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Biomedical subjects

A A Sapega

Publications and source records attributed to A A Sapega.

At least 19 recordsLinked to original sources
PubMed1995

The posteromedial portal in knee arthroscopy: an analysis of diagnostic and surgical utility.

We reviewed 400 consecutive knee arthroscopy cases in a predominantly sports medicine practice to determine (1) the frequency of posteromedial portal usage under a prospectively established set of indications, and (2) the impact of posteromedial portal access on patient diagnosis and management. Diagnostic posteromedial portals were used in 22% of anterior cruciate ligament (ACL)-deficient knees, and in 11% of stable knees with nonpatellar (usually meniscal) lesions. When used, posteromedial portal visualization showed treatable lesions 64% of the time, the majority of which were repairable peripheral meniscus tears. In 63% of these cases, no definite lesion had been identified by initial routine anterior portal viewing and probing. Of the 22 patients with posteromedial meniscus tears that were discovered only via posteromedial portal access, 9 had recently undergone anterior portal arthroscopy by other surgeons, during which none of these tears were detected. Posteromedial surgical portals (19 cases) were most useful for synovectomy, posterior cruciate stump resection before arthroscopic reconstruction, and posterior horn medial meniscectomy in exceptionally tight knees. Posteromedial portal access is often useful diagnostically in cases where (1) posteromedial meniscal lesions are frequent (i.e., ACL-deficient knees) and/or suspected on the basis of preoperative symptoms or imaging studies, and (2) full, direct visualization of the entire superior meniscosynovial junction is not possible via standard anterior portals. The option of a surgical posteromedial portal should be entertained whenever frontal approaches for posteromedial instrument work prove inefficient or unsuccessful.

Anterior Cruciate Ligament↗
PubMed1994

Anatomy and function of the posterior cruciate ligament.

At the present time, our understanding of the PCL still lags behind that of the ACL. This knowledge gap has narrowed over the past few years, however, as more basic research has shed new light on the complex anatomy and functional mechanical behavior of the PCL and the nearby capsuloligamentous structures. Recent insights have included recognition that the PCL is composed of a fiber continuum rather than morphologically separate bands or bundles, a better appreciation of the predominantly nonisometric behavior of the intact PCL, and a greater awareness of the PCLs importance in preserving normal articular kinematics. Continued advances in the basic science of the PCL are a prerequisite for improvements in the treatment and rehabilitation of its injury.

Biomechanical Phenomena↗
PubMed1993

Arthroscopic visual field mapping at the periphery of the medial meniscus: a comparison of different portal approaches.

The posteromedial compartment, particularly the posterior horn of the medial meniscus, has been shown by many investigators to be a common source of diagnostic errors in knee arthroscopy when access is limited to anterior portals. To better understand the anatomical basis of this apparent technical limitation, we quantified the visible versus the "blind" zones of the posteromedial meniscal periphery present when using the following arthroscopic approaches in six fresh knee specimens: (a) direct anteromedial frontal view with a 30 degrees arthroscope (AM-30 degrees); (b) anterolateral portal, 30 degrees arthroscope, transnotch view (AL-30 degrees); (c) anterolateral portal, 70 degrees arthroscope, transnotch view (AL-70 degrees); (d) central portal, 70 degrees arthroscope, transnotch view (C-70 degrees); and (e) posteromedial portal, 30 degrees arthroscope, direct rear view (PM-30 degrees). The AM-30 degrees approach visualized only the anterior 50% or less of the total superior meniscosynovial junction length, in all knees. The AL-30 degrees, C-70 degrees, AL-70 degrees, and PM-30 degrees portal approaches visualized the posteriormost 16.4%, 24.2%, 31.6%, and 54.9% of the upper meniscal rim, respectively. In conjunction with the AM-30 degrees visual field, the PM-30 degrees approach provided the most complete overall visualization of the superior meniscosynovial junction, leaving a mean blind zone of only 8.4% (12 mm) between the anterior and posterior visual fields. The AL-30 degrees, C-70 degrees, and AL-70 degrees approaches left significantly greater portions (means of 47%, 39.1%, and 31.7%, respectively) of the meniscal rim universalized.

