Quantitative anatomy of the extensor digiti minimi muscle in the growing human fetus.

Introduction Age-specific reference intervals for the extensor digiti minimi muscle (EDMM) in the human fetus may be relevant in the detailed evaluation of the musculoskeletal systems with potential relevant aspects for surgical treatment. The aim of the study was to examine the age-specific reference intervals and growth dynamics of the EDMM in relation to its length, width, projection surface area and volume. Material and methods The examined material included 70 human formalin-fixed fetuses of both sexes (37♀, 33♂) aged from 17 to 29 weeks. With the use of anatomical dissection every EDMM was visualized, recorded in a form of JPG formats and analyzed by the digital image analysis system and statistical methods. Results No variability of the EDMM was found. All the morphometric parameters of the EDMM revealed neither sex nor laterality differences. With fetal age most linear parameters of the EDMM concerning its examined lengths and widths increased in accordance with natural logarithmic functions. The only two exceptions to this referred to the belly width of EDMM measured at its mid-length and the tendon width of EDMM measured proximal to the extensor retinaculum of wrist, which both followed square root functions. The projection surface areas of the EDMM followed natural logarithmic functions, while the volumetric growth of the EDMM was proportionate to fetal age. Conclusions The variability of the EDMM in the human fetus is minimal. The morphometric data of the EDMM represents age-specific reference intervals of clinical significance. Morphometric parameters of the EDMM reveal neither sex nor laterality differences. The EDMM displays three different growth dynamics: from gradual growth deceleration according to both natural logarithmic functions (total length of the muscle and its tendons, belly length, tendon lengths, belly width at its origin, tendon width at its insertion, and projection surface areas) and square root functions (belly width at its mid-length and tendon width in the pre-retinacular segment) to a proportionate growth (total volume).

Plantar Fasciitis with Chronic Baxter's Neuropathy Causing Hindfoot Pain - A Case Report.

Introduction: The main differentials of non-traumatic heel pain are plantar fasciitis (PF), plantar heel fat pad atrophy, worn-out footwear, especially asymmetric wear and tear, hyperuricemia, corns, callosities, tumors of the calcaneum, osteomyelitis, calcaneal stress fractures due to overweight or unaccustomed over usage, radiating pain from S1 nerve root compression, and seronegative spondyloarthropathies. Compression of the tibial nerve or the medial calcaneal nerve at or around the flexor retinaculum is the other possibility. In this case report, we want to highlight a sparsely known pathology, caused due to the entrapment of the first branch of the lateral plantar nerve or inferior calcaneal nerve, also known as Baxter's nerve that may present independently or accompany the common PF. Non-steroidal anti-inflammatory medications or injections of local steroids are typically used for conservative management. However, hydro-dissection or surgical release may be needed in non-responsive cases. Case Report: We present the case of a 57-year-old female with complaints of chronic pain and tenderness in the middle of the heel radiating laterally. She underwent magnetic resonance imaging that revealed chronic denervation changes in the form of marked atrophy and near complete fatty replacement of abductor digiti minimi muscle suggesting chronic Baxter neuropathy. A mildly thickened and hyperintense plantar fascia adjacent to the calcaneal spur and significant heel fat pad edema were seen too. The patient responded well to a local steroid injection and remains pain-free at the 1-year follow-up. Conclusion: When heel pain is present, Baxter's nerve impingement presents as a challenging clinical diagnosis that may accompany the common PF and is often overlooked. MRI can be used to assess the denervation effects of both the acute and chronic stages of Baxter's nerve impingement by identifying abnormalities of the abductor digiti minimi muscle belly.

Subacute Ulnar Nerve Compression Neuropathy Following Hand Crush Injury in the Setting of Intracanal Accessory Abductor Digiti Minimi: A Double Crush Phenomenon.

