Sex differences in quadriceps rate of torque development within 1 year of ACL reconstruction

Comparison of physical therapy utilization, timing of return-to-sport test completion, and hop test performance by age and between sexes in youth athletes after anterior cruciate ligament reconstruction

OBJECTIVE

To compare physical therapy (PT) utilization, timing of return-to-sport (RTS) test and hop test performance by age and between sexes in youth after anterior cruciate ligament reconstruction (ACLR).

DESIGN

Multicenter retrospective cohort.

METHODS

A retrospective review of adolescents after primary ACLR was conducted. Participants completed return-to-sport (RTS) tests including single-legged hop testing. PT frequency, average weekly visits, and timing of RTS test were calculated. T-tests assessed the effect of age and sex on average weekly PT visits and multivariable logistic regressions assessed odds of passing hop tests.

RESULTS

289 participants were included (15.7 ± 1.9 years). There was no difference in average weekly PT visits (p = 0.321) or time to RTS test (p = 0.162) by age. There were significant differences in average weekly PT visits (p = 0.047) and mean time from surgery to RTS test (p = 0.048) between sexes with small effect sizes (d = 0.24 and d = 0.21, respectively). Age and sex had no effect on odds of passing hop tests (OR, 1.29; 95% CI, 0.71-2.35 and OR, 0.79; 95%CI, 0.43-1.45, respectively).

CONCLUSION

In a youth cohort, age and sex may have no clinically important effect on PT visit utilization, timing of RTS test or hop test performance.

Sex Differences in Quadriceps Atrophy After Anterior Cruciate Ligament Tear

BACKGROUND

Female athletes lag behind their male counterparts in recovery from anterior cruciate ligament (ACL) injury. Quadriceps muscle size and strength are crucial factors for regaining function after ACL injury, but little is known about how these metrics vary due to biological sex.

HYPOTHESIS

Female patients have reduced vastus lateralis fiber cross-sectional area (CSA) and lower quadriceps strength after ACL injury than male patients.

STUDY DESIGN

Cross-sectional study.

LEVEL OF EVIDENCE

Level 4.

METHODS

A total of 60 participants with recent ACL tear were evaluated for vastus lateralis muscle fiber CSA, isometric quadriceps peak torque, and quadriceps rate of torque development. Linear mixed models were fit to determine differences across sex and limb for each variable of interest.

RESULTS

The female group averaged almost 20% atrophy between limbs (P < 0.01), while the male group averaged just under 4% (P = 0.05). Strength deficits between limbs were comparable between female and male groups.

CONCLUSION

Immediately after ACL injury, female patients have greater between-limb differences in muscle fiber CSA but between-limb strength deficits comparable with those of male patients.

CLINICAL RELEVANCE

These results indicate that the underpinnings of strength loss differ based on biological sex, and thus individual patients could benefit from a sex-specific treatment approach to ACL injury.

Sex Differences in Knee Extensor Neuromuscular Function in Individuals With and Without Patellofemoral Pain

BACKGROUND

Impaired knee extensor neuromuscular function has been frequently observed in individuals with patellofemoral pain (PFP); however, few researchers have aimed to understand the influence of sex on knee extensor neuromuscular function in this pathological population. The authors aimed to determine whether there are differences in knee extensor neuromuscular function between sexes in individuals with and without PFP.

HYPOTHESIS

Women with PFP would exhibit greater deficits in knee extensor neuromuscular function than men with PFP, compared with sex-matched individuals without PFP.

STUDY DESIGN

Cross-sectional, case-control study.

LEVEL OF EVIDENCE

Level 4.

METHODS

A total of 110 individuals were classified into 4 groups: women with PFP (n = 25); men with PFP (n = 30); women without PFP (n = 25); and men without PFP (n = 30). Knee extensor strength (isometric peak torque [PT]), activation (central activation ratio), early, late, and total phase rate of torque development (RTD0-100, RTD100-200, and RTD20-80%), and endurance (isokinetic average PT) were assessed using an isokinetic dynamometer. Group differences were assessed using a 2-way multivariate analysis of variance (sex by PFP).

RESULTS

Both women and men with PFP exhibited lower knee extensor strength, activation, early, late, and total phase RTD, and endurance versus sex-matched individuals without PFP (P < 0.05 for all comparisons). Women with PFP exhibited lower early phase (7.91 ± 2.02 versus 9.78 ± 2.43 N·m/s/kg; P < 0.01; Cohen d = 0.83), late phase (5.34 ± 1.02 versus 7.28±2.28 N·m/s/kg; P < 0.01; Cohen d = 1.37), and total phase (7.40 ± 2.57 versus 8.72 ± 2.57 N·m/s/kg; P = 0.03; Cohen d = 0.51) RTD than men with PFP.

CONCLUSION

Compared with sex-matched pain-free individuals, women with PFP displayed lower RTD than men with PFP. Clinicians should note that among individuals with PFP, women are more likely to experience a greater impairment in their knee extensor torque-generating capacity than men.

CLINICAL RELEVANCE

Additional treatment strategies that effectively improve the ability to rapidly generate torque should be developed and implemented, especially when treating women with PFP.

