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Biomedical subjects

J Perry

Publications and source records attributed to J Perry.

At least 145 records · Page 8Linked to original sources
PubMed1993

Determinants of muscle function in the spastic lower extremity.

The upper motor neuron lesion that causes hemiplegia impairs the patient's selective control and exposes primitive modes of muscle activation. Significant inconsistency between the clinical findings and the patient's gait may result. Dynamic electromyography revealed the primitive mechanisms leading to these inconsistencies. The rate of stretch does not differentiate spasticity from contracture, since either a quick or slow stretch frequently causes a sustained muscle response. Using knee flexion to differentiate gastrocnemius and soleus spasticity is not reliable, since the change in neurologic input with flexion may inhibit the extensor muscle's response to stretch so that the soleus is also relaxed. The change in body position from lying supine to sitting can double the intensity of soleus spasticity, and standing further increases the tone. Primitive patterns of mass extension and flexion, while voluntary, inhibit normal progression during walking. Simultaneous activation of the soleus and gastrocnemius with the knee's quadriceps causes premature ankle plantar flexion as the limb is loaded in stance. The primitive flexion synergy between the hip, knee, and ankle (dorsiflexion) inhibits terminal swing knee extension while the hip remains flexed. Consequently, surgical planning for the hemiparetic limb must rely heavily on gait analysis findings (systematic observation or by instrumentation).

Adolescent↗
PubMed1993

Quadriceps force and myoelectric activity during flexed knee stance.

The purpose of this study was to determine the quadriceps demand during single limb stance with the knee in five positions of flexion (0 degree -60 degrees). Two variables were used to estimate the quadriceps demands: the integrated electromyogram (EMG) of three vasti and the torque about the knee joint. Ten normal subjects 23-29 years of age were tested. Myoelectric activity was recorded with intramuscular electrodes and knee joint angle with an electrogoniometer. The EMG data were integrated and normalized. A visible vector system was used to determine knee flexion torque. A significant linear correlation was found between values of patellar ligament force and knee angle (R2 = 0.86). The patellar ligament force increased 4.16% of body weight per degree of knee flexion between 0 degree and 60 degrees. Both vector-estimated quadriceps force and normalized EMG showed significant correlations with knee angle (R2 = 0.91 and R2 = 0.88, respectively). Both exhibited a slower rate of rise below 30 degrees flexion and a higher rate of rise above 30 degrees. The authors' findings suggest that the stabilizing effects of plantar flexors (except gastrocnemius) on the knee joint, changing muscle moment arm length, and force ratio between the patellar ligament and quadriceps muscle with respect to knee angle are primary reasons for the quadratic normalized integrated EMG (NIEMG)-force nonlineality during flexed stance. This might indicate the existence of a critical angle of knee flexion contracture beyond which patients cope poorly with standing and functional ambulation.

Adult↗
PubMed1993

The normal shoulder during the butterfly swim stroke. An electromyographic and cinematographic analysis of twelve muscles.

This study describes shoulder muscle activity during the butterfly stroke. Upon hand entry, the deltoids and rotator cuff muscles demonstrated activity as the humerus was abducted, extended, and externally rotated. The rhomboids and upper trapezius were also active, retracting and upwardly rotating the scapula, which positioned the glenoid for the humerus. During propulsion, the pectoralis major and latissimus dorsi generated power. The subscapularis and teres minor were active to control humeral rotation. The serratus anterior helped to pull the body over the arm by reversing its origin and insertion. The posterior deltoid completed humeral extension at the end of propulsion and began to lift the arm out of the water. Then, the middle and anterior deltoids fired with the supraspinatus and infraspinatus to abduct and externally rotate the arm. The scapular muscles were also active, retracting the proximal portion of the scapula while protracting and upwardly rotating the distal tip. The glenoid then provided a platform for the humerus. Overall, the serratus anterior and the subscapularis maintained a high level of activation throughout the stroke; thus, these muscles were highly susceptible to fatigue and vulnerable to injury.

Adult↗
PubMed1993

The painful shoulder during the butterfly stroke. An electromyographic and cinematographic analysis of twelve muscles.

