Aims. The aim of this study was to assess the clinical and radiological outcomes of an antiprotrusio acetabular cage (APC) when used in the surgical treatment of periacetabular bone metastases. Methods. This retrospective cohort study using a prospectively collected database involved 56 patients who underwent acetabular reconstruction for periacetabular bone metastases or haematological malignancy using a single APC between January 2009 and 2020. The mean follow-up was 20 months (1 to 143). The primary outcome measure was implant survival. Postoperative radiographs were analyzed for loosening and failure. Patient and implant survival were assessed using a competing risk analysis. Secondary parameters included primary malignancy, oncological treatment, surgical factors, length of stay in hospital, and postoperative complications. Results. A total of 33 patients (59%) died during the study period at a mean of 15 months postoperatively (1 to 63). No patient had radiological evidence of loosening or failure. Acetabular component survival was 100%. Three patients (5.4%) had further surgery; one (1.8%) underwent revision of the femoral component for dislocation, one required debridement with implant retention for periprosthetic joint infection, and one required closed reduction for dislocation. Using death as a competing risk, at 100 months, the probability of revision was 0.036 and the risk of death was 0.84. Conclusion. With appropriate patient selection, the antiprotrusio cage offers good implant survival, with a reasonable perioperative complication rate in this high-risk group of patients when managing metastatic disease or haematological malignancy around the acetabulum. Cite this article: Bone Joint J 2022;104-B(4):504–509

Aims. Although periacetabular osteotomies are widely used for the treatment of symptomatic dysplastic hips, long-term surgical outcomes and patient-reported outcome measures (PROMs) are still unclear. Accordingly, we assessed hip survival and PROMs at 20 years after transpositional osteotomy of the acetabulum (TOA). Methods. A total of 172 hips in 159 patients who underwent TOA were followed up at a mean of 21.02 years (16.6 to 24.6) postoperatively. Kaplan-Meier analysis was used to assess survivorship with an endpoint of total hip arthroplasty (THA). PROMs included the visual analogue scale (VAS) Satisfaction, VAS Pain, Oxford Hip Score (OHS), and Forgotten Joint Score-12 (FJS-12). Thresholds for favourable outcomes for OHS (≥ 42) and FJS-12 (≥ 51) were obtained using the receiver operating characteristic curve with VAS Satisfaction ≥ 50 and VAS Pain < 20 as anchors. Results. THA was performed on 37 hips (21.5%) by the latest follow-up. Kaplan-Meier analysis indicated that the hip survival rate at 20 years was 79.7% (95% confidence interval (CI) 73.7 to 86.3). Multivariate analysis showed that preoperative Tönnis grade significantly influenced hip survival. Tönnis grades 0, 1, and 2 were associated with 20-year survival rates of 93.3% (95% CI 84.8 to 100), 86.7% (95% CI 79.8 to 94.3), and 54.8% (95% CI 41.5 to 72.3), respectively. More than 60% of the patients exhibited favourable PROMs. An advanced Tönnis grade at the latest follow-up and a higher BMI were both significantly associated with unfavourable OHS, but not with other PROMs. Conclusion. This study demonstrated the durability of TOA for hips with Tönnis grades 0 to 1 at 20 years. While the presence of advanced osteoarthritis and higher BMI was associated with lower hip functions (OHS), it was not necessarily associated with worse patient satisfaction and joint awareness. Cite this article: Bone Joint J 2022;104-B(7):767–774

Aims. The aim of this study was to determine the clinical outcomes and factors contributing to failure of transposition osteotomy of the acetabulum (TOA), a type of spherical periacetabular osteotomy, for advanced osteoarthritis secondary to hip dysplasia. Methods. We reviewed patients with Tönnis grade 2 osteoarthritis secondary to hip dysplasia who underwent TOA between November 1998 and December 2019. Patient demographic details, osteotomy-related complications, and the modified Harris Hip Score (mHHS) were obtained via medical notes review. Radiological indicators of hip dysplasia were assessed using preoperative and postoperative radiographs. The cumulative probability of TOA failure (progression to Tönnis grade 3 or conversion to total hip arthroplasty) was estimated using the Kaplan-Meier product-limited method. A multivariate Cox proportional hazards model was used to identify predictors of failure. Results. This study included 127 patients (137 hips). Median follow-up period was ten years (IQR 6 to 15). The median mHHS improved from 59 (IQR 52 to 70) preoperatively to 90 (IQR 73 to 96) at the latest follow-up (p < 0.001). The survival rate was 90% (95% CI 82 to 95) at ten years, decreasing to 21% (95% CI 7 to 48) at 20 years. Fair joint congruity on preoperative hip abduction radiographs and a decreased postoperative anterior wall index (AWI) were identified as independent risk factors for failure. The survival rate for the 42 hips with good preoperative joint congruity and a postoperative AWI ≥ 0.30 was 100% at ten years, and remained at 83% (95% CI 38 to 98) at 20 years. Conclusion. Although the overall clinical outcomes of TOA in patients with advanced osteoarthritis are suboptimal, favourable results can be achieved in selected cases with good preoperative joint congruity and adequate postoperative anterior acetabular coverage. Cite this article: Bone Joint J 2024;106-B(8):783–791

