ABSTRACT Eighty-four patients whose knees showed symptoms of chronic anterior cruciate laxity wer... more ABSTRACT Eighty-four patients whose knees showed symptoms of chronic anterior cruciate laxity were treated by rehabilitation, activity modification designed to avoid recurrent symptoms, the use of a knee brace for activities, and periodic examination and close follow-up to detect progressive deterioration of the joint. The objective of this study was to observe the effect of rehabilitation and activity modification on functional disability. Failure of this program was considered to be an indication for surgical reconstruction. The results were evaluated after three years by both subjective and objective criteria. The patients in the study had sustained the original knee injury an average of eight years earlier, were an average of twenty-eight years old, and wished to continue an athletic or recreationally active lifestyle. The patients showed a wide spectrum of initial disability. Under the non-operative management program, more than one-third of the patients improved and were well compensated with no or minimum symptoms during activities of daily living or during recreational activities that before treatment could not be performed. However, these knees could still not be considered normal and continued to have symptoms to some degree, usually during strenuous sports activity. One-third of the patients became worse and failed the program, complaining of symptoms of pain, swelling, or giving-way that prevented any recreational activities and often were present with daily activities. Eighteen of the eighty-four patients subsequently required reconstructive surgery because of such a functional disability, and an additional eighteen patients became worse and were considering surgery. Thus, thirty-six (43 per cent) of the eighty-four patients were not benefited by the program. It was often difficult to predict initially which knees would not improve with the program, which emphasizes the necessity for an initial nonoperative approach. Also, given the present uncertain long-term success rate of the currently available reconstructive surgical procedures of the knee, it is advisable that the functional disability of the laxity be clearly established. The frequency with which the knee was reinjured had a statistically significant correlation with chronic pain and swelling and the over-all severity of the condition of the knee. We concluded that recurrent giving-way injuries, even if occurring only two or three times a year, may in time produce significant damage to the joint. Athletic activities that cause even sporadic reinjuries are to be avoided even when the symptoms between injuries are negligible. The individuals who continued active sports despite symptoms had an over-all poor prognosis. One-third of the patients did not comply with recommended modifications or substitution of activities in order to prevent reinjuries or recurrent symptoms. The results of our study validate the usefulness of the eight-point treatment program, including the need for close follow-up, determining the individual patient's goals and demands, and activity modification and counseling. Arthroscopy is indicated in certain knees to detect the true extent of joint deterioration and, in some patients, the necessity for early surgical intervention.
Mechanische Faktoren beeinflussen nicht nur die Entwicklung, Differenzierung und das Remodeling d... more Mechanische Faktoren beeinflussen nicht nur die Entwicklung, Differenzierung und das Remodeling des gesunden Knochens [1, 2, 3, 4], sondern sind auch fur die Frakturheilung von groser Bedeutung. Interfragmentare Bewegungen im Frakturspalt konnen je nach Ausmas die Kallusbildung induzieren und den Heilungsprozes beschleunigen oder aber zur Knochenresorption oder Pseudarthrose fuhren [5, 6, 7, 8]. Es ist daher anzunehmen, das unterschiedliche mechanische Einflusse verschiedene zellularen Reaktionen bewirken, die letztendlich fur Erfolg oder Miserfolg der Heilung entscheidend sind. Um die zellularen Ursachen mechanischer Effekte bei der Frakturheilung zu untersuchen, wurde ein Zellstimmulationsgerat entwickelt, das es erlaubt, isolierte Zellen durch zyklische Dehnungen zu stimulieren. Wichtige Fragen, die mit diesem System untersucht werden sollen, sind die Auswirkungen verschieden groser Dehnungen auf die Zellaktivitat von Osteoblasten und Fibroblasten. Es soll gezeigt werden, welchen Einflus zyklische Dehnungen auf die Proliferation, alkalische Phosphataseaktivitat, Lactatdehydrogenaseaktivitat, Kollagenbiosynthese und Orientierung der Zellen haben. Die Reaktionen der Osteoblastenkulturen sollen mit Fibroblastenkulturen derselben Spender verglichen werden.
