ACL Injury

Effects of Volitional Preemptive Abdominal Contraction on Trunk and Lower Extremity Biomechanics and Neuromuscular Control During a Drop Vertical Jump

Submitted by Ram Haddas

The purpose of this study was to determine whether performance of a volitional preemptive abdominal bracing maneuver (VPAC) during a drop vertical jumping (DVJ) task alters lower extremity (LE) kinematics, kinetics and muscle electromyography (EMG). Subjects performed DVJs with and without performance of the ABM from a 30 cm and 50 cm height. Differences in EMG values before and after landing were compared with and without VPAC using repeated measures t-tests. Differences between each kinematic and kinetic dependent variable were assessed using 2 (abdominal contractile state) X 2 (landing phase) within design ANOVAs using SPSS. At the 30 cm landing height, VPAC resulted in statistically significant increases in: knee internal rotation angle, knee flexion angle, knee internal abduction moment, knee energy absorption, medial hamstring post contact activity, trunk left rotation, and external oblique activity pre- and post-contact. At the 50 cm landing height, VPAC resulted in statistically significant decreases in ankle inversion angle, hip energy absorption, and external oblique muscle activity post-contact. In addition, increases in knee flexion angle at contact, medial hamstring activity pre-contact, hip flexion angle at contact, trunk left rotation angle post-contact, trunk left rotation angle at contact, and greater external oblique muscle activity pre-contact. The use of VPAC altered LE and trunk biomechanics and neuromuscular control when performing DVJ from 30 and 50 cm heights. The demands of the 50 cm DVJ may have superseded the effectiveness of VPAC. These results suggest an enhanced protective knee response and improved trunk stability with VPAC use.


Listed In: Biomechanics, Physical Therapy, Sports Science 




  

    			
Immediate Decreases in Peak Vertical Ground Reaction Force following Real-time Feedback during Jump Landing

		    
        

      Submitted by Hayley Ericksen
    

    
        	

    		
    		

    			    			    		

    		

    			
Context: Feedback has been used to reduce peak vertical ground reaction (VGRF) during landing, yet the use of technology to allow for real-time adjustments during landing has not been evaluated. Objective: Determine effects of real-time feedback (RTF) and traditional feedback (TF) on VGRF and inter-limb VGRF symmetry during landing compared to jumping and control conditions. Design: Single blinded, randomized controlled trial. Participants: Thirty healthy females randomized into 4 groups(RTF:n=7,21.1±1.5yrs,164.0±5.5cm,63.4±7.1kg; TF:n=8,20.8±2.1yrs, 165.4± 5.2cm,61.6±3.4kg;Control:n=8,21.3±1.2yrs,162.6±6.8cm,66.0±18.5kg;Jumping:n=7,22.7±3.5yrs,166.6±6.2cm,68.6±14.22 kg). Interventions: RTF and TF participants completed 18 jump-landings with feedback following each set. RTF group was equipped with markers on the lower extremity. Markers on patella and great-toe were highlighted, and connected with a line. RTF participants aligned their knee-foot segment with vertical reference line during landing. Control participants sat quietly for 10 minutes. Jumping participants performed 18 jumps without feedback. Outcome Measures: Three pre-intervention jumps and three post-intervention jumps were recorded. Peak VGRF was calculated for each limb and normalized to mass. Repeated measures ANOVA and Tukey post hoc comparisons assessed changes in VGRF, and inter-limb symmetry ((dominant VGRF/non-dominant VGRF)*100). Pre-intervention VGRF values were used as a covariate, accounting for baseline group differences in right VGRF analysis. Alpha was set a priori at P<0.05. Results: Post-intervention right RTF VGRF was lower than control (RTF vs. control:1.47±0.29, 2.27±0.36;P=0.001) and jumping (RTF vs. jumping:1.47±0.29, 2.03±0.23,P=0.018). Left RTF(1.24±0.16) VGRF was lower compared to control(1.82±0.24,P=0.006). No significant group by time interaction for inter-limb symmetry on landing observed(P=0.448). Conclusion: Reduction in VGRF observed following RTF without a change in inter-limb symmetry.



