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.

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.

Growth hormone secretagogue increases muscle strength during remobilization after canine hindlimb immobilization.

Twenty-two beagles were divided into two equal groups, and the right hindlimb of each animal was immobilized at 105 degrees of knee flexion by external fixation. After 10 weeks of fixation, the device was removed, allowing free mobility for the following 5 weeks. Each day throughout the 15 weeks, one group received a growth hormone secretagogue (treatment) at a dose of 5 mg/kg, and the other received a lactose placebo (control).

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.

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.

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.

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.

Effects of a functional knee brace on leg muscle function.

The effects of a functional knee brace on local intramuscular pressures and on calculated blood perfusion pressure in the tibialis anterior muscle of the legs of six volunteers were determined. Torque generation during dorsiflexion of the ankle joint was measured with a Kinetic Computerized ergometer, and the time to elicit muscle fatigue during exercise was recorded. For each experimental subject studies compared right with left unbraced legs, then right braced with left unbraced legs, and finally right unbraced with left braced legs.

Effect of ankle position and a plaster cast on intramuscular pressure in the human leg.

Intramuscular pressure was measured with transducer-tipped catheters that had been inserted into the anterior and deep posterior compartments of the leg in seven healthy adults. Intramuscular pressure increased three to sevenfold (depending on the position of the ankle) in both compartments after the application of a plaster cast from the proximal part of the thigh to the malleoli. While the cast was in place, the baseline intramuscular pressure was elevated by the inflation of a tourniquet, which was located on the proximal part of the thigh, to a pressure of sixty millimeters of mercury (8.

Muscle functional deficits after tourniquet ischemia.

The contractile properties of the rabbit tibialis anterior muscle were studied 48 hours after an ischemic episode induced by pneumatic tourniquet compression of the thigh. Forty animals were divided into five groups, each of which had continuous ischemia of either 1, 2, or 4 hours, or a total of 2 or 4 hours of ischemia interrupted by 10 minutes of reperfusion at 1-hour intervals. Contralateral limbs served as controls.

Intramuscular pressure varies with depth. The tibialis anterior muscle studied in 12 volunteers.

Pressures in the tibialis anterior muscle were recorded at rest and during exercise with transducer-tipped catheters in 12 volunteers while they were supine or standing. The recordings were repeated with venous stasis created by an inflated tourniquet cuff on the thigh. Catheters were placed at 3 different sites in the muscle: catheter I adjacent to the deep surface of the fascia over the anterior compartment; catheter II between the fascia and the central tendon; and catheter III deep in the muscle close to the interosseous membrane.

The use of lower tourniquet inflation pressures in extremity surgery facilitated by curved and wide tourniquets and an integrated cuff inflation system.

Use of the lowest possible cuff inflation pressure should minimize the pathogenic effects of compression beneath the pneumatic tourniquet. Curved tourniquets (designed to fit conically shaped limbs) and wider tourniquets were associated with significantly lower arterial occlusion pressure (AOP) than standard, straight tourniquets on the arms and legs of 26 normal volunteers. These tourniquets were used with an integrated tourniquet inflation system in 29 upper-extremity and 31 lower-extremity surgeries.

The effects of non-weight-bearing and limited motion on the tensile properties of the meniscus.

Recent clinical studies have suggested that many of the complications of prolonged immobilization after knee surgery can be prevented by permitting early motion while minimizing loading of healing tissues. The purpose of this study was to determine the effects of such a regimen on the tensile properties of the meniscus. The right knee of 10 skeletally mature sheep received a sham operation after which the hindlimb was placed in a harness that prevented weight bearing while permitting limited knee motion.

Effects of reperfusion intervals on skeletal muscle injury beneath and distal to a pneumatic tourniquet.

To date there have been no experimental studies specifically directed at effects of reperfusion intervals on skeletal muscle injury beneath the tourniquet. 99mTechnetium pyrophosphate (Tc 99) incorporation and correlative histology were used to assess injury 2 days after tourniquet application in muscles beneath (thigh) and distal (leg) to the cuff. Tourniquets were applied to rabbit hindlimbs for a total of either 2 or 4 hours.

Functional knee braces increase intramuscular pressures in the anterior compartment of the leg.

The effect of three different functional knee braces on intramuscular pressures in the anterior compartment of the leg was investigated in 8 healthy subjects. Pressures were recorded with the microcapillary infusion technique while the subjects were either supine, sitting, or standing. Pressures at rest in the anterior tibial muscle increased significantly following application of each of the three knee braces regardless of posture.

