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.     

Neuromuscular function after anterior cruciate ligament reconstruction with autologous semitendinosus-gracilis graft.

BACKGROUND: The quadrupled autologous semitendinosus-gracilis graft is the first choice of many orthopaedic surgeons when reconstructing the anterior cruciate ligament. The effect that this procedure has on voluntary muscle control remains unclear. The purpose of this study was to evaluate the effect that anterior cruciate ligament reconstruction with autologous semitendinosus-gracilis graft has on voluntary muscle control by assessing subjects' specificity of muscle action. METHODS: The voluntary muscle control of 10 people (seven males, three females) with acute, isolated ACL ruptures was assessed in the days prior to when they underwent anterior cruciate ligament reconstruction with quadrupled autologous semitendinosus-gracilis grafts and after they had returned to play in sports requiring quick changes of direction and jumping (approximately 6 months later). The experimental protocol included the use of an established target-matching protocol that requires subjects to produce and modulate force with fine control, electromyographic recordings from 11 muscles about the knee, and the use of circular statistics to calculate specificity indices that describe the degree of focus (specificity) associated with the activity pattern of each muscle. Data were analyzed by performing pre-surgery and post-return to sports side-to-side comparisons, as well as, pre-surgery to post-surgery ipsilateral comparisons. RESULTS: Diminished specificity of muscle action was observed in the activity patterns of most of the muscles of the subjects' anterior cruciate ligament deficient knees prior to surgery. The quadriceps muscles were particularly affected. Post-return to sports results indicated that voluntary muscle control had improved in most muscles. There was no significant difference in pre-surgery and post-return to sports semitendinosus and gracilis muscle control. The semimembranosus muscle displayed less specific muscle activity patterns following surgery, which may represent a compensation strategy for minor changes in neuromuscular function. CONCLUSIONS: Voluntary muscle control improved in most muscles following ACL reconstruction with semitendinosus-gracilis autografts. Semitendinosus and gracilis muscle control did not appear to be altered significantly by the procedure.     

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.     

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.     

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.     

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.     

A novel device to apply controlled flexion and extension to the rat knee following anterior cruciate ligament reconstruction

We designed and validated a novel device for applying flexion-extension cycles to a rat knee in an in vivo model of anterior cruciate ligament reconstruction (ACL-R). Our device is intended to simulate rehabilitation motion and exercise post ACL-R to optimize physical rehabilitation treatments for the improved healing of tendon graft ligament reconstructions. The device was validated for repeatability of the knee kinematic motion by measuring the force versus angular rotation response from repeated trials using cadaver rats. The average maximum force required for rotating an ACL reconstructed rat knee through 100 degrees of flexion-extension was 0.4 N with 95% variability for all trials within ±0.1 N.     

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。     

Static and fatigue strength of a fixation device transducer for measuring anterior cruciate ligament graft tension

To determine which exercises do not overload the graft-fixation complex during intensive rehabilitation from reconstructive surgery of the anterior cruciate ligament (ACL), it would be useful to measure ACL graft loads during rehabilitative activities in vivo in humans. A previous paper by Ventura et al. (1998) reported on the design of an implantable transducer integrated into a femoral fixation device and demonstrated that the transducer could be calibrated to measure graft loads to better than 10 percent full-scale error in cadaveric knees. By measuring both the static and fatigue strengths of the transducer, the purpose of the present study was to determine whether the transducer could be safely implanted in humans without risk of structural failure. Eight devices were loaded to failure statically. Additionally, seven devices were tested using the up-and-down method to estimate the median fatigue strength at a life of 225,000 cycles. The average ultimate strength was 1856 +/- 74 N and the median fatigue strength was 441 N at a life of 225,000 cycles. The maximum graft load during normal daily activities is estimated to be 500 N and the 225,000 cycle life corresponds to that of the average healthy individual during a 12-week period. Considering that patients who have had an ACL reconstruction are less ambulatory than normal immediately following surgery and that biologic incorporation of the graft should be well developed by 12 weeks thus decreasing the load transmitted to the fixation device, the FDT can be safely implanted in humans without undue risk of structural failure.     

