competing risk analysis at one and seven years. Confounders were investigated with a Cox proportional-hazards model. Results. Median follow-up was 868 days (interquartile range 418 to 1,364). The offset liner design reduced the risk of revision (hazard ratio (HR) 0.68 (95% confidence interval (CI) 0.50 to 0.92)), while the angulated/offset liner increased the risk of revision for mechanical failure (HR 1.81 (95% CI 1.38 to 2.36)). The cumulative incidence of revision was lowest for the offset liner at one and seven years (1.0% (95% CI 0.7 to 1.3) and 1.8% (95% CI 1.0 to 3.0)). No difference was found between standard, lipped, and angulated liner designs. Higher age at index primary THA and an Elixhauser Comorbidity Index greater than 0 increased the revision risk in the first year after surgery. Implantation of a higher proportion of a single design of liner in a hospital reduced revision risk slightly but significantly (p = 0.001). Conclusion. The use of standard acetabular component liners remains a good choice in primary uncemented THA, as most modified liner designs were not associated with a reduced risk of revision for mechanical failure. Offset liner designs were found to be beneficial and angulated/offset liner designs were associated with higher risks of revision. Cite this article: Bone Joint J 2022;104-B(7):801–810

Introduction. Cup malpositioning remains a common cause of dislocation, wear, osteolysis, and revision. The concept of a “Safe Zone” for acetabular component orientation was introduced more than 35 years ago1. The current study assesses CT studies of replaced hips to assess the concept of a safe zone for acetabular orientation by comparing the orientation of acetabular components revised due to recurrent instability and to a series of stable hip replacements. Methods. Cup orientation in 50 hips revised for recurrent instability was measured using CT. These hips were compared to a group of 184 stable hips measured using the same methods. Femoral anteversion in the stable hips was also measured. Images to assess femoral anteversion in the unstable group were not available. An application specific software modules was developed to measure cup orientation using CT (HipSextant Research Application 1.0.13 Surgical Planning Associates Inc., Boston, Massachusetts). The cup orientation was determined by first identifying Anterior Pelvic Plane Coordinate system landmarks on a 3D surface model. A multiplanar reconstruction module then allowed for the creation of a plane parallel with the opening plane of the acetabulum. The orientation of the cup opening plane in the AP Plane coordinate space was calculated according to Murray's definitions of operative anteversion and operative inclination2. Both absolute cup position relative to the APP and tilt-adjusted cup position3 were calculated. Results. Supine tilt-adjusted Operative anteversion for the anteriorly unstable hips was significantly higher than in the stable hips (p< .0001). Supine tilt-adjusted Operative anteversion for the posteriorly unstable hips was significantly lower than in the stable hips (p<.01). Alt in the supine position, all unstable hips had operative anteversion of less than 22.9 or more than 38.6 degrees or operative inclination of less than 30.6 or more than 55.9 degrees or both. The center of the “safe zone” is 30.7 +/− 7.8 degrees of tilt-adjusted operative anteversion and 42.4 +/− 13.5 degrees of operative inclination (Figure 1). Conclusions. The current study demonstrates that most conventionally placed acetabular components are malpositioned but not all malpositioned acetabular components are associated with dislocation. Using acetabular revision for recurrent instability as the end point, a safe zone for acetabular component orientation does exist. The range is narrower for anteversion than for inclination. Improved methods of defining component positioning goals on a patient-specific basis and accurately placing the acetabular component may reduce the incidence of cup mal-position and its associated complications. For figures and tables, please contact authors directly

Abstract. Background. Optimal acetabular component position in Total Hip Arthroplasty is vital for avoiding complications such as dislocation, impingement, abductor muscle strength and range of motion. Transverse acetabular ligament (TAL) and posterior labrum have been shown to be a reliable landmark to guide optimum acetabular cup position. There have been reports of iliopsoas impingement caused by both cemented and uncemented acetabular components. Acetabular component mal-positioning and oversizing of acetabular component are associated with iliopsoas impingement. The Psoas fossa (PF) is not a well-regarded landmark to help with Acetabular Component positioning. Our aim was to assess the relationship of the TAL and PF in relation to Acetabular Component positioning. Methods. A total of 12 cadavers were implanted with the an uncemented acetabular component, their position was initially aligned to TAL. Following optimal seating of the acetabular component the distance of the rim of the shell from the PF was noted. The Acetabular component was then repositioned inside the PF to prevent exposure of the rim of the Acetabular component. This study was performed at Smith & Nephew wet lab in Watford. Results. Out of the twelve acetabular components that were implanted parallel to the TAL, all had the acetabular rim very close or outside to the psoas notch with a potential to cause iliopsoas impingement. Alteration of the acetabular component position was necessary in all cadavers to inside the PF to prevent iliopsoas impingement. It was evident that the edge of PF was not aligned with TAL. Conclusion. Optimal acetabular component position is vital to the longevity and outcome following THA. TAL provides a landmark to guide acetabular component position. We feel the PF is a better landmark to allow appropriate positioning of the acetabular component inside bone without exposure of the component rim and thus preventing iliopsoas impingement at the psoas notch. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Objectives. In order to address acetabular defects, porous metal revision acetabular components and augments have been developed, which require fixation to each other. The fixation technique that results in the smallest relative movement between the components, as well as its influence on the primary stability with the host bone, have not previously been determined. Methods. A total of 18 composite hemipelvises with a Paprosky IIB defect were implanted using a porous titanium 56 mm multihole acetabular component and 1 cm augment. Each acetabular component and augment was affixed to the bone using two screws, while the method of fixation between the acetabular component and augment varied for the three groups of six hemipelvises: group S, screw fixation only; group SC, screw plus cement fixation; group C, cement fixation only. The implanted hemipelvises were cyclically loaded to three different loading maxima (0.5 kN, 0.9 kN, and 1.8 kN). Results. Screw fixation alone resulted in up to three times more movement (p = 0.006), especially when load was increased to 100% (p < 0.001), than with the other two fixation methods (C and SC). No significant difference was noted when a screw was added to the cement fixation. Increased load resulted in increased relative movement between the interfaces in all fixation methods (p < 0.001). Conclusion. Cement fixation between a porous titanium acetabular component and augment is associated with less relative movement than screw fixation alone for all implant interfaces, particularly with increasing loads. Adding a screw to the cement fixation did not offer any significant advantage. These results also show that the stability of the tested acetabular component/augment interface affects the stability of the construct that is affixed to the bone. Cite this article: N. A. Beckmann, R. G. Bitsch, M. Gondan, M. Schonhoff, S. Jaeger. Comparison of the stability of three fixation techniques between porous metal acetabular components and augments. Bone Joint Res 2018;7:282–288. DOI: 10.1302/2046-3758.74.BJR-2017-0198.R1

