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Biomechanical evaluation of fixation of posterior acetabular wall fractures.

Reproducible fractures of the posterior wall of the acetabulum were created in 10 paired hemipelves from fresh human cadavers. Under anterior-to-posterior loading by a Materials Testing System machine, the load to failure of fixation of the acetabular fractures treated with steel pelvic reconstruction plates and steel screws was significantly higher than that of fixation with titanium ribbons and titanium screws. Forces as little as 725 newtons applied directly to the fragment caused fixation failure; even the most secure form of fixation failed when a relatively small force of 2,123 newtons was applied. These results emphasize the importance of appropriate postoperative measures, such as limitation of hip flexion and restricted weightbearing, to minimize the force directed against the posterior wall until the fracture has healed. Secure fixation of fractures of the posterior wall of the acetabulum is critical, since loss of fixation results in instability and joint incongruity, which limit the options for reconstruction.

Acetabulum↗

Total hip replacement combined with bone grafting for acetabular dysplasia causing severe osteoarthritis of the hip joint.

Over a 10 year period 18 total hip joint arthroplasties (THJA) were performed on 15 patients with disabling osteoarthritis of the hip joint secondary to congenital dislocation or subluxation. In all cases reconstruction of the deficient acetabulum was necessary in order to provide total bony containment of the acetabular prosthesis. This was achieved using a bone graft, fashioned from the femoral head and securing it above the true acetabulum. At follow-up all patients were pain free. Radiographically, there had been no loosening of the acetabular prosthesis and all grafts appear to have united. The operative technique is described in detail.

Acetabulum↗

Chondrocyte apoptosis in response to dislocation of the hip in the rat model.

BACKGROUND: Joint dislocation is a traumatic event that can lead to osteoarthritis. The purpose of this paper is to study cartilage changes following prolonged joint dislocation for 1, 2 or 8 h. METHODS: Sprague-Dawley rats (n = 27) were used in this study. Surgical dislocation of the hip under anaesthesia was carried out on the animals. The joints remained dislocated for 1, 2 or 8 h. The joints were subsequently harvested and terminal deoxnucleotidyl transferase-mediated dUTP nick-end labelling testing was carried out to show chondrocyte apoptosis in the femoral head and acetabulum. Using this test, the apoptotic index, which is the proportion of apoptotic chondrocytes to total number of chondrocytes, was calculated. A comparison of apoptotic indices was made among the three groups. RESULTS: The mean apoptotic indices for the femoral head for the 1-, 2- and 8-h groups were 0.065 +/- 0.025, 0.162 +/- 0.031 and 0.201 +/- 0.030, respectively. There was a significant difference (P < 0.05) in the mean apoptotic indices between each of the three groups. For the acetabulum, the mean apoptotic indices were 0.046 +/- 0.012, 0.051 +/- 0.023 and 0.057 +/- 0.031 for the 1-, 2- and 8-h groups, respectively. There was no significant difference (P > 0.05) between each of the three groups. CONCLUSIONS: Dislocation of a joint causes chondrocyte apoptosis. There is a progressive increase in the apoptotic index with prolonged dislocation of the rat hip.

Acetabulum↗

Three-dimensional study of pelvic asymmetry on anatomical specimens and its clinical perspectives.

The aim of this study was to assess pelvic asymmetry (i.e. to determine whether the right iliac bone and the right part of the sacrum are mirror images of the left), both quantitatively and qualitatively, using three-dimensional measurements. Pelvic symmetry was described osteologically using a common reference coordinate system for a large sample of pelvises. Landmarks were established on 12 anatomical specimens with an electromagnetic Fastrak system. Seventy-one paired variables were tested with a paired t-test and a non-parametric test (Wilcoxon). A Pearson correlation matrix between the right and left values of the same variable was applied exclusively to values that were significantly asymmetric in order to calculate a dimensionless asymmetry index, ABGi, for each variable. Fifteen variables were significantly asymmetric and correlated with the right vs. left sides for the following anatomical regions: sacrum, iliac blades, iliac width, acetabulum and the superior lunate surface of the acetabulum. ABGi values above a threshold of +/- 4.8% were considered significantly asymmetric in seven variables of the pelvic area. Total asymmetry involving the right and the left pelvis seems to follow a spiral path in the pelvis; in the upper part, the iliac blades rotate clockwise, and in the lower part, the pubic symphysis rotates anticlockwise. Thus, pelvic asymmetry may be evaluated in clinical examinations by measuring iliac crest orientation.

