In this study, bone ingrowth was investigated in three-different cementless acetabular cups, titanium fiber mesh cup (non-HA), hydroxyapatite tricalcium phosphate sprayed cup (HA/TCP), alkali- and heat-treated titanium porous cup (AH). “Gap filling” was evaluated as the finding of the bone ingrowth on X-ray. The phenomenon is that slight gap between acetabulum and the cup observed after total hip arthroplasty (THA) disappear gradually. One hundred and thirty-seven consecutive primary THAs using cementless cups were evaluated for the rate of bone ingrowth. Patients were divided into three groups based on the different types of cups, 51 non-HA cups, 51 HA/TCP cups and 35 AH cups. The groups were similar with regards to age, sex, body mass index, original diagnosis, surgical technique and post operative rehabilitation. Average follow up period was35months, 33 month and 32 months respectively. Initial gap between acetabulum and the cup after operation was observed in 44 hips of non HA group, 39 hips of HA/TCP group and 33 hips of AH group. Rate of the gap filling at the last follow up was 2 hips (4.5%) in non-HA, 31 hips (79.5%) in HA/TCP and 33 hips (100%) in AH. Early gap filling that occurred for less than three months was 17.9% (7 of 39) in HA/TCP and 72.7% (24 of 33) in AH. The HA/TCP coated cup and the alkali- and heat-treated cup had the high frequency which gap filling occurred compared with the cup of only titanium fiber mesh processing. Additionally, in the AH cup more gap filling for less than three months had occurred compared with the HA/TCP cup, so AH cup is the most effective implant to obtain the bone ingrowth at an early stage and it is expected to acquire the better results

Aims. The aim of this study was to identify the optimal lip position for total hip arthroplasties (THAs) using a lipped liner. There is a lack of consensus on the optimal position, with substantial variability in surgeon practice. Methods. A model of a THA was developed using a 20° lipped liner. Kinematic analyses included a physiological range of motion (ROM) analysis and a provocative dislocation manoeuvre analysis. ROM prior to impingement was calculated and, in impingement scenarios, the travel distance prior to dislocation was assessed. The combinations analyzed included nine cup positions (inclination 30-40-50°, anteversion 5-15-25°), three stem positions (anteversion 0-15-30°), and five lip orientations (right hip 7 to 11 o’clock). Results. The position of the lip changes the ROM prior to impingement, with certain combinations leading to impingement within the physiological ROM. Inferior lip positions (7 to 8 o’clock) performed best with cup inclinations of 30° and 40°. Superior lip positions performed best with cup inclination of 50°. When impingement occurs in the plane of the lip, the lip increases the travel distance prior to dislocation. Inferior lip positions led to the largest increase in jump distance in a posterior dislocation provocation manoeuvre. Conclusion. The lip orientation that provides optimal physiological ROM depends on the orientation of the cup and stem. For a THA with stem anteversion 15°, cup inclination 40°, and cup anteversion 15°, the optimal lip position was posterior-inferior (8 o’clock). Maximizing jump distance prior to dislocation while preventing impingement in the opposite direction is possible with appropriate lip positioning. Cite this article: Bone Joint Res 2023;12(9):571–579

Aims. Limited implant survival due to aseptic cup loosening is most commonly responsible for revision total hip arthroplasty (THA). Advances in implant designs and materials have been crucial in addressing those challenges. Vitamin E-infused highly cross-linked polyethylene (VEPE) promises strong wear resistance, high oxidative stability, and superior mechanical strength. Although VEPE monoblock cups have shown good mid-term performance and excellent wear patterns, long-term results remain unclear. This study evaluated migration and wear patterns and clinical and radiological outcomes at a minimum of ten years’ follow-up. Methods. This prospective observational study investigated 101 cases of primary THA over a mean duration of 129 months (120 to 149). At last follow-up, 57 cases with complete clinical and radiological outcomes were evaluated. In all cases, the acetabular component comprised an uncemented titanium particle-coated VEPE monoblock cup. Patients were assessed clinically and radiologically using the Harris Hip Score, visual analogue scale (pain and satisfaction), and an anteroposterior radiograph. Cup migration and polyethylene wear were measured using Einzel-Bild-Röntgen-Analyze software. All complications and associated treatments were documented until final follow-up. Results. Clinical assessment showed persistent major improvement in all scores. On radiological assessment, only one case showed a lucent line (without symptoms). At last follow-up, wear and migration were below the critical thresholds. No cup-related revisions were needed, indicating an outstanding survival rate of 100%. Conclusion. Isoelastic VEPE cups offer high success rates and may prevent osteolysis, aseptic loosening, and the need for revision surgeries in the long term. However, longer follow-up is needed to validate our findings and confirm the advantages offered by this cup. Cite this article: Bone Jt Open 2024;5(10):825–831

