Abbey C. Thomas

Lower Extremity Muscle Strength After Anterior Cruciate Ligament Injury and Reconstruction

CONTEXT Quadriceps and hamstrings weakness occurs frequently after anterior cruciate ligament (ACL) injury and reconstruction. Evidence suggests that knee injury may precipitate hip and ankle muscle weakness, but few data support this contention after ACL injury and reconstruction. OBJECTIVE To determine if hip, knee, and ankle muscle weakness present after ACL injury and after rehabilitation for ACL reconstruction. DESIGN Case-control study. SETTING University research laboratory. PATIENTS OR OTHER PARTICIPANTS Fifteen individuals with ACL injury (8 males, 7 females; age = 20.27 ± 5.38 years, height = 1.75 ± 0.10 m, mass = 74.39 ± 13.26 kg) and 15 control individuals (7 men, 8 women; age = 24.73 ± 3.37 years, height = 1.75 ± 0.09 m, mass = 73.25 ± 13.48 kg). INTERVENTION(S) Bilateral concentric strength was assessed at 60°/s on an isokinetic dynamometer. The participants with ACL injury were tested preoperatively and 6 months postoperatively. Control participants were tested on 1 occasion. MAIN OUTCOME MEASURES Hip-flexor, -extensor, -abductor, and -adductor; knee-extensor and -flexor; and ankle-plantar-flexor and -dorsiflexor strength (Nm/kg). RESULTS The ACL-injured participants demonstrated greater hip-extensor (percentage difference = 19.7, F1,14 = 7.28, P = .02) and -adductor (percentage difference = 16.3, F1,14 = 6.15, P = .03) weakness preoperatively than postoperatively, regardless of limb, and greater postoperative hip-adductor strength (percentage difference = 29.0, F1,28 = 10.66, P = .003) than control participants. Knee-extensor and -flexor strength were lower in the injured than in the uninjured limb preoperatively and postoperatively (extensor percentage difference = 34.6 preoperatively and 32.6 postoperatively, t14 range = -4.59 to -4.23, P ≤ .001; flexor percentage difference = 30.6 preoperatively and 10.6 postoperatively, t14 range = -6.05 to -3.24, P < .05) with greater knee-flexor (percentage difference = 25.3, t14 = -4.65, P < .001) weakness preoperatively in the injured limb of ACL-injured participants. The ACL-injured participants had less injured limb knee-extensor (percentage difference = 32.0, t28 = -2.84, P = .008) and -flexor (percentage difference = 24.0, t28 = -2.44, P = .02) strength preoperatively but not postoperatively (extensor: t28 = -1.79, P = .08; flexor: t28 = 0.57, P = .58) than control participants. Ankle-plantar-flexor weakness was greater preoperatively than postoperatively in the ACL-injured limb (percentage difference = 31.9, t14 = -3.20, P = .006). CONCLUSIONS The ACL-injured participants presented with hip-extensor, -adductor, and ankle-plantar-flexor weakness that appeared to be countered during postoperative rehabilitation. Our results confirmed previous findings suggesting greater knee-extensor and -flexor weakness postoperatively in the injured limb than the uninjured limb. The knee extensors and flexors are important dynamic stabilizers; weakness in these muscles could impair knee joint stability. Improving rehabilitation strategies to better target this lingering weakness seems imperative.

Muscle Strength and Functional Recovery During the First Year After THA

BackgroundPatients undergoing total hip arthroplasty (THA) often are satisfied with the decrease in pain and improvement in function they achieve after surgery. Even so, strength and functional performance deficits persist after recovery, but these remain poorly characterized; knowledge about any ongoing strength or functional deficits may allow therapists to design rehabilitation programs to optimize recovery after THA.Questions/purposesThe purposes of this study were to (1) evaluate postoperative muscle strength, function, and quality of life during the first year after THA; and (2) compare strength and function in patients 1 year after THA with a cohort of healthy peers.MethodsTwenty-six patients undergoing THA were assessed 1, 3, 6, and 12 months postoperatively, and 19 adults with no hip pathology were tested as a control group. Isometric muscle strength (hip flexors, extensors, abductors, knee extensors, and flexors), functional performance (stair climbing, five times sit-to-stand, timed-up-and-go, 6-minute walk, and single-limb stance tests), and self-reported function (Hip Disability and Osteoarthritis Score, SF-36, and UCLA activity score) were compared.ResultsOne month after THA, patients had 15% less hip flexor and extensor torque, 26% less abductor torque, 14% less knee extensor and flexor torque, and worse performance on the stair climbing, timed-up-and-go, single-limb stance, and 6-minute walk. Compared with healthy adults, patients 12 months after THA had 17% less knee extensor and 23% less knee flexor torque; however, the functional testing (including stair climbing, five times sit-to-stand, and the 6-minute walk) showed no significant differences with the patient numbers available between individuals undergoing THA and healthy control subjects. SF-36 Physical Component Scores, although significantly improved from preoperative levels, were significantly worse than healthy adults 1 year after THA (p < 0.01).ConclusionsPatients experience early postoperative strength losses and decreased functional capacity after THA, yet strength deficits may persist after recovery. This may suggest that rehabilitation may be most effective in the first month after surgery.Level of EvidenceLevel II, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Osteoarthritis-related biomarkers following anterior cruciate ligament injury and reconstruction: a systematic review