    			Listed In: Biomechanics
    		

    	

        
      









  

    			
A COMPARISON OF KNEE MOMENTS DURING A LATERAL CUTTING MANEUVER: SHOD VS. BAREFOOT

		    
        

      Submitted by Brianna Bisesti
    

    
        	

    		
    		

    			    			    		

    		

    			
BACKGROUND: Noncontact anterior cruciate ligament (ACL) injuries often occur during lateral cutting maneuvers. The combination of extension, adduction, and external rotation during lateral cutting maneuvers creates the highest load on the ACL, possibly causing a rupture. Lateral cutting maneuvers have been studied in the shod condition, however there is no evidence pertaining to barefoot sports, in areas around the world such as Brazil and Africa. PURPOSE: To examine if knee moments of extension, adduction, and external rotation differ between shod (SD) and barefoot (BF) conditions during lateral cutting maneuvers. METHODS: Twelve NCAA Division III athletes (6 female, and 6 male; aged 20.2 ± 1.5 yr; mass 71.2 ± 11.3 kg; height, 1.7 ± .06 m) were analyzed during 5 trials of 45 degree lateral cutting maneuvers for each limb in both BF and SD conditions. Peak extension, adduction, and external rotation knee moments were measured by an eight camera motion capture system, and a force plate, and compared by paired t-tests. RESULTS: No significant difference (p <.05) was found in the peak knee extension or peak external rotation moments. However the SD condition produced a significantly greater peak knee adduction moment (1.50 ± 1.04 Nm/kg) than the BF condition (0.71± 0.33). CONCLUSIONS: Findings suggest that lateral cutting while BF provides no more stress on the ACL than when SD. Further studies should focus on other structures of the lower limb.



    			Listed In: Biomechanics, Sports Science
    		

    	

        
      









  

    			
Differences in internal-external rotational knee joint moments between ACL deficient and healthy subjects. 

		    
        

      Submitted by Amelia Lanier
    

    
        	

    		
    		

    			    			    		

    		

    			
Impairment of the anterior cruciate ligament (ACL) is a common injury causing rotational instability of the knee joint. It is difficult to directly evaluate ACL-deficient patients in internal/external rotations due to risk of further injury. The aim of this study was to evaluate standing target matching’s ability to challenge ACL-deficient patients in internal/external rotational moments. We hypothesized ACL injured subjects would exhibit larger external rotation moments during knee extension when compared to healthy subjects. Ten subjects participated in this study; four (2 males, 2 females) had no history of knee injury and six (3 males, 3 females) sustained ACL rupture within 6 months prior to testing. All subjects were regular participants (> 50 hrs/year) in level I and II sports. Standing target matching required subjects to position the cursor on a target consisting of two concentric circles using anterior/posterior and medial/lateral shear forces and internal/external rotation moments. The limb controlling the cursor was coined the mobilizer. The limb not controlling the cursor but still maintaining stability for the subject was coined the stabilizer. External rotation, negative transverse knee moment, of the stabilizing limb during knee extension was observed to be higher in ACL-d subjects when compared to healthy subjects. We believe that the standing target matching protocol is effectively challenging ACL deficient subjects in internal and external rotations in a safe manner. The ACL deficient limb is exhibiting higher external rotation moments during knee extension as a preventative measure in the absence of the passive restraint provided by the ACL.



    			Listed In: Biomechanical Engineering, Biomechanics, Mechanical Engineering
    		

    	

        
      









  

    			
A Novel Technique to Simulate Landing Biomechanics: a Cadaveric Model of ACL Injury

		    
        

      Submitted by Ata Kiapour
    

    
        	

    		
    		

    			    			    		

    		

    			INTRODUCTION
Acute ACL injury can be devastating, and often results in clinical sequelae including long-term disability and osteoarthritis. To study loading factors independently and in combination, such a model must be capable of consistent independent control of each parameter. We hypothesized that an unconstrained test configuration capable of independent application of loads about all anatomical axes of loading would allow us to evaluate each mode of loading separately an in combination, while generating realistic injuries patterns. 
METHODS 
19 cadaveric legs (45±7 years) were tested under multiple combinations of anterior shear, abduction and internal rotation moments utilizing a novel drop stand. Landing was simulated by releasing either half or full body weight from 30 or 60 cm above the foot. Specimens were tested at 25o of flexion under simulated muscle loads. Joint kinematics and ACL strain were collected.

 RESULTS and DISCUSSION
Our test setup was able to deliver a consistent impact load-time history.  Experiments produced ACL failure in the majority of specimens. A clinically relevant distribution of failure patterns was observed. Detailed attention to impact parameters including mass, drop height and interface helped to generate an in vitro load-time history similar to in vivo data. This setup was designed to replicate the ranges of loading determined from in vivo studies of ACL injury mechanisms undertaken by our group. This evolution of experimental design facilitates the use of this experimental model to independently evaluate the effects of single and multi-axis loads on ACL injury, while recreating injury patterns observed in vivo.



    			Listed In: Biomechanical Engineering, Biomechanics, Sports Science