Aims. This study aimed to determine clinical outcomes; relationships between postoperative anterior, lateral, and posterior acetabular coverage and joint survival; and prognostic factors for joint survival after transposition osteotomy of the acetabulum (TOA). Methods. Data from 616 patients (800 hips) with hip dysplasia who underwent TOA between November 1998 and December 2019 were reviewed. The median follow-up period was 8.9 years (IQR 5 to 14). A medical notes review was conducted to collect demographic data, complications, and modified Harris Hip Score (mHHS). Radiological indicators of acetabular coverage included lateral centre-edge angle (LCEA), anterior wall index (AWI), and posterior wall index (PWI). The cumulative probability of TOA failure (progression to Tönnis grade 3 or conversion to total hip arthroplasty) was estimated using the Kaplan-Meier product-limited method. A multivariate Cox proportional hazards model was used to identify predictors for failure. Results. Median mHHS improved from 68 preoperatively to 96 at the latest follow-up (p < 0.001). The overall joint survival rate was 97% at ten years and 70% at 20 years. For the postoperative LCEA subgroups, survival in the deficient group was lower than that in the excessive (p = 0.006) and normal (p = 0.007) groups. For the postoperative AWI subgroups, survival in the deficient group was lower than that in the excessive (p = 0.015) and normal (p < 0.001) groups. Multivariate analysis identified age (p = 0.010), Tönnis grade 2 (p < 0.001), roundness index (p = 0.003), fair joint congruity (p = 0.004), and postoperative AWI (p = 0.002) as independent risk factors. Conclusion. Deficient postoperative AWI adversely affected joint survival after TOA, underscoring the importance of sufficient anterior acetabular coverage, along with precise surgical indications, to ensure successful hip joint preservation in the treatment of hip dysplasia. Cite this article: Bone Joint J 2024;106-B(12):1399–1407

Acetabulum fractures caused by civilian firearms represent a unique challenge for orthopaedic surgeons. Treatment strategies should include the assessment of infection risk due to frequently associated abdominal injuries and maintenance of joint function. Still, internationally accepted treatment algorithms are not available. The aim of the study was to increase knowledge about civilian gunshot fractures of the acetabulum by describing their characteristics and management at a high-volume tertiary hospital. All adult patients admitted to our hospital between January 2009 and December 2022 with civilian gunshot fractures of the acetabulum were included in this descriptive retrospective study. In total our institution treated 301 patients with civilian gunshot fractures of the hip joint and pelvis during the observation period, of which 54 involved the acetabulum. Most patients were young males (88,9%) with a mean age of 29 years. Thirty patients (55,6%) had associated intraabdominal or urological injuries. Fracture patterns were mostly stable fractures with minor joint destruction amenable to conservative fracture treatment (n=48, 88,9%). Orthopaedic surgical interventions were performed in 21 patients (38,9%) with removal of bullets in contact with the hip joint via arthrotomy or surgical hip dislocation as most frequent procedures. Most patients received antibiotics on admission (n=49, 90,7%). Fracture related infections of the acetabulum were noted in six patients (11,1%) while the mortality in the study population was low with one demised patient (1,9%) due to the trauma burden. Most civilian acetabulum gunshot fractures are associated with intraabdominal or urological injuries. In comparison to the literature on extremity gunshot fractures, there is an increased risk of infection in our study population. The decision for surgical wash-out and bullet removal should be based on contamination and anticipated joint destruction, while osteosynthesis or primary arthroplasty are rarely necessary for these injuries

