Yu Konishi

Mechanism of quadriceps femoris muscle weakness in patients with anterior cruciate ligament reconstruction

The purpose of this study was to investigate gamma loop function in the quadriceps femoris muscle in patients who with less than 6 month‐history of anterior cruciate ligament (ACL) reconstruction. For this purpose, we compared the response to vibration stimulation in 10 patients with ACL repair and 12 normal healthy subjects, by measuring the maximal voluntary isometric contraction (MVC) and integrated electromyograms (I‐EMG) of the quadriceps muscles. Pre‐vibration data were obtained from each subject by measuring the MVC of the knee extension and the I‐EMG from the vastus medialis, vastus lateralis, and rectus femoris muscles. Vibration stimulation was applied to the infrapatellar tendons, followed immediately by repeating the MVC and I‐EMG recording. Prolonged vibration resulted in a significant decrease of both MVC and I‐EMG in the control group. In contrast, the same stimulus failed to elicit changes in ACL‐repair group. Our results suggest the presence of abnormal gamma loop function in the quadriceps femoris muscle of patients with ACL repair, which may explain the muscle weakness often described in such patients.

Gamma loop dysfunction in quadriceps on the contralateral side in patients with ruptured ACL

PURPOSE The aim of our study was to test for any neurophysiological abnormality in the gamma loop in the quadriceps femoris muscle on the uninjured side of patients with unilateral rupture of the anterior cruciate ligament (ACL). METHODS Maximal voluntary contraction of knee extension and integrated electromyography (I-EMG) of the vastus medialis, vastus lateralis, and rectus femoris were measured in the uninjured limb of 13 patients with unilateral ACL rupture and 10 normal subjects, before and after 20-min vibration stimulation applied to the infrapatellar tendon. RESULTS The mean percentage changes of maximal voluntary contraction and I-EMG in quadriceps femoris of the uninjured side of patients with ACL rupture were significantly different from those of the control group. Maximal voluntary contraction and I-EMG after prolonged vibration stimulation did not decrease as much as those of the control group even though the same protocol of vibration stimulation was applied. CONCLUSION The abnormal response to prolonged vibration stimulation could represent abnormal gamma loop in the quadriceps femoris muscle of the uninjured side in patients with ACL rupture since the normal response of maximal voluntary contraction and I-EMG to prolonged vibration stimulation could not be evoked without normal function of the gamma loop.

Tactile stimulation with kinesiology tape alleviates muscle weakness attributable to attenuation of Ia afferents.

OBJECTIVE Prolonged vibration stimulation to normal individuals could lead to muscle weakness attributable to attenuation of afferent feedback. This weakness is neurophysiologically similar to that seen in patients with knee injury. Theoretically, increasing input to gamma motor neurons could reverse this weakness. Sensory input to these neurons from skin could indirectly increase Ia afferent feedback. The present study examined the effect of this tactile stimulation in the form of Kinesiology tape on muscle weakness attributable to attenuation of afferent feedback. DESIGN Randomized, crossover design. METHODS All participants were measured their eccentric maximal voluntary contractions under the 2 conditions (taping and non-taping). First, maximal voluntary contraction during eccentric contraction was measured as baseline. For the taping condition, Kinesiology tape was applied around each subjects knee joint during maximal voluntary contraction measurement after vibration. For the non-taping condition, tape was not applied during maximal voluntary contraction measurement after vibration. Mean percentage changes between pre- and post-vibration stimulation were compared between two conditions. RESULTS Maximal voluntary contraction and average electromyography of taping condition was significantly larger than that of non-taping condition. CONCLUSIONS Our results suggest that tactile stimulation in the form of Kinesiology tape inhibits the decline of both strength and electromyography. Alpha motor neuron activity attenuated by prolonged vibration would thus be partially rescued by tactile stimulation. These results indirectly suggest that stimulation of skin around the knee could counter quadriceps femoris weakness due to attenuated Ia afferent activity.

Relationship between muscle volume and muscle torque of the hamstrings after anterior cruciate ligament reconstruction.

