ROTATOR CUFF REPAIR: AN EX-VIVO OVINE BIOMECHANICAL STUDY

Abstract

Purpose: The purpose of our work was to assess sutures, suturing techniques, and suture anchors used in rotator cuff surgery in order to explore weak parts in our repair.

Material and Methods: Ten types of sutures, four types of suturing techniques and eight types of sutures anchors commonly used in shoulder surgery were tested. Vicryl, Ticron, Dexon, PDS, Panacryl, Ethibond, Durabraid, Fiberwire, HiFi and Orthocord sutures were tested. Simple, mattress, massive cuff tear (MCT) technique and modified Mason Allen.

(MMA) suturing technique in ex-vivo ovine healthy rotator cuff were tested. Four metallic and four bioabsorbable anchors: Arthrex, Smith+Nephew, Linvatec, Mitek and bio respectively were tested. Their pull-out strength and failure mode was determined in ex-vivo ovine humeral heads. Materials Testing Machine and attached load cell run with Emperor Software (MEC-MESIN, UK) was used for the tests with application of tensile load(60mm/min). Load and displacement were recorded at a sampling rate of 100 Hz and breaking load and stiffness were recorded.

Results: The suture mean breaking strength (N) was: Vicryl 89.0, Ticron 70.9, Dexon 111.7, PDS 92.9, Panacryl 52.9, Ethibond 64.5, Durabraid 72.6, Fiber-wire 127.2, HiFi 163.0 and Orthocord 141.8. The mean suture stiffness (N/mm) was: Vicryl 3.4, Ticron 3.0, Dexon 2.4, PDS 1.2, Panacryl 0.7, Ethibond 2.5, Durabraid 3.1, Fiberwire 9.7, HiFi 11.1, and Orthocord 6.9. The technique’s mean breaking strength (N) was: simple 54.1, mattress 102.8, MCT 194.0, MMA 227.7 and their mean stiffness (N/mm) was: simple 10.4, mattress 13.1, MCT 26.0 and MMA 18.9. The anchors had mean pull-out strength (N): Arthrex 534.0 and Smith & Nephew 574.0, Linvatec 707.2N, Mitek 736.4N and Arthrex Bio 257.4, Linvatec Bio 305.2, Mitek Bio 359.6, S& N Bio 330.6. Often either in metallic (10/20) or in bioabsorbable anchors (11/20) the eyelet fails first.

Conclusion: Modern non absorbable sutures (HiFi Orthocord Fiberwire) have higher breaking strength and stiffness than absorbable ones (p< 0.05). MCT suturing technique, arthroscopically applicable, and MMA technique, which is most commonly used in open surgery have no great differences in strength and stiffness (p=0.046 and p=0.352 respectively). Both of them have higher strength and stiffness than simple and mattress technique (p< 0.05). Metallic anchors have a higher pull-out strength than bioabsorbable ones (p< 0.05) and the eyelet is a weak point in both.