The Precision of the Human Hand: Variability in Pinch Strength and Manual Dexterity

Changes in hand morphology throughout human evolution have facilitated the use of forceful pad-to-pad precision grips, contributing to the development of fine motor movement and dexterous manipulation typical of modern humans. Today, variation in human hand function may be affected by demographic and/or lifestyle factors, but these remain largely unexplored. We measured pinch grip strength and dexterity in a heterogeneous cross-sectional sample of human participants (n = 556) to test for the potential effects of sex, age, hand asymmetries, hand morphology, and frequently practiced manual activities across the lifespan. We found a significant effect of sex on pinch strength, dexterity, and different directional asymmetries, with the practice of manual musical instruments, significantly increasing female dexterity for both hands. Males and females with wider hands were also stronger, but not more precise, than those with longer hands, while the thumb-index ratio had no effect. Hand dominance asymmetry further had a significant effect on dexterity but not on pinch strength. These results indicate that different patterns of hand asymmetries and hand function are influenced in part by life experiences, improving our understanding of the link between hand form and function and offering a referential context for interpreting the evolution of human dexterity.

A prospective comparative study of surgical release of carpal tunnel syndrome with and without flexor tenosynovectomy

Background: Carpal tunnel syndrome (CTS) is a common condition causing hand pain and numbness. The rationale of tenosynovectomy is to remove the flexor tenosynovium that is contributing to increased volume within the carpal canal, thus removal of this tenosynovium should give more space for the median nerve and there by relief from symptoms. Aims and Objectives: The main objective of our study was to assess the role of routine flexor tenosynovectomy in the treatment of CTS. Materials and Methods: Eighty-six hands with CTS were randomized into two groups, either to carpal tunnel release with or without flexor tenosynovectomy. All patients were requested to fill up the self-administered questionnaire for the assessment of symptom severity and functional status, examined for 2-point discrimination, grip and pinch strength, scar tenderness and patient satisfaction score preoperatively, 2 weeks, 1 month, and 6 months follow-up. Results: After the surgical release, both groups improved significantly with respect to symptom severity and functional status, 2-point discrimination, grip and pinch strength, scar tenderness and patient satisfaction score but there was no significant difference between the two groups. There were two cases of post-operative wound infection and one case of mild reflex sympathetic dystrophy. Conclusion: We conclude that routine flexor tenosynovectomy during surgical release of carpal tunnel in patients with CTS does not provide any added benefit nor does it increase any morbidity.

A Musculoskeletal Model of the Hand and Wrist Capable of Simulating Functional Tasks

Objective: The purpose of this work was to develop an open-source musculoskeletal model of the hand and wrist and to evaluate its performance during simulations of functional tasks. Methods: The musculoskeletal model was developed by adapting and expanding upon existing musculoskeletal models. An optimal control theory framework that combines forward-dynamics simulations with a simulated-annealing optimization was used to simulate maximum grip and pinch force. Active and passive hand opening were simulated to evaluate coordinated kinematic hand movements. Results: The model's maximum grip force production matched experimental measures of grip force, force distribution amongst the digits, and displayed sensitivity to wrist flexion. Simulated lateral pinch strength fell within variability of in vivo palmar pinch strength data. Additionally, predicted activation for 7 of 8 muscles fell within variability of EMG data during palmar pinch. The active and passive hand opening simulations predicted reasonable activations and demonstrated passive motion mimicking tenodesis, respectively. Conclusion: This work advances simulation capabilities of hand and wrist models and provides a foundation for future work to build upon. Significance: This is the first open-source musculoskeletal model of the hand and wrist to be implemented during both functional kinetic and kinematic tasks. We provide a novel simulation framework to predict maximal grip and pinch force which can be used to evaluate how potential surgical and rehabilitation interventions influence these functional outcomes while requiring minimal experimental data.

Association of Age with Hand Grip Strength, Pinch Strength and Reaction Time in Gynaecologists and Obstetricians

According to scientific literature, evidence of relationship exists between dexterity and age. With increasing age, the performances get slower, less smooth, less coordinated and less controlled. Lesser the reaction time, better is the achievement seen sports, music, driving, academics and also in day-to-day activities. We can always predict reacting abilities of an individual based on his reaction time. In case of surgeons, this helps us to identify the surgeons with prolonged reaction time and identify the cause. Some studies suggest that there is direct relationship that exists between muscle strength and increased age. Aim: This study aimed in assessing the association of age with hand grip strength, pinch strength and reaction time in Gynaecologists and Obstetricians. Methods: This study involved 30 Gynaecologists and Obstetricians. Hand grip strength, Pinch Grip Strength and Reaction time were assessed on both dominant and non- dominant hand. Results: The result showed positive correlation of age with hand grip strength and pinch strength and negative correlation of age with reaction in Gynaecologists and Obstetricians. Conclusion: There is low association of age with hand grip strength and pinch strength, there is reduction in reaction time as age increases in Gynaecologists and Obstetricians. Key words: Age, Hand grip strength, Pinch Grip Strength, Reaction time, Gynecologists.

