Linking Gait Biomechanics and Daily Steps After ACL Reconstruction

Acutely Normalizing Walking Speed Does Not Normalize Gait Biomechanics Post-Anterior Cruciate Ligament Reconstruction

PURPOSE

To determine the effect of acutely increasing walking speed on gait biomechanics in ACLR individuals compared with their habitual speed and uninjured matched-controls.

METHODS

Gait biomechanics were collected on 30 ACLR individuals (20 females; age, 22.0 ± 4.2 yr; body mass index, 24.0 ± 3.0 kg·m -2 ) at their habitual speed and at 1.3 m·s -1 , a speed similar to controls, and 30 uninjured matched-controls (age: 21.9 ± 3.8, body mass index: 23.6 ± 2.5) at their habitual speed. Functional waveform analyses compared biomechanics between: i) walking at habitual speed vs 1.3 m·s -1 in ACLR individuals; and ii) ACLR individuals at 1.3 m·s -1 vs controls.

RESULTS

In the ACLR group, there were no statistically significant biomechanical differences between walking at habitual speed (1.18 ± 0.12 m·s -1 ) and 1.3 m·s -1 (1.29 ± 0.05 m·s -1 ). Compared with controls (habitual speed: 1.34 ± 0.12 m·s -1 ), the ACLR group while walking at 1.3 m·s -1 exhibited smaller vertical ground reaction force (vGRF) during early and late stance (13-28, 78-90% stance phase), greater midstance vGRF (47-61%), smaller early-to-midstance knee flexion angle (KFA; 1-44%), greater mid-to-late stance KFA (68-73, 96-101%), greater internal knee abduction moment (69-101%), and smaller internal knee extension moment (4-51, 88-96%).

CONCLUSIONS

Increasing walking speed to a speed similar to uninjured controls did not elicit significant changes to gait biomechanics, and ACLR individuals continued to demonstrate biomechanical profiles that are associated with PTOA development and differ from controls.

Organization of sensorimotor activity in anterior cruciate ligament reconstructed individuals: an fMRI conjunction analysis

Introduction

Anterior cruciate ligament reconstruction (ACLR) is characterized by persistent involved limb functional deficits that persist for years despite rehabilitation. Previous research provides evidence of both peripheral and central nervous system adaptations following ACLR. However, no study has compared functional organization of the brain for involved limb motor control relative to the uninvolved limb and healthy controls. The purpose of this study was to examine sensorimotor cortex and cerebellar functional activity overlap and non-overlap during a knee motor control task between groups (ACLR and control), and to determine cortical organization of involved and uninvolved limb movement between groups.

Methods

Eighteen participants with left knee ACLR and 18 control participants performed a knee flexion/extension motor control task during functional magnetic resonance imaging (fMRI). A conjunction analysis was conducted to determine the degree of overlap in brain activity for involved and uninvolved limb knee motor control between groups.

Results

The ACLR group had a statistically higher mean percent signal change in the sensorimotor cortex for the involved > uninvolved contrast compared to the control group. Brain activity between groups statistically overlapped in sensorimotor regions of the cortex and cerebellum for both group contrasts: involved > uninvolved and uninvolved > involved. Relative to the control group, the ACLR group uniquely activated superior parietal regions (precuneus, lateral occipital cortex) for involved limb motor control. Additionally, for involved limb motor control, the ACLR group displayed a medial and superior shift in peak voxel location in frontal regions; for parietal regions, the ACLR group had a more posterior and superior peak voxel location relative to the control group.

Conclusion

ACLR may result in unique activation of the sensorimotor cortex via a cortically driven sensory integration strategy to maintain involved limb motor control. The ACLR group's unique brain activity was independent of strength, self-reported knee function, and time from surgery.

In vitro fatigue behavior and in vivo osseointegration of the auxetic porous bone screw

The incidence of screw loosening, migration, and pullout caused by the insufficient screw-bone fixation stability is relatively high in clinical practice. To solve this issue, the auxetic unit-based porous bone screw (AS) has been put forward in our previous work. Its favorable auxetic effect can improve the primary screw-bone fixation stability after implantation. However, porous structure affected the fatigue behavior and in vivo longevity of bone screw. In this study, in vitro fatigue behaviors and in vivo osseointegration performance of the re-entrant unit-based titanium auxetic bone screw were studied. The tensile-tensile fatigue behaviors of AS and nonauxetic bone screw (NS) with the same porosity (51%) were compared via fatigue experiments, fracture analysis, and numerical simulation. The in vivo osseointegration of AS and NS were compared via animal experiment and biomechanical analysis. Additionally, the effects of in vivo dynamic tensile loading on the osseointegration of AS and NS were investigated and analyzed. The fatigue strength of AS was approximately 43% lower while its osseointegration performance was better than NS. Under in vivo dynamic tensile loading, the osseointegration of AS and NS both improved significantly, with the maximum increase of approximately 15%. Preferrable osseointegration of AS might compensate for the shortage of fatigue resistance, ensuring its long-term stability in vivo. Adequate auxetic effect and long-term stability of the AS was supposed to provide enough screw-bone fixation stability to overcome the shortages of the solid bone screw, developing the success of surgery and showing significant clinical application prospects in orthopedic surgery. STATEMENT OF SIGNIFICANCE: This research investigated the high-cycle fatigue behavior of re-entrant unit-based auxetic bone screw under tensile-tensile cyclic loading and its osseointegration performance, which has not been focused on in existing studies. The fatigue strength of auxetic bone screw was lower while the osseointegration was better than non-auxetic bone screw, especially under in vivo tensile loading. Favorable osseointegration of auxetic bone screw might compensate for the shortage of fatigue resistance, ensuring its long-term stability and longevity in vivo. This suggested that with adequate auxetic effect and long-term stability, the auxetic bone screw had significant application prospects in orthopedic surgery. Findings of this study will provide a theoretical guidance for design optimization and clinical application of the auxetic bone screw.

