Artificial Rotator Cuff for Shoulder Joint-Its Mechanical Properties and Load Distribution-

1997 Fiscal Year Final Research Report Summary

• Project/Area Number: 08671695
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Orthopaedic surgery
• Research Institution: Tokai University
• Principal Investigator: NAKAJIMA Tomotaka Tokai University, School of Medicine Instructor, 医学部, 助手 (90227794)
• Co-Investigator(Kenkyū-buntansha): MIYAKE Hisato Tokai University, School of Medicine Instructor, 医学部, 助手 (30266423)
• Project Period (FY): 1996 – 1997
• Keywords: Shoulder joint / Rotator cuff tear / Artificial rotator cuff / Mechanical Properties / Finite Elemental Method

Research Abstract

Introduction : To. clarify the mechanical properties of an artificial polyethylene telephtharate tendon (PET cuff ; 20mm Iong, 20mm wide, and 7mm thick) as a substitute of the rotator cuff in the shoulder joint.
Methods : Quasi-static tensile and compression strength of PET cuffs was measured with Instron type-1000 and Servo testing machine, respectively. Ultimate strength, Young ratio, ultimate strain to a yield point, and stiffness of 10,15, and 20-layred PET cuffs were evaluated. Based on these mechanical properties, finite elemental meshes (FEM) showing the distribution of subacromial compression were created at neutral, 45ﾟ internal/external rotation in the 45ﾟ and 90ﾟ glenohumeral abduction postures using the computer program. ABAQUS.The FEM meshes were compared to 3D morphological deformation of the supraspinatus tendon created by MR images. Moreover, the time-depending change in the PET cuff properties was studied after grafting under the rat skin.
Results : A 15-layred PET cuff composed of fibers 0.46mm in diameter was found to have similar mechanical properties to those of a human supraspinatus tendon. A proximal segment near the muscle-tendon junction and middle/posterior portion could be easily deformed with glenohumeral abduction and axial rotation of the humerus. Similarly, compression force in the deformed portion was higher than in the other portions. Ultimate tensile strength was 76% and 60% of the initial value in 4 and 8 weeks after the grafting, respectively.
Discussion : An artificial PET cuff showed that anterior bundles could be resistive against a tensile load, and middle and posterior portions can absorb morphological deformation. The PET cuff having similar fiber arrangement to the supraspinatus tendon was found to decrease a tensile load by supraspinatus muscle and subacromial compression. There were still some problems unsolves ; crosselasticity between fibers, and compression after impact. In the following period, the connecting substance between PET fibers, the mechanical meaning of collagen fibers newly generated as mechanoreceptors would be studied.