OBJECTIVE There is an increased risk of developing knee osteoarthritis (OA) following anterior cruciate ligament (ACL) injury. Biomarkers may provide diagnostic, prognostic, or burden of disease indicators of OA before radiographic changes become apparent. Unfortunately, there has been no systematic review to clarify which biomarkers may be most informative following injury. Therefore, this review critically investigated existing studies of OA-related biomarkers in ACL-deficient (ACL-D) and reconstructed (ACL-R) patients to summarize the current evidence and identify knowledge gaps. DESIGN A systematic review of the literature in Web of Science and PubMed databases (1960-June 2014) was performed. All English-language case-control and longitudinal studies assessing OA-related biomarkers in ACL-D and ACL-R patients were considered. Data regarding biomarker changes over time within ACL-D and ACL-R patients as well as differences in ACL-D/ACL-R patients compared with a control group were extracted from pertinent studies. RESULTS A descriptive summary of 20 included studies was produced. In ACL-D patients compared with controls, synovial fluid biomarkers indicated elevated collagen turnover, while the inflammatory cytokine response was inconclusive. In ACL-R patients, serum concentrations indicated decreased collagen breakdown, but urine concentrations were indicative of greater collagen breakdown when compared to controls. Compared to preoperative values, the overall inflammatory cytokine response measured with synovial fluid biomarkers increased while plasma biomarkers did not change following reconstruction. CONCLUSION Patients with ACL-D or ACL-R have altered biomarkers indicative of OA. More research with standardized reporting is needed to effectively determine which biomarkers are the most indicative for OA development and progression following ACL injury.

Quadriceps neural alterations in anterior cruciate ligament reconstructed patients: A 6-month longitudinal investigation

The purpose of this investigation was to evaluate differences in quadriceps corticospinal excitability, spinal‐reflexive excitability, strength, and voluntary activation before, 2 weeks post and 6 months post‐anterior cruciate ligament reconstruction (ACLr). This longitudinal, case‐control investigation examined 20 patients scheduled for ACLr (11 females, 9 males; age: 20.9 ± 4.4 years; height:172.4 ± 7.5 cm; weight:76.2 ± 11.8 kg) and 20 healthy controls (11 females, 9 males; age:21.7 ± 3.7 years; height: 173.7 ± 9.9 cm; weight: 76.1 ± 19.7 kg). Maximal voluntary isometric contractions (MVIC), central activation ratio (CAR), normalized Hoffmann spinal reflexes, active motor threshold (AMT), and normalized motor‐evoked potential (MEP) amplitudes at 120% of AMT were measured in the quadriceps muscle at the specific time points. ACLr patients demonstrated bilateral reductions in spinal‐reflexive excitability compared with controls before surgery (P = 0.02) and 2 weeks post‐surgery (P ≤ 0.001). ACLr patients demonstrated higher AMT at 6 months post‐surgery (P ≤ 0.001) in both limbs. No MEP differences were detected. Quadriceps MVIC and CAR were lower in both limbs of the ACLr group before surgery and 6 months post‐surgery (P ≤ 0.05) compared with controls. Diminished excitability of spinal‐reflexive and corticospinal pathways are present at different times following ACLr and occur in combination with clinical deficits in quadriceps strength and activation. Early rehabilitation strategies targeting spinal‐reflexive excitability may help improve postoperative outcomes, while later‐stage rehabilitation may benefit from therapeutic techniques aimed at improving corticospinal excitability.