Aims. Accurate placement of the acetabular component during total hip arthroplasty (THA) is an important factor in the success of the procedure. However, the reported accuracy varies greatly and is dependent upon whether free hand or navigated techniques are used. The aim of this study was to assess the accuracy of an instrument system that incorporates 3D printed, patient-specific guides designed to optimise the placement of the acetabular component. Patients and Methods. A total of 100 consecutive patients were prospectively enrolled and the accuracy of placement of the acetabular component was measured using post-operative CT scans. Results. The mean absolute deviation from the planned inclination and anteversion was 3.9° (0.0° to 13.6°) and 3.6° (0.0° to 12.9°), respectively. In 91% of cases the planned target of +/-10° was achieved for both inclination and anteversion. Conclusion. Accurate placement of the acetabular component can be achieved using patient-specific guides and is superior to free hand techniques and comparable to navigated and robotic techniques. Cite this article: Bone Joint J 2016;98-B:1342–6

Introduction. Cup malpositioning remains a common cause of dislocation, wear, osteolysis, and revision. The concept of a “Safe Zone” for acetabular component orientation was introduced more than 35 years ago1. The current study assesses CT studies of replaced hips to assess the concept of a safe zone for acetabular orientation by comparing the orientation of acetabular components revised due to recurrent instability and to a series of stable hip replacements. Methods. Cup orientation in 21 hips revised for recurrent instability was measured using CT. These hips were compared to a group of 115 stable hips measured using the same methods. Femoral anteversion in the stable hips was also measured. Images to assess femoral anteversion in the unstable group were not available. An application specific software modules was developed to measure cup orientation using CT (HipSextant Research Application 1.0.13 Surgical Planning Associates Inc., Boston, Massachusetts). The cup orientation was determined by first identifying Anterior Pelvic Plane Coordinate system landmarks on a 3D surface model. A multiplanar reconstruction module then allowed for the creation of a plane parallel with the opening plane of the acetabulum. The orientation of the cup opening plane in the AP Plane coordinate space was calculated according to Murray's definitions of operative anteversion and operative inclination2. Both absolute cup position relative to the APP and tilt-adjusted cup position3 were calculated. Results. Operative anteversion for the anteriorly unstable hips was significantly higher than in the stable hips (p < .001). Operative anteversion for the posteriorly unstable hips was significantly lower than in the stable hips (p=.01). Adjusting for pelvic tilt in the supine position, all unstable hips had operative anteversion of less than 22.9 or more than 38.6 degrees or operative inclination of less than 28.9 or more than 55.9 degrees or both. The center of the “safe zone” is 30.7 +/− 7.8 degrees of tilt-adjusted operative anteversion and 42.4 +/− 13.5 degrees of operative inclination. Conclusions. The current study demonstrates that most conventionally placed acetabular components are malpositioned but not all malpositioned acetabular components are associated with dislocation. Using acetabular revision for recurrent instability as the end point, a safe zone for acetabular component orientation does exist. The range is narrower for anteversion than for inclination. Improved methods of defining component positioning goals on a patient-specific basis and accurately placing the acetabular component may reduce the incidence of cup malposition and its associated complications

Orientation of the acetabular component influences wear, range of movement and the incidence of dislocation after total hip replacement (THR). During surgery, such orientation is often referenced to the anterior pelvic plane (APP), but APP inclination relative to the coronal plane (pelvic tilt) varies substantially between individuals. In contrast, the change in pelvic tilt from supine to standing (dPT) is small for nearly all individuals. Therefore, in THR performed with the patient supine and the patient’s coronal plane parallel to the operating table, we propose that freehand placement of the acetabular component placement is reliable and reflects standing (functional) cup position. We examined this hypothesis in 56 hips in 56 patients (19 men) with a mean age of 61 years (29 to 80) using three-dimensional CT pelvic reconstructions and standing lateral pelvic radiographs. We found a low variability of acetabular component placement, with 46 implants (82%) placed within a combined range of 30° to 50° inclination and 5° to 25° anteversion. Changing from the supine to the standing position (analysed in 47 patients) was associated with an anteversion change < 10° in 45 patients (96%). dPT was < 10° in 41 patients (87%). In conclusion, supine THR appears to provide reliable freehand acetabular component placement. In most patients a small reclination of the pelvis going from supine to standing causes a small increase in anteversion of the acetabular component. Cite this article: Bone Joint J 2013;95-B:1326–31

We report the outcome of the flangeless, cemented all-polyethylene Exeter acetabular component at a mean of 14.6 years (10 to 17) after operation. Of the 263 hips in 243 patients, 122 prostheses are still in situ; 112 patients (119 hips) have died, 18 hips have been revised, and three patients (four hips) were lost to follow-up. Radiographs at the final review were available for 110 of the 122 surviving hips. There were acetabular radiolucent lines in 54 hips (49%). Two acetabular components had migrated but neither patient required revision. The Kaplan-Meier survivorship at 15 years with 61 hips at risk with revision for any cause as the endpoint was 89.9% (95% confidence interval (CI) 84.6 to 95.2) and for aseptic loosening of the acetabular component or lysis 91.7% (95% CI 86.6 to 96.8). In 210 hips with a diagnosis of primary osteoarthritis, survivorship with revision for any cause as the endpoint was 93.2% (95% CI 88.1 to 98.3), and for aseptic loosening of the acetabular component 95.0% (95% CI 90.3 to 99.7). The cemented all-polyethylene Exeter acetabular component has an excellent long-term survivorship