Sex differences in corticospinal excitability and quadriceps performance after anterior cruciate ligament reconstruction

Anterior cruciate ligament (ACL) ruptures result in lasting quadriceps dysfunction that contributes to secondary injury risk and development of osteoarthritis. There is evidence of persistent reduced nervous system drive (corticospinal excitability [CSE]) to the quadriceps and sex differences in both quadriceps performance and CSE post-ACL reconstruction (ACLR). The purposes of this study were to investigate the differences in CSE and quadriceps dysfunction after ACLR between sexes and relative to controls. Twenty subjects 4-9 months post-ACLR and 20 age, sex, and activity matched controls participated in this study. Quadriceps performance (peak torque, PT; rate of torque development from onset to 100 ms, RTD100; and RTD from 100 to 200ms, RTD200) and CSE (active motor threshold; slope of the stimulus response (SR) curve, SR curve slope) were measured using an isokinetic dynamometer (HUMAC NORM) and transcranial magnetic stimulation respectively. Significant group differences were found for SR curve slope, PT, RTD100, and RTD200 on the surgical limb. Males after ACLR had higher slopes (higher CSE) than females. Females after ACLR had worse surgical limb quadriceps PT than control males and slower RTD100 and RTD200 than control males and control females. Higher CSE in males after ACLR may point to a potentially adaptive neurological change in males post-ACLR and indicate greater need for novel interventions to address cortical drive in females after ACLR.

The association between knee muscle performance and clinical outcomes of knee function 1-4 years after a sport-related knee joint injury

OBJECTIVE

Estimate the association between index leg knee muscle strength and rate of torque development (RTD), and self-reported and performance-based (i.e., hop) knee function in persons 1-4 years after a sport-related knee joint injury.

METHODS

Data were collected at baseline of a clinical trial. Assessments included the Knee injury and Osteoarthritis Outcome Score Sport & Recreation subscale (KOOSsport), 6-m timed hop (TH), and peak concentric isokinetic knee extensor and flexor torque and isometric RTD. Associations between peak torque and RTD with KOOSsport and TH were assessed using multivariable regression with nonlinear transformations.

RESULTS

53 participants (64.2% female) were included. Knee extensor peak torque was nonlinearly related to TH time, with a strong inverse relationship at lower torque values that changed as torque increased. Results were inconsistent for flexor peak torque, extensor RTD and flexor RTD, with inconsistencies in relationship shape and estimates of association between primary and sensitivity analyses. There was no association between strength/RTD and KOOSsport.

CONCLUSION

There was a nonlinear relationship between knee extensor strength and hop function, with lower strength being associated with a stronger relationship. As strength values increased, the relationship attenuated. Knee extensor and flexor strength, or RTD, were not associated with self-reported function.

The Impact of Meniscal Tear Type and Surgical Treatment on Quadriceps Strength: A Study of Adolescent Patients Post Anterior Cruciate Ligament Reconstruction

BACKGROUND

Treatment of meniscal injuries at the time of anterior cruciate ligament reconstruction (ACLR) can result in restrictions on weightbearing and range of motion in the early rehabilitative phases. What is unknown is the effect of (1) meniscal tear type and location at the time of anterior cruciate ligament injury and (2) meniscal treatment at the time of ACLR on quadriceps strength in adolescents during the late rehabilitative phase.

HYPOTHESIS

Meniscal tears involving the root and requiring repair would adversely affect quadriceps strength at 6 to 9 months postoperatively.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients who underwent ACLR at 1 of 2 research sites between 2013 and 2021 were identified. Adolescent participants were included if they were between the ages of 12 and 20 years at the time of assessment and had undergone primary unilateral ACLR in the previous 6 to 9 months. Participants were subgrouped by meniscal tear type (no tear, nonroot tear, root tear) and meniscal treatment at the time of ACLR (no treatment, meniscectomy, meniscal repair), which were confirmed via chart review. Isokinetic strength testing occurred at 60 deg/s, and quadriceps strength and quadriceps strength limb symmetry index were compared between the meniscal tear type and meniscal procedure subgroups using analysis of covariance while controlling for the effects of age, sex, and ACLR graft source.

RESULTS

An overall 236 patients were included in this analysis (109 male, 127 female; mean ± SD age, 16.0 ± 1.9 years). There were no significant differences in ACLR limb quadriceps strength based on meniscal tear type (P = .61) or meniscal procedure at the time of ACLR (P = .61), after controlling for age, biological sex, and ACLR graft source. Similarly, quadriceps strength limb symmetry index did not differ by meniscal tear type (P = .38) or meniscal procedure at the time of ACLR (P = .40).

CONCLUSION

Meniscal tear type and treatment at the time of ACLR did not affect quadriceps strength or quadriceps strength symmetry in adolescents 6 to 9 months after ACLR.

Dynamic knee joint stiffness during bilateral lower extremity landing 6 months after ACL reconstruction

BACKGROUND

Anterior cruciate ligament (ACL) reconstructions are associated with long-term functional impairments. Improved understanding of dynamic knee joint stiffness and work may provide insights to help address these poor outcomes. Defining the relationship between knee stiffness, work and quadriceps muscle symmetry may reveal therapeutic targets. The purposes of this study were to investigate between-limb differences in knee stiffness and work during early phase landing 6-months after an ACL reconstruction. Additionally, we investigated relationships among symmetry of knee joint stiffness and work during early-phase landing and quadriceps muscle performance symmetry.

METHODS

Twenty-nine participants (17 M, 20.0 ± 5.3 years) were tested 6-months after ACL reconstruction. Motion capture analysis was used to assess between-limb differences in knee stiffness and work during the first 60 ms of a double-limb landing. Quadriceps peak strength and rate of torque development (RTD) were assessed with isometric dynamometry. Paired t-tests and Pearson's product moment correlations were used to determine between-limb differences of knee mechanics and correlations of symmetry respectively.

