Effect of laterality and fatigue in peroneal electromechanical delay.

INTRODUCTION: Extremity dominance is one of the intrinsic factors that have been identified for ankle sprains. Electromechanical delay (EMD) is an integral part of the peroneal motor response and, therefore, substantial in preventing ankle sprains. This study aimed to investigate the effect of laterality on EMD times before and after fatigue. METHODS: Fifteen healthy male volunteers participated in the study. Measurements were taken with the ankle in a neutral (0°) position, and all subjects followed an isokinetic fatigue protocol. Repeated ANOVA was used for statistical analysis, and the α level was set a priori at p ≤ 0.05. RESULTS: No significant difference was noted in EMD times between the dominant and non-dominant legs of the volunteers (p = 0.940). Fatigue caused a significant increase in EMD by 10-15 ms (p = 0.003), while the leg × fatigue interaction was not significant (p = 0.893). CONCLUSIONS: In a non-injured athlete, both ankles seem to be under the same protection of the reactive response of the peroneal muscles. Therefore, athletes should be aware that both their extremities are equally exposed to the danger of an ankle injury. Also, fatigued ankles demonstrate longer EMD times, implying that improving resistance to fatigue may add another layer of protection that has the potential to prevent ankle sprain recurrence.

COVID-19 Infection among Elite Football Players: A Nationwide Prospective Cohort Study.

Little is known about the risk of COVID-19 infection among footballers. We aimed to investigate the incidence and characteristics of COVID-19 infection among footballers. In total, 480 football players of Super League Greece and 420 staff members participated in a prospective cohort study, which took place from May 2020 to May 2021. Nasopharyngeal swabs were collected from footballers and staff members weekly. All samples (n = 43,975) collected were tested using the reverse transcriptase polymerase chain reaction (RT-PCR) test for the detection of "SARS-CoV-2". In total, 190 positive cases (130 among professional football players and 60 among staff) were recorded. Out of the 190 cases that turned positive, 64 (34%) cases were considered as symptomatic, and 126 (66%) cases were asymptomatic. The incidence rate of a positive test result for footballers was 0.57% (confidence interval (CI) 0.48−0.68%) and for staff members it was 0.27% (CI 0.20%, 0.34%), respectively. Footballers recorded a twofold increased risk of COVID-19 infection in comparison to staff members (relative risk = 2.16; 95% CI = 1.59−2.93; p-value < 0.001). No significant transmission events were observed during the follow-up period. We found a low incidence of COVID-19 infection among professional footballers over a long follow-up period. Furthermore, the implementation of a weekly diagnostic testing (RT-PCR) was critical to break the transmission chain of COVID-19, especially among asymptomatic football players and staff members.

A longitudinal investigation of landing biomechanics following anterior cruciate ligament reconstruction.

OBJECTIVE: Abnormal movement patterns have been shown during landing in patients who have undergone anterior cruciate ligament (ACL) reconstruction surgery. The purpose of this study was to investigate landing biomechanics over time in this patient group to determine whether asymmetry between limbs reduced with time and after a return to physical activity. DESIGN: Prospective longitudinal study. SETTING: Biomechanics laboratory. PARTICIPANTS: Fourteen patients who had undergone ACL reconstruction surgery. MAIN OUTCOME MEASURE: Single limb landing assessments were made at two time points; within the first year (mean of 10 months) and at 3 years (after patients had returned to sport) following ACL reconstruction. Three-dimensional motion analysis was used to record kinematic and kinetic variables, which were compared across time and limb using ANOVA models. RESULTS: Most biomechanical variables showed little change over time except for the external knee adduction moment at the operated knee, which increased (effect size d = 0.5), but remained less than the contralateral side. In the sagittal plane, asymmetrical landing patterns were seen at both assessments. Patients landed with reduced knee flexion angles (effect size range 0.76-0.9) and moments (effect size range 0.56-0.9) compared to the uninjured limb and made compensations for this by increasing the hip flexion moment (effect size range d = 0.6-0.75). CONCLUSIONS: Asymmetrical landing biomechanics persisted at three years after ACL reconstruction in athletes who returned to sporting activity. Long term implications of controlling the landing by increasing the hip moment are unknown and require further investigation.

