Influence of forebrain periventricular lesions on the development of renal hypertension in rabbits.

Ablation of tissue surrounding the anteroventral third cerebral ventricle (AV3V) has been demonstrated to prevent and reverse renal hypertension in the rat. The contribution of this brain area to the maintenance of hypertension in other species has not been examined. In the present investigation, an attempt was made to produce two-kidney, one clip renal hypertension in rabbits with histologically and functionally defined AV3V destruction. Electrolytic lesion of the AV3V in rabbits produced effects closely resembling those previously seen in rats: increased plasma volume and plasma sodium, temporary adipsia, no change in resting arterial pressure or heart rate, and significant attenuation of pressor responsiveness to angiotensin II (AII) delivered intracranially. However, the increase in arterial pressure observed over a 4-week period following the application of a 0.5 mm silver clip to the left renal artery (opposite kidney intact) was identical in 12 AV3V-lesioned and 12 sham-operated rabbits. Hypertension development was not accompanied by significant sodium retention, water retention, or plasma/extracellular fluid volume expansion in either group of rabbits. Pressor responses to intravenous infusions of AII and norepinephrine were identical in sham and AV3V-X rabbits. Thus, destruction of the AV3V, and the attendant reduction in the central pressor action of AII, does not alter the pattern of development of two-kidney, one clip renal hypertension in the rabbit. The contrasting results in rats and rabbits could be explained by the differing contribution of the area postrema to the pressor action of AII in the two species.

Pathogenesis of hypertension in rats with chronic aortic baroreceptor deafferentation.

In an attempt to produce a form of chronic neurogenic hypertension without the increased blood pressure lability which is characteristic of total baroreceptor removal, selective aortic baroreceptor deafferentation (ABD) was performed in rats. Blood pressure, blood pressure variability, heart rate, plasma and extracellular fluid volumes, and the effect of total autonomic blockade were determined in male rats 1 month following ABD. Rats with ABD had significantly higher systolic, diastolic, and mean arterial blood pressures than did sham-operated animals, but the standard deviation of pressure measured repetitively over a 1-hour period was not significantly greater. Total autonomic blockade with atropine, propranolol, and phentolamine lowered blood pressure and heart rate to a similar level in ABD and sham-operated rats. Extracellular fluid volume was not different in the two groups of rats, but plasma volume was significantly lower in rats with ABD. Despite the overall reduction in plasma volume, there was a significant positive correlation between plasma volume and blood pressure in ABD rats; no such correlation was observed in sham-operated rats. It was concluded that ABD produces a mild, chronic hypertension in rats without marked pressure lability. Although the hypertension appears to be Neurogenic in that it is ABOLIshed by autonomic blockade, volume factors also may contribute to the increased blood pressure.

Methylmethacrylate stabilization for enhancement of posterior cervical arthrodesis in rheumatoid arthritis.

Stainless-steel wire, titanium mesh, and perforated titanium sheets and methylmethacrylate were used in conjunction with autogenous iliac-bone grafts to provide immediate stability in difficult or long posterior cervical fusions in eleven patients with rheumatoid arthritis, who were followed for three to 12.5 years. Two surgical techniques, using methylmethacrylate and metal supplementation of a traditional posterior cervical arthrodesis, are described. One technique includes the occiput, while the other consists of a long posterior fusion that excludes the occiput. In ten of the eleven patients, permanent radiographic stability was maintained as well as a significant reduction of pain and resolution of neural dysfunction. In the eleventh patient a cervical subluxation developed at the distal end of the rigidly fused segment, and eventually the patient died. Four patients who were seen early in the series had wound dehiscences, two of which were infected. Subsequently the methacrylate-metal composite was reduced in volume, and this problem did not recur. In summary, this technique has provided immediate internal splinting and avoided bulky external-fixation devices. It was most useful in fusions of the occiput to the upper part of the cervical spine, in long posterior cervical arthrodesis, and for the repair of pseudarthroses when traditional arthrodesis techniques had failed.

The axillary nerve and its relationship to common sports medicine shoulder procedures.

Cadaveric dissections have demonstrated the precarious nature of the axillary nerve with relationship to three common sports medicine shoulder procedures: the anteroinferior acromioplasty and rotator cuff repair incision, the inferior capsular shift procedure, and the posterior portal for shoulder arthroscopy.

Rehabilitation parameters in total knee replacement patients undergoing epidural vs. conventional analgesia.

