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Biomedical subjects

R A Pedowitz

Publications and source records attributed to R A Pedowitz.

At least 19 recordsLinked to original sources
PubMed2006

Lower body negative pressure treadmill exercise is more comfortable and produces similar physiological responses as weighted vest exercise.

Lower body negative pressure (LBNP) treadmill exercise can generate a hypergravity load on the lower body that may improve athlete performance by mechanical and cardiovascular adaptations. This study compared the cardiovascular responses, subjective exertion and discomfort levels produced by LBNP exercise with those generated by a weighted vest (WV). We hypothesized that LBNP exercise is more comfortable than WV exercise at comparable levels of exercise. Nine subjects exercised on a treadmill at nine conditions, at 5.5 mph for 15 minutes, in which they ran in random order to avoid confounding effects: 100 %, 110 %, 120 %, 130 %, and 140 % body weight (BW), the latter four conditions were achieved by either LBNP chamber or WV. Heart rate (HR) and oxygen consumption (.VO(2)) were monitored continuously using ECG and open circuit spirometry. At the end of each test, subjects were asked to give discomfort and exertion scores using a ten-point visual analog scale (10 = maximal discomfort and exertion). For both HR and .VO(2), no significant differences were observed between LBNP and WV. Subjects reported significantly higher discomfort levels when exercising with the WV than with the LBNP at 120 % BW (5.1 +/- 0.55 vs. 3.1 +/- 0.64; p < 0.05), 130 % BW (6.2 +/- 0.42 vs. 2.3 +/- 0.44; p < 0.01) and 140 % BW (6.9 +/- 0.27 vs. 4.7 +/- 0.60; p < 0.01), while maintaining similar exertions at all conditions. Based on these results, LBNP exercise is more comfortable than standard WV exercise, while maintaining similar exertion, HR and .VO(2) values.

Adult↗
PubMed1999

Intermittent reperfusion fails to prevent posttourniquet neurapraxia.

This study examined the effects of intermittent reperfusion on peripheral nerve function. Rabbits were randomized to undergo 4 hours of 350 mm Hg tourniquet compression to a hind limb either continuously, interrupted by a single 10-minute reperfusion interval after 2 hours, or interrupted by 10 minutes of reperfusion after each hour. A control group had the tourniquet applied for 4 hours but it was never inflated. The animals were examined clinically for neuromuscular dysfunction and the structure and function of the peripheral nerves were evaluated 1 week after tourniquet compression. Animals that underwent compression had a foot drop and decreased toe-spread reflex. There was greater intraneural edema and slower nerve conduction velocity in nerve segments that were directly compressed by the tourniquet but no apparent abnormalities in segments distal to the tourniquet. Intermittent reperfusion failed to diminish the clinical, structural, or functional consequence of the neurologic injury.

Animals↗
PubMed1999

Effects of tourniquet compression on neuromuscular function.

Neuromuscular function in New Zealand White rabbits was evaluated after thigh tourniquet compression in the directly compressed quadriceps muscles and the distal tibialis anterior by measuring isometric contractile function after supramaximal stimulation of the motor nerve. Tourniquet compression resulted in markedly decreased force production beneath and distal to the tourniquet. Two days after compression, maximal quadriceps force production was decreased to 46% of control values with 125 mm Hg compression and 21% of control values after 350 mm Hg compression. Maximum tibialis anterior force production declined to 70% of control values after 125 mm Hg thigh compression and 24% of control values after 350 mm Hg thigh compression. Functional deficits were greater in the directly compressed quadriceps muscles, but the quadriceps and tibialis anterior had significantly increased impairment when the tourniquet inflation pressure was increased from 125 mm Hg to 350 mm Hg. Three weeks after compression, quadriceps function had returned to 94% of control value after 125 mm Hg compression and 83% after 350 mm Hg. Tibialis anterior function returned to 88% of control values after 125 mm Hg thigh compression and 83% after 350 mm Hg. Clinically, the use of lower inflation pressures may minimize the complications of tourniquet use and enhance postoperative recovery.

Animals↗
PubMed1999

Symptomatic pseudarthrosis of the acromion: report of a case and review of the literature.

The case of a twenty-three-year-old male with a symptomatic pseudarthrosis of the acromion is presented. Open reduction and internal fixation with a plate, screw, and tension band construct supplemented with a bone graft was performed and early range of motion was initiated. Nine months after surgery, the fracture was healed and the patient had excellent function of the shoulder. The literature on pseudarthrosis of the acromion is reviewed.

Acromion↗
PubMed1998

Evaluation of patellar cartilage in cadavers with a low-field-strength extremity-only magnet: comparison of MR imaging sequences, with macroscopic findings as the standard.

