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Biomedical subjects

M J O'Malley

Publications and source records attributed to M J O'Malley.

At least 19 recordsLinked to original sources
PubMed2003

EMG amplitude in maximal and submaximal exercise is dependent on signal capture rate.

This study analysed the effect of different electromyographic (EMG) capture rates during maximal voluntary contraction, submaximal and maximal dynamic cycling activity on EMG amplitude and signal characteristics. Ten healthy subjects participated in this study. Peak power output (PPO) and maximal isometric force output (MVC) were measured, followed by a progressive cycle ride on a cycle ergometer. Electromyographic (EMG) data were simultaneously captured during the MVC and cycling activities at frequencies of 32, 64, 128, 256, 512, 1024 and 1984 Hz. Significant differences in amplitude were found (p < 0.01) between MVC, submaximal (SUB) and maximal cycling activities (PWATT) for all capture rates. Asymptote values for IEMG amplitude occurred at EMG capture rates of 1604 +/- 235.6 Hz during MVC, 503.1 +/- 236.2 Hz during PWATT and 326.2 +/- 105.4 Hz during SUB cycling activity and were significantly different (p < 0.01). No significant differences were found for force/EMG ratios between PWATT and MVC at 1984 Hz capture rates (3.8 +/- 1.7 N/V vs 2.5 +/- 0.9 N/V) while significant differences occurred at 32 Hz capture rate (6.2 +/- 3.8 vs 16.0 +/- 8.0; p < 0.01). Low correlations were found between EMG activity captured at 1984 Hz during PWATT and lean thigh volume (r = 0.36) and MVC (r = 0.32). Asymptote values found on this study suggest that data captured below 326 Hz for SUB, 503 Hz for PWATT and 1604 Hz for MVC are not reliable. Therefore apparatus capturing EMG data at low frequencies from these values cannot be used for quantitative data analyses.

Adult↗
PubMed2000

Spectral compression of the electromyographic signal due to decreasing muscle fiber conduction velocity.

Spectral compression of the electromyographic (EMG) signal, due largely to decreasing muscle fiber conduction velocity, is commonly used as an indication of muscle fatigue. Current methods of estimating conduction velocity using characteristic frequencies such as the median frequency of the power spectrum, are based on an assumption of uniform spectral compression. To examine changes in the EMG frequency spectrum during fatigue, muscle fiber conduction velocity was measured during sustained, isometric contractions of the biceps brachii. Compression of the EMG power and amplitude spectra was simultaneously examined using the median frequency and an alternative method-the spectral distribution technique. The spectral distribution technique consistently gave a better estimate of the relative change in muscle fiber conduction velocity than either of the median frequencies. This was further examined using a physiologically based EMG simulation model, which confirmed these findings. The model indicated that firing statistics can significantly influence spectral compression, particularly the behavior of characteristic frequencies in the vicinity of the firing rates. The relative change in the median frequency, whether of the amplitude or frequency spectrum, was consistently greater than the relative change in conduction velocity. The most accurate indication of the relative change in conduction velocity was obtained by calculating the mean shift in the midfrequency region of the EMG amplitude spectrum using the spectral distribution technique.

Action Potentials↗
PubMed2000

Endoscopic plantar fasciotomy for chronic heel pain.

The purpose of our study was to determine whether endoscopic plantar fasciotomy is a safe and effective operation in this patient population. We reviewed our surgical results following endoscopic plantar fasciotomy in sixteen patients (twenty feet) with an average preoperative duration of symptoms of four years. Of the 20 feet, 9 had complete relief of pain while symptoms were improved in nine feet. One patient with bilateral symptoms had no relief in either foot. The average AOFAS hindfoot score improved from 62 to 80, a statistically significant difference. Unilateral patients did better than bilateral with no bilateral patients reporting complete resolution of symptoms. There were no iatrogenic nerve injuries. On the basis of our review, we recommend endoscopic plantar fasciotomy as an alternative to open plantar fascial release for those patients with recalcitrant heel pain.

Chronic Disease↗
PubMed2000

Deltoid ligament strain after correction of acquired flatfoot deformity by triple arthrodesis.

