Abstract
Tightrope fixation is known method for reconstructing acromioclavicular joint and the presence of good bone stock around the two drillholes is the most important determining factor for preventing failure.
Aim
Arthroscopic-assisted tightrope stabilisation involve drilling clavicle and coracoids in a straight line. This leads to eccentric drillholes with inadequate bone around it. Open tightrope fixation involves drilling holes under direct vision, independently and leading to centric hole with adequate bone around it. Our study assesses the hypothesis of tightrope fixation in relation to location of drillholes using CT-scan and cadaveric models for arthroscopic and open technique for ACJ fixation.
Methods
CT-scans of 20 shoulders performed. Special software used to draw straight line from distal end of clavicle to coracoid. Bone volume around coracoid drillhole was calculated. Cadaveric shoulder specimens were dissected. The arthroscopic technique was performed under vision by drilling both clavicle and base of coracoid holes in one direction. Same specimens were used for open technique. Base of coracoid crossectioned and volume calculated.
Results
40 shoulders were included(20 cadaveric specimens&20 CT). Bone stock was adequate in both techniques. Variable angle for insertion of drillholes using arthroscopic technique were needed depending on shape of shoulder.
Conclusion
Tightrope allows nonrigid anatomic fixation of acromioclavicular joint. Published studies showed high rate of fixation failure with tightrope system but with patient satisfaction and high functional results. Our study showed adequate bone stock around coracoid in both open and arthroscopic technique. Mode of failure remains unclear and we recommend further biomechanical studies to assess failure factors
