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Papers by joseph cowan

Plastic and Reconstructive Surgery, 2003

We present the use of dynamic electromyographic analysis (DEMG) in the diagnosis of muscle patter... more We present the use of dynamic electromyographic analysis (DEMG) in the diagnosis of muscle patterning instability. DEMG’s were requested in 168 of 562 muscle patterning shoulders with suspected subclinical or clinically complex muscle patterning instability. An experienced neurophysiologist (blinded to the clinical findings and direction of instability) inserted dual-wire tungsten electrodes into pectoralis major, latissimus dorsi, infraspinatus and anterior deltoid. Muscle activity was recorded during rest, flexion, abduction, extension, and cross-body adduction. 5 investigations were abandoned. The timing and magnitude of muscle activity was noted and compared to the clinical diagnosis and direction of instability. DEMG identified a total of 204 abnormal muscle patterns in 163 shoulders. The examination was normal in 13 patients (8%). A single muscle was abnormal in 63 shoulders, 2 muscles in 55, 3 muscles in 9, and all 4 muscles in one shoulder. Over-activation of pectoralis major was identified in 58%, and latissimus dorsi in 70%, of shoulders with anterior instability. In posterior instability, latissimus dorsi was overactive in 76%, anterior deltoid in 14% and infraspinatus was under-active in 24%. Pectoralis major and Latissimus dorsi were both overactive in 38% of anterior, 29% of posterior and 38% of multidirectional instability. Abnormal muscle patterns were identified in 52 shoulders with subclinical muscle patterning. A further 98 shoulders had 134 clinically abnormal muscle patterns. These were confirmed by DEMG in 57 cases (sensitivity 43%), and DEMG’s were normal in 77 (specificity 43%). DEMG also identified 65 additional muscles as abnormal in the 98 clinically abnormal shoulders. DEMG performed by an experienced neurophysiologist provides additional information regarding abnormal muscle activation in selected complex or subtle cases of muscle patterning instability in which clinical examination has a low sensitivity and specificity.

Postgraduate medical journal, Jan 14, 2018

As a tertiary referral centre of spinal surgery, the Royal National Orthopaedic Hospital (RNOH) h... more As a tertiary referral centre of spinal surgery, the Royal National Orthopaedic Hospital (RNOH) handles hundreds of spinal cases a year, often with complex pathology and complex care needs. Despite this, issues were raised at the RNOH following lack of sufficient documentation of preoperative and postoperative clinical findings in spinal patients undergoing major surgery. This is not in keeping with guidelines provided by the Royal College of Surgeons. The authors believe that a standardised clerking pro forma for surgical spinal patients admitted to RNOH would improve the quality of care provided. Therefore, the use of a standard clerking pro forma for all surgical spinal patients could be a useful tool enabling improvements in patients care and safety in keeping with General Medical Council/National Institute for Health and Care Excellence guidelines. An audit (with closure of loop) looking into the quality of the preoperative and postoperative clinical documentation for surgical ...

SPINE, 2015

Retrospective OBJECTIVE.: Rate of neurological injuries is widely reported for spinal deformity s... more Retrospective OBJECTIVE.: Rate of neurological injuries is widely reported for spinal deformity surgery. However, few have included the influence of the subtypes and severity of the deformity, or anterior versus posterior corrections. The purpose of this study is to quantify these risks. The risk of neurological injuries was examined in a single institution. Quantification of risk was made between operations, and for different subtypes of spinal deformity. Prospectively entered neuromonitoring database between 2006 and 2012 was interrogated. Including all deformity cases under 21 years old. Tumour, fracture, infection and revision cases were excluded. All major changes in monitoring ("red alerts") were identified and detailed examinations of the neuromonitoring records, clinical notes and radiographs were made. Diagnosis, deformity severity and operative details were recorded. Of 2291 deformity operations: 2068 scoliosis (1636 idiopathic, 204 neuromuscular, 216 syndromic, 12 others), 89 kyphosis, 54 growing rod procedures, and 80 operations for hemivertebra. 696 anterior and 1363 posterior operations were performed for scoliosis (9 not recorded), and 38 anterior and 51 posterior kyphosis correction. 67 "red alerts" were identified (62 posterior, 5 anterior). Average Cobb angle was 88°. There were 14 transient and 6 permanent neurological injuries. 1 permanent injury was sustained during kyphosis correction, and 5 during scoliosis correction. Common surgeon reactions after "red alerts" were surgical pause with anaesthetic interventions (n = 39) and the Stagnara wake-up test (n = 22). Metalwork was partially removed in 20, revised in 12 and completely removed in 9. 13 procedures were abandoned. The overall risk of permanent neurological injury was 0.2%. The highest risk groups were posterior corrections for kyphosis, and scoliosis associated with a syndrome. 4% of all posterior deformity corrections had "red alerts", and 0.3% resulted in permanent injuries; compared to 0.6% "red alerts" and 0.3% permanent injuries for anterior surgery. The overall risk for idiopathic scoliosis was 0.06%. 3.

