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Biomedical subjects

L Snyder-Mackler

Publications and source records attributed to L Snyder-Mackler.

At least 37 records · Page 2Linked to original sources
PubMed1998

Failure properties of suture anchors in the glenoid and the effects of cortical thickness.

The ultimate pullout strength and fatigue properties of a screw-design suture anchor implanted in the anterior glenoid rim were investigated and compared with results from a nonscrew-design suture anchor. Twenty-two cadaveric glenoids were harvested and one to two anchors were implanted in the superior and inferior quadrants. Fifty-seven Statak 3.5 anchors (Zimmer, Warsaw, IN) were tested and compared with results obtained in a previous study on 50 Mitek GII anchors (Mitek Products, Inc, Westwood, MA). The specimens were mounted on an Instron fatigue testing machine (Instron Corp, Canton, MA) and cycled between preselected minimum and maximum loads until pullout. The Mitek GII maintained a higher pullout strength than the Statak 3.5 after cyclic loading. Cortical thickness at the implantation sites was measured, and found to decrease monotonically from superior to inferior positions. The ultimate pullout strength, and subsequently the fatigue life, of both types of suture anchors depended directly on cortical thickness. The significantly lower performance of both anchors when placed inferiorly emphasizes the importance of correct anchor selection, number, and placement in this region. All anchors settled during the first 10 to 100 cycles, resulting in partial exposure of the implant. Intraoperative cycling of the anchors before suture tying may be necessary to achieve complete settling and prevent subsequent loss of coaptation between capsule and glenoid. The study shows that for the anchors to last 1,000 cycles or more, less than 50% of the theoretical ultimate pullout strength should be applied cyclically. With aggressive early rehabilitation exercises, this significant decrease in fixation strength could shift reconstruction failure from suture breakage or soft tissue tearing to anchor pullout.

Aged↗
PubMed1998

1998 Basmajian Student Award Paper: Movement patterns after anterior cruciate ligament injury: a comparison of patients who compensate well for the injury and those who require operative stabilization.

The purpose of this study was to describe kinematic and kinetic differences between a group of ACL deficient subjects who were grouped according to functional ability. Sixteen patients with complete ACL rupture were studied; eight subjects had instability with activities of daily living (non-copers) and eight subjects had returned to all pre-injury activity without limitation (copers). Three-dimensional joint kinematics and kinetics were collected from the knee and ankle during walking, jogging and going up and over a step. Results showed that both groups mitigated the force with which they contacted the floor but non-copers consistently demonstrated less knee flexion in the involved limb. The copers used joint kinematics similar to those of their uninvolved knees and similar to knee motions reported in uninjured subjects. The reduced knee motion in the involved knee of the non-copers did not correlate directly with quadriceps femoris muscle weakness. The data suggest that the non-copers utilize a stabilization strategy which stiffens the knee joint which not only is unsuccessful but may lead to excessive joint contact forces which have the potential to damage articular structures. The copers use a strategy which permits normal knee kinematics and bodes well for joint integrity.

Adult↗
PubMed1998

Development of a patient-reported measure of function of the knee.

