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The flexor pollicis longus muscle and flexor digitorum profundus muscle are innervated by the branches of the anterior interosseous nerve (AIN). Therefore, the commonly used methods of restoring the fingers and thumb flexion in lower brachial plexus injury have mainly focused on the AIN. We transferred the brachialis muscle branch of the musculocutaneous nerve (brachialis nerve) to the AIN using the vascularized lateral antebrachial cutaneous nerve (LACN) as a nerve graft to restore the flexion function of the fingers and thumb. This anatomical study was performed in 16 formalin-fixed upper extremities from 8 frozen cadavers. The brachialis nerve and the AIN were dissected. The bridged portion of the transected LACN was not dissected; only the two transected ends of the LACN were dissected, which kept the native blood supply of the intervening graft of the LACN from being destroyed. The diameters of the transected nerve ends of the brachialis nerve, AIN, and proximal and distal ends of the LACN were measured separately. Specimens of the measured nerve tissue were sent for toluidine blue staining, and the number of nerve fibers in each transected nerve branch was counted. The diameters of the brachialis nerve, AIN, and proximal and distal transected ends of LACN were 1.37 SD0.25 mm, 1.54 SD0.14 mm, 2.07 SD0.29, and 1.76 SD0.14 mm, with 1109 SD422, 1318 SD546, 1684 SD327, and 1378 SD667 myelinated nerve fibers, respectively. The fingers and thumb flexion function of the patient recovered gradually from 8 months after surgery. Using the vascularized LACN as an in situ nerve graft to transfer the brachialis nerve to the AIN was a feasible alternative technique to restore the flexion function of fingers and thumb in lower brachial plexus injury.

Background: Cases of nerve entrapment are commonly seen in medical practice. The flexor pollicis longus muscle of the front of the forearm sometimes may have an accessory head. The accessory head of flexor pollicis longus muscle (AHFPL) may compress the anterior interosseus nerve (AIN) to cause weakness of the deep muscles of the front of the forearm. The aim of the present study is to find the incidence of AHFPL and to identify its structural relationships to the median nerve and AIN. Methods: A total of sixty upper limbs of thirty embalmed cadavers were dissected and studied for the presence of AHFPL. Parameters studied were incidence of AHFPL, whether it is bilateral or unilateral, its origin and insertion, and its relationship with AIN. Results: AHFPL was found in 16 cadavers (53%). In 7 out of the 16 cadavers (43.75%), AHFPL was bilateral and in 9 out of 16 cadavers (56.25%), AHFPL was unilateral. AIN was located below the AHFPL in 14 cadavers and in 2 cadavers, it was passing above the AHFPL. The nerve supply of AHFPL was through AIN in the 16 cadavers. Conclusion: Knowledge of AHFPL and its relations with AIN may help medical professionals in diagnosis and treatment as this anatomical variation can lead to compression neuropathy.

Background: The accessory head of the flexor pollicis longus (AHFPL) has an oblique trajectory from medial to lateral aspect of the forearm below the flexor digitorum superficialis muscle and then joins the flexor pollicis longus muscle. When the anterior interosseous nerve (AIN) courses underneath the muscle belly of the AHFPL an entrapment neuropathy may occur, known as anterior interosseous nerve syndrome (AINS). Materials and methods: This descriptive cross-sectional study evaluated 106 fresh upper extremities. When the AHFPL was present, its fascicle was traced up to evaluate the origin site. The morphometric variables were measured using a digital micrometre (Mitutoyo, Japan). The relationship between the AHFLP and the AIN was evaluated. Results: The AHFPL was found in 34 (32.1%) of the 106 forearms. The AHFPL arose from the flexor digitorum superficialis muscle in 16 (47.1%) forearms, the medial epicondyle of the humerus in 10 (29.4%) forearms and the coronoid process of ulna in 8 (23.5%) forearms. The average total length of the AHFPL was 94.11 ± ± 10.33 mm. The AIN was located lateral to the AHFPL in 3 (8.8%) forearms, posterolateral in 7 (20.6%) forearms and posterior in 24 (70.6%) forearms. Conclusions: This study performed in a South American population sample revealed a prevalence of the AHFPL in a lower range compared to previous studies in North Americans and Asians. The AIN coursed more frequently underneath the muscle belly of AHFPL. This finding has clinical significance in the onset of the AINS and the subsequent surgical procedure for the AIN decompression.

Objective The aim of this study was to investigate the interrater reliability and intrarater reliability of the flexor pollicis longus muscle stretch reflex (FPLR) and compare it with clinically established reflexes. Design A total of 71 healthy volunteers participated. The FPLR, biceps reflex, brachioradialis reflex, and patellar tendon reflex of each participant were tested bilaterally and rated by eight examiners (four experienced, four inexperienced). For intrarater reliability evaluation, five examiners rated the reflexes of four volunteers at four different points in time. Results Analysis of the interrater reliability with Gwet's AC1 demonstrated almost perfect agreement for FPLR (Gwet's AC1 = 0.90), biceps reflex (Gwet's AC1 = 0.90), and patellar tendon reflex (Gwet's AC1 = 0.95) when using binary data (reflex present vs. absent). Only fair agreement was found for the brachioradialis reflex (Gwet's AC1 = 0.56). Experienced raters had a higher agreement than inexperienced raters did when rating the biceps reflex and the patellar tendon reflex. The intrarater reliability was almost perfect for the patellar tendon reflex (Gwet's AC1 = 0.94), followed by the FPLR (Gwet's AC1 = 0.83) with substantial agreement and the biceps reflex (Gwet's AC1 = 0.57) with moderate agreement. Conclusion The FPLR is a reliable diagnostic neuromuscular test and may therefore be useful in the clinical examination for C8/T1 nerve root lesions or pathologies of the interosseous anterior nerve. To claim cme credits Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME. Cme objectives Upon completion of this article, the reader should be able to: (1) Elicit the flexor pollicis longus muscle stretch reflex; (2) Discuss the disadvantage of kappa statistics in assessing the interrater reliability when the prevalence of the studied trait is very high or very low; and (3) Name the spinal nerves involved in the innervation of the flexor pollicis longus muscle. Level Advanced. Accreditation The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Summary An important accessory anatomical variation, exclusively human, and related to the muscular ventres of the flexor pollicis longus and flexor digitorum profundus is frequently denominated Gantzer. These variations have close relations with the anterior interosseous nerve (AIN), which provides, for many authors, by direct compression, one of the rare neuropathic syndromes. In this work, thirty-four forearms were dissected from the collections of the Medical School of the Federal University of Minas Gerais and the Department of Basic Sciences of the Federal University of Juiz de Fora, with a prevalence of 50% of the 34 forearms studied for the Gantzer muscle. The muscle relationship was mainly with the flexor pollicis longus muscle and only one occurrence related to the flexor digitorum profundus muscle, described as a rare occurrence of unilateral double formation of Gantzer muscle. Bilaterality was observed in 88.23% of the findings and the dominant innervation for this muscle variation occurred in 82.35% by the anterior interosseous nerve (AIN). The type morphological in all forms found was the fusiform, with 10.5 cm of total length and an average of 0.3 cm in diameter and all related, as origin, in the medial aspect of the coronoid process of the ulna, next to the origin of the flexor digitorum superficialis muscle. Our work largely reflected the findings of most publications and, considering the controversy of the occurrence of a compressive neuropathy, the data were not sufficient, from a strictly anatomical point of view, to confirm or refute the hypothesis.