FINDINGS

Knee joint stiffness and work were significantly reduced (p < 0.01, p < 0.01) in the surgical limb (0.021 ± 0.01 Nm*(deg*kg*m)-1, -0.085 ± 0.06 J*(kg*m) -1) compared to the uninvolved limb (0.045 ± 0.01 Nm*(deg*kg*m)-1, -0.256 ± 0.10 J*(kg*m) -1). Greater knee stiffness (51 ± 22%) and work (35 ± 21%) symmetry were significantly associated with greater RTD symmetry (44.5 ± 19.4%) (r = 0.43, p = 0.02; r = 0.45, p = 0.01) but not peak torque symmetry (62.9 ± 16.1%) (r = 0.32, p = 0.10; r = 0.34, p = 0.10).

INTERPRETATION

Dynamic stiffness and energy absorption are lower in the surgical knee during landing from a jump. Therapeutic interventions that target increasing quadriceps RTD may help optimize dynamic stability and energy absorption during landing.

Let's talk about sex (and gender) after ACL injury: a systematic review and meta-analysis of self-reported activity and knee-related outcomes

OBJECTIVE

Investigate sex/gender differences in self-reported activity and knee-related outcomes after anterior cruciate ligament (ACL) injury.

DESIGN

Systematic review with meta-analysis.

DATA SOURCES

Seven databases were searched in December 2021.

ELIGIBILITY CRITERIA

Observational or interventional studies with self-reported activity (including return to sport) or knee-related outcomes after ACL injury.

RESULTS

We included 242 studies (n=123 687, 43% females/women/girls, mean age 26 years at surgery). One hundred and six studies contributed to 1 of 35 meta-analyses (n=59 552). After ACL injury/reconstruction, very low-certainty evidence suggests females/women/girls had inferior self-reported activity (ie, return to sport, Tegner Activity Score, Marx Activity Scale) compared with males/men/boys on most (88%, 7/8) meta-analyses. Females/women/girls had 23%-25% reduced odds of returning to sport within 1-year post-ACL injury/reconstruction (12 studies, OR 0.76 95% CI 0.63 to 0.92), 1-5 years (45 studies, OR 0.75 95% CI 0.69 to 0.82) and 5-10 years (9 studies, OR 0.77 95% CI 0.57 to 1.04). Age-stratified analysis (<19 years) suggests female athletes/girls had 32% reduced odds of returning to sport compared with male athletes/boys (OR 0.68, 95% CI 0.41 to 1.13, I² 0.0%). Very low-certainty evidence suggests females/women/girls experienced inferior knee-related outcomes (eg, function, quality of life) on many (70%, 19/27) meta-analyses: standardised mean difference ranging from -0.02 (Knee injury and Osteoarthritis Outcome Score, KOOS-activities of daily living, 9 studies, 95% CI -0.05 to 0.02) to -0.31 (KOOS-sport and recreation, 7 studies, 95% CI -0.36 to -0.26).

CONCLUSIONS

Very low-certainty evidence suggests inferior self-reported activity and knee-related outcomes for females/women/girls compared with males/men/boys after an ACL injury. Future studies should explore factors and design targeted interventions to improve outcomes for females/women/girls.

PROSPERO REGISTRATION NUMBER

CRD42021205998.

Evidence Review for Preventing Osteoarthritis After an Anterior Cruciate Ligament Injury: An Osteoarthritis Action Alliance Consensus Statement

CONTEXT

The Osteoarthritis Action Alliance formed a secondary prevention task group to develop a consensus on secondary prevention recommendations to reduce the risk of osteoarthritis after a knee injury.

OBJECTIVE

Our goal was to provide clinicians with secondary prevention recommendations that are intended to reduce the risk of osteoarthritis after a person has sustained an anterior cruciate ligament injury. Specifically, this manuscript describes our methods, literature reviews, and dissenting opinions to elaborate on the rationale for our recommendations and to identify critical gaps.

DESIGN

Consensus process.

SETTING

Virtual video conference calls and online voting.

PATIENTS OR OTHER PARTICIPANTS

The Secondary Prevention Task Group consisted of 29 members from various clinical backgrounds.

MAIN OUTCOME MEASURE(S)

The group initially convened online in August 2020 to discuss the target population, goals, and key topics. After a second call, the task group divided into 9 subgroups to draft the recommendations and supportive text for crucial content areas. Twenty-one members completed 2 rounds of voting and revising the recommendations and supportive text between February and April 2021. A virtual meeting was held to review the wording of the recommendations and obtain final votes. We defined consensus as >80% of voting members supporting a proposed recommendation.

RESULTS

The group achieved consensus on 15 of 16 recommendations. The recommendations address patient education, exercise and rehabilitation, psychological skills training, graded-exposure therapy, cognitive-behavioral counseling (lacked consensus), outcomes to monitor, secondary injury prevention, system-level social support, leveraging technology, and coordinated care models.

CONCLUSIONS

This consensus statement reflects information synthesized from an interdisciplinary group of experts based on the best available evidence from the literature or personal experience. We hope this document raises awareness among clinicians and researchers to take steps to mitigate the risk of osteoarthritis after an anterior cruciate ligament injury.

