Lateral Extra-articular Tenodesis Restores Knee Rotational and Translational Stability Regardless of Fixation Type: A Matched-Pair Cadaveric Study

Abstract

Background:

Lateral extra-articular tenodesis (LET) is used as an adjunct to anterior cruciate ligament reconstruction (ACLR) to enhance stability. However, understanding of the optimal fixation method is limited.

Purpose/Hypothesis:

The purpose was to compare biomechanical knee stability using 3 femoral LET fixation methods before and after cyclic loading. It was hypothesized that the fixation achieved with a suture anchor or an interference screw would demonstrate greater stability than that achieved with a metallic staple.

Study Design:

Controlled laboratory study.

Methods:

Ten matched pairs of cadaveric knees (mean age 64 years) underwent modified Lemaire LET. Each pair received suture anchor fixation on 1 knee and either interference screw (arm A) or metallic staple (arm B) fixation on the contralateral knee. Specimens were tested in 4 states: intact (native), anterolateral knee lesion, modified Lemaire (LET) procedure, and modified Lemaire (LET) procedure after cyclic loading. Cyclic loading consisted of 2000 cycles of 5 N·m internal rotation at 1 Hz. Anterior translation was applied at 90 N of force using visual marker motion capture. Internal rotation was measured using a 5 N·m moment and a digital inclinometer.

Results:

No significant differences in anterior translation were observed between the different states (anterolateral lesion, LET, and post–cyclic loading) for all constructs. The mean increase in internal rotation among the subgroups after undergoing anterolateral lesion ranged from 2.1° to 4.0°. No significant difference was found in mean internal rotation after samples underwent cyclic loading in both arms of the study (arm A [suture anchor vs screw], P = .262; arm B [suture anchor vs staple], P = .450). Specimen undergoing suture anchor fixation demonstrated significantly greater change in internal rotation from pre– to post–cyclic loading than those using screw fixation (arm A, 7.2% ± 2.3% vs −1.3% ± 2.6%, respectively; P = .011) but not staple fixation (arm B, 14.3% ± 16.7% vs 5.3% ± 3.1%; P = .338). Internal rotatory stability was restored by all LET methods even after undergoing cyclic loading.

Conclusion:

All fixation methods restored rotational stability to near-native levels even after loading. Suture anchor fixation appeared more vulnerable to cyclic loading than the other 2 methods.

Clinical Relevance:

Suture anchors appeared most vulnerable to cyclic loading. No significant difference was found in absolute mean internal rotation values between suture anchors and screws or staples. Clinically, all 3 methods remain viable options for LET fixation. Staples and screw may better resist cyclic physiologic stress when compared with suture in controlled settings; however, this may not be clinically significant.