It is little wonder that the casual reader of knee orthopedic articles is left somewhat bewildere... more It is little wonder that the casual reader of knee orthopedic articles is left somewhat bewildered about ligament function and the clinical laxity tests used in assessing knee stability. In the past there has been wide disagreement about these issues among many knowledgeable knee surgeons. Newer clinical and biomechanical information has helped to clear up some important areas of disagreement, but correct diagnosis of knee instability is not a simple matter. Knee examinations must be very precise and meticulous to diagnose the straight and rotatory laxities. Some laxities are obscured and others are very straightforward. Still, there are practical biomechanical concepts that govern the successful interpretation of clinical laxity tests. This paper describes two of these concepts that are common to all laxity tests. Once recognized, the concepts clarify much prior confusion and help the examiner correctly interpret results of the laxity examinations.
The amount of local tissue deformation at the equatorial region of the left ventricle is quantita... more The amount of local tissue deformation at the equatorial region of the left ventricle is quantitated by the ratio of the instantaneous cross-sectional area of a tissue element to the cross-sectional area at end-diastole. The area ratio, AR, was computed for the circumferential and longitudinal, apex to base, direction throughout the cardiac cycle from catheterization and cineangiographic data on 36 patients. The patients were divided into four groups: normal left ventricualr function—15, compensated volume overload—6, decompensated volume overload—9, and congestive cardiomyopathy—6. The peak longitudinal area ratio was elevated in the compensated group (P <0.001) and not statistically significant from normal in the decompensated group. A larger fraction of the cardiac cycle was required to reach the peak longitudinal (p <0.01) and circumferential (p <0.05) area ratio in the compensated group. The volume overload compensatory process apparently involves a change in the relative magnitude and timing of tissue deformation. The hypo-contractile ventricle was characterized by a reduction in the sum of the logitudinal and circumferential area ratios, which for all six patients in the congestive cardiomyopathy group, had a value less than any of the other thirty patients.
Tissue grafts are widely used in the repair of damaged tendons and ligaments. However, studies ha... more Tissue grafts are widely used in the repair of damaged tendons and ligaments. However, studies have shown that these grafts rapidly lose their strength shortly after implantation [1]. One possible mechanism for such behavior is the degradation of the extracellular matrix (ECM) due to the action of collagenase, a matrix metalloprotenase. Studies investigating the effects of water content and uniaxial tension on collagen degradation by bacterial collagenase have been performed in the rabbit model [2]. However, results obtained using bacterial collagenase cannot be extrapolated to mammalian collagenase due to their differences in activity. In addition, the limited availability of mammalian collagenase makes it difficult to use in the relatively large rabbit model. The purpose of this study was to replicate bacterial collagenase experiments [2] using rat tail tendons in order to determine the feasibility of using the smaller rat model to study the effects of mammalian collagenase on tendon degradation.
A three-dimensional composite model of heart muscle is proposed, consisting of one-dimensional (u... more A three-dimensional composite model of heart muscle is proposed, consisting of one-dimensional (uniaxial) active contractile filaments embedded in a passive elastic binder. Equations are developed which relate the force developed by the filaments to the local tissue stress. An approximate analysis is employed to determine the time variation of the contractile filament stress throughout the cardiac cycle from catheterization data. Results from 15 patients with normal left ventricles demonstrate that the stress developed by the contractile filaments is up to 25 percent more tensile than the wall stress, and that the binder stress is compressive during most of systole. In contrast, the one-dimensional lumped parameter muscle models previously employed predict active (CE) stresses less tensile than the wall stress and binder (PE) stresses that are tensile. We conclude that the use of a one-dimensional muscle model results in a significant underestimation of the active force generation required for pressure development and the power requirements for ejection. Prior studies relating muscle work and power to ventricular oxygen consumption should be re-examined in this light.
It is increasingly accepted that successful reconstruction of the anterior cruciate ligament requ... more It is increasingly accepted that successful reconstruction of the anterior cruciate ligament requires selecting an attachment location and method of tensioning that restores normal joint laxity without subjecting the substitute to large forces during flexion-extension motions. This can be accomplished by either “over the top” placement or use of an intra-articular drill hole located to produce minimal stretching of the substitute.
