Mary Lloyd Ireland

Impaired Quadriceps Rate of Torque Development and Knee Mechanics After Anterior Cruciate Ligament Reconstruction With Patellar Tendon Autograft

Background: Rate of torque development (RTD) measures the ability of a muscle to produce torque quickly. Decreased quadriceps RTD may impair performance of sporting tasks after surgery. Currently, little is known about variations in quadriceps RTD between anterior cruciate ligament (ACL)–reconstructed and noninjured limbs. Purpose: To determine the differences in RTD of the quadriceps, the rate and timing of knee extensor moment (KEM) development, and knee flexion excursion during running after ACL reconstruction with patellar tendon autograft. Study Design: Cross-sectional study; Level of evidence, 3. Methods: This study involved 21 patients (11 female) 6 months after ACL reconstruction with patellar tendon autograft (median [IQR]: age, 18 [16-20] years; mass, 68.18 [61.34-75] kg; height, 1.74 [1.66-1.78] m). Patients performed four 5-second maximal voluntary isometric strength trials of both limbs on an isokinetic dynamometer. RTD was calculated as the mean slope of the torque-time curve between 20% and 80% of total time to peak torque. Then, patients underwent 3-dimensional motion analysis while running on an instrumented treadmill at a self-selected running speed (mean ± SD, 2.68 ± 0.28 m/s). The rate of knee extensor moment (RKEM) was calculated as the mean slope of the moment curve between 10% and 30% of stance phase. Between-limb comparisons were determined with a paired t test for peak KEM, RKEM, knee flexion excursion during 10% to 30% of stance, and time to generate KEM. Results: In the reconstructed limb, deficits in the peak rate of quadriceps torque development compared with the noninjured limb existed both isometrically (RTD, 257.56 vs 569.11 Nm/s; P < .001) and dynamically (RKEM, 16.47 vs 22.38 Nm/kg·m·s; P < .001). The reconstructed limb also generated a KEM later in the stance phase compared with the noninjured limb (11.37% vs 9.61% stance; P < .001) and underwent less knee flexion excursion (15.5° vs 19.8°; P < .001). Conclusion: After ACL reconstruction with patellar tendon autograft, patients have lower RTD and RKEM in the reconstructed limb. Deviations in RTD and the timing of the KEM can change the way the knee is loaded and can potentially increase injury risk and future development of posttraumatic osteoarthritis. Rehabilitation should consider exercises designed to improve RTD and prepare the limb for the demands of sport performance.

Evaluation of proximal joint kinematics and muscle strength following ACL reconstruction surgery in female athletes.

Despite the intense focus on outcomes following an anterior cruciate ligament (ACL) reconstruction, it is not yet known whether unresolved abnormal hip and trunk neuromuscular control exists. The purpose of this study was to compare trunk and hip kinematics during running, hip abductor and external rotator strength, and trunk control between females who had undergone an ACL reconstruction and healthy control participants. We compared 20 ACL reconstructed females to 20 healthy individuals, measuring abduction and external rotation strength, a trunk control test, and performed an instrumented gait evaluation during running. Comparisons between groups were made for non‐sagittal peak hip angles, forward trunk lean, trunk ipsilateral lean at initial contact, trunk control and hip abduction, and external rotation strength. We found no significant differences in hip abduction (pu2009=u20090.25), hip external rotation strength (pu2009=u20090.63), peak hip adduction (pu2009=u20090.11) or hip internal rotation angle (pu2009=u20090.47). The ACL group did have a significantly greater ipsilateral trunk lean (pu2009=u20090.028), forward lean (pu2009=u20090.004), and had higher errors on the trunk stability test (pu2009=u20090.007). We found significant differences in trunk control, suggesting further attention should be devoted to this component of rehabilitation.

