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Biomedical subjects

L K Hung

Publications and source records attributed to L K Hung.

At least 19 recordsLinked to original sources
PubMed2005

Firing properties of motor units during fatigue in subjects after stroke.

The purpose of this work was to investigate the electromyographic (EMG) fatigue representations in muscles of subjects after stroke at the level of motor unit, based on the analysis of mean power frequency (MPF) in the power density spectrum (PDS) for intramuscular EMG and our previous modeling and experiment studies on the neuromuscular transmission failure (NTF). NTF due to the local muscular fatigue had been captured in motor unit signals from healthy subjects during a submaximal fatigue contraction previously. In this study, the EMG signals for the biceps brachii muscles were collected by needle electrodes from the affected and unaffected arms of six hemiplegic subjects after stroke, and from the dominated arm of six healthy subjects during a full maximum voluntary contraction (MVC) and a subsequent 20% MVC. The MPF of EMG trials detected intramuscularly during the full and 20% MVCs, and the parameters of motor unit action potential trains (MUAPTs) during 20% MVC were analyzed in three groups: the normal (from healthy subjects), unaffected (from subjects after stroke), and affected (from subjects after stroke). It was found that during the full MVC the MPFs of the normal and unaffected groups decreased more than the affected when monitored by a moving time window of 2 s. The comparison on the overall MPF during the full MVC for these three groups over the whole time course of the EMG signal (18 s) were: the affected overall MPF was higher than the unaffected (P < 0.05); and the unaffected overall MPF was larger than the normal (P < 0.05). However, no significant decrease in MPF was found for these three groups during 20% MVC. The NTF was captured in most MUAPTs in the groups of the normal and unaffected rather than in the affected group, symbolized by the lowered rates of change (RCs) of firing rate (FR) (P < 0.05), more MUAPTs with positive RCs of maximum oscillation (MO) in MUAPT power density spectra (P < 0.05), and the significant higher RCs of minimum inter-pulse interval (MINI) (P < 0.05) in the normal and unaffected compared to the affected group. Enhanced neural drives to the motor units of the unaffected and affected groups were observed during 20% MVC, which possibly came from the bilateral neural inputs due to the disinhibition of the ipsilateral projections in subjects after stroke. For identifying the fatigue associated with NTF, the motor unit firing parameters, FR, MINI, and MO, were more sensitive than the MPF. The results obtained in this work provided a further understanding on the EMG of the fatigue processes in paretic and non-paretic muscles during voluntary contractions.

Action Potentials↗
PubMed2005

Is symptomatology useful in distinguishing between carpal tunnel syndrome and cervical spondylosis?

Hand paraesthesia is a common symptom found in patients either with carpal tunnel syndrome or cervical spondylosis. To differentiate between the two conditions, it is important to identify additional diagnostic symptoms. Ninety-two patients with operated carpal tunnel syndrome and 138 patients with spinal surgery for cervical spondylosis were reviewed. After exclusion of cases co-morbid with both cervical spondylosis and carpal tunnel syndrome or other neurological disorders, 44 patients with carpal tunnel syndrome and 41 patients with cervical spondylosis were compared. There were significant differences in the symptomatology between the two groups. In carpal tunnel syndrome, 84% had nocturnal paraesthesia, 82% hand paraesthesia were aggravated by hand activity, and hand pain occurred in 64%. The incidences were only 10%, 7% and 10%, respectively in cervical spondylosis. Neck pain was present in 76% of cervical spondylosis but only in 14% of carpal tunnel syndrome, and lower limb symptoms were present in 44% of cervical spondylosis and only 9% in carpal tunnel syndrome.

Carpal Tunnel Syndrome↗
PubMed2005

Active mobilisation after flexor tendon repair: comparison of results following injuries in zone 2 and other zones.

PURPOSE: To prospectively study the role of active mobilisation after flexor tendon repair. METHODS: The standard modified Kessler's technique was used to repair 46 digits in 32 patients with flexor tendon injuries. Early active mobilisation of the repaired digit was commenced on the third postoperative day. Range of movement was monitored and recovery from injury in zone 2 was compared with injury in other zones. RESULTS: There were 24 and 22 injuries in zone 2 and other zones respectively. The total active motion score of the American Society for Surgery of the Hand was measured. Patients with zone-2 injuries achieved similar results to those with other-zone injuries apart from a 3-week delay in recovery. The final results were good to excellent in 71% and 77% of zone-2 and other-zone cases respectively (p < 0.05). There were 2 ruptures in zone-2 and one rupture in zone-3 repairs (6.5%). CONCLUSION: Preliminary results of this study showed that active mobilisation following flexor tendon repair provides comparable clinical results and is as safe as conventional mobilisation programmes although recovery in patients with zone-2 injury was delayed.

Adolescent↗
PubMed2004

Oscillations in the power spectra of motor unit signals caused by refractoriness variations.