Aims. We analyzed the acetabular morphology of Crowe type IV hips using CT data to identify a landmark for the ideal placement of the centre of the acetabular component, as assessed by morphometric geometrical analysis, and its reliability. Patients and Methods. A total of 52 Crowe IV hips (42 patients; seven male, 35 female; mean age 68.5 years (32 to 82)) and 50 normal hips (50 patients; eight male, 42 female; mean age 60.7 years (34 to 86)) undergoing total hip arthroplasty were retrospectively identified. In this CT-based simulation study, the acetabular component was positioned at the true acetabulum with a radiological inclination of 40° and anteversion of 20°. Acetabular shape and the position of the centre of the acetabular component were analyzed by morphometric geometrical analysis using the generalized Procrustes analysis. Results. The acetabular shapes of Crowe IV hips were distinctively triangular; the ideal position of the centre of the acetabular component was superior on the posterior bony wall. The first and second relative warps explained 34.2% and 18.4% of the variance, respectively, compared with that of 28.6% and 18.0% in normal hips. We defined the landmark as one-third the distance from top on the posterior bony wall in Crowe IV hips. The average distance from the centre of the acetabular component was 5.6 mm. Conclusion. Crowe IV hips are distinctively triangular; the point one-third from the top on the posterior bony wall was a useful landmark for placing the acetabular component

Orientation of the native acetabular plane as defined by the transverse acetabular ligament (TAL) and the posterior labrum was measured intra-operatively using computer-assisted navigation in 39 hips. In order to assess the influence of alignment on impingement, the range of movement was calculated for that defined by the TAL and the posterior labrum and compared with a standard acetabular component position (abduction 45°/anteversion 15°). With respect to the registration of the plane defined by the TAL and the posterior labrum, there was moderate interobserver agreement (r = 0.64, p < 0.001) and intra-observer reproducibility (r = 0.73, p < 0.001). The mean acetabular component orientation achieved was abduction of 41° (32° to 51°) and anteversion of 18° (−1° to 36°). With respect to the Lewinnek safe zone (abduction 40° ±10°, anteversion 15° ±10°), 35 of the 39 acetabular components were within this zone. However, there was no improvement in the range of movement (p = 0.94) and no significant difference in impingement (p = 0.085). Alignment of the acetabular component with the TAL and the posterior labrum might reduce the variability of acetabular component placement in total hip replacement. However, there is only a moderate interobserver agreement and intra-observer reliability in the alignment of the acetabular component using the TAL and the posterior labrum. No reduction in impingement was found when the acetabular component was aligned with the TAL and the posterior labrum, compared with a standard acetabular component position

In a prospective randomised clinical study acetabular components were implanted either freehand (n = 30) or using CT-based (n = 30) or imageless navigation (n = 30). The position of the component was determined post-operatively on CT scans of the pelvis. Following conventional freehand placement of the acetabular component, only 14 of the 30 were within the safe zone as defined by Lewinnek et al (40° inclination . sd. 10°; 15° anteversion . sd. 10°). After computer-assisted navigation 25 of 30 acetabular components (CT-based) and 28 of 30 components (imageless) were positioned within this limit (overall p < 0.001). No significant differences were observed between CT-based and imageless navigation (p = 0.23); both showed a significant reduction in variation of the position of the acetabular component compared with conventional freehand arthroplasty (p < 0.001). The duration of the operation was increased by eight minutes with imageless and by 17 minutes with CT-based navigation. Imageless navigation proved as reliable as that using CT in positioning the acetabular component

INTRODUCTION. Cup malpositioning remains a common cause of dislocation, wear, osteolysis, and revision. The concept of a “Safe Zone” for acetabular component orientation was introduced more than 35 years ago. 1. The current study assesses CT studies of replaced hips to assess the concept of a safe zone for acetabular orientation by comparing the orientation of acetabular components revised due to recurrent instability and to a series of stable hip replacements. METHODS. Cup orientation in 30 hips revisedin 27patients for recurrent instability was measured using CT. These hips were compared to a group of 115 stable hips measured using the same methods. Femoral anteversion in the stable hips was also measured. Images to assess femoral anteversion in the unstable group were not available. An application specific software modules was developed to measure cup orientation using CT (HipSextant Research Application 1.0.13 Surgical Planning Associates Inc., Boston, Massachusetts). The cup orientation was determined by first identifying Anterior Pelvic Plane Coordinate system landmarks on a 3D surface model. A multiplanar reconstruction module then allowed for the creation of a plane parallel with the opening plane of the acetabulum. The orientation of the cup opening plane in the AP Plane coordinate space was calculated according to Murray's definitions of operative anteversion and operative inclination. 2. Both absolute cup position relative to the APP and tilt-adjusted cup position. 3. were calculated. RESULTS. Operative anteversion for the anteriorly unstable hips was significantly higher than in the stable hips (p < 0.001). Operative anteversion for the posteriorly unstable hips was significantly lower than in the stable hips (p < 0.01). Adjusting for pelvic tilt in the supine position, all unstable hips had operative anteversion of less than 21.8 or more than 42.6 degrees or operative inclination of less than 30.6 or more than 55.9 degrees or both. The center of the “safe zone” is 32.2 ± 10.4 degrees of tilt-adjusted operative anteversion and 45.3 ± 8.7 degrees of operative inclination (Figure 1). CONCLUSIONS. The current study demonstrates that most conventionally placed acetabular components are malpositioned but not all malpositioned acetabular components are associated with dislocation. Using acetabular revision for recurrent instability as the end point, a safe zone for acetabular component orientation does exist. The range is narrower for anteversion than for inclination. Improved methods of accurately placing the acetabular component placement may reduce the incidence of cup malposition and its associated complications

