Biomedical subjects

W E Garrett

Publications and source records attributed to W E Garrett.

At least 73 records · Page 4Linked to original sources

PubMedDate not supplied

The effects of passive warming on muscle injury.

This study investigated the effects of passive warming on the biomechanical properties of the musculotendinous unit. Paired tibialis anterior (TA) and extensor digitorum longus (EDL) muscles in the rabbit hindlimb were passively heated to different temperatures and then subjected to controlled strain injury. The parameters examined were: 1) percent increase in length to failure, 2) force to failure, 3) energy absorbed by the musculotendinous unit to failure, and 4) site of failure. Warmed (39 degrees C +/- 0.5 degrees C) TA (P less than or equal to 0.01) and EDL (P less than or equal to 0.05) muscles achieved a greater increase in length from rest before failing than did their contralateral controls at 35 degrees C +/- 0.5 degrees C. In both the TA and EDL the force at failure was greater at 35 degrees C than at 39 degrees C, although the difference was significant for only the EDL (P less than or equal to 0.05). The energy absorbed (area beneath the length-tension curve) by both the TA and EDL was greater at 39 degrees C, but these differences were not significant. All muscles failed at the distal musculotendinous junction. These data suggest that passive warming increases the extensibility of the musculotendinous unit and may thereby reduce its susceptibility to strain injury.

Animals↗

PubMedDate not supplied

Viscoelastic properties of muscle-tendon units. The biomechanical effects of stretching.

Most muscle stretching studies have focused on defining the biomechanical properties of isolated elements of the muscle-tendon unit or on comparing different stretching techniques. We developed an experimental model that was designed to evaluate clinically relevant biomechanical stretching properties in an entire muscle-tendon unit. Our objectives were to characterize the viscoelastic behavior of the muscle-tendon unit and to consider the clinical applications of these viscoelastic properties. Rabbit extensor digitorum longus and tibialis anterior muscle-tendon units were evaluated using methods designed to simulate widely used stretching techniques. Additionally, the effects of varying stretch rates and of reflex influences were evaluated. We found that muscle-tendon units respond viscoelastically to tensile loads. Reflex activity did not influence the biomechanical characteristics of the muscle-tendon unit in this model. Experimental techniques simulating cyclic stretching and static stretching resulted in sustained muscle-tendon unit elongations, suggesting that greater flexibility can result if these techniques are used in the clinical setting. With repetitive stretching, we found that after four stretches there was little alteration of the muscle-tendon unit, implying that a minimum number of stretches will lead to most of the elongation in repetitive stretching. Also, greater peak tensions and greater energy absorptions occurred at faster stretch rates, suggesting that the risk of injury in a stretching regimen may be related to the stretch rate, and not to the actual technique. All of these clinically important considerations can be related to the viscoelastic characteristics of the muscle-tendon unit.

Animals↗

PubMedDate not supplied

Abdominal musculature abnormalities as a cause of groin pain in athletes. Inguinal hernias and pubalgia.

There has been increasing interest within the European sports medicine community regarding the etiology and treatment of groin pain in the athlete. Groin pain is most commonly caused by musculotendinous strains of the adductors and other muscles crossing the hip joint, but may also be related to abdominal wall abnormalities. Cases may be termed "pubalgia" if physical examination does not reveal inguinal hernia and there is an absence of other etiology for groin pain. We present nine cases of patients who underwent herniorrhaphies for groin pain. Two patients had groin pain without evidence of a hernia preoperatively (pubalgia). In the remaining seven patients we determined the presence of a hernia by physical examination. At operation, eight patients were found to have inguinal hernias. One patient had no hernia but had partial avulsion of the internal oblique fibers from their insertion at the public tubercle. The average interval from operation to return to full activity was 11 weeks. All patients returned to full activity within 3 months of surgery. One patient had persistent symptoms of mild incisional tenderness, but otherwise there were no recurrences, complications, or persistence of symptoms. Abnormalities of the abdominal wall, including inguinal hernias and microscopic tears or avulsions of the internal oblique muscle, can be an overlooked source of groin pain in the athlete. Operative treatment of this condition with herniorrhaphy can return the athlete to his sport within 3 months.