Decreased muscle speed, strength and fatigability following two hours of tourniquet-induced ischaemia.

Contractile and morphological properties of the rabbit tibialis anterior muscle were measured 48 hours following a two-hour ischaemic episode. Ischaemia was induced using a specially-designed pneumatic tourniquet placed on the rabbit thigh. Maximum tetanic tension of muscle subjected to ischaemia (381 +/- 77 g) was only about 30% of the tension generated by control muscles (1,212 +/- 67 g).

Viscoelastic shear properties of the equine medial meniscus.

Recent studies have shown that the meniscus is highly anisotropic in tension and that its compressive creep behavior can be modeled using biphasic theory. In this study, an alternative approach is used, where viscoelastic shear properties of the meniscal fibrocartilage are measured to determine the anisotropy and inhomogeneity of this tissue with respect to specimen location and fiber orientation. Medial menisci were obtained from eight skeletally-mature horses.

Muscle injury induced beneath and distal to a pneumatic tourniquet: a quantitative animal study of effects of tourniquet pressure and duration.

Previous recommendations regarding the "safe" period of tourniquet hemostasis were based largely on studies of ischemia distal to the tourniquet. This study quantitatively analyzed skeletal muscle injury induced beneath and distal to a pneumatic tourniquet applied to the hindlimbs of rabbits for 1, 2, or 4 hours with a cuff inflation pressure of 125, 200, or 350 mm Hg. Technetium Tc 99m pyrophosphate incorporation after systemic injection (Tc 99 uptake) and correlative histology were used to evaluate tissue damage 2 days after tourniquet application.

Effects of an in-substance conduit with injection of a blood clot on tears in the avascular region of the meniscus.

The purpose of this study was to test the hypothesis that healing of a stable tear in the avascular region of the meniscus occurs when a horizontal conduit, extending from the periphery to the defect, is filled with an exogenous fibrin clot. In 6 sheep a full-thickness laceration was made in the lateral meniscus, and autologous blood clot was then injected into the conduit. Three animals in the control group received identical meniscal tears but no additional treatment.

An animal model for the study of neuromuscular injury induced beneath and distal to a pneumatic tourniquet.

A well-controlled animal model is presented for the study of neuromuscular injury induced by a pneumatic tourniquet. This model comprises a curved tourniquet surrounded by a stiff exterior shell, both of which were specifically designed to fit the conical and oblong shape of the rabbit hindlimb. Computed tomographic imaging was used to assess transverse tissue displacement induced by tourniquet compression.

Modified criteria for the objective diagnosis of chronic compartment syndrome of the leg.

One hundred fifty-nine patients were referred to the authors for evaluation of chronic exertional leg pain from 1978 to 1987. The records of 131 patients were complete and available for retrospective review. Forty-five patients were diagnosed as having a chronic compartment syndrome (CCS) and seventy-five patients had the syndrome ruled out by intramuscular pressure recordings.

Effects of abrasion therapy on tears in the avascular region of sheep menisci.

This study was designed to test the hypothesis that abrasion of the parameniscal synovium aids healing of a stable tear in the avascular region of the meniscus in a sheep model. In six sheep, a 5-7-mm longitudinal full-thickness tear was made in the avascular inner half of the anterior part of the lateral meniscus. The parameniscal synovium was abraded superiorly and inferiorly from the meniscus periphery to the lesion.

Experimental models to promote healing of tears in the avascular segment of canine knee menisci.

Longitudinal tears were created in canine lateral menisci and techniques were applied to induce healing by removal of a core of tissue from the periphery of the meniscus to the tear or by implantation of a vascularized synovial flap into the tear. The meniscal tears did not heal in knees that were not immobilized, and they healed poorly and sporadically in knees that were immobilized in a cast but bore some weight. However, a higher percentage of tears that were treated by the core-removal or synovial-flap technique healed when the knee was firmly immobilized and weight-bearing was prevented by the use of an external skeletal fixator across the joint for eight to twelve weeks.

Intraarticular pressure during continuous passive motion of the human knee.

Intraarticular pressure (IAP) was continuously monitored during continuous passive motion (CPM) of five normal and 11 abnormal human knees using a new fiberoptic, transducer-tipped Camino catheter. IAP varied in a consistent hysteresis pattern in the normal knees, with subatmospheric pressures recorded at intermediate angles of joint flexion. A similar pattern was recorded in the abnormal knees without cruciate ligament pathology, whereas considerable variability was noted in the knees with cruciate ligament abnormality.