Aged↗
PubMed1993

Phosphorus nuclear magnetic resonance: a non-invasive technique for the study of muscle bioenergetics during exercise.

Phosphorus nuclear magnetic resonance (31P NMR) spectroscopy is a non-destructive analytical laboratory technique that, due to recent technical advances, has become applicable to the study of high-energy phosphate metabolism in both animal and human extremity muscles (in vivo). 31P NMR can assay cellular phosphocreatine, ATP, inorganic phosphate, the phosphorylated glycolytic intermediates, and intra-cellular pH in either resting or exercising muscle, in a non-invasive manner. NMR uses non-perturbing levels of radio-frequency energy as its biophysical probe and can therefore safely study intact muscle in a repeated fashion while exerting no artifactual influence on ongoing metabolic processes. Compared with standard tissue biopsy and biochemical assay techniques, NMR possesses the advantages of being non-invasive, allowing serial in situ studies of the same tissue sample, and providing measurements of only active (unbound) metabolites. NMR studies of exercising muscle have yielded information regarding fatigue mechanisms at the cellular level and are helping resolve long-standing questions regarding the metabolic control of glycolysis, oxidative phosphorylation, and post-exercise phosphocreatine re-synthesis. NMR is also being utilized to measure enzymatic reaction rates in vivo. In the near future, other forms of NMR spectroscopy may also permit the non-invasive measurement of tissue glycogen and lactate content.

Animals↗
PubMed1990

Arthroscopically-assisted anterior cruciate ligament reconstruction: a follow-up study.

In order to determine the early results of arthroscopically-assisted reconstruction of the anterior cruciate ligament (ACL), a comprehensive follow-up evaluation of 20 athletes with an average postoperative time of 26 months was performed. Clinical knee examination and measurements of thigh circumference, range of motion, and maximum quadriceps/hamstring strength were obtained. A detailed personal interview regarding activity level, subjective ratings, and functional status was conducted. At follow-up, anterior knee laxity was dramatically reduced, with no patients demonstrating a pivot-shift. Thigh circumference, range of motion, and maximum muscle strength were not significantly different than in the normal, uninvolved leg. Sixteen patients (80%) had returned to their preinjury activity level. Only one of the remaining four cited knee problems as part of the reason for not returning to preinjury athletic activities. Patients' subjective ratings were highly favorable. The findings in this study led to the conclusion that modifying traditional open methods of ACL reconstruction to an arthroscopically-assisted technique is an attractive surgical option.

Adolescent↗
PubMed1990

Testing for isometry during reconstruction of the anterior cruciate ligament. Anatomical and biomechanical considerations.

Instrumented tibiofemoral (bone-to-bone) excursion wires were implanted in the mid-substance of the anteromedial, central, and posterior fiber-regions of the anterior cruciate ligament through limited anterior and posterior arthrotomies in eight fresh knees from cadavera. The change in the distance of linear separation between each pair of osseous fiber-insertion sites was measured and was plotted against the angle of flexion of the knee as the knee was cycled through a 120-degree range of motion. Testing conditions likely to be present during intraoperative testing for isometry were used (anterior cruciate fibers transected, quadriceps relaxed, femur stabilized with the patient in the supine position and the leg freely dependent, and motion of the knee induced in neutral rotation by force applied at the level of the foot). In no instance did the insertion-site centers of any fiber-region exhibit isometric behavior (change in the distance of linear separation of 1.0 millimeter or less). The least deviations from isometry (range, 1.4 to 3.1 millimeters) were observed for the anteromedial sites, under conditions when the gravitational dependency of the lower leg was constrained. When the leg hung in a dependent manner during passive motion, the deviation from isometry of the anteromedial sites of insertion increased significantly (range, 2.8 to 5.6 millimeters). The central sites of insertion were generally less isometric than the anteromedial sites, and the posterior sites were the least isometric, regardless of testing conditions.