Introduction. Impaction bone grafting (IBG) is a reliable technique for acetabular revision surgery with large segmental defects. However, bone graft resorption and cup migration are some of the limitations of this tecnique. We assess frequency and outcome of these complications in a large acetabular IBG series. Patients and Methods. We analysed 330 consecutive hips that received acetabular IBG and a cemented cup in revision surgery with large bone defects (Paprosky types 3A and 3B). Fresh-frozen femoral head allograft was morselized manually. The mean follow-up was 17 years (3–26). All data were prospectively collected. Kaplan-Meier survivorship analysis was performed. Changes in different paremeters regarding cup position were assessed pre- and postoperatively and at the follow- up controls. Only variations greater than 5º and 3 mm were considered. Results. The mean Harris Hip Score improved from 48.3+8.5 to 84.6+12.8 at final follow-up. The radiological analysis showed cup migration in 42 hips. The mean appearance time was 4.3 years (range, 1–25). Migration was progressive and painful in 27 hips (67.5%) requiring cup revision. Lateral mesh was more frequently associated with migrated cups (p=0.034). Cup tilt was found in 37 out 42 migrated cups, however cranial migration was more frequent in progressive migrated cups (p=0.02). There were 34 re-revisions, 27 due to aseptic cup loosening, 6 due to dislocation and one due to infection. The survival rate for any cause at 16 years was 81.2% (95% Confidence Interval (CI): 74.0 to 88.4) and for aseptic cup loosening was 83.4% (95% CI: 76.2–90.6). In all surviving hips trabecular incorporation was observed without radiolucent lines. Conclusions. IBG continues to be a reliable technique for large defects in acetabular revision surgery. Bone graft resorption and cup migration was not frequent in this large series and one-third of cases were not progressive. Cup migration was more frequent in cases with a segmental roof defect in which a lateral mesh was used

Purpose. Cementless cup with structural allograft is one of option for acetabular revision in the cases which has severe bone loss. This study was performed to verify that the structural allograft with cementless cup could be one of good options for revision of acetabular cup with severe bone defect and to verify that the allograft resorption affect the stability of cementless acetabular cup. Materials and Methods. We reviewed 25 cases of 25 patients who underwent acetabular cup rvision using cementless porous coated hemispherical cup with structural allograft from May 1992 to July 2011 July 2011. There were nine males and sixteen females with an average age of 50.0 years. The average follow-up period was 76.7(28∼212) months. The clinical evaluation was performed using Harris Hip Score(HHS) and UCLA activity score. Radiologically, the degree of resorption of grafted bone, incorporation of allograft bone with normal bone, osteolysis and cup loosening were evaluated. Results. Clinically, the average Harris hip score was improved from 54 preoperatively to 93.4 at the last follow-up. The average UCLA activity score was also improved from 4.3 preoperatively to 6.4 at the last follow-up. Radiologically, the incorporation of allograft was accomplished in 11.4 months and the resorption of grafted bone was noted in 3 cases(12%), but the allograft resorption had not progressed to moderate degree even in long term follow-up. There was no cup loosening and average survivor rate was 100% in 6 years. There was no infection, allograft nonunion, osteolysis. Conclusion. Cementless cup with structural allograft in acetabular cup reconstruction can provide excellent mi-term results in both clinical and radiological aspects. Structural allograft can provide strong mechanical support for the bone ingrowth of cementless cup. The clinical result of this study auggest that cementless cup with structural allograft can be a good option for acetabular cup revision with severe bone defect. Resorption of structural allograft rarely occurred, and the resorption of structural allograft does not affect stablility of cup even in long term follow-up

