Compensatory mechanisms in anterior cruciate ligament deficiency

The literature cites numerous studies involving the analysis of movement patterns in anterior cruciate ligament deficient (ACLD) patients. Although several in vivo biomechanical studies have shown that ACLD patients develop protective mechanisms against degenerative diseases, it seems that these adaptations fail to protect the knee from future pathology. Some authors state that ACLD patients adapt to the injury by avoiding quadriceps contraction during gait when the knee is near full extension. However, others have found increased hamstrings and decreased gastrocnemius activity, which normally contribute to the stability of the knee. It seems that further in vivo biomechanical investigation is required to understand the mechanisms of pathological knee joint motions and develop rehabilitation programs, which would delay the progress of developing long-term degenerative diseases.     

Central quadriceps free tendon for anterior cruciate ligament reconstruction

Central quadriceps free tendon provides an outstanding autograft alternative for routine anterior cruciate ligament (ACL) reconstruction, allowing preservation of hamstring tendons and eliminating the morbidity of bone plug harvest from the patella. Correct graft harvest technique, proper tunnel/graft sizing, accurate fixation, and adherence to the methods described will permit excellent ACL reconstruction with low morbidity.     

Impaired voluntary quadriceps force control following anterior cruciate ligament reconstruction: relationship with knee function

Purpose

Impairments in quadriceps force control and altered quadriceps and hamstring muscle activation strategies have been observed following anterior cruciate ligament reconstruction; however, the functional implications of these impairments are unclear. This study examined the cross-sectional associations between quadriceps force control, quadriceps activation, hamstring coactivation and clinically assessed knee function following anterior cruciate ligament reconstruction with a hamstring graft.

Methods

Sixty-six patients (18 ± 3 months following surgery) and 41 uninjured individuals participated. Quadriceps force control was assessed using an isometric knee extension task. Participants cyclically increased and decreased quadriceps force at slow speeds between 5 and 30 % maximum voluntary isometric contraction matching a moving target displayed on a screen. Quadriceps activation and hamstring coactivation were assessed concurrently using surface electromyography. Knee function was assessed with the Cincinnati Knee Rating Scale and three single-leg hop tests.

Results

The reconstructed group completed the task with 48 % greater root-mean-square error (RMSE), indicating significantly worse quadriceps force control (p < 0.001). In a multivariable model adjusted for sex, greater RMSE and greater lateral hamstring coactivation were significantly associated with worse knee function that is greater odds of scoring <85 % on one or more knee functional assessment.

Conclusions

Less-accurate quadriceps force output and greater hamstring coactivation are associated with worse knee joint function following anterior cruciate ligament reconstruction and may contribute to irregular knee joint loading and the onset or progression of knee osteoarthritis. Impairments in quadriceps force control and altered muscle activation strategies may be modifiable through neuromuscular training, and this is an area for future research.

Level of evidence

Case–control study, Level III.

     

Response of hamstring muscles to a perturbation in people with chronic anterior cruciate ligament deficiency

A number of strength parameters were investigated in a group of subjects with chronic anterior cruciate ligament deficiency; The response of subjects' hamstring muscles to a perturbation on an isokinetic dynamometer was fractionated into the premotor and motor times. Rate of force development in the 75 ms following the perturbation was also measured. The functional ability of the subjects was examined using the Noyes knee rating system. The results showed that the motor time was significantly correlated with the rate of force development and functional ability of the subjects. The ratio of hamstring to quadriceps torque recorded at peak and 30° flexion during isokinetic muscle work at 180°/s was also investigated. No significant relationship was observed between these ratios and functional ability. These findings indicate that factors other than peak hamstring muscle torque may be important to the level of functional ability attained by people with chronic anterior cruciate ligament deficiency.     