Hazards in industry, wars and serious medical reasons determined the increase of the number of amputations and, thus, the need for designing prosthetics that replace the missing segment by imitating its natural movements. Research in prosthetics domain became, consequently, a primary activity both for engineers and physicians. Due to structural and functional acclimation to the complexity of human activities, one of the most difficult to approach limb of the human body is the hand. This paper is aimed to design an anthropomorphic prosthetic hand controlled based on surface electromyography sensors data acquired from two important muscles: flexor pollicis longus muscle and flexor digitorum profundus muscle. Another purpose of the paper consists in providing two main functions of the prosthetic hand, prehension and fingers flexion.

In lower brachial plexus injury, finger flexion after brachialis motor branch transfer is relatively weak. We sought to screen potential branches of the median nerve from the upper trunk for strengthening finger flexion in addition to the brachialis motor branch. However, the spinal origin of the muscular branches of the median nerve based on electrophysiological study was unclear.To determine the spinal origin of the muscular branches of the median nerve.An intraoperative electrophysiological study was carried out in 18 patients who underwent contralateral C7 nerve transfer. After exposure of the brachial plexus nerve roots on the healthy side, the amplitude of the compound muscle action potential of each median nerve-innervated muscle was recorded while the different nerve roots were stimulated.The pronator teres received fibers from C5, C6, and C7. It had more contribution from C5 and C6 than from C7 (P.05). The flexor carpi radialis was innervated mainly by C6 and C7. The nerve branches of the palmaris longus and flexor digitorum superficialis stemmed primarily from C7 and the lower trunk, and no significant difference was found between them (P.05). The flexor digitorum profundus, flexor pollicis longus, pronator quadratus, and abductor pollicis brevis were innervated predominantly by the lower trunk (P.05).This electrophysiological study indicates that the pronator teres branch might be the most feasible alternative donor nerve to supplement the brachialis motor branch and strengthen finger flexion after lower brachial plexus injury.

OBJECTIVE: The relationship of Gantzer muscle to the median and anterior interosseous nerve is debated. METHODS: Ìn an anatomical study with 80 limbs from 40 cadavers the incidence, origin, insertion, nerve supply and relations of Gantzer muscle have been documented. RESULTS: The muscle was found in 54 forearms (68% of limbs) and was supplied by the anterior interosseous nerve. It arose from the deep surface of the flexor digitorum superficialis muscle, (42 limbs), coronoid process (eight limbs) and medial epicondyle (seven limbs). Its insertion was to the ulnar part of flexor pollicis longus muscle. The Gantzer muscle always lay posterior to both the median and anterior interosseous nerve. CONCLUSION: The Gantzer muscle may contribute to the median nerve and anterior interosseous nerve compression. The muscle was found in 68% of limbs and should be considered a normal anatomical pattern rather than an anatomical variation. Level of Evidence IV, Case Series .

Incidence of auxiliary head of the flexor pollicis longus muscle has been described repeatedly. Accessory head has been noted arising from the lateral or more rarely from the medial border of the coronoid process of the ulna. During routine dissection, we found a rare case of an additional slip of tendinous origin of flexor pollicis longus muscle from the medial epicondyle of the humerus. However, such anomaly was not found on the left side. The embryological source and clinical impact of the current incident are discussed.

BACKGROUND: Accessory head of Flexor pollicis longus in the forearm is one of the factors for causing anterior interosseous nerve syndrome. The objectives were to study the incidence, morphology of accessory head of flexor pollicis longus and its relation with median nerve and anterior interosseous nerve. METHODS: The present study was observational and descriptive type. A total of 60 upper limbs from 30 cadavers were dissected in the Department of Anatomy. The accessory head of flexor pollicis longus muscle was identified and its relation with median and anterior interosseous nerve was observed. The shape, origin and insertion of accessory head of flexor pollicis longus were noted. The length and width of the muscle belly and tendon were measured with digital vernier caliper. The findings were compared with that of previous studies. RESULTS: The accessory head of flexor pollicis longus was present in 13(43.3%) cadavers. The shape of muscle was fusiform in 84.61% and slender in 19.38%.Commonest site of origin was coronoid process of ulna (53.33%)., from the medial epicondyle 33.33% and 6.66% each form tendon of brachialis and deep head of pronator teres respectively. The average length and width of muscle belly were 93.48 ± 1.76mm and 7.03 ± 1.43 respectively. The tendon length and width were 20 ± 8.09mm and 0.55 ± 0.23mm. The median nerve was running anteriorly and the anterior interosseous nerve laterally to the muscle belly in all the cases. CONCLUSION: The presence of accessory head of flexor pollicis longus can be an important factor in anterior interosseous nerve syndrome, pronator teres syndrome. The results obtained in the present study would be useful for both physicians and surgeons to know the cause and therefore an appropriate management of the clinical syndromes.

