Strength measurements of the intrinsic hand muscles: a review of the development and evaluation of the Rotterdam intrinsic hand myometer

Automatic Quantitative Assessment of Muscle Strength Based on Deep Learning and Ultrasound

Skeletal muscle is a vital organ that promotes human movement and maintains posture. Accurate assessment of muscle strength is helpful to provide valuable insights for athletes' rehabilitation and strength training. However, traditional techniques rely heavily on the operator's expertise, which may affect the accuracy of the results. In this study, we propose an automated method to evaluate muscle strength using ultrasound and deep learning techniques. B-mode ultrasound data of biceps brachii of multiple athletes at different strength levels were collected and then used to train our deep learning model. To evaluate the effectiveness of this method, this study tested the contraction of the biceps brachii under different force levels. The classification accuracy of this method for grade 4 and grade 6 muscle strength reached 98% and 96%, respectively, and the overall average accuracy was 93% and 87%, respectively. The experimental results confirm that the innovative methods in this paper can accurately and effectively evaluate and classify muscle strength.

Distal nerve transfers for peripheral nerve injuries: indications and outcomes

Distal nerve transfer is a refined surgical technique involving the redirection of healthy sacrificable nerves from one part of the body to reinstate function in another area afflicted by paralysis or injury. This approach is particularly valuable when the original nerves are extensively damaged and standard repair methods, such as direct suturing or grafting, may be insufficient. As the nerve coaptation is close to the recipient muscles or skin, distal nerve transfers reduce the time to reinnervation. The harvesting of nerves for transfer should usually result in minimal or no donor morbidity, as any anticipated loss of function is compensated for by adjacent muscles or overlapping cutaneous territory. Recent years have witnessed notable progress in nerve transfer procedures, markedly enhancing the outcomes of upper limb reconstruction for conditions encompassing peripheral nerve, brachial plexus and spinal cord injuries.

A randomized controlled trial on the effectiveness of mirror therapy in improving strength, range of movement and muscle activity, in people with carpal tunnel syndrome

BACKGROUND

There is little information on the potential effects of mirror therapy (MT) on motor recovery in individuals with Carpal Tunnel Syndrome (CTS).

PURPOSE

To compare the effectiveness of a MT protocol versus a therapeutic exercise (TE) protocol, in improving strength, range of motion (ROM), muscle activity, pain, and functionality in patients with CTS.

STUDY DESIGN

Randomized clinical trial.

METHODS

Thirty-nine participants with unilateral CTS were divided into two groups: (i) MT group (n = 20) that followed an exercise protocol applied to the unaffected hand reflected in a mirror, and (ii) TE group (n = 19) that followed the same exercise protocol using the unaffected hand but without a mirror. Strength, wrist ROM, muscle activity, pain and functionality, were assessed at baseline (T0), after treatment (T1) and one month after treatment (T2).

RESULTS

At T1, the MT group showed significantly higher wrist flexion-extension ROM compared to TE (p = 0.04, d = 0.8), maintained at T2 (p = 0.02, d = 0.8). No significant changes were observed in ulnar-radius deviation, pronosupination, or fatigue following either MT or TE (p > 0.05). MT exhibited enhanced handgrip strength at T1 (p = 0.001, d = 0.7), as well as an increase in the extensor carpi radialis (ECR) and flexor carpi radialis (FCR) maximum muscle activity (p = 0.04, d = 1.0; p = 0.03, d = 0.4). At T1, both groups decreased pain (p = 0.002, d = 1.1; p = 0.02, d = 0.7), and improved functionality (p < 0.001, d = 0.8; p = 0.01, d = 0.5) (MT and TE respectively).

DISCUSSION

MT led to enhancements in wrist flexion-extension movement, handgrip strength and functionality unlike TE. MT notably increased muscle activity, particularly in the ECR and FCR muscles.

CONCLUSIONS

MT is a favorable strategy to improve wrist flexion-extension ROM, handgrip strength, ECR and FCR muscle activity, and functionality in people with unilateral CTS.

Psychometric properties of body structures and functions measures in non-surgical thumb carpometacarpal osteoarthritis: A systematic review

BACKGROUND

Measurement of treatment outcomes and change in health status over time is a critical component of clinical practice and research for people with osteoarthritis. Numerous clinical tools are used to assess the structures and function of the thumb in persons with thumb carpometacarpal osteoarthritis however their psychometrics have not yet been systematically explored.

PURPOSE

The purpose of this study was to explore the psychometric properties of clinical tools used in persons with non-surgical thumb carpometacarpal osteoarthritis to objectively measure thumb structures and function, evaluate the quality of such studies, and subsequently make clinical and future research recommendations.

STUDY DESIGN

Systematic review.

METHODS

A systematic search and screening was conducted across nine databases. Original research published between 2002 and 2022 that involved the assessment of psychometric properties (validity, reliability, precision, responsiveness, sensitivity, specificity, and minimal clinically important difference) of clinical tools were included. Sample characteristics, methods, and psychometric findings from each study were compiled. The methodological quality of included studies was evaluated using the COnsensus-based Standards for the selection of health Measurement Instruments' checklist. Two independent researchers screened articles and assessed methodological quality and when not in agreement, a third party was consulted.

RESULTS

Eleven studies were included in the review. The mean age of all participants in the studies was 69 years of age. The study designs included prospective case-control, prospective cohort, and cross-sectional to determine the psychometric properties of the measurements and tools. The included studies examined techniques to assess range of motion, strength, and pain-pressure thresholds, and screen for arthritis (ie, provocative tests). The intermetacarpal distance method, Kapandji index, pain-pressure threshold test, and pain-free grip and pinch dynamometry demonstrate excellent reliability and acceptable precision. Metacarpal extension, adduction, and pressure-shear provocative tests have superior sensitivity and specificity and the extension and adduction tests have excellent reliability. Other assessments included in the review yielded less robust psychometric properties. Studies were of variable methodological quality spanning from inadequate to very good.

CONCLUSIONS

Based on the available literature on the psychometric properties of assessments of body structures and functions in persons with non-operative thumb carpometacarpal osteoarthritis, we offer a limited set of recommendations for use when screening for arthritis symptomology and measuring hand strength, thumb mobility, and pain thresholds. Additional psychometric research is needed in these domains as well as in dexterity, sensation, and objective measures of hand function. Future research should employ best practices in psychometric research.

Clinical and neurophysiological recovery of ulnar nerve conduction block at the elbow

INTRODUCTION/AIMS

An important mechanism of peripheral nerve motor and sensory dysfunction is conduction block (CB). However, recovery from mechanically induced CB has been rarely studied in humans. The aim of this study was to describe clinical, electrodiagnostic (EDx), and ultrasonographic (US) characteristics of CB recovery in ulnar neuropathy at the elbow (UNE).

METHODS

We recruited a group of consecutive patients presenting to our EDx laboratory with UNE and >50% motor CB. Patients' histories were obtained and neurologic, EDx, and US examinations were repeated every 1-3 mo for at least 12 mo.

