We have studied the radiographic and CT features of 120 displaced intra-articular fractures of the calcaneum in order to define the pathological anatomy. In 96% of cases, the CT scans identified three main fragments: sustentacular, lateral joint and body. The sustentacular fragment was often rotated into varus, the lateral joint fragment into valgus and the body fragment impacted upwards, in varus and displaced laterally. The displacement of these fragments varied according to which of three fracture types was present, as defined by the composition of the fractured lateral wall of the calcaneum. In type 1 it was formed by the lateral joint fragment alone; in type 2 by both body and lateral joint fragments; and in type 3 by the body fragment alone. Fracture fragment displacement differs from that previously described, in that true uniform depression of the lateral joint fragment is rare

Biological fixation of cementless femoral implants requires primary stability by optimal fit in the proximal femur. The anatomy of the bone must then be known precisely. We analysed in vitro the accuracy of bone measurements of 32 femurs and compared the dimensions obtained from radiographs and CT scans with the true anatomical dimensions. Standard radiographs gave only a rough approximation of femoral geometry (mean difference: 2.4 +/- 1.4 mm) insufficiently accurate to allow selection of the best fitting prosthesis from a range of sizes and altogether inadequate to design a custom-made prosthesis. CT scans give greater accuracy (mean difference: 0.8 +/- 0.7 mm) in our experimental conditions, but in clinical practice additional sources of error exist

Aims

The objectives of this study were to assess the effect of anterior cruciate ligament (ACL) resection on flexion-extension gaps, mediolateral soft tissue laxity, maximum knee extension, and limb alignment during primary total knee arthroplasty (TKA).

Although much has been published on the causes of slipped upper femoral epiphysis and the results of treatment, little attention has been given to the mechanism of the slip. This study presents the results of the analysis of 13 adolescent femora, and the attempts to reproduce the radiological appearances of a typical slip. The mean age of the skeletons was 13 years (11 to 15). It was found that the internal bony architecture in the zone of the growth plate was such that a slip of the epiphysis on the metaphysis (in the normal meaning of the word slip) could not take place, largely relating to the presence of a tubercle of bone projecting down from the epiphysis. The only way that the appearance of a typical slipped upper femoral epiphysis could be reproduced was by rotating the epiphysis posteromedially on the metaphysis. The presence and size of this peg-like tubercle was shown radiologically by CT scanning in one pair of intact adolescent femurs

Sacral insufficiency fractures are not uncommon in elderly patients. We have diagnosed 20 cases in a five-year period, and have reviewed the clinical records, radiographs, CT and bone scans. We also assessed the degree of osteoporosis by measuring bone density using dual-energy X-ray absorptiometry and bone histomorphometry, and monitored the patients' functional outcome. Bone scans were positive in all 20 patients, CT showed a fracture or sclerosis in 7 of 12 patients and was useful in excluding malignancy. Plain radiographs were the least helpful, showing sclerosis in only 4 of the 20 patients. Involutional osteoporosis with a reduced bone formation rate was the most common underlying cause. Seventeen patients had complete resolution of pain within nine months, and no patient lost independence in daily activities. Increased awareness of these fractures may help to avoid unnecessary investigation and treatment. Bedrest and analgesia followed by rehabilitation provide good relief of symptoms

Over a nine-year period, 20 feet with persistently symptomatic talocalcaneal coalition were treated by resection of the bar. The 17 patients were all under 16 years of age. Excellent or good long-term results were achieved in the ten feet in which preoperative coronal CT had shown that the area of coalition measured 50% or less of the area of the posterior facet of the calcaneum. In these feet heel valgus was less than 16 degrees and there were no radiographic signs of arthritis of the posterior talocalcaneal joint. Talar beaking was present in 70% of these feet but it did not impair the clinical result. Fair or poor results were observed in the ten feet in which preoperative CT had shown the area of relative coalition to be greater than 50%. In these feet, heel valgus was greater than 16 degrees and most had narrowing of the posterior talocalcaneal joint and impingement of the lateral process of the talus on the calcaneum

We describe a case of lumbosacral plexopathy caused by an isolated aneurysm of the common iliac artery. The patient presented with worsening low back pain, progressive numbness and weakness of the right leg in the L2-L4 distribution. This had previously been diagnosed as sciatica. A CT scan showed an aneurysm of the right common iliac artery which measured 8 cm in diameter. Despite being listed for emergency endovascular stenting, the aneurysm ruptured and the patient died. It is important to distinguish a lumbosacral plexopathy from sciatica and to bear in mind its treatable causes which include aneurysms of the common and internal iliac arteries

We used MRI to examine the hips of 32 asymptomatic patients at 9 to 21 months after renal transplantation covered by high-dose corticosteroids. Five hips in three patients showed changes which indicate avascular necrosis, although radiographs, CT scans and isotope scans were normal. These patients had repeat MRI scans after another two years and three years. One patient with bilateral MRI changes developed symptoms and abnormal radiographs and CT and isotope scans in one hip nine months after the abnormal MRI. Intraosseous pressure was found to be raised in both hips, and core biopsies revealed necrotic bone on both sides. The other three hips have remained asymptomatic with unchanged MRI appearances three years after the initial MRI. It seems that idiopathic avascular necrosis does not always progress to bone collapse in the medium term

