Hypothenar Research Articles

Atypical Presentation of Hypothenar Hammer Syndrome.

Hypothenar hammer syndrome (HHS) is a rare vascular disease caused by repetitive trauma to the hypothenar eminence, leading to thrombi and sometimes aneurysm development in the ulnar artery. This case report presents an atypical presentation of HHS with pathology extending distally into the digital arteries, complicated by an unclear history and unique genetic contributions. The patient, a 58-year-old male with a distant history of jackhammer work, presented with progressive pain in his fourth and fifth digits. CT angiography revealed patchy vascular lesions in the palmar arch. He developed another thrombi despite being treated initially with heparin. Genetic analysis revealed that he was heterozygous for Factor V Leiden with decreased protein C levels. Following surgical intervention, he recovered well. The author report a case of HHS in which medical management was superior to surgical treatment due to combined occupational and genetic predisposition for vascular pathology with findings extending beyond the ulnar artery.

An unreported variant of palmaris longus muscle.

Palmaris longus is a highly variable muscle of the forearm. Knowledge of its variability is of importance to plastic surgeons, hand surgeons and radiologists. During our routine dissection classes for undergraduate medical students, a peculiar palmaris longus muscle was noted in the left upper limb of an adult male cadaver. The muscle had a fleshy belly in the middle and two tendons: a proximal and distal. The distal tendon of palmaris longus gave origin to a variant fleshy slip of muscle which was inserted partly to the pisiform bone and partly merged with the hypothenar muscles. The ulnar nerve and artery passed deep to this variant fleshy slip. The ulnar artery was tortuous both proximal and distal to this slip. The distal loop of the ulnar artery was very superficial and was in the median position. Both the palmaris longus and the variant fleshy slip were innervated by median nerve.

Nerve conduction study on the split-hand plus index in Amyotrophic lateral sclerosis: correlations with lower motor neuron impairment.

In the arms of patients with Amyotrophic lateral sclerosis (ALS) two peculiar patterns of dissociated muscular atrophy have been described: the split-hand sign (with predominant atrophy of the lateral aspect of the hand, compared to hypothenar eminence) and the split-hand-plus sign (SHPS), a predominant abductor pollicis brevis (ABP) atrophy with sparing of flexor pollicis longus (FPL). In this case-control study, we evaluated the diagnostic utility of a neurophysiological indicator of SHPS and assessed its association with clinical features. We prospectively studied 59 incident ALS patients, 61 patients with ALS-mimic disorders (OND) and 61 non-neurological controls (NNCs). ABP and FPL compound muscle action potentials (CMAP) amplitudes were obtained by supramaximal stimulation of median nerve at elbow. Split-hand plus index (SHPI) was calculated according to the formula: APB-CMAP/FPL-CMAP. SHPI was significantly lower in ALS compared to OND patients and NNCs (p < 0.0001). SHPI value < 1 was observed in 2% of NNCs and 9% of OND patients and demonstrated an accuracy of 71% in differentiating ALS from OND and an accuracy of 74% in differentiating ALS from NNC. SHPI was associated with higher LMN score, and higher disease severity as quantified by the ALSFRS-r. Our results indicate that SHPI is a reliable indicator to distinguish ALS patients from ONDs and NNCs. SHPI was significantly associated to the degree of lower motor neuron impairment but showed no association with upper motoneuron impairment.

Palmaris brevis spasm syndrome: The treatable hypothenar dimpling

Abstract Palmaris brevis spasm syndrome is a rare disorder, mostly reported with occupational overuse of a computer keyboard, mouse, pipette, and vibratory tools or after the use of arm braces. Rarely, it can be spontaneous. It is clinically characterized by spontaneous contraction of the palmaris brevis muscle over the hypothenar eminence. Here, we report a patient with long-standing, spontaneous, and bilateral palmaris brevis spasm syndrome without any occupational exposure who demonstrated excellent response to botulinum toxin therapy. Clinicians should be aware of this rare but treatable entity in patients presenting with hypothenar spasms.

Accessory Flexor Carpi Ulnaris Muscle in Humans: A Rare Anatomical Case with Clinical Considerations.