Abdominal Muscles↗

PubMedDate not supplied

Magnetic resonance imaging of traumatic knee articular cartilage injuries.

The purpose of this study was to assess the sensitivity of magnetic resonance imaging in determining the presence of articular cartilage injuries of the knee with arthroscopy as the standard for comparison. Forty-nine articular cartilage lesions were documented in 28 knees (27 patients) by arthroscopy. There were 22 men and 5 women with an average age of 29 years. Multiplanar magnetic resonance imaging was performed with spin echo and gradient-refocused acquisition in a steady state pulse technique. All of the knees had magnetic resonance imaging done within 4 weeks prior to arthroscopy. The magnetic resonance images were interpreted before arthroscopy and interpreted again after the results of arthroscopy were known to better define the potential learning curve for evaluating chondral lesions and to identify the technical limits of the existing imaging protocol/software. For full-thickness articular cartilage lesions, the prearthroscopy sensitivity of magnetic resonance imaging was 41% (12/29) and the postarthroscopy sensitivity was 83% (24/29). For partial-thickness chondral injury, the prearthroscopy sensitivity of magnetic resonance imaging was 15% (3/20) and the postarthroscopy sensitivity was 55% (11/20). The presence of an intraarticular effusion assisted the detection of chondral lesions because of an "arthrogram" effect. As a noninvasive method of evaluating articular cartilage and despite experienced interpretation and the benefit of retrospective analysis, both the prearthroscopy and the postarthroscopy sensitivity of magnetic resonance imaging was low using the imaging parameters described. Injury to articular cartilage is a frequent cause of knee pain and knee surgery; it is important to note at this time that magnetic resonance imaging cannot reliably exclude the presence of an articular cartilage injury.

Adolescent↗

PubMedDate not supplied

An algorithm for arthroscopy in the over-50 age group.

We conducted a retrospective study to identify the preoperative variables that correlated with a successful outcome for knee arthroscopy in patients over the age of 50. We mailed questionnaires to 94 patients (57 responded) and reviewed their medical records and radiographs. A modified Hospital for Special Surgery knee rating system was devised. The average follow-up was 33 months. The percentage of those who felt they had successful results decreased with time: 82.8% felt their knees had improved immediately after postoperative rehabilitation; this decreased to 78.1% at 6 months, 73.5% at 1 year, 65.5% at 2 years, and 50.0% at 3 years. Therefore, the subjective success rate was 67%. We performed statistical analysis of all variables to determine which had a beneficial or detrimental effect on outcome. In addition, we devised an equation to allow postoperative prediction of score. We found that age was not a factor and that radiographic findings had the greatest impact on postoperative results.

Aged↗

PubMedDate not supplied

Osseous injury associated with acute tears of the anterior cruciate ligament.

Multiplanar spin-echo magnetic resonance imaging was performed on 54 patients with acute complete anterior cruciate ligament tears. Imaging was done within 45 days of index anterior cruciate ligament injury. Spin-echo T1- and T2-weighted images were used to determine the lesion morphology and location. Only the T2-weighted sagittal images were used for the incidence assessment; T2-weighted spin-echo imaging reflects free water shifts and best indicates the acute edema and inflammatory changes from injury. Eighty-three percent (45 of 54) of the knees had an osseous contusion directly over the lateral femoral condyle terminal sulcus. The lesion was highly variable in size and imaging intensity; however, the most intense signal was always contiguous with the subchondral plate. Posterolateral joint injury was seen in 96% (43 of 45) of the knees that had a terminal sulcus osseous lesion determined by magnetic resonance imaging. This posterolateral lesion involves a spectrum of injury, including both soft tissue (popliteus-arcuate capsuloligamentous complex) and hard tissue (posterolateral tibial plateau) injuries. The consistent location of the osseous and soft tissue injuries underscores a necessary similar mechanism of injury associated with these acute anterior cruciate ligament tears. Based on these characteristic findings, several proposed mechanisms of injury are discussed.