Acetabulum↗

Computed tomographic measurements of the hip morphology of 10 healthy German shepherd dogs.

Linear measurements were made by computed tomography of the diameter of the femoral head, the width and depth of the acetabulum and the dorsal and ventral acetabular rim distances in 10 healthy German shepherd dogs, and angular measurements were made of the axial acetabular index, acetabular anteversion, and the dorsal and ventral centre-edge angles. There were no significant differences between the measurements made on the left and right sides. The width of the acetabulum was about twice its depth, and was a little larger than the diameter of the femoral head. The mean values of the axial acetabular index, acetabular anteversion, and ventral and dorsal centre-edge angles were 100.9 degrees, 25.1 degrees, 48.0 degrees and 12.2 degrees, respectively.

Acetabulum↗

Therapeutic percutaneous injections in the treatment of malignant acetabular osteolyses.

Percutaneous injection of methylmethacrylate or ethanol may provide marked pain relief or bone strengthening in patients with malignant acetabular osteolyses who are unable to tolerate surgery. Injection of methylmethacrylate is usually indicated when osteolysis involves the weight-bearing part of the acetabulum (ie, the acetabular roof); in all other cases, ethanol injection is preferred. Ethanol and methylmethacrylate injections may be performed together if both weight-bearing and nonweight-bearing parts of the acetabulum are involved or extensive soft-tissue involvement is present. Moreover, these injections may be performed prior to radiation therapy, which complements their action due to similar but delayed effects on pain, or after radiation therapy that failed to relieve pain or in cases of local recurrence. Radiography and computed tomography must be performed prior to therapeutic percutaneous injection to assess the location and extent of the lytic process, the presence of cortical destruction or fracture, and the presence of soft-tissue involvement. Fever and transitory worsening in pain may occur secondary to inflammatory reaction in the hours following injection; however, these side effects usually resolve spontaneously within 1-3 days. The decision to perform therapeutic percutaneous injections should be made by a multidisciplinary team because the choice between this option and alternative methods of treatment depends on several factors including the location of the lesion, the local and general extent of the disease, the pain and functional disability experienced by the patient, and the patient's state of health and life expectancy.

Acetabulum↗

Comparison of Z-axis automatic tube current modulation technique with fixed tube current CT scanning of abdomen and pelvis.

PURPOSE: To compare image quality, diagnostic acceptability, and radiation exposure associated with 16-section multi-detector row computed tomographic (CT) examinations of abdomen and pelvis performed with z-axis modulation technique of automatic tube current modulation and with manual selection of fixed tube current. MATERIALS AND METHODS: Sixty-two consecutive subjects (mean age, 60 years; age range, 19-84 years; male-to-female ratio, 35:27) underwent follow-up CT of abdomen and pelvis with use of a 16-section multi-detector row scanner and z-axis modulation technique (10.5-12.0-HU noise index, 10-380 mA). Scanning parameters included 140 kVp, 0.5-1.0-second gantry rotation time, 0.938:1 beam pitch, and 5-mm reconstructed section thickness. For each subject, images obtained with z-axis modulation were compared with previous images obtained with fixed tube current (200-300 mA) and with other parameters identical. Images were compared for noise and diagnostic acceptability by two subspecialty radiologists using a five-point scale (1, unacceptable; 3, acceptable; 5, excellent) at five levels: upper liver at diaphragm, porta hepatis, right kidney hilum, iliac crest, and upper margin of acetabulum. Tube current and gantry rotation time used for acquisitions at these levels were recorded. Data were analyzed with parametric and nonparametric statistical tests. RESULTS: Although no significant differences were found (P =.34), images acquired with z-axis modulation at the levels of the upper liver (diaphragm) and acetabulum had a higher noise and lower diagnostic quality, compared with images acquired with fixed tube current. Compared with fixed tube current, z-axis modulation resulted in tube current-time product reduction in 54 (87%) of 62 examinations (mean reduction, 71.2 mAs) and increase in eight (13%) (mean increase, 17.0 mAs). CONCLUSION: Compared with manually selected fixed tube current, z-axis automatic tube current modulation resulted in reduced tube current-time product and similar image noise and diagnostic acceptability at CT of abdomen and pelvis.