Anatomical variations of the forearm flexor muscles are occasionally encountered. Though usually observed incidentally during autopsies or imaging studies, they may at times cause concern due to associated clinical symptoms. This report presents a case of unilateral accessory flexor carpi ulnaris (AFCU) muscle observed in a human male cadaver aged 78 years. During routine cadaveric dissection, an anomalous AFCU muscle was observed in the left forearm of a human male cadaver aged 78 years. Standard institutional guidelines pertaining to the use of human cadaver for teaching and research were followed. A thorough literature review about the flexor carpi ulnaris (FCU) through the PubMed, Embase and Google scholar databases was undertaken, using the keywords - accessory flexor carpi ulnaris muscle, aberrant flexor carpi ulnaris muscle and anatomical variation of flexor carpi ulnaris muscle. Relevant gross anatomical findings were recorded and photographed. AFCU was identified on the medial aspect of the distal third of the left forearm. The AFCU was found originating from the ante-brachial fascia and the fascia covering the FCU on the left forearm, forming a small separate belly deep to the main muscle. It terminated as a thin tendon running alongside the hypothenar muscles and attached distally to the base of the proximal phalanx of the little finger. The AFCU was found to be innervated by a branch of the ulnar nerve. Awareness about the rare AFCU muscle is clinically important as a possible cause of ulnar nerve compression but also as a possible graft in reconstruction surgeries.

Irregular tonic contractions in hypothenar muscles: An unusual presentation

Irregular tonic contractions in hypothenar muscles: An unusual presentation

Giant Lipoma of the Hypothenar Eminence A Case Report and Review of Literature

Lipomas are very frequent benign soft tissue tumors. They are ubiquitous in the human body but their incidence in the hand is rare. This is a case report of a 20-year-old female who presented with a 10-month history of painful swelling over her palm. Surgical excision of the tumor was done without any consequences on the hand’s function and no signs of recurrence at the latest follow-up of 2 years. Although hand lipomas are rare, they should not be neglected. The anatomic particularities of the hand require special care in the diagnostic and therapeutic approach to these tumors.

Ultrasound of the palmar aspect of the hand: normal anatomy and clinical applications of intrinsic muscles imaging.

Intrinsic hand muscles play a fundamental role in tuning the fine motricity of the hand and may be affected by several pathologic conditions, including traumatic injuries, atrophic changes induced by denervation, and space-occupying masses. Modern hand surgery techniques allow to target several hand muscle pathologies and, as a direct consequence, requests for hand imaging now carry increasingly complex diagnostic questions. The progressive refinement of ultrasound technology and the current availability of high and ultra-high frequency linear transducers that allow the investigation of intrinsic hand muscles and tendons with incomparable resolution have made this modality an essential tool for the evaluation of pathological processes involving these tiny structures. Indeed, intrinsic hand muscles lie in a superficial position and are amenable to investigation by means of transducers with frequency bands superior to 20 MHz, offering clear advantages in terms of resolution and costs compared to magnetic resonance imaging. In addition, ultrasound allows to perform dynamic maneuvers that can critically enhance its diagnostic power, by examining the questioned structure during stress tests that simulate the conditions eliciting clinical symptoms. The present article aims to review the anatomy, the ultrasound scanning technique, and the clinical application of thenar, hypothenar, lumbricals and interossei muscles imaging, also showing some examples of pathology involving these structures.

Influence of Surface Geometry on Palm and Fist Contact Pressure Distribution During Strikes With the Hand in Automotive Assembly.

The increase in repetitive strain injuries to the hand underscores the need for assessing and preventing musculoskeletal overuse associated with hand-intensive tasks. This study investigates the risk of overload injuries in soft tissue structures of the hand by analyzing the pressure distribution and location of peak pressure in the hand during snap-fit connection assembly in the automotive industry. The influence of the surface geometry of automotive trim components the pressure distribution and force imparted during strikes with the palm and the fist are investigated in a cohort of 30 subjects with extensive experience installing trim parts with snap-fit connections. Using the palm or fist (ulnar hand side) of the dominant hand, the subjects struck a simulation device with a flat, rounded, or edged surface geometry. The average peak force applied was 600N (±122N), nearly 3 times the force required to overcome the technical resistance of the snap-fit connector (220N). Fist strikes exerted a 40% higher mean peak pressure and 18% higher mean pressure than did palm strikes. The pressure distribution in the region of the thenar eminence and soft tissue of the ulnar side of the hand did not differ between fist strikes on flat and edged surfaces. Considering the delicate anatomy of the hand, especially the hypothenar muscles on the ulnar side, assembling connection claps using the fist instead of the palm may prevent repetitive blunt trauma to the sensitive blood vessels and nerves in the palm.