Epidural analgesia for total knee replacement (TKR) surgery has been proposed as a means of enhancing patient comfort, thereby expediting rehabilitation and reducing hospital stay. This study was done to determine differences in rehabilitation parameters of range of motion and mobility in patients receiving epidural vs. conventional (intravenous) analgesia following TKR surgery. Chart reviews were done of 52 patients who underwent consecutive unilateral TKR, with 26 patients in each analgesia group. There were 21 males and 31 females, ages 24-88 years (median 65), with diagnoses of osteoarthritis (45), rheumatoid arthritis (4), and other (3). The surgeon, procedure, type of prosthesis, and physical therapy protocol were the same for all subjects. Demographics, range of motion, distance walked, assistance required for gait and transfers, assistive device, and exercise competence data were studied at the first postoperative day and at time of discharge. No significant difference was found in the length of stay at the p < .05 level. Significant differences at the first postoperative day favored the epidural group: in knee flexion range--median difference was 0.26 rad [95% confidence interval (CI): 0.09-0.52, p < .05] ie., 15 degrees (95% CI: 5-30); in total range of motion--median difference was 0.30 rad (95% CI: 0.09-0.58, p < .05), ie., 17 degrees (95% CI: 5-33); and in assistance required for gait and transfers (p < .05). At discharge, the epidural group required significantly less assistance (p < .05). There was a trend toward greater walking distance in the epidural group, who walked a median of 15.2 m farther than the conventional analgesia group.(ABSTRACT TRUNCATED AT 250 WORDS)

Pediatric pelvic fractures: review of 52 patients.

Fifty-two patients (ages 1 to 16 years) with pelvic fractures were hospitalized at an urban medical center during a 5-year period. All patients with acetabular fractures had adjacent hemipelvis fractures. None were seen to develop symptomatic acetabular dysplasia. Stable breaks in the ring (anterior ring fracture) were encountered most frequently. While many patients were discharged ambulating within a short time, over 50% had prolonged hospitalizations due to associated truma. Only one child had serious urologic trauma, demonstrating that isolated anterior ring fractures in children are not as treacherous in terms of pelvic content injury as those one might encounter in adults. Unstable breaks (anterior and posterior ring fractures) pose acute and chronic management problems and associated injuries are often fatal. Life-threatening complications may overshadow proper fracture management. It is critical to maintain a symmetrical pelvis in order to prevent either cephalad translation or anterior-posterior hemipelvis rotation. A child with the latter problem is presented in detail.

Renal vascular resistance and reactivity in the neurogenic hypertensive rat.

Increased sympathetic nervous system activity in the kidney has been postulated as a possible etiologic factor in some forms of hypertension. The present investigation sought to document the possibility of a chronic increase in neurogenic renal vasoconstriction in an experimental model in which increased nervous activity would be expected--neurogenic hypertension resulting from partial baroreceptor deafferentation. In anesthetized rats with chronic neurogenic hypertension, renal vascular resistance was significantly higher than in sham-operated rats. After acute renal denervation, there was no statistically significant difference in renal vascular resistance between the two groups. Thus, a chronic increase in neurogenic renal vascular resistance was apparent in the hypertensive rats. Since renal vascular responses to direct renal nerve activation, norepinephrine, and other exogenous vasoactive hormones were not altered in the hypertensive rats, the increased neurogenic vasoconstriction was probably the result of increased renal nerve discharge. Unaltered neurotransmission and reactivity further indicated a failure of the renal nerves or blood vessels to "adapt" to increased nervous activity. These results support previous suggestions that increased renal sympathetic nerve activity could result in sustained neurogenic renal vasoconstriction and thereby contribute to the development of hypertension.

Forebrain control of fluid and electrolyte homeostasis and angiotensin sensitivity in rabbit.

A small discrete area near the optic recess of the anterior ventral third ventricle (AV3V) in the rat brain has been shown to be an important mediator of cardiovascular and dipsogenic response to angiotensin II and osmotic stimuli and to be involved in normal day-to-day regulation of water and electrolyte balance. However, no attempt has been made until now to explore the function of the AV3V in species other than the rat. In the present study, rabbits subjected to electrolytic lesion of the AV3V exhibited expanded plasma volume and plasma sodium concentration, and significantly attenuated pressor responses to angiotensin II and hypertonic sodium chloride solutions injected via the lateral ventricles. Resting arterial pressure, plasma potassium concentration, extracellular fluid volume, and pressor responses to intravenous angiotensin II were not changed by lesioning. Thus, the effects of AV3V lesions in rabbits are similar, but not identical, to those previously observed in rats. Rabbits should be a suitable species in which to carry out studies aimed at distinguishing central and peripheral cardiovascular effects of angiotensin II.

Displaced Salter-Harris type I injury in a gymnast. A slipped capital humeral epiphysis?