Peroneal electromechanical delay and fatigue in patients with chronic ankle instability.

PURPOSE: The purpose of this study was to investigate the effect of chronic ankle instability (CAI) on electromechanical delay times (EMD) before and after fatigue. Understanding the mechanisms that contribute to CAI is essential for the development of effective rehabilitation programmes. It was hypothesized that patients with CAI will demonstrate prolonged EMD times compared to healthy subjects and that fatigue will cause greater increases in EMD times in the CAI group. METHODS: Twenty-one male volunteers participated in the study providing data on 16 ankles with CAI and 26 with no history of ankle injury. EMD was measured on an isokinetic dynamometer. Measurements were taken with the ankle in neutral (0°) and at 30° of inversion. All subjects followed an isokinetic fatigue protocol until eversion torque fell below 50 % of initial torque for three consecutive repetitions. A 2 × 2 × 2 ANOVA was used to calculate the effect of ankle status (CAI vs. healthy), fatigue, angle (0° vs. 30°) and their interactions on EMD. RESULTS: Fatigue caused a significant increase on EMD [non-fatigued: 122(29)ms vs. fatigue 155(54)ms; p < 0.001]. EMD times were shorter at 30° of inversion compared to neutral [neutral: 145(39)ms vs. 30° of inversion: 132(40)ms, p = 0.015]. An interaction effect for ankle status and angle was found (p = 0.026) with CAI ankles demonstrating longer EMD [CAI: 156(45)ms vs. healthy: 133(40)ms] in neutral but not at 30° of inversion [CAI: 133(46)ms vs. 132(33)ms]. CONCLUSIONS: Patients with CAI had longer EMD times in neutral, but not when the ankle was placed in inversion. This suggests that rehabilitation programmes may be more effective when retraining occurs with the ankle in neutral position. It is likely that low EMD times prevent ankle acceleration at the beginning of the mechanism of injury, but they are less important when the ankle has already inverted at 30°. Both CAI and healthy subjects demonstrated longer EMD after fatigue, emphasizing the importance of proper conditioning in the prevention of delayed peroneal response and subsequent ankle injury. Improving resistance to fatigue of the peroneals may prove to be an effective prevention tool of ankle sprain recurrence in patients with CAI. LEVEL OF EVIDENCE: III.

Plantaris Excision and Ventral Paratendinous Scraping for Achilles Tendinopathy in an Athletic Population.

BACKGROUND: Achilles tendinopathy is a frequent problem in high-level athletes. Recent research has proposed a combined etiologic role for the plantaris tendon and neovascularization. Both pathologies can be observed on ultrasound imaging.(1,13) However, little is known about the change in structure of the Achilles tendon following the surgical treatment of these issues. The purpose of the study was to assess if excising the plantaris and performing ventral paratendinous "scraping" of the neovascularization improved symptoms of Achilles tendinopathy and whether there was a change in the fibrillar structure of the tendon with ultrasound tissue characterization (UTC) following this operation. METHODS: This prospective consecutive case series included 15 professional/semiprofessional athletes (17 Achilles tendons) who underwent plantaris excision and paratendinous scraping to treat noninsertional Achilles tendinopathy. The plantaris tendon was excised if adherent to the Achilles tendon, and the area of neovascularization for scraping was demarcated on preoperative imaging. Preoperative and postoperative Victorian Institute of Sports Assessment-Achilles (VISA-A) scores were taken. UTC was performed on 11 of 17 tendons preoperatively and postoperatively. The mean follow-up was for 25 months. RESULTS: Fourteen of 15 patients had a successful outcome after the surgery. The mean VISA-A improved from 51 to 95 (p=.0001). There was a statistically significant (p=.04) improvement in the aligned fibrillar structure of the tendon confirmed with UTC scanning following surgery from 90% (±8) to 96% (±5). CONCLUSION: This group of high-level athletes derived an excellent clinical result from this operation. Furthermore, UTC scanning offered an objective method to evaluate the healing of Achilles tendons. LEVEL OF EVIDENCE: Level IV, case series.

Lateral versus medial approach for intra-articular knee injections.

