Extensor Indicis Research Articles

Extensor indicis opponensplasty: a modified evaluation system

Extensor indicis opponensplasty is the gold standard treatment for the restoration of opposition in individuals with median nerve injuries, and it has excellent outcomes. Most authors have used the Sundraraj and Mani scoring system, which considered a thumb reaching any fingertip as a good or excellent outcome. To refine the technique for extensor indicis opponensplasty, we propose an informative yet simple system to describe outcomes. This study included 13 patients who underwent extensor indicis opponensplasty for median nerve injuries, with four isolated and nine combined. Six patients had triple insertions, and seven had single/double insertions. The patients were evaluated using the Sundraraj and Mani system and our proposed system for the primary outcome. Secondary outcomes included return to productivity and complications. We demonstrated that 92% of the patients achieved excellent results according to the Sundraraj and Mani system. We achieved pulp to little pulp (5A) in seven patients, tip to little pulp (5B) in two patients, pulp to ring pulp (4A) in one patient, tip to ring pulp (4B) in one patient, pulp to middle finger pulp (3A) in one patient, and fair opposition (1) in one patient. A 5A score was achieved in five patients with triple insertion. The new system proposed in this study better facilitates the comparison of technical variations of opponensplasty. Level of evidence:Level IV, therapeutic study.

Transposition of the Extensor Indicis Proprius (EIP) for inveterate post-traumatic rupture of the Extensor Pollicis Longus (EPL) of the hand. 12 clinical cases.

Background and aim of work: Subcutaneous tendon rupture of the Extensor Pollicis Longus (EPL) is one of the most frequent injuries of the extensor tendons of the hand. In this paper, we report our experience on 12 cases of atraumatic subcutaneous EPL lesions treated in our hospital with Extensor Indicis Proprius (EIP) transposition. Methods: This observational study was conducted between January 2015 and December 2018 in the Casa di Cura “Prof. Nobili”, Castiglione dei Pepoli (Bologna). Twelve patients were included in the study, nine of whom were females and three were males, with an average age of 72 years (range: 40-84 aa). The average follow-up was 32.4 months. The preoperative diagnosis was subcutaneous atraumatic rupture of the EPL tendon in all cases. Results: The clinical outcome was excellent in all the patients at the end of follow-up. At the second clinical control, all patients achieved complete active extension of the distal phalanx of the first finger. We did not notice any intra- or extra-operative complications, and the post-operative course was regular in all cases. Conclusion: EIP transposition has allowed an almost complete recovery of the ability to extend the first finger in patients treated in our hospital, in line with what is described in the literature. In addition, patients’ satisfaction rate was excellent in all cases. Based on the good results and the low rate of complications affecting the donor area, we consider EIP transposition surgery to be a valid option for inveterate EPL ruptures. (www.actabiomedica.it)

Morphological study of anomalous deep extensors of the hand

Background Anomalous muscles on the dorsum of the hand include the extensor medii proprius (EMP), extensor indicis et medii communis (EIMC), extensor digitorum brevis manus (EDBM), and anomalous extensor indicis proprius (aEIP). They are commonly seen during routine cadaveric dissections and hand surgeries. There are very few studies on them in the recent past. Hence, this study was conducted with the aim of studying their incidence and morphology. Materials and Methods This study was conducted at the Pushpagiri Institute of Medical Sciences and Research Centre, Thiruvalla, Kerala, over a period of 15 months, on 80 free upper limbs. Deep extensor muscles of the forearm were dissected. The frequency of the anomalous muscles was noted. Length and width of the muscles and tendons were measured using thread, ruler, and vernier calipers. The median and range were calculated. The musculotendinous (MT) junction of the EIP was observed. It was considered to be aEIP if its MT junction was beyond the distal edge of the extensor retinaculum in wrist flexion. Results EMP was seen in 8.75% of the limbs, with average muscle length and width of 4.53 ± 0.7 cm and 3.7 ± 0.8 mm and average tendon length and width of 9.7 ± 1.2 cm and 1.6 ± 0.8 mm, respectively. Frequency of EIMC was 3.75%, its average muscle length and width being 3.67 ± 1.14 cm and 2.3 ± 0.6 mm and its tendon length and width being 9.8 ± 0.61 cm and 2.0 ± 1.7 mm. Incidence of EDBM was 2.5%; its average muscle length and width being 4.5 ± 0.71 cm and 1.25 ± 0.3 mm and tendon length and width being 3.15 ± 0.91 cm and 3.5 ± 0.7 mm. Frequency of aEIP was observed to be 6.25%. Conclusion Anomalous extensors have a frequency of less than 10%. Tendons of the EMP and EIMC are very thin and asymptomatic. The EDBM belly is distal to the retinaculum and does not cause symptoms, unless hypertrophied. aEIP passes through the narrow compartment and is more likely to cause pain.

