Exploratory analysis using machine learning algorithms to predict pinch strength by anthropometric and socio-demographic features

Objectives. This study examines the role of different machine learning (ML) algorithms to determine which socio-demographic factors and hand-forearm anthropometric dimensions can be used to accurately predict hand function. Methods. The cross-sectional study was conducted with 7119 healthy Iranian participants (3525 males and 3594 females) aged 10-89 years. Seventeen hand-forearm anthropometric dimensions were measured by JEGS digital caliper and a measuring tape. Tip-to-tip, key and three-jaw chuck pinches were measured using a calibrated pinch gauge. Subsequently, 21 features pertinent to socio-demographic factors and hand-forearm anthropometric dimensions were used for classification. Furthermore, 12 well-known classifiers were implemented and evaluated to predict pinches. Results. Among the 21 features considered in this study, hand length, stature, age, thumb length and index finger length were found to be the most relevant and effective components for each of the three pinch predictions. The k-nearest neighbor, adaptive boosting (AdaBoost) and random forest classifiers achieved the highest classification accuracy of 96.75, 86.49 and 84.66% to predict three pinches, respectively. Conclusions. Predicting pinch strength and determining the predictive hand-forearm anthropometric and socio-demographic characteristics using ML may pave the way to designing an enhanced tool handle and reduce common musculoskeletal disorders of the hand.

Efficacy of Abductor Pollicis Longus Suspension Arthroplasty Combined With Mini TightRope for Osteoarthritis of Thumb Carpometacarpal Joint

BACKGROUND

We aimed to evaluate the efficacy of abductor pollicis longus (APL) suspension arthroplasty with trapeziectomy combined with first and second metacarpal fixation using suture button device.

METHODS

Thirteen patients (14 thumbs) who underwent APL suspension arthroplasty combined with suture button device for osteoarthritis of the carpometacarpal joint of the thumb (Eaton grade III: 6 and IV: 8 thumbs) at our institution between 2015 and 2019 and were followed up for more than 24 months were included in the study. Preoperative and postoperative range of motion (ROM) of radial and palmar abduction, grip and key pinch strength, visual analog scale (VAS) scores for pain, and the trapezial space ratio (TSR) on radiographic images before and after surgery were statistically examined.

RESULTS

The mean age of the patients was 59.6 ± 8.1 years, and the mean follow-up period was 45.4 ± 12.2 months. While grip and pinch strength did not significantly change between preoperative and final follow-up measurements, the ROM of radial and palmar abduction and the VAS score at the latest follow-up were significantly better than the preoperative values (P < .05). The mean TSR immediately after surgery and at the latest follow-up was 0.28 ± 0.089 and 0.22 ± 0.084, respectively, indicating a mean reduction rate of 23.3 ± 15.2%.

CONCLUSIONS

This surgical technique showed significant improvement in the ROM of radial and palmar abduction and the VAS score for pain, and the combined fixation of the first and second metacarpals with suture button device suppressed the subsidence of the first metacarpal.

Effect of extension of the ulnar fingers on force control and muscle activity of the hand during a precision pinch

Some individuals extend the three ulnar fingers when performing a precision pinch. The aim of the present study was to investigate the mechanisms and effect of the extension of the ulnar fingers during a pinch. When performing a pulp pinch task with the ulnar fingers in two positions (extension and flexion), 27 participants maintained 5% of their maximum force. The mean pinch force, force variability and time taken to reach the targeted force (reaching time) were calculated. Muscle activity was simultaneously measured, using surface electromyography, for nine muscles: the flexor pollicis brevis; abductor pollicis brevis; flexor pollicis longus; first lumbrical; first dorsal interosseous; flexor digitorum superficialis of the index finger; extensor indicis; and extensor digitorum of the index and ring fingers. No significant differences in the mean pinch force or force variability were found. However, the reaching time was significantly shorter (approximately 20% reduction) in the extension position and the activities in the flexor pollicis brevis, first lumbrical, extensor indicis and extensor digitorum of the ring finger were significantly higher. These findings suggest that extending the ulnar fingers during pinching enhances the activity of key muscles involved in the movement and allows for more rapid force exertion.

Carpal tunnel syndrome prediction with machine learning algorithms using anthropometric and strength-based measurement

OBJECTIVES

Carpal tunnel syndrome (CTS) stands as the most prevalent upper extremity entrapment neuropathy, with a multifaceted etiology encompassing various risk factors. This study aimed to investigate whether anthropometric measurements of the hand, grip strength, and pinch strength could serve as predictive indicators for CTS through machine learning techniques.

METHODS

Enrollment encompassed patients exhibiting CTS symptoms (n = 56) and asymptomatic healthy controls (n = 56), with confirmation via electrophysiological assessments. Anthropometric measurements of the hand were obtained using a digital caliper, grip strength was gauged via a digital handgrip dynamometer, and pinch strengths were assessed using a pinchmeter. A comprehensive analysis was conducted employing four most common and effective machine learning algorithms, integrating thorough parameter tuning and cross-validation procedures. Additionally, the outcomes of variable importance were presented.

RESULTS

Among the diverse algorithms, Random Forests (accuracy of 89.474%, F1-score of 0.905, and kappa value of 0.789) and XGBoost (accuracy of 86.842%, F1-score of 0.878, and kappa value of 0.736) emerged as the top-performing choices based on distinct classification metrics. In addition, using variable importance calculations specific to these models, the most important variables were found to be wrist circumference, hand width, hand grip strength, tip pinch, key pinch, and middle finger length.

CONCLUSION

The findings of this study demonstrated that wrist circumference, hand width, hand grip strength, tip pinch, key pinch, and middle finger length can be utilized as reliable indicators of CTS. Also, the model developed herein, along with the identified crucial variables, could serve as an informative guide for healthcare professionals, enhancing precision and efficacy in CTS prediction.

Assessment and treatment of nonsurgical thumb carpometacarpal joint osteoarthritis: A modified Delphi-based consensus paper of the American Society of Hand Therapists

BACKGROUND

While the literature is abundant on hand therapy assessment and treatment of nonsurgical thumb carpometacarpal (CMC) osteoarthritis (OA), clarity and uniformity are meager, making it a desirable diagnosis to establish expert consensus.

PURPOSE

This study aimed to ascertain if consensus exists for the assessment and treatment of nonsurgical management of thumb CMC OA in the hand therapy clinical setting.

STUDY DESIGN

This was a consensus paper via the modified Delphi approach.

