Abstract
Purpose of study
To determine whether cycles of pivot shift testing prior to anterior cruciate ligament (ACL) reconstruction alters metabolite levels in synovial fluid.
Method
Testing for pivot shift is a standard aspect of the EUA prior to an ACL reconstruction. Teaching 2 trainees to perform the pivot test will result in the knee being pivoted 5 times. All cases were isolated ACL deficiency, without meniscal or chondral damage (n=3). Each knee had synovial fluid extracted under aseptic conditions following anaesthesia. The pivot shift test was then performed and demonstrated 5 times. After preparation of the knee for surgery, a second synovial fluid sample was extracted. The time between samples was 5 minutes. Synovial fluids were analysed using 500 MHz 1H NMR spectroscopy. Chemical shifts were referenced to known concentration NMR internal standard (TSP), peaks identified and peak integrals measured using the Bruker software Topspin 2.0.
Results
NMR revealed 26 metabolite-specific peaks in synovial fluid spectra. Some specific metabolite concentrations varied in response to pivot shift testing. For example, we found increases of up to 94% lactate, 48% n-acetyl glycoproteins, 14% arginine, 44% alanine, 38% CH lipids and 45% valine levels in synovial fluid following pivot shifting.
Conclusion
Our pilot data indicates that the metabolic profile of synovial fluid varies before and after pivot shift testing. The results suggest that low energy shear force in the ACL deficient knee, in the absence of meniscal or chondral damage, is sufficient to alter metabolite levels in the synovial fluid. This may represent the first indication of specific metabolites that change in response to altered biomechanical loading in the human knee.