Aged↗
PubMed1989

Compartment syndrome: a quantitative study of high-energy phosphorus compounds using 31P-magnetic resonance spectroscopy.

The purpose of this study was to quantitate the intracellular high-energy phosphate compounds during 6 hours of tissue ischemia in the anterior tibial compartment of beagles subjected to an induced traumatized compartment syndrome. The goal of this work was to provide clinicians with objective criteria to augment clinical judgment regarding surgical intervention in the impending compartment syndrome. A beagle model was utilized in which the Delta pressure (difference between the mean arterial pressure and compartment pressure) could be controlled. The model, in conjunction with 31P-magnetic resonance spectroscopy (MRS), allowed a measure of high-energy phosphate compounds and pH in the compartment at various Delta pressures. The extent of ischemic metabolic insult in the compartment was then quantitated. Our data suggest the following: 1) lower Delta pressures result in a proportionally greater drop in the intracellular phosphocreatine ratio and pH; 2) at lower Delta pressures, there is proportionally greater decline in the percentage recovery post-fasciotomy; 3) blood pressure is extremely important and periods of hypotension may result in increased muscle damage at lower compartment pressures.

Animals↗
PubMed1988

The bioenergetics of preservation of limbs before replantation. The rationale for intermediate hypothermia.

Of all tissues of the extremities, muscle is the least tolerant of ischemia. Hypothermia of tissue is considered beneficial for the maintenance of viability of muscle in amputated limbs before surgical replantation, but it has never been established that conventional cooling in an ice bath or its equivalent (temperature of tissue, approximately 1 degree Celsius) is the optimum level of hypothermia for minimizing metabolic derangement in ischemic muscle. In this study, we first defined the time course and level of metabolic derangement of muscle in twenty-eight ischemic hind limbs in cats at 22, 15, 10, 5, and 1 degree Celsius. The levels of adenosine triphosphate and phosphocreatine and the mean intracellular pH of the muscles in the lateral aspect of the thigh in each limb were monitored with phosphorus nuclear magnetic-resonance spectroscopy over time. The excised muscles from six freshly amputated legs of live humans were then similarly studied to determine whether muscles from cats and from humans exhibit comparable bioenergetic responses to hypothermic ischemia. A final series of ten ischemic hind limbs from cats was studied by nuclear magnetic resonance and muscle biopsy for direct biochemical assay of tissue energy metabolites to compare the metabolic benefits of two different methods of preserving limbs: continuous cooling in an ice bath, and a newly devised protocol for the rapid induction and maintenance of so-called intermediate (10 +/- 5 degrees Celsius) hypothermia of tissue. Ischemic skeletal muscle in cats exhibited a paradoxical metabolic response to extreme cold (1 degree Celsius). The rate of metabolic deterioration progressively declined with decreasing temperature of tissue to 10 degrees Celsius. However, at 5 degrees Celsius, no additional benefit was detected, and at 1 degree Celsius, there was a significant acceleration in the rates of degradation of adenosine triphosphate and phosphocreatine and in the production of lactate. The rate of degradation of adenosine triphosphate in human ischemic muscle was also faster at 1 degree Celsius than at 10 degrees Celsius. This paradoxical response is apparently due to a severe inhibition of the calcium pump of the sarcoplasmic reticulum of the muscle cell at temperatures of less than 5 degrees Celsius. The inhibition permits an efflux of calcium to the myofibrils, which stimulates both glycolysis and the degradation of adenosine triphosphate by myofibrillar adenosine triphosphatase.

Adenosine Triphosphate↗
PubMed1988

The compartment syndrome. An experimental and clinical study of muscular energy metabolism using phosphorus nuclear magnetic resonance spectroscopy.