Evaluation of hop performance in children with anterior cruciate ligament reconstruction using healthy reference data: A cross-sectional study

BACKGROUND

Hop performance evaluation in children after anterior cruciate ligament (ACL) reconstruction may benefit from comparison to healthy controls. Thus, the purpose was to investigate the hop performance in children one year after ACL reconstruction with a comparison to healthy controls.

METHODS

Hop performance data from children with ACL reconstruction one year post-surgery and healthy children were compared. Four one-legged hop test data were analyzed: 1) single hop (SH), 2) 6 m timed hop (6 m-timed), 3) triple hop (TH), and 4) cross-over hop (COH). Outcomes were the best result (longest/fastest hop) from each leg and limb asymmetry. Differences in hop performance between-limbs (operated versus non-operated) and between-groups were estimated.

RESULTS

98 children with ACL reconstruction and 290 healthy children were included. Few statistically significant group differences were observed. Girls with ACL reconstruction outperformed healthy controls in two tests on the operated leg SH, COH) and in three tests on the non-operated leg (SH, TH, COH). However, the girls performed 4-5% worse on the operated leg when compared to the non-operated leg in all hop tests. No statistically significant between-group differences in the limb asymmetry were found.

CONCLUSION

The hop performance in children with ACL reconstruction one year post-surgery was largely comparable to the level of healthy controls. Despite this, we cannot exclude that neuromuscular deficits exist among the children with ACL reconstruction. The inclusion of a healthy control group for evaluating hop performance evoked complex findings regarding the ACL reconstructed girls. Thus, they may represent a selected group.

Explosive hamstrings strength asymmetry persists despite maximal hamstring strength recovery following anterior cruciate ligament reconstruction using hamstring tendon autografts

PURPOSE

To investigate the differences in maximal (isometric and concentric peak torque) and explosive (rate of torque development (RTD)) hamstring and quadriceps strength symmetry between males and females during early- and late-phase rehabilitation after anterior cruciate ligament reconstruction (ACLR) using hamstring tendon (HT) autografts and to determine the interaction of time and sex on maximal and explosive strength symmetry.

METHODS

A total of 38 female and 51 male participants were assessed during early (3-6 months post-operative) and late (7-12 months post-operative) phases of rehabilitation following ACLR. Maximal (concentric and isometric peak torque) and explosive (isometric RTD) hamstring and quadriceps strength were assessed and presented as limb symmetry index (LSI).

RESULTS

Maximal concentric hamstrings asymmetry (Early: 86 ± 14; Late 92 ± 13; p = 0.005) as well as maximal concentric (Early, 73 ± 15; Late 91 ± 12; p < 0.001) and explosive (Early: 82 ± 30; Late: 92 ± 25; p = 0.03) quadriceps asymmetry decreased from early to late rehabilitation. However, there were no significant changes in maximal isometric quadriceps strength and explosive isometric hamstring strength in the same time period. Females had a larger asymmetry in maximal concentric (Females: 75 ± 17; Males: 81 ± 15; p = 0.001) and explosive (Females: 81 ± 32; Males: 89 ± 25; p = 0.01) quadriceps strength than males throughout rehabilitation. There were no sex differences in maximal and explosive hamstring strength. There were no sex by time interactions for any variables.

CONCLUSION

Explosive hamstring strength asymmetry did not improve despite recovery of maximal hamstring strength during rehabilitation following ACLR with HT autografts. While sex did not influence strength recovery, females had larger maximal and explosive quadriceps strength asymmetry compared to males throughout rehabilitation following ACLR.

LEVEL OF EVIDENCE

Level III.

Rate of Torque Development in the Quadriceps after Anterior Cruciate Ligament Reconstruction with Hamstring Tendon Autografts in Young Female Athletes

This study aims to compare the limb symmetry index (LSI) of the rate of torque development (RTD) of the quadriceps with that of the peak torque after anterior cruciate ligament reconstruction (ACLR) using semitendinosus and gracilis tendon (STG) autografts and to investigate the associations of the LSI of torque parameters with patient-reported knee function. The participants included 23 female athletes after ACLR with STG grafts. Isometric quadriceps tests were performed using an isokinetic dynamometer. The peak torque, RTD₁₀₀ (0 to 100 ms) and RTD₂₀₀ (100 to 200 ms) were determined using torque-time curves. Comparisons of the LSI of torque parameters was performed by ANOVA. Univariate regression analysis was used to examine the relationship between the LSI of torque parameters and the patient-reported knee function. The LSIs of the peak torque and RTD₂₀₀ were significantly lower than that of the RTD₁₀₀ (p = 0.049, p = 0.039, respectively). Regression analysis showed that the LSI of the peak torque was associated with the patient-reported knee function (R² = 0.40, p = 0.001). It would be useful to evaluate the peak torque in young female athletes under the age of 18 and at 8-10 months after ACLR with STG grafts.

Quadriceps muscle strength at 2 years following anterior cruciate ligament reconstruction is associated with tibiofemoral joint cartilage volume

PURPOSE

Quadriceps strength deficits following anterior cruciate ligament reconstruction (ACLR) are linked to altered lower extremity biomechanics, tibiofemoral joint (TFJ) space narrowing and cartilage composition changes. It is unknown, however, if quadriceps strength is associated with cartilage volume in the early years following ACLR prior to the onset of posttraumatic osteoarthritis (OA) development. The purpose of this cross-sectional study was to examine the relationship between quadriceps muscle strength (peak and across the functional range of knee flexion) and cartilage volume at ~ 2 years following ACLR and determine the influence of concomitant meniscal pathology.