The refractory period of a motor unit is an important mechanism that regulates the motor unit firing, and its variation has been found in many physiological cases. In this study, a new observation that an increase in the motor unit refractoriness results in an enhancement of oscillations, or ripple effects, in the motor unit output power density spectra (PDS) has been identified and studied. The effects of the refractoriness variation on the PDS of motor unit firing were investigated on three levels: theoretical modeling, simulation and electromyographic (EMG) experimentation on human subjects. Both theoretical modeling and simulation showed the enhanced oscillations, ripple effects, in MUAPT PDS, given the increase in the refractoriness. It was also found that the extent of the increment in output PDS oscillation could be related to the motor unit size and the mean firing rate of the stimulation. A needle EMG experiment on biceps brachii muscles of five healthy human subjects was carried out during isometric contraction at 20% maximum voluntary contraction (MVC) for 20 s with a fatigue effort proceeded by MVC. The increased oscillations in the PDS of the real MUAPTs were observed with the rising of the motor unit refractoriness due to fatigue. The study gives new information for EMG spectra interpretation, and also provides a potential method for accessing neuromuscular transmission failure (NTF) due to fatigue during voluntary contraction.

Action Potentials↗
PubMed2004

Long-term outcome of carpal tunnel syndrome after conservative treatment.

The purpose of this study was to investigate the long-term prognosis of patients with carpal tunnel syndrome (CTS). We prospectively followed-up patients with CTS for 80 weeks. Thirty cases had been treated with a single injection of methylprednisolone acetate and another 30 with a 10-day course of prednisolone. At the end of the follow-up period, there were no significant differences in symptoms as measured by global symptom score and in the proportion of patients who progressed to decompressive surgery. Few patients who were not operated on (11.4%) remain asymptomatic.

Administration, Oral↗
PubMed2004

Ultrasound for the detection of vegetative foreign body in hand--a case report.

Foreign bodies in soft tissues are commonly encountered in daily orthopaedic practice. While most of the metals and glass foreign bodies can be detected by plain radiograph, organic substances such as wood and vegetative materials are radiolucent. Unfortunately, these radiolucent foreign bodies are usually more prone to cause an inflammatory reaction and infection. The detection can be even more difficult in cases of multiple foreign bodies and in penetrating injuries with small innocuous skin wounds. Ultrasonography is a sensitive and reliable investigation for detection of foreign bodies in soft tissue. We present a case of penetration injury to thumb with residual radiolucent foreign bodies and demonstrate the proper role of ultrasonography in the management of foreign bodies in soft tissues.

Adult↗
PubMed2004

Suicidal mercury injection into the upper limb: a case study.

We report a rare case of self-injection of mercury into the subcutaneous tissue of the upper limb. A multi-disciplinary management approach was adopted including cooperation between toxicologists, orthopaedic surgeons, radiologists and environment safety personnel. Surgical removal of mercury under radiological screening and systemic intoxication treated by chelating agents, namely dimercaprol and succimer. Serial serum and urine mercury levels showed an initial rise despite surgical removal and returned to normal after a prolonged period of time. Safety precautions were taken during surgery to avoid inadvertent intoxication of staff. Contamination of the operation theatre was monitored by the amount of mercury vapour released into the air. All personnels involved in the management of the patient did not show any evidence of mercury intoxication.

Adult↗
PubMed2003

Enhanced localization of osteoid osteoma with radiolabeling and intraoperative gamma counter guidance: a case report.

Osteoid osteoma is a benign bone tumor that can be removed by marginal excision. Excessive removal of reactive bone may result in significant morbidity. We made use of the highly specific radioactive technetium uptake characteristic of osteoid osteoma for its localization. Radioactive technetium (25 mCi) was injected intravenously 2 hours before surgery to a 21-year-old male patient with an osteoid osteoma over the left distal radius. Tumor tissue was localized intraoperatively by a portable hand-held radioactive gamma counter to detect a focal high intensity of radioactivity. Complete tumor removal was shown by reduction of radioactivity to background level. This was confirmed by bone scintigraphy of the specimen and the forearm immediately after surgery. The defect was packed with cancellous bone graft taken from the ipsilateral distal radius through the same wound. Postoperative recovery was very satisfactory. We found this approach useful in limiting resection margin and surgical site morbidity in resection of osteoid osteoma.

Adult↗
PubMed2003

Carpal tunnel release. A prospective, randomised study of endoscopic versus limited-open methods.