Aims. Surgical approaches that claim to be minimally invasive, such as the direct anterior approach (DAA), are reported to have a clinical advantage, but are technically challenging and may create more injury to the soft-tissues during joint exposure. Our aim was to quantify the effect of soft-tissue releases on the joint torque and femoral mobility during joint exposure for hip resurfacing performed via the DAA. Methods. Nine fresh-frozen hip joints from five pelvis to mid-tibia cadaveric specimens were approached using the DAA. A custom fixture consisting of a six-axis force/torque sensor and motion sensor was attached to tibial diaphysis to measure manually applied torques and joint angles by the surgeon. Following dislocation, the torques generated to visualize the acetabulum and proximal femur were assessed after sequential release of the joint capsule and short external rotators. Results. Following initial exposure, the ischiofemoral ligament (7 to 8 o’clock) was the largest restrictor of exposure of the acetabulum, contributing to a mean 25% of overall external rotational restraint. The ischiofemoral ligament (10 to 12 o’clock) was the largest restrictor of exposure of the proximal femur, contributing to 25% of overall extension restraint. Releasing the short external rotators had minimal contribution in torque generated during joint exposure (≤ 5%). Conclusion. Adequate exposure of both proximal femur and acetabulum may be achieved with minimal torque by performing a full proximal circumferential capsulotomy while preserving short external rotators. The joint torque generated and exposure achieved is dependent on patient factors; therefore, some cases may necessitate further releases. Cite this article: Bone Joint J 2024;106-B(3 Supple A):59–66

Aims. Limb salvage for pelvic sarcomas involving the acetabulum is a major surgical challenge. There remains no consensus about what is the optimum type of reconstruction after resection of the tumour. The aim of this study was to evaluate the surgical outcomes in these patients according to the methods of periacetabular reconstruction. Methods. The study involved a consecutive series of 122 patients with a periacetabular bone sarcoma who underwent limb-salvage surgery involving a custom-made prosthesis in 65 (53%), an ice-cream cone prosthesis in 21 (17%), an extracorporeal irradiated autograft in 18 (15%), and nonskeletal reconstruction in 18 (15%). Results. The rates of major complications necessitating further surgery were 62%, 24%, 56%, and 17% for custom-made prostheses, ice-cream cone prostheses, irradiated autografts and nonskeletal reconstructions, respectively (p = 0.001). The ten-year cumulative incidence of failure of the reconstruction was 19%, 9%, 33%, and 0%, respectively. The major cause of failure was deep infection (11%), followed by local recurrence (6%). The mean functional Musculoskeletal Tumour Society (MSTS) scores were 59%, 74%, 64%, and 72%, respectively. The scores were significantly lower in patients with major complications than in those without complications (mean 52% (SD 20%) vs 74% (SD 19%); p < 0.001). For periacetabular resections involving the ilium, the mean score was the highest with custom-made prostheses (82% (SD 10%)) in patients without any major complication; however, nonskeletal reconstruction resulted in the highest mean scores (78% (SD 12%)) in patients who had major complications. For periacetabular resections not involving the ilium, significantly higher mean scores were obtained with ice-cream cone prostheses (79% (SD 17%); p = 0.031). Conclusion. Functional outcome following periacetabular reconstruction is closely associated with the occurrence of complications requiring further surgery. For tumours treated with periacetabular and iliac resection, skeletal reconstruction may result in the best outcomes in the absence of complications, whereas nonskeletal reconstruction is a reasonable option if the risk of complications is high. For tumours requiring periacetabular resection without the ilium, reconstruction using an ice-cream cone prosthesis supported by antibiotic-laden cement is a reliable option. Cite this article: Bone Joint J 2021;103-B(4):795–803

In late developmental dysplasia of the hip in childhood, the deformed dysplastic acetabulum is malaligned and has lost its shape due to pressure from the subluxed femoral head. The outer part of the acetabulum involves the upper part of the original acetabulum, thereby giving a bipartite appearance. A clear edge separates the outer from inner part which represents the lower part of the original acetabulum and has no direct contact with the femoral head. Combined pelvic osteotomy (CPO) using a Lance acetabuloplasty with either a Salter or a Pemberton procedure restores the original shape and realigns the acetabulum. A total of 20 children (22 hips), with a mean age of 46 months (28 to 94) at primary operation underwent CPO with follow-up for between 12 and 132 months. In each case concentric stable reduction with good acetabular cover was achieved and maintained throughout the period of follow-up

