A critical analysis of limb symmetry indices of hop tests in athletes after anterior cruciate ligament reconstruction: A case control study.

BACKGROUND: Hop tests are frequently used to determine return to sports (RTS) after anterior cruciate ligament reconstruction (ACLR). Given that bilateral deficits are present after ACLR, this may result in a falsely high limb symmetry index (LSI), since LSI is calculated as a ratio between the values of the limbs. HYPOTHESIS: Athletes after ACLR would achieve LSI>90% for the hop test. Secondly, athletes after ACLR demonstrate decreased jump distance on the single hop for distance (SLH) and triple leg hop for distance (TLH) and decreased number of hops for the side hop (SH) for both involved and uninvolved limbs compared to normative data of sex, age and type of sports matched healthy athletes. MATERIALS AND METHODS: Fifty-two patients (38 males mean age 23.9±3.5years; 14 females mean age 21.7±3.5 years) who had undergone an ACLR participated in this study. Patients performed the 3 hop tests at a mean time of 7 months after ACLR. Hop distance, number of side hops and LSI were compared with normative data of 188 healthy athletes. RESULTS: The differences between the involved limb and the uninvolved limb were significant in all hop tests (SLH P=0.003, TLH P=0.003, SH P=0.018). For females, only significant between limb differences were found in the SLH (P=0.049). For both the SLH and the TLH, significant differences were found between the involved limb and the normative data (males; SLH P<0.001, TLH P<0.001; females; SLH P<0.001, TLH P=0.006) and between the uninvolved limb and the normative data for both males and females (males; SLH P<0.001, TLH P<0.001; females; SLH P=0.003, TLH P=0.038). For the SH, only significant differences were found between the involved limb and the normative values in males (P=0.033). CONCLUSION: Athletes who have undergone an ACLR demonstrate bilateral deficits on hop tests in comparison to age and sex matched normative data of healthy controls. Using the LSI may underestimate performance deficits and should therefore be analyzed with caution when used as a criterion for RTS after ACLR. LEVEL OF EVIDENCE: III, case control study.

Effect of fatigue on landing performance assessed with the landing error scoring system (less) in patients after ACL reconstruction. A pilot study.

BACKGROUND: Fatigue has been shown to affect performance of hop tests in patients after anterior cruciate ligament reconstruction (ACLR) compared to uninjured controls (CTRL). This may render the hop test less sensitive in detecting landing errors. The primary purpose of this study was to investigate the effect of lower extremity fatigue on landing performance assessed with the Landing Error Scoring System (LESS) in patients after ACLR compared to a CTRL group. It is plausible that fatigue would have an effect on confidence and risk appraisal in the ACLR group. The secondary purpose was to determine the relationship between psychological responses and LESS scores after fatigue. METHODS: Twelve patients following ACLR (6 males, 6 females) who were tested at 10 ± 2.4 months after surgery participated in the current study and were compared to 10 subjects in the control group (5 males, 5 females). Subjects performed a jump-landing task and the landing was assessed using the Landing Error Scoring System (LESS) both before and after fatigue. Digital video camcorders recorded frontal and sagittal plane views of the subject performing the task. The LESS was scored using video replay. Psychological responses in the ACLR group were assessed with the ACL-RSI questionnaire. RESULTS: Patients after ACLR had a median LESS of 6.5 which reflects a poor result (LESS >6) in the pre-fatigue condition compared to controls who had a LESS of 2.5 which is considered excellent (≤4). In the post-fatigue condition, median LESS in patients after ACLR increased to 7.0 whereas in the control group the LESS increased to 6.0 both of which reflect a poor result. The median increase in LESS was larger in the control (2.0) group compared to patients after ACLR (1.0) but the difference was not significant (p=0.165). CONCLUSIONS: Patients after ACLR have higher LESS scores at baseline compared to a control group. Fatigue resulted in an increase in scores on the LESS in both groups. LEVEL OF EVIDENCE: 3b.

Bioconcentration kinetics of the organophosphorus insecticide chlorpyrifos in guppies (Poecilia reticulata).

The bioconcentration kinetics of chlorpyrifos (O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate) in guppies (Poecilia reticulata) were investigated. A static exposure was used to study the uptake of the compound. The amount absorbed was calculated from the difference in disappearance rates from the water phase in aquaria with and without fish. The uptake rate was found to be first-order with respect to the exposure concentration, and amounts to ca. 38 ml g-1 (fish) hr-1. The elimination rate was studied in separate experiments. Guppies were first given the opportunity to accumulate chlorpyrifos and, following transfer to clean water, the clearance of the compound was measured by determining the residual chlorpyrifos in the fish. It was found that the elimination rate was first-order with respect to the concentration in fish, but depended slightly on the length of the preexposure period. The half-life of tissue chlorpyrifos varied from 31 to 38 hr. Release of unchanged chlorpyrifos turned out to be negligible relative to the amount eliminated. This indicates that metabolic breakdown is the only pathway for elimination. From the kinetic rate parameters, a bioconcentration factor was calculated of about 1700. This value is very similar to that measured directly after an 8-day semistatic exposure. A two-compartment model is proposed to describe the kinetics of the bioconcentration process. The conditions limiting the applicability of the indirect method for measuring the toxicokinetics of chlorpyrifos are discussed.

Inhibition of acetylcholinesterase in guppies (Poecilia reticulata) by chlorpyrifos at sublethal concentrations: methodological aspects.

Acetylcholinesterase activity is a potential biochemical indicator of toxic stress in fish and a sensitive parameter for testing water for the presence of organophosphates. A number of methodological aspects regarding the determination of the in vivo effect of chlorpyrifos on acetylcholinesterase in guppies have been investigated. It was found that with acetylthiocholine as a substrate, the contribution of pseudocholinesterase to the total cholinesterase activity can be neglected. Protection of acetylcholinesterase of guppies exposed to chlorpyrifos from additional, artifactual in vitro enzyme inhibition during homogenization is necessary. Very low concentrations of acetone in the exposure medium, resulting from dilution of the stock solution of chlorpyrifos in acetone, can result in large decreases in the oxygen content of this medium. This may affect the uptake rate of the toxic compound and, thereby, cholinesterase inhibition. Very low, sublethal concentrations of chlorpyrifos result in high inhibition levels of acetylcholinesterase (80-90%) in guppies within 2 weeks of continuous exposure. Recovery of the enzyme activity occurs after the exposed animals are kept in clean medium for 4 days, but the rate of recovery is considerably lower than the rate of inhibition.