Midterm Functional Outcome of the Linked Semiconstrained Distal Radioulnar Joint Prosthesis

Background A painful unstable distal radioulnar joint (DRUJ) can seriously compromise hand and wrist function. The semiconstrained prosthesis was developed to restore DRUJ function. To date, most outcome reports are coauthored by the designer. Questions Does independent reporting confirm the promising results of the semiconstrained DRUJ prosthesis? Are complication and failure rates acceptable? Patients and Methods We evaluated patients with the semiconstrained DRUJ implant and a minimum follow-up of 2 years. We monitored patient satisfaction and function with functionality questionnaires and measured wrist range of motion, grip, and key pinch strength. Statistical analysis was done using descriptive statistics, Pearson correlation coefficients, linear and logistic regression. Results We included 41 patients with 42 implants. Mean follow-up was 46 months (range: 24–102 months). Eighty percent of wrist had undergone previous surgery. We found a mean pronation of 83 degrees (0–90 degrees), supination of 70 degrees (0–90 degrees), flexion of 42 degrees (0–90 degrees), extension of 49 degrees (0–90 degrees), ulnar deviation of 24 degrees (0–60 degrees), and radial deviation of 14 degrees (0–40 degrees). Grip and key pinch strength were 20.1 (1–50 kg) and 6 kg (1–12 kg), respectively. Average patient-rated wrist and hand evaluation score was 42.7 (0–95), disabilities of the arm, shoulder and hand score was 38 (0–88), and visual analog scale score was 3.6 (0–8). We found a 43% complication rate (mostly minor: ulnar or radial tendinopathy, temporary hypoesthesia) with 24% reoperation and 92% prosthesis survival rate. Conclusion The linked semiconstrained DRUJ prosthesis has its value in the surgical treatment of DRUJ failure. Currently, most implants are used in secondary surgery and multioperated wrists. More research is required to assess the value of the DRUJ prosthesis as a primary procedure. Level of evidence This is a level IV, therapeutic study.

Evaluation of outcome after primary median and/or ulnar nerve(s) repair at wrist: clinical, functional, electrophysiologic, and ultrasound study

Background A major problem in surgery of peripheral nerve injuries of the upper extremities is the unpredictable final outcome. More insight and understanding of the proper methods of outcome assessment and the prognostic factors is necessary to improve functional outcome after repair of peripheral nerves. The objective of this study is to assess the outcome and identify possible prognostic factors for functional recovery of median and/or ulnar nerves repairs at wrist. Forty patients with median, ulnar or combined median-ulnar nerve injuries were included. Smoking, age, sex, repaired nerve, associated artery and/ or tendon repairs, joint stiffness and scar tissue were analyzed as prognostic factors for functional outcome after repair. Outcome parameters were medical research counsel (MRC) scoring for sensory and motor recovery, grip and pinch strength, disability of arm, shoulder and hand (DASH) questionnaire, electrophysiology and ultrasonographic evaluation. Results The mean age of the studied patients was 29.1 ± 8.3 and it was statistically correlated with grip strength (p = 0.045), DASH score (p = 0.046) and hyperesthesia score (p = 0.040). EMG results showed signs of regeneration in all patients in the form of small nascent MUAPs and polyphasic MUAPs. CMAP amplitudes of median and ulnar nerves positively correlated with the MRC scale for muscle strength (p = 0.001) There were statistically significant negative correlations between DASH score and MRC score for sensory evaluation (p = 0.016), grip (p = 0.001), and pinch strength (p = 0.001). There were statistically significant positive correlations between patient's opinion of recovery and MRC score for sensory evaluation (p = 0.029), grip (p = 0.001), and pinch strength (p = 0.001). The MRC score for muscle strength has statistical significant positive correlations with the MRC score for sensory evaluation, grip (p = 0.003), and pinch strength (p = 0.040) Conclusions It was concluded that; MRC scale for muscle power, MRC scale for sensory evaluation, functional scores, grip and pinch strength are valuable tools for evaluation of functional outcome. Age, smoking, associated tendon repair, damaged nerve, compliance to rehabilitation protocol, return to work, clinically visible wound adhesions, residual hand joint stiffness, and scar tissue detected by ultrasound were found to be prognostic factors for outcome after nerve repair.

