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Biomedical subjects

P A Torzilli

Publications and source records attributed to P A Torzilli.

At least 55 records · Page 3Linked to original sources
PubMed1985

Mechanical properties of three orthopedic wire configurations.

An 18-gauge stainless steel wire was applied to a transverse fracture model to determine the antirotational effectiveness of cruciate, horizontal mattress, and simple interrupted interfragmentary wire configurations. The number of twists used to tighten the configuration and the distance from the fracture were compared in the cruciate and horizontal mattress patterns. In a 2nd experiment, the compressive forces generated at the fracture by cruciate and horizontal mattress configurations tightened with 1 and 2 twists were determined. The cruciate configuration was better than the horizontal mattress and simple interrupted configurations in preventing rotation (P less than 0.001). Increasing the distance from the fracture line to the wire holes decreased antirotational effectiveness. Tightening the cruciate and horizontal mattress configurations with 2 twists produced significantly greater compressions across the fracture line than did tightening with 1 twist (P less than 0.0001).

Animals↗
PubMed1984

Medial restraints to anterior-posterior motion of the knee.

We investigated the motion of cadaver knees before and after section of the medial structures and anterior cruciate ligament. The knees were tested using a 5-degrees-of-freedom in vitro knee-testing apparatus that measured anterior-posterior, medial-hateral, and axial displacement as well as internal-external and valgus-varus rotation. The fiexion angle could be varied but was fixed for each individual test. A 125-newton anterior-posterior force was applied perpendicular to the tibial shaft and the resulting motion of the knee was measured. In five knees the anterior cruciate ligament was cut first, followed by progressive cuts of the structures on the medial side (superficial medial collateral ligament, deep medial ligament, oblique fibers of the superficial medial ligament, and the posteromedial part of the capsule). Conversely, in five knees the medial structures were progressively cut first, followed by section of the anterior cruciate ligament. Tests were performed after each cut. With an intact anterior cruciate ligament, progressive cutting of the medial side had no effect on anterior and posterior displacements. When section of the medial structures followed cutting of the anterior cruciate ligament, anterior displacement exceeded that seen after isolated section of the anterior cruciate ligament. The anterior and posterior load-tests were repeated with the tibia fixed in 5 degrees of internal and 5 degrees of external rotation. Fixed external notation had no effect on anterior and posterior displacements. Fixed internal rotation significantly decreased anterior displacement only when both the anterior cruciate ligament and the medial structures were cut. The amounts of tibial rotation and tibial torque resulting from the applied anterior and posterior forces were low compared with our previous results, and we attributed this to decreased constraints on motion of the knee in the current testing apparatus. CLINICAL RELEVANCE: Athletic injuries of the knee frequently involve both the anterior cruciate ligament and the medial side of the knee. Clinical studies have demonstrated that combined injuries of the anterior cruciate and medial collateral ligaments often cannot be successfully managed conservatively. Our in vitro findings support the clinical data and suggest that injuries to the medial structures further compromise anterior stability when they accompany anterior cruciate injuries.

Adult↗
PubMed1984

Measurement of diffusion of uncharged molecules in articular cartilage.

The diffusion of glucose (180 M.W.), inulin (5,000 M.W.) and dextran (20,000 M.W.) into mature bovine and equine articular cartilage was studied. Concentration profiles were determined using a one-dimensional experimental configuration and the diffusion coefficient and partition coefficient calculated from a theoretical model. Glucose was found to diffuse the fastest, followed by inulin and dextran. The partition coefficient was similarly ordered. The rate of diffusion was found to decrease with increasing diffusion time, indicating a dependence on solute concentration. No time variation was evident in the partition coefficient. In addition, no difference was found between species or between the location sites within the animal joint.

Animals↗
PubMed1984

Measurement of anterior-posterior motion of the knee in injured patients using a biomechanical stress technique.

We performed biomechanical stress tests preoperatively on the knees of fifty-one patients with an injury to the knee. We measured the amount of anterior and posterior tibial translation at 90 degrees of knee flexion using a roentgenographic technique and a fifty-newton joint load. Knees with an isolated meniscal tear exhibited no abnormal motion. There was no difference in motion of the knee between patients with a rupture of the anterior cruciate ligament and patients with this injury who had had a prior medial meniscectomy. We found that prior knee surgery that was not associated with stability did not adversely affect the test procedure. A significant finding, however, was that only nineteen of twenty-five patients with a ruptured anterior cruciate ligament had greater excursion on the injured side compared with the uninjured knee. Because of this inconsistent result, a biomechanical stress test at 90 degrees of knee flexion measuring anterior and posterior translation under a fifty-newton joint load appears insufficient in itself to be of clinical use.