European Spine Journal, 2015

There are very few reported cases of compartment syndrome of the leg following spinal surgery via... more There are very few reported cases of compartment syndrome of the leg following spinal surgery via a posterior approach. An association between compartment syndrome and muscle over-activity via nerve stimulation during evoked potential monitoring was first suggested in 2003. No further reports have suggested this link. We present a multicentre retrospective review of a series of five patients who developed compartment syndrome of the leg following spinal surgery via a posterior approach, whilst un-paralysed and with combined sensory (SSEP)/motor evoked potential (MEP) monitoring with an aim of highlighting this possible causative factor. All data were collected contemporaneously and retrospective analysis was performed. We then arranged for a multidisciplinary review of the cases including surgeons, anaesthetists, radiologists, neurophysiologists and theatre and ward nursing staff. Finally, the literature was reviewed. All patients were operated on by three different surgeons, on different operating tables/mattresses in the prone position. The common factors were un-paralysed patients having motor/sensory monitoring, mechanical calf pumps and total intravenous anaesthesia. Three patients underwent surgical decompression of their compartments and two were treated expectantly. Three patients had confirmed intra-compartmental changes on MRI consistent with compartment syndrome and one had intra-compartmental pressure monitoring which confirmed the diagnosis. Previous cases in the literature have related to mal-positioning on the Jackson table or use of the knee-chest position for surgery. This was not the case for our patients; therefore, we suspect an association between overactive muscle stimulation and muscle necrosis. Further experimental studies investigating this link are required.

The Journal of physiology, 1986

The technique of electrical stimulation of the brain via scalp electrodes has been used to activa... more The technique of electrical stimulation of the brain via scalp electrodes has been used to activate corticospinal pathways in intact man. The intensity of stimulation was adjusted to be below the threshold necessary to evoke a direct electromyographic response when the muscles being tested were totally relaxed. Changes in spinal cord excitability were measured using H-reflex (monosynaptic) testing. By this means it was found that subthreshold scalp stimulation can produce a descending corticospinal volley even in the absence of a direct muscle response. The time course of changes in spinal cord excitability was evaluated by evoking test H reflexes at different intervals relative to the scalp stimulus. In wrist and finger flexor muscles of seven subjects, a single subthreshold scalp shock produced an initial peak facilitation of the H reflex which on average lasted for 2.5 ms. The end of the initial facilitation was marked by a return of the H reflex towards basal levels and on one o...

Shoulder & Elbow, 2014

Nerve injury is an acknowledged complication of total shoulder arthroplasty (TSA). Although the i... more Nerve injury is an acknowledged complication of total shoulder arthroplasty (TSA). Although the incidence of postoperative neurological deficit has been reported to be between 1% and 16%, the true incidence of nerve damage is considered to be higher. The present study aimed to identify the rate of intraoperative nerve injury during total shoulder arthroplasty and to determine potential risk factors. A prospective study of nerve conduction in 21 patients who underwent primary or revision TSA was carried out over a 12-month period. Nerve conduction was monitored by measuring intraoperative sensory evoked potentials (SEP). A significant neurophysiological signal change was defined as either a unilateral or bilateral decrease in SEP signal of ≥50%, a latency increase of ≥10% or a change in waveform morphology, not caused by operative or anaesthetic technique. Seven (33%) patients had a SEP signal change. The only significant risk factor identified for signal change was male sex (odds ratio 15.00, 95% confidence interval). The median nerve was the most affected nerve in the operated arm. All but one signal change returned to normal before completion of the operation and no patient had a persisting postoperative clinical neurological deficit. The incidence of intraoperative nerve damage may be more common than previously reported. However, the loss of SEP signal is reversible and does not correlate with persisting clinical neurological deficits. The median nerve appears to be most at risk. Monitoring SEPs in the operated limb during TSA may be a valuable tool during TSA.

Physiotherapy Research International, 2006

Background and Purpose. The subscapularis (SSc) muscle is considered to perform a variety of role... more Background and Purpose. The subscapularis (SSc) muscle is considered to perform a variety of roles during normal shoulder movement. The SSc is innervated by two or more discrete motor nerves and previous studies have indicated some difference in electromyographic (EMG) activity between the upper and lower portions of the muscle. The purpose of the present study was to compare EMG activity between the upper and lower portions of the SSc muscle during voluntary shoulder movements in normal healthy subjects. Method. Eight subjects were evaluated. A pair of intramuscular electrodes was inserted into each portion of the muscle. EMG data were recorded during the following movements: sagittal flexion; abduction in the coronal plane; and abduction in the scapular plane. Results. EMG onset of the upper portion of subscapularis occurred significantly earlier compared to the lower portion. Differences were also seen in the level and pattern of activation between the two portions, with upper SSc demonstrating higher levels of activation than the lower portion. Conclusions. These findings suggest that the upper and lower portions of SSc are differentially active during voluntary shoulder movements.