PURPOSE: To assess a low-field-strength extremity-only magnet in the evaluation of patellar cartilage abnormalities. MATERIALS AND METHODS: Four regions in each of 10 patellae from cadavers were examined in the transaxial plane with a 0.2-T extremity-only magnet and the following sequences: T1-weighted spin echo, proton density- and T2-weighted turbo spin echo, short inversion time inversion recovery, and two- and three-dimensional gradient echo with and without magnetization transfer contrast subtraction. Lesions depicted with MR imaging and seen in anatomic sections of the patellae were classified according to a modified standardized arthroscopic grading system. MR imaging and pathologic correlation was then analyzed. RESULTS: On the basis of macroscopic findings, 14 of 40 cartilage regions were found to be intact, grade 2A lesions were present in eight regions, grade 2B lesions in eight, and grade 3 lesions in 10. For the various MR imaging techniques, sensitivity was 25%-62% for grade 2A lesions, 50%-75% for grade 2B lesions, and 60%-90% for grade 3 lesions. Specificity was 81%-97% for grades 2A and 2B lesions, and 80%-97% for grade 3 lesions. Accuracy was 75%-82% for grade 2A lesions, 75%-92% for grade 2B lesions, and 80%-92% for grade 3 lesions. CONCLUSION: High-grade cartilaginous lesions can be evaluated reliably with low-field-strength MR imaging by using a combination of imaging sequences.

Aged↗
PubMed1998

Exertional compartment syndrome of the upper extremity.

Exertional compartment syndrome is characterized by intracompartmental pressures that rise transiently following repetitive motion or exercise, thereby producing temporary, reversible ischemia, pain, weakness, and, occasionally, neurologic deficits. The exact cause or pathogenesis remains unclear; a disturbance of microvascular flow caused by elevated intramuscular pressure leads to tissue ischemia, depletion of high-energy phosphate stores, and cellular acidosis. Anatomic contributing factors may include a limited compartment size, increased intracompartmental volume, constricted fascia, loss of compartment elasticity, poor venous return, or increased muscle bulk. The diagnosis is suspected based on history and confirmed with physical examination and intramuscular pressure evaluation before and after exercise (stress test). Differential diagnosis includes claudication or other vascular abnormalities, myositis, tendinitis, periostitis, chronic strains or sprains, stress fracture, other compression or systemic neuropathies, and cardiac abnormalities with angina or referred extremity pain. Initial treatment includes activity modification; refractory symptoms can be managed with elective fasciotomy.

Chronic Disease↗
PubMed1997

Short echo time projection reconstruction MR imaging of cartilage: comparison with fat-suppressed spoiled GRASS and magnetization transfer contrast MR imaging.

PURPOSE: To evaluate short echo time (TE) projection reconstruction magnetic resonance (MR) imaging in the detection of cartilage lesions. MATERIALS AND METHODS: Twenty-seven cartilage regions of 10 human patellar specimens were examined with the following MR sequences: short TE projection reconstruction (repetition time msec/TE msec, 400/0.15), fat-suppressed three-dimensional spoiled gradient-recalled acquisition in the steady state (Spoiled GRASS) (50/10, 60 degrees flip angle), and magnetization transfer contrast (MTC) subtraction (400/6). MR findings were correlated with histopathologic grading of the cartilage. RESULTS: For detection of cartilage lesions, sensitivity of projection reconstruction imaging (100%) was significantly greater (P = .03) than that of MTC (62%) but not significantly greater (P > .05) than that of Spoiled GRASS (81%) imaging. Accuracy of projection reconstruction was significantly greater than that of MTC (P = .004) and Spoiled GRASS (P = .03) imaging. Unmasking of collagen fibers was most predictive of abnormal signal intensity of the cartilage with all sequences. CONCLUSION: In vitro, short TE projection reconstruction MR imaging provides superior delineation of cartilage lesions when compared with two other sequences. On Spoiled GRASS and MTC images, signal intensity of the superficial layer of cartilage is not a reliable sign for surface integrity.

Aged↗
PubMed1997

Intramuscular deoxygenation during exercise in patients who have chronic anterior compartment syndrome of the leg.

