Tibial Acceleration Research Articles

Impact loading in female runners with single and multiple bone stress injuries during fresh and exerted conditions

BackgroundBone stress injuries (BSIs) are common in female runners, and recurrent BSI rates are high. Previous work suggests an association between higher impact loading during running and tibial BSI. However, it is unknown whether impact loading and fatigue-related loading changes discriminate women with a history of multiple BSIs. This study compared impact variables at the beginning of a treadmill run to exertion and the changes in those variables with exertion among female runners with no history of BSI as well as among those with a history of single or multiple BSIs. MethodsWe enrolled 45 female runners (aged 18–40 years) for this cross-sectional study: having no history of diagnosed lower extremity BSI (N-BSI, n = 14); a history of 1 lower extremity BSI (1-BSI, n = 16); and diagnosed by imaging, or a history of multiple (≥3) lower extremity BSIs (M-BSI, n = 15). Participants completed a 5-km race speed run on an instrumented treadmill while wearing an Inertial Measurement Unit. The vertical average loading rate (VALR), vertical instantaneous loading rate (VILR), vertical stiffness during impact via instrumented treadmill, and tibial shock determined as the peak positive tibial acceleration via Inertial Measurement Unit were measured at the beginning and the end of the run. ResultsThere were no differences between groups in VALR, VILR, vertical stiffness, or tibial shock in a fresh or exerted condition. However, compared to N-BSI, women with M-BSI had greater increase with exertion in VALR (–1.8% vs. 6.1%, p = 0.01) and VILR (1.5% vs. 4.8%, p = 0.03). Similarly, compared to N-BSI, vertical stiffness increased more with exertion among women with M-BSI (–0.9% vs. 7.3%, p = 0.006) and 1-BSI (–0.9% vs. 1.8%, p = 0.05). Finally, compared to N-BSI, the increase in tibial shock from fresh to exerted condition was greater among women with M-BSI (0.9% vs. 5.5%, p = 0.03) and 1-BSI (0.9% vs. 11.2%, p = 0.02). ConclusionWomen with 1-BSI or M-BSIs experience greater exertion-related increases in impact loading than women with N-BSI. These observations imply that exertion-related changes in gait biomechanics may contribute to risk of BSI.

Foot strike determines the center of pressure behavior and affects impact severity in heel-toe running

ABSTRACT This study assessed the centre of pressure (COP) behaviour and the relationship with impact severity during heel-toe running in conventional athletic footwear. We hypothesized that the COP behaviour depends on its location at foot strike, which would be associated with the vertical loading rate and peak tibial accelerations in heel-toe running. Ground reaction force and tibial acceleration were measured in 104 distance runners running level at ~3.2 m/s. High-speed plantar pressure captured at high temporal resolution (500 Hz) and spatial resolution (7.62 · 5.08 mm/sensor) allowed for localization of the COP directly in the footprint during running in self-selected athletic footwear. More lateral X-coordinates of the COP at first foot contact had, in general, more anterior Y-coordinates (adj.R2:0.609). In heel-toe running, a more anterior foot strike had a greater refined strike index, which was associated with a quicker roll-over in the rearfoot zone. This strike index contributed to greater maximum vertical loading rates (R2:0.121), and greater axial (R2:0.047) and resultant (R2:0.247) peak tibial accelerations. These findings indicate that (1) the COP progression is dependend on the COP location at foot strike; (2) more anterior rearfoot strikes are more likely to have greater impact severity than posterior rearfoot strikes.

Reducing the peak tibial acceleration of running by music-based biofeedback: A quasi-randomized controlled trial.

