Hamstring Strength Asymmetry at 3 Years After Anterior Cruciate Ligament Reconstruction Alters Knee Mechanics During Gait and Jogging

Reducing Walking Speed Decreases Surgical Knee Loading but Not Between-Limb Symmetry in Individuals With Anterior Cruciate Ligament Reconstruction

A higher risk of knee osteoarthritis (OA) has been identified in patients with slower walking speeds following anterior cruciate ligament reconstruction (ACLR). Given that altered loading of the surgical knee has been the most proposed mechanism for early knee OA post-ACLR, understanding how modulating walking speed may modify knee joint loading is essential for developing strategies to reduce the risk of knee OA in ACLR patients. The purpose of this study was to determine how modulation of walking speed affects knee joint loading during overground walking post-ACLR. Lower extremity kinematics and kinetics were recorded during overground walking at a self-selected, slower, and faster speed from 16 patients with unilateral ACLR. The results showed that ACLR patients demonstrated lesser peak knee flexion and adduction moments of the surgical knees when walking at slower speeds. However, modulating walking speed did not alter between-limb knee loading asymmetry. The ACLR limbs had lower peak knee flexion moments than the uninjured limbs across all 3 walking speeds. Although interventions that increase walking speed may deter the onset of knee OA by elevating the mechanical stimulation at the surgical knee, additional gait training strategies may be needed to restore the between-limb loading symmetry in ACLR patients.

Impact of spinal-hip types on gait patterns in patients with end-stage hip disease

BACKGROUND

Patients with end-stage hip disease are classified into distinct spinal-hip types according to sagittal spinal-hip parameters. Each type employs specific compensatory strategies to maintain balance, but the associated alterations in gait patterns remain unclear. This study characterized the gait differences among patients with different spinal-hip types.

METHODS

This prospective observational study used EOS imaging to obtain full-length sagittal images and classify patients into spinal-hip types. The study included 10 patients in each type (A, B, and C) and 10 healthy controls. Gait analysis was performed to evaluate the spatiotemporal and kinematic parameters, followed by the gait profile score (GPS) analysis. The Kruskal-Wallis test was used to compare relevant parameters across the four groups, with post-hoc comparisons conducted using the Bonferroni method.

RESULTS

Significant differences among the types were observed in stride length (P = 0.003), stance phase percentage (P = 0.001), and swing phase percentage (P < 0.001), with type C showing the shortest stride and type A exhibiting the shortest stance phase. The sagittal range of motion (ROM) of the pelvis and hip varied significantly across the gait cycle (both P < 0.001), with type A exhibiting the largest pelvic ROM and the smallest hip ROM. Types A and C showed lower sagittal center of mass displacement during the stance phase (P < 0.001). Type A exhibited the most restricted knee ROM during the swing phase (P < 0.001). The GPS was highest in type A, followed by type C, while type B and healthy controls had the lowest scores (P < 0.001).

CONCLUSIONS

Patients with different spinal-hip types exhibited distinct gait adaptations to compensate for sagittal deformities. Patients with severe sagittal imbalance exhibited compensatory increased pelvic swing and demonstrated diminished functional scores. Preoperative assessment is essential for optimizing total hip arthroplasty outcomes and guiding rehabilitation.

Muscle Strength Outcomes After ACL Reconstruction Before, During, and After COVID-19-Related Rehabilitation Disruptions

Background: Healthcare restrictions on non-urgent services during the COVID-19 pandemic led to limited access to rehabilitation and delayed treatment, potentially affecting early and mid-term recovery following anterior cruciate ligament reconstruction (ACLR). However, little is known about its specific consequences on muscle strength recovery in recreational and amateur athletes. Objectives: This study aimed to compare short-term clinical outcomes in ACLR patients before, during, and after the pandemic, spanning from 2020 to 2022. Methods: We conducted a retrospective review of 126 patients who underwent ACLR using a hamstring tendon autograft. Patients were grouped based on the timing of surgery and matched for gender. Clinical outcomes and muscle strength parameters were evaluated using an isokinetic dynamometer. Results: Male patients exhibited no significant differences in muscle strength across all time frames (control, 2020, 2021, and 2022). In contrast, female patients who underwent surgery in 2020 and 2021 showed higher extension asymmetry index deficits (Q-AI: 34.09 ± 14.59% and 36.47 ± 16.36%, respectively) and increased flexion deficits in 2021 (H-AI: 25.14 ± 11.41%). Significant differences were observed in quadriceps and hamstring peak torque values, both absolute and normalized. By 2022, the female group exhibited a reduced extension deficit (Q-AI: 18.64 ± 14.49%) comparable to pre-pandemic levels (Q-AI: 19.84 ± 12.37%), indicating a recovery of knee extensor strength. Conclusion: Our study showed gender-specific differences in muscle strength recovery after ACLR during the COVID-19 pandemic, with females showing poorer outcomes than males at 5 months post-operation. Larger studies with extended follow-up are needed to clarify the pandemic's impact and gender-specific responses.

Using the Single-Leg Hop Test to Determine Knee Extension Strength After Anterior Cruciate Ligament Reconstruction

Background

Strength assessment and the single-leg hop test are used to assess an athlete's readiness to return to sports after anterior cruciate ligament (ACL) reconstruction (ACLR). Other factors may confound this relationship, limiting the clinical utility of the single-leg hop test.

Purposes

To determine whether the relationship between single-leg hop performance and knee extension/flexion torque is affected by confounding variables and to assess whether the strength of the ACL-reconstructed limb could be predicted using the single-leg hop distance.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Included were 35 men (age, 29.5 ± 6 years; weight, 83.5 ± 8.9 kg) who had undergone ACLR with hamstring tendon autografts. A homogeneous participant population was intentionally recruited to limit variation in outcome measures, increasing the likelihood of successfully predicting strength. The single-leg hop distance and knee extension/flexion strength were assessed. Correlation coefficients were calculated to assess the relationship between single-leg hop test, knee extension/flexion strength, and age. Linear modeling was used to predict knee extension strength, and logistic regression was used to predict which participants met commonly used clinical cutoff values of strength symmetry-measured as the limb symmetry index (LSI).

Results

Strength variables were moderately related to knee extension strength and the single-leg hop distance, although these relationships exhibited wide 95% CIs. The mean error when predicting knee extension strength based on the single-leg hop distance, eccentric knee flexion strength, and age was 0.38 N·m/kg (18%). Eight participants (23%) were incorrectly classified as having a knee extension strength LSI of <85% when using logistic regression to determine whether clinical cutoff values for symmetry were met.

Conclusion

Although the relationship between the single-leg hop test and knee extension strength was moderate, this relationship was imprecise, and predicting strength based on the single-leg hop test resulted in a clinically meaningful amount of error. Based on study findings, it is unlikely that the single-leg hop test provides clinical utility if the goal is to assess knee extension strength.

Hip and knee joints mechanics and asymmetries in individuals with a history of anterior cruciate ligament reconstruction during overground running

BACKGROUND

Individuals with a history of anterior cruciate ligament reconstruction (ACLR) represent altered knee joint mechanics in running. Hip joint can make subtle compensations in response to ACLR. Effects of ACLR on hip joint compensatory mechanisms is not well known. The aim of this study was to evaluate the hip join mechanics and asymmetry in individuals with ACLR history. We hypothesized that ACLR individuals' hip exhibit altered mechanics which can increase the risk of hip overuse or osteoarthritis.

METHODS

Kinetic and kinematic data of 20 males with ACLR history and 20 healthy males were collected bilaterally while running at 3.3 m·s-1. Hip and knee joints peak angles, peak moments, peak negative and positive power and negative and positive work in the sagittal plane were calculated. Also, asymmetry of the outcomes was calculated. A mixed design MANOVA was used to detect between-group and within-group (side-by-group interaction) effects of ACLR on outcomes.

RESULTS

Involved knee showed smaller flexion angle and negative work compared to uninvolved and control knee. In the hip joint, involved leg showed a higher flexion angle, extension moment, and peak positive and negative power as well as negative and positive work compared to uninvolved and control leg. ACLR group showed greater asymmetries in knee flexion angle, knee flexion moment, hip flexion angle, hip extension angle and hip negative power compared to healthy group.

CONCLUSION

Hip and knee joints mechanics of involved and uninvolved sides of the ACLR individuals are different. These results show that ACLR affects hip joint as well as knee joint. When returning to activity and sport, mechanics of the hip joint as well as knee joint, must be considered in ACLR individuals.

Potential financial loss and risk factors for hamstring muscle injuries in elite male Brazilian soccer players: a season-long prospective cohort pilot study

Purpose

The aim of this pilot study was to analyze the potential financial loss and a range of potential risk factors for hamstring muscle injuries in elite Brazilian soccer.

Methods

Thirty-four male players (age: 25 ± 6 years; stature: 180 ± 8 cm; body mass: 78 ± 9 kg; minutes played in matches: 2243 ± 1423 min) from an elite professional soccer club were monitored during a 12-month season. Muscle injury was identified by magnetic resonance imaging and the severity was defined according to the number of days away: minimal (1-3 days), mild (4-7 days), moderate (8-28 days), severe (>28 days). Potential financial loss due to the team's under achievements was determined. Dorsiflexion range of motion, eccentric knee flexor strength and isokinetic tests were performed during the pre-season. Association between dependent variables and the occurrence of injury was evaluated.

Results

Nine hamstring muscle injuries with moderate severity were found in 8 athletes. Recovery time was 22 days off the field on average. Potential financial loss was $-43.2 million USD and earnings on merit money was 21%. Previous injury, increased flexor deficit 60° /sec and increased flexor fatigue index 300°/sec were all associated with a greater chance of hamstring muscle injury. Ankle dorsiflexion range of motion was significantly lower in the injured group (35.6 ± 3° vs. 39.1 ± 4.9°; p = 0.017, effect size = -0.74).

Conclusion

High financial burden was found in elite Brazilian soccer during one full season. Injured athletes had high hamstring fatigue index, knee flexor strength deficit, ankle range of motion restriction and previous hamstring muscle injury when compared to non-injured athletes. Therefore, preventive approaches in professional soccer players with previous hamstring injuries should be a priority.

Bridge-Enhanced Anterior Cruciate Ligament Restoration: 6-Year Results From the First-in-Human Cohort Study

Background

Bridge-enhanced anterior cruciate ligament restoration (BEAR) combines suture repair of the anterior cruciate ligament (ACL) with an extracellular matrix implant plus autologous blood to facilitate native ACL healing.