Wrist is an extremely significant and important part of our body. It is the performance index of our work. Previous research has shown that wrist flexion can lead to compression of the median nerve in the carpal tunnel, resulting in numbness, parenthesis and muscle weakness in hand. We present an effective optical approach for the measurement of strain on superficial muscles and tendons due to wrist extension, a remedy for carpal tunnel syndrome. The 3D correlation software computes the in-plane and out of plane strain using pictures taken, using 2 charge coupled device cameras, before and after extension. Strain plots obtained after comparison indicates the strain distribution in anterior compartment of the forearm muscle. The experiment is then repeated for four other participants and the trends are observed. The effect of stretching on the two important anterior components of the forearm muscles, namely the flexor pollicis longus muscle, flexor carpi ulnaris muscle is studied. This study can assist practitioners working in the field of applied anthropology to develop advanced diagnosis methodologies.

Parameters derived from EMG power spectrum are beneficial methods for assessing muscle fatigue. Two important indices are median frequency and mean frequency (MDF and MNF). They have been established as the global muscle fatigue indices, particularly in static muscle contraction of biceps brachii muscle. However, a major problem of these parameters is a nonlinear relationship between muscle load/force and feature value, particularly in cyclic dynamic muscle contraction of forearm muscles. In this study, EMG feature indices that can simultaneously identify both fatigue and load are proposed. Instead of using an entire EMG signal fast Fourier transformation (FFT), a concept of using consecutive FFT has been proposed as known as the “Time-Dependent MDF and MNF” (TD-MDF and TDMNF). The success of TD-MDF and TD-MNF features used to determine muscle fatigue have been presented in a lot of research works, whereas the performance of TD-MDF and TD-MNF used to determine muscle load have been proposed in a few research works. Moreover, it has not previously been evaluated with the forearm muscles. Thus it has been investigated in this study. Four forearm muscles are evaluated including flexor pollicis longus, supinator longus, extensor carpi radialis longus and pronator radii teres. The results showed that the proposed methods have a linear relationship with muscle load in some selected range of TD-MNF for flexor pollicis longus muscle that were not found for traditional MDF and MNF. Moreover, a statistically significant difference between TD-MNF values for different loading conditions (p < 0.2) was observed. The optimal method of TD-MNF was successful when overlapping consecutive window was performed with 512-sample window size and 128-sample window increment.

Biomechanical simulations of tendon transfers performed following tetraplegia suggest that surgical tensioning influences clinical outcomes. However, previous studies have focused on the biomechanical properties of only the transferred muscle. We developed simulations of the tetraplegic upper limb following transfer of the brachioradialis (BR) to the flexor pollicis longus (FPL) to examine the influence of residual upper limb strength on predictions of post-operative transferred muscle function. Our simulations included the transfer, ECRB, ECRL, the three heads of the triceps, brachialis, and both heads of the biceps. Simulations were integrated with experimental data, including EMG and joint posture data collected from five individuals with tetraplegia and BR-FPL tendon transfers during maximal lateral pinch force exertions. Given a measured co-activation pattern for the non-paralyzed muscles in the tetraplegic upper limb, we computed the highest activation for the transferred BR for which neither the elbow nor the wrist flexor moment was larger than the respective joint extensor moment. In this context, the effects of surgical tensioning were evaluated by comparing the resulting pinch force produced at different muscle strength levels, including patient-specific scaling. Our simulations suggest that extensor muscle weakness in the tetraplegic limb limits the potential to augment total pinch force through surgical tensioning. Incorporating patient-specific muscle volume, EMG activity, joint posture, and strength measurements generated simulation results that were comparable to experimental results. Our study suggests that scaling models to the population of interest facilitates accurate simulation of post-operative outcomes, and carries utility for guiding and developing rehabilitation training protocols.

Two women, aged 37 and 38, with definite myotonic dystrophy are presented. Neither patient had clinical myotonia although both experienced intermittent jaw tightness. Electromyographic (EMG) myotonia was seen only in the masseter muscle in one and in the masseter and flexor pollicis longus muscle in the other patient. The detection rate of EMG-myotonia in clinically normal heterozygotes increases if distal, proximal and cranial nerve innervated muscles are examined.

Background and Purpose. The extensibility of the paralysed flexor pollicis longus (FPL) muscle is an important determinant of an effective tenodesis grip in people with C6 and C7 tetraplegia. Therapists believe that splinting can reduce the extensibility of the FPL muscle and thus improve hand function. However, there remains much controversy around the optimal position of splinting and its effectiveness is yet to be verified. The aim of the present study was to determine whether a three-month thumb splinting protocol reduces extensibility of the FPL muscle in people with tetraplegia. Method. An assessor-blinded, within-subject, randomized controlled trial was undertaken. Twenty people with tetraplegia and bilateral paralysis of all thumb muscles were recruited from a sample of convenience. One randomly selected hand of each subject was splinted each night for three months. The splint immobilized the FPL muscle in a relatively shortened position by positioning the carpometacarpal and metacarpophalangeal joint of the thumb in flexion. The other hand remained unsplinted for the duration of the study. Carpometacarpal angle was measured with the application of a standardized torque by a blinded assessor at the beginning and end of the three-month study period. A device specifically designed for this purpose that stabilized the wrist and other joints of the thumb in full extension was used. Results. No subject withdrew from the study. The three-month splinting protocol had a mean treatment effect on carpometacarpal joint angle of 0° (95% CI, −6° to 6°). Conclusion. Splinting the FPL muscle in a relatively shortened position each night for three months does not reduce its extensibility. Copyright © 2006 John Wiley & Sons, Ltd.

