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ABSTRACT: Background: Intraoperative femoral fracture is a complication of cementless total hip arthroplasty (THA), the number of which is increasing. This fracture may occur when the force applied to the femur exceeds the bone strength. The force applied to the femur during THA is basically the impact force required for insertion of femoral components. The purpose of the present study was to investigate the relationship of the impact force required for insertion of femoral components and intraoperative femoral fracture in THA.
Methods: Two types of femoral components, a short double-wedge type in 20 patients (group S) and a long conventional type in 20 patients (group L), were implanted by the same surgeon. The impact force of the femoral component was measured at final rasping, trial and final seating.
Results: The impact force at final rasping, trial and final seating of the femoral component averaged 2241.9 N, 1716.9 N and 1409.2 N in group S, respectively, and 1729.7 N, 1508.9 N and 1570.6 N in group L, respectively. The impact force required for insertion of femoral components in group S was larger than that in group L (P < 0.05). Intraoperative femoral fracture occurred in four patients in group S during final rasping and in none in group L.
Conclusions: Surgeons should be more cautious when short femoral components with wedges, such as those used in the present study, are inserted.
Current Orthopaedic Practice 09/2009; 20(5):552–556.
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ABSTRACT: Background: Most acetabular labral tears have been shown to occur in the anterosuperior quadrant of the acetabulum. This region may represent a weak area that predisposes the labrum to detachments later in age. Labral detachments may be potentiated by acetabular dysplasia as well. We examined tensile properties and histological appearance of human acetabular labra for regional differences.
Methods: Human acetabular labra were harvested from 45 patients who underwent total hip arthroplasty for the treatment of secondary osteoarthritis caused by developmental dysplasia of the hip (DDH), primary osteoarthritis or idiopathic necrosis of the femoral head. Thereafter, the tensile properties of the human acetabular labra were investigated using a uniaxial tension testing apparatus. In addition, the pathological findings of the harvested labra were observed.
Results: For all specimens, the mean tensile stresses at failure of the anterosuperior and posteroinferior labra were 4.0 ± 1.6 MPa and 4.6 ± 1.8 MPa, the mean strains were 31.9 ± 28.3% and 22.3 ± 5.4%, and the mean tensile moduli were 38.3 ± 16.9 MPa and 47.3 ± 22.2 MPa, respectively. No significant difference was found between the tensile properties of the anterosuperior and posteroinferior labra. Moreover, no significant differences were found among the tensile properties in the three groups. However, a negative correlation was found between the tensile stress at failure of the anterosuperior labrum and age in DDH group (P = 0.004, R2 = 0.392). In addition, the pathological findings revealed that the degeneration of the anterosuperior labrum was more severe than that of the posteroinferior labrum in the DDH group. Our results further revealed that the tensile stress at failure of the anterosuperior or posteroinferior labrum was frailer than that of the posterosuperior labrum in a similar group in a previous study.
Conclusions: The degenerative changes observed in the anterosuperior labrum may influence the occurrence of labral tears in DDH.
Current Orthopaedic Practice 08/2008; 19(5):564–569.
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ABSTRACT: Medial displacement of the femoral head reduces the force transmitted across the hip joint. Since 2005, we have performed a modified Ganz's osteotomy with curved periacetabular osteotomy (CPO) to obtain medialization of the femoral head. The modification involves cutting of the pubis at 30 degrees to the horizontal line. Here, we examined whether this modified CPO procedure medialized the femoral head more than the conventional CPO procedure.
69 patients (mean age 37 years, 72 hips) treated with the modified CPO procedure (the M group) were compared with 68 patients (mean age 38 years, 72 hips) previously treated with conventional CPO (the C group). All patients were operated because of dysplastic hips. We used radiographic measurements from anteroposterior radiographs. The magnitude of the resultant hip force normalized with respect to the body weight (R/WB) and hip contact joint stress (Pmax/ WB) was calculated in all cases.