Acute Disease↗

PubMedDate not supplied

Radiographic imaging of muscle strain injury.

We reviewed our experience with computed tomography and magnetic resonance imaging of acute muscle strain injury. We imaged 50 athletes (average age, 28 years; range, 17 to 42) who had an acute muscle strain involving either the adductor, hamstring, quadriceps, or triceps surae muscles. Computed tomography (axial imaging) was used from 1982 to 1987 for 27 athletes. Spin-echo magnetic resonance imaging (axial, coronal, sagittal imaging) was used from 1987 to 1991 for 23 athletes. Computed tomography and magnetic resonance imaging localize the strain injury to a single muscle within a group of synergists; the adductor longus, rectus femoris, and medial head of gastrocnemius muscles are most prone to strain injury. A disruption occurs predictably at the myotendinous junction; fluid collects at the disruption site and dissects along the epimysium and subcutis. Muscle tissue remote from the myotendinous junction clearly demonstrates extensive injury with abundant magnetic resonance imaging signal changes consistent with edema and inflammation. Follow-up computed tomographic and magnetic resonance imaging studies can clearly demonstrate atrophy, fibrosis, and calcium deposition.

Acute Disease↗

PubMedDate not supplied

Experimental muscle strain injury. Early functional and structural deficits and the increased risk for reinjury.

The structural and functional strength of a muscle immediately after an experimentally created strain injury was examined to provide clinically relevant information for the early treatment of muscle strain injuries. The extensor digitorum longus muscles of 12 adult male rabbits were studied. Contractile force and shortening, and peak load were determined for control muscles. A nondisruptive strain injury was created by stretching the experimental muscles just short of complete rupture. Contractile force generation and shortening, and peak load were determined after the experimental strain injury. Peak load was 63% and elongation to rupture was 79% for the experimental muscles relative to the controls. Statistically significant lower values for contractile force generation and shortening were also seen in the experimental muscles. Histologic and gross examinations revealed that incomplete disruptions occurred near the distal muscle-tendon junction. These experimental data suggest clinical implications, such as 1) a muscle-tendon unit is significantly more susceptible to injury following a strain injury than normal muscle, 2) early return to the uncontrolled environment of athletic competition may place the injured muscle at risk for further injury, and 3) therapeutic regimens designed to achieve an early return to competition may further increase the risk for additional injury by eliminating protective pain mechanisms. Although the decrements in peak load and elongation to failure are less than normal muscle, the values seem high enough to allow mobilization of the injured extremity and functional rehabilitation.

Animals↗

PubMedDate not supplied

Thermal effects on skeletal muscle tensile behavior.

The effect of temperature on the mechanical failure properties of rabbit skeletal muscle (tibialis anterior and extensor digitorum longus) was examined. For all tests, one leg was maintained at 25 degrees C and the contralateral leg at 40 degrees C. Muscles were pulled to failure according to assignment into one of three groups: 1) passive failure at 10 cm/sec, 2) passive failure at 1 cm/sec, or 3) active (muscle is stimulated to contract as it is pulled) failure at 10 cm/sec. Load to failure was higher in the cold muscle for all groups tested. Total deformation was the same except in Group 1, when the warm muscle had a greater deformation. Energy absorbed before failure was greater in the cold muscle in Groups 2 and 3. Stiffness was higher in cold muscles for all muscles except the extensor digitorum longus in Group 1. In this study, temperature had a significant effect on the tensile properties; these thermal effects were dependent on both loading rate and contractile state. Comparing loading rates, warm muscle tested at 10 cm/sec had higher failure loads than that tested at 1 cm/sec. Comparing stimulated versus unstimulated muscle (Group 1 versus Group 3), the stimulated tibialis anterior muscle absorbed more energy than unstimulated ones. Stimulated extensor digitorum longus muscles had higher failure loads, absorbed more energy, and were stiffer than nonstimulated muscles. This study offers experimental data to support the theory that warming muscles can aid in injury prevention and improvement in athletic performance.

