Biomedical subjects
Publications and source records attributed to D R Roy.
Paraplegia immediately following spinal fusion is a known problem. This case demonstrates the importance of long-term follow-up of fusion patients. Prompt attention must be given to any change in neurological status. A careful check must be made for pseudarthrosis and for secondary compression of the spinal cord as possible causes of neurological compromise.
Effects of acute-base disturbances on fractional delivery of potassium to the juxtamedullary end-descending limb were examined by micropuncture in the rat to test the hypothesis that potassium is reabsorbed from the collecting duct and is secreted in juxtamedullary pars recta or descending limb in the renal medulla. In metabolic acidosis, fractional potassium delivery was only slightly reduced compared with control values and was a function of potassium excretion, as the hypothesis predicts. Fractional potassium delivery was sharply reduced both in respiratory acidosis and metabolic alkalosis and was no longer a function of potassium excretion. Although seemingly inconsistent with the recycling hypothesis, the latter finding may be reconciled by the following observations. In respiratory acidosis, vasa recta blood flow nearly doubled, which would lead to vascular washout of interstitial potassium. In metabolic alkalosis, flow rate in the pars recta or descending limb was reduced by 28%, which would limit transepithelial potassium addition. The results indicate complex effects of acid-base disturbances on fractional potassium delivery to the end-descending limb, which can be unified by postulated changes in transepithelial potassium concentration differences across the juxtamedullary pars recta or descending limb. An unexpected observation emerged--fractional delivery of water to the end-descending limb declined as a function of plasma bicarbonate concentration when all groups were combined.
The effects of acute metabolic and respiratory acidosis and acute metabolic alkalosis on magnesium excretion and on fractional magnesium delivery to the end-accessible proximal tubule of the superficial nephron and the end-descending limb of the juxtamedullary nephron were examined by micropuncture in anesthetized thyroparathyroid-intact rats. Compared with normal control rats, acute metabolic acidosis (HCl infusion) did not produce any significant change. Acute respiratory acidosis (15% CO2 in inspired air) significantly increased the absolute but not the fractional excretion of magnesium and did not alter fractional delivery of magnesium to the end-accessible superficial proximal tubule or juxtamedullary end-descending limb. Acute metabolic alkalosis (NaHCO3 infusion) significantly reduced absolute and fractional magnesium excretion and fractional magnesium delivery to the end-descending limb of the juxtamedullary nephron but did not affect fractional magnesium delivery to the end-accessible proximal tubule of the superficial nephron. Tubule fluid-to-ultrafilterable magnesium ratio was a function of tubule fluid-to-plasma inulin ratio in the end-descending limb when all groups were combined. These results suggest that although acute metabolic or respiratory acidosis has no significant effect, acute metabolic alkalosis enhances magnesium reabsorption in the juxtamedullary proximal nephron--possibly in the pars recta.
Urine was observed to flow intermittently in the collecting ducts of the extrarenal papilla of antidiuretic rats. The purpose of this investigation was to test Reinking and Schmidt-Nielsen's hypothesis that intermittent flow plays an important role in the production of maximally concentrated urine. Samples of collecting duct fluid were obtained from the base and tip of the papilla by micropuncture through the intact ureter. Fluid osmolality rose sharply from base, 894+/-120 mosmol/kg H(2)O(-1) (mean+/-SE), to tip, 1,667+/-114 (P<0.001), a distance of only 2 mm, and was due exclusively to reabsorption of water. After excision of the ureter, which abolished intermittent flow, osmolality fell modestly at the base to 723+/-82 mosmol/kg H(2)O(-1) (P < 0.02), but strikingly at the tip to 1,012+/-103 (P < 0.001). The pelvic ureter was paralyzed by topical verapamil and dimethylsulfoxide, which abolished intermittent flow. Osmolality of urine at the tip was not changed (1,959+/-184 mosmol/kg H(2)O(-1) before, vs. 1,957+/-126 after paralysis). The ureter was severed just beyond the papillary tip, a maneuver which preserved intermittent flow but abolished urinary reflux over the papilla. Urinary osmolality fell from 1,876+/-134 mosmol/kg H(2)O(-1) to 1,284+/-115 (P < 0.005). These findings demonstrate that when the ureter is intact, over half of the increase in urinary osmolality above isotonicity occurs in the terminal one-fourth of the medullary collecting duct and is due exclusively to water reabsorption (no net solute addition). It is the continuity of the ureter, rather than intermittent flow due to ureteral peristalsis, which is essential for the formation of a maximally concentrated urine.