This paper compares the muscle firing patterns of 12 shoulder girdle muscles in competitive butterfly swimmers with painful and normal shoulders. Seven of the 12 muscles revealed statistically significant differences between the two populations. The posterior deltoid demonstrated more activity in the painful shoulders during hand entry while the upper trapezius and serratus anterior exhibited less activity. This alteration in muscle firing patterns allowed for the humerus to be positioned for a wider hand entry, which decreased the pain of impingement of the supraspinatus on the coracoacromial arch. Correspondingly, there was significantly less activity in the supraspinatus. The teres minor and serratus anterior revealed significantly less muscle action throughout pulling as they respectively failed to balance the humeral rotation and did not reverse their origins and insertions to pull the body over the arm. Also, the subscapularis and infraspinatus displayed increased activity in the painful shoulders as they depressed the humeral head to avoid impingement. There were no significant differences between the two groups in the rhomboids, pectoralis major, latissimus dorsi, or the anterior and middle deltoids. From this information, accurate preventative and rehabilitative exercise programs for the competitive butterfly swimmer can be developed.

Adult↗
PubMed1993

Functional recovery of noncemented total hip arthroplasty.

Eighteen patients with unilateral hip disease had noncemented total hip arthroplasty. Clinical follow-up data were complete to five years postsurgery. Gait analysis was done preoperatively, at three and six months, and at one and two years. Force plate data showed continued weakness of the operated hip in all patients at two years postsurgery. Preoperative dynamic electromyograms (EMGs) were abnormal in eight patients and showed two patterns. Stance loss seen in three patients was characterized by absence of activity of the gluteus medius and upper and lower gluteus maximus muscles. In five patients, continuous activity occurred in the tensor fascia lata, rectus femoris, and adductor longus muscles during the entire gait cycle. Postoperatively, all abnormal EMGs returned to normal. Four patients with a normal preoperative EMG developed abnormal EMG patterns postoperatively, demonstrating either a prolonged stance or stance loss pattern. All four of these hips have been revised. Although gait characteristics return to normal by two years postsurgery, weakness of the hip persists. This weakness jeopardizes the implant fixation interface. This study supports the prohibition of activities that cause high impact loading of total hip arthroplasties and suggests that a prolonged exercise program be employed postoperatively.

Adult↗
PubMed1993

Contribution of rectus femoris and vasti to knee extension. An electromyographic study.

Electromyographic (EMG) activity was recorded from the five components of the quadriceps during maximum knee extension with the limb in six combinations of hip and knee flexion: the hip at 0 degrees, 40 degrees, and 80 degrees with the knee at 15 degrees and 60 degrees. None of the six positions could isolate the vasti from the rectus femoris. The highest EMG activity of all five muscles was recorded with the limb in 40 degrees hip flexion and 15 degrees knee flexion. The lowest EMG activity was recorded with the hip at 0 degrees and the knee at 60 degrees flexion. Overall, the knee extension torques were 40% higher with the knee at 60 degrees flexion than at 15 degrees flexion. The lowest torques were generated with the limb positioned at 80 degrees hip flexion and 15 degrees knee flexion. During maximum knee extension, the vasti muscles do not work in isolation of the rectus femoris, regardless of the amount of hip flexion. All portions of the quadriceps worked in all positions, which suggests these muscles may be strengthened effectively in many different positions to accommodate the patient's comfort and interest.

Adult↗
PubMed1993

Baseball batting. An electromyographic study.

The muscle firing pattern in 12 muscles throughout the lower extremity, trunk, and upper extremity during the batting swing is described in this study. The two hamstring muscles studied and the gluteal muscle had a similar pattern of high muscle activity during pre-swing and early swing, and then rapidly diminished. The vastus medialis demonstrated peak activity between 95 and 110% maximum muscle test (MMT) throughout the swing phases and follow-through. The erector spinae demonstrated activity from 85 to 185% MMT during the swing phases. The abdominal obliques showed greater than 100% MMT during the swing phases and follow-through. The supraspinatus and serratus anterior showed relatively low muscle activity (less than 40% MMT). These results show that batting is a sequence of coordinated muscle activity, beginning with the hip, followed by the trunk, and terminating with the arms. Power in the swing is initiated in the hip, and therefore exercises that emphasize such strength development are indicated. The maintained, high muscle activity in the trunk muscles indicates a need for back and abdominal stabilization and rotation exercises. The relatively low level of activity in the four scapulohumeral muscles tested indicated that emphasis should be placed on the trunk and hip muscles for a batter's strengthening program.

