Opponens Pollicis Research Articles

Spaghetti wrist: management and outcome.

To determine the outcome of emergency management of the spaghetti wrist. Descriptive study. Department of General Surgery, Sir Ganga Ram Hospital Lahore, Pakistan, from January 2000 to December 2003. During this period, all patients of more than 12 years, with sharp clean cut volar forearm lacerations (spaghetti wrist) of <6 hours were included, with a follow-up of one year, clinically and with nerve conduction studies, where appropriate. Sensory and motor recovery was evaluated according to S0-S4 and MRC (medical research council) scale respectively. The power of first dorsal interosseous and adductor pollicis was used to monitor the recovery of ulnar nerve; and abductor pollicis brevis and opponens pollicis for the median nerve. The tendon recovery was evaluated by Strickland Adjusted System Score. This study comprised of 10 patients (M:F, 4:1), of 14 to 38 years (mean 22.9 years). Injury was accidental in 70%; due to broken glass in 50% and kite string in 40%; involving right hand in 70%. 8.2 (4-12) structures per patient were involved. The injury involved median nerve in 70%, ulnar nerve in 60%, (30% had both nerves involved), flexor carpi ulnaris in 70%. There was predilection of injury for medial structures. In 80%, wrist flexors were involved, and all wrist joints recovered to the full range of movements and power. The ulnar nerve showed less total motor and sensory recovery than median nerve. However, sensory and motor recovery was good. Overall functional results were good and did not correlate with neurophysiological studies. Immediate primary repair is safe and has good outcome, which also depends upon good physiotherapy, close follow-up and patients' compliance. Overall clinical and functional assessment is more appropriate than series of individual observations and neurophysiological studies.

Suppression of the transcallosal motor output: a transcranial magnetic stimulation study in healthy subjects.

We tested the hypothesis that transcranial magnetic stimulation (TMS), in addition to its inhibitory action on the corticospinal output, can also exert some inhibitory effect on the transcallosal system connecting the two motor cortices. In seven normal subjects, instructed to keep their right opponens pollicis (OP) muscle fully relaxed and their left OP muscle voluntarily contracted, we used a paired-pulse TMS protocol, to stimulate the left motor cortex. We evaluated the effect of low-intensity conditioning stimulation on the ipsilateral silent period (iSP) elicited by the subsequent test stimulus. Compelling evidence exists to support that this iSP is mediated by the activation of transcallosal motor fibres. Simultaneously, the inhibition of the motor evoked potential (MEP) in the right OP muscle was also investigated. At the interstimulus interval (ISI) of 3 ms, the iSP was significantly (P<0.0001, repeated-measures ANOVA) suppressed by conditioning intensities ranging from 1.2 to 0.6 of MEP threshold. The assessment of the time-course showed that iSP inhibition was present in all the tested subjects only at ISIs of 2 and 3 ms (for each subject P<0.05, repeated-measures ANOVA). Several findings suggest that the suppression of iSP is brought about by the activation of inhibitory mechanisms operating in the stimulated (left) motor cortex. We propose that the assessment of iSP suppression could be a method to study the excitability of intracortical inhibitory circuits in the affected hemisphere of patients with unilateral damage of the corticospinal tract.

Reliability of the motor evoked potentials elicited through magnetic stimulation at three sites

Background Motor evoked potentials (MEPs) obtained from magnetic stimulation allow the measurement of the excitability of motor nerve cells. Although this technique is becoming widely used, its reliability has yet to be established. Objective To determine the reliability of MEPs and evaluate their stability. Design Subjects received magnetic stimulation at 3 different sites: cranial, cervical, and peripheral. Three stimulations were given at each site. Stimulations were given under 4 conditions: eyes open or closed and with or without controlled mental activity. Setting The study was performed in a research laboratory setting. Participants Nine healthy subjects (mean age = 21 years ± 0.9), asymptomatic of any neural or musculoskeletal dysfunctions. Main outcome measures Normalized peak-to-peak amplitude of MEPs at the opponens pollicis muscle. Results Intraclass correlations were high for all conditions ( R > 0.90). The amplitude of the MEPs elicited from the transcranial site during the controlled mental activity condition was increased by 26.6% ( P = .017). No other significant differences ( P > .05) were obtained among the other conditions. Conclusion Intraclass correlation results reveal that MEP measurements are highly reliable in a controlled environment. The increase of MEPs during the controlled mental activity condition could be attributed to an elevation of neural activity of different nonmotor areas of the brain increasing corticospinal excitability.

Impairment of transcallosal inhibition in patients with corticobasal degeneration.