Glucose ingestion or infusion increases calcium and magnesium excretion in the human. To assess the role of renal tubular glucose reabsorption and of the parathyroid glands in this phenomenon, we performed standard two-phase clearance experiments in fed, volume-expanded male Sprague-Dawley rats. When compared with a group of animals receiving only 0.9% NaCl (group I), animals infused with glucose (group II) excreted significantly more calcium at any given level of sodium excretion (delta FECa, 1.95 +/- 0.24 vs. 0.69 +/- 0.18, P < 0.001). Normoglycemic hyperinsulinemia (group III) did not reproduce this increase in calcium excretion. In the group given phloridzin during sustained hyperglycemia (group IV), calcium excretion was well below that of control animals at any given level of sodium excretion. The glycosuric-hyperglycemia group (group V) used to assess the effect of glycosuria seen in group IV responded with a striking calciuria (delta FECa, 3.31 +/- 0.43, P < 0.001, compared with group IV). TPTX animals responded to glucose in the same way as intact animals (delta FECa, 4.8 +/- 0.5 vs. 2.18 +/- 0.3 in TPTX saline controls, P < 0.001). Magnesium excretion in all groups followed the same pattern as calcium. We conclude that renal tubular glucose reabsorption is essential for glucose to augment calcium and magnesium excretion. The presence of the parathyroid glands was not required for this phenomenon to occur.
A micropuncture study of Perognathus penicillatus, a small rodent native to the deserts of the southwestern United States was performed to evaluate the function of the superficial nephron. Data are reported for 12 animals of 17 g average body wt. Mean glomerular filtration rate was 475 +/- 73 microliter X min-1 X g kidney wt-1. Urine osmolality averaged 1,154 +/- 197 mosmol/kg H2O. Single nephron glomerular filtration rate averaged 43 nl X min-1 X g kidney wt-1 in the proximal tubule and 48 in the distal tubule, values that are not significantly different. In terms of the filtered load remaining unreabsorbed at the end of the accessible proximal tubule, the average percentages were 46 water, 48 total solute, 45 sodium, 56 phosphorus, 62 potassium, 71 magnesium, and 54 calcium. The concentrations of potassium and magnesium in fluid samples increased significantly along the proximal tubule. Approximately at the midpoint of the distal tubule, fractional delivery of water, 13.1%, was greater than that for total solute, 10%, or sodium, 7%, indicating that the intervening segment of nephron reabsorbed solute and sodium in excess of water. The function of the superficial nephron resembles that of species previously investigated except for potassium reabsorption in the proximal convoluted tubule.
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We describe the temporal pattern of mRNA expression of some of the molecular components of the NO/cGMP second messenger system in the developing rat visual cortex and the effect of dark rearing on their expression levels using semiquantitative RT-PCR. mRNA expression for these molecules was altered by dark rearing in one of three ways: (1) no change--rod, olfactory, and cone/testis CNG channels, nonselective cation channels gated by cyclic nucleotides and highly permeable to Ca2+; (2) decrease--cyclic nucleotide phosphodiesterases which regulate cyclic nucleotide levels, and soluble guanylyl cyclase, the key synthetic enzyme producing cGMP and potently activated by nitric oxide; and (3) increase--cGMP kinase 1, a key enzyme activated by cGMP to phosphorylate a variety of intracellular proteins including cytoskeletal elements. These data suggest important and distinct roles for the cGMP system in both early and late developmental events in the rat visual cortex.
The records of 43 patients who underwent 64 open bone peg epiphysiodeses for slipped capital femoral epiphysis were retrospectively reviewed. There were 18 unstable and 46 stable slips. The average duration of follow-up was 35 months (range, 12-100). Healing occurred in all cases at an average of 17 weeks after surgery. At the time of healing, 27 hips (42%) showed a change in the degree of slip. At the most recent visit, the head-shaft angle had improved in 19 hips (30%), although the majority of hips showed resorption of the anterior neck prominence. The degree of remodeling showed no correlation with time to healing, duration of follow-up, or the status of the triradiate cartilage. The average operating time and blood loss per hip were 122 +/- 34 min and 426 +/- 238 ml, respectively. Complications included four hips with avascular necrosis and three with chondrolysis, three infections, four delayed wound healings, seven cases of transient anterolateral thigh hypesthesia, and 44 hips with hetertopic ossification. Because of the potential morbidity of this procedure, we no longer perform it as a primary operation for stable slipped capital femoral epiphysis.
Torticollis in childhood may be a sign of many disorders. Five cases, with torticollis as the initial sign of a posterior fossa tumor, are presented. The diagnosis and treatment of the tumor was considerably delayed in all patients because posterior fossa tumor was not considered in the initial differential diagnosis. In two patients, operative procedures on the sternocleidomastoid muscle were performed before discovering the underlying causative tumors. Four of the five patients also had other associated symptoms such as headache, nausea, and vomiting. It is stressed that in acquired torticollis, posterior fossa tumor be considered in the differential diagnosis.