Running retraining with the use of biofeedback on an impact measure has been executed or evaluated in the biomechanics laboratory. Here, the execution and evaluation of feedback-driven retraining are taken out of the laboratory. To determine whether biofeedback can reduce the peak tibial acceleration with or without affecting the running cadence in a 3-week retraining protocol. Quasi-randomized controlled trial. Twenty runners with high peak tibial acceleration were allocated to either the retraining (n=10, 32.1±7.8years, 10.9±2.8g) or control (n=10, 39.1±10.4years, 13.0±3.9g) groups. They performed six running sessions in an athletic training environment. A body-worn system collected axial tibial acceleration and provided real-time feedback. The retraining group received music-based biofeedback in a faded feedback scheme. Pink noise was superimposed on tempo-synchronized music when the peak tibial acceleration was ≥70% of the runner's baseline. The control group received tempo-synchronized music, which acted as a placebo for blinding purposes. Speed feedback was provided to obtain a stable running speed of ~2.9m·s-1 . Peak tibial acceleration and running cadence were evaluated. A significant group-by-feedback interaction effect was detected for peak tibial acceleration. The experimental group had a decrease in peak tibial acceleration by 25.5% (mean: 10.9±2.8g versus 8.1±3.9g, p=0.008, d=1.08, mean difference=2.77 [0.94, 4.61]) without changing the running cadence. The control group had no statistically significant change in peak tibial acceleration nor in running cadence. The retraining protocol was effective at reducing the peak tibial acceleration in high-impact runners by reacting to music-based biofeedback that was provided in real time per wearable technology in a training environment. This reduction magnitude may have meaningful influences on injury risk.

Effect of foot pronation during distance running on the lower limb impact acceleration and dynamic stability

Purpose: Foot pronation is not an isolated factor influencing lower limb functions. Exploring gait variability and impact loading associated with the foot posture are crucial for understanding foot pronation-related injury mechanisms. This study aimed to evaluate how foot posture affects impact loading and running variability during running. Methods: Twenty-five male participants were recruited into this study. Pressure under the foot arch, acceleration and marker trajectory were recorded in the right limb for each runner after 1, 4, 7 and 10 km running, respectively. Linear mixed effects models were used to analyze the statistical difference of the data. Results: FPI-6 has significantly increased after the 10 km running (p < 0.01). For the tibial acceleration, peak resultant acceleration after 10 km running was significantly increased than after 4 km running (p = 0.02). At the dorsum of the foot, the short-time largest Lyapunov exponent (LyE) after 10 km running decreased 0.28 bit/s compared with LyE after 7 km running (p = 0.03). In the tibia, LyE after 4 km and 10 km running was decreased significantly (p < 0.01 and p = 0.01). Conclusions: The foot was significantly pronated at the middle and at the end of running. Foot pronation during distance running increased the distal tibia peak impact acceleration but did not increase running instability

Surface EMG variability while running on grass, concrete and treadmill

This study aimed to investigate whether inter-trial variability in muscle activity (electromyography, EMG) during running is influenced by the number of acquired steps and running surface. Nine healthy participants ran at preferred speed on treadmill, concrete, and grass. Tibial acceleration and surface EMG from 12 lower limb muscles were recorded. The coefficient of variation (CV) from the average EMG and peak EMG were computed from 5, 10, 25, 50 and 100 steps in each running surface. Data average stability was computed using sequential estimation technique (SET) from 100 steps. The CV for average and peak EMG was lower during treadmill running compared to running on grass (−11 ± 2.88%) or concrete (−9 ± 2.94%) (p < 0.05), without differences across the different number of steps. Moreover, the peak EMG CV from peroneus longus was lower on concrete (p < 0.05), whereas gluteus maximus presented greater variability on grass compared to concrete (p < 0.05). The SET analysis revealed that average stability is reached with up to 10 steps across all running conditions. Therefore, treadmill running induced greater variability compared to overground, without influence of the number of steps on EMG variability. Moreover, average stability for EMG recordings may be reached with up to 10 steps.

