Early reattachment does not reverse atrophy and fat accumulation of the supraspinatus--an experimental study in rabbits.
BACKGROUND
Reattachment of the supraspinatus (SSP) tendon after spontaneous rupture leads to improved shoulder function. Whether this improvement of function is due to a reversal of muscle atrophy and fat accumulation known to occur after SSP rupture is still debated. Our previous study of late reattachment of SSP (12 weeks) failed to confirm a reversal of muscle atrophy and of fat accumulation.


OBJECTIVE
To find out whether earlier reattachment (6 weeks) reverses atrophy and fat accumulation of the SSP.


METHODS
Reattachment group: in seven rabbits unilateral supraspinatus detachment, reattachment after 6 weeks and killing 6 weeks later. Detachment group: in seven rabbits unilateral supraspinatus detachment and killing 12 weeks later. The contralateral shoulders served as controls (n=14). Determination of the supraspinatus constituents: muscle, extra- and intramuscular fat in volume and cross-sectional area.


RESULTS
Muscle tissue in the reattachment group (8.6 ml+/-1s.d.=0.6) and in the detachment group (8.9 ml+/-0.9) were less than in control supraspinati (10.2 ml+/-0.9, both p<0.05). Extra- and intramuscular fat in the reattachment group (8.7%+/-3.2) was greater than in both, the detachment group (4.6%+/-3.5), and control supraspinati (2.8%+/-1.7, both p<0.05).


CONCLUSIONS
In the rabbit, reattachment of the SSP at 6 weeks did neither reverse muscle atrophy nor fat accumulation during the ensuing 6 weeks. However, earlier reattachment (6 weeks) when compared with later reattachment (12 weeks) prevented an increase in fat accumulation. On the other hand, the delay before reattaching the tendon did not lead to an increase in muscle atrophy.
Uhthoff
Hans K
HK
Bone and Joint Research Laboratory, University of Ottawa, Ontario, Canada. hans.uhthoff@sympatico.ca
Matsumoto
Fujio
F
Trudel
Guy
G
Himori
Ko
K
D000273:Adipose Tissue / Q000473:pathology*; D000818:Animals; D018482:Muscle, Skeletal / Q000473:pathology; D009133:Muscular Atrophy / Q000473:pathology* / Q000601:surgery*; D011817:Rabbits; D020127:Recovery of Function; D017006:Rotator Cuff / Q000473:pathology / Q000601:surgery*; D000070636:Rotator Cuff Injuries; D012785:Shoulder Joint / Q000473:pathology / Q000601:surgery; D013708:Tendon Injuries / Q000473:pathology / Q000601:surgery; D013997:Time Factors