A variety of radiological methods of measuring version of the acetabular component after total hip replacement (THR) have been described. The aim of this study was to evaluate the reliability and validity of six methods (those of Lewinnek; Widmer; Hassan et al; Ackland, Bourne and Uhthoff; Liaw et al; and Woo and Morrey) that are currently in use. In 36 consecutive patients who underwent THR, version of the acetabular component was measured by three independent examiners on plain radiographs using these six methods and compared with measurements using CT scans. The intra- and interobserver reliabilities of each measurement were estimated. All measurements on both radiographs and CT scans had excellent intra- and interobserver reliability and the results from each of the six methods correlated well with the CT measurements. However, measurements made using the methods of Widmer and of Ackland, Bourne and Uhthoff were significantly different from the CT measurements (both p < 0.001), whereas measurements made using the remaining four methods were similar to the CT measurements. With regard to reliability and convergent validity, we recommend the use of the methods described by Lewinnek, Hassan et al, Liaw et al and Woo and Morrey for measurement of version of the acetabular component

Background. Ultraporous metals have now been used in acetabular reconstruction for two decades with excellent survival. The purpose of this study is to evaluate a newer porous metal made from Ti6Al4V titanium alloy in complex primary and revision hip arthroplasty. Methods. A retrospective review as performed on all total hip arthroplasty (THA) procedures in which a G7 Osseo-Ti (Zimmer Biomet, Warsaw, IN) acetabular component was used between 2015 and 2017. Patients with 2-year minimum follow-up or failure were included, yielding a cohort of 123 patients (126 hips). There were 50 male patients (41%; 51 hips) and 73 females (59%; 75 hips). Mean age was 65 years (range, 43–88) and mean BMI was 30.7 kg/m. 2. (range, 18–56). Indications for ultraporous metal components were in hips with compromised bone stock or severe acetabular deformity. Procedures were 35 complex primary THA and 91 revision THA that included 12 conversions and 24 reimplantations as part of 2-staged exchange for treatment of infection. Results. With an average 3.3-year follow-up (range, 2–5 years), 1 hip in the primary series (2.9%) and 4 hips in the revision series (4.4%) were revised for aseptic loosening of the acetabular component. Three of these re-revisions required custom triflange devices. Five patients (4%) failed for periprosthetic infection, which included 1 primary THA done for rheumatoid arthritis and post-radiation necrosis, and 4 second-stage reimplantation revision THAs for prior infection. Two revision patients, one done for active instability and one multiply revised, subsequently dislocated and required liner revision to constrained constructs. Kaplan-Meier analysis to endpoint of acetabular revision for aseptic loosening was 96.6% (±3.4%) in the primary series and 95.3% (±2.3%) in the revision series. Conclusion. This three-dimensionally printed ultraporous titanium acetabular component demonstrated promising early results in complex primary and revision total hip arthroplasty

A well-fixed uncemented acetabular component is most commonly removed for chronic infection, malposition with recurrent dislocation, and osteolysis. However, other cups may have to be removed for a broken locking mechanism, a bad “track record”, and for metal-on-metal articulation problems. Modern uncemented acetabular components are hemispheres which have 3-dimensional ingrowth patterns. Coatings include titanium or cobalt-chromium alloy beads, mesh, and now the so-called “enhanced coatings”, such as tantalum trabecular metal, various highly porous titanium metals, and 3-D printed metal coatings. These usually pose a problem for safe removal without fracture of the pelvis or creation of notable bone deficiency. Preoperative planning is essential for safe and efficient removal of these well-fixed components. Strongly consider getting the operative report, component “stickers”, and contacting the implant manufacturer for information. There should a preoperative check list of the equipment and trial implants needed, including various screwdrivers, trial liners, and a chisel system. The first step in component removal is excellent 360-degree exposure of the acetabular rim, and this can be accomplished by several approaches. Then, the acetabular polyethylene liner is removed; a liner that is cemented into a porous shell can be “reamed out” using a specific device. Following this, any central or peripheral screws are removed; broken or stripped screw heads add an additional challenge. A trial acetabular liner is placed, and an acetabular curved chisel system is used. There are two manufacturers of this type of system. Both require the known outer acetabular diameter and the inner diameter of the trial liner. With the curved chisel system and patience, well-fixed components can be safely removed, and the size of the next acetabular component to be implanted is usually 4mm larger than the one removed. There are special inserts for removal of monobloc metal shells. Remember that removal of these well-fixed components is more difficult in patients compared to models, and is just the first step of a successful acetabular revision

A modular layered acetabular component (metal-polyethylene-ceramic) was developed in Japan for use in alumina ceramic-on-ceramic total hip replacement. Between May 1999 and July 2000, we performed 35 alumina ceramic-on-ceramic total hip replacements in 30 consecutive patients, using this layered component and evaluated the clinical and radiological results over a mean follow-up of 5.8 years (5 to 6.5). A total of six hips underwent revision, one for infection, two for dislocation with loosening of the acetabular component, two for alumina liner fractures and one for component dissociation with pelvic osteolysis. There were no fractures of the ceramic heads, and no loosening of the femoral or acetabular component in the unrevised hips was seen at final follow-up. Osteolysis was not observed in any of the unrevised hips. The survivorship analysis at six years after surgery was 83%. The layered acetabular component in our experience, has poor durability because of unexpected mechanical failures including alumina liner fracture and component dissociation