Joint and Limb Loading during Gait in Adults with ACL Reconstruction: Comparison between Single-Step and Cumulative Load Metrics

PURPOSE

Individuals with anterior cruciate ligament reconstruction (ACLR) generally exhibit limb underloading behaviors during walking, but most research focuses on per-step comparisons. Cumulative loading metrics offer unique insight into joint loading as magnitude, duration, and total steps are considered, but few studies have evaluated if cumulative loads are altered post-ACLR. Here, we evaluated if underloading behaviors are apparent in ACLR limbs when using cumulative load metrics and how load metrics change in response to walking speed modifications.

METHODS

Treadmill walking biomechanics were evaluated in 21 participants with ACLR at three speeds (self-selected (SS); 120% SS and 80% SS). Cumulative loads per step and per kilometer were calculated using knee flexion and adduction moment (KFM and KAM) and vertical ground reaction force (GRF) impulses. Traditional magnitude metrics for KFM, KAM, and GRF were also calculated.

RESULTS

The ACLR limb displayed smaller KFM and GRF in early and late stances, but larger KFM and GRF during midstance compared with the contralateral limb ( P < 0.01). Only GRF cumulative loads (per step and per kilometer) were reduced in the ACLR limb ( P < 0.01). In response to speed modifications, load magnitudes generally increased with speed. Conversely, cumulative load metrics (per step and per kilometer) decreased at faster speeds and increased at slow speeds ( P < 0.01).

CONCLUSIONS

Patients with ACLR underload their knee in the sagittal plane per step, but cumulatively over the course of many steps/distance, this underloading phenomenon was not apparent. Furthermore, cumulative load increased at slower speeds, opposite to what is identified with traditional single-step metrics. Assessing cumulative load metrics may offer additional insight into how load outcomes may be impacted in injured populations or in response to gait modifications.

Monitoring External Workload With Wearable Technology After Anterior Cruciate Ligament Reconstruction: A Scoping Review

Background

Current sports medicine and rehabilitation trends indicate an increasing use of wearable technology. The ability of these devices to collect, transmit, and process physiological, biomechanical, bioenergy, and environmental data may aid in anterior cruciate ligament reconstruction (ACLR) workload monitoring and return-to-sport decision-making. In addition, their ease of use allows assessments to occur outside the clinical or laboratory settings and across a broader timeline.

Purpose

To (1) determine how wearable technology can assess external workload deficits between limbs (involved and uninvolved) and between groups (healthy controls vs patients with ACLR) during physical activity (PA) or sport and (2) describe the types of sensors, sensor specifications, assessment protocols, outcomes of interest, and participant characteristics from the included studies.

Study Design

Scoping review; Level of evidence, 4.

Methods

In February 2023, a systematic search was performed in the MEDLINE, EMBASE, CINAHL, SPORTDiscus, Scopus, IEEE Xplore, Compendex, and ProQuest Dissertations and Theses Global databases. Eligible studies included assessments of PA or sports workloads via wearable technology after ACLR.

Results

Twenty articles met eligibility criteria and were included. The primary activity assessed was activities of daily living, although rehabilitation, training, and competition were also represented. Accelerometers, global positioning system units, pedometers, and pressure sensor insoles were worn to collect external workload data, which was quantified as kinetic, kinematic, and temporospatial data. Daily steps (count) and moderate to vigorous PA (min/day or week) were the most common units of measurement. A limited number of studies included outcomes related to between-limb asymmetries.

Conclusion

The findings of this scoping review highlight the versatility of wearable technologies to collect patients' kinetic, kinematic, and temporospatial data and assess external workload outcomes after ACLR. In addition, some wearable technologies identified deficits in workload compared with healthy controls and between reconstructed and unaffected limbs.

Return to sports after ACL injury 5 years from now: 10 things we must do

Background

The outcome after ACL reconstruction (ACLR) is in general disappointing with unacceptable number of athletes that do not return to pre-injury level of sports, high re-injury rates, early development of osteoarthritis and shorter careers. Athletes after ACLR have high expectation to return to sports which is in contrast with the current outcomes. The aim of this manuscript is to present an overview of factors that are needed to be incorporated and to personalize the rehabilitation process for an athlete who has undergone an ACLR.

Level of evidence

4.