METHODS

A modified Delphi method was used to determine consensus among an expert panel, including hand therapists and hand surgeons, via two online surveys. A consensus paper steering committee (from the American Society of Hand Therapist's research division) designed the surveys and analyzed responses. Consensus was established as 75% agreement among the expert panel. Demographic information was collected from the expert panel.

RESULTS

The expert panel included 34 hand therapists and seven hand surgeons. The survey response rates were 93.6% for the first survey and 90.2% for the second survey. Consensus recommendations were classified according to the World Health Organization categorization. These included evaluating the body structures for clinical signs/clinical testing and body functions for pain, range of motion for palmar abduction, radial abduction, opposition, and thumb metacarpal phalangeal flexion/extension, and grip and tripod pinch strength. Further consensus recommendations were for the assessment of function using a region-specific, upper extremity patient-reported outcome measure (activity and participation), environmental factors, outcome expectation, and illness perception within the patient's unique environmental and social contexts. Treatment recommendations included the use of an orthosis during painful activities, a dynamic stability program (stable C posture, release of tight adductors, and strengthening of stabilizers), patient education, joint protection techniques, adaptive equipment, and functional-based intervention.

CONCLUSIONS

The findings describe the consensus of a group of experts and provide a clinical reference tool on the hand therapy assessment and treatment of nonsurgical thumb CMC joint OA.

The impact of diabetic peripheral neuropathy on pinch proprioception

This study aims to investigate the impact of type 2 diabetes (T2D) and diabetic peripheral neuropathy (DPN) on pinch proprioception and to establish the correlations with sensory impairments. We collected data from a total of 36 participants (healthy, n = 12; T2D without DPN, n = 11; and T2D + DPN, n = 13), all matched for age, 60 ± 6 years. Pinch proprioception was determined through 3 trials of attempts to actively reproduce 15° of pinch position without visual feedback. Target accuracy and precision was compared between groups using Kruskal-Wallis test. Sensation was tested through the two-point discrimination and Semmes-Weinstein monofilaments applied on the fingers. Sensory measures were correlated with pinch proprioception measures via Spearman's rank test. The T2D + DPN group showed significant decrements in accuracy and precision as compared to the T2D-only (p = 0.003 and p = 0.006, respectively) and the healthy groups (both p = 0.002); no significant differences were found between T2D-only and healthy. Spearman's rank showed moderate (r = 0.45-0.66, p < 0.001) correlations between pinch proprioception and sensory measures. Our results showed pinch proprioception disruption in people with T2D + DPN, but not in people with T2D-only. The awareness of pinch proprioceptive deficits is paramount for the safety of individuals with T2D and DPN. Moderate correlations between sensory impairments and pinch proprioceptive deficits suggest that not only superficial/discriminative sensation is implicated in proprioceptive decrements. Other mechanisms such as damage to muscle spindles or central nervous system associated with T2D + DPN warrant further investigations.

Influences of gender, hand dominance, and anthropometric characteristics on different types of pinch strength: A partial least squares (PLS) approach

The relationships of demographic and anthropometric characteristics (17 dimensions related to the hand, wrist, and arm) with four different pinch strengths (lateral pinch, key pinch, three-jaw chuck pinch and tip-to-tip pinch strengths) were evaluated among 196 (96 males and 100 females) young adults aged 19-30 years. For both dominant and non-dominant hands, the lateral pinch was greatest, followed by the key pinch, three-jaw chuck pinch and tip-to-tip pinch strengths. Mean pinch strengths of the dominant and non-dominant hands of females varied between 62%-78% and 61%-73% of those exerted by males, respectively. Strength of the dominant hand was 5.3%-7.5% stronger than of that of the non-dominant hand, with this difference being generally higher in females than in males. Hand length and forearm length showed the strongest correlation with all types of pinch strengths exerted by both the dominant and non-dominant hands. In the partial least squares analysis, 10 out of 17 anthropometric indices including hand length, forearm length, arm length, middle finger width, thumb length, index finger width, thumb width, wrist depth, palm depth and index finger depth had considerable loadings in the extracted component, explaining 37% of the total variance. These findings can fill the gap in the strength data, or used by health professionals and designers in the field.

Classifying hand sensorimotor functions of the chronic kidney disease patients using novel manual tactile test and pinch-holding-up activity

Hand function deterioration brings about inconvenience to the daily lives of the chronic kidney disease patients. However, a full spectrum of hand function examination is absent. Therefore, this study aimed to classify the hand sensorimotor functions of the chronic kidney disease patients using the novel sensorimotor assessment tools, manual tactile test (MTT) and pinch-holding-up activity (PHUA) test, and explore the feasibility in comparison with traditional evaluations in the clinical practice. 68 stage-5 chronic kidney disease patients and 50 healthy subjects were recruited in this study. A series of conventional evaluations and two novel hand function tools, manual tactile test and pinch-holding-up activity test were conducted from the perspective of hand dexterity, sensory input threshold, force generation and sensorimotor control. Independent t-test was used to find out group differences and the receiver operating characteristic curve was used to determine accuracy of the tests. In our results, significant reduction of hand dexterity, sensory input, force generation and sensorimotor control was found in patients from an overall perspective. This trend was discovered to be the same when dividing the subjects into the old and young age group. From the receiver operator characteristic curves, nearly all the areas under the curve of all tests were over 0.8. The novel evaluation tools, the manual tactile test and pinch-holding-up activity, were found to have comparable or even better accuracy than the traditional ones. The shape and weight subtests of the manual tactile test displayed the highest accuracy. To sum up, by incorporating the novel and conventional assessment tests, this study built up the fundamental understanding of the hand functions in multiple dimensions and consolidate the clinical merits of applying the two novel tools, manual tactile test and pinch-holding-up activity, on chronic kidney disease patients.

Is the evidence strong enough for acupuncture ameliorates clinical symptoms in patients with amyotrophic lateral sclerosis: A protocol for a systematic review and meta-analysis

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is the most common form of motor neuron diseases. Until now, it lacks effective drugs for its treatment, and the median survival time of ALS is reported as only 20 to 48 months after the onset of symptoms. Acupuncture served as part of traditional Chinese therapy, has been widely applied to clinical practice for patients with ALS but lacks studies to verify its efficacy. This study provides a protocol of systematic review, with which we will comprehensively verify the effects of acupuncture on ALS with evidence-based studies.

METHODS

The eligible studies will be collected from 4 English databases (the MEDLINE via PubMed, the Cochrane Library, EMBASE, the Web of Science, and Ovid database), and 4 Chinese databases (China Science and Technology Journal Database, Chinese Biomedical Literature Database, Wan-fang Database, China National Knowledge Infrastructure) from October 2000 to October 2022. The primary outcome measure is the change in amyotrophic lateral sclerosis functional rating scale-revised (ALSFRS-R) scores. We will use RevMan V.5.3 software to calculate the data synthesis and will conduct meta-analysis based on the collected data.