We carried out a morphometric analysis of acetabular dysplasia in patients with cerebral palsy requiring hip surgery using three-dimensional CT. We evaluated 54 hips in 27 patients. The contralateral normal hips of ten patients with unilateral Perthes’ disease were used as a control group. The acetabular defects were assessed qualitatively as anterior, posterior or global. Quantitative assessments were made using three-directional acetabular indices (anterosuperior, superolateral and posterosuperior) and measured by multiplanar reformation, from which we calculated the acetabular volume. In the qualitative study, posterior defects were most common in the subluxation group whereas global defects predominated in the dislocation group. In the quantitative study, all acetabular indices in both the subluxation and dislocation groups were higher than those in the control group and the superolateral indices showed a tendency to elevation in the dislocation group. The acetabular volume was largest in the control group, smallest in the dislocation group, and intermediate between the two in the subluxation group

Digital radiography is becoming widespread. Accurate pre-operative templating of digital images of the hip traditionally involves positioning a calibration object at its centre. This can be difficult and cause embarrassment. We have devised a method whereby a planar disc placed on the radiographic cassette accounts for the expected magnification. Initial examination of 50 pelvic CT scans showed a mean hip centre distance of 117 mm (79 to 142) above the gluteal skin. Further calculations predicted that a disc of 37.17 mm diameter, placed on the cassette, would appear identical to a 30 mm sphere placed at the level of the centre of the hip as requested by our templating software. We assessed accuracy and reproducibility by ‘reverse calibration’ of 20 radiographs taken three months after hip replacement using simultaneous sphere and disc methods, and a further 20 with a precision disc of accurate size. Even when variations in patient size were ignored, the disc proved more accurate and reliable than the sphere. The technique is reliable, robust, cost effective and acceptable to patients and radiographers. It can easily be used in any radiography department after a few simple calculations and manufacture of appropriately-sized discs

Specific radiological features identified by Brandser and Marsh were selected for the analysis of acetabular fractures according to the classification of Letournel and Judet. The method employs a binary approach that requires the observer to allocate each radiological feature to one of two groups. The inter- and intra-observer variances were assessed. The presence of articular displacement, marginal impaction, incongruity, intra-articular fragments and osteochondral injuries to the femoral head were analysed by a similar method. These factors were termed ‘modifiers’ and are generally considered when planning operative intervention and, critically, they may influence prognosis. Six observers independently assessed 30 sets of plain radiographs and CT scans on two separate occasions, 12 weeks apart. They were asked to determine the presence or absence of specific radiological features. This simple binary approach to classification yields an inter- and intra-observer agreement which ranges from moderate to near-perfect (κ = 0.49 to 0.88 and κ = 0.57 to 0.88, respectively). A similar approach to the modifiers yields only slight to fair inter-observer agreement (κ = 0.20 to 0.34) and slight to moderate intra-observer agreement (κ = 0 to 0.55)

Aims

Second-generation metal-on-metal (MoM) articulations in total hip arthroplasty (THA) were introduced in order to reduce wear-related complications. The current study reports on the serum cobalt levels and the clinical outcome at a minimum of 20 years following THA with a MoM (Metasul) or a ceramic-on-polyethylene (CoP) bearing.

We released the infraspinatus tendons of six sheep, allowed retraction of the musculotendinous unit over a period of 40 weeks and then performed a repair. We studied retraction of the musculotendinous unit 35 weeks later using CT, MRI and macroscopic dissection. The tendon was retracted by a mean of 4.7 cm (3.8 to 5.1) 40 weeks after release and remained at a mean of 4.2 cm (3.3 to 4.7) 35 weeks after the repair. Retraction of the muscle was only a mean of 2.7 cm (2.0 to 3.3) and 1.7 cm (1.1 to 2.2) respectively at these two points. Thus, the musculotendinous junction had shifted distally by a mean of 2.5 cm (2.0 to 2.8) relative to the tendon. Sheep muscle showed an ability to compensate for approximately 60% of the tendon retraction in a hitherto unknown fashion. Such retraction may not be a quantitatively reliable indicator of retraction of the muscle and may overestimate the need for elongation of the musculotendinous unit during repair

We report 17 patients (20 hips) in whom metal-on-metal resurfacing had been performed and who presented with various symptoms and a soft-tissue mass which we termed a pseudotumour. Each patient underwent plain radiography and in some, CT, MRI and ultrasonography were also performed. In addition, histological examination of available samples was undertaken. All the patients were women and their presentation was variable. The most common symptom was discomfort in the region of the hip. Other symptoms included spontaneous dislocation, nerve palsy, a noticeable mass or a rash. The common histological features were extensive necrosis and lymphocytic infiltration. To date, 13 of the 20 hips have required revision to a conventional hip replacement. Two are awaiting revision. We estimate that approximately 1% of patients who have a metal-on-metal resurfacing develop a pseudotumour within five years. The cause is unknown and is probably multifactorial. There may be a toxic reaction to an excess of particulate metal wear debris or a hypersensitivity reaction to a normal amount of metal debris. We are concerned that with time the incidence of these pseudotumours may increase. Further investigation is required to define their cause