Purpose/Hypothesis

The purpose of this study was to compare the 6-year follow-up outcomes of patients who underwent the BEAR procedure with those of a nonrandomized concurrent control group receiving autograft ACL reconstruction (ACLR) in the first-in-human safety study of the BEAR implant (BEAR I trial). Based on the 2-year results, it was hypothesized that isometric hamstring strength after the BEAR procedure would be greater than that after ACLR and that there would be no other differences in outcomes at 6 years.

Study Design

Cohort study, Level of evidence, 2.

Methods

Ten patients underwent BEAR and 10 received ACLR with a 4-stranded hamstring autograft. Outcomes assessed included the record of subsequent surgeries, the International Knee Documentation Committee (IKDC) Subjective Knee Score, IKDC physical examination grade, the Knee injury and Osteoarthritis Outcome Score, instrumented knee laxity, functional outcomes (ie, muscle strength assessments and hop testing), and qualitative magnetic resonance imaging assessment. Comparisons between treatments were based on computations of the mean differences and the associated 95% CIs.

Results

One patient in the BEAR group and 3 patients in the ACLR group were lost to follow-up. In the period between 2 and 6 years, 1 patient in each group underwent revision surgery. There were no differences between groups at the 6-year follow-up in any of the outcome measures except for isometric hamstring strength, which was approximately equal to that of the contralateral knee in the BEAR group and <44% of that in the contralateral knee in the ACLR group (P < .01).

Conclusion

This preliminary study suggests that the outcomes of BEAR and ACLR with a hamstring tendon graft may be similar at the 6-year follow-up and warrants investigation of the BEAR procedure in a larger cohort of patients.

There is more to the knee joint than just the quadriceps: A systematic review with meta-analysis and evidence gap map of hamstring strength, flexibility, and morphology in individuals with gradual-onset knee disorders

BACKGROUND

Impairments in hamstring strength, flexibility, and morphology have been associated with altered knee biomechanics, pain, and function. Determining the presence of these impairments in individuals with gradual-onset knee disorders is important and may indicate targets for assessment and rehabilitation. This systematic review aimed to synthesize the literature to determine the presence of impairments in hamstring strength, flexibility, and morphology in individuals with gradual-onset knee disorders.

METHODS

Five databases (MEDLINE, Embase, CINAHL, SPORTDiscus, and Web of Science) were searched from inception to September 2022. Only studies comparing hamstring outcomes (e.g., strength, flexibility, and/or morphology) between individuals with gradual-onset knee disorders and their unaffected limbs or pain-free controls were included. Meta-analyses for each knee disorder were performed. Outcome-level certainty was assessed using the Grading of Recommendations Assessment, Development, and Evaluation, and evidence gap maps were created.

RESULTS

Seventy-nine studies across 4 different gradual-onset knee disorders (i.e., knee osteoarthritis (OA), patellofemoral pain (PFP), chondromalacia patellae, and patellar tendinopathy) were included. Individuals with knee OA presented with reduced hamstring strength compared to pain-free controls during isometric (standard mean difference (SMD) = -0.76, 95% confidence interval (95%CI) : -1.32 to -0.21) and concentric contractions (SMD = -0.97, 95%CI : -1.49 to -0.45). Individuals with PFP presented with reduced hamstring strength compared to pain-free controls during isometric (SMD = -0.48, 95%CI : -0.82 to -0.14), concentric (SMD = -1.07, 95%CI : -2.08 to -0.06), and eccentric contractions (SMD = -0.59, 95%CI : -0.97 to -0.21). No differences were observed in individuals with patellar tendinopathy. Individuals with PFP presented with reduced hamstring flexibility when compared to pain-free controls (SMD = -0.76, 95%CI : -1.15 to -0.36). Evidence gap maps identified insufficient evidence for chondromalacia patellae and hamstring morphology across all gradual-onset knee disorders.

CONCLUSION

Our findings suggest that assessing and targeting impairments in hamstring strength and flexibility during rehabilitation may be recommended for individuals with knee OA or PFP.

Hamstring Tendon Autograft Is Associated With Increased Knee Valgus Moment After Anterior Cruciate Ligament Reconstruction: A Biomechanical Analysis

BACKGROUND

There is limited evidence related to the effects of autograft type on functional performance after anterior cruciate ligament reconstruction (ACLR).

PURPOSE/HYPOTHESIS

This study aimed to compare biomechanical outcomes during a drop vertical jump (DVJ) between patients with a hamstring tendon (HT) autograft, quadriceps tendon (QT) autograft with bone block, QT autograft without bone block, and bone-patellar tendon-bone autograft at 6 months postoperatively in an adolescent population. The authors' hypothesized there would be differences in DVJ biomechanics between athletes depending on the type of autograft used.

STUDY DESIGN

Controlled laboratory study.

METHODS

Patients aged 8 to 18 years who underwent primary ACLR were included for analysis. Kinematic and kinetic data collected during a DVJ using a 3-dimensional computerized marker system were assessed at 6 months after ACLR and compared with the uninjured contralateral limb.

RESULTS

A total of 155 participants were included. There were no significant differences in terms of age, sex, or affected leg (P≥ .1973) between groups. The HT group was significantly associated with a larger knee valgus moment at initial contact compared with the QT group (28 × 10-2 vs -35 × 10-2 N·m/kg, respectively; P = .0254) and a significantly larger maximum hip adduction moment compared with the QT with bone block group (30 × 10-2 vs -4 × 10-2 N·m/kg, respectively; P = .0426). Both the QT with bone block (-12 × 10-2 vs -3 × 10-2 N·m/kg, respectively; P = .0265) and QT (-13 × 10-2 vs -3 × 10-2 N·m/kg, respectively; P = .0459) groups demonstrated significantly decreased mean knee extension moments compared with the HT group.

CONCLUSION

The findings of this study suggest that utilizing an HT autograft resulted in a significantly increased knee valgus moment at initial contact compared with a QT autograft without bone block at 6 months after ACLR in adolescent patients performing a DVJ. A QT autograft was found to be associated with significantly decreased extensor mechanism function compared with an HT autograft.

CLINICAL RELEVANCE

This study adds unique kinematic and kinetic information regarding various ACLR autograft options and highlights the biomechanical deficits that should be taken into consideration in rehabilitation.

Mechanical energy flow analysis in athletes with and without anterior cruciate ligament reconstruction during single-leg drop landing

Techniques that reduce mechanical energy have been linked to lower chances of experiencing an Anterior Cruciate Ligament (ACL) injury. Although there is evidence that movement patterns are altered in athletes who have undergone Anterior Cruciate Ligament Reconstruction (ACLR), energy transfer mechanisms have not been examined. This study aimed to compare energy flow mechanisms during single-leg drop landing between athletes with and without history of ACLR. A total of 20 female athletes were included in this study. Ten participants underwent ACLR 12 months ago (mean age, 21.57 ± 0.41 years) and 10 were healthy controls (mean age, 20.89 ± 0.21 years). Participants executed the single-leg drop landing (SLL) maneuver by descending from a 30 cm wooden box and landing on the tested leg on an embedded force plate. Information collected during the SLL trials was refined using rigid-body analysis and inverse dynamics within Nexus software, ultimately allowing construction of skeletal models of the athletes. Ankle and knee mechanical energy expenditure (MEE) was higher in the control participants during landing. However, the result for the hip MEE demonstrated that MEE of the control group was significantly lower compared with the ACLR group, but MEE of the control subjects was higher as compared to ACLR group (p ˂ 0.05). Results suggest the avoidant use of the quadriceps muscle post ACLR leads to knee-avoidant mechanics and loss of knee joint power generation during a SLL task.

Deficits in muscle strength are not seen following recovery from augmented primary repair of anterior cruciate ligament tears

OBJECTIVES

Anterior cruciate ligament (ACL) repair for proximal tears, where the ligament is re-attached and augmented with suture tape, can negate the need for graft harvest, thereby maintaining native anatomy. Autograft harvest has been associated with persistent deficits in lower limb muscle strength after recovery from ACL reconstruction. The aim of this study is to compare lower limb muscle strength following ACL repair and reconstruction.

METHODS

Nineteen ACL repair patients augmented with suture tape and nineteen ipsilateral semitendinosus-gracilis autograft ACL reconstruction patients (both mean 4 years postoperatively) were recruited, along with twenty healthy volunteers. Patient-reported outcome measures (PROMs) were obtained using the Knee Injury and Osteoarthritis Outcome Score (KOOS), Lysholm, and Tegner scores. Maximal isometric quadriceps and hamstring strength at 90° knee flexion were measured using a fixed Myometer after a warm-up and three maximal-effort contractions.

RESULTS

Mean hamstring strength of the reconstructed legs was lower than that of healthy volunteers by 0.29 Nm/kg. The hamstring strength ratio of the operated side to the uninjured side was greater in the repair (95% ​± ​13) than in the reconstruction (81% ​± ​18) group. There were no statistically significant differences between sides for quadriceps peak torque or for hamstrings in the volunteer or repair group. PROMs scores for the reconstruction group were significantly lower than volunteers across all domains and lower than repair for KOOS activities of daily living and Lysholm scores.

CONCLUSION

Hamstring weakness seen following ACL reconstruction is not evident following ACL repair with suture tape augmentation. Strength asymmetry could contribute to re-injury risk and influence functional performance, while altered loads affect knee biomechanics and may lead to osteoarthritis progression. The absence of these deficits in the repair group demonstrates a potential benefit of this technique when used in appropriate patients.

LEVEL OF EVIDENCE

II.

