E-Poster at the Arthroscopy Association of North America Annual Meeting 2012 - PASTA Bridge - A New Technique in PASTA Repairs: A Biomechanical Evaluation of Construct Strength vs. Suture Anchors

1. PASTA Bridge - A New Technique in PASTA
Repairs: A Biomechanical Evaluation of
Construct Strength vs Suture Anchors
Alan M Hirahara, MD, FRCSC
Private Practice
Sacramento, CA USA

2. Objective of Study
• To evaluate the biomechanical strength of a new
PASTA repair technique – PASTA Bridge
• To introduce a novel technique in PASTA repair
that is significantly easier, carries less risk, does
not require arthroscopic knot tying, and is as
effective as current trans-tendon techniques

3. Introduction
• In the literature, PASTA lesions can cause significant
pain for patients
• Debridement alone of tears < 50% thickness can result in
good/excellent outcomes but can progress on to full
thickness tears (6.5-34.6%)
• Current repair techniques can lead to excellent results
but are technically challenging

4. Study Design
• Case-control study
• Six matched pairs of fresh frozed cadaver
shoulders
– 3 male / 3 female
– Average age = 49 ± 12 years

5. Study Design
• For each sample, a partial tear of supraspinatus tendon was
replicated by using a sharp blade to transect 50% of the medial
side of supraspinatus from tuberosity 1 cm wide
• From each matched pair, one humerus selected to receive a PASTA
repair using one 4.5mm titanium Corkscrew FT
• Contralateral repair done using a PASTA Bridge repair
• Half of the samples of each repair were performed on the right
humeri to avoid a mechanical bias
• All repairs performed by an orthopaedic surgeon

6. Study Design
• Biomechanical testing conducted using an INSTON 8871 Axial Table Top
Servohydraulic Testing System, with a 5kN load cell attached to cross-
head
• System calibrated using FastTrack software, and load & position controls
run through WaveMaker software
• Each sample positioned on a fixed angle fixture & secured to testing
surface so direction of pull performed 45° to humeral shaft
• Custom fixture with inter-digitated brass clamps attached to cross-head,
and dry ice was used to freeze the tendon to the clamp

7. Study Design
• For each sample, we determined
– Ultimate load, yield load, and stiffness
– Cyclic displacement and strain of each sample at both
the articular margin and at the repair site
– Paired t-tests (α = 0.05) to determine if differences in
ultimate load or strain between the two repairs were
significant

8. PASTA Bridge Technique
• 17 gauge spinal needle punctures supraspinatus
tendon anterior and medial to tear
• 1.1 mm blunt Nitinol wire through spinal needle
followed by a 2.4 mm portal dialation instrument
followed by the drill spear & drill
• Create pilot hole and insert 2.4 mm
BioComposite SutureTak

9. PASTA Bridge Technique
• Repeat for second anchor posterior to tear
• A strand of suture from each anchor was tied in a
similar manner as the “double pulley” method
• Opposing two limbs were tensioned to pull the
knot taunt over the repair site, and fixated laterally
with a 4.75 mm BioComposite SwiveLock

10. PASTA Bridge Technique

11. PASTA Bridge: Construct Strength
Comparison Study
SutureTak and SwiveLock PASTA Repair
Ultimate Yield Stiffness Displacement (mm) Strain (mm/mm)
Donor # Side Gender Age Mode of Failure
Load (N) Load (N) (N/mm) Repair Margin Repair Margin
10-09064 R M 62 1637 1637 144 0.12 0.12 1.015 1.009 humeral head broke
10-08024 L M 27 1499 1308 136 0.52 0.21 1.056 1.014 tendon tore mid-substance
10-11021 R F 53 811 811 65 0.29 0.63 1.041 1.043 tendon tore at repair
10-09062 R F 52 899 899 61 0.63 0.44 1.177 1.048 humeral head broke
11-01032 L M 46 402 402 74 0.78 0.36 1.133 1.027 muscle body tore from tendon
10-10068 L F 53 810 660 81 0.48 0.21 1.062 1.016 muscle body tore from tendon
Average 49 1010 953 94 0.47 0.33 1.081 1.026
Standard Deviation 12 468 449 37 0.24 0.19 0.061 0.016
Titanium Corkscrew PASTA Repair
Ultimate Yield Stiffness Displacement (mm) Strain (mm/mm)
Donor # Side Gender Age Mode of Failure
Load (N) Load (N) (N/mm) Repair Margin Repair Margin
10-09064 L M 62 1398 1395 112 0.24 0.22 1.026 1.013 muscle body tore from tendon
10-08024 R M 27 1642 1642 122 0.14 0.36 1.024 1.022 tendon tore at repair
10-11021 L F 53 922 922 58 0.37 0.53 1.091 1.033 humeral head broke
10-09062 L F 52 969 969 132 0.34 0.54 1.052 1.041 tendon tore at repair
11-01032 R M 46 1003 1003 88 0.58 0.27 1.094 1.021 muscle body tore from tendon
10-10068 R F 53 575 575 82 0.27 0.49 1.050 1.034 tendon tore at repair
Average 49 1085 1084 99 0.32 0.40 1.056 1.027
Standard Deviation 12 378 378 28 0.15 0.14 0.030 0.010

12. Modes of Failure
• Failure occurred at:
– Bone
– Tendon
– Muscle
• No failures of the repair in either group

13. Results
• No significant difference in the two groups in
all parameters
• Mode of failure was always biological, not
mechanical

14. Discussion
• Despite using smaller anchors, we have created a sturdy,
reliable, easy, percutaneous repair technique that is just as
strong as conventional larger suture anchors
• Minimal risk of damaging shoulder during surgery
• Proven biomechanical strength
• Study to evaluate clinical effectiveness in progress

15. Conclusion
• The PASTA Bridge is a viable, simple
technique to repair PASTA lesions that carries
minimal risk, compared with current trans-
tendon techniques