PubMed Health⌕ Search

Biomedical subjects

M A Posner

Publications and source records attributed to M A Posner.

At least 55 records · Page 3Linked to original sources

Irreducible dorsal dislocations of the proximal interphalangeal joint.

Dorsal dislocations of the proximal interphalangeal joint are common injuries, and reduction is usually obtained by manipulation. We describe four cases of dorsal dislocation in which attempts at reduction by manipulation were not successful. Three of these injuries were open and one was closed. At surgery, the main block to reduction in all cases was the palmar plate that had ruptured from its proximal attachment and was interposed between the joint surfaces.

Adolescent↗

Ventral medullary pH and ventilatory responses to hyperperfusion and hypoxia.

The role of a sudden increase in brain perfusion on ventral medullary surface pH (Vm pH) and minute ventilation (VI) was assessed in anesthetized peripherally chemo denervated cats. Acute hypertension (AH), produced by rapid inflation of an aortic balloon, and hypoxemia, produced with either inhalation of 1% CO (COHx) or inhalation of a hypoxic gas (HHx), were used to increase brain blood flow. In the AH group, increasing arterial blood pressure (from 122 +/- 3 to 180 +/- 5 mmHg) caused a rapid (less than 5 s) increase in Vm pH in every trial (n = 18). Associated with the mean peak increases in Vm pH (0.003 +/- 0.0004 pH units) were significant decrease in tidal volume (7-9%). In the COHx group, 17% HbCO caused a significant increase in Vm pH (0.003 +/- 0.0005 pH unit) and diminution of VI (9%). Further increases in HbCO caused a progressive ventral medullary acidosis and greater reductions in VI. The results from the HHX group were qualitatively similar to the COHx group; there was a biphasic response of Vm pH, i.e., an initial increase in Vm pH (0.008 +/- 0.001) followed by a steady decrease in Vm pH, with reductions in VI associated with both phases. We conclude that hyperperfusion, per se, produces an increase in Vm pH and a reduction in VI equivalent in magnitude to that predicted from the CO2 stimulus-response curve; the alkalotic shift in Vm pH and concomitant diminution in VI associated with mild hypoxia is probably related to an increase in ventral medullary perfusion; and the ventilatory depression associated with the medullary acidosis of moderate brain hypoxia must be attributed to another mechanism.

Acid-Base Equilibrium↗

Compartment syndrome caused by a traumatized vascular hamartoma.

A case report is presented of a traumatized vascular hamartoma producing a forearm flexor compartment syndrome; such a case has not been reported previously. The role of minor trauma in this case was important. There is a need for a high degree of suspicion in order to make an early, accurate diagnosis. Delayed surgical decompression and resection of the pathologic muscle resulted in a dramatic improvement in sensibility and digital mobility.

Adult↗

Submuscular transposition for the ulnar nerve at the elbow.

Forty patients who underwent submuscular transpositions of the ulnar nerve at the elbow (41 operations) were evaluated. A grading system was formulated to compare the preoperative and postoperative condition of each patient with respect to tenderness over the nerve, numbness, paresthesia, and muscle weakness. Thirty-seven of the 41 cases showed an improvement in grade. Of the 34 cases that demonstrated muscle weakness preoperatively, 25 improved following surgery, including five patients who had severe intrinsic muscle weakness with clawing of the ring and little finger. Muscle reattachment following nerve transposition was secure, even in a professional athlete.

Adolescent↗

Flexor superficialis tendon transfers to the thumb--an alternative to the free tendon graft for treatment of chronic injuries within the digital sheath.

Transfer of a flexor digitorum superficialis tendon is an effective procedure in restoring active flexion of the thumb following old lacerations or ruptures of the flexor pollicis longus tendon within the digital sheath when tendon repair or advancement is not possible. The ample length of the transferred tendon and, more importantly, its normal excursion make it the preferred procedure to the alternative tendon graft. The operation is usually carried out as a one-stage procedure, but, if there is severe scarring, it can follow the preliminary insertion of a silicone rod. For 23 patients, the operation was performed in a single stage in 18 and in 5 after insertion of a silicone rod. Postoperative mobility of the interphalangeal joint averaged 53.5 degrees. Mobility of the donor ring finger was complete in all patients.

Adolescent↗

Glomus tumors of the wrist.

Glomus tumors about the wrist area are rare. Three new cases are presented. A provocative diagnostic test using ethyl chloride spray has been found useful. This test is superior to the use of ice because application can be to a very small area.

Ethyl Chloride↗

Differential paraquat uptake and redox kinetics of rat granular pneumocytes and alveolar macrophages.

