Palmar Interosseous Research Articles

Development of the Interosseous Muscles of the Human Hand: Morphological and Functional Aspects of the Terminal Insertion.

To date, there have been no studies conducted on the development of interosseous muscles (IO) in the human hand. This study aimed to investigate the development of these muscles in order to clarify their terminal insertions and their relationship with the metacarpophalangeal joints. Serial sections of 25 human specimens (9 embryos and 16 fetuses) between the 7th and 14th weeks of development, sourced from the Collection of the Department of Anatomy and Embryology at UCM Faculty of Medicine, were analyzed bilaterally using a conventional optical microscope. Our findings revealed that, during the 7th week of development, the metacarpophalangeal interzone mesenchyme extended into the extensor apparatus of the fingers. Furthermore, we observed that the joint capsule and the tendon of the IO derive from the articular interzone mesenchyme. By the end of the 7th week, corresponding to Carnegie stage 21, the myotendinous junction appeared, initiating cavitation of the metacarpophalangeal joint. During the fetal period, the terminal insertions of the IO were identified: both the dorsal interosseous (DI) and palmar interosseous (PI) muscles insert into the metacarpophalangeal joint capsule and establish a connection with the volar plate located at the base of the proximal phalanx and the extensor apparatus. Some muscle fibers also attach to the joint capsule at the level of the proximal synovial cul-de-sac. The functional implications of these findings are discussed within this work. This study provides the first detailed description of the development of the interosseous muscles in the human hand.

Normal Values of the Second Interosseous Pinch: A Measurement of Pure Ulnar-Innervated Intrinsic Muscles of the Hand

The second palmar interosseous muscle is innervated solely by the ulnar nerve, and second palmar interosseous pinch (2IP) strength may be a good indicator of ulnar nerve motor function. The goal of this study was to describe the 2IP test and establish its normative values, stratified by age, sex, and dominance. Volunteers were recruited to participate in this study at various community locations. Patients over the age of 18 years were eligible for this study. Demographic information on all subjects was collected. The volunteers were asked to pinch a hydraulic pinch gauge between the index and middle finger proximal phalanges with the proximal and distal interphalangeal joints flexed and without recruiting the thumb. Three 2IP measurements were taken for each hand. Descriptive statistics and analysis of covariance were performed to determine the effect of age, sex, dominance, and side on 2IP. We analyzed the 2IP strength using the 2IP test across 3 trials to determine whether it was affected by repeated testing. Two hundred thirty-eight patients met the inclusion criteria (45 ± 21 years, 55% women, 87% right-hand dominant). There was no statistically significant difference between dominant and nondominant hands or among the 3 trials. There was a statistically significant correlation between age and 2IP strength ranging between 0.32 and 0.44 kg. Age and sex showed a statistically significant association with 2IP strength, with patients of older age and women having weaker 2IP. We determined normative values for 2IP strength using a sample from a normal population. More studies are needed to validate these results. Second interosseous pinch strength may be a useful tool to assess ulnar nerve function.

Targeted Muscle Reinnervation in the Hand: A Technical Roadmap

Targeted muscle reinnervation (TMR) transfers cut the nerve endings to the motor nerves of the nearby muscles to reduce neuroma pain and/or enhance prosthetic function. To guide surgeons, anatomic "roadmaps" describe nerve transfer options for TMR at various locations. This study aimed to landmark and measure motor entry points (MEPs) to the hand interossei muscles in the context of TMR for digital nerve neuroma management. Ten fresh-frozen cadaveric hands were dissected to describe the innervation arising from the deep branch of the ulnar nerve to the dorsal interossei (DIs) and palmar interossei (PIs) muscles. The location of MEPs relative to the bone and soft tissue landmarks and the size of the target nerves were measured. The MEPs for the DIs and PIs were found in the central third of the metacarpal. The MEPs to the PIs averaged 23.3-24.7 mm from the median nerve. The length of nerve proximal to the MEP was limited, ranging between 6.5 ± 2.6 mm for the first PI and 10.5 ± 2.7 mm for the second PI. Similarly, minimal nerve proximal to the MEP of the DI was available for mobilization. Access to the first PI innervation required substantial release of the thenar musculature. Motor nerve diameter averaged 0.85-0.97 mm. In considering TMR for the management or prevention of digital nerve neuromas, the motor branches to the second and third PIs are the most accessible and best approached volarly, whereas motor branches to the DIs take more direct routes into the muscle, making volar exposure difficult. Nerve length proximal to the MEP is short, requiring that most of the nerve length for neurorrhaphy comes from the digital nerve. Size mismatch at the neurorrhaphy site is favorable compared to more proximal TMR. Targeted muscle reinnervation in the hand is technically feasible for a patient with a symptomatic neuroma after digital amputation.

