Biochemical properties of cortical allograft bone using a new method of bone strength measurement. A comparison of fresh, fresh-frozen and irradiated bone.

There have been conflicting reports on the effects of gamma irradiation on the material properties of cortical allograft bone. To investigate changes which result from the method of preparation, test samples must be produced with similar mechanical properties to minimise variations other than those resulting from treatment. We describe a new method for the comparative measurement of bone strength using standard bone samples. We used 233 samples from six cadavers to study the effects of irradiation at a standard dose (28 kGy) alone and combined with deep freezing. We also investigated the effects of varying the dose from 6.8 to 60 kGy (n = 132). None of the treatments had any effect on the elastic behaviour of the samples, but there was a reduction in strength to 64% of control values (p < 0.01) after irradiation with 28 kGy. There was also a dose-dependent reduction in strength and in the ability of the samples to absorb work before failure. We suggest that irradiation may cause an alteration in the bone matrix of allograft bone, but provided it is used in situations in which loading is within its elastic region, then failure should not occur.

The use of enzyme activated milk for in vitro simulation of prosthetic valve thrombosis.

BACKGROUND AND AIM OF THE STUDY: Thrombosis remains a serious risk for patients with artificial heart valves and may be attributed in part to adverse blood flow patterns. Although the final assessment of a valve must follow years of clinical experience, in vitro flow analyses give valuable information prior to implantation. Laser Doppler velocimetry and computational fluid dynamics enable quantitative flow analyses to be made in vitro. Whilst these techniques highlight features such as areas of stasis, turbulence and high shear which may predispose to thrombus formation, the complex and time varying nature of the flow through valves makes it difficult to predict accurately potential sites of thrombus deposition and accumulation. METHODS: A technique is described which uses enzyme activated milk as a coagulable blood analogue to indicate flow related clotting. Milk flowing past a test valve or object was activated to clot downstream of the test piece after a certain time period. Milk clot was deposited clot at sites determined by the local flow disturbances. Milk clotting patterns produced on and around standard objects were compared with the transient flow patterns predicted around identical configurations to test the validity of computational flow analyses for predicting flow disturbances leading to clotting. Milk clots on valves were compared with examples of thrombus found on explanted valves of the same design. RESULTS: The sites of deposition were consistent with the predicted flow patterns around the two configurations of flow obstruction studied. Milk clotting patterns on valves corresponded with the early stages of thrombus on explanted valves of the same design. CONCLUSIONS: Whilst a coagulable milk mixture may be used to evaluate the risk of flow induced clot adherence, care must be taken when extrapolating to the clinical situation as other factors such as material properties, blood chemistry and concomitant disease must also be considered.

A new method of comparative bone strength measurement.

Most investigations of the material properties of bone have been concerned with the measurement of absolute values for various mechanical parameters. It can be necessary, however, to produce test samples with similar mechanical properties in order to assess the effect on these properties of particular treatments. Absolute values for these properties may not be as important as any changes observed. We describe here a new method whereby many bone test samples with very similar mechanical properties can be produced. If the femoral shaft at the diaphysis is cut in transverse section, it is possible to produce many similar shaped rings of bone. We compared the material properties of 48 ring samples with 65 beam specimens. Both were tested in three-point bending. Global estimates of coefficient of variation (CV) for each parameter were used to assess similarity within each group. All the rings had very similar ash weights (1.98%), thicknesses (1.97%), and diameters (< 0.01%). Values of load/deflection of the rings were more similar than the values of Young's modulus (E) for the beams (7.06 versus 9.9%), and the maximum loads sustainable by the rings were more similar than the bending strengths of the beams (5.7 versus 13.6%). The energy absorbed by the ring samples were more consistent than the beams (14.31 versus 34.41%). We suggest that there is improved similarity in mechanical characteristics within groups of samples produced in this manner than with more conventional sample configurations.

Post-operative retention associated with acute prostatic infarction.

