Abstract
Background
Rotator cuff tears pose a huge socioeconomic burden. Our study uses Fourier transform infrared spectroscopy (FTIR) as it is a quick, non-manipulative and non-destructive test, which can identify a wide range of chemical targets from small intraoperatively obtained specimens. The aim of this study was (i) to characterise the chemical and structural composition of rotator cuff tendons and (ii) to identify structural differences between anatomically distinct tear sizes. Such information may help to identify specific biomarkers of rotator cuff tear pathologies, which in turn could allow early identification and monitoring of disease progression. FTIR may provide insight into the different healing rates of different tear sizes.
Methods
The infrared spectra of 81 torn rotator cuff tendons were measured using a FTIR spectrometer. The rotator cuff tear sizes were classified as partial, small, medium, large and massive, and compared to 14 normal controls. All spectra were classified using standard multivariate analysis; principal component analysis, partial least square and discriminant function analysis.
Results
FTIR readily differentiated between normal and torn tendons, and different tear sizes. We identified the key discriminating molecules and spectra altered in torn tendons as: (i) carbohydrates/phospholipids (1030-1200 cm-1), (ii) collagen (1300-1700, 3000-3350 cm-1) and (iii) lipids (2800-3000 cm-1). Partial tears were chemically distinct from normal and small tears, and primarily involved a reduction in collagen type II.
Conclusion
This study has demonstrated that FTIR can identify different sizes of rotator cuff tear based upon distinguishable chemical and structural features. The onset of rotator cuff tear pathology is mainly due to alterations of the collagen structural arrangements, with associated changes in lipids and carbohydrates. The approach described is rapid and has the potential to be used intraoperatively to determine the quality of the tendon and extent of disease, thus guiding surgical repairs or for monitoring of treatments.
