Aims. Radiostereometric analysis (RSA) is the most accurate radiological method to measure in vivo wear of highly cross-linked polyethylene (XLPE) acetabular components. We have previously reported very low wear rates for a sequentially irradiated and annealed X3 XLPE liner (Stryker Orthopaedics, USA) when used in conjunction with a 32 mm femoral heads at ten-year follow-up. Only two studies have reported the long-term wear rate of X3 liners used in conjunction with larger heads using plain radiographs which have poor sensitivity. The aim of this study was to measure the ten-year wear of thin X3 XLPE liners against larger 36 or 40 mm articulations with RSA. Methods. We prospectively reviewed 19 patients who underwent primary cementless THA with the XLPE acetabular liner (X3) and a 36 or 40 mm femoral head with a resultant liner thickness of at least 5.8 mm. RSA radiographs at one week, six months, and one, two, five, and ten years postoperatively and femoral head penetration within the acetabular component were measured with UmRSA software. Of the initial 19 patients, 12 were available at the ten-year time point. Results. The median proximal, 2D, and 3D wear rates calculated between one and ten years were all less than 0.005 mm/year, with no patient recording a proximal wear rate of more than 0.021 mm/year. Importantly, there was no increase in the wear rate between five and ten years. Conclusion. The very low wear rate of X3 XLPE liners with larger articulations remains encouraging for the future clinical performance of this material. Cite this article: Bone Jt Open 2023;4(11):839–845

High doses of intra-articular (IA) antibiotics has been shown to effectively achieve a minimal biofilm eradication concentration which could mitigate the need for removal of infected but well-ingrown cementless components of a total hip arthroplasty (THA). However, there are concerns that percutaneous catheters could lead to multi-resistance or multi-organism peri-prosthetic joint infections (PJI) following single stage THA revisions for PJI. Eighteen single-stage revision procedures were performed for acute (N=9) or chronic (N=9) PJI following a primary (N=12) or revision (N=6) cementless THA. Modular and loosened components were replaced. All well ingrown components were retained. Two Hickmann catheters were placed in the joint space. Along with intravenous antibiotics, IA antibiotics were injected twice a day for two weeks, followed by 3 months of oral antibiotics. Per-operative cultures demonstrated 4 multi-bacterial PJIs. None of the patients developed post-operatively an AB related renal or systemic dysfunction. At a mean follow-up of 38 months [range, 8–72] all patients had normal erythrocyte sedimentation rate and white blood cell count. Four had a slightly elevated C-reactive protein but were completely symptom free and did not show any sign of loosening at a mean of 27 months [range, 16–59]. Addition of high doses of IA antibiotics following single-stage revision for PJI in cementless THA, is an effective and safe treatment option that allows for retention of well-ingrown components. We found no evidence for residual implant infection or catheter induced multi-resistance. Total hip arthroplasty, revision surgery, Periprosthetic Joint Infection, Intra-articular antibiotics. Level 4 (Case series)

Aims. We present the clinical and radiological results at a minimum follow-up of 20 years using a second-generation uncemented total hip arthroplasty (THA). These results are compared to our previously published results using a first-generation hip arthroplasty followed for 20 years. Methods. A total of 62 uncemented THAs in 60 patients were performed between 1993 and 1994. The titanium femoral component used in all cases was a Taperloc with a reduced distal stem. The acetabular component was a fully porous coated threaded hemispheric titanium shell (T-Tap ST). The outcome of every femoral and acetabular component with regard to retention or revision was determined for all 62 THAs. Complete clinical follow-up at a minimum of 20 years was obtained on every living patient. Radiological follow-up was obtained on all but one. Results. Two femoral components (3.2%) required revision. One stem was revised secondary to a periprosthetic fracture one year postoperatively and one was revised for late sepsis. No femoral component was revised for aseptic loosening. Six acetabular components had required revision, five for aseptic loosening. One additional acetabular component was revised for sepsis. Radiologically, all femoral components remained well fixed. One acetabular was judged loose by radiological criteria. The mean Harris Hip Score improved from 46 points (30 to 67) preoperatively to 89 points (78 to 100) at final follow-up. With revision for aseptic loosening as the endpoint, survival of the acetabular component was 95% (95% confidence interval (CI) 90 to 98) at 25 years. Femoral component survival was 100%. Conclusion. The most significant finding of this report was the low prevalence of aseptic loosening and revision of the femoral component at a mean follow-up of 22 years. A second important finding was the survival of over 90% of the hemispheric threaded ring acetabular components. While these shells remain controversial, in this series they performed well. Cite this article: Bone Jt Open 2021;2(1):33–39