Twenty-one patients with post-operative retention following unassociated surgery and requiring transurethral resection of the prostate were compared with patients with acute retention (control group). Histological evidence of acute prostatic infarction was significantly increased in the post-operative retention group. Prolonged operative hypotension was associated with acute prostatic infarction, as were smoking and pre-existing cardiovascular disease.

Malignancy following ureterosigmoidostomy in patients with exstrophy.

Forty-two patients with exstrophy underwent a urothelial colonic anastomosis. Eight developed a tumour at the ureterocolic anastomosis and in another two patients a malignant lesion occurred in the bladder remnant.

Twenty-year follow-up of primary mega-ureter.

47 children diagnosed as having obstructed or non-refluxing, non-obstructed, primary mega-ureters were followed up by questionnaire. 2 patients had developed renal failure over 20 years, the remainder were free of urinary tract infection or hypertension. 21 of these patients were followed up with clearance and differential renal function studies. All but 4 kidneys associated with operated mega-ureters at long term follow-up had good function.

Prostacyclin in the treatment of painful Peyronie's disease.

The effect of a prostacyclin infusion was studied in 5 men with persistent pain associated with Peyronie's disease. Marked side effects were associated with the infusion, which was of limited benefit.

Retrograde ejaculation owing to ectopic erectile tissue.

We report a case of retrograde ejaculation caused by ectopic erectile tissue in the posterior urethra. Transurethral resection of the tissue resulted in antegrade ejaculation.

Kinetic changes in experimental colonic urinary diversion.

An experimental model of colonic urinary diversion was performed on male Wistar rats to see if faeces, urine or a faeces and urine mixture produces tumours. Cell kinetic techniques, including the crypt cell production rate, and cellular DNA measurement were used to examine the effect of urine and of faeces on the colonic mucosa. Urinary diversion into the colon significantly increased colonic crypt activity. Tumours were found at the anastomosis when urine and faeces were mixed at 4 months, and at 6 months with urine alone.

Diagnostic intracorporeal papaverine and erectile dysfunction.

Intracorporeal papaverine has been used as an out-patient procedure to assess the erectile dysfunction of 129 men. The technique is a valuable diagnostic aid and has few side effects. Prolonged tumescence occurred in four patients, two of whom required treatment with intracorporeal metaraminol.

Mucin changes adjacent to carcinoma following ureterosigmoidostomy.

A patient with epispadias had a ureterosigmoidostomy. This was converted to an ileal conduit 3.5 years later. 24 years after this, he developed an adenocarcinoma at the site of the ureteric stump. Abnormal mucin staining was found in the resected colon. This stain is not predictive of malignant change, and therefore regular colonoscopy is required for these patients.

Long-term management of patients who have had urinary diversions into colon.

Thirty-four patients with urinary-colonic diversions have been followed up for 13 to 41 years (mean 20.3). The commonest long-term complication was hyperchloraemic acidosis (50%). The most serious was neoplasm at the anastomotic site: benign lesions occurred in three patients and carcinomas in two (15%). Staining for sialomucins in colonic biopsies adjacent to the anastomoses was positive in 17 of 19 patients. It has been suggested that this represents a pre-malignant change. Analysis of faecal flora in 17 diverted patients and 27 controls revealed a significant difference in the carriage rate and viable count of Peptostreptococcus species. This finding has not been reported previously and the species could have a role in the aetiology of the neoplasms.

Histochemical changes after ureterosigmoidostomies and colonic diversion.

Forty patients with colonic urinary diversions were studied for morphological and histochemical changes in the colon using haematoxylin and eosin, and high iron diamine alcian blue stains. Eighty-nine per cent of ureterosigmoidostomies biopsied at the ureteric orifice and 44% biopsied distal to the orifice showed "transitional" changes thought to represent a pre-malignant state. Thirty-eight per cent of patients who had had ureterosigmoidostomies in the past and 100% of the colon conduits also demonstrated this change. The earliest "transitional" change occurred 1 year after the diversion. This and the low incidence of morphological changes in this group of patients suggest that the finding of "transitional" mucosa is of no value in the follow-up of patients with colonic urinary diversions.