Abdominal Muscles↗
PubMed1992

Evaluation of a prolonged infusion of recombinant tissue-type plasminogen activator (Duteplase) in preventing reocclusion following successful thrombolysis in acute myocardial infarction.

The hypothesis that an infusion of recombinant tissue-type plasminogen activator (rt-PA) maintained for up to 24 hours could prevent reocclusion after early coronary patency had been established was evaluated in patients with acute myocardial infarction. The rt-PA studied was an investigational double chain rt-PA (Duteplase, Burroughs Wellcome Co.), administered according to body weight. Coronary patency was documented in 139 of 213 patients who had 90-minute angiograms recorded after an initial lytic dose of rt-PA. In these responders a further 90-minute infusion at one third the initial lytic dose was given before assignment to 1 of 4 maintenance dose rates (0.012, 0.024, 0.036, 0.048 MIU/kg/hour) which were continued for the subsequent 9 to 21 hours. The principal end point was the status of the infarct-related coronary artery 12 to 24 hours after the start of therapy, and before termination of rt-PA, in patients with initially patent vessels at 90 minutes. Of the 103 responders with repeat angiograms after a 9 to 21 hour maintenance infusion of rt-PA, a total of 17 (16.5%) patients reoccluded across all doses administered. There was no significant relationship between the maintenance dose rate and the incidence of reocclusion. However, there was strong association between total dose of rt-PA administered and the incidence (16%) of serious or life-threatening bleeding exclusive of surgery. Other factors associated with serious bleeding included low body weight, female gender, and total duration of rt-PA infusion. Reocclusion was independent of the 90-minute Thrombolysis in Myocardial Infarction trial perfusion grade and diameter of infarct vessel. Rethrombosis after establishment of early patency after rt-PA remains a significant problem that is unaffected by sustained rt-PA infusion in doses that can be tolerated.

Female↗
PubMed1992

An electromyographic analysis of the shoulder during cones and planes of arm motion.

Shoulder motion has traditionally been described in reference to arbitrarily defined planes of motion (e.g., sagittal/flexion, coronal/abduction). This study examined shoulder muscle recruitment during conical arm movements, which include all planes of motion. Electromyographic (EMG) data was collected with intramuscular wire electrodes from ten muscles in five normal volunteers. Each muscle showed peak EMG activity in association with a direction of action consistent with its anatomic alignment. These findings were similar for movements in both the sagittal and coronal planes, calling into question conventionally held designations of shoulder muscles as flexors and abductors. Muscle recruitment was as follows: Clavicular pectoralis major, to move the arm medially along the horizontal; anterior deltoid, to move the arm obliquely upward inclined toward the midline; middle deltoid, to move the arm obliquely upward inclined away from the midline; posterior deltoid, to move the arm laterally along the horizontal; and teres major and latissimus dorsi, to move the arm obliquely downward away from the midline. Rotator cuff muscles were maximally active during elevation, consistent with the concept of a force couple.

Adult↗
PubMed1992

Computer algorithms to characterize individual subject EMG profiles during gait.

Three methods of precisely determining onset and cessation times of gait EMG were investigated. Subjects were 24 normal adults and 32 individuals with gait pathologies. Soleus muscle EMG during free speed level walking was obtained with fine wires, and was normalized by manual muscle test (%MMT). Linear envelopes were generated from the rectified, integrated EMG at each percent gait cycle (%GC) of each stride in individual gait trials. Three methods were used to generate EMG profiles for each tested subject. The ensemble average (EAV) was determined for each subject from the mean relative intensity of the linear envelopes. Low relative intensity or short duration EMG was removed from the ensemble average to create the intensity filtered average (IFA). The packet analysis method (PAC) created an EMG profile from the linear envelopes in successive strides whose respective centroid %GC locations were within +/- 15%GC of each other. Control values for onset and cessation times of individual gait trials were calculated after spurious outliers were removed. Mean onset and cessation times across subjects for control values and the experimental methods (EAV, IFA, and PAC) were calculated. Dunnett's test (p less than .05) was performed to compare control and experimental groups in patient and normal trials. EAV differed from control values for onsets (p less than .01), cessations (p less than .01), and durations (p less than .01) in both normal and patient trials. IFA and PAC had no significant differences from control value means. IFA was selected for clinical use as automatic analysis could be performed on all trials and a minimum number of decision rules were needed.