The Evaluation of Asymmetry in Isokinetic and Electromyographic Activity (sEMG) of the Knee Flexor and Extensor Muscles in Football Players after ACL Rupture Reconstruction and in the Athletes following Mild Lower-Limb Injuries

This study was aimed at evaluating knee stabilizer (quadriceps and hamstring) muscle strength and the medio-lateral symmetry of hamstring fatigue in football players after ACL reconstruction and with mild lower extremity injuries. The study comprised 65 professional football players who were divided into three groups: Group 1 (n = 24; 22.7 ± 3.6 years; 175 ± 4 cm; 77.3 ± 7.6 kg) after ACL reconstruction, Group 2 (n = 21; 20.5 ± 3.7 years; 177 ± 6 cm; 74.3 ± 9.1 kg) with mild lower-limb injuries (grade 1 muscle strains) and Group 3 (n = 20; 23.1 ± 2.8 years; 178 ± 6 cm; 75.8 ± 8.8 kg) without injuries in the past 3 years. The concentric isokinetic test (10 knee flexions and extensions at 60, 180 and 300°/s with a 30 s interval for rest) was performed on both limbs. Fatigue symmetry between the medial and lateral hamstrings was measured with sEMG during 60 s of isometric contractions. In comparison to the other groups, the injured leg demonstrated significantly lower values of peak torque for the quadriceps (G1-G2 = 48%, 38%, 14%; G1-G3 = 49%, 25%, 14%) and hamstring muscles (G1-G2 = 36%, 35%, 18%; G1-G3 = 64%, 28%, 17%) as well as lower values of hamstring muscle work (G1-G2 = 262 J, 157 J; G1-G3 = 219 J, 179 J) and power (G1-G2 = 34 W; 11 W; G1-G3 = 29 W, 12 W). No significant differences were noted in strength between Groups 2 and 3. The significantly higher fatigue of the BF compared to the SEM muscle was seen in Group 1 for the involved (mean difference = 0.12) and uninvolved limbs (mean difference = -0.10), but in Group 2, a non-significant trend towards asymmetry was also noted. No asymmetry in hamstring muscle fatigue was determined in Group 3. The results of our study allow us to indicate that active football players who previously met the RTS criteria, had deficits in lower-limb muscle performance 2-3 years after reconstruction, which could lead to ACL re-injury. This observation is potentially of importance because these deficits may not be subjectively reported by such athletes and also may not be visible in regular orthopedic and physiotherapeutic assessment.

Composite Score of Readiness (CSR) as a Data Reduction Technique for Monitoring the RTS Process in Footballers following ACL Reconstruction

In recent years, many studies on the safe return to sport (RTS) have been published, but there are still no clear and validated guidelines. After ACL reconstruction between limbs, asymmetry of muscle strength affects knee mechanics during walking and running, and asymmetrical joint kinematics and kinetics are considered as a strong risk factor of musculoskeletal injury. Therefore, proper diagnosis of any motor deficits remaining after ACL reconstruction seems particularly important. The aim of this study was to analyze how many tests should be included in the RTS test battery and which of them are most indicative for functional deficits related to anterior cruciate ligament (ACL) reconstruction. Sixty-five male football players (age 18–25 years) were divided into three groups: ACL group—after ACL rupture and reconstruction, mild injury group—post mild lower limb injuries, and the control group—without injuries. They performed five tests: Functional Movement Screen, Tuck Jump Assessment, Y-balance Test, Hop Test for Distance, and Isokinetic Test. The Composite Score of Readiness (CSR) index was calculated and expressed as the sum of z-scores. The multiple regression model for all tests was calculated, and then redundant variables were excluded. We observed that all tests significantly influenced the final CSR index. The Y-balance Test, Tuck Jump Assessment, and Isokinetic Test for knee flexion influenced the final CSR index the most, which means that these tests are greatly indicative of functional deficits related to ACL reconstruction. The strength of the extensor (quadriceps) muscle and the quadriceps/hamstring ratio appeared to be non-sensitive for testing functional deficits related to ACL reconstruction. If the test battery includes 4–5 tests, it better differentiates the athletes following ACL reconstruction from those after mild injuries, even if they all were cleared to play.

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.

Effect of Time After Injury on Tibiofemoral Joint Kinematics in Anterior Cruciate Ligament-Deficient Knees During Gait

Background:

Anterior cruciate ligament (ACL) injury can lead to changes in tibiofemoral kinematics during gait, but the detailed short-term kinematic changes after ACL injury are still unknown.

Purpose:

To measure tibiofemoral kinematics during gait in ACL-deficient (ACLD) knees over time after ACL injury.

Study Design:

Controlled laboratory study.

Methods:

The authors categorized 76 patients with unilateral ACLD knees into 4 groups based on the time from injury: <3 months (group 1), 3 to 6 months (group 2), >6 to 12 months (group 3), and >12 months (group 4). The controls were 20 participants with ACL-intact knees. Changes in the knee kinematics and range of motion during gait were compared among ACLD groups and those with ACL-intact knees.

Results:

Compared with controls, the range of motion of flexion in group 1 was significantly lower (6°; P = .033), and the mean knee flexion was significantly increased (0.7°-3.4°) in groups 1 to 4 (all P ≤ .004). There was more internal tibial rotation (2.9°-4.3°) in group 1 and 2, and more anterior tibial translation (4.3 mm) in group 1 during the stance or swing phases than in controls (P ≤ .049 for all). The mean internal tibial rotation and anterior tibial translation significantly decreased from group 1 to group 4 (P < .001 for both). Compared with controls, the mean medial tibial translation was significantly greater (1.2-2.5 mm) in all groups, and more medial tibial translations (2.4-3.7 mm) were observed during the stance phase in groups 1, 3, and 4 (P ≤ .047 for all).

Conclusion:

ACLD knees displayed a motion impairment walking strategy within 3 months, and a higher-flexion walking strategy increased with time after injury. Excessive anterior translation and internal rotation of the tibia tended to return to normal, while excessive medial translation of the tibia increased in ACLD knees after 6 months postinjury. These results may provide new insight into the compensatory mechanisms and risk factors for premature osteoarthritis in ACLD knees.

Early Superimposed NMES Training is Effective to Improve Strength and Function Following ACL Reconstruction with Hamstring Graft regardless of Tendon Regeneration

The study aimed at investigating the effects of neuromuscular electrical stimulation superimposed on functional exercises (NMES+) early after anterior cruciate ligament reconstruction (ACLr) with hamstring graft, on muscle strength, knee function, and morphology of thigh muscles and harvested tendons. Thirty-four participants were randomly allocated to either NMES+ group, who received standard rehabilitation with additional NMES of knee flexor and extensor muscles, superimposed on functional movements, or to a control group, who received no additional training (NAT) to traditional rehabilitation. Participants were assessed 15 (T1), 30 (T2), 60 (T3), 90 (T4) and at a mean of 380 days (T5) after ACLr. Knee strength of flexors and extensors was measured at T3, T4 and T5. Lower limb loading asymmetry was measured during a sit-to-stand-to-sit movement at T1, T2, T3, T4 and T5, and a countermovement-jump at T4 and T5. An MRI was performed at T5 to assess morphology of thigh muscles and regeneration of the harvested tendons. NMES+ showed higher muscle strength for the hamstrings (T4, T5) and the quadriceps (T3, T4, T5), higher loading symmetry during stand-to-sit (T2, T3, T4, T5), sit-to-stand (T3, T4) and countermovement-jump (T5) than NAT. No differences were found between-groups for morphology of muscles and tendons, nor in regeneration of harvested tendons. NMES+ early after ACLr with hamstring graft improves muscle strength and knee function in the short- and long-term after surgery, regardless of tendon regeneration.

Design Features and Rationale of the BEAR-MOON (Bridge-Enhanced ACL Restoration Multicenter Orthopaedic Outcomes Network) Randomized Clinical Trial

Background:

BEAR (bridge-enhanced anterior cruciate ligament [ACL] restoration), a paradigm-shifting technology to heal midsubstance ACL tears, has been demonstrated to be effective in a single-center 2:1 randomized controlled trial (RCT) versus hamstring ACL reconstruction. Widespread dissemination of BEAR into clinical practice should also be informed by a multicenter RCT to demonstrate exportability and compare efficacy with bone--patellar tendon–bone (BPTB) ACL reconstruction, another clinically standard treatment.

Purpose:

To present the design and initial preparation of a multicenter RCT of BEAR versus BPTB ACL reconstruction (the BEAR: Multicenter Orthopaedic Outcomes Network [BEAR-MOON] trial). Design and analytic issues in planning the complex BEAR-MOON trial, involving the US National Institute of Arthritis and Musculoskeletal and Skin Diseases, the US Food and Drug Administration, the BEAR implant manufacturer, a data and safety monitoring board, and institutional review boards, can usefully inform both clinicians on the trial’s strengths and limitations and future investigators on planning of complex orthopaedic studies.

Study Design:

Clinical trial.

Methods:

We describe the distinctive clinical, methodological, and operational challenges of comparing the innovative BEAR procedure with the well-established BPTB operation, and we outline the clinical motivation, experimental setting, study design, surgical challenges, rehabilitation, outcome measures, and planned analysis of the BEAR-MOON trial.

Results:

BEAR-MOON is a 6-center, 12-surgeon, 200-patient randomized, partially blinded, noninferiority RCT comparing BEAR with BPTB ACL reconstruction for treating first-time midsubstance ACL tears. Noninferiority of BEAR relative to BPTB will be claimed if the total score on the International Knee Documentation Committee (IKDC) subjective knee evaluation form and the knee arthrometer 30-lb (13.61-kg) side-to-side laxity difference are both within respective margins of 16 points for the IKDC and 2.5 mm for knee laxity.

Conclusion:

Major issues include patient selection, need for intraoperative randomization and treatment-specific postoperative physical therapy regimens (because of fundamental differences in surgical technique, initial stability construct, and healing), and choice of noninferiority margins for short-term efficacy outcomes of a novel intervention with evident short-term advantages and theoretical, but unverified, long-term benefits on other dimensions.

Efficacy of the SOAR knee health program: protocol for a two-arm stepped-wedge randomized delayed-controlled trial

BACKGROUND

Knee trauma permanently elevates one's risk for knee osteoarthritis. Despite this, people at-risk of post-traumatic knee osteoarthritis rarely seek or receive care, and accessible and efficacious interventions to promote knee health after injury are lacking. Exercise can ameliorate some mechanisms and independent risk factors for osteoarthritis and, education and action-planning improve adherence to exercise and promote healthy behaviours.

METHODS

To assess the efficacy of a virtually-delivered, physiotherapist-guided exercise-based program (SOAR) to improve knee health in persons discharged from care after an activity-related knee injury, 70 people (16-35 years of age, 12-48 months post-injury) in Vancouver Canada will be recruited for a two-arm step-wedged assessor-blinded delayed-control randomized trial. Participants will be randomly allocated to receive the intervention immediately or after a 10-week delay. The program consists of 1) one-time Knee Camp (group education, 1:1 individualized exercise and activity goal-setting); 2) weekly individualized home-based exercise and activity program with tracking, and; 3) weekly 1:1 physiotherapy-guided action-planning with optional group exercise class. Outcomes will be measured at baseline, 9- (primary endpoint), and 18-weeks. The primary outcome is 9-week change in knee extension strength (normalized peak concentric torque; isokinetic dynamometer). Secondary outcomes include 9-week change in moderate-to-vigorous physical activity (accelerometer) and self-reported knee-related quality-of-life (Knee injury and OA Outcome Score subscale) and self-efficacy (Knee Self Efficacy Scale). Exploratory outcomes include 18-week change in primary and secondary outcomes, and 9- and 18- week change in other components of knee extensor and flexor muscle function, hop function, and self-reported symptoms, function, physical activity, social support, perceived self-care and kinesiophobia. Secondary study objectives will assess the feasibility of a future hybrid effectiveness-implementation trial protocol, determine the optimal intervention length, and explore stakeholder experiences.

