Hop tests can result in higher limb symmetry index values than isokinetic strength and leg press tests in patients following ACL reconstruction

Single-leg hop distance normalized to body height is associated with the return to sports after anterior cruciate ligament reconstruction

Purpose

To investigate the relationship between single-leg hop distance (SLHD), normalized body height, and return-to-sports (RTS) status after anterior cruciate ligament reconstruction (ACLR) and to identify the cut-off value for SLHD on the operated side.

Methods

Seventy-three patients after primary ACLR (median 13.5 months) participated in this cross-sectional study. Participants were divided into ‘‘Yes-RTS’’ (YRTS) or ‘‘No-RTS’’ (NRTS) groups based on a self-reported questionnaire. SLHD was measured, and the limb symmetry index (LSI) and SLHD (%body height) were calculated. A minimum p-value approach was used to calculate the SLHD cut-off points (%body height) on the operated side that were strongly associated with the RTS status. Logistic regression analysis was used to analyse the association between RTS status and SLHD cut-off point (%body height). Isokinetic strength and Tampa scale for kinesiophobia (TSK) were measured as covariates.

Results

Among 73 patients, 43 (59%) were assigned to the YRTS and 30 (41%) to the NRTS group. The 70% body height cut-off point for SLHD on the operated side was most strongly associated with RTS status. In a logistic regression analysis including other covariates, SLHD (%body height) < 70% and TSK were negatively associated with RTS status. Except for two participants, the LSI of the SLHD exceeded 90% and there was no significant association between the LSI of the SLHD and RTS status.

Conclusion

Even after improvement in the LSI of the SLHD, planning rehabilitation with the goal of achieving SLHD over 70% body height may be important for supporting RTS after ACLR.

Level of evidence

Cross-sectional study, Level IV

Single leg hop for distance symmetry masks lower limb biomechanics: time to discuss hop distance as decision criterion for return to sport after ACL reconstruction?

Background

We evaluated the lower limb status of athletes after anterior cruciate ligament reconstruction (ACLR) during the propulsion and landing phases of a single leg hop for distance (SLHD) task after they had been cleared to return to sport. We wanted to evaluate the biomechanical components of the involved (operated) and uninvolved legs of athletes with ACLR and compare these legs with those of uninjured athletes (controls).

Methods

We captured standard video-based three-dimensional motion and electromyography (EMG) in 26 athletes after ACLR and 23 healthy controls during SLHD and calculated lower limb and trunk kinematics. We calculated lower limb joint moments and work using inverse dynamics and computed lower limb muscle forces using an EMG-constrained musculoskeletal modelling approach. Between-limb (within ACLR athletes) and between-group differences (between ACLR athletes and controls) were evaluated using paired and independent sample t-tests, respectively.

Results

Significant differences in kinematics (effect sizes ranging from 0.42 to 1.56), moments (0.39 to 1.08), and joint work contribution (0.55 to 1.04) were seen between the involved and uninvolved legs, as well as between groups. Athletes after ACLR achieved a 97%±4% limb symmetry index in hop distance but the symmetry in work done by the knee during propulsion was only 69%. During landing, the involved knee absorbed less work than the uninvolved, while the uninvolved knee absorbed more work than the control group. Athletes after ACLR compensated for lower knee work with greater hip work contribution and by landing with more hip flexion, anterior pelvis tilt, and trunk flexion.

Conclusion

Symmetry in performance on a SLHD test does not ensure symmetry in lower limb biomechanics. The distance hopped is a poor measure of knee function, and largely reflects hip and ankle function. Male athletes after ACLR selectively unload the involved limb but outperform controls on the uninvolved knee.

Single-leg hop can result in higher limb symmetry index than isokinetic strength and single-leg vertical jump following anterior cruciate ligament reconstruction

BACKGROUND

A single-leg vertical jump height (SLVJ) may reflect knee extension strength more than a single-leg hop for distance (SLH). This study aimed to examine the relationships between the isokinetic knee extension torque, SLH, and SLVJ after anterior cruciate ligament reconstruction (ACLR).

METHODS

Forty-four patients post-ACLR (median 12.0 months) participated in the study. The isokinetic knee extension peak torque at 60°/s and 180°/s (Ext 60, 180), SLH, and SLVJ were measured. The limb symmetry index (LSI) was calculated as the ratio of the operated side to the unoperated side.