Animals↗

PubMedDate not supplied

Identification of a threshold for skeletal muscle injury.

This study was designed to detect the first evidence of injury to muscle induced by passive stretching. Rabbit extensor digitorum longus and tibialis anterior skeletal muscles were subjected to passive stretching at set force levels of 20% or 30% of load to failure. Both tibialis anterior and extensor digitorum longus muscles that were stretched to 30% exhibited no difference in the three tensile parameters when compared with their contralateral control specimens. Maximum contractile force was decreased after stretching. Tibialis anterior and extensor digitorum muscles that were stretched to 20% of control failure force showed no decrement in the tensile parameters or maximum contractile force. Histology of the extensor digitorum longus muscles stretched to 30% of failure force showed small focal areas of muscle fiber rupture and hemorrhage near the distal myotendinous junction. Tibialis anterior and extensor digitorum longus muscle-tendon units stretched to 30% of failure force suffered functional injury as their contractile ability decreased after stretching. In contrast, muscle-tendon units stretched to 20% of failure force suffered no decrement in contractile ability; therefore, a threshold for passive muscle stretch injury has been found. Furthermore, changes in contractile properties and histologic assessment appear to be more sensitive predictors of injury than measurement of structural failure properties.

Animals↗

PubMedDate not supplied

Biomechanical and histologic assessment of a controlled muscle strain injury treated with piroxicam.

This study was designed to observe the effect of the nonsteroidal antiinflammatory piroxicam on a controlled muscle strain injury in the rabbit model. The tibialis anterior tendons of 90 New Zealand White rabbits were detached at their distal insertions, and the right tendon was stretched to the yield point of the deformation curve. One group of 50 rabbits received piroxicam treatment and the others received no treatment. At 1, 2, 4, and 7 days the parameters of muscle function, tensile strength, and histology were examined. Muscle contractile force was significantly greater in the piroxicam-treated group at Day 1, but no difference was noted at any other time period. Tensile strength was not significantly different at any time period in either group. Histology revealed delayed degradation of damaged tissue and slowed regeneration of muscle tissue at the injury site in the piroxicam-treated group. Piroxicam and other anti-inflammatories are frequently given to athletes being treated for muscle strain injuries to control pain through their effect on the inflammatory process. This study demonstrates that piroxicam does not adversely influence the recovery of contractile and tensile strength in a followup period of 1 week. Therefore, antiinflammatory treatment may be beneficial early in the course of muscle injury.

Animals↗

PubMedDate not supplied

A threshold and continuum of injury during active stretch of rabbit skeletal muscle.

Previous studies of acute muscle injury with active stretch used cyclic stretching or stretching the muscle to complete muscle-tendon dissociation. This study tried to determine minimal force required for skeletal muscle injury with one active stretch to establish an injury "threshold." Tibialis anterior and extensor digitorum longus rabbit muscles were actively stretched at 10 cm/sec to 60%, 70%, 80%, or 90% of the force required to passively fail tibialis anterior and extensor digitorum longus muscles of the control (contralateral) limb. Maximal isometric contractile force, tensile properties, histology, and electromyography were measures of injury. Both muscles of the 60% group showed no abnormalities in maximal isometric contractile force, tensile properties, histology, or electromyographic activity; 70%, 80%, and 90% groups showed diminished maximal isometric contractile force, muscle fiber disruption, edema, hemorrhage, and decreased electromyographic maximal voltage amplitude. The 90% group also showed alterations in tensile properties at failure along with connective tissue damage. Injury site included fiber disruption both at the distal myotendinous junction and muscle belly, with injury noted initially at the distal myotendinous junction in the 70% group. Electromyographic studies showed maximal isometric contractile force and maximal voltage correlated well as indices of damage. This study shows that a threshold and continuum for active stretch-induced injury exist, with muscle fiber disruption occurring initially and connective tissue disruption occurring only with larger muscle displacements.