In this study, we analyzed the existence of rate-dependent hysteresis in the electromyography (EMG)-force relationship. Eight able-bodied subjects participated in the experiment. Surface EMG signals were acquired from flexor pollicis longus muscle from 0% to 100% maximum voluntary contraction (MVC). The subject was asked to gradually increase grasping force from 0% to 100% MVC and decrease grasping force from 100% to 0% MVC at five different frequencies (1.5, 1, 0.5, 0.25 and 0.125 Hz). Mean absolute value (MAV) was chosen to represent the EMG signals and force signals. In order to compare differences in force between contraction and relaxation periods to EMG activity among different frequency conditions, a hysteresis index (HI), defined as an area inside the hysteresis cycle, was adopted. The results showed that all mean values of HI in different frequency conditions were larger than 0, which proved that hysteresis cycles existed in all frequency conditions. The results also showed that the HI values in different frequency conditions were significantly different from each other (p < 0.005), which proved hysteresis effects in EMG-force relationship were rate-dependent. The rate-dependent hysteresis in EMG-force relationship has a huge potential to improve the estimation performance of grasping force from EMG.

Object There are scant data regarding the anterior interosseous nerve (AIN) in the neurosurgical literature. In the current study the authors attempt to provide easily identifiable superficial osseous landmarks for the identification of the AIN. Methods The AIN in 20 upper extremities obtained in adult cadaveric specimens was dissected and quantified. Measurements were obtained between the nerve and surrounding superficial osseous landmarks. The AIN originated from the median nerve at mean distances of 5.4 cm distal to the medial epicondyle of the humerus and 21 cm proximal to the ulnar styloid process. The distance from the origin of the AIN to its branch leading to the flexor pollicis longus muscle and to the point it travels deep to the pronator quadratus (PQ) muscle measured a mean 4 and 14.4 cm, respectively. The mean distance from the AIN branch leading to the flexor pollicis longus muscle to the proximal PQ muscle was 12.1 cm, and the mean distance between this branch and the ulnar styloid process was 7.2 cm. The mean diameter of the AIN was 1.6 mm at the midforearm. Conclusions Additional landmarks for identification of the AIN can aid the neurosurgeon in more precisely isolating this nerve and avoiding complications. Furthermore, after quantitation of this nerve, the AIN branches can be easily used for neurotization of the median and ulnar nerves, and with the aid of a transinterosseous membrane tunneling technique, passed to the posterior interosseous nerve.

A novel myoelectric hand prosthesis consisting of electromyogram (EMG) signal processing units, a microprocessor-based dc motor servo system, and a 1 degree-of-freedom (DOF) end effector has been developed. The flexion angle and compliance of the finger of this prosthesis can be voluntarily controlled with EMG signals. The biomimetic controller for the myoelectric hand incorporated a model of the neuromuscular control system constructed from an analysis of the force response to length perturbation of the flexor pollicis longus muscle, processing of EMG signals, and the configuration of the hand. Basic functions of the human neuromuscular control system are realized by using position control, force feedback, and variable gain, modulated by EMG signal amplitude. A limb-absent person and four healthy subjects were able to voluntarily control the finger angle and compliance of the prosthesis and were able to easily grasp a soft object after a short training period.

Repeat measures design. The purpose of this study was firstly, to describe a simple clinical tool that can be used to measure the extensibility of the flexor pollicis longus (FPL) muscle; secondly, to test its reliability; and thirdly, to attain some ‘normative’ data of the extensibility of the FPL muscle in a representative sample of people with tetraplegia. A spinal cord injury unit in Sydney. A total of 37 people (62 hands) with C4–C7 tetraplegia. Angle of the carpometacarpal (CMC) joint of the thumb was measured in all subjects with the application of a series of thumb extensor torques. A device specifically designed for this purpose was used to standardize the torque and objectively quantify the CMC joint angle. In addition, repeat measurements were taken 3–5 days later in one subgroup of 13 subjects (one hand per subject) and 3 months later in another subgroup of 13 subjects (one hand per subject). Intraclass correlation coefficients and percent close agreement scores were derived to quantify the 3–5 days and 3-month reliability between repeat measurements. The median CMC angle of the thumb with the application of a 0.044 Nm torque was 63 degrees (range, 20–93 degrees). The intraclass correlation coefficients with the application of a 0.044 Nm torque were 0.88 (95% CI, 0.65–0.96) for measurements taken 3–5 days apart, and 0.90 (95% CI, 0.67–0.97) for measurements taken 3 months apart. This study describes a simple and reliable way of measuring the extensibility of the FPL muscle in people with tetraplegia. This assessment tool and the ‘normative’ data provided in this study can be used to further investigate the contribution of the passive mechanical properties of the FPL muscle to hand function of people with C6 and C7 tetraplegia.

A detailed description of the accessory head of flexor pollicis longus muscle (AHFPL) in the Thai population has not been reported. Because it is one of the causes of anterior interosseous nerve syndrome (AINS), a study was carried out on 120 Thai cadavers (70 embalmed, 50 fresh; 78 male, 42 female) to elucidate the prevalence of AHFPL, its morphology and relationship with the anterior interosseous nerve (AIN). The prevalence of AHFPL was 62.1% (149/240) with 74.5% (111/149) of its origin on medial epicondyle, 23.5% (35/149) on coronoid process and 2% (3/149) on flexor digitorum superficialis muscle. One hundred percent of its insertion was on the ulnar border of flexor pollicis longus tendon, and it was 98% (146/149) fusiform-shaped and 2% (3/149) slender shaped, with a diameter between 0.8-16.0 mm (average 6.7 mm), averaging 6.5 mm on the right and 4.2 mm on the left. The right was significantly statistically larger than the left (P < 0.05). The average distance from the mid-point of the distal wrist crease to the insertion point of AHFPL was 12.8 cm. Four patterns of relationship with AIN were noted including: 1) I AIN passed anterior to AHFPL, 13.4% (20/149); 2) AIN passed lateral to AHFPL, 65.8% (98/149); 3) AIN passed posterior to AHFPL, 8.1% (12/149); and 4) AIN passed both lateral and posterior to AHFPL, 12.8% (19/149). We believe that the latter two patterns (3 and 4) with AIN passing posteriorly would be more likely to be associated with AINS due to anatomic considerations.