RESULTS

There were moderate-to-strong positive correlations between isokinetic knee extension torque and both SLH (r = 0.72-0.77, P < 0.001) and SLVJ (r = 0.73-0.79, P < 0.001). Significant side-to-side differences in isokinetic knee extension torque and SLVJ between the operated and unoperated sides were found (P < 0.05), but not for SLH (P = 0.065). The results of the analysis of variance (ANOVA) and post hoc analyses showed that the LSI of SLH (98.2%) was higher than that of the LSI of Ext 180 and SLVJ (P < 0.05). Fisher's exact test showed a significant relationship between the LSI of Ext 180 and that of SLVJ (cut-off 85%; P = 0.041). No patients had LSI < 85% in SLH.

CONCLUSIONS

Even though SLH asymmetry improved approximately 12 months after ACLR, the asymmetry of isokinetic knee extension torque and SLVJ remained. The LSI of SLVJ could be an indicator of the recovery of isokinetic knee extension torque.

Vertical and Horizontal Hop Performance: Contributions of the Hip, Knee, and Ankle

BACKGROUND

Single-leg vertical and horizontal hop tests are commonly used to assess performance of healthy athletes and as a measure of progress during rehabilitation from knee injury. It is unclear if they measure similar aspects of leg function, as the relative joint contributions of the hip, knee, and ankle joints during propulsion and landing are unknown.

HYPOTHESIS

The proportion of work done by the hip, knee, and ankle will not be the same for these 2 jump types and will vary for propulsive and landing phases.

STUDY DESIGN

Cross-sectional cohort study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Twenty physically active participants completed instrumented single-leg hop analysis in both vertical and horizontal directions. Joint peak power, work generated or absorbed, and percentage contribution of each joint during propulsive and landing phases were compared between tasks using paired t tests.

RESULTS

Vertical hop was performed with roughly similar contributions of the hip, knee, and ankle for both propulsion (31%, 34%, 35%, respectively) and landing (29%, 34%, 37%, respectively). Horizontal hop distance was mostly (87%) determined by the hip and ankle (44% and 43%), but landing was mostly (65%) performed by the knee with lesser contribution from the hip and ankle (24% and 11%). Propulsive phase showed a proximal-to-distal temporal sequence for both hop types, but landing was more complex.

CONCLUSION

Performance during vertical and horizontal hops (jump height and jump distance, respectively) measures different aspects of hip, knee, and ankle function during the propulsive and landing phases.

CLINICAL RELEVANCE

Assessment of knee joint function during rehabilitation should not be done using a horizontal hop. The knee contributes about a third to vertical hop height, but only about an eighth to horizontal hop distance. Practitioners carrying out performance testing using either vertical or horizontal hops should be mindful of the relative contributions for meaningful training inferences to be derived.

Quadriceps Strength Influences Patient Function More Than Single Leg Forward Hop During Late-Stage ACL Rehabilitation

BACKGROUND

A comprehensive battery of tests are used to inform return to play decisions following anterior cruciate ligament (ACL) reconstruction. Performance measures contribute to patient function, but it is not clear if achieving symmetrical performance on strength and hop tests is sufficient or if a patient also needs to meet minimum unilateral thresholds.

HYPOTHESIS/PURPOSE

To determine the association of quadriceps strength and single-leg forward hop performance with patient-reported function, as measured by the IKDC Subjective Knee Form (IKDC), during late-stage ACL rehabilitation. A secondary purpose was to determine which clinical tests were the most difficult for participants to pass.

STUDY DESIGN

Descriptive Laboratory Study.

METHODS

Forty-eight individuals with a history of ACL-R (32 female, 16 male; mean±SD age=18.0±2.7 y; height=172.4±7.6 cm; mass=69.6±11.4 kg; time since surgery=7.7±1.8 months; IKDC=86.8±10.6) completed the IKDC survey, quadriceps isometric strength, and single-leg forward hop performance. The relationship between IKDC scores and performance measures (LSI and involved limb) was determined using stepwise linear regression. Frequency counts were used to determine whether participants met clinical thresholds (IKDC ≥ 90%, quadriceps and single-leg forward hop LSI ≥ 90%, quadriceps peak torque ≥ 3.0 Nm/kg, and single-leg forward hop ≥ 80% height for females and ≥ 90% height for males).

RESULTS

Quadriceps LSI and involved limb peak torque explained 39% of the variance in IKDC scores while measures of single-leg forward hop performance did not add to the predictive model. Nearly 90% of participants could not meet established clinical thresholds on all five tests and quadriceps strength (LSI and peak torque) was the most common unmet criteria (71% of participants).

CONCLUSIONS

During late-stage ACL rehabilitation deficits in quadriceps strength contribute more to patient function and are greater in magnitude compared to hop test performance.