Innervation and vascular supply of the first dorsal interosseous muscle and palmar interosseous muscle of the index: An anatomic descriptive study

The first dorsal interosseous muscle (FDI) and palmar interosseous muscle of the index (P2I) are essential for the strength and mobility of the index finger. This study aims to describe the course of the deep branch of the ulnar nerve (DBUN) and the blood supply to these muscles. An anatomical cadaver study was carried out with 14 upper limbs from fresh, non-embalmed cadavers. All limbs were filled with an equal amount, based on weight, of colored silicone and diluent that was combined and catalyzed with 5% curing agent. The location of the DBUN's termination was specified relative the carpometacarpal joint. Every artery supplying either muscle was identified and documented. The DBUN had a slightly convex path, distal to the hook of the hamate and penetrated the FDI muscle at an average 41% of the second metacarpal length. An average of 1.3 branches to the P2I and 2.6 branches to the FDI were found. Four artery pedicles coming from the deep palmar arch supply the FDI with an average of one consistent and exclusive pedicle to the FDI and three pedicles heading to the P2I. According to the classification of Mathes and Nahai, the FDI has a type 2 blood supply and the P2I has a type 3 blood supply. In-depth knowledge of the vascular network supplying the FDI and P2I muscles and the course of the DBUN is essential when the DBUN is damaged or when dissecting these muscles for index pollicization.

Abstract 118: Targeted Muscle Reinnervation In The Hand: An Anatomical Study For Identification Of Target Motor Entry Points

Purpose: Targeted muscle reinnervation has emerged as a treatment for and prevention of symptomatic neuromas and may be beneficial in the hand. Anatomic studies establishing feasibility in the hand or landmarks to identify the motor entry points to the intrinsic muscles have not been performed. The purpose of this study was to provide details regarding the motor entry points to the intrinsic muscles, determine which motor entry points are identifiable dorsally, and develop recommended sensory to motor entry point nerve coaptations for prophylactic TMR at the time of ray amputation or for management of symptomatic neuromas. Methods: Motor entry points to the intrinsic hand muscles were dissected in five fresh latex-injected cadavers. Number of motor entry points, diameter, surface of entry, and distance from dorsal (Lister’s tubercle) and volar (hamate hook) landmarks was recorded for each target muscle. The digital sensory nerve diameters were measured for size comparison. Results: Motor entry points were identified to all nineteen intrinsic muscles through a volar approach and twelve muscles through dorsal approach. For all fingers there were at least two motor entry points consistently identified dorsally at the base of each amputation site innervating expendable muscles. Motor entry points to the thenar muscles were only reliably identified through a volar approach. Two recommended nerve coaptations for each digit amputation were identified. All had favorable sensory:MEP diameter ratio of less than 2:1. Recommended targets for index finger amputation include transfer of the radial digital nerve to the MEP to first dorsal interossei (1.46mm average diameter, 62.69% distance from Lister’s tubercle to the metacarpophalangeal joint of amputated finger; sensory:MEP diameter ratio of 1.32) and ulnar digital nerve to first palmar interossei (0.98mm, 58.32%; 1.69). The long finger radial digital nerve is best coapted to the MEP for second dorsal interossei (1.26mm, 60.11%; 1.48) and ulnar digital nerve to third dorsal interossei (1.26mm, 57.41%; 1.24). Ring finger ideal targets include the radial digital nerve to the MEP for fourth dorsal interossei (1.22mm, 62.75%; 1.46) and ulnar digital nerve to third lumbrical (1.12mm, 81.62%; 1.5). Lastly, the ideal target for the small finger radial digital nerve is to the MEP for third palmar interossei (0.76mm, 64.11%; 1.95) and ulnar digital nerve to fourth lumbrical (0.9mm, 82.04%; 1.71). Conclusion: Targeted muscle reinnervation is feasible to be performed in the hand. The intrinsic muscles have motor entry points found at consistent distances from bony landmarks both dorsally and volarly. These results can be applied clinically to assist surgeons in identifying the locations of motor entry points to the intrinsic muscles when performing targeted muscle reinnervation in the hand for both neuroma treatment and prevention.

