| BackgroundRotator cuff tear is one of the most common shoulder diseases with an increasing morbidity. Rotator cuff repair is an effective method for the treatment of rotator cuff tear. There are open surgery, mini-open surgery and arthroscopic surgery with suture techniques, which include transosseous fixation, anchor fixation with sutures, and so on. The tendon-bone healing is the key issue. There are many factors in tendon-bone healing process, for instance, suture patterns, fixation methods and varying interface treatment.Few reports were found in the research of interface management, and most of them were on debate. As we know, it would take long operative time and loose bone bed to burr the bone side of bone-tendon interface. Owing to osteoporosis in elderly patients and decorticalized dealing in greater tuberosity, which decreases the stability, the rate of fixation failure may be increased. The focus of this study is whether the bone-tendon interface should be burred to the layer of cancellous bone.Firstly, we set up two different techniques to deal bone-tendon interface, based upon animal model observation. And then, the bone-tendon healing was compared between two techniques to deal bone-tendon interface of cuff insertion in biomechanics and biology. Finally, the patients, who underwent rotator cuff repair with decorticalized dealing of bone-tendon interface, were followed up to evaluate its clinical outcome.Section 1:Comparision of bone-tendon healing of cuff insertion between two techniques to deal bone-tendon interface in biologyIt is imperative to set up a suitable model for rotator cuff repairs. Then it evaluated two techniques to deal bone-tendon interface in biology.1. Methods1). Set up the model of rotator cuff repairThe adult rabbits were performed with a sharply left-lateral tenotomy of the supraspinatus tendon with subsequent re-attachment of the tendon.2). According to the depth of re-attachment, eight animals were equally randomized into two groups:cancellous-fixation group, and cortical-fixation group. Histological results were observed subsequently by HE stain, Safranin O stain, Picrosirus red stain.2. Results1). Set up model of rotator cuff repair4 weeks after operation, the supraspinatus-humerus specimens morphologically showed atrophy and vague between tendon and bone in cancellous-fixation group and cortical-fixation group; at 8 weeks, no obvious differences were observed between two groups.2). Results of histological observationThe histological results of cortical-fixation group at 4th weeks revealed the interface between tendon and new bone became smooth. The fibrous interzone became transitional at 8th weeks, and the shape of bone tissue was nearly normal. The interface obtained from cancellous-fixation group at 4 weeks became sclerotic, and collagen fibers formed in disorder. With ingrowth of new bone and re-establishment of collagen-fiber continuity at 8th weeks, thickness of interface became thin, and bone tissue was remodeling.3. ConclusionThe animal model designed in this study is reproducible. Then we noted the effects of two different techniques to deal bone-tendon interface:It displayed higher osteogenesis activity that the bony recovery below tide-line structure in cancellous-fixation group. A larger amount of type I collagen was observed at tendon side in cortical-fixation group.Section 2:Comparision of bone-tendon healing of cuff insertion between two techniques to deal bone-tendon interface in mechanicsThe samples were obtained relying upon those findings in Section One. The goal of this section was to compare the time-dependent changes in the biomechanical properties of two different techniques to deal bone-tendon interface.1. Methods1). To measure the footprint of the rotator cuff by length and width and angle between the axis of supraspinatus and humerus.2). According to the depth of re-attachment, twenty-eight animals were equally randomized into two groups:cancellous-fixation group, and cortical-fixation group. The remainder of cuff insertion was debrided within 3.5mm×2.5mm, which dual-lateral and border of the footprint were cut off. 3). A 2N-3N preload was applied to pre-tension the specimen. The tendon was then cyclically loaded form 5N to 30N at 0.25Hz for 40 cycles. Following cyclical loading, each tendon specimen was loaded to failure under displacement control at a rate of 1mm/s. Ultimate tensile load, stiffness, energy to failure, and mean increase rate of maximum load were recorded until failure. Ultimate tensile load was defined as the peak force.2. Results1). The average angle was 163.3°; the average maximum length was 10.4 mm, and the average maximum width was 3.4 mm.2). The ultimate to failure were significantly higher in cortical-fixation group than in cancellous-fixation at both 4th and 8th weeks, and the results gained at 8th weeks is significantly higher than that at 4th weeks in each group (P<0.05). Besides energy at 4th weeks between two groups and all stiffness (P>0.05), there was significantly different in the results of others.3. ConclusionCombining with the result of biological outcomes, we noted that tendon-bone healing in cancellous-fixation group was mainly represented recovery of bone side biologically. Cortical-fixation group was superior to cancellous-fixation group in mechanics.Section 3:The clinaical follow-up of rotator cuff repair with two techniques to deal bone-tendon interfaceFrom Oct.,2005 to Feb.,2010,29 patients underwent repairs due to rotator cuff tears. The patient who underwent rotator cuff repair with decorticalized dealing of bone-tendon interface, were followed up to evaluate its clinical outcome.1. MethodsAll patients were evaluated preoperatively and postoperatively by clinical outcome and Constant-Murley scoring system and normalized Constant score system for functions of the shoulder joint. All needed were evaluated by X-ray and MRI scans.29 patients due to rotator cuff tears, in which 17 patients underwent decorticalized dealing of bone-tendon interface. The ones who underwent non-decorticalized dealing were exclusived.2. ResultsAll except twelve patients were satisfied. The Constant scores and the normalized Constant scores increased. The range of motion was increased and there was no complication through the time. MRI showed that the tendons of rotator cuff were low signal continually and uniformly at twelve months post operation.3. ConclusionThe patients who underwent decorticalized dealing of bone-tendon interface in greater tuberosity of humerus presented excellent outcomes. |