In an experimental ischemic compartment syndrome in dogs, phosphorus (31P) nuclear magnetic resonance (NMR) spectroscopy was used to determine the tissue pressure threshold at which resting skeletal muscle begins to use anaerobic energy sources due to insufficient cellular oxygen delivery. The interactive effects of systemic perfusion pressure and moderate muscle trauma on this anaerobic threshold were also evaluated. The severity of cell injury produced by various degrees of compartment pressurization over an eight-hour period was concomitantly studied using muscle biopsy and electron microscopy. Clinical correlation of a preliminary patient series studied using 31P-NMR demonstrated that the threshold for cellular metabolic derangement in skeletal muscle subjected to increased tissue pressure was more closely associated with the difference between mean arterial blood pressure (MABP) and compartment pressure than with the absolute compartment pressure alone. The difference is termed MABP-compartment pressure, or delta P. The lowest delta P at which a normal cellular metabolic state can be maintained is approximately 30 mmHg in normal muscle and 40 mmHg in moderately traumatized muscle. It is imperative to interpret compartment pressure measurements in light of the degree of soft tissue trauma sustained and the patient's blood pressure, as well as the clinical signs and symptoms.

Animals↗
PubMed1987

Osteochondritis dissecans: analysis of mechanical stability with radiography, scintigraphy, and MR imaging.

Twenty-one joints with stable (n = 9) or loose (n = 12) osteochondritis dissecans (OCD) lesions were examined in 15 subjects with plain radiography, three-phase bone scintigraphy, and magnetic resonance (MR) imaging. The lesion size and the thickness of the sclerotic margin as measured on plain radiographs were good parameters for predicting loosening. However, bone scintigraphy was more sensitive and specific in determining the mechanical stability of OCD lesions. MR imaging permitted direct visualization of loosening and fragment displacement; the latter permits differentiation of in situ loosening from a grossly unstable lesion. The noninvasive nature of bone scintigraphy and MR imaging makes them potentially preferable diagnostic modalities to arthrography for evaluating the mechanical status of OCD lesions.

Adolescent↗
PubMed1987

Phosphorus nuclear magnetic resonance: a non-invasive technique for the study of muscle bioenergetics during exercise.

Phosphorus nuclear magnetic resonance (31P NMR) spectroscopy is a non-destructive analytical laboratory technique that, due to recent technical advances, has become applicable to the study of high-energy phosphate metabolism in both animal and human extremity muscles (in vivo). 31P NMR can assay cellular phosphocreatine, ATP, inorganic phosphate, the phosphorylated glycolytic intermediates, and intra-cellular pH in either resting or exercising muscle, in a non-invasive manner. NMR uses non-perturbing levels of radio-frequency energy as its biophysical probe and can therefore safely study intact muscle in a repeated fashion while exerting no artifactual influence on ongoing metabolic processes. Compared with standard tissue biopsy and biochemical assay techniques, NMR possesses the advantages of being non-invasive, allowing serial in situ studies of the same tissue sample, and providing measurements of only active (unbound) metabolites. NMR studies of exercising muscle have yielded information regarding fatigue mechanisms at the cellular level and are helping resolve long-standing questions regarding the metabolic control of glycolysis, oxidative phosphorylation, and post-exercise phosphocreatine re-synthesis. NMR is also being utilized to measure enzymatic reaction rates in vivo. In the near future, other forms of NMR spectroscopy may also permit the non-invasive measurement of tissue glycogen and lactate content.

Adenosine Triphosphate↗
PubMed1986

Electrical stimulation of human muscle studied using 31P-nuclear magnetic resonance spectroscopy.

This study used phosphorous nuclear magnetic resonance (31P-NMR) spectroscopy to examine the metabolic demand resulting from electrical muscle stimulation (EMS) applied to human skeletal muscle. For each of six subjects, the forearm flexor muscle group was monitored with 31P-NMR during both maximum voluntary and 6-s EMS-induced contractions. A simple protocol using a tourniquet was added in one subject to assess the role of blood flow in this model. Eight hertz (nontetanic) EMS showed less (p less than 0.025) depletion of phosphocreatine (36%) than did tetanic 70-Hz EMS (60%), voluntary isometric (66%), and voluntary isokinetic (68%). The results of the tourniquet studies suggested that the nontetanic EMS allowed relatively increased muscle blood flow and oxygen supply during contraction. Tetanic EMS provided a similar metabolic demand to that of conventional resistive exercise, as measured by 31P-NMR spectroscopy.