RESULTS

We studied 10 patients (5 men), with a mean age of 63 y (range, 51-81 y). In all affected arms CB was localized to the retrocondylar groove. Following conservative management, myometrically measured index finger abduction improved from a median of 49% to 100% relative to the contralateral index finger, and ulnar nerve CB decreased from a median of 74% to 6%. Most of the improvement took place within 8 mo of symptom onset, and 6 mo after receiving treatment instructions. Mean motor nerve conduction velocity improved from 15 to 27 m/s in the most affected 2-cm ulnar nerve segment.

DISCUSSION

The resolution of CB after typical chronic compression may take longer than after acute compression. This should be considered by clinicians when estimating prognosis for discussions with patients.

Test-retest Reliability and Precision of the Rotterdam Intrinsic Hand Myometer

PURPOSE

The purpose of this study was to determine the test-retest reliability and precision of Rotterdam Intrinsic Hand Myometer (RIHM) in healthy adults.

METHODS

Twenty-nine participants originally recruited via convenience sampling at a Midwestern state fair returned approximately 8 days later for retest. An average of three trials for each of the five intrinsic hand strength measurements were collected using the same technique that was used during initial testing. Test-retest reliability was assessed using the intraclass correlation coefficient or ICC(2,3) and precision was evaluated using the standard error of measurement (SEM), and the minimal detectable change (MDC90)/MDC%.

RESULTS

Across all measures of intrinsic strength, the RIHM and its standardized procedures had excellent test-retest reliability. Index finger metacarpophalangeal flexion demonstrated the lowest reliability, and right small finger abduction, left thumb carpometacarpal abduction, and index finger metacarpophalangeal abduction tests had the highest reliability. Precision, as evidenced by SEM and MDC values, was excellent for tests of left index and bilateral small finger abduction strength and acceptable for all other measurements.

CONCLUSIONS

Test-retest reliability and precision of RIHM across all measurements was excellent.

CLINICAL RELEVANCE

These findings indicate that RIHM is a reliable and precise tool in measuring intrinsic strength of hands of healthy adults, although further research is needed in clinical populations.

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

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

We determined normative values for 2IP strength using a sample from a normal population. More studies are needed to validate these results.

CLINICAL RELEVANCE

Second interosseous pinch strength may be a useful tool to assess ulnar nerve function.

Evaluation of functional recovery in the intrinsic and flexor muscles after nerve transfer for ulnar nerve lesion. A new measurement method: The Cha method

"Supercharge" end-to-side (SETS) nerve transfer for lesions of the proximal ulnar nerve is a recognized novel option, but improvement in motor function after surgery has not been properly evaluated. We therefore propose a modified method for quantitative evaluation of improvement in the intrinsic hand strength. We screened 216 patients with proximal ulnar nerve lesions who presented to our outpatient department from 2012 to 2020. Of these, 101 met our inclusion/exclusion criteria and were evaluated just before surgery. We used a novel method to measure finger abduction ("2nd-abd"), adduction ("5th-add"), and ring and little finger flexion strength ("4,5 grip"), and analyzed correlations with established pinch strength data. The male:female sex ratio was 86:15, and the ratio dominant to nondominant arm involvement was 68:33. All strength measurements were analyzed as percentage affected to contralateral normal side. On Pearson correlation analysis, the strength ratios for "4,5 grip", "2nd-abd", and "5th-add", but not "5 fingers (total) grip", showed significant positive correlation with key and oppositional pinch strength (all p &lt; 0.001). Additionally, linear regression analysis showed identical results for each strength correlation with key/oppositional pinch, except for "5 fingers total) grip" (all, p &lt; 0.001). SETS is a reasonable alternative for lesions of the proximal ulnar nerve. The measurement method we propose is feasible for specific assessment of intrinsic muscle strength, which improves after surgery. LEVEL OF EVIDENCE: Diagnostic, level IV.

Predicting metacarpal length using paired ratios with bilateral X-ray films

Introduction:

When the metacarpal bones sustain severe osseous injury requiring reconstruction, functional recovery relies on the precise distribution of tension throughout full range of motion. While the small scale of hand structures compounds the effects of altering normal anatomy, literature lacks consensus recommendations for the acceptable degree of length alteration and/or appropriate methods of length estimation in reconstructive procedures. Length asymmetry has been reported in human metacarpal bones; however, studies assessing this phenomenon in living subjects with attention to functional implications or length prediction are lacking.

Methods:

Hand X-rays were obtained for 34 patients aged 25–80 without history of metacarpal trauma, joint degeneration, or pathologic bone metabolism. A scaled bivariate model predicted metacarpal length using an ipsilateral paired metacarpal and matching contralateral ratio: Estimate_Dx_R = Median_Dy_R * (Median_Dx_L/Median_Dy_L). A second set of predictions used the contralateral metacarpal as a control. Pearson correlation coefficients, paired t-tests, and chi-square tests evaluated the symmetry between bilateral metacarpal lengths and paired metacarpal ratios as well as the accuracy of each predictive method.

Results:

The contralateral control and target metacarpal differed significantly in digits 1, 2, 3, and 5. No significant difference in matched metacarpal ratios of the right and left hands was found. For all digits except 5D, bivariate model predictions generated were more strongly correlated with actual target length. Chi-square tests did not detect a significant difference in predictive value of the two models.

Conclusion:

The scaled bivariate model we describe may be useful and economic in generating accurate length estimates of metacarpals for reconstructive procedures.

Clinical evaluation of thumb base osteoarthritis: A scoping review

Introduction

Thumb base osteoarthritis (OA) is a prevalent hand OA phenotype, associated with specific risk factors, treatment strategies, and requiring a distinct subset of evaluative approaches. This paper aimed at surveying our clinical evaluative methods and identifying gaps in our ability to capture the thumb's unique attributes and how they could impact our treatment recommendations.

Methods

A scoping review was conducted in accordance with the Joanna Briggs Institute methodology to gather relevant published and non-published articles regarding clinical tests currently available to assess the physical presentation of thumb base OA with special consideration of its specific multifactorial parameters namely architecture, ligaments, biomechanics, neuromuscular control, and proprioception. A full search strategy of MEDLINE, CINAHL, EMBASE, Scopus, Google Scholar, and Clinical Trials.gov from their inception through May 2020 was performed.

Results

Of 1936 citation identified, 54 met the inclusion criteria. Fifty-two clinical physical tests for the evaluation of thumb base OA were extracted, most of which well suited to address research questions regarding efficacy of clinical intervention, however providing limited information regarding the underlying impairments of ligaments, biomechanics, neuromuscular or proprioceptive components.

Conclusions

The tests and measures specific to the basal thumb OA phenotype, and capable of isolating its multifactorial contributors are scarce. Our limited physical assessment repertoire impedes our ability to describe and answer explicative research questions. Without these we cannot evaluate the effect of conservative management and provide specific treatment recommendations. Further research is needed to develop and validate distinct clinical tools for this debilitating pathology.

Effectiveness of Distal Nerve Transfers for Claw Correction With Proximal Ulnar Nerve Lesions

PURPOSE

To evaluate claw deformity correction following anterior interosseous nerve (AIN) end-to-end transfer to the deep motor branch of the ulnar nerve (DMBUN) in high ulnar nerve injuries.