Objective assessment of fast bowling delivery intensity in amateur male cricketers

ABSTRACT Wearable microtechnology is effective in detecting fast deliveries in cricket, however methods to quantify delivery intensity have not been established. This study aimed to investigate the utility of wearable sensors in quantifying cricket fast bowling intensity. Fifteen sub-elite male fast bowlers performed deliveries at warm-up, match, and maximal intensities. A principal component analysis resulted in the selection of perceived exertion and seven variables of bowling exertion derived from trunk- (PlayerLoad™, trunk flexion velocity, trunk forward rotation velocity) and tibia-mounted (tibial acceleration at back foot contact, front foot contact, back foot re-contact and front foot re-contact) inertial measurement units for further analysis. Repeated measures ANOVAs were used to investigate the effect of intensity on outcome variables. Significant main effects of intensity and large effect sizes were identified for all variables (p < .05, np 2 > 0.14). Measures from the match and maximal conditions were significantly larger compared with the warm-up condition (Pholm < .05). No differences were observed between the match and maximal conditions (p > .05). Inertial measurement metrics can distinguish between a warm-up effort and both match and maximal fast bowling delivery intensity. These devices provide a unique, time-efficient approach to cricket fast bowling exertion quantification.

Bilateral Symmetry Analysis Of Tibial Accelerations During Single Leg Hop For Distance In Healthy Collegiate Soccer Players

Bilateral comparative analysis has commonly been used to aid return-to-sport (RTS) decision making during functional testing. Different symmetry thresholds have been used as a criteria to determine RTS, however, knowledge of normative symmetries are prerequisite to establishing any criterion. Normative bilateral symmetry of tibial acceleration metrics during the single leg hop for distance (SLH) have never been reported. PURPOSE: To determine if bilateral differences exist in tibial acceleration metrics (PA: peak acceleration, TPA: time to peak acceleration, AS: acceleration slope) during the SLH and to report normative symmetry within a healthy group of collegiate soccer players. METHODS: Twenty-four collegiate soccer players (4F, 20 M; 19.5 ± 1.2 yrs) granted informed consent and performed three SLH trials with both legs (D = dominant, ND = non-dominant) while wearing inertial measurement units (IMU; 9.5 g, 1500 Hz) fixated with a silicon strap 3-cm proximal to both medial malleoli. A Matlab script processed triaxial acceleration data for the SLH of greatest distance with a 60-Hz, fourth-order, dual-pass Butterworth filter before resultant acceleration was computed. Bilateral PA, TPTA and AS were tested for significant differences between legs with a series of paired t-tests. Significance level was set apriori at 0.05. Symmetry angle % was then computed for hop distance and all tibial acceleration metrics. RESULTS: Hop distance (D: 53.8 ± 7.6 cm, ND: 54.4 ± 7.3 cm, p = 0.42), PTA (D: 35.5 ± 5.4 g, ND: 38.3 ± 10.1 g, p = 0.06), TPTA (D: 15.9 ± 5.2 ms, ND: 16.5 ± 6.1 ms) and AS (D: 3233.0 ± 1222.2 g/ms, ND: 2990.3 ± 1233.9 g/ms) did not significantly differ between legs. All average symmetry angle %s were < 10% (hop distance: 1.6 ± 1.5%; PTA: 4.0 ± 3.8%; TPTA: 8.0 ± 7.5%; AS 9.1 ± 5.9%). CONCLUSIONS: Within a group of healthy collegiate soccer players, no significant differences in either hop distance or tibial acceleration metrics existed when comparing dominant and non-dominant legs. Seven of the participants (29.2%) displayed bilateral differences in peak tibial acceleration greater than the MDC95 level indicating a meaningful difference. Clinicians are encouraged to perform baseline testing to establish player-specific symmetry angle %s for establishing RTS criteria in tibial acceleration metrics during the SLH.