LEVEL OF EVIDENCE

Cross-Sectional Study, Level 3.

Reliability and validity of a return to sports testing battery for the shoulder

OBJECTIVE

To determine the validity, intra- and inter-rater, and absolute reliability of a return to sport testing battery for the shoulder in a healthy cohort.

DESIGN

Cross-sectional design. All participants completed a battery of strength (isokinetic, isometric, and repetition to failure) and functional assessments on two occasions. Concurrent validity to isokinetic testing was assessed, and intra-rater, inter-rater, and absolute reliability were established for all assessments.

SETTING

Controlled clinical environment.

PARTICIPANTS

Thirty healthy adults active in recreational sports participated, mean age 24.0 ± 1.6 years; MAIN OUTCOME MEASURES: Correlations (Pearson's r), reliability (Intraclass Correlation Coefficient), Standard error of the measurement, Minimal detectable change.

RESULTS

Correlations to isokinetic assessments at 60° & 180°/second were moderate to strong for isometric (r: 0.68-0.80) and functional testing (r: 0.55-0.83) and weak for repetition to failure testing (r: 0.37-0.74). All isokinetic (ICC: 0.88-0.94), isometric (ICC: 0.83-0.94), and functional assessments (ICC: 0.80-0.92) had good to excellent intra-rater reliability, while repetition to failure testing had poor to moderate reliability (ICC: 0.48-0.57). The inter-rater reliability of the isometric assessments was moderate to excellent (ICC: 0.71-0.92) across movements. Expressed as a percentage of the mean, the standard error of the measurement ranged from 7% to 25% and the minimal detectable change ranged from 20% to 69% across all assessment methods.

CONCLUSION

The isokinetic, isometric, and functional assessments used in this return to sports testing battery demonstrates acceptable validity and reliability. Further refinement to the methods used to assess muscular endurance is needed to improve reliability. This study offers clinicians information that can be utilized in clinical decision-making as it relates the testing battery's psychometric properties.

The single-leg vertical hop provides unique asymmetry information in individuals after anterior cruciate ligament reconstruction

BACKGROUND

Traditional testing to identify asymmetries after anterior cruciate ligament reconstruction include four similar horizontal hopping tests. The purpose of this study was to determine whether a single-leg vertical hopping test can identify performance and biomechanical asymmetries, and whether performance asymmetries provide unique information compared to traditional tests.

METHODS

Twelve women with history of anterior cruciate ligament reconstruction [age: 21.1 years (SD 3.2), height: 165.8 cm (SD 6.0), mass: 68.3 kg (SD 8.8)] completed traditional horizontal hop testing. Participants also performed a single-leg vertical hop for maximal height while instrumented for three-dimensional motion analysis. Paired t-tests were performed to identify side-to-side differences in performance variables and Spearman's rank correlations were performed of limb symmetry indices to identify whether the single-leg vertical hop test provides unique information. Repeated measures MANOVAs were performed to identify single-leg vertical hop biomechanical asymmetries.

FINDINGS

Participants exhibited significant side-to-side performance differences during the single-leg vertical hop [mean difference = 0.02 m (SD 0.03), P = .04]. Only weak to moderate relationships were identified between limb symmetry indices of the single-leg vertical hop and other horizontal hopping tests. The vertical hop elicited significant asymmetries of joint kinematics (P = .04) and angular impulse (P = .04). Specifically, the involved limb showed lower peak ankle dorsiflexion (P = .004) and knee abduction (P = .02) angles, lower sagittal plane impulse at the knee (P = .02) and greater sagittal plane impulse at the hip (P = .03).

INTERPRETATION

The single-leg vertical hop can identify performance and biomechanical asymmetries in individuals after anterior cruciate ligament reconstruction, potentially providing complementary information to standard horizontal hopping tests.

Functional progression milestones following anterior cruciate ligament reconstruction are more appropriate than time-based criteria: a survey among the ESSKA

PURPOSE

The aim of this study was to report current rehabilitation recommendations after ACL reconstruction in ESSKA community, with a particular focus on the specific criteria utilized to guide activity progression METHODS: A web-based survey was developed to investigate preferences between time-based and functional ACL reconstruction rehabilitation progression milestones of ESSKA community.

RESULTS

Eight hundred and twenty completed questionnaires were received. Responders were from 86 different countries worldwide, 63% of them from European countries. Functional criteria were considered more appropriate to decide if a patient can start specific activities/exercises by 67% of the responders. Good core and lower extremity neuromuscular control were the most often used functional criteria for decision-making regarding readiness for sport-specific rehabilitation (66%), sport-specific drills without (65%) and with contact (66%). Strength assessed with an isokinetic dynamometer was considered by about half of the responders a determinant to initiate sport-specific drills without (51%-isokinetic strength, LSI > 80%) and with contact (58%-isokinetic strength, LSI > 85-90%). To determine readiness for sport-specific drills, hop tests were used by 40% of respondents for drills without contact and 48% of respondents for drills with contact.