RESULTS

The primary outcome measure is the change in ALSFRS-R scores, and secondary outcome measures included changes in forced vital capacity, grasping power, pinch strength, modified Norris Scale, ALS assessment questionnaire-40, and time to activity of daily living-independent will be measured and comprehensively assessed to evaluate the effect of acupuncture on ALS from this systematic review and meta-analysis.

CONCLUSION

The systematic review and meta-analysis will assess the effect of acupuncture in the treatment of ALS with up-to-date clinical evidence.

PROSPERO REGISTRATION NUMBER

PROSPERO CRD 42019124785.

The comparison of pinch strength among female typists and female non-typists

BACKGROUND

Typing is a common activity involving repetitive motion that can increase the risk of work-related injuries. To the best of our knowledge, the effect of typing on the pinch strength has not been investigated so far.

OBJECTIVE

To investigate the pinch strength amongst female typists and non-typists.

METHOD

Thirty female typists and 30 female non-typists, aged 20-30 years old, participated in this prospective study. The pinch strength of the second, third, fourth and fifth fingers of the dominant hand was measured in a sitting position, using a pinch gauge. The data were analyzed using independent sample t-test.

RESULTS

The results showed that there were significant differences in the pinch strength of the second, third and fourth fingers between the two groups. The strength of these fingers was reduced more than that in female non-typists.

CONCLUSION

Our results suggest that pinch strength might have decreased in female typists due to sharing common attentional resources, muscle fiber composition, and muscle fiber fatigue.

Conformity of modified O-ring test and maximal pinch strength for cross tape application direction

BACKGROUND

Although cross tape has recently been used by clinicians for various musculoskeletal conditions, scientific studies on the direction of cross tape application are lacking.

METHODS

The present study aimed to investigate whether the direction of cross tape application affected the outcomes of the modified O-ring test and maximal pinch strength using a pinch gauge and the conformity between these 2 tests when cross tape was applied to the forearm muscles of individuals with no upper extremity pain and no restriction of joint range of motion.This study used a single-blinding crossover design. The subjects comprised 39 adults (16 men and 23 women). Cross tape was applied to the dominant hand so that the 4 rows were at an angle of 45° to the right or left of the direction of the flexor digitorum superficialis muscle fibers, and then the subjects underwent a modified O-ring test and a test of maximal pinch strength using a pinch gauge. Both tests were performed in both directions, and the order of the directions and tests was randomized. SPSS 18.0 was used for statistical analysis. Cohen's kappa coefficient was used to analyze the conformity of the results from the 2 tests. The statistical significance level was P < .05.

RESULTS

A positive response in the modified O-ring test and maximal pinch strength were both affected by cross tape direction. The modified O-ring test and maximal pinch strength using pinch gauge results were in agreement (P < .00), and the kappa coefficient was significant at 1.00.

CONCLUSION

The direction of cross tape application that produced a positive response in the modified O-ring test also produced greater maximal pinch strength. Thus, we propose that when applying cross tape to muscles, the direction of the 4 lines of the cross tape should be 45° relative to the direction of the muscle fibers, toward the side that produces a positive response in the modified O-ring test or produces the greatest maximal pinch strength using a pinch gauge.

Relationship of side dominance and ultrasonographic measurements of pronator quadratus muscle along with handgrip and pinch strength

AIMS

We ascertained effects of hand dominance in both right and left-handed volunteers on the thickness and cross sectional area (CSA) of pronator quadratus (PQ) muscle as measured by the axial and sagittal views of ultrasound imaging. Secondly, we also aimed to document the extent of the relationship between the PQ measurements and handgrip.

MATERIALS AND METHODS

Healthy adults from the volunteer medical staff were included in the study. Handedness was assessed via The Flinders Handedness survey. The sonographic appearance of the PQ was evaluated on sagittal and axial images for both hands. CSA of PQ muscle was digitally drawn and calculated on the axial plane. Handgrip was measured by using adjustable-handle dynamometer.

RESULTS

Eighty-nine healthy volunteers were included (54 right and 35 left-handed). Significant difference was detected between dominant and non-dominant hands in CSA and muscle thickness in both right and left-handed volunteers (p<0.05). These measurements were correlated with the handgrip strength (p<0.05, r=0.55, and r=0.43 for right-handed volunteers, r=0.67 and r=0.48 for left-handed volunteers, respectively). There were also significantly high correlations between the measurements of CSA and PQ thickness of the corresponding extremity in both right-handed and left-handed volunteers (p<0.05).

CONCLUSIONS

A statistically significant difference exists between dominant and non-dominant hands in CSA and muscle thickness measured by US in both right and left handed volunteers, and this is correlated with handgrip strength. Hand dominance should be considered to compare healthy and affected sites during US of PQ while investigating for occult fractures of distal forearm or PQ atrophy due to anterior interosseous nerve injury.

Contributions of Subsurface Cortical Modulations to Discrimination of Executed and Imagined Grasp Forces through Stereoelectroencephalography

Stereoelectroencephalographic (SEEG) depth electrodes have the potential to record neural activity from deep brain structures not easily reached with other intracranial recording technologies. SEEG electrodes were placed through deep cortical structures including central sulcus and insular cortex. In order to observe changes in frequency band modulation, participants performed force matching trials at three distinct force levels using two different grasp configurations: a power grasp and a lateral pinch. Signals from these deeper structures were found to contain information useful for distinguishing force from rest trials as well as different force levels in some participants. High frequency components along with alpha and beta bands recorded from electrodes located near the primary motor cortex wall of central sulcus and electrodes passing through sensory cortex were found to be the most useful for classification of force versus rest although one participant did have significant modulation in the insular cortex. This study electrophysiologically corroborates with previous imaging studies that show force-related modulation occurs inside of central sulcus and insular cortex. The results of this work suggest that depth electrodes could be useful tools for investigating the functions of deeper brain structures as well as showing that central sulcus and insular cortex may contain neural signals that could be used for control of a grasp force BMI.

