Biomechanical Measures to Assess Recovery from Anterior Cruciate Ligament Injury and Reconstructive Surgery
Creators: name: Author, Unknown
Publisher: name: University of Lincoln
Year: 2023

description: Anterior cruciate ligament (ACL) injuries are a debilitating injury resulting in abnormal biomechanics. Treatment commonly involves reconstructive surgery, however the tools used to assess the changes in biomechanics due to this procedure may fail to assess movement deficiencies. Therefore, the aim of this thesis was to explore what biomechanical variables are affected by ACL injury and reconstructive surgery and to assess their worth in the monitoring of recovery from ACL injuries and reconstructive surgery. A systematic review of the changes in lower limb biomechanics that occur due to ACL reconstruction identified 51 articles that presented evidence on balance, joint position sense, gait, pivoting, stair ambulation, and landing tasks. Despite trends in certain variables, such as increased knee flexion excursion, there were inconsistencies between articles in presented changes of gait, pivoting, and landing movements. Tasks that related to the proprioceptive function of the limb exhibited consistent improvements due to surgery. This was the first review to provide a synthesis of the evidence around biomechanical changes due to ACL reconstruction and supported the exploration of variables related to the proprioceptive capacity of the injured limb for the use in assessing function. Balance data were collected for eight ACL injured participants before and after surgery, and 45 uninjured participants using collection methods that were integrated into clinical practice. The two samples were similar in age, anthropometrics, and sex. Linear measures of the centre of pressure (CoP) provided a measure of balance performance, and complexity at varying timescales calculated using multiscale sample entropy, an approach that had yet to be explored in ACL injured participants, and complexity index, a summary statistic of the sample entropy at numerous timescales, provided details on the non-linear characteristics of the CoP. Despite previous evidence linking ACL injuries to a reduction in balance performance, the data did not support the use of linear measures. Linear measures had greater variation in uninjured participants than non-linear measures (e.g. coefficient of variation; CoP path length: 16%; mediolateral CoP complexity index: 10%). No trends, supported by a lack of statistical significance, between the involved and comparison limbs were identified (mean±SD pre-surgery CoP path length; ACL involved: 76±19 cm; ACL uninvolved: 87±27 cm; uninjured controls: 93±28 cm). No significant differences were observed due to surgery (mean±SD post-surgery CoP path length; ACL involved: 79±27 cm). Complexity of the CoP, in addition to having a reduced variation in uninjured participants, supported that ACL injury was related to a loss of complexity (mean±SD pre-surgery mediolateral complexity index; ACL involved: 4.9±1.3; uninjured controls: 6.0±0.9) and that reconstructive surgery was able to restore this loss (mean±SD ACL involved mediolateral sample entropy at 6.7 Hz; pre-surgery: 0.9±0.3; 19 weeks post-surgery: 1.2±0.2). The findings provide new evidence to support that ACL injury results in a loss of complexity and that the multiscale sample entropy of the CoP may provide an insight into the changes in lower limb biomechanics that occur due to ACL injury and reconstructive surgery. Comparison of the magnitude of changes in complexity due to ACL reconstructive surgery to uninjured participants, supported that increased complexity may be clinically meaningful. The link between increased complexity and functional outcomes however, is not understood and therefore further research is required to understand this link to establish the usability of complexity as a clinical measure.