Can Locking Screws Allow Smaller, Low-Profile Plates to Achieve Comparable Stability to Larger, Standard Plates?
ABSTRACT The open reduction and internal fixation of radial shaft fractures and osteotomies with standard 3.5-mm plates can be complicated by tendon irritation, hardware prominence, and fracture through the screw holes. With the advent of locking plate technology, implant companies and some surgeons have recommended expanding the indications for these devices; for example, using smaller, low-profile locking plates to suffice where a standard, larger plate would traditionally be used. We analyzed whether there is merit to this strategy. We hypothesized that, in an established cadaveric fracture fixation model, a smaller, low-profile plate with multiple locking screws could maintain adequate fixation stiffness with the potential to minimize hardware-related complications.
Seven matched pairs of fresh-frozen cadaver radii were used. A 5-mm osteotomy gap was created at the midpoint of each specimen and the simulated fracture in one radius from each pair was fixed with a 3.5-mm plate and six nonlocking, standard screws. The contralateral radius was fixed using an equivalent-length 2.7-mm plate with eight locking screws. The radii were subjected to controlled bending and torsional loads and the bending and torsional stiffnesses were documented. Cyclic dorsal-to-volar bending was then applied and resistance to fatigue bending assessed.
The 2.7-mm locking plate was approximately one third as stiff as the 3.5-mm nonlocking plate (P < 0.02). Under physiological loading conditions, the 3.5-mm plate was superior to the 2.7-mm plate with respect to bending stiffness in all four directions, torsional stiffness in both directions, osteotomy gapping, and osteotomy angulation (P < 0.02 for all tests). The performance gap did not narrow with cyclic testing.
The theoretical structural benefit from the locking screws did not make up for the smaller size of the 2.7-mm plate. This held true in all bending planes, torsion, and cyclic loading, and outweighed any biologic differences between the specimens, including the presence or absence of osteoporosis. This is the first study to rigorously compare these two constructs and we conclude that the mechanical properties of the standard 3.5-mm plate are superior to the locking 2.7-mm plate in all regimes tested.
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ABSTRACT: The use of locking plate technology in foot and ankle surgery has increased over the last decade. Reported applications include fracture repair, deformity correction, and arthrodesis. There is limited evidence, however, to guide clinicians with regard to the appropriate and optimal use of this technology. This work aims to examine the current biomechanical and clinical evidence comparing locking construct technology to other forms of fixation in the field of foot and ankle surgery.02/2014; 35(5). DOI:10.1177/1071100714523274
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ABSTRACT: Options for surgical correction of acquired flexible flatfoot deformity involve bone and soft-tissue reconstruction. We used an advanced cadaver model to evaluate the ability of key surgical procedures to correct the deformity and to resist subsequent loss of correction. Stage-IIB flatfoot deformity was created in ten cadaver feet through ligament sectioning and repetitive loading. Six corrective procedures were evaluated: (1) lateral column lengthening, (2) medial displacement calcaneal osteotomy with flexor digitorum longus transfer, (3) Treatment 2 plus lateral column lengthening, (4) Treatment 3 plus "pants-over-vest" spring ligament repair, (5) Treatment 3 plus spring ligament repair with use of the distal posterior tibialis stump, and (6) Treatment 3 plus spring ligament repair with suture and anchor. Correction of metatarsal dorsiflexion and of navicular eversion were quantified initially and periodically during postoperative cyclic loading. Metatarsal dorsiflexion induced by arch flattening was initially corrected by 5.5° to 10.6°, depending on the procedure. Navicular eversion was initially reduced by 2.1° to 7.7°. The correction afforded by Treatments 1, 3, 4, 5, and 6 exceeded that of Treatment 2 initially and throughout postoperative loading. Inclusion of spring ligament repair did not significantly enhance correction. Under the tested conditions, medial displacement calcaneal osteotomy with flexor digitorum longus tendon transfer was inferior to the other evaluated treatments for stage-IIB deformity. Procedures incorporating lateral column lengthening provided the most sagittal and coronal midfoot deformity correction. Addition of spring ligament repair to a combination of these three procedures did not substantially improve correction. An understanding of treatment effectiveness is essential for optimizing operative management of symptomatic flatfoot deformity. This study provides empirical evidence of the advantage of lateral column lengthening and novel information on resistance to postoperative loss of correction.The Journal of Bone and Joint Surgery 03/2014; 96(6):e45. DOI:10.2106/JBJS.L.00258 · 5.28 Impact Factor