Long-term followup of anterior cruciate ligament reconstruction using the quadriceps tendon substitution for chronic anterior cruciate ligament insufficiency

At The Hospital for Special Surgery, the quadriceps tendon substitution (QTS), as described by Marshall, was performed for ACL insufficiency from 1973 to 1980. A review of the initial 60 patients with a minimum of 4 years followup (average, 5.5 years) has been concluded. Thirty-eight patients returned for examinations, and 11 returned questionnaires. Associated medial procedures were performed in 29 of the 38 examined patients. Medial meniscus surgery was performed in 86% and lateral meniscus surgery in 28.9%. At followup, giving way, which was the main preoperative complaint, was eliminated in 30/38 examined and 9/11 questionnaire patients (79%). In the examined group, three patients were clear failures and five had mild transient instability. The pivot shift was present in 17 of 38 (45%) patients examined: 21 patients were negative, 9 were 1+ or a grind, 8 were 2+, and none were 3+. We have concluded that the QTS procedure will eliminate symptomatic instability in 79% of our patients, but the high rate of a residual pivot shift (45%) and symptoms of instability (21%) require the addition of an extraarticular sling procedure. This appears to be related to the relatively poor strength characteristics of the tissue used in the QTS substitution.     

Aggressive quadriceps loading can induce noncontact anterior cruciate ligament injury

BACKGROUND: The force responsible for noncontact anterior cruciate ligament (ACL) injuries remains controversial. The patella tendon to tibial shaft angle causes an anterior tibial shear force with quadriceps activation. HYPOTHESIS: An aggressive quadriceps contraction can injure the ACL. METHODS: The authors characterized noncontact ACL injury and kinematics with aggressive quadriceps loading. Thirteen fresh-frozen knees were potted in a jig held in 20 degrees of flexion while a 4500 N quadriceps contraction was simulated. Knee kinematics were recorded. A KT-1000 arthrometer and a simulated active quadriceps test assessed anterior displacement. Statistics were performed using paired t tests and 1-way analysis of variance. RESULTS: Kinematics revealed the following mean values: anterior displacement, 19.5 mm; valgus, 2.3 degrees; and internal rotation, 5.5 degrees. Mean KT-1000 and active quadriceps test differences were 4.0 mm and 2.7 mm, respectively (statistically significant P =.002 and P =.002). Six knees showed gross ACL injury at the femoral insertion. Based on ACL injury, KT-1000 differences were statistically significant (P =.029). CONCLUSIONS: Aggressive quadriceps loading, with the knee in slight flexion, produces significant anterior tibial translation and ACL injury. This suggests that the quadriceps is the intrinsic force in noncontact ACL injuries, producing a model for further investigation.     

Possible mechanism of quadriceps femoris weakness in patients with ruptured anterior cruciate ligament

PURPOSE: The purpose of this study was to test the hypothesis that loss of afferent feedback due to rupture of anterior cruciate ligament (ACL) is the cause of quadriceps femoris (QF) weakness through gamma loop. Two experiments were designed to prove our hypothesis. METHODS: In experiment 1, the maximal voluntary contraction (MVC) of knee extension and integrated electromyogram (I-EMG) of vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) were measured in 13 patients with ruptured ACL and 7 healthy volunteers before and after injection of anesthetic agent into the knee. In experiment 2, MVC of knee extension and I-EMG of the VM, VL, and RF were measured in 13 patients with ruptured ACL, 7 knee-anesthetized healthy subjects, and 12 normal subjects, before and after 20-min vibration stimulation applied to the infrapatellar tendon. RESULTS: The results of experiment 1 revealed that injection of anesthetic agent into the knee capsule resulted in significant decrease of MVC and I-EMGs. In experiment 2, the mean percentage change of MVC in the control group was significantly lower than that in the other two groups. There was no significant difference between knee-anesthetized group and patients with ruptured ACL. The mean percentage change of I-EMG showed a pattern similar to that of MVC. CONCLUSION: Our results suggest that loss of feedback from mechanoreceptors in ACL is the underlying mechanism of weakness of QF in patients with ACL lesion. This conclusion is based on chronic suppression of recruitment of high-threshold motor units during voluntary contraction because ACL lesion leads to chronic reduction in Ia-feedback to muscles around the knee due to a lack of feedback from ACL to gamma motor neurons.     

