Neuromuscular training techniques to target deficits before return to sport after anterior cruciate ligament reconstruction

Surgical intervention and early-phase rehabilitation after anterior cruciate ligament (ACL) reconstruction have undergone a relatively rapid and global evolution over the past 25 years. Despite the advances that have significantly improved outcomes, decreases in healthcare coverage (limited visits allowed for physical therapy) have increased the role of the strength and conditioning specialist in the rehabilitation of athletes returning to sport after ACL reconstruction. In addition, there is an absence of standardized, objective criteria to accurately assess an athlete's ability to progress through the end stages of rehabilitation and safely return to sport. The purpose of this Scientific Commentary is to present an example of a progressive, end-stage return to sport protocol that is targeted to measured deficits of neuromuscular control, strength, power, and functional symmetry that are rehabilitative landmarks after ACL reconstruction. The proposed return to sport training protocol incorporates quantitative measurement tools that will provide the athlete with objective feedback and targeted goal setting. Objective feedback and targeted goal setting may aid the strength and conditioning specialist with exercise selection and progression. In addition, a rationale for exercise selection is outlined to provide the strength and conditioning specialist with a flexible decision-making approach that will aid in the modification of return to sport training to meet the individual athlete's abilities and to target objectively measured deficits. This algorithmic approach may improve the potential for athletes to return to sport after ACL reconstruction at the optimal performance level and with minimized risk of reinjury.     

The effects of femoral graft placement on cartilage thickness after anterior cruciate ligament reconstruction

Altered joint motion has been thought to be a contributing factor in the long-term development of osteoarthritis after ACL reconstruction. While many studies have quantified knee kinematics after ACL injury and reconstruction, there is limited in vivo data characterizing the effects of altered knee motion on cartilage thickness distributions. Thus, the objective of this study was to compare cartilage thickness distributions in two groups of patients with ACL reconstruction: one group in which subjects received a non-anatomic reconstruction that resulted in abnormal joint motion and another group in which subjects received an anatomically placed graft that more closely restored normal knee motion. Ten patients with anatomic graft placement (mean follow-up: 20 months) and 12 patients with non-anatomic graft placement (mean follow-up: 18 months) were scanned using high-resolution MR imaging. These images were used to generate 3D mesh models of both knees of each patient. The operative and contralateral knee models were registered to each other and a grid sampling system was used to make site-specific comparisons of cartilage thickness. Patients in the non-anatomic graft placement group demonstrated a significant decrease in cartilage thickness along the medial intercondylar notch in the operative knee relative to the intact knee (8%). In the anatomic graft placement group, no significant changes were observed. These findings suggest that restoring normal knee motion after ACL injury may help to slow the progression of degeneration. Therefore, graft placement may have important implications on the development of osteoarthritis after ACL reconstruction.     

The effects of femoral graft placement on in vivo knee kinematics after anterior cruciate ligament reconstruction

Achieving anatomical graft placement remains a concern in Anterior Cruciate Ligament (ACL) reconstruction. The purpose of this study was to quantify the effect of femoral graft placement on the ability of ACL reconstruction to restore normal knee kinematics under in vivo loading conditions. Two different groups of patients were studied: one in which the femoral tunnel was placed near the anterior and proximal border of the ACL (anteroproximal group, n=12) and another where the femoral tunnel was placed near the center of the ACL (anatomic group, n=10) MR imaging and biplanar fluoroscopy were used to measure in vivo kinematics in these patients during a quasi-static lunge. Patients with anteroproximal graft placement had up to 3.4mm more anterior tibial translation, 1.1mm more medial tibial translation and 3.7° more internal tibial rotation compared to the contralateral side. Patients with anatomic graft placement had motion that more closely replicated that of the intact knee, with anterior tibial translation within 0.8mm, medial tibial translation within 0.5mm, and internal tibial rotation within 1°. Grafts placed anteroproximally on the femur likely provide insufficient restraint to these motions due to a more vertical orientation. Anatomical femoral placement of the graft is more likely to reproduce normal ACL orientation, resulting in a more stable knee. Therefore, achieving anatomical graft placement on the femur is crucial to restoring normal knee function and may decrease the rates of joint degeneration after ACL reconstruction.     