METHODS

Eleven patients were retrospectively evaluated for metacarpophalangeal joint hyperextension and proximal interphalangeal joint extension lag in the fourth and fifth digits following ulnar nerve injury adjacent or proximal to the elbow, who underwent AIN end-to-end transfer to the DMBUN.

RESULTS

Patients underwent surgery an average of 5 months following injury (range, 2-9 months) and were followed for an average of 19 months after surgery (range, 12-30 months). At the last follow-up, clawing was observed in all patients, with proximal interphalangeal joint extension lag averaging 46.8° (SD, ±20°) in the fourth digit and 57.7° (SD, ±12°) in the little finger.

CONCLUSIONS

None of our patients experienced claw correction after AIN end-to-end transfer to the DMBUN.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Evaluation of muscle strength following peripheral nerve surgery: A scoping review

Peripheral nerve injury (PNI) can result in devastating loss of function, often with poor long-term prognosis. Increased use of peripheral nerve surgical techniques (eg, nerve transfer, nerve grafting, and nerve repair) has resulted in improved muscle strength and other functional outcomes in patients with PNI. Muscle strength has largely been evaluated with the British Medical Research Council (MRC) scale. MRC is convenient to use in clinical settings, but more robust measures of muscle function are necessary to fully elucidate patient recovery. This scoping review aims to examine alternative instruments used to assess muscle function in studies of peripheral nerve surgery for PNI of the upper and lower limbs. A scoping review was conducted using Ovid MEDLINE, CINAHL, EMBASE, and PubMed databases in May and December of 2020, yielding a total of 20 studies pertaining to the review question. Studies pertaining to handheld dynamometry, grip and pinch dynamometry, Rotterdam Intrinsic Hand Myometers, isokinetic dynamometry, ultrasonography, and electromyography were reviewed. We provide a synopsis of each method and current clinical applications and discuss potential benefits, disadvantages, and areas of future research.

Determining Isolated Thumb Forces in Osteoarthritic and Healthy Persons

Carpometacarpal (CMC) osteoarthritis (OA) can dramatically impair thumb function resulting in the inability to complete basic tasks. Development of a method to detect thumb forces changes is essential to understand of the progression of carpometacarpal osteoarthritis and the effects of treatment. The goals of this study were to (1) develop a method to measure thumb forces in multiple directions, (2) perform an initial demonstration of this method on three populations, young healthy (YH), older healthy (OH), and older participants with carpometacarpal osteoarthritis, and (3) determine the effects of short-term exercises on thumb force production in these pilot groups. A multi-axis load cell with a custom-built apparatus and a hand grip dynamometer were used to measure thumb and grip forces. Forces were collected in four directions: radial abduction and adduction, and palmar abduction and adduction. All participants completed thumb and grip testing prior to (week 0), during (week 2), and following (week 6), a hand exercise regimen. Group differences and the effects of exercise on force production were determined. Hand exercises improved thumb forces in young healthy female participants during radial (p = 0.017) and palmar abduction (p = 0.031) and female participants with osteoarthritis during palmar abduction (p = 0.010). Exercise improved grip strength in young healthy males (p = 0.028), young healthy females (p = 0.041), and females with osteoarthritis (p = 0.027). This research demonstrates the successful use of a new device to determine isolated thumb forces, and its clinical utility to identify changes after a short exercise regimen.

Age- and gender-stratified adult myometric reference values of isometric intrinsic hand strength

STUDY DESIGN

Descriptive normative.

INTRODUCTION

Intrinsic hand strength can be impacted by hand arthritis, peripheral nerve injuries, and spinal cord injuries. Grip dynamometry does not isolate intrinsic strength, and manual muscle testing is not sensitive to change in grades 4 and 5. The Rotterdam Intrinsic Hand Myometer is a reliable and valid test of intrinsic hand strength; however, no adult normative data are available.

PURPOSE OF THE STUDY

To describe age- and gender-stratified intrinsic hand strength norms in subjects aged 21 years and above and to determine if factors known to predict grip dynamometry also predict measures of intrinsic hand strength.

METHODS

Three trials of 5 measures of maximal isometric intrinsic strength were performed bilaterally by 607 "healthy-handed" adult males and females. Average strength values were stratified by age and gender. Data were analyzed to determine the influence of demographic and anthropometric variables on intrinsic strength.

RESULTS

Intrinsic strength generally followed age and gender trends similar to grip dynamometry. Age, gender, body mass index, and the interaction between gender and body mass index were predictors of intrinsic strength, whereas in most cases, the hand being tested did not predict the intrinsic strength.

DISCUSSION

With the addition of these findings, age- and gender-stratified hand intrinsic strength norms now span from age 4 through late adulthood. Many factors known to predict grip dynamometry also predict intrinsic myometry. Additional research is needed to evaluate the impact of vocational and avocational demands on intrinsic strength.

CONCLUSIONS

These norms can be referenced to evaluate and plan hand therapy and surgical interventions for intrinsic weakness.

Intrarater and interrater reliability of a hand-held dynamometric technique to quantify palmar thumb abduction strength in individuals with and without carpal tunnel syndrome

STUDY DESIGN

Clinical measurement.

INTRODUCTION

Individuals with carpal tunnel syndrome (CTS) sometimes exhibit weakness of palmar abduction strength (TAS). Reliable assessment of this strength in both subjects with and without CTS with the commonly available Microfet 2 is not known.

PURPOSE OF THE STUDY

The purpose of this study was to determine the intrarater and interrater reliabilities of a handheld dynamometric (HHD) method to assess TAS in individuals with and without CTS using the commercially available MicroFET2 and to examine the association between TAS in individuals with CTS and the Carpal Tunnel Symptom Questionnaire (CTSQ) scores.

METHODS

In 2 different study phases, individuals with and without CTS were assessed for TAS by 2 different examiners. The CTSQ was administered to the individuals with CTS.

RESULTS

Intrarater and interrater reliability coefficients (0.89-0.93 and 0.82-0.90, respectively) were excellent in individuals with and without CTS. Weak negative correlations were found between TAS and overall CTSQ and symptom severity subscale scores, and a moderate negative correlation was found between TAS and functional Status Subscale score.

DISCUSSION

This HHD method of reliably assessing TAS better quantifies deficits and progress than traditional manual muscle testing for muscle grades greater than 3/5.

CONCLUSION

This method of HHD reliably quantifies TAS but is more reliable with the same than different raters.

Measuring intrinsic hand strength in healthy adults: The accuracy intrarater and inter-rater reliability of the Rotterdam Intrinsic Hand Myometer

STUDY DESIGN

Clinical measurement study.

INTRODUCTION

Measuring the isometric strength generated during isolated hand joint motions is a challenging feat. The Rotterdam Intrinsic Hand Myometer (RIHM; med.engineers, Rotterdam, Netherlands) permits measurement of isolated movements of the hand. To date, there is limited evidence on the inter-rater reliability and limited adult normative data of RIHM. Given that multiple raters, often with varying degrees of experience, are needed to collect normative data, inter-rater reliability testing and a comparison of novice and experienced raters are needed.

PURPOSES OF THE STUDY

The purposes of this study were to test the accuracy, intrarater reliability, and inter-rater reliability of the RIHM in healthy-handed adults.

