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Robert A Pedowitz

Publications and source records attributed to Robert A Pedowitz.

14 recordsLinked to original sources
PubMed2006

Ambulation in simulated fractional gravity using lower body positive pressure: cardiovascular safety and gait analyses.

The purpose of this study is to assess cardiovascular responses to lower body positive pressure (LBPP) and to examine the effects of LBPP unloading on gait mechanics during treadmill ambulation. We hypothesized that LBPP allows comfortable unloading of the body with minimal impact on the cardiovascular system and gait parameters. Fifteen healthy male and female subjects (22-55 yr) volunteered for the study. Nine underwent noninvasive cardiovascular studies while standing and ambulating upright in LBPP, and six completed a gait analysis protocol. During stance, heart rate decreased significantly from 83 +/- 3 beats/min in ambient pressure to 73 +/- 3 beats/min at 50 mmHg LBPP (P < 0.05). During ambulation in LBPP at 3 mph (1.34 m/s), heart rate decreased significantly from 99 +/- 4 beats/min in ambient pressure to 84 +/- 2 beats/min at 50 mmHg LBPP (P < 0.009). Blood pressure, brain oxygenation, blood flow velocity through the middle cerebral artery, and head skin microvascular blood flow did not change significantly with LBPP. As allowed by LBPP, ambulating at 60 and 20% body weight decreased ground reaction force (P < 0.05), whereas knee and ankle sagittal ranges of motion remained unaffected. In conclusion, ambulating in LBPP has no adverse impact on the systemic and head cardiovascular parameters while producing significant unweighting and minimal alterations in gait kinematics. Therefore, ambulating within LBPP is potentially a new and safe rehabilitation tool for patients to reduce loads on lower body musculoskeletal structures while preserving gait mechanics.

Adult↗
PubMed2006

Comparison and performance characteristics of 3 different knots when tied with 2 suture materials used for shoulder arthroscopy.

PURPOSE: To compare the performance of a standard suture material with that of a new material across several arthroscopic knot configurations. METHODS: Three knots were evaluated (Duncan loop, Weston, and San Diego knots) with the use of 2 suture materials (No. 2 Ethibond [Ethicon, Somerville, NJ] and No. 2 Force Fiber [Stryker Endoscopy, San Jose, CA]). Ten samples were tested for each knot and suture configuration. Samples were pretensioned to 10 N and were mechanically loaded from 10 to 45 N for 1,000 cycles. The number of cycles to 3 mm of loop elongation was recorded as "early" slippage. Intact knots with no evidence of early slippage were then subjected to a load-to-failure test so that the ultimate failure strength of the knot/material could be determined. RESULTS: Force Fiber knots required a statistically greater number of cycles to reach 3 mm of slippage compared with Ethibond knots (P < .0001). A single Force Fiber knot experienced 3 mm of displacement during cyclic loading; all others survived to 1,000 cycles. One third of all Ethibond knots were displaced to 3 mm during cyclic loading. For Ethibond sutures, no significant differences in ultimate failure strength were observed between knots (average, 143 N across knot types). For Force Fiber sutures, the San Diego knot (279 +/- 41 N) was statistically similar in ultimate failure strength to the Weston knot (254 +/- 41 N), but it was significantly stronger than the Duncan knot (224 +/- 70 N) (P < .03). CONCLUSIONS: The higher failure loads associated with Force Fiber may allow the surgeon to increase suture tension during knot tying, thereby creating a tighter knot. Loop elongation with Force Fiber occurred at loads that were greater than the typical breakage load for No. 2 Ethibond. Force Fiber is a new material that may be useful for various arthroscopic procedures. CLINICAL RELEVANCE: Force Fiber provided increased biomechanical stability compared with Ethibond regardless of knot type. The cost benefit of using very strong yet very stiff sutures must be clinically evaluated.

Arthroscopy↗
PubMed2005

Knee instability: the orthopedic approach.