Neuromuscular and psychological influences on range of motion recovery in anterior cruciate ligament reconstruction patients

To identify distinguishing characteristics for knee surgery patients who experience a protracted recovery process, we sought to determine if there is an association between the neuromuscular stretch reflex and psychological factors of pain perception and anxiety on the range of motion (ROM) recovery rate of post-operative anterior cruciate ligament reconstruction (ACLR) rehabilitation patients. The ACLR participants were categorized into a slow recovery group (SRG: >6 weeks to recover 0–125° knee flexion [n = 10]) and a normal recovery group (NRG: <6 weeks to recovery 0–125° knee flexion [n = 12]). Control participants (n = 22) were age, gender and activity-level matched to the surgical participants. Neuromuscular testing consisted of sagittal plane video kinematics of the Wartenberg Pendulum Test for determining lower limb stiffness indices and electromyography-monitored patellar tendon tap reflex responses. Psychological and health status assessments consisted of the State–Trait Anxiety Inventory and SF-36? Health Survey. Data revealed that neuromuscular reflex profiles, lower limb stiffness indices, pain, anxiety and SF-36? indices of function were not significantly different between the two surgical groups (SRG and NRG). The surgical groups exhibited significantly greater pain (2.67 ± 2.27 SRG, 1.49 ± 1.15 NRG) than the control group (p ? .05). SF-36? indices were significantly lower for the surgical groups for total score (546.55 ± 94.70 SRG, 577.57 ± 125.58 NRG), function 69.00 ± 20.24 SRG, 67.08 ± 19.12 NRG), role physical (53.75 ± 22.85 SRG, 53.12 ± 23.15 NRG), social (76.24 ± 25.31 SRG, 65.62 ± 27.24 NRG), and emotional (82.49 ± 19.81 SRG, 81.38 ± 23.02 NRG) subscales (p ? .05). These results suggest that neuromuscular reflex responses, visual analogue scale (VAS) pain, and anxiety are not distinguishing factors for ROM recovery rate between the SRG and NRG. Decreased SF-36? indices, including pain as it influences function, though clinically relevant factors, were not statistically associated with post-operative ROM recovery rate.     

Muscle co-contraction after anterior cruciate ligament reconstruction: Influence of functional level

Background

ACL reconstruction is recommended to improve function in subjects with ligament injuries. However, after surgery, some individuals are not able to return to their pre-injury functional level. The mechanisms related to this incapacity are not well understood.

Study design

Cross-sectional study.

Methods

Co-contraction levels were assessed in individuals who returned to their pre-injury functional level and in 10 individuals who were not able to return to full activity after unilateral ACL reconstruction. Electromyography of the vastus lateralis and biceps femoris muscles before and after sudden perturbations applied during the stance phase of walking was used to calculate co-contraction.

Results

The involved limb had lower co-contraction pre-perturbation than the non-involved limb in both groups (p = 0.049). The co-contraction level post-perturbation was significantly higher in the limited return group than in the full return group (p = 0.03).

Conclusion

Decreased co-contraction in the involved limb before perturbation may be caused by sensorial changes resulting from surgery or injury. Increased co-contraction levels observed in the limited return group after perturbation may be a compensatory mechanism to make up for possible decreased intrinsic stability of the knee joint.

Clinical relevance

Increased co-contraction after perturbation does not contribute to knee stability.     

Gait adaptation in ACL deficient patients before and after anterior cruciate ligament reconstruction surgery.

The objective of this study is to determine how kinematical parameters and electromyography data of selected muscles may change as a result of anterior cruciate ligament (ACL) deficiency and following ACL reconstruction. The study was conducted on 25 anterior cruciate ligament deficient subjects prior to and 6 weeks, 4 months, 8 months and 12 months following ACL reconstructive surgery using the bone-patellar tendon-bone technique. Gait analysis was performed by applying the zebris three-dimensional ultrasound-based system with surface electromyograph (zebris). Kinematic data were recorded for the lower limb. The muscles surveyed include vastus lateralis and medialis, biceps femoris and adductor longus. The results obtained from the injured subjects were compared with those of 51 individuals without any ACL damage whatsoever. Acute ACL deficient patients exhibited a quadriceps avoidance pattern prior to and 6 weeks following surgery. No quadriceps avoidance phenomenon develops in chronic ACL deficient patients. In operated individuals, tempo-spatial parameters and the knee angle regained a normal pattern for the ACL-deficient limb during gait as early as 4 months following surgery. However, the relative ACL movement parameter, which describes the tibial translation into the direction of ACL, and the EMG traces show no significant statistical difference compared with the same values of the healthy control group just 8 months following surgery. The analysis of spatial-temporal parameters and EMG traces show that the development of a quadriceps avoidance pattern is less common than previously reported. These data suggest that anterior cruciate ligament deficiency and reconstruction produce considerable changes in the lower extremity gait pattern. The results suggest that gait parameters tend to shift towards a normal value pattern; and the re-establishment of pre-injury gait patterns-including the normal biphase of muscles-takes at least 8 months to occur.     

