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J Orthop Res. 2015 Nov;33(11):1680-6. doi: 10.1002/jor.22934. Epub 2015 May 18.

Trabecular bone strength is not an independent predictive factor for dynamic hip screw migration--A prospective multicenter cohort study.

Author information

1
Department of Orthopedic Surgery and Traumatology, University Hospital Basel, Switzerland.
2
Department of Trauma Surgery and Sports Medicine, University Hospital Innsbruck, Austria.
3
Department of Trauma Surgery, Hannover Medical School, Germany.
4
Department of Surgery, Ziekenhuis Groep Twente, Almelo, The Netherlands.
5
Department of Trauma Surgery, Wilhelminenspital, Vienna, Austria.
6
Department of Trauma, Hand and Reconstructive Surgery, University Hospital Münster, Germany.
7
Trauma, Hand and Recovery Surgery Hospital, University of Jena, Germany.
8
Division of Trauma Surgery, Department of Surgery, Stadtspital Triemli, Zurich, Switzerland.

Abstract

This study assessed whether mechanically measured trabecular bone strength is an independent predictor of dynamic hip screw (DHS) stability, i.e., DHS migration (DHSM) after the fixation of proximal femoral fractures. One-hundred and seven patients older than 50 years with proximal femoral fractures were included. During fracture fixation, a mechanical probe (DensiProbe™ Hip) was inserted at the site where the DHS tip would ultimately be positioned. Peak torque to breakaway the trabecular bone was measured. Fracture reduction, primary implant position and postoperative DHSM were assessed by radiographs taken postoperatively, at 6 and 12 weeks after surgery. Univariate regression analysis revealed no association between peak torque and DHSM (R(2) = 0.025, p = 0.135). DHSM correlated with the primary DHS position, i.e., the distance between the DHS and (i) the central femoral neck axis (CNFAD, R(2) = 0.230; p < 0.0001) and (ii) the apex of the femoral head (R(2) = 0.110; p = 0.001). DHSM did not correlate with areal BMD of the contralateral proximal femur. Multivariable regression modeling revealed the CFNAD as predictive factor for screw migration. The primary implant position measured by the CFNAD, rather than DensiProbe™ Hip measured bone strength, is an independent predictor of DHSM.

KEYWORDS:

bone strength; dynamic hip screw migration; implant stability

PMID:
25929756
DOI:
10.1002/jor.22934
[Indexed for MEDLINE]
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