[OES-1-4] Postoperative changes in grip force control during precision grasp in cervical myelopathy
Introduction
Hand dysfunction is one of the representative clinical symptoms in cervical myelopathy (CM). Although various studies have assessed postoperative recovery of hand function, kinetic aspect has not been adequately discussed. The aim of this study was to investigate the post-operative changes of grip force (GF) control during precision grip and its relationship with other clinical tests.
Method
Seven right-handed patients (6 males and 1 female, mean age, 63.5 ± 8.4 years) undergoing cervical decompression surgery participated in this study. Participants gripped and lifted a 150 g iron cube by pulp pinch using the thumb and index finger of the dominant hand. Because small GF indicates higher GF control, participants were instructed to use minimal GF to perform the task. We monitored individual finger grip force (N) during first 5 seconds while lifting and holding an object pre- (1.0 ± 0.0 days) and postoperatively (36.7 ± 30.4 days). The severity of neurological/motor/sensory function in CM was assessed by Japanese Orthopedic Association (JOA) score. Higher JOA scores indicate healthy body function and better activity level. The other clinical upper extremity tests of the dominant hand were assessed as follows; grip and pinch strength, 10-second grip and release test, two-point discrimination, cutaneous pressure threshold of the thumb and index finger, and three subtests time (number 8, 9, and 10) of the Simple Test for Evaluating Hand Function (STEF). We evaluated post-operative changes of grip force control and clinical tests using Paired t-test or the Wilcoxon signed-rank test. Moreover, Pearson’s correlation coefficient was used to investigate the relationship between GF control and other clinical outcomes. The study was approved by ethic committee of the hospital and written informed consent was obtained from all patients.
Results
The thumb GF significantly decreased (p = 0.04), and the JOA score improved after surgery (p = 0.02). Thumb GF was negatively correlated with the JOA score (r = -0.86, p = 0.01) and grip strength (r = -0.98, p = 0.01). Likewise, index GF was also correlated with the JOA score (r = -0.80, p = 0.03) and grip strength (r = -0.81, p = 0.03) negatively.
Discussion
Improvement of GF control was found after surgery. It suggests GF control during a precision grip and lift task might capture the early post-operative changes of the hand function at the fundamental level in CM. In addition, it is worth noting that GF was negatively correlated with the JOA score. The result may imply that a therapeutic approach incorporating kinetic feature of hand function could contribute to the improvement of activity and participation in CM patients.
Hand dysfunction is one of the representative clinical symptoms in cervical myelopathy (CM). Although various studies have assessed postoperative recovery of hand function, kinetic aspect has not been adequately discussed. The aim of this study was to investigate the post-operative changes of grip force (GF) control during precision grip and its relationship with other clinical tests.
Method
Seven right-handed patients (6 males and 1 female, mean age, 63.5 ± 8.4 years) undergoing cervical decompression surgery participated in this study. Participants gripped and lifted a 150 g iron cube by pulp pinch using the thumb and index finger of the dominant hand. Because small GF indicates higher GF control, participants were instructed to use minimal GF to perform the task. We monitored individual finger grip force (N) during first 5 seconds while lifting and holding an object pre- (1.0 ± 0.0 days) and postoperatively (36.7 ± 30.4 days). The severity of neurological/motor/sensory function in CM was assessed by Japanese Orthopedic Association (JOA) score. Higher JOA scores indicate healthy body function and better activity level. The other clinical upper extremity tests of the dominant hand were assessed as follows; grip and pinch strength, 10-second grip and release test, two-point discrimination, cutaneous pressure threshold of the thumb and index finger, and three subtests time (number 8, 9, and 10) of the Simple Test for Evaluating Hand Function (STEF). We evaluated post-operative changes of grip force control and clinical tests using Paired t-test or the Wilcoxon signed-rank test. Moreover, Pearson’s correlation coefficient was used to investigate the relationship between GF control and other clinical outcomes. The study was approved by ethic committee of the hospital and written informed consent was obtained from all patients.
Results
The thumb GF significantly decreased (p = 0.04), and the JOA score improved after surgery (p = 0.02). Thumb GF was negatively correlated with the JOA score (r = -0.86, p = 0.01) and grip strength (r = -0.98, p = 0.01). Likewise, index GF was also correlated with the JOA score (r = -0.80, p = 0.03) and grip strength (r = -0.81, p = 0.03) negatively.
Discussion
Improvement of GF control was found after surgery. It suggests GF control during a precision grip and lift task might capture the early post-operative changes of the hand function at the fundamental level in CM. In addition, it is worth noting that GF was negatively correlated with the JOA score. The result may imply that a therapeutic approach incorporating kinetic feature of hand function could contribute to the improvement of activity and participation in CM patients.