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

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

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

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

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. Modular dual mobility (DM) prostheses in which a cobalt-chromium liner is inserted into a titanium acetabular shell (vs a monoblock acetabular component) have the advantage of allowing supplementary screw fixation, but the potential for corrosion between the liner and acetabulum has raised concerns. While DM prostheses have shown improved stability in patients deemed ‘high-risk’ for dislocation undergoing total hip arthroplasty (THA), their performance in young, active patients has not been reported. This study’s purpose was to assess clinical outcomes, metal ion levels, and periprosthetic femoral bone mineral density (BMD) in young, active patients receiving a modular DM acetabulum and recently introduced titanium, proximally coated, tapered femoral stem design. Patients and Methods. This was a prospective study of patients between 18 and 65 years of age, with a body mass index (BMI) < 35 kg/m. 2. and University of California at Los Angeles (UCLA) activity score > 6, who received a modular cobalt-chromium acetabular liner, highly crosslinked polyethylene mobile bearing, and cementless titanium femoral stem for their primary THA. Patients with a history of renal disease and metal hardware elsewhere in the body were excluded. A total of 43 patients (30 male, 13 female; mean age 52.6 years (. sd. 6.5)) were enrolled. All patients had a minimum of two years’ clinical follow-up. Patient-reported outcome measures, whole blood metal ion levels (ug/l), and periprosthetic femoral BMD were measured at baseline, as well as at one and two years postoperatively. Power analysis indicated 40 patients necessary to demonstrate a five-fold increase in cobalt levels from baseline (alpha = 0.05, beta = 0.80). A mixed model with repeated measures was used for statistical analysis. Results. Mean Harris Hip Scores improved from 54.1 (. sd. 20.5) to 91.2 (. sd. 10.8) at two years postoperatively (p < 0.001). All patients had radiologically well-fixed components, no patients experienced any instability, and no patients required any further intervention. Mean cobalt levels increased from 0.065 ug/l (. sd. 0.03) preoperatively to 0.30 ug/l (. sd. 0.51) at one year postoperatively (p = 0.01) but decreased at two years postoperatively to 0.16 ug/l (. sd. 0.23; p = 0.2). Four patients (9.3%) had a cobalt level outside the reference range (0.03 ug/l to 0.29 ug/l) at two years postoperatively, with values from 0.32 ug/l to 0.94 ug/l. The mean femoral BMD ratio was maintained in Gruen zones 2 to 7 at both one and two years postoperatively using this stem design. At two years postoperatively, mean BMD in the medial calcar was 101.5% of the baseline value. Conclusion. Use of a modular DM prosthesis and cementless, tapered femoral stem has shown encouraging results in young, active patients undergoing primary THA. Elevation in mean cobalt levels and the presence of four patients outside the reference range at two years postoperatively demonstrates the necessity of continued surveillance in this cohort. Cite this article: Bone Joint J 2019;101-B:365–371

Purpose: Coxa magna is well known in Perthes’ disease but a quantitative evaluation of the early, in particular cartilaginous, enlargement of the femoral head and the necessary adaptive changes of the acetabulum (widening and/or growth) does not exist. We would like to present MR-based volumetric data. Methods: We measured the volume of the femoral head and the acetabulum in MRI by means of a software established for the sizing of tumours before therapy and the determination of liver lobe volume prior to transplantation. We evaluated MRI exams in 47 children with Perthes’ disease and 72 normal children from 4 to 9 years and present data of the affected hip in comparison to the unaffected hip and to normal hips. Results:. Femoral head:. On the average the affected head had a volume that was 47% (range 42 – 57%) larger than on the unaffected side and 44 % (range 13 – 59%) larger than in hips of healthy children. Cases with serial exams showed that the volume of the affected head increased in the course of time. Acetabulum:. On the average the acetabular volume was 21% (range 13 to 30%) larger on the affected side than on the unaffected side and 20% (range 10 to 29%) larger than in healthy children. In patients who underwent surgery (pelvic osteotomy, alone or together with intertrochanteric varus osteotomy) the acetabular volume was 24% larger (range 9 – 33%) on the affected side than on the unaffected side. In patients without surgery the acetabular volume was 16% larger (range 10 to 33%) on the affected side. Conclusions:. We found that Perthes’ disease is associated with an average increase of femoral head volume of 47% in comparison to the unaffected side and of 44% in comparison to healthy children. There was an average increase of the acetabular volume of 21% in comparison to the unaffected side and of 20% in comparison to healthy children. These data may allow a better understanding of the disease and a reappraisal of current forms of treatment. Significance: Given a chronic disproportion between the size of the femoral head and the acetabulum therapy should aim at:. Retardation of the (cartilaginous) enlargement of the femoral head. Promotion of widening or growth of the acetabulum. We believe that current conservative modes of treatment are effective through rationale A and B. Operative modalities, in particular pelvic osteotomies and/or intertrochanteric varus osteotomy, seem to be mainly effective through rationale B. By reorientation of the acetabulum and/or the proximal femur they should favour a better distribution of forces through the hip joint allowing for a gradual widening of the acetabulum. In addition, the operative trauma in the vicinity of the triradiate cartilage may have a stimulating effect on acetabular growth