Clinical management of knee ligament injuries ranges from simple observation to complex multiligament reconstruction. Radiographic evaluation, including magnetic resonance imaging, is an important part of the diagnostic regimen that may significantly alter the treatment plan. This article reviews the clinical presentation and evaluation of isolated and combined knee ligament injuries and presents the indications, utility, and clinical impact of radiographic imaging on surgical management.

Humans↗
PubMed2005

Lower body positive-pressure exercise after knee surgery.

Lower body positive pressure allows unloading of the lower extremities during exercise in a pressurized treadmill chamber. This study assessed the preliminary feasibility of lower body positive pressure exercise as a rehabilitation technique by examining its effects on gait mechanics and pain, postoperatively. Fifteen patients who had arthroscopic meniscectomy or anterior cruciate ligament reconstruction participated in this study. Patients exercised for 5 minutes at 2.0 mph under three body weight conditions (normal body weight, 60% body weight, and 20% body weight) in random order. Bilateral ground reaction force, electromyographs, and dynamic knee range of motion were collected, and pain was assessed using a visual analog scale. Ground reaction forces for surgically treated and contralateral extremities were reduced 42% and 79% from normal body weight conditions when ambulating at 60% and 20% body weight, respectively. After meniscectomy, ambulatory knee range of motion decreased only at 20% body weight (37 degrees), compared with normal body weight conditions (49 degrees). Peak electromyographic activity of the biceps was maintained at all body weight conditions, whereas that of the vastus medialis was reduced at 20% body weight. Pain relief was significant with lower body positive pressure ambulation after anterior cruciate ligament reconstruction. This study showed that lower body positive pressure exercise is effective at reducing ground reaction forces, while safely facilitating gait postoperatively.

Adult↗
PubMed2005

Use of tissue ultrafiltration for treatment of compartment syndrome: a pilot study using porcine hindlimbs.

OBJECTIVES: To demonstrate the efficacy of compartment syndrome ultrafiltration for the treatment of acute compartment syndrome in an animal model. Our hypothesis is the removal of interstitial fluid will result in a reduction of intramuscular pressure compared with untreated controls in a model of bilateral induced compartment syndrome. DESIGN: Controlled experimental model. SETTING: Animal research facility. PATIENTS/PARTICIPANTS: Three pairs of porcine hindlimbs. INTERVENTION: Acute compartment syndrome was created in the pig hindlimb by infusion of saline to maintain the intramuscular pressure 30 mm Hg greater than the animal's mean arterial pressure for 8 hours. After a 2-hour reperfusion interval, ultrafiltration (removal of fluid through 1 mm diameter porous catheters, connected to -500 mm Hg suction) was commenced in 1 limb only and continued for 9.5 hours. MAIN OUTCOME MEASURES: Intramuscular pressure, ultrafiltrate volume, ultrafiltrate and serum levels of creatine kinase and lactate dehydrogenase, histologic measurement of extracellular and intracellular edema, as well as the degree of cellular necrosis. RESULTS: Intramuscular pressure tended to be lower on the treated side at the end of the treatment period [treated leg: 9.3 +/- 4.0 mm Hg (+/- SE), control leg: 19.3 +/- 1.4 mm Hg, P = 0.03]. Analysis of ultrafiltrate fluid showed that levels of creatine kinase and lactate dehydrogenase were elevated compared with serum levels. Creatine kinase levels in serum were measured at 4150 +/- 780 U/L, whereas ultrafiltrate levels of creatine kinase were 28,700 +/- 17,700 U/L (+/- SE) (P = 0.1). Lactate dehydrogenase was measured at 1950 +/- 180 U/L in serum, but markedly elevated in ultrafiltrate [160,000 +/- 88,900 U/L (+/- SE), P = 0.05]. Quantification of cellular and interstitial dimensions showed no difference in control and experimental limbs. Quantification of the degree of muscle necrosis revealed 6.1 +/- 2.7% necrosis in the treated limb compared to 11.3 +/- 1.6% necrosis in the control group (P = 0.02, df = 2, 1-tailed paired t test). CONCLUSION: This pilot study demonstrates the feasibility of tissue ultrafiltration for reduction of intramuscular pressure in this porcine model. Further studies are underway. Compartment syndrome ultrafiltration may be useful prophylactically in patients at risk for acute compartment syndrome. Sampling of interstitial fluid and frequent measurement of intramuscular pressure may allow earlier diagnosis and treatment of acute compartment syndrome, whereas the reduction of tissue pressure by compartment syndrome ultrafiltration may prevent acute compartment syndrome from occurring. Additionally, compartment syndrome ultrafiltration will not hinder the ability of clinicians to use the clinical examination and pressure monitoring as the gold standard.