Aims. This study aims to: determine the difference in pelvic position that occurs between surgery and radiographic, supine, postoperative assessment; examine how the difference in pelvic position influences subsequent component orientation; and establish whether differences in pelvic position, and thereafter component orientation, exist between total hip arthroplasties (THAs) performed in the supine versus the lateral decubitus positions. Patients and Methods. The intra- and postoperative anteroposterior pelvic radiographs of 321 THAs were included; 167 were performed with the patient supine using the anterior approach and 154 were performed with the patient in the lateral decubitus using the posterior approach. The inclination and anteversion of the acetabular component was measured and the difference (Δ) between the intra- and postoperative radiographs was determined. The target zone was inclination/anteversion of 40°/20° (± 10°). Changes in the tilt, rotation, and obliquity of the pelvis on the intra- and postoperative radiographs were calculated from Δinclination/anteversion using the Levenberg–Marquardt algorithm. Results. The mean postoperative inclination/anteversion was 40° (± 8°)/23° (± 9°) with Δinclination and/or Δanteversion > ± 10° in 74 (21%). Intraoperatively, the pelvis was anteriorly tilted by a mean of 4° (± 10°), internally rotated by a mean of 1° (± 10°) and adducted by a mean of 1° (± 5°). Having Δinclination and/or Δanteversion > ± 10° was associated with a 3.5 odds ratio of having the acetabular component outside the target zone. A greater proportion of THAs that were undertaken with the patient in the lateral decubitus position had Δinclination and/or Δanteversion > ± 10° (35.3%, 54/153) compared with those in the supine position (4.8%, 8/167; p < 0.001). A greater number of acetabular components were within the target zone in THAs undertaken with the patient in the supine position (72%, 120/167), compared with those in the lateral decubitus position (44%, 67/153; p < 0.001). Intraoperatively, the pelvis was more anteriorly tilted (p < 0.001) and more internally rotated (p = 0.04) when the patient was in the lateral decubitus position. Conclusion. The pelvic position is more reliable when the patient is in the supine position, leading to more consistent orientation of the acetabular component. Significant differences in pelvic tilt and rotation are seen with the patient in the lateral decubitus position. Cite this article: Bone Joint J 2018;100-B:1280–8

Aims. Accurate positioning of the acetabular component is essential for achieving the best outcome in total hip arthroplasty (THA). However, the acetabular shape and anatomy in severe hip dysplasia (Crowe type IV hips) is different from that of arthritic hips. Positioning the acetabular component in the acetabulum of Crowe IV hips may be surgically challenging, and the usual surgical landmarks may be absent or difficult to identify. We analyzed the acetabular morphology of Crowe type IV hips using CT data to identify a landmark for the ideal placement of the centre of the acetabular component as assessed by morphometric geometrical analysis and its reliability. Patients and Methods. A total of 52 Crowe IV and 50 normal hips undergoing total hip arthroplasty were retrospectively identified. In this CT-based simulation study, the acetabular component was positioned at the true acetabulum with a radiographic inclination of 40° and anteversion of 20° (Figure 1). Acetabular shape and the position of the centre of the acetabular component were analyzed by morphometric geometrical analysis using the generalized Procrustes analysis (Figure 2). To describe major trends in shape variations within the sample, we performed a principal component analysis of partial warp variables (Figure 3). Results. The plot of the landmarks showed that the centre of the acetabular component of normal hips was positioned around the centre of the acetabulum and superior and slightly posterior on the acetabular fossa (Figure 3). The acetabular shapes of Crowe IV hips were distinctively triangular; the ideal position of the centre of the acetabular component was superior on the posterior bony wall (Figure 3). The first and second relative warps explained 34.2% and 18.4% of the variance, respectively, compared with that of 28.6% and 18.0% in normal hips. We defined the landmark as one-third the distance from top on the posterior bony wall in Crowe IV hips. The average distance from the centre of the acetabular component was 5.6 mm. There were 24 hips (50%) for which the distance from 1/3 pbw was within 5 mm, and 43 hips (89.6%) for which the distance was within 10 mm. Conclusions. Morphometric geometrical analysis showed that the acetabulum shape of Crowe type IV hips was distinctively triangular; the centre of the acetabular component was not positioned at the centre of the acetabulum, but rather superior on the posterior bony wall. The point one-third from the top on the posterior bony wall was a useful landmark for surgeons to set the acetabular component in the precise position in Crowe IV hips. This avoids the risk of using a smaller acetabular component and destruction of the anterior wall. For any figures or tables, please contact the authors directly

Aims. The stability of cementless acetabular components is an important factor for surgical planning in the treatment of patients with pelvic osteolysis after total hip arthroplasty (THA). However, the methods for determining the stability of the acetabular component from pre-operative radiographs remain controversial. Our aim was to develop a scoring system to help in the assessment of the stability of the acetabular component under these circumstances. Patients and Methods. The new scoring system is based on the mechanism of failure of these components and the location of the osteolytic lesion, according to the DeLee and Charnley classification. Each zone is evaluated and scored separately. The sum of the individual scores from the three zones is reported as a total score with a maximum of 10 points. The study involved 96 revision procedures which were undertaken for wear or osteolysis in 91 patients between July 2002 and December 2012. Pre-operative anteroposterior pelvic radiographs and Judet views were reviewed. The stability of the acetabular component was confirmed intra-operatively. Results. Intra-operatively, it was found that 64 components were well-fixed and 32 were loose. Mean total scores in the well-fixed and loose components were 2.9 (0 to 7) and 7.2 (1 to 10), respectively (p < 0.001). In hips with a low score (0 to 2), the component was only loose in one of 33 hips (3%). The incidence of loosening increased with increasing scores: in those with scores of 3 and 4, two of 19 components (10.5%) were loose; in hips with scores of 5 and 6, eight of 19 components (44.5%) were loose; in hips with scores of 7 or 8, 13 of 17 components (70.6%) were loose; and for hips with scores of 9 and 10, nine of nine components (100%) were loose. Receiver-operating-characteristic curve analysis demonstrated very good accuracy (area under the curve = 0.90, p < 0.001). The optimal cutoff point was a score of ≥ 5 with a sensitivity of 0.79, and a specificity of 0.87. Conclusion. There was a strong correlation between the scoring system and the probability of loosening of a cementless acetabular component. This scoring system provides a clinically useful tool for pre-operative planning, and the evaluation of the outcome of revision surgery for patients with loosening of a cementless acetabular component in the presence of osteolysis. Cite this article: Bone Joint J 2017;99-B:601–6