An alternative method of anthropometry of anterior cruciate ligament through 3-D digital image reconstruction

Accurate and flexible measurements of length, area, and volume are important in evaluation of the mechanical properties of soft tissue. Although a number of contact-based and non-contact techniques have been reported in the literature, due to a variety of reasons such as cost, complexity, and low accuracy, the research community has not adopted a standardized technique. In this paper, an alternative method of measuring the geometric parameters of cadaver anterior cruciate ligament (ACL) is presented. In this method, a 3-D scan of the ACL is constructed using a simple, commercially available, scanning system. The 3-D scan is then analyzed using the 3-D Doctor Software to extract important information regarding the length, cross-sectional area, and volume of the ACL. The accuracy and repeatability of measurements obtained by this method are acceptable and comparable to existing non-contact methods. The limitation of the method is that surface concavities cannot be detected. However, the non-contact optical method, described here, has inherent advantages over the existing methods: (1) it is inexpensive; (2) it allows the determination of area at any distance along the length of the tissue of interest; (3) all relevant information including minimum area is extracted from one single application of the method; (4) the volume can be calculated with a simple additional step of length measurement although, for accurate results, condylar blockage must be minimized by coring the ACL out. The entire process of scanning takes less than 30 min. This technique has the potential to become a standard method in anthropometry of soft tissue.     

In vivo evaluation of two types of bioactive scaffold used for tendon-bone interface healing in the reconstruction of anterior cruciate ligament

Fibrin glue combined with bone morphogenetic protein (BMP) and recombined bone xenograft (RBX), were compared to evaluate their effect on the tendon–bone interface healing. The interface of fibrin glue-BMP developed new cartilage but the new bone was thinner whereas the interface of RBX had large areas of chondrocyte-like cells, bone formation and an immature neo-enthesis structure. At 12 weeks, bone mineral density of RBX group (152 ± 52 cm³) and fibrin glue-BMP group (109 ± 13 cm³) was calculated by micro-computed tomography. The ultimate load of fibrin glue-BMP group (60 ± 18 and 51 ± 14 N) and RBX group (65 ± 21 and 57 ± 15 N) was shown by biomechanics at 6 and 12 weeks. RBX thus has an advantage on accelerating tendon–bone interface healing.     

Computer-assisted evaluation of kinematics of the two bundles of the anterior cruciate ligament.

The aim of this cadaveric study was to describe the kinematics of the anterior cruciate ligament (ACL)-intact, posterolateral (PL) bundle-deficient and ACL-deficient knee by applying a protocol for computer-assisted evaluation of knee kinematics. The hypothesis that the PL bundle functions mainly at low knee flexion angles was tested. An optical tracking system was used to acquire knee joint motion on 10 knees during clinical evaluations by tracking markers rigidly attached to the bones. The protocol included acquisition of anterior-posterior (AP) translations and internal-external (IE) rotations, and evaluation of three clinical knee laxity tests (anterior drawer, manual and instrumented Lachman). The data demonstrated no significant contribution to AP translation and IE laxity from the PL bundle over the entire range of motion. The clinical knee laxity tests showed no significant differences between the ACL-intact and PL bundle-deficient states. The hypothesis could not be proven. Current clinical knee laxity measurements may not be suited for detecting subtle changes such as PL bundle deficiency in the ACL anatomy. The computation of knee laxity might be a step towards a more precise kinematic test of knee stability not only in the native and torn ACL state of the knee but also in the reconstructed knee.     

High articular levels of the angiogenetic factors VEGF and VEGF-receptor 2 as tissue healing biomarkers after single bundle anterior cruciate ligament reconstruction

Various factors may account for the positive association between meniscal repair and anterior cruciate ligament reconstruction, one being the modulation of healing response of meniscal fibrochondrocytes by growth factors released with intra-articular bleeding and fibrin clot formation. Analysis of vascular endothelial growth factor (VEGF) and its receptors, VEGFR1 and VEGFR2, may be useful in the clinical assessment of bone and soft-tissue remodeling. We measured systemic and local levels of VEGF (VEGF165), VEGFR1 and VEGFR2 after either arthroscopic partial meniscectomy (APM) or single-bundle anterior cruciate ligament reconstruction (ACLR) in order to determine the local effect of bone tunnelling and notchplasty on the release of these growth factors. The study population included 40 patients: 20 consecutive patients had undergone ACLR with hamstring grafts and 20 had undergone APM. Thirty minutes after the end of the operation, knee joint fluid samples were collected via the drainage tube and at the same time venous blood samples were drawn. In both sets of samples, VEGF, VEGFR1 and VEGFR2 concentrations were determined by enzyme-linked immunosorbent assay (ELISA). No significant differences in VEGF, VEGFR1 or VEGFR2 concentrations in the venous blood were observed between the two treatment groups. In contrast, VEGF and VEGFR2 levels were significantly higher in the knee joint fluid of the ACLR group; furthermore, VEGF and VEGFR1 were significantly higher in the knee joint fluid than in the venous blood, whereas VEGFR2 was lower in the knee joint fluid than in the venous blood. Local release of VEGF and its angiogenetic receptor VEGFR2, but not the negative regulator VEGFR1, was significantly higher after ACLR than after APM, indicating a better vasculogenic potential for enhanced bone-graft and meniscus healing. These results could suggest that VEGF and VEGFRs could be considered as good biomarkers of tissue healing after knee joint surgery.     