OBJECTIVE: The aim of this study was to determine whether the medial or the lateral mid-patellar approach is the most reliable for intra-articular knee injections. METHODS: The study included 76 knees of 76 patients divided into 2 groups. The first group consisted of 38 patients with a knee injury and resultant knee effusion. The second group included 38 patients without any known knee pathology. Patients were matched according to age and gender. The medial joint opening (medial patellofemoral angle) was calculated on a T1-weighted transverse image by measuring the anatomic angle between the femur and the patella. The lateral joint opening (lateral patellofemoral angle) was calculated in a similar way. RESULTS: The medial patellofemoral angle was significantly higher than the lateral patellofemoral angle in both groups (p<0.001). CONCLUSION: The medial patellofemoral angle is significantly higher than the lateral patellofemoral angle in both healthy knees and knees with effusion. Therefore, the medial approach appears to be more accurate for intra-articular knee injection due to the medial joint's larger opening.

Evaluation with contrast-enhanced magnetic resonance imaging of the anterior cruciate ligament graft during its healing process: a two-year prospective study.

OBJECTIVE: The aim of this study was to evaluate, with contrast-enhanced-magnetic resonance imaging (MRI), the changing imaging appearance of an anterior cruciate ligament (ACL) graft during the revascularization phase by quantitatively assessing the morphological and signal intensity changes taking place at its cross-sectional surface over time. MATERIALS AND METHODS: Fifty patients underwent contrast-enhanced-MRI on the third postoperative day and at a mean of 6, 12, and 24 months time interval after surgery. Proton-density images were obtained to evaluate morphological and signal intensity characteristics. Oblique-axial T1-weighted images obtained before and after intravenous gadolinium administration were used for quantitative analysis. Enhancement index (EI: signal-to-noise quotient(after gadolinium)÷signal-to-noise quotient(before gadolinium)) and cross-sectional area (CSA) were calculated for two regions of interest: the transplanted graft and its surrounding hypervascular tissue, and at three distinct graft sites (intra-articular, intraosseous tibial tunnel, and intraosseous juxta screw sites). Comparisons of EI and CSA at every site and time interval were performed using analysis of variance. RESULTS: A variable MRI appearance of the graft during the different time intervals was attributed to the varying amount of the hypervascular tissue gradually surrounding the graft. Graft EI and peripheral tissue CSA progress in a parallel, time- and site-related pattern along the graft course. The initial heterogeneity with intermediate signal intensity at the intra-articular graft site reflected intense revascularization. A slower revascularization progress was noticed at the other two intraosseously enclosed sites. CONCLUSION: During the healing process the amount of revascularization tissue influences the MR imaging characteristics of the graft according to the examined site and the time interval after surgery. By 2 years postoperatively, revascularization completion coincides with the homogeneously low signal intensity of the graft, closely resembling native ACL.

Huge recurrent tumoral calcinosis needing extensive excision and reconstruction: report of a rare case and brief literature review.

UNLABELLED: Tumoral calcinosis, a rare benign clinical condition resembling a neoplasm, is characterized by calcium deposits, usually located in the soft tissues around the large joints. It can be primary or secondary to renal failure and hyperparathyroidism. This report describes an unusual case of recurrent tumoral calcinosis presenting as a huge mass infiltrating the skin and muscles of the lumbosacral area. The patient underwent wide excision and reconstruction with bilateral V-Y advancement gluteal fasciocutaneous flaps and at this writing remains disease free 4 years postoperatively. A concise review of the pertinent literature focusing on the diagnosis, treatment options, and preventive measures also is reported. LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article.

Hamstring-dominant strategy of the bone-patellar tendon-bone graft anterior cruciate ligament-reconstructed leg versus quadriceps-dominant strategy of the contralateral intact leg during high-intensity exercise in male athletes.