METHODS

RIHM accuracy was tested through use of precision class F weights. Adults 18 years or older without upper limb dysfunction were recruited. Each participant was tested by 4 raters, 3 occupational therapy graduate students, and an experienced certified hand therapist, through use of a calibrated RIHM. Five strength measures were tested bilaterally (ie, thumb carpometacarpal palmar abduction, index finger metacarpophalangeal [MP] abduction, index finger MP flexion, thumb MP flexion, and small finger MP abduction) 3 times per a standardized protocol. Statistical methods were used to test accuracy, inter-rater reliability, and intrarater/response stability.

RESULTS

The accuracy of RIHM device error was 5% or less. Reliability testing included the participation of 19 women and 10 men (n = 29). All raters were in excellent agreement across all muscles (intraclass correlation coefficient, ≥0.81). Low standard error of measurement values of ≤8.3 N (1.9 lb) across raters were found. The response stability and/or intrarater reliability of the novice and certified hand therapist raters were not statistically different.

DISCUSSION

The RIHM has an acceptable instrument error; the RIHM and its standardized procedure have excellent inter-rater reliability and response stability when testing those without hand limitations; and the response stability and/or intrarater reliability of expert and novice raters were consistent.

CONCLUSIONS

The use of the RIHM is justified when multiple raters of varying expertise collect normative data or conduct cohort studies on persons with healthy hands. Future research is warranted.

LEVEL OF EVIDENCE

Not applicable.

Transcutaneous high-frequency alternating current for rapid reversible muscle force reduction below pain threshold

OBJECTIVE

The development of non-invasive, quickly reversible techniques for controlling undesired muscle force production (e.g. spasticity) could expand rehabilitation approaches in those with pathology by increasing the type and intensity of exercises that can be performed. High-frequency alternating current (HFAC) has been previously established as a viable method for blocking neural conduction in peripheral nerves. However, clinical application of HFAC for nerve conduction block is limited due to the invasiveness of surgical procedures and the painful onset response. This study aimed to examine the use of transcutaneous HFAC (tHFAC) at various stimulation frequencies to address these shortfalls.

APPROACH

Ten individuals participated in the study. Surface electrodes were utilized to apply tHFAC (0.5-12 kHz) to the median and ulnar nerves. Individual pain threshold was determined by gradual increase of stimulation amplitude. Subjects then performed a force-matching task by producing grip forces up to the maximal voluntary contraction level with and without application of tHFAC below the pain threshold.

MAIN RESULTS

Pain threshold current amplitude increased linearly with stimulation frequency. Statistical analysis showed that both stimulation frequency and charge injected per phase had significant effects (p   <  0.05) on grip force reduction. At the group level, application of tHFAC below pain threshold reduced grip force by a maximum of 40.7%  ±  8.1%. Baseline grip force trials interspersed between tHFAC trials showed consistent grip force, indicating that fatigue was not a factor in force reduction.

SIGNIFICANCE

Our results demonstrate the effectiveness of tHFAC at reducing muscle force when applied below the pain threshold, suggesting its potential clinical viability. Future studies are necessary to further elucidate the mechanism of force reduction before clinical application.

Advancing System Performance with Redundancy: From Biological to Artificial Designs

Redundancy is a fundamental characteristic of many biological processes such as those in the genetic, visual, muscular, and nervous systems, yet its driven mechanism has not been fully comprehended. Until recently, the only understanding of redundancy is as a mean to attain fault tolerance, which is reflected in the design of many man-made systems. On the contrary, our previous work on redundant sensing (RS) has demonstrated an example where redundancy can be engineered solely for enhancing accuracy and precision. The design was inspired by the binocular structure of human vision, which we believe may share a similar operation. In this letter, we present a unified theory describing how such utilization of redundancy is feasible through two complementary mechanisms: representational redundancy (RPR) and entangled redundancy (ETR). We also point out two additional examples where our new understanding of redundancy can be applied to justify a system's superior performance. One is the human musculoskeletal system (HMS), a biological instance, and the other is the deep residual neural network (ResNet), an artificial counterpart. We envision that our theory would provide a framework for the future development of bio-inspired redundant artificial systems, as well as assist studies of the fundamental mechanisms governing various biological processes.

Reference values of intrinsic muscle strength of the hand of adolescents and young adults

STUDY DESIGN

A cross-sectional clinical measurement study.

INTRODUCTION

Measuring intrinsic hand muscle strength helps evaluate hand function or therapeutic outcomes. However, there are no established normative values in adolescents and young adults between 13 and 20 years of age.

PURPOSE OF THE STUDY

To measure hand intrinsic muscle strength and identify associated factors that may influence such in adolescents and young adults through use of the Rotterdam intrinsic hand myometer.

METHODS

A total of 131 participants (male: 63; female: 68) between 13 and 20 years of age completed the strength measurements of abductor pollicis brevis, first dorsal interosseus (FDI), deep head of FDI and lumbrical of second digit, flexor pollicis brevis (FPB), and abductor digiti minimi. Two trials of the measurements of each muscle were averaged for analyses. Self-reported demographic data were used to examine the influences of age, sex, and body mass index (BMI) on intrinsic hand muscle strength.

RESULTS

Normative values of intrinsic hand muscle strength were presented by age groups (13, 14, 15-16, 17-18, 19-20 year olds) for each sex category (male, female). A main effect of sex, but not age, on all the muscles on both the dominant (FPB: P = .02, others: P < .001) and non-dominant (FDI: P = .005, FPB: P = .01, others: P < .001) sides was found. A significant effect of BMI was found on dominant (P = .009) and non-dominant abductor pollicis brevis (P = .002). In addition, FDI (P = .005) and FPB (P = .002) were stronger on the dominant side than the non-dominant side.

DISCUSSION

Intrinsic hand muscle strength may be influenced by different factors including sex, BMI, and hand dominance. A larger sample is needed to rigorously investigate the influence of age on intrinsic strength in male and female adolescents and young adults.

CONCLUSION

The results provide reference values and suggest factors to be considered when evaluating hand function and therapeutic outcomes in both clinical and research settings. Further study is recommended.

LEVEL OF EVIDENCE

VI.

Botulinum Toxin Type A Injections as Monotherapy for Upper Limb Essential Tremor Using Kinematics

Background:There is a significant need for a targeted therapy for essential tremor (ET), as medications have not been developed specifically for ET, and the ones prescribed are often not well-tolerated, so that many patients remain untreated. Recent work has shown that, unlike previous experience, kinematically guided individualized botulinum toxin type A (BoNT-A) injections provide benefit along with minimal weakness. Ours is the first long-term (96-week) safety and efficacy study of BoNT-A as monotherapy for ET using kinematically driven injection parameters.Methods:Ten ET patients were administered six serial BoNT-A treatments every 16 weeks and were assessed at 6 weeks following treatment. During each study visit, the Fahn–Tolosa–Marin (FTM) scale, the Unified Parkinson’s Disease Rating Scale, and the Quality of Life for Essential Tremor Questionnaire (QUEST) were administered along with kinematic assessment of the treated limb. Participants performed scripted tasks with motion sensors placed over each arm joint. Dosing patterns were determined using the movement disorder neurologist’s interpretation of muscles contributing to the kinematically analyzed upper limb tremor biomechanics.Results:There was a 33.8% (p<0.05) functional improvement (FTM part C) and a 39.8% (p<0.0005) improvement in QUEST score at week 96 compared to pretreatment scores at week 0. Although there was a 44.6% (p<0.0005) non-dose-dependent reduction in maximal grip strength, only 2 participants complained of mild weakness. Following the fourth serial treatment, mean action tremor score was reduced by 62.9% (p=0.001) in the treated and by 44.4% (p=0.03) in the untreated arm at week 96 compared to week 48.Conclusions:Individualized BoNT-A dosing patterns to each individual’s tremor biomechanics provided an effective monotherapy for ET as function improved without functionally limiting muscle weakness.