Long-term recovery of upper limb motor function and self-reported health: results from a multicenter observational study 1 year after discharge from rehabilitation

Background Impaired motor functions after stroke are common and negatively affect patients' activities of daily living and quality of life. In particular, hand motor function is essential for daily activities, but often returns slowly and incompletely after stroke. However, few data are available on the long-term dynamics of motor recovery and self-reported health status after stroke. The Interdisciplinary Platform for Rehabilitation Research and Innovative Care of Stroke Patients (IMPROVE) project aims to address this knowledge gap by studying the clinical course of recovery after inpatient rehabilitation. Methods In this prospective observational longitudinal multicenter study, patients were included towards the end of inpatient rehabilitation after ischemic or hemorrhagic stroke. Follow-up examination was performed at three, six, and twelve months after enrollment. Motor function was assessed by the Upper Extremity Fugl-Meyer Assessment (FMA), grip and pinch strength, and the nine-hole peg test. In addition, Patient-Reported Outcomes Measurement Information System 10-Question Short Form (PROMIS-10) was included. Linear mixed effect models were fitted to analyze change over time. To study determinants of hand motor function, patients with impaired hand function at baseline were grouped into improvers and non-improvers according to hand motor function after twelve months. Results A total of 176 patients were included in the analysis. Improvement in all motor function scores and PROMIS-10 was shown up to 1 year after inpatient rehabilitation. FMA scores improved by an estimate of 5.0 (3.7–6.4) points per year. In addition, patient-reported outcome measures increased by 2.5 (1.4–3.6) and 2.4 (1.4–3.4) per year in the physical and mental domain of PROMIS-10. In the subgroup analysis non-improvers showed to be more often female (15% vs. 55%, p = 0.0155) and scored lower in the Montreal Cognitive Assessment (25 [23–27] vs. 22 [20.5–24], p = 0.0252). Conclusions Continuous improvement in motor function and self-reported health status is observed up to 1 year after inpatient stroke rehabilitation. Demographic and clinical parameters associated with these improvements need further investigation. These results may contribute to the further development of the post-inpatient phase of stroke rehabilitation. Trial registration: The trial is registered at ClinicalTrials.gov (NCT04119479).

Opponensplasty using the extensor indicis proprius tendon for severe carpal tunnel syndrome in 40 patients

The aim of this study was to assess the clinical results after extensor indicis proprius opponensplasty in patients with carpal tunnel syndrome and severe thenar muscle atrophy. Forty patients who underwent this procedure during open carpal tunnel releases. The mean follow-up period was 17 months (range 10 to 36). Kapandji scores significantly improved from 5.5 before surgery to 9.6 at final follow-up. Thumb pronation angle also significantly improved from 111° before surgery to 149°. Side and pulp pinch strength significantly improved postoperatively, as well as DASH scores at final follow-up. In conclusion, the extensor indicis proprius tendon transfer technique represents a reliable opponensplasty procedure to achieve consistent results in patients with severe carpal tunnel syndrome. Level of evidence: IV

Anterior Interosseous Nerve to Ulnar Nerve Transfers: A Systematic Review

Background There has been an increasing utilization of end-to-end (ETE) and reverse “supercharged” end-to-side (SETS) anterior interosseous nerve (AIN) to ulnar nerve transfers (NTs) for treatment of high ulnar nerve injury. This study aimed to review the potential indications for, and outcomes of, ETE and SETS AIN–ulnar NT. Methods A literature review was performed, and 10 articles with 156 patients who had sufficient follow-up to evaluate functional outcomes were included. English studies were included if they reported the outcome of patients with ulnar nerve injuries treated with AIN to ulnar motor NT. Outcomes were analyzed based on the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire scores, grip and key pinch strength, and interosseous Medical Research Council–graded motor strength. Comparisons were made using the independent t-test and the chi-square test. No nerve graft control group was required for eligibility. Ulnar nerve injury types varied. Results NT resulted in 77% of patients achieving M3+ recovery, 53.7 ± 19.8 lb grip strength recovery, 61 ± 21% key pinch recovery, and a mean DASH score of 33.4 ± 16. In this diverse group, NT resulted in significantly greater M3+ recovery and grip strength recovery measured in pounds than in the nerve graft/conventional treatment group, and ETE repairs had significantly better outcomes compared with SETS repairs for grip strength, key pinch strength, and DASH scores, but heterogeneity limits interpretation. Conclusion ETE and SETS AIN–ulnar NTs produce significant restoration of ulnar nerve motor function for high ulnar nerve injuries. For ulnar nerve transection injuries at or above the elbow, ETE NT results in superior motor recovery compared with nerve grafting/conventional repair. However, further research is needed to determine the best treatment for other types of ulnar nerve injury and the role of SETS NT.