Several studies have shown that meniscectomy causes an immediate, acute increase in knee joint co... more Several studies have shown that meniscectomy causes an immediate, acute increase in knee joint contact pressure and that changes in pressure distribution cause remodeling of bone and soft tissue. Presumably, this remodeling in turn affects contact pressures. This study tested the hypothesis that medial compartment contact pressure increases immediately after medial meniscectomy and then decreases with time. Supporting hypotheses regarding medial compartment contact area and lateral compartment pressures also were tested. Unilateral medial meniscectomy was performed on seven adult goats. Four or 8 months later, contact pressure and area were measured in vitro in the involved joints, as well as in the contralateral joints, before and after removal of the meniscus. The medial compartment pressures of the chronically meniscectomized joints were significantly less than those of the acutely meniscectomized paired joints but remained significantly greater than those of the intact joints. F...
The Journal of Bone and Joint Surgery. British volume, 2003
Techniques for the selective cutting of ligaments in cadaver knees defined the static contributio... more Techniques for the selective cutting of ligaments in cadaver knees defined the static contributions of the posterolateral structures to external rotation, varus rotation and posterior tibial translation from 0° to 120° of flexion under defined loading conditions. Sectioning of the popliteofibular ligament (PFL) (group 1) produced no significant changes in the limits of the knee movement studied. Sectioning of the PFL and the popliteus tendon (femoral attachment, group 2) produced an increase of only 5° to 6° in external rotation from flexion of 30° to 120° (p < 0.001). Even when other ligaments were sectioned first (group 3), the maximum effect of the PFL was negligible. Our findings show that the popliteus muscle-tendon-ligament complex, lateral collateral ligament, and posterolateral capsular structures function as a unit. No individual structure alone is the primary restraint for the movements studied. Operative reconstruction should address all of the posterolateral structure...
A five-parameter transfer function has been used to characterize the input impedance of the human... more A five-parameter transfer function has been used to characterize the input impedance of the human systemic circulation. Aortic pressure and flow measurements obtained at cardiac catheterization are employed to evaluate the model parameters in individual patients. The appropriate parameters are chosen using a standard optimization technique to minimize the difference between pressures computed from the model and the measured values. Impedance parameters calculated for 19 patients showed considerable variation with no apparent correlation with the type of heart disease. The model is useful in describing the loading of the left ventricle produced by the systemic circulation. It may also have application to the study of vascular disease.
ABSTRACT Eighty-four patients whose knees showed symptoms of chronic anterior cruciate laxity wer... more ABSTRACT Eighty-four patients whose knees showed symptoms of chronic anterior cruciate laxity were treated by rehabilitation, activity modification designed to avoid recurrent symptoms, the use of a knee brace for activities, and periodic examination and close follow-up to detect progressive deterioration of the joint. The objective of this study was to observe the effect of rehabilitation and activity modification on functional disability. Failure of this program was considered to be an indication for surgical reconstruction. The results were evaluated after three years by both subjective and objective criteria. The patients in the study had sustained the original knee injury an average of eight years earlier, were an average of twenty-eight years old, and wished to continue an athletic or recreationally active lifestyle. The patients showed a wide spectrum of initial disability. Under the non-operative management program, more than one-third of the patients improved and were well compensated with no or minimum symptoms during activities of daily living or during recreational activities that before treatment could not be performed. However, these knees could still not be considered normal and continued to have symptoms to some degree, usually during strenuous sports activity. One-third of the patients became worse and failed the program, complaining of symptoms of pain, swelling, or giving-way that prevented any recreational activities and often were present with daily activities. Eighteen of the eighty-four patients subsequently required reconstructive surgery because of such a functional disability, and an additional eighteen patients became worse and were considering surgery. Thus, thirty-six (43 per cent) of the eighty-four patients were not benefited by the program. It was often difficult to predict initially which knees would not improve with the program, which emphasizes the necessity for an initial nonoperative approach. Also, given the present uncertain long-term success rate of the currently available reconstructive surgical procedures of the knee, it is advisable that the functional disability of the laxity be clearly established. The frequency with which the knee was reinjured had a statistically significant correlation with chronic pain and swelling and the over-all severity of the condition of the knee. We concluded that recurrent giving-way injuries, even if occurring only two or three times a year, may in time produce significant damage to the joint. Athletic activities that cause even sporadic reinjuries are to be avoided even when the symptoms between injuries are negligible. The individuals who continued active sports despite symptoms had an over-all poor prognosis. One-third of the patients did not comply with recommended modifications or substitution of activities in order to prevent reinjuries or recurrent symptoms. The results of our study validate the usefulness of the eight-point treatment program, including the need for close follow-up, determining the individual patient&#39;s goals and demands, and activity modification and counseling. Arthroscopy is indicated in certain knees to detect the true extent of joint deterioration and, in some patients, the necessity for early surgical intervention.