The Use of Composite Tissue Spare Parts to Restore Tripod Hand Function in Post-Traumatic and Congenital Hand Deficiency

The principle aim in complex defects in hand is to restore a functioning tripod pinch. Among the various options, the use of locally available spare parts offers to improve both functions and cosmetics. 10 patients underwent surgeries to restore tripod pinch using this concept of spare parts. Four of them were children with congenital differences and the rest were adults with post traumatic defects. Eight of them underwent on-top plasty out of which four underwent an island pedicled transfer of phalanges and the rest involved distraction lengthening and transfer of metacarpals. One patient underwent a vascularized tenocutaneous joint transfer and another, a non-vascularized metacarpal transfer. At last follow up, eight of them were using hand with tripod pinch and one, using a lateral pinch. A carefully planned use of local tissues as spare part results in satisfactory outcome without the need for additional graft material in hands with absent or poor function.

Upper limb evaluation and one-year follow up of non-ambulant patients with spinal muscular atrophy: an observational multicenter trial

Assessment of the upper limb strength in non-ambulant neuromuscular patients remains challenging. Although potential outcome measures have been reported, longitudinal data demonstrating sensitivity to clinical evolution in spinal muscular atrophy patients are critically lacking. Our study recruited 23 non-ambulant patients, 16 patients (males/females = 6/10; median age 15.4 years with a range from 10.7 to 31.1 years) with spinal muscular atrophy type II and 7 patients (males/females = 2/5; median age 19.9 years with a range from 8.3 to 29.9 years) with type III. The Brooke functional score was on median 3 with a range from 2 to 6. The average total vital capacity was 46%, and seven patients required non-invasive ventilation at night. Patients were assessed at baseline, 6 months, and 1 year using the Motor Function Measure and innovative devices MyoGrip, MyoPinch, and MoviPlate, which assess handgrip strength, key pinch strength, and hand/finger extension-flexion function, respectively. The study demonstrated the feasibility and reliability of these measures for all patients, and sensitivity to negative changes after the age of 14 years. The younger patients showed an increase of the distal force in the follow-up period. The distal force measurements and function were correlated to different functional scales. These data represent an important step in the process of validating these devices as potential outcome measures for future clinical trials.

Functional range of movement of the hand: declination angles to reachable space

The measurement of the range of hand joint movement is an essential part of clinical practice and rehabilitation. Current methods use three finger joint declination angles of the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints. In this paper we propose an alternate form of measurement for the finger movement. Using the notion of reachable space instead of declination angles has significant advantages. Firstly, it provides a visual and quantifiable method that therapists, insurance companies and patients can easily use to understand the functional capabilities of the hand. Secondly, it eliminates the redundant declination angle constraints. Finally, reachable space, defined by a set of reachable fingertip positions, can be measured and constructed by using a modern camera such as Creative Senz3D or built-in hand gesture sensors such as the Leap Motion Controller. Use of cameras or optical-type sensors for this purpose have considerable benefits such as eliminating and minimal involvement of therapist errors, non-contact measurement in addition to valuable time saving for the clinician. A comparison between using declination angles and reachable space were made based on Hume's experiment on functional range of movement to prove the efficiency of this new approach.

Effects of glovebox gloves on grip and key pinch strength and contact forces for simulated manual operations with three commonly used hand tools

This study examined the effects of glovebox gloves for 11 females on maximum grip and key pinch strength and on contact forces generated from simulated tasks of a roller, a pair of tweezers and a crescent wrench. The independent variables were gloves fabricated of butyl, CSM/hypalon and neoprene materials; two glove thicknesses; and layers of gloves worn including single, double and triple gloving. CSM/hypalon and butyl gloves produced greater grip strength than the neoprene gloves. CSM/hypalon gloves also lowered contact forces for roller and wrench tasks. Single gloving and thin gloves improved hand strength performances. However, triple layers lowered contact forces for all tasks. Based on the evaluating results, selection and design recommendations of gloves for three hand tools were provided to minimise the effects on hand strength and optimise protection of the palmar hand in glovebox environments.

PRACTITIONER SUMMARY

To improve safety and health in the glovebox environments where gloves usage is a necessity, this study provides recommendations for selection and design of glovebox gloves for three hand tools including a roller, a pair of tweezers and a crescent wrench based on the results discovered in the experiments.

Does living and working in a hot environment induce clinically relevant changes in immune function and voluntary force production capacity?

This study investigated the effect of living (summer vs. winter) and working (morning vs. afternoon) in a hot environment on markers of immune function and forearm strength. Thirty-one healthy male gas field employees were screened before (between 05:30 and 07:00) and after their working day (between 15:30 and 17:00) during both seasons. Body core temperature and physical activity were recorded throughout the working days. The hot condition (i.e. summer) led a higher (p≤0.05) average body core temperature (~37.2 vs. ~37.4 °C) but reduced physical activity (-14.8%) during the work-shift. Our data showed an increase (p≤0.05) in lymphocyte and monocyte counts in the summer. Additionally, work-shift resulted in significant (p≤0.001) changes in leukocytes, lymphocytes and monocytes independently of the environment. Handgrip (p=0.069) and pinch (p=0.077) forces tended to be reduced from pre-to post-work, while only force produced during handgrip manoeuvres was significantly reduced (p≤0.05) during the hot compared to the temperate season. No interactions were observed between the environment and work-shift for any marker of immune function or forearm strength. In summary, working and living in hot conditions impact on markers of immune function and work capacity; however by self-regulating energy expenditure, immune markers remained in a healthy reference range.

The effects of an exercise training program on hand and wrist strength, and function, and activities of daily living, in adults with severe cerebral palsy

The purpose of the current study was to establish measurement reliability in adults with Cerebral Palsy (CP), and to examine the feasibility and outcomes of an upper extremity strength training program (three times per week for 90 min each time). A control group design mixed with a prospective time series design for the intervention group was completed, including a pre-test, a post-test after a 12-week intervention period, and a follow-up in the intervention group after an additional 10-week period. Seventeen adults with CP with severe motor impairment took part in the study (10 in the intervention and seven in the control group). The test battery was comprised of wrist and hand dynamometry; dominant hand upper-extremity function measures (Jebsen Hand Function Test=JHFT, Minnesota Manual Dexterity Test=MMDT, and the Nine Hole Peg Test=NHPT); and activity of daily living with the Barthel Index. The results indicated that in both the control and the intervention groups, the strength tests exhibited good-to-excellent reliability during pre-test and post-test. The group comparison revealed that while in the pre-test no between-group differences existed, in the post-test the strength training group demonstrated significantly higher values in five out of eight strength measures, as well as in the MMDT. Discontinuing the program for eight weeks reversed the effects almost to baseline. In conclusion, the outcomes demonstrated the reliability of the assessments utilized in this study, as well as the feasibility of the strength training program, in adults with severe motor impairment due to CP.

Variation in work tasks in relation to pinch grip strength among middle-aged female dentists

OBJECTIVES

We aimed to investigate the relationship of task variation during dental work history with pinch grip strength among dentists.

