Knee extensor strength and hop test performance following anterior cruciate ligament reconstruction

BACKGROUND

Knee extensor strength and single limb hop for distance have been suggested as useful measures to evaluate readiness to return to sport after anterior cruciate ligament (ACL) reconstruction. The aim of the study was to examine the association between knee extensor strength and single leg hop for distance following ACL reconstruction and to determine the proportion of patients with knee extensor strength symmetry deficits at six and 12 months.

METHODS

From December 2013 to December 2015 69 patients aged 14 to 45 undergoing primary ACL reconstruction were recruited. Isokinetic concentric knee extensor strength testing and single limb hop for distance were performed six and 12 months postoperatively. Satisfactory knee extensor strength was defined as a leg symmetry index (LSI) ≥85%.

RESULTS

At six months 27.5% (19/69) of patients had recovered satisfactory knee extensor strength in the injured leg, improving to 46.4% (32/69) at 12 months. Recovery of satisfactory strength was associated with hopping distance. Hop symmetry was achieved considerably faster than knee extensor symmetry, with 66.7% (46/69) of patients demonstrating satisfactory hopping symmetry at six months, 89.9% (62/69) at 12 months. Recovery of hopping distance was not associated with knee extensor strength.

CONCLUSIONS

Single leg hop test cannot be used as a surrogate measure for knee extensor strength as no association was found between hop tests and knee extensor strength. Less than one in three patients at six months and one in two at 12 months had recovered satisfactory knee extensor strength.

Ribavirin is not a functional mimic of the 7-methyl guanosine mRNA cap

Ribavirin is a guanosine ribonucleoside analog that displays broad-spectrum anti-viral activity and is currently used for the treatment of some viral infections. Ribavirin has recently been proposed to also be a mimic of the 7-methyl guanosine cap found at the 5' end of mRNAs. To obtain supporting functional data for this hypothesis, we assessed the ability of ribavirin triphosphate to interfere with the interaction between eIF4E and 7-methyl guanosine capped mRNA. In chemical cross-linking assays, cap-affinity chromatography, and cap-dependent translation assays, ribavirin was unable to function as a cap analog.