Anatomical variations within Guyon's canal such as an accessory abductor digiti minimi are described as causes of ulnar nerve compression. Here we present a unique case of delayed ulnar neuropathy following treatment of left fourth metacarpal base fracture with percutaneous pinning fixation and an uncomplicated two month postoperative course. He returned with new ulnar sensory loss and motor weakness. EMG demonstrated nerve compression with CT identifying an accessory abductor digiti minimi in Guyon's canal. Following Guyon's canal release with partial accessory muscle resection, there was immediate sensory and progressive motor recovery with resolution of clawing. Delayed compression by an accessory abductor digiti minimi following trauma has not been described, suggestive of double-crush phenomenon. The accessory muscle was an asymptomatic variable (first "crush") and with the second "crush" of post-surgical changes resulting in pathological nerve compression. With delayed onset ulnar neuropathy after trauma, surgeons should consider possible accessory structures.

Attritional Extensor Digiti Minimi Tendon Rupture Associated With a Distal Ulna Fracture.

Attritional extensor tendon ruptures are common in the setting of arthritis but, to our knowledge, have never previously been reported in the setting of a distal ulna fracture. This case report describes a 56-year-old male patient who sustained a left-hand dog bite resulting in crush injuries to the thumb and ring finger and a minimally displaced distal ulna fracture. The patient initially underwent appropriate surgical intervention for the thumb and finger crush injuries and non-operative management of the distal ulna fracture with splint immobilization. He experienced an extensor digiti minimi tendon (EDM) rupture two and a half weeks post-operatively. Radiographs demonstrated interval distal ulna fracture displacement with a prominent dorsal spike and absence of arthritis. He subsequently underwent distal ulna open reduction internal fixation and an extensor indicis proprius (EIP) to EDM tendon transfer. This case demonstrates a novel complication following non-operative management of a distal ulna fracture in which the prominent dorsal distal ulna resulted in direct irritation to the extensor tendon and subsequent attritional extensor tendon rupture. This potential complication should be considered in determining appropriate treatment for distal ulna fractures.

Anomalous Extensor Digiti Minimi with Multiple Slips and Bulbous Appearance.

The extensor digiti minimi is a muscle in the posterior compartment of the forearm that extends the fifth digit. Variations of the extensor tendons of the hand are common and mostly asymptomatic, however, some may impinge and occupy the narrow dorsal compartments of the wrist causing dorsal wrist pain and impairment of digital movement. Orthopedic literature illustrates how frequent anomalies of the extensor indicis proprius, extensor digitorum brevis manus, and extensor medii proprius occur; however, minimal literature documents a bulbous, multi slip extensor digiti minimi. Within this case, a 30-year-old, right-handed woman with no prior hand trauma presented with recurrent snapping localized to her right fifth digit, causing intermittent pain and an audible "click". This study aims to provide a thorough anatomical description of a rare extensor digit minimi anomaly and a viable option to treat successfully an inflamed, symptomatic extensor retinaculum affecting the extensor digiti minimi.

Is It Possible to Perform Fifth Carpometacarpal Joint Arthroscopy? Cadaveric Study on Its Feasibility, Safety, and Potential Hazards in Portal Creation.