To evaluate the motor function of the transcallosal pathways in patients with clinical diagnosis of corticobasal degeneration (CBD). In a group of 7 patients (4 males, 3 females; mean age 70.6 years) with clinical diagnosis of probable CBD (and in 8 age-matched normal controls) we evaluated the suppression of the ongoing voluntary EMG activity in the opponens pollicis muscle induced by focal transcranial magnetic stimulation (TMS) of the ipsilateral hand motor cortex. Such ipsilateral silent period (iSP) is mediated from one motor cortex to the contralateral side via a transcallosal pathway. In addition, CBD patients were investigated with magnetic resonance imaging (MRI) and neuropsychological assessment. iSP was normal in 4 CBD patients, while it was bilaterally disrupted in the other 3. MRI showed an atrophy of the corpus callosum (middle-posterior part of the trunk) in the CBD patients with iSP disruption. Neuropsychological evaluation showed in patients with iSP impairment a decrease of verbal fluencies associated with an impairment of attentive function. A proportion of CBD patients shows physiological evidence of impaired callosal motor function and atrophy of the corpus callosum on MRI, possibly correlated to dysphasic and cognitive disorders.

Influence of proprioceptive input on parkinsonian tremor.

Previous studies have shown a modification of parkinsonian tremor (PT) by proprioceptive input induced by passive joint movements. The authors investigated the impact of electrically evoked proprioceptive input on PT. In eight patients with PT they recorded surface EMG from the opponens pollicis muscle, and forearm extensors and flexors. Rhythmic electrical stimulation was applied to the ipsilateral median nerve at the wrist using a submaximal stimulus intensity and stimulus frequencies between two stimuli per second and five stimuli per second. The tremor frequency did not adapt to the stimulus frequency. Tremor frequency of parkinsonian resting tremor increased significantly in the directly stimulated opponens pollicis muscle (mean +/- standard deviation, 4.35 +/- 0.64 Hz without stimulation versus 4.53 +/- 0.68 Hz with stimulation; P < 0.05, paired t-test), the not directly stimulated forearm muscles (4.90 +/- 0.72 Hz versus 5.18 +/- 0.73 Hz, P < 0.001), and the upper arm muscles (5.13 +/- 0.61 Hz versus 5.36 +/- 0.68 Hz, P < 0.01). Furthermore, the parkinsonian postural tremor accelerated significantly during ipsilateral median nerve stimulation (5.31 +/- 0.99 Hz versus 5.44 +/- 1.03 Hz, P < 0.05). Parkinsonian resting tremor in the forearm muscles also accelerated significantly during ipsilateral ulnar nerve stimulation (4.85 +/- 0.57 Hz versus 5.05 +/- 0.65 Hz, P < 0.05). Contralateral median nerve stimulation had no significant effect. These results suggest a close interaction between proprioceptive input and PT generation.

The Effect of Flexible Magnets on Hand Muscle Strength: A Randomized, Double-Blind Study

The purpose of this study was to determine the effect of a flexible magnet on hand grip and thumb-forefinger pinch strength. Flexible magnet use has become popular in sports medicine and rehabilitation for a number of reasons, including augmenting muscle force output. Thirty-five university students (18 men and 17 women) volunteered for this study. Each subject was tested for grip strength (grip dynamometer) and thumb-forefinger pinch strength (pinch gauge) under 3 different treatment conditions: baseline (no magnet), sham magnet (placebo), and flexible magnet (700-G intensity). The order of treatments was randomly assigned, and all data collection followed a double-blind format. For grip strength measurements, magnet placement was over the bellies of the flexor digitorum profundus and flexor digitorum superficialis, and for pinch strength measurements, it was over the bellies of the flexor pollicis brevis and opponens pollicis. Three trials for each strength measurement for each of the 3 conditions were performed. Magnets (700 G or sham) were placed on the appropriate areas of the skin 3 minutes before the first test trial, with each subsequent test trial separated by 1 minute. Comparison among the 3 treatment conditions was analyzed using a 1-way analysis of variance (ANOVA) with repeated measures. ANOVA revealed no statistically significant (p > 0.05) mean differences for strength among any of the 3 treatments (baseline, 700-G magnet, or sham magnet) for either hand grip or thumb-forefinger pinch within each sex subgroup or for the combined group. The findings indicate that flexible magnets with a field strength of 700 G do not increase muscle strength.

