Original article
A Biomechanical and Radiographic Analysis of Standard and Intracortical Suture Anchors for Arthroscopic Rotator Cuff Repair

https://doi.org/10.1016/j.arthro.2005.08.042Get rights and content

Purpose: To compare the fixation strength and radiographic motion of an anchor designed for intracortical (IC) fixation (FT Anchor, Arthrex, Naples, FL) with that of standard anchors used for rotator cuff repair. Type of Study: In vitro human cadaveric biomechanical study. Methods: Four types of metallic suture anchors (8 per group) were randomly inserted into human cadaveric humeri using an IC anchor and 3 types of standard anchors. Anchors were inserted 45° to the humeral head surface and 90° to the rotator cuff line of action. Anchors were tested under physiologic loads for 500 cycles followed by a failure test. The number of cycles, failure mode, and failure load were recorded. Fluoroscopy was used to measure rotation and displacement of the anchor within the humeral head during testing. Data were analyzed using a 1-way analysis of variance with a correction for multiple comparisons. Results: There were no significant differences in anchor displacement or rotation measured by fluoroscopy after cyclic loading. Total construct displacement across anchors ranged from 4.9 to 7.8 mm, well beyond the 3-mm failure criterion reported in the literature. The IC anchor had a statistically significant greater failure load than the other devices. There was no significant difference in failure load between the other 3 anchors. The anchor had the greatest number of cycles to 3 mm of failure. This was not significantly different than the TwinFix anchor (Smith & Nephew, Andover, MA), but both values were significantly greater than both the Super Revo (Linvatec, Largo, FL) and Fastin RC (DePuy Mitek, Raynham, MA) anchors. Conclusions: Anchor motion accounted for about one third of total displacement of the suture/anchor construct. IC fixation anchors performed well compared with standard anchors in human cadaveric bone. Clinical Relevance: Fluoroscopic imaging showed both rotation and displacement of the anchor within the humeral head which may contribute to early gap formation after rotator cuff repairs.

Section snippets

Methods

Sixteen human cadaveric humeri (8 pairs) were sectioned at the mid-diaphysis and cleaned of soft tissue (age range, 57 to 81 years). Care was taken not to decorticate the supraspinatus tendon footprint on the humeral head. Bone density was measured with a Lunar Dual-Energy X-Ray Absorptiometry (DEXA) machine (GE Medical Systems, Waukesha, WI). These data revealed a relatively osteoporotic sample population (0.34 ± 0.09 g/cm2) compared with previously reported densities (0.78 g/cm2) for young

Results

There were no significant differences in radiographic measures for angle change (range, 12.6° to 21.3°) (Table 1). The IC anchor had an angle change of 12.6° ± 10.6° and the Super Revo had an angle change of 15.3° ± 21.9°. The TwinFix anchor had an angle of 17.0° ± 15.4° and the FastinRC had an angle change of 21.3° ± 23.8°. There were no significant differences between anchor types for displacement change (range, 1.3 to 2.1 mm). The IC anchor had 1.3 ± 1.3 mm of displacement within the humeral

Discussion

Previous studies have reported adequate to excellent performance of suture anchors used commonly in clinical practice.1, 2, 3, 4, 5, 6, 23, 24 To obtain clinically relevant biomechanical data, the present study used a cyclic load protocol with oblique loads on the suture-anchor construct.

The magnitude of total construct displacement of the suture-anchor construct observed in this study was concerning. The average displacement of the 3 conventional suture-anchor constructs following cyclic

Conclusion

Data from the current study indicate that an IC suture anchor may provide the surgeon with biomechanical stability and failure loads similar to other anchors. The total construct displacements for all anchors represent magnitudes of clinical concern. It is also of clinical concern that anchor motion within the humeral head contributed approximately one third of this total displacement. This type of analysis, with particular focus on the movement of suture anchors within the humeral head,

References (32)

Cited by (33)

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    With an extension rate of 20 mm/min on the crosshead, 50 cycles were performed per tensile load starting at 75 N. Starting from the preload tension at 20 N the anchor system was strained until the 75 N threshold was reached and then the tension was reduced back to the preload of 20 N before initiating the next cycle. After 50 cycles at 75 N, the strain was increased in 25 N steps to 100 N, 125 N, 150 N, etc. until system failure occurred.15–19 The maximum failure loads (Fmax), the initial system displacement at 75 N and the respective modes of failure (anchor dislocation, suture slippage, suture rupture) were recorded.

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    Repairs were tested in air, at room temperature, and kept moist by spraying with saline solution. Repairs were preconditioned with 100 cycles from 5 to 100 N at 0.25 Hz and then immediately tested to failure with uniaxial loading in tension at 30 mm/min.32,33,40 The preconditioning loads were determine to be within physiologic limits for a passive range-of-motion physical therapy program based on electromyographic analysis, magnetic resonance imaging, and ultrasound imaging of rotator cuff muscle volumes.2,25,26,34

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Supported by an unrestricted research grant from Arthrex, Inc, Naples, Florida.

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