The bicompartmental acetabulum is one of the morphological changes which may be seen in children with Legg-Calvé-Perthes’ disease. Three-dimensional CT and MRI were used to analyse the detailed morphology of the acetabulum with special reference to its inner surface, in 16 patients with Perthes’ disease and a bicompartmental acetabulum. The bicompartmental appearance was seen on the coronal plane image through the acetabular fossa. The lunate surface was seen to grow laterally resulting in an increased mediolateral thickness of the triradiate cartilage. On the horizontal plane images, the acetabular fossa had deepened and had a distinct prominence at its posterior border. The combination of these morphological changes resulted in a bicompartmental appearance on plain radiography. Acetabular bicompartmentalisation appears to be the result of an imbalance of growth between the cartilage-covered lunate surface and the cartilage-devoid acetabular fossa

Aims. To clarify the mid-term results of transposition osteotomy of the acetabulum (TOA), a type of spherical periacetabular osteotomy, combined with structural allograft bone grafting for severe hip dysplasia. Methods. We reviewed patients with severe hip dysplasia, defined as Severin IVb or V (lateral centre-edge angle (LCEA) < 0°), who underwent TOA with a structural bone allograft between 1998 and 2019. A medical chart review was conducted to extract demographic data, complications related to the osteotomy, and modified Harris Hip Score (mHHS). Radiological parameters of hip dysplasia were measured on pre- and postoperative radiographs. The cumulative probability of TOA failure (progression to Tönnis grade 3 or conversion to total hip arthroplasty) was estimated using the Kaplan–Meier product-limited method, and a multivariate Cox proportional hazard model was used to identify predictors for failure. Results. A total of 64 patients (76 hips) were included in this study. The median follow-up period was ten years (interquartile range (IQR) five to 14). The median mHHS improved from 67 (IQR 56 to 80) preoperatively to 96 (IQR 85 to 97) at the latest follow-up (p < 0.001). The radiological parameters improved postoperatively (p < 0.001), with the resulting parameters falling within the normal range in 42% to 95% of hips. The survival rate was 95% at ten years and 80% at 15 years. Preoperative Tönnis grade 2 was an independent risk factor for TOA failure. Conclusion. Our findings suggest that TOA with structural bone allografting is a viable surgical option for correcting severely dysplastic acetabulum in adolescents and young adults without advanced osteoarthritis, with favourable mid-term outcomes. Cite this article: Bone Joint J 2023;105-B(7):743–750

Aims. The aim of this study was to compare the biomechanical models of two frequently used techniques for reconstructing severe acetabular defects with pelvic discontinuity in revision total hip arthroplasty (THA) – the Trabecular Metal Acetabular Revision System (TMARS) and custom triflange acetabular components (CTACs) – using virtual modelling. Methods. Pre- and postoperative CT scans from ten patients who underwent revision with the TMARS for a Paprosky IIIB acetabular defect with pelvic discontinuity were retrospectively collated. Computer models of a CTAC implant were designed from the preoperative CT scans of these patients. Computer models of the TMARS reconstruction were segmented from postoperative CT scans using a semi-automated method. The amount of bone removed, the implant-bone apposition that was achieved, and the restoration of the centre of rotation of the hip were compared between all the actual TMARS and the virtual CTAC implants. Results. The median amount of bone removed for TMARS reconstructions was significantly greater than for CTAC implants (9.07 cm. 3. (interquartile range (IQR) 5.86 to 21.42) vs 1.16 cm. 3. (IQR 0.42 to 3.53) (p = 0.004). There was no significant difference between the median overall implant-bone apposition between TMARS reconstructions and CTAC implants (54.8 cm. 2. (IQR 28.2 to 82.3) vs 56.6 cm. 2. (IQR 40.6 to 69.7) (p = 0.683). However, there was significantly more implant-bone apposition within the residual acetabulum (45.2 cm. 2. (IQR 28.2 to 72.4) vs 25.5 cm. 2. (IQR 12.8 to 44.1) (p = 0.001) and conversely significantly less apposition with the outer cortex of the pelvis for TMARS implants compared with CTAC reconstructions (0 cm. 2. (IQR 0 to 13.1) vs 23.2 cm. 2. (IQR 16.4 to 30.6) (p = 0.009). The mean centre of rotation of the hip of TMARS reconstructions differed by a mean of 11.1 mm (3 to 28) compared with CTAC implants. Conclusion. In using TMARS, more bone is removed, thus achieving more implant-bone apposition within the residual acetabular bone. In CTAC implants, the amount of bone removed is minimal, while the implant-bone apposition is more evenly distributed between the residual acetabulum and the outer cortex of the pelvis. The differences suggest that these implants used to treat pelvic discontinuity might achieve short- and long-term stability through different biomechanical mechanisms. Cite this article: Bone Joint J 2024;106-B(5 Supple B):74–81