Analysis of Variance↗

PubMedDate not supplied

An explanation for various rectus femoris strain injuries using previously undescribed muscle architecture.

We performed cadaveric dissection of the rectus femoris muscle to correlate the various lesions of strain injury seen with imaging studies to the muscular anatomy. The proximal tendon is composed of a superficial, anterior portion from the direct head, and a deep intramuscular portion from the indirect head. The muscle fibers arising from the anterior superficial tendon of the direct head travel in a posterior and distal direction to insert on the posterior tendon of insertion, giving the proximal muscle a unipennate architecture. Muscle fibers from the intramuscular tendon of the indirect head originate on both the medial and lateral sides of the tendon and insert on the distal posterior tendon to create its bipennate structure. Three chronic strain injuries involving the midmuscle belly substance were explored grossly and microscopically. It appears that one type of acute strain injury occurs in the midmuscle belly with disruption of the muscle-tendon junction of the intramuscular tendon resulting in local hemorrhage and edema. More chronically, this hematoma organizes into a fatty, loose connective tissue encasement of the deep intramuscular proximal tendon. Serous fluid from the hematoma may remain within the connective tissue sheath, creating a pseudocyst with the deep intramuscular tendon of the indirect head at its center. The muscle's anatomy helps to explain a different rectus femoris strain injury.

Athletic Injuries↗

PubMedDate not supplied

Incomplete, intrasubstance strain injuries of the rectus femoris muscle.

Rectus femoris muscle strain injuries commonly occur at the distal muscle-tendon junction of the quadriceps tendon. However, we have recently recognized a pattern of strain injury that consists of an incomplete intrasubstance tear at the muscle-tendon junction formed by the deep tendon of the muscle's indirect head and those muscle fibers originating from this tendon. These injuries are found more proximally within the thigh than the "classic" distal rectus femoris muscle strain. We reviewed 10 athletes with these intrasubstance tears, all of whom had diagnostic imaging performed using computed tomography or magnetic resonance imaging or both. Two of these patients required surgical intervention. The mechanism of injury usually involved kicking or sprinting. All patients had chronic thigh pain or an anterior thigh mass or both. Physical examination revealed thigh asymmetry and a nontender to mildly tender intrasubstance muscle mass. Magnetic resonance imaging demonstrated abnormal signal intensity centered about the intramuscular tendon of the indirect head of the muscle. Surgical findings included a mass of fibrous scar and fatty tissue encasing the deep tendon. Surgical removal of this fibrous mass appears curative. We contrast this injury from distal strains of the rectus femoris muscle, as well as from soft tissue neoplasms.

Adolescent↗

PubMedDate not supplied

Acute dislocation of the patella. A correlative pathoanatomic study.

The objective of our study was to elucidate the characteristic pathoanatomy associated with patellar dislocation and report the preliminary results of early surgical repair. Twenty-three patients with documented patellar dislocation had standard radiographs and a magnetic resonance imaging scan. Intraarticular lesions were evaluated and treated arthroscopically followed by an open exploration of the medial aspect of the knee in 16 patients. Twelve patients were observed for a minimum of 2 years after surgical repair (average, 34 months). Eleven patients returned for a follow-up examination. Magnetic resonance imaging revealed effusion (100%), tears of the femoral insertion of the medial patellofemoral ligament (87%), increased signal in the vastus medialis muscle (78%), and lateral femoral condyle (87%) and medial patellar (30%) bone bruises. Arthroscopic examination revealed osteochondral lesions involving the patella and the lateral femoral condyle in 68% of cases. Open surgical exploration revealed tears of the medial patellofemoral ligament off the femur in 15 of 16 patients (94%). After medial patellofemoral ligament repair, none of the patients experienced recurrent dislocation. Overall 58% of the results were considered to be good or excellent and 42% were fair. Fifty-eight percent of the group returned to their previous sport with no or minor limitations.