The purpose of the present study was to demonstrate the reliability, validity, and responsiveness of the Activities of Daily Living Scale of the Knee Outcome Survey, a patient-reported measure of functional limitations imposed by pathological disorders and impairments of the knee during activities of daily living. The study comprised 397 patients; 213 were male, 156 were female, and the gender was not recorded for the remaining twenty-eight. The mean age of the patients was 33.3 years (range, twelve to seventy-six years). The patients were referred to physical therapy because of a wide variety of disorders of the knee, including ligamentous and meniscal injuries, patellofemoral pain, and osteoarthrosis. The Activities of Daily Living Scale was administered four times during an eight-week period: at the time of the initial evaluation and after one, four, and eight weeks of therapy. Concurrent measures of function included the Lysholm Knee Scale and several global measures of function. The subjects also provided an assessment of the change in function, with responses ranging from greatly worse to greatly better, at one, four, and eight weeks. The Activities of Daily Living Scale was administered to an additional sample of fifty-two patients (thirty-two male and twenty female patients with a mean age of 31.6 years [range, fourteen to sixty-six years]) before and after treatment within a single day to establish test-retest reliability. Factor analysis revealed two dominant factors: one that reflected a combination of symptoms and functional limitations and the other, only symptoms. The internal consistency of the Activities of Daily Living Scale was substantially higher than that of the Lysholm Knee Scale (coefficient alpha, 0.92 to 0.93 compared with 0.60 to 0.73), resulting in a smaller standard error of measurement for the former scale. Validity was demonstrated by moderately strong correlations with concurrent measures of function, including the Lysholm Knee Scale (r = 0.78 to 0.86) and the global assessment of function as measured on a scale ranging from 0 to 100 points (r = 0.66 to 0.75). Analysis of variance with repeated measures revealed significant improvements in the score on the Activities of Daily Living Scale during the eight weeks of physical therapy (F2,236 = 108.13; p < 0.0001); post hoc testing indicated that the change in the score at eight weeks was significantly greater than the change at four weeks and that the change at four weeks was significantly greater than that at one week (p < 0.0001 for both). As had been hypothesized, the patients in whom the knee had somewhat improved had a significantly smaller change in the score, both at four weeks (F1,189 = 33.50; p < 0.001) and at eight weeks (F1,156 = 22.48; p < 0.001), compared with those in whom the knee had greatly improved. The test-retest reliability coefficient (intraclass correlation coefficient[2,1]) was 0.97. These results suggest that the Activities of Daily Living Scale is a reliable, valid, and responsive instrument for the assessment of functional limitations that result from a wide variety of pathological disorders and impairments of the knee.

Activities of Daily Living↗
PubMed1996

Fatigue properties of suture anchors in anterior shoulder reconstructions: Mitek GII.

Suture anchors have simplified anterior capsule labral reconstruction. During rehabilitation the shoulder goes through many repetitions of range of motion exercises. These exercises will repetitively submaximally load the anchor and in theory should reduce the pullout strength of the suture anchor. No published reports exist on the fatigue strengths and properties of one of the most commonly used anchors: Mitek GII suture anchors. Fifty trials of cyclic submaximal load were done on 22 cadaveric glenoids with an average age of 66.8 years (range, 40 to 90 years). At two to three different sites on the same specimen, the anchors were inserted according to manufacturer's specifications. The anchors were tested to failure on a Instron 1331 servohydraulic mechanical testing system at 2 Hertz sinusoidal loading pattern using steel sutures and a predetermined load. There were 22 (44%) tests performed in the superior quadrant and 28 (56%) tests in the inferior quadrant. All anchors pulled out, and no wires broke. There were statistically significant differences between the superior and inferior portion of the glenoid with regard to number of cycles to failure at a given maximum load. The anchors underwent an average of 6,220 cycles before pullout at an average load of 162 N (SD = 73 N). In the superior quadrant, the average ultimate pullout strength was 237 N (SD = 42 N), whereas in the inferior quadrant the average ultimate pullout strength was 126 N (SD = 36 N). Hence, the ultimate pullout strength of the Mitek GII anchor was significantly higher (P < .002) in the superior quadrant than in the inferior quadrant. Using a least squares regression analysis, it was possible to predict the fatigue life of the superiorly and inferiorly placed suture anchors over a wide range of cycles. The R-squared values for trendlines showed good reliability (superior R2 = 0.55; inferior R2 = 0.28). The fatigue life curves for the two different quadrants were normalized using the ultimate pullout strength. This new, universal curve predicts the fatigue life of the Mitek GII anchor as a percentage of the ultimate pullout strength for any selected location. For a clinically relevant number of cycles, no more than approximately 40% to 50% of the ultimate pullout strength of the suture anchor can be cyclically applied to the anchor to guarantee a life for the duration of rehabilitation. For the entire system, the inferiorly placed anchors dictate the amount of cyclically applied load the system can experience without failing, and rehabilitation should be adjusted accordingly.

