Analysis of limb kinetic asymmetry during a drop vertical jump in adolescents post anterior cruciate ligament reconstruction

BACKGROUND

Limb asymmetry after ACL reconstruction is often cited as a risk factor for ACL reinjury. We assessed ground reaction forces on each limb during a drop vertical jump, and compared kinetic symmetry between limbs in adolescents post-ACL reconstruction versus healthy controls.

METHODS

Forty-four participants who underwent an ACL reconstruction (16 male/28 female, mean age 16.1 ± 1.5, mean 7.3 ± 0.9 months post-ACL reconstruction) and 34 controls (20 male/14 female, mean age 14.9 ± 1.1) completed a drop vertical jump captured on a Vicon system and Bertec force plates. Kinetic variables were calculated individually for each limb. Inter-limb asymmetry was calculated as an index between each limb (involved versus uninvolved for the ACL reconstruction group, and left versus right for controls), and was compared between groups using independent t-tests.

FINDINGS

Asymmetry was significantly more pronounced in the ACL reconstruction group versus the controls for peak contact ground reaction force (11.6% vs 4.4%, p = 0.009), eccentric impulse (8.8% vs 3.8%, p = 0.009), eccentric mean force (8.0% vs 3.4%, p = 0.006), concentric peak ground reaction force (4.1% vs 0.8%, p = 0.003), concentric impulse (5.1% vs 1.1%, p = 0.001), and peak landing ground reaction force (12.7% vs 1.7%, p < 0.001).

INTERPRETATION

Limb kinetic asymmetry during a drop vertical jump was more pronounced in adolescents post-ACL reconstruction versus controls for both eccentric- and concentric-phase variables, which may indicate the use of compensatory strategies to offload the post-operative limb. Targeted interventions to produce more symmetric loading and unloading during jumping tasks should be developed, tested, and monitored to determine the impact on rehabilitation programs, return-to-sport evaluations, and injury prevention outcomes.

Reliability of a simple fluoroscopic image to assess leg length discrepancy during direct anterior approach total hip arthroplasty

BACKGROUND

Direct anterior approach (DAA) total hip arthroplasty (THA) in a supine position provides a unique opportunity to assess leg length discrepancy (LLD) intra-operatively with fluoroscopy. Reported fluoroscopic techniques are useful but are generally complicated or costly. Despite the use of multiple techniques for leg length assessment, LLD continues to be a major post-operative source of patient dissatisfaction further emphasizing the importance of near-anatomic restoration. The utility of an alternative direct measurement of LLD on an intra-operative fluoroscopic pelvic image during DAA THA has not been reported.

AIM

To determine the reliability of a novel simple intra-operative measurement of LLD using a parallel line technique on a single fluoroscopic digital image of the pelvis.

METHODS

One hundred and seventy-one patients who underwent DAA THA were included for analysis. Intra-operative fluoroscopic and post-operative anterior-posterior radiographs were imported to TraumaCad and calibrated for LLD measurement. LLD was measured on each image using the right-left hip differences in lesser trochanter to pelvic reference line distances. Pelvic reference points included the teardrops and ischia. Fluoroscopic LLD was compared to the gold-standard measurement of LLD measured on a post-operative radiograph.

RESULTS

Mean absolute difference in teardrop referenced LLD between fluoroscopic and post-operative radiographs was 2.17 mm and based on the ischia mean absolute difference was 2.63 mm. Linear regression of fluoroscopic and post-operative radiograph LLD based on teardrop and ischia LLD found r² values of 0.57 and 0.84, respectively. Mean absolute difference between fluoroscopic and post-operative x-ray LLD was within 5 mm in 95% of cases regardless of pelvic reference.

CONCLUSION

This study demonstrates that a single fluoroscopic view obtained during DAA THA for leg length assessment is clinically useful.

Side-to-side asymmetry in lower limb strength and hamstring-quadriceps strength ratio among collegiate American football players

[Purpose] The present study aimed to investigate the lower limbs injury risk factors that are based on conventional Hamstring to Quadriceps ratio and limb asymmetry index in varsity American football players. [Participants and Methods] Twenty-six varsity American football players aged 19–27 years and with 2.31 ± 1.29 years of American football experience from Dogu Akdeniz University volunteered to undergo measurements of average peak torque for isokinetic flexion and extension of dominant limb and non-dominant limb at 60°·s⁻¹ and 300°·s⁻¹. Hamstring to Quadriceps ratio and limb asymmetry index were also calculated for Hamstring and Quadriceps muscles. [Results] Statistical analysis revealed that dominant Quadriceps is stronger than non-dominant Quadriceps at 60°·s⁻¹ speed. No statistical difference was found between dominant and non-dominant Hamstring peak torque at 60°·s⁻¹ . Hamstring to Quadriceps ratio determined as normal both for 60°·s⁻¹ and 300°·s⁻¹according to the currently reported cut off value (H:Q ratio >60). Hamstring and Quadriceps limb asymmetry index also determined as normal (cut off value for LSI 10%) at 60°·s⁻¹. However, for both Hamstring and Quadriceps, side- to- side strength asymmetry at 300°·s⁻¹ was observed. [Conclusion] To prevent possible lower limb injury and to increase performance, varsity American football players who are actively training and competing might consider taking strength asymmetry into account to tailor their strength training program accordingly.

No shortage of disagreement between biomechanical and clinical hop symmetry after anterior cruciate ligament reconstruction

BACKGROUND

Evaluating average performance on functional hop tasks can potentially overestimate physical function, as it masks variability present within individual trials and may lead to clinician oversight regarding the overall movement quality. The purpose was to evaluate the trial-by-trial agreement between hop-distance symmetry and knee biomechanics (knee flexion angle, knee extension moment) to reveal the full extent of agreement between these measures.

METHODS

Sixteen individuals with primary, unilateral anterior cruciate ligament reconstruction participated (age: 22(2) y; height: 1.71(0.11) m; mass: 68.94(13.06) kg; gender: 8 males, 8 females; years' post-surgery:4(3) y) in a cross-sectional study. Knee kinematics and kinetics were measured using 3D motion analysis and hop distance was collected during the triple hop for distance. Individual limb difference values for individual hop trials were calculated and values for each trial were dichotomized as pass/fail based on achieving a limb difference of <10%. Cohen's Kappa and confirmatory McNemar's test were performed to determine the level of agreement between measures of physical and biomechanical function between trials.

FINDINGS

No agreement between triple hop and peak knee flexion angle symmetry (κ = 0.033, p = 0.387) and peak internal knee extension moment (κ = 0.022, p = 0.475) were found. McNemar tests confirmed no agreement between hop-distance %LD and knee flexion angle/knee extension moment %LD (p = 0.000).

INTERPRETATION

These findings suggest that while individuals after ACLR may on average achieve symmetrical hop-distance, they may not necessarily pass subsequent functional tasks. Further, individual trial-by-trial analyses may provide insight into an individual's true physical capability compared to simply evaluating the average, which may overestimate physical function or mask altered movement strategies.