Test-retest Reliability Of Tibial Accelerations During Single Leg Hop For Distance In Healthy Collegiate Soccer Players

Test-retest Reliability Of Tibial Accelerations During Single Leg Hop For Distance In Healthy Collegiate Soccer Players

Study on Automobile Front-End Structure Based on Pedestrian Leg Protection

According to the pedestrian leg protection regulations, a collision with the simplified finite element model of the leg was carried out on the basis of incorporating EPP foam materials with different foaming rates and cushioning into the simplified front-end structure of the car. The results show that the front-end foam energy-absorbing structure of the vehicle cannot meet the pedestrian leg protection regulations. This paper designs a thin-walled steel structure and applies it to the front-end structure of the vehicle. After collision simulation with a simplified finite element model of the leg, the pedestrian’s tibial acceleration, knee joint shear displacement and knee joint bending angle are compared and analyzed. Pedestrian leg injury parameters, the results show that thin-walled steel structure is more suitable for giving full play to the energy absorption effect in an environment with insufficient energy absorption space than foam energy absorption structure.

Tibial Accelerations During the Single-Leg Hop Test: Influence of Fixation.

Performance on single-leg hopping (SLH) assessments is commonly included within return-to-sport criteria for rehabilitating athletes. Triaxial accelerometers have been used to quantify impact loading in a variety of movements, including hopping; however, they have never been attached to the tibia during SLH, and their method of fixation has not been investigated. The purpose of this study was to quantify triaxial accelerations and evaluate the influence of the fixation method of a lightweight inertial measurement unit (Blue Trident) mounted to the tibia during SLH performance. Single cohort, repeated-measures experimental design. Sixteen healthy participants (10 females and 6 males; 20 [0.9]y; 1.67 [0.08]m; 66.0 [8.5]kg) met the inclusion criteria, volunteered, and completed this study. Participants performed 2 sets of 3 SLH trials with an inertial measurement unit (1500Hz) fixated to the tibia, each set with 1 of 2 attachment methods (double-sided tape [DST] with athletic tape and silicon strap [SS] with Velcro adhesion). Hop distance, peak tibial acceleration (PTA), time to PTA, and the acceleration slope were assessed during each hop landing. Repeated-measures analysis of variance determined no significant effect of the attachment method on hop metrics (P = .252). Across 3 trials, both fixation methods (DST and SS) had excellent reliability values (intraclass correlation coefficient: .868-.941) for PTA and acceleration slope but not for time to PTA (intraclass correlation coefficient: .397-.768). The PTA for DST (27.22 [7.94] g) and SS (26.21 [10.48]g) was comparable and had a moderate, positive relationship (DST: r = .72, P < .01; SS: r = .77, P < .01) to SLH distance. Tibial inertial measurement units with triaxial accelerometers can reliably assess PTA during performance of the SLH, and SS is a viable alternative tibial attachment to DST.

Influence of music-based feedback training on peak tibial acceleration during running outside of the biomechanics laboratory

Gait retraining that stimulates impact reduction has resulted in fewer injuries in novice runners (Chan et al., 2018). However, feedback-driven retraining performed at a fixed running speed has bee...

Validity and reliability of innovative field measurements of tibial accelerations and spinal kinematics during cricket fast bowling

The use of inertial sensors in fast bowling analysis may offer a cheaper and portable alternative to current methodologies. However, no previous studies have assessed the validity and reliability of such methods. Therefore, this study aimed to assess the validity and reliability of collecting tibial accelerations and spinal kinematics using inertial sensors during in vivo fast bowling. Thirty-five elite male fast bowlers volunteered for this study. An accelerometer attached to the skin over the tibia was used to determine impacts and inertial sensors over the S1, L1 and T1 spinous processes used to derive the relative kinematics. These measurements were compared to optoelectronic and force plate data for validity analysis. Most acceleration and kinematics variables measured report significant correlations > 0.8 with the corresponding gold standard measurement, with intraclass correlation coefficients greater than 0.7. Low standard error of measurement and consequently small minimum detectable change (MDC) values were also observed. This study demonstrates that inertial sensors are as valid and reliable as current methods of fast bowling analysis and may provide some advantages over traditional methods. The novel metrics and methods described in this study may aid coaches and practitioners in the design and monitoring of fast bowling technique.Graphical abstractGraphical abstract illustrating the synopsis of the findings from this paper.