PURPOSE: The purpose of this study was to investigate the effect of anterior cruciate ligament (ACL) reconstruction on the quadriceps-dominant strategy as a parameter associated with the neuromuscular control of the knee joint. METHODS: In this study 14 competitive soccer players who had undergone ACL reconstruction with bone-patellar tendon-bone autograft and 14 healthy competitive soccer players performed two 10-minute treadmill runs, 1 at moderate intensity and 1 at high intensity. Electromyographic recordings were acquired by use of a telemetric system at the third, fifth, seventh, and tenth minute of the runs from the vastus lateralis and the biceps femoris bilaterally. The dependent variable examined was the peak electromyographic amplitude during the stance phase. Analyses of variance were used to examine significant main effects and interactions. RESULTS: Vastus lateralis electromyographic activity during high-intensity running increased for both the control leg and intact leg (F = 4.48, P < .01), whereas it remained unchanged for the reconstructed leg (P > .05). Biceps femoris electromyographic activity during high-intensity running increased for the reconstructed leg only compared with both the control leg (F = 3.03, P < .05) and intact leg (F = 3.36, P < .03). CONCLUSIONS: There is no presence of the quadriceps-dominant strategy in ACL-reconstructed athletes during moderate-intensity exercise. During high-intensity exercise, the intact contralateral leg develops the quadriceps-dominant strategy whereas the reconstructed leg does not. The reconstructed leg instead increases biceps femoris activity, developing a "hamstring-dominant" strategy, and this "asymmetry" may theoretically be in favor of the reconstructed knee. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Knee flexor muscle responses under fatigue after harvesting the hamstrings for anterior cruciate ligament reconstruction. [corrected].

OBJECTIVE: To investigate if harvesting of semitendinosus (ST) and gracilis for anterior cruciate ligament (ACL) reconstruction will have an effect in coordinative firing pattern of the hamstrings under fatigue. We hypothesized that fatigue will increase the electromechanical delay (EMD) of the hamstrings on the harvested site and impair the synchronization between the medial and lateral hamstrings, in terms of muscle activity onsets. DESIGN: Prospective nonrandomized study. SETTING: Institutional. PATIENTS: Twelve ACL reconstructed patients with hamstrings, 2 years postoperatively. INTERVENTIONS: The patients performed a fatigue protocol with 25 continuous maximal isometric voluntary contractions of 8-second duration with 2-second intervals. MAIN OUTCOME MEASURES: The electromyography activity of biceps femoris (BF) and ST was recorded bilaterally and simultaneously with the torque measurements. The dependent variable examined was the EMD difference between BF and ST (muscle activation pattern). RESULTS: The fatigue protocol caused significant differences for the EMD values for both the intact and the reconstructed leg, demonstrating the influence of fatigue in EMD. However, the synchronization pattern between the medial and lateral hamstrings did not change significantly throughout the fatiguing protocol, revealing a balanced effect of fatigue. CONCLUSIONS: Although the EMD of ST and BF was significantly increased due to fatigue, as expected, their synchronization pattern as identified by the difference in their EMDs remained the same. Thus, the reconstructed knee responded in a balanced manner and the hamstrings firing pattern remained the same, despite the intervention to the ST tendon.

Revascularization process of the bone--patellar tendon--bone autograft evaluated by contrast-enhanced magnetic resonance imaging 6 and 12 months after anterior cruciate ligament reconstruction.

BACKGROUND: Contrast-enhanced magnetic resonance imaging (MRI) studies conducted on animal models have shown that the observed signal intensity changes are related to the degree of graft vascularity and its biomechanical properties. PURPOSE: To evaluate by contrast-enhanced MRI the revascularization process at 3 distinct sites discerned in relation to the surrounding microenvironment along the course of bone-patellar tendon-bone (BPTB) autograft in uncomplicated human anterior cruciate ligament (ACL)-reconstructed knees. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Thirty-two male patients were assessed with a 3-dimensional fast field echo/short tau inversion recovery (FFE/STIR) MRI sequence at the third postoperative day and at time intervals of 6 and 12 months after surgery. Signal-to-noise quotient (SNQ) was calculated for 3 specific graft sites (intra-articular site, intraosseous tibial tunnel site, and intraosseous juxta screw site) before and after gadolinium administration. Comparisons of the enhancement index (EI: SNQ(after)/SNQ(before) gadolinium) were performed independently for each graft site and time interval. RESULTS: Three days postoperatively, insufficient vascularization was noticed at the 3 sites. Six and 12 months after surgery, the enhancement index was significantly increased in all 3 sites (P < .001). The intra-articular site, 6 months postoperatively, achieved satisfactory contrast medium uptake (enhancement index >1), with significantly higher enhancement index values compared with the other 2 sites (P < .001). Twelve months after surgery, only the intraosseously enclosed sites displayed an increase of the enhancement index, although nonsignificant (P = .09 and P = .07, respectively). CONCLUSION: Revascularization of the graft occurs gradually along its length, with the intra-articular site being the first and the faster part to complete this phase, while both the intraosseous sites are still in progress throughout the first postoperative year. Revascularization is an important link at the intrinsic healing chain of the ACL graft. The surrounding microenvironment does seem to play a significant role in this process, and the differences in its composition along the graft course are reflected at the revascularization progress of the corresponding sites.