METHODS

The involved limb of 51 ACLR participants (31 isolated ACLR; 20 combined meniscal pathology) aged 18-40 years were tested at 2.4 ± 0.4 years post-surgery. Isokinetic knee extension torque generated in 10° intervals between 60° and 10° knee flexion (i.e. 60°-50°, 50°-40°, 40°-30°, 30°-20°, 20°-10°) together with peak extension torque were measured. Tibial and patellar cartilage volumes were measured using magnetic resonance imaging (MRI). The relationships between peak and angle-specific knee extension torque and MRI-derived cartilage volumes were evaluated using multiple linear regression.

RESULTS

In ACLR participants with and without meniscal pathology, higher knee extension torques at 60°-50° and 50°-40° knee flexion were negatively associated with medial tibial cartilage volume (p < 0.05). No significant associations were identified between peak concentric or angle-specific knee extension torques and patellar cartilage volume.

CONCLUSION

Higher quadriceps strength at knee flexion angles of 60°-40° was associated with lower cartilage volume on the medial tibia ~ 2 years following ACLR with and without concomitant meniscal injury. Regaining quadriceps strength across important functional ranges of knee flexion after ACLR may reduce the likelihood of developing early TFJ cartilage degenerative changes.

LEVEL OF EVIDENCE

III.

Skeletal muscle cellular contractile dysfunction after anterior cruciate ligament reconstruction contributes to quadriceps weakness at 6-month follow-up

Muscle dysfunction following anterior cruciate ligament reconstruction (ACLR) may evolve from alterations in muscle contractility at the myofilament protein level. Using a prospective, within-subject case-control design, we evaluated cellular-level contractility, cross-sectional area (CSA), and myosin heavy chain (MHC) isoform expression on single muscle fibers 3 weeks post ACLR, and evaluated their relationship to whole muscle strength and patient-oriented outcomes 6 months post operation. Biopsies of the vastus lateralis were performed 3 weeks post ACLR in 11 subjects (5 females, mean age ± SD = 24.7 ± 6.5 years, height = 172.7 ± 8.2 cm, mass = 75.7 ± 12.5 kg) following first-time ACL rupture and whole muscle strength and self-reported pain, function, and quality of life assessed 6 months post ACLR. At 3 weeks post ACLR, force production was reduced (p < 0.01) in MHC I (-36%) and IIA (-48%) fibers compared with the non-injured leg. When force production was expressed relative to CSA to account for fiber atrophy, reductions remained in MHC IIA fibers (-40%; p < 0.001), but MHC I fibers showed only a trend toward being lower (-13%; p = 0.09). Finally, skeletal muscle fiber functional deficits at 3 weeks post ACLR were associated with whole muscle weakness and less favorable patient-reported outcomes at 6-month follow-up. Thus, ACLR promotes early cellular contractile dysfunction that may contribute to decreased whole muscle strength and patient function, and increased patient-reported symptoms, at 6-month follow-up.

Sex-Specific Outcomes After Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis

Background:

Despite the significant difference between men and women in incidence of anterior cruciate ligament (ACL) injuries, there is a paucity of consistent information on the influence of patient sex on outcomes after ACL reconstruction. A previous meta-analysis has demonstrated that female patients have worse outcomes with regard to laxity, revision rate, Lysholm score, and Tegner activity score and are less likely to return to sports (RTS).

Purpose:

To conduct a systematic review and meta-analysis to evaluate and compare sex-specific outcomes after ACL reconstruction.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A systematic review was performed using PubMed, PubMed Central, Embase, OVID, and Cochrane databases per PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The following search terms were used: “anterior cruciate ligament reconstruction” OR “ACL reconstruction” OR “anterior cruciate ligament” OR “ACL” AND “gender” OR “sex” OR “male” OR “female” AND “outcome” AND “2015-Present” to gather all relevant articles between 2015 and 2020. A risk-of-bias assessment and quality assessment was conducted on included studies.

Results:

Of 9594 studies initially identified, 20 studies with 35,935 male and 21,455 female patients were included for analysis. The 7 studies reporting International Knee Documentation Committee (IKDC) scores showed that male patients had statistically significantly higher postoperative scores (mean difference, 3.02 [95% CI, 1.19-4.84]; P< .01; I² = 66%), and 7 studies that reported the rate of ACL revision showed there was no significant difference between male and female patients (odds ratio, 0.85 [95% CI, 0.45-1.60]; P = .61; I² = 94%). The 7 studies that reported rates of rerupture showed that males were significantly more likely than females to have a graft rerupture (odds ratio, 1.35 [95% CI, 1.22-1.50]; P < .01; I² = 0%). Male patients reported a higher RTS rate than did their female counterparts (59.82% compared with 42.89%); however, no formal statistical analysis could be done because of the variability in reporting techniques.

Conclusion:

Male and female patients with ACL injuries demonstrated similar outcomes regarding their rates of revision; however, male patients were found to have statistically significantly higher postoperative IKDC scores but at the same time higher rerupture rates. Our findings suggest that sex-based differences in outcomes after ACL reconstruction vary based on which metric is used. These results must be considered when counseling patients with ACL injuries.