METHODS

We measured pinch grip strength among 295 female Finnish dentists aged 45-63 years. Variation in dental work tasks during work history was empirically defined by cluster analysis. Three clusters of task variation emerged: low (most work time in restoration treatment/endodontics), moderate (about 50% in the former and 50% in prosthodontics/periodontics/surgery), and high (variable tasks including administrative duties). Hand radiographs were examined for the presence of OA in the wrist and each joint of the 1-3rd fingers. Information on hand-loading leisure-time activities, and joint pain was obtained by questionnaire. Glove size was used as a proxy for hand size. BMI (kg/m2) was based on measured weight and self-reported height.

RESULTS

Dentists with low variation of work task history had an increased risk of low pinch grip strength in the right hand (OR 2.3, 95% CI 1.2-4.3), but not in the left (1.13, 0.62-2.08), compared to dentists with high task variation, independent of age, hand size, hand-loading leisure-time activities, BMI and symptomatic hand OA.

CONCLUSION

The dentists with the most hand-loading tasks were at an increased risk of low pinch grip strength, independent of e.g. symptomatic hand OA. It is advisable among dentists to perform as diverse work tasks as possible to reduce the risk of decreased pinch grip strength.

Reliability of a modified motor unit number index (MUNIX) technique

INTRODUCTION

The purpose of this study was to examine the relative and absolute between-day reliability of the motor unit number index (MUNIX).

METHODS

Young, healthy adults (n=19) attended two testing sessions separated by 4-weeks where their maximal pinch-grip strength, MUNIX, and motor unit size index (MUSIX) were assessed in the abductor pollicis brevis muscle. Reliability was assessed by intraclass correlation coefficients (ICC), coefficient of variation (CV) and limits of agreement (LOA).

RESULTS

No mean differences were observed for MUNIX or MUSIX. The CV for the MUNIX and MUSIX measures were between 13.5% and 17.5%. The ICC for both measures were moderate to moderately-high (0.73-0.76), The LOA for both indicated a homoscedastic relationship.

DISCUSSION

Our findings indicate moderate to moderately-high reliability for both MUNIX and MUSIX. Future work is needed to ensure both measures are reliable in other muscles and cohorts, and further investigations are required to examine the validity of MUNIX.

The impact of digit-related radiographic osteoarthritis of the hand on grip-strength and upper extremity disability

BACKGROUND

Interpreting the impact of hand osteoarthritis (OA) on hand function is complicated owing to the multiple digits and joints in the hand.

QUESTIONS/PURPOSE

We determined the impact of digit-related radiographic OA on hand function in patients 65 years or older.

METHODS

We evaluated hand radiographs in 196 men and 182 women older than 65 years without shoulder or elbow pain who participated in the Korean Longitudinal Study on Health and Aging. Using the Kellgren and Lawrence criteria, we graded the 15 joints in each hand from 0 to 4 for OA, and evaluated hand function by measuring DASH scores and grip and pinch strength of dominant hands. We performed multiple linear regression analyses to evaluate associations between hand functions and the sum of Kellgren and Lawrence grade of each digit.

RESULTS

The sums of Kellgren and Lawrence grades for thumbs and middle fingers were independently associated with grip strength, and the sums of the Kellgren and Lawrence grades for thumbs and index fingers were independently associated with pinch strength after controlling for age and sex. DASH scores were independently associated with OA of the thumb, or index or middle finger, but not with OA of the ring or small finger.

CONCLUSIONS

This study revealed cumulative effects of joint involvement and Kellgren and Lawrence grades of thumb and middle finger OA on grip strength, and thumb and index finger OA on pinch strength. Furthermore, OA of either of three radial digits was associated with more severe upper extremity disabilities.

LEVEL OF EVIDENCE

Level IV, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Grip surface affects maximum pinch force

OBJECTIVE

The aim of this study was to investigate whether people change their isometric pinch grip generation depending on the surface they gripped. Specifically, the effect of grip surface friction condition on (a) maximum force produced in the direction normal to the contact surface, (b) fluctuation of normal force, and (c) the digit force's angular deviation from the direction normal to the grip surface was quantified.

BACKGROUND

Isometric pinch grip has been traditionally thought to be independent from the friction condition between the finger and gripped surface, which may be questionable.

METHOD

For this study, 12 healthy participants performed maximum isometric pinch grip exertion on high-friction rubber and low-friction paper surfaces. Maximum normal force, normal force variance,and digit force's angular deviation from the normal direction were quantified.

RESULTS

Pinch grip on the high-friction rubber surface was associated with 10% greater maximum normal force and 50% reduced normal force variance, compared with the low-friction paper surface (p < .05). Digit force's angular deviation was not significantly different between the two surface friction conditions.

CONCLUSION

The data support that people do change their pinch grip generation (maximum normal force and normal force variance) depending on the surface they gripped, potentially by using sensory feedback. The results of this study demonstrate that even a simple isometric pinch grip (no lifting associated) is affected by grip surface friction.

APPLICATION

Grip surface condition should be considered for clinical assessments, biomechanical investigation, and motor control studies to ensure consistency in measurements and validity of comparisons.

Coherence between surface electromyograms is influenced by electrode placement in hand muscles

We used multi-channel surface electromyograms (EMGs) to examine if electrode location influences coherence measures derived from pairs of EMGs recorded from two hand muscles during a pinch task. A linear probe of 16 electrodes was used to estimate the location of the innervation zone in first dorsal interosseous (FDI) and abductor pollicis brevis (APB). Four electrodes were then placed on the skin overlying each muscle and three bipolar electrode configurations were constructed with their center points directly over the innervation zone, and 15mm distal and proximal to the innervation zone. Ten subjects performed two force-matching tasks for 120s at 2N and 3.5N by pressing a force sensor held between the thumb and index finger. Coherence spectra were calculated from pairs of EMGs recorded from the two muscles. Maximal coherence from 1 to 15Hz and 16 to 32Hz was calculated at both force levels from the EMGs with electrodes centered over the innervation zones of FDI and APB. These values were compared to the maximal coherence from all other EMG comparisons across muscles recorded with electrodes that avoided the innervation zones. ANOVA revealed significant main effects only for electrode location, with a 58.1% increase (p=0.001) in maximal coherence for EMGs detected from pairs of electrodes that avoided the innervation zone (from 0.11±0.02 to 0.18±0.03; mean±95% confidence interval). These results indicate that electrode location relative to the innervation zone influences EMG-EMG coherence and should be carefully considered when placing EMG electrodes on hand muscles.

