Animal models and clinical outcomes of massive rotator cuff tears repaired at different timings

Abstract

Objective To study the effect of operative timing on repairing massive rotator cuff tears (RCT) before fatty infiltration and atrophic degeneration in animal models and clinic as well.Methods Sixty New Zealand rabbits were used to set up models of massive RCT without fatty infiltration and atrophic degeneration and randomly divided into 2 equal groups.The operative repair was performed at one week after injury in group A and at 4 weeks in group B.At 2,4 and 8 weeks after operation,healing of tendon-bone interface was observed by H.E.staining,collagens were observed by Sirius Red F 3B (SR) in saturated carbazotic acid staining and areas of type Ⅰ and Ⅲ collagens were measured by imaging analysis software.Failure loads of supraspinatus on both sides were measured.All data were compared at the same time between the 2 groups.Clinically,from January 2008 to January 2011,51 patients with massive RCT without fatty infiltration and atrophic degeneration were arthroscopically repaired.They were divided into 3 groups according to different operative timings:an acute group (n =18) in which operation was conducted in less than 6 weeks,a subacute group (n =17) in which operation was conducted in 6 weeks to 3 months and a chronic group (n =16) in which operation was conducted in more than 3 months.All the shoulders were repaired using the double-row technique.The range of motion (ROM),visual analog scale (VAS) for pain,Constant-Murley score,University of California,Los Angeles (UCLA) score,simple shoulder test (SST) score were recorded and compared among the 3 groups at the last follow-up.Results The animal experiments showed no significant differences between the 2 groups at any time point histologically and biomechanically (P ＞ 0.05).The data showed significant differences in group A between 2 weeks and 4/8 weeks and in group B between 2/4weeks and 8 weeks (P ＜ 0.05).Clinically,follow-ups from 12 to 18 months (average,18 months) showed the 51 patients were cured with no complications.There were significant differences regarding the ROM,VAS,SST,UCLA and Constant-Murley scores between preoperation and postoperation in all the 3 groups (P ＜0.05) but there were no significant differences among the 3 groups regarding RM,functional recovery and pain score at the last follow-up (P ＞ 0.05).Conclusion Animal models and clinical outcomes indicate no effect of operative timing on the repair of massive RCT before fatty infiltration and atrophic degeneration. Key words: Shoulder joint; Wounds and injuries; Histology; Biomechanics; Controlled clinical trial