Currently, the definitive diagnosis of chronic compartment syndrome is based on invasive measurements of intracompartmental pressure. We measured the intramuscular pressure and the relative oxygenation in the anterior compartment of the leg in eighteen patients who were suspected of having chronic compartment syndrome as well as in ten control subjects before, during, and after exercise. Chronic compartment syndrome was considered to be present if the intramuscular pressure was at least fifteen millimeters of mercury (2.00 kilopascals) before exercise, at least thirty millimeters of mercury (4.00 kilopascals) one minute after exercise, or at least twenty millimeters of mercury (2.67 kilopascals) five minutes after exercise. Changes in relative oxygenation were measured with use of the non-invasive method of near-infrared spectroscopy. In all patients and subjects, there was rapid relative deoxygenation after the initiation of exercise, the level of oxygenation remained relatively stable during continued exercise, and there was reoxygenation to a level that exceeded the pre-exercise resting level after the cessation of exercise. During exercise, maximum relative deoxygenation in the patients who had chronic compartment syndrome (mean relative deoxygenation [and standard error], -290 +/- 39 millivolts) was significantly greater than that in the patients who did not have chronic compartment syndrome (-190 +/- 10 millivolts) and that in the control subjects (-179 +/- 14 millivolts) (p < 0.05 for both comparisons). In addition, the interval between the cessation of exercise and the recovery of the pre-exercise resting level of oxygenation was significantly longer for the patients who had chronic compartment syndrome (184 +/- 54 seconds) than for the patients who did not have chronic compartment syndrome (39 +/- 19 seconds) and the control subjects (33 +/- 10 seconds) (p < 0.05 for both comparisons).

Case-Control Studies↗
PubMed1996

Comparison of functional deficits in the rabbit tibialis anterior following tourniquet ischemia and tourniquet compression.

The purpose of this study was to measure the contractile properties of skeletal muscle after direct compression with a tourniquet and to compare these properties with those found after a similar period of tourniquet ischemia. A rabbit model of tourniquet compression of the tibialis anterior was developed and tested for this investigation. Fifty-seven animals then were divided into four protocol groups: (a) thigh tourniquet (ischemia) at 350 mm Hg (46.7 kPa), (b) leg tourniquet (compression) at 350 mm Hg (46.7 kPa), (c) leg tourniquet at 125 mm Hg (16.7 kPa), and (d) controls. A significant decrease in maximum tetanic tension was demonstrated in all three experimental groups. Direct compression at 350 mm Hg resulted in the greatest decline in maximum tetanic tension (22.6% of control), followed by compression at 125 mm Hg (30.5%) and ischemic injury (40.2%). In addition, direct compression at 350 mm Hg resulted in a significantly greater loss of force-generating capacity when compared with the ischemic group (p < 0.01). A similar pattern was noted for the rate of rise in maximum tetanic tension. Gross histologic examination of the tibialis anterior sections was consistent with the results of functional testing, with the more severe abnormalities noted in the compressed specimens. These results clearly demonstrate that tourniquet compression injury results in a more significant loss of functional strength and contractile speed than tourniquet ischemia. Further investigations on the safe limits of tourniquet use thus should be directed toward measuring the effect of the pneumatic tourniquet on the underlying soft tissues.

Animals↗
PubMed1996

Effects of an antioxidant in a rabbit model of tourniquet-induced skeletal muscle ischemia-reperfusion injury.

The purpose of this study was to evaluate the effects of U74006F, a new antioxidant, on isometric contractile function after tourniquet-induced ischemia-reperfusion injury. Twenty-six NZW rabbits underwent either 2 or 4 hr of thigh tourniquet compression. Animals were randomized to receive U74006F or an equal volume of its citrate vehicle. When tibialis anterior function was tested 2 days later, there was no difference between treatment groups in peak tension, rate of force production, contraction time, half relaxation time, or resistance to fatigue. The use of U74006F failed to improve functional outcome in this model of ischemia-reperfusion injury.

Animals↗
PubMed1996

A surgical algorithm for treatment of cystic degeneration of the Meniscus.

Cystic degeneration of the meniscus is not uncommon. Recent reports suggest that most (or all) meniscal cysts are associated with a meniscal tear, and that the treatment of choice is arthroscopic partial meniscectomy with cyst decompression. This report describes a case of a symptomatic lateral meniscal cyst that was suspected clinically and confirmed by magnetic resonance imaging, but was not associated with a meniscal tear at arthroscopy. Open cyst extirpation and peripheral meniscal repair were performed to maximize preservation of meniscal tissue. A clinical algorithm is presented for management of meniscal cysts.

Adult↗
PubMed1996

What would you do? Acute extension block caused by anterior cruciate ligament tear: a case report.

Acute knee locking is usually attributed to a displaced meniscus tear. This case involved late diagnosis of mechanical extension block caused by anterior displacement of a torn anterior cruciate ligament (ACL) with impingement in extension. Definitive reconstruction was delayed after debridement of the ACL stump to improve preoperative range of motion. Despite this, the patient still had difficulty regaining extension after surgery. Early treatment of mechanical extension block may facilitate motion recovery after ACL reconstruction.

