Between-limb Differences In Dynamic Postural Stability In Individuals With ACL Reconstruction Utilizing Various Processing Techniques

Dynamic postural control following anterior cruciate ligament reconstruction (ACLR) influences neuromuscular control and secondary ACL injury risk. Force plate data is typically utilized to evaluate dynamic postural control during single-leg (SL) landing tasks, but multiple analysis techniques are reported in previous literature, and it is unclear if they yield similar findings. PURPOSE: To compare dynamic postural control between limbs in those with ACLR during a SL landing task utilizing two common data processing techniques. METHODS: Thirty-five participants with unilateral ACLR performed three SL landing trials, bilaterally. Participants jumped from a 30 cm box located 50% of their height away from two force plates and were asked to maintain balance upon landing for 10s. Time to stabilization (TTS) was calculated in the anterior-posterior (TTSap) and medial-lateral (TTSml) directions by sequentially averaging the force time series data, with TTS defined as the point when the sequential average remained within ±0.25 SD of the overall series mean. The Dynamic Postural Stability Index (DPSI) was calculated over the first 3 s of landing as the composite of deviations of ground reaction force components from 0 in the AP and ML directions and weight in the vertical direction at each timepoint. SL trials were averaged for each outcome for each limb and paired samples t-tests were used to compare the outcomes between limbs. RESULTS: TTSap (P = 0.006; ACLR = 4.4 ± .1 s, Uninvolved = 4.3 ± .1 s) and TTSml (P = 0.012; ACLR = 3.5 ± .5 s, Uninvolved = 3.2 ± .6 s) were significantly longer (poorer postural control) in the ACLR limb compared to the contralateral limb. However, DPSI was significantly lower (better postural control) in the ACLR limb (P < 0.001; ACLR = 260 ± 49, Uninvolved = 276 ± 50). CONCLUSIONS: Dynamic postural control differs between limbs in those with ACLR. However, the method of assessment is a critical consideration, as TTS revealed poorer dynamic postural control in the ACLR limb, while DPSI identified poorer postural control in the contralateral limb during the same task. These analysis approaches appear to elucidate different underlying phenomena, thus, the selection of landing task and subsequent measurement technique for assessing dynamic postural control is not trivial and must be carefully considered. Supported by: This project was funded by the National Athletic Trainers’ Association Research & Education Foundation Doctoral Grant #2021DGP01.