Aims. It is important to analyze objectively the hammering sound in cup press-fit technique in total hip arthroplasty (THA) in order to better understand the change of the sound during impaction. We hypothesized that a specific characteristic would present in a hammering sound with successful fixation. We designed the study to quantitatively investigate the acoustic characteristics during cementless cup impaction in THA. Methods. In 52 THAs performed between November 2018 and April 2022, the acoustic parameters of the hammering sound of 224 impacts of successful press-fit fixation, and 55 impacts of unsuccessful press-fit fixation, were analyzed. The successful fixation was defined if the following two criteria were met: 1) intraoperatively, the stability of the cup was retained after manual application of the torque test; and 2) at one month postoperatively, the cup showed no translation on radiograph. Each hammering sound was converted to sound pressures in 24 frequency bands by fast Fourier transform analysis. Basic patient characteristics were assessed as potential contributors to the hammering sound. Results. The median sound pressure (SP) of successful fixation at 0.5 to 1.0 kHz was higher than that of unsuccessful fixation (0.0694 (interquartile range (IQR) 0.04721 to 0.09576) vs 0.05425 (IQR 0.03047 to 0.06803), p < 0.001). The median SP of successful fixation at 3.5 to 4.0 kHz and 4.0 to 4.5 kHz was lower than that of unsuccessful fixation (0.0812 (IQR 0.05631 to 0.01161) vs 0.1233 (IQR 0.0730 to 0.1449), p < 0.001; and 0.0891 (IQR 0.0526 to 0.0891) vs 0.0885 (IQR 0.0716 to 0.1048); p < 0.001, respectively). There was a statistically significant positive relationship between body weight and SP at 0.5 to 1.0 kHz (p < 0.001). Multivariate analyses indicated that the SP at 0.5 to 1.0 kHz and 3.5 to 4.0 kHz was independently associated with the successful fixation. Conclusion. The frequency bands of 0.5 to 1.0 and 3.5 to 4.0 kHz were the key to distinguish the sound characteristics between successful and unsuccessful press-fit cup fixation. Cite this article: Bone Jt Open 2024;5(3):154–161

Aims. It is important to analyze objectively the hammering sound in cup press-fit technique in total hip arthroplasty (THA) in order to better understand the change of the sound during impaction. We hypothesized that a specific characteristic would present in a hammering sound with successful fixation. We designed the study to quantitatively investigate the acoustic characteristics during cementless cup impaction in THA. Methods. In 52 THAs performed between November 2018 and April 2022, the acoustic parameters of the hammering sound of 224 impacts of successful press-fit fixation, and 55 impacts of unsuccessful press-fit fixation, were analyzed. The successful fixation was defined if the following two criteria were met: 1) intraoperatively, the stability of the cup was retained after manual application of the torque test; and 2) at one month postoperatively, the cup showed no translation on radiograph. Each hammering sound was converted to sound pressures in 24 frequency bands by fast Fourier transform analysis. Basic patient characteristics were assessed as potential contributors to the hammering sound. Results. The median sound pressure (SP) of successful fixation at 0.5 to 1.0 kHz was higher than that of unsuccessful fixation (0.0694 (interquartile range (IQR) 0.04721 to 0.09576) vs 0.05425 (IQR 0.03047 to 0.06803), p < 0.001). The median SP of successful fixation at 3.5 to 4.0 kHz and 4.0 to 4.5 kHz was lower than that of unsuccessful fixation (0.0812 (IQR 0.05631 to 0.01161) vs 0.1233 (IQR 0.0730 to 0.1449), p < 0.001; and 0.0891 (IQR 0.0526 to 0.0891) vs 0.0885 (IQR 0.0716 to 0.1048); p < 0.001, respectively). There was a statistically significant positive relationship between body weight and SP at 0.5 to 1.0 kHz (p < 0.001). Multivariate analyses indicated that the SP at 0.5 to 1.0 kHz and 3.5 to 4.0 kHz was independently associated with the successful fixation. Conclusion. The frequency bands of 0.5 to 1.0 and 3.5 to 4.0 kHz were the key to distinguish the sound characteristics between successful and unsuccessful press-fit cup fixation. Cite this article: Bone Jt Open 2024;4(3):154–161