Adolescent↗
PubMed1996

Imaging of osseous and cartilaginous intraarticular bodies in the knee: comparison of MR imaging and MR arthrography with CT and CT arthrography in cadavers.

PURPOSE: To compare magnetic resonance (MR) imaging and MR arthrography with computed tomography (CT) and CT arthrography in the detection of intraarticular bodies in the knee. MATERIALS AND METHODS: Cuboid (3- or 6-mm-long sides) osseous and cartilaginous bodies were implanted in 16 cadaveric knee specimens. MR imaging was performed with T1-weighted spin-echo (SE), T2-weighted SE, proton-density-weighted SE, gradient recalled acquisition in the steady state (GRASS), and spoiled GRASS sequences. MR arthrography was performed in two phases with saline and 2 mmol/L gadopentetate dimeglumine. CT and CT arthrography were performed in the transaxial plane. RESULTS: MR arthrography yielded the highest accuracy for the detection of osseous and cartilaginous bodies combined (92%) and was significantly (P < .01) better than MR imaging (57%-70%), CT arthrography (80%), and CT (74%). Accuracy of CT arthrography was significantly better than that of MR imaging and that of CT. Accuracy of saline-enhanced MR arthrography was significantly inferior (P < .001) to that of gadolinium-enhanced MR arthrography. CONCLUSION: MR arthrography is the best imaging technique for detection of individual intraarticular bodies. CT arthrography is the second most accurate method. Spoiled GRASS and T2-weighted SE sequences are the most accurate at MR imaging. The presence of intraarticular fluid and performance of saline-enhanced MR arthrography improve detectability of intraarticular bodies.

Arthrography↗
PubMed1996

Shoulder impingement syndrome: influence of shoulder position on rotator cuff impingement--an anatomic study.

OBJECTIVE: The purpose of the study was to investigate the relationship of the distal supraspinatus tendon to the coracoacromial arch on radiographs and MR imaging at various shoulder positions. MATERIALS AND METHODS: Radiopaque and gadolinium-impregnated markers were sutured to the distal aspect of the supraspinatus tendon and along the coracoacromial ligament in three cadavers. While varying positions of the shoulder, we obtained gross anatomic visualization, radiographs, and MR images. RESULTS: Impingement of the distal aspect of the supraspinatus tendon between the acromion and the greater tuberosity of the humerus was well visualized during forward flexion and abduction of more than 30 degrees. Shoulder impingement was best seen at 60 degrees forward flexion, 60 degrees abduction, and internal rotation. CONCLUSION: MR imaging of different shoulder positions may help reveal the pathogenesis of shoulder impingement syndrome.

Aged↗
PubMed1996

Pressure generation beneath a new thermoplastic cast.

A new cast immobilizer that is heat-shrunk to conform to an injured extremity was examined. The purpose of these studies was to compare pressures beneath the thermoplastic cast with those beneath fiberglass casts on a laboratory model and on the forearms of human volunteers. Pressures measured beneath fiberglass casts on metal cylinders averaged 36 mm Hg. Thermoplastic casts on the smaller cylinder that allowed 42% shrinkage produced a mean pressure of 25 mm Hg; those placed on the larger cylinder that allowed 17% shrinkage produced a mean pressure of 39 mm Hg. Pressures measured on the forearms of healthy volunteers averaged 22 mm Hg beneath fiberglass casts and 31 mm Hg beneath the thermoplastic casts. These pressures were considerably less than pressures that have been shown to occlude the microcirculation of the skin. Acute compartment syndromes result from swelling within a limited space and remain a serious concern clinically when swelling is anticipated under any type of constraining cast. The results of these studies indicate that the new cast should not produce a greater risk of circulatory compromise to the limb than previously used fiberglass materials.

Analysis of Variance↗
PubMed1995

Effects of tourniquet use in anterior cruciate ligament reconstruction.

Although tourniquets are used commonly during anterior cruciate ligament (ACL) surgery, little data are available regarding their effects on postoperative function. This retrospective study evaluated 94 patients who had an arthroscopically assisted, autogenous bone-patellar ligament-bone ACL reconstruction between 1988 and 1991 at the San Diego Kaiser Hospital. A tourniquet was used in 48 patients (T+ group). No tourniquet was used in 46 patients (T- group). The surgical and postoperative protocols were identical for the two groups. There were no bleeding complications. There was no significant difference in anesthesia time between the two groups. This study has shown that ACL surgery can be performed expeditiously without a pneumatic tourniquet. Quadriceps strength recovery after surgery was less in the T+ group at 12 weeks after surgery, but there was no significant difference between the groups 52 weeks after surgery. Difference in thigh girth was greater in T+ group 6 and 12 weeks after surgery, but there was no significant difference between the groups 52 weeks after surgery.

Adult↗