Background Fifth carpometacarpal joint (CMCJ) fracture dislocation is a relatively rare injury and most will require operative treatment because of its unstable nature. Improper reduction and fixation lead to joint surface destruction, pain, and reduced grasping power. Intra-articular fragment reduction is often obscured by dorsally displaced ulnar fragment. Therefore, fifth CMCJ arthroscopy can be advantageous in assisting intra-articular fragment reduction. However, there is no detailed description of the portal landmarks or portals' relationship with adjacent important structures in the literature. Purposes To explore the feasibility and safety of fifth CMCJ arthroscopy, locations of the portals are examined in cadaveric hand specimens. Their proximity to important anatomical structures such as dorsal cutaneous branch of ulnar nerve (DCBUN), ring finger and little finger extensor digitorum communis (EDC), and extensor digiti minimi (EDM) is measured. Methods Fifth CMCJ arthroscopy is performed on 11 cadaveric hand specimens by specialist-level surgeon. The portals are marked and portal positions are further confirmed under the fluoroscopy. Then the cadaveric specimens were undergone anatomical dissection by specialist-level surgeon. During dissection, the spatial relationship between the portal positions and DCBUN, EDC to ring finger and little finger, and EDM is identified. The distance between the portals and the above important structures was measured in millimeters. Results DCBUN was consistently found between fourth metacarpohamate (4-MH) and fifth metacarpohamate (5-MH) portals, with it being closer to the latter (mean distance, 2.03 mm; range, 0-4.43 mm; standard deviation [SD], 1.09 mm). The closest tendon for 4-MH portal is ring finger EDC (mean distance, 2.65 mm; range, 0-5.89 mm; SD, 1.78 mm), while 5-MH portal and accessory portal were closest to EDC (mean distance, 1.88 mm; range, 0-3.69 mm; SD, 1.25 mm) and EDM (mean distance, 7.79 mm; range, 6.63-10.72 mm; SD, 1.49 mm), respectively. During the process of specimen dissection, we found no damage to the above structures after portal introduction. Conclusion The above findings support the use of fifth CMCJ arthroscopy, which can be used for assisted reduction in fifth metacarpal base fracture dislocation and hamate body fracture. Gentle soft tissue spreading technique during portal creation prevents injury to the important structure surrounding the portals. Level of evidence This is a Level V study.

Aberrant accessory abductor digiti minimi manus muscle: a rare anatomical variation.

The hypothenar muscle with the greatest frequency of variations is the abductor digiti minimi manus. Except from morphological variations of this muscle, have also been reported cases of an extra wrist muscle, the accessory abductor digiti minimi manus muscle. This case report presents a rare case of an accessory abductor digiti minimi muscle characterized by an unusual origin from the tendons of the flexor digitorum superficialis. This anatomical variation was identified on a formalin - fixed male cadaver of Greek origin during routine dissection. This anatomical variation, which may result in Guyon's canal syndrome or complicate common wrist and hand surgical procedures such as the carpal tunnel release, should be known to orthopedic surgeons and hand surgeons in particular.

New Insights into Boxer's Knuckle Injury of the Little Finger.

BACKGROUND: The original description of boxer's knuckle injury of the fifth ray mentions that the injury occurs between the extensor digitorum communis (EDC) and the extensor digiti minimi (EDM). Subsequent reports claim similar findings. Anatomical studies show that the EDC of the fifth ray is absent in most patients, while the EDM is generally composed of two slips. We present a modification of the current description of boxer's knuckle injury of the little finger based on the correlation between advanced preoperative 3D imaging and intraoperative findings. METHODS: Five patients were investigated preoperatively using high-resolution ultrasound and 3D tendon reconstruction-based MR arthrography. Surgical exploration identified the lesion site relative to the EDM and EDC. RESULTS: All patients had two slips of the EDM and no EDC to the fifth ray. The injury appeared as a longitudinal tear of the EDM between its two slips. The mean gap was 7.8 mm (range 4.5-10 mm) on the pathological side vs. 1.3 mm (range 1-2 mm) on the healthy contralateral side. CONCLUSIONS: We believe that previous descriptions of boxer's knuckle of the fifth ray are inaccurate. High-resolution ultrasound and 3D reconstructions based on MR arthrography are reliable diagnostic tools allowing to locate the injury with precision.

Personalized approach for complex bilateral calcaneal osteomyelitis and defect reconstruction with bilateral abductor digiti minimi flaps.

Objectives: The best treatment for displaced, intra-articular fractures of the calcaneus remains controversial and it is generally agreed, that there is no single method that is suitable for all patients. Case presentation: Here we report a rare case of bilateral calcaneal osteomyelitis with fistula formation following open reduction and plate fixation via an extensile lateral approach that could be salvaged with an interdisciplinary approach including orthopedic and plastic surgeons. We are not aware of a similar case in the literature. Abductor digit minimi flaps is a well-established procedure in plastic and reconstructive surgery with a minimal functional defect and morbidity at the donor site. This treatment protocol resulted in minimal donor-site morbidity and good bone remodeling in the further course. We believe that it may be of use for complicated courses even with limited resources. Conclusions: Abductor digit minimi flaps is a well-established procedure in plastic and reconstructive surgery with a minimal functional defect and morbidity at the donor site.