Arthrogenic Muscle Inhibition Following Anterior Cruciate Ligament Injury

Arthrogenic muscle inhibition (AMI) is a common impairment in individuals who sustain an anterior cruciate ligament (ACL) injury. The AMI causes decreased muscle activation, which impairs muscle strength, leading to aberrant movement biomechanics. The AMI is often resistant to traditional rehabilitation techniques, which leads to persistent neuromuscular deficits following ACL reconstruction. To better treat AMI following ACL injury and ACL reconstruction, it is important to understand the specific neural pathways involved in AMI pathogenesis, as well as the changes in muscle function that may impact movement biomechanics and long-term structural alterations to joint tissue. Overall, AMI is a critical factor that limits optimal rehabilitation outcomes following ACL injury and ACL reconstruction. This review discusses the current understanding of the: (1) neural pathways involved in the AMI pathogenesis following ACL injury; (2) consequence of AMI on muscle function, joint biomechanics, and patient function; and (3) development of posttraumatic osteoarthritis. Finally, the authors review the evidence for interventions specifically used to target AMI following ACL injury.

Disparities in ACL Reconstruction: the Influence of Gender and Race on Incidence, Treatment, and Outcomes

PURPOSE OF REVIEW

Anterior cruciate ligament (ACL) rupture is a common injury that has important clinical and economic implications. We aimed to review the literature to identify gender, racial and ethnic disparities in incidence, treatment, and outcomes of ACL injury.

RECENT FINDINGS

Females are at increased risk for ACL injury compared to males. Intrinsic differences such as increased quadriceps angle and increased posterior tibial slope may be contributing factors. Despite lower rates of injury, males undergo ACL reconstruction (ACLR) more frequently. There is conflicting evidence regarding gender differences in graft failure and ACL revision rates, but males demonstrate higher return to sport (RTS) rates. Females report worse functional outcome scores and have worse biomechanical metrics following ACLR. Direct evidence of racial and ethnic disparities is limited, but present. White athletes have greater risk of ACL injury compared to Black athletes. Non-White and Spanish-speaking patients are less likely to undergo ACLR after ACL tear. Black and Hispanic youth have greater surgical delay to ACLR, increased risk for loss to clinical follow-up, and less physical therapy sessions, thereby leading to greater deficits in knee extensor strength during rehabilitation. Hispanic and Black patients also have greater risk for hospital admission after ACLR, though this disparity is improving. Females have higher rates of ACL injury with inconclusive evidence on anatomic predisposition and ACL failure rate differences between genders. Recent literature has suggested inferior RTS and functional outcomes following ACLR in females. Though there is limited and mixed data on incidence and outcome differences between races and ethnic groups, recent studies suggest there may be disparities in those who undergo ACLR and time to treatment.

The effectiveness of preoperative exercise programmes on quadriceps strength prior to and following anterior cruciate ligament (ACL) reconstruction: A systematic review

OBJECTIVES

to evaluate the effectiveness of preoperative exercise programmes on quadriceps strength prior to and following anterior cruciate ligament (ACL) reconstruction.

DESIGN

Systematic review.

METHODS

a systematic review was undertaken, included studies were evaluated using the Modified Downs and Black checklist which is appropriate for determining the quality of randomised and non-randomised studies. Scientific databases searched included PubMED, EBSCO Health, CINAHL, Medline, and Cochrane Library databases from inception to March 2021.

RESULTS

Ten studies met the inclusion criteria. There were six randomised studies and four prospective studies. The level of evidence is categorised as 'limited' due to heterogenicity and only six studies reported quadriceps strength increases. Five studies demonstrated preoperative exercise of 4-16 weeks duration can significantly increase preoperative quadriceps strength. One study demonstrated preoperative OKC exercise produced significantly stronger preoperative quadriceps compared to CKC exercise. One study showed no between group (intervention vs control) quadriceps strength difference pre or 12 weeks postoperatively.

CONCLUSIONS

4-16 weeks of preoperative exercise could increase quadriceps strength preoperatively but any persistent postoperative strength benefit from undertaking a standardised preoperative intervention is unclear. There is considerable variation and methodological limitations across the included studies and the composition of optimal preoperative ACLR exercise is currently unknown.

The Minimally Clinically Important Difference and Substantial Clinical Benefit in Anterior Cruciate Ligament Reconstruction: A Time-to-Achievement Analysis

This study examined the time-dependent course of the minimally clinically important difference (MCID) and the substantial clinical benefit (SCB) achievement for International Knee Documentation Committee (IKDC) and Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales following anterior cruciate ligament reconstruction (ACLR). A prospective institutional registry was queried for patients receiving ACLR. The patient-reported outcome measures (PROMs) of interest included the IKDC score and KOOS sub-scales. One hundred forty-three patients (mean±SD age, 30.86±12.78 years; mean±SD body mass index, 25.51±4.64 kg/m²) were included in the analysis. Threshold values for the MCID/SCB were 18.9 of 29.6 on IKDC score, 15.7 of 25.3 on KOOS Symptom, 11.9 of 15.5 on KOOS Pain, 13.3 of 20.0 on KOOS ADL, 25.9 of 35.8 on KOOS Quality of Life (QoL), and 27.0 of 43.0 on KOOS Sport (area under the curve, 0.74-0.91). Overall, MCID achievement rates increased from 28.0% to 42.7% at 6 months to 41.9% to 70.8% at 12 months. Achievement rates of SCB increased from 16.1% to 30.4% at 6 months to 29.3% to 51.8% at 12 months. Statistically significant increases in MCID achievement (chi-square=47.95-79.36, all P<.001) and SCB achievement (chi-square=26.02-53.24, all P<.001) occurred from preoperative to 6-month time points across PROMs. From 6-month to 12-month time points, increases in MCID achievement occurred on IKDC score and KOOS QoL (chi-square=5.53-15.11, P<.001-.009). Statistically significant increases in MCID and SCB achievement occurred from preoperative to 6-month time points across IKDC score and KOOS subscales; however, statistically significant increases in achievement rates from 6 months to 1 year occurred on IKDC score, KOOS QoL, and KOOS Sport. This study underlines the importance of considering psychological factors and rehabilitative milestones when examining the achievement MCID and SCB after ACLR. [Orthopedics. 2021;44(5):299-305.].