Introduction. The success of total hip replacement (THR) is closely linked to the positioning of the acetabular component. Malalignment increases rates of dislocation, impingement, acetabular migration, pelvic osteolysis, leg length discrepancy and polyethylene wear. Many surgeons orientate the cup to inherent anatomy of the acetabulum. Detailed understanding of the anatomy and orientation of the acetabulum in arthritic hips is therefore very important. The aim of this study was to describe the anteversion and inclination of the inherent acetabulum in arthritic hips and to identify the number that fall out with the ‘safe zone’ of acetabular position described by Lewinnek et al. (anteversion 15°±10°; inclination 40°±10°). Materials and Methods. A series of 65 hips all with symptomatic osteoarthritis undergoing THR were investigated. Patients with dysplastic hips were excluded. All patients had a navigated THR as part of their normal clinical treatment. A commercially available non image based computer navigation system (Orthopilot BBraun Aesculap, Tuttlingen, Germany) was used. Anterior pelvic plane was registered using the two anterior superior iliac spines and pubic symphysis. Inner size of the empty acetabulum was sized with cup trials and appropriately size trial fixed with a computer tracker was then aligned in the orientation of the natural acetabulum as defined by the acetabular rim ignoring any osteophytes. The inclination and anteversion were calculated by the software. The acetabular inclination in all hips was also measured on pre-operative anteroposterior pelvic digital radiographs. Acetabular inclination was measured using as the angle between a line passing through the superior and inferior rim of the acetabulum and a line parallel to the pelvis as identified by the tear drops, using the method described by Atkinson et al. Results. All patients were Caucasian and had primary osteoarthritis. There were 29 males and 36 females. The average age was 68 years (SD 8). The inclination was 50.4(SD 7.4) and 58.8(SD 5.7) on navigation and radiographs respectively. The anteversion was 9.3(SD 10.3) on navigation. Anteversion for males was significantly lower than females with a mean difference of −5.5° (95% CI −10.5°, −0.5°) with a p value of 0.033. There was no significant difference with respect to inclination. Overall 69% of patients had a combined inclination and anteversion of the native acetabulum that fell outside the “safe zone” of Lewinnek. Conclusions. Inherent acetabular orientation in arthritic hips falls out with the safe zone defined by Lewinnek in 69% of cases. When using the natural acetabular orientation as a guide for positioning implants it should therefore not be assumed this will fall with in the safe zone although the validity of safe zones itself is questionable. Variation between patients must be taken into account. The difference between males and females, particularly in terms of anteversion, should also be considered

Background. CT-based navigation system in total hip arthroplasty(THA) is widely used to achieve accurate implant placement. The purpose of this study was to evaluate the influence of initial error correction according to the differences in the shape of the acetabulum, and correction accuracy associated with operation approach after localization of registration points at anterior or posterior area of the acetabulum. Methods. We set the anterior pelvic plane(APP) as the reference plane, and defined the coordinates as follows: X-axis for external direction, Y-axis for anterior direction, and Z-axis for proximal direction. APP is defined by the anterior superior iliac spines and anterior border of the pubic symphysis. We made a bone model of bilateral acetabular dysplasia of the hip, after rotational acetabulum osteotomy(RAO) on one side, and performed registration using infrared-reflective markers. At first, we registered the initial error on navigation system, and calculated the accuracy of the error correction based on each shape of the acetabulum as we increased the surface matching points. Based on the actual operation approach, we also examined the accuracy of the error correction when concentrating the matching points in anterior or posterior areas of the acetabulum. Results. For the rotational acetabular osteotomy model, the range of possible initial error correction increased as the surface matching points increased on both X-axis and Y-axis: On the X-axis, the range increased from 6mm to 10mm as the surface matching point increased from 10 to 20; and on the Y-axis, the range increased from 2mm to 10mm as the point increased 10 to 50. The range did not increase on the Z-axis. For the acetabular dysplasia model, the range of possible initial error correction increased on the X-axis(the range increased from 2mm to 8mm as the point increased from 10 to 50); however, no increase was observed for the Y- and Z-axis. Furthermore, concentrating the surface matching points in the posterior area around the acetabulum was more effective for the correction of the initial rotational error. Discussion. Because of the different anatomical shapes of the acetabulum, the error directions that were difficult to correct tended to vary between dysplasia and post-RAO. The error correction of Z-axis was difficult on both shapes of the acetabulum. Thus, the careful initial setting on Z-axis is important to minimize the error. Surface matching point on the posterior part of the acetabulum is more effective in correcting the initial rotational error compared with the anterior part of the acetabulum. It was shown that the difference in the error correction was affected by the localization of the registration points around the acetabulum. We presumed that using surface matching points on posterior area of the acetabulum improves the accuracy of the CT-based navigation system on the anterior approach. When using the system, it is important to understand the tendency that the shape of the acetabulum and the localization of the surface matching points have influence on correction of the initial error