A novel nerve transfer: The first palmar interosseous motor branch of the ulnar nerve to the recurrent motor branch of the median nerve

IntroductionThe recovery of recurrent motor branch of the median nerve might be delayed in high level median nerve injuries due to the long reinnervation distance. The aim of this study is to define a novel nerve transfer to restore the opposition and pinch. MethodsTwo fresh frozen hand cadavers were used for the study. The motor branch of the first palmar interosseous muscle of the ulnar nerve was identified and dissected. Thenar branch of the median nerve was dissected from its insertion site. The motor branch of the first palmar interosseous muscle of the ulnar nerve was transferred to the thenar motor branch of the median nerve. Axon counts were examined histopathologically. Clinically this nerve transfer was performed for two female patients with a high-level median nerve injury. Mehta opposition scores were 21 and 20, respectively and the results were satisfactory six months after the surgery. DiscussionAlthough exploration and repair are recommended as the first treatment for median nerve injuries, the waiting time until the motor branch is reinnervated is critical in high level lesions. Nerve transfers become very important for fast recovery. ConclusionsThis new nerve transfer proposal may be an important step in nerve transfer surgery.

Intrinsic Muscles of Human-like Robotic Hand using McKibben Actuators

This paper presents the intrinsic muscles of a Human-like Robotic Hand (HR-Hand), with a focus on dorsal interossei and palmar interossei muscles. Three links of palmar and four links of dorsal interossei muscles were fabricated according to human hand anatomy using 1.3 mm thin McKibben actuators. The experimental result using single index finger shows that the robotic hand could achieve palmar adduction and dorsal abduction and assist in flexion of fingers that imitate the actual function in the human hand.

Long term results of primary repair of combined cuts of median and ulnar nerves on forearm

The objective of this clinical study was to evaluate sensory and motor functions in the later period following primary repair of combined injuries of the ulnar and median nerves in the forearm at proximal, middle, and distal levels. Later period sensory evaluation of ulnar and median combined cuts was performed using two-point discrimination and monofilament tests. On the other hand, motor evaluation was performed by determining dorsal palmar interosseus strength for the ulnar nerve and abductor pollicis brevis muscle strength for the median nerve. Cold intolerance, object recognition, and weight discrimination were also reviewed. In total, 26 patients with ulnar-median combined cut and aged between 5 and 59 years were included in this study. Although no deficiency was observed in the sensory functions of any of the patients, a decrease in tactile sensation was detected in the median sensory region in 12 (46%) patients and in the ulnar sensory region in 7 (26%) patients. The most significant loss in terms of motor functions was detected in the opposition pinch strength. Two patients developed claw hand and two showed joint contracture. Ideal treatment for peripheral nerve injuries should be primary repair. Restoration of the motor function in the median nerve is relatively easier than that in the ulnar nerve. No significant difference was observed in terms of sensory function. An alternative is needed for primary repair because of lack of motor function in proximal ulnar incisions. There is no standardization of tests performed for peripheral nerve repair.

A case of The third palmar interosseous muscle hypoplasia

A case of The third palmar interosseous muscle hypoplasia

A case of restriction of little finger adduction by rupture of 3rd palmar interosseous muscles

A case of restriction of little finger adduction by rupture of 3rd palmar interosseous muscles

A Novel Variation of the 3rd Palmar Interosseous Muscle, with Functional Analysis of the Effect on Moment Arms About the Metacarpophalangeal Joint

A Novel Variation of the 3rd Palmar Interosseous Muscle, with Functional Analysis of the Effect on Moment Arms About the Metacarpophalangeal Joint

Differentiating C8–T1 Radiculopathy from Ulnar Neuropathy: A Survey of 24 Spine Surgeons