Periprosthetic femoral fractures (PFFs) remain a major concern following cementless total hip arthroplasty (THA). This study aimed to evaluate the association between different types of cementless tapered stems and the risk of postoperative PFF. A retrospective review of primary THAs performed at a single center from January 2011 to December 2018 included 3,315 hips (2,326 patients). Cementless stems were classified according to their design geometry using the system proposed by Radaelli et al. The incidence of PFF was compared between flat taper porous-coated stems (type A), rectangular taper grit-blasted stems (type B1), and quadrangular taper hydroxyapatite-coated stems (type B2). Multivariate regression analyses were performed to identify independent factors related to PFF. The mean follow-up duration was 61 months (range, 12‒139 months). Overall, 45 (1.4%) postoperative PFFs occurred. The incidence of PFF was significantly higher in type B1 stems than in type A and type B2 stems (1.8 vs. 0.7 vs. 0.7%; P=0.022). Additionally, more surgical treatments (1.7 vs. 0.5 vs. 0.7%; P=0.013) and femoral revisions (1.2 vs. 0.2 vs. 0%; P=0.004) were required for PFF in type B1 stems. After controlling for confounding variables, older age (P<0.001), diagnosis of hip fracture (P<0.001), and use of type B1 stems (P=0.001) were significant factors associated with PFF. Type B1 rectangular taper stems were found to have higher risks for postoperative PFF and PFF requiring surgical management than type A and type B2 stems in THA. Femoral stem geometry should be considered when planning for cementless THA in elderly patients with compromised bone quality

Aims. The aim of this study was to evaluate the performance of first-generation annealed highly cross-linked polyethylene (HXLPE) in cementless total hip arthroplasty (THA). Methods. We retrospectively evaluated 29 patients (35 hips) who underwent THA between December 2000 and February 2002. The survival rate was estimated using the Kaplan-Meier method. Hip joint function was evaluated using the Japanese Orthopaedic Association (JOA) score. Two-dimensional polyethylene wear was estimated using Martell’s Hip Analysis Suite. We calculated the wear rates between years 1 and 5, 5 and 10, 10 and 15, and 15 and final follow-up. Results. The mean follow-up period was 19.1 years (SD 0.6; 17.3 to 20.1). The 19-year overall survival rate with the end point of all-cause revision was 97.0% (95% confidence interval (CI) 91 to 100). The mean JOA score improved from 43.2 (SD 10.6; 30 to 76) before surgery to 90.2 (SD 6.4; 76 to 98) at the final follow-up (p < 0.001). There was no osteolysis or loosening of the acetabular or femoral components. The overall steady-state wear rate was 0.013 mm/year (SD 0.012). There was no hip with a steady-state wear rate of > 0.1 mm/year. There was no significant difference in wear rates for each period. We found no significant correlation between the wear rate and age, body weight, BMI, or cup inclination. Conclusion. First-generation annealed HXLPE shows excellent wear resistance and no acceleration of wear for approximately 20 years, with low all-cause revision rates. Cite this article: Bone Joint J 2022;104-B(2):200–205

Aims. Hip arthroplasty aims to accurately recreate joint biomechanics. Considerable attention has been paid to vertical and horizontal offset, but femoral head centre in the anteroposterior (AP) plane has received little attention. This study investigates the accuracy of restoration of joint centre of rotation in the AP plane. Methods. Postoperative CT scans of 40 patients who underwent unilateral uncemented total hip arthroplasty were analyzed. Anteroposterior offset (APO) and femoral anteversion were measured on both the operated and non-operated sides. Sagittal tilt of the femoral stem was also measured. APO measured on axial slices was defined as the perpendicular distance between a line drawn from the anterior most point of the proximal femur (anterior reference line) to the centre of the femoral head. The anterior reference line was made parallel to the posterior condylar axis of the knee to correct for rotation. Results. Overall, 26/40 hips had a centre of rotation displaced posteriorly compared to the contralateral hip, increasing to 33/40 once corrected for sagittal tilt, with a mean posterior displacement of 7 mm. Linear regression analysis indicated that stem anteversion needed to be increased by 10.8° to recreate the head centre in the AP plane. Merely matching the native version would result in a 12 mm posterior displacement. Conclusion. This study demonstrates the significant incidence of posterior displacement of the head centre in uncemented hip arthroplasty. Effects of such displacement include a reduction in impingement free range of motion, potential alterations in muscle force vectors and lever arms, and impaired proprioception due to muscle fibre reorientation. Cite this article: Bone Joint Res 2022;11(3):180–188