The success of total hip replacement (THR) is closely linked to the positioning of the acetabular component. Malalignment increases rates of dislocation, impingement, acetabular migration, pelvic osteolysis, leg length discrepancy and polyethylene wear. Many surgeons orientate the cup in the same anteversion and inclination as the inherent anatomy of the acetabulum. The transverse acetabular ligament and acetabular rim can be used as a reference points for orientating the cup this way. Low rates of dislocation have been reported using this technique. Detailed understanding of the anatomy and orientation of the acetabulum in arthritic hips is therefore very important. The aim of this study was to describe the anteversion and inclination of the inherent acetabulum in arthritic hips and to identify the number that fall out with the ‘safe zone’ of acetabular position described by Lewinnek et al. (anteversion 15°±10°; inclination 40°±10°). A series of 65 hips, all with symptomatic osteoarthritis undergoing THR were investigated. Patients with developmental dysplastia of hip (DDH) were excluded. All patients had a navigated THR as part of their normal clinical treatment. A posterior approach to the hip was used. A commercially available non image based computer navigation system (Orthopilot BBraun Aesculap, Tuttlingen, Germany) was used. Rigid bodies (using active trackers) were attached to pelvis and femur. Anterior pelvic plane was registered using the two anterior superior iliac spines and pubic symphysis. The femoral head dislocated and removed and the labrum and soft tissue were excised to clear floor and rim of the acetabulum. Inner size of the empty acetabulum was sized with cup trials and appropriately size trial fixed with a computer tracker was then aligned in the orientation of the natural acetabulum as defined by the acetabular rim ignoring any osteophytes. The inclination and anteversion were calculated by the software. Surgery then proceeded with guidance of the computer navigation system. The computer software defines the anatomical values of orientation, to allow comparison with radiographs these were converted to radiological values as described by Murray et al. The acetabular inclination in all hips was also measured on pre-operative anteroposterior pelvic radiographs. This was done using digital radiographs analysed with the PACS system (Kodak, Carestream PACS Client, version 10.0). Acetabular inclination was measured using as the angle between a line passing through the superior and inferior rim of the acetabulum and a line parallel to the pelvis as identified by the tear drops, using the method described by Atkinson et al. All patients were Caucasian and had primary osteoarthritis. There were 29 males and 36 females. The average age was 68 years (SD 8). Mean anteversion was 9.3° (SD 10.3°). Anteversion for males was significantly lower than females with a mean difference of −5.5° (95%CI −10.5°,−0.5°) p = 0.033 but there was no significant difference in the number falling outside the “safe zone”. Mean inclination was 50.4° (SD 7.4°). There was no significant difference between males and females with respect to inclination angle or the number that fell outside the “safe zone”. Overall 69% of patients had a combined inclination and anteversion of the native acetabulum that fell outside the “safe zone” of Lewinnek. Mean acetabular inclination falls out with the ‘safe zone’. This trend has been seen in a recent study of arthritic hips using CT scans which found that the average angle of inclination in both males and females was greater than the upper limit of the safe zone. This study using CT also demonstrated a statistically significant 5.5° difference between males and females in terms of anteversion. This is the same as the figure we have found in our work. Inherent acetabular orientation in arthritic hips falls out with the safe zone defined by Lewinnek in 69% of cases. When using the natural acetabular orientation as a guide for positioning implants it should therefore not be assumed this will fall with in the safe zone although the validity of safe zones itself is questionable. Variation between patients must be taken into account and the difference between males and females, particularly in terms of anteversion, should also be considered

