Abstract
Context: Lower extremity alignment, range of motion (ROM), gait kinematics, and strength has been reported to be predisposed condition of Medial Tibial Stress Syndrome (MTSS). However, foot related measures were selectively assessed to examine the characteristics of MTSS. Moreover, previous studies examined only direct effect of potential risk factors on MTSS, however, there should be indirect effect of lower extremity alignment on MTSS by altering lower extremity gait biomechanics during running. Objectives: The purposes of this study are: 1) to investigate the characteristics of lower extremity static alignment, ROM, and strength, and gait kinematic measures among those with MTSS; and second, to identify the strongest factors that account for MTSS status in runners; 2) to investigate the direct and indirect effects of lower extremity alignment and gait kinematic measures on MTSS status, while relevant extrinsic factors are controlled, 3) to classify measures of static proximal and distal alignment and gait kinematics that are highly correlated to each other in order to develop latent variables (factors) that reduce the dimensionality of potential predictor measures. Design: A case control design. Setting: Laboratory Patients or other participant: A total of 74 recreational and competitive runners (37 normal, 37 MTSS injured) were recruited. Intervention: The independent variable was MTSS status. Main Outcome Measures: The dependent variables include 13 lower extremity alignment, 10 lower extremity (ROM), 7 strength, 20 maximum joint kinematics, and 10 total excursion measures during running (2.6m/s). All the measurements were performed three times by a single examiner who established intersession intra-tester reliability of at least ICC=.80 for each alignment measures. The difference between the MTSS and the control in all measures 111 was analyzed via independent T-test analysis. Those measures identified as being statistically significant (P<.05) were then used in a series o.f discriminant function analyses. Therefore, 13 measures were entered into the first discriminant function analyses in order to identify the factors that were most strongly statistically associated with MTSS status. Canonical correlation and r2 change were reported for this analysis. The statistical analysis to examine second objectives is as follow. An exploratory factor analysis using principle component analysis (PCA) was conducted to reduce the dimensionality of the lower extremity alignment measures by categorizing dependent variables which have high correlation. Then alignment measures were rescaled through changing individual values into Z-scores. The sum of Z-scores of composite measurements was the value of each latent alignment variable. Finally, Path analysis was used to construct models to identify direct and indirect effects of the alignment, gait measures on MTSS status. Separate two (MTSS and control) exploratory factor analysis was used to reduce dimension of measure to examine third objective of this study. The alpha level was set a priori at P<.05 for all analysis. Results: MTSS is associated with increase femoral anteversion, valgus knee alignment, tibial torsion, pronated foot type, NWB varus rearfoot alignment, valgus alignment during weight bearing, hip internal rotation, hip adduction, knee internal rotation, rearfoot eversion during gait, increased hip internal rotation ROM, restricted dorsiflexion ROM, and decreased inversion strength. The strongest risk factors associated with MTSS status in this study were tibial torsion followed by reafoot eversion. MTSS is associated with increase femoral anteversion, valgus knee alignment, tibial torsion, pronated foot type, NWB varus rearfoot alignment, valgus alignment during weight bearing, hip internal rotation, hip adduction, knee IV internal rotation, rearfoot eversion during gait, increased hip internal rotation ROM, restricted dorsiflexion ROM, and decreased inversion strength. The strongest risk factors associated with MTSS status in this study were tibial torsion followed by reafoot eversion. Two groups had different construct to categorize static alignment and gait kinematics. The 15 lower extremity measures and gait kinematics used in this study demonstrated three distinct sets of information: 1) Standing rearfoot, navicular drop test, rearfoot alignment, and maximum eversion; 2) Maximum hip internal rotation, genu recurvatum, femoral anteversion, maximum hip adduction, and pelvic tilt; 3) maximum pelvic anterior rotation, Q-angle, maximum knee internal rotation, maximum knee valgus, tibial varum, maximum tibial internal rotation, and tibial torsion. Unlike to the MTSS group, the 15 lower extremity measures and gait kinematics used in this study demonstrated five distinct sets of information: 1) Maximum tibial internal rotation, maximum rearfoot eversion, and maximum knee valgus; 2) femoral anteversion, maximum hip internal rotation, standing rearfoot, and rearfoot alignment; 3) tibial torsion, maximum hip adduction, navicular drop test, and Q-angle; 4) pelvic tilt and genu recurvatum; 5) maximum pelvic anterior rotation, tibial varum, and maximum knee internal rotation. Conclusions: The effect of the proximal and distal lower extremity alignment should be thoroughly considered in order to accurately understand what truly causes MTSS. Furthermore, clinicians should note that the proximal and the distal lower extremity alignments associated with MTSS may cause alteration of gait biomechanics as well.
Note: Abstract extracted from PDF file via OCR.