Aims. Cementless primary total hip arthroplasty (THA) is associated with risks of bleeding and thromboembolism. Anticoagulants are effective as venous thromboprophylaxis, but with an increased risk of bleeding. Tranexamic acid (TXA) is an efficient antifibrinolytic agent, but the mode and timing of its administration remain controversial. This study aimed to determine whether two intravenous (IV) TXA regimens (a three-hour two-dose (short-TXA) and 11-hour four-dose (long-TXA)) were more effective than placebo in reducing perioperative real blood loss (RBL, between baseline and day 3 postoperatively) in patients undergoing THA who receive rivaroxaban as thromboprophylaxis. The secondary aim was to assess the non-inferiority of the reduction of blood loss of the short protocol versus the long protocol. Patients and Methods. A multicentre, prospective, randomized, double-blind, placebo-controlled trial was undertaken involving 229 patients undergoing primary cementless THA using a posterior approach, whose extended rivaroxaban thromboprophylaxis started on the day of surgery. There were 98 male and 131 female patients, with a mean age of 65.5 years (32 to 91). The primary outcome, perioperative RBL, was evaluated at 72 hours postoperatively. The efficacy of short- and long-TXA protocols in the reduction of perioperative RBL was compared with a placebo group. Results. TXA significantly reduced perioperative blood loss compared with placebo (p < 0.001); the mean differences were 525.3 ml (short-TXA vs placebo) and 550.1 ml (long-TXA vs placebo). No venous or arterial thromboembolic complications were reported. The upper boundary of the 95% confidence interval, when comparing short and long protocols, was below the pre-specified margin of non-inferiority (p = 0.027). Conclusion. In patients undergoing primary cementless THA, using a posterior approach, who are treated with rivaroxaban for thromboembolic prophylaxis, short- and long-TXA IV protocols are significantly more effective than placebo in reducing perioperative RBL, without any thromboembolic complications. Non-inferiority of a short- versus a long-TXA protocol in reducing perioperative RBL was supported in a secondary analysis

Aims. Our aim was to report survivorship data and lessons learned with the Corail/Pinnacle cementless total hip arthroplasty (THA) system. Patients and Methods. Between August 2005 and March 2015, a total of 4802 primary cementless Corail/Pinnacle THAs were performed in 4309 patients. In March 2016, we reviewed these hips from a prospectively maintained database. Results . A total of 80 hips (1.67%) have been revised which is equivalent to a cumulative risk of revision of 2.5% at ten years. The rate of revision was not significantly higher in patients aged ≥ 70 years (p = 0.93). The leading indications for revision were instability (n = 22, 0.46%), infection (n = 20, 0.42%), aseptic femoral loosening (n = 15, 0.31%) and femoral fracture (n = 6, 0.12%). There were changes in the surgical technique with respect to the Corail femoral component during the ten-year period involving a change to collared components and a trend towards larger size. These resulted in a decrease in the rate of iatrogenic femoral fracture and a decrease in the rate of aseptic loosening. Conclusion. The rate of revision in this series is comparable with the best performing THAs in registry data. Most revisions were not directly related to the implants. Despite extensive previous experience with cemented femoral components, the senior author noted a learning curve requiring increased focus on primary stability. The number of revisions related to the femoral component is reducing. Any new technology has a learning curve that may be independent of surgical experience. Cite this article: Bone Joint J 2016;98-B:1589–96