Anatomical Description of the Forelimb Muscles of the Brown-Throated Sloth (Bradypus variegatus)

Background: Brown-throated sloths are mammals of the order Xenarthra, suborder Pilosa, family Bradypodidae. These folivorous and arboreal animals, which possess a peculiar type of arboreal quadrupedalism, move through the forest canopy by means of suspensory locomotion. On the ground, their extremely slow movements make them easy targets for road accidents, often leading to serious injury or even death. This paper describes the forelimb muscles of the brown-throated sloth (Bradypus variegatus), updating the literature on the subject to help veterinarians in clinical and surgical interventions on this species, and to provide data for comparative animal anatomy.Materials, Methods & Results: Five brown-throated sloths (Bradypus variegatus Schinz, 1825), two adults and three babies were dissected. The animals were donated by the Arruda Câmara Zoo and Botanical Park in João Pessoa, state of Paraíba, Brazil, where they were thawed and fixed in 10% formalin. The sloths’ forelimbs were dissected by lifting and folding over a skin flap to expose, identify and describe the underlying musculature. The dissection revealed the following muscles: supraspinatus, infraspinatus, deltoideus, teres major, subscapularis, coracobrachialis, brachialis, biceps brachii, triceps brachii, anconeus epitrochlearis, dorsoepitrochlearis, brachioradialis, supinator, pronator teres, pronator quadratus, extensor carpi radialis, extensor carpi ulnaris, extensor carpi obliquus, flexor carpi radialis, flexor carpi ulnaris, extensor digitorum communis, extensor digitorum lateralis, palmaris longus, flexor digitorum superficialis, flexor digitorum profundus, extensor indicis longus second finger, extensor indicis brevis second finger, extensor digitorum third finger, abductor digitorum second finger, abductor digitorum third finger, palmaris brevis, and interosseous muscles. Characteristics found in this species revealed differences in the muscular development of the upper forelimb, whose muscles are less developed than those of the lower forelimb, which are visibly more developed with greater muscle density. An interesting feature of this musculature is the presence of three flexor tendons, short and thick, originating from the flexor muscles, which give the hand of the brown-throated sloth a hook-like aspect.Discussion: Our observations indicate that some of the muscles are very similar to those of other animals of this order and also of domestic mammals. However, the most relevant characteristics resemble those of arboreal animals and humans, since the forearm and hand pronation and supination muscles are essential for their arboreal habits. Therefore, all the pronator and supinator muscles of the brown-throated sloth are well developed. Due to the functional adaptations of the species of the family Bradypodidae, the shoulder muscles, especially the deltoideus, are more developed, providing greater support to the shoulder joint, and their origin and insertion assist in faster and easier movements, albeit exerting less force. The group of flexor muscles in this species gives the forearm stronger and more concentrated action than the extensor muscles. This study enabled us not only to produce a more precise description of the muscles of the forelimb of this species but also to update the literature, since there are few relevant studies on the subject and the terms in the literature are outdated and no longer in use. Keywords: sloth, Bradypodidae, morph

Optimal Placement of Needle Electromyography in Extensor Indicis: A Cadaveric Study.