Study Design Questionnaire. Objective To evaluate the ability of spine surgeons to distinguish C8–T1 radiculopathies from ulnar neuropathy. Methods Twenty-four self-rated “experienced” cervical spine surgeons completed a questionnaire with the following items. (1) If the ulnar nerve is cut at the elbow, which of the following would be numb: ulnar forearm, small and ring fingers; only the ulnar forearm; only the small and ring fingers; or none of the above? (2) Which of the following muscles are weak with C8–T1 radiculopathies but intact with ulnar neuropathy at the elbow: flexor digiti minimi brevis, flexor pollicis brevis, abductor digiti minimi, abductor pollicis brevis, adductor pollicis, opponens digiti minimi, opponens pollicis, medial lumbricals, lateral lumbricals, dorsal interossei, palmar interossei? Results Fifteen of 24 surgeons (63%) correctly answered the first question—that severing the ulnar nerve results in numbness of the fifth and fourth fingers. None correctly identified all four nonulnar, C8–T1-innervated options in the second question without naming additional muscles. Conclusion The ulnar nerve provides sensation to the fourth and fifth fingers and medial border of the hand. The medial antebrachial cutaneous nerve provides sensation to the medial forearm. The ulnar nerve innervates all intrinsic hand muscles, except the abductor and flexor pollicis brevis, opponens pollicis, and lateral two lumbricals, which are innervated by C8 and T1 via the median nerve. By examining these five muscles, one can clinically differentiate cubital tunnel syndrome from C8–T1 radiculopathies. Although all participants considered themselves to be experienced cervical spine surgeons, this study reveals inadequate knowledge regarding the clinical manifestations of C8–T1 radiculopathies and cubital tunnel syndrome.

Origin of surface motor unit potentials in hypothenar motor unit number estimation

Far-field potentials (FFPs) from muscles other than the abductor digiti minimi (ADM) may interfere with motor unit number estimation (MUNE) from that muscle. We identified the origin of each surface motor unit potential (SMUP) during hypothenar MUNE using the multiple point stimulation method in 20 control subjects by recording from individual ulnar-innervated muscles with a common proximal reference (pref). ADM SMUPs comprised 39.0% of the accepted SMUPs, followed by those from the fourth dorsal interosseous muscle (14.0%), the fourth lumbrical muscle (9.2%), and the second and third palmar interosseous muscles (8.8% each). The percentage of ADM SMUPs varied from 18% to 73% of accepted SMUPs among individual subjects. Accepted non-ADM SMUPs were usually much smaller than ADM SMUPs, and many more non-ADM SMUPs were excluded due to their small size. A large contribution from non-ADM or non-hypothenar SMUPs obscures the meaning of the MUNE value.

Gross anatomical observations of the palmar interossei muscles in humans: A cadaveric study

Objectives: The interossei muscles of the hand provide a foundation for all the intrinsic hand movements. They occupy the intervals between the metacarpal bones and are divided into a palmar and dorsal set. The palmar interossei are smaller than dorsal interossei and lie on the palmar surface of the metacarpal bones rather than between them. The present study aimed to evaluate the number and variations in the palmar interosseous muscles. Methods: Thirty hands from 15 human cadavers (10 males and 5 females, of age ranging from 50 to 65 years) in the Department of Anatomy, Kasturba Medical College, Manipal were studied to explore the prevalence of palmar interosseous. Results: The palmar interossei showed variations, i.e., bipennate, hypertrophied muscle and absence of first palmar interossei. These findings are rare and are less reported. The study also agrees upon the prevalence of four palmar interossei as suggested by different studies. The nerve supply to the interossei when traced was normal in all the specimens and was provided by the deep branch of the ulnar nerve. Conclusion: Ample knowledge of the possible variations in these muscles is very essential for clinicians and surgeons dealing with fractures, stiff joints, claw toe or tendon transfers.

Nerve conduction studies of median motor nerve and median sensory branches according to the severity of carpal tunnel syndrome.