Mechanism of quadriceps femoris muscle weakness in patients with anterior cruciate ligament reconstruction

The purpose of this study was to investigate gamma loop function in the quadriceps femoris muscle in patients who with less than 6 month-history of anterior cruciate ligament (ACL) reconstruction. For this purpose, we compared the response to vibration stimulation in 10 patients with ACL repair and 12 normal healthy subjects, by measuring the maximal voluntary isometric contraction (MVC) and integrated electromyograms (I-EMG) of the quadriceps muscles. Pre-vibration data were obtained from each subject by measuring the MVC of the knee extension and the I-EMG from the vastus medialis, vastus lateralis, and rectus femoris muscles. Vibration stimulation was applied to the infrapatellar tendons, followed immediately by repeating the MVC and I-EMG recording. Prolonged vibration resulted in a significant decrease of both MVC and I-EMG in the control group. In contrast, the same stimulus failed to elicit changes in ACL-repair group. Our results suggest the presence of abnormal gamma loop function in the quadriceps femoris muscle of patients with ACL repair, which may explain the muscle weakness often described in such patients.     

The effects of dual-tasking on postural control in people with unilateral anterior cruciate ligament injury

Several studies have investigated postural control in anterior cruciate ligament (ACL) deficient patients; yet the contribution of cognitive processing (attention) in the postural control of these patients is still unclear. A dual-task design was used to determine the effects of a concurrent digit span memory task on standing balance in a group of ACL patients (n = 27) compared with a group of matched, healthy participants (n = 27). In double limb stance, three levels of postural difficulty were studies on a force platform (rigid surface with eyes open, rigid surface with eyes closed, and foam surface with eyes closed). There were three cognitive conditions (no cognitive task, easy cognitive task and difficult cognitive task). For double limb stance, a mixed model analysis of variance showed that in the presence of a cognitive task, postural control was compromised yet there was no interaction between cognitive task difficulty and group (ACL or control). For single limb stance, the more difficult cognitive tasks were associated with lower standard deviations for velocity in the antero-posterior direction and the phase plane portraits. This cognitive task did not appear to compromise postural control in ACL injured patients to a greater extent than unimpaired people. Future studies should examine ACL patients with more severe disabilities and expose them to more demanding dynamic balance conditions to further explore dual-tasking effects.     

The effects of dual-tasking on postural control in people with unilateral anterior cruciate ligament injury

Several studies have investigated postural control in anterior cruciate ligament (ACL) deficient patients; yet the contribution of cognitive processing (attention) in the postural control of these patients is still unclear. A dual-task design was used to determine the effects of a concurrent digit span memory task on standing balance in a group of ACL patients (n = 27) compared with a group of matched, healthy participants (n = 27). In double limb stance, three levels of postural difficulty were studies on a force platform (rigid surface with eyes open, rigid surface with eyes closed, and foam surface with eyes closed). There were three cognitive conditions (no cognitive task, easy cognitive task and difficult cognitive task). For double limb stance, a mixed model analysis of variance showed that in the presence of a cognitive task, postural control was compromised yet there was no interaction between cognitive task difficulty and group (ACL or control). For single limb stance, the more difficult cognitive tasks were associated with lower standard deviations for velocity in the antero-posterior direction and the phase plane portraits. This cognitive task did not appear to compromise postural control in ACL injured patients to a greater extent than unimpaired people. Future studies should examine ACL patients with more severe disabilities and expose them to more demanding dynamic balance conditions to further explore dual-tasking effects.     