Deltoid insufficiency represents a difficult surgical challenge. We have witnessed patients who have developed a valgus tibiotalar deformity following a properly positioned triple arthrodesis. To investigate whether the triple arthrodesis itself, by creating a rigid triple joint complex below the ankle, leads to increased strain of the deltoid complex, a flatfoot model was created in 8 fresh-frozen below-knee amputation specimens. Each specimen was loaded in three gait cycle (GC) positions: Heel strike (0% GC), midstance (10% GC), and heel rise (40% GC). The three components of the ground reaction force (GRF) and the tendon forces consistent with those respective positions were applied. To simulate a posterior tibial tendon insufficient state the posterior tibial tendon was not loaded. Strain at the tibiocalcaneal fibers of the superficial deltoid ligament complex was determined at each of the three foot positions. A triple arthrodesis was performed and the deltoid strains were again recorded for each position. A significant increase in the strain of the deltoid ligament was observed for only the heel rise position (p=0.007) in our cadaver model following triple arthrodesis. The results favor medializing the calcaneus following arthrodesis to protect the deltoid complex.

Adult↗
PubMed1999

Adaptive noncontact gesture-based system for augmentative communication.

An adaptive noncontact gesture-based system for augmentative communication is described. The system detects movement of any anatomical site through the analysis of reflected speckle. This movement is converted into two-dimensional (2-D) cursor coordinates and an adaptive software interface provides click actions and decision strategies. The system requires no accessory to be placed on the user. The system was developed in conjunction with user groups, who participated in the evaluation of the system. The usability results obtained illustrate the utility of the system. The system also compared favorably with other interface solutions.

Adolescent↗
PubMed1999

Idiopathic pseudoaneurysm of the dorsalis pedis artery mimicking pigmented villonodular synovitis.

Pseudoaneurysm of the dorsalis pedis artery is uncommon and is usually associated with a history of trauma to the vessel. Without such a history, the diagnosis may be challenging, because the mass may be confused with other common soft tissue masses in the foot. This case report describes a 67-year-old man with an idiopathic pseudoaneurysm of the dorsalis pedis artery that mimicked pigmented villonodular synovitis.

Aged↗
PubMed1998

Rheumatoid arthritis of the ankle and hindfoot.

Rheumatoid arthritis frequently affects the hindfoot and ankle and may present a considerable source of dysfunction. Awareness of characteristic clinical and radiographic findings and other diagnostic modalities help the clinician to evaluate the progression of the disease and determine the best methods of management. A variety of nonoperative treatments may slow progression of deformities, improve function, and provide symptomatic relief. If these measures fail, surgical intervention, including soft-tissue procedures as well as a variety of arthrodesis techniques, can return patients to a more active lifestyle.

Ankle Joint↗
PubMed1998

A mathematical model for skeletal muscle activated by N-let pulse trains.

A physiologically based mathematical model for skeletal muscle activated by neural impulses is presented. This model is developed specifically to capture the behavior for mammalian skeletal muscle activated by N-lets (sets of N high-frequency pulses with variable interpulse intervals). N-let pulse trains have been demonstrated as a possible means of producing contractions with reduced fatigue and fiber-type transformation, while maximizing the force-time integral per pulse (FTIpP) of electrically stimulated muscle. This model is developed by modeling the underlying biophysical processes responsible for the initiation and maintenance of force generation in muscle. The release and reaccumulation dynamics of calcium ions from the sarcoplasmic reticulum are modeled and proposed as the governing mechanism for the observed N-let effects. It is found that the new model is robust, numerically stable and easily implemented. Simulation results are presented that demonstrate the model's ability to capture a variety of the nonlinear summation, force and stiffness variation effects seen experimentally when activating skeletal muscle with N-lets. General properties of FES muscle are also predicted by the model. The significant insight provided by this model into the internal dynamics of skeletal muscle is used to assess a variety of mechanisms proposed for N-let behavior. It is postulated that the calcium release and reaccumulation dynamics, as incorporated in this model, are responsible for the N-let effects found in experiment.

Calcium↗
PubMed1997

A nonlinear mathematical model of electrically stimulated skeletal muscle.