Knee braces can decrease tibial rotation during pivoting that occurs in high demanding activities.

PURPOSE: The purpose of this study was to investigate whether knee braces could effectively decrease tibial rotation during high demanding activities. METHODS: Using an in vivo three-dimensional kinematic analysis, 21 physically active, healthy, male subjects were evaluated. Each subject performed two tasks that were used extensively in the literature because they combine increased rotational and translational loads on the knee, (1) descending from a stair and subsequent pivoting and (2) landing from a platform and subsequent pivoting under three conditions: (A) wearing a prophylactic brace (braced), (B) wearing a patellofemoral brace (sleeved), and (C) unbraced condition. RESULTS: In the first task, tibial rotation during the pivoting phase was significantly decreased in the braced condition as compared to the sleeved condition (P = 0.019) and the non-braced condition (P = 0.002). In the second task, the same variable was significantly decreased in the braced condition as compared to the sleeved (P = 0.001) and the unbraced condition (P < 0.001). The sleeved condition also produced significantly decreased tibial rotation with respect to the unbraced condition (P = 0.021). CONCLUSIONS: Bracing decreased tibial rotation in activities where increased translational and rotational forces were applied. Because knee braces decreased tibial rotation, they can possibly be used with ACL-reconstructed and ACL-deficient patients to prevent such problems. LEVEL OF EVIDENCE: Case-control study, Level III.

ACL reconstructed patients with a BPTB graft present an impaired vastus lateralis neuromuscular response during high intensity running.

The purpose of the present study was to investigate whether the electromyographic response of the vastus lateralis (VL) muscle in the anterior cruciate ligament (ACL) reconstructed leg is similar to that of the intact contralateral leg and healthy controls, during moderate and high intensity running. Fourteen bone-patellar tendon-bone (BPTB) ACL reconstructed amateur soccer players and fourteen healthy control amateur soccer players volunteered to participate in the study. Electromyographic (EMG) traces from the vastus lateralis (VL) muscle were collected bilaterally, as athletes ran on a treadmill for 10 min on separate occasions, at moderate and high intensity. The dependent variable examined was the EMG amplitude during stance. During the moderate intensity running, EMG amplitude of the VL did not increase with time for any of the tested legs. During the high intensity running, the EMG amplitude of the VL increased significantly with time for the intact (F=6.747, p=0.001) and the control leg (F=4.258, p=0.008), but remained unchanged for the ACL reconstructed leg. During moderate intensity running, there was no difference in the neuromuscular response of the VL in the reconstructed leg compared to the intact and control leg. High intensity running resulted in an impaired neuromuscular response of the VL in the reconstructed leg compared to the intact and control leg. It seems that potential impairments of the neuromuscular response after ACL reconstruction should be tested under high rather than moderate intensity efforts.

Effect of femoral tunnel placement for reconstruction of the anterior cruciate ligament on tibial rotation.