Objective To identify the center of extensor indicis (EI) muscle through cadaver dissection and compare the accuracy of different techniques for needle electromyography (EMG) electrode insertion.MethodsEighteen upper limbs of 10 adult cadavers were dissected. The center of trigonal EI muscle was defined as the point where the three medians of the triangle intersect. Three different needle electrode insertion techniques were introduced: M1, 2.5 cm above the lower border of ulnar styloid process (USP), lateral aspect of the ulna; M2, 2 finger breadths (FB) proximal to USP, lateral aspect of the ulna; and M3, distal fourth of the forearm, lateral aspect of the ulna. The distance from USP to the center (X) parallel to the line between radial head to USP, and from medial border of ulna to the center (Y) were measured. The distances between 3 different points (M1– M3) and the center were measured (marked as D1, D2, and D3, respectively).ResultsThe median value of X was 48.3 mm and that of Y was 7.2 mm. The median values of D1, D2 and D3 were 23.3 mm, 13.3 mm and 9.0 mm, respectively.ConclusionThe center of EI muscle is located approximately 4.8 cm proximal to USP level and 7.2 mm lateral to the medial border of the ulna. Among the three methods, the technique placing the needle electrode at distal fourth of the forearm and lateral to the radial side of the ulna bone (M3) is the most accurate and closest to the center of the EI muscle.

Predicting Tendon Tissue Grafting Source From the Extensors of Long Fingers: A Systematic Review of Cadaveric Studies

Background: The use of tendon tissue for transfer and grafting is a common practice in hand surgery. Many local tendons are usually used, mainly that of the palmaris longus muscle. However, this tendon could be absent in up to 46%. Extra slips of the extensor digitorum communis (EDC) and extra tendons such as the extensor indicis (EI) and the extensor digiti minimi (EDM) could be valuable sources for tendon tissue. Methods: A systematic review was conducted to quantify the proportion of extra slips in relation to each tendon and extra tendons in relation to each long finger. The aim is to better predict the location of tendon tissue sources on the dorsum of the hand in reconstructive surgery. Results: Based on 39 studies including 7847 hands, the cumulative frequencies of extra slips and extra tendons and the association between double-slip frequency and ancestry were as follows: (1) the little finger showed the highest cumulative frequency of extra slips (96.54%), followed by the ring (37.5%), long (30.6%), and index (9.5%) fingers; (2) the index with its EI and its variants and the little finger with its EDM bear by far the highest cumulative frequency of extra tendons (≈100%); and (3) double slips are found to be rare in Indian populations, most prevalent in Japanese populations, more prevalent in the index and little fingers of Caucasians, and more prevalent in the ring fingers of Middle Eastern populations. Conclusions: Knowledge of the frequencies of extra slips for each long extensor tendon and extra tendons for each long finger along with their prevalence in different populations would improve: (1) location prevision of tendon source for tendon grafting; and (2) surgical planning while supporting a patient-centered approach. Evidence-based hand anatomy would have a major potential to contribute to the practice of an evidence-based hand surgery. Predicting the possible tendon sources that could be present on the dorsum of the hand is thought to be very valuable for hand surgeons. In addition and from an evolutionary perspective, we hypothesized that the observed significantly higher frequency values of the double-slip and triple-slip types of the EDC of the ring finger, EDC of the little finger, and EDM might indicate a natural selection tendency for a higher independence of the former digits in the future evolution of the human hand.

T125. Neural oscillatory changes by the co-ordinated multifocal transcranial magnetic burst stimulation in the motor cortex

Abnormal neural oscillation in human brains such as overt synchronous beta oscillation in Parkinson’s disease can be one of the neural pathological signatures. How to desynchronize the abnormal oscillation is an important issue for treating the Parkinson’s disease. Therefore, neurologists tried to adopt multiple external oscillatory stimulation to desynchronize the neuronal oscillation of the target frequency as clinical treatment. The concept has been approved by coordinated reset neuromodulation in the deep brain stimulation setting. However, it’s unclear if similar effect can be made through noninvasive stimulation. The noninvasive Co-Ordinated Multifocal Burst Stimulation (COMBS) method by utilizing multiple transcranial magnetic stimulation is proposed in this study for investigating the neural oscillatory changes in the motor cortex. Five healthy volunteer subjects including four females were recruited. Three independent figure of eight coils surrounded the motor hot-spot of extensor indicis proprius (EIP) muscle in the left primary motor cortex. We conducted 50 Hz bursts composed of three pulses with 80% active motor threshold intensity of EIP. To desynchronize the target frequency around 6 Hz, we set one stimulation cycle as every coil firing once randomly, with total duration last for 172.5 ms. Three cycles composed one stimulation block. Total 65 blocks with 315 ms pause between each block were conducted. We implemented finger rapid alternative movement task, which was consisted of three behavioral states including preparation, movement, and resting state. Each subject performed 40 trials before and after COMBS session. EEG signal were collected through 64 EEG channels Neuroscan amplifier system. EEG signal processing contained (1) power spectrum density analysis on the C3 or FC3 channel corresponding to the motor cortex, (2) comparison of the event-related synchronization (ERS) or desynchronization (ERD) before and after the COMBS protocol. The experiment results showed the increasing frequency power from 5 to 20 Hz in the C3 and FC3 electrodes after the COMBS. However, the target frequency around 6 Hz was not desynchronized after stimulation. Consistent ERD and ERS of both α and β frequency during the task were observed. Whereas after COMBS, both α and β frequency spectrum power increased in all behavioral states, without changing desynchronization or synchronization ratio. This study proposed an innovative Co-Ordinated Multifocal Burst Stimulation (COMBS). Experimental findings revealed that the neural oscillation change in the target frequency cannot be decreased effectively by COMBS on healthy motor cortex, but it can increase the power spectrum in the 5–20 Hz frequency composition. In the future work, we will adopt this paradigm on the Parkinson’s disease patients for understanding the further neural oscillation changes on the motor cortex.