Knee strength outcomes in adolescents by age and sex during late-stage rehabilitation after anterior cruciate ligament reconstruction

OBJECTIVE

To determine if knee strength differences exist according to age group and sex among adolescents during late-stage anterior cruciate ligament reconstruction (ACLR) rehabilitation.

DESIGN

Retrospective cohort study.

METHODS

Consecutive patients who had undergone ACLR with a hamstring autograft completed isokinetic knee strength assessment. Patients were categorized into early (ages 11-14 years) and middle (ages 15-17 years) adolescence. A two-way MANOVA was used to examine strength differences according to age group and sex.

RESULTS

144 patients were included in the analysis (56.9% females, age = 15.3 ± 1.5 years; days since surgery = 228.2 ± 41.2). Differences in quadriceps peak torque were identified between age groups on the involved (p = 0.001) and uninvolved limbs (p < 0.001), however, no differences in quadriceps peak torque were found between age groups when normalized to body mass (p = 0.16-0.49). Differences between groups according to sex were identified for each strength outcome (p < 0.01), with decreased normalized quadriceps (12-13%) and hamstring (13-16%) peak torque for females. No interactions between age group and sex were noted, F(8, 133) = 1.48, p = 0.17.

CONCLUSION

Early adolescents produced less quadriceps and hamstring peak torque compared to middle adolescents after ACLR. No differences were found between age groups when normalized to body mass.

Twelve-Week Quadriceps Strength as A Predictor of Quadriceps Strength At Time Of Return To Sport Testing Following Bone-Patellar Tendon-Bone Autograft Anterior Cruciate Ligament Reconstruction

BACKGROUND

Restoration of quadriceps strength following anterior cruciate ligament reconstruction (ACL-R) continues to challenge both patients and clinicians. Failure to adequately restore quadriceps strength has been linked to decreased patients' self-reported outcomes and an increased risk for re-injury. Early identification of quadriceps strength deficits may assist in tailoring early interventions to better address impairments.

PURPOSE

The purpose of this study was to assess the relationship between early (12 weeks following ACL-R) isokinetic peak torque and isokinetic peak torque at time of return to sport (RTS) testing.

STUDY DESIGN

Cohort Study.

METHODS

A total of 120 participants (males = 55; females =65) were enrolled in the study (age = 16.1±1.4 yrs; height = 1.72±10.5 m; mass = 70.7±16.3 kg). All participants were level 1 or 2 cutting and pivoting sport athletes who underwent a primary bone-patellar tendon-bone autograft ACL-R. Participants were tested at two time points: 12 weeks following surgery and again at time of RTS testing. A linear regression model was carried out to investigate the relationship between age, sex, and isokinetic peak torque at 12 weeks following ACL-R and isokinetic peak torque at time of RTS testing.

RESULTS

When 12-week isokinetic peak torque was entered first for the hierarchy regression analysis, this factor was predictive of the peak torque at the time of RTS testing, F(1, 118) = 105.6, p < 0.001, R 2 = 0.472, indicating that the 12-week quadriceps strength accounted for 47% of the variance in the quadriceps strength at the time of RTS testing. When age and sex were added in the regression analysis, both factors only added 0.8% of variance for the quadriceps strength at the time of RTS testing.

CONCLUSION

Isokinetic peak torque at 12 weeks following surgery was shown to be a significantly strong predictor (47%) for isokinetic quadriceps strength recovery at time of RTS. This finding underscores the importance of early restoration of quadriceps strength and that while non-modifiable factors such as sex and age are important, early restoration of quadriceps strength most strongly influences late stage quadriceps strength.

LEVEL OF EVIDENCE

3.

Thigh-Muscle and Patient-Reported Function Early After Anterior Cruciate Ligament Reconstruction: Clinical Cutoffs Unique to Graft Type and Age

CONTEXT

Patient-reported function is an important outcome in anterior cruciate ligament rehabilitation. Identifying which metrics of thigh-muscle function are indicators of normal patient-reported function can help guide treatment.

OBJECTIVE

To identify which metrics of thigh-muscle function discriminate between patients who meet and patients who fail to meet age- and sex-matched normative values for patient-reported knee function in the first 9 months after anterior cruciate ligament reconstruction (ACLR) and establish cutoffs for these metrics by covariate subgroups.

DESIGN

Cross-sectional retrospective study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 256 patients (129 females, 128 males; age = 17.1 ± 3.0 years, height = 1.7 ± 0.1 m, mass = 74.1 ± 17.9 kg, months since surgery = 6.4 ± 1.4), 3 to 9 months after primary unilateral ACLR.

MAIN OUTCOME MEASURE(S)

We stratified the sample into dichotomous groups by the International Knee Documentation Committee (IKDC) score (IKDCMET, IKDCNOT MET) using sex- and age-matched normative values. We measured quadriceps and hamstrings isokinetic (60°/s) torque and power bilaterally. Normalized quadriceps and hamstrings peak torque (Nm/kg) and power (W/kg), limb symmetry indices (LSI, %), and hamstrings : quadriceps ratios were calculated. Logistic regression indicated which of these metrics could predict IKDC classification while controlling for age, graft type, and sex. Receiver operating characteristic curves established cutoffs for explanatory variables for both total cohort and covariate subgroups. Odds ratios (OR) determined the utility of each cutoff to discriminate IKDC status.