An implantable transducer for measuring tension in an anterior cruciate ligament graft.

The goal of this study was to develop a new implantable transducer for measuring anterior cruciate ligament (ACL) graft tension postoperatively in patients who have undergone ACL reconstructive surgery. A unique approach was taken of integrating the transducer into a femoral fixation device. To devise a practical in vivo calibration protocol for the fixation device transducer (FDT), several hypotheses were investigated: (1) The use of a cable versus the actual graft as the means for applying load to the FDT during calibration has no significant effect on the accuracy of the FDT tension measurements; (2) the number of flexion angles at which the device is calibrated has no significant effect on the accuracy of the FDT measurements; (3) the friction between the graft and femoral tunnel has no significant effect on measurement accuracy. To provide data for testing these hypotheses, the FDT was first calibrated with both a cable and a graft over the full range of flexion. Then graft tension was measured simultaneously with both the FDT on the femoral side and load cells, which were connected to the graft on the tibial side, as five cadaver knees were loaded externally. Measurements were made with both standard and overdrilled tunnels. The error in the FDT tension measurements was the difference between the graft tension measured by the FDT and the load cells. Results of the statistical analyses showed that neither the means of applying the calibration load, the number of flexion angles used for calibration, nor the tunnel size had a significant effect on the accuracy of the FDT. Thus a cable may be used instead of the graft to transmit loads to the FDT during calibration, thus simplifying the procedure. Accurate calibration requires data from just three flexion angles of 0, 45, and 90 deg and a curve fit to obtain a calibration curve over a continuous range of flexion within the limits of this angle group. Since friction did not adversely affect the measurement accuracy of the FDT, the femoral tunnel can be drilled to match the diameter of the graft and does not need to be overdrilled. Following these procedures, the error in measuring graft tension with the FDT averages less than 10 percent relative to a full-scale load of 257 N.     

Results of the surgical reconstruction of the anterior cruciate ligament

Results of the surgical reconstruction of the anterior cruciate ligament (ACL), using as a graft fourfold hamstring tendons (gracilis and semitendinosus) and middle third of the patellar ligament, were compared. In all patients that were participating in this study clinical examination and magnetic resonance showed ACL rupture, and apart from the choice of the graft, surgical technique was identical. We evaluated 112 patients with implemented patellar ligament graft and fourfold hamstring tendons graft six months after the procedure. Both groups were similar according to age, sex, activity level, knee instability level and rehabilitation program. The results showed that there was no significant difference between groups regarding Lysholm Knee score, IKDC 2000 score, activity level, musculature hypotrophy, and knee joint stability 6 months after the surgery. Anterior knee pain incidence is significantly higher in the group with patellar ligament graft (44% vs. 21%). Both groups had a significant musculature hypotrophy of the upper leg of the knee joint that was surgically treated, six months after the procedure. Both grafts showed good subjective and objective results.     

Time course of the effects of vibration on quadriceps function in individuals with anterior cruciate ligament reconstruction

Quadriceps dysfunction is a common, chronic complication following anterior cruciate ligament reconstruction (ACLR) that contributes to aberrant gait biomechanics and poor joint health. Vibration enhances quadriceps function in individuals with ACLR, but the duration of these effects is unknown. This study evaluated the time course of the effects of whole body vibration (WBV) and local muscle vibration (LMV) on quadriceps function. Twenty-four volunteers with ACLR completed 3 testing sessions during which quadriceps isometric peak torque, rate of torque development, and EMG amplitude were assessed prior to and immediately, 10, 20, 30, 45, and 60 min following a WBV, LMV, or control intervention. WBV and LMV (30 Hz, 2g) were applied during six one-minute bouts. WBV increased peak torque 5–11% relative to baseline and control at all post-intervention time points. LMV increased peak torque 6% relative to baseline at 10 min post-intervention and 4–6% relative to control immediately, 10 min, and 20 min post-intervention. The interventions did not influence EMG amplitudes or rate of torque development. The sustained improvements in quadriceps following vibration, especially WBV, suggest that it could be applied at the beginning of rehabilitation sessions to “prime” the central nervous system, potentially improving the efficacy of ACLR rehabilitative exercise.     

In vitro evaluation of combined graft deformation in anterior cruciate ligament reconstructions

In this paper, we present a simple method of calculating deformation of an anterior cruciate ligament graft in combined elongation, bending and total twisting. We also report our results on these deformations for three types of ligament reconstruction in cadaver knees: two isometric reconstructions, using either a biological bone-patellar tendon-bone autograft or an artificial Trevira prosthesis, and modified over-the-top reconstruction with the prosthesis. The data show that the modified OTT technique produced elongation of the graft equivalent to that of the synthetic isometric technique, but significantly less than isometric reconstruction with the biological graft (p<0.05, ANOVA). Moreover, the grafts were subjected to bending and twisting.     