Physiotherapy Research International, 2009

Background. This pilot study assesses level of agreement between surface and fi ne-wire electromy... more Background. This pilot study assesses level of agreement between surface and fi ne-wire electromyography (EMG), in order to establish if surface is as reliable as fi ne wire in the diagnosis and treatment of abnormal muscle patterning in the shoulder. Method. Eighteen participants (11 female) with unstable shoulders were recruited after written consent and ethical approval. Anthropometric information and mean skinfold size for triceps, subscapular, biceps and suprailiac sites were obtained. Triple-stud self-adhesive surface electrodes ('Triode'; Thermo Scientifi c, Physio Med Services, Glossop, Derbyshire, England) were placed over pectoralis major (PM), latissimus dorsi (LD), anterior deltoid (AD) and infraspinatus (IS) at standardized locations. Participants performed fi ve identical uniplanar standard movements (fl exion, abduction, external rotation, extension and cross-body adduction). After a 20-minute rest period, a dual-needle technique for fi ne-wire insertion was performed and the standard movements were repeated. An experienced examiner in each technique reported if muscle activation patterns differed from agreed normal during any movement and were blinded to the other test results. Sensitivity, specifi city and Kappa values for level of agreement between methods were calculated for each muscle according to the method of Altman (1991). Results. Fifteen participants were successfully tested. Sensitivity, specifi city and Kappa values between techniques for each muscle were PM (57%, 50%, 0.07), LD (38%, 85%, 0.22), AD (0%, 76%, −0.19) and IS (85%, 75%, 0.6). Only IS demonstrated high sensitivity and specifi city and a moderate level of agreement between the two techniques. There was no correlation between skinfold size and agreement levels. Conclusion. The use of surface EMG may help to classify types of shoulder instability and recognize abnormal muscle patterns. It may allow physiotherapists to direct specifi c rehabilitation strategies, avoiding strengthening of inappropriate muscles. It has a reasonable degree of confi dence to evaluate IS but may have poor sensitivity in detecting abnormal patterns in PM, LD and AD. Further work is required to see if investigator interpretation may have been a factor for the poor level of agreement.

The Lancet, 1984

The technique of scalp stimulation of the motor cortex was used to demonstrate abnormalities in t... more The technique of scalp stimulation of the motor cortex was used to demonstrate abnormalities in the corticomotoneuron pathway in multiple sclerosis. Unilateral or bilateral delays in corticomotoneuron conduction, dispersion of corticomotoneuron volleys, or both, were shown to occur in such patients. Changes may be seen even in patients with little clinical evidence of corticomotoneuron deficit.

Journal of Neurology, Neurosurgery & Psychiatry, 1985

Nine patients with tremor on writing and one patient with tremor only on swinging a golf club wer... more Nine patients with tremor on writing and one patient with tremor only on swinging a golf club were investigated. None of the patients had any other neurological symptoms or signs. The frequency of the tremor ranged from 5 to 6 Hz. Rapid passive supination or pronation of the forearm by a torque motor evoked a short burst of alternating tremor in seven patients. The tremor was improved by alcohol or propranolol in six patients. These characteristics of writing tremor (and of other isolated action tremors) suggest that it is a variant of benign essential tremor.

Journal of Neurology, Neurosurgery & Psychiatry, 1990

Eight patients are described who presented with hemiparesis which involved the face in seven. Six... more Eight patients are described who presented with hemiparesis which involved the face in seven. Six of the eight subsequently developed clinically definite multiple sclerosis and in the remaining two patients multiple sclerosis was the likely diagnosis. Magnetic resonance imaging gave useful information about the site of the lesions responsible for the presenting syndrome and provided ailditional information in support of a diagnosis of multiple sclerosis. Hemiparesis which involves the face is uncommon as the presenting feature of multiple sclerosis (MS), and may lead to diagnostic confusion, particularly when the syndrome is progressive or stuttering in onset. In recent years various investigations have enabled the diagnosis of MS to be pursued in patients who, because of their unusual clinical picture, previously might not have been suspected of suffering from the disease. Of these investigative techniques magnetic resonance imaging (MRI) of the brain and spinal cord is the most sensitive. In this article patients with hemiparetic MS are described in whom MRI scanning gives useful information about the probable sites of the lesions responsible for the hemiparetic episodes. Other patients with an acute hemiparetic syndrome are described in whom MS is the most likely diagnosis.

Journal of Neurology, Neurosurgery & Psychiatry, 1986

Spinal cord potentials produced by high voltage electrical stimulation of the scalp over the moto... more Spinal cord potentials produced by high voltage electrical stimulation of the scalp over the motor cortex were recorded intraoperatively from bipolar electrodes inserted into the epidural space of eleven patients undergoing corrective surgery for scoliosis. Responses to single stimuli could be recorded from the cord at all levels from cervical to low thoracic regions. The potentials were larger in the cervical than in the thoracic region and sometimes were followed by later waves at high stimulation intensities. Conduction velocity in large corticomotoneuron fibres was estimated to be between 50-74ms-1in different patients. This technique for monitoring motor tract function may be a useful adjunct to conventional monitoring of the sensory pathways during surgery.