Animals↗
PubMed2005

Space exercise and Earth benefits.

The detrimental impact of long duration space flight on physiological systems necessitates the development of exercise countermeasures to protect work capabilities in gravity fields of Earth, Moon and Mars. The respective rates of physiological deconditioning for different organ systems during space flight has been described as a result of data collected during and after missions on the Space Shuttle, International Space Station, Mir, and bed rest studies on Earth. An integrated countermeasure that simulates the body's hydrostatic pressure gradient, provides mechanical stress to the bones and muscles, and stimulates the neurovestibular system may be critical for maintaining health and well being of crew during long-duration space travel, such as a mission to Mars. Here we review the results of our studies to date of an integrated exercise countermeasure for space flight, lower body negative pressure (LBNP) treadmill exercise, and potential benefits of its application to athletic training on Earth. Additionally, we review the benefits of Lower Body Positive Pressure (LBPP) exercise for rehabilitation of postoperative patients. Presented first are preliminary data from a 30-day bed rest study evaluating the efficacy of LBNP exercise as an integrated exercise countermeasure for the deconditioning effects of microgravity. Next, we review upright LBNP exercise as a training modality for athletes by evaluating effects on the cardiovascular system and gait mechanics. Finally, LBPP exercise as a rehabilitation device is examined with reference to gait mechanics and safety in two groups of postoperative patients.

Bed Rest↗
PubMed2004

Ischemic-preconditioning does not prevent neuromuscular dysfunction after ischemia-reperfusion injury.

The primary purpose of this study was to evaluate ischemic-preconditioning (IPC) as a means of improving tolerance to ischemia-reperfusion (IR) stress on neuromuscular function. A secondary objective was to isolate the area of injury within the neuromuscular unit responsible for contractile dysfunction after IR injury. Twenty-eight male rabbits were randomly assigned to four groups (sham, IPC only, sustained ischemia only, IPC and sustained ischemia). The IPC protocol consisted of three cycles of 10 min of tourniquet-induced ischemia (125 mmHg) followed by 10 min of reperfusion. Sustained ischemia was induced by 350 mmHg external compression for 2 h. Peak tetanic tension of the tibialis anterior (TA) muscle was evaluated 48 h after the tourniquet protocol by both peroneal nerve and direct muscle stimulation, with and without pharmacologic neuromuscular junction blockade. Animals subjected to combined IPC and sustained ischemia had an equivalent loss of contractile force to those undergoing sustained ischemia alone. Two hours of tourniquet-induced ischemia resulted in marked dysfunction of the TA neuromuscular unit when evaluated by peroneal nerve stimulation (p < 0.0001). Isolation of the TA muscle from the peroneal nerve with direct muscle stimulation and neuromuscular junction blockade preserved muscle function after 3 h of ischemia. In our model, these results clearly demonstrate that IPC provides no significant protective effect from IR injury to either nerve or muscle function in our model. In addition, nerve or neuromuscular junction injury, rather than muscle damage, is identified as primarily responsible for IR-related muscle dysfunction.

Algorithms↗
PubMed2004

Initial laxity does not correlate with subsequent laxity after ACL reconstruction in humans: a prospective evaluation.