辛伐他汀/脱蛋白骨对兔前交叉韧带重建腱-骨早期愈合的影响

目的探讨不同浓度辛伐他汀/脱蛋白骨复合物对兔前交叉韧带(ACL)重建腱-骨早期愈合的影响。方法选取80只实验兔随机分为4组各20只,A组(0.125%复合物)、B组(0.25%复合物)、C组(0.5%复合物)及D组(空白对照),均行ACL重建。实验组腱-骨界面分别相应植入不同浓度复合物,D组不作处理。术后4、8、12周取材行生物力学测试及病理观察。结果0.5%复合物组移植肌腱抗拉性能、腱-骨界面成熟度均优于其余3组。结论辛伐他汀/脱蛋白骨可促进ACL重建腱-骨早期愈合,且以浓度为0.5%时效果最佳。     

Limb and sex-related differences in knee muscle co-contraction exist 3 months after anterior cruciate ligament reconstruction

Interlimb and sex-based differences in gait mechanics and neuromuscular control are common after anterior cruciate ligament reconstruction (ACLR). Following ACLR, individuals typically exhibit elevated co-contraction of knee muscles, which may accelerate knee osteoarthritis (OA) onset. While directed (medial/lateral) co-contractions influence tibiofemoral loading in healthy people, it is unknown if directed co-contractions are present early after ACLR and if they differ across limbs and sexes. The purpose of this study was to compare directed co-contraction indices (CCIs) of knee muscles in both limbs between men and women after ACLR. Forty-five participants (27 men) completed overground walking at a self-selected speed 3 months after ACLR during which quadriceps, hamstrings, and gastrocnemii muscle activities were collected bilaterally using surface electromyography. CCIs of six muscle pairs were calculated during the weight acceptance interval. The CCIs of the vastus lateralis/biceps femoris muscle pair (lateral musculature) was greater in the involved limb (vs uninvolved; p = 0.02). Compared to men, women exhibited greater CCIs in the vastus medialis/lateral gastrocnemius and vastus lateralis/lateral gastrocnemius muscle pairs (p < 0.01 and p = 0.01, respectively). Limb- and sex-based differences in knee muscle co-contractions are detectable 3 months after ACLR and may be responsible for altered gait mechanics.     

Quadriceps strength and weight acceptance strategies continue to improve two years after anterior cruciate ligament reconstruction

The anterior cruciate ligament (ACL) is the most commonly-injured knee ligament during sporting activities. After injury, most individuals experience episodes of the knee giving way during daily activities (non-copers). Non-copers demonstrate asymmetrical quadriceps strength and movement patterns, which could have long-term deleterious effects on the integrity of the knee joint. The purpose of this study was to determine if non-copers resolve their strength and movement asymmetries within two years after surgery. 26 Non-copers were recruited to undergo pre-operative quadriceps strength testing and 3-dimensional gait analysis. Subjects underwent surgery to reconstruct the ligament followed by physical therapy focused on restoring normal range of motion, quadriceps strength, and function. Subjects returned for quadriceps strength testing and gait analysis six months and two years after surgery. Acutely after injury, quadriceps strength was asymmetric between limbs, but resolved six months after surgery. Asymmetric knee angles, knee moments, and knee and hip power profiles were also observed acutely after injury and persisted six months after surgery despite subjects achieving symmetrical quadriceps strength. Two years after surgery, quadriceps strength in the involved limb continued to improve and most kinematic and kinetic asymmetries resolved. These findings suggest that adequate quadriceps strength does not immediately resolve gait asymmetries in non-copers. They also suggest that non-copers have the capacity to improve their quadriceps strength and gait symmetry long after ACL reconstruction.     

