Biomechanical Evaluation of a Novel Anchorless Transosseous Suture: The Open-Box Technique in Rotator Cuff Repair

Some early biomechanical studies have pointed out that the strength of transosseous suturing is not quite satisfactory. Based on previous studies, we enhanced the strength-related factors and developed a high-strength transosseous suture method, open-box (OBOX), which may offer superior biomechanical strength.

The purpose of this study was to compare cyclic loading, ultimate load to failure, and failure mode of OBOX configuration with those of the anchorless X-box (XBOX) construct and the anchored double-row suture bridge (ADRSB) construct. It was hypothesized that the ultimate strength (US) of the OBOX configuration is similar to that of the ADRSB construct and higher than that of the XBOX construct.

Controlled laboratory study.

A total of 24 fresh-frozen porcine cadaveric shoulders were randomized to 3 repair constructs (8 cases per group). The infraspinatus tendon was detached and repaired to the footprint of the supraspinatus with different repair constructs. Biomechanical testing involved initial preload, cyclic loading, and ultimate failure load. Cameras recorded the bare footprint area (BFA, %), optical markers monitored first-cycle excursion (FCE, mm), and cyclic elongation (CE, %). The US (N) was measured by a mechanical testing machine, and the failure mode was recorded.

The mean US in the OBOX group (708.91 ± 116.34 N) was significantly higher than that in the XBOX group (466.58 ± 70 N) (P < .001) and similar to that in the ADRSB group (630.21 ± 106.52 N) (P = .387). CE significantly differed between XBOX and ADRSB (P = .019), but not between OBOX and XBOX, or between OBOX and ADRSB. The ADRSB group had better fatigue resistance than the OBOX group. In addition, there were no significant intergroup differences in FCE or BFA in the initial and final cycles. The order of the failure mode incidence was as follows: XBOX > OBOX = ADRSB for type 1 tendon tear, OBOX > XBOX = ADRSB for type 2 tendon tear, and ADRSB > OBOX = XBOX for fixing material-related failure.

The OBOX construct demonstrated significantly higher mean US than the XBOX construct in the porcine cadaveric model and was comparable with ADRSB repair. The most common failure modes were type 2 tendon tear for OBOX, type 1 tendon tear for XBOX, and fixing material-related failure for ADRSB.

The OBOX configuration represents a novel transosseous repair method with high fixation strength comparable with the ADRSB construct and stronger than the XBOX construct. However, caution is necessary because of the potential for type 2 tendon tear associated with OBOX, which could complicate revision procedures.