F163. Role of ultrasonography in severe distal median nerve neuropathy

Patients with severe carpal tunnel syndrome may present with atrophy of thenar muscles and loss of sensations in the median nerve distribution. Nerve conduction studies do not provide precise localization especially when compound muscle action potential (CMAP) is absent over the abductor pollicis brevis (APB) and the 2nd lumbrical and no senssory action potential is recordable. In such patients, presumptive diagnosis of entrapment at the carpal tunnel is made based upon topography of denervation observed on needle EMG; however, denervation limited to the APB points to median nerve involvement distal to the branching of anterior interoseous nerve and not necessarily to the carpal tunnel. This study was aimed at determining how often a localization other than carpal tunnel results when ultrasound imaging is used as a complementary test. Patients with a clinical diagnosis of severe carpal tunnel syndrome seen in 2 years with the following criteria were included in the study: 1. Absent CMAP over APB and 2nd lumbrical on stimulation of the median nerve at the wrist and the elbow; 2. Absent sensory potentials over digits on median nerve stimulation at the wrist; 3. Needle EMG showing denervation of APB with normal findings in flexor pollicis longus, pronator teres, first dorsal interosseous and extensor indicis. Patients with diabetes mellitus and other causes of neuropathy or those with prior history of carpal tunnel release were excluded. Ultrasonic studies were done with 8–18 MgHz probe. CSA of median nerve was measured at the level of distal wrist crease and mid forearm (short axis view). The nerve was also studied in the long axis view across the carpal tunnel measuring the diameter at the carpal tunnel inlet and at the narrowest part of the nerve within the carpal tunnel. Measurements included cross sectional area (CSA) at wrist and forearm as well as diameter at the carpal tunnel inlet and within carpal tunnel. Wrist/forearm CSA ratio was calculated. Ratio between diameter at the carpal tunnel inlet and the smallest diameter within the tunnel was also calculated. A total of 18 patients were included consisting of 10 males and 8 females; age range was 30–91 with a mean of 70. 12 involved the right and 6 the left hand. CSA at wrist was 22.5 ± 7.4 mm2. Wrist forearm ratio was 2.8 ± 0.9. Ratio between diameter at inlet and within carpal tunnel was 0.49 ± 0.1. In 16 patients ultrasonic imaging confirmed entrapment at carpal tunnel. In 2 patients abnormality was found proximal to the carpal tunnel, one instance of neuroma and one of dislocated lunate. In 16 out of 18 patients presenting with no CMAP over APB and 2nd lumbrical and with absent SNAPs, presumptive diagnosis of CTS was further supported by ultrasonic imaging. In 2 patients additional diagnostic features were detected by ultrasonic imaging.

Myopathy With SQSTM1 and TIA1 Variants: Clinical and Pathological Features.