Adult↗
PubMed1995

The diagnostic process: examples in orthopedic physical therapy.

Diagnosis by the physical therapist has received increased attention in the physical therapy literature. The contributions thus far are in agreement that although physical therapists do not identify disease in the sense of pathology, they certainly can identify clusters of signs, symptoms, symptom-related behavior, and other data from patient history and other testing. These clusters can be labeled as classifications or diagnoses by physical therapists and can guide management of the patient. The purpose of this article is to discuss what has yet to be included in articles about diagnosis: the diagnostic process. We first acknowledge the complexity of the diagnostic process, reviewing the study of clinical diagnosis mostly from the field of medicine, including statistical as well as process-tracing approaches. We next discuss steps we believe are important to consider in order to interface the diagnostic process into entry-level training curricula, urging teachers and mentors of future physical therapists to rethink our emphasis on the problem-oriented medical record's "SOAP" type of approach as a clinical decision-making format. We next discuss error and clinical judgment and strategies to constructively deal with error in the clinical environment. We urge physical therapists to strive to reach a point at which we can (1) identify and classify patients in such a manner that allows for more efficient treatment management and (2) demonstrate such abilities in peer-reviewed publication form.

Aged↗
PubMed1995

Strength of the quadriceps femoris muscle and functional recovery after reconstruction of the anterior cruciate ligament. A prospective, randomized clinical trial of electrical stimulation.

Immediately after reconstruction of the anterior cruciate ligament, 110 patients were randomly assigned to treatment with high-intensity neuromuscular electrical stimulation (thirty-one patients), high-level volitional exercise (thirty-four patients), low-intensity neuromuscular electrical stimulation (twenty-five patients), or combined high and low-intensity neuromuscular electrical stimulation (twenty patients). All treatment was performed isometrically with the knee in 65 degrees of flexion. All of the patients participated in an intensive program of closed-kinetic-chain exercise. After four weeks of treatment, the strength of the quadriceps femoris muscle and the kinematics of the knee during stance phase were measured. Quadriceps strength averaged 70 per cent or more of the strength on the uninvolved side in the two groups that were treated with high-intensity electrical stimulation (either alone or combined with low-intensity electrical stimulation), 57 per cent in the group that was treated with high-level volitional exercise, and 51 per cent in the group that was treated with low-intensity electrical stimulation. The kinematics of the knee joint were directly and significantly (p < 0.05) correlated with the strength of the quadriceps. There was a clinically and statistically significant (p < 0.05) difference in the recovery of the quadriceps and the gait parameters according to the type of operation that had been performed: the patients who had had reconstruction of the anterior cruciate ligament with use of an autologous patellar-ligament graft did poorly compared with the other patients.

Adult↗
PubMed1994

Use of electrical stimulation to enhance recovery of quadriceps femoris muscle force production in patients following anterior cruciate ligament reconstruction.