Introduction. Cup malposition in hip arthroplasty and hip resurfacing is associated with instability, accelerated wear, and the need for revision. A recent study measuring cup orientation on conventional radiodiographs demonstrated an incidence of cup malpositioning of 50% according to the safe zone that they defined 1,2. A prior study of 105 conventionally placed cups using CT demonstrated a cup malpositioning incidence of 74%3. The current study similarly assesses the variation in cup position using conventional techniques as measured by CT. Methods. CT studies of 123 hips in 119 patients with total hip arthroplasties performed using conventional techniques were used for this study. The indications for the CT studies were for CT-based surgical navigation of the contralateral side or for assessment of periprosthetic osteolysis. 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. Since these studies including images through the femoral condyles, femoral anteversion could be measured on these hips as well (Osirix v5.6, Pixmeo SARL, Bernex, Switzerland). Results. Cup orientation for the 123 hips is shown in Figure 1. Operative anteversion averaged 29.7 degrees with a standard deviation of 12.2 and a range of −24.4 to 57.5. Operative inclination averaged 37.5 degrees with a standard deviation of 7.7 and a range of 18.4 to 68.2. Femoral anteversion averaged 21.1 degrees with a standard deviation of 14.0 and a range of −20.5 to 60.9. Using 25 degrees of operative anteversion and 45 degrees of operative inclination as the center of a safe zone for example, 78 of 123 (63%) were more than 10 degrees off in either anteversion and inclination and 23 of 123 (19%) were more than 10 degrees off in both anteversion and inclination. Discussion and Conclusion. Most conventionally placed acetabular components are malpositioned. While the incidence of cup malorientation using conventional techniques is quite high, the incidence in our series appears to be lower than that reported by Saxler et al. It is curious that most experienced surgeons who perform total hip arthroplasty using conventional methods of cup alignment believe that their accuracy quite good. Yet, multiple objective studies of cup alignment demonstrate that accuracy is quite poor. Since cup malposition is so closely associated with instability, impingement, wear, bearing fracture, osteolysis and loosening, questions remain as to how conventional methods of cup alignment remain an acceptable standard of care in our field

Aims. This study aimed to evaluate the accuracy of implant placement with robotic-arm assisted total hip arthroplasty (THA) in patients with developmental dysplasia of the hip (DDH). Methods. The study analyzed a consecutive series of 69 patients who underwent robotic-arm assisted THA between September 2018 and December 2019. Of these, 30 patients had DDH and were classified according to the Crowe type. Acetabular component alignment and 3D positions were measured using pre- and postoperative CT data. The absolute differences of cup alignment and 3D position were compared between DDH and non-DDH patients. Moreover, these differences were analyzed in relation to the severity of DDH. The discrepancy of leg length and combined offset compared with contralateral hip were measured. Results. The mean values of absolute differences (postoperative CT-preoperative plan) were 1.7° (standard deviation (SD) 2.0) (inclination) and 2.5° (SD 2.1°) (anteversion) in DDH patients, and no significant differences were found between non-DDH and DDH patients. The mean absolute differences for 3D cup position were 1.1 mm (SD 1.0) (coronal plane) and 1.2 mm (SD 2.1) (axial plane) in DDH patients, and no significant differences were found between two groups. No significant difference was found either in cup alignment between postoperative CT and navigation record after cup screws or in the severity of DDH. Excellent restoration of leg length and combined offset were achieved in both groups. Conclusion. We demonstrated that robotic-assisted THA may achieve precise cup positioning in DDH patients, and may be useful in those with severe DDH. Cite this article: Bone Joint Res 2021;10(10):629–638

In total hip arthroplasty (THA), cementless cup without screw holes has the putative benefits of maximizing host bone contact and reducing osteolysis by eliminating channels to backside wear particles. However, supplemental trans-acetabular screws cannot be used. 74 hips in 60 patients receiving same model of cementless cup without screw holes (Depuy Duraloc 100 HA cup) from 6/1999 to 3/2003 were prospectively followed up. All patients were allowed to have immediate full weight bearing. Age at THA was 53 ± 13 (range 24–74) years. Osteonecrosis was the leading hip disease (45% of hips). Survivorship was assessed using revision of the cup as the end point. Radiological parameters, including lateral opening angle, vertical and horizontal migration distances of the cups were measured. Paired t-test was used to compare between the measurements in early postoperative period and at final follow up. 51 hips were assessed at minimum 20 years follow-up. The mean follow-up was 22.6 (range 21 – 25) years. All the cups were well fixed. There were two cup revisions. Conventional polyethylene (PE) was used in both hips; osteolysis occurred 17 and 18 years later. Both cups were well fixed but were revised, one due to cup mal-positioning, one due to need in upsizing the articulation. 14 other hips were revised but these cups were well fixed and not revised; 9 loosened stems (most were cemented Elite plus stems), 5 PE wear and osteolysis (all were conventional PE). At 20 years, the survivorship of cups was 96.1%. Changes in lateral opening angle, vertical and horizontal migration distances were 0.44±1.59°, 0.01±1.52mm and -0.32±1.47mm respectively, without statistical significance. This study provided evidence of excellent long-term survivorship of cementless cup without screw holes. Immediate postoperative weight-bearing also did not lead to cup migration in the long-term