Fifty-seven patients without other ligament injury underwent anterior cruciate ligament reconstruction (50 B-L-B, 7 hamstring). KT-1000 assessments were made preoperatively in clinic under anesthesia before and immediately after fixation and at 6-month follow-up. Preoperative manual maximum (ManMax) side-to-side difference (ManMaxdelta) under anesthesia (9.2 +/- 3.5 mm) was significantly larger than in clinic (6.1 +/- 1.8 mm), P < .0001. This difference is important when arthrometer thresholds are used for decision making. ManMaxdelta increased significantly from -0.7 +/- 2.5 mm immediately after surgery to 2.1 +/- 2.3 mm at 6 months (P < .0001). There was no significant correlation between immediate postoperative and 6-month ManMaxdelta (r = .125).

Adolescent↗
PubMed2003

EMG power spectra of intercollegiate athletes and anterior cruciate ligament injury risk in females.

PURPOSE: Females have a disproportionately high incidence of anterior cruciate ligament (ACL) injuries compared with males in analogous sports. Although the pathogenesis of this higher frequency has not been elucidated, gender differences in neuromuscular control of the knee may play an important role. This study evaluates EMG power spectra of the quadriceps and hamstring muscles during dynamic, fatiguing exercise to examine differences between male and female intercollegiate athletes. METHODS: Fifty-one collegiate basketball and soccer players (25 female, 26 male) were studied. Maximum voluntary contraction (MVC) was determined for knee flexion and extension. Three consecutive 2-min bouts of isokinetic knee flexion and extension exercise were performed at 40% MVC. EMG activity in the biceps femoris and vastus medialis obliquus was recorded using bipolar surface electrodes. RESULTS: MVC normalized to body weight was significantly greater in males than in females for the quadriceps (P< 0.01). Quadriceps coactivation ratios were significantly higher in females than in males during knee flexion exercises (P< 0.01). CONCLUSIONS: This study demonstrates differences in the EMG power spectra for females when compared with a matched group of males. Increased quadriceps coactivation in females may increase anterior tibial loads under dynamic conditions, thus placing the ACL at higher risk for injury in the female athlete.

Adolescent↗
PubMed2002

Effect of gravity on localization of chondrocytes implanted in cartilage defects.

The transplantation of autologous chondrocytes under a periosteal flap has been used to treat focal cartilage defects. Results have been promising but occasionally involve complications ranging from graft hypertrophy to detachment. The objective of this study was to determine if gravitational forces affect the uniformity of cell distribution within the defect. Using an ex vivo bovine model, the orientation relative to gravity of a repaired full-thickness articular cartilage defect was found to affect the initial distribution of transplanted chondrocytes, prelabeled with 3H-thymidine. After 4 hours, the injected cells (3H-radioactivity) were primarily at the base of the defect (79%) in samples oriented in the up position, primarily at the dependent semicylindrical half of the defect (83%) in samples oriented to the side, and primarily at the periosteal top of the defect (78%) in samples oriented upside-down. Subsequently, the cell distribution remained unchanged after reorientation into other positions. These results indicate that injected chondrocytes localize under the influence of gravity within the initial few hours after injection. Therefore, the defect orientation during this time can be an important factor in the uniformity of cell distribution in the autologous chondrocyte implantation procedure and may be an important determinant of the ultimate clinical outcome.

Analysis of Variance↗
PubMedDate not supplied

Increasing the insertion depth of suture anchors for rotator cuff repair does not improve biomechanical stability.