Introduction. Success of total hip replacement (THR) is closely linked to positioning of the acetabular component. Malalignment increases complication rates. Our aim was to describe the anteversion and inclination of the inherent acetabulum in arthritic hips and identify the number that fall out with the ‘safe zone’ of acetabular position described by Lewinnek et al. (anteversion 15±10 degrees; inclination 40±10 degrees). Materials/Methods. A series of 65 hips undergoing non-image based computer navigated THR for Osteoarthritis were investigated. Anteversion and inclination was measured with the help of cup trials fixed with computer trackers aligned in orientation of the natural acetabulum. The acetabular inclination in all hips was measured on pre-operative digital radiographs. Results. There were 29 males and 36 females with average age of 68 years. Anteversion of males was significantly lower than females with a mean difference of −5.5 degrees (95% CI-10.5–0.5 degrees) with p value of 0.033. There was no significant difference with respect to inclination. Overall 69 % of patients had a combined inclination and anteversion that fell outside the ‘safe zone’. Conclusion. Mean acetabular inclination falls outwith the ‘safe zone’ but mean anteversion falls within. The inherent acetabular anatomy of arthritic hips varies widely. Females have significantly more anteversion. Care should be taken when using inherent anatomy of acetabulum as a guide when doing a THR

A secure bone/cement interface at the bone cement junction is an important requirement for the long-term success in the cemented hip arthroplasty. Cementing techniques have evolved and now involve pressurisation of the acetabulum and femur. It can be difficult to get a complete rim seal and hence adequate pressurisation due to the unique anatomy of the acetabulum and the contyloid notch. Several acetabular pressurisers are commercially available. We have developed an instrument for controlled and reproducible cement pressurisation in the acetabulum before socket insertion. It is a T-bar incorporating a central plunger, which protrudes from an outer sleeve when force is applied. The protrusion of the central plunger and hence the amount of force applied can be limited by a stop-sleeve. A laboratory saw bone model was designed to assess this system and compare it with two existing pressurisers. A polypropylene model of the acetabulum was used. Included in the model were two 1.3mm diameter capillary outlets, one at its pole and one at a point close to its rim opposite the cotyloid notch. Water was free to flow through the capillaries at a pressure of 13.5” WG to represent blood flow. 5 test per pressuriser were performed. CMW 1 Gentamicin bone cement was mixed as per manufacturers instruction in a Vacuum Mix system. The cement was then pressurised using one of three systems; the Depuy T handle pressuriser, the Exeter pressuriser and our new instrument. The cement mantle produced with the Depuy T-handle and the Exeter pressuriser was thicker at the pole than the rim and the cement intrusion was not consistent nor reproducible. The new pressurizer produced a cement mantle equal at the pole and the rim to within 1mm. A reproducible cement mantle compatible to the shape of the socket and with cement intrusion of 5mm (+/− 1mm) could be achieved. We recommend the use of this pressuriser

Various assumptions must be made during total hip replacement when placing the acetabular component within the reamed acetabulum with regards to its orientation. Various methods have been described for different acetabular components, some relying on knowledge of the existing anatomy and some relying on the use of jigs to align the component. Many of these assumptions are based on opinion rather than science and the current study was designed to define the position of the acetabulum in relation to a fixed position of the pelvis. A neutral position of the pelvis must be defined and this is represented by having a line from the anterior superior iliac spine to the pubis fixed in the coronal plane and taking measurements of the perpendicular axis of the pelvis taken from this. A variety of measurements were made using measurement techniques and the conclusion was reached that the average angle for operative inclination is 43 degrees ± 5 degrees and the average angle for operative anteversion is 29 degrees ± 8 degrees. These figures should give a preliminary guide to the correct placement of the acetabular socket in total hip replacement although other factors may need to be taken into account