Radial sesamoid bone as a part of the manipulation system in the lesser panda ( Ailurus fulgens)

The well-developed radial sesamoid bone presented a rod-like shape in the lesser panda. It could be separated into two components: (1) an ulnar cartilaginous, (2) a radial osseous part. The radial sesamoid bone was connected with four elements as follows: (1) the tendon of the M. abductor pollicis longus, (2) M. abductor pollicis brevis and M. opponens pollicis, (3) Aponeurosis palmaris, and (4) Flexor retinaculum. The bone made no articulation with the first metacarpal. The movement of the radial sesamoid bone may be controlled by the connecting muscles and muscle-related structures. It is suggested that the bone acts as a supporting ridge in the gripping action in the lesser panda. However, we suggest that the grasping mechanism is obviously different from that of the giant panda, in which the radial sesamoid bone is connected strongly with the first metacarpal.

Estudio electrofisiológico de la inervación anómala de la mano

The innervation of the hand frequently differs from the usual description that we can find in text books. The most frequent anomalies consist on communications among the median and cubital nerves at level of either forearm (Martin-Gruber anastomosis) or to more distal level (Richie-Cannieu anastomosis), although they are not the only possibilities. To study from a electrophysiological point of view or the variants of the normality in the innervation of the hand and to define their functional characteristics. We performed an electromyographic and electroneurographic studies on patients that suffered wounded (fundamentally) or other pathologies in the forearm. The presence of double innervation in abductor pollicis brevis and opponens pollicis muscles has been verified in 2.48% of the patients. Although, it has not been possible to determine the prevalence of other anomalies, the presence of several types of anastomosis has been observed: Martin-Gruber types I and III, as well as the incomplete innervation on the part of the cubital nerve of the muscles of the tenar muscles (only of the opponens pollicis). The correct methodology is fundamental in the electrophysiological study, so several pitfalls can take place. It would be desirable to employ techniques that minimize the problems of dispersion of the current, by means of needles. It is very important to keep in mind these variations of the normality in the innervation of the hand, specially when pronostic and surgical treatment are considered.

Thenar branch of the median nerve and innervation of the trapeziometacarpal joint

Denervation has been proposed successfully for chronic wrist pain. This procedure is not commonly performed for degenerative osteoarthritis of the trapeziometacarpal joint. According to the classic anatomical descriptions of the wrist innervation, it seems that the thenar branch of the median nerve (TBMN) is the only nerve of the wrist for which no articular branches are clearly defined. The aim of this study is to complete the few anatomical descriptions of the trapeziometacarpal joint innervation with microdissections of the TBMN. Ten wrist and hand specimens from fresh cadavers were dissected by the same operator under magnification (3.5-12x). The TBMN was identified at its origin from the median nerve and followed in the thenar muscles. All the divisions of the TBMN were identified and followed to their terminal branches. The TBMN divided in at least two main branches, one each to the opponens and to the abductor pollicis brevis. In all but one specimen, the branch to the opponens pollicis muscle passed over or into its medial aspect to spread on the palmar side of the trapezium. Each dissected articular branches were histologically confirmed. Our results show a clear participation of the TBMN in the innervation of the trapeziometacarpal joint. The lack of knowledge of this anatomical feature may explain the inconstant results obtained with selective denervation of the trapeziometacarpal joint.

Intracortical inhibitory circuits and sensory input: a study with transcranial magnetic stimulation in humans

We compared intracortical inhibition (ICI) following paired transcranial magnetic stimulation (TMS) (interstimulus interval, ISI: 3 ms) and the inhibition of motor evoked potentials (MEPs) to TMS induced by stimulation of the median nerve (ISI: 200 ms) in six normal subjects. MEPs evoked by focal TMS were recorded in the relaxed opponens pollicis muscle and the size of the conditioned responses was expressed as a percentage of the size of the non-conditioned responses. Maximal ICI, ranging from 4 to 40%, and inhibition after median nerve stimulation, ranging from 11 to 68%, were significantly correlated. The results suggest that both phenomena are possibly mediated by the same γ aminobutyric acid-ergic (GABAergic) inhibitory circuits and that afferent inputs to the cortex may contribute to their physiological activation.

CT examination of the manipulation system in the giant panda (Ailuropoda melanoleuca).

The manipulation mechanism of the giant panda (Ailuropida melanoleuca) was examined by means of CT (computed tomography) and 3-dimensional (3-D) Volume Rendering techniques. In the 3-D images of the giant panda hand, not only the bones but also the muscular system was visualised. Sections of the articulated skeleton were obtained. It was demonstrated that the hand of the panda is equipped with separately moulded manipulation units as follows: (1) the radial sesamoid (RS), the radial carpal, and the first metacarpal (R-R-M) complex; and (2) the accessory carpal (AC) and the ulnar (A-U) complex. When the giant panda grasps anything, the R-R-M complex strongly flexes at the wrist joint, the RS becomes parallel with the AC, and the phalanges bend and hold the object. It is shown that the well-developed opponens pollicis and abductor pollicis brevis muscles envelop and fix the objects between the R-R-M complex and the phalanges during grasping.