Background and Objectives.The accessory head of the flexor pollicis longus muscle (AHFPL), also known as the Gantzer’s muscle, was first described in 1813. The prevalence rates of an AHFPL significantly vary between studies, and no consensus has been reached on the numerous variations reported in its origin, innervation, and relationships to the Anterior Interosseous Nerve (AIN) and the Median Nerve (MN). The aim of our study was to determine the true prevalence of AHFPL and to study its associated anatomical characteristics.Methods.A search of the major electronic databases PubMed, EMBASE, Scopus, ScienceDirect, and Web of Science was performed to identify all articles reporting data on the prevalence of AHPFL in the population. No date or language restriction was set. Additionally, an extensive search of the references of all relevant articles was performed. Data on the prevalence of the AHFPL in upper limbs and its anatomical characteristics and relationships including origin, insertion, innervation, and position was extracted and pooled into a meta-analysis using MetaXL version 2.0.Results.A total of 24 cadaveric studies (n= 2,358 upper limb) were included in the meta-analysis. The pooled prevalence of an AHFPL was 44.2% (95% CI [0.347–0.540]). An AHFPL was found more commonly in men than in women (41.1% vs. 24.1%), and was slightly more prevalent on the right side than on the left side (52.8% vs. 45.2%). The most common origin of the AHFPL was from the medial epicondyle of the humerus with a pooled prevalence of 43.6% (95% CI [0.166–0.521]). In most cases, the AHFPL inserted into the flexor pollicis longus muscle (94.6%, 95% CI [0.731–1.0]) and was innervated by the AIN (97.3%, 95% CI [0.924–0.993]).Conclusion.The AHFPL should be considered as more a part of normal anatomy than an anatomical variant. The variability in its anatomical characteristics, and its potential to cause compression of the AIN and MN, must be taken into account by physicians to avoid iatrogenic injury during decompression procedures and to aid in the diagnosis and treatment of Anterior Interosseous Nerve Syndrome.

Isolated neuropathy of the superficial branch of the radial nerve (SBRN) is a rarely recognized pathology. It was initially described by Wartenberg in 1932. Various causes have been published. We report a case of an unusual injury of the SBRN at the wrist, never been previously reported in the literature. A 40-year-old woman presented with pain and paresthesia over the area of the lateral aspect of the wrist, thumb and first web two months after a blunt trauma of the left forearm. After failure of conservative treatment, surgical exploration found a neuroma of one branch of the SBRN. No distal nerve stump was found. Neuroma resection was performed and the nerve was transposed and embedded into the flexor pollicis longus muscle. With a six months follow-up, the result was satisfactory.

Our previous work in an animal model showed that neuromuscular damping properties help maintain limb posture by effectively dissipating mechanical energy arising from disturbances. The purpose of this study was to determine whether similar damping properties were expressed in intact, normal human muscles. To review briefly, when the reflexively active soleus muscle in a decerebrate cat is coupled to an inertial load, application of a force impulse to the load results in lightly damped oscillations. By calculating the logarithmic decrement in muscle velocity following the impulse (the decrement being related to the amount of energy dissipated from the inertia), we found that damping increased with oscillation amplitude, a nonlinear property. This nonlinearity represents an automatic compensation for larger perturbations. Our findings in parallel experiments on the interphalangeal joint of the human thumb were that the long thumb flexor, the flexor pollicis longus (FPL), displayed mechanical and reflex behavior closely comparable to that reported earlier for the cat soleus, despite differences in architectural and metabolic properties between these muscles. Specifically, by selecting experimental trials that did not include voluntary interventions, we observed amplitude-dependent differences in damping in which larger amplitude movements elicited larger damping than did smaller movements. In addition, even after accounting for amplitude-dependent differences in damping, damping was found to be larger in later cycles than in the first cycle. This nonlinearity indicates that both mechanical properties of muscle and reflex mechanisms are dependent on prior movement history. We propose that this history-dependent behavior arises from the effects of prior movement on stretch reflex gain, and these effects are mediated primarily via changes in muscle spindle properties. Recordings of electromyographic activity from the FPL, during the first and second cycles of oscillation supported this postulate of a reduced reflex gain following prior motion. The functional significance of these nonlinear damping properties is that during the initial muscle stretch, the stiffness is high, which helps to preserve the initial position (although at the expense of promoting oscillation). Subsequently, the ensuing increase in damping helps suppress continuing oscillation. This sequence of varying mechanical properties is broadly analogous to the features of a predictive, or feed-forward controller, designed to produce a response that initially maintains position, and subsequently dampens oscillations. These results show that the intrinsic properties of muscle and spinal reflexes automatically provide a complex time-varying response, appropriate for maintenance of stable limb posture.

The authors report a case of incomplete anterior interosseous nerve syndrome due to mechanical compression by Gantzer's muscle. This accessory muscle induced an isolated paralysis of the flexor pollicis longus with a characteristic pinch attitude. No improvement was shown after six weeks of medical treatment. Recovery was rapid and complete following surgical relief of compression. Anatomical considerations, clinical features, and treatment are discussed.

This is a retrospective study of primary repairs of flexor pollicis longus in 16 children under 15 years of age. Patients with injuries to the median or ulnar nerve at the wrist, crush injuries, skin loss or fracture were excluded. Repairs were carried out within 24 hours using a modified Kessler technique. The mean follow-up was for two years. The final results were evaluated using the criteria of Buck-Gramko and Tubiana. They were good or excellent in all except one patient who had a secondary tendon rupture. When compared with the non-injured thumb, however, there was a significant decrease in active interphalangeal flexion (> 30°) in one-third of cases. A new method of assessment is proposed for the recovery of function of the flexor pollicis tendon which is more suitable for children. Postoperative immobilisation using a short splint had a negative effect on outcome. The zone of injury, an early mobilisation programme or concurrent injury to the digital nerve had no significant effect on the final result.