Relationship of Thenar and Hypothenar Muscle Thickness with Clinical Factors, Thigh Muscle Thickness and Physical Performance in Female Patients with Rheumatoid Arthritis

Relationship of Thenar and Hypothenar Muscle Thickness with Clinical Factors, Thigh Muscle Thickness and Physical Performance in Female Patients with Rheumatoid Arthritis

PA14 Aquagenic palmar wrinkling in a 15-year-old swimmer

Abstract A 15-year-old girl presented with a 1-year history of recurrent palmar wrinkling on contact with water. This was associated with a burning sensation within minutes of water exposure and progressive persistent thickening of the palmar skin. She was otherwise well, with no family history of note, including cystic fibrosis (CF). She had no regular medication or newly introduced medications before the onset of wrinkling. Moderate improvement in hyperkeratosis was seen with twice-daily use of urea 10% and salicylic acid 10% creams; however, the discomfort experienced in water was negatively affecting her ability to continue competitive swimming. On examination, there was palmar hyperlinearity with focal hyperkeratosis over the thenar and hypothenar eminences. Immersion of the hands in lukewarm water resulted in wrinkling within 2 min and peaking at 3 min, at which point the patient reported a burning sensation. Wrinkling resolved within 30 min of drying her hands. Baseline laboratory investigations were normal. Biopsy of the palm in the wrinkled state showed subtle prominence and dilation of sweat gland ducts. A diagnosis of aquagenic syringeal keratoderma (ASK) was made. At the 3- and 6-month reviews, the patient reported spontaneous resolution of wrinkling on contact with water, which was confirmed clinically. Residual hyperkeratosis had similarly resolved, although subtle palmar hyperlinearity persisted. She was able to resume competitive swimming activities without symptoms. The ASK is a rare condition, classically affecting the palms of young women, in which palmar wrinkling occurs within minutes of immersion in water. It may be asymptomatic or associated with stinging, burning or paraesthesia. Palmar wrinkling typically resolves after drying of the hands without persisting signs. The mechanism for this phenomenon is unclear, with theories including acquired abnormalities in eccrine glands, an underlying primary keratoderma, or potential induction by cyclooxygenase. Aquagenic palmar wrinkling is also recognized in association with CF, both in individuals with the disease and carriers, with more rapid onset of wrinkling in the former. In this case, there was no suggestion of personal or family histories of CF, and hyperkeratosis persisted for months at a time until liberal regular use of keratolytic topical agents was introduced. Hereditary papulotranslucent acrokeratoderma, a differential diagnosis in this case, was considered; however, in this condition once papules and wrinkling appear, they typically remain and are further exacerbated by water exposure. For this patient, a diagnosis of atypical ASK was favoured due to the persisting sequelae, with probable mild atopic dermatitis reflected by palmar hyperlinearity. This case serves to highlight this rare dermatological phenomenon and its impact on a teenage swimmer.

THENAR AND HYPOTHENAR THICKNESS: DOES IT VARY AND DOES THAT ALTER THE RISK OF DISTAL RADIUS FRACTURES?

Distal radius fractures are common, particularly in post-menopausal women. Several factors have been identified such as osteopenia and an increased risk of falling. We hypothesised that increased soft tissue padding from muscle and fat in the volar hand may confer an element of protection against fractures more in men than women and more in younger than older patients.The aim of the study was to assess for thenar and hypothenar thickness and assess whether it varies between sexes and changes with age.We retrospectively evaluated hand MRI scans performed for non-acute conditions in adults without previous injury or surgery. Using the Patient Archiving and Communication System (PACS) we measured the distance (mm) from the volar surface of the trapezium to the skin, the hook of the hamate to skin and the pisiform to skin as measures of thenar and hypothenar thickness. We also recorded the sex and age of the subjects.Soft tissue thickness was corrected for hand size by dividing by capitate length which we measured; we have already established this as a surrogate measure of hand size.The scans of 51 men (mean age 35, range 19–66) years and 27 women (mean age 49, range 19–79) years were reviewed. Men had significantly thicker soft tissues compared to women over both the thenar and hypothenar eminences (p=0.0001). Soft tissue thickness did not change significantly with age (p&gt; 0.05).The study confirms a significant difference in volar hand soft tissue thickness between men and women accounting for differences in hand size. Our previous research has shown how we fall onto our outstretched hands in the upper limb falling reflex and we have shown that padding the thenar and hypothenar eminences reduces force transmission to the forearm bones. In theory thicker thenar and hypothenar musculature would help protect against distal radius fractures following a fall on an outstretched hand. The thinner musculature on women may further predispose them to an increased risk of distal radius fractures. Further research is needed to assess for any loss of volar hand soft tissue thickness beyond age 75 years.