Although periacetabular osteotomies are widely used for the treatment of symptomatic acetabular dysplasia, the surgical outcomes after long term follow-up are still limited. Thus, we assessed hip survival and patient-reported outcomes (PROMs) at 20 years after the transposition osteotomy of acetabulum (TOA). Among 260 hips in 238 patients treated with TOA, 172 hips in 160 patients were evaluated at average 20.8 years, excluding patients who died or lost to follow-up. Kaplan-Meier analysis was used to assess survivorship with an end-point of THA. PROMs were evaluated using the VAS satisfaction, VAS pain, Oxford hip score (OHS), and Forgotten joint score (FJS). The thresholds of favorable outcomes of FJS and OHS were obtained using the receiver-operating characteristic curve with VAS satisfaction ≥ 50 and VAS pain < 20 as anchors. Thirty-three hips (19.2%) underwent THA at average 13.3 years after TOA. Kaplan-Meier analysis revealed hip survival rate at 20 years was 79.7%. Multivariate analysis showed the preoperative Tönnis grade significantly influenced hip survival. Survival rates with Tönnis grade 0, grade 1, and grade 2 were 93.3%, 86.7%, and 54.8% at 20 years, respectively. More than 60% of the patients showed favorable PROMs (VAS satisfaction ≥ 50, VAS pain < 20, OHS ≥ 42, FJS ≥ 51). Advanced Tönnis grade at the latest follow-up and higher BMI were significantly associated with unfavorable OHS, but not with other PROMs. This study demonstrated the durability of TOA for hips with Tönnis grade 0–1 and favorable satisfaction in majority of the patients at 20 years after surgery. Current presence of advanced osteoarthritis is associated with the lower hip function (OHS), but not necessarily associated with subjective pain and satisfaction. Higher BMI also showed a negative impact on postoperative function

Thirty-four patients were studied through the whole of the Perthes’ disease in Alder Hey Children’s Hospital, Liverpool. The acetabular changes included osteopaenia of the roof, irregularity of its contour, and decrease in the depth. These changes were proportional to the femoral head involvement. The purpose of the study was to know the effect of the morphological changes of the femoral head on the acetabulum and its outcome. Radioisotope scans of the hip were examined in fourteen children with unilateral Perthes’ disease and comparison was made with the contralateral hip. These scans showed increased uptake on the lateral part of the acetabulum and no uptake over the avascular part of the femoral head. Average follow-up was ten years and on an average children were followed up from six years to fifteen years of age. Six readings of the measurements of various dimensions of the acetabulum and the femoral head were done. CT scan also showed irregularity in the acetabulum. Statistical tests lead to the conclusion that the decrease in the depth of the acetabulum was secondary to the femoral head involvement and the extent of its dimensional changes affected the final congruity between the femoral head and the acetabulum. Also the remodelling potential of acetabulum decreases as the child grows older. Therefore containment procedures could be done by femoral osteotomy in younger children and acetabular osteotomy may benefit older children

The purpose of this study is to determine how the lateral shape of the acetabulum changes during Perthes disease and if there is any correlation between the lateral acetabulum shape and final result and type of treatment. The study population consisted of 243 patients with unilateral involvement who had reached skeletal maturity at last follow up. There were 35 (14.4%) female and 208 (85.6%) male patients. The mean age at the onset of symptoms was 7 years and 1 month. AP X-ray films were estimated during fragmentation, reossification and last follow up. Group A consisted of 56 hips, 126 hips were classified as group B and 61 hips as group C according to the Herring classification. For the lateral acetabular shape we proposed a classification: group A – a normal concave acetabular roof, group B – a horizontal flat roof and group C – a roof convexly rounded and up going. All hips were treated by containment methods (bed rest and traction in abduction-78 hips, Petri cast-31 hips, brace-94 hips, varus osteotomy-20 hips, Salter oste-otomy-12 hips and shelf arthroplasty-8 hips). The outcomes of treatment were evaluated according to the Stulberg classification. During fragmentation stage we found 78 (32.1%) hips with normal lateral acetabular shape-type A. Horizontal roof-type B was noted in 136 (56%) hips and in 29 (11.9%) type C was observed. We observed improvement in the shape of lateral acetabulum after treatment. At the last follow up there were 124 (51%) hips with type A, 81 (33.3%) with type B and 38 (15.7%) with type C. Statistical analysis revealed significant correlation between lateral acetabular shape and Stulberg classification. A normal concave acetabular roof at the fragmentation stage leaded mainly to Stulberg group 1and 2 whereas a roof convexly rounded and up going leaded to Stulberg group 3, 4 or 5 (p< 0.0001). Analysis showed no statistical significant correlation between treatment by using bed rest and traction in abduction, Petri cast, braces and development the lateral acetab-ular shape (p=0.09). Only treatment by using surgical methods improved the lateral acetabular shape at the last follow up (p=0.0015). The acetabulum is a mould for remodeling of the deformed femoral head in Perthes disease and the lateral acetabulum plays the most important role. We can expect that normal shape of the acetabulum gives good result at final follow up whereas a roof convexly rounded usually follows to Stulberg group 3, 4 or 5. Only surgical treatment improves the shape of the acetabulum