Introduction. Optimal alignment of the acetabulum cup component is crucial for good outcome of Total Hip Arthroplasty (THA). A patient-specific instrumentation (PSI) for cup alignment manufactured by 3D printing might improve cup alignment in conventional THAs with patient's lateral decubitus position. In this study, we developed PSI for cup alignment which transferred preoperatively planned cup alignment to the operation room as a linear visual reference(Figure 1), then investigated its accuracy in terms of fitting of PSI on the bony surface and angle deviation between pre- and post-operative cup alignments. Methods. 3-Dimensional bone models created from CT images of both sides of 6 cadaveric specimens were used in the current study. In the first experiment (first 3 specimens and six hips), we designed PSI to fit on the acetabular rim, and we inserted a Kirschner wire (K-wire) through PSI after PSI's fitting. In the second experiment (remaining 3 specimens and six hips), after the same steps like the first experiment were done, we reamed and finally impacted plastic cups with the visual reference of the K-wire. Using postoperative CT images taken after both experiments, we measured deviation of the K-wire placement for the first experiment, and measured deviation of the cup placement from planned cup alignment. Results. The angle deviation of the K-wire alignment on the basis of radiographic inclination and anteversion angles was on average 2.2°±2.5° and 1.0°±1.3° respectively in the first experiment. The angle deviation of the cup alignment with the same definition was on average 2.88°±1.63° and 4.15°±2.56°. For one cadaveric specimen data for the first experiment were missing. Conclusion. We conclude that the accuracy of acetabular cup placement can be improved by the use of patient-specific cup orientation guides

Introduction. Revision Total Hip Arthroplasties (THA) have a significantly higher failure rate than primary THA's and the most common cause is aseptic loosening of the cup. To reduce this incidence of loosening various porous metal implants with a rough surface and a porous architecture have been developed which are said to increase early osteointegration. However, for successful osteointegration a minimal micromotion between the implant and the host bone (primary stability) is beneficial. It has not been previously determined if the primary stability for the new Gription® titanium cup differs from that of the old Porocoat® titanium cup. Material and Methods. In 10 cadaveric pelvises, divided into 20 hemipelvises, bilateral THA's were performed by an experienced surgeon (RGB) following the implant manufacturer's instructions and with the original surgical instruments provided by the company. In randomized fashion the well established Porocoat® titanium implant was implanted on one side of each each hemipelvis whereas on the corresponding opposite side the modified implant with a Gription® coating was inserted. Radiographs were taken to confirm satisfactory operative results. Subsequently, the hemipelvis and cups were placed in a biomechanical testing machine and subjected to physiological cyclic loading. Three-dimensonal loading corresponded to 30% of the load experienced in normal gait was imposed reflecting the limited weight bearing generally prescribed postoperatively. The dynamic testing took place in a multi-axial testing machine for 1000 cycles. Relative motion and micromotion were quantified using an optical measurement device (Pontos, GOM mbh, Braunschweig, Germany). Statistical evaluation was performed using the Wilcoxon signed-rank test. Results and conclusion. The standard Porocoat® titanium cups showed a mean relative motion with respect to the host bone of 54.74µm (Range 26.04 – 127.06µm), while the porous Gription® titanium cup displayed a relative motion with respect to the host bone of 49.77µm (Range 24.69 – 128.37µm). The Wilcoxon test did not reveal a significant difference between the two surfaces. The in-vitro biomechanical evaluation of both acetabular cups under a physiologic loading scenario showed no significant difference with regard to primary stability. Both the extensively tried and clinically successful Porocoat® titanium cup and the newer Gription® coated cup showed very little micromotion and both implants should therefore allow good osteointegration