A Cross-sectional Study to Associate BMI with Pressure Pain Threshold and Pain Tolerance Among Healthy Young Individuals

Background: Although pain is common for everyone, it is a subjective sensation influenced by different variables. One factor that influences pain threshold and perception is body mass index (BMI). This study investigates the connection between BMI and pain by assessing the pressure pain threshold and tolerance on the median and ulnar nerves in the palms. Methods: The PPT and PT of 120 participants were measured with a digital pressure algometer (FPIX50; Wagner Instruments). Measurement sessions consisted of consecutive PPT and PT readings on the thenar and hypothenar eminence of the dominant and non-dominant hand. In addition, the PPT and PT were compared between BMI, thenar and hypothenar, dominant and non-dominant hand, and sexes. Results: The results have shown that the PPT and PT increased with BMI. However, only three out of the eight readings were significant (p = &lt;0.05). When comparing the thenar and hypothenar, the results revealed significantly higher PPT and PT levels in the hypothenar (p = &lt; 0.001). The results comparing the PPT and PT between the dominant and non-dominant hand revealed a significantly higher PPT in the non-dominant hand reflected across the thenar and hypothenar (t= -6.197, p= &lt;0.01) (t= -2.550, p= 0.012), respectively. In addition, males had higher PPT and PT values (p = &lt;0.05). Conclusion: The results suggest that individuals with higher BMI can tolerate more pain. They also indicate that the hypothenar eminence could withstand higher pain levels than the thenar eminence. In addition, our assessment also revealed a higher pain threshold observed in participants' nondominant hands, but the same could not be deduced for the pressure pain tolerance. Furthermore, the results have shown that males could tolerate more pain than females.

Presence of accessory abductor digiti minimi muscle in two cadavers.

During routine cadaveric dissection, accessory hypothenar muscles were incidentally discovered in two cadavers, both males, aged 86 and 92. Both muscles originated from the palmaris longus tendon in the distal portion of the forearm and were identified as accessory abductor digiti minimi (AADM) muscles, based on their association with abductor digiti minimi. While AADM is a common variant in the antebrachium, it is less typical for them to originate from the palmaris longus tendon. The presence of such an AADM could complicate surgical procedures requiring resection of the palmaris longus tendon. Moreover, the surrounding neurovasculature - namely the ulnar nerve as it passes through the ulnar canal between the pisiform and hook of the hamate - could be compressed by contractions of an AADM with such a proximal origin. This can manifest as ulnar neuropathies resulting in pain, weakness, or protracted flexion of the fourth and fifth digits (ulnar claw). Our description of these muscles adds to previous accounts of variation of the palmaris longus and abductor digiti minimi muscles while considering potential clinical implications.

EFFECT OF MAGNESIUM SULPHATE PRETREATMENT ON ONSET, DURATION OF ACTION AND RECOVERY OF NEUROMUSCULAR BLOCKADE WITH VECURONIUM

Aim: To determine the effectiveness of magnesium sulphate pretreatment on the onset of action of vecuronium and on the duration of action of vecuronium. 100 patients of aged between 18-55 years of ASA grade I and II undergoing surgery under Material And Methods: general anaesthesia were included and devided in two groups. Fifteen minutes before induction of anaesthesia, patients in Group- I received magnesium sulphate 40mg/kg in 0.9% normal saline 100 ml as an intravenous infusion over 15 minutes, and Group-II received 0.9% normal saline 100 ml without magnesium sulphate. After the end of surgery, when the amplitude of T1 was recovered to 10%, patients in both groups received inj. neostigmine 0.05 mg/kg and inj. glycopyrolate 0.02mg/kg IV. After neostigmin-glycopyrolate administration, T1 was measured up to 10 minutes in both groups. Neuromuscular transmission was assessed by electromyography on the left hypothenar muscle, using trans-cutaneous electrodes. The measurement was done after induction of anaesthesia. reduction in mean onse Result: t time was statistically highly signicant in magnesium sulphate group 171.26±30.97 sec vs control group 281.02 ± 33.22 second, (p&lt;0.0001). The mean duration of action was prolonged in magnesium sulphate group 44.26±9.92min vs control group 28.6±6.83m ,and was statistically highly signicant, (p&lt;0.0001). We used neuromuscular monitoring by train of four (TOF) because the response of neuromuscular blocking drugs is not predictable. Hence, TOF monitoring by NMT provided more predictable and rational approach to the use of muscle relaxants. Ma Conclusion: gnesium hastens the onset of neuromuscular blockade as well as reduces the variability of onset time of neuromuscular blockade and decreases the recovery rate of vecuronium and so prolonges the duration of action of blockade

