Stimulated grip strength measurement: Validation of a novel method for functional assessment

Abstract

Background Reliable measurement of functional recovery is critical in translational peripheral nerve regeneration research. Behavioral functional assessments such as volitional grip strength testing (vGST) are limited by inherent behavioral variability. Isometric tetanic force testing (ITFT) is highly reliable but precludes serial measurements. Combining elements of vGST and ITFT, stimulated grip strength testing (sGST) involves percutaneous median nerve stimulation to elicit maximal tetanic contraction of digital flexors, thereby allowing for consistent measurement of maximal grip strength. Methods We measured side‐to‐side equivalence of force using sGST, vGST, and ITFT to determine relative reliability and repeatability. We also performed weekly force measurements following median nerve repair. Results sGST demonstrated greater reliability and inter‐trial repeatability than vGST and similar reliability to ITFT, with the added benefit of serial measurements. Conclusions sGST is a valid method for assessing functional recovery that addresses the limitations of the currently available modalities used in translational peripheral nerve regeneration research.

Evaluation of Functional Recovery in Rats After Median Nerve Resection and Autograft Repair Using Computerized Gait Analysis

“…This limitation was impressively confirmed in our experiments, in which 40% of animals had to be excluded from RMANOVA analysis of grasping strength assessments. As shown by our as well as other authors' data (Daeschler et al, 2018b;Marchesini et al, 2018;Hanwright et al, 2019), a high degree of inter-animal variation is observable, complicating statistical analysis of the assessed data. In regard to our study, it is noteworthy that grasping strength was significantly altered from baseline at WPO2 and WPO4, statistically indifferent from baseline at WPO6 and WPO8, but markedly decreased at WPO10 before increasing to baseline levels again at WPO12.…”

“…Most importantly, the grasping test does not allow for standardization of the speed with which the animals are lifted after grasping the bar that therefore depends on the individual investigator (Tos et al, 2009). Recent efforts to circumvent this problem by stimulated grasping strength measurements while the animal is in anesthesia are a valuable refinement (Hanwright et al, 2019). However, data acquisition is further complicated by this approach, which in our opinion is also concerning regarding the need for weekly anesthesia of the animals.…”

“…Additionally, although neuropathic pain is induced after median nerve injury (Lue et al, 2002), cases of automutilation are extremely rare in this model (Papalia et al, 2003). A plethora of evaluation methods is used for the assessment of functional recovery after median nerve injury (Stossel et al, 2017), of which the grasping test is the predominant one Hanwright et al, 2019). In rats, unlike in humans, the superficial and deep finger flexor muscles are predominantly innervated by the median nerve.…”

Mechanisms and outcomes of the supercharged end-to-side nerve transfer: a review of preclinical and clinical studies

“…Nadi et al were unable to demonstrate any functional effects in their model using a ladder rung analysis and noted that transfers between antagonistic nerve and muscle units can negatively impact functional performance. 16,54 The use of an upper limb ulnar nerve to median nerve model in conjunction with weekly stimulated grip strength testing 55 could overcome some of these limitations. The SETS transfer has been shown to increase muscle mass, 14 although this finding has not been consistent across different experimental models.…”

Evolution of the rat hind limb transplant as an experimental model of vascularized composite allotransplantation: Approaches and advantages

“…However, as the field continues to grow, models focusing on forelimb function in the rat are being developed. 67,68 Kern et al developed a rat allogeneic (BN to Lewis) midhumeral forelimb transplant model that includes cooptation of the median, ulnar and radial nerves. 67 Importantly, this model allowed the investigators to study recovery of not only grip strength but also of behavioral function.…”