2015 ISAKOS Biennial Congress ePoster #1278
Hamstring Activity in the ACL Injured Patient: Injury Implications and Comparison to Quadriceps Activity
Rachel M. Frank, MD, Aurora, CO UNITED STATES
Hannah Lundberg, PhD, Chicago UNITED STATES
Robert Trombley, PhD, Chicago, IL UNITED STATES
Markus Wimmer, MD, Chicago, IL UNITED STATES
Charles A. Bush-Joseph, MD, Chicago, IL UNITED STATES
Bernard R. Bach, Jr., MD, Chicago, IL UNITED STATES
Nikhil N. Verma, MD, Chicago, IL UNITED STATES
Brian J. Cole, MD, MBA, Chicago, IL UNITED STATES
Rush University Medical Center, Chicago, IL, USA
FDA Status Not Applicable
Summary: In patients with acute ACL injury, there are significant differences in the timing and duration of quadriceps and hamstring muscle group activation in the injured compared to the contralateral leg.
Regaining terminal extension is paramount for successful outcomes following anterior cruciate ligament (ACL) reconstruction. While the lack of terminal knee extension following acute ACL injury is thought to be due to reflexive inhibition of the quadriceps, it is possible that hamstring spasm may also play a role. The purpose of this study was to investigate the potential causes of diminished knee extension following acute ACL injury using both surface electromyography (sEMG) as well as gait analysis.
Consecutive patients with an acute ACL tear underwent sEMG and gait analysis within 2 weeks of injury, prior to ACL reconstruction. Standard motion analysis techniques were used to obtain knee joint flexion angle and external knee joint moments during walking, using a twelve-camera optoelectronic system at 120Hz. Three normal gait trials were obtained for each subject at a self-selected walking speed, and sEMG data was collected simultaneously with gait data from four muscle groups: bicep femoris, semimembranosus/semitendinosus, rectus femoris, and vastus medialis. Paired t-tests were used to determine differences between the ACL deficient and contralateral limb in knee flexion angles, peak external knee joint moments, and total time that a muscle was activated (“on”) during the gait cycle. External knee moments were expressed as a percentage of body weight times height (%BW*Ht).
Ten patients with a mean age of 24±4 years were included at a mean 7.6 days between injury and analysis. Range of motion in the injured knee was significantly lower compared to the contralateral knee (50 vs 63°, P=0.004), respectively. Motion analysis showed a significant increase in minimum flexion angle at both heel strike (5.9 vs -2.0°, P=0.003) and midstance (14.1 vs 5.9°, P=0.001) in the injured leg compared to the contralateral leg, respectively. There was a significantly lower maximum external flexion moment during the first half of stance in the injured leg compared to the contralateral leg (2.6 vs 3.6 %BW*Ht, P=0.010). There was a significantly lower maximum external extension moment during midstance in the injured leg compared to the contralateral leg (-0.56 vs -2.03 %BW*Ht, P=0.012, Figure 1). The rectus femoris was "on" significantly longer during gait in the contralateral leg (54.8±49.1 vs 49.1±7.8%, P=0.034) than the injured leg.
In patients with acute ACL injury, there are significant differences in the timing and duration of activation of quadriceps and hamstring muscle groups in the injured compared to the contralateral leg. Notably, the ACL deficient limb does not reach as much extension as the contralateral limb, the sagittal plane flexion moment was reduced in the injured limb, and the rectus femoris was “on” for shorter periods during the gait cycle in the injured limb.