The authors dissected 72 paired arm to study the anatomy of Gantzer's muscle. The dissection explored course of the median nerve from the elbow to the distal end of the forearm. The following anatomical structures and variations were noted;(1) The presence of a Gantzer's muscle, as well as its relationship to the median and anteriorinterosseous nerves.(2) The origin and insertion of Gantzer's muscle.Results: Gantzer's muscle arose from the medial epicondyle of the humerus in 45 arms (90%), from the coronoid process of the ulna in 3 arms (6%), from the intermuscular fascia in 1 arm (2%), and from a double origin- the medial epicondyle and the coronoid presess-in 1 arm (2%). Insertion was to the proximal part of the tendon of the flexor pollicis longus muscle in all arms.Gantzer's muscle always lies posterior to the median nerve. In 12 out of 50 arms, the muscle passed posterior to the anterior interosseous nerve, and in the remaining 38 arms, the anterior interosseous nerve ran proximal to the muscle along its proximal border and never cross Gantzer's muscle and its tendon.Based on these findings, the authors concluded that Gentzer's muscle rarely contributes to anterior interosseous nerve compression in the proximal forearm.

Anterior interosseous nerve palsy is known to occur uncommonly due to the compression of the nerve by the accessory head of flexor pollicis longus (AHFPL). This study was conducted to investigate the prevalence and origin of the AHFPL and the topographical relationship between the AHFPL and the anterior interosseous nerve in Asians. The AHFPL was present in 48 of 72 arms examined (66.7%), a majority of which originated from the coronoid process. The anterior interosseous nerve was observed to arise from both the medial and posterior aspects of the median nerve. The topographical relationship between the anterior interosseous nerve and the AHFPL was classified into three types depending on if the anterior interosseous nerve crossed the muscular part, or the tendinous part of the AHFPL, or coursed lateral to the AHFPL. The case in which the anterior interosseous nerve crossed the muscular part of the AHFPL occurred most frequently in the current study. The types in which the anterior interosseous nerve may be compressed were also discussed. Clin. Anat. 13:434–438, 2000. © 2000 Wiley-Liss, Inc.

This study reports the treatment of divided flexor pollicis longus (FPL) tendons from 1989 to 1998. The first 30 patients, in whom the tendon was repaired with a Kessler suture and simple epitendinous suture and mobilized using early active motion with only the thumb splinted, achieved 70/73% (White/Buck-Gramcko assessments respectively), excellent or good results and a rupture rate of 17%. The next 39 patients underwent the same treatment but in a splint with the thumb position altered and the fingers also splinted, with 67/72% excellent or good results and a rupture rate of 15%. The next 49 patients underwent repair with a Kessler suture and a reinforced epitendinous suture and the same mobilization as group 2, with 76/80% excellent or good results and a rupture rate of 8%. The final combination of repair and early active mobilization for primary repair of FPL tendons compares favourably with previous methods of treatment.

The split flexor pollicus longus (FPL) tendon transfer is a surgical technique using the radial half of the FPL tendon rerouted dorsally and inserted into the extensor pollicis longus tendon for correction of Froment's sign. A cadaveric model was designed to investigate the effects of the split FPL tendon transfer on pinch strength. Pinch strength was compared for extrinsic thumb flexion (1) without the split FPL and (2) with the split FPL, tensioned at 3 different positions (0 degrees flexion, 30 degrees flexion, and 60 degrees flexion). We report the clinical results of key pinch strength using split FPL tendon transfer as part of thumb reconstruction for 12 thumbs in 10 patients at an average follow-up time of 2 years. The cadaveric study showed no significant difference in pinch force between specimens with or without split FPL transfer or when comparing tensioning at 0 degrees versus 30 degrees versus 60 degrees. Froment's sign wa s reproduced in all cadavers with pinch activation without split FPL transfer and was eliminated in all specimens after the split FPL transfer. In the clinical portion of this study 12 transfers in 10 patients had an average follow-up pinch strength of 33.7 N (range, 18-80 N) and no evidence of Froment's sign. We conclude that the split FPL tendon transfer is an effective method for correction of Froment's sign due to intrinsic paralysis of the thumb.

The reflex responses to brisk, ramp stretch perturbations of the human flexor pollicis longus muscle (FPL) were recorded during isometric and slow concentric or eccentric contractions at similar levels of muscle excitation. The subjects flexed their thumb to push down against a thumb-rest, whose position was controlled by a servo-controlled motor. In different runs, the stretch perturbations were imposed when the thumb-rest was stationary (isometric) or was flexing or extending the interphalangeal joint of the thumb at a constant velocity, i.e. during concentric or eccentric contractions of FPL. The latency of the most prominent component of the electromyographic reflex in the isometrically contracting muscle was about 60 ms, measured from the command signal. The amplitude of this response was sharply reduced during the non-isometric contractions. While not dependent on the direction, this modulation of the reflex response increased with the speed of active movement of the interphalangeal joint (flexion or extension). The response was greatly reduced during concentric or eccentric movements as slow as 1.6 mm x s[-1] (approximately 5 degrees x s (-1) at the joint). When the force rather than the position of the thumb-rest was servo-controlled, the stretch response to perturbation again diminished with speed in a self-paced flexion task, compared with an isometric "hold" condition.

In 1813 Gantzer described 2 accessory muscles in the human forearm which bear his name (Wood, 1868; Macalister, 1875; Testut, 1884; Le Double, 1897). The more frequent of the 2 accessory muscles or ‘accessorius ad pollicem’ was found to arise from the coronoid process of the ulna, coursing distally to attach into the flexor pollicis longus muscle (flexor pollicis longus accessory head, FPLah). The less frequently observed or ‘accessorius ad flexorem profundum digitorum’ was again found to arise from the coronoid process and course to join into the flexor digitorum profundus (flexor digitorum profundus accessory head, FDPah). Since their initial description, they have been examined in further detail by a number of authors (Wood, 1868; Macalister, 1875; Le Double, 1897; Dykes & Anson, 1944; Mangini, 1960; Malhotra et al. 1982; Dellon & McKinnon, 1987; Kida, 1988). These studies, most of them focusing on the FPLah, all show different results of prevalence, origin, insertion, relations and nerve supply. We undertook this study with the aim of providing a more accurate account of the detailed morphology of both accessory muscles because of the above-mentioned inconsistent anatomical descriptions and the lack of information as to important aspects such as vascular supply, morphology (shape and length) and the coexistence of both accessory heads.

