Biomedical subjects

S Grampp

Publications and source records attributed to S Grampp.

78 records · Page 5Linked to original sources

PubMedDate not supplied

[Risk factors for dislocation of a cementless total hip endoprosthesis--a statistical analysis].

AIM: This retrospective study aimed at the statistical identification of risk factors for dislocation for a certain cementless hip endoprothesis. MATERIAL AND METHOD: At our department 2605 primary total hip arthroplasties were performed between 1987 and 1997. In 40 patients (1.5%) a dislocation occurred. These patients were compared with a control group matched in number. RESULTS: No difference was found in both groups with respect to age, height, weight, body-mass index, and diagnosis. A tendency was found that more males were involved in the dislocation group. There were more previous operations found in this group (p = 0.005). Also significant was the fact, that patients in the dislocation group more often had epidural anaesthesia (p = 0.02), more often the implantation of the smaller 28-mm head (vs. 32 mm) (p = 0.02), and a higher inclination angle of the acetabular component (p = 0.02). No difference was found in terms of the surgeons experience, the postoperative leg length, femoral offset, medialisation, cranialisation and antetorsion of the acetabular component. CONCLUSION: Dislocation after total hip arthroplasty is a multifactorial complication. With the use of the Alloclassic/Zweymüller total hip endoprothesis, a higher risk for dislocation was found for patients with previous hip surgery, the use of the smaller endoprosthesis head, a high acetabular inclination angle, and in the use of epidural anaesthesia.

Aged↗

PubMedDate not supplied

Significance of QCT bone mineral density and its standard deviation as parameters to evaluate osteoporosis.

OBJECTIVE: A study using quantitative CT (QCT) of the spine was carried out to determine whether the standard deviation (SD) of the bone mineral density (BMD) within a given region of interest (ROI) could be used as a parameter to evaluate osteoporosis. MATERIALS AND METHODS: A low dose single energy protocol was used. The elliptical ROIs inside the trabecular bone of the vertebral bodies T12-L3 were analyzed for four patient groups: Group 1, 52 healthy premenopausal women (age 41 +/- 2 years); group 2, 119 healthy early postmenopausal women (53 +/- 4 years); group 3, 45 postmenopausal relatively healthy women (age 65 +/- 5 years); group 4, 26 osteoporotic women (age 67 +/- 5 years). Average group mean BMD values and their coefficients of variation (CV = SD/BMD) were calculated. The t values, percent decrements, z-scores, and analysis of variance (ANOVA) served to compare capabilities of the BMD and the CV to discriminate groups pairwise using all possible group combinations. RESULTS: The use of z-scores and percent decrements gave ambivalent and mostly insignificant results. The CV performed better than BMD in separating group pairs (1,3), (1,4), (2,3), and (2,4), but BMD was superior for group pairs (1,2) and (3,4). Using SD as an independent variable in addition to age and BMD in the ANOVA did not significantly change r2 or the standard error of the estimate. The t test showed highly significant better discriminatory capabilities for BMD compared to CV> CONCLUSION: The results of our study did not indicate a significant potential of the BMD SD as measured in trabecular single energy low dose spinal QCT to improve the discriminatory capabilities of BMD for a separation of osteoporotic from nonosteoporotic subjects.

Adult↗

PubMedDate not supplied

Relationships between young modulus of elasticity, ash density, and MRI derived effective transverse relaxation T2* in tibial specimens.