Cellular and Morphological Alterations in the Vastus Lateralis Muscle as the Result of Acl Injury and Reconstruction

BACKGROUNDnIndividuals who have had an anterior cruciate ligament (ACL) tear and reconstruction continue to experience substantial knee extensor strength loss despite months of physical therapy. Identification of the alterations in muscle morphology and cellular composition are needed to understand potential mechanisms of muscle strength loss, initially as the result of the injury and subsequently from surgery and rehabilitation.nnnMETHODSnWe performed diffusion tensor imaging-magnetic resonance imaging and analyzed muscle biopsies from the vastus lateralis of both the affected and unaffected limbs before surgery and again from the reconstructed limb following the completion of rehabilitation. Immunohistochemistry was done to determine fiber type and size, Pax-7-positive (satellite) cells, and extracellular matrix (via wheat germ agglutinin straining). Using the diffusion tensor imaging data, the fiber tract length, pennation angle, and muscle volume were determined, yielding the physiological cross-sectional area (PCSA). Paired t tests were used to compare the effects of the injury between injured and uninjured limbs and the effects of surgery and rehabilitation within the injured limb.nnnRESULTSnWe found significant reductions before surgery in type-IIA muscle cross-sectional area (CSA; p = 0.03), extracellular matrix (p < 0.01), satellite cells per fiber (p < 0.01), pennation angle (p = 0.03), muscle volume (p = 0.02), and PCSA (p = 0.03) in the injured limb compared with the uninjured limb. Following surgery, these alterations in the injured limb persisted and the frequency of the IIA fiber type decreased significantly (p < 0.01) and that of the IIA/X hybrid fiber type increased significantly (p < 0.01).nnnCONCLUSIONSnSignificant and prolonged differences in muscle quality and morphology occurred after ACL injury and persisted despite reconstruction and extensive physical therapy.nnnCLINICAL RELEVANCEnThese results suggest the need to develop more effective early interventions following an ACL tear to prevent deleterious alterations within the quadriceps.

Relationship of Hip and Trunk Muscle Function with Single Leg Step-Down Performance: Implications for Return to Play Screening and Rehabilitation

OBJECTIVESnEvaluate the relationship of hip and trunk muscle function with the Single Leg Step-Down test (SLSD).nnnSTUDY DESIGNnLaboratory study.nnnSETTINGnBiomechanics Laboratory.nnnPARTICIPANTSn71 healthy participants with no history of anterior cruciate ligament (ACL) or lower extremity injury in the last 3 months completed this study (38 males, 33 females; mean 25.49xa0±xa00.62 years).nnnMAIN OUTCOMESnHip abduction (HABD), external rotation (HER), and extension (HEXT) peak isometric force were measured. Trunk endurance was measured with plank (PL) and side plank (SPL) tests. SLSD repetitions in 60-sxa0and dynamic knee valgus (VAL) were recorded.nnnRESULTSnPL, SPL, HABD, HER, and HEXT were positively correlated with SLSD repetitions. PL (rxa0=xa00.598, pxa0<xa00.001) was most correlated with SLSD repetitions, and regression demonstrated that PL (pxa0=xa00.001, R2xa0=xa00.469) was a predictor of SLSD repetitions. VAL trended toward negative correlation with PL and SPL. Sex-specific differences were present, with PL, SPL, HABD, and HER showing stronger relationships with SLSD in females.nnnCONCLUSIONnHip and trunk muscle function were positively correlated with SLSD performance, and these relationships were strongest in females. PL predicted performance on the SLSD. Further research is needed to investigate the utility of SLSD as a screening or return-to-play test for lower extremity conditions such as ACL injury and patellofemoral pain.