The aim of this study is to identify the molecular defect of three unrelated individuals with late-onset predominant distal myopathy; to describe the spectrum of phenotype resulting from the contributing role of two variants in genes located on two different chromosomes; and to highlight the underappreciated complex forms of genetic myopathies. Clinical and laboratory data of three unrelated probands with predominantly distal weakness manifesting in the sixth-seventh decade of life, and available affected and unaffected family members were reviewed. Next-generation sequencing panel, whole exome sequencing, and targeted analyses of family members were performed to elucidate the genetic etiology of the myopathy. Genetic analyses detected two contributing variants located on different chromosomes in three unrelated probands: a heterozygous pathogenic mutation in SQSTM1 (c.1175C>T, p.Pro392Leu) and a heterozygous variant in TIA1 (c.1070A>G, p.Asn357Ser). The affected fraternal twin of one proband also carries both variants, while the unaffected family members harbor one or none. Two unrelated probands (family 1, II.3, and family 3, II.1) have a distal myopathy with rimmed vacuoles that manifested with index extensor weakness; the other proband (family 2, I.1) has myofibrillar myopathy manifesting with hypercapnic respiratory insufficiency and distal weakness. The findings indicate that all the affected individuals have a myopathy associated with both variants in SQSTM1 and TIA1, respectively, suggesting that the two variants determine the phenotype and likely functionally interact. We speculate that the TIA1 variant is a modifier of the SQSTM1 mutation. We identify the combination of SQSTM1 and TIA1 variants as a novel genetic defect associated with myofibrillar myopathy and suggest to consider sequencing both genes in the molecular investigation of myopathy with rimmed vacuoles and myofibrillar myopathy although additional studies are needed to investigate the digenic nature of the disease.

Electrophysiologic Features of Radial Neuropathy in Childhood and Adolescence

BackgroundWe analyzed the clinical and electrophysiologic patterns of nerve injury in pediatric patients with radial neuropathy. MethodsThis is a retrospective analysis of 19 children and adolescents with radial neuropathy. ResultsThe mean subject age was 12 years (range one month to 19 years), 56% were female, and 53% had traumatic etiologies. Weakness in the finger and wrist extensors was the prevailing complaint (82%). Predominant localization was at the posterior interosseous nerve (37%), followed by the radial nerve below the spiral groove (32%), the radial nerve at the spiral groove (26%), and the radial nerve above the spiral groove (5%). Extensor indicis proprius compound muscle action potential amplitude was reduced in 86% of cases when tested, with a median axon loss estimate of 78%. The radial sensory nerve action potential amplitude was reduced in 53% of all cases, and in 83% of cases affecting the main radial trunk with a median axon loss estimate of 100%. For neuropathy affecting the main radial trunk, there was a high correlation of extensor indicis proprius median axon loss estimate and radial sensory nerve action potential median axon loss estimate (r = 0.72, P = 0.02). Neurogenic changes were seen in the extensor indicis proprius, extensor digitorum communis, extensor carpi radialis, and brachioradialis in 88%, 94%, 60%, and 44% of cases, respectively. Pathophysiology was demyelinating in 10%, axonal in 58%, and mixed in 32%. ConclusionsIn contrast to adults, where localization at the spiral groove predominates, radial neuropathy in children and adolescents is commonly localized at the posterior interosseous nerve or at the distal main radial trunk. Pediatric radial neuropathy is frequently of traumatic etiology and axonal pathophysiology.

Extensor indicis proprius muscle and its variants together with the extensor digitorum brevis manus muscle: a common classification. Clinical significance in hand and reconstructive surgery.

The extensor indicis proprius (EIP) is a muscle of the forearm that originates from the posterior surface of the ulna and the adjacent interosseous membrane and attaches to the index finger. Many anatomical variations of this muscle have been reported in the literature. The extensor digitorum brevis manus (EDBM) is a variant muscle found on the back of the wrist and hand. These muscle variants should be considered in the context of clinical syndromes and reconstructive hand surgery. The aim of the present study was to describe in detail the normal and variant anatomy of these muscles and propose new systematic classifications. Formol-carbol-fixed Europid upper limbs (n = 176) were examined in the Department of Anatomy, Histology and Embryology at the Medical University of Sofia for variations of the EIP and occurrences of the EDBM. We found normal anatomy in 147 (84%) of the specimens examined and we measured the length and width of the muscle belly and tendon of the EIP. Variations of the EIP in the other 29 upper limbs (16%) included replacement of the EIP by an EIB, coexistence of the EIP and EIB, presence of accessory tendons, and additional muscles. Knowledge of anatomical variations of forearm muscles is important because they can cause clinical syndromes or have implications for reconstructive surgery, most often as tendon transfers in response to functional loss of other forearm muscles.