Purpose: The distribution of weight bearing area within the acetabulum is of importance in addressing trauma to the acetabulum, hip joint deformities and causes of osteoarthritis. According to Wolf’s law, bone density can indicate loading patterns experienced. The objective of this study was to characterize distributions of acetabular bone density patterns by regions in the normal population. Method: CT scans of 22 subjects, mean age 70.6 with no evidence to hip joint pathologies were analysed. Bone density distribution maps were generated within AmiraDEV4.1 image analysis software using custom written plugins (Visage Imaging, Carlsbad, USA). Acetabular cup surfaces were semi-automatically segmented from the reconstructed CT volumes with an atlas-based approach. The acetabular cups were expanded 2.5 mm into the acetabular bone, and surface bone densities were calculated as the average bone density within ±2.5mm. The distribution maps were analysed using zones to spatially classify areas of high and low bone density in a healthy population. The acetabular cups were aligned using the acetabular rim plane that was landmarked, and by rotating the cups, such that a 900 abduction angle and a 00 anteversion angle were achieved. The grid used was divided to quadrants, and subdivided into radial thirds of the average rim radius. The correspondence of left and right density maps was investigated by comparing the average bone density in corresponding zones and across the population. Results: High bone densities were found around the roof of the acetabulum aligning with the femoral mechanical axis during standing. The highest average bone density were found to be the superior and posterior walls of the acetabulum, corresponding to regions 8, 9, and 12 compared to other regions of the acetabuli (P< 0.01). A strong correlation was found between left and right sides within subjects (R=0.91, P< 0.05); and weaker correlation was also found for overall average bone density, (R=0.77, P< 0.05). Conclusion: The location of the zones with the highest average bone density agrees with cadaveral studies of the maximum contact stress in the acetabulum (zones 9 and 12). [1,2]. It may explain why trauma to these areas carries a higher risk for early arthritic changes

The JRI cemented total hip replacement consisted of an acetabulum with a gamma irradiated UHMW polyethylene cup encased in a titanium metal shell, a 32 mm titanium head, and forged titanium alloy stem. Revision of this implant for failure, in particular that of the acetabulum, and the lack of published survivorship prompted a retrospective review of the local series. Data was compiled from theatre log books, patient records and X-rays. During the period 1989–1997 a single surgeon performed 304 total hip replacements using this JRI prosthesis through an anterior lateral approach. The average age was 70 (48–96), with 186 (61%) female and 85% performed for osteoarthritis. Complete data was available in 236 cases to allow further analysis. The average follow up was 9.3 (1–17) years. During this period 37 hips had to be revised: 28 for a loose acetabulum, both components were loose in 5, and 3 had revision for infection. The mean time to revision was 7.4 (1–17) years. This data provides a revision rate of at least 16% at ten years. This data does not take potential earlier radiographic failure nor patient function into account. This prosthesis therefore fails to comply with modern benchmarks for survivorship of implants. Furthermore this study highlights the importance of ongoing review of patients who have undergone joint replacement, in particular those with implants that have problems with design, as has been demonstrated in other metal backed components

Fracture of the acetabulum can lead to degenerative arthritis of the hip, avascular necrosis of the femoral head, or both. Total hip arthroplasty is a common form of surgical treatment when significant joint changes and pain are present. Ten patients with fracture acetabulum were treated in this study using metal on metal total hip arthoplasty. The initial fracture was posterior wall fracture in one patient, posterior column fracture in one patient, transverse fracture in 2 patients, fracture dislocation in 3 patients and fracture posterior wall and column in 3 patients. The indications of arthroplasty were secondry osteoarthritis after internal fixation or after conservative management or collapse of the femoral head. Arthroplasty was done after an average period of 1.8 years (range from 1 to 4 years). After a follow up period ranged from 3 to 7 years with a mean of 4.6 years, the Harris hip score was improved from a mean of 51 (range 20 to 65) to a mean of 92.5 (range 90 to 95). Infection occurred in one case and two stages revision was done. Another case developed loosening of the acetabular component and was revised using cementless cup fixed with screws and bone graft. Metal on metal THR after acetabular fracture are relatively uncomplicated and lead to a good outcome despite the difficulties faced during the procedure

As our understanding of hip function and disease improves, it is evident that the acetabular fossa has received little attention, despite it comprising over half of the acetabulum’s surface area and showing the first signs of degeneration. The fossa’s function is expected to be more than augmenting static stability with the ligamentum teres and being a templating landmark in arthroplasty. Indeed, the fossa, which is almost mature at 16 weeks of intrauterine development, plays a key role in hip development, enabling its nutrition through vascularization and synovial fluid, as well as the influx of chondrogenic stem/progenitor cells that build articular cartilage. The pulvinar, a fibrofatty tissue in the fossa, has the same developmental origin as the synovium and articular cartilage and is a biologically active area. Its unique anatomy allows for homogeneous distribution of the axial loads into the joint. It is composed of intra-articular adipose tissue (IAAT), which has adipocytes, fibroblasts, leucocytes, and abundant mast cells, which participate in the inflammatory cascade after an insult to the joint. Hence, the fossa and pulvinar should be considered in decision-making and surgical outcomes in hip preservation surgery, not only for their size, shape, and extent, but also for their biological capacity as a source of cytokines, immune cells, and chondrogenic stem cells. Cite this article: Bone Joint Res 2020;9(12):857–869