Motor and sensory reinnervation in the hand after an end-to-side median to ulnar nerve coaptation in the forearm

End-to-side coaptation of the median to ulnar nerve through an epineurial window was performed 5 cm proximal to the wrist in a patient with high median nerve injury associated with a 35 cm long nerve gap. Forty-three months after the operation, sensory examination revealed the presence of diminished protective sensation (3.61–4.31 NCM Semmes–Weinstein monofilament) in the large part of the median nerve dermatome. In the two-point discrimination test, single point was perceived in the median nerve dermatome pointing to the presence of protective sensation. MRI and EMG studies indicated limited motor reinnervation in the opponens pollicis muscle. This novel method of nerve repair may be chosen in the management of very long nerve gaps, where conventional methods are likely to give an unsuccessful result.

Intracortical inhibition after paired transcranial magnetic stimulation depends on the current flow direction

Objectives: To assess whether cortico-cortical inhibition (CCI) induced by paired-pulse transcranial magnetic stimulation (TMS) is influenced by ‘preferential’ or ‘non-preferential’ activation of the motor cortex.Methods: Paired-pulse TMS (conditioning-test paradigm with interstimulus intervals of 2–5 ms) with a round coil centered over the vertex was performed in 10 normal subjects using opposite current flow directions. The amount of CCI in the opponens pollicis and first dorsal interosseus muscles was determined.Results: When a clockwise current was induced in the brain (side A of the coil uppermost) a ‘preferential’ activation of the left hemisphere (right hand muscles) was observed, but the suppression of the test response by the conditioning stimulus (i.e. the CCI) was significantly greater in the left hand muscles. The situation was reversed when an anticlockwise current (side B of the coil uppermost) was induced in the brain. These effects occurred independently of the interstimulus interval, or of the absolute conditioning stimulus strength.Conclusions: CCI is more effective in the ‘non-preferentially’ stimulated hemisphere, and the neural elements generating the indirect I3 wave are more sensitive to intracortical inhibition than those generating the I1 wave.

Changes of intracortical inhibition during motor imagery in human subjects

Paired-pulse transcranial magnetic stimulation with a conditioning-test paradigm was used to assess changes of cortico-cortical inhibition and facilitation during mental simulation of sequential finger movements in normal subjects. The cortico-cortical inhibition (at interstimulus interval, ISI, of 3 ms) was significantly reduced in the relaxed opponens pollicis (OP) muscle during motor imagery, regardless of the absolute size of the test motor evoked potential. The amount of cortico-cortical inhibition was similar to that observed during a mild voluntary contraction of the OP. No change of cortico-cortical facilitation was observed at the ISI of 12 ms. The data support the hypothesis that similar neural structures, including the primary motor cortex, are activated during both mental simulation and actual execution of motor activities.

In-vivo function of the thumb muscles

Objective. The purpose of this study is to quantify the electrical activity of the thumb muscles responsible for the production of force in different directions of thumb movement. Design. The isometric forces and electromyographic activity generated by seven thumb muscles were measured on five normal healthy test subjects. Background. The thumb is very important for proper hand function. Presently available electromyographic studies of the thumb muscles provide only limited information. Most thumb muscles have more than one function. Additional studies are required to carefully examine and confirm the in-vivo relationship between the thumb muscle electromyogram and mechanical output. Methods. The direction and magnitude of the force vector generated at the interphalangeal joint and the relative electrical activity were obtained for eight directions of thumb action. The regions of function were defined for the abductor pollicis brevis, opponens pollicis, flexor pollicis brevis, adductor pollicis, flexor pollicis longus, extensor pollicis longus, and the abductor pollicis longus. Data was collected during voluntary isometric contraction, both before and after blocking the median nerve at the wrist. Results. The highest force production was obtained during flexion. The region of maximal muscle electrical activity varied for each muscle studied. The areas of maximal in-vivo muscle activity agreed with the moment arm data reported in the literature. The median nerve block eliminated the ability to produce force in abduction. Conclusions. This study has demonstrated that by combining electromyographic measurement and biomechanical analysis it is possible to confirm the relationship between in-vivo thumb muscle function and muscle mechanics in a novel manner. The findings of this study indicate the importance of the local anatomy in controlling the direction of force production.