Journal of Neurology, Neurosurgery & Psychiatry, 1986

A patient is described who had a combination of stimulus-sensitive cortical myoclonus, epilepsia ... more A patient is described who had a combination of stimulus-sensitive cortical myoclonus, epilepsia partialis continua, and Jacksonian motor epilepsy. He eventually required surgery because of the severity of his seizures. Electrophysiological recordings made before and during surgery, and PET scans performed before surgery identified an abnormal area of cerebral cortex in the postcentral parietal region. It is suggested that the stimulus-sensitive myoclonus arose because input into this region from peripheral sensory afferents produced an abnormal discharge which was fed forwards via cortico-cortical connections to the precentral motor cortex, to produce a reflex muscle jerk. The epilepsia partialis continua may have been caused by spontaneous discharges arising in the same region of parietal cortex. Both forms of jerking disappeared after resection of this part of the

Journal of Neurology, Neurosurgery & Psychiatry, 1989

SP, et al. earlier, over a week he developed severe Single photon emission computed tomograprogre... more SP, et al. earlier, over a week he developed severe Single photon emission computed tomograprogressive ataxia, complete external and phy in Alzheimer's disease. Arch Neurol internal ophthalmoplegia, the eyes remain-1988;45:392-6. ing in neutral position ptotic but without 13 Foster NL, Chase TN, Fedio P, et al Alz-dingin ane posiion ptotic butwitout heimer's disease: focal cortical changes diplopia, and general arreflexia. Consclousshown by positron emission tomography. ness was normal. CSF showed 0 cells, Neurology 1983;33:961-5. glucose 0-68 g/l and protein 0-63 g/l. In the 14 Taboeda E, Dickson D, Horoupian D, Davies next few days, transitory breathing and P. Clinicopathologic and neurochemical swallowing difficulties developed, as well as studies of one case of dysphasic dementia. J mild weakness of the facial musculature. In Neuropathol Exp Neurol 1986;45:323. this situation of complete ocular paralysis, 15 Morris JC, Cole M, Banker BQ, Wright D. the patient made constant gesticulation due Hereditary dysphasic dementia and the Pick-.. o Alzheimer spectrum. Ann Neurol to frequent, occasionallytsustained, bilateral 1984;16:455-66. blepharospasm attacks. This picture regres-16 Tissot R, Constantinidis J, Richard J. Picks sed to the previous situation after the ophdisease. In: Vinken PJ, Bruyn GW, Klawans thalmoplegia resolved some months later. HL, Fredriks JAM, eds. Handbook of Clin-The severe aggravation of facial spasms in ical Neurology Neurobehavioural disorders. our case was striking, well in excess of what Amsterdam, 1985;46:233-46. could have been expected from the emotional 17 Hudson AJ. Amyotrophic lateral sclerosis and stress of hospitalisation or appearance of

International Journal of Shoulder Surgery, 2012

} Muscle activation patterns in patients with recurrent shoulder instability } Symptomatic chroni... more } Muscle activation patterns in patients with recurrent shoulder instability } Symptomatic chronic long head of biceps rupture: Surgical results } Does age or gender of the patient influence the outcome of type II superior labrum anterior and posterior repair? } Surgical treatment of lateral clavicle fractures associated with complete coracoclavicular ligament disruption: Clinico-radiological outcomes of acromioclavicular joint sparing and spanning implants } Septic failure is not a septic loosening: A case report of a failed shoulder prosthesis } Locking plates for displaced fractures of the lateral end of clavicle: Potential pitfalls } Improved clinical utility in clavicle fracture decision-making with true orthogonal radiographs C o n t e n t s

Brain, 1987

ABSTRACT Using an isometric strain gauge, we measured the twitch force produced in the first dors... more ABSTRACT Using an isometric strain gauge, we measured the twitch force produced in the first dorsal interosseous (FDI) muscle by a single anodal shock to the contralateral scalp. At high intensities of stimulation this twitch can greatly exceed the force produced by supramaximal stimulation of peripheral nerve. This indicates that a single cortical shock can cause repetitive firing of some or all FDI motoneurons. Such repetitive firing was demonstrated using a collision technique in which a supramaximal ulnar nerve stimulus was given at the wrist shortly after a cortical shock. The antidromic volley from the peripheral nerve stimulation failed to obliterate completely the response to cortical stimulation. Additional EMG activity was visible in the normally silent period between ulnar M and F waves. This activity must have been due to the presence of repetitive volleys of activity set up in spinal motoneurons by the cortical shock. Such activity summates with the twitch produced by the ulnar M wave to produce a very large force twitch of the muscle. Multiple firing of some motoneurons can be observed in some individuals at cortical stimulation intensities below that necessary to evoke activity in all the motoneurons in the FDI pool. Multiple firing probably was caused by repetitive excitatory inputs impinging on spinal motoneurons. These could be demonstrated using poststimulus time histogram techniques on single motor units. Low intensities of cortical stimulation produced a single short duration (mean 1.8 ms) peak of increased motor unit firing 20 to 30 ms after the shock. At high intensities, this was followed by extra peaks some 4 to 5 ms later. H reflex testing showed that the threshold of the initial descending volley, produced by the cortical stimulus was uninfluenced by a voluntary contraction. These results are discussed with reference to the D and I waves recorded from pyramidal tract after anodal stimulation of the exposed cortex in animals.

Physiotherapy …, 2009

Background. This pilot study assesses level of agreement between surface and fine-wire electromyo... more Background. This pilot study assesses level of agreement between surface and fine-wire electromyography (EMG), in order to establish if surface is as reliable as fine wire in the diagnosis and treatment of abnormal muscle patterning in the shoulder. Method. ...