Two-stage extensor tendon graft using the Paneva-Holevitch procedure: A new technique

Reconstruction of the extensor tendons remains a therapeutic challenge. Tendon transfers and grafts are a potential source of morbidity at the donor site, and the graft stock is limited. In the index finger, the tendon of the extensor indicis proprius can be anastomosed to the tendon of the extensor digitorum, and then the extensor digitorum tendon turned over after being cut at the forearm. We assessed the feasibility of this reconstruction on 12 upper limbs from 6 cadavers and we report the case of a 24-year-old patient who suffered destruction of the extensor apparatus in the index and middle fingers. For the cadaver study, in each case, the tendon could be moved onto the proximal interphalangeal joint, after having done an anastomosis downstream of the extensor retinaculum. The mean graft length was 13cm (9.7–15.2). This method was used in one clinical case with an excellent outcome. This is a simple technique that is without consequences since the tendons used are already cut, therefore saving a tendon graft. This technique should be part of our therapeutic arsenal.

Variations in distal attachment of muscles of the leg, foot and the hand and their clinical implications in population of central Ethiopia

Anatomical variations in the distal attachment of lower and upper limb muscles are of paramount importance in surgical and clinical practice. Reports show variations in the insertion of the fibularis longus and brevis tendon from the lateral compartment of the leg, extensor hallucis longus and fibularis tertius from the anterior compartment of the leg, flexor digitorium brevis from the sole of the foot and the existence of accessory muscles in the dorsum of the hand. However, reports are scanty from Ethiopia. The present study was aimed at assessing the existence of variation in the distal attachments of muscles of the lower and upper limbs in the central Ethiopia population. Twenty-two formalin fixed cadavers were used. Careful dissection, critical observation and imaging were done accordingly. We have found the presence of two tendons of extensor halluces longus in one cases, absence of the lateral tendon to the 5thdigit of the flexor digitorum brevis of the sole of the foot in another case and the presence of the accessory extensor indicis muscle on the dorsum of the hand in a third case. These variations are important owing to the use of the tendons in tendon transfer surgeries to correct deformities of the hand, foot and ankle joint, and also for radiologists, clinicians, and surgeons in order to prevent adverse surgical events.

In vivo confirmation of the reliability of the dorsal tangential view of the wrist

The purpose of the study was to evaluate the reliability of the dorsal tangential view (DTV) of the wrist using direct visualization of the extensor compartments in vivo. Twelve patients with extensor tendon complications [nine patients with extensor synovitis, two patients with isolated extensor pollicis longus (EPL) rupture, one patient with EPL and extensor indicis proprius rupture] after volar plating of a distal radius fracture were enrolled in the study. We obtained DTVs in the operating room before implant removal and explored the extensor compartments during synovectomy or tendon reconstruction to confirm suspected screw penetration. We confirmed screw penetration on 10 patients during exploration of the extensor compartments. DTV was able to detect seven of these dorsal cortex breaches. There were no false positive results, which we had defined as a screw penetrating an extensor compartment preoperatively, but not visible on the DTV. Of these seven breaches, one was in the second compartment, four were in the third compartment, and the remaining two were in the fourth compartment. The DTV is sufficiently reliable to be used routinely to reduce postoperative extensor tendon complications during volar plating of the distal radius. Level of evidence4 (case series) diagnostic.

The Relationships Between Surface Measurements and Underlying Tendon Autograft Length for Upper Extremity Reconstructive Surgery

