Transcript
Page 1: Biomechanical Evaluation of Threaded Headless … · Headless Screws Compared to Traditional ... Biomechanical Evaluation of Threaded Headless ... • 2 screw fixation of the subtalar

Biomechanical Evaluation of Threaded

Headless Screws Compared to Traditional

Headed Screws in Subtalar Fusion Model

David E. Oji, Brent Parks, Mark Reed, Josh Nadaud, Michael Tsai, Alan

Yan, Stuart Miller

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Page 2: Biomechanical Evaluation of Threaded Headless … · Headless Screws Compared to Traditional ... Biomechanical Evaluation of Threaded Headless ... • 2 screw fixation of the subtalar

Biomechanical Evaluation of Threaded Headless

Screws Compared to Traditional Headed Screws

in Subtalar Fusion Model

David Oji

Stuart Miller

My disclosure is in the

Final AOFAS Program Book.

I have no potential conflicts

with this presentation

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Page 3: Biomechanical Evaluation of Threaded Headless … · Headless Screws Compared to Traditional ... Biomechanical Evaluation of Threaded Headless ... • 2 screw fixation of the subtalar

Background:

• Headless screws shown to be equal or superior to traditional screws in: – maintaining fixation in an osteotomy

– fracture reduction and fixation

• Headless screws provide a locking mechanism in the setting of lower compressive strength versus traditional screws

• Hypothesis: – Headless screws hold a subtalar arthrodesis fusion model

with less deformity in cyclic loading than conventional screws

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Page 4: Biomechanical Evaluation of Threaded Headless … · Headless Screws Compared to Traditional ... Biomechanical Evaluation of Threaded Headless ... • 2 screw fixation of the subtalar

Method:

• 12 matched pairs -> subtalar arthrodesis

in-situ

• 2 screw fixation of the subtalar joint

– 1 extremity w/ Integra 7.5mm headless cannulated screws

– Contralateral side w/ AO 7.3mm partially threaded cannulated

screws

– Joint surface was not prepared

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Page 5: Biomechanical Evaluation of Threaded Headless … · Headless Screws Compared to Traditional ... Biomechanical Evaluation of Threaded Headless ... • 2 screw fixation of the subtalar

Method:

• Talus / calcaneus excised and mounted on loading frame

• Differential variable reluctance transducers used to measure motion

• Torque applied rate of 1 degree / sec

• 0 N of axial load

• Stiffness and subtalar motion was assessed

• Paired t-test to determine statistical significance

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Page 6: Biomechanical Evaluation of Threaded Headless … · Headless Screws Compared to Traditional ... Biomechanical Evaluation of Threaded Headless ... • 2 screw fixation of the subtalar

Results:

• Headless screws compared to traditional screws demonstrated less motion before and after cyclical loading to internal and external rotation (p<0.05)

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Initial Rotation Final Rotation

Headless Screw 7.73 8.28

Traditional Screw 11.20 13.01

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

Ro

tati

on

(de

gre

e)

Internal Rotation

Initial Rotation Final Rotation

Headless Screw 4.95 7.81

Traditional Screw 9.40 12.06

-1.90

0.10

2.10

4.10

6.10

8.10

10.10

12.10

14.10

16.10

Ro

tati

on

(de

gre

e)

External Rotation

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Results:

• Statistically significant higher initial stiffness to internal and external rotation (p<0.02 & p<0.0002)

• Higher final stiffness to internal and external rotation but not statistically significant

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Initial Stiffness Final Stiffness

Headless Screw 0.97 1.14

Traditional Screw 0.57 0.90

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80 St

iffn

ess

(N

m/d

egr

ee

) Stiffness to Internal Rotation

Headless Screw 1.25 1.23

Traditional Screw 0.56 1.00

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

Stif

fne

ss (

Nm

/de

gre

e)

Stiffness to External Rotation

Page 8: Biomechanical Evaluation of Threaded Headless … · Headless Screws Compared to Traditional ... Biomechanical Evaluation of Threaded Headless ... • 2 screw fixation of the subtalar

Discussion:

• Headless screws demonstrated statistically significant increased stiffness and less motion compared to traditional screws

• Possible improved biomechanical properties due to proximal locking mechanism

• Clinical application in fusions that require more stability or in patients with osteopenic bone

• Provide less soft tissue irritation

• Further studies are needed to determine the clinical significance of using headless screws in subtalar fusion

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Page 9: Biomechanical Evaluation of Threaded Headless … · Headless Screws Compared to Traditional ... Biomechanical Evaluation of Threaded Headless ... • 2 screw fixation of the subtalar

Conclusion:

• The headless screw model was able to hold a

subtalar arthrodesis with less deformity to cyclic

loading compared to conventional headed

screws

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References

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3. Kokubu T, Nagura I, Mifune Y, Kurosaka M. Arthroscopic bony bankart repair using double-threaded headless screw: a case report. Case Rep Orthop. 2012

4. Ball B, Bergman JW. Scaphoid excision and 4-corner fusion using retrograde headless compression screws. Tech Hand Up Extrem Surg. 2012 Dec;16(4):204-9

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7. Capelle JH, Couch CG, Wells KM, Morris RP, Buford WL Jr, Merriman DJ, Panchbhavi VK. Fixation strength of anteriorly inserted headless screws for talar neck fractures. Foot Ankle Int. 2013 Mar 1

8. Hintermann B, Valderrabano V, Nigg B. Influence of screw type on obtained contact area and contact force in a cadaveric subtalar arthrodesis model. Foot Ankle Int. 2002 Nov;23(11):986-91

9. Sides SD, Fetter NL, Glisson R, Nunley JA. Bending stiffness and pull-out strength of tapered, variable pitch screws, and 6.5mm cancellous screws in acute Jones fractures. Foot Ankle Int. 2006 Oct;27(10):821-5

10. Eddy AL, Galuppo LD, Stover SM, Taylor KT, Jensen DG. A biomechanical comparison of headless tapered variable pitch compression and AO cortical bone screws for fixation of a simulated midbody transverse fracture of the proximal sesamoid bone in horses. Vet Surg. 2004 May-Jun;33(3):253-62

11. Chuckpaiwong B, Easley ME, Glisson RR. Screw placement in subtalar arthrodesis: a biomechanical study. Foot Ankle Int. 2009 Feb;30(2):133-41

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