Possible causes for differences in cellular susceptibility to paraquat (PQ) toxicity were investigated with isolated lung cells and perfused lungs. Uptake of radiolabeled PQ was measured as a function of both time and concentration (1 x 10(-6)-1 x 10(-3) M). With alveolar macrophages, uptake was linear with concentration but with time reached a plateau as internal approached external concentration. With granular pneumocytes, uptake was linear with time but nonlinear with external concentration. Accumulation above external concentration occurred and was prevented by inhibitors of ATP synthesis. Apparently, PQ can enter both cell types by diffusion, but granular pneumocytes can also accumulate PQ by an energy-dependent process. With lungs, uptake was nonlinear with time; in the 1st hr a plateau occurred when the intracellular approached extracellular (1 x 10(-5) M) concentration, but a slower second process resulted in a 6-fold accumulation by 4 hr. The effect of PQ on NADPH oxidation was measured with the supernatant fraction (12000 x g. 10 min) from cells and lungs. The maximal rate was about 2 times higher (6.8 +/- 0.8 nmol/mg of protein . min) in granular pneumocytes than in alveolar macrophages, but the estimated kinetic constants were similar (Km-NADPH approximately 5 x 10(-6) M; Km-PQ approximately 2 x 10(-4) M). The results suggest that PQ-dependent NADPH oxidation rates would differ markedly between cell types at low PQ concentration because of energy-dependent transport into granular pneumocytes but would be fairly close at high PQ concentration where diffusion predominates. These conclusions suggest a mechanistic explanation for how differences in the toxic effects of PQ exposure might occur over a range of PQ concentrations.

Animals↗

Ray transposition for central digital loss.

In fourteen cases transposition of either the second or fifth ray was used following traumatic amputation of one or both central digits, or in conjunction with surgical removal of either the middle or ring finger when it was rendered useless by trauma, involved with a malignancy, or congenitally hypoplastic. The operative technique consisted of osteotomies at the base of the metacarpals with internal fixation of the transposed ray. When the fifth ray was transposed, the level of division of the bone was such as to provide the appearance of a more normal length of the digit.

Adolescent↗

Some aspects of bone grafting for non-union of the carpal navicular. Analysis of 41 cases.

Forty-one patients with established non-union of the carpal navicular are presented. Forty patients were treated by bone grafting, using the same operative technique in all of them. All operated fractures healed and were free of pain at the time of union. Vascularization did not seem to interfere with union in the different types of fractures. Radial styloidectomy, performed in addition to bone grafting in 26 of the patients, who had arthritic changes, improved their wrist mobility.

Adolescent↗

Management of bleeding and associated complications of hemophilia in the hand and forearm.

Hemorrhage into the hand and forearm in hemophiliacs can be devastating if not treated early and properly. Of 200 hemophiliacs followed from 1969 to 1976, thirty-four had lesions of the hand and forearm. Hemarthrosis, the most common musculo-skeletal manifestation of hemophilia, occurred in the wrist and hand on only ten occasions. Superficial hemorrhage in the seven cases seen was not followed by significant sequelae. Bleeding into the anterior muscles and into the volar aspect of the wrist, on the other hand, was complicated by contracture, neuropathy, or both in six cases. Early diagnosis, replacement of the missing clotting factor, and immobilization are essential. Fasciotomy should also be considered, though it was not done in this series. Once a Volkmann's contracture is established, surgical reconstruction is required. The fractures in the hemophiliacs in this series, as in others, healed with normal periosteal callus formation and at a normal rate. Pseudotumors of the small bones of the hand have been described but were not seen in this series. Conservative therapy is suggested. After appropriate hematological evaluation to identify the missing factor and to exclude the presence of antibodies, it is now possible to control bleeding while proceeding with the necessary treatment to restore function and prevent deformity.

Compartment Syndromes↗

Injuries to the hand and wrist in athletes.

Injuries involving tendons, ligaments, and bones are commonplace with many physical activities. Although the majority of these injuries are minor and cause only temporary discomfort, their potential for producing serious and occasionally permanent disabilities must not be ignored. The initial physical and roentgenographic examination of the injured part must be thorough. Only then can the severity of the injury be recognized and appropriate treatment undertaken. Promptness will limit the period of disability and minimize the chances of development of a chronic condition.

Athletic Injuries↗

Hydroxocobalamin therapy of cyanide intoxication in guinea pigs.

The efficacy of hydroxocobalamin (vitamin B12a) as a specific, nontoxic antidote in acute cyanide poisoning was tested. Guinea pigs receiving lethal intravenous NaCN injections were treated with either vitamin B12a or saline solution. There was a statistically significant antidotal effect of the vitamin. No toxic effect was observed with large doses of the vitamin.

Animals↗

Nitroprusside-induced cyanide poisoning: antidotal effect of hydroxocobalamin.

Sodium nitroprusside was investigated as a potential source of cyanide poisoning, Whole-blood cyanide determinations were performed on arterial samples from baboons receiving nitroprusside while anesthetized. There was a statistically significant increase in cyanide levels, as well as development of tachyphylaxis and severe metabolic acidosis. Hydroxocobalamin (vitamin B12a) infused simultaneously with nitroprusside significantly lessened the increase in cyanide levels and eliminated the development of metabolic acidosis. Nitroprusside can cause cyanide intoxication in the baboon, and hydroxocobalamin appears to be an effective antidote.

Acid-Base Equilibrium↗