Adult↗
PubMed1991

Chemotherapy of disseminated Merkel-cell carcinoma.

Six patients developed metastatic merkel-cell carcinoma and were treated with a combination chemotherapy frequently used for small-cell lung cancer. Five of six patients had a complete response for a median of 3.5 months. Overall survival from initiation of chemotherapy was a median of 6.5 months. Two patients died from major complications of therapy.

Adult↗
PubMed1991

Stiff-legged gait in spastic paresis. A study of quadriceps and hamstrings muscle activity.

Stiff-legged gait, ascribed to limited knee flexion during swing in spastic paresis, has previously received little detailed investigation. In this study, data from 23 patients referred for dynamic electromyographic evaluation of spastic stiff-legged gait were analyzed to identify timing of the activity of eight muscles during the gait cycle. Stride characteristics and foot switch data were also analyzed. Inappropriate activity in at least one of the quadriceps muscles during the preswing and/or initial swing phases was found in all 23 patients. Nine patients (39%) had hamstring activity during preswing. This group of 9, compared with the other 14 patients, had a significant reduction in average gait velocity and stride length (P less than 0.05) suggesting that preswing hamstring activity in stiff-legged gait may be counterproductive. No relation was found between biceps femoris (short head) activity and the amount of peak knee flexion attained in swing indicating that other factors are more important in attaining knee flexion. Delayed heel rise was observed in 21 patients (91%), which could imply insufficient calf muscle strength. Further, patients with markedly delayed heel rise achieved less peak knee flexion in swing than patients with normal or only moderately delayed heel rise (P less than 0.05). This may support the notion that adequate calf muscle strength is important in initiating knee flexion in the terminal stance/preswing phase. Results from this study provide preliminary quantitative information about stiff-legged gait that may prove useful in guiding management techniques.

Adult↗
PubMed1991

Cocaine in decomposed human remains.

From March 1988 through March 1990, at the Philadelphia Medical Examiner's Office toxicology laboratory, samples from 77 decomposed human bodies were tested for the presence of cocaine, employing gas chromatography/mass spectrometry (GC-MS). The material analyzed included decomposed soft tissue, bloody decomposition fluid, mummified tissue, maggots, and beetle feces. Twenty-two cases (28.6%) were positive for cocaine, many of these cases in states of advanced decomposition. These findings indicate the usefulness of testing decomposed tissue for cocaine in all cases where its presence is suspected. This is contrary to what might be expected, since cocaine is generally labile and rapidly broken down by both enzymatic and nonenzymatic mechanisms.

Animals↗
PubMed1991

Valgus deformities of the feet and characteristics of gait in patients who have rheumatoid arthritis.

To investigate the cause of valgus deformity of the hindfoot in patients who have rheumatoid arthritis and to characterize the effects of the deformity on gait, two groups of patients were evaluated clinically, radiographically, and with gait analysis in the laboratory. Group 1 consisted of seven patients who had seropositive rheumatoid arthritis and normal alignment of the feet and Group 2, of ten patients who had rheumatoid arthritis and valgus deformity of the hindfoot. In Group 2, the disease was of longer duration and the feet were more painful than in Group 1. There was no evidence of muscular imbalance, equinus contracture, valgus deformity of the tibiotalar joint, or isolated deficiency of the tibialis posterior (such as weakness, tenosynovitis, or rupture of the tendon) that could have contributed to the development of the valgus deformity. In the patients who had valgus deformity, quantitated electromyography demonstrated that the intensity and duration of activity of the tibialis posterior was significantly increased, apparently in an effort to support the collapsing longitudinal arch of the foot. Gait studies revealed decreases in velocity, stride length, and single-limb-support time, as well as delayed heel-rise in both groups, but the decreases were more marked in the patients who had valgus deformity. The results of this study suggest that valgus deformity of the hindfoot in rheumatoid patients results from exaggerated pronation forces on the weakened and inflamed subtalar joint. These forces are caused by alterations in gait secondary to symmetrical muscular weakness and the effort of the patient to minimize pain in the feet. Radiographs also suggested an association between the valgus deformity of the feet and valgus deformity of the knees in patients who have rheumatoid arthritis.

Adult↗