Prediction of Lateral Ankle Sprains in Football Players Based on Clinical Tests and Body Mass Index

Background: The lateral ankle sprain (LAS) is the most common injury suffered in sports, especially in football. While suggested in some studies, a predictive role of clinical tests for LAS has not been established. Purpose: To determine which clinical tests, focused on potentially modifiable factors of movement patterns and body mass index (BMI), could best demonstrate risk of LAS among high school and collegiate football players. Study Design: Case-control study; Level of evidence, 3. Methods: A total of 539 high school and collegiate football players were evaluated during the preseason with the Star Excursion Balance Test (SEBT) and Functional Movement Screen as well as BMI. Results were compared between players who did and did not suffer an LAS during the season. Logistic regression analyses and calculated odds ratios were used to determine which measures predicted risk of LAS. Results: The LAS group performed worse on the SEBT–anterior reaching direction (SEBT-ANT) and had higher BMI as compared with the noninjured group (P < .001). The strongest prediction models corresponded with the SEBT-ANT. Conclusion: Low performance on the SEBT-ANT predicted a risk of LAS in football players. BMI was also significantly higher in football players who sustained an LAS. Identifying clinical tools for successful LAS injury risk prediction will be a critical step toward the creation of effective prevention programs to reduce risk of sustaining an LAS during participation in football.

Corticospinal and intracortical excitability of the quadriceps in active older and younger healthy adults

Age-related declines in neuromuscular function are well-documented, though the mechanisms underlying these deficits are unclear. Specific changes in corticospinal and intracortical neurophysiology may contribute, but have not been well studied, especially in lower extremity muscles. Furthermore, variations in physical activity levels may potentially confound the interpretation of neurophysiologic findings. Therefore, the purpose of this study was to quantify differences in transcranial magnetic stimulation (TMS) measures of corticospinal and intracortical excitability of the quadriceps between healthy, active older and younger adults. Twenty younger (age: 25.2 ± 2.4 years; body mass index [BMI]: 22.1 ± 3.0 kg/m(2); 11 males and 9 females) and twenty older (age: 67.7 ± 5.5 years; BMI: 26.8 ± 3.8 kg/m(2); 11 males and 9 females) subjects who exercised regularly (at least 30 min, 3 times/week) completed testing. Motor evoked potentials (MEPs) were measured by superficial electromyographic recordings of the vastus lateralis (VL). Measures of corticospinal excitability using a double cone TMS coil included resting motor thresholds (RMT), resting recruitment curves (RRCs) and silent periods (SP). Intracortical excitability was measured using paired pulse paradigms for short interval intracortical inhibition (SICI) and intracortical facilitation (ICF). No statistically significant differences between older and younger adults were found for RMT, RRC slopes, SP, SICI or ICF measures (p>0.05). The physically active nature of the older adults included in this study may have contributed to the lack of differences in corticospinal and intracortical excitability since physical activity in older adults attenuates age-related declines in neuromuscular function.

Strength and functional deficits in individuals with hip osteoarthritis compared to healthy, older adults

Abstract Purpose: Hip osteoarthritis (OA) compromises quality of life for many individuals. This study quantified deficits in functional capacity for use in rehabilitation goal setting by combining assessments of muscle strength, function and physical activity in patients with hip OA and healthy adults. Method: Twenty-six patients with end-stage hip OA and 18 healthy adults participated. Isometric muscle strength around the hip and knee was measured. Function was assessed using stair climbing, five-time-sit-to-stand, timed-up-and-go and 6-minute walk tests. The UCLA activity rating scale assessed physical activity. Analyses of covariance (ANCOVA) were used to assess differences between groups. Results: Patients had 30% less knee extensor (p < 0.001), 38% less knee flexor (p < 0.001), 10% less hip flexor (p = 0.47), 23% less hip extensor (p = 0.24) and 17% less hip abductor strength (p = 0.23) than healthy adults. Hip adductor strength was equal between groups (p = 0.93). Patients were 50% slower on the stair climbing test (p = 0.001), 34% slower on the timed-up-and-go test (p = 0.004), 34% slower on the five-time-sit-to-stand test (p = 0.001), and walked 28% less during the 6-min walk test (p < 0.001). Patients were less physically active (p = 0.001). Conclusions: Patients had deficits in muscle strength, function and physical activity compared to healthy adults. Quantifying these deficits provides benchmarks for improvement during rehabilitation. Implications for Rehabilitation Hip osteoarthritis (OA) affects up to 28% of adults over the age of 65 and many individuals report functional and activity limitations directly related to their arthritic condition, posing a risk for future morbidity Total hip arthroplasty (THA) is the treatment of choice for decreasing pain and improving function, however, some individuals suffering from end-stage hip OA are not candidates for THA, and effective rehabilitation interventions to improve physical function are crucial Establishing estimates of the deficits in muscle strength, physical function and physical activity in people with and without hip OA can aid rehabilitation professionals in their goal setting and intervention planning Rehabilitation interventions should not only consist of muscle strengthening and functional training, but interventions to improve physical activity levels are required to improve overall physical functioning and to decrease risks for additional health complications