Inflammatory and healing environment in synovial fluid after anterior cruciate ligament reconstruction: Granulocytes and endogenous opioids as new targets of postoperative pain

BackgroundBiological processes after anterior cruciate ligament reconstruction (ACLR) is crucial for recovery. However, alterations in the of synovial fluid cell population during the acute phase following ACLR and the relationship between these cells and postoperative pain is unclear. The goal of this study was to reveal alterations in synovial fluid cell population during the acute phase following ACLR and relationship between postoperative pain and proportion of synovial fluid cells.MethodsSynovial fluids were obtained from all patients (n = 50) before surgery and from patients who showed hydrarthrosis at days 4 (n = 25), and 21 (n = 42) post-surgery. The cell population was analyzed by flow cytometry. IL1β, IL8, and met-enkephalin in synovial fluid were quantitated by enzyme-linked immunosorbent assay. Patients answered numerical rating scale (NRS) questionnaire at 4 days and approximately 4 weeks postoperatively.ResultsThe granulocyte population was significantly higher at 4 days after surgery than at any other time points. The population of macrophages was 3.2 times and 7.7 times as high as at surgery on days 4 and 21, respectively. T cell population was significantly higher 21 days after surgery compared to 4 days after surgery. All NRS 4 weeks after surgery showed a significant negative correlation with the granulocyte population in synovial fluid 4 days after surgery. Granulocyte population in synovial fluid significantly correlated with the levels of IL1β and IL8. Postoperative pain at rest tended to decrease with an increase in met-enkephalin concentration 4 days after ACLR.ConclusionsSynovial fluid after ACLR had an inflammatory environment at early time points and a healing environment in the subsequent phase about concerning to the cellular composition. A proportion of synovial fluid cells and endogenous opioids affected postoperative pain.     

Association between matrix metalloproteinase-3 polymorphism and anterior cruciate ligament ruptures

Anterior cruciate ligament (ACL) ruptures are considered to be the most severe joint injury in sports. However, the precise etiologies of ACL injuries are not fully understood. Recently, the gene encoding the matrix metalloproteinase-3 (MMP-3, stromelysin-1) was shown to be associated with anterior cruciate ligament ruptures. The 5A/6A polymorphism in the promoter of the MMP-3 gene affects the regulation of MMP-3 gene expression. We examined the association between polymorphism within -1612 of the MMP-3 gene and ACL rupture in an independent population. Eighty-six participants between 20 and 40 years of age with surgically diagnosed ACL ruptures and 100 healthy controls between 18 and 28 years of age without history of ligament or tendon injuries were recruited for the study. All participants were genotyped for the MMP-3 polymorphism (-1612 5A/6A). Statistical analyses of genotype frequencies between patients and healthy controls were performed by the chi-square test. A significant difference was found between ACL rupture subgroups in terms of genotype association (5A+ (5A/5A, 5A/6A): 37.5% in contact sports vs 20% in non-contact sports; P = 0.02). In allelic association, there were significant differences (6A: 81.2% in contact sports vs 89.1% in non-contact sports, 5A: 18.8% in contact sports vs 10.9% in non-contact sports, P = 0.01). The 5A+ genotype of MMP-3 was represented in ACL ruptures in contact sport participants. We propose that this sequence variant is a specific genetic element that should be included in a multifactorial model to understand the etiologies and risk factors for ACL rupture.     

