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

Rhizarthrosis Part II: A New Approach of Manual Therapy and Therapeutic Exercise

Rhizarthrosis (RA), also known as trapezium-metacarpal osteoarthritis, is a degenerative condition affecting the thumb's first joint, leading to functional impairment and pain. Conservative treatment options are preferred for mild to moderate cases (Eaton-Littler grades I and II) and typically encompass a range of therapeutic modalities, including manual therapy. However, for the existing manual therapy techniques, there is a lack of comparative studies for efficacy, and therapeutic exercises are often generic and non-specific to RA. This study proposes a novel treatment protocol that combines manual therapy with specific therapeutic exercises grounded in the biomechanical analysis of the trapeziometacarpal joint. The focus is on enhancing joint stability, reducing pain, and improving function. The manual therapy component includes three phases. A passive phase, during which joint distractions are applied to alleviate discomfort and improve joint mobility. An active phase that addresses joint mobility on the adduction-abduction plane, the first plane of movement to suffer limitation: the therapist facilitates the isometric adduction of the thumb, followed by an assisted abduction. A second active phase is where Mulligan's Mobilization With Movement concept is applied. This technique involves passive pain-free joint mobilization with simultaneous active finger movements, to provide additional therapeutic benefits. The therapeutic exercises component focuses on strengthening the first dorsal interosseous muscle as an abductor to reduce thumb adductor muscle activation and joint stress. Patients are encouraged to perform finger spreading exercises using a rubber band between the first and fifth fingers, emphasizing first dorsal interosseous activation and stability of the thumb. This type of muscle strengthening does not involve movement of the trapeziometacarpal joint. It is recommended to start performing 5-10 repetitions or 5 seconds of isometric contraction, repeat throughout the day, and progressively increase the load by adding a turn to the rubber band or changing it, increasing the number of repetitions bringing it to 15 and/or increase the isometric contraction time to 10/15 seconds. The proposed therapeutic rationale, informed by biomechanical insights, lays a promising foundation for further investigation. Nevertheless, empirical validation through rigorous clinical trials remains essential to substantiate its clinical utility and advance the management of RA.

Rhizarthrosis Part I: A Literature Review

Rhizarthrosis (RA), or trapeziometacarpal osteoarthritis, is an arthritic degenerative process that affects the first joint of the thumb. The objective of this work is to provide therapists with an overview of the fundamental issues related to the therapeutic management of trapeziometacarpal joint instability. Prevalent in females, especially post-menopause, and linked to age, RA involves ligament and muscle structures, with causes ranging from hormonal influences to mechanical factors. Understanding the biomechanics, stability, and factors contributing to RA is crucial for effective intervention. This study explores the role of ligaments, muscles, and anatomical variants in thumb joint degeneration, emphasizing the importance of stability and congruence. RA manifests as pain at the base of the thumb, limiting grip strength and hindering everyday tasks. Pain initially occurs during specific movements but can progress to constant discomfort, affecting sleep. Chronic RA leads to joint stiffness, deformities like the "Z thumb," and muscle atrophy, impacting daily functions. Clinical evaluation involves pain assessment, joint mobility examination, and palpation. Diagnostic tests like the grind test and lever test aid in confirming RA. Radiographic examination reveals joint space degeneration and osteophytes and helps classify RA stages using the Eaton-Littler classification. Conservative treatment aims to alleviate pain, reduce joint stress, and enhance function. Orthoses help stabilize the joint. Therapeutic exercises, emphasizing muscle strength and dynamic stability, prove beneficial. Manual therapies like neurodynamic, Kaltenborn, Mulligan, and Maitland techniques target pain reduction and improve joint mechanics. The studies on conservative approaches provide evidence that a multimodal intervention consisting of joint mobilization, neural mobilization, and exercise is beneficial in reducing pain in patients with RA. When conservative therapy fails, surgical intervention is indicated.

First dorsal interosseous muscle reconstruction: a systematic review of its attachments

PURPOSE

The first dorsal interosseous (FDI) muscle, when impaired due to traumatic injuries or degenerative conditions, can be reanimated in various ways to restore pinch grip. These reconstructive techniques are planned based on a precise anatomical understanding of the FDI muscle. However, a review of the existing literature has brought to light controversy regarding its insertions. A systematic review of these descriptions is presented to appreciate these variations.