Purpose of the study: Reconstruction of the acetabulum is becoming increasingly necessary due to the longer life expectancy of patients with a total hip arthroplasty (THA); it can also be needed after trauma or resection of a bone tumour. Material and methods: For 39 cases, we used a bone bank acetabulum with variable size for simple reconstruction of a part of the acetabulum (n=6) or to replace the entire acetabulum (n=19) or even an entire hemi-pelvis (n=14) in patients with more or less extensive bone loss. For 18 cases, resection was necessary to remove a bone tumour (16 chondrosarcomas and two giant-cell tumours), in 19 cases the reconstruction was necessary after multiple operations, and in four others due to traumatic destruction. Results: Allograft integration was successful in nearly all patients (two cases of necrosis required a secondary prosthesis, 12.5%) and in two cases we noted immunological reactions with a serous effusion. There were no local infections. For osteocartilaginous acetabuli (n=7) the integration was quite satisfactory, certain patients have been followed for more than 26 years with no evidence of osteoarthritis. Discussion: Use of a well-established protocol for hypothermia and the absence of secondary sterilisation yields grafts with preserved mechanical properties. The use of cyropreserved osteocartilaginous allografts offers hip for good integration free from degenerative osteoarthritis

Aims. Accumulated evidence indicates that local cell origins may ingrain differences in the phenotypic activity of human osteoblasts. We hypothesized that these differences may also exist in osteoblasts harvested from the same bone type at periarticular sites, including those adjacent to the fixation sites for total joint implant components. Methods. Human osteoblasts were obtained from the acetabulum and femoral neck of seven patients undergoing total hip arthroplasty (THA) and from the femoral and tibial cuts of six patients undergoing total knee arthroplasty (TKA). Osteoblasts were extracted from the usually discarded bone via enzyme digestion, characterized by flow cytometry, and cultured to passage three before measurement of metabolic activity, collagen production, alkaline phosphatase (ALP) expression, and mineralization. Results. Osteoblasts from the acetabulum showed lower proliferation (p = 0.034), cumulative collagen release (p < 0.001), and ALP expression (p = 0.009), and produced less mineral (p = 0.006) than those from the femoral neck. Osteoblasts from the tibia produced significantly less collagen (p = 0.021) and showed lower ALP expression than those from the distal femur. Conclusion. We have demonstrated for the first time an anatomical regional variation in the biological behaviours of osteoblasts on either side of the hip and knee joint. The lower osteoblast proliferation, matrix production, and mineralization from the acetabulum compared to those from the proximal femur may be reflected in differences in bone formation and implant fixation at these sites. Cite this article: Bone Joint Res 2021;10(9):611–618

This is a retrospective case review of 237 patients with displaced fractures of the acetabulum presenting over a ten-year period, with a minimum follow-up of two years, who were studied to test the hypothesis that the time to surgery was predictive of radiological and functional outcome and varied with the pattern of fracture. Patients were divided into two groups based on the fracture pattern: elementary or associated. The time to surgery was analysed as both a continuous and a categorical variable. The primary outcome measures were the quality of reduction and functional outcome. Logistic regression analysis was used to test our hypothesis, while controlling for potential confounding variables. For elementary fractures, an increase in the time to surgery of one day reduced the odds of an excellent/good functional result by 15% (p = 0.001) and of an anatomical reduction by 18% (p = 0.0001). For associated fractures, the odds of obtaining an excellent/good result were reduced by 19% (p = 0.0001) and an anatomical reduction by 18% (p = 0.0001) per day. When time was measured as a categorical variable, an anatomical reduction was more likely if surgery was performed within 15 days (elementary) and five days (associated). An excellent/good functional outcome was more likely when surgery was performed within 15 days (elementary) and ten days (associated). The time to surgery is a significant predictor of radiological and functional outcome for both elementary and associated displaced fractures of the acetabulum. The organisation of regional trauma services must be capable of satisfying these time-dependent requirements to achieve optimal patient outcomes