ObjectiveTo evaluate each digital branch of the median sensory nerve and motor nerves to abductor pollicis brevis (APB) and 2nd lumbrical (2L) according to the severity of carpal tunnel syndrome (CTS).MethodsA prospective study was performed in 67 hands of 41 patients with CTS consisting of mild, 23; moderate, 27; and severe cases, 17. Compound muscle action potentials (CMAPs) were obtained from APB and 2L, and median sensory nerve action potentials (SNAPs) were recorded from the thumb to the 4th digit. Parameters analyzed were latency of the median CMAP, latency difference of 2L and first palmar interosseous (PI), as well as latency and baseline to peak amplitude of the median SNAPs.ResultsThe onset and peak latencies of the median SNAPs revealed significant differences only in the 2nd digit, according to the severity of CTS, and abnormal rates of the latencies were significantly lower in the 2nd digit to a mild degree. The amplitude of SNAP and sensory nerve conduction velocities were more preserved in the 2nd digit in mild CTS and more affected in the 4th digit in severe CTS. CMAPs were not evoked with APB recording in 4 patients with severe CTS, but obtained in all patients with 2L recording. 2L-PI showed statistical significance according to the severity of CTS.ConclusionThe branch to the 4th digit was mostly involved and the branch to the 2nd digit and 2L were less affected in the progress of CTS. The second digit recorded SNAPs and 2L recorded CMAPs would be valuable in the evaluation of severe CTS.

And then there were four: Anatomical observations on the pollical palmar interosseous muscle in humans

Although anatomists generally agree upon the presence of four interosseous muscles in the human hand, the number and identity of the palmar interosseous muscles remains contentious. Recent studies suggest that a majority of human hands possess four palmar interossei, yet most contemporary texts suggest the presence of only three. The pollical palmar interosseous muscle (PPIM), associated with the first digit, has been alternatively interpreted as a distinct muscle, part of another hand muscle, or nonexistent. We examined 45 hands from 23 human cadavers to investigate the prevalence of this muscle and found it to occur in varying degrees of expression in 91% of specimens. We also tested the hypothesis that the PPIM forms the smaller part of a "parallel muscle combination" and is therefore ideally suited to act as a proprioceptive organ. Results do not show a significantly higher density of muscle spindles in the PPIM relative to the adjacent adductor pollicis, provisionally refuting this hypothesis. The presence of the PPIM, observed in the majority of hands from several populations, indicates that it should be regularly included in mainstream anatomy texts and atlases.

Aging and movement errors when lifting and lowering light loads

The purpose was to determine the influence of movement variability and level of muscle activation on the accuracy of targeted movements performed with the index finger by young and older adults. Twelve young (27.4 ± 4.4 years) and 12 older adults (74.5 ± 8.9 years) attempted to match the end position of an index finger movement to a target position when lifting and lowering a light load (10% of the maximum). Visual feedback was provided after each trial. Movement error was calculated as the absolute distance from the target. Movement variability was quantified as the standard deviation of finger acceleration and the variability of end position across trials. The EMG activity of first dorsal interosseus (FDI) and second palmar interosseus (SPI) muscles was measured with intramuscular electrodes. Older adults exhibited greater spatial and temporal errors and greater variability in finger acceleration and end position during both the lifting and lowering tasks. Older adults lifted the load by activating FDI less but SPI the same as young adults, whereas they lowered the load by activating SPI less and FDI the same as young adults. In addition, older adults exhibited lower variability across trials in SPI activation when lifting the load and lower variability for FDI activation when lowering the load. The findings demonstrate that the decrease in spatial and temporal accuracy observed in older adults when lifting and lowering a light load to a target position was due to greater movement variability and differences in antagonistic muscle activity.

Timing variability and not force variability predicts the endpoint accuracy of fast and slow isometric contractions