BACKGROUND AND PURPOSE: Electrical stimulation has been shown to be effective in aiding the recovery of quadriceps femoris muscle force production after anterior cruciate ligament reconstruction. The actual dosage of stimulation (training intensity) has not been well described. The purpose of this investigation was to establish a dose-response curve for electrical stimulation regimens designed to improve quadriceps femoris muscle recovery in patients after anterior cruciate ligament reconstruction. SUBJECTS AND METHODS: We analyzed data from a subsample (n = 52) of patients receiving electrical stimulation (N = 110) who were involved in a large, multicenter randomized clinical trial investigating treatment strategies designed to enhance quadriceps femoris muscle recovery. Fifty-two subjects (40 male, 12 female), with an age range of 15 to 43 years (mean = 25, SD = 7), participated in 4 weeks of quadriceps femoris muscle training using either portable, battery-powered home stimulators or console stimulators designed for clinical use. Training intensities were monitored by logging the electrically elicited knee extension torque and expressing this torque as a percentage of the uninvolved quadriceps femoris muscles' maximal voluntary contraction force. After the 4 weeks of training, isometric muscle torque was assessed and a dose-response curve was generated. The relationship between training intensity and quadriceps femoris muscle torque was assessed with Pearson Product-Moment Correlation Coefficients. RESULTS: A significant, linear correlation was found between training intensity and quadriceps femoris muscle torque. Subjects training with console, clinical generators trained at higher intensities than those training with portable, battery-operated generators; such training resulted in higher quadriceps femoris muscle torque. CONCLUSION AND DISCUSSION: These results support the use of high-intensity electrical stimulation and do not support the use of low-intensity or battery-powered stimulators when the goal is recovery of quadriceps femoris muscle force production in the early phases of rehabilitation after anterior cruciate ligament surgery. [Snyder-Mackler L, Delitto A, Stralka SW, Bailey SL. Use of electrical stimulation to enhance recovery of quadriceps femoris muscle force production in patients following anterior cruciate ligament reconstruction.

Adolescent↗
PubMed1994

Reflex inhibition of the quadriceps femoris muscle after injury or reconstruction of the anterior cruciate ligament.

A burst-superimposition technique was used to assess the strength of the quadriceps femoris muscle in three groups of patients. Group 1 comprised twenty patients who had had a torn anterior cruciate ligament of the knee and had a reconstruction of the ligament one to six months after the injury. Group 2 comprised twelve patients who had had a torn anterior cruciate ligament for an average of three months (a subacute tear). Group 3 comprised eight patients who had had a torn anterior cruciate ligament for an average of two years (a chronic tear). The patients in Groups 2 and 3 had not had an operation for the torn ligament. The patients in Groups 1 and 3 had no evidence of failure of activation of the involved quadriceps, but nine of the twelve patients in Group 2 had reflex inhibition of contraction of the muscle.

Adolescent↗
PubMed1994

Instrumented examination of knee laxity in patients with anterior cruciate deficiency: a comparison of the KT-2000, Knee Signature System, and Genucom.

Knee ligament arthrometers are used during rehabilitation to assess changes in knee laxity after anterior cruciate ligament injury. This study investigated the reliability and error associated with measurements of knee laxity using three different instrumented devices: the KT-2000, the Knee Signature System (KSS), and the Genucom Knee Analysis System to aid in the interpretation of instrumented laxity measurements during rehabilitation. Ten subjects with unilateral anterior cruciate deficiency were examined by two testers on two separate days. Measurement error was calculated as the minimum difference required to assume a true change in laxity between two measurements (p < 0.05). Between-day reliability was relatively high for both the KSS and the KT-2000 (.95 and .83, respectively) but substantially lower for the Genucom (.22). Intertester reliability was slightly lower for the KT-2000 and the KSS (.92 and .78, respectively) and slightly higher but still low for the Genucom (.27). When monitoring changes in anterior laxity of an anterior-cruciate-deficient knee, the following error values were determined to be needed in order to assume a true difference between successive measurements: KT-2000, 2.0 mm; KSS, 4.2 mm; and Genucom, 5.9 mm. The results of this study suggest that measurements of anterior laxity taken by a single examiner using the KT-2000 provide the most reliable measurements.

Adult↗
PubMed1993

Muscle fatigue: clinical implications for fatigue assessment and neuromuscular electrical stimulation.