There are numerous studies in the current literature that have demonstrated altered levels of various biomarkers in the serum of patients with implant loosening. Despite increasing interest in the biology of implant incorporation there are no studies investigating the changes in biological marker (of either osteoblastic or osteoclastic activity) levels during the integration of the bone-implant interface. Such a study would provide data about the biological profile of normal integration and would be helpful for future monitoring of implant prosthetic performance (either normal or abnormal). We present data from a study performed on 100 osteoarthritic patients, who underwent cementless THA (Synergy, Reflexion Interfit, Smith & Nephew) and 100 non arthritic volunteers. Serial measurements of serum biochemical markers (bone formation and resorption), of cytokines and of other biological mediators and growth factors were evaluated at regular intervals over the course of six years. Curves of per cent changes from baseline and marker variability curves have been created for each marker which are indicative of the incorporation process. Evaluating markers of osteoblastic activity, a first response, with average values below baseline, was observed at the level of the seventh day (perhaps as a response to local trauma). A second osteo-productive response was observed between the third week and 9 months (peak average values at the level of the 6. th. month). At the 1st year time interval, average values reached baseline and remained at this level up to the 6th postoperative year. Evaluating markers of osteoclastic activity, a first response, with average values above baseline, was observed at the level of the seventh day (perhaps as a response to local trauma). A second osteoclastic response was observed between the third week and 3 months (perhaps a coupling response to enhanced osteoblastic activity). At 6 months, average values reached baseline and remained at this level up to the 6th postoperative year. It seems that bone implant interface in cementless total hip arthroplasty remains active up to the 9. th. postoperative month. Possible future deviation from such ‘individual normal’ curves will be indicative of the initiation of the osteolysis process and loss of fixation

Aims

The purpose of this study is to report our updated results at a minimum follow-up of 30 years using a first generation uncemented tapered femoral component in primary total hip arthroplasty (THA).

Young patients are at increased risk of revision after primary THA (THA). The bearing surface may be of importance for the longevity of the joint. We aimed to compare the risk of revision of primary stemmed cementless THA with MoM and CoC with metal-on-highly-crosslinked-polyethylene (MoXLP) bearings in patients between 20–54 years. From NARA, we included 2,153 MoM, 4,120 CoC and 10,329 MoXLP THA operated between 1995 and 2017. Kaplan-Meier estimator was used for calculation of THA survivorship and Cox regression to estimate the hazard ratio (HR) of revision (95% CI) due to any and specific causes. MoXLP was reference. The median follow-up was 10.3 years for MoM, 6.6 years for CoC and 4.8 years for MoXLP. 15 years postoperatively the Kaplan-Meier survival estimates were 80% (78–83%) for MoM, 92% (91–93%) for CoC and 94% (93–95%) for MoXLP. The 0–2, 2–7 and 7–15 years adjusted HRs of revision by any cause were 1.4 (0.9–2.4), 3.2 (2.1–5.1) and 3.9 (1.9–7.9) for MoM and 1.1 (0.8–1.4), 1.0 (0.7–1.3) and 2.5 (1.3–4.8) for CoC bearings. After 7–15 years follow-up, the unadjusted HR of revision due to aseptic loosening was 5.4 (1.2–24) for MoM and 4.2 (0.9–20) for CoC THA. MoM and CoC had a 7–15 year adjusted HR of revision due to ‘other’ causes of 4.8 (1.6–14) and 2.1 (0.8–5.8). MoXLP bearings were associated with better survival than MoM and CoC bearings, mainly because of lower risk of revision due to aseptic loosening and ‘other’ causes

Aims

“Get It Right First Time” (GIRFT) and NHS England’s Best Practice Tariff (BPT) have published directives advising that patients over the ages of 65 (GIRFT) and 69 years (BPT) receiving total hip arthroplasty (THA) should receive cemented implants and have brought in financial penalties if this policy is not observed. Despite this, worldwide, uncemented component use has increased, a situation described as a ‘paradox’. GIRFT and BPT do, however, acknowledge more data are required to support this edict with current policies based on the National Joint Registry survivorship and implant costs.

Short stems have been developed to conserve bone stock, especially in younger populations undergoing a total hip arthroplasty (THA), and showed similar functional outcomes compared to conventional stems. Recent literature suggested that stem length might be an independent risk factor for acute periprosthetic femoral fracture in direct anterior THA (1) or with different short stem designs (2). The purpose of the present study was to compare the incidence of acute periprosthetic femoral fractures, between stems of the same manufacture (Taperloc microplasty vs Taperloc complete), which have the same stem characteristics, except for the stem length which is 35 mm shorter in Taperloc microplasty during posterior and lateral THA.