MR evaluation of anterior cruciate ligament reconstruction with quadriceps tendon. Preliminary experience

PURPOSE: Anterior cruciate ligament reconstructions are becoming increasingly frequent, and MRI has been shown to be the best imaging modality for the non-invasive assessment of surgical outcome. Use of the quadriceps tendon as a biological replacement for injured cruciate ligament is a recent innovation. This study evaluated by MRI the results of anterior cruciate reconstruction in 27 consecutive patients who underwent arthroscopic reconstruction with homologous quadriceps tendon. MATERIAL AND METHODS: MRI was carried out on 27 patients who had undergone anterior cruciate ligament reconstruction with the middle third of the homolateral quadriceps tendon. The examinations were performed on two MRI units: a permanent 0.2-Tesla dedicated magnet (Artoscan, Esaote Italy) and whole-body 1.5-Tesla superconducting magnet (Signa, GE Medical Systems Milwaukee, Winsconsin USA). Axial, sagittal and coronal images were acquired with SE, GE and STIR fat suppression sequences. The examinations were performed 1, 3, and 6 months post-operatively in 16 patients, and 1 and 3 post-operatively in 11 patients. The same arthroscopic surgical technique was employed in all patients, with 20 cases of tibial mono-tunnel femoral semi-tunnel, and 7 cases with tibial bi-tunnel technique. All patients were assessed by arthrometric and clinical tests after surgery. Bioabsorbable interference screws were used for tibial fixation in all patients and metallic interference screws were used for femoral graft fixation in 8 patients. RESULTS: In all cases MRI correctly visualised the tunnel positions, the articular portion and the bone-portion of the graft inside the tibial and femoral tunnels. The absence of paramagnetic artefacts in the tibia allowed complete visualisation on the axial, sagittal and coronal MRI images with optimal spatial and contrast resolutions. In 6 cases, the presence of metal residues from the surgical cutter prevented correct evaluation of femoral tunnel content. No new graft or articular lesions were found. In 18/27 cases peri-focal marrow edema around the tibial tunnel had disappeared 3 months after surgery. The process of synovial incorporation was judged to be correct in all cases. DISCUSSION: The use of anterior cruciate ligament reconstruction with the quadriceps tendon is a important innovation given the size of the harvested material and the possibility of completely filling the osseous tunnels, without interposition of synovial proliferation or fluid collection between tendon and bone, as confirmed by MRI. Furthermore, the use of non-metallic screws allows MRI evaluation of tunnel content and oedema in the spongy bone around the tunnel. The study of the double tibial tunnel requires specific obliqueness in the coronal plane scans. CONCLUSIONS: This arthroscopic technique for anterior cruciate ligament reconstruction allows thorough MRI evaluation of all portions of the transplant, and in particular those coursing within the tibia and femur. The absence of bone oedema around the tunnels and synovial proliferation within the tunnels may be predictive of faster healing and complete bone incorporation of the grafts.     

Strain within the anterior cruciate ligament during hamstring and quadriceps activity

The objectives of this study were to measure strain in the ACL during simulated: hamstring activity alone, quadriceps activity alone, and simultaneous quadriceps and hamstring activity. Seven knee specimens removed from cadavers were studied. Heavy sutures applied to load cells were attached to the hamstring and quadriceps tendons. Loads were then applied manually (hamstrings) and/or with an Instron testing machine (quadriceps) to simulate isometric contractions of the various muscle groups. Strain was measured using a Hall effect transducer. Acting alone, the isometric hamstring activity decreased ACL strain relative to the passive normal strain at all positions tested. Thus, hamstring exercises are not detrimental to ACL repairs or reconstruction and can be included early in the rehabilitation program after ACL surgery. Acting alone, at flexion angles of 0 degree to 45 degrees, the quadriceps significantly increased the strain within the ACL relative to the passive normal strain. Strain in the ACL during simultaneous hamstring and quadriceps activity was significantly higher than that during passive normal motion from full extension to 30 degrees of flexion. The hamstrings are not capable of masking the potentially harmful effects of simultaneous quadriceps contraction on freshly repaired or reconstructed ACLs unless the knee flexion angle exceeds 30 degrees.     