DISCUSSION

This study will assess the efficacy of a novel, virtually-delivered, physiotherapist-guided exercise-based program to optimize knee health in persons at increased risk of osteoarthritis due to a past knee injury. Findings will provide valuable information to inform the management of osteoarthritis risk after knee trauma and the conduct of a future effectiveness-implementation trial.

TRIAL REGISTRATION

Clinicaltrials.gov reference: NTC04956393. Registered August 5, 2021, https://clinicaltrials.gov/ct2/show/NCT04956393?term=SOAR&cond=osteoarthritis&cntry=CA&city=Vancouver&draw=2&rank=1.

The Calculation, Thresholds and Reporting of Inter-Limb Strength Asymmetry: A Systematic Review

The prevalence of inter-limb strength differences is well documented in the literature however, there are inconsistencies related to measurement and reporting, and the normative values and effects associated with inter-limb asymmetry. Therefore, the aims of this systematic review were to: 1) assess the appropriateness of existing indices for the calculation of asymmetry, 2) interrogate the evidence basis for literature reported thresholds used to define asymmetry and 3) summarise normative levels of inter-limb strength asymmetry and their effects on injury and performance. To conduct this systematic review, scientific databases (PubMed, Scopus, SPORTDiscus and Web of Science) were searched and a total of 3,594 articles were retrieved and assessed for eligibility and article quality. The robustness of each identified asymmetry index was assessed, and the evidence-basis of the identified asymmetry thresholds was appraised retrospectively using the references provided. Fifty-three articles were included in this review. Only four of the twelve identified indices were unaffected by the limitations associated with selecting a reference limb. Eighteen articles applied a threshold to original research to identify "abnormal" asymmetry, fifteen of which utilised a threshold between 10-15%, yet this threshold was not always supported by appropriate evidence. Asymmetry scores ranged between and within populations from approximate symmetry to asymmetries larger than 15%. When reporting the effects of strength asymmetries, increased injury risk and detriments to performance were often associated with larger asymmetry, however the evidence was inconsistent. Limitations of asymmetry indices should be recognised, particularly those that require selection of a reference limb. Failure to reference the origin of the evidence for an asymmetry threshold reinforces doubt over the use of arbitrary thresholds, such as 10-15%. Therefore, an individual approach to defining asymmetry may be necessary to refine robust calculation methods and to establish appropriate thresholds across various samples and methodologies that enable appropriate conclusions to be drawn.

Effect of Concomitant Meniscal Tear on Strength and Functional Performance in Young Athletes 6 Months After Anterior Cruciate Ligament Reconstruction With Hamstring Autograft

Background:

The effect of concomitant meniscal tears, and their associated treatment, on strength and functional recovery after anterior cruciate ligament reconstruction (ACLR) has not been adequately investigated in young populations.

Hypothesis:

Concomitant meniscal tears, treated with or without repair, would not adversely affect strength, balance, or functional hop test performance at 6 months postoperatively.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

The authors retrospectively analyzed return-to-sports (RTS) assessments prospectively collected 6 months after ACLR with hamstring autograft in 165 patients ≤25 years of age. Descriptive, surgical, and RTS testing data were analyzed, and subgroups were compared using analysis of covariance models designed to assess the effects of sex, meniscal tear, and meniscal repair on RTS performance.

Results:

Included were 115 female (70%) and 50 male (30%) patients with a mean age of 16.4 years (range, 12.3-25 years). Of these patients, 58% had concomitant meniscal tears (59% lateral, 27% medial, 14% lateral + medial), comprising 53% of the female and 70% of the male patients. The authors treated 61% of the tears with repair, with range of motion (ROM) and weightbearing limitations imposed within the first 6 weeks postoperatively, whereas 39% were treated with partial meniscectomy, rasping, or trephination (no ROM or weightbearing restrictions). The mean deficit in hamstring strength at 6 months postoperatively was significantly greater in the meniscal tear group than in those without a tear (32.3% vs 24.6%; P = .028). The meniscal repair group had greater hamstring strength deficits than the group with meniscectomy, rasping or trephination (34.3% vs 26.2%; P = .023). Performance on dynamic balance and functional hop tests was similar among all meniscus subgroups. There were no sex-based effects on any subgroup comparisons.

Conclusion:

At 6 months postoperatively, both young male and young female patients who underwent ACLR with hamstring autograft demonstrated significant hamstring strength deficits compared with their nonoperative leg. The presence of a meniscal tear and subsequent repair, or its related rehabilitation restrictions, appears to have adverse effects on the postoperative recovery of hamstring strength.

Anterior Cruciate Ligament Reconstruction Increases the Risk of Hamstring Strain Injury Across Football Codes in Australia

OBJECTIVE

The aim of this study was to determine the impacts of anterior cruciate ligament reconstruction (ACLR) and recent (< 12 months) hamstring strain injury (HSI) on (1) future HSI risk, and (2) eccentric knee flexor strength and between-limb imbalance during the Nordic hamstring exercise. A secondary goal was to examine whether eccentric knee flexor strength was a risk factor for future HSI in athletes with prior ACLR and/or HSI.

METHODS

In this prospective cohort study, 531 male athletes had preseason eccentric knee flexor strength tests. Injury history was also collected. The main outcome was HSI occurrence in the subsequent competitive season.

RESULTS

Overall, 74 athletes suffered at least one prospective HSI. Compared with control athletes, those with a lifetime history of ACLR and no recent HSI had 2.2 (95% confidence interval [CI] 1.1-4.4; p = 0.029) times greater odds of subsequent HSI while those with at least one HSI in the previous 12 months and no history of ACLR had 3.1 (95% CI 1.8-5.4; p < 0.001) times greater odds for subsequent HSI. Only athletes with a combined history of ACLR and recent HSI had weaker injured limbs (p = 0.001) and larger between-limb imbalances (p < 0.001) than uninjured players. An exploratory decision tree analysis suggested eccentric strength may protect against HSI after ACLR.

CONCLUSION

ACLR and recent HSI were similarly predictive of future HSI. Lower levels of eccentric knee flexor strength and larger between-limb imbalances were found in athletes with combined histories of ACLR and recent HSI. These findings may have implications for injury rehabilitation.

The correlation between posterior tibial slope and dynamic anterior tibial translation and dynamic range of tibial rotation

Purpose

The amount of passive anterior tibial translation (ATT) is known to be correlated to the amount of posterior tibial slope (PTS) in both anterior cruciate ligament-deficient and reconstructed knees. Slope-altering osteotomies are advised when graft failure after anterior cruciate ligament (ACL) reconstruction occurs in the presence of high PTS. This recommendation is based on studies neglecting the influence of muscle activation. On the other hand, if dynamic range of tibial rotation (rTR) is related to the amount of PTS, a “simple” anterior closing-wedge osteotomy might not be sufficient to control for tibial rotation. The purpose of this study was to evaluate the correlation between the amount of PTS and dynamic ATT and tibial rotation during high demanding activities, both before and after ACL reconstruction. We hypothesized that both ATT and rTR are strongly correlated to the amount of PTS.

Methods

Ten subjects were studied both within three months after ACL injury and one year after ACL reconstruction. Dynamic ATT and dynamic rTR were measured using a motion-capture system during level walking, during a single-leg hop for distance and during a side jump. Both medial and lateral PTS were measured on MRI. A difference between medial and lateral PTS was calculated and referred to as Δ PTS. Spearman’s correlation coefficients were calculated for the correlation between medial PTS, lateral PTS and Δ PTS and ATT and between medial PTS, lateral PTS and Δ PTS and rTR.

Results

Little (if any) to weak correlations were found between medial, lateral and Δ PTS and dynamic ATT both before and after ACL reconstruction. On the other hand, a moderate-to-strong correlation was found between medial PTS, lateral PTS and Δ PTS and dynamic rTR one year after ACL reconstruction.

Conclusion

During high-demand tasks, dynamic ATT is not correlated to PTS. A compensation mechanism may be responsible for the difference between passive and dynamic ATT in terms of the correlation to PTS. A moderate-to-strong correlation between amount of PTS and rTR indicates that such a compensation mechanism may fall short in correcting for rTR. These findings warrant prudence in the use of a pure anterior closing wedge osteotomy in ACL reconstruction.

Trial registration

Netherlands Trial Register, Trial 7686. Registered 16 April 2016—Retrospectively registered.

Level of evidence

Level 2, prospective cohort study

Knee muscle strength after quadriceps tendon autograft anterior cruciate ligament reconstruction: systematic review and meta-analysis

PURPOSE

Restoration of knee muscle strength is associated with better outcomes following anterior cruciate ligament (ACL) reconstruction, but little is known about the outcome of strength following quadriceps tendon autograft (QT) ACL reconstruction in relation to other graft types. The aim of this review was to evaluate strength outcomes of the knee extensors and knee flexors following QT ACL reconstruction compared to (1) the non-reconstructed contralateral limb and (2) alternative ACL graft types.

METHODS

Four electronic databases were searched up until 21st February 2020. Summary meta-analyses were performed comparing knee strength outcomes following QT ACL reconstruction to the contralateral limb by way of limb symmetry index (LSI). Comparative meta-analyses were performed comparing QT ACL reconstruction to alternative ACL grafts for the two most frequently reported strength outcome measures which were peak knee extensor torque LSI, and peak knee flexor torque LSI at the following post-operative periods: 3, 5-8, 9-15, 24, 36-60 months.

RESULTS

In total, 18 studies met the inclusion criteria. Knee strength outcomes of 952 QT ACL reconstructions were included and compared to either the contralateral limb or 1 of 4 alternative ACL graft types; 245 hamstring tendon autograft (HT), 143 patellar tendon autograft (PT), 45 quadriceps tendon allograft, and 21 tibialis anterior allograft. Knee extensor strength LSI following QT ACL reconstruction did not reach 90% even at 24 months post-operatively. Conversely, knee flexor strength LSI following QT ACL reconstruction exceeded 90% at the 9-15 months post-operative period. Knee extensor strength at 5-8 months following QT ACL reconstruction appears similar to PT but weaker than HT ACL reconstruction. In addition, peak knee flexor LSI was significantly greater at 5-8 months in QT ACL reconstruction patients compared to HT patients.