METHODS

An electronic database search without exclusion by publication year and language was performed according to the Checklist for Anatomical Reviews and Meta-Analyses (CARMA) guidelines, using the PubMed, Scopus, Web of Science and Embase databases. An assessment of the methodological quality was performed.

RESULTS

Thirteen studies were included in this article. There is general agreement that the FDI muscle contains two bellies and a bony insertion into the index finger proximal phalanx base. However, due to wide anatomic variation, differences were reported on whether there is a soft tissue insertion. When this was found, the included studies differed on how commonly this occurs (between 1.4% and 78%), where it inserts. Other sites of distal insertions reported include the metacarpophalangeal capsule, the interosseous hood and an assemblage nucleus on the volar plate.

CONCLUSIONS

Our systematic review, focusing on the insertion of the FDI muscle, summarizes the existing knowledge on its anatomy and variations, thereby facilitating better understanding of its function and surgical planning for reconstruction.

First dorsal interosseous muscle transfer to restore opposition of the new thumb after index pollicization: anatomical description of an original technique and case report

Index pollicization in severe thumb hypoplasia or aplasia in children or for the reconstruction of a mutilated thumb in adults is a rare and technically demanding procedure. Weakness of the new thumb is routinely reported after index pollicization. An inappropriate position of the first dorsal interosseous muscle (FDIM) can partly explain this strength deficit. Here, we report an original anatomical study on FDIM transfer for reanimation of the new thumb's opposition function and its clinical application. An anatomical study was carried out on three upper limbs from fresh, non-embalmed adult cadavers. We demonstrated the feasibility of an FDIM transfer pedicled on the proper FDIM artery and the deep branch of the ulnar nerve. The proximal FDIM insertions were sutured to the lateral border of the flexor retinaculum to recreate the superficial thenar musculature. This procedure was performed on a 52-year-old man who was referred to us with swelling on his hand. We discovered a myxoid inflammatory fibroblastic sarcoma of the thumb that required proximal thumb amputation while preserving the base of the first metacarpal. To our knowledge, this is the first description of FDIM pedicled flap transfer during an index pollicization procedure among an adult population. However, in severe thumb hypoplasia or aplasia cases, this procedure is limited by the size and anatomical variations of the neurovascular structures among a population affected by radial longitudinal deficiency.

Proactive inhibition is marked by differences in the pattern of motor cortex activity during movement preparation and execution

Successful human behavior relies on the ability to flexibly alter movements depending on the context in which they are made. One such context-dependent modulation is proactive inhibition, a type of behavioral inhibition used when anticipating the need to stop or change movements. We investigated how the motor cortex might prepare and execute movements made under different contexts. We used transcranial magnetic stimulation (TMS) in different coil orientations [postero-anterior (PA) and antero-posterior (AP) flowing currents] and pulse widths (120 and 30 µs) to probe the excitability of different inputs to corticospinal neurons while participants performed two reaction time tasks: a simple reaction time task and a stop-signal task requiring proactive inhibition. We took inspiration from state space models to assess whether the pattern of motor cortex activity changed due to proactive inhibition (PA and AP neuronal circuits represent the x and y axes of a state space upon which motor cortex activity unfolds during motor preparation and execution). We found that the rise in motor cortex excitability was delayed when proactive inhibition was required. State space visualizations showed altered patterns of motor cortex activity (combined PA₁₂₀ and AP₃₀ activity) during proactive inhibition, despite adjusting for reaction time. Overall, we show that the pattern of neural activity generated by the motor cortex during movement preparation and execution is dependent upon the context under which the movement is to be made.

NEW & NOTEWORTHY Using directional TMS, we find that the human motor cortex flexibly changes its pattern of neural activity depending on the context in which a movement is due to be made. Interestingly, this occurs despite adjusting for reaction time. We also show that state space and dynamical systems models of movement can be noninvasively visualized in humans using TMS, thereby offering a novel method to study these powerful models in humans.