Treatment of Recurrent Carpal Tunnel Syndrome with the Abductor Digiti Minimi Flap: A Case Series.

Background: Approximately 5% of patients experience recurrent symptoms after carpal tunnel release (CTR) and need revision surgery. Several surgical techniques have been described for recurrent carpal tunnel syndrome (CTS) and the abductor digiti minimi (ADM) flap is one of them. Literature concerning clinical results of the ADM flap for recurrent CTS is lacking. The aim of this study is to evaluate the outcomes of the ADM flap for recurrent CTS. Methods: We treated seven patients with the ADM flap (eight hands) between July 2016 and February 2019. Patient characteristics were assessed, and patients were asked about their symptoms (pain, sensation and paresthesia) before and after surgery. Postoperatively, we administered CTS symptoms, satisfaction with the surgery, patient-reported outcome measurements (BCTQ and QuickDASH) and whether they would undergo the same surgery again. Complications were also recorded Results: The median follow-up was 14 months. The success rate measured by CTS symptoms was 88%. Seven out of eight patients were satisfied with the results and two patients would not elect to undergo the same procedure again. Two patients reported having a weaker grip at the donor site. The median BCTQ symptom and function scores were 2.9 (1.7-3.5) and 2.6 (1.8-3.0) respectively. The median QuickDASH score was 41 (IQR 22-52). Complications reported were wound dehiscence (n = 1) and hypertrophic scar (n = 1). Conclusions: The outcomes of the ADM flap in patients with recurrent CTS were like other commonly used procedures in recurrent CTS. Level of Evidence: Level IV (Therapeutic).

A comparison between the adductor pollicis muscle and the abductor digiti minimi muscle using electromyography AF-201P in rocuronium-induced neuromuscular block: a prospective comparative study.

BACKGROUND: The AF-201P, a new electromyography (EMG)-based neuromuscular monitor has been developed recently. The aim of this clinical study was to compare two ulnar nerve innervated muscles: the adductor pollicis (AP) muscle and the abductor digiti minimi (ADM) muscle during the recovery from rocuronium-induced neuromuscular block by using EMG AF-201P. METHODS: Twenty patients undergoing surgery with general anesthesia were enrolled in the study. During total intravenous general anesthesia, train-of-four (TOF) and post-tetanic counts (PTC) responses following 0.9 mg/kg rocuronium administration were concurrently monitored at the AP and the ADM muscles with EMG AF-201P on the opposite arms. At the end of the surgery, sugammadex 2 mg/kg was administered when TOF counts of 2 (TOFC2) was observed at both muscles. The primary outcome of the study was time from administration of rocuronium to first appearance of PTC response (first PTC). The secondary outcomes of the study were time from administration of rocuronium to TOF count of 1 (TOFC1), time from first PTC to TOFC1 (PTC-TOF time), time to TOFC2, and time from administration of sugammadex to TOF ratio ≥ 0.9. Agreement between the two muscles was assessed using the Bland-Altman analysis. Data are expressed as mean ± standard deviation. RESULTS: Nineteen patients were included in the analysis. Time to first PTC was significantly faster at the ADM muscle than the AP muscle (24.4 ± 11.4 min vs 32.4 ± 13.1 min, p = 0.006). PTC-TOF time was significantly longer with the ADM muscle than the AP muscle (19.4 ± 7.3 min vs 12.4 ± 10.6 min, p = 0.019). There were no significant differences in time to TOFC2 and sugammadex-facilitated recovery between the two muscles. Bland-Altman analyses showed acceptable ranges of bias and limits of agreement of the two muscles. CONCLUSIONS: The ADM muscle showed a good agreement with the AP muscle during rocuronium-induced neuromuscular block but faster recovery of PTC response when using EMG. TRIAL REGISTRATION: UMIN-CTR (Registration No. UMIN000044904 ). Registered 19 July 2021 -Retrospectively registered, https://center6.umin.ac.jp/cgi-bin/ctr_e/ctr_view.cgi?recptno=R000051290 .