Plastic and Reconstructive Surgery, 2003

We present the use of dynamic electromyographic analysis (DEMG) in the diagnosis of muscle patter... more We present the use of dynamic electromyographic analysis (DEMG) in the diagnosis of muscle patterning instability. DEMG’s were requested in 168 of 562 muscle patterning shoulders with suspected subclinical or clinically complex muscle patterning instability. An experienced neurophysiologist (blinded to the clinical findings and direction of instability) inserted dual-wire tungsten electrodes into pectoralis major, latissimus dorsi, infraspinatus and anterior deltoid. Muscle activity was recorded during rest, flexion, abduction, extension, and cross-body adduction. 5 investigations were abandoned. The timing and magnitude of muscle activity was noted and compared to the clinical diagnosis and direction of instability. DEMG identified a total of 204 abnormal muscle patterns in 163 shoulders. The examination was normal in 13 patients (8%). A single muscle was abnormal in 63 shoulders, 2 muscles in 55, 3 muscles in 9, and all 4 muscles in one shoulder. Over-activation of pectoralis major was identified in 58%, and latissimus dorsi in 70%, of shoulders with anterior instability. In posterior instability, latissimus dorsi was overactive in 76%, anterior deltoid in 14% and infraspinatus was under-active in 24%. Pectoralis major and Latissimus dorsi were both overactive in 38% of anterior, 29% of posterior and 38% of multidirectional instability. Abnormal muscle patterns were identified in 52 shoulders with subclinical muscle patterning. A further 98 shoulders had 134 clinically abnormal muscle patterns. These were confirmed by DEMG in 57 cases (sensitivity 43%), and DEMG’s were normal in 77 (specificity 43%). DEMG also identified 65 additional muscles as abnormal in the 98 clinically abnormal shoulders. DEMG performed by an experienced neurophysiologist provides additional information regarding abnormal muscle activation in selected complex or subtle cases of muscle patterning instability in which clinical examination has a low sensitivity and specificity.

Postgraduate medical journal, Jan 14, 2018

As a tertiary referral centre of spinal surgery, the Royal National Orthopaedic Hospital (RNOH) h... more As a tertiary referral centre of spinal surgery, the Royal National Orthopaedic Hospital (RNOH) handles hundreds of spinal cases a year, often with complex pathology and complex care needs. Despite this, issues were raised at the RNOH following lack of sufficient documentation of preoperative and postoperative clinical findings in spinal patients undergoing major surgery. This is not in keeping with guidelines provided by the Royal College of Surgeons. The authors believe that a standardised clerking pro forma for surgical spinal patients admitted to RNOH would improve the quality of care provided. Therefore, the use of a standard clerking pro forma for all surgical spinal patients could be a useful tool enabling improvements in patients care and safety in keeping with General Medical Council/National Institute for Health and Care Excellence guidelines. An audit (with closure of loop) looking into the quality of the preoperative and postoperative clinical documentation for surgical ...

SPINE, 2015

Retrospective OBJECTIVE.: Rate of neurological injuries is widely reported for spinal deformity s... more Retrospective OBJECTIVE.: Rate of neurological injuries is widely reported for spinal deformity surgery. However, few have included the influence of the subtypes and severity of the deformity, or anterior versus posterior corrections. The purpose of this study is to quantify these risks. The risk of neurological injuries was examined in a single institution. Quantification of risk was made between operations, and for different subtypes of spinal deformity. Prospectively entered neuromonitoring database between 2006 and 2012 was interrogated. Including all deformity cases under 21 years old. Tumour, fracture, infection and revision cases were excluded. All major changes in monitoring ("red alerts") were identified and detailed examinations of the neuromonitoring records, clinical notes and radiographs were made. Diagnosis, deformity severity and operative details were recorded. Of 2291 deformity operations: 2068 scoliosis (1636 idiopathic, 204 neuromuscular, 216 syndromic, 12 others), 89 kyphosis, 54 growing rod procedures, and 80 operations for hemivertebra. 696 anterior and 1363 posterior operations were performed for scoliosis (9 not recorded), and 38 anterior and 51 posterior kyphosis correction. 67 "red alerts" were identified (62 posterior, 5 anterior). Average Cobb angle was 88°. There were 14 transient and 6 permanent neurological injuries. 1 permanent injury was sustained during kyphosis correction, and 5 during scoliosis correction. Common surgeon reactions after "red alerts" were surgical pause with anaesthetic interventions (n = 39) and the Stagnara wake-up test (n = 22). Metalwork was partially removed in 20, revised in 12 and completely removed in 9. 13 procedures were abandoned. The overall risk of permanent neurological injury was 0.2%. The highest risk groups were posterior corrections for kyphosis, and scoliosis associated with a syndrome. 4% of all posterior deformity corrections had "red alerts", and 0.3% resulted in permanent injuries; compared to 0.6% "red alerts" and 0.3% permanent injuries for anterior surgery. The overall risk for idiopathic scoliosis was 0.06%. 3.

