Influences of Functional and Psychological Factors on Biomechanics Following an Anterior Cruciate Ligament (ACL) Reconstruction

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DOI: 10.13023/etd.2020.391

Abstract and keywords

Objective: The aims of this research were to identify gaps in the literature related to return to sport (RTS) test batteries following primary anterior cruciate ligament reconstruction (ACLR) (Aim 1) and define recovery in athletes from 4-9 months after ACLR across three domains: 1) psychological recovery and biomechanics (Aim 2), 2) rehabilitation quantity and biomechanics (Aim 3), and 3) functional performance and biomechanics (Aim 4). Ultimately, the results of this research would quantify recovery following ACLR in athletes with a desire to RTS and identify objective criteria throughout rehabilitation prior to RTS.

Participants: Twenty-two post-ACLR athletes 17 females, 8 males, age: 16.22 ± 2.83, height: 1.70 ± 0.08, mass: 65.18 ± 10.28, BMI: 22.90 ± 3.66) completed the study protocol.

Methods: For Aim 1, a systematic review of the literature related to the current test batteries reported in the literature was performed to determine how the batteries align with the recommendation made by the American Academy of Orthopedic Surgeons (AAOS). In Aims 2-4, a longitudinal design with 4-months, 4-6-months, 6-months, and 9-months post-ACLR were used for all subjects in the study. At 4-months, subjects completed patient reported outcomes PROs including the International Knee Documentation Committee (IKDC) and the ACL-Return to Sport after Injury (ACL-RSI) scales. From 4-6-months, subjects completed a four-question survey once per week about the quantity of rehabilitation and exercise sessions completed. Subjects performed a functional assessment at 6-months including knee flexion and extension range of motion (ROM), a 60-second single leg step down test (SLSD), and trunk test. Finally, subjects underwent a biomechanical assessment during a commonly performed drop vertical jump (DVJ) task.

Main Outcome Measures: Outcome measures were assessed across the four domains. The first domain included subjective and objective RTS assessments in subjects following ACLR. The second domain represented a subjective assessment from the IKDC and ACL-RSI. The third domain represented the quantity of rehabilitation on a scale of 0-7 days per week. The questions inquired about supervised physical therapy (PT), home exercise program (HEP), lifting, and running. The final domain represented functional performance as assessed by knee ROM, the SLSD, and the trunk test. Domains 2-4 are all assessed in relation to hip and knee kinetics and kinematics using three-dimensional motion analysis during a DVJ task.

Statistical Analysis: Aim 1: no formal statistics were utilized in the systematic review other than percentages. In Aims 2-4, Pearson product-moment correlations were performed to assess the relationship between IKDC, ACL-RSI, rehabilitation quantity, knee ROM, SLSD, and trunk test to knee extensor moment (KEM), knee valgus angle (KVA), and hip adduction angle (HAA) during the DVJ at peak ground reaction force (GRF).

Results: Aim 1: The most implemented functional assessments were a hop test, quadriceps strength test, and a PRO. However, no study met all criteria recommended by the AAOS. Aim 2: The 4-month IKDC and ACL-RSI were not significantly related to the 9-month KEM, KVA, or HAA during the DVJ. However, a large amount of variability existed within the PROs and biomechanics. Aim 3: Non-significant results were observed between rehabilitation quantity, however a small relationship between running and lifting to supervised PT was revealed. Additionally, a small non-significant relationship was observed between running, lifting, and HEP to a decreased KVA. Aim 4: There was a significant moderate negative relationship between increased knee ROM and increased KEM. Additionally, a moderate positive relationship was observed between increased step downs on the injured limb and decreased KVA. Finally, there was a significant moderate positive relationship between increased errors on the trunk test and increased HAA.

Conclusions: Gaps in the literature exist between what is recommended and what is currently practiced. The assessments implemented in the current study are recommended from both previous literature and the AAOS. Although non-significant, early PROs and rehabilitation quantity may be critical as protocols increase dynamic activity from 4-6- months. Increased fear and decreased overall self-reported function may be detrimental to recovery following ACLR. Reduced supervised PT was reported as increases in HEP occurred, indicating the importance of non-supervised rehabilitation and its potential to reduce biomechanical deficits associated with increased injury risk. Additionally, clinically applicable functional assessments utilized in this study all moderately related to a specific aspect of function that can be addressed clinically without the use of a motion capture system. Early assessment of psychological and physical function may better guide rehabilitation for safer movement patterns and potentially lower the risk of injury at the time of RTS.

Keywords: anterior cruciate ligament reconstruction; return to sport; biomechanics; functional test

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