We describe a case of Scheie's syndrome with a closed rupture of the flexor pollicis longus tendon, probably caused by a combination of extrinsic and intrinsic tendon changes. Early detection of carpal tunnel syndrome in all patients who have some form of mucopolysaccharidosis in which this is a universal occurrence (such as Scheie's syndrome), is recommended. Release of the carpal tunnel prevents long term complications, as described in this case report.

Purpose To evaluate the natural history and etiology of decreased thumb interphalangeal (IP) joint flexion after volar plate fixation of distal radius fractures. Methods A total of 46 patients who underwent volar plating of 48 distal radius fractures by a single surgeon were retrospectively studied. Of those patients, 24 (24 wrists) exhibited loss of thumb IP joint flexion (group 1) and 22 (24 wrists) retained thumb IP joint flexion (group 2) with attempted thumb opposition to the small finger after surgery. All patients were seen at regular intervals until IP joint flexion returned and fracture healing was confirmed radiographically. Patient demographics, fracture patterns, surgical variables, and final radiographs were compared between groups. Twenty patients in group 1 were seen after a mean of 6.5 months (range, 5–12 mo) for specific outcome measurements. Eight cadaveric specimens were used to replicate the flexor carpi radialis approach to the distal radius and evaluate flexor pollicis longus tendon excursion. Results There were no significant differences in fracture pattern, patient age or sex, injured extremity dominance, time to surgery, incision length, plate composition, plate length, tourniquet time, or final wrist radiographs between groups. In group 1, active thumb IP joint flexion returned on average 52 days (range, 19–143 d) postoperatively. At final evaluation in this group, mean IP joint flexion was 11° less than the contralateral thumb IP joint; however, patient-determined outcomes were favorable in most cases. In the cadaveric specimens, excursion of the flexor pollicis longus tendon decreased with sequential soft tissue dissection and retraction. Conclusions Loss of thumb IP joint flexion after volar plating of distal radius fractures was common, and motion returned to near normal in most cases within 2 months. Partial stripping of the flexor pollicis longus muscle from investing fascia and bone and retraction of soft tissues are likely etiological factors. Type of study/level of evidence Prognostic III.

Introduction: The present study was planned to analyze the Accessory Head of the Flexor Pollicis Longus muscle’ (AHFPL) or Gantzer’s muscle and its incidence. It is an additional muscle in the forearm which might cause pressure symptoms to the underlying structures, especially to the anterior interosseus nerve. Materials and Methods: This study was performed on 180 upper limbs (90 right and 90 left). The morphology and the morphometry of AHFPL was done. In this investigation, we observed the various shapes, origins, insertions, nerve supplies and relations of the muscle. Observations and Results: The incidence of the accessory head of the flexor pollicis longus muscle was seen in 92 cases (51.11%). It was found bilaterally in 66 (71.73%) cases and unilaterally in 26 cases (28.26%), among which, in 16, it was seen on the right side and in 10 on the left side. With the increasing incidence of the Gantzer’s muscle, one can call it as an evolutionary muscle. Conclusion: The present study supplements the knowledge on the morphology of AHFPL muscle and its relationship with the anterior interosseus nerve. An increased incidence of this muscle may be the causative factor for the complete anterior interosseous nerve syndrome.

We investigated the role of local cutaneous signals and of co-contraction of antagonists in repeated judgements of heaviness of weights lifted by flexor pollicis longus. A reference weight lifted by right thumb flexion was matched to a weight lifted by left thumb flexion. Anaesthesia of the right thumb, or of the superficial radial, dorsal ulnar or mixed radial nerves failed to impair accuracy of weight judgements. However, perceived heaviness significantly increased by 85% and 20% following anaesthesia of the thumb and dorsal radial surface of the hand, respectively, confirming a role for cutaneous inputs from these areas in motor control of the thumb.

Background In tetraplegics, thumb and finger motion traditionally has been reconstructed via orthopedic procedures. Although rarely used, nerve transfers are a viable method for reconstruction in tetraplegia. Objective To investigate the anatomic feasibility of transferring the distal branch of the extensor carpi radialis brevis (ECRB) to the flexor pollicis longus (FPL) nerve and to report our first clinical case. Methods We studied the motor branch of the ECRB and FPL in 14 cadaveric upper limbs. Subsequently, a 24-year-old tetraplegic man with preserved motion in his shoulder, elbow, wrist, and finger extension, but paralysis of thumb and finger flexion underwent surgery. Seven months after trauma, we transferred the brachialis muscle with a tendon graft to the flexor digitorum profundus. The distal nerve of the ECRB was transferred to the FPL nerve. Results The branch to the ECRB entered the muscle in its anterior and proximal third. After sending out a first collateral, the nerve runs for 2.4 cm alongside the muscle and bifurcates intramuscularly. A main branch from the anterior interosseous nerve, which entered the muscle 3 cm from its origin on the radius, innervated the FPL. The ECRB and FPL nerves had similar diameters (∼1 mm) and numbers of myelinated fibers (∼180). In our patient, 14 months after surgery, pinching and grasping were restored and measured 2 and 8 kg strength, respectively. Conclusion Transfer of the ECRB distal branch to the FPL is a viable option to reconstruct thumb flexion.

We re-examined the issue of how a subject's intention to react to a joint perturbation may modulate the long-latency M2 stretch reflex response. The experiments were done on the flexor pollicis longus muscle (FPL) of the human thumb, for which there is evidence that its M2 reflex response is mediated, at least in part, by a pathway that traverses the motor cortex. The participation of the cerebral cortex in the genesis of the M2 reflex response may allow for a modulation of its amplitude, based on the intention of the subject. To test whether the M2 response is genuinely modulated by the subject's intention, we examined the magnitude of this response as a function of the FPL background level of activation, measured by the surface rectified and filtered EMG. The subject was instructed either to oppose the perturbation as quickly as possible, not to react, or to relax as quickly as possible after the onset of the perturbation. The time integral of the long latency FPL EMG response, computed between 40 and 70 ms following the onset of stretch, was plotted against the mean torque produced by the distal inter-phalangeal joint of the thumb, or against the mean background FPL EMG. There were no significant differences in the FPL M2 EMG responses for different instructions. The amplitude of the reflex response was dependent only--in an approximately linear manner--on the background level of muscle activation. The total joint stiffness (intrinsic plus reflex) was also calculated for each combination of instruction and background torque.(ABSTRACT TRUNCATED AT 250 WORDS)