Diagnosis of motor fascicle compression in carpal tunnel syndrome

INTRODUCTION

Median nerve motor fascicle compression in patients with carpal tunnel syndrome is usually characterised by reduced finger grip and pinch strength, loss of thumb abduction and opposition strength and thenar atrophy. The functional outcome in patients with advanced changes may be poor due to irreversible intraneural changes.

HYPOTHESIS

The aim of this study was to investigate patient-reported symptoms, which may enable a clinical diagnosis of median nerve motor fascicle compression to be made irrespective of the presence of advanced signs.

PATIENTS AND METHODS

One hundred and twelve patients (166 hands) with a clinical diagnosis of carpal tunnel syndrome were referred to the neurophysiology department and completed symptom severity questionnaires with subsequent neurophysiological testing.

RESULTS

An increasing frequency of pain experienced by patients was significantly associated with an increased severity of median nerve motor fascicle compression with prolonged motor latencies measured in patients that described pain as a predominant symptom. An increasing frequency of paraesthesia and numbness and weakness associated with dropping objects was significantly associated with both motor and sensory involvement but not able to distinguish between them.

CONCLUSION

This study suggests that patients presenting with a clinical diagnosis of carpal tunnel syndrome with pain as a frequently experienced and predominant symptom require consideration for urgent investigation and surgical treatment to prevent chronic motor fascicle compression with permanent functional deficits.

[Is intraoperative luxation of the ulnar nerve a criterion for transposition?]

BACKGROUND

The relevance of subcutaneous transposition of the ulnar nerve in the therapy of cubital tunnel syndrome is still under debate. The aim of this study was to compare the results after decompression to additional transposition in cases of intraoperative luxation.

METHODS

A total of 54 cases after surgery of cubital tunnel syndrome between 2000 and 2006 were analyzed. Nerve transposition was performed in cases of intraoperatively apparent nerve luxation.

RESULTS

Of the patients 12 were treated by decompression alone and 42 by additional subcutaneous transposition. There was no significant difference concerning symptom amelioration, usage properties of the hand, sensation impairment and duration of disability. Force measurements of grip strength and pinch strength revealed no significant differences between either hand in both groups. The 2-point discrimination ability of the 8th to 10th finger nerves was not significantly different between the groups either.

CONCLUSION

Nerve transposition revealed no benefits in the treatment of cubital tunnel syndrome when performed in cases of intraoperative nerve luxation.

Handle grip span for optimising finger-specific force capability as a function of hand size

Five grip spans (45 to 65 mm) were tested to evaluate the effects of handle grip span and user's hand size on maximum grip strength, individual finger force and subjective ratings of comfort using a computerised digital dynamometer with independent finger force sensors. Forty-six males participated and were assigned into three hand size groups (small, medium, large) according to their hands' length. In general, results showed the 55- and 50-mm grip spans were rated as the most comfortable sizes and showed the largest grip strength (433.6 N and 430.8 N, respectively), whereas the 65-mm grip span handle was rated as the least comfortable size and the least grip strength. With regard to the interaction effect of grip span and hand size, small and medium-hand participants rated the best preference for the 50- to 55-mm grip spans and the least for the 65-mm grip span, whereas large-hand participants rated the 55- to 60-mm grip spans as the most preferred and the 45-mm grip span as the least preferred. Normalised grip span (NGS) ratios (29% and 27%) are the ratios of user's hand length to handle grip span. The NGS ratios were obtained and applied for suggesting handle grip spans in order to maximise subjective comfort as well as gripping force according to the users' hand sizes. In the analysis of individual finger force, the middle finger force showed the highest contribution (37.5%) to the total finger force, followed by the ring (28.7%), index (20.2%) and little (13.6%) finger. In addition, each finger was observed to have a different optimal grip span for exerting the maximum force, resulting in a bow-contoured shaped handle (the grip span of the handle at the centre is larger than the handle at the end) for two-handle hand tools. Thus, the grip spans for two-handle hand tools may be designed according to the users' hand/finger anthropometrics to maximise subjective ratings and performance based on this study. Results obtained in this study will provide guidelines for hand tool designers and manufacturers for designing grip spans of two-handle tools, which can maximise handle comfort and performance.

Pinch and elbow extension restoration in people with tetraplegia: a systematic review of the literature

PURPOSE

We conducted a systematic review of the literature to summarize the available data on reconstructive surgeries involving pinch reconstruction and elbow extension restoration in people with tetraplegia.

METHODS

English-language and French-language articles and abstracts published between 1966 and February 2007, identified through MEDLINE and EMBASE searches, bibliography review, and expert consultation, were reviewed for original reports of outcomes with pinch reconstruction and elbow extension restoration in tetraplegic patients after a spinal cord injury. Two reviewers independently extracted data on patient characteristics, surgical methods, and patient outcomes.

RESULTS

Our search identified 765 articles, of which 37 met eligibility criteria (one article contained information on both elbow and pinch procedures). Results from 377 pinch reconstructions in 23 studies and 201 elbow extension restorations in 14 studies were summarized. The mean Medical Research Council score for elbow extension went from 0 to 3.3 after reconstruction. The overall mean postoperative strength measured after surgery for pinch reconstruction was 2 kg.

CONCLUSIONS

More than 500 patients having these procedures experienced a clinically important improvement for both procedures-one restoring elbow extension, and the other, pinch strength. Upper-limb surgeries markedly improved the hand function of people with tetraplegia.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Biomechanical analysis of subjective pinching effort based on tendon-skeletal model

In this paper, the influence of the finger posture on the subjective effort during pinching motion is investigated by using a tendon-skeletal finger model. The experimental results show that the subjective effort human feels is affected by the size of the object he/she pinches, and the subjective effort correlates with the finger length. The simulation results show that the pattern of the tendon forces is similar to that of the EMG activity measured in the experiment, and the positive correlation was observed between the finger length and the object size where the summation of the tendon forces becomes the minimum. These results suggest that the reason why subjective pinching effort is influenced by the finger posture is the difference in the efficiency of the force transmission from the muscles.

Evaluation of hand functions in women with polycystic ovary syndrome

OBJECTIVES

Polycystic ovary syndrome (PCOS) is characterized by hyperandrogenemia and androgen levels are associated with muscle size and strength; thus we aimed to investigate the hand functions of women with PCOS.