Introduction:. Cup malposition in hip arthroplasty and hip resurfacing is associated with instability, accelerated wear, and the need for revision. A recent study measuring cup orientation on conventional radiodiographs demonstrated an incidence of cup malpositioning of 50% according to the safe zone that they defined. 1,2. A prior study of 105 conventionally placed cups using CT demonstrated a cup malpositioning incidence of 74%. 3. The current study similarly assesses the variation in cup position using conventional techniques as measured by CT. Methods:. We have performed CT-based navigation of hip arthroplasty and revision arthroplasty on a routine basis since 2003 and also use CT imaging to quantify periprosthetic osteolysis. In our image database from these, we have identified 98 hips and y patients who had a previously conventionally-placed cup on CT imaging. For each hip, cup orientation was determined in operative anteversion and operative inclination (according to the definitions of Murray) using an application specific software application (HipSextant Research Application 1.0.7, Surgical Planning Associates Inc., Boston, Massachusetts). This application allows for determination of the Anterior Pelvic Plane coordinates from a 3D surface model. A multiplanar reconstruction module allows for creation of a plane parallel with the opening plane of the acetabulum and subsequent calculation of plane orientation in the AP Plane coordinate space. Results:. 16 of 53 or 30.2% of hips in the control group were within 7.5 degrees of the safe zone center for both for both anteversion and inclination. 29 of 53 or 51.9% of hips in the control group were within 10 degrees of the safe zone center for both for both anteversion and inclination. Discussion and Conclusion:. Most conventionally placed acetabular components are malpositioned. While the incidence of cup malorientation using conventional techniques is quite high, the incidence in our series appears to be lower than that reported by Saxler et al. It is curious that most experienced surgeons who perform total hip arthroplasty using conventional methods of cup alignment believe that their accuracy quite good. Yet, multiple objective studies of cup alignment demonstrate that accuracy is quite poor. Since cup malposition is so closely associated with instability, impingement, wear, bearing fracture, osteolysis and loosening, questions remain as to how conventional methods of cup alignment remain an acceptable standard of care in our field

Introduction. Cup malposition in hip arthroplasty and hip resurfacing is associated with instability, accelerated wear, and the need for revision. The current study similarly assesses the variation in cup position using conventional techniques as measured by CT. Methods. We have performed CT-based navigation of hip arthroplasty and revision arthroplasty on a routine basis since 2003 and also use CT imaging to quantify periprosthetic osteolysis. In our image database, we have identified 91 hips in 87 patients (51 female, 36 male) who had a previously conventionally-placed cup on CT imaging. For each hip, cup orientation was determined in operative anteversion and operative inclination (according to the definitions of Murray) using an application specific software application (HipSextant Research Application 1.0.7, Surgical Planning Associates Inc., Boston, Massachusetts). This application allows for determination of the Anterior Pelvic Plane coordinates from a 3D surface model. A multiplanar reconstruction module allows for creation of a plane parallel with the opening plane of the acetabulum and subsequent calculation of plane orientation in the AP Plane coordinate space. Results. The conventionally placed cups ranged from −7.2° to 57.5° in operative anteversion (mean = 30.2°, SD = 11.6°) and 18.4° to 68.1° in operative inclination (mean = 37.6, SD = 8.2°). If a safe zone goal of 27 degrees of operative anteversion (± 10°) and 42 degrees of operative inclination (± 10°) is assumed, 29.7% of hips are out of the safe zone of operative anteversion, and 25.3% of hips are out of the safe zone of operative inclination. 45.1% of all hips are out of the safe zone in either operative anteversion, operative inclination, or both. If a goal of 20° of operative anteversion (± 10°) and 45° of operative inclination (± 10°) is assumed, 55.0% of hips are out of the safe zone in operative anteversion, 44.0% of hips are out of the safe zone in operative inclination, and 70.3% of hips are out of one or both safe zones. Discussion. Most conventionally placed acetabular components are malpositioned and the current study confirms prior reports of the incidence of cup malposition as measure both by CT and plain radiographs. It is curious that most experienced surgeons who perform total hip arthroplasty using conventional methods of cup alignment believe that their accuracy quite good. Yet, multiple objective studies of cup alignment demonstrate that accuracy is quite poor. Since cup malposition is so closely associated with instability, impingement, wear, bearing fracture, osteolysis and loosening, questions remain as to how conventional methods of cup alignment remain an acceptable standard of care in our field

Custom acetabular components have become an established method of treating massive acetabular bone defects in hip arthroplasty. Complication rates, however, remain high and migration of the cup is still reported. Ischial screw fixation (IF) has been demonstrated to improve mechanical stability for non-custom, revision arthroplasty cup fixation. We hypothesise that ischial fixation through the flange of a custom acetabular component aids in anti-rotational stability and prevention of cup migration. Electronic patient records were used to identify a consecutive series of 49 custom implants in 46 patients from 2016 to 2022 in a unit specializing in complex joint reconstruction. IF was defined as a minimum of one screw inserted into the ischium passing through a hole in a flange on the custom cup. The mean follow-up time was 30 months. IF was used in 36 cups. There was no IF in 13 cups. No difference was found between groups in age (68.9 vs. 66.3, P = 0.48), BMI (32.3 vs. 28.2, P = 0.11) or number of consecutively implanted cups (3.2 vs. 3.6, P = 0.43). Aseptic loosening with massive bone loss was the primary indication for revision. There existed no difference in Paprosky grade between the groups (P = 0.1). 14.2% of hips underwent revision and 22.4% had at least one dislocation event. No ischial fixation was associated with a higher risk of cup migration (6/13 vs. 2/36, X2 = 11.5, P = 0.0007). Cup migration was associated with an increased risk for all cause revision (4/8 vs. 3/38, X2 = 9.96, P = 0.0016, but not with dislocation (3/8 vs. 8/41, X2 = 1.2, P = 0.26). The results suggest that failure to achieve adequate ischial fixation, with screws passing through the flange of the custom component into the ischium, increases the risk of cup migration, which, in turn, is a risk factor for revision