CONCLUSION

The decision to utilize a QT graft for ACL reconstruction should include consideration of strength outcomes. Knee extensor strength recovery following QT ACL reconstruction appears not to be restored before 24 months.

LEVEL OF EVIDENCE

Level IV.

Biceps Femoris Compensates for Semitendinosus After Anterior Cruciate Ligament Reconstruction With a Hamstring Autograft: A Muscle Functional Magnetic Resonance Imaging Study in Male Soccer Players

BACKGROUND

Rates of reinjury, return to play (RTP) at the preinjury level, and hamstring strain injuries in male soccer players after anterior cruciate ligament reconstruction (ACLR) remain unsatisfactory, due to multifactorial causes. Recent insights on intramuscular hamstring coordination revealed the semitendinosus (ST) to be of crucial importance for hamstring functioning, especially during heavy eccentric hamstring loading. Scientific evidence on the consequences of ST tendon harvest for ACLR is scarce and inconsistent. This study intended to investigate the repercussions of ST harvest for ACLR on hamstring muscle function.

HYPOTHESIS

Harvest of the ST tendon for ACLR was expected to have a significant influence on hamstring muscle activation patterns during eccentric exercises, evaluated at RTP in a population of male soccer athletes.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 30 male soccer players with a history of ACLR who were cleared for RTP and 30 healthy controls were allocated to this study during the 2018-2019 soccer season. The influence of ACLR on hamstring muscle activation patterns was assessed by comparing the change in T2 relaxation times [ΔT2 (%) = post-exercise-T2pre-exerciseT2pre-exercise] of the hamstring muscle tissue before and after an eccentric hamstring loading task between athletes with and without a recent history of ACLR through use of muscle functional magnetic resonance imaging, induced by an eccentric hamstring loading task between scans.

RESULTS

Significantly higher exercise-related activity was observed in the biceps femoris (BF) of athletes after ACLR compared with uninjured control athletes (13.92% vs 8.48%; P = .003), whereas the ST had significantly lower activity (19.97% vs 25.32%; P = .049). Significant differences were also established in a within-group comparison of the operated versus the contralateral leg in the ACLR group (operated vs nonoperated leg: 14.54% vs 11.63% for BF [P = .000], 17.31% vs 22.37% for ST [P = .000], and 15.64% vs 13.54% for semimembranosus [SM] [P = .014]). Neither the muscle activity of SM and gracilis muscles nor total posterior thigh muscle activity (sum of exercise-related ΔT2 of the BF, ST, and SM muscles) presented any differences in individuals who had undergone ACLR with an ST tendon autograft compared with healthy controls.

CONCLUSION

These findings indicate that ACLR with a ST tendon autograft might notably influence the function of the hamstring muscles and, in particular, their hierarchic dimensions under fatiguing loading circumstances, with increases in relative BF activity contribution and decreases in relative ST activity after ACLR. This between-group difference in hamstring muscle activation pattern suggests that the BF partly compensates for deficient ST function in eccentric loading. These alterations might have implications for athletic performance and injury risk and should probably be considered in rehabilitation and hamstring injury prevention after ACLR with a ST tendon autograft.

Copers and Noncopers Use Different Landing Techniques to Limit Anterior Tibial Translation After Anterior Cruciate Ligament Reconstruction

Background:

At 1 year after anterior cruciate ligament reconstruction (ACLR), two-thirds of patients manage to return to sports (copers), whereas one-third of patients do not return to sports (noncopers). Copers and noncopers have different muscle activation patterns, and noncopers may not be able to control dynamic anterior tibial translation (ATTd) as well as copers.

Purpose/Hypothesis:

To investigate whether (1) there is a positive correlation between passive ATT (ATTp; ie, general joint laxity) and ATTd during jump landing, (2) whether ATTd is moderated by muscle activating patterns, and (3) whether there is a difference in moderating ATTd between copers and noncopers. We hypothesized that patients who have undergone ACLR compensate for ATTd by developing muscle strategies that are more effective in copers compared with noncopers.

Study Design:

Controlled laboratory study.

Methods:

A total of 40 patients who underwent unilateral ACLR performed 10 single-leg hops for distance with both legs. Lower body kinematic and kinetic data were measured using a motion-capture system, and ATTd was determined with an embedded method. Muscle activity was measured using electromyographic signals. Bilateral ATTp was measured using a KT-1000 arthrometer. In addition, the Beighton score was obtained.

Results:

There was no significant correlation between ATTp and ATTd in copers; however, there was a positive correlation between ATTp and ATTd in the operated knee of noncopers. There was a positive correlation between the Beighton score and ATTp as well as between the Beighton score and ATTd in both copers and noncopers in the operated knee. Copers showed a negative correlation between ATTd and gastrocnemius activity in their operated leg during landing. Noncopers showed a positive correlation between ATTd and knee flexion moment in their operated knee during landing.

Conclusion:

Copers used increased gastrocnemius activity to reduce ATTd, whereas noncopers moderated ATTd by generating a smaller knee flexion moment.

Clinical Relevance:

This study showed that copers used different landing techniques than noncopers. Patients who returned to sports after ACLR had sufficient plantar flexor activation to limit ATTd.

Optimising the 'Mid-Stage' Training and Testing Process After ACL Reconstruction

Outcomes following anterior cruciate ligament (ACL) reconstruction need improving, with poor return-to-sport rates and high risk of secondary re-injury. There is a need to improve rehabilitation strategies after ACL reconstruction, if we can support enhanced patient outcomes. This paper discusses how to optimise the mid-stage rehabilitation process after ACL reconstruction. Mid-stage is a difficult and vitally important stage of the functional recovery process and provides the foundation on which to commence late-stage rehabilitation training. Often many aspects of mid-stage rehabilitation (e.g. knee extensors isolated muscle strength) are not actually restored prior to return-to-sport. In addition, if we are to allow time for optimal late-stage rehabilitation and return-to-sport training, we need to optimise the mid-stage rehabilitation approach and complete it in a timely manner. This paper forms a key part of a strategy to optimise the ACL rehabilitation approach and considers factors more specific to mid-stage rehabilitation characterised in 3 areas: (1) muscle strength: muscle and joint specific, in particular at the knee level, with the knee extensors and flexors and distally with the triceps surae and proximally with the lumbo-pelvic-hip complex, as well as closed kinetic chain strength; (2) altered basic motor patterning (movement quality) and (3) fitness re-conditioning. In addition, the paper provides recommendations on how to implement these into practice, discussing training planning and programming and suggests specific screening to monitor work and when the athlete is able to progress to the next stage (e.g. late-stage rehabilitation criteria).

How does anterior cruciate ligament reconstruction affect the functioning of the brain and spinal cord? A systematic review with meta-analysis

OBJECTIVE

To examine the effect of anterior cruciate ligament (ACL) reconstruction on spinal-reflex and corticospinal excitability of the quadriceps muscle.

METHODS

A comprehensive electronic database search was performed to identify studies that objectively measured Hoffmann reflex to muscle response ratio, motor threshold, and motor evoked potentials after ACL reconstruction. Pooled standardized mean differences (SMDs) were computed using a random effects meta-analysis model.

RESULTS

A total of 13 studies were eligible for analysis. The Hoffmann reflex to muscle response ratio was significantly higher on both the reconstructed and non-reconstructed legs when compared with the healthy control leg (SMD = 0.28, 95% confidence interval (95%CI): 0.08-0.49, p = 0.006 and SMD = 0.22, 95%CI: 0.04-0.40, p = 0.016, respectively) but did not differ between legs (SMD = 0.10, 95%CI: -0.01 to 0.21, p = 0.078). The motor threshold was significantly higher on both the reconstructed (SMD = 0.76, 95%CI: 0.40-1.12, p < 0.001) and non-reconstructed legs (SMD = 0.47, 95%CI: 0.00-0.95, p = 0.049) when compared with the legs of healthy controls. The reconstructed leg also had a higher motor threshold when compared with the non-reconstructed leg (SMD = 0.20, 95%CI: 0.06-0.34, p = 0.005). These changes were paralleled by bilateral reductions in quadriceps strength (ACL reconstructed: SMD = -0.78, 95%CI: -1.07 to -0.49, p < 0.001; non-reconstructed: SMD = -0.32, 95%CI: -0.63 to -0.01, p = 0.042) and quadriceps voluntary activation (ACL reconstructed: SMD = -0.73, 95%CI: -0.97 to -0.50, p < 0.001; non-reconstructed: SMD = -0.55, 95%CI: -0.82 to -0.27, p < 0.001) when compared with healthy controls.

CONCLUSION

There is increased excitability of the spinal-reflex pathways and reduced excitability of the corticospinal pathways following ACL reconstruction. These changes are paralleled by reductions in quadriceps strength and voluntary activation, suggesting that rehabilitation interventions should focus on normalizing the excitability of neural pathways to effectively address quadriceps dysfunction after ACL reconstruction.

Return to Sport Composite Test After Anterior Cruciate Ligament Reconstruction (K-STARTS): Factors Affecting Return to Sport Test Score in a Retrospective Analysis of 676 Patients

BACKGROUND

Return to sport (RTS) to the preinjury level is the main purpose after anterior cruciate ligament (ACL) reconstruction but the factors affecting the RTS are not completely known. Knee Santy Athletic Return to Sport (K-STARTS) is a composite test designed to assess readiness for RTS after ACL reconstruction.

PURPOSE

To determine the key factors that influence K-STARTS scores in a large cohort of patients after ACL reconstruction.

STUDY DESIGN

Case-control study.

LEVEL OF EVIDENCE

Level 3.

METHODS

A retrospective analysis of prospectively collected data was undertaken. All patients who underwent ACL reconstruction surgery between March 2016 and May 2017 and also had a K-STARTS assessment at 6 months postoperatively were included. To identify factors influencing the K-STARTS score, an analysis of variance was performed. Age, sex, sports level, delay between injury and surgery, concomitant lesions, graft type, additional lateral tenodesis procedure, and participation in the RTS program were analyzed to identify factors influencing the K-STARTS score.