The purpose of this study was to evaluate whether deeper-than-recommended insertion of a suture anchor within the rotator cuff footprint of human cadaveric humeri affects fixation characteristics. Metallic 5-mm screw-in anchors loaded with a single No. 2 suture were placed in the infraspinatus footprint of 8 human cadaveric humeri at standard and deep depths. Specimens were cyclically loaded from 10 to 45 N for 500 cycles and then loaded to failure. Cylic displacement, failure load, and failure mode were compared. All deep anchors became flush within a few cycles, and both anchor depths displaced and rotated at the bone surface. Displacement of the deep anchors was significantly greater than that of standard anchors. There was no difference in failure load. Cyclic testing showed significant displacement, regardless of anchor position, possibly leading to gap formation of the repair. Deep placement of suture anchors for increased purchase caused greater displacement and is not recommended.

Aged↗
PubMedDate not supplied

Evaluation of a virtual reality simulator for arthroscopy skills development.

We evaluated a virtual reality shoulder arthroscopy simulator using a standardized skills-assessment algorithm in 3 specific groups with various degrees of surgical expertise. The simulator (Mentice Corp, Gothenberg, Sweden) consists of a computer-based, dual-force feedback system with video monitor. Modeled structures include cartilage, labrum, ligaments, biceps tendon, and rotator cuff. The study included 3 groups of volunteers: group 1, medical students interviewing for orthopaedic residency (n = 35); group 2, orthopaedic residents interviewing for sports medicine fellowship (n = 22); and group 3, experienced faculty at a shoulder surgery course (n = 21). Data were collected anonymously and subjects completed a standardized test protocol designed to assess accuracy and efficiency. Subjects used the probe to "touch" a sphere that appeared at various locations within the joint (11 positions total). The sphere changed location immediately on contact with the tip of the probe. The following parameters were calculated by the computer: time (from touching the first ball until touching the eleventh ball), path ratio (percent of measured path length relative to the ideal path), collisions (number of times the probe / arthroscope contacted any tissue), and injuries (collisions beyond a threshold force). Test time and path ratio differed significantly as a function of surgical experience. There was no significant difference in probe collisions between the groups. Arthroscope collisions and injuries averaged 2 or less in all of the groups. There was significant correlation between path ratio and time to complete the test in groups 1 and 2 (r =.527 and r =.827, respectively, P <.001), but not in group 3 (r =.376, P =.10). There was essentially normal distribution of time performance in groups 1 and 2. Time was shorter and more consistent in group 3, suggesting greater consistency in the experienced surgeons. These data suggest that this arthroscopy simulator facilitates discrimination of arthroscopic skills. Computer-based simulation technology provides a major opportunity for surgical skills development without morbidity and operating room inefficiency.

Arthroscopy↗
PubMedDate not supplied

Biomechanical evaluation of a new technique for rotator cuff repair.

BACKGROUND: In recent studies, investigators have used a cyclic loading model to investigate the efficacy of rotator cuff fixation modalities. HYPOTHESIS: A bioabsorbable poly-D-lactic acid screw and toothed washer implant will provide more stable fixation of rotator cuff repairs than standard suture anchor techniques. STUDY DESIGN: Controlled laboratory study. METHODS: Forty bovine shoulders (ages 3 to 6 months) had 1 x 2 cm defects created in the infraspinatus tendon. There were five repair groups (eight specimens per group) consisting of either two screw and washer implants or two suture anchors. Four suture techniques were tested: single-loaded anchors with simple sutures, double-loaded anchors with simple sutures, single-loaded anchors with horizontal mattress sutures, or single-loaded anchors with modified Mason-Allen sutures. Repairs were loaded at 5-second cycles from 10 to 180 N with use of a hydraulic testing machine. The number of cycles to gap formation of 5 and 10 mm was recorded. RESULTS: Gap formation of 5 and 10 mm occurred significantly later for the screw repair group than for any of the suture anchor groups. There was no significant difference between suture groups. CONCLUSIONS: The bioabsorbable screw and washer provided more stable fixation than suture anchor techniques under isometric cyclic loading conditions. CLINICAL RELEVANCE: This is a time-zero study of implant performance. The results indicate that the implant may decrease clinical failures in the early postoperative period under standard rehabilitation protocols.

Analysis of Variance↗