SUTURE ANCHOR VS DRILL TUNNEL PRIMARY ACL REPAIR:

AN IN VITRO COMPARISON OF GAP FORMATION

Gregory S. DiFelice, M.D.*Jeffrey M. DeLong, B.S.#

Christine Villegas, M.B.S.‡

*Hospital for Special Surgery, New York, NY#Med. Univ. of South Carolina, Charleston, SC

‡Rutgers New Jersey Medical School, Newark, NJ

DISCLOSURES

• Gregory DiFelice, MD:

– Consulting Income: Arthrex, Inc.,

• Jeffrey DeLong, BS: None

• Christine Villegas, MBS: None

• Thank you to Arthrex, Inc., for providing the specimens, instruments and testing apparatus to complete this study.

INTRODUCTION

• Primary ACL suture repair techniques fell out of favor decades agodue to unpredictable and varied outcomes1-20

• Traditional primary ACL repair approaches attempted to repair alltypes of tears regardless of tear pattern via long, morbid, openprocedures followed by long leg cast immobilization.1-20

• Using a modern day approach, the senior surgeon (GD), hasdeveloped an arthroscopic suture anchor repair for proximalavulsion type tears identified preoperatively by MRI.

• This technique dramatically reduces the morbidity of the procedure,and has shown early success when used specifically on proximaltears.

PURPOSE• Comparison of in vitro gap formation of primary ACL

repair on simulated proximal avulsion type tears

Modern knotless suture anchor fixation

Vs.Traditional bone-tunnel bone-bridge with suture-button fixation

• 1° Hypothesis – Suture repair would not result insignificant gap formation with either bone tunnels orsuture anchors after 100 cycles of simulated active motion

• 2° Hypothesis – No difference in gap formation withsuture repair utilizing either bone tunnels or sutureanchors after 100 cycles of simulated active motion.

METHODS• 6 matched-pairs

• 3M/3F• Avg. age, 52.3 ± 3.3 years (range, 48-56 years)

• Simulated proximal ACL tear with scalpel• Half suture repair through drill holes, tied over button• Half suture repair to knotless suture anchors (4.75 mm)• Simulated active ROM by cycling knee from 90° flexion to

full extension via mechanically activating the quadricepstendon

• Gap measured with high resolution photography at 0, 5, 50,100 cycles

• Pairwise comparisions performed to determine significantdifference in gap formation

Knotless suture anchor fixation

1 2 3

4 5 6

(1) Suture passage begins at intact portion of ACL (2) Fiberwire passage progresses in each bundle towards the avulsedend (3) Once both sutures are passed, control of stump is achieved (4) Drill holes placed in femoral footprint fromsimulated accessory inferomedial portal (5) Fixation of 2 suture anchors into ACL bundle footprints (6) Final Primary ACLrepair construct with 2 knotless anchors.

Bone-tunnel bone-bridge with suture-button fixation

1 2 3

4 5 6

(1) Suture passage begins at intact portion of ACL (2) Fiberwire passage progresses in each bundle towards the avulsedend (3) Once both sutures are passed, control of stump is achieved (4) Drill holes into femoral bundle footprints viasimulated accessory inferomedial portal (5) sutures tied over cortical suture-button (6) Final Primary ACL repair constructwith suture-button

RESULTS

• No significant difference in gap formation at 5, 50 or 100 cycles (p = 0.110, p = 0.835, p = 0.625, respectively)

• Average cyclic displacement:– Bone Bridge: .20 / .81 / .83– Knotless Anchors: .40 / .72 / 1.11

Bone Bridge and Suture Button Samples

Donor Side Age / Gender

Cyclic Displacement (mm)

Cycle 5 Cycle 50 Cycle 10013-03586 R 53 / M 0.05 0.17 0.1713-01228 L 51 / F 0.49 2.13 2.1313-03592 R 56 / F 0.42 1.01 1.0113-02400 L 56 / M 0.03 0.49 0.5513-03528 R 50 / F 0.02 0.26 0.3413-02457 L 48 / M 0.17 0.78 0.78

Average 52.3 0.20 0.81 0.83St Dev 3.3 0.21 0.72 0.70

Knotless Anchor samples

Donor Side Age / Gender

Cyclic Displacement (mm)Cycle 5 Cycle 50 Cycle 100

13-03586 L 53 / M 0.47 1.34 1.3413-01228 R 51 / F 0.20 0.25 0.2713-03592 L 56 / F 0.76 0.81 1.1613-02400 R 56 / M 0.26 0.69 0.9013-03528 L 50 / F 0.21 0.71 2.3813-02457 R 48 / M 0.49 0.49 0.61

Average 52.3 0.40 0.72 1.11St Dev 3.3 0.22 0.37 0.73

Significance p = 0.110 p = 0.835 p = 0.625

Discussion

• Sherman’s landmark ACL repair paper showed that patients with proximal tears and good tissue quality tended to have better outcomes than the group overall. 17

• Modern day, arthroscopic suture anchor repair resisted gap formation in vitro at least as well as historic procedure using a simulated active motion model.

• <1 mm gap formation is likely to be clinically insignificant as this will fill with clot quickly after surgery.

Discussion

• MRI enables preoperative identification of those tears that may be amenable to repair, and technological advances allow minimal morbidity repair procedures to be performed. Perhaps, ACL repair should be reconsidered only in carefully selected, proximal tear types?

• Further study is warranted.

LIMITATIONS

• Does not account for dynamic in vivo structural interactions and biomechanics of other associated ligamentous and muscular structures

• Kinematics may be greatly affected by muscular activation and interactions

• Post-mortem cadaveric knee model

• Unknown combined effects of weight bearing rehabilitation protocols and biologic healing on final strength and stiffness

• Small sample size

CONCLUSIONS

• Gap formation for both fixation methods for primary ACL repair after 100 cycles of simulated active motion was approximately 1mm

• No significant difference in gap formation noted between repair techniques.

• Equivalent gap formation existed among primary ACL repair utilizing knotless suture anchors versus primary ACL repair utilizing a bone-bridge and suture-button

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