Muscle fatigue can be defined as a decrease in the force-generating ability of a muscle that resulted from recent activity. Recent studies of muscle fatigue are reviewed that are relevant to two areas of interest to physical therapists: clinical assessment of muscle fatigue and neuromuscular electrical stimulation. Volitional and electrical tests have been used to quantify muscle fatigue. Several variations on each type of test are discussed, as are the possible sites in which fatigue might occur. The rate of fatigue during the therapeutic application of electrical stimulation of skeletal muscle is much greater than that seen during volitional contractions. Factors contributing to this phenomenon are examined. The unique requirements affecting how stimulus variables can be manipulated to minimize muscle fatigue in three specific therapeutic uses of neuromuscular electrical stimulation are addressed.

Electric Stimulation↗
PubMed1993

Fatigability of human quadriceps femoris muscle following anterior cruciate ligament reconstruction.

The responses of quadriceps femoris muscles to an electrically elicited fatigue test were recorded from both lower extremities of 18 patients who had recently undergone unilateral, anterior cruciate ligament reconstruction. The fatigue test consisted of 40 pps, 13-pulse electrical trains that were repeated once per second for 3 min. The intensity of stimulation was set for each extremity to produce 20% of the maximum voluntary isometric contraction of the uninvolved muscle. The uninvolved quadriceps femoris muscle showed a significantly greater rate of decline in force over the first minute than the involved muscle (0.803%.s-1 for uninvolved muscle vs 0.620%.s-1 for involved muscle). Similarly, the average forces produced over the last minute were significantly lower for the uninvolved than the involved quadriceps femoris muscle (uninvolved = 42.6%, involved = 50.4% of their original forces). These surprising results showed that the involved quadriceps femoris muscles were more endurant than the uninvolved muscles. It is suggested that the increases in endurance of the involved muscle may have been due, in part, to greater recruitment of Type I fibers with electrical stimulation or selective Type II fiber atrophy in the involved muscle.

Adolescent↗
PubMed1991

Comparison of spinal mobility and isometric trunk extensor forces with electromyographic spectral analysis in identifying low back pain.

This study compared conventional clinical measurements with electromyographic (EMG) spectral measurements for identification of individuals with low back pain (LBP). Twenty freshman sweep rowers were subjects for this study. Range-of-motion (ROM) measurements were taken for forward bending (FB), backward bending (BB) (double inclinometers), lateral bending (LB) (tape measure), and rotation (double-arm goniometer). Intratester reliability for ROM was also assessed. The Back Analysis System was used to determine static trunk extensor strength (ie, maximal voluntary contraction [MVC]) and to compute EMG spectral parameters from a paraspinal multi-electrode array. A two-group stepwise discriminant-analysis procedure for the ROM and MVC variables correctly identified 57% of the rowers with LBP and 63% of the rowers without LBP. A similar discriminant-analysis procedure for EMG spectral parameters correctly identified either 88% of the rowers with LBP and 100% of the rowers without LBP or 100% of the rowers with LBP and 88% of the rowers with LBP, depending on whether EMG measurements of recovery were calculated at 1 minute or at 2 minutes into the recovery period. Sensitivity (66%) and specificity (71%) results from the more traditional tests suggest that these techniques may be of limited usefulness for LBP screening or diagnosis.

Adult↗
PubMed1991

Interrater reliability of videotaped observational gait-analysis assessments.

The purpose of this study was to determine the interrater reliability of videotaped observational gait-analysis (VOGA) assessments. Fifty-four licensed physical therapists with varying amounts of clinical experience served as raters. Three patients with rheumatoid arthritis who demonstrated an abnormal gait pattern served as subjects for the videotape. The raters analyzed each patient's most severely involved knee during the four subphases of stance for the kinematic variables of knee flexion and genu valgum. Raters were asked to determine whether these variables were inadequate, normal, or excessive. The temporospatial variables analyzed throughout the entire gait cycle were cadence, step length, stride length, stance time, and step width. Generalized kappa coefficients ranged from .11 to .52. Intraclass correlation coefficients (2,1) and (3,1) were slightly higher. Our results indicate that physical therapists' VOGA assessments are only slightly to moderately reliable and that improved interrater reliability of the assessments of physical therapists utilizing this technique is needed. Our data suggest that there is a need for greater standardization of gait-analysis training.