BACKGROUND: Rotational knee movement after reconstruction of the anterior cruciate ligament has been difficult to quantify. The purpose of this study was to identify in vivo whether a more horizontal placement of the femoral tunnel (in the ten o'clock position rather than in the eleven o'clock position) can restore rotational kinematics, during highly demanding dynamic activities, in a knee in which a bone-patellar tendon-bone graft had been used to reconstruct the anterior cruciate ligament. METHODS: We evaluated ten patients in whom a bone-patellar tendon-bone graft had been used to reconstruct the anterior cruciate ligament with the femoral tunnel in the eleven o'clock position, ten patients who had had the same procedure with the femoral tunnel in the ten o'clock position, and ten healthy controls. Kinematic data were collected while the subjects (1) descended from a stairway, made foot contact, and then pivoted 90 degrees on the landing lower limb and (2) jumped from a platform, landed with both feet on the ground, and pivoted 90 degrees on the right or left lower limb. The dependent variable that we examined was tibial rotation during pivoting. RESULTS: The results demonstrated that reconstruction of the anterior cruciate ligament with the femoral tunnel in either the ten or the eleven o'clock position successfully restored anterior tibial translation. However, both techniques resulted in tibial rotation values, during the dynamic activities evaluated, that were significantly larger than those in the intact contralateral lower limbs and those in the healthy controls. Tibial rotation did not differ significantly between the two reconstruction groups or between the healthy controls and the intact contralateral lower limbs. However, we noticed that positioning the tunnel at ten o'clock resulted in slightly decreased rotation values that may have clinical relevance but not statistical significance. CONCLUSIONS: Regardless of which of the two tested positions was utilized to fix the graft to the femur, reconstruction of the anterior cruciate ligament did not restore normal tibial rotation during dynamic activities.

Electromechanical delay of the knee flexor muscles is impaired after harvesting hamstring tendons for anterior cruciate ligament reconstruction.

BACKGROUND: Changes in electromechanical delay during muscle activation are expected when there are substantial alterations in the structural properties of the musculotendinous tissue. In anterior cruciate ligament reconstruction, specific tendons are being harvested for grafts. Thus, there is an associated scar tissue development at the tendon that may affect the corresponding electromechanical delay. PURPOSE: This study was conducted to investigate whether harvesting of semitendinosus and gracilis tendons for anterior cruciate ligament reconstruction will affect the electromechanical delay of the knee flexors. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: The authors evaluated 12 patients with anterior cruciate ligament reconstruction with a semitendinosus and gracilis autograft, 2 years after the reconstruction, and 12 healthy controls. Each participant performed 4 maximally explosive isometric contractions with a 1-minute break between contractions. The surface electromyographic activity of the biceps femoris and the semitendinosus was recorded from both legs during the contractions. RESULTS: The statistical comparisons revealed significant increases of the electromechanical delay of the anterior cruciate ligament-reconstructed knee for both investigated muscles. Specifically, the electromechanical delay values were increased for both the biceps femoris (P = .029) and the semitendinosus (P = .005) of the reconstructed knee when compared with the intact knee. Comparing the anterior cruciate ligament-reconstructed knee against healthy controls revealed similar significant differences for both muscles (semitendinosus, P = .011; biceps femoris, P = .024). CONCLUSION: The results showed that harvesting the semitendinosus and gracilis tendons for anterior cruciate ligament reconstruction significantly increased the electromechanical delay of the knee flexors. Increased hamstring electromechanical delay might impair knee safety and performance by modifying the transfer time of muscle tension to the tibia and therefore affecting muscle response during sudden movements in athletic activities. However, further investigation is required to identify whether the increased electromechanical delay of the hamstrings can actually influence optimal sports performance and increase the risk for knee injury in athletes with anterior cruciate ligament reconstructions.

High intensity running results in an impaired neuromuscular response in ACL reconstructed individuals.

Anterior cruciate ligament (ACL) reconstruction reestablishes electromyographic activity during moderate activities such as walking but is unclear if this is also the case in sports activities such as high intensity running that results in accumulation of metabolic fatigue. Nine bone-patella tendon-bone ACL reconstructed athletes were evaluated 19.2 (5.7) months post-operatively using a telemetric electromyographic system. The neuromuscular response of vastus lateralis and biceps femoris muscles was tested bilaterally on separate occasions during 10 min running at moderate intensity (20% below the lactate threshold) and 10 min running at high intensity (40% above the lactate threshold). During moderate intensity running, electromyographic activity did not change for either leg. During high intensity running, electromyographic activity did not change for the vastus lateralis of the ACL reconstructed leg [267.8 (142.8)-263.8 (128.9) microV, P > 0.05] while it increased significantly [294.2 (120.6)-317.1 (140.5) microV, P = 0.03] for the vastus lateralis of the intact leg. High intensity exercise that is associated with accumulation of metabolic fatigue, results in an impaired neuromuscular response for the vastus lateralis muscle of the ACL reconstructed leg.