The muscle torque per unit volume of the hamstrings on the injured and uninjured sides in patients with ACL reconstruction were compared with participants with no history of knee injury to examine whether a similar mechanism leading to quadriceps weakness exists in the hamstrings of these patients. The study population consisted of 18 and 52 patients at <or=6 and 12 months after ACL reconstruction, respectively, and 35 healthy controls. The hamstring volume was measured on MRI. To identify the muscle torque per unit volume, the peak torque of knee flexion was divided by the hamstring volume. Most muscle torque per unit volume indexes were not significantly different between the patients at <or=6 months (injured side: 0.133+/-0.03 Nm/cm(3), 60 degrees /s; 0.107+/-0.03 Nm/cm(3), 180 degrees /s; uninjured side: 0.139+/-0.02 Nm/cm(3), 60 degrees /s; 0.107+/-0.02 Nm/cm(3), 180 degrees /s) and controls (0.170+/-0.05 Nm/cm(3), 60 degrees /s; 0.121+/-0.05 Nm/cm(3), 180 degrees /s). However, the muscle torque per unit volume of patients at 12 months in both injured (0.118+/-0.03 Nm/cm(3), 60 degrees /s; 0.092+/-0.02 Nm/cm(3), 180 degrees /s) and uninjured sides (0.120+/-0.03 Nm/cm(3) at 60 degrees /s; 0.094+/-0.02 Nm/cm(3), 180 degrees /s) were significantly lower than those of controls (P<0.01). We found no evidence of recruitment disorder in the hamstrings of the patients. The results of this study indicated that the mechanism of muscle weakness of the hamstrings after reconstruction was different from that of the quadriceps, although the precise mechanism remains to be determined.

Relationship between quadriceps femoris muscle volume and muscle torque after anterior cruciate ligament rupture

PurposeThe purpose of this study was to obtain evidence to support the hypothesis that motor unit recruitment is reduced in the quadriceps femoris (QF) of patients with ACL rupture.MethodsWe compared muscle torque per unit volume in the QF from injured and uninjured sides to normal subjects. If high-threshold motor unit recruitment is reduced in patients with ACL rupture, this reduction will theoretically lead to a reduction in muscle torque per unit volume compared to the control group. The subjects included 22 patients with ACL rupture and 22 subjects with no history of knee injury. To identify the muscle torque per unit volume, the isokinetic peak torque was divided by QF volume which was obtained by MRI.ResultsTests revealed that the mean muscle torque per unit volume of the uninjured and injured sides was significantly lower than those of the control group.ConclusionThis study demonstrated that the values of the muscle torque per unit volume of both injured and uninjured sides of patients with ACL rupture were significantly lower than those of the control group, thereby providing indirect evidence of the hindrance of motor unit recruitment in these patients. The results of the present study also indicate that there may be bilateral QF weakness in patients with ACL rupture. Since persistent QF weakness is a significant barrier to effective rehabilitation in patients with ACL injuries, a better understanding of the underlying mechanisms will allow clinicians and scientists to develop more effective therapeutic strategies for patient rehabilitation.

Effects of lidocaine into knee on QF strength and EMG in patients with ACL lesion

PURPOSE In our previous study, we found that injection of lidocaine into intact knees reduced the maximal voluntary contraction (MVC) and integrated electromyogram (I-EMG) of the quadriceps femoris (QF). This study was designed to investigate changes in the MVC and I-EMG of the QF in response to lidocaine, in patients with anterior cruciate ligament (ACL) lesion, to evaluate alpha-motoneuron activity innervating the QF. METHODS The MVC of knee extension and I-EMG of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscles were measured in eight patients with ruptured ACL, before and after lidocaine injection into the knee. RESULTS There were no significant differences between preinjection and postinjection values of MVC (preinjection: 167 +/- 49 N.m; postinjection: 164 +/- 55 N.m) and I-EMG (preinjection: VL: 0.11 +/- 0.06, VM: 0.13 +/- 0.10, RF: 0.09 +/- 0.04) (postinjection: VL: 0.12 +/- 0.07, VM: 0.13 +/- 0.10, RF: 0.09 +/- 0.05). CONCLUSION Our results indicated that hindrance of afferent feedback from the knee in patients with ACL rupture did not significantly change alpha-motoneuron activity. Lidocaine injection into the knee joint of the subjects in this study only attenuated afferent feedback from mechanoreceptors in the knee joint cavity, but not in the ACL, as afferent feedback from ACL was already lost due to ACL rupture. This indicated that attenuation of afferent feedback from mechanoreceptors in the knee joint cavity other than the ACL did not significantly decrease the activity of alpha-motoneurons innervating the QF during MVC exertion. Therefore, our findings provide evidence that afferent feedback from the ACL has a major influence on the MVC exertion of the QF.