Elucidation of abductor digiti minimi activity in chronic ankle instability.

[Purpose] This study aimed to compare the muscle activity around the foot and ankle joints, notably of the abductor digiti minimi, between affected and unaffected sides of individuals with chronic ankle instability. [Participants and Methods] Twelve adult males with chronic ankle instability in one ankle (age, 27.7 ± 5.4 years; height, 172.5 ± 8.1 cm; weight, 67.5 ± 8.1 kg) were included and underwent surface electromyography assessments in multiple positions on both affected and unaffected sides. Measurements were obtained for eight muscles including the abductor digiti minimi. Each measurement included a 5-s segment of the stable waveform, with the root mean square-processed and normalized to the resting position set to 1. [Results] Abductor digiti minimi activity on the affected side was significantly reduced during maximal toe extension/abduction with both ankle dorsiflexion and plantarflexion. Peroneus longus activity on the affected side was significantly greater during maximal toe extension/abduction with ankle plantarflexion; peroneus longus and tibialis anterior muscle activities were significantly greater on the affected side during maximal toe extension/abduction with ankle dorsiflexion. [Conclusion] In the absence of load, muscle imbalance in the intrinsic and extrinsic muscles of the foot was suggested. However, no significant differences were observed under loading conditions.

The senile hand: Age effects on intrinsic hand muscle CMAP amplitudes influence split-hand index calculations.

INTRODUCTION/AIMS: Age can affect hand muscles non-uniformly. We investigated the influence of age on the compound muscle action potential (CMAP) amplitude of the hand muscles and the derived split-hand index (SHI). METHODS: We studied 244 subjects investigated for suspected myasthenia gravis but without neuromuscular disorders. Abductor pollicis brevis (APB), first dorsal interosseous (FDI), and abductor digiti minimi (ADM) CMAPs were obtained by supramaximal stimulation at the wrist, recording with surface electrodes while checking the best recording site. We applied Tukey's HSD and Kruskal-Wallis one-way analysis of variance for comparing age groups defined by median and interquantile ranges (IQRs). Spearman's rank correlation coefficient and linear regression were used for testing age-dependence of measurements. RESULTS: Median age was 61.5 y (first IQR, 44.5; third IQR, 72.0; range 18-89). Age and neurophysiological measurements were similar between genders. APBCMAP , FDICMAP , ADMCMAP , and SHI were correlated with age (P < .001). Median and cutoff values were significantly different between age groups. APBCMAP , FDICMAP , and ADMCMAP decreased by 0.8/0.7/0.3 mV/y, respectively, and SHI decreased 0.15/y. DISCUSSION: The CMAP amplitudes of hand muscles and derived SHI were strongly age-dependent, although this effect was less in ADM. This represents a physiological phenomenon. Future studies using the SHI should consider age effects.

Thenar Muscle Motor Imagery Increases Spinal Motor Neuron Excitability of the Abductor Digiti Minimi Muscle.

