Biomedical subjects

M R Safran

Publications and source records attributed to M R Safran.

28 records · Page 2Linked to original sources

PubMed1994

The effect of experimental hemarthrosis on joint stiffness and synovial histology in a rabbit model.

The effect of a single injection of unpreserved blood on joint stiffness and on synovial and cartilage histomorphology in the ankle joints of rabbits was determined at ten and 28 days after injection. The same volume of saline was placed in the contralateral ankle for comparison. After ten days, the hemarthrosis ankle was stiffer than the control ankle (p < 0.027), whereas at 28 days there was no statistical difference in stiffness between the hemarthrosis and control ankles, regardless of whether the limbs had been immobilized. Also after ten days, the hemarthrosis ankles had varying amounts of clotted blood, darkened articular cartilage, hypertrophic synovium with reactive blood vessels, and macrophages containing heme. The gross and histologic appearance of the saline ankles was normal. After 28 days, there were no differences in gross or microscopic appearance between the two ankles of the caged or immobilized rabbits. All ankles exhibited retreating inflammatory response in the synovium and mild synovial thickening. Acute hemarthrosis, unassociated with fracture or discernible joint injury, caused only transient changes in joint stiffness and synovial histology. These results indicate that the presence of blood in an otherwise grossly uninjured joint should not lead to ultimate compromise in cartilage integrity or joint function. Therapeutic arthrocentesis for acute posttraumatic hemarthrosis does not appear to be necessary for the prevention of permanent problems.

Animals↗

PubMed1993

Expandable endoprosthetic reconstruction of the skeletally immature after malignant bone tumor resection.

The mainstay of local control of primary bone malignancies in the skeletally immature has been amputation or, in selected cases, rotationplasty. The development of expandable endoprostheses has permitted an alternative approach for local control in the growing child. Between January 1985 and December 1987, 12 skeletally immature patients with primary malignant bone tumors were treated with extremity reconstruction with cemented custom-expandable endoprostheses after wide resection of their lesions. All patients were observed until death (four) or revision (two) with a minimum two-year follow-up period for the survivors (average, 3.1 years). Seven patients have undergone a total of 11 expansions and one patient was lengthened with a revision-expandable prosthesis. Four patients have not needed expansion. Eight patients have had a total of ten complications. Seven of the ten complications (70%) were prosthesis related and associated with failure of the expansion mechanism. The Musculoskeletal Tumor Society (MSTS) overall rating was good to excellent in seven patients (58%), fair in three (25%), and poor in two (17%). In five distal femoral arthroplasties and one total femoral arthroplasty where the tibial bearing component was cemented through the physis, tibial and epiphyseal growth was observed to be normal and equal to the nonoperative side. This suggests that partial central epiphyseal and physeal ablation does not cause physeal arrest. Although the high rate of expansion mechanism failure necessitates redesign, preliminary results suggest that expandable endoprostheses do offer an alternative to amputation and rotationplasty as a means of local control and extremity reconstruction in children with primary malignant bone tumors.

Adolescent↗

PubMed1992

Continued growth of the proximal part of the tibia after prosthetic reconstruction of the skeletally immature knee. Estimation of the minimum growth force in vivo in humans.

We studied five skeletally immature patients who had a cemented endoprosthetic replacement involving the proximal part of the tibia because of a malignant tumor. In each patient, the cement-column fractured, allowing additional physeal growth. With plain radiographs and scanograms, we determined the cross-sectional areas of the physes, the cement-mantle, and the tibial component. Using the known tensile strength of polymethylmethacrylate cement, we then calculated the minimum force that the growth plates must have overcome to fracture the cement. This averaged 584 newtons per square centimeter. This observation of continued tibial growth after partial physeal ablation with a cemented prosthesis in skeletally immature patients presented a unique opportunity to estimate the force generated in the human physis during growth.

Biomechanical Phenomena↗

PubMed1989

Warm-up and muscular injury prevention. An update.

Musculotendinous injuries are responsible for a significant proportion of injuries incurred by athletes. Many of these injuries are preventable. Importantly, musculotendinous injuries have a high incidence of recurrence. Thus, muscle injury prevention is advocated by coaches and trainers. Yet, most of the recommendations for muscle injury prevention are attempted by athletes and taught by coaches without supporting scientific evidence. This paper reviews the mechanics of muscular injury, associated and predisposing factors, and methods of prevention with a review of the supporting research and rationale for these methods with an emphasis on warm-up, stretching and strengthening. Muscles that are capable of producing a greater force, a faster contraction speed and subjected to a greater stretch are more likely to become injured. Many factors have been associated with muscular injury. From current research, some conclusions and recommendations for muscle injury prevention can be made. Overall and muscular conditioning and nutrition are important. Proper training and balanced strengthening are key factors in prevention of musculotendinous injuries as well. Warm-up and stretching are essential to preventing muscle injuries by increasing the elasticity of muscles and smoothing muscular contractions. Improper or excessive stretching and warming up can, however, predispose to muscle injury. Much research is still needed in this important aspect of sports medicine.

Athletic Injuries↗

PubMedDate not supplied

Shoulder proprioception in baseball pitchers.

We examined proprioceptive differences between the dominant and nondominant shoulders of 21 collegiate baseball pitchers without a history of shoulder instability or surgery. A proprioceptive testing device was used to measure kinesthesia and joint position sense. Joint position sense was significantly (P =.05) more accurate in the nondominant shoulder than in the dominant shoulder when starting at 75% of maximal external rotation and moving into internal rotation. There were no significant differences for proprioception in the other measured positions or with kinesthesia testing. Six pitchers with recent shoulder pain had a significant (P =.04) kinesthetic deficit in the symptomatic dominant shoulder compared with the asymptomatic shoulder, as measured in neutral rotation moving into internal rotation. The net effect of training, exercise-induced laxity, and increased external rotation in baseball pitchers does not affect proprioception, although shoulder pain, possibly due to rotator cuff inflammation or tendinitis, is associated with reduced kinesthetic sensation.