Our institution's arthroplasty database was searched for all primary total hip arthroplasties utilizing short femoral stems performed between August 2016 and August 2023. Pre-operative X-rays for each case were analysed to characterize the proximal femoral geometry, specifically the canal bone ratio (CBR) and canal flare index (CFI). Data analysis was performed to identify risk factors for periprosthetic fractures.

For the time period assessed, 2107 femoral stems (Taperloc Microplasty:1727, Taperloc complete: 380) were implanted. Females constituted 53% of the cohort. The average patient age was 70±11 years. The periprosthetic fracture rate was 0.94%, with 20 periprosthetic fractures (Taperloc Microplasty:17, Taperloc complete: 3) excluding 2 greater trochanteric fractures (1 at each group), identified at follow-up of three months. There was no significant difference between the periprosthetic fracture rates between the two stems (0.98% vs 0.79%, p>0.72) The multivariate regression analysis demonstrated that the stem length, CBR, CFI, age, and gender were not risk factors for periprosthetic fracture.

The present study demonstrated that both Taperloc Microplasty and Taperloc complete stems had similar rates of periprosthetic fractures, and the stem length was not a risk factor for a periprosthetic fracture during uncemented THA.

1. Tamaki T, Cementless Tapered-Wedge Stem Length Affects the Risk of Periprosthetic Femoral Fractures in Direct Anterior Total Hip Arthroplasty. J Arthroplasty. 2018 Mar;33(3):805-809. 2. Staunton P. Acute Periprosthetic Hip Fracture with Short Uncemented Femoral Stems. J Arthroplasty 2024 accepted.

We reviewed 80 patients (87 hips) who were older than 80 years of age at the time of cementless total hip arthroplasty. An Alloclassic SL stem had been implanted in all patients. A variety of cementless acetabular components was used. After a mean follow-up of 69.3 months (39.2 to 94.1) 48 hips in 43 patients were analysed clinically and radiologically. One patient had sustained a traumatic periprosthetic fracture of the femur with subsequent exchange of the stem 73 months after operation. Thirty-two patients (34 hips) had died and five patients (five hips) were unavailable for follow-up because of health reasons (four patients) or lack of co-operation (one patient). If the endpoint is defined as removal of the prosthesis because of aseptic loosening, the survival rate was 100% for the cup and stem after 78 months. The mean Harris hip score was 81.9 points. Radiolucent lines and osteolysis were seldom found

Two-stage reconstruction with total implant removal and re-implantation after infection control is considered the gold standard treatment forinfection after hip arthroplasty. However, removal of the well-fixed stem or cup may cause substantial bone loss and other complications, thereby making reconstruction difficult. We evaluated whether an infection posttotal hip arthroplasty can be treated without removal of the radiographically and clinically well-fixed femoral stem or acetabular cup. Patients with a chronic infection aftertotal hip arthroplasty, with a radiographically well-fixed, cementless stem or cup, were selected. During the first surgical stage, we retained the stem or cup if we were unable to removethese with a stem or cup extractor. An antibiotic-impregnated cement spacer was then implanted. After control of infection (C-reactive proteinlevel within normal value), we performed the secondstage of re-implantation surgery. Treatment failure was defined as uncontrolled infection requiringremoval of the retained implant. From January 2004 to December 2013, 16 patients underwent partial component-retained 2-stage reconstruction. Thirteen patients (81.3%) were free of infection, with a mean follow-up time of 5 years. The remaining 3 patients, who had high-risk comorbidities and, of whom, 2 were infected by high-virulence organism, had uncontrolled infection and required furthersurgery to remove the retained implant. We conclude that partial component-retained 2-stage reconstruction could be an alternative treatment option for chronic infection afteran uncemented total hip arthroplasty with a radiographically and clinically well-fixed component in selected patients, who are notimmunocompromised and are infected by a low-virulence organism

Femoral stem design affects periprosthetic bone mineral density (BMD), which may impact long term survival of cementless implants in total hip arthroplasty (THA). The aim of this study was to examine proximal femoral BMD in three morphologically different uncemented femoral stems designs to investigate whether one particular design resulted in improved preservation of BMD.

119 patients were randomized to receive either a proximally coated dual taper wedge stem, a proximally coated anatomic stem or a fully coated collarless triple tapered stem. Dual energy x-ray absorptiometry scans (Lunar iDXA, GE Healthcare, Madison, WI) assessed BMD across the seven Gruen zones pre-operatively, and post-operatively at 6-weeks, 1-year, and 2-years comparing the unoperated contralateral femur as a control.