Feasibility assessment of transfer functions describing biomechanics of the human lower limb during the gait cycle

Background and objectiveTransfer functions could model biomechanical parameters to conveniently analyze the system dynamics of the lower limb during daily activities, e.g., walking. The current study evaluates the feasibility of transfer functions as a means of predicting surface electromyography (sEMG) of lower limb muscles based on axial tibial (ATA) and femoral (FA) accelerations. Since the transfer functions are comparable in accuracy to commonly used long short-term memory models (LSTM), the transfer function-based methodology can assist in the design of novel prostheses while being competitive with mainstream models. MethodsData were collected from eight participants with no medical history that would alter their gait cycles. The data included the sEMG of four primary muscle groups, ATA and FA, and heel-strike triggering signal, while the subjects walked at 5.28 km/h on a treadmill. A fast Fourier transform (FFT) was performed on the filtered ensemble averages of the ATA, FA and normalized average rectified sEMG signals, which were used to approximate the time domain Fourier series. Transfer functions relating ATA-to-sEMG and FA-to-sEMG were derived from the Fourier series equations to generate time-domain intra-subject predictions of sEMG signals. With respect to predictive accuracy, these transfer functions were compared with sEMG-to-sEMG LSTM models trained on sEMG data from some of the participants. It was hypothesized that the transfer functions would be at least comparable to the LSTM models. ResultsThe results indicate that the predicted sEMG signals were able to capture the temporal characteristics of the measured sEMG signal based on either ATA or FA. The muscle activities and acceleration were in good agreement with the walking gait cycle events. Only 13 Fourier terms were needed to effectively predict the sEMG from the acceleration signals, indicating the computational efficiency of the investigated analysis framework. For the ATA-to-sEMG transfer functions, the mean square difference (MSD) between the predicted and measured sEMG signals was low and comparable to the LSTM models. ConclusionsOverall, the feasibility and competitiveness of the transfer functions with LSTM models was confirmed with respect to predictive accuracy. Potential applications of the transfer functions include the control of powered prosthetics and the detection of gait pathologies.

Acute Effects on Impact Accelerations Running with Objects in the Hand.

Amateur runners usually run carrying implements in their hands (keys, a mobile phone, or a bottle of water). However, there is a lack of literature about the effects of different handloads on impact accelerations. Thus, this study aimed to analyse the effects of carrying different objects in the hand on impact accelerations during running. Nineteen male recreational runners (age 24.3 ± 6.8 years, training volume of 25 ± 7.38 km/week) performed twenty minutes of running on a treadmill at 2.78 m/s with four different conditions: no extra weight, with keys, with a mobile phone, and with a bottle of water. Impact acceleration and spatio-temporal parameters were analysed through a wireless triaxial accelerometry system composed of three accelerometers: two placed in each tibia and one placed on the forehead. A higher tibia acceleration rate in the dominant leg was observed when participants ran holding both a mobile phone (p = 0.027; ES = 0.359) and a bottle of water (p = 0.027; ES = 0.359), compared to no extra weight. No changes were observed in peak acceleration, acceleration magnitude, and shock attenuation in any other conditions. Likewise, neither stride frequency nor step length was modified. Our results suggest that recreational runners should not worry about carrying objects in their hands, like a mobile phone or a bottle of water, in short races because their effect seems minimal.

Self-selected running gait modifications reduce acute impact loading, awkwardness, and effort

ABSTRACT Impact loading has been associated with running-related injuries, and gait retraining has been suggested as a means of reducing impact loading and lowering the risk of injury. However, gait retraining can lead to increased perceived awkwardness and effort. The influence of specifically trained and self-selected running gait modifications on acute impact loading, perceived awkwardness and effort is currently unclear. Sixteen habitual rearfoot/midfoot runners performed forefoot strike pattern, increased step rate, anterior trunk lean and self-selected running gait modifications on an instrumented treadmill based on real-time biofeedback. Impact loading, perceived awkwardness and effort scores were compared among the four gait retraining conditions. Self-selected gait modification reduced vertical average loading rate (VALR) by 25.3%, vertical instantaneous loading rate (VILR) by 27.0%, vertical impact peak (VIP) by 16.8% as compared with baseline. Forefoot strike pattern reduced VALR, VILR and peak tibial acceleration. Increased step rate reduced VALR. Anterior trunk lean did not reduce any impact loading. Self-selected gait modification was perceived as less awkward and require less effort than the specifically trained gait modification (p < 0.05). These findings suggest that self-selected gait modification could be a more natural and less effortful strategy than specifically trained gait modification to reduce acute impact loading, while the clinical significance remains unknown.