Endoscopic carpal tunnel release has the advantage over open release of reduced tissue trauma and postoperative morbidity. Limited open carpal tunnel release has also been shown to have comparable results, but is easier to perform and is safer. We have compared the results of both techniques in a prospective, randomised trial. Thirty patients with bilateral carpal tunnel syndrome had simultaneous bilateral release. The technique of release was randomly allocated to either two-portal endoscopic release (ECTR) or limited open release using the Strickland instrumentation (LOCTR). The results showed that the outcome was similar at follow-up of one year using both techniques. However, the LOCTR group had significantly less tenderness of the scar at the second and fourth postoperative week (p < 0.01). There was also less thenar and hypothenar (pillar) pain after LOCTR. Subjective evaluation showed a preference for LOCTR.

Adult↗
PubMed2002

Reconstruction of shoulder function using a reflected long head biceps: a moment arm study.

A tendon transfer technique is proposed for the reconstruction of the paralyzed shoulders secondary to brachial plexus injury. This innovative technique does not require bone-to-bone or tendon to-bone fixation, and attempts to overcome other clinical limitations such as those due to insufficient length of donor muscle. The approach is referred to as the reflected long head biceps (RLHB) technique. The long head of biceps tendons is utilized as a bridging tendon graft. Two surgical alternatives, namely the through-deltoid (TD) pathway and the sub-deltoid (SD) pathway, were studied. The moment arms of the transferred tendons were assessed and reported. The TD technique yielded a larger moment than the SD technique. In the plane 30 degrees anterior to the scapular plane, the average moment arms were 3.8cm TD and 3.0cm SD at zero elevation. Such differences tended to further widen with increasing elevation. At 80 degrees elevation, the moment arms became 3.2cm TD and 1.2cm SD. The results supported the clinical feasibility of this RLHB tendon transfer approach.

Aged↗
PubMed2002

In vivo determination of subject-specific musculotendon parameters: applications to the prime elbow flexors in normal and hemiparetic subjects.

OBJECTIVE: This study aimed at estimating the musculotendon parameters of the prime elbow flexors in vivo for both normal and hemiparetic subjects. DESIGN: A neuromusculoskeletal model of the elbow joint was developed incorporating detailed musculotendon modeling and geometrical modeling. BACKGROUND: Neuromusculoskeletal modeling is a valuable tool in orthopedic biomechanics and motor control research. However, its reliability depends on reasonable estimation of the musculotendon parameters. Parameter estimation is one of the most challenging aspects of neuromusculoskeletal modeling. METHODS: Five normal and five hemiparetic subjects performed maximum isometric voluntary flexion at nine elbow positions (0 degrees -120 degrees of flexion with an increment of 15 degrees ). Maximum flexion torques were measured at each position. Computational optimization was used to search for the musculotendon parameters of four prime elbow flexors by minimizing the root mean square difference between the predicted and the experimentally measured torque-angle curves. RESULTS: The normal group seemed to have larger maximum muscle stress values as compared to the hemiparetic group. Although the functional ranges of each selected muscle were different, they were all located at the ascending limb of the force-length relationship. The muscle optimal lengths and tendon slack lengths found in this study were comparable to other cadaver studies reported in the literature. CONCLUSION: Subject-specific musculotendon parameters could be properly estimated in vivo. RELEVANCE: Estimation of subject-specific musculotendon parameters for both normal and hemiparetic subjects would help clinicians better understand some of the effects of this pathological condition on the musculoskeletal system.

Adult↗
PubMed2002

Effects of antioxidants on pyridinoline cross-link formation in culture supernatants of fibroblasts from normal skin and hypertrophic scars.

Free radicals are normally generated in many metabolic pathways. They are closely associated with inflammatory diseases. The aim of this study was to investigate the effects of free radicals and their antioxidants on the formation of pyridinoline using human fibroblasts from normal skin and hypertrophic scars. The significance of the increase in pyridinoline cross-links is that large quantities have been found in hypertrophic scars formed post-burn than in normal skin, and that catalase was effective in reducing the pyridinoline cross-link formation in hypertrophic scars. The pyridinoline cross-link concentration expressed in nM/ micro g hydroxyl proline was found to be higher in the culture supernatants of the fibroblasts from hypertrophic scars (9.04 +/- 2.74) than that of normal skin (7.55 +/- 2.1). When the human fibroblasts from normal skin and hypertrophic scar were subject to hydroxyl radicals generated by the Fenton reaction, there was no significant increase in pyridinoline cross-link concentration (nm/ micro g hydroxyl proline) in the supernatants compared with the control. When the controls plus various treatments with free radicals were subject to different antioxidants, including superoxide dismutase, catalase, glutathione peroxidase, and desferrioxamine, it was found that catalase alone was most effective in scavenging hydroxyl radicals as determined by the decrease in pyridinoline cross-links.

Amino Acids↗
PubMed2001

Local vs systemic corticosteroids in the treatment of carpal tunnel syndrome.

The authors compared the effectiveness of low-dose, short-term oral prednisolone vs local methylprednisolone injection in a prospective, double-blinded, parallel treatment study of carpal tunnel syndrome (CTS). A single injection of 15 mg methylprednisolone resulted in significant improvement in global symptom scores over a 12-week period. This study demonstrated the superiority of local steroid injection to oral steroid in the treatment of CTS.