Muscle atrophy contributes to quadriceps weakness after anterior cruciate ligament reconstruction

OBJECTIVES Quadriceps weakness persists after anterior cruciate ligament reconstruction. Muscle atrophy and activation failure may contribute. This study examined the roles of atrophy and activation failure in quadriceps weakness after anterior cruciate ligament reconstruction. DESIGN Case series. METHODS Twenty patients six months post-anterior cruciate ligament reconstruction participated. Atrophy was determined as peak quadriceps cross sectional area from magnetic resonance images. Quadriceps activation was quantified via the central activation ratio, while muscle strength was measured isometrically. All testing was performed bilaterally. Hierarchical linear regression and one-way ANOVAs were performed to examine the relation of muscle strength with activation and atrophy. RESULTS Cross sectional area (R(2)=0.307; p=0.011) explained more of the variance in quadriceps strength than central activation ratio (R(2)<0.001; p=0.987). Strength and cross sectional area were lower in the injured (strength: 2.03±0.51Nm/kg; cross sectional area: 68.81±17.80cm(2)) versus uninjured limb (strength: 2.89±0.81Nm/kg; cross sectional area: 81.10±21.58cm(2); p<0.001). There were no side-to-side differences in central activation ratio; however, quadriceps activation failure was present bilaterally (injured: 0.87±0.12; uninjured: 0.85±0.14; p=0.571). CONCLUSIONS Quadriceps cross sectional area was strongly related to muscle strength six months after anterior cruciate ligament reconstruction and substantial injured versus uninjured limb deficits were demonstrated for strength and cross sectional area. Patients may benefit from exercises aimed at improving quadriceps cross sectional area post-operatively.

Alterations in stride-to-stride variability during walking in individuals with chronic ankle instability

The aim of this study was to evaluate stride-to-stride variability of the lower extremity during walking in individuals with and without chronic ankle instability (CAI) using a nonlinear analysis. Twenty-five participants with self-reported CAI and 27 healthy control participants volunteered for this study. Participants walked on a motor-driven treadmill for 3 min at their selected speed. Lower extremity kinematics in the sagittal and frontal planes were recorded using a passive retroreflective marker motion capture system. The temporal structure of walking variability was analyzed with sample entropy (SampEn). The CAI group produced lower SampEn values in frontal-plane ankle kinematics compared to the control group (P=.04). No significant group differences were observed for SampEn values of other kinematics (P>.05). Participants with CAI demonstrated less stride-to-stride variability of the frontal plane ankle kinematics compared to healthy controls. Decreased variability of walking patterns demonstrated by participants with CAI indicates that the presence of CAI may be associated with a less adaptable sensorimotor system to environmental changes. The altered sensorimotor function associated with CAI may be targets for clinical interventions, and it is critical to explore how interventions protocols affect sensorimotor system function.

Muscle activation and coactivation during five-time-sit-to-stand movement in patients undergoing total knee arthroplasty

Quadriceps weakness is prevalent with knee osteoarthritis (OA) and after total knee arthroplasty (TKA). To compensate for quadriceps dysfunction, patients often alter movement strategies. Little is known about muscle coordination during sit-to-stand (concentric) and stand-to-sit (eccentric) movements in the acute postoperative period. This investigation characterized the distribution of muscle activation between the concentric and eccentric phases during a five-time-sit-to-stand (FTSTS) movement in late stage OA and one month after TKA. Patients and healthy participants performed a FTSTS while recording bilateral ground reaction forces (GRFs) and electromyography (EMG). Concentric and eccentric ensemble averages of the GRF and EMG were calculated for the concentric and eccentric phases. Coactivation indices, integrated EMG, and GRF were calculated for each limb and phase. Patients demonstrated higher eccentric coactivation than the healthy group. Postoperative loading was higher in the nonsurgical limb. Postoperative quadriceps activity was lower in the concentric phase and higher in the eccentric phase than the healthy group. Higher coactivation in the patients resulted from sustained distribution of quadriceps activity throughout the eccentric phase. This indicated an inability to coordinate muscle firing when rapidly lowering to a chair and occurred despite unloading of the surgical limb. Although these patterns may serve as a protective strategy, they may also impede recovery of muscle function after TKA.