CONCLUSION

The results of this survey involving mainly orthopaedic surgeons indicate that functional measures are considered more appropriate than milestones based on time from surgery to guide progression through the postoperative rehabilitation process after ACLR. The main clinical relevance of this study is that updated information on collective agreement could be useful for clinicians and physiotherapists to delineate their postoperative treatments after ACLR. These results should be interpreted with caution, as this sample represents only a small portion of ESSKA community involved in knee surgery and treating patients following ACLR.

LEVEL OF EVIDENCE

III.

Individual hop analysis and reactive strength ratios provide better discrimination of ACL reconstructed limb deficits than triple hop for distance scores in athletes returning to sport

BACKGROUND

The triple hop for distance test commonly uses a limb symmetry index (LSI) 'pass' threshold of >90% for total hop distance following anterior cruciate ligament reconstruction (ACLR). However, understanding the manner in which athletes generate and dissipate forces during consecutive hops within the test may provide greater insight into residual limb deficits. The aim of the study was to examine reactive strength ratios (RSR) of individual hops during a triple hop test in a cohort of ACLR patients at discharge prior to return-to-sport.

METHODS

Twenty male athletes (24.6 ± 4.2 years; height 175.3 ± 10.2 cm; mass 73.6 ± 14.5 kg) completed the test on both non-operated and operated limbs. Total distance hopped, contact times, flight times and RSR were collected for each hop using a floor-level optical measurement system.

RESULTS

Significant, small to moderate between-limb differences (p < 0.05; d = 0.45-0.72) were shown for triple hop distance, flight time and RSR for each hop, with lower performance consistently displayed in the operated limb. Large, significant differences in RSR were evident between hops one and two on the operated limb (p < 0.05; d = 0.97). Despite 80% of participants achieving >90% LSI for total hop distance, less than 50% of participants reached the >90% LSI threshold for RSR.

CONCLUSIONS

Standardised LSI 'pass' thresholds (>90% LSI) for triple hop distance may mask residual deficits in reactive strength performance of operated limbs; therefore, more detailed analyses of individual hop performance may be warranted to enhance return to sport criteria following ACLR.

Who's Afraid of the Big Bad Wolf? Open-Chain Exercises After Anterior Cruciate Ligament Reconstruction

Restoring quadriceps muscle strength is integral to recovery following an anterior cruciate ligament reconstruction. We argue that clinicians should re-evaluate their beliefs about open-chain exercises and measure this important variable to improve outcomes for their patients. J Orthop Sports Phys Ther 2020;50(9):473-475. doi:10.2519/jospt.2020.0609.

One-repetition submaximal protocol to measure knee extensor muscle strength among older adults with and without sarcopenia: a validation study

Background

Dynamic knee extensor muscle strength is a valid measure among healthy older adults but has not been tested in the sarcopenia condition. This study’s objective was to test the validity of a one-repetition submaximal strength protocol to measure dynamic knee extension strength in older adults with and without sarcopenia.

Methods

Ninety-four physically independent older adults (female: n = 64, 60 to 85 years; male: n = 29, 60 to 85 years) participated in this study in Brazil during 2016–2017. Sarcopenia was classified and isokinetic unilateral knee extension strength was measured at 60°/s. Bilateral dynamic knee extension strength was estimated with an extensor chair using one-repetition submaximal protocol. Validity was determined using Spearman’s correlation with isokinetic muscle strength.

Results

The frequency of sarcopenia was 11.7%. Sarcopenic individuals presented lower body mass, body mass index and skeletal muscle index. Only chronological age was higher among the sarcopenic individuals. A high correlation was found between isokinetic unilateral knee extension strength and bilateral estimated one-repetition with submaximal protocol (r = 0.74; p <  0.001), when the presence (r = 0.71; p = 0.014) and absence of sarcopenia (r = 0.74; p <  0.001) were considered. The validity of the one-repetition submaximal protocol for bilateral knee extension was confirmed.

Conclusions

The estimated measure of bilateral knee extension muscle strength can be used to monitor adaptations promoted by physical exercise for older adults with and without sarcopenia. The validation enable studies that will propose cutoff points to identify sarcopenia with this submaximal protocol. This will enable early diagnosis and better management of sarcopenia, a disease with adverse impacts for older adults.