The effect of anterior cruciate ligament reconstruction on stride-to-stride variability.

PURPOSE: The purpose of our study was to investigate the functional outcome after anterior cruciate ligament (ACL) reconstruction using bone-patellar tendon-bone (BPTB) and quadrupled semitendinosus and gracilis tendon (ST/G) autografts by evaluating stride-to-stride variability. METHODS: Six patients with BPTB and 6 patients with STG ACL reconstruction, 2 years postoperatively, and 6 healthy control subjects walked on a treadmill at a self-selected pace while 2 minutes of continuous kinematic data were recorded with a 6-camera optoelectronic system. Stride-to-stride variability was calculated from the knee flexion/extension data using the nonlinear measure of approximate entropy, which estimates the regularity of movement patterns over time. RESULTS: ACL reconstruction affects stride-to-stride variability. Both the BPTB and the ST/G groups had significantly larger approximate entropy values than the healthy controls. No differences were found between the BPTB and the ST/G approximate entropy values. CONCLUSIONS: After ACL reconstruction using either BPTB or quadrupled ST/G, there is increased gait variability as compared to healthy individuals. This could be caused by the altered neuromuscular activity found in ACL-reconstructed limbs. LEVEL OF EVIDENCE: Level III, case control study.

ACL deficiency affects stride-to-stride variability as measured using nonlinear methodology.

Previous studies suggested that the small fluctuations present in movement patterns from one stride to the next during walking can be useful in the investigation of various pathological conditions. Previous studies using nonlinear measures have resulted in the development of the "loss of complexity hypothesis" which states that disease can affect the variability and decrease the complexity of a system, rendering it less able to adjust to the ever changing environmental demands. The nonlinear measure of the Lyapunov Exponent (LyE) has already been used for the assessment of stride-to-stride variability in the anterior cruciate ligament (ACL) deficient knee in comparison to the contralateral intact knee. However, there is biomechanical evidence that after ACL rupture, adaptations are also present in the contralateral intact knee. Thus, our goal was to investigate stride-to-stride variability in the ACL deficient knee as compared to a healthy control knee. Seven subjects with unilateral ACL deficiency and seven healthy controls walked at their self-selected speed on a treadmill, while three-dimensional knee kinematics was collected for 80 consecutive strides. A nonlinear measure, the largest LyE was calculated from the resulted knee joint flexion-extension data of both groups. Larger LyE values signify increased variability and increased sensitivity to initial conditions. Our results showed that the ACL deficient group exhibited significantly less variable walking patterns than the healthy control. These changes are not desirable because they reflect decreases in system's complexity, which indicates narrowed functional responsiveness, according to the "loss of complexity hypothesis." This may be related with the increased future pathology found in ACL deficient patients. The methods used in the present paper showed great promise to assess the gait handicap in knee injured patients.

Tibial rotation in anterior cruciate ligament (ACL)-deficient and ACL-reconstructed knees: a theoretical proposition for the development of osteoarthritis.

Excessive tibial rotation has been documented in anterior cruciate ligament (ACL) deficiency during walking. ACL reconstruction has been unable to correct this abnormality in activities that are more demanding than walking and involve both anterior and rotational loading of the knee. These findings persist regardless of graft selection for the ACL reconstruction (bone-patellar tendon-bone or semitendinosus gracilis). Based on this research work, we propose a theoretical perspective for the development of osteoarthritis in both the ACL-deficient and the ACL-reconstructed knee. We propose that excessive tibial rotation will lead to abnormal loading of the cartilage areas that are not commonly loaded in the healthy knee. Over time, this abnormal loading will lead to osteoarthritis. We hypothesise that the development of new surgical procedures and grafts, such as a more horizontally oriented femoral tunnel or a double-bundle ACL reconstruction, could possibly restore tibial rotation to normal levels and prevent future knee pathology. However, in vivo gait analysis studies are needed to examine the effects of these surgical procedures on tibial rotation. Prospective in vivo and in vitro studies are also necessary to verify or refute our theoretical proposition for the development of osteoarthritis.