RESULTS

Quadriceps torque LSI (≥69.4%, OR = 3.6), hamstrings torque (≥1.11 Nm/kg, OR = 2.1), and quadriceps power LSI (≥71.4%, OR = 2.0) discriminated between IKDC classification in the total cohort. Quadriceps torque LSI discriminated between IKDC classification in the patellar-tendon graft (≥61.6%, OR = 5.3), hamstrings-tendon graft (≥71.8%, OR = 10.5), and age <18 years (≥74.3%, OR = 5.2) subgroups. Hamstrings torque discriminated between IKDC classifications in the age <18 years (≥1.10 Nm/kg, OR = 2.6) subgroup.

CONCLUSIONS

Quadriceps torque LSI, hamstrings torque, and quadriceps power LSI were the most useful metrics for predicting normal patient-reported knee function early after ACLR. Further, cutoff values that best predicted normal patient-reported function differed by graft type and age.

RETURN TO PLAY AFTER ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION

ABSTRACT The anterior cruciate ligament (ACL) tear represents more than half of all knee injuries in sports that involve body rotations and sudden changes of direction. Discharging the athlete for return to play (RTP) post-ACL reconstruction (ACLR) is a difficult task with multidisciplinary responsibility. For many years, a six-month period post-ACLR was adopted as the only criterion for RTP. However, it is now suggested that RTP should not be exclusively time-based, but to clinical data and systematic assessments. Despite the importance of post-ACLR factors for RTP, pre- and peri-ACLR factors must also be considered. Historically, ACLR is performed with the hamstring or autologous patellar tendons, although the choice of graft is still an open and constantly evolving theme. Anterolateral ligament reconstruction and repair of meniscal ramp tear associated with ACLR have recently been suggested as strategies for improving knee joint stability. Subjective questionnaires are easy to apply, and help identify physical or psychological factors that can hamper RTP. Functional tests, such as hop tests and strength assessment by means of isokinetic dynamometers, are fundamental tools for decision making when associated with clinical evaluation and magnetic resonance imaging. Recently, the capacity to generate force explosively has been incorporated into the muscle strength assessment. This is quantified through the rate of torque development (RTD). Due to characteristics inherent to the practice of sport, there is an extremely short time available for produce strength. Thus, RTD seems to better represent athletic demands than the maximum strength assessment alone. This review investigates the pre-, peri- and post-ACLR factors established in the literature, and shares our clinical practice, which we consider to be best practice for RTP. Level of evidence V; Specialist opinion.

Rate of Force Development Remains Reduced in the Knee Flexors 3 to 9 Months After Anterior Cruciate Ligament Reconstruction Using Medial Hamstring Autografts: A Cross-Sectional Study

BACKGROUND

Anterior cruciate ligament (ACL) rupture is a serious injury with a high prevalence worldwide, and subsequent ACL reconstructions (ACLR) appear to be most commonly performed using hamstring-derived (semitendinosus tendon) autografts. Recovery of maximal muscle strength to ≥90% of the healthy contralateral limb is considered an important criterion for safe return to sports. However, the speed of developing muscular force (ie, the rate of force development [RFD]) is also important for the performance of many types of activities in sports and daily living, yet RFD of the knee extensor and flexor muscles has apparently never been examined in patients who undergo ACLR with hamstring autograft (HA).

PURPOSE

To examine potential deficits in RFD, maximal muscle strength (ie, maximal voluntary isometric contraction [MVIC]), and functional capacity of ACLR-HA limbs in comparison with the healthy contralateral leg and matched healthy controls 3 to 9 months after surgery.

STUDY DESIGN

Cross-sectional study; Level of evidence: 3.

METHODS

A total of 23 young patients who had undergone ACLR-HA 3 to 9 months earlier were matched by age to 14 healthy controls; both groups underwent neuromuscular screening. Knee extensor and flexor MVIC and RFD, as well as functional capacity (single-leg hop for distance [SLHD] test, timed single-leg sit-to-stand [STS] test), were assessed on both limbs. Furthermore, patient-reported knee function (Knee injury and Osteoarthritis Outcome Score) was assessed.

RESULTS

Knee extensor and flexor MVIC and RFD were markedly compromised in ACLR-HA limbs compared with healthy contralateral limbs (MVIC for extensor and flexor, 13% and 26%, respectively; RFD, 14%-17% and 32%-39%) and controls (MVIC, 16% and 31%; RFD, 14%-19% and 30%-41%) (P < .05-.001). Further, ACLR-HA limbs showed reduced functional capacity (reduced SLHD and STS performance) compared with contralateral limbs (SLHD, 11%; STS, 14%) and controls (SLHD, 20%; STS, 31%) (P < .01-.001). Strength (MVIC) and functional (SLHD) parameters were positively related to the duration of time after surgery (P < .05), although this relationship was not observed for RFD and STS.

CONCLUSION

Knee extensor and flexor RFD and maximal strength, as well as functional single-leg performance, remained substantially reduced in ACLR-HA limbs compared with noninjured contralateral limbs and healthy controls 3 to 9 months after reconstructive surgery.