Mechanische Faktoren beeinflussen nicht nur die Entwicklung, Differenzierung und das Remodeling d... more Mechanische Faktoren beeinflussen nicht nur die Entwicklung, Differenzierung und das Remodeling des gesunden Knochens [1, 2, 3, 4], sondern sind auch fur die Frakturheilung von groser Bedeutung. Interfragmentare Bewegungen im Frakturspalt konnen je nach Ausmas die Kallusbildung induzieren und den Heilungsprozes beschleunigen oder aber zur Knochenresorption oder Pseudarthrose fuhren [5, 6, 7, 8]. Es ist daher anzunehmen, das unterschiedliche mechanische Einflusse verschiedene zellularen Reaktionen bewirken, die letztendlich fur Erfolg oder Miserfolg der Heilung entscheidend sind. Um die zellularen Ursachen mechanischer Effekte bei der Frakturheilung zu untersuchen, wurde ein Zellstimmulationsgerat entwickelt, das es erlaubt, isolierte Zellen durch zyklische Dehnungen zu stimulieren. Wichtige Fragen, die mit diesem System untersucht werden sollen, sind die Auswirkungen verschieden groser Dehnungen auf die Zellaktivitat von Osteoblasten und Fibroblasten. Es soll gezeigt werden, welchen Einflus zyklische Dehnungen auf die Proliferation, alkalische Phosphataseaktivitat, Lactatdehydrogenaseaktivitat, Kollagenbiosynthese und Orientierung der Zellen haben. Die Reaktionen der Osteoblastenkulturen sollen mit Fibroblastenkulturen derselben Spender verglichen werden.
It is little wonder that the casual reader of knee orthopedic articles is left somewhat bewildere... more It is little wonder that the casual reader of knee orthopedic articles is left somewhat bewildered about ligament function and the clinical laxity tests used in assessing knee stability. In the past there has been wide disagreement about these issues among many knowledgeable knee surgeons. Newer clinical and biomechanical information has helped to clear up some important areas of disagreement, but correct diagnosis of knee instability is not a simple matter. Knee examinations must be very precise and meticulous to diagnose the straight and rotatory laxities. Some laxities are obscured and others are very straightforward. Still, there are practical biomechanical concepts that govern the successful interpretation of clinical laxity tests. This paper describes two of these concepts that are common to all laxity tests. Once recognized, the concepts clarify much prior confusion and help the examiner correctly interpret results of the laxity examinations.
The amount of local tissue deformation at the equatorial region of the left ventricle is quantita... more The amount of local tissue deformation at the equatorial region of the left ventricle is quantitated by the ratio of the instantaneous cross-sectional area of a tissue element to the cross-sectional area at end-diastole. The area ratio, AR, was computed for the circumferential and longitudinal, apex to base, direction throughout the cardiac cycle from catheterization and cineangiographic data on 36 patients. The patients were divided into four groups: normal left ventricualr function—15, compensated volume overload—6, decompensated volume overload—9, and congestive cardiomyopathy—6. The peak longitudinal area ratio was elevated in the compensated group (P &amp;amp;amp;amp;amp;amp;lt;0.001) and not statistically significant from normal in the decompensated group. A larger fraction of the cardiac cycle was required to reach the peak longitudinal (p &amp;amp;amp;amp;amp;amp;lt;0.01) and circumferential (p &amp;amp;amp;amp;amp;amp;lt;0.05) area ratio in the compensated group. The volume overload compensatory process apparently involves a change in the relative magnitude and timing of tissue deformation. The hypo-contractile ventricle was characterized by a reduction in the sum of the logitudinal and circumferential area ratios, which for all six patients in the congestive cardiomyopathy group, had a value less than any of the other thirty patients.