The average lateral center-edge (CE) angle, acetabular roof obliquity (ARO), and acetabulum-head index (AHI) improved in both groups. The CE angle, ARO, and AHI were similar in the 2 groups before and after surgery. Medialization of the femoral head was larger in the M group than in the C group (p < 0.001). The average value of the resultant hip force decreased from 3.2 to 2.9 in the M group and remained unchanged, at 3.1, in the C group. In addition, the average value of the peak contact stress decreased more in the M group (from 9.4 kPa/N to 3.4 kPa/N) than in the C group (from 9.1 kPa/N to 4.3 kPa/N).
In dysplastic hips, the modified CPO reduces the contact hip stress more than the conventional CPO because of better medialization of the femoral head.
Acta Orthopaedica 08/2008; 79(4):474-82. · 2.17 Impact Factor
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ABSTRACT: Dysfunction of the hip secondary to dysplasia is a complex problem that includes excessive stresses on the articular cartilage, dynamic hip instability, and muscular fatigue, eventually leading to degenerative arthritis if left uncorrected. Mechanical stress on the dysplastic hip has been widely described, but dynamic instability requires further evaluation. The purpose of this study was to investigate dynamic instability of the dysplastic hip with use of triaxial accelerometry.
We evaluated forty-eight hips of twenty-four patients with unilateral hip dysplasia (a center-edge angle of <25 degrees ). All contralateral hips were disease-free with normal radiographic findings. An accelerometer was used to record triaxial acceleration while the patient was walking (x-axis: superoinferior direction, y-axis: anteroposterior direction, and z-axis: mediolateral direction). Sensors were attached to the skin, with adhesive tape, over the greater trochanter and the anterior superior iliac spine bilaterally. The time of heel-strike was confirmed visually and by superoinferior acceleration. The averages of the peak values of the middle three gait cycles were used for data analysis. The overall magnitude of acceleration was calculated to evaluate hip instability. The overall magnitudes of acceleration of the dysplastic and contralateral, normal hips were compared with the radiographic data.
The three directions of acceleration were the same in all cases. The overall magnitude of acceleration of the dysplastic hips was significantly larger than that of the contralateral, normal hips (p < 0.0001). There was a negative correlation between the overall magnitude of acceleration and both the center-edge angle and the acetabular head index, and there was a positive correlation between the overall magnitude of acceleration and both the acetabular roof angle and the Sharp angle.
Hip instability is increased in proportion to the degree of dysplasia. Triaxial accelerometry is helpful in the evaluation of dynamic instability of the dysplastic hip. The center-edge angle can be used as an indicator of hip instability.
The Journal of Bone and Joint Surgery 01/2008; 90(1):85-92. · 3.27 Impact Factor
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ABSTRACT: The tensile properties of the human acetabular labrum were investigated using a uniaxial tension testing apparatus. The superior quadrant of the acetabular labrum was harvested from patients who underwent hip surgery. The obtained labra were sliced and shaped into rectangles for measuring uniaxial tension. We hypothesized that several characteristics such as gender, age, degeneration due to primary ailment, and the severity of the acetabular dysplasia would influence the tensile properties of the labrum. Antero-posterior radiographs of the pelvis have been used to evaluate the severity of the acetabular dysplasia and to diagnose the developmental dysplasia of the hip joint (DDH) clinically. Thus, we investigated the correlation between each of two representative radiological measurements-the CE angle and the Sharp angle-and tensile properties to assess the influence of the severity of the acetabular dysplasia. The tensile stress-strain curves for the labrum assumed a sigmoid shape. The mean tensile stress at failure for all specimens was 8.8+/-4.1 MPa. The mean strain at failure for all specimens was 48.5+/-10.4%. The mean tensile modulus was 66.4+/-42.2 MPa. Mean tensile stress at failure for specimens from males was greater than that of specimens from females. A significant difference was found in the maximum stress at failure among the three diagnosis-based groups: the other group withstood the highest stress before failure, whereas the osteoarthritis (OA) group withstood the lowest. No significant correlations with age or radiological characteristics were found for tensile stress, strain at failure, or tensile modulus. Our results suggest that labra obtained from male patients have stronger tensile stress than those from female patients, and that degenerative changes may influence the properties of the acetabular labrum.
Journal of Orthopaedic Research 12/2005; 23(6):1448-53. · 2.81 Impact Factor