European Spine Journal, 2015

There are very few reported cases of compartment syndrome of the leg following spinal surgery via... more There are very few reported cases of compartment syndrome of the leg following spinal surgery via a posterior approach. An association between compartment syndrome and muscle over-activity via nerve stimulation during evoked potential monitoring was first suggested in 2003. No further reports have suggested this link. We present a multicentre retrospective review of a series of five patients who developed compartment syndrome of the leg following spinal surgery via a posterior approach, whilst un-paralysed and with combined sensory (SSEP)/motor evoked potential (MEP) monitoring with an aim of highlighting this possible causative factor. All data were collected contemporaneously and retrospective analysis was performed. We then arranged for a multidisciplinary review of the cases including surgeons, anaesthetists, radiologists, neurophysiologists and theatre and ward nursing staff. Finally, the literature was reviewed. All patients were operated on by three different surgeons, on different operating tables/mattresses in the prone position. The common factors were un-paralysed patients having motor/sensory monitoring, mechanical calf pumps and total intravenous anaesthesia. Three patients underwent surgical decompression of their compartments and two were treated expectantly. Three patients had confirmed intra-compartmental changes on MRI consistent with compartment syndrome and one had intra-compartmental pressure monitoring which confirmed the diagnosis. Previous cases in the literature have related to mal-positioning on the Jackson table or use of the knee-chest position for surgery. This was not the case for our patients; therefore, we suspect an association between overactive muscle stimulation and muscle necrosis. Further experimental studies investigating this link are required.

The Journal of physiology, 1986

The technique of electrical stimulation of the brain via scalp electrodes has been used to activa... more The technique of electrical stimulation of the brain via scalp electrodes has been used to activate corticospinal pathways in intact man. The intensity of stimulation was adjusted to be below the threshold necessary to evoke a direct electromyographic response when the muscles being tested were totally relaxed. Changes in spinal cord excitability were measured using H-reflex (monosynaptic) testing. By this means it was found that subthreshold scalp stimulation can produce a descending corticospinal volley even in the absence of a direct muscle response. The time course of changes in spinal cord excitability was evaluated by evoking test H reflexes at different intervals relative to the scalp stimulus. In wrist and finger flexor muscles of seven subjects, a single subthreshold scalp shock produced an initial peak facilitation of the H reflex which on average lasted for 2.5 ms. The end of the initial facilitation was marked by a return of the H reflex towards basal levels and on one o...

Shoulder & Elbow, 2014

Nerve injury is an acknowledged complication of total shoulder arthroplasty (TSA). Although the i... more Nerve injury is an acknowledged complication of total shoulder arthroplasty (TSA). Although the incidence of postoperative neurological deficit has been reported to be between 1% and 16%, the true incidence of nerve damage is considered to be higher. The present study aimed to identify the rate of intraoperative nerve injury during total shoulder arthroplasty and to determine potential risk factors. A prospective study of nerve conduction in 21 patients who underwent primary or revision TSA was carried out over a 12-month period. Nerve conduction was monitored by measuring intraoperative sensory evoked potentials (SEP). A significant neurophysiological signal change was defined as either a unilateral or bilateral decrease in SEP signal of ≥50%, a latency increase of ≥10% or a change in waveform morphology, not caused by operative or anaesthetic technique. Seven (33%) patients had a SEP signal change. The only significant risk factor identified for signal change was male sex (odds ratio 15.00, 95% confidence interval). The median nerve was the most affected nerve in the operated arm. All but one signal change returned to normal before completion of the operation and no patient had a persisting postoperative clinical neurological deficit. The incidence of intraoperative nerve damage may be more common than previously reported. However, the loss of SEP signal is reversible and does not correlate with persisting clinical neurological deficits. The median nerve appears to be most at risk. Monitoring SEPs in the operated limb during TSA may be a valuable tool during TSA.

Physiotherapy Research International, 2006

Background and Purpose. The subscapularis (SSc) muscle is considered to perform a variety of role... more Background and Purpose. The subscapularis (SSc) muscle is considered to perform a variety of roles during normal shoulder movement. The SSc is innervated by two or more discrete motor nerves and previous studies have indicated some difference in electromyographic (EMG) activity between the upper and lower portions of the muscle. The purpose of the present study was to compare EMG activity between the upper and lower portions of the SSc muscle during voluntary shoulder movements in normal healthy subjects. Method. Eight subjects were evaluated. A pair of intramuscular electrodes was inserted into each portion of the muscle. EMG data were recorded during the following movements: sagittal flexion; abduction in the coronal plane; and abduction in the scapular plane. Results. EMG onset of the upper portion of subscapularis occurred significantly earlier compared to the lower portion. Differences were also seen in the level and pattern of activation between the two portions, with upper SSc demonstrating higher levels of activation than the lower portion. Conclusions. These findings suggest that the upper and lower portions of SSc are differentially active during voluntary shoulder movements.