The case of an adolescent Olympic-level gymnast with insidious onset shoulder pain is presented. Radiographic evaluation revealed bilateral physeal irregularities of the proximal humerus similar to those seen in Little Leaguer's shoulder. Roentgenograms of the involved shoulder also demonstrated Salter-Harris type I displacement at this physis and a slipped capital humeral epiphysis was diagnosed. A discussion reviewing proximal humeral physeal injury follows the case presentation.

Replacement of the patello-femoral joint with the total condylar knee arthroplasty.

We have studied 241 total condylar knee arthroplasties with replacement of the articular surface of the patella in 206 patients. The average age was 65 years. The technique of replacement of the patellofemoral joint emphasises realignment of the quadriceps mechanism, minimal excision of the patella to preserve subchondral bone, preservation of soft tissue attachments including the infrapatellar fat pad, and closure of the quadriceps without tension. The results of replacement have been good to excellent in 95 per cent of patients followed for two years or more. There were no subluxations, dislocations or fractures. Loosening was noted in one case associated with anterior knee pain. Discomfort was also noted with eccentric placement of the prosthesis where bone was left uncovered. We consider that routine replacement of the patello-femoral joint is advisable with total condylar knee arthroplasty.

Hemodynamic and neural mechanisms of acute neurogenic hypertension in the rat.

Experiments were performed to test the hypothesis that acute hypertension caused by aortic baroreceptor deafferentation (ABD) is the result of sympathetic vasoconstriction. Cardiac output (CO), mean arterial pressure (MAP), and total peripheral resistance (TPR) were measured before and after ABD in anesthetized and conscious rats. The role of the sympathetic nervous system in acute ABD-induced hypertension was evaluated by examining the ability of adrenalectomy, adrenal demedullation, guanethidine or combined adrenal demedullation, and guanethidine pretreatment to prevent, and total autonomic blockade to reverse, ABD-induced hypertension. CO did not change significantly after ABD at any time, whereas MAP and TPR increased significantly (P less than 0.05). Only combined adrenal demedullation and guanethidine pretreatment prevented ABD-induced hypertension, and autonomic blockade normalized MAP in ABD rats. Normalization of blood pressure was the result of a decreased TPR. It is concluded that acute ABD-induced hypertension results from vasoconstriction caused by neurally released and/or circulating catecholamines.

Effect of forebrain lesions on response to chronic intraventricular angiotensin II.

We previously reported that chronic (10 days) intracerebroventricular (ivt) infusion of angiotensin II (ANG II) into conscious rabbits produced a significant rise in mean arterial pressure (MAP), water intake (WI), and urinary sodium excretion (UNaV), and a significant fall in plasma sodium (PNa) and potassium (PK) concentrations. Urinary potassium excretion (UKV) and body fluid volume were not changed significantly. In the present experiments, similar chronic infusions were carried out in intact rabbits and in rabbits with an electrolytic lesion placed in the anteroventral third cerebral ventricle (AV3V) region. Integrity of the AV3V area is essential for normal expression of a variety of acute physiological responses to ANG II injected into the brain. In rabbits with AV3V lesions, chronic ivt infusion of ANG II did not significantly alter MAP, but WI and fractional UNaV increased, and PNa decreased in a manner identical to that of sham-lesioned control rabbits. Plasma and extracellular fluid volumes increased, and body weight and food intake decreased in all rabbits during ANG II infusion, but to a slightly greater extent in the AV3V-lesioned rabbits. We conclude that an intact AV3V region is crucial for the hypertensive effect of chronic ivt fusions of ANG II in the rabbit but is not necessary for most of the fluid and electrolyte alterations associated with such infusions.

Ischemic necrosis of multiple major joints: report of two cases.

Two patients with idiopathic ischemic necrosis of multiple major joints are described. One had both humeral and femoral heads involved and the other had involvement of the humeral heads and one femoral head. These combinations are uncommon. Specific causes could not be found in the histories, although one patient was a chronic alcoholic and and other was severely allergic to coffee dust. In the care and follow-up of patients with ischemic necrosis, attention should be given to the possibility of involvement of multiple major joints.

Hip endoprosthesis stabilization with a porous low modulus stem coating: factors influencing stabilization.

A polytetrafluoroethylene/vitreous carbon porous material has been investigated as an alternative to acrylic for hip endoprosthesis fixation. This material, which is mechanically fused to the endoprosthesis stem, has been shown to promote soft-tissue ingrowth. In 29 patients receiving a porous-coated Thompson endoprosthesis, stabilization of the porous-coated stem as observed by acceptable clinical results occurred in only about 50%. Stabilization of porous-coated endoprostheses is unsatisfactory for the following reasons: lack of press-fit, inadequate prosthetic design, infection, and technical difficulties. The major cause of 40% failure in this series was an initially inadequate press-fit.