Abdominal Neoplasms↗

Cam and pincer femoroacetabular impingement: characteristic MR arthrographic findings in 50 patients.

PURPOSE: To retrospectively characterize magnetic resonance (MR) arthrographic findings in patients with cam femoroacetabular impingement (FAI) and in those with pincer FAI. MATERIALS AND METHODS: Institutional review board approval and informed consent were not required. MR arthrographic studies obtained in 50 consecutive patients (30 men, 20 women; mean age, 28.8 years) with FAI were analyzed for labral abnormalities, cartilage lesions, and osseous abnormalities of the acetabular rim. The nonspherical shape of the femoral head at the head-neck junction was measured in eight positions around the femoral head and neck and used to calculate the alpha angle. Acetabular depth was measured. Surgical diagnosis served as the reference standard. The Wilcoxon rank sum test was used for statistical analysis. RESULTS: At surgery, hips in 33 patients were classified as having cam FAI and hips in 17 patients were classified as having pincer FAI. In both groups, the mean age of patients was 28.8 years. There were significantly more men (n = 27) with cam FAI and more women (n = 14) with pincer FAI. The alpha angle was significantly larger in patients with cam FAI at the anterior and anterosuperior positions. The acetabulum was significantly deeper in patients with pincer FAI than in patients with cam FAI. Cartilage lesions at the anterosuperior and superior positions were significantly larger in patients with cam FAI than in patients with pincer FAI. Cartilage lesions at the posteroinferior position were significantly larger and labral lesions at the posterior and posteroinferior positions were more pronounced in patients with pincer FAI than in patients with cam FAI. Osseous abnormalities were not significantly different between the groups. Osseous bump formation at the femoral neck was significantly more common in patients with cam FAI than in patients with pincer FAI. CONCLUSION: Characteristic MR arthrographic findings of cam FAI include large alpha angles and cartilage lesions at the anterosuperior position and osseous bump formation at the femoral neck; characteristic findings of pincer FAI include a deep acetabulum and posteroinferior cartilage lesions.

Acetabulum↗

Ultrasonographic assessment of bone maturity in newborns.

BACKGROUND: Traditionally, the bone maturity at birth has been estimated from the radiological presence and size of the ossified distal femoral epiphysis. This study was conducted in a search for a sonographic tool for the evaluation of neonatal bone maturity. METHODS: We examined sonographically 256 neonates within 24 h of birth. Gestational ages ranged from 36 to 42 weeks (mean: 39.4; median: 40). Birth weights ranged from 1,945 to 5,000 g (mean: 3,175; median: 3,180). The distal femoral epiphysis was imaged on the coronal plane sonogram of the distal femur with the knee at 90 degrees flexion and the distal femoral epiphysis maximal height was recorded. The acetabulum was imaged using Graf's method in the coronal plane image and the acetabular diameter recorded. RESULTS: It was found that plotting the distal femoral epiphysis against neonatal birth weight and gestational age provided a simple method for assessing the bone maturity. According to our study, a neonate can be regarded as bone maturity percentile X when plotting distal femoral epiphysis height or acetabulum diameter against birth weight and gestational age or when averaging the four readings. CONCLUSIONS: We suggest performing sonography of the distal femoral epiphysis as a bedside tool for the assessment of skeletal maturity in newborns.

Acetabulum↗

Influence of the hip joint position on the intraosseous pressures in the juxta-articular bones. An experimental investigation in dogs.