Gait biomechanics in individuals with patellar tendon and hamstring tendon anterior cruciate ligament reconstruction grafts

Anterior cruciate ligament reconstruction (ACLR) restores joint stability following ACL injury but does not attenuate the heightened risk of developing knee osteoarthritis. Additionally, patellar tendon (PT) grafts incur a greater risk of osteoarthritis compared to hamstring grafts (HT). Aberrant gait biomechanics, including greater loading rates (i.e. impulsive loading), are linked to the development of knee osteoarthritis. However, the role of graft selection on walking gait biomechanics linked to osteoarthritis is poorly understood, thus the purpose of this study was to compare walking gait biomechanics between individuals with HT and PT grafts. Ninety-eight (74 PT; 24 HT) subjects with a history of ACLR performed walking gait at a self-selected speed from which the peak vertical ground reaction force (vGRF) during the first 50% of the stance phase and its instantaneous loading rate, peak internal knee extension and valgus moments, and peak knee flexion and varus angles were obtained. When controlling for time since ACLR and quadriceps strength, there were no differences in any kinetic or kinematic variables between graft types. While not significant, 44% of the PT cohort were identified as impulsive loaders (displaying a heelstrike transient in the majority of walking trials) compared to only 25% of the HT cohort (odds ratio = 2.3). This more frequent observation of impulsive loading may contribute to the greater risk of osteoarthritis with PT grafts. Future research is necessary to determine if impulsive loading and small magnitude differences between graft types contribute to osteoarthritis risk when extrapolated over thousands of steps per day.     

Human patellar tendon stiffness is restored following graft harvest for anterior cruciate ligament surgery

Minimising post-operative donor site morbidity is an important consideration when selecting a graft for surgical reconstruction of the torn anterior cruciate ligament (ACL). One of the most common procedures, the bone-patellar tendon-bone (BPTB) graft involves removal of the central third from the tendon. However, it is unknown whether the mechanical properties of the donor site (patellar tendon) recover. The present study investigated the mechanical properties of the human patellar tendon in 12 males (mean±S.D. age: 37±14 years) who had undergone surgical reconstruction of the ACL using a BPTB graft between 1 and 10 years before the study (operated knee; OP). The uninjured contralateral knee served as a control (CTRL). Patellar tendon mechanical properties were assessed in vivo combining dynamometry with ultrasound imaging. Patellar tendon stiffness was calculated from the gradient of the tendon's force–elongation curve. Tendon stiffness was normalised to the tendon's dimensions to obtain the tendon's Young's modulus. Cross-sectional area (CSA) of OP patellar tendons was larger by 21% than CTRL tendons (P<0.01). Patellar tendon stiffness was not significantly different between OP and CTRL tendons, but the Young's modulus was lower by 24% in OP tendons (P<0.01). A compensatory enlargement of the patellar tendon CSA, presumably due to scar tissue formation, enabled a recovery of tendon stiffness in the OP tendons. The newly formed tendon tissue had inferior properties as indicated by the reduced tendon Young's modulus, but it increased to a level that enabled recovery of tendon stiffness.     

Range of motion specificity resulting from closed and open kinetic chain resistance training after anterior cruciate ligament reconstruction

The purpose of this study was to examine whether joint angle specificity occurs in open and closed kinetic chain resistance training of the knee extensors after anterior cruciate ligament reconstruction (ACLR). Isokinetic knee extensor strength was measured at 60 and 210 degrees.s(-1) in 32 patients, 2 and 6 weeks after surgery. Between test sessions, patients participated in a 4-week program of injured leg resistance training of the knee extensors in either open kinetic chain (OKC) knee extension or leg press exercises. Isokinetic testing knee range of motion (ROM) was divided into 5 equal portions from flexion to extension, and the mean torque was calculated over those divisions: 0-20%, 20-40%, 40-60%, 60-80%, and 80-100% ROM. Analysis of variance indicated that there were no significant differences between patients in the knee extension or leg press exercise groups.     

Early regional adaptation of periarticular bone mineral density after anterior cruciate ligament injury.

The present study measured early-stage adaptation of bone mineral (BMD) in the periarticular cancellous bone of the canine knee (stifle) joint after anterior cruciate ligament (ACL) transection (ACLX). Regional changes in BMD in the tibia and femur were analyzed by using quantitative computed tomography (qCT) at 3 wk and 12 wk after unilateral ACLX to determine whether there were focal points for BMD changes and whether these changes occurred early after the induced knee injury. BMD decreased rapidly after ACLX, and the more pronounced response was in the femur. In the 3-wk group, there were decreases in BMD in the tibia and the femur, and these changes were significant in the posterior-medial region of the femur, which showed a decrease of BMD in the ACLX limb (-0.048 +/- 0.011 g/cm(3)). In the 12-wk group, all regions in the tibia and femur exhibited significant decreases in BMD, and the average decrease was greatest in the posterior-medial region of the femur (-0.142 +/- 0.021 g/cm(3)). The regions of pronounced periarticular cancellous BMD adaptation corresponded to observed focal cartilage defects. Early decreases in BMD in the injured knee may be related to altered loading and kinematics in the knee and may be an important link in the pathogenesis of posttraumatic osteoarthritis.