New Device for Intrinsic Hand Muscle Strength Measurement: An Alternative to Strain Gauge Handheld Dynamometer

An accurate measurement of intrinsic hand muscle strength (IHMS) is required by clinicians for effective clinical decision-making, diagnosis of certain diseases, and evaluation of the outcome of treatment. In practice, the clinicians use Intrins-o-meter and Rotterdam Intrinsic Hand Myometer for IHMS measurement. These are quite bulky, expensive, and possess poor interobserver reliability (37–52%) and sensitivity. The purpose of this study was to develop an alternative lightweight, accurate, cost-effective force measurement device with a simple electronic circuit and test its suitability for IHMS measurement. The device was constructed with ketjenblack/deproteinized natural rubber sensor, 1-MΩ potential divider, and Arduino Uno through the custom-written software. Then, the device was calibrated and tested for accuracy and repeatability within the force range of finger muscles (100 N). The 95% limit of agreement in accuracy from −1.95 N to 2.06 N for 10 to 100 N applied load and repeatability coefficient of ±1.91 N or 6.2% was achieved. Furthermore, the expenditure for the device construction was around US$ 53. For a practical demonstration, the device was tested among 16 participants for isometric strength measurement of the ulnar abductor and dorsal interossei. The results revealed that the performance of the device was suitable for IHMS measurement.

First dorsal interosseous muscle contraction results in radiographic reduction of healthy thumb carpometacarpal joint

INTRODUCTION

Hand therapists selectively strengthen the first dorsal interosseus (FDI) to stabilize arthritic joints yet the role of the FDI has not yet been radiographically validated.

PURPOSE

To determine if FDI contraction reduces radial subluxation (RS) of the thumb metacarpal (MC).

METHODS

Fluoroscopy was used to obtain true anterior-posterior radiographs of non-arthritic CMC joints: 1) at rest, 2) while stressed and 3) while stressed with maximal FDI contraction. Maximal FDI strength during CMC stress and thumb MC RS and trapezial articular width were measured. The ratio of RS to the articular width was calculated.

RESULTS

Seventeen participants (5 male, 12 female) participated. Subluxation of a stressed CMC significantly reduced and the subluxation to articular width ratio significantly improved after FDI activation.

CONCLUSIONS

Contraction of the FDI appears to radiographically reduce subluxation of the healthy thumb CMC joint. Further exploration on the FDI's reducibility and its carry-over effects in arthritic thumbs is needed.

LEVEL OF EVIDENCE

4.

Cadaveric Study on Morphology of Dorsal Interossei of Hand and its Anatomical Variation

INTRODUCTION

The dorsal interossei are the abductors of the fingers and the knowledge of its variation help the surgeon in treatment of fractures, claw hand and compartment syndromes.

AIM

To note the origin, insertion, pattern of muscle fibres and tendon length of all the dorsal interossei of hand.

MATERIALS AND METHODS

Routinely dissected 30 formalin fixed hand in the Department of Anatomy, KMC, Manipal, were observed for origin, insertion and tendon length and muscle pattern of dorsal interossei.

RESULTS

Out of 30 hands, presence of supernumerary muscle was observed in three hands. Presence of three heads of dorsal interossei was noted in one hand.

CONCLUSION

The finding of present study is of importance to surgeons and orthopaedicians during conservative and surgical management of hand deformity. Adequate knowledge of these muscular variations is also important in treatment of fractures, stiff hand, claw hand or tendon transfer.

Carpal tunnel release with subneural reconstruction of the transverse carpal ligament compared with isolated open and endoscopic release

We report a new surgical technique of open carpal tunnel release with subneural reconstruction of the transverse carpal ligament and compare this with isolated open and endoscopic carpal tunnel release.

Between December 2007 and October 2011, 213 patients with carpal tunnel syndrome (70 male, 143 female; mean age 45.6 years; 29 to 67) were recruited from three different centres and were randomly allocated to three groups: group A, open carpal tunnel release with subneural reconstruction of the transverse carpal ligament (n = 68); group B, isolated open carpal tunnel release (n = 92); and group C, endoscopic carpal tunnel release (n = 53).

At a mean final follow-up of 24 months (22 to 26), we found no significant difference between the groups in terms of severity of symptoms or lateral grip strength. Compared with groups B and C, group A had significantly better functional status, cylindrical grip strength and pinch grip strength. There were significant differences in Michigan Hand Outcome scores between groups A and B, A and C, and B and C. Group A had the best functional status, cylindrical grip strength, pinch grip strength and Michigan Hand Outcome score.

Subneural reconstruction of the transverse carpal ligament during carpal tunnel decompression maximises hand strength by stabilising the transverse carpal arch.

Cite this article: Bone Joint J 2015;97-B:221–8

The added value of measuring thumb and finger strength when comparing strength measurements in hypoplastic thumb patients

BACKGROUND

When interventions to the hand are aimed at improving function of specific fingers or the thumb, the RIHM (Rotterdam Intrinsic Hand Myometer) is a validated tool and offers more detailed information to assess strength of the involved joints besides grip and pinch measurements.

METHODS

In this study, strength was measured in 65 thumbs in 40 patients diagnosed with thumb hypoplasia. These 65 thumbs were classified according to Blauth. Longitudinal radial deficiencies were also classified. The strength measurements comprised of grip, tip, tripod and key pinch. Furthermore palmar abduction and opposition of the thumb as well as abduction of the index and little finger were measured with the RIHM.

FINDINGS

For all longitudinal radial deficiency patients, grip and pinch strength as well as palmar abduction and thumb opposition were significantly lower than reference values (P<0.001). However, strength in the index finger abduction and the little finger abduction was maintained or decreased to a lesser extent according to the degree of longitudinal radial deficiency. All strength values decreased with increasing Blauth-type. Blauth-type II hands (n=15) with flexor digitorum superficialis 4 opposition transfer including stabilization of the metacarpophalangeal joint showed a trend toward a higher opposition strength without reaching statistical significance (P=0.094),however compared to non-operated Blauth-type II hands (n=6) they showed a lower grip strength (P=0.019).

INTERPRETATION

The RIHM is comparable in accuracy to other strength dynamometers. Using the RIHM, we were able to illustrate strength patterns on finger-specific level, showing added value when evaluating outcome in patients with hand related problems.

Assessing weakness in patients with ulnar neuropathy: comparison between a custom hand muscle dynamometer and a pinch dynamometer

OBJECTIVE

The aim of this study was to compare the use of a custom intrinsic hand dynamometer (HD) with that of a standard pinch dynamometer (PD) in assessing strength in patients with ulnar neuropathy at the elbow.