Accurate Impact Loading Rate Estimation During Running via a Subject-Independent Convolutional Neural Network Model and Optimal IMU Placement.

Enable accurate estimation of vertical average loading rate (VALR) in runners with one or more wearable inertial measurement units (IMUs). A subject-independent convolutional neural network (CNN) model was developed to estimate VALR from wearable IMUs. Fifteen runners wore IMUs at the trunk, pelvis, thigh, shank, and foot and ran on an instrumented treadmill for combinations of the following conditions: foot-strike (forefoot, mid-foot, rear-foot), step rate (90% to 110% of baseline), running speed (2.4m/s and 2.8m/s) and footwear (standard and minimalist running shoes). Thirty-one IMU placement configurations with combinations of one to five IMUs were evaluated. VALR estimations from the wearable IMUs were compared with force-plate VALR measurements. VALR estimations via the subject-independent CNN model with a single shank-worn IMU were highly correlated (ρ = 0.94) with force-plate VALR measurements and were substantially higher than previously reported peak tibial acceleration correlations with force-plate VALR measurements from shank-worn accelerometers (ρ = 0.44-0.66). Correlation results from the CNN model for a single IMU placed at the foot, pelvis, trunk, and thigh were ρ = 0.91, 0.76, 0.69, and 0.65, respectively. There was no improvement in accuracy from the shank-worn IMU when adding 1-4 additional IMUs from the trunk, pelvis, thigh, or foot. The proposed subject-independent CNN model with a single shank-worn IMU provides more accurate estimation of VALR than previous wearable sensing approaches. This could enable runners to more accurately assess impact loading rates and potentially provide insights into running-related injury risk and prevention.

Tibial acceleration and shock attenuation while running over different surfaces in a trail environment

ObjectivesIncreased tibial axial acceleration and reduced shock attenuation are associated with running injuries and are believed to be influenced by surface type. Trail running has increased in popularity and is thought to have softer surface properties than paved surface, but it is unclear if trail surfaces influence tibial acceleration and shock attenuation. The purpose of this study was to investigate peak triaxial and resultant tibial acceleration as well as axial and resultant shock attenuation among dirt, gravel, and paved surfaces. DesignFifteen recreational runners (12 females, 3 males, age=27.7±9.1 years) ran over dirt, gravel, and paved surfaces in a trail environment while instrumented with triaxial tibial and head accelerometers. MethodsDifferences between tri-planar peak tibial accelerations (braking, propulsion, axial, medial, lateral, and resultant) and shock attenuations (axial and resultant) among surface types were assessed with one-way ANOVAs with Bonferroni post-hoc tests. ResultsNo significant differences were found for tibial accelerations or shock attenuations among surface types (p>0.05). ConclusionsDirt and gravel trail running surfaces do not have lower tibial accelerations or greater shock attenuation than paved surfaces. While runners are encouraged to enjoy the psychological benefits of trail running, trail surfaces do not appear to reduce loading forces associated with running-related injuries.