METHODS

Thirty-seven patients with PCOS and 35 age-matched healthy women were included in the study as PCOS and control groups. Age, body mass index, dominant hand, physical activity level, lean/fat mass ratio, percentage of body fat, Beck Depression Inventory (BDI) score and Duruoz Hand Index (DHI) score were recorded. Hand grip and pinch strengths were tested in the dominant hand using a hand dynamometer and a pinch meter, respectively. Manual dexterity was tested by the grooved pegboard test. Serum concentrations of total testosterone, estradiol, dehydroepiandrosterone sulfate, follicle-stimulating hormone, luteinizing hormone, thyroid-stimulating hormone and progesterone were measured.

RESULTS

Patients with PCOS had high total testosterone levels (p < 0.001). There were no differences between groups in all of the hand strengths or dexterity. No correlations between hand parameters and hormones were found. DHI and BDI scores were high in the PCOS group (p = 0.002 and 0.039, respectively). There was a correlation between DHI and BDI scores. Depressive patients had higher BMI (p = 0.021) and body fat percentage (p = 0.05) than non-depressive patients in the PCOS group.

CONCLUSION

Hand strength and dexterity did not change in patients with PCOS. Depression risk increased especially in the patients with high BMI and affected hand functional status in PCOS.

Measuring pad–pad pinch strength in a non-human primate: Macaca fascicularis

The primary purpose of this study was to establish a methodology for determining and perhaps predicting (via regression analysis of anthropometric measures) Macaca fascicularis isometric pinch strength for a specific task. The larger purpose of this work was to properly scale a pinching task for the monkeys in order to study dose-response relationships in a non-human primate model for carpal tunnel syndrome. Three female and one male macaque (n=4) of varying size and age were trained to perform a left-handed pad-pad pinch. The task required 60 degrees of wrist flexion at a static pinching distance of 3 cm between the thumb and fingers. Subjects were trained for a period of 20-weeks. After that time, an analysis of performance gradients found that they had each reached a plateau in their force output. Pinch strength for the four animals ranged from 29.4 to 59.8 N. Regression analysis revealed that body mass (kg) and wrist circumference (cm) were both predictive of pinch strength, exhibiting adjusted R(2) values of 0.93 (p=0.024) and 0.96 (p=0.015), respectively. Thus, the results suggest that maximal pinch strength could be acceptably estimated in future subjects using either the wrist circumference or the body mass measures, as both were strong predictors of pad-pad pinch strength.

Strength training improves the tri-digit finger-pinch force control of older adults

OBJECTIVE

To investigate the effect of unilateral upper-limb strength training on the finger-pinch force control of older men.

DESIGN

Pretest and post-test 6-week intervention study.

SETTING

Exercise science research laboratory.

PARTICIPANTS

Eleven neurologically fit older men (age range, 70-80y).

INTERVENTION

The strength training group (n=7) trained twice a week for 6 weeks, performing dumbbell bicep curls, wrist flexions, and wrists extensions, while the control group subjects (n=4) maintained their normal activities.

MAIN OUTCOME MEASURES

Changes in force variability, targeting error, peak power frequency, proportional power, sample entropy, digit force sharing, and coupling relations were assessed during a series of finger-pinch tasks. These tasks involved maintaining a constant or sinusoidal force output at 20% and 40% of each subject's maximum voluntary contraction. All participants performed the finger-pinch tasks with both the preferred and nonpreferred limbs.

RESULTS

Analysis of covariance for between-group change scores indicated that the strength training group (trained limb) experienced significantly greater reductions in finger-pinch force variability and targeting error, as well as significantly greater increases in finger-pinch force, sample entropy, bicep curl, and wrist flexion strength than did the control group.

CONCLUSIONS

A nonspecific upper-limb strength-training program may improve the finger-pinch force control of older men.

Comparison of responsiveness of the Japanese Society for Surgery of the Hand version of the carpal tunnel syndrome instrument to surgical treatment with DASH, SF-36, and physical findings

BACKGROUND

The Japanese Society for Surgery of -the Hand version of the Carpal Tunnel Syndrome Instrument (CTSI-JSSH), which consists of two parts--one for symptom severity (CTSI-SS) and the other for functional status (CTSI-FS)--is a self-administered questionnaire specifically designed for carpal tunnel syndrome. The responsiveness of the CTSI-JSSH was compared with that of the JSSH version of the Disability of Arm, Shoulder, and Hand questionnaire (DASH), the official Japanese version of the 36-Item Short Form Health Survey (SF-36, version 1.2), and physical examinations to elucidate the role of the CTSI-JSSH for evaluating patients with carpal tunnel syndrome.

METHODS

Preoperatively, a series of 60 patients with carpal tunnel syndrome completed the CTSI-JSSH, DASH, and SF-36. Results of physical examinations, including grip strength, pulp pinch, and static two-point discrimination of the thumb, index, and long fingers, were recorded. Three months after carpal tunnel release surgery the patients were asked to fill out the same questionnaires, and the physical examinations were repeated. The responsiveness of all the instruments was examined by calculating the standardized response mean (SRM) and effect size (ES). Correlation coefficients were calculated between questionnaire change scores and patient satisfaction scores as well as between the CTSI change scores and those of the DASH and SF-36.

RESULTS

The largest responsiveness was observed in the CTSI-SS (SRM/ES: -1.00/-1.08) followed by the CTSI-FS (-0.76/-0.63), and bodily pain subscale of SF-36 (SF-36-BP, 0.45/0.55), and the DASH (-0.46/-0.47). Only the change scores of the CTSI-SS had significant correlation with patient satisfaction (r = 0.34, P < 0.01). An absolute value of Spearman's correlation coefficient of >0.5 was observed between the change scores of the CTSI-SS and the DASH, the CTSI-SS and the SF-36-BP, the CTSI-FS and the DASH, and the DASH and the SF-36-BP.

CONCLUSION

The CTSI-JSSH was proven to be more sensitive to clinical changes after carpal tunnel release than the other outcome measures and should be used to evaluate patients with carpal tunnel syndrome who speak Japanese as their native language.

Extended reverse dorsal metacarpal artery flap: clinical experience and donor site morbidity

Extended reverse dorsal metacarpal artery (RDMA) flaps use the skin from the dorsum of the hand to cover defects of the long fingers up to the distal phalanx. The authors present a series of 12 patients who underwent closure of defects of the long fingers with these flaps. As relevant literature is scarce, special emphasis was put on donor site morbidity. Active and passive total range of motion (TRM) and pinch grip strength of the finger neighbouring the reconstructed one were evaluated and compared to the corresponding finger of the contralateral hand. The donor site was furthermore evaluated for cosmetic appearance and pain. There was no statistically significant difference for active and passive TRM. The difference for pinch grip reached statistical significance (p=0.04). Subjective evaluation of pain and cosmetic appearance by the patients revealed a mean pain value of 1.25 on a visual analogue scale (0=no pain, 10=maximal imaginable pain) and a mean estimation of cosmetic appearance of 8 (visual analogue scale, 0=worst cosmetic result, 10=best cosmetic result). In conclusion, compared to other flaps, the extended RDMA flap is a fast, secure and single-stage procedure for defect coverage on the long fingers with low donor site morbidity.