RESULTS

A total of 676 patients were included in the study. The K-STARTS score was significantly higher in male patients than in female patients (13.9 vs 12.4; P < 0.001), in younger patients (those aged <30 years vs older patients; 14.2 vs 12; P < 0.001), ACL reconstructions performed with hamstring tendon autografts compared with bone-patellar tendon-bone (13.5 vs 13.1; P = 0.03) and in those who completed a specific RTS program in addition to standard rehabilitation, compared with those who did not participate (17.1 vs 13.1; P < 0.001). However, the only factor that significantly influenced the K-STARTS score beyond the minimal detectable change threshold was the completion of the additional RTS program. The preinjury frequency of sports participation, whether the dominant limb was injured, time from injury to surgery, the presence of associated meniscal injuries, and whether a lateral tenodesis was performed did not significantly influence the K-STARTS score.

CONCLUSION

Completion of a specific RTS program, in addition to standard rehabilitation, was the most important factor influencing the K-STARTS composite functional and psychological RTS test score at 6 months after ACL reconstruction.

CLINICAL RELEVANCE

This study shows that the completion of a specific RTS program affects positively the RTS test score at 6 months after ACL reconstruction.

Neural Correlates of Knee Extension and Flexion Force Control: A Kinetically-Instrumented Neuroimaging Study

Background: The regulation of muscle force is a vital aspect of sensorimotor control, requiring intricate neural processes. While neural activity associated with upper extremity force control has been documented, extrapolation to lower extremity force control is limited. Knowledge of how the brain regulates force control for knee extension and flexion may provide insights as to how pathology or intervention impacts central control of movement.

Objectives: To develop and implement a neuroimaging-compatible force control paradigm for knee extension and flexion.

Methods: A magnetic resonance imaging (MRI) safe load cell was used in a customized apparatus to quantify force (N) during neuroimaging (Philips Achieva 3T). Visual biofeedback and a target sinusoidal wave that fluctuated between 0 and 5 N was provided via an MRI-safe virtual reality display. Fifteen right leg dominant female participants (age = 20.3 ± 1.2 years, height = 1.6 ± 0.10 m, weight = 64.8 ± 6.4 kg) completed a knee extension and flexion force matching paradigm during neuroimaging. The force-matching error was calculated based on the difference between the visual target and actual performance. Brain activation patterns were calculated and associated with force-matching error and the difference between quadriceps and hamstring force-matching tasks were evaluated with a mixed-effects model (z > 3.1, p < 0.05, cluster corrected).

Results: Knee extension and flexion force-matching tasks increased BOLD signal among cerebellar, sensorimotor, and visual-processing regions. Increased knee extension force-matching error was associated with greater right frontal cortex and left parietal cortex activity and reduced left lingual gyrus activity. Increased knee flexion force-matching error was associated with reduced left frontal and right parietal region activity. Knee flexion force control increased bilateral premotor, secondary somatosensory, and right anterior temporal activity relative to knee extension. The force-matching error was not statistically different between tasks.

Conclusion: Lower extremity force control results in unique activation strategies depending on if engaging knee extension or flexion, with knee flexion requiring increased neural activity (BOLD signal) for the same level of force and no difference in relative error. These fMRI compatible force control paradigms allow precise behavioral quantification of motor performance concurrent with brain activity for lower extremity sensorimotor function and may serve as a method for future research to investigate how pathologies affect lower extremity neuromuscular function.

Effect of Graft Rupture Prevention Training on Young Athletes After Anterior Cruciate Ligament Reconstruction: An 8-Year Prospective Intervention Study

Background:

There is a lack of research on the effects of a postoperative rehabilitation program on anterior cruciate ligament (ACL) graft rupture.

Hypothesis:

We hypothesized that a hip-focused rehabilitation protocol with graft rupture education and avoidance training (HIP-GREAT program) would demonstrate lower ACL graft rupture rates compared with a traditional physical therapy (PT) program.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

This study consisted of young athletes who had undergone ACL reconstruction at a single institution. Postoperatively, 136 participants (mean age, 16.9 ± 2.4 years) were enrolled in a traditional PT protocol between 2006 and 2010, and 153 participants (mean age, 17.0 ± 2.3 years) were enrolled in the HIP-GREAT protocol between 2011 and 2015. Follow-up rates were 31% (42/136) and 27% (41/153) in the traditional PT and HIP-GREAT groups, respectively, at 3 years postoperatively. The hazard ratio was calculated, and absolute risk reduction (ARR) and number-needed-to-treat (NNT) analyses were performed to compare the 2 protocols.

Results:

ACL graft rupture occurred in 10 patients (7.4%) in the traditional PT group and 5 patients (3.3%) in the HIP-GREAT group. This difference was not statistically significant (hazard ratio, 0.39; 95% CI, 0.14 to 1.16; P = .09). The ARR was 0.041 (95% CI, –0.011 to 0.093), and the NNT was 24.5.

Conclusion:

This study did not demonstrate a statistically significant reduction of ACL graft rupture in patients in the HIP-GREAT group. However, high ARR values and low NNT values were found, which suggests the possible effectiveness of the HIP-GREAT protocol to reduce ACL graft ruptures in young athletes.

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.

Trunk Muscle Endurance in Individuals With and Without a History of Anterior Cruciate Ligament Reconstruction

ABSTRACT

Werner, DM and Barrios, JA. Trunk muscle endurance in individuals with and without a history of anterior cruciate ligament reconstruction. J Strength Cond Res 35(1): 118-123, 2021-Anterior cruciate ligament (ACL) rupture is one of the most common knee injuries and often leads to surgery. Second injury after an ACL reconstruction (ACLR) is a major risk after rehabilitation, and may be linked to persistent postoperative deficits in muscular strength and endurance. Trunk muscle endurance has not been well studied after ACLR. Therefore, the purpose of this study was to compare trunk endurance using the established McGill testing battery in 20 individuals who had previously undergone ACLR at least 1 year before with 20 controls matched for sex frequency, limb dominance, age, body mass index, and activity level. Four static positional holds to failure were performed in random order, with time in seconds recorded as the primary dependent variable. Mann-Whitney U tests using an alpha level of 0.05 were conducted comparing hold times for all positions between groups. Effect sizes were also calculated between groups. Deficits in trunk extension endurance were observed in the surgical group. The results of this study suggest that contemporary rehabilitation schemes after ACLR do not fully address trunk endurance deficits. Health care professionals delivering postoperative rehabilitation after ACLR may consider direct assessment of trunk endurance and targeted exercise training to address potential deficits.

Patient function in serial assessments throughout the post-ACL reconstruction progression

OBJECTIVE

To assess the changes in patient strength and function from 4- to 6-month assessments following ACLR, determine relationships between changes in strength to changes in subjective function, and identify factors that predict patients that fail to increase in strength.

DESIGN

Prospective, Cohort Study.

SETTING

Controlled Laboratory.

PARTICIPANTS

Forty-seven patients(27 female, 24.3 ± 11.1 years) completed a battery of performance assessments at approximately 4- and 6-months following primary ACLR (4.03 ±0 .49 and 6.46 ±0 .68 months).

MAIN OUTCOME MEASURES

Subjective scores and isokinetic knee flexor and extensor strength were compared across visits. Patients were categorized per their ability to increase in strength beyond a previously defined threshold(0.22 Nm/kg). Binary logistic regression models were used to determine predictors of patients that failed to meet strength changes.

RESULTS

Patients demonstrated improvements in patient-reported outcomes and strength measures between visits(P's < 0.05). Higher age (B = -0.073, P = .039), lower pre-injury activity levels (B = 0.61, P = .022), and higher limb symmetry indexes (B = -0.044, P = .05) at 4-months were predictors of patients that did not achieve improvements in quadriceps strength between assessments.

CONCLUSIONS

From 4- to 6-months post-ACLR, increases in subjective function, strength and symmetry were observed. High quadriceps symmetry at interim assessments without consideration of the magnitude of strength values could overestimate recovery of quadriceps function.

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.

Innovative rehabilitative bracing with applied resistance improves walking pattern recovery in the early stages of rehabilitation after ACL reconstruction: a preliminary investigation

BACKGROUND

The use of knee braces early after anterior cruciate ligament (ACL) reconstruction is a controversial issue. The study preliminarily compares the effect of a traditional brace blocked in knee extension and a new functional brace equipped with a spring resistance on walking and strength performance early after ACL reconstruction performed in the acute/subacute stage.

METHODS

14 ACL-reconstructed patients wore either a traditional (Control group: CG, 7 subjects) or a new functional brace (Experimental group: EG 7 subjects) until the 30th post-operative day. All patients were tested before surgery (T0), 15, 30, and 60 days after surgery (T1, T2, and T3, respectively). Knee angular displacement and ground reaction forces (GRF) during the stance phase of the gait cycle were analyzed at each session and, at T3, maximal voluntary isometric contraction (MVIC) for knee flexor/extensor muscles was performed. Limb symmetry indexes (LSI) of GRF and MVIC parameters were calculated.

RESULTS

At T3, EG showed greater peak knee flexion angle of injured limb compared to CG (41 ± 2° vs 32 ± 1°, p < 0.001). During weight acceptance, a significant increase of anteroposterior GRF peak and vertical impulse from T1 to T3 was observed in the injured limb in EG (p < 0.05) but not in CG (p > 0.05). EG showed a greater side-to-side LSI of weight acceptance peak of anteroposterior GRF at T2 (113 ± 23% vs 69 ± 11%, p < 0.05) and T3 (112 ± 23% vs 84 ± 10%, p < 0.05).

CONCLUSIONS

The preliminary findings from this study indicate that the new functional brace did help in improving gait biomechanical pattern in the first two months after ACL reconstruction compared to a traditional brace locked in knee extension.

Transphyseal anterior cruciate ligament reconstruction using living parental donor hamstring graft: excellent clinical results at 2 years in a cohort of 100 patients

PURPOSE

To determine outcomes of transphyseal ACL reconstruction using a living parental hamstring tendon allograft in a consecutive series of 100 children.

METHODS

One hundred consecutive juveniles undergoing ACL reconstruction with a living parental hamstring allograft were recruited prospectively and reviewed 2 years after ACL reconstruction with IKDC Knee Ligament Evaluation, and KT1000 instrumented laxity testing. Skeletally immature participants obtained annual radiographs until skeletal maturity, and long leg alignment radiographs at 2 years. Radiographic Posterior tibial slope was recorded.