When a person attempts intended finger movements, unintended finger movement also occur, a phenomenon called "enslaving". Given that motor imagery (MI) and motor execution (ME) share a common neural foundation, we hypothesized that the enslaving effect on the spinal motor neuron excitability occurs during MI. To investigate this hypothesis, electromyography (EMG) and F-wave analysis were conducted in 11 healthy male volunteers. Initially, the EMG activity of the left abductor digiti minimi (ADM) muscle during isometric opposition pinch movement by the left thumb and index finger at 50% maximal effort was compared with EMG activity during the Rest condition. Next, the F-wave and background EMG recordings were performed under the Rest condition, followed by the MI condition. Specifically, in the Rest condition, subjects maintained relaxation. In the MI condition, they imagined isometric left thenar muscle activity at 50% maximal voluntary contraction (MVC). During ME, ADM muscle activity was confirmed. During the MI condition, both F-wave persistence and the F-wave/M-wave amplitude ratio obtained from the ADM muscle were significantly increased compared with that obtained during the Rest condition. No difference was observed in the background EMG between the Rest and MI conditions. These results suggest that MI of isometric intended finger muscle activity at 50% MVC facilitates spinal motor neuron excitability corresponding to unintended finger muscle. Furthermore, MI may induce similar modulation of spinal motor neuron excitability as actual movement.

Comparison of the electromyographic activity of different zones of the abductor digiti minimi manus muscle in search of a functional compartmentalisation / Comparación de la actividad electromiográfica de diferentes zonas del músculo abductor digiti minimi manus en busca de una compartimentación funcional

SUMMARY: There is evidence demonstrating the presence of functional compartmentalisation (FC) in some skeletal muscles. This means that the motor units (MU), grouped in certain areas of the muscle, show different levels of activation in comparison to those located in other zones. This has only been described in large muscles whose morphology proves the existence of a FC. However, there is no background information about small muscles, such as the Abductor digiti minimi manus (ADM). The objective of this study was to compare the activation of the MU in different zones of the ADM to support the hypothesis of the existence of a FC in the ADM. By using a cross- sectional, analytical, observational study, the activity of the MUs in the ADM was assessed in 12 volunteers (age 21 ± 1.6 years old; weight 75.3 ± 8 kg; height 176.2 ± 7.3 cm; average ± standard deviation). The activity of MUs was evaluated using high-density surface electromyography (HD-sEMG) with an array of 64 electrodes arranged two-dimensionally. This allowed us to record the activity of the MUs in three zones of the ADM (Z1: dorsal zone; Z2: dorsal-palmar zone and Z3: palmar zone). Electromyographic recordings were obtained during voluntary isometric contractions of the ADM at 20, 40, 60 and 80 % of the maximum voluntary contraction (MVC). The comparison of the activation levels of MUs between the three zones was carried out using a mixed model analysis of covariance. The results showed a significant difference between the dorsal and palmar zones at 40 % of the MVC (p= 0.03), and between the dorsal and dorsal- palmar zone at 80 % of the MVC (p= 0.03). The results obtained in the evaluated sample support the hypothesis of the existence of FC in the ADM. However, further research is needed to determine with greater certainty the presence of this compartmentalisation in the ADM.

RESUMEN: Existe evidencia que demuestra la presencia de una compartimentalización funcional (CF) en algunos músculos esqueléticos. Aquello se traduce en que las unidades motoras (UM) agrupadas en ciertas zonas del músculo, presentan diferentes niveles de activación a las ubicadas en otras regiones. Esto solo ha sido descrito en músculos grandes, cuya morfología justifica la existencia de una CF. Sin embargo, no existen antecedentes de aquello en músculos pequeños, tales como el abductor digiti minimi manus (ADM). El objetivo de este estudio fue comparar la activación de las UM en distintas zonas del ADM, con la finalidad sostener la hipótesis de la existencia de una CF en el ADM. Mediante un estudio observacional analítico transversal se evaluó la actividad de las UM del ADM en 12 voluntarios (edad 21±1,6 años; peso 75,3±8 kg; altura 176,2 ± 7,3 cm; promedio ± desviación estándar). La actividad de las UM, se evaluó mediante electromiografía de superficie alta densidad usando una matriz de 64 electrodos dispuestos bidimensionalmente. Esta permitió registrar la actividad de las UM en tres zonas del ADM (Z1: zona dorsal; Z2: zona dorso-palmar y Z3: zona palmar). Los registros electromiográficos fueron obtenidos durante contracciones isométricas voluntarias del ADM al 20, 40, 60 y 80 % de la contracción voluntaria máxima (CVM). La comparación de los niveles de activación de las UM entre las tres zonas fue realizada mediante un análisis de modelos mixtos de covarianza. Los resultados indicaron que existió diferencia significativa entre la zona dorsal y palmar al 40 % de la CVM (p=0,03), y entre la zona dorsal y dorso-palmar al 80 % de la CVM (p=0,03). Los resultados obtenidos en la muestra evaluada sostienen la hipótesis de la existencia de una CF en el ADM. Sin embargo, son necesarias más investigaciones para establecer con mayor certeza la presencia de esta compartimentalización en el ADM.