Background. A few patients undergoing a total hip replacement need a subsequent revision of the cup. In some of these cases, the treating surgeon may be confronted with Unexpected Positive Intraoperative Cultures (UPIC). The exact incidence of this finding is unclear. Moreover, it is unknown what the clinical outcome of these patients is when the stem is left in situ. The aim of our study was to describe the incidence of UPIC in patients undergoing cup revision and to determine the need for total revision in this patient group during follow-up. Methods/design. In this retrospective multicenter cohort study, we included all consecutive patients that underwent a cup revision between 2015–2017 and had a minimal follow-up of 2 years. Patients were divided in 3 cohorts: i) no positive intra operative cultures; ii) one UPIC; iii) two or more UPIC. Cases in whom 2 or fewer cultures were obtained during cup revision were excluded from the analysis. Results. From the 334 evaluated cases, 77 were excluded because an inadequate number of cultures were obtained. From the total of 257 included cases, the incidence of UPIC was 16% (n=39). 21 cases had one (8%), and 18 cases had two or more UPIC (7%). After two years of follow up, implant survival in the no UPIC group was 88% (95% CI 0.83 – 0.93), in the one UPIC group 95% (95% CI 0.86 – 1.0), and in the two or more UPIC group 77% (95% CI 0.57 – 0.97). Survival analysis showed no statistically significant differences between the cohorts as determined by cox regressive analysis and log rank test (P = 0.19). Conclusion. The incidence of UPIC in patients who undergo cup revision is relatively high but does not seem to have a major influence on the need for total revision of the hip during a follow-up of 2 years

In 2021, Vigdorchik et al. published a large multicentre study validating their simple Hip-Spine Classification for determining patient-specific acetabular component positioning in total hip arthroplasty (THA). The purpose of our study was to apply this Hip-Spine Classification to a sample of Australian patients undergoing THA surgery to determine the local acetabular component positioning requirements. Additionally, we propose a modified algorithm for adjusting cup anteversion requirements. 790 patients who underwent THA surgery between January 2021 and June 2022 were assessed for anterior pelvic plane tilt (APPt) and sacral slope (SS) in standing and relaxed seated positions and categorized according to their spinal stiffness and flatback deformity. Spinal stiffness was measured using pelvic mobility (PM); the ΔSS between standing and relaxed seated. Flatback deformity was defined by APPt <-13° in standing. As in Vigdorchik et al., PM of <10° was considered a stiff spine. For our algorithm, PM of <20° indicated the need for increased cup anteversion. Using this approach, patient-specific cup anteversion is increased by 1° for every degree the patient's PM is <20°. According to the Vigdorchik simple Hip-Spine classification groups, we found: 73% Group 1A, 19% Group 1B, 5% Group 2A, and 3% Group 2B. Therefore, under this classification, 27% of Australian THA patients would have an elevated risk of dislocation due to spinal deformity and/or stiffness. Under our modified definition, 52% patients would require increased cup anteversion to address spinal stiffness. The Hip-Spine Classification is a simple algorithm that has been shown to indicate to surgeons when adjustments to acetabular cup anteversion are required to account for spinal stiffness or flatback deformity. We investigated this algorithm in an Australian population of patients undergoing THA and propose a modified approach: increasing cup anteversion by 1° for every degree the patient's PM is <20°

