Biomedical subjects

I Harrington

Publications and source records attributed to I Harrington.

6 recordsLinked to original sources

PubMed2001

Limitation on stabilizing plane waves via time-delay feedback.

Previous work has demonstrated the possibility of stabilizing plane wave solutions of one-dimensional systems using a spatially local form of time-delayed feedback. We show that the natural extension of this method to two-dimensional systems fails due to the presence of torsion-free unstable perturbations. Linear stability analysis of the complex Ginzburg-Landau equation reveals that long wavelength, transverse wave instabilities cannot be suppressed by the method of extended time-delay autosynchronization. The conclusion follows from symmetry considerations and therefore applies to a wide class of models with simple plane wave solutions.

Journal Article↗

PubMed1994

Biomechanical analysis of the Gamma nail and sliding hip screw.

Nine pairs of human cadaveric femora were used to study the biomechanical characteristics of the Gamma nail and a standard telescoping screw plate implant (Ambi) to determine whether there were any mechanical advantages of one system over the other. Parameters studied included structural stiffness, strain distribution, and failure modes for intertrochanteric and subtrochanteric fractures. There was no significant difference in structural stiffness for stable intertrochanteric and subtrochanteric fractures. The Gamma Nail composites, however, were stiffer than the Ambi for unstable subtrochanteric fractures. Both implants effectively unloaded the proximal medial cortex. In each instance, failure of the Gamma nail composite occurred through the distal locking screws. The Gamma nail does not appear to offer any distinct biomechanical advantage over the sliding hip screw system in the treatment of stable and unstable intertrochanteric fractures, but it may play a role in the treatment of unstable subtrochanteric fractures.

Biomechanical Phenomena↗

PubMed1991

Effect of stem modulus in a total hip arthroplasty model.

The purpose of this study was to determine the biological effects of the elastic modulus of the femoral stem in canine hip arthroplasty. Cementless total hip arthroplasty was performed in 12 dogs, six had a low elastic modulus polyacetal resin stem and six had a high modulus stainless steel stem. The components were otherwise similar. At six and 12 months after operation, radiographic and histomorphometric analysis showed that those with steel implants had more cortical porosity than did the other group (p less than 0.01). We suggest that the elastic modulus of the implant is an important factor in controlling cortical bone resorption. A low modulus femoral prosthesis can significantly decrease bone resorption which might otherwise eventually lead to implant failure.

Animals↗

PubMed1991

Pseudoaneurysm of the popliteal artery as a complication of an osteochondroma. A review of the literature and a case report.

False aneurysm of the femoral artery was associated with a solitary osteochondroma of the femur in a 22-year-old man. An extensive review of the literature and the problems related to diagnosis revealed that the aneurysm was apparently unique. Contrary to previous reports, computed tomography and angiography did not establish the diagnosis. The physical findings were more informative.

Adult↗

PubMed1986

Cauda equina syndrome and lumbar disc herniation.

In a retrospective chart review of the cases of thirty-one patients with cauda equina syndrome secondary to a central disc lesion, we identified two modes of presentation. The first was an acute mode (ten patients) in which there were abrupt, more severe symptoms and signs and a slightly poorer prognosis after decompression, especially for the return of bladder function. The second mode of presentation (twenty-one patients) was a slower onset, characterized by prior symptoms for varying time-intervals before the more gradual onset of the cauda equina syndrome. All patients had urinary retention preoperatively. Bladder function was the most seriously affected function preoperatively and remained so postoperatively. The prognosis for return of motor function was good, since twenty-seven of the thirty patients who were operated on regained normal motor function. Preoperatively all patients had sciatica, which was bilateral in fourteen and unilateral in seventeen. The average time to surgical decompression after the patient was seen ranged from 1.1 days for the more acute lesions to 3.3 days for the second group. There was no correlation of these times with return of function. Therefore, even though early surgery is recommended, decompression does not have to be performed in less than six hours if recovery is to occur, as has been suggested in the past.

Adult↗

PubMed1978

Pemphigus vulgaris in a 15-year-old girl.

Pemphigus vulgaris is uncommon in adolescence and only ten well documented cases in this age group were found in a recent review (5). Because the condition is often more severe in the younger age group it is important to consider it in the differential diagnosis of bullous eruptions of childhood and to perform direct and indirect immunofluorescence studies.

Adolescent↗