All-suture anchor arthroscopic repair of the distal biceps tendon: impact of suture cross-section on fixation strength and gap formation resistance.

BACKGROUND: A minimally invasive arthroscopic technique may reduce complications such as heterotopic ossification, synostosis and arthrofibrosis after distal biceps brachii tendon repair. Ensuring adequate postoperative mechanical performance is crucial to minimize complications during healing. This study evaluated the mechanical performance-with a special focus on gap resistance-of a minimally invasive arthroscopic technique performed using two all-suture anchors, with different suture cross-sectional shapes. METHODS: Single-incision repair was performed on twelve arms using two all-suture anchors loaded with either two round (wire) or two flat (tape) sutures. One wire/tape from each anchor was used to grasp the tendon with four Krackow locking loops, while the other was used to stitch a transversal Mattress. Each repair underwent loading cycles, followed by a load-to-failure test. Subsequently, the anchor fixation and the suture-tendon construct underwent the same loading cycles separately to determine their individual gap resistance. RESULTS: All 12 repairs successfully completed the cyclic test. No significant differences were found in ultimate load values (wire group: median 350 N, range 236-623 N; tape group: median 349N, range 271-483 N; p = 0.63). The most common failure mode (N = 6) was by loosening of both Krackow stitches while the paired Mattress cut through the tendon. A large unrecoverable elongation was measured at the 500th cycle, regardless of the suture cross-sectional shape (wire group: median 5.2 mm, range: 4.0-8.1 mm; tape group: median 5.1 mm, range: 4.2-7.0 mm; p = 0.87). Of this, only 0.7-1.3 mm was due to all-suture anchor seating and suture elongation, the remaining elongation being a combination of tendon strangulation/tearing and stretching. Increasing tendon thickness from 1.7-1.8 to 3.0 mm reduced unrecoverable repair elongation by approximately 50%, from 7-8 to about 4 mm. CONCLUSIONS: Suture cross-section does not seem to affect the mechanical performance of the repair. The minimally invasive arthroscopic technique provides fixation strength that can safely withstand early mobilisation exercises. However, progressive loading, i.e. flexion against resistance, must be allowed with caution to minimise the risk of soft tissue damage, especially in thin tendons, and the associated risk of gap formation and delayed healing. LEVEL OF EVIDENCE: Basic science study; Biomechanics.