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


METHODS
We 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.


RESULTS
Tests revealed that the mean muscle torque per unit volume of the uninjured and injured sides was significantly lower than those of the control group.


CONCLUSIONS
This 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.
Department of Physical Education, National Defence Academy, 1-10-20 Hashirimizu, Yokosuka City, 239-8686, Kanagawa, Japan. yu57@nda.ac.jp
Yu
Y
Konishi
Toshiaki
T
Oda
Satoshi
S
Tsukazaki
Ryuta
R
Kinugasa
Norikazu
N
Hirose
Toru
T
Fukubayashi
D000328:Adult; D000704:Analysis of Variance; D016118:Anterior Cruciate Ligament / Q000503:physiopathology; D000070598:Anterior Cruciate Ligament Injuries; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D015601:Injury Severity Score; D007718:Knee Injuries / Q000150:complications* / Q000175:diagnosis; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018908:Muscle Weakness / Q000209:etiology* / Q000503:physiopathology; D009929:Organ Size / Q000502:physiology; D010808:Physical Examination / Q000379:methods; D052097:Quadriceps Muscle / Q000503:physiopathology*; D012016:Reference Values; D012421:Rupture / Q000150:complications / Q000175:diagnosis; D019415:Torque; D055815:Young Adult