Music-based biofeedback to reduce tibial shock in over-ground running: a proof-of-concept study

Methods to reduce impact in distance runners have been proposed based on real-time auditory feedback of tibial acceleration. These methods were developed using treadmill running. In this study, we extend these methods to a more natural environment with a proof-of-concept. We selected ten runners with high tibial shock. They used a music-based biofeedback system with headphones in a running session on an athletic track. The feedback consisted of music superimposed with noise coupled to tibial shock. The music was automatically synchronized to the running cadence. The level of noise could be reduced by reducing the momentary level of tibial shock, thereby providing a more pleasant listening experience. The running speed was controlled between the condition without biofeedback and the condition of biofeedback. The results show that tibial shock decreased by 27% or 2.96 g without guided instructions on gait modification in the biofeedback condition. The reduction in tibial shock did not result in a clear increase in the running cadence. The results indicate that a wearable biofeedback system aids in shock reduction during over-ground running. This paves the way to evaluate and retrain runners in over-ground running programs that target running with less impact through instantaneous auditory feedback on tibial shock.

Relationships between tibial acceleration and ground reaction force measures in the medial-lateral and anterior-posterior planes

Peak vertical tibial accelerations during running have shown strong correlations with vertical ground reaction force loading rates and some associations with injury. However, little attention has been given to tibial accelerations along the medial–lateral and anterior-posterior axes. Therefore, our purpose was to examine the correlation between peak tibial accelerations and ground reaction force loading rates in the medial–lateral and posterior directions. Eighteen recreational runners were recruited who ran with a rearfoot strike pattern (10 men/ 8 women, mean age (yrs) = 33 ± 11). Tibial accelerations and ground reaction forces were collected while participants ran on an instrumented treadmill at a self-selected speed. Correlations were developed for: a) peak medial and lateral accelerations with lateral and medial loading rates, respectively, b) peak anterior tibial accelerations and posterior loading rates. Significant correlations were found between tibial accelerations and loading rates in all planes. Peak medial tibial accelerations were correlated with lateral loading rates (Rs = 0.86, p < 0.001) and peak lateral tibial accelerations were correlated with peak medial loading rates (Rs = 0.91, p < 0.001). A lower correlation was found between anterior accelerations and posterior loading rates (Rs = 0.51, p = 0.030). Tibial accelerations in the medial–lateral plane seem to be a valid surrogate for the respective ground reaction force measures during running on a treadmill, explaining 74–83% of the variance in loading rates. However, with only 26% of the variance explained, the same may not be true for anterior tibial accelerations and posterior loading rates.

Anatomic double-bundle anterior cruciate ligament reconstruction could not achieve sufficient control of pivot-shift when accompanying tibial tunnel coalition.

To evaluate the effect of tibial tunnel coalition on knee rotatory laxity and clinical outcomes after double-bundle (DB) anterior cruciate ligament (ACL) reconstruction. Forty-one patients who underwent anatomic DB ACL reconstruction were included prospectively. Three-dimensional computed tomography of the knee joint was obtained at approximately 1year postoperatively to determine if tunnel coalition occurred. After excluding seven cases of femoral tunnel coalition, two groups were established based on the existence of a tibial tunnel coalition. The pivot-shift test was quantitatively evaluated on the basis of tibial acceleration preoperatively and at 1year postoperatively. Two subjective scores, the International Knee Documentation Committee (IKDC) subjective and Lysholm scores, were also collected. The pivot-shift measurement and subjective scores were compared between the ACL-reconstructed knees with and without tibial tunnel coalition. The independent t test, Pearson's chi-square test, and Student t tests were used in data analysis. Twenty-one knees had tibial tunnel coalition (group C), whereas 13 knees did not have tunnel coalition(group N). Pivot-shift was significantly diminished postoperatively in both groups on the basis of the clinical examination and quantitative evaluations (p < 0.05). However, there was a small but significant difference in tibial acceleration demonstrating larger pivot-shift in group C (1.0 ± 0.6m/s2) than in group N (0.5 ± 0.3m/s2, p < 0.05). No significant difference was observed in the IKDC subjective and Lysholm scores (both n.s.). When the tibial tunnel coalition occurs after DB ACL reconstruction, knee rotatory laxity may not be restored in ACL-reconstructed knees, as expected in those without tunnel coalition. It is recommended that two tibial tunnels should be created separately when performing DB-ACL reconstruction to achieve better control of rotatory knee laxity. III.