Anatomic Femoral and Tibial Tunnel Placement During Anterior Cruciate Ligament Reconstruction: Anteromedial Portal All-Inside and Outside-In Techniques

Tunnel malposition is one of the most common technical reasons for anterior cruciate ligament reconstruction failure. Small changes in tunnel placement can result in significant differences in outcome. More anatomic placement of the tunnels can lead to greater knee stability and a more accurate reproduction of native knee kinematics. This Technical Note describes 2 tibial tunnel-independent methods to obtain anatomic femoral tunnel placement. The all-inside anteromedial portal technique requires only minimal surgical incisions but allows precise femoral tunnel placement. However, hyperflexion of the knee is required, adequate surgical assistance is necessary, and this technique may be susceptible to graft-tunnel mismatch. The outside-in technique may be more beneficial in obese patients, skeletally immature patients, or revision cases. On the downside, it does require an additional 2-cm surgical incision. This article also provides surgical pearls to fine-tune tibial tunnel placement.

Gender Differences in Core Strength and Lower Extremity Function During the Single-Leg Squat Test

This chapter discusses the principles of core stability in terms of its importance on lower extremity function. The use of the single-leg squat test to measure core stability is described, which is a practical tool that can easily be used in the clinical setting. The test protocol and methods for interpretation of the results are provided. Reliability and validity data are cited. Associations between core strength, neuromuscular activity, and lower extremity function during the test are described. Differences in core strength, lower limb position, and posture between male and female subjects depicted by the single-leg squat are summarized.

Hip external rotation strength predicts hop performance after anterior cruciate ligament reconstruction

PurposeQuadriceps strength and single-leg hop performance are commonly evaluated prior to return to sport after anterior cruciate ligament reconstruction (ACLR). However, few studies have documented potential hip strength deficits after ACLR, or ascertained the relative contribution of quadriceps and hip strength to hop performance.MethodsPatients cleared for return to sports drills after ACLR were compared to a control group. Participants’ peak isometric knee extension, hip abduction, hip extension, and hip external rotation (HER) strength were measured. Participants also performed single-leg hops, timed hops, triple hops, and crossover hops. Between-limb comparisons for the ACLR to control limb and the non-operative limb were made using independent two-sample and paired sample t tests. Pearson’s correlations and stepwise multiple linear regression were used to determine the relationships and predictive ability of limb strength, graft type, sex, and limb dominance to hop performance.ResultsSixty-five subjects, 20 ACLR [11F, age 22.8 (15–45) years, 8.3xa0±xa02xa0months post-op, mass 70.47xa0±xa012.95xa0kg, height 1.71xa0±xa00.08xa0m, Tegner 5.5 (3–9)] and 45 controls [22F, age 25.8 (15–45) years, mass 74.0xa0±xa015.2xa0kg, height 1.74xa0±xa00.1xa0m, Tegner 6 (3–7)], were tested. Knee extension (4.4xa0±xa01.5 vs 5.4xa0±xa01.8xa0N/kg, pxa0=xa00.02), HER (1.4xa0±xa00.4 vs 1.7xa0±xa00.5xa0N/kg, pxa0=xa00.04), single-leg hop (146xa0±xa037 vs 182xa0±xa038% limb length, pxa0<xa00.01), triple hop (417xa0±xa0106 vs 519xa0±xa0102% limb length, pxa0<xa00.01), timed hop (3.3xa0±xa02.0 vs 2.3xa0±xa00.6xa0s, pxa0<xa00.01), and crossover hop (364xa0±xa0107 vs 446xa0±xa0123% limb length, pxa0=xa00.01) were significantly impaired in the operative versus control subject limbs. Similar deficits existed between the operative and non-operative limbs. Knee extension and HER strength were significantly correlated with each of the hop tests, but only HER significantly predicted hop performance.ConclusionsAfter ACLR, patients have persistent HER strength, knee extension strength, and hop test deficits in the operative limb compared to the control and non-operative limbs, even after starting sport-specific drills. Importantly, HER strength independently predicted hop performance. Based on these findings, to resolve between-limb deficits in strength and hop performance clinicians should include HER strengthening exercises in post-operative rehabilitation.Level of evidencePrognostic Study, Level II.