We treated 34 patients with recurrent dislocation of the hip with a constrained acetabular component. Roentgen stereophotogrammetric analysis was performed to assess migration of the prosthesis. The mean clinical follow-up was 3.0 years (2.2 to 4.8) and the radiological follow-up was 2.7 years (2.0 to 4.8). At the latest review six patients had died and none was lost to follow-up. There were four acetabular revisions, three for aseptic loosening and one for deep infection. Another acetabular component was radiologically loose with progressive radiolucent lines in all Gruen zones and was awaiting revision. The overall rate of aseptic loosening was 11.8% (4 of 34). Roentgen stereophotogrammetric analysis in the non-revised components confirmed migration of up to 1.06 mm of translation and 2.32° of rotation at 24 months. There was one case of dislocation and dissociation of the component in the same patient. Of the 34 patients, 33 (97.1%) had no further episodes of dislocation. The constrained acetabular component reported in our study was effective in all but one patient with instability of the hip, but the rate of aseptic loosening was higher than has been reported previously and requires further investigation

Introduction:. Wear, wear-associated osteolysis, and instability are the most common reasons for revision total hip arthroplasty. These failures have been shown to be associated with acetabular component malpositioning. However, optimal acetabular component orientation on a patient-specific basis is currently unknown. The current study uses CT to assess acetabular orientation in a group of unstable hips as compared to a control group of stable hips. Methods:. Our institutional database of CT studies performed in the region of the hip beginning in February of 1998 (41,975 CT studies) was compared against our institutional database of revision total hip arthroplasties beginning in August of 2003 (2262 Revision THA) to identify CT studies of any hip treated for recurrent instability by revision of the acetabular component. Twenty hips in 20 patients with suitable CT studies were identified for the study group. Our control group consisted of 99 hips in 93 patients who had CT studies either for computer-assisted surgery on the contralateral side or for assessment of osteolysis. Using the CT data, the AP plane (APP) was defined, supine pelvic tilt was measured, and cup orientation was calculated by fitting a best fit plane to 6 points on the rim of the acetabular component. Cup orientation was calculated in degrees of operative anteversion and operative inclination according to the definitions of Murray. Both absolute cup position relative to the APP and tilt-adjusted cup position. 1. were calculated. Results:. The study group of 20 hips treated for instability showed a mean operative anteversion of 30.3 degrees (SD 17.6, range 1.0 to 58.1), a mean operative inclination of 35.9 degrees (SD 8.4, range 25.1 to 55.9), and a mean tilt-adjusted operative anteversion of 29.7 (SD 14.2, range 1.8 to 53). The control group of 99 hips showed a mean operative anteversion of 30.5 degrees (SD 10.7, range −1.9 to 57.5), a mean operative inclination of 37.7 degrees (SD 8.0, range 18.4 to 68.1), and a mean tilt-adjusted operative anteversion of 26.7 (SD 10.8, range −0.2 to 47.3). Most interestingly. all of the hips treated for instability had an operative anteversion of either 22.9 degrees or less or 38.67 degrees or more of tilt-adjusted operative inclination of either 30.5 degrees or less or 55.9 degrees or more, or both. The center of the safe zone in this study is 30.7 of tilt-adjusted operative anteversion and 43.2 degrees of operative inclination (Figure 1). There was no discernable safe zone in the non tilt-adjusted group. Discussion and Conclusion:. Most conventionally placed acetabular components are malpositioned but not all malpositioned acetabular components are associated with dislocation. The hip dislocation safe zone appears to be narrower in operative anteversion than in operative inclination. Improved methods of improving the accuracy and reliability of acetabular component placement may reduce the incidence of cup malposition and its associated complications

Abstract. Objectives. Accurate orientation of the acetabular component during a total hip replacement is critical for optimising patient function, increasing the longevity of components, and reducing the risk of complications. This study aimed to determine the validity of a novel VR platform (AescularVR) in assessing acetabular component orientation in a simulated model used in surgical training. Methods. The AescularVR platform was developed using the HTC Vive® VR system hardware, including wireless trackers attached to the surgical instruments and pelvic sawbone. Following calibration, data on the relative position of both trackers are used to determine the acetabular cup orientation (version and inclination). The acetabular cup was manually implanted across a range of orientations representative of those expected intra-operatively. Simultaneous readings from the Vicon® optical motion capture system were used as the ‘gold standard’ for comparison. Correlation and agreement between these two methods was determined using Bland-Altman plots, Pearson's correlation co-efficient, and linear regression modelling. Results. A total of 55 separate orientation readings were obtained. The mean average difference in acetabular cup version and inclination between the Vicon and VR systems was 3.4° (95% CI: −3–9.9°), and −0.005° (95% CI: −4.5–4.5°) respectively. Strong positive correlations were demonstrated between the Vicon and VR systems in both acetabular cup version (Pearson's R = 0.92, 99% CI: 0.84–0.96, p<0.001), and inclination (Pearson's R = 0.94, 99% CI: 0.88–0.97, p<0.001). Using linear regression modelling, the adjusted R. 2. for acetabular version was 0.84, and 0.88 for acetabular inclination. Conclusion. The results of this study indicate that the AescularVR platform is highly accurate and reliable in determining acetabular component orientation in a simulated environment. The AescularVR platform is an adaptable tracking system, which may be modified for use in a range of simulated surgical training and educational purposes, particularly in orthopaedic surgery. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Aims. To compare the in vivo long-term fixation achieved by two acetabular components with different porous ingrowth surfaces using radiostereometric analysis (RSA). Methods. This was a minimum ten-year follow-up of a prospective randomized trial of 62 hips with two different porous ingrowth acetabular components. RSA exams had previously been acquired through two years of follow-up. Patients returned for RSA examination at a minimum of ten years. In addition, radiological appearance of these acetabular components was analyzed, and patient-reported outcome measures (PROMs) obtained. Results. In all, 15 hips were available at ten years. There was no statistically significant difference in PROMS between the two groups; PROMs were improved at ten years compared to preoperative scores. Conventional radiological assessment revealed well-fixed components. There was minimal movement for both porous surfaces in translation (X, Y, Z, 3D translation in mm (median and interquartile range (IQR)), StikTite (Smith and Nephew, Memphis, Tennessee, USA): 0.03 (1.08), 0.12 (0.7), 0.003 (2.3), 0.37 (0.30), and Roughcoat (Smith and Nephew): -0.6 (0.59),–0.1 (0.49), 0.1 (1.12), 0.48 (0.38)), and rotation (X, Y, Z rotation in degrees (median and IQR), (Stiktite: -0.4 (3), 0.28 (2), -0.2 (1), and Roughcoat: - 0.4 (1),–0.1 (1), 0.2 (2)). There was no statistically significant difference between the two cohorts (p-value for X, Y, Z, 3D translation - 0.54, 0.46, 0.87, 0.55 and for X, Y, Z rotation - 0.41, 0.23, 0.23 respectively) at ten years. There was significant correlation between two years and ten years 3D translation for all components (r = 0.81(p =< 0.001)). Conclusion. Both porous ingrowth surfaces demonstrated excellent fixation on plain radiographs and with RSA at ten years. Short-term RSA data are good predictors for long-term migration data