OBJECTIVE: It has been hypothesized that the MR relaxation time T2* of bone marrow present in the intertrabecular spaces may be related to the density of the trabecular network and may be a predictor of trabecular bone properties. MATERIALS AND METHODS: To derive a relationship between the marrow relaxation time T2* and biomechanical properties of trabecular bone, we studied two sets of trabecular bone specimens from human tibiae. The first set consisted of 12 specimens that were defatted and immersed in saline; the second set consisted of 18 specimens with marrow in the trabecular spaces. The MR studies were conducted on a 1.5 T imaging system. In the first set of specimens, a GE sequence (TR = 70 ms; TE = 5, 10, 15, 20, 25 ms) was used to obtain images in the axial plane. In the second set, a water suppression pulse was used prior to an asymmetric SE sequence (TR = 300 ms; TE = 4, 8, 12, 16, 20, 24 ms) to obtain images in the axial, coronal, and sagittal planes. The T2* of the intertrabecular saline of the marrow fat was calculated assuming a monoexponential decay. In both sets, the elastic moduli were measured in three orthogonal directions (superoinferior, anteroposterior, and mediolateral). The ash density was determined after the completion of the experiments. RESULTS: Our results indicate a moderate significant negative correlation between T2* and ash density or elastic modulus (E) in both sets of specimens. The correlation coefficients were slightly improved between the transverse relaxation rate 1/T2* and bone density or E. We found a good correlation between T2* and the reciprocal ash density (r = 0.88) and between T2* and the reciprocal elastic modulus 1/E (r = 0.87 to r = 0.95) in the first set, while in the second set the correlation remained moderate. With use of a multiple linear regression model (1/E = a x T2* + b x 1/T2* + n), the reciprocal elastic moduli 1/E were predicted to > 90% by T2* and 1/T2* in the first set of specimens. This finding was not replicated with the second set of specimens. In the second set of specimens, we found poor to moderate correlation coefficients between the T2* times in the three orthogonal planes (r = 0.45 to r = 0.71). CONCLUSION: Trabecular bone properties such as density and strength may potentially be assessed with quantitative MR techniques. However, especially for in vitro studies, specimen preparation, acquisition parameters, and specimen geometry may have a significant impact on the obtained results.

Bone Density↗

PubMedDate not supplied

Scimitar syndrome: MR assessment of hemodynamic significance.

We report a case of anomalous pulmonary venous drainage into the inferior vena cava (scimitar syndrome) in which the hemodynamic significance was noninvasively assessed by means of velocity-encoded cine MR. Left-to-right shunt was calculated from direct blood flow measurements performed in the ascending aorta, main pulmonary artery, and aberrant pulmonary vein.

Aged↗

PubMedDate not supplied

Overuse edema in the bone marrow of the hand: demonstration with MRI.

In MRI of the skeleton, marrow edema is a frequent finding that can be caused by avascular necrosis, fracture, bone bruises, transient osteoporosis, osteomyelitis, primary tumors, metastases, and altered biomechanical properties. We examined a 29-year-old woman golfer with mild pain and swelling of the proximal phalanx II of the left hand. No signs of a stress fracture were seen on the MR images or plain radiographs. MRI revealed increased signal intensity on T2-weighted images in the metacarpal and proximal phalanx II in the left hand. We concluded that bone marrow edema may be the result of physiologic bone response to stress and may not necessarily correspond with severe trauma. Our case complements recent observations outlining the influence of altered biomechanics as a reason for marrow edema.

Adult↗

PubMedDate not supplied

Liver transplantation: significance of the periportal collar on MRI.

OBJECTIVE: Liver transplantation is performed with increasing success and frequency all over the world. Experience with MRI of the liver allograft is, however, limited. This study was designed to correlate MRI to clinical-laboratory findings, CT, and biopsy and to evaluate the significance of the periportal collar on MRI. MATERIALS AND METHODS: Fourteen patients who had undergone orthotopic liver transplantation were studied by CT and MRI [T1-weighted imaging: gradient-echo, repetition time/echo time (TR/TE) 306/14 ms, theta 90 degrees; proton density and T2-weighted imaging: spin-echo, TR/TE 1,600/30-120 ms]. Three patients also had follow-up MR examinations 43 days, 89 days, and 5 months after transplantation. RESULTS: Magnetic resonance imaging demonstrated a perivascular collar around central portal venous branches in all 14 patients and around peripheral portal branches in 10 of the 14 patients on the initial MRI study. The perivascular collar showed low signal intensity on T1-weighted imaging and an increase in signal intensity on T2-weighted multiecho imaging. The distribution and prevalence of central and peripheral periportal collars were identical on MR and CT. Peripheral periportal collars were seen in 9 patients who had no clinical-laboratory signs of rejection. In 3 patients with biopsy-proved rejection, the periportal collar was less prominent on MR at the time of rejection when compared with MR performed when the patient had no signs of transplant rejection. CONCLUSION: A perivascular collar in a patient with liver transplantation is likely to be related to impaired lymph drainage after surgical interruption of the draining lymph vessels and lymphedema. In contrast to previous CT reports, however, a perivascular collar around peripheral portal branches does not appear to correlate to rejection, since it is frequently observed in the normal liver allograft.

Adult↗