Assessing the Usability of Flexor Digiti Minimi Muscle for Opponensplasty: An Anatomic Study.

PURPOSE: The abductor digiti minimi (ADM) and flexor digiti minimi (FDM) muscles have a similar vascular and nerve supply. The purpose of this study was to assess the feasibility of transferring the FDM instead of ADM for thumb opposition. METHODS: Thirty cadaver hands were dissected under loupe magnification to assess the presence of the ADM and FDM muscles as well as their blood and nerve supply. The length of these muscles and their location in relation to the radial aspect of the thumb metacarpophalangeal joint were assessed. RESULTS: The ADM muscle was present in all cadavers whereas the FDM muscle was absent in 33% of hands. When the dimensions were suitable (53%), the more radially located FDM muscle reached the thumb metacarpophalangeal joint more easily. CONCLUSIONS: Although the dissections revealed considerable variability in FDM anatomy, when present, it can have positional advantage over the ADM for opponensplasty. CLINICAL RELEVANCE: In some cases with radial longitudinal deficiency, preservation of ADM function is essential. In these children, the FDM can potentially be explored and transferred if it is found to be suitable.

Accessory abductor digiti minimi muscle, less muscular than thought: an update on prevalence, morphology, and review of the literature.

OBJECTIVE: To update the prevalence and morphology of the accessory abductor digiti minimi muscle using 3T MRI. MATERIALS AND METHODS: A retrospective study of 3T wrist MRI was performed. Presence and morphology of the accessory abductor digiti minimi were evaluated in addition to its relationship to the ulnar nerve. Charts were reviewed for demographics, EMG, neuropathic symptoms, and initial MRI interpretation. RESULTS: Analysis of 396 wrist MRI studies yielded 25% prevalence of the accessory abductor digiti minimi, of which the majority (69%) demonstrated fascial-type morphology proximal to Guyon's canal. A minority (31%) demonstrated a contiguous muscle belly throughout its course. Overall, prevalence of a muscular type was only 8%. All patients were asymptomatic with normal EMG, unremarkable ulnar nerve, and no significant nerve compression. Anterior-posterior muscle dimension was larger in males. Only 1 of 98 accessory abductor digiti minimi muscles was prospectively identified. CONCLUSION: The accessory abductor digiti minimi is not uncommon; however, patients are usually asymptomatic without neuropathic symptoms. The most common anatomic variant is a small muscle belly at the level of the pisiform with fascial morphology proximal to Guyon's canal and origin from the distal antebrachial fascia. A contiguous muscle belly extending from the distal forearm through the wrist occurs much less frequently. Clinicians should be familiar with these anatomic variants to enhance its recognition, understanding that a muscular variant is rarer than previously reported, but historically can serve as a potential source of clinical symptomatology and could be encountered during physical examination or wrist surgery.

Clinical Features of Ulnar Tunnel Syndrome and the Diagnostic Value of Nerve Conduction Measurements.