The availability of tendon grafts is an important consideration for successful upper extremity reconstructive surgery, including flexor or extensor tendon reconstructions, tendon transfers, and ligament reconstructions. Graft selection is based on availability, expendability, ease of harvest, and length. Given variations in patient height and extremity length, existing average values may provide suboptimal insight into actual tendon lengths available. The purpose of this study is, therefore, to pursue a method of estimating available donor tendon lengths based on easily measured anatomical surface landmarks. Thirty cadaveric upper and lower extremity limbs were dissected and the length of commonly harvested tendon grafts including the palmaris longus, extensor indicis proprius, extensor digiti minimi, plantaris, and second long toe extensor was measured. Surface forearm length (from finger tip to cubital fossa) and surface fibular length (from lateral malleolus to fibular head) were also measured. Correlations between surface measurements and underlying tendon lengths were analyzed, and linear models were generated that predicted tendon length as a function of surface measurements. Surface measurements were correlated with underlying tendon length (R= 0.46 - 0.66). Linear models could predict tendon lengths based on surface measurements. A ratio of donor tendon length compared with the limb segment measured was established for each tendon and can be applied to estimate donor tendon length. For the upper extremity tendons, the multipliers for the palmaris longus, extensor indicis proprius, and extensor digiti minimi were 0.51, 0.20, and 0.18, respectively. Lower extremity tendon ratios for the plantaris and extensor digitorum longus were 0.69 and 0.60, respectively. Although length of available donor tendon can be a limiting variable at the time of surgery, surgeons may be better able to estimate underlying tendon lengths using easily obtained superficial measurements. Information obtained from these cadaveric measurements may aid in preoperative planning in hand and upper extremity surgery.

Extensor indicis proprius tendon transfer using shear wave elastography

The means for judging optimal tension during tendon transfers are approximate and not very quantifiable. The purpose of this study was to demonstrate the feasibility of quantitatively assessing muscular mechanical properties intraoperatively using ultrasound elastography (shear wave elastography [SWE]) during extensor indicis proprius (EIP) transfer. We report two cases of EIP transfer for post-traumatic rupture of the extensor pollicis longus muscle. Ultrasound acquisitions measured the elasticity modulus of the EIP muscle at different stages: rest, active extension, active extension against resistance, EIP section, distal passive traction of the tendon, after tendon transfer at rest and then during active extension. A preliminary analysis was conducted of the distribution of values for this modulus at the various transfer steps. Different shear wave velocity and elasticity modulus values were observed at the various transfer steps. The tension applied during the transfer seemed close to the resting tension if a traditional protocol were followed. The elasticity modulus varied by a factor of 37 between the active extension against resistance step (565.1 kPa) and after the tendon section (15.3 kPa). The elasticity modulus values were distributed in the same way for each patient. The therapeutic benefit of SWE elastography was studied for the first time in tendon transfers. Quantitative data on the elasticity modulus during this test may make it an effective means of improving intraoperative adjustments.

Neuromorphic meets neuromechanics, part II: the role of fusimotor drive

Objective. We studied the fundamentals of muscle afferentation by building a Neuro–mechano–morphic system actuating a cadaveric finger. This system is a faithful implementation of the stretch reflex circuitry. It allowed the systematic exploration of the effects of different fusimotor drives to the muscle spindle on the closed-loop stretch reflex response. Approach. As in Part I of this work, sensory neurons conveyed proprioceptive information from muscle spindles (with static and dynamic fusimotor drive) to populations of α-motor neurons (with recruitment and rate coding properties). The motor commands were transformed into tendon forces by a Hill-type muscle model (with activation-contraction dynamics) via brushless DC motors. Two independent afferented muscles emulated the forces of flexor digitorum profundus and the extensor indicis proprius muscles, forming an antagonist pair at the metacarpophalangeal joint of a cadaveric index finger. We measured the physical response to repetitions of bi-directional ramp-and-hold rotational perturbations for 81 combinations of static and dynamic fusimotor drives, across four ramp velocities, and three levels of constant cortical drive to the α-motor neuron pool. Main results. We found that this system produced responses compatible with the physiological literature. Fusimotor and cortical drives had nonlinear effects on the reflex forces. In particular, only cortical drive affected the sensitivity of reflex forces to static fusimotor drive. In contrast, both static fusimotor and cortical drives reduced the sensitivity to dynamic fusimotor drive. Interestingly, realistic signal-dependent motor noise emerged naturally in our system without having been explicitly modeled. Significance. We demonstrate that these fundamental features of spinal afferentation sufficed to produce muscle function. As such, our Neuro–mechano–morphic system is a viable platform to study the spinal mechanisms for healthy muscle function—and its pathologies such as dystonia and spasticity. In addition, it is a working prototype of a robust biomorphic controller for compliant robotic limbs and exoskeletons.