DESIGN

Nine patients (age, 53 ± 3 yrs) with clinical and electrophysiological features of ulnar neuropathy at the elbow with conduction block (CB) were studied. All underwent bilateral ulnar motor nerve conduction studies recording from the first dorsal interosseous and a quantitative measurement of strength of the first dorsal interosseous using a custom-made HD and a standard PD.

RESULTS

The maximal strength of the ulnar neuropathy at the elbow-affected side (16.2 ± 8.0 N) was found to be significantly lower than that of the unaffected side (27.9 ± 11.2 N), as measured by HD. Strength differences were not significant between the affected (62.7 ± 26.4 N) and unaffected sides (48.0 ± 20.5 N) using PD. HD force decrement (in comparison with the unaffected limb) correlated strongly with CB percentage (r = 0.74). No relationship was found between PD and CB (r = 0.05).

CONCLUSIONS

HD was better able to measure the weakness of affected muscles than did PD, and its results correlated well with the extent of electrophysiological CB. Therefore, a custom HD would provide a better indication of disease severity, progression, or improvement in strength in studies of ulnar neuropathy at the elbow with CB.

Outcome following nerve repair of high isolated clean sharp injuries of the ulnar nerve

OBJECTIVE

The detailed outcome of surgical repair of high isolated clean sharp (HICS) ulnar nerve lesions has become relevant in view of the recent development of distal nerve transfer. Our goal was to determine the outcome of HICS ulnar nerve repair in order to create a basis for the optimal management of these lesions.

METHODS

High ulnar nerve lesions are defined as localized in the area ranging from the proximal forearm to the axilla just distal to the branching of the medial cord of the brachial plexus. A meta-analysis of the literature concerning high ulnar nerve injuries was performed. Additionally, a retrospective study of the outcome of nerve repair of HICS ulnar nerve injuries at our institution was performed. The Rotterdam Intrinsic Hand Myometer and the Rosén-Lundborg protocol were used.

RESULTS

The literature review identified 46 papers. Many articles presented outcomes of mixed lesion groups consisting of combined ulnar and median nerves, or the outcome of high and low level injuries was pooled. In addition, outcome was expressed using different scoring systems. 40 patients with HICS ulnar nerve lesions were found with sufficient data for further analysis. In our institution, 15 patients had nerve repair with a median interval between trauma and reconstruction of 17 days (range 0-516). The mean score of the motor and sensory domain of the Rosen's Scale instrument was 58% and 38% of the unaffected arm, respectively. Two-point discrimination never reached less then 12 mm.

CONCLUSION

From the literature, it was not possible to draw a definitive conclusion on outcome of surgical repair of HICS ulnar nerve lesions. Detailed neurological function assessment of our own patients showed that some ulnar nerve function returned. Intrinsic muscle strength recovery was generally poor. Based on this study, one might cautiously argue that repair strategies of HICS ulnar nerve lesions need to be improved.

An involuntary stereotypical grasp tendency pervades voluntary dynamic multifinger manipulation

We used a novel apparatus with three hinged finger pads to characterize collaborative multifinger interactions during dynamic manipulation requiring individuated control of fingertip motions and forces. Subjects placed the thumb, index, and middle fingertips on each hinged finger pad and held it-unsupported-with constant total grasp force while voluntarily oscillating the thumb's pad. This task combines the need to 1) hold the object against gravity while 2) dynamically reconfiguring the grasp. Fingertip force variability in this combined motion and force task exhibited strong synchrony among normal (i.e., grasp) forces. Mechanical analysis and simulation show that such synchronous variability is unnecessary and cannot be explained solely by signal-dependent noise. Surprisingly, such variability also pervaded control tasks requiring different individuated fingertip motions and forces, but not tasks without finger individuation such as static grasp. These results critically extend notions of finger force variability by exposing and quantifying a pervasive challenge to dynamic multifinger manipulation: the need for the neural controller to carefully and continuously overlay individuated finger actions over mechanically unnecessary synchronous interactions. This is compatible with-and may explain-the phenomenology of strong coupling of hand muscles when this delicate balance is not yet developed, as in early childhood, or when disrupted, as in brain injury. We conclude that the control of healthy multifinger dynamic manipulation has barely enough neuromechanical degrees of freedom to meet the multiple demands of ecological tasks and critically depends on the continuous inhibition of synchronous grasp tendencies, which we speculate may be of vestigial evolutionary origin.

A systematic review of dynamometry and its role in hand trauma assessment

The dynamometer was developed by American neurologists and came into general use in the late 19th century. It is still used in various ways as a diagnostic and prognostic tool in clinical settings. In this systematic review we assessed in detail the different uses of dynamometry, its reliability, different dynamometers used and the influence of rater experience by bringing together and evaluating all published literature in this field. It was found that dynamometry is applied in a wide range of medical conditions. Furthermore, the great majority of studies reported acceptable to high reliability of dynamometry. Jamar mechanical dynamometer was used most often in the studies reviewed. There were mixed results concerning the effect of rater experience. The factors influencing the results of dynamometry were identified as age, gender, body weight, grip strength, BMI, non/dominant hand, assessing upper/lower limbs, rater and patient’s strength and the distance from the joint where the dynamometer is placed. This review provides an understanding of the relevance and significance of dynamometry which should serve as a starting point to guide its use in hand trauma assessment. On the basis of our findings, we suggest that hand dynamometry has a great potential, and could be used more often in clinical practice.

Modifying the Medical Research Council grading system through Rasch analyses

The Medical Research Council grading system has served through decades for the evaluation of muscle strength and has been recognized as a cardinal feature of daily neurological, rehabilitation and general medicine examination of patients, despite being respectfully criticized due to the unequal width of its response options. No study has systematically examined, through modern psychometric approach, whether physicians are able to properly use the Medical Research Council grades. The objectives of this study were: (i) to investigate physicians’ ability to discriminate among the Medical Research Council categories in patients with different neuromuscular disorders and with various degrees of weakness through thresholds examination using Rasch analysis as a modern psychometric method; (ii) to examine possible factors influencing physicians’ ability to apply the Medical Research Council categories through differential item function analyses; and (iii) to examine whether the widely used Medical Research Council 12 muscles sum score in patients with Guillain–Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy would meet Rasch model's expectations. A total of 1065 patients were included from nine cohorts with the following diseases: Guillain–Barré syndrome (n = 480); myotonic dystrophy type-1 (n = 169); chronic inflammatory demyelinating polyradiculoneuropathy (n = 139); limb-girdle muscular dystrophy (n = 105); multifocal motor neuropathy (n = 102); Pompe's disease (n = 62) and monoclonal gammopathy of undetermined related polyneuropathy (n = 8). Medical Research Council data of 72 muscles were collected. Rasch analyses were performed on Medical Research Council data for each cohort separately and after pooling data at the muscle level to increase category frequencies, and on the Medical Research Council sum score in patients with Guillain–Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy. Disordered thresholds were demonstrated in 74–79% of the muscles examined, indicating physicians’ inability to discriminate between most Medical Research Council categories. Factors such as physicians’ experience or illness type did not influence these findings. Thresholds were restored after rescoring the Medical Research Council grades from six to four options (0, paralysis; 1, severe weakness; 2, slight weakness; 3, normal strength). The Medical Research Council sum score acceptably fulfilled Rasch model expectations after rescoring the response options and creating subsets to resolve local dependency and item bias on diagnosis. In conclusion, a modified, Rasch-built four response category Medical Research Council grading system is proposed, resolving clinicians’ inability to differentiate among its original response categories and improving clinical applicability. A modified Medical Research Council sum score at the interval level is presented and is recommended for future studies in Guillain–Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy.