RESULTS

Of 100 juveniles, the median age was 14 years (range 8-16) and 68% male. At surgery, 30 juveniles were graded Tanner 1 or 2, 21 were Tanner 3 and 49 were Tanner 4 or 5. There were no cases of iatrogenic physeal injury or leg length discrepancy on long leg radiographs at 2 years, despite a median increase in height of 8 cm. Twelve patients had an ACL graft rupture and 9 had a contralateral ACL injury. Of those without further ACL injury, 82% returned to competitive sports, IKDC ligament evaluation was normal in 52% and nearly normal in 48%. The median side to side difference on manual maximum testing with the KT1000 was 2 mm (range - 1 to 5). A radiographic PTS of 12° or more was observed in 49%.

CONCLUSIONS

ACL reconstruction in the juvenile with living parental hamstring tendon allograft is a viable procedure associated with excellent clinical stability, patient-reported outcomes and return to sport over 2 years. Further ACL injury to the reconstructed and the contralateral knee remains a significant risk, with identical prevalence observed between the reconstructed and contralateral ACL between 12 and 24 months after surgery.

LEVEL OF EVIDENCE

III (Cohort Study).

Bridge-Enhanced Anterior Cruciate Ligament Repair Is Not Inferior to Autograft Anterior Cruciate Ligament Reconstruction at 2 Years: Results of a Prospective Randomized Clinical Trial

BACKGROUND

Preclinical studies suggest that for complete midsubstance anterior cruciate ligament (ACL) injuries, a suture repair of the ACL augmented with a protein implant placed in the gap between the torn ends (bridge-enhanced ACL repair [BEAR]) may be a viable alternative to ACL reconstruction (ACLR).

HYPOTHESIS

We hypothesized that patients treated with BEAR would have a noninferior patient-reported outcomes (International Knee Documentation Committee [IKDC] Subjective Score; prespecified noninferiority margin, -11.5 points) and instrumented anteroposterior (AP) knee laxity (prespecified noninferiority margin, +2-mm side-to-side difference) and superior muscle strength at 2 years after surgery when compared with patients who underwent ACLR with autograft.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

One hundred patients (median age, 17 years; median preoperative Marx activity score, 16) with complete midsubstance ACL injuries were enrolled and underwent surgery within 45 days of injury. Patients were randomly assigned to receive either BEAR (n = 65) or autograft ACLR (n = 35 [33 with quadrupled semitendinosus-gracilis and 2 with bone-patellar tendon-bone]). Outcomes-including the IKDC Subjective Score, the side-to-side difference in instrumented AP knee laxity, and muscle strength-were assessed at 2 years by an independent examiner blinded to the procedure. Patients were unblinded after their 2-year visit.

RESULTS

In total, 96% of the patients returned for 2-year follow-up. Noninferiority criteria were met for both the IKDC Subjective Score (BEAR, 88.9 points; ACLR, 84.8 points; mean difference, 4.1 points [95% CI, -1.5 to 9.7]) and the side-to-side difference in AP knee laxity (BEAR, 1.61 mm; ACLR, 1.77 mm; mean difference, -0.15 mm [95% CI, -1.48 to 1.17]). The BEAR group had a significantly higher mean hamstring muscle strength index than the ACLR group at 2 years (98.2% vs 63.2%; P < .001). In addition, 14% of the BEAR group and 6% of the ACLR group had a reinjury that required a second ipsilateral ACL surgical procedure (P = .32). Furthermore, the 8 patients who converted from BEAR to ACLR in the study period and returned for the 2-year postoperative visit had similar primary outcomes to patients who had a single ipsilateral ACL procedure.

CONCLUSION

BEAR resulted in noninferior patient-reported outcomes and AP knee laxity and superior hamstring muscle strength when compared with autograft ACLR at 2-year follow-up in a young and active cohort. These promising results suggest that longer-term studies of this technique are justified.

REGISTRATION

NCT02664545 (ClinicalTrials.gov identifier).

Recalibrating the risk of hamstring strain injury (HSI): A 2020 systematic review and meta-analysis of risk factors for index and recurrent hamstring strain injury in sport

OBJECTIVE

To systematically review risk factors for hamstring strain injury (HSI).

DESIGN

Systematic review update.

DATA SOURCES

Database searches: (1) inception to 2011 (original), and (2) 2011 to December 2018 (update). Citation tracking, manual reference and ahead of press searches.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies presenting prospective data evaluating factors associated with the risk of index and/or recurrent HSI.

METHOD

Search result screening and risk of bias assessment. A best evidence synthesis for each factor and meta-analysis, where possible, to determine the association with risk of HSI.

RESULTS

The 78 studies captured 8,319 total HSIs, including 967 recurrences, in 71,324 athletes. Older age (standardised mean difference=1.6, p=0.002), any history of HSI (risk ratio (RR)=2.7, p<0.001), a recent HSI (RR=4.8, p<0.001), previous anterior cruciate ligament (ACL) injury (RR=1.7, p=0.002) and previous calf strain injury (RR=1.5, p<0.001) were significant risk factors for HSI. From the best evidence synthesis, factors relating to sports performance and match play, running and hamstring strength were most consistently associated with HSI risk. The risk of recurrent HSI is best evaluated using clinical data and not the MRI characteristics of the index injury.

SUMMARY/CONCLUSION

Older age and a history of HSI are the strongest risk factors for HSI. Future research may be directed towards exploring the interaction of risk factors and how these relationships fluctuate over time given the occurrence of index and recurrent HSI in sport is multifactorial.

Hamstring muscle activation and morphology are significantly altered 1-6 years after anterior cruciate ligament reconstruction with semitendinosus graft

PURPOSE

Harvest of the semitendinosus (ST) tendon for anterior cruciate ligament reconstruction (ACLR) causes persistent hypotrophy of this muscle even after a return to sport, although it is unclear if hamstring activation patterns are altered during eccentric exercise. It was hypothesised that in comparison with contralateral control limbs, limbs with previous ACLR involving ST grafts would display (i) deficits in ST activation during maximal eccentric exercise; (ii) smaller ST muscle volumes and anatomical cross-sectional areas (ACSAs); and (iii) lower eccentric knee flexor strength.

METHODS

Fourteen athletes who had successfully returned to sport after unilateral ACLR involving ST tendon graft were recruited. Median time since surgery was 49 months (range 12-78 months). Participants underwent functional magnetic resonance imaging (MRI) of their thighs before and after the Nordic hamstring exercise (NHE) and percentage change in transverse (T2) relaxation time was used as an index of hamstring activation. Muscle volumes and ACSAs were determined from MRI and distal ST tendons were evaluated via ultrasound. Eccentric knee flexor strength was determined during the NHE.

RESULTS

Exercise-induced T2 change was lower for ST muscles in surgical than control limbs (95% CI - 3.8 to - 16.0%). Both ST muscle volume (95% CI - 57.1 to - 104.7 cm³) and ACSA (95% CI - 1.9 to - 5.0 cm²) were markedly lower in surgical limbs. Semimembranosus (95% CI 5.5-14.0 cm³) and biceps femoris short head (95% CI 0.6-11.0 cm³) volumes were slightly higher in surgical limbs. No between-limb difference in eccentric knee flexor strength was observed (95% CI 33 N to - 74 N).

CONCLUSION

ST activation is significantly lower in surgical than control limbs during eccentric knee flexor exercise 1-6 years after ACLR with ST graft. Lower levels of ST activation may partially explain this muscle's persistent hypotrophy post ACLR and have implications for the design of more effective rehabilitation programs.

LEVEL OF EVIDENCE

IV.

Platelet-rich Blood Derivatives for Tendon Regeneration

Tendon injuries constitute a significant healthcare problem with variable clinical outcomes. The complex interplay of tissue homeostasis, degeneration, repair, and regeneration makes the development of successful delivery therapeutic strategies challenging. Platelet-rich hemoderivatives, a source of supra-physiologic concentrations of human therapeutic factors, are a promising application to treat tendon injuries from the perspective of tendon tissue engineering, although the outcomes remain controversial.

Quadriceps and Hamstring Strength Symmetry After Anterior Cruciate Ligament Reconstruction: A Prospective Study

OBJECTIVES

To evaluate change in involved and uninvolved quadriceps and hamstring strength and limb symmetry indices (LSI) in regular intervals over the first 6 months following anterior cruciate ligament reconstruction (ACLR).

DESIGN

Prospective cohort study.

PARTICIPANTS

Thirty-eight male participants (mean age: 24.2 [6.4] y, mean body mass index: 23.6 [4.2] kg/m2), who underwent ACLR were included.

MAIN OUTCOME MEASURES

Isometric strength testing of the quadriceps and hamstring muscles was performed at 1, 2, 3, and 6 months after ACLR. Quadriceps and hamstring peak torques for each limb and LSI were calculated. Repeated-measures analysis of covariance and paired t tests were used to evaluate changes in strength over time and between limbs, respectively.

RESULTS

Quadriceps and hamstring peak torques of the involved limb consistently increased between each time point from 1 to 6 months (P < .001 and P = .01, respectively), whereas the uninvolved limb values did not change after ACLR (P > .05). In addition, uninvolved limb peak torque values were higher than involved limb values at each time point after ACLR for both the quadriceps and hamstrings (all P < .01). At 6 months after ACLR, 28.9% of participants demonstrated LSI greater than 90% for quadriceps strength, 36.8% demonstrated LSI greater than 90% for hamstring strength, and 15.8% of participants demonstrated greater than 90% LSI for both quadriceps and hamstring strength.

CONCLUSIONS

Participants demonstrated a consistent increase in quadriceps and hamstring strength of the involved limb, with no notable change in uninvolved limb strength over the 6 months after ACLR. However, at 6 months after ACLR, only approximately 16% of participants demonstrated both quadriceps and hamstring strength LSI greater than 90%, the typically recommended cutoff value for return to sport.

Change in Drop-Landing Mechanics Over 2 Years in Young Athletes After Anterior Cruciate Ligament Reconstruction

BACKGROUND

While between-limb landing asymmetries after anterior cruciate ligament reconstruction (ACLR) are linked with poor function and risk of additional injury, it is not currently understood how landing symmetry changes over time after ACLR.

