Effect Of Fascia-bone Healing On Revascularization Of Autologous Fascia Graft After Superior Capsule Reconstruction

BackgroundThe rotator cuff is a complex structure formed by tendons of supraspinatus,infraspinatus,subscapularis and teres minor,which envelops the entire humeral head.Its function is to transfer the force of muscle contraction and ultimately act on the bone part of the humerus to complete the corresponding form of movement.RCT are one of the most common injuries of the shoulder joint,according to tear size,it can be divided into: small RCT(anterior and posterior tear diameter d=0-1 cm),medium RCT(d=1-3 cm),large RCT(d=3-5 cm)and massive RCT(d>5 cm);a massive rotator cuff tear is defined as a tear >5 cm in length or the tears involving two or more rotator cuff tendons.Irreparable massive rotator cuff tears(IMRCT)can be defined as an inability to reconstruction rotator cuff tendon-bone healing under appropriate tension during the repair of massive rotator cuff tear.The current surgical treatment for IMRCT could be divided into two surgical treatments:joint preservation and joint replacement treatments.Joint preservation operations include partial repair,tendon transfer and alleviative treatment.Partial repair is prone to tendon re-rupture,tendon transfer changes the anatomical insertion of the tendon and the post-operative outcome varies greatly;alleviative treatment can only relieve short-term pain symptoms,but the long-term effects are not significant;joint replacement surgery could be chosen as the final treatment and has narrow clinical indications,once the surgery fails,only reversal shoulder replacement or shoulder fusion surgery can be performed.In 2013,Mihata,performed SCR technique to treat IMRCT,which is a new type of joint preservation surgery treatment.The early and mid-term clinical outcomes of SCR showed a significant improvement in shoulder function and mobility after surgery.Different graft patches(autologous fascia lata,decellularized allograft dermal patch,long head of biceps tendon)have been biomechanically proven to restore stability over the glenohumeral joint.Autologous fascia lata is still one of the commonly used grafts for SCR due to its advantages of convenient collection of materials,good healing and no immune rejection.Good graft-bone healing is the theoretical basis for restoring the upper stability of the shoulder joint and obtaining good postoperative clinical effect.Li et al.demonstrated that fascial autograft patches effectively promoted histological healing of the fascial-bone interface after massive RCT in rats and achieve better mechanical properties.Mihata et al.reported that SCR using autologous fascia lata in a rabbit model was effective in regenerating fibrocartilage at the fascial bone healing site to achieve good healing.However,there are no studies about vascular reconstruction on the healing of fascia-bone interface after SCR.MRI is routinely used as a noninvasive test for postoperative orthopedic evaluation.However,plain MRI can’t directly determine the blood supply status of soft tissue.Contrast agents were injected intravenously to make it circulate into the observed target tissue,which can indirectly show the blood supply of tissue by enhanced MRI.Ntoulia et al.evaluated the process of blood supply reconstruction after ACL reconstruction using autologous patellar tendon and thus the healing process of the graft by enhanced MRI.Previous studies have confirmed that graft-bone healing was closely related to blood supply reconstruction,so graft-bone healing directly affected the long-term postoperative outcome.The fascia lata is a tissue with a rich blood supply,and it is important to clarify the process of blood supply reconstruction after grafting it over the shoulder joint.Clarification of the blood supply reconstruction and the corresponding biological changes during the fascial-bone healing process can provide theoretical support for the SCR.Therefore,in this study,we evaluated the process of graft blood supply reconstruction after SCR by enhanced magnetic resonance,and also observed the biological changes of graft blood supply reconstruction and its fascial-bone healing through a rat SCR model to elucidate the study of MRI assessment of fascial graft blood supply reconstruction after SCR and its effect on fascial-bone healing from clinical studies and basic research.MethodA prospective study of 19 patients with IMRCT underwent ASCR with autologous fascia lata grafts from September 2019 to April 2021.Radiography examinations and clinical evaluations were performed preoperatively and postoperatively at 6 weeks and 3,6,and 12 months.The signal-to-noise quotient(SNQ)value and enhancement index(EI)of autologous fascia lata grafts in the great tubercle insertion(GTI),midpoint of the graft(MG),and glenoid insertion(GI)were compared for radiography examination.Clinical evaluation included the ASES,UCLA shoulder score and VAS score.The SNQ values and EI values of different locations at different time points were compared,and correlation analysis was performed based on the clinical scores and the EI values of different locations at different time points.The model of massive rotator cuff tear in SD rats was established.Thoracolumbar fascia was used as autograft graft to superior capsule reconstruction.Samples were collected at 2,4,8 and 16 weeks,respectively,to observe and analyze the gross view of the fascial bone interface.HE staining and Senna O solid green staining were used to histologically observe the healing process of fascia-bone interface,and semi-quantitative Score was performed on the MTMS.CD31 immunohistochemical staining was used to determine the angiogenesis between different sites.The correlation between the degree of fascia-bone healing and the number of blood vessels was analyzed.ResultsThe SNQ values in T1 WI enhancement at GI and GTI were significantly higher than those at the plain MRI scan at all postoperative observation timepoints;however,the SNQ values in T1 WI enhancement at MG did not show a significant difference until 3 months postoperation.EI values at GTI and GI were significantly higher than those at MG at 6 weeks and 3 months postoperation,while there was no significant difference in the EI value between GTI and GI.At 6 months postoperation,the EI value at GI was significantly higher than those at MG.At 12 months postoperation,the EI value at GI was significantly higher than those at MG and GTI;however,there was no significant difference between GTI and MG.The EI values at GTI and MG peaked at 3 months and 6 months postoperation,respectively,and then plateaued at 12 months postoperation.However,there was no significant difference in the EI value among the different postoperative timepoints at GI.The EI value did not correlate with the VAS and ASES,UCLA scores at any time point or any postoperative observation location.The samples were free of graft tears at all time points after SCR and the inflammatory response at the fascial-bone junction as well as at the fascial part gradually decreased.As the healing time increased,the tissue arrangement in the healed fascial-bone junction became progressively more orderly,and cartilage began to appear at 8 weeks postoperatively,with a distinct cartilage layer forming at 16 weeks postoperatively.At 4 and 16 weeks postoperatively,the degree of healing at the glenoid insertion was significantly higher than that at the great tubercle insertion according to the modified tendon maturation score,with no significant differences between the two at the remaining time points.Reconstruction of the blood supply to the fascia graft probably proceeded gradually from the fascial-bone junction to the middle of the fascial graft and reached a stable state at the articular glenoid stop at 8weeks postoperatively,whereas the great tubercle insertion and the middle of the graft reached stability at 16 weeks.SummaryEnhanced MRI can be used to assess the revascularization process of the autologous fascia lata graft after SCR.The blood supply reconstruction of the graft first develops at the greater tuberosity insertion and the glenoid insertion,and then extends to the middle of the graft.The revascularization at the glenoid insertion reached a stable state earlier,while the greater tuberosity insertion and the middle part of the graft reached stability at 12 months postoperatively.Thoracodorsal myofascial autograft was effective in promoting histological healing at the fascial-bone interface after SCR in rats,and reconstruction of the blood supply to the fascial graft proceeds gradually from the fascial-bone junction to the middle of the graft,with the revascularization at the glenoid insertion reaching a stable state earlier than the remaining two sites.