Clinical application of prong-type tissue anchors in small animal surgery

In vitro acute load to failure and eyelet abrasion testing of a novel veterinary screw-type mini-anchor design

OBJECTIVE

To determine acute load to failure (ALF) and suture abrasion (SA) at 0° and 90° for a novel screw-type mini-anchor design.

STUDY DESIGN

Biomechanical in vitro study.

SAMPLE POPULATION

Synthetic bone.

METHODS

Twenty mini-anchors were inserted into synthetic bone blocks assigned to 1 of 2 groups (0° ALF, 90° ALF). Pullout was performed at 5 mm/min. ALF, yield strength and stiffness were calculated. SA constructs were created with 4 groups of 5 anchors each with either 30 lb nylon leader line (NLL), 40 lb NLL, #2 Fiberwire or #5 Fiberwire. SA was performed at 0° and 90° with a sinusoidal wave form at 0.5 Hz and 10 N load for 1000 cycles or until failure. Data were summarized as mean ± SD. ALF data were analyzed using t-tests. SA data were analyzed using log rank, Tukey-adjusted pairwise comparisons and sign tests. Significance was set at P = .05.

RESULTS

Mean ± SD ALF at 0° and 90° was 431.8 ± 70.8 N and 683 ± 48.7 N, respectively. 90° ALF was significantly higher. Yield strength and stiffness were not significantly different at 0° and 90°. #5 and #2 Fiberwire survived significantly more cycles than 40 lb and 30 lb NLL at 90°. At 0°, 30 lb NLL survived significantly less cycles than either Fiberwire size. Suture orientation did not have a significant effect on SA for Fiberwire constructs.

CONCLUSION

The novel mini-anchor has ALF comparable to other mini-anchors. Fiberwire survived more cycles in the novel anchor eyelet than NLL and FW suture orientation in the eyelet did not affect SA.

The use of a stifle flexion device to manage avulsion of the lateral head of the gastrocnemius muscle in a cat

This report describes the diagnosis and treatment of a traumatic avulsion of the lateral head of the gastrocnemius muscle in a three-and-a-half-year-old male neutered Domestic Shorthaired cat. Surgical repair was achieved using a modified three-loop pulley suture pattern passed through a suture anchor inserted at the point of origin of the tendon and around the fabella. A stifle flexion device was utilised during the postoperative period to protect the repair. Follow-up at five months showed a return to normal function. This is the first report of avulsion of the lateral head of the gastrocnemius in a cat.

Analysis of suture anchor eyelet position on suture failure load

OBJECTIVE

To compare mechanical performance of 2 orientations of the 5 mm Corkscrew® suture anchor with #5 Fiberwire® .

STUDY DESIGN

In vitro biomechanical study.

SAMPLE POPULATION

Suture anchor-suture constructs (n=40).

METHODS

Acute and cyclic tensile loads were applied to suture threaded through eyelets of 40 anchors perpendicular to the long axis of the anchor. Eyelets were positioned so that the suture pull was in line with (anchor rotation angle of 0° [ARA 0]) or 90° (ARA 90) to the eyelet plane. Load at failure, stiffness, and cycles to failure were determined.

RESULTS

All constructs failed by suture breakage at the eyelet. Mean load at failure was significantly higher in the ARA 90 group (634 ± 93 N) compared with the ARA 0 group (495 ± 52 N; P=.0015). No significant difference was found between groups for mean number of cycles to failure (270 ± 177 versus 178 ± 109; P=.2166) and stiffness (50 ± 4 versus 48 ± 5 N/mm; P=.3141).

CONCLUSIONS

The Corkscrew® 5 mm suture anchor with Fiberwire® suture fails via suture breakage at the eyelet under higher acute loads if the suture is loaded at an angle of 90° compared with 0° with respect to the plane of the eyelet.

In vitro evaluation of screws and suture anchors in metaphyseal bone of the canine tibia

OBJECTIVE

To compare ease of insertion, load to failure, and mode of failure of cortical and cancellous screws, BoneBiter, IMEX, and TwinFix suture anchors in canine metaphyseal tibial bone.

STUDY DESIGN

Experimental biomechanical study.

ANIMALS

Canine cadaveric tibias.

METHODS

One investigator inserted all anchors and subjectively evaluated ease of placement. Anchor systems were loaded to failure along axis of insertion with audio-video recording to determine failure mode.

RESULTS

BoneBiter was the most difficult anchor to insert successfully. Mean+/-SD loads to failure were cancellous screw (711+/-193 N), IMEX 4.7 mm 18 g wire (661+/-163 N), IMEX 4.0 mm 18 g wire (661+/-165 N), cortical screw (635+/-184 N), BoneBiter #5 Kevlar suture (393+/- 109 N), and TwinFix 5.0 mm #2 polyester (267+/-73 N). No significant differences were noted among the cortical screw, cancellous screw, IMEX 4.7 and 4.0 mm, all of which were significantly (P<.001) greater than BoneBiter and TwinFix . Failure modes were pullout of bone, suture-wire breakage, eyelet breakage, or no failure to 1000 N: screws (18,0,0,2), IMEX (18,1,1,0), BoneBiter (2,8,0,0), and TwinFix (0,10,0,0).

CONCLUSIONS

Fixation devices were user friendly, with the exception of BoneBiter. Mode of failure is dependent on suture material and anchor design. Cortical and cancellous screws, and IMEX anchors with 18 g wire have significantly greater load to failure compared with BoneBiter and TwinFix suture anchors.

CLINICAL RELEVANCE

Based on load to failure, ease of use, design characteristics, and cost, IMEX anchors may have advantages over other comparable soft tissue fixation devices.