We reviewed 15 consecutive patients, 11 women and four men, with a mean age of 48.7 years (37.3 to 62.6), who between July 2004 and August 2007 had undergone percutaneous sacroiliac fusion using hollow modular anchorage screws filled with demineralised bone matrix. Each patient was carefully assessed to exclude other conditions and underwent pre-operative CT and MR scans. The diagnosis of symptomatic sacroiliac disease was confirmed by an injection of local anaesthetic and steroid under image intensifier control. The short form-36 questionnaire and Majeed’s scoring system were used for pre- and post-operative functional evaluation. Post-operative radiological evaluation was performed using plain radiographs. Intra-operative blood loss was minimal and there were no post-operative clinical or radiological complications. The mean follow-up was for 17 months (9 to 39). The mean short form-36 scores improved from 37 (23 to 51) to 80 (67 to 92) for physical function and from 53 (34 to 73) to 86 (70 to 98) for general health (p = 0.037). The mean Majeed’s score improved from 37 (18 to 54) pre-operatively to 79 (63 to 96) post-operatively (p = 0.014). There were 13 good to excellent results. The remaining two patients improved in short form-36 from a mean of 29 (26 to 35) to 48 (44 to 52). Their persistent pain was probably due to concurrent lumbar pathology. We conclude that percutaneous hollow modular anchorage screws are a satisfactory method of achieving sacroiliac fusion

We performed CT to investigate how treatment may modify the basic skeletal pathology of congenital club foot. Two homogenous groups of patients treated by one of the authors (EI) or under his supervision were studied. The first included 32 patients with 47 club feet reviewed at a mean age of 25 years and treated by manipulation, application of toe-to-groin plaster casts and an extensive posteromedial release. The second included 32 patients with 49 club feet reviewed at a mean age of 19 years and treated by the Ponseti manipulation technique, application of toe-to-groin plaster casts and a limited posterior release. At follow-up the shape of the subtalar, talonavicular and calcaneocuboid joints was found to be altered in many feet in both groups. This did not appear to be influenced significantly by the type of treatment performed. Correction of the heel varus and the increased declination angle of the neck of the talus was better in the club feet of the second group, whereas reduction of the medial subluxation of the navicular was better in the first. There was a marked increase in the external ankle torsion angle in the first group and a moderate increase of this angle in the second group, in which medial subluxation of the cuboid on the anterior apophysis of the calcaneum was always corrected. Equinus was corrected in both groups but three-dimensional CT reconstruction of the whole foot showed that cavus, supination and adduction deformities were corrected much better in the second group

Three-dimensional surface models of the normal hemipelvis derived from volumetric CT data on 42 patients were used to determine the radius, depth and orientation of the native acetabulum. A sphere fitted to the lunate surface and a plane matched to the acetabular rim were used to calculate the radius, depth and anatomical orientation of the acetabulum. For the 22 females the mean acetabular abduction, anteversion, radius and normalised depth were 57.1° (50.7° to 66.8°), 24.1° (14.0° to 33.3°), 25 mm (21.7 to 30.3) and 0.79 mm (0.56 to 1.04), respectively. The same parameters for the 20 males were 55.5° (47.7° to 65.9°), 19.3° (8.5° to 32.3°), 26.7 mm (24.5 to 28.7) and 0.85 mm (0.65 to 0.99), respectively. The orientation of the native acetabulum did not match the safe zone for acetabular component placement described by Lewinnek. During total hip replacement surgeons should be aware that the average abduction angle of the native acetabulum exceeds that of the safe zone angle. If the concept of the safe zone angle is followed, abduction of the acetabular component should be less than the abduction of the native acetabulum by approximately 10°

The rotational alignment of the tibia is an unresolved issue in knee replacement. A poor functional outcome may be due to malrotation of the tibial component. Our aim was to find a reliable method for positioning the tibial component in knee replacement. CT scans of 19 knees were reconstructed in three dimensions and orientated vertically. An axial plane was identified 20 mm below the tibial spines. The centre of each tibial condyle was calculated from ten points taken round the condylar cortex. The tibial tubercle centre was also generated as the centre of the circle which best fitted eight points on the outside of the tubercle in an axial plane at the level of its most prominent point. The derived points were identified by three observers with errors of 0.6 mm to 1 mm. The medial and lateral tibial centres were constant features (radius 24 mm (. sd. 3), and 22 mm (. sd. 3), respectively). An anatomical axis was created perpendicular to the line joining these two points. The tubercle centre was found to be 20 mm (. sd. 7) lateral to the centre of the medial tibial condyle. Compared with this axis, an axis perpendicular to the posterior condylar axis was internally rotated by 6° (. sd. 3). An axis based on the tibial tubercle and the tibial spines was also internally rotated by 5° (. sd. 10). Alignment of the knee when based on this anatomical axis was more reliable than either the posterior surfaces or any axis involving the tubercle which was the least reliable landmark in the region

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