Associations among serum VEGF and CGRP levels with the peripheral vascular blood flow of the skin of the hands in women with Fibromyalgia

BackgroundFibromyalgia (FM) is a long-term condition of unknown physiopathology, whose hallmark symptoms are diffuse musculoskeletal chronic pain and fatigue. ObjectivesWe aimed to analyze the associations among serum vascular endothelial growth factor (VEGF) and calcitonin gene-related peptide (CGRP) levels with the peripheral temperature of the skin of both hands and the core body temperature in patients with FM and healthy controls. MethodsWe conducted a case-control observational study with fifty-three women diagnosed with FM and twenty-four healthy women. VEGF and CGRP levels were spectrophotometrically analyzed in serum by enzyme-linked immunosorbent assay. We used an infrared thermography camera to assess the peripheral temperature of the skin of the dorsal thumb, index, middle, ring, and pinkie fingertips and dorsal centre as well as the palm thumb, index, middle, ring, and pinkie fingertips, palm centre and thenar and hypothenar eminences of both hands and an infrared thermographic scanner to record the tympanic membrane and axillary temperature. ResultsLinear regression analysis adjusting for age, menopause status, and body mass index showed that serum VEGF levels were positively associated with the maximum (β = 65.942, 95% CI [4.100,127.784], p = 0.037), minimum (β = 59.216, 95% CI [1.455,116.976], p = 0.045), and mean (β = 66.923, 95% CI [3.142,130.705], p = 0.040) temperature of the thenar eminence of the non-dominant hand, as well as with the maximum temperature of the hypothenar eminence of the non-dominant hand (β = 63.607, 95% CI [3.468,123.747], p = 0.039) in women diagnosed with FM. ConclusionsMild associations were observed between serum VEGF levels and the peripheral temperature of the skin in hand areas in patients with FM; therefore, it is not possible to establish a clear relationship between this vasoactive molecule and vasodilation of the hands in these patients.

Blood Ammonia Concentration in Children with Chronic Liver Disease: A Tool for Prediction of Esophageal Varices

Background: Esophageal varices (EVs) are a serious complication of portal hypertension in patient with chronic liver disease (CLD). The major portion of ammonia carried by portal blood is shunted into systemic circulation in chronic liver disease. The upper GI endoscopy is currently the best reliable method to diagnose the presence of esophageal varices. But it is invasive, relatively expensive and not easily available. Blood ammonia is a noninvasive and easily accessible laboratory parameter that can predict the presence of esophageal varices.&#x0D; Objectives: To observe the blood ammonia concentration in children with chronic liver disease: a tool for prediction of esophageal varices.&#x0D; Methods: This cross sectional observational study was conducted at the Department of Paediatric Gastroenterology and Nutrition, BSMMU, Dhaka, Bangladesh from January 2018 to December 2019. A total of 63 cases of CLD were selected. Study sample were selected according to the inclusion and exclusion criteria. Along with proper clinical history, examination &amp; initial investigation, fasting venous blood ammonia level and upper GI endoscopy were done in all patients. Receiver-Operator Characteristic (ROC) curve was analysis to set up a cut-off value of blood ammonia for prediction of esophageal varices. Sensivity, specificity, positive predictive value, negative predictive value and accuracy were determined to see the performance of blood ammonia value as a diagnostic test for esophageal varices.&#x0D; Results: Among the 63 patients, (74.6%) had esophageal varices. Wilson disease was the most common etiology of CLD (43; 68.3%) among the studied patients. The mean blood ammonia level were 40.5± 18.0 (µmol/L), 50.5± 14.3 (µmol/L), 50.7± 9.9 (µmol/L), 53.1± 26.9 (µmol/L) and 71.9± 19.0 (µmol/L) in absent esophageal varices, grade-I, grade-II, grade-III and grade-IV esophageal varices respectively. The difference was statistically significant (&lt;0.05). Moderate correlation (r= 0.452; p value = 0.001) between blood ammonia level and grades of esophageal varices was found. It was observed that wasting of thenar and hypothenar muscle was the most common stigmata, seen in 15 (23.8%) cases, 2 (3.2%) had clubbing, 7 (11.1%) had leuconychia, 1 (1.6%) had palmer erythema, 3 (4.8%) had gynacomasia and 1 (1.6%) had testicular atrophy. Wilson disease was the most common 43 (68.3%). It was observed that 45 (71.4 %) patients had raised serum ALT and 45 (71.4%) had low serum albumin (&lt;3.5 g/dl). Low haemoglobin (&lt;9 gm/dl) was found in 47 (74.6%) cases, raised serum bilirubin level (&gt;1.2 mg/dl) in 29 (46.03%) cases, thrombocytopenia (platelet count &lt;1.50×109/mm3) in 36 (57.1%) patients and prolonged INR (&gt;1.5) in 29 (46.03%) cases, blood ammonia was raised (&gt;32 µmol/L) in 52 (82.5%) cases. It was observed that the mean ± SD blood ammonia level was 56.2± 17.9 µmol/L in esophageal varices present group (n = 47) and 40.5± 18.0 µmol/L in absent esophageal varices group (n = 16). Here p value is 0.004, which is statistically significant.&#x0D; Conclusion: Blood ammonia concentration is a biochemical predictor for assessing the grading of esophageal varices. In the present study, a moderate positive correlation was found between blood ammonia concentration and grades of esophageal varices in children with CLD.

