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. 2016 Apr 19;4(4):2325967116643533.
doi: 10.1177/2325967116643533. eCollection 2016 Apr.

Latarjet Fixation: A Cadaveric Biomechanical Study Evaluating Cortical and Cannulated Screw Fixation

Hasham M Alvi  1 , Emily J Monroe  1 , Muturi Muriuki  2 , Rajat N Verma  3 , Guido Marra  1 , Matthew D Saltzman  1
Affiliations

Latarjet Fixation: A Cadaveric Biomechanical Study Evaluating Cortical and Cannulated Screw Fixation

Hasham M Alvi et al. Orthop J Sports Med. .

Abstract

Background: Attritional bone loss in patients with recurrent anterior instability has successfully been treated with a bone block procedure such as the Latarjet. It has not been previously demonstrated whether cortical or cancellous screws are superior when used for this procedure.

Purpose: To assess the strength of stainless steel cortical screws versus stainless steel cannulated cancellous screws in the Latarjet procedure.

Study design: Controlled laboratory study.

Methods: Ten fresh-frozen matched-pair shoulder specimens were randomized into 2 separate fixation groups: (1) 3.5-mm stainless steel cortical screws and (2) 4.0-mm stainless steel partially threaded cannulated cancellous screws. Shoulder specimens were dissected free of all soft tissue and a 25% glenoid defect was created. The coracoid process was osteomized, placed at the site of the glenoid defect, and fixed in place with 2 parallel screws.

Results: All 10 specimens failed by screw cutout. Nine of 10 specimens failed by progressive displacement with an increased number of cycles. One specimen in the 4.0-mm screw group failed by catastrophic failure on initiation of the testing protocol. The 3.5-mm screws had a mean of 274 cycles (SD, ±171 cycles; range, 10-443 cycles) to failure. The 4.0-mm screws had a mean of 135 cycles (SD, ±141 cycles; range, 0-284 cycles) to failure. There was no statistically significant difference between the 2 types of screws for cycles required to cause failure (P = .144).

Conclusion: There was no statistically significant difference in energy or cycles to failure when comparing the stainless steel cortical screws versus partially threaded cannulated cancellous screws.

Clinical relevance: Latarjet may be performed using cortical or cancellous screws without a clear advantage of either option.

Keywords: Latarjet; biomechanics; general sports trauma; glenoid bone loss; shoulder instability.

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Conflict of interest statement

One or more of the authors has declared the following potential conflict of interest or source of funding: A Northwestern University Department of Orthopaedic Surgery institutional department research grant of $5000 was received for this cadaveric study. M.D.S. receives royalties from Tornier and is a paid consultant for Tornier and Medacta. G.M. receives royalties from and is a paid consultant for Zimmer.

Figures

Figure 1.
Figure 1.
(A) Glenoid dissected free of all soft tissue. (B) Osteotomy depicting 25% attritional bone loss as previously described by Itoi et al. (C) Glenoid after completion of osteotomy.
Figure 2.
Figure 2.
Points along the interface between the graft and the glenoid surface were obtained using a digitizing probe. Two infrared emitting targets can be seen: one attached to the graft and the other to the glenoid of the potted specimen.
Figure 3.
Figure 3.
The graft was loaded using a hemispherical plastic piece acting as a simulation of the humeral head. The graft was directly loaded to mimic maximum abduction and external rotation of the arm.
Figure 4.
Figure 4.
The experiment proceeded until 1 of the 5 defined failure points was reached. Note the medial displacement of coracoid graft.
Figure 5.
Figure 5.
Individual plot of energy comparing 3.5-mm cortical screws with 4.0-mm cannulated screws.
See this image and copyright information in PMC

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