Adult↗
PubMed1985

Optimizing tourniquet application and release times in extremity surgery. A biochemical and ultrastructural study.

Despite numerous studies investigating the pathophysiology of tourniquet ischemia, definitive data at the cellular level have been lacking and no consensus regarding safe tourniquet-application times in extremity surgery has emerged. In light of the particular vulnerability of skeletal muscle to ischemic injury, we determined the degree of muscular metabolic derangement and cell damage produced by seven different protocols of tourniquet application and release, each providing three hours of total tourniquet time. We performed thirty-six experiments on canine hind limbs, comparing the following time-patterns of tourniquet application: I--three sequential one-hour periods, II--two sequential one and one-half-hour periods, III--two hours followed by one hour, and IV--a single continuous three-hour application. Five and fifteen-minute reperfusion intervals between ischemic periods were compared for the first three time-patterns, creating a total of seven different tourniquet protocols. Muscular metabolic derangement and cell injury were evaluated by monitoring changes in the cellular bioenergetic state (high-energy phosphate profile), cell pH, post-ischemic leakage of creatine phosphokinase, and ultrastructural cell degeneration. At the intracellular level, the metabolic recovery of muscle during reperfusion was much faster than previous studies focusing on extracellular parameters have indicated. In all instances complete intracellular bioenergetic recovery occurred within five minutes after tourniquet release. The use of one or more five-minute reperfusion intervals significantly reduced the degree of ischemic cell injury, as indicated by a decrease in creatine phosphokinase leakage and myofibrillar destruction. No additional benefit was derived by extending the reperfusion periods to fifteen minutes. The longest period of continuous ischemia in each tourniquet-application protocol bore the closest relationship with the amount of cell damage produced. Within the spectrum of observed pathological changes, time-patterns I and II produced comparatively little muscle damage.

Animals↗
PubMed1984

Muscle ischemia and hypothermia: a bioenergetic study using 31phosphorus nuclear magnetic resonance spectroscopy.

UNLABELLED: Following traumatic limb amputation it is common clinical practice to maintain the ischemic tissues in a hypothermic state until surgical reimplantation. Of all extremity tissues, muscle is the most sensitive to ischemia; it is therefore imperative that reperfusion be established before diffuse muscle necrosis. Although it has been shown both clinically and experimentally that hypothermia prolongs the viability of ischemic skeletal muscle, the presumed mechanism by which this occurs has not been confirmed at the cellular level. This study was undertaken to quantify the effect of conventional iced-saline hypothermia on anaerobic cell metabolism and high-energy phosphate depletion in traumatically devascularized muscle. METHODS: Phosphorus nuclear magnetic resonance spectroscopy (31P NMR) was employed to noninvasively monitor cellular phosphocreatine (PCr), ATP, and intracellular pH over time in ischemic cat hindlimb muscle under room temperature (22 degrees C) and 1 degree C hypothermic conditions. RESULTS: Muscular PCr depletion was significantly retarded by tissue hypothermia but the rate of ATP depletion was not. A progressive, severe cellular acidosis was observed in the room-temperature muscle. Iced tissue cooling produced a dramatic initial rise in cell pH which significantly reduced the absolute degree of subsequent acidotic changes. SIGNIFICANCE: These findings question our understanding of hypothermic tissue preservation, which has generally been assumed to work on the basis of decreased tissue metabolism, thus conserving critical cellular ATP levels. The empirical benefit derived by cooling muscle in an iced medium may actually be related to the cellular alkalinization produced by tissue cooling, as this significantly mitigates the profound acidosis that would otherwise occur.

Adenosine Triphosphate↗