Adolescent↗

PubMedDate not supplied

Dorsal defect of the patella.

Dorsal defect of the patella is a benign subchondral lesion of unknown etiology, located in the superolateral region of the patella. The lesion presents with a characteristic radiographic appearance consisting of a rounded focus of radiolucency surrounded by a sclerotic margin. Although often an incidental finding on knee radiographs, it occasionally may be symptomatic. It occurs in males and females with equal frequency, is bilateral in up to one third of individuals, and is most frequently found in adolescents. This report describes a series of eight such lesions in five patients.

Adolescent↗

PubMedDate not supplied

Biomechanical comparison of stimulated and nonstimulated skeletal muscle pulled to failure.

We compared the biomechanical properties of passive and stimulated muscle rapidly lengthened to failure in an experimental animal model. The mechanical parameters compared were force to tear, change in length to tear, site of failure, and energy absorbed by the muscle-tendon unit before failure. Paired comparisons were made between 1) muscles stimulated at 64 Hz (tetanic stimulation) and passive (no stimulation) muscles, 2) muscles stimulated at 16 Hz (wave-summated stimulation) and passive muscles, and 3) muscles stimulated at 64 Hz and at 16 Hz. Both tetanically stimulated and wave-summation contracted muscles required a greater force to tear (at 64 Hz, 12.86 N more, P less than 0.0004; and at 16 Hz, 17.79 N more, P less than 0.003) than their nonstimulated controls, while there was no statistical difference in failure force between muscles stimulated at 16 Hz and 64 Hz. The energy absorbed was statistically greater for the stimulated muscles than for the passive muscles in Groups 1 and 2 (at 64 Hz, 100% more, P less than 0.0003; and 16 Hz, 88% more, P less than 0.0002). In Group 3, the tetanically contracted muscle-tendon units absorbed 18% more energy than the wave-summated stimulated muscles (P less than 0.01). All muscles tore at the distal musculotendinous junction, and there was no difference in the length increase at tear between muscles in each group. These findings may lead to enhanced understanding of the mechanism and physiology of muscle strain injuries.

Animals↗

PubMedDate not supplied

The role of warmup in muscular injury prevention.

This study is an attempt to provide biomechanical support for the athletic practice of warming up prior to an exercise task to reduce the incidence of injury. Tears in isometrically preconditioned (stimulated before stretching) muscle were compared to tears in control (nonstimulated) muscle by examining four parameters: 1) force and 2) change of length required to tear the muscle, 3) site of failure, and 4) length-tension deformation. The tibialis anterior (TA), the extensor digitorum longus (EDL), and flexor digitorum longus (EDL) muscles from both hindlimbs of rabbits comprised our experimental model. Isometrically preconditioned TA (P less than 0.001), EDL (P less than 0.005), and FDL (P less than 0.01) muscles required more force to fail than their contralateral controls. Preconditioned TA (P less than 0.05), EDL (P less than 0.001), and FDL (P less than 0.01) muscles also stretched to a greater length from rest before failing than their nonpreconditioned controls. The site of failure in all of the muscles was the musculotendinous junction; thus, the site of failure was not altered by condition. The length-tension deformation curves for all three muscle types showed that in every case the preconditioned muscles attained a lesser force at each given increase in length before failure, showing a relative increase in elasticity, although only the EDL showed a statistically significant difference. From our data, it may be inferred that physiologic warming (isometric preconditioning) is of benefit in preventing muscular injury by increasing the and length to failure and elasticity of the muscle-tendon unit.

Animals↗

PubMedDate not supplied

Local anesthesia for knee arthroscopy. Efficacy and cost benefits.

We performed a retrospective review of a series of knee arthroscopic procedures that were completed using local, general, or regional anesthesia to evaluate the efficacy of these anesthetic techniques. Operative time, complications or failures, procedures successfully performed, recovery room time and postoperative stay, and patient satisfaction were recorded. Local anesthesia with intravenous sedation compared favorably with the other techniques: operative time was not increased, a large variety of operative procedures were successfully completed, recovery time was significantly shortened, and patient satisfaction remained high. This technique offers several advantages over other types of anesthesia for knee arthroscopy, including improved cost effectiveness.

Adolescent↗

PubMedDate not supplied

The effects of joint position and direction of joint motion on proprioceptive sensibility in anterior cruciate ligament-deficient athletes.

We studied a group of anterior cruciate ligament-deficient athletes to identify whether joint position and direction of joint motion have a significant effect on proprioception. Twenty-nine anterior cruciate ligament-deficient athletes were tested for their threshold to detect passive motion at both 15 degrees and 45 degrees moving into the directions of both flexion and extension. The single-legged hop test was used to identify function in the deficient limb. Results demonstrated statistically significant deficits in threshold to detect passive motion for the deficient limb at 15 degrees moving into extension. For the deficient limb, threshold to detect passive motion was significantly more sensitive moving into extension than flexion at a starting angle of 15 degrees; at a starting angle of 15 degrees moving into extension threshold was significantly more sensitive than at a starting angle of 45 degrees moving into extension. We conclude that in deficient limbs proprioception is significantly more sensitive in the end ranges of knee extension (15 degrees) and is significantly more sensitive moving into the direction of extension. To effectively restore reflex stabilization of the lower limb we recommend a rehabilitation program emphasizing performance-based, weightbearing, closed kinetic chain exercise for the muscle groups that act on the knee joint.

Adolescent↗