OBJECTIVES: The purposes of this study were to assess the clinical features of ulnar tunnel syndrome (UTS) and to investigate the diagnostic value of nerve conduction measurements for UTS. METHODS: Eighteen patients with UTS were reviewed retrospectively. Fifteen patients had intrinsic muscle atrophy and motor weakness, and 15 had numbness with hypesthesia. The compound muscle action potentials (CMAPs) from the first dorsal interosseous (FDI) muscle and the abductor digiti minimi (ADM) muscle and the sensory nerve action potential (SNAP) from the little finger were recorded and analyzed. All patients underwent ulnar tunnel release surgery and neurolysis. Static two-point discrimination test results and pinch strengths were assessed before and after surgery. RESULTS: Before surgery, FDI-CMAP was recorded in 17 patients, and ADM-CMAP in 16, and all showed delayed latency and/or low amplitude. SNAP was recorded in eight patients and two showed delayed latency. The causes of ulnar nerve lesions were ganglion in five patients, traumatic adhesion in four, ulnar artery aberrancy in four, pisohamate arch in three, anomalous muscle in one, and ulnar vein varix in one. The sites of the lesions were in zone 1 of the ulnar tunnel anatomy in 12 patients, in zone 2 in 2, and in zones 1 and 2 in 4. After surgery, all patients obtained recovery of motor function and sensation; however, postoperative FDI-CMAP and ADM-CMAP did not improve to the normal range. CONCLUSIONS: The causes of UTS were ganglion, traumatic adhesion, ulnar artery aberrancy, and pisohamate arch. Both FDI-CMAP and ADM-CMAP were valuable for electrophysiological diagnosis of UTS.

[Selective nerve transfers for thenar branch reconstruction]. / Selektive Nerventransfers zur Reinnervation des motorischen Thenarastes.

OPERATIVE: Reconstruction of thump opposition with selective nerve transfer of the motor branch of the abductor digiti minimi muscle (ADM) to the thenar motor branch. INDICATIONS: Injury of the median nerve or thenar motor branch and resulting loss of thumb opposition. CONTRAINDICATIONS: Combined median and ulnar nerve injuries or brachial plexus lesions of C8-Th1, or a time interval >12 months since denervation of the thenar branch. SURGICAL TECHNIQUE: The ADM motor branch is microsurgically dissected and transferred to the thenar branch. POSTOPERATIVE MANAGEMENT: After successful reinnervation, regular follow-ups and intensive physiotherapy are important for operative outcome. RESULTS: Reconstruction of the opposition of the thumb results in improved range of motion as well as a gain of grip and pinch force.

An accessory abductor digiti minimi as possible risk factor of the median and ulnar nerves compression / Músculo abductor digiti minimi accesorio como posible factor de riesgo de la compresión de los nervios mediano y ulnar

SUMMARY: During routine dissection of a left upper limb of a 68-year-old male human cadaver, an unusual muscle was observed originating from the radius and flexor retinaculum, and continued in the hypothenar region with the muscle belly of the abductor digiti minimi. We checked that it was an accessory abductor digiti minimi (ADM). Its muscular belly was in close relation to the median and ulnar nerves. We review the literature regarding such muscle variations and discuss the potential for compression of the median and ulnar nerves. Although the accessory ADM is usually asymptomatic and only rarely results in nerve compression, it should be taken into account by surgeons when establishing a differential diagnosis in the compression neuropathies of the median and ulnar nerves. An ultrasound scanning can help establish the differential diagnosis.

RESUMEN: Durante la disección de rutina de un miembro superior izquierdo de un cadáver humano masculino de 68 años, se observó un músculo inusual que se originaba en el radio y el retináculo flexor del carpo, y continuuaba en la región hipotenar con el vientre muscular del abductor digiti minimi manus. Verificamos que se trataba del músculo abductor digiti minimi accessorius (ADMA). Su vientre muscular se encontraba en estrecha relación con los nervios mediano y ulnar. Revisamos la literatura sobre variaciones musculares y discutimos la potencial compresión de los nervios mediano y ulnar. Aunque el ADMA suele ser asintomático y rara vez produce compresión nerviosa, los cirujanos deben tenerlo en cuenta al establecer un diagnóstico diferencial en las neuropatías de compresión de los nervios mediano y ulnar. Una ecografía puede ayudar a establecer el diagnóstico diferencial.