Administration, Oral↗
PubMed2001

Sonography of the normal scapholunate ligament and scapholunate joint space.

PURPOSE: The aims of this study were to assess the visibility of the normal scapholunate ligament on sonography and to establish the normal scapholunate joint space width in the neutral position and radial and ulnar deviation. METHODS: Two hundred normal wrists in 100 subjects (55 men and 45 women; mean age, 40 years; range, 19-83 years) were examined with high-resolution sonography (5-12-MHz linear-array transducer). The visibility and thickness of the scapholunate ligament were recorded. The width of the scapholunate joint space, or interval, was measured in the neutral position and radial and ulnar deviation. The width of the distal radius was recorded as a comparative standard for the patients' body habitus. RESULTS: The dorsal scapholunate ligament was completely (100%) visible in 95 wrists (48%), partially (> or = 50%) visible in 60 (30%), barely (< 50%) visible in 15 (8%), and not visible in 30 (15%). The volar scapholunate ligament was completely visible in 13 wrists (7%), partially visible in 17 (9%), barely visible in 15 (8%), and not visible in 151 (76%). The proximal component of the ligament was not visible in any subject. Measurement of the scapholunate interval was limited by the lack of identifiable anatomic marks for reference. The mean width of the dorsal scapholunate interval was 4.2 mm (range, 2.3-6.3 mm) in the neutral position. The interval did not differ more than 2.5 mm between the left and right wrists. No predictable change in width on ulnar or radial deviation was evident. The mean scapholunate intervals and mean distal radial width were significantly wider in men than in women and on the right side than on the left side. CONCLUSIONS: The dorsal scapholunate ligament is completely or partially visible in 78% of normal wrists. Its detection following injury may help to exclude the possibility of scapholunate dissociation. There is a quite wide variation in scapholunate interval widths on sonography and an unpredictable response with stress testing. The absence of a visible scapholunate ligament on sonography does not indicate injury.

Adult↗
PubMed2001

Applied anatomy of the axillary nerve for selective neurotization of the deltoid muscle.

Morphologic and internal topographic features of the axillary nerve were studied in 40 cadaveric shoulders to provide anatomic data for selective neurotization of the deltoid muscle in axillary nerve injury. The axillary nerve can be divided into three segments. Proximal to the subscapularis muscle, the axillary nerve is a single nerve trunk. Nerve fascicles to the deltoid muscle are identified at its lateral part. In front of the subscapularis muscle, the axillary nerve forms into the lateral and medial fasciculi groups. Distal to the subscapularis muscle, the nerve divides into anterior and posterior branches, which are continuations of the lateral and medial fasciculi groups, respectively. The anterior branch contains all fibers that innervate to the anterior and middle deltoid muscle. In 90% of cases, the posterior branch contains part or all nerve fibers to the posterior deltoid muscle. Nerve fibers to the teres minor and cutaneous sensory fibers are found in the posterior branch. In neurotization of the deltoid muscle, the best approach is to match the donor nerve to the lateral fasciculi group, which will give the highest percentage of reinnervation of the deltoid muscle.

Adult↗
PubMed2001

Stability of reconstructed paralyzed shoulders using a reflected long head biceps technique.

A new tendon transfer technique is proposed for the reconstruction of the paralyzed shoulders secondary to Brachial Plexus Injury (BPI). In this tendon transfer, the long head of the biceps tendons is utilized as a bridging tendon graft. It is reflected at the exit of the bicipital groove, passed through the deltoid and directed to the trapezius. The technique is referred to here as the Reflected Long Head Bicepts (RLHB) technique. This study evaluated the effect of this tendon transfer on the anterior, posterior, and inferior stability of the reconstructed should using cadaveric specimens. It was shown that loading of the RLHB contributed significantly to anterior stability of the reconstructed shoulder for 90 deg elevation in the scapula plane. The mean displacement was reduced by 56 percent with RLHB loaded (p<0.01), by 56 percent with the rotator cuff loaded (p <0.005), and by 67 percent with both the RLHB and the rotator cuff loaded (p<0.004). For the post-operation conditions, variation of the directions of RLHB had no significant effect on joint displacement in response to anterior loading. The RLHB tendon also contributed to the posterior and inferior stability for the low and middle elevations in the plane of scapula. Two variations of the RLHB tendon transfer procedures, namely the "Sub-Deltoid" and the "Through-Deltoid" techniques, were introduced and studied. These two techniques did not seem to have significantly different effects on the displacement of the humeral head in response to both posterior and inferior loading. The results of this study seemed to support the clinical feasibility of this tendon transfer approach as far as the biomedical stability of the reconstruction is concerned.

Adult↗