We reviewed 32 children with 41 radiation-therapy associated slipped capital femoral epiphyses (RTASCFE). Ten were from the authors' institutions and 22 from the literature. Gender distribution was equal. The age at diagnosis of the malignancy was 4.3 +/- 3.1 years; the amount of radiation was 4,240 +/- 1,445 rads. Children with RTASCFE presented younger (10.4 +/- 3.2 years) than a routine SCFE. The average symptom duration was 5 +/- 6 months. Children with RTASCFE are usually thin (median weight, 10th percentile) in contrast to children with typical SCFE, who are usually obese (<95th percentile). The majority (82%) of the slips were mild, compared to routine SCFEs (approximately 50%); 28% were bilateral. There was a positive linear relationship between the age at presentation of the SCFE and the age at diagnosis of the malignancy; there was a negative linear relationship between the age at presentation of the SCFE and the amount of radiation therapy.
We evaluated the utility of limited magnetic resonance imaging (MRI) after surgical reduction and spica casting for developmental dysplasia of the hip (DDH) with respect to feasibility, time, need for sedation, and charge. Eighteen limited MRI examinations were performed in 10 children (mean age, 9 months) with a 1.5-T magnet. Twenty-eight dysplastic hips were imaged within 4 hours of surgery. Mean imaging time for two sequences was approximately 3 minutes. All examinations were interpretable, although three were degraded by motion. No child required sedation, additional sequences, or repeat study. Two thirds of the dysplastic hips had no proximal femoral ossification center on MRI. A reduced charge was assigned to the examination. We conclude that using limited MRI to confirm intraoperative reduction for DDH is feasible and desirable. The lack of radiation or need for sedation, the reduced charge that reflects the short time needed for imaging, and the superb visualization of nonosseous structures have made it our preferred method to evaluate surgical reduction of DDH.
Questionnaires sent to chairpersons of orthopedic surgery residency programs and to private practitioners were analyzed to determine how training in children's orthopedics is accomplished, to define which procedures should be taught to residents, and to describe what the private practitioner perceives as appropriate education in children's orthopedics. The amount of time spent on children's orthopedics is adequate by present standards. For most procedures, the residency directors and private practitioners were in agreement concerning what was appropriate to teach. Education during the residency continues to be the most important resource used by the practicing orthopedic surgeon in pediatric problems.
The records of 29 patients who underwent epiphyseodesis of 56 physes in which a percutaneous (minimal incision) technique was used were reviewed. Length of surgery averaged 36 min per physis. Growth arrest was achieved in every instance. There were no cases of unplanned angular growth, no deep infections, and no difficulties in regaining full joint motion were reported. Epiphyseodesis of the proximal tibial physis was performed on 16 patients without epiphyseodesis of the proximal fibula, yet symptoms attributable to fibular overgrowth were not reported. Some technical variations that have evolved in our procedure are described.
Adolescent and adult hip dysplasia can be surgically treated by rotating the acetabulum into a better weight-supporting position; however, open pelvic osteotomies are among the most invasive of all pediatric orthopaedic procedures. Endoscopic pelvic osteotomy offers the theoretical advantages of magnified visualization of the bone cuts, minimized surgical dissection, and rapid postoperative recovery. The technique of endoscopically assisted triple innominate osteotomy requires the combination of endoscopic skills and facility with more standard surgical approaches.
The purpose of this study was to quantify the forces produced by the growth plates of the adolescent human proximal tibia and distal femur. The postoperative deformations of staples used to treat genu valgum were correlated with similar staple deformations produced by mechanical testing. Staple deformation was measured in sequential radiographs of 35 knees in 20 patients. Mechanical tests were performed on new staples to determine the force necessary to bend the staples to the observed displacements. Based on deformation at final examination, the static equivalent loads exerted at the joint centerline by the growth plates of the proximal tibia and distal femur were 0.5 kN per physis. The estimated corresponding stress was 1 MPa. These results indicated that successful lower limb hemiepiphysiodesis suppressed a longitudinally directed, centrally applied compressive force on the order of body weight.
The early diagnosis of osteomyelitis of the patella in children can be difficult due to the rarity of this infection and to the vagaries of presentation which may be either acute with systemic signs or insidious with mild local signs. We present four cases of patellar osteomyelitis to illustrate the spectrum of this disorder. There should be a high index of suspicion with persistent pain and swelling above the knee, septic prepatellar bursitis, and septic knees that do not respond to conventional management. Management parallels treatment of osteomyelitis of other bones.
Percutaneous quadriceps recession was compared with open quadricepsplasty in the Finder's type 5 category of congenital hyperextension deformities. Six open quadricepsplasties and six percutaneous recessions were performed between the ages of 5 and 58 days. Follow-up averaged 2 years 3 months. All knees remained reduced and maintained an improved range of motion (ROM). Percutaneous recession avoids a long incision, requires less dissection and surgical time, and has a shorter healing time. When performed in the neonate, percutaneous recession eases management of the child and treatment of coexistent deformities.