The effects of NF-I on the hip have been underreported in literature. The bony changes in the hip can be mild to severe and are often present, but not diagnosed. Dislocation of the hip has been described but protrusio acetabulum is underdiagnosed and has only been reported from one institute. This is the first case where an open biopsy has been taken from the hip joint by surgical dislocation with preservation of the blood supply to the femoral head. Gross and microscopic pathology in the neurofibromatosis of the hip has been described for the first time in our report. A 16-year-old girl presented with history of pain, limp and stiffness in the right hip for several years. Radiographs, CT scan showed severe protrusio acetabulum. Histological analysis from the tissue taken from the hip was a neurofibroma. There was very minimal hyaline cartilage in the acetabulum at operation. Therefore the floor of the acetabulum was grafted with the autologous cancellous bone chips obtained from her greater trochanter. The aim of this was to lateralize the hip center to a normal position. At six months follow up she was doing well. Her range of movements had increased by 20%

Previous work has demonstrated vulnerability of the femoral nerve to damage by anterior acetabular retractors during THA. The aim of this study was to quantify the proximity of the femoral nerve to the anterior acetabulum, on cadaveric material and MRI studies. A standard posterior approach to the hip was carried out in 6 fresh frozen cadaveric hemipelves. Following dislocation and removal of the femoral head, measurements were taken from the anterior acetabular lip to the posterior aspect of the femoral nerve as it passed over this point. 14 MRI studies of the hip were obtained from the local PACS database (7 male, 7 female; mean age 58 (range 32–80)). T1 weighted axial scans were reviewed. Measurements were obtained from the anterior acetabular lip to the posterior surface of the femoral nerve and artery, and the cross-sectional area of iliopsoas was calculated. There was no significant difference between the mean distances to the femoral nerve in the cadaveric (24 mm) and MRI groups (25.3mm) (p=0.7). On MRI images, the distance between the acetabular wall and both the femoral artery (p=0.003) and femoral nerve (p=0.007) was significantly larger in men. The femoral artery is strikingly close to the acetabulum in females, passing a mean distance of 14.8 mm, whereas in males this was 23.9 mm. The mean femoral nerve distance was 28.7 mm in males and 21.9 mm in females. The cross-sectional area of iliopsoas was significantly smaller in women (5.97 cm. 2. compared to 11.37 cm. 2. , p<0.001). Both the femoral artery and nerve run in close proximity to the anterior acetabular lip. Care should be taken when placing instruments in this area to avoid neurovascular injury. The increased incidence of femoral nerve damage in women following THA may be due to the significantly smaller bulk of iliopsoas

Purpose: The surgical approach is an essential element for precise reduction and rigid fixation of fractures of the acetabulum. In cases where the anterior column is mainly involved and total hip arthroplasty (THA) is indicated, classical approaches do not allow double assess to the anterior column necessary for reduction and fixation and to the femoral canal for insertion of the prosthesis. Combining Heuter’s anterior approach and Letournel’s ilio-femoral approach provides access to the anterior column and to the often associated posterior hemi-transverse fracture, while allowing insertion of the total hip prosthesis. Material and method: This combined approach was used for ten among 60 THA performed for fracture of the acetabulum. Seven were primary procedures and three were differed reconstruction procedures. Mean patient age was 60.6 years (range 50 – 85 years). Fracture types were: acetabular wall and anterior column (n=8), anterior column and posterior hemi-transverse (n=2). All fresh fractures exhibited major acetabular damage associated with fracture of the femoral neck. A hybrid THA was used for all cases after fixation of the fracture. The femoral heads were used as graft material for deficient anterior columns in two patients and as “piecemeal” grafts for the others. Results: Mean follow-up was 36 months (range 24–35 months). At last follow-up all fractures had healed and all acetabular components exhibited solid fixation with no sign of migration. The mean outer diameter of the ace-tabular components inserted was 56 mm (52–64) using a 2 mm press-fit and one screw. The only complication was one postoperative anterior dislocation. Pain relief and function were satisfactory in all patients at last follow-up with a Postel Merle d’Aubigné score of 16 (13–18). Discussion: This anterior surgical approach enables good access to the acetabular walls and anterior columns, allowing solid fixation and relatively easy THA. The Kocher-Langenbech approach is still better in case of posterior deficiency or when posterior fixation requires space for inserting an acetabular component. We reserve it for THA used to treat fresh fractures of the acetabulum with major damage to the acetabulum and/or the femoral head, with or without neck fracture in patients aged 55 years or more. For differed reconstruction, we also use this approach if the acetabular damage involves the anterior column