Physiotherapy Research International, 2009

Background. This pilot study assesses level of agreement between surface and fi ne-wire electromy... more Background. This pilot study assesses level of agreement between surface and fi ne-wire electromyography (EMG), in order to establish if surface is as reliable as fi ne wire in the diagnosis and treatment of abnormal muscle patterning in the shoulder. Method. Eighteen participants (11 female) with unstable shoulders were recruited after written consent and ethical approval. Anthropometric information and mean skinfold size for triceps, subscapular, biceps and suprailiac sites were obtained. Triple-stud self-adhesive surface electrodes ('Triode'; Thermo Scientifi c, Physio Med Services, Glossop, Derbyshire, England) were placed over pectoralis major (PM), latissimus dorsi (LD), anterior deltoid (AD) and infraspinatus (IS) at standardized locations. Participants performed fi ve identical uniplanar standard movements (fl exion, abduction, external rotation, extension and cross-body adduction). After a 20-minute rest period, a dual-needle technique for fi ne-wire insertion was performed and the standard movements were repeated. An experienced examiner in each technique reported if muscle activation patterns differed from agreed normal during any movement and were blinded to the other test results. Sensitivity, specifi city and Kappa values for level of agreement between methods were calculated for each muscle according to the method of Altman (1991). Results. Fifteen participants were successfully tested. Sensitivity, specifi city and Kappa values between techniques for each muscle were PM (57%, 50%, 0.07), LD (38%, 85%, 0.22), AD (0%, 76%, −0.19) and IS (85%, 75%, 0.6). Only IS demonstrated high sensitivity and specifi city and a moderate level of agreement between the two techniques. There was no correlation between skinfold size and agreement levels. Conclusion. The use of surface EMG may help to classify types of shoulder instability and recognize abnormal muscle patterns. It may allow physiotherapists to direct specifi c rehabilitation strategies, avoiding strengthening of inappropriate muscles. It has a reasonable degree of confi dence to evaluate IS but may have poor sensitivity in detecting abnormal patterns in PM, LD and AD. Further work is required to see if investigator interpretation may have been a factor for the poor level of agreement.

The Lancet, 1984

The technique of scalp stimulation of the motor cortex was used to demonstrate abnormalities in t... more The technique of scalp stimulation of the motor cortex was used to demonstrate abnormalities in the corticomotoneuron pathway in multiple sclerosis. Unilateral or bilateral delays in corticomotoneuron conduction, dispersion of corticomotoneuron volleys, or both, were shown to occur in such patients. Changes may be seen even in patients with little clinical evidence of corticomotoneuron deficit.

Journal of Neurology, Neurosurgery & Psychiatry, 1985

Nine patients with tremor on writing and one patient with tremor only on swinging a golf club wer... more Nine patients with tremor on writing and one patient with tremor only on swinging a golf club were investigated. None of the patients had any other neurological symptoms or signs. The frequency of the tremor ranged from 5 to 6 Hz. Rapid passive supination or pronation of the forearm by a torque motor evoked a short burst of alternating tremor in seven patients. The tremor was improved by alcohol or propranolol in six patients. These characteristics of writing tremor (and of other isolated action tremors) suggest that it is a variant of benign essential tremor.

Journal of Neurology, Neurosurgery & Psychiatry, 1990

Eight patients are described who presented with hemiparesis which involved the face in seven. Six... more Eight patients are described who presented with hemiparesis which involved the face in seven. Six of the eight subsequently developed clinically definite multiple sclerosis and in the remaining two patients multiple sclerosis was the likely diagnosis. Magnetic resonance imaging gave useful information about the site of the lesions responsible for the presenting syndrome and provided ailditional information in support of a diagnosis of multiple sclerosis. Hemiparesis which involves the face is uncommon as the presenting feature of multiple sclerosis (MS), and may lead to diagnostic confusion, particularly when the syndrome is progressive or stuttering in onset. In recent years various investigations have enabled the diagnosis of MS to be pursued in patients who, because of their unusual clinical picture, previously might not have been suspected of suffering from the disease. Of these investigative techniques magnetic resonance imaging (MRI) of the brain and spinal cord is the most sensitive. In this article patients with hemiparetic MS are described in whom MRI scanning gives useful information about the probable sites of the lesions responsible for the hemiparetic episodes. Other patients with an acute hemiparetic syndrome are described in whom MS is the most likely diagnosis.

Journal of Neurology, Neurosurgery & Psychiatry, 1986

Spinal cord potentials produced by high voltage electrical stimulation of the scalp over the moto... more Spinal cord potentials produced by high voltage electrical stimulation of the scalp over the motor cortex were recorded intraoperatively from bipolar electrodes inserted into the epidural space of eleven patients undergoing corrective surgery for scoliosis. Responses to single stimuli could be recorded from the cord at all levels from cervical to low thoracic regions. The potentials were larger in the cervical than in the thoracic region and sometimes were followed by later waves at high stimulation intensities. Conduction velocity in large corticomotoneuron fibres was estimated to be between 50-74ms-1in different patients. This technique for monitoring motor tract function may be a useful adjunct to conventional monitoring of the sensory pathways during surgery.