Tissue grafts are widely used in the repair of damaged tendons and ligaments. However, studies ha... more Tissue grafts are widely used in the repair of damaged tendons and ligaments. However, studies have shown that these grafts rapidly lose their strength shortly after implantation [1]. One possible mechanism for such behavior is the degradation of the extracellular matrix (ECM) due to the action of collagenase, a matrix metalloprotenase. Studies investigating the effects of water content and uniaxial tension on collagen degradation by bacterial collagenase have been performed in the rabbit model [2]. However, results obtained using bacterial collagenase cannot be extrapolated to mammalian collagenase due to their differences in activity. In addition, the limited availability of mammalian collagenase makes it difficult to use in the relatively large rabbit model. The purpose of this study was to replicate bacterial collagenase experiments [2] using rat tail tendons in order to determine the feasibility of using the smaller rat model to study the effects of mammalian collagenase on tendon degradation.
A three-dimensional composite model of heart muscle is proposed, consisting of one-dimensional (u... more A three-dimensional composite model of heart muscle is proposed, consisting of one-dimensional (uniaxial) active contractile filaments embedded in a passive elastic binder. Equations are developed which relate the force developed by the filaments to the local tissue stress. An approximate analysis is employed to determine the time variation of the contractile filament stress throughout the cardiac cycle from catheterization data. Results from 15 patients with normal left ventricles demonstrate that the stress developed by the contractile filaments is up to 25 percent more tensile than the wall stress, and that the binder stress is compressive during most of systole. In contrast, the one-dimensional lumped parameter muscle models previously employed predict active (CE) stresses less tensile than the wall stress and binder (PE) stresses that are tensile. We conclude that the use of a one-dimensional muscle model results in a significant underestimation of the active force generation required for pressure development and the power requirements for ejection. Prior studies relating muscle work and power to ventricular oxygen consumption should be re-examined in this light.
It is increasingly accepted that successful reconstruction of the anterior cruciate ligament requ... more It is increasingly accepted that successful reconstruction of the anterior cruciate ligament requires selecting an attachment location and method of tensioning that restores normal joint laxity without subjecting the substitute to large forces during flexion-extension motions. This can be accomplished by either “over the top” placement or use of an intra-articular drill hole located to produce minimal stretching of the substitute.
Several studies have shown that meniscectomy causes an immediate, acute increase in knee joint co... more Several studies have shown that meniscectomy causes an immediate, acute increase in knee joint contact pressure and that changes in pressure distribution cause remodeling of bone and soft tissue. Presumably, this remodeling in turn affects contact pressures. This study tested the hypothesis that medial compartment contact pressure increases immediately after medial meniscectomy and then decreases with time. Supporting hypotheses regarding medial compartment contact area and lateral compartment pressures also were tested. Unilateral medial meniscectomy was performed on seven adult goats. Four or 8 months later, contact pressure and area were measured in vitro in the involved joints, as well as in the contralateral joints, before and after removal of the meniscus. The medial compartment pressures of the chronically meniscectomized joints were significantly less than those of the acutely meniscectomized paired joints but remained significantly greater than those of the intact joints. F...
The Journal of Bone and Joint Surgery. British volume, 2003
Techniques for the selective cutting of ligaments in cadaver knees defined the static contributio... more Techniques for the selective cutting of ligaments in cadaver knees defined the static contributions of the posterolateral structures to external rotation, varus rotation and posterior tibial translation from 0° to 120° of flexion under defined loading conditions. Sectioning of the popliteofibular ligament (PFL) (group 1) produced no significant changes in the limits of the knee movement studied. Sectioning of the PFL and the popliteus tendon (femoral attachment, group 2) produced an increase of only 5° to 6° in external rotation from flexion of 30° to 120° (p < 0.001). Even when other ligaments were sectioned first (group 3), the maximum effect of the PFL was negligible. Our findings show that the popliteus muscle-tendon-ligament complex, lateral collateral ligament, and posterolateral capsular structures function as a unit. No individual structure alone is the primary restraint for the movements studied. Operative reconstruction should address all of the posterolateral structure...
A five-parameter transfer function has been used to characterize the input impedance of the human... more A five-parameter transfer function has been used to characterize the input impedance of the human systemic circulation. Aortic pressure and flow measurements obtained at cardiac catheterization are employed to evaluate the model parameters in individual patients. The appropriate parameters are chosen using a standard optimization technique to minimize the difference between pressures computed from the model and the measured values. Impedance parameters calculated for 19 patients showed considerable variation with no apparent correlation with the type of heart disease. The model is useful in describing the loading of the left ventricle produced by the systemic circulation. It may also have application to the study of vascular disease.
Uploads