BMD increased in zones one (2.5%), two (17.1%), three (13.0%), five (10%) and six (17.9%) for all stems. Greater preservation of BMD was measured on the lateral cortex (zone 2) for both the dual taper wedge and anatomic stems (p = 0.019). The dual taper wedge stem also demonstrated preservation of BMD in the medial calcar (zone 7) whilst the anatomic and triple taper stem declined in this region, however this was not statistically significant (p = 0.059). BMD decreased on average by 2.1% in the mid-diaphysis region, distal to the stem tip (zone 4) for all implants. All stems performed equivalently at final follow-up in all patient reported outcome measures.

Implant design was shown to impact BMD changes. All stems preserved bone at the metaphyseal level in early follow-up, which theoretically indicates favorable implant fixation. There was no significant stress shielding observed, however longer follow-up is required to elucidate the impact of this finding on implant survivorship.

Aims

Femoral bone preparation using compaction technique has been shown to preserve bone and improve implant fixation in animal models. No long-term clinical outcomes are available. There are no significant long-term differences between compaction and broaching techniques for primary total hip arthroplasty (THA) in terms of migration, clinical, and radiological outcomes.

Accurate cup placement in total hip arthroplasty (THA) for the patients with developmental dysplasia of the hip (DDH) is one of the challenges due to distinctive bone deformity. Robotic-arm assisted system have been developed to improve the accuracy of implant placement. This study aimed to compare the accuracy of robotic-arm assisted (Robo-THA), CT-based navigated (Navi-THA), and manual (M-THA) cup position and orientation in THA for DDH.

A total of 285 patients (335 hips) including 202 M-THAs, 45 Navi-THAs, and 88 Robo-THA were analyzed. The choice of procedure followed the patient's preferences. Horizontal and vertical center of rotation (HCOR and VCOR) were measured for cup position, and radiographic inclination (RI) and anteversion (RA) were measured for cup orientation. The propensity score-matching was performed among three groups to compare the absolute error from the preoperative target position and angle.

Navi-THA showed significantly smaller absolute errors than M-THA in RI (3.6° and 5.4°) and RA (3.8° and 6.0°), however, there were no significant differences between them in HCOR (2.5 mm and 3.0 mm) or VCOR (2.2 mm and 2.6 mm). In contrast, Robo-THA showed significantly smaller absolute errors of cup position than both M-THA and Navi-THA (HCOR: 1.7 mm and 2.9 mm, vs. M-THA, 1.6 mm and 2.5 mm vs. Navi-THA, VCOR:1.7 mm and 2.4 mm, vs. M-THA, 1.4 mm and 2.2 mm vs. Navi-THA). Robo-THA also showed significantly smaller absolute errors of cup orientation than both M-THA and Navi-THA (RI: 1.4° and 5.7°, vs. M-THA, 1.5° and 3.6°, vs. Navi-THA, RA: 1.9° and 5.8° vs. M-THA, 2.1° and 3.8° vs. Navi-THA).

Robotic-arm assisted system showed more accurate cup position and orientation compared to manual and CT-based navigation in THA for DDH. CT-based navigation increased the accuracy of cup orientation compared to manual procedures, but not cup position.

Aims

The diversity of femoral morphology renders femoral component sizing in total hip arthroplasty (THA) challenging. We aimed to determine whether femoral morphology and femoral component filling influence early clinical and radiological outcomes following THA using fully hydroxyapatite (HA)-coated femoral components.

The ABG I cementless hip prosthesis has demonstrated unacceptably high rates of wear and osteolysis in our patients. We performed a retrospective study of 97 hips implanted between 1992 and 1998. Radiographic analysis revealed high rates of wear of the polyethylene liner with marked periacetabular osteolysis. Clinical examination indicated that many of these patients were initially asymptomatic. Wear-related problems have required ten hips to be revised and a furher 13 are awaiting revision.

This gives a failure rate of 24% at a mean follow-up of 69 months. Contributing factors are likely to include poor wear characteristics of the polyethylene liners which were gamma irradiated in air, and increased wear debris caused by a poor fit of the polyethylene liner within the shell. We believe that all ABG I implants should be immediately reviewed and remain under careful, long-term follow-up.