Journal of Neurology, Neurosurgery & Psychiatry, 1986

A patient is described who had a combination of stimulus-sensitive cortical myoclonus, epilepsia ... more A patient is described who had a combination of stimulus-sensitive cortical myoclonus, epilepsia partialis continua, and Jacksonian motor epilepsy. He eventually required surgery because of the severity of his seizures. Electrophysiological recordings made before and during surgery, and PET scans performed before surgery identified an abnormal area of cerebral cortex in the postcentral parietal region. It is suggested that the stimulus-sensitive myoclonus arose because input into this region from peripheral sensory afferents produced an abnormal discharge which was fed forwards via cortico-cortical connections to the precentral motor cortex, to produce a reflex muscle jerk. The epilepsia partialis continua may have been caused by spontaneous discharges arising in the same region of parietal cortex. Both forms of jerking disappeared after resection of this part of the

Journal of Neurology, Neurosurgery & Psychiatry, 1989

SP, et al. earlier, over a week he developed severe Single photon emission computed tomograprogre... more SP, et al. earlier, over a week he developed severe Single photon emission computed tomograprogressive ataxia, complete external and phy in Alzheimer's disease. Arch Neurol internal ophthalmoplegia, the eyes remain-1988;45:392-6. ing in neutral position ptotic but without 13 Foster NL, Chase TN, Fedio P, et al Alz-dingin ane posiion ptotic butwitout heimer's disease: focal cortical changes diplopia, and general arreflexia. Consclousshown by positron emission tomography. ness was normal. CSF showed 0 cells, Neurology 1983;33:961-5. glucose 0-68 g/l and protein 0-63 g/l. In the 14 Taboeda E, Dickson D, Horoupian D, Davies next few days, transitory breathing and P. Clinicopathologic and neurochemical swallowing difficulties developed, as well as studies of one case of dysphasic dementia. J mild weakness of the facial musculature. In Neuropathol Exp Neurol 1986;45:323. this situation of complete ocular paralysis, 15 Morris JC, Cole M, Banker BQ, Wright D. the patient made constant gesticulation due Hereditary dysphasic dementia and the Pick-.. o Alzheimer spectrum. Ann Neurol to frequent, occasionallytsustained, bilateral 1984;16:455-66. blepharospasm attacks. This picture regres-16 Tissot R, Constantinidis J, Richard J. Picks sed to the previous situation after the ophdisease. In: Vinken PJ, Bruyn GW, Klawans thalmoplegia resolved some months later. HL, Fredriks JAM, eds. Handbook of Clin-The severe aggravation of facial spasms in ical Neurology Neurobehavioural disorders. our case was striking, well in excess of what Amsterdam, 1985;46:233-46. could have been expected from the emotional 17 Hudson AJ. Amyotrophic lateral sclerosis and stress of hospitalisation or appearance of

International Journal of Shoulder Surgery, 2012

} Muscle activation patterns in patients with recurrent shoulder instability } Symptomatic chroni... more } Muscle activation patterns in patients with recurrent shoulder instability } Symptomatic chronic long head of biceps rupture: Surgical results } Does age or gender of the patient influence the outcome of type II superior labrum anterior and posterior repair? } Surgical treatment of lateral clavicle fractures associated with complete coracoclavicular ligament disruption: Clinico-radiological outcomes of acromioclavicular joint sparing and spanning implants } Septic failure is not a septic loosening: A case report of a failed shoulder prosthesis } Locking plates for displaced fractures of the lateral end of clavicle: Potential pitfalls } Improved clinical utility in clavicle fracture decision-making with true orthogonal radiographs C o n t e n t s

Brain, 1987

ABSTRACT Using an isometric strain gauge, we measured the twitch force produced in the first dors... more ABSTRACT Using an isometric strain gauge, we measured the twitch force produced in the first dorsal interosseous (FDI) muscle by a single anodal shock to the contralateral scalp. At high intensities of stimulation this twitch can greatly exceed the force produced by supramaximal stimulation of peripheral nerve. This indicates that a single cortical shock can cause repetitive firing of some or all FDI motoneurons. Such repetitive firing was demonstrated using a collision technique in which a supramaximal ulnar nerve stimulus was given at the wrist shortly after a cortical shock. The antidromic volley from the peripheral nerve stimulation failed to obliterate completely the response to cortical stimulation. Additional EMG activity was visible in the normally silent period between ulnar M and F waves. This activity must have been due to the presence of repetitive volleys of activity set up in spinal motoneurons by the cortical shock. Such activity summates with the twitch produced by the ulnar M wave to produce a very large force twitch of the muscle. Multiple firing of some motoneurons can be observed in some individuals at cortical stimulation intensities below that necessary to evoke activity in all the motoneurons in the FDI pool. Multiple firing probably was caused by repetitive excitatory inputs impinging on spinal motoneurons. These could be demonstrated using poststimulus time histogram techniques on single motor units. Low intensities of cortical stimulation produced a single short duration (mean 1.8 ms) peak of increased motor unit firing 20 to 30 ms after the shock. At high intensities, this was followed by extra peaks some 4 to 5 ms later. H reflex testing showed that the threshold of the initial descending volley, produced by the cortical stimulus was uninfluenced by a voluntary contraction. These results are discussed with reference to the D and I waves recorded from pyramidal tract after anodal stimulation of the exposed cortex in animals.

Physiotherapy …, 2009

Background. This pilot study assesses level of agreement between surface and fine-wire electromyo... more Background. This pilot study assesses level of agreement between surface and fine-wire electromyography (EMG), in order to establish if surface is as reliable as fine wire in the diagnosis and treatment of abnormal muscle patterning in the shoulder. Method. ...