Key result
Supraspinatus tendon release in rabbits yields ~1.8 cm musculotendinous retraction linked to shorter total length.
Why the study?
A well-defined, reproducible small animal model allowing quantitative assessment of musculotendinous changes is needed for rotator cuff pathology investigations.
Tendon release using osteotomy of the rabbit greater tuberosity provides a reproducible model for measuring musculotendinous retraction and functional changes in rotator cuff pathology.
Answers are grounded in this paper and cite their sources.
Supports rabbit osteotomy model for rotator cuff retraction studies; clinical translation remains unproven.
Background A well-defined, reproducible small animal model that allows quantitative assessment of musculotendinous changes would be desirable for investigations concerning rotator cuff pathology. Methods The supraspinatus tendon was released by osteotomy of the greater tuberosity in seven New Zealand rabbits. The musculotendinous unit was then allowed to retract during 6 weeks. Retraction was monitored with computed tomography (CT). At sacrifice, CT measurements of retraction were validated by measurement of the total length of the musculotendinous unit after sacrifice and by correlation with functional and structural properties of the musculotendinous unit at tendon release and at sacrifice. Results Mean (SD) retraction of the musculotendinous unit was 1.8 (0.2) cm on CT, precisely, and negatively correlated with the total length of the retracted musculotendinous unit at sacrifice ( r = –0.87, p = 0.011) but not significantly correlated with CT measurements of atrophy ( r = 0.20, p = 0.699) or fatty infiltration ( r = 0.13, p = 0.78). Mean (SD) muscle work decreased from 1.6 (0.23) Nm to 1.2 (1) Nm ( p = 0.056). Mean (SD) muscle fibre diameter decreased from 65 (10) μm to 48 (16) μm ( p = 0.063). This decrease was significantly correlated with the amount of fatty infiltration ( r = 0.79, p = 0.033). Discussion Tendon release using osteotomy of the rabbit greater tuberosity allows precise measurement of musculotendinous retraction and offers the possibility for functional muscular testing. Changes in the rabbit supraspinatus muscle caused by myotendinous retraction correspond to those observed in established sheep models.
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Farshad et al. (2011) studied Rotator cuff tendon tears (n=7). Supraspinatus tendon release by osteotomy vs. Baseline was evaluated on Retraction of the musculotendinous unit on CT (r = -0.87, p=0.011). In a rabbit model, supraspinatus tendon release resulted in a mean musculotendinous retraction of 1.8 cm at 6 weeks, which correlated negatively with total length at sacrifice (r=-0.87, p=0.011).
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