Reliability of Ulnar Nerve Sensation Tests in Patients with Cubital Tunnel Syndrome and Healthy Subjects.

Static two-point discrimination (2PD) and Semmes–Weinstein monofilament (SWM) tests are commonly used to evaluate sensory disorders in the hand. The aim of this study was to evaluate the reliability of 2PD and SWM tests in the ulnar nerve innervation area in patients with cubital tunnel syndrome (CuTS) and healthy individuals. This was a two-group repeated-measures inter-rater and intra-rater reliability study. Twenty-one patients with CuTS and 30 healthy adults participated. The static 2PD test was performed using a standardized Dellon discriminator, whereas the SWM test was conducted using TOUCH TEST monofilaments. Two examiners performed both tests at the hypothenar eminence and the fourth and fifth digits (ulnar nerve innervation hand territory). First, examiner A conducted three series of 2PD and SWM tests twice with a 15-min rest period (within-day intra-rater reliability). Next, examiner B repeated the same examination 5 min after (inter-rater reliability). Examiner A conducted the same examination 7 days after (between-day intra-rater reliability). For single measurements, the inter-rater reliability and within-day intra-rater reliability in the 2PD was at least 0.81 in patients with CuTS or healthy subjects. The between-days intra-rater reliability for a single measurement varied from 0.56 to 0.95 in CuTS patients and healthy subjects. The between-days intra-rater reliability for mean value from three measurements was above 0.80. The kappa for SWM was above 0.8 and the percentage of agreement was at least 90% for all sessions and trials. In conclusion, the 2PD and SWM tests are reliable for assessing sensation in the ulnar nerve innervation area of the hand in patients with CuTS and healthy subjects.

A Young Man With Acute-Onset Bilateral Arm Weakness After Traumatic Sciatic Neuropathy: A Clinical Vignette.

A Young Man With Acute-Onset Bilateral Arm Weakness After Traumatic Sciatic Neuropathy: A Clinical Vignette.

A new method to quantify innervation of the ulnar intrinsic hand muscles by the anterior interosseous nerve in Martin‐Gruber anastomosis and nerve transfer surgery

It is important to quantify the amount of crossover innervation from the anterior interosseous nerve (AIN) through Martin-Gruber anastomosis (MGA) particularly in patients with high ulnar nerve injury who undergo nerve transfer surgery. The objective of this study is to describe a novel electrophysiological method for quantifying innervation from the AIN that can be done using conventional nerve conduction study setup and commonly available software for analysis. Seven subjects with MGA and nine patients who had undergone AIN to ulnar nerve transfer underwent conventional motor nerve conduction studies. Recording was done over the hypothenar and first dorsal interosseous muscles while stimulating the median and ulnar nerves at the wrist and elbow. Datapoint-by-datapoint subtraction of the compound muscle action potentials evoked at the elbow and wrist was performed after they had been onset-aligned. The results were compared to the collision technique and innervation ratio method. Results from the digital subtraction method were highly correlated with the collision technique (r= 0.96, p< 0.05). In contrast, its correlation with the innervation ratio method is substantially lower. In comparison to previously described techniques, the digital subtraction method has a number of practical advantages. It uses conventional nerve conduction study setup, and the added step of digital alignment and subtraction can be done through commonly available software. With the increasing use of nerve transfer surgery in severe high ulnar nerve injury, this could be a useful method to identify the presence of MGA prior to surgery and for evaluating nerve recovery following surgery.