Electromyographic predictors of residual quadriceps muscle weakness after anterior cruciate ligament reconstruction

BACKGROUND: Despite the high prevalence of residual quadriceps muscle weakness after anterior cruciate ligament reconstruction, specific predictive factors have not been identified. HYPOTHESIS: Electromyographic analysis is a better predictor of residual muscle weakness than is preoperative strength. STUDY DESIGN: Prospective cohort study. METHODS: The quadriceps muscle strength of 37 patients (25 men, 12 women) was measured before reconstruction and 5 weeks and 6 months after surgery. Quadriceps surface electromyographic signals were recorded during all of the strength tests. Integrated electromyographic analysis and median frequency measurements were computed as deficits on the involved side. Patients also performed a single-legged hop test at the 6-month follow-up examination. RESULTS: The patients had significantly lower strength, integrated electromyographic analysis, and median frequency measurements on the involved side at all three time intervals. The best predictor of the quadriceps muscle strength deficit at 6 months was the combination of the preoperative median frequency deficit and the 5-week postoperative strength deficit. The best predictor of the hop test deficit at 6 months was the combination of preoperative deficits in integrated electromyographic analysis and median frequency. CONCLUSION: Preoperative electromyographic indices of quadriceps muscle function and early postoperative strength were predictive of residual weakness and impaired function 6 months after reconstruction.     

A deficient anterior cruciate ligament does not lead to quadriceps avoidance gait

Without an intact anterior cruciate ligament (ACL) to resist anterior tibial translation, it is commonly believed that ACL-deficient patients employ alterations in walking. Although there is no consensus in the literature about the specific kinematic and kinetic adaptations in these patients with ACL tears, the gait adaptation of quadriceps avoidance is perhaps the one most popularized. The purpose of our study was to determine whether quadriceps avoidance is common in patients with ACL-deficiency. We used a video-based motion analysis system and surface electromyography (EMG) to study 18 patients with ACL-deficiency. All patients demonstrated an internal knee extension moment during early mid-stance (similar to normal subjects). Quadriceps EMG activity was noted throughout most of stance. No patients demonstrated an internal knee flexion moment, a decreased internal knee extension moment or a decreased duration of quadriceps EMG activity during stance. The findings of this study would suggest that quadriceps avoidance as a gait adaptation in ACL-deficient patients may be less common than previously reported.     

Knee extensors kinetic chain training in anterior cruciate ligament deficiency

Open kinetic chain (OKC) knee extensor resistance training has lost favour in rehabilitation of patients with knee ACLD due to concerns that this exercise is harmful to the remaining portion of the ACL and its secondary stabilizers, and will be less effective in improving function. In this randomized, single-blind clinical trial, closed and OKC knee extensor training were compared for their effects on knee laxity and function in patients with ACLD knees. Sixty-four patients with a diagnosis of knee ACLD (49 M, 15 F; mean age=30 years) were measured for knee laxity, using a ligament arthrometer, and function with the Hughston Clinic knee self-assessment questionnaire and maximal effort single leg jump testing. Between the above tests and identical tests carried out 6 weeks later, subjects trained using either open or closed kinetic chain resistance of their knee and hip extensors as part of formal physical therapy sessions three times per week for 6 weeks. The groups exhibited no statistically significant differences (p<0.083) in outcome. These results indicate that knee extensor OKC training, as used in this study, can be safely applied to patients with knee ACL deficiency, and shows no superiority to CKC training.     

Altered timing of hamstring muscle action in anterior cruciate ligament deficient patients

Recent studies indicate that the hamstrings are essential antagonists in ACL deficient patients. In order to evaluate muscle coordination under physiologic conditions, nine patients with arthroscopically verified total ACL ruptures were compared with nine control volunteers. This comparison was made from electromyograms of the thigh muscles and heel contact recordings made while walking on a treadmill. While walking on a horizontal level, the patient's muscle activity did not differ from controls, but when the knee load was increased by walking uphill, the hamstring muscles in patients were activated significantly earlier than among controls. It is proposed that an altered muscle coordination is probably essential in ACL deficient patients to secure knee stability. This study suggests a new approach to investigate the coordination of muscles under physiologic conditions in ACL deficient patients, and may guide rehabilitation programs in the future.     