The effects of low median nerve block on thumb abduction strength

The relative contributions of the abductor pollicis longus (APL) and abductor pollicis brevis (APB) to thumb abduction strength (TAS) were determined after a selective nerve block in 21 normal volunteers. The median nerve was anesthetized (blocked) at the wrist. Needle electromyography verified paralysis of the APB and usually the opponens pollicis; in 6 study subjects, the superficial head of the flexor pollicis brevis (FPB) was also paralyzed. The APL, innervated by a branch of the posterior interosseous nerve, remained functionally intact. TAS was measured by a mechanical device before and after median nerve block. Median nerve block at the wrist resulted in a dramatic decrease in TAS in all volunteers. The mean loss of TAS was 70.3% in men and 74.3% in women. Postblock TAS tended to be greater in those subjects with retained function of the FPB. This study verifies that TAS is primarily a function of the APB.

Experiences with endoscopic surgery in treatment of carpal tunnel syndrome. Preliminary results of a prospective study

Endoscopic carpal tunnel release is a new technique for treatment of carpal tunnel syndrome. The benefits of this procedure are a small skin wound with less local pain, the fact that the hand can quickly be used again, and earlier return to work or other activities. We present the preliminary results of the 3-month follow-up of 88 patients out of a prospective study of 100 patients. All patients were operated on using the one-port technique. Six additional decompressions had to be abandoned and open release was performed. Of the patients with pain, 73.6% (68/88) were completely pain-free and in 13.2% (9/68) pain improved in more than 50%. Subjective symptoms like paresthesia and numbness of the hand disappeared completely in 77.2% (64/83). Sensory deficits disappeared in 50% (33/66). Ten of 17 patients with preoperative paresis of the abductor pollicis brevis muscle and 11/14 with paresis of the opponens pollicis muscle had normal motor function 3 months after the operation. The complication rate concerning nerve lesions was 2.3%. The return to work time was 21 days (range 3-49 days). According to clinical symptoms, our preliminary results do not seem to have any benefits compared to the conventional open technique, and the costs for the endoscopic procedure are markedly higher. The complication rate after the learning curve period is approximately the same as open carpal tunnel release.

Intracortical inhibition and facilitation are abnormal in Huntington's disease: a paired magnetic stimulation study

Transcranial magnetic stimulation with a conditioning-test paradigm was used to assess cortico-cortical interactions in the motor cortex of 11 patients with Huntington's disease (HD) as compared to normal controls (NC). In the HD patients, threshold and amplitude of motor potentials evoked in the opponens pollicis muscle at rest were not significantly different from NC. The cortico-cortical inhibition at interstimulus intervals of 2–5 ms was significantly reduced and the cortico-cortical facilitation at longer intervals (10–25 ms) was significantly enhanced. Changes of intracortical inhibition and facilitation were related to clinical rating of choreic dyskinesias. The data support the hypothesis of a functional impairment of the motor cortex-basal ganglia loop in HD patients.

Primary epineural repair of the median nerve in children

We report 18 children (12 boys and six girls) with a mean age of 6.1 years who sustained lacerations of the median nerve. Associated injuries to other structures occurred in 15 children. Treatment was by primary epineural repair. All the children were assessed at least 1 year after injury. The mean return of motor power to the opponens pollicis was 4.5 with a range of 3 to 5 (MRC scale) and the mean static 2-point discrimination was 5 mm (range 2-10 mm). All children showed a full functional recovery as assessed by the Bruininks-Oseretsky test. Primary epineurial repair in children leads to very satisfactory motor and sensory results. A fully functional hand can be expected.

Vascular and neural anatomy of the thenar area of the hand: its surgical applications.

Thirty fresh cadaver hands were injected with a silicone rubber compound (Microfil) and dissected to examine the vascular and neural supplies of the thenar area. In 10 specimens, a selective injection technique was used to determine the extent of skin territory nourished by the superficial palmar branch of the radial artery. The purpose of this study was to clarify the anatomic basis for clinical applications of vascularized free- or island-flap transfers from the thenar area. The superficial palmar branch of the radial artery was found in all hands; the average diameter of the branch measured at its bifurcation site was 1.4 mm (0.8 to 3.0 mm). The constant area nourished by the superficial palmar branch was an area approximately 4 x 3 cm located over the proximal parts of the abductor pollicis brevis and opponens pollicis muscles. These results indicate that a fasciocutaneous flap from the radial thenar region can be raised based on the superficial palmar branch and consistently transferred as a free flap. In 63 percent of the hands dissected, the superficial palmar branch was connected to other arteries in the palm, suggesting that the flap can be transferred as a reverse-pedicle island flap in such hands. Innervation of the flap was provided chiefly by a branch of the superficial radial nerve. The radial aspect of the thenar eminence can provide a new and useful donor source for an innervated and vascularized free- or island-flap transfer for reconstruction of various skin defects of the volar side of the fingers.