A COMPARISON OF THE STRENGTH OF THE ABDUCTION OF THE LITTLE AND INDEX FINGERS AND PALMAR ABDUCTION AND OPPOSITION OF THE THUMB BETWEEN COLLEGE BASEBALL PLAYERS AND INEXPERIENCED SPORTS PLAYERS

The purpose of this study was to investigate the strengths of four intrinsic muscles of the hand of college baseball players. The strengths of four intrinsic muscle groups were measured by the Rotterdam Intrinsic Hand Myometer (RIHM) which has been developed to assess the abduction of the little finger and index finger, and palmar abduction and opposition of the thumb. The strengths of these four intrinsic muscle groups were compared between baseball players and inexperienced sports players.

The abduction of the little finger and index finger, and the opposition of the thumb in both the dominant and nondominant hands of the baseball players were notably stronger than those of the inexperienced sports players. There was no statistical difference in the strength of the palmar abduction of the thumb between the two groups. The results suggest that the specific intrinsic muscles in both the dominant and nondominant hands might be strengthened by repeated baseball practices, such as a batting performance, which requires strain in both the dominant and nondominant hands repeatedly.

The responsiveness of sensibility and strength tests in patients undergoing carpal tunnel decompression

BACKGROUND

Several clinical measures of sensory and motor function are used alongside patient-rated questionnaires to assess outcomes of carpal tunnel decompression. However there is a lack of evidence regarding which clinical tests are most responsive to clinically important change over time.

METHODS

In a prospective cohort study 63 patients undergoing carpal tunnel decompression were assessed using standardised clinician-derived and patient reported outcomes before surgery, at 4 and 8 months follow up. Clinical sensory assessments included: touch threshold with monofilaments (WEST), shape-texture identification (STI™ test), static two-point discrimination (Mackinnon-Dellon Disk-Criminator) and the locognosia test. Motor assessments included: grip and tripod pinch strength using a digital grip analyser (MIE), manual muscle testing of abductor pollicis brevis and opponens pollicis using the Rotterdam Intrinsic Handheld Myometer (RIHM). The Boston Carpal Tunnel Questionnaire (BCTQ) was used as a patient rated outcome measure.

RESULTS

Relative responsiveness at 4 months was highest for the BCTQ symptom severity scale with moderate to large effects sizes (ES = -1.43) followed by the BCTQ function scale (ES = -0.71). The WEST and STI™ were the most responsive sensory tests at 4 months showing moderate effect sizes (WEST ES = 0.55, STI ES = 0.52). Grip and pinch strength had a relatively higher responsiveness compared to thenar muscle strength but effect sizes for all motor tests were very small (ES ≤0.10) or negative indicating a decline compared to baseline in some patients.

CONCLUSIONS

For clinical assessment of sensibility touch threshold assessed by monofilaments (WEST) and tactile gnosis measured with the STI™ test are the most responsive tests and are recommended for future studies. The use of handheld myometry (RIHM) for manual muscle testing, despite more specifically targeting thenar muscles, was less responsive than grip or tripod pinch testing using the digital grip analyser (MIE). When assessing power and pinch strength the effect of other concomitant conditions such as degenerative joint disease on strength needs to be considered.

Peg Restrained Intrinsic Muscle Evaluator (PRIME): development, reliability, and normative values of a device to quantify intrinsic hand muscle strength in children

PURPOSE

There is a need for objective measures of pediatric intrinsic hand muscle strength as the current standard, the manual muscle test, lacks sensitivity to clinically important changes in muscle strength. We report the development, reliability, and normative values of the Peg Restrained Intrinsic Muscle Evaluator (PRIME), a device that quantifies intrinsic hand muscle strength.

METHODS

Typically developing children, ages 4 to 16 years (n = 119), established normative values of intrinsic strength for thumb palmar abduction, thumb opposition, and index and small finger abduction. A subset of 30 children (15 boys, 15 girls), ages 7 to 16 years, determined inter-rater and intra-rater reliability. We calculated mean, standard deviation, intraclass correlation coefficients, and smallest detectable differences.

RESULTS

Normative results indicate that gender and age were significant predictors of strength. Although the dominant hand generated higher strength measurements on average, differences were not statistically significant. Mean index and small finger abduction strength was significantly lower than thumb abduction and opposition in both genders. Intraclass correlation coefficients ranged from 0.85 to 0.94 for inter-rater reliability and 0.88 to 0.98 for intra-rater reliability. Bland-Altman plots showed an even distribution across the zero line.

CONCLUSIONS

The PRIME device is a reliable tool for the quantification of intrinsic hand muscle strength in children. Age-specific and gender-specific normative values in typically developing children can serve as a future resource for clinicians treating pediatric hand or neuromuscular conditions.

Muscle redundancy does not imply robustness to muscle dysfunction

It is well-known that muscle redundancy grants the CNS numerous options to perform a task. Does muscle redundancy, however, allow sufficient robustness to compensate for loss or dysfunction of even a single muscle? Are all muscles equally redundant? We combined experimental and computational approaches to establish the limits of motor robustness for static force production. In computer-controlled cadaveric index fingers, we find that only a small subset (<5%) of feasible forces is robust to loss of any one muscle. Importantly, the loss of certain muscles compromises force production significantly more than others. Further computational modeling of a multi-joint, multi-muscle leg demonstrates that this severe lack of robustness generalizes to whole limbs. These results provide a biomechanical basis to begin to explain why redundant motor systems can be vulnerable to even mild neuromuscular pathology.

Growth diagrams for individual finger strength in children measured with the RIHM

BACKGROUND

Although grip and pinch strength provide a more global measure of a large number of digits and muscles, measuring strength of individual fingers or the thumb can provide additional and more detailed information regarding hand strength.

QUESTIONS/PURPOSES

We developed growth diagrams for individual finger strength in children.

PATIENTS AND METHODS

We measured thumb palmar abduction, thumb opposition, and thumb flexion in the metacarpophalangeal joint, and abduction of the index and little fingers in 101 children (4-12 years old) using a myometer. We recorded hand dominance, gender, height, and weight. All measurements were performed in a randomized order by the same researcher. We developed statistical models for drawing growth diagrams using estimated percentiles for each strength measurement. Separate models for dominant and nondominant hands of boys and girls were developed, in addition to a combined model.

RESULTS

Because there was no difference in strength between boys and girls and between dominant and nondominant hands, both hands and genders were combined in one growth diagram for each measurement. The normative data were presented in a table format and in growth diagrams for each myometer measurement.

CONCLUSIONS

These diagrams can be used for pediatric patients such as patients with congenital malformations or neuromuscular disorders who receive interventions or therapy aimed at function of the hand, fingers, or thumb. The growth diagrams facilitate distinguishing between the effects of growth and intervention on strength development.