Adult↗
PubMed1991

Electrical stimulation of the thigh muscles after reconstruction of the anterior cruciate ligament. Effects of electrically elicited contraction of the quadriceps femoris and hamstring muscles on gait and on strength of the thigh muscles.

The effects of neuromuscular electrical stimulation on the strength of the thigh muscles and on gait were examined in ten patients after reconstruction of the anterior cruciate ligament. The patients were randomly assigned to one of two treatment groups: neuromuscular electrical stimulation and volitional exercise, or volitional exercise alone. A four-week course of electrically elicited co-contraction of the thigh muscles resulted in significant attenuation of the characteristic loss of strength of the quadriceps as compared with volitional exercise. There was no significant difference between groups in any measure of performance of the hamstring muscles. In the group that received neuromuscular electrical stimulation, the values for cadence, walking velocity, stance time of the involved limb, and flexion-excursion of the knee during stance were significantly different from those of the volitional exercise group. Flexion-excursion of the knee during stance was directly and significantly correlated with strength of the quadriceps femoris muscle. Flexion of the knee during stance was qualitatively different in the involved extremity as compared with the uninvolved extremity in all patients. There is a rapid flexion of the knee at weight acceptance that is maintained throughout stance and probably reflects stabilization of the joint by muscular coactivation to compensate for weakness of the quadriceps. The patients who received neuromuscular electrical stimulation had stronger quadriceps muscles and more normal gait patterns than those in the volitional exercise group.

Adolescent↗
PubMed1990

Two theories of muscle strength augmentation using percutaneous electrical stimulation.

Electrical stimulation of muscle is a commonly used, well-substantiated strategy that physical therapists use to augment strength in patients with muscle weakness. Two distinctly different theories of strength augmentation using percutaneous muscle stimulation are presented. The first theory proposes that augmentation of muscle strength with electrically elicited muscle contractions occurs in a similar manner to augmentation of muscle strength with voluntary exercise. Electrically elicited muscle contractions of relatively high intensity with low numbers of repetitions strengthen muscle proportionally to the external load on the muscle in a manner that is equivalent to voluntary contraction. The second theory proposes that augmentation of muscle strength using percutaneous stimulation is fundamentally different from augmentation of strength with voluntary exercise. This theory uses the physiological differences between electrically elicited and voluntary contractions, such as the reversal of motor unit recruitment order, as a basis for argument. Both theories are partially substantiated using published literature. Strategies for testing both theories are also presented.

Electric Stimulation Therapy↗
PubMed1990

Fatigue, recovery, and low back pain in varsity rowers.

The purpose of this study was to determine whether surface electromyography (EMG) from the erector spinae muscles could correctly identify individuals with low back pain without a population of elite athletes. A similar technique had previously been successful in identifying low back pain patients within a non-athletic population. A Back Analysis System was used to compute the median frequency of the EMG power density spectrum to monitor metabolic changes in back muscles associated with muscle fatigue. Twenty-three members of a men's collegiate varsity crew team consisting of port (N = 13) and starboard (N = 10) rowers were tested in a laboratory during a fatigue-inducing isometric contraction sustained at a relatively high, constant force. Six of the rowers tested were further classified as having low back pain. A brief test contraction was repeated at a fixed interval following the fatiguing contraction to monitor recovery. A two-group discriminant analysis procedure correctly classified 100% of the rowers with low back pain and 93% of the rowers without back pain on the basis of the median frequency data. The median frequency parameters related to recovery were the best discriminators of back pain. A similar analysis correctly classified 100% of the port rowers and 100% of the starboard rowers on the basis of their spectral parameters. The best discriminating variables in this instance were the median frequency parameters relating to both fatigability and recovery. Results from this study demonstrate that low back pain and asymmetrical muscle function in rowers can be assessed on the basis of EMG spectral analysis.

Adult↗