Objectives. This study evaluated the mechanical performance, under low-load cyclic loading, of two different knotless suture anchor designs: sutures completely internal to the anchor body (SpeedScrew) and sutures external to the anchor body and adjacent to bone (MultiFIX P). Methods. Using standard suture loops pulled in-line with the rotator cuff (approximately 60°), anchors were tested in cadaveric bone and foam blocks representing normal to osteopenic bone. Mechanical testing included preloading to 10 N and cyclic loading for 500 cycles from 10 N to 60 N at 60 mm/min. The parameters evaluated were initial displacement, cyclic displacement and number of cycles and load at 3 mm displacement relative to preload. Video recording throughout testing documented the predominant source of suture displacement and the distance of ‘suture cutting through bone’. Results. In cadaveric bone and foam blocks, MultiFIX P anchors had significantly greater initial displacement, and lower number of cycles and lower load at 3 mm displacement than SpeedScrew anchors. Video analysis revealed ‘suture cutting through bone’ as the predominant source of suture displacement in cadaveric bone (qualitative) and greater ‘suture cutting through bone’ comparing MultiFIX P with SpeedScrew anchors in foam blocks (quantitative). The greater suture displacement in MultiFIX P anchors was predominantly from
Introduction: We have devised a new technique of lesser tuberosity osteotomy with double row fixation of the subscapularis using suture anchors. Aim: To evaluate the biomechanical properties of this novel technique against two established methods of subscapularis repair including tendon to tendon and transosseous repairs. Method: Matched pairs of human cadaveric shoulders were allocated into 3 groups. Group 1 consisted of the double row technique with incision of the subscapularis along the bicipital groove with a lesser tuberosity osteotomy. A double loaded suture anchor was placed along the medial border of the osteotomy site and sutures were passed through subscapularis medial to the bone island in a horizontal mattress manner. A second anchor was inserted along the lateral border of the osteotomy site and the two sutures were tied onto the subscapularis holding sutures. In group 2, the subscapularis was divided 1cm medial to the bicipital groove and repaired with tendon to tendon suturing. In group 3, the subscapularis was repaired to the cut humeral neck through transosseous tunnels. The cyclic elongation, load to failure, displacement and mode of failure were analysed. Results: All specimens in Group 1 and 40% of Group 2 and 3 passed the cyclic loading test. The ultimate tensile strength in Group 1 was found to be 2.8 times that of Group 2 and 2.4 times that of Group 3 (p<
0.05). Simple suturing failed by suture cutting out of soft tissue and tranosseous repair failed by a combination of the
Introduction: A secure repair of the subscapularis represents an integral part of any surgery involving the anterior approach to the shoulder. Dysfunction of the subscapularis leads not only to poor functional results but also to anterior joint instability which is potentially untreatable. We have devised a new technique of double row fixation of the subscapularis using two suture anchors. Aim: To evaluate the biomechanical strength of this double row technique against the established methods of simple suturing and transosseous repair techniques. Method: Twenty matched pairs of human cadaveric shoulders were allocated into 3 groups. Group 1 consisted of 10 shoulders repaired with the double row technique. This involved incising the subscapularis along the bicipital groove and a lesser tuberosity osteotomy carried out leaving the subscapularis attached to a thin island of bone. A suture anchor (Twinfix) was then inserted just medial to the osteotomy site and the tendon repaired to bone using two horizontal mattress sutures. A second anchor was inserted laterally to supplement the repair with two simple suture knots. The remaining 10 contralateral shoulders were allocated equally between groups 2 and 3. In group 2, the subscapularis was divided longitudinally 1cm medial to the bicipital groove and repaired with simple interrupted suture knots. In group 3, the subscapularis was incised at its insertion to lesser tuberosity and the tendon repaired to the osteotomy site by multiple transosseous sutures through drill holes in the anterior humeral cortex. The suture material used in all three groups was identical and consisted of an ultra high molecular weight poly-ethylene suture (Ultrabraid). To simulate the direction of pull of the subscapularis, the testing block was tilted 45 degrees while a vertically applied distraction force was applied. A custom made jig was used to measure the amount of displacement in response to a gradually applied load. All specimens were tested to failure. The mode of failure of each fixational construct was recorded. Results: The load to failure was found to be significantly higher in the double row repair technique compared to simple suturing and transosseous methods. Simple suturing failed by suture cutting out of soft tissue and tranosseous repair failed by a combination of the