Evaluation of function and appearance of adults with untreated triphalangeal thumbs

PURPOSE

Triphalangeal thumb is a congenital malformation characterized by an additional phalanx of the thumb. Although surgical treatment of this condition is common practice, in the past this was not generally advised. Therefore, a population with an untreated triphalangeal thumb is still present. The purpose of this study is to compare function and appearance of adults with an untreated triphalangeal thumb to a normal population.

METHODS

Twelve adults with 23 hands with an untreated triphalangeal thumb, unilateral or bilateral, were examined using objective measurements (thumb movement, joint instability, pain, and strength) and subjective measurements (visual analog scale; Disabilities of the Arm, Shoulder, and Hand questionnaire; and Short Form 36 health survey).

RESULTS

Objective measurements showed no limitations in range of motion or in grip and pinch strength. No joint instability was found in the interphalangeal joints. Five thumbs had instability in the metacarpophalangeal joint. Strength of the thumb in anteposition was diminished to 64% compared to a normal population. Opposition was diminished to 62%, and metacarpophalangeal joint flexion strength was diminished to 61%. The patients scored lower compared to a normal population for the domain of social functioning in the Medical Outcome Study 36-item short form health survey; the Disabilities of the Arm, Shoulder, and Hand questionnaire showed no differences. Visual analog scale scores for appearance of the thumb were scored low (2.2 of 10) by the adults, in contrast to visual analog scale scores for function (7.7).

CONCLUSIONS

The examined group of adults with an untreated triphalangeal thumb had adequate thumb movement. Thumb strength was diminished for all specific thumb functions (anteposition, opposition, and thumb flexion), as low as 55%, compared to normal controls. Self-rated scores indicate that patients perceived their functionality as good. The appearance, however, was rated much lower, implying a dislike of the thumb by the patients. This indicates that the main impact of an untreated triphalangeal thumb in daily functioning might not be the diminished function but rather the dissimilar appearance.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Maximal voluntary fingertip force production is not limited by movement speed in combined motion and force tasks

Numerous studies of limbs and fingers propose that force-velocity properties of muscle limit maximal voluntary force production during anisometric tasks, i.e., when muscles are shortening or lengthening. Although this proposition appears logical, our study on the simultaneous production of fingertip motion and force disagrees with this commonly held notion. We asked eight consenting adults to use their dominant index fingertip to maximize voluntary downward force against a horizontal surface at specific postures (static trials), and also during an anisometric "scratching" task of rhythmically moving the fingertip along a 5.8 +/- 0.5 cm target line. The metronome-timed flexion-extension movement speed varied 36-fold from "slow" (1.0 +/- 0.5 cm/s) to "fast" (35.9 +/- 7.8 cm/s). As expected, maximal downward voluntary force diminished (44.8 +/- 15.6%; p = 0.001) when any motion (slow or fast) was added to the task. Surprisingly, however, a 36-fold increase in speed did not affect this reduction in force magnitude. These remarkable results for such an ordinary task challenge the dominant role often attributed to force-velocity properties of muscle and provide insight into neuromechanical interactions. We propose an explanation that the simultaneous enforcement of mechanical constraints for motion and force reduces the set of feasible motor commands sufficiently so that force-velocity properties cease to be the force-limiting factor. While additional work is necessary to reveal the governing mechanisms, the dramatic influence that the simultaneous enforcement of motion and force constraints has on force output begins to explain the vulnerability of dexterous function to development, aging, and even mild neuromuscular pathology.

Reliability of hand strength measurements using the Rotterdam Intrinsic Hand Myometer in children

PURPOSE

Grip strength and pinch strength measurements are often used to assess hand function. However, both measure a number of muscle groups in combination, and grip strength in particular is dominated by extrinsic hand muscles. The Rotterdam Intrinsic Hand Myometer (RIHM) was recently introduced to measure the force that individual fingers and thumb can exert in different directions. The aim of this study was to establish the reliability of these measurements with use of the RIHM in children.

METHODS

Sixty-three healthy children between 4 and 12 years of age participated in this study. The RIHM was used to measure thumb palmar abduction, thumb opposition, thumb flexion at the metacarpal-phalangeal (MP) joint, index finger abduction, and little finger abduction. A retest was performed with an average test-retest interval of 26 days.

RESULTS

For the thumb, palmar abduction strength had intraclass correlation coefficients (ICCs) of .98 for both hands. For both thumb opposition and flexion at the MP joint, ICCs were .97 for the dominant hands and .98 for the nondominant hands. Index finger abduction had ICCs of .94 and .95 and little finger abduction had ICCs of .90 and .92 for the dominant and nondominant hands, respectively. The smallest detectable differences for dominant and nondominant hands respectively were thumb palmar abduction, 15% and 15%; thumb opposition, 12% and 9%; thumb flexion (at the MP joint), 12% and 9%; abduction of the index finger, 17% and 17%; and little finger abduction, 26% and 26%.

CONCLUSIONS

We found that the RIHM was reliable for use in children. Intraclass correlation coefficients and smallest detectable differences were comparable with those obtained with use of the RIHM in adults and with values found for pinch and grip strength in children. Because the RIHM measures more specific aspects of hand function than grip and pinch, adding the RIHM to measurement protocols may contribute to a more complete overview of a child's hand function.

Power grip, pinch grip, manual muscle testing or thenar atrophy - which should be assessed as a motor outcome after carpal tunnel decompression? A systematic review

Background

Objective assessment of motor function is frequently used to evaluate outcome after surgical treatment of carpal tunnel syndrome (CTS). However a range of outcome measures are used and there appears to be no consensus on which measure of motor function effectively captures change. The purpose of this systematic review was to identify the methods used to assess motor function in randomized controlled trials of surgical interventions for CTS. A secondary aim was to evaluate which instruments reflect clinical change and are psychometrically robust.

Methods

The bibliographic databases Medline, AMED and CINAHL were searched for randomized controlled trials of surgical interventions for CTS. Data on instruments used, methods of assessment and results of tests of motor function was extracted by two independent reviewers.

Results

Twenty-two studies were retrieved which included performance based assessments of motor function. Nineteen studies assessed power grip dynamometry, fourteen studies used both power and pinch grip dynamometry, eight used manual muscle testing and five assessed the presence or absence of thenar atrophy. Several studies used multiple tests of motor function. Two studies included both power and pinch strength and reported descriptive statistics enabling calculation of effect sizes to compare the relative responsiveness of grip and pinch strength within study samples. The study findings suggest that tip pinch is more responsive than lateral pinch or power grip up to 12 weeks following surgery for CTS.

Conclusion

Although used most frequently and known to be reliable, power and key pinch dynamometry are not the most valid or responsive tools for assessing motor outcome up to 12 weeks following surgery for CTS. Tip pinch dynamometry more specifically targets the thenar musculature and appears to be more responsive. Manual muscle testing, which in theory is most specific to the thenar musculature, may be more sensitive if assessed using a hand held dynamometer – the Rotterdam Intrinsic Handheld Myometer. However further research is needed to evaluate its reliability and responsiveness and establish the most efficient and psychometrically robust method of evaluating motor function following surgery for CTS.