In 6 mongrel dogs (eleven hips) the intraosseous pressure was measured in the femoral head as well as acetabulum in various hip joint positions. The control position for the measurements was 90 degrees flexion in which the pressures were found low and stable. The intraosseous pressure in both locations were subjected to consistent pronounced variations when the joint position was altered. In the femoral head, significant pressure increases (p less than or equal to 0.01) were found in maximal extension, maximal flexion, maximal adduction, 90 degrees external rotation, 45 degrees internal rotation, and maximal internal rotation. The pressure in acetabulum rose significantly in maximum flexion, 45 degrees internal rotation, and maximum internal rotation, whereas the pressure increase in maximal extension and maximum adduction was consistent but not significant. The pressure increase is most probably caused by inhibition of the venous drainage changing the bone hemodynamics in the juxta-articular bones. A complete obstruction of venous drainage was not observed since the intraosseous pressure in none of the measurements reached the level of the arterial pressure.

Acetabulum↗

Congenital dislocation of the hip. A review.

Congenital dislocation of the hip usually results from capsular stretching caused by fetal malposition and crouching late in the third trimester. Early recognition of hip dislocation or instability soon after birth permits prompt treatment. Ortolani's and Barlow's maneuvers, respectively, reduce into and displace from the acetabulum a femoral head that is insecurely contained therein. The diagnosis of CDH in the first month of life usually depends on these clinical components of the physical examination of the newborn, because similar device, in this age group can usually maintain the displaced hip in sufficient flexion and abduction to permit reduction and normal development. By 3 months of age, the nuclei of the pelvis and upper femur have ossified enough to permit radiologic diagnosis of CDH. Problems related to treatment increase as the child grows older. In infants up to 6 months of age, closed methods with a harness usually succeed. Beyond 6 months, the soft tissues shorten and prevent easy reduction. These patients almost always require pre-reduction traction. An adductor tenotomy also facilitates reduction and apparently lessens compressive forces on the femoral head, an important consideration in preventing avascular necrosis of the head. Children over 1 year old develop bony changes, such as excessive femoral valgus and anteversion and deformity of the acetabulum. Treatment in these patients requires realignment of bony deformities with femoral or pelvic osteotomies in addition to the measures noted previously. The gentleness and high success rate of early treatment make early diagnosis of CDH an important consideration in infants and newborns.

Acetabulum↗

The natural history of congenital disease of the hip.

Fifty-four adults with eighty hips affected by congenital disease which had not been treated have been reviewed. Fifty-nine per cent of forty-two dislocated hips had fair or poor grading scores. The incidence of osteoarthritis was markedly increased in the presence of a well-developed false acetabulum. Unilateral dislocation led to valgus deformity and degenerative changes in the ipsilateral knee in seven of twenty-two patients. Dislocation did not increase the incidence of symptomatic lumbar spondylosis. The height of the dislocated head on the ilium was not found to be related to the prognosis for the hip, the knee or the lumbar spine and did not correlate with the development of the false acetabulum. Frank congenital subluxation eventually led to osteoarthritis of the hip.

Acetabulum↗

The use of stereophotogrammetry to measure acetabular and femoral anteversion.

Stereoradiography with a base shift of the source of illumination was used to produce pairs of radiographs to be measured by stereophotogrammetric techniques. The direction of shift was parallel with the longitudinal axis of the body, so that each radiograph in the stereopair could be used for other clinical purposes. A base shift of 10 centimetres with a distance of 100 centimetres between the focus and the film gave acceptable value of stereoscopic parallax. The radiographs were measured using a Hilger and Watts medical stereometer. This method was checked with test specimens, namely an osteotomised pelvis in which one acetabulum could be rotated and an osteotomised femur in which the whole upper portion could be rotated against the shaft. Measurements made on the acetabulum and its radiographs showed a correlation coefficient of 0.9838 over the range 0 to 30 degrees of anteversion, with a mean error +2.54 degrees and a standard deviation of +/- 1.52 degrees (n = 21). For the femoral neck, over the range from 10 degrees of retroversion to 80 degrees of anteversion, the correlation coefficient was 0.9979, the mean error +2.46 and the standard deviation +/- 1.48 degrees (n = 30).

Acetabulum↗

Chiari innominate osteotomy in adults. Technique, indications and contra-indications.

