What is the underlying mechanism for the failure mode observed in the proximal femoral locking compression plate? A biomechanical study. Issue 8 (August 2015)

• Record Type: Journal Article
• Authors: Schneider, Kerstin; Oh, Jong-Keon; Zderic, Ivan; Stoffel, Karl; Richards, R. Geoff; Wolf, Stefan; Gueorguiev, Boyko; Nork, Sean E.
• Is Part Of: Injury. Volume 46:Issue 8(2015)
• Page Start: 1483
• Page End: 1490
• Publication Date: 2015-08
• Subjects: Wounds and injuries -- Surgery -- Periodicals; Accidents -- Periodicals; Wounds and Injuries -- surgery -- Periodicals; Lésions et blessures -- Chirurgie -- Périodiques; Electronic journals; Electronic journals; 617.1
• DOI: 10.1016/j.injury.2015.05.034
• Languages: English
• ISSNs: 0020-1383

Abstract

<abstract abstract-type="author" id="abs0005"> <title id="sect0005">Abstract</title> <sec> <title id="sect0010">Purpose</title> <p id="spar0005">Recently, several cases of clinical failure have been reported for the Proximal Femoral Locking Compression Plate (PF-LCP). The current study was designed to explore biomechanically the underlying mechanism and to determine whether the observed failure was due to technical error on insertion or to implant design.</p> </sec> <sec> <title id="sect0015">Methods</title> <p id="spar0010">A foam block model simulating an unstable intertrochanteric fracture was created for 3 study groups with 6 specimens each. Group C was correctly instrumented according to the manufacturer's guidelines. In Group P and Group A, the first or second proximal screw was placed with a posterior or anterior off-axis orientation by 2° measured in the transversal plane, respectively. Each construct was cyclically tested until failure using a test setup and protocol simulating complex axial and torsional loading. Radiographs were taken prior to and after the tests. Force, number of cycles to failure and failure mode were compared.</p> </sec> <sec> <title id="sect0020">Results</title> <p id="spar0015">A screw deviation of 2° from the nominal axis led to significantly earlier construct failure in Group P and Group A in comparison to Group C. The failure mode was characterised by loosening of the off-axis screw due to disengagement with the plate, resulting in loss of construct stiffness and varus collapse of the fracture.</p> </sec> <sec> <title id="sect0025">Conclusions</title> <p id="spar0020">In our biomechanical test setup, the clinical failure modes observed with the PF-LCP were reproducible. A screw deviation of 2° from the nominal axis consistently led to the failure. This highlights how crucial is the accurate placement of locking screws in the proximal femur.</p> </sec> </abstract>