Changes in T<sub>2</sub>-weighted MRI of supinator muscle, pronator teres muscle, and extensor indicis muscle with manual muscle testing

[Purpose] In order to detect muscle activity with manual muscle testing, T2-weighted magnetic resonance (T2w-MR) images were detected by a 0.2 T compact MRI system. [Subjects and Methods] The subjects were 3 adult males. Transverse T2-weighted multi-slice spin-echo images of the left forearm were measured by a 39 ms echo-time with a 2,000 ms repetition time, a 9.5 mm slice thickness, 1 accumulation and a total image acquisition time of 4 min 16 s. First, T2w-MR images in the resting condition were measured. Then, manipulative isometric contraction exercise (5 sec duration) to the supinator muscle, the pronator teres muscle or the extensor indicis muscle was performed using Borg’s rating of perceived exertion (RPE) scale of 15–17. The T2w-MR images were measured immediately after the exercise. [Results] T2w-MR image intensities increased significantly in the supinator muscle, the pronator teres muscle and the extensor indicis muscle after the exercise. However, the image intensities in the rest of the muscle did not change. [Conclusion] Using T2w-MR images, we could detect muscle activity in a deep muscle, the supinator muscle, and a small muscle, the extensor indicis muscle. These results also support the reliability of the manual muscle testing method.

Optimal Radial Motor Nerve Conduction Study Using Ultrasound in Healthy Adults.

ObjectiveTo obtain reference values, to suggest optimal recording and stimulation site for radial motor nerve conduction study (RmNCS), and to analyze the correlation among RmNCS parameters, demographics and ultrasonography (US) findings.MethodsA total of 55 volunteers participated in this study. We hypothesized that ‘lateral edge of spiral groove (A)’ was the optimal stimulation site, and the ‘largest cross-sectional area (CSA) of extensor indicis proprius (EIP) muscle (B)’ was the optimal recording site. The surface distance between ‘A’ and the lateral epicondyle of the humerus divided by upper arm length, was named the spiral groove ratio. The surface distance between ‘B’ and the ulnar styloid process divided by forearm length, was named the EIP ratio. Using US, we identified these sites, and further conducted RmNCS.ResultsData was collected from 100 arms of the 55 volunteers. Mean amplitude and latency were 5.7±1.1 mV and 5.7±0.5 ms, respectively, at the spiral groove, and velocity between elbow and spiral groove was 73.7±7.0 m/s. RmNCS parameters correlated significantly with height, weight, arm length, and CSA of the EIP muscle. Spiral groove ratio and EIP ratio were 0.338±0.03 and 0.201±0.03, respectively; both values were almost the same, regardless of age, sex and handedness.ConclusionWe established a reference value and standardized method of RmNCS using US. Optimal RmNCS can be conducted by placing the recording electrode 20% (about one-fifth) of forearm length from the ulnar styloid process, and stimulating at 34% (about one-third) of the humeral length from the lateral epicondyle.

Transfer of the extensor indicis proprius branch of posterior interosseous nerve to reconstruct ulnar nerve and median nerve injured proximally: an anatomical study.

Proximal or middle lesions of the ulnar or median nerves are responsible for extensive loss of hand motor function. This occurs even when the most meticulous microsurgical techniques or nerve grafts are used. Previous studies had proposed that nerve transfer was more effective than nerve grafting for nerve repair. Our hypothesis is that transfer of the posterior interosseous nerve, which contains mainly motor fibers, to the ulnar or median nerve can innervate the intrinsic muscles of hands. The present study sought to investigate the feasibility of reconstruction of the deep branch of the ulnar nerve and the thenar branch of median nerve by transferring the extensor indicis proprius branch of the posterior interosseous nerve obtained from adult cadavers. The results suggested that the extensor indicis proprius branch of the posterior interosseous nerve had approximately similar diameters and number of fascicles and myelinated nerve fibers to those of the deep branch of ulnar nerve and the thenar branch of the median nerve. These confirm the feasibility of extensor indicis proprius branch of posterior interosseous nerve transfer for reconstruction of the deep branch of the ulnar nerve and the thenar branch of median nerve. This procedure could be a novel and effective method for the functional recovery of the intrinsic muscles of hands after ulnar nerve or median nerve injury.