Assessment of standing balance deficits in people who have undergone anterior cruciate ligament reconstruction using traditional and modern analysis methods

Modern methods of assessing standing balance such as wavelet and entropy analysis could provide insight into postural control mechanisms in clinical populations. The aim of this study was to examine what effect anterior cruciate ligament reconstruction (ACLR) has on traditional and modern measures of balance. Ninety subjects, 45 who had undergone ACLR and 45 matched controls, performed single leg static standing balance tests on their surgical or matched limb on a Nintendo Wii Balance Board. Data were analysed in the anterior–posterior axis of movement, which is known to be affected by ACLR. The traditional measures of path velocity, amplitude and standard deviation were calculated in this plane. Additionally, sample entropy and discrete wavelet transform derived assessment of path velocity in four distinct frequency bands related to (1) spinal reflexive loops and muscle activity, (2) cerebellar, (3) vestibular, and (4) visual mechanisms of postural control were derived. The ACLR group had significantly increased values in all traditional measures and all four frequency bands. No significant difference was observed for sample entropy. This indicated that whilst postural sway was amplified in the ACLR group, the overall mechanism used by the patient group to maintain balance was similar to that of the control group. In conclusion, modern methods of signal analysis may provide additional insight into standing balance mechanisms in clinical populations. Future research is required to determine if these results provide important and unique information which is of benefit to clinicians.     

The effect of weightbearing and external loading on anterior cruciate ligament strain

A force balance between the ligaments, articular contact, muscles and body weight maintains knee joint stability. Thus, it is important to study anterior cruciate ligament (ACL) biomechanics, in vivo, under weightbearing conditions. Our objective was to compare the ACL strain response under weightbearing and non-weightbearing conditions and in combination with three externally applied loadings: (1) anterior-posterior shear forces, (2) internal-external torques, and (3) varus-valgus moments. A strain transducer was implanted on the ACL of 11 subjects. All joint loadings were performed with the knee at 20 degrees of flexion. A significant increase in ACL strain was observed as the knee made the transition from non-weightbearing to weightbearing. During anterior shear loading, the strain values produced during weightbearing were greater than those of the non-weightbearing knee (shear loads <40N). At higher shear loads, the strain values became equal. During axial torsion, an internal torque of 10Nm strained the ACL when the knee was non-weightbearing while an equivalent external torque did not. Weightbearing significantly increased ACL strain values in comparison to non-weightbearing with the application of external torques and low internal torques (<3Nm). The strains became equal for higher internal torques. For V-V loading, the ACL was not strained in the non-weightbearing knee. However, weightbearing increased the ACL strain values over the range of moments tested. These data have important clinical ramifications in the development of rehabilitation protocols following ACL reconstruction since weightbearing has been previously thought to provide a protective mechanism to the healing graft.     

Modulation of inflammation by vitamin E and C supplementation prior to anterior cruciate ligament surgery

Muscle atrophy commonly follows anterior cruciate ligament (ACL) injury and surgery. Proinflammatory cytokines can induce and exacerbate oxidative stress, potentiating muscle atrophy. The purpose of this study was to evaluate the influence of prior antioxidant (AO) supplementation on circulating cytokines following ACL surgery. A randomized, double-blind, placebo-controlled trial was conducted in men undergoing ACL surgery, who were randomly assigned to either: (1) AO (200 IU of vitamin E (50% d-alpha-tocopheryl acetate and 50% d-α-tocopherol) and 500 mg ascorbic acid), or (2) matching placebos (PL). Subjects took supplements twice daily for 2 weeks prior to and up to 12 weeks after surgery. Each subject provided five blood samples: (1) baseline (Bsl, prior to supplementation and ～2 weeks prior to surgery), (2) presurgery (Pre), (3) 90 min, (4) 72 h, and (5) 7 days postsurgery. Following surgery, inflammation and muscle damage increased in both groups, as assessed by increased circulating IL-6, C-reactive protein, and creatine kinase. During AO supplementation, plasma α-T and AA increased while γ-T concentrations decreased significantly (P <  0.05). At 90 min the AO group displayed a significant decrease in AA, an inverse correlation between AA and (interleukin) IL-8 (r² =  0.50, P <  0.05), and a significantly lower IL-10 response than that of the PL group. IL-10 was significantly elevated at 90 min and 72 h in the PL group. In summary, our findings show that circulating inflammatory cytokines increase and AO supplementation attenuated the increase in IL-10 in patients post-ACL surgery.