A new biophysically based mathematical model for a human musculotendon system is presented. This model is developed specifically for skeletal muscle activated by functional electrical stimulation (FES). The reverse-order recruitment dynamics of FES activated systems are modeled, as are the underlying processes of force generation in mammalian muscle. The resulting system model is both nonlinear and highly coupled, reflecting the fundamental structure and behavior of skeletal muscle. A new heterogeneous model structure for a contractile element is also presented that overcomes many of the problems which arise when attempting to describe all possible contraction modes. It is found that the new model is robust, numerically stable, and easily implemented. Simulation results are presented that demonstrate the model's ability to capture a variety of nonlinear behaviors observed in skeletal muscle activated by FES. Significant insight into the internal dynamics of force development in FES muscle may also be gained from the model. This model is intended as a possible alternative to those currently available in the literature. It may be of use to those conducting research into the modeling, control and optimization of FES generated motion, and neural feedback systems.

Electric Stimulation↗
PubMed1997

Fuzzy clustering of children with cerebral palsy based on temporal-distance gait parameters.

Temporal-distance parameters for 88 children with the spastic diplegia form of cerebral palsy (CP) are grouped using the fuzzy clustering paradigm. The two features chosen for clustering are stride length and cadence which are normalized for age and leg length using a model based on a population of 68 neurologically intact children. Using information provided by the neurologically intact population and cluster validity techniques, five clusters for the children with cerebral palsy are identified. The five cluster centers represent distinct walking strategies adopted by children with cerebral palsy. Utilizing just four easily obtained parameters--stride length, cadence, leg length and age--and a small number of simple equations, it is possible to classify any child with spastic diplegia and to generate an individual's membership values for each of the five clusters. The clinical utility of the fuzzy clustering approach is demonstrated with pre- and post-operative test data for subjects with cerebral palsy (one neurosurgical and one orthopaedic) where changes in membership of the five clusters provide an objective technique for measuring improvement. This approach can be adopted to study other clinical entities where different cluster centers would be established using the algorithm provided here.

Adolescent↗
PubMed1997

Roger Mann Award 1995. Capsular interposition arthroplasty for severe hallux rigidus.

Thirty patients (37 feet) with severe hallux rigidus underwent resection arthroplasty of the first metatarsophalangeal joint with our modification (reattachment of the extensor hood and extensor brevis to the flexor hallucis brevis as a capsular interposition arthroplasty, with minimal bone resection). Pain and function were significantly improved. Transfer metatarsalgia was not seen. All patients had at least 4/5 plantarflexion strength and averaged 50 degrees of dorsiflexion. In patients with severe hallux rigidus and nearly equal length of first and second metatarsals, capsular interposition arthroplasty offers a surgical option that relieves pain without sacrificing motion or strength.

Arthroplasty↗
PubMed1997

Treatment of established nonunions of Mitchell osteotomies.

The Mitchell distal metatarsal stepcut osteotomy for the treatment of hallux valgus is a technically demanding procedure with a high complication rate. Reported complications include metatarsal shortening with lateral metatarsalgia, partial avascular necrosis of the distal fragment, and loss of position with incomplete correction. Nonunion, however, has only rarely been reported. We describe our experience with the treatment of three nonunions of Mitchell osteotomies reconstructed using a tricortical iliac crest bone graft.

Adult↗
PubMed1996

Normalization of temporal-distance parameters in pediatric gait.

Several techniques for the normalization of temporal-distance parameters in pediatric gait are given. The resulting normalized data can be used to compare (or discriminate) individuals or groups of individuals without the effect of variables such as age and height. The normalization with respect to a reference data set or with respect to the data set itself can be accommodated. Three novel techniques for normalization of gait data have been given: offset, decorrelation and detrending. For normalization of stride length with respect to height, all three are superior to the commonly accepted technique of dividing by the height. The offset technique has obscure units and will have a residual correlation. The decorrelation technique also has obscure units but will have zero correlation provided it is being normalized using a linear model (or piecewise linear model) fitted to the data in a least-squares sense. The detrending technique will also result in a zero correlation if piecewise linear or polynomial models, fitted to the data in a least-squares sense, are used. The detrending technique is the most useful of the three techniques proposed as it will also generate the same units as the original data set and can be easily scaled so that its magnitude is also comparable with the original data. Both the decorrelation and detrending techniques can be used simultaneously to normalize data with respect to two or more variables.

Age Factors↗
PubMed1996

Stress fractures at the base of the second metatarsal in ballet dancers.