INTER-RATER AND TEST-RETEST RELIABILITY OF TWO NEW SINGLE LEG SIT-TO-STAND TESTS

BACKGROUND

The single leg sit-to-stand test (SLSTST) is a functional test that assesses quadriceps strength. The original SLSTST was used to diagnose lumbar nerve root impingement/radiculopathy - specifically at the L3 and L4 level. The original SLSTST used one repetition as the requirement for a successful test, therefore it may not identify quadriceps weakness in highly functional individuals with or recovering from an athletic injury.

PURPOSE/HYPOTHESIS

The purpose of this study was to determine the interrater and test-retest reliability of two new SLSTSTs, one for maximum number of repetitions over 30 seconds and one for time to complete five repetitions.

STUDY DESIGN

Cross-sectional, reliability study.

METHODS

Twenty healthy college-aged individuals (12 males, age: 22.5 years ± 1.37, height: 1.72 m ± 0.09; weight: 70.2 kg ± 11.0) participated in the study. Two testing sessions were held three to seven days apart, and two second-year physical therapy students served as examiners. The objective of the 30-second SLSTST was for the participant to perform as many single leg sit-to-stand repetitions they could in thirty seconds, while the five repetitions SLSTST measured how quickly the subjects could perform five single leg sit to stand repetitions. Both lower extremities were tested and Intraclass Correlation Coefficients (ICC) were calculated to determine reliability.

RESULTS

Both SLSTSTs were found to have excellent interrater and good to excellent test-retest reliability. The 30-second SLSTSTs had inter-rater ICC = 0.99 on the right and 0.98 on the left while the test-retest ICCs ranged from 0.92 to 0.94. The five repetition SLSTSTs had an inter-rater ICC = .99 on both legs while the test-retest ICC ranged from 0.87 to 0.94.

CONCLUSIONS

The results of the current study indicate that the two new SLSTSTs had good to excellent test-retest and excellent inter-rater reliability. However, more research is needed to determine if SLSTSTs can be used to identify quadriceps weakness in individuals with recovering from an athletic injury or to be used as a return-to-sport (RTS) assessment.

LEVELS OF EVIDENCE

Level 2.

Leg asymmetry and muscle function recovery after anterior cruciate ligament reconstruction in elite athletes: a pilot study on slower recovery of the dominant leg

The aim of this study was to examine performance in hopping tests in male athletes after anterior cruciate ligament reconstruction (ACLR) in the 4-to-6 months post-surgery period. A total of 36 athletes (24 ACLR and 12 controls) participated in this study. The ACLR group consisted of athletes who had undergone an ACLR on their dominant side (ACL DG n=16) or non-dominant side (ACL NDG n=8). Participants completed the following functional tests: a single-leg hop (SLH), single-leg triple hop (SL3H) and single-leg counter movement jump (SLCMJ), then the limb symmetry index (LSI) was calculated. There were no significant differences between the dominant and the non-dominant legs for all functional tests when comparing the ACL DG and the ACL NDG at 6 months after surgery. At 6 months after ACLR, the LSI of the two legs was within acceptable values, whether the athlete had the operation on their dominant or non-dominant leg (except the mean LSI for the ACL DG in the SLCMJ test). Furthermore, the control group showed higher performances as compared to the ACL group for all variables at 6 months after surgery, despite acceptable LSI. We concluded that an early return to “full participation to training” is not recommended in participants who have undergone an ACLR with patellar tendon grafts.

A novel method for measuring asymmetry in kinematic and kinetic variables: The normalized symmetry index

Gait and movement asymmetries are important variables for assessing locomotor mechanics in humans and other animals and as a predictor of injury risk and success of clinical interventions. The four indices used most often to assess symmetry are not well designed for different variable types, perform poorly when presented with cases of high asymmetry or when variables are of low magnitude, and are easily influenced by small variation in the signal. The purpose of the present study was to test the performance of these indices on previously unpublished data on ACL-R patients and to propose a new index to resolve some of these limitations. The performance of four currently used indices and a new index-the Normalized Symmetry Index (NSI), which is scaled to the range of variables being tested across multiple trials-were compared using force and angular data on participants who had undergone anterior cruciate ligament reconstruction and healthy controls. The NSI performed well compared to all other indices with all variables and had the additional benefit of returning values that range from 0% (full symmetry) to ±100% (full asymmetry). Therefore, the NSI can serve as a universal index for assessing asymmetry in humans, nonhuman animal models, and in a clinical context for assessing risk for injury and clinical outcomes.