Resume Les auteurs rapportent le cas d'une tumeur a cellules geantes de la gaine tendineuse du long flechisseur propre du pouce chez une enfant. Cette tumeur benigne habituellement rencontree chez la femme de 30 a 50 ans reste d'etiopathogenie tres contreversee ; l'existence d'un traumatisme initial est retrouvee dans 50 % des cas. L'observation concerne une petite fille de 7 ans ayant une tumefaction du pouce droit depuis deux ans. L'exerese chirurgicale a permis de faire le diagnostic de certitude par l'examen anatomo-pathologique. Le recul est actuellement de deux ans, sans recidive locale.

This study was conducted to examine the accessory head of flexor pollicis longus muscle (ahFPL) and its relation with the anterior interosseous nerve (AIN) in human fetuses and adult cadavers. Ninety fetus forearms and 52 adult cadaver forearms were dissected to evaluate the incidence, morphology, and innervation of the ahFPL. The ahFPL was observed in 29/90 (32%) of the fetus forearms and 20/52 (39%) of the adult cadaver forearms. The overall side incidence was 34.5% (49/142) among total forearms examined. On the other hand, the population incidence of ahFPL was 42% (19/45) in fetuses while it was 50% (12/24) in adult cadavers. So, the overall incidence in humans was 44.9% (31/69) in the population studied. Compression of the AIN in the forearm by the ahFPL is known as one of the causes of the anterior interosseous nerve syndrome (AINS). So, the relation of ahFPL with the AIN was evaluated, and in light of previous classifications a modified new classification is proposed. The most common relation detected in this study was Type IVa (71.4%) (AIN and its branches coursed posterior to the ahFPL). While Type I was not observed in this study, the incidences of Type II, Type III, and Type IVb (all AIN branches 'without AIN itself' coursed posterior to the ahFPL) were 2%, 14.3%, and 12.3%, respectively. The Types I, IVa, and IVb are thought to be associated with complete or incomplete types of AINS and Type III with incomplete type of AINS only.

Background The origin of the flexor pollicis longus muscle can vary, causing compression of the anterior interosseous nerve in the forearm. The topographic relationship of the flexor pollicis longus to the median and anterior interosseous nerves must be considered when these nerves are decompressed. The anterior interosseous nerve is a motor nerve supplying the flexor pollicis longus, the flexor digitorum profundus, and the pronator quadratus. Unusual etiologic conditions can occasionally cause isolated neuropathy of the flexor pollicis longus branch from the anterior interosseous nerve. Methods Six patients presented with isolated paralysis of the flexor pollicis longus, four following venipuncture in the cubital fossa and two following arthroscopy of the elbow joint. Cadaveric dissections were performed to examine any anatomy clinically relevant to the above techniques. The structure of the flexor pollicis longus nerve branch at different levels was examined with macroscopic and microscopic dissections and immunohistochemistry. Results In each case, clinical symptoms resolved completely with conservative treatment. Dissection of cadaver arms showed that the nerve branch to the flexor pollicis longus joins the anterior interosseous nerve in the proximal third of the forearm and shares a common epineurium, but has its own fascicle up to the proximal aspect of the elbow. The branch to the flexor pollicis longus has no proximal interneural cross-connections up to the main trunk of the median nerve. Conclusion The variable relationship of the superficial cubital veins to the underlying muscles and minimally invasive approaches to the elbow joint may cause an isolated neuropathy in the motor branch to the flexor pollicis longus, with a resultant solitary paralysis of the muscle.

1. Human manual dexterity has been linked by some to biomechanical adaptations of the hand and by others to neural adaptations. To investigate neural adaptations, the present study using the performance of four muscles acting on the index and thumb, quantified weight matching and electromyography. 2. The accuracy (i.e. reproducibility) of weight matching was used to investigate whether thumb muscles (i.e. flexor pollicis longus (FPL) and adductor pollicis (AP)) perform differently from index muscles (i.e. flexor digitorum profundus (FDP) and first dorsal interosseous (FDI)), and whether intrinsic hand muscles (AP and FDI) perform differently from extrinsic ones (FPL and FDP). 3. Subjects lifted reference weights on the right which represented predetermined percentages of a force generated in a maximum voluntary contraction (MVC) ranging from 2.5% to 35% MVC (and to 50% MVC in two muscles) and matched them with a variable weight lifted in the same way on the left. 4. Analysis of the coefficients of variation (c.v., expressed as a percentage) and the standard deviations calculated for repeated estimates of perceived heaviness, revealed significant differences in the accuracy of weight matching between different muscles and between reference weights. Based on the c.v., subjects lifted more accurately with FPL and AP (the two thumb muscles) than with the two index muscles. The two intrinsic hand muscles (FDI and AP) were equally accurate, and significantly more accurate than FDP which was the least accurate muscle. The high accuracy for FPL remained when accuracy was expressed in terms of the torque produced by the muscles when lifting the reference weights, and also when the torques were converted to absolute intramuscular forces. 5. Accuracy (based on c.v.) decreased significantly with light weights and increased with heavy weights for all muscles except FPL, which was equally accurate over a very wide range of weights (< 2.5% to 50% MVC). When data from all muscles were pooled, the c.v. increased from 12.9 to 19.1 as the weights lifted decreased from 35% to 2.5% MVC. 6. To examine the functional implications of the weight-matching study, electromyographic activity (EMG) was recorded with fine-wire electrodes from the same four muscles while subjects lifted cylinders of different widths (17-50 mm) and weights (15-1000 g). For recordings in which integrated EMG was linearly related to force up to maximal levels, the amplitudes of the EMGs at 'lift off' and at the mid-point of the 'hold' phase of the task were expressed relative to the maximal EMG during a MVC.(ABSTRACT TRUNCATED AT 400 WORDS)