Effects of the deep anterior oblique and dorsoradial ligaments on trapeziometacarpal joint stability

PURPOSE

Osteoarthritis of the trapeziometacarpal (TMC) joint of the thumb affects as many as 25% of postmenopausal women and 5% of middle-aged men. This study investigated the relative contribution of the dorsoradial ligament (DRL) and the deep anterior oblique ligament (dAOL) to the stability of the TMC joint. This knowledge will improve our understanding of the pathomechanics of osteoarthritis at the base of the thumb and may help to design novel reconstructive surgical procedures.

METHODS

Seventeen intact cadaver hands were dissected to reveal the DRL and dAOL. Either the DRL or dAOL was transected randomly, physiologic muscle loads were applied to simulate lateral key pinch or thumb opposition, or a 3-dimensional magnetic tracking system was used to record the position of the thumb metacarpal relative to the trapezium. The differences in the 3-dimensional positions between the control and transected states were determined.

RESULTS

In lateral pinch, transection of the DRL resulted in a mean increased 3-dimensional translation of 1.3 mm, whereas transection of the dAOL resulted in a mean increased 3-dimensional translation of 0.6 mm. Statistically significant 2-dimensional findings in lateral pinch after transecting the DRL or dAOL included an increased palmar subluxation of 0.3 mm and 0.2 mm, an increased radial (1.0 mm) and ulnar (0.3 mm) translation, and an increased pronation of 4.1 degrees and 2.4 degrees, respectively. In thumb opposition, transection of the DRL resulted in a mean increased 3-dimensional translation of 1.0 mm, whereas transection of the dAOL resulted in a mean increased 3-dimensional translation of 0.5 mm.

CONCLUSIONS

In most degrees of freedom of metacarpal movement relative to the trapezium, the DRL is relatively more important than the dAOL in providing stability to the TMC joint.

Functional magnetic resonance imaging shows cortical activation on sensory stimulation of an osseointegrated prosthetic thumb

Functional magnetic resonance imaging (fMRI) was used to study the cortical integration of an osseointegrated prosthetic thumb that had been attached to the amputee's hand 13 years ago. We found that tactile stimuli applied to the prosthesis activated the primary somatosensory cortex on both sides.

The effects of shoulder load and pinch force on electromyographic activity and blood flow in the forearm during a pinch task

The object of the current study was to determine whether static contraction of proximal musculature has an effect on the blood flow more distally in the upper extremity. Static contractions of muscles in the neck shoulder region at three levels (relaxed, shoulders elevated and shoulders elevated loaded with 4.95 kg each) were combined with intermittent pinch forces at 0, 10 and 25% of the maximum voluntary contraction (MVC). Blood flow to the forearm was measured with Doppler ultrasound. Myoelectric activity of the forearm and neck-shoulder muscles was recorded to check for the workload levels. Across all levels of shoulder load, blood flow increased significantly with increasing pinch force (21% at 10% MVC and by 44% at 25% MVC). Blood flow was significantly affected by shoulder load, with the lowest blood flow at the highest shoulder load. Interactions of pinch force and shoulder load were not significant. The myoelectric activity of forearm muscles increased with increasing pinch force. The activation of the trapezius muscle decreased with increasing pinch force and increased with increasing shoulder load. The precise mechanisms accounting for the influence of shoulder load remains unclear. The results of this study indicate that shoulder load might influence blood flow to the forearm.

Total joint arthroplasty in the treatment of advanced stages of thumb carpometacarpal joint osteoarthritis

PURPOSE

Osteoarthritis of the thumb basal joint is a very common and disabling condition that frequently affects middle-aged women. Many different surgical techniques have been proposed for extensive degenerative arthritis of the first carpometacarpal (CMC) joint. Joint replacement has been an effective treatment of this condition. The purpose of this article is to present the outcome of a total cemented trapeziometacarpal implant in the treatment of more advanced stages of this disease.

METHODS

Total joint arthroplasty of the trapeziometacarpal joint was performed on 26 thumbs in 25 patients to treat advanced osteoarthritis (Eaton and Littler stages III and IV) between 1998 and 2003. Indications for surgery after failure of conservative treatment were severe pain, loss of pinch strength, and diminished thumb motion that limited activities of daily living. A trapeziometacarpal joint prosthesis was the implant used in this series. The average follow-up time was 59 months.

RESULTS

At the final follow-up evaluation, thumb abduction averaged 60 degrees and thumb opposition to the base of the small finger was present. The average pinch strength was 5.5 kg (85% of nonaffected side). One patient had posttraumatic loosening, which was revised with satisfactory results. Radiographic studies at the final follow-up evaluations did not show signs of atraumatic implant loosening. One patient complained of minimal pain, and the remaining 24 patients were pain free.

CONCLUSIONS

In our series, total joint arthroplasty of the thumb CMC joint has proven to be efficacious with improved motion, strength, and pain relief. We currently recommend this technique for the treatment of stage III and early stage IV osteoarthritis of the CMC joint in older patients with low activity demands.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Key pinch force in children

The key pinch force in a group of 262 healthy children between 5 and 12 years was measured. A clear correlation was observed between age and key pinch strength. The differences between the left and right hand grips and between girls and boys were not significant.

Calibrating Borg scale ratings of hand force exertion

A study was conducted to assess the efficacy of calibrating subjective worker ratings of hand exertions to reduce error in estimates of applied force. Twenty volunteer subjects applied pinch and power grip forces corresponding to their perceptions of different Borg CR-10 scale levels using both "grip-to-scale" and "guided-grip" procedures. These data were used separately to define relationships between scale ratings and actual force application. Two gripping tasks were performed and corresponding subjective hand force ratings were calibrated using the grip-to-scale calibration data. Results showed that the mean estimation error for a 44.5 N (10 lb) power grip task was significantly reduced from 142.8 (+/-69.0) to 62.3 (+/-58.3) N. The guided-grip calibration method also significantly reduced rating error for the power grip task, however the estimates were biased toward zero. Neither calibration procedure improved rating accuracy of an 8.9 N (2 lb) pinch grip task. The study results indicate that calibration of hand force ratings using the grip-to-scale procedure may improve the accuracy of hand exertion measurements using the Borg CR-10 scale.