Adolescent↗
PubMed1983

Movement of interstitial water through loaded articular cartilage.

Water transport through articular cartilage and across the articular surface is a major factor controlling the amount and rate of tissue deformation. To study water movement concentration profiles within the tissue were determined using radiotracer techniques. Water movement was spatially and temporally mapped for unloaded, undeformed tissue, after cyclic and dead weight creep, and for recovery following dead weight creep using a uniaxial confined compression configuration to produce one-dimensional fluid movement. In unloaded tissue diffusion rapidly exchanged water by 15 minutes while the gross efflux of fluid during cyclic and dead weight creep compression effectively inhibited any external water influx. During recovery fluid inhibition was restricted when a small surface load was present, and only after complete removal of all surface traction was a large fluid efflux found. The compression and/or collapse of the uppermost surface layer of the tissue is believed responsible for controlling tissue fluid transport and mechanical response.

Animals↗
PubMed1982

The material properties of immature bone.

The age-related material properties of developing immature canine bone were determined for the femora, tibiae, humeri, radii, and ulnae in animals from 1 wk of age to maturity. These properties included bone geometry changes, material tissue properties, and qualitative and quantitative morphological evaluations. All bones exhibited a two-phase growth cycle, an initial rapid phase (20 wk) followed by a substantially slower growth to maturation (48 wk). All properties showed age-related changes except bone tissue strain to failure.

Age Factors↗
PubMed1982

Equilibrium water partition in articular cartilage.

Water partition between the interstitial fluid in articular cartilage and an external bathing solution was found using a new in-situ method. This consisted of measuring the concentration of radioactive water allowed to diffuse through the articular surface of laterally constrained cartilage-subchondral bone plugs. Incubation times ranged from 15 minutes to 48 hours. Tracer solutions included: Hank's Balanced Salt Solution with and without antibiotics and enzyme inhibitors, and distilled water. Bulk partition coefficients ranged from 0.305 to 0.811. Both the hydration and partition coefficients varied spatially with depth, while no association was found between them. The macromolecular structure of the collagen and proteoglycan components are believed responsible for these findings.

Animals↗
PubMed1982

The effect of medial meniscectomy on anterior-posterior motion of the knee.

We used an in vitro knee-testing apparatus to measure anterior-posterior displacement of the tibia on the femur and the accompanying tibial rotation in response to an applied anterior-posterior force. Testing was performed on nine intact knees, on five knees after medial meniscectomy, on three knees after isolated section of the anterior cruciate ligament, and on eight knees after both excision of the medial meniscus and section of the anterior cruciate ligament. The induced anterior-posterior displacement and the coupled rotation were unaffected by meniscectomy. Isolated section of the anterior cruciate ligament allowed a significant (p less than 0.05) increase in anterior displacement but had no effect on posterior displacement. The coupled internal rotation associated with anterior displacement was lost after section of the anterior cruciate ligament. Excision of the medial meniscus and section of the anterior cruciate ligament allowed significantly (p less than 0.05) greater increases in anterior displacement than those already increased by isolated section of the anterior cruciate ligament.

Aged↗
PubMed1982

An in vitro biomechanical evaluation of anterior-posterior motion of the knee. Tibial displacement, rotation, and torque.

We tested the anterior-posterior motion of nine normal cadaver knees in zero to 90 degrees of flexion using a specially designed apparatus. This apparatus applied a dynamic anterior-posterior force to each knee and measured the resulting tibial displacement, rotation, and torque. In the intact knee, an anterior force produced an internal tibial torque and internal tibial rotation, while a posterior force produced an external torque and external rotation. Anterior-posterior displacement increased by 30 per cent when the tibia was allowed to rotate freely about its neutral rotation position. Isolated section of the anterior cruciate ligament produced more than double the amount of anterior displacement without affecting posterior displacement. Isolated section of the posterior cruciate ligament produced almost triple the amount of posterior displacement without affecting anterior displacement. After cutting either the anterior or the posterior cruciate ligament, the resulting internal or external secondary tibial rotation disappeared. It appears, therefore, that the anterior and posterior cruciate ligaments are the primary restraints to motion in the anterior and posterior directions as well as the causes of internal and external tibial rotation during anterior and posterior motion.

Aged↗
PubMed1981

Structural properties of immature canine bone.