Aims. Dual-mobility acetabular components (DMCs) have improved total hip arthroplasty (THA) stability in femoral neck fractures (FNFs). In osteoarthritis, the direct anterior approach (DAA) has been promoted for improving early functional results compared with the posterolateral approach (PLA). The aim of this study was to compare these two approaches in FNF using DMC-THA. Methods. A prospective continuous cohort study was conducted on patients undergoing operation for FNF using DMC by DAA or PLA. Functional outcome was evaluated using the Harris Hip Score (HHS) and Parker score at three months and one year. Perioperative complications were recorded, and radiological component positioning evaluated. Results. There were 50 patients in the DAA group and 54 in the PLA group. The mean HHS was 85.5 (SD 8.8) for the DAA group and 81.8 (SD 11.9) for the PLA group (p = 0.064). In all, 35 patients in the DAA group and 40 in the PLA group returned to their pre-fracture Parker score (p = 0.641) in both groups. No statistically significant differences between groups were found at one year regarding these two scores (p = 0.062 and p = 0.723, respectively). The DAA was associated with more intraoperative complications (p = 0.013). There was one dislocation in each group, and four revisions for DAA and one for PLA, but this difference was not statistically significant. There were also no significant differences regarding blood loss, length of stay, or operating time. Conclusion. In DMC-THA for FNF, DAA did not achieve better functional results than PLA, either at three months or at one year. Moreover, DAA presented an increased risk of intra-operative complications. Cite this article: Bone Joint J 2024;106-B(5 Supple B):133–138

Aims. The aim of this study was to compare the incidence of aseptic loosening after the use of a cemented acetabular component and a Trabecular Metal (TM) acetabular component (Zimmer Inc., Warsaw, Indiana) at acetabular revision with bone impaction grafting. Patients and Methods. A total of 42 patients were included in the study. Patients were randomised to receive an all- polyethylene cemented acetabular component (n = 19) or a TM component (n = 23). Radiostereometric analysis and conventional radiographic examinations were performed regularly up to two years post-operatively or until further revision. Results. The proximal migration was significantly higher in the cemented group. At two years, the median proximal migration was 1.45 mm and 0.25 mm in the cemented and TM groups, respectively (p = 0.02). One cemented component was revised due to dislocation. There were no revisions in the TM group. Conclusion. Lower proximal migration in the TM group suggests that this design might be associated with a lower risk of aseptic loosening in the long term compared with an all polyethylene cemented component. Longer follow-up is required to confirm the clinical advantages of using this component at acetabular revision. Cite this article: Bone Joint J 2017;99-B:880–6

Introduction. The optimal acetabular component orientation in general or on a patient-specific basis is currently unknown. In order to answer this question, the current study uses CT to assess acetabular orientation in a group of unstable hips as compared to a control group of stable hips. Methods. Our institutional database of CT studies performed in the region of the hip beginning in February of 1998 (41,975 CT studies) was compared against our institutional database of revision total hip arthroplasties beginning in August of 2003 (2262 Revision THA) to identify CT studies of any hip treated for recurrent instability by revision of the acetabular component. Twenty hips in 20 patients with suitable CT studies were identified for the study group. Our control group consisted of 101 hips in patients who had CT studies either for computer-assisted surgery on the contralateral side or for assessment of osteolysis. Using the CT data, the AP plane (APP) was defined, supine pelvic tilt was measured, and cup orientation was calculated by fitting a best fit plane to 6 points on the rim of the acetabular component. Cup orientation was calculated in degrees of operative anteversion and operative inclination according to the definitions of Murray. Both absolute cup position relative to the APP and tilt-adjusted cup position were calculated. Results. The study group of 20 hips treated for instability showed a mean operative anteversion of 29.6 degrees (SD 14.3, range 1.8 to 58) and a mean operative inclination of 35.8 degrees (SD 8.3, range 25.1 to 55.9). The control group of 101 hips showed a mean operative anteversion of 26.7 degrees (SD 10.7, range 0.2 to 47.3) and a mean operative inclination of 37.7 degrees (SD 7.9, range 18.4 to 68.1). Most interestingly. all of the hips treated for instability had a tilt-adjusted operative anteversion of either 22.9 degrees or less or 38.6 degrees or more or operative inclination of either 28.9 degrees or less or 55.9 degrees or more, or both. The center of the safe zone in this study is 30.7 degrees of tilt-adjusted operative anteversion and 42.4 degrees of operative inclination. Discussion and Conclusion. Most conventionally placed acetabular components are malpositioned but not all malpositioned acetabular components are associated with dislocation. The hip dislocation safe zone appears to be narrower in operative anteversion than in operative inclination and so the safe zone is better represented graphically as an oval as opposed to a box. The safe zone identified in the current study relates only to instability. Optimal positioning for reducing wear may narrow the safe zone further, particularly as it relates to the upper limit of operative inclination. Improved methods of achieving better accuracy and reliability of acetabular component placement may reduce the incidence of cup malposition and its associated complications