PURPOSE/HYPOTHESIS

The purpose was to investigate how double-legged drop vertical jump (DVJ) landing and single-legged drop-landing symmetry changed from the time of return-to-sport (RTS) clearance to 2 years later in a prospective cohort of young athletes after ACLR. It was hypothesized that double-legged DVJ landing and single-legged drop-landing symmetry would improve from the time of RTS to 2 years later.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The authors followed 64 young athletes with primary, unilateral ACLR for 2 years after RTS clearance. At the time of RTS and 2 years later, between-limb symmetry values for biomechanical variables of interest (VOIs) were calculated with 3-dimensional motion analysis during double-legged DVJ and single-legged drop-landing tasks. VOIs included knee flexion excursion, peak internal knee extension moment, peak vertical ground-reaction force, and peak trunk flexion (for single-legged task only). Symmetry values and proportions of participants meeting 90% symmetry cutoffs were compared between time points.

RESULTS

For double-legged DVJ landing, symmetry values for all VOIs and the proportions meeting 90% cutoffs for peak internal knee extension moment and peak vertical ground-reaction force were higher at 2 years after RTS as compared with RTS. For single-legged drop-landing, symmetry values were higher for knee flexion excursion and lower for peak trunk flexion at 2 years after RTS as compared with RTS, but the proportions meeting 90% cutoffs for all VOIs did not differ between time points.

CONCLUSION

Double-legged DVJ landing symmetry improved across VOIs over the 2 years after RTS following ACLR, while single-legged drop-landing did not improve as consistently. The implications of longitudinal landing asymmetry after ACLR should be further studied.

Bridge-Enhanced Anterior Cruciate Ligament Repair: Two-Year Results of a First-in-Human Study

Background

Bridge-enhanced anterior cruciate ligament repair (BEAR) combines suture repair of the anterior cruciate ligament (ACL) with a specific extracellular matrix scaffold (the BEAR scaffold) that is placed in the gap between the torn ends of the ACL to facilitate ligament healing.

Purpose/Hypothesis

The purpose of this study was to report the 12- and 24-month outcomes of patients who underwent the BEAR procedure compared with a nonrandomized concurrent control group who underwent ACL reconstruction (ACLR) with an autograft. We hypothesized that the BEAR group would have physical examination findings, patient-reported outcomes, and adverse events that were similar to those of the ACLR group.

Study Design

Cohort study; Level of evidence, 2.

Methods

Ten patients underwent BEAR, and 10 underwent ACLR with a 4-stranded hamstring autograft. At 24 months, 9 of the 10 BEAR patients and 7 of the 10 ACLR patients completed a study visit. Outcomes reported included International Knee Documentation Committee (IKDC) subjective and objective results, knee anteroposterior (AP) laxity findings via an arthrometer, and functional outcomes.

Results

There were no graft or repair failures in the first 24 months after surgery. The IKDC subjective scores in both groups improved significantly from baseline (P < .0001) at 12 and 24 months, to 84.6 ± 17.2 in the ACLR group and to 91.7 ± 11.7 in the BEAR group. An IKDC objective grade of A (normal) was found in 44% of patients in the BEAR group and in 29% of patients in the ACLR group at 24 months; no patients in either group had C (abnormal) or D (severely abnormal) grades. Arthrometer testing demonstrated mean side-to-side differences in AP laxity that were similar in the 2 groups at 24 months (BEAR, 1.94 ± 2.08 mm; ACLR, 3.14 ± 2.66 mm). Functional hop testing results were similar in the 2 groups at 12 and 24 months after surgery. Hamstring strength indices were significantly higher in the BEAR group compared with the ACLR group (P = .0001).

Conclusion

In this small, first-in-human study, BEAR produced similar outcomes to ACLR with a hamstring autograft. BEAR may result in knee stability and patient-reported outcomes at 2 years sufficient to warrant longer term studies of efficacy in larger groups of patients.

Return to Sport and Reoperation Rates in Patients Under the Age of 20 After Primary Anterior Cruciate Ligament Reconstruction: Risk Profile Comparing 3 Patient Groups Predicated Upon Skeletal Age

BACKGROUND

With sports specialization and level of competition on the rise, anterior cruciate ligament reconstruction (ACLR) in athletes under the age of 20 has increased significantly in recent years. Reports have demonstrated that the revision ACLR rate is higher and return to sport (RTS) rate is lower in this population.

PURPOSE

To evaluate the 2-year clinical outcomes of 3 cohorts of primary ACLR in pediatric and adolescent athletes under the age of 20 based on skeletal age with a focus on RTS and the incidence of second surgery.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

This is a prospective evaluation of 324 athletes younger than 20 years of age who underwent ACLR with minimum 2-year follow-up. The surgical technique was selected predicated on skeletal age, which includes the all-epiphyseal technique with hamstring autograft in the youngest cohort in elementary and middle school (group 1), the partial transphyseal and complete transphyseal with hamstring autograft performed for athletes in the middle cohort (group 2), and bone-tendon-bone autograft in the skeletally mature high school athletes (group 3).

RESULTS

The mean chronological age of the entire cohort was 15 years (range, 8-19 years) with 55% males. The 3 cohorts included 49 patients (15%) in group 1 (mean age, 12 years), 66 (20%) in group 2 (mean age, 14.3 years), and 209 (65%) in group 3 (mean age, 16.2 years). Group 2 athletes had a significantly higher revision ACLR rate (20%) compared with group 1 (6%; P = .039) and group 3 (6%; P = .001). Similarly, group 2 athletes had significantly lower RTS rates (85%) compared with group 1 (100%) and group 3 (94%).

CONCLUSION

The rate of revision ACLR was significantly higher and the RTS rates significantly lower in group 2 compared with groups 1 and 3. This age-related risk profile may be used to counsel athletes and parents preoperatively regarding the expectations of surgery with respect to revision ACLR and RTS rates.

Anatomy of proximal attachment, course, and innervation of hamstring muscles: a pictorial essay

Hamstring injuries are very common in sports medicine. Knowing their anatomy, morphology, innervation, and function is important to provide a proper diagnosis, treatment as well as appropriate prevention strategies. In this pictorial essay, based on anatomical dissection, the detailed anatomy of muscle-tendon complex is reviewed, including their proximal attachment, muscle course, and innervation. To illustrate hamstrings' role in the rotational control of the tibia, the essay also includes the analysis of their biomechanical function.Level of evidence V (expert opinion based on laboratory study).

5-Year Survival of Pediatric Anterior Cruciate Ligament Reconstruction With Living Donor Hamstring Tendon Grafts

BACKGROUND

It is well accepted that there is a higher incidence of repeat anterior cruciate ligament (ACL) injuries in the pediatric population after ACL reconstruction (ACLR) with autograft tissue compared with adults. Hamstring autograft harvest may contribute to the risk for repeat ACL injuries in this high functional demand group. A novel method is the use of a living donor hamstring tendon (LDHT) graft from a parent; however, there is currently limited research on the outcomes of this technique, particularly beyond the short term.

PURPOSE/HYPOTHESIS

The purpose was to determine the medium-term survival of the ACL graft and the contralateral ACL (CACL) after primary ACLR with the use of an LDHT graft from a parent in those aged less than 18 years and to identify factors associated with subsequent ACL injuries. It was hypothesized that ACLR with the use of an LDHT provides acceptable midterm outcomes in pediatric patients.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Between 2005 and 2014, 247 (of 265 eligible) consecutive patients in a prospective database, having undergone primary ACLR with the use of an LDHT graft and aged less than 18 years, were included. Outcomes were assessed at a minimum of 2 years after surgery including data on ACL reinjuries, International Knee Documentation Committee (IKDC) scores, and current symptoms, as well as factors associated with the ACL reinjury risk were investigated.

RESULTS

Patients were reviewed at a mean of 4.5 years (range, 24-127 months [10.6 years]) after ACLR with an LDHT graft. Fifty-one patients (20.6%) sustained an ACL graft rupture, 28 patients (11.3%) sustained a CACL rupture, and 2 patients sustained both an ACL graft rupture and a CACL rupture (0.8%). Survival of the ACL graft was 89%, 82%, and 76% at 1, 2, and 5 years, respectively. Survival of the CACL was 99%, 94%, and 86% at 1, 2, and 5 years, respectively. Survival of the ACL graft was favorable in patients with Tanner stage 1-2 at the time of surgery versus those with Tanner stage 3-5 at 5 years (87% vs 69%, respectively; hazard ratio, 3.7; P = .01). The mean IKDC score was 91.7. A return to preinjury levels of activity was reported by 59.1%.

CONCLUSION

After ACLR with an LDHT graft from a parent in those aged less than 18 years, a second ACL injury (ACL graft or CACL injury) occurred in 1 in 3 patients. The 5-year survival rate of the ACL graft was 76%, and the 5-year survival rate of the CACL was 86%. High IKDC scores and continued participation in sports were maintained over the medium term. Importantly, there was favorable survival of the ACL graft in patients with Tanner stage 1-2 compared with patients with Tanner stage 3-5 over 5 years. Patients with Tanner stage 1-2 also had a significantly lower incidence of second ACL injuries over 5 years compared with those with Tanner stage 3-5, occurring in 1 in 5 patients. Thus, an LDHT graft from a parent is an appropriate graft for physically immature children.

CORRELATION BETWEEN ECCENTRIC TRAINING AND FUNCTIONAL TESTS IN SUBJECTS WITH RECONSTRUCTED ACL

ABSTRACT Introduction: Eccentric training and jump tests are widely used to recover and measure deficits in knee strength and functionality after anterior cruciate ligament (ACL) reconstruction. Objective: To correlate knee extension and flexion torque generated by eccentric isokinetic training, with functional jump tests in subjects with reconstructed ACL. Method: Sixteen men with unilateral ACL reconstruction were assessed before and after 12 weeks of eccentric isokinetic training of knee flexors and extensors (3×10 MVC, 2x/week) at 30°/s for extension and flexion torque (isometric; concentric and eccentric at 30 and 120°/s) and functional jump tests (single, triple, cross and figure of 8). Inter- and intra-limb pre- and post-training mean peak torque (MPT), distance and jump test times were compared along with the correlations between these variables, considering P<0.05. Results: The affected limb (AL) showed significant gain of extension and flexion torque (P<0.01) in the different test categories and velocities evaluated. In the non-affected limb (NAL), this only occurred in the eccentric category (30 and 120°/s), in the extension (P<0.01) and flexion (P<0.05 and P<0.01) torques, respectively. In the jumps, there was an increase in distance (single and triple; P<0.05) and a decrease in time (crossed and figure of 8; P<0.01), however, MPT x Jump correlations were weak (r<0.3) in the pre and post-training period in both limbs. Conclusion: Despite the gain in knee extension and flexion torque and jumping performance, the expected correlation was not satisfactory, suggesting that knee functionality involves other variables inherent to motor control. Level of Evidence IV; Type of study: Case series.