Structural properties of growing canine long bones were determined from three and four-point bending tests. Mechanical and geometric properties were found to follow a biphasic growth process, with a rapid increase in bending strength and moment of inertia from l to 24 wk of age and a substantially decreased rate thereafter to maturity. Predicted bone tissue material properties were also found to follow this biphasic developmental process.

Age Factors↗
PubMed1979

A method for the postmortem evaluation of an in situ total hip replacement.

A method was developed for the post-mortem evaluation of a total hip replacement retrieved in situ. The hip replacement had been implanted for six years. The evaluation procedure employed existing techniques in a logical sequence such that earlier tests would not compromise results from subsequent ones. These techniques included the measurement of range of motion, aspiration of the joint for analysis of debris, radionuclide arthrograms for determination of looseness of the components, gross and histological inspection of the capsule and synovial tissue, serial sectioning of the femoral component, determination of some mechanical properties of the bone and femoral stem, and scanning electron microscopy of the articulating surfaces of the prosthetic components. Positive findings in the specimen studied were: excessive wear of the articulating surface of the acetabular component, and associated polyethylene debris in the aspirate and surrounding synovial and granulation tissue.

Acetabulum↗
PubMedDate not supplied

Capsular restraints to anterior-posterior motion of the abducted shoulder: a biomechanical study.

Twenty-three fresh-frozen cadaver shoulders free of degenerative arthritis or rotator cuff disease were tested biomechanically to quantitate the contribution of specific capsular structures to restricting anterior-posterior translation of the abducted shoulder. With the glenohumeral joint in 90 degrees of abduction on a servohydraulic control testing system, translation was measured in 30 degrees of forward flexion (with regard to the coronal plane of the scapula), 0 degree, and 30 degrees of extension while a 25 N anterior-posterior load was applied. Measurements were taken both in the intact (vented) shoulder and after selective cutting of different capsuloligamentous structures was performed. In the intact shoulder the largest anterior-posterior translation occurred in 0 degree of horizontal flexion and extension with regard to the scapular plane, with equal amounts of anterior and posterior translation noted. The primary anterior-posterior stabilizer of the abducted shoulder is the inferior glenohumeral ligament complex. The anterior band is the primary stabilizer in 30 degrees of horizontal extension and at 0 degree (neutral). The posterior band is the primary stabilizer in 30 degrees of horizontal flexion. This study quantifies for the first time the normal amount of anterior-posterior translation in the intact cadaveric shoulder model. In addition, it demonstrates the relative role of the anterior and posterior band of the inferior glenohumeral ligament complex in stabilizing the glenohumeral joint at 90 degrees of abduction, where most clinical instability of the shoulder occurs.

Adult↗
PubMedDate not supplied

Role of the long head of the biceps brachii in glenohumeral stability: a biomechanical study in cadavera.

Ten cadaveric shoulders were tested to evaluate the effect of simulated contraction of the long head of the biceps brachii on glenohumeral translation. The shoulders were mounted on a special apparatus attached to a servo-controlled hydraulic testing device. Sequential 50 N anterior, posterior, superior, and inferior forces and a 22 N joint compressive load were applied to the shoulders. An air cylinder applied a constant force to the tendon of the long head of the biceps brachii. The shoulders were tested in seven positions of glenohumeral elevation and rotation. Application of a force to the long head of the biceps brachii resulted in statistically significant decreases in humeral head translation. The influence of the long head of the biceps was more pronounced at middle and lower elevation angles. When the shoulder was placed in 45 degrees of elevation and neutral rotation, application of a 55 N force to the biceps tendon reduced anterior translation by 10.4 mm (p = 0.001), inferior translation by 5.3 mm (p = 0.01), and superior translation by 1.2 mm (p = 0.004).

Analysis of Variance↗
PubMedDate not supplied

Dissociation of modular humeral head components: a biomechanical and implant retrieval study.

In vivo dissociation of the Morse-taper of shoulder arthroplasty modular humeral components has been reported. The incidence of this complication appears to be approximately 1:1000. The objective of this study was to identify conditions that might affect the Morse-taper interface strength in humeral components. Mechanical tests were performed to load and dissociate humeral heads from the humeral stems (titanium). The effect of loading rate, load amplitude, and number of impactions was investigated. Dissociation force was measured after the taper was contaminated with water, oil, blood, and bone cement particles. The mean dissociation force after two impactions with a mallet was 2926 +/- 955 N. Dissociation force was linearly proportional to impaction force. Repetitive loading beyond two impactions did not significantly increase taper strength. Contamination of the taper with as little as 0.4 ml of fluid could prevent fixation of the taper.

Biomechanical Phenomena↗