The results are reported of 44 consecutive Chiari innominate osteotomies performed on 39 adult patients aged between 18 and 55 years for symptoms arising from disproportion between the acetabulum and the femoral head. Predisposing causes included congenital dysplasia of the acetabulum, congenital subluxation of the hip, and Perthes' disease. Follow-up averaged 5 years 2 months. Four pre-operative categories of dysplasia and degeneration were recognised. The analysis of the results from each category made possible the recognition of clinical and radiological features likely to provide a satisfactory result. Of 32 cases now considered to have been selected appropriately, 29 (90%) achieved a significant and apparently lasting improvement. In the other 12 cases there were 9 failures--an unacceptable proportion. The features predisposing to these poor results are discussed. The operation is not difficult. It is safe, and is less demanding than the complex alternative "double", "triple" and "dial" osteotomies. In successful cases there is reduction in symptoms and in limp, and improvement of radiological appearances beginning six months after surgery and progressing to a maximum recovery two to three years later.

Acetabulum↗

Bone grafting for protrusio acetabuli during total hip replacement. A review of the Wrightington method in 61 hips.

Total hip replacement has been very successful in patients with painful, stiff hips associated with protrusio acetabuli, but the heat of polymerisation of methylmethacrylate cement may cause necrosis of the thin medial wall with consequent danger of migration of the cup. Since 1968 at Wrightington, thin slices of the head of the femur have been used as bone grafts to reinforce the acetabulum. We have reviewed 61 hips in 51 patients at an average of 4 years 3 months after operation. Grading for severity is discussed and the degree of physiological remodelling of the medial wall of the acetabulum after grafting assessed. There was an average of about 4 mm of remodelling, but this varied considerably; most took place within the first year. In no case was there relapse of the protrusio.

Acetabulum↗

Homograft bone in revision acetabular arthroplasty. A clinical and radiographic study.

Thirty-seven patients with extensive acetabular defects due to loose implants had revisions with uncemented components, the acetabulum being augmented with homograft bone. In six of these, a histological study of graft incorporation was made. At a mean follow-up of 1.5 years 34 patients were free of pain and 35 could walk for 30 minutes or longer. No graft had obviously sequestrated. Two components had radiological evidence of migration but remain asymptomatic. We conclude that cementless revision surgery with homograft supplementation of the acetabulum is clinically successful in the short-term. The long-term outcome is unknown.

Acetabulum↗

Early deterioration after modified rotational acetabular osteotomy for the dysplastic hip.

We performed a modified, rotational acetabular osteotomy through a lateral transtrochanteric approach on 19 hips in 18 patients with a dysplastic joint. Six hips in six patients were operated on using the original approach. The mean age at operation was 28 years (14 to 54) and the mean period of follow-up 2.3 years (1 to 4.4). Clinical evaluation using the Merle d'Aubigne score showed excellent or good results in 76%. Radiologically, 15 hips showed good acetabular remodelling and no signs of progressive osteoarthritis. In ten hips (40%) there was chondrolysis and collapse of the transferred acetabulum or both within one year, although this gave only mild pain in some patients. Factors which were significantly associated with the grade of outcome included age at the time of operation, the thickness of the transferred acetabulum, failure to use a bone graft, and a transtrochanteric approach.

Acetabulum↗

Acetabular development after bipolar hemiarthroplasty for osteosarcoma in children.

A retrospective analysis was performed of eight patients with an open triradiate cartilage, who underwent resection for osteosarcoma and reconstruction of the proximal femur with a hemiarthroplasty, in order to identify changes of acetabular development. An analysis of the centre-edge angle, teardrop-to-medial prosthesis distance, superior joint space, teardrop-to-superior prosthesis distance, degree of lateral translation, and arthritic changes, was performed on serial radiographs. The median age at the time of the initial surgery was 11 years (5 to 14). All patients developed progressive superior and lateral migration of the prosthetic femoral head. Following hemiarthroplasty in the immature acetabulum, the normal deepening and enlargement of the acetabulum is arrested. The degree of superior and lateral migration of the prosthetic head depends on the age at diagnosis and the length of follow-up.

Acetabulum↗