Purpose
To compare the outcome of 2 bioabsorbable screws for tibial interference fixation
in anterior cruciate ligament reconstruction with reference to rate of absorption,
osteoconductive properties, and clinical outcome.
Methods
Patients undergoing primary anterior cruciate ligament reconstruction with hamstring
autograft in a single unit were invited to participate in this study. Patients were
randomized to receive either the Calaxo screw (Smith & Nephew, Andover, MA) or Milagro
screw (DePuy Mitek, Raynham, MA) for tibial fixation. Patients were reviewed with
subjective and objective evaluation by use of the International Knee Documentation
Committee form, Lysholm score, KT-1000 arthrometry (MEDmetric, San Diego, CA), and
clinical examination. Magnetic resonance imaging was performed at 1 year and computed
tomography scanning at 1 week and at 6, 12, and 24 months.
Results
Sixty patients agreed to participate in the study, with 32 patients randomized to
the Calaxo screw and 28 to the Milagro screw for tibial fixation. There was no significant
difference in subjective or objective clinical outcome between the 2 groups. At 24
months, 88% of Calaxo screws showed complete screw resorption compared with 0% of
Milagro screws (P < .001). Tibial cysts were present in 88% of the Calaxo group and 7% of the Milagro
group (P = .001). At 24 months, the mean volume of new bone formation for the Calaxo group
was 21% of original screw volume. Ossification of the Milagro screw was unable to
be accurately assessed as a result of incomplete screw resorption.
Conclusions
Both screws showed similar favorable objective and subjective outcomes at 2 years.
The Calaxo screw resorbed completely over a period of 6 months and was associated
with a high incidence of intra-tunnel cyst formation. The Milagro screw increased
in volume over a period of 6 months, followed by a gradual resorption, which was still
ongoing at 2 years. Both screws were associated with tunnel widening, and neither
showed evidence of significant tunnel ossification. We conclude that, despite satisfactory
clinical outcomes, the addition of “osteoconductive” materials to bioabsorbable screws
is not associated with bone formation at the screw site at 2 years.
Level of Evidence
Level I, randomized controlled trial.
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Article Info
Publication History
Accepted:
October 24,
2012
Received:
April 17,
2012
Footnotes
The authors report the following potential conflict of interest or source of funding in relation to this article: Smith & Nephew and Johnson & Johnson for institutional research support. Smith & Nephew Endoscopy for financial support to the Cleveland Clinic for development and validation of the quantitative CT techniques for assessment of bioabsorbable ACL screws.
Identification
Copyright
© 2013 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.