We have previously reported on the improved all-cause revision and improved revision for instability risk in lipped liner THAs using the NJR dataset. These findings corroborate studies from the Australian (AOANJRR) and New Zealand (NZOA) joint registries. The optimal orientation of the lip in THAs utilising a lipped liner remains unclear to many surgeons. The aim of this study was to identify impingement-free optimal liner orientations whilst considering femoral stem version, cup inclination and cup version. A cementless THA kinematic model was developed using a 20 degree XLPE liner. Physiological ROM and provocative dislocation manoeuvre analyses were performed. A total of 9 cup positions were analysed (inclination 30–40–50 degrees, anteversion 5-15-25 degrees) and combined with 3 stem positions (anteversion 0-15-30 degrees) and 5 lip orientations (right hip 11 to 7 o'clock). Some lip orientation/component position combinations lead to impingement within the physiological ROM range. Using a lipped liner increases the femoral head travel distance prior to dislocation when impingement occurs in the plane of the lip. In THAs with a cup inclination of 30 and 40 degrees, inferior lip orientations (7–8 o'clock for a right hip) performed best. Superior lip orientation performed best with a cup inclination of 50 degrees. Femoral stem version has a significant effect on the range of movement prior to impingement and hence the preferred lip orientation. The optimal orientation of the lip in lipped liner THA is dependent on the position of both the acetabular and femoral components. In the common component orientation combination of stem anteversion 15, cup inclination 40 and cup anteversion 15, the optimal lip orientation was postero-inferiorly (8 o'clock for a right hip). Preventing impingement during physiological ROM is possible with appropriate lip liner orientation

There remains concern with the use of constrained liners (CL) implanted at the time of acetabular cup revision in revision total hip replacement (rTHA). The aim of this study was to determine the implant survival in rTHA when a CL was implanted at the same time as acetabular cup revision. We reviewed our institutional database to identify all consecutive rTHAs where a CL was implanted simultaneously at the time acetabular cup revision from 2001 to 2021. One-hundred and seventy-four revisions (173 patients) were included in the study. Mean follow-up of 8.7 years (range two – 21.7). The most common indications for rTHA were instability (35%), second-stage periprosthetic joint infection (26.4%), and aseptic loosening (17.2%). Kaplan Meier Analysis was used to determine survival with all-cause re-revision and revision for cup aseptic loosening (fixation failure) as the endpoints. A total of 32 (18.3%) patients underwent re-revision at a mean time of 2.9 years (range 0.1 – 14.1). The most common reasons for re-revision were instability (14), periprosthetic joint infection (seven), and loosening of the femoral component (four). Three (1.7%) required re-revision due to aseptic loosening of the acetabular component (fixation failure) at a mean of two years (0.1 – 5.1). Acetabular component survival free from re-revision due to aseptic loosening was 98.9% (95% CI 97.3 – 100) at five-years and 98.1% (95% CI 95.8 – 100) at 10-years. There were no acetabular component fixation failures in modern highly porous shells. CLs implanted at the time acetabular cup revision in rTHA have a 98.1% 10-year survival free from acetabular cup aseptic loosening (fixation failure). There were no cup fixation failures in modern highly porous shells. Thus, when necessary, implanting a CL during revision of an acetabular component with stable screw fixation is safe with an extremely low risk of cup fixation failure

The effect of cup geometry in uncemented Total Hip Arthroplasty has not been investigated. We reviewed the radiological and clinical results of 527 primary total hip arthroplasties. We assessed the bone ingrowth potential of two geometric variations of an uncemented cup and compared hydroxyappetite and porous coated shells. Patients undergoing primary hip arthroplasty between 1997 and 2004 were prospectively entered into an arthroplasty database. Patients were reviewed at 1,2,4,5,8 and 10 years post surgery. Three acetabular shell types were used. These included hemispherical cups with porous or hydroxyapatite coating, and cups with peripheral expansion with porous coating. Radiographs with minimum 1-year follow-up were examined in 542 cases, using digital templating software. Radiographs were assessed for signs of bone in-growth, lucent lines, migration and polyethylene wear. Survivorship analysis was performed using Kaplan-Meier analysis with 95% confidence intervals. Radiological findings and cup type were analysed using Fishers exact test. Radiological evidence of bone ingrowth was seen in 82% of hemispherical cups, compared with 59% of peripherally expanded cups, which was significant (p,0.05). Bone ingrowth was not affected by the presence of HA coating. The most common diagnoses were osteoarthritis (67%) and avascular necrosis (12%). The mean age was 56 years. Survivorship with revision or impending revision for aseptic loosening was 95.6% at 7 years (95%CI 1.0134-0.8987). The 3 revisions and 1 impending revision for loosening were in patients with avascular necrosis (3) or previous acetabular and femoral osteotomies for DDH (1), with a mean age of 44 years. Hemispherical shells have improved radiographic outcome in comparison with peripherally expanded components. At 7 years, clinical results are similar for both components