The Grasping Test Revisited: A Systematic Review of Functional Recovery in Rat Models of Median Nerve Injury

Abstract

The rat median nerve model is a well-established and frequently used model for peripheral nerve injury and repair. The grasping test is the gold-standard to evaluate functional recovery in this model. However, no comprehensive review exists to summarize the course of functional recovery in regard to the lesion type. According to PRISMA-guidelines, research was performed, including the databases PubMed and Web of Science. Groups were: (1) crush injury, (2) transection with end-to-end or with (3) end-to-side coaptation and (4) isogenic or acellular allogenic grafting. Total and respective number, as well as rat strain, type of nerve defect, length of isogenic or acellular allogenic allografts, time at first signs of motor recovery (FSR) and maximal recovery grasping strength (MRGS), were evaluated. In total, 47 articles met the inclusion criteria. Group I showed earliest signs of motor recovery. Slow recovery was observable in group III and in graft length above 25 mm. Isografts recovered faster compared to other grafts. The onset and course of recovery is heavily dependent from the type of nerve injury. The grasping test should be used complementary in addition to other volitional and non-volitional tests. Repetitive examinations should be planned carefully to optimize assessment of valid and reliable data.

End-to-side neurorrhaphy in the reconstruction of peripheral segmental neural loss: an experimental study

“…Relating the amplitude of the median nerve, a significant increase was observed over the weeks in GA and GE, with the latter having the lowest total values, while in the GD there was a small decrease in amplitude from the 4th to the 12th week, but still higher than the GE. This demonstrates an increase in the activation of motor units in all experimental groups 21 , despite GD having decreased, in Table 4 . This corroborates the findings of the grasping test.…”

“…Both the ENMG and the weight assessment of the muscle did not show, at the end of the 12th week, favorable statistical differences for neural regeneration, about the data obtained in the 4th week. Such observations suggest that the functional grasping test has greater sensitivity than the ENMG and the weight assessment of the muscle in quantifying signs of neural regeneration after neurorrhaphy 21 , 22 .…”

“…Among the muscles analyzed, the flexor carpi ulnaris, flexor carpi radialis, digitorum superficialis, and palmaris longus were the most important for the grip strength of the limb and the ones which had the greatest difference between the groups 21 , 23 , 24 . According to the weight of each muscle, it was possible to verify the difference in atrophy between the groups, demonstrating less loss of muscle mass in GA when compared to the other groups, which corroborates the functional findings of the grasping test (Tables 4 and 5).…”

“…ENMG was used to compare nerve conduction between groups, over four and 12 weeks, analyzing the degree of reinnervation over time. The amplitude assessment indicates the number of functioning nerve fibers and motor units recruited to conduct the electrical stimulus through the axonal fibers 18 – 21 . In the present study, there was a significant increase in the amplitude of the ulnar nerve in the 4th and 12th weeks, being greater in GA, with significant elevations in GE and GD, the latter being greater.…”

“…Regarding latency, this parameter allows checking the time needed for the action potential to travel a certain length of fibers, a direct product of myelination and the diameter of axonal fibers, wherefore the shorter the latency, the better the quality of neural regeneration 18 - 21 . When dealing with GD and GE, both presented an increase in latency between the 4th and 12th week, and in the GE the increase was minimally greater than in the GD, in both the median and ulnar nerves.…”