Isokinetic evaluation of anterior cruciate ligament reconstruction: quadriceps tendon versus patellar tendon

AIM: The goal of this prospective randomized study was to compare the isokinetic recovery of thigh strength after anterior cruciate ligament (ACL) reconstruction by using patellar or quadriceps tendon as graft at the 6th month follow-up. METHODS: The authors evaluated 48 patients who underwent arthroscopic ACL reconstruction using patellar tendon (PT group) or quadriceps tendon (QT group) as autograft after a 6 months follow-up undergoing the following tests: the Ergojump Bosco System springboard and Universal's FITNET computerized isokinetic system. RESULTS: The counter movement jump (CMJ) test showed a 24% (p<0.01) strength deficit in patients operated with patellar tendon and 11% in the quadriceps tendon group. Also in the leg press test the greater differences in strength (p<0.05) were verified in the patellar tendon group, above all the peak torque (PT) test carried out at 3 repetitions (15%). CONCLUSIONS: The strength deficit found in the subjects operated with quadriceps tendon were statistically lower in comparison to that verified in the patellar tendon group. A good recovery in thigh strength after 6 months in patients operated with quadriceps tendon could encourage the use of this kind of graft in order to achieve an easier rehabilitation and a faster release of the patient to daily and sports activity.     

Mechanisms of compensating for anterior cruciate ligament deficiency during gait

INTRODUCTION: The quadriceps avoidance gait pattern may not be as common in ACL deficient (ACLd) gait as previously described. PURPOSE: The purpose of this study was to investigate the existence of the quadriceps avoidance pattern in ACL deficient patients and to further identify gait compensations that may exist in this subject pool. METHODS: In the present study, hip, knee, and ankle gait kinematics, and kinetics and thigh EMG profiles were recorded and compared for 16 ACLd and 8 control subjects. RESULTS: The quadriceps avoidance gait pattern was not observed for any of the subjects. Hip, knee, and ankle kinematics and kinetics were not different between groups. However, nine ACLd subjects (group A) demonstrated a normal biphasic knee moment pattern, whereas seven (group B) demonstrated an all knee extensor pattern. This indicates different adaptive mechanisms may be present in ACLd gait. Group A exhibited a hip strategy that increased hip extensor output, decreased knee extensor output, and allowed normal knee kinematics. Group B demonstrated a knee strategy that increased the stiffness of the joint and utilized a flexed knee gait. CONCLUSION: The prevalence of multiple adaptive strategies to compensate for ACL deficiency has several important ramifications. First, an ACLd subject pool with mixed compensating strategies may deter the identification of specific coping mechanisms and account for the confounding results in the literature. Second, the importance of the hip extensors should not be overlooked when studying this population.     

Relationship between quadriceps femoris muscle volume and muscle torque after anterior cruciate ligament repair

This study was performed to obtain evidence regarding bilateral hindrance of motor unit (MU) recruitment in the quadriceps femoris (QF) of patients with anterior cruciate ligament (ACL) reconstruction. The subjects included 70 patients who underwent ACL reconstruction and 35 healthy subjects. To identify the muscle torque per unit volume (MTPUV), the peak torque of each velocity of isokinetic performance was divided by muscle volume of the QF measured by a series of cross-sectional images obtained by magnetic resonance imaging scans. Tests revealed that the mean MTPUV of the uninjured (0.113+/-0.03 N m/cm3 at 60 degrees /s, 0.081+/-0.02 N m/cm3 at 180 degrees /s) and injured sides (0.109+/-0.03 N m/cm3 at 60 degrees /s, 0.079+/-0.023 N m/cm3 at 180 degrees /s) were significantly lower than those of the control group (0.144+/-0.05 N m/cm3 at 60 degrees /s, 0.096+/-0.04 N m/cm3 at 180 degrees /s). Previous studies suggested that MU recruitment in the QF of patients with ACL injury was hindered bilaterally. However, the design of their studies could not provide evidence of bilateral hindrance of MU recruitment in the QF. The results of the present study demonstrated that the MTPUV of both injured and uninjured sides of patients were significantly lower than those of the control group.