The purpose of the study was to determine the contributions of endpoint variance and trajectory variability to the endpoint accuracy of goal-directed isometric contractions when the target force and contraction speed were varied. Thirteen young adults (25 +/- 6 years) performed blocks of 15 trials at each of 2 contraction speeds and 4 target forces. Subjects were instructed to match the peak of a parabolic force trajectory to a target force by controlling the abduction force exerted by the index finger. The time to peak force was either 150 ms (fast) or 1 s (slow). The target forces were 20, 40, 60, and 80% of the maximal force that could be achieved in 150 ms during an MVC. The same absolute forces were required for both contraction speeds. Endpoint accuracy and variability in force and time along with intramuscular EMG activity of the agonist (first dorsal interosseus) and antagonist (second palmar interosseus) muscles were quantified for each block of trials. The principal dependent variables were endpoint error (shortest distance between the coordinates of the target and the peak force), endpoint variance (sum of the variance in peak force and time to peak force), trial-to-trial variability (SD of peak force and time to peak force), SD of the force trajectory (SD of the detrended force from force onset to peak force), normalized peak EMG amplitude, and the SD of normalized peak EMG amplitude. Stepwise multiple linear regression models were used to determine the EMG activity parameters that could explain the differences observed in endpoint error and endpoint variance. Endpoint error increased with target force for the fast contractions, but not for the slow contractions. In contrast, endpoint variance was greatest at the lowest force and was not associated with endpoint error at either contraction speed. Furthermore, force trajectory SD was not associated with endpoint error or endpoint variance for either contraction speed. Only the trial-to-trial variability of the timing predicted endpoint accuracy for fast and slow contractions. These findings indicate that endpoint error in tasks that require force and timing accuracy is minimized by controlling timing variability but not force variability, and that endpoint error is not related to the amplitude of the activation signal.

Myofascial Compartments of the Hand in Relation to Compartment Syndrome: A Cadaveric Study

Acute compartment syndrome of the hand is an emergency requiring prompt surgical decompression. This cadaveric study aims to identify the myofascial compartments of the hand by detailed dissection and direct visualization, to provide an accurate anatomical basis for surgical decompression. Fourteen fresh-frozen cadaveric hands were dissected. The findings were recorded by still digital photography. There was no well-defined tough fascia overlying the thenar muscles, the hypothenar muscles, or the adductor pollicis. Areolar tissue was present between the individual thenar and hypothenar muscles. A distinct band of fascia was noted over the entire length of the ulnar three dorsal interosseous muscles. A band of fascia was noted over the distal portion of the palmar interossei but not over the proximal aspect. The above findings were found in all 14 specimens. A layer of loose areolar tissue was noted over the dorsal aspect of the first web space in eight specimens, whereas a distinct band of fascia was noted overlying the first dorsal interosseous muscle in the remaining six. This study has shown that no distinct tough fascia surrounded any of the intrinsic muscles of the hand completely. The thin filmy fascia partially encasing some of the muscles is unlikely to contribute to development of compartment syndrome. It is postulated that the unyielding overlying skin may serve as a constricting layer in addition to the fascia and contribute to raised intracompartmental pressures.

Endpoint accuracy for a small and a large hand muscle in young and old adults during rapid, goal-directed isometric contractions

The minimum variance theory proposes that stronger (larger) muscles produce less variable trajectories compared with weaker (smaller) muscles and thus can accomplish more accurate contractions. The purpose of the study was to determine the influence of muscle size and trajectory variability on the endpoint accuracy of goal-directed isometric contractions. Twelve young (25 +/- 5 years) and 12 old adults (76 +/- 6 years) performed 100 trials with each of two muscles in both hands. Subjects were instructed to match the peak of a force trajectory to a target force by controlling either the abduction (first dorsal interosseus muscle; FDI) or adduction force (second palmar interosseus muscle; SPI) exerted by the index finger of each hand. The time to peak force was 150 ms and the peak force required was 25% of the maximal force that could be achieved in 150 ms. Endpoint accuracy and variability in force and time along with intramuscular EMG activity of the agonist muscle (FDI and SPI) involved in each task were quantified for each set of 100 trials. The MVC force was less for the SPI muscle, and the force endpoint error and variance were greater in the SPI muscle compared with the FDI muscle. Conversely, endpoint measures that included timing were similar for the two muscles. Trajectory variability was greater for the FDI muscle, but did not influence endpoint error for either muscle. The young and old adults had similar strength values, but the old adults were less accurate and more variable than the young subjects. Nonetheless, the accuracy and variability displayed by the old adults for the two muscles was the same as that observed for the young adults. The force accuracy and variability findings are consistent with the predictions of the minimum variance theory that motor-output variability is inversely related to muscle size, strength, and motor unit number.