Recently, new metallurgical techniques allowed the creation of 3D metal matrices for cementless acetabular components. Among several different products now available on the market, the Biofoam Dynasty cup (MicroPort Orthopedics® Inc., Arlington, TN, USA) uses an ultraporous Titanium technology but has never been assessed in literature. Coping with this lack of information, our study aims to assess its radiological osteointegration at two years in a primary total hip arthroplasty and compares it to a successful contemporary cementless acetabular cup. This monocentric retrospective study includes 96 Dynasty Biofoam acetabular components implanted between March 2010 and August 2014 with a minimum 2 years radiographic follow-up. Previous acetabular surgery, any septic issue or re-operation for component malposition were exclusion criteria. They were compared to 96 THA using the Trident PSL matched for age, gender, BMI and follow-up. Presence of radiolucencies and sclerotic lines were described on AP pelvis views using the classification of DeLee and Charnley. There was no statistical difference between the two groups concerning demographics and mean follow-up (p> 0.05). Shell's anteversion was similar but inclination was greater in the biofoam group (p=0.006). 27,17% of the Biofoam shells presented radiolucencies in 2 zones or more and 0% of the Trident shells. 11,96% of Biofoam cups showed radiolucencies in the 3 zones of DeLee comparing to 0% of the Trident cups. There was no statistical difference between the Biofoam group (n=54/96) and the Trident PSL group (n=57/96) in pre-operative functional scores for both WOMAC subscales and SF-12. When evaluating last follow-up PROM's, no significant differences were found comparing the entirety of both groups, 56 Biofoam and 51 Trident PSL. No difference was found either when comparing Biofoam patients with ³ 2 zones of radiolucencies (n=15) to the whole Trident group (n=51). This study raises concerns about radiologic evidence of osteointegration of the Biofoam acetabular cup. Nevertheless, these radiological findings do not find any clinical correlation considering clinical scores. Thus, it may question the real meaning of these high-rated radiolucencies, which at first sight reflect a poorer osteointegration. The first possible limitation with this study is an overinterpretation of the radiographs. Nevertheless, both observers were blinded regarding the patients groups and clinical outcomes and there was a strong inter-observer reliability. Although both cohorts were matched on their demographics and were similar on the cup anteversion, we noticed a slightly lower abduction angle in the Biofoam population. It could reduce the bone-implant coverage area and hence hinders the bony integration, but this difference was small and both groups remained in the Lewinneck security zone. Furthermore, even if patients were matched on age, gender, BMI and follow-up, other variables can influence early osteointegration (smoke status, osteoporosis) and have not been controlled even though we have no reasons to think their distribution could differ in the 2 groups. The real clinical meaning of these findings remains unknown but serious concerns are raised about the radiographic osteointegration of the Dynasty Biofoam acetabular components. Concerns are all the more lawful that this implants aim to enhance osteointegration

Introduction. Proper acetabular component orientation is an important part of successful total hip replacement surgery. Poorly positioned implants can lead to early complications, such as dislocation. Mal-positioned acetabular components can also generate increase wear debris due to edge loading which can cause pre-mature loosening. It is essential to be able to measure post-operative implant orientation accurately to assure that implants are positioned properly. It is difficult and potentially inaccurate to manually measure implant orientation on a post-op radiograph. This is particularly true for the immediate post-op radiograph where the patient is not as well aligned relative to the x-ray beam. However, the best time to determine if an acetabular component is mal-aligned is immediately following surgery so the patient could be taken back to the OR for immediate revision. Taking post-op CT scans is expensive and subjects the patient to increased radiation exposure, so using CT post-operatively is not done routinely. With the increased use of robotics and computer navigation at surgery there are often pre-op CT scans for total hip replacement patients. Current radiological tools do not take advantage of this pre-op CT scan for assessment of acetabular component orientation. A new software module for Mimics medical imaging software (Materialise, Leuven, Belgium) is able to overlay 3D CT data onto radiographs. We used this x-ray module to see if we could measure acetabular component orientation using the pre-op CT scan and the routine post-op x-ray that is taken immediately following total hip arthroplasty at our institution. Methods. From a prior study, we had pre-op, and post-op CT scans of a group of twenty patients who received a total hip replacement. The post-op scan was used to measure the actual acetabular component orientation, both inclination and anteversion (Figure 1). We then measured component orientation using only the pre-op CT scan and the initial post-op x-ray using the Mimics x-ray module. We created a 3D model of the pelvis from the pre-op CT using Mimics. Then, the x-ray module was used to import the post-op radiograph into the Mimics file. Using the software, the x-ray was registered to the pre-op 3D pelvis. A 3D .stl file of the acetabular component used at surgery was then imported into the Mimics file and also registered according to the post-op radiograph (Figures 2 and 3). Once the cup and pelvis were both registered to the post-op radiograph, they were exported as .stl files and the acetabular anteversion and inclination were measured using the same method we used for the post-op scan. We then compared the results of our measurements from the post-op 3D reconstruction to the 2D overlay method to determine the accuracy of this new measurement technique. Results. The average error for anteversion and inclination was 1.5±1.5 and −0.8±1.6 degrees respectively. Maximum error for anteversion and inclination was 5.7 and −5.0 degrees respectively. Conclusion. The x-ray module could be a powerful tool in the assessment of post-operative orientation of the acetabular component in total hip arthroplasty