Acute Disease↗

PubMedDate not supplied

Hamstring muscle injuries among water skiers. Functional outcome and prevention.

Water skiing is associated with severe injuries to the proximal hamstring muscles. We wanted to define the mechanism of injury, describe the associated pathologic changes, determine the functional limitations of patients, and suggest measures to prevent injury. Twelve patients with water skiing-related hamstring injuries were included. Six patients were experienced skiers and six were novices. The mechanism of injury was identical in five of six novice skiers. Each sustained the injury while attempting to get up on one or two skis from a submerged position. In contrast, the expert skiers all sustained injury secondary to a fall while skiing. Physical examination documented evidence of complete or partial avulsion of the proximal hamstring muscle origins in all patients. In addition, six patients had magnetic resonance imaging or computed tomography scans that confirmed the location and extent of the tear. Convalescence ranged from 3 months to 1.5 years before the patient could return to vigorous activities. Seven patients (58%) returned to most of their preinjury sports, albeit at a lower level. Five patients (42%), all with complete disruptions, were unable to run or participate in sports requiring agility. Two of these patients required delayed surgical repairs because of persistent functional limitations.

Adolescent↗

PubMedDate not supplied

The role of fatigue in susceptibility to acute muscle strain injury.

We investigated the role of fatigue in muscle strain injuries using the extensor digitorum longus muscles of 48 rabbits. The muscles of the rabbits were fatigued by 25% or 50% then stretched to failure and compared with the contralateral controls. Three rates of stretch were used. The force to muscle failure was reduced in the fatigued leg in all groups (range, 93% to 97.4% compared with the controls). The change in muscle length in the fatigue groups was not different from the controls. The amount of energy absorbed in the fatigued muscle was 69.7% to 92% that of the energy absorbed in the control muscle. The lowest energy absorption occurred in muscles that were more fatigued. In eight additional rabbits, fatigued extensor digitorum longus muscles were compared with submaximally stimulated muscles with the equivalent contractile properties, and no difference was seen. Muscles subjected to strains are frequently injured under high-intensity eccentric loading conditions. Under these conditions, muscles absorb energy and provide control and regulation of limb movement. Our data showed that muscles are injured at the same length, regardless of the effects of fatigue. However, fatigued muscles are able to absorb less energy before reaching the degree of stretch that causes injuries.

Acute Disease↗

PubMedDate not supplied

Concussion incidence in elite college soccer players.

A unique aspect of soccer is the use of the head for directing the ball. The potential for resultant head injuries has been the focus of discussions worldwide. Prior work has attributed neuropsychologic deficits to the cumulative effects of heading, without evaluating concussion rates in soccer players. We prospectively studied the seven men's and eight women's varsity soccer teams in the Atlantic Coast Conference during two seasons to document concussion incidence. The 29 concussions diagnosed over the 2 years in 26 athletes, 17 (59%) concussions in men and 12 (41%) in women, resulted from contact with an opponent's head (8, 28%), elbow (4, 14%), knee (1, 3%), or foot (1, 3%); the ball (7, 24%); the ground (3, 10%); concrete sidelines (1, 3%); goalpost (1, 3%); or a combination of objects (3, 10%). Twenty concussions (69%) occurred in games; none resulted from intentional heading of the ball. The basic incidence was 0.96 concussions per team per season. The overall incidence was 0.6 per 1000 athlete-exposures for men, and 0.4 per 1000 athlete-exposures for women. By concussion grade, there were 21 (72%) grade 1, 8 (28%) grade 2, and no grade 3 concussions. These findings suggest that concussions are more common in soccer than anticipated and that acute head injuries may have potential for long-term neuropsychologic changes.

Brain Concussion↗