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Am J Sports Med. 2014 Feb;42(2):343-9. doi: 10.1177/0363546513507769. Epub 2013 Oct 24.

Femoral suspension devices for anterior cruciate ligament reconstruction: do adjustable loops lengthen?

Author information

1
Travis C. Burns, Deparment of Orthopedics and Rehabilitation, San Antonio Military Medical Center, 3551 Roger Brooke Drive, Fort Sam Houston, TX 78234. travis.c.burns.mil@mail.mil.

Abstract

BACKGROUND:

Cortical suspension devices are commonly used for femoral graft fixation during anterior cruciate ligament (ACL) reconstructive surgery. Adjustable-length fixation devices provide technical advantages over fixed-length loops but may be more susceptible to lengthening during cyclic loading.

HYPOTHESIS:

Both fixed-length and adjustable-length femoral cortical suspension devices would withstand ultimate loads greater than those normally experienced by the native ACL and would prevent clinically significant lengthening during prolonged cyclic loading.

STUDY DESIGN:

Controlled laboratory study.

METHODS:

Mechanical testing was performed on 3 ACL graft cortical suspensory devices by use of an extended cyclic loading (4500 cycles at 10-250 N) and pull-to-failure protocol. Two adjustable-length devices were additionally tested with the free suture ends tied.

RESULTS:

Total displacement after 4500 cycles of tensioning at variable loads (expressed as mean ± SD) was 42.45 mm (±7.01 mm) for the Arthrex TightRope RT, 5.76 mm (±0.35 mm) for the Biomet ToggleLoc, and 1.34 mm (±0.03 mm) for the Smith & Nephew EndoButton CL Ultra (P < .001). The Arthrex TightRope reached clinical failure of 3 mm lengthening after fewer cycles (1349 ± 316) than the Biomet ToggleLoc (2576 ± 73) (P < .001). The Smith & Nephew EndoButton did not reach clinical failure during cyclic testing. With the free suture ends tied, after 4500 cycles, the Arthrex TightRope had a significant decrease in lengthening to 13.36 ± 1.86 mm (P < .037) There was also a significant difference in ultimate load between the TightRope (809.11 ± 52.94 N) and the other 2 constructs (P < .001).

CONCLUSION:

The ultimate load of all graft-fixation devices exceeded the forces likely to be experienced in a patient's knee during the early postoperative rehabilitation period. However, the adjustable-length fixation devices experienced a clinically significant increase in loop lengthening during cyclic testing. This lengthening is partially caused by suture slippage into the adjustable-length loop.

CLINICAL RELEVANCE:

Adjustable-length ACL graft cortical suspension devices lengthen under cyclic loads because free suture ends are pulled into the adjustable loop. This may allow for graft-fixation device lengthening during the acute postoperative period.

KEYWORDS:

ACL reconstruction; EndoButton; TightRope; ToggleLoc; cortical button; cortical suspension; cyclic loading; soft tissue graft

PMID:
24158183
DOI:
10.1177/0363546513507769
[Indexed for MEDLINE]
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