ACL injury reduces satellite cell abundance and promotes fibrogenic cell expansion within skeletal muscle

Anterior cruciate ligament (ACL) injuries are associated with significant loss of strength in knee extensor muscles that persists despite physical therapy. The underlying mechanisms responsible for this protracted muscle weakness are poorly understood; however, we recently showed significant myofiber atrophy and altered muscle phenotype following ACL injury. We sought to further explore perturbations in skeletal muscle morphology and progenitor cell activity following an ACL injury. Muscle biopsies were obtained from the injured and non‐injured vastus lateralis of young adults (nu2009=u200910) following ACL injury, and histochemical/immunohistochemical analyses were undertaken to determine collagen content, abundance of connective tissue fibroblasts, fibrogenic/adipogenic progenitor (FAP) cells, satellite cells, in addition to indices of muscle fiber denervation and myonuclear apoptosis. The injured limb showed elevated collagen content (pu2009<u20090.05), in addition to a greater abundance of fibroblasts and FAPs (pu2009<u20090.05) in the injured limb. Fibroblast content was correlated with increased accumulation of extracellular matrix in the injured limb as well. A higher frequency of interstitial nuclei were positive for phospho‐SMAD3 in the injured limb (pu2009<u20090.05), providing some evidence for activation of a fibrogenic program through transforming growth factor β following an ACL injury. The injured limb also displayed reduced satellite cell abundance, increased fiber denervation and DNA damage associated with apoptosis (pu2009<u20090.05), indicating alterations within the muscle itself after the ligament injury. Injury of the ACL induces a myriad of negative outcomes within knee extensor muscles, which likely compromise the restorative capacity and plasticity of skeletal muscle, impeding rehabilitative efforts.

Gender Differences in Core Strength and Lower Extremity Function During Static and Dynamic Single-Leg Squat Tests

This chapter discusses the principles of core strength and stability with regard to noncontact ACL injury. The single-leg squat test is described as a useful clinical tool to determine core stability. Associations between core strength, neuromuscular activity, and lower extremity function during this test are detailed. In addition, a newer dynamic single-leg squat test is described. These assessment tools are recommended to determine impairments, prescribe individualized interventions, and assess those athletes who may benefit from an ACL injury prevention training program.

Neuromuscular compensatory strategies at the trunk and lower limb are not resolved following an ACL reconstruction

BACKGROUNDnFollowing anterior cruciate ligament reconstruction (ACLR), patients present with greater trunk ipsilateral lean, which may affect knee kinetics and increase re-injury risk. However, there has been little research into neuromuscular factors controlling the trunk and their relation to the knee between healthy and ACLR subjects. This is critical to establish in order to develop more directed and effective interventions.nnnHYPOTHESISnAs compared to healthy control subjects, ACLR subjects will demonstrate increased erector spinae and rectus abdominis co-contraction, greater rectus abdominis force and greater hamstring force that is correlated to increased forward trunk lean.nnnSTUDY DESIGNnCross-sectional study, Level of Evidence: 3.nnnMETHODSnEleven healthy and eleven ACLR subjects were matched for age, mass and height. Subjects were asked to run at a self-selected speed while instrumented gait analysis was performed. An anthropometrically scaled OpenSim model was created for each subject. Trunk and hamstring muscle forces from Static Optimization were analyzed at impact peak. Additionally, directed co-contraction ratios were calculated for the erector spinae and erector spinae/rectus abdominis combinations.nnnRESULTSnACLR subjects showed more balanced erector spinae co-contraction [p<0.01], and greater hamstring force [biceps femoris long head (p=0.02), semimembranosus (0.01), semitendinosus (0.01)]. There was no statistical difference for any other muscle group.nnnCONCLUSIONnDespite release to return to sport, ACLR subjects are continuing to increase the stiffness of their trunk as well increase their hamstring force to potentially reduce anterior tibial translation.nnnCLINICAL RELEVANCEnClinicians may anticipate ACLR subjects using their erector spinae and hamstrings to maintain a sense of stability in their trunk and at their knee.