Stress fractures are a frequent injury in ballet companies and the most common location is at the base of the second metatarsal. While previous reports have focused on risk factors for this injury (overtraining, delayed menarche, poor nutrition), there is no published series describing the natural history and outcome following this fracture. We reviewed the office records of the senior author and identified 51 professional dancers (64 fractures) who sustained a stress fracture at the base of the second metatarsal. History of a previous stress fracture in the lower extremity was seen in 19 patients and delayed menarche in the women was common. The clinical presentation was insidious onset of midfoot pain an average of 2.5 weeks prior to seeking medical care. The initial radiographs of the foot were positive in 19 patients, questionable in 3 patients, and negative in 42 patients. The usual location of the fracture was at the proximal metaphyseal-diaphyseal junction (three fractures extended into the tarsometatarsal joint). Treatment consisted of a short leg walking cast for 6 patients, and a wooden shoe and symptomatic treatment for the remainder. At follow-up, 14% of patients still had occasional pain or stiffness in the midfoot with dancing. The patients returned to performance at an average of 6.2 weeks following diagnosis. No patients required bone grafting for persistent symptoms. There were eight refractures (at the same site) occurring an average of 4.3 years, all of which healed with conservative care. Stress fractures at the base of the second metatarsal are common in ballet dancers and can usually be treated with symptomatically. The results of this study are discussed in terms of risk factors, the use of a posterior-anterior view of the foot to eliminate overlap at Lisfranc's joint, and our present treatment regimen.

Adolescent↗
PubMed1995

Selective hindfoot arthrodesis for the treatment of adult acquired flatfoot deformity: an in vitro study.

An acquired flatfoot deformity with significant laxity at the transverse tarsal joint was created experimentally and the amount of correction that was obtained with selective hindfoot fusions was measured radiographically. Results showed that the talonavicular, double (talonavicular and calcaneocuboid), and triple arthrodeses were able to fully correct the deformity, including correction of hindfoot valgus with just a talonavicular fusion. Subtalar and calcaneocuboid fusions failed to completely correct the deformity. This study provides experimental evidence that although the triple joints are interconnected, they differ with respect to their ability to malalignment. We conclude that talonavicular or double arthrodesis will correct deformity in a flatfoot with considerable laxity through the transverse tarsal joint, but that a subtalar fusion will not provide consistent correction.

Adult↗
PubMed1993

Triple arthrodesis in rheumatoid arthritis.

Fifty-five patients with rheumatoid arthritis were treated with 65 triple arthrodeses of the hindfoot from March 1975 through July 1985. Twelve patients (12 procedures) have died, and follow-up evaluation could not be completed on three patients (four procedures), leaving 40 patients (49 procedures) available for clinical and roentgenographic evaluation. There were 32 women and eight men, with an average age at the time of surgery of 50 years. The follow-up period averaged five years. Standard operative technique involved medial and lateral incisions with staple fixation and local bone grafting. Correction of deformity was performed with closing wedge osteotomies. All patients had moderate to severe pain preoperatively and difficulty with ambulation. Postoperatively, 94% of the patients had significant pain relief and 83% had complete pain relief. Ambulatory status was improved in 80% of the patients. Ninety percent were at least community ambulators at the time of review, whereas more than half the patients were limited to household ambulation preoperatively. Complications included four superficial wound infections, all of which responded to local care. One patient required revision surgery for pseudarthrosis, and three patients had progression of ankle disease and required pantalar arthrodeses. There was no significant progression of fore-foot or knee symptoms, however, and there was no progression of ankle symptoms in patients whose hindfeet were corrected to 0 degrees-10 degrees valgus. Triple arthrodesis in the rheumatoid population has a high union rate. Pain relief and ambulation improvement can be expected.

Adolescent↗
PubMed1992

Factors that determine reexploration treatment of carpal tunnel syndrome.

Eighteen patients (20 hands) underwent reexploration of the carpal tunnel after a primary carpal tunnel release. The patients complained of unrelieved symptoms after their initial surgical procedures. We recommend reexploration for patients with unrelieved carpal tunnel syndrome if they have a positive Phalen's test, have symptoms that cause nocturnal wakening or are exacerbated by activities, or have a short or transverse initial incision. If the incision is adequate and these symptoms are not present, we believe that reexploration will not result in a satisfactory outcome.

Adult↗