Repair of Pars Interarticularis Defect Utilizing a Pedicle and Laminar Screw Construct: A New Technique Based on Anatomic and Biomechanical Analysis

Object The theoretical advantage of pars interarticularis repair over spinal fusion to correct pars defects is that the treatment is a direct osteosynthesis that preserves motion at the involved functional spinal unit. Several techniques and constructs have been used to achieve greater rigidity, but these techniques may risk entry into the spinal canal, and adverse events are common. A pedicle and laminar screw construct placed entirely outside the spinal canal may offer greater stiffness and achieve higher pars defect healing rates. The purpose of this study was to biomechanically assess an intralaminar screw construct in cadaveric lumbar spines in comparison with other types of constructs typically used in pars repair and to quantify the sizes of screws that can be placed safely in both normal and spondylolytic vertebrae. Methods The L-4 and L-5 laminae in patients with spondylolysis and in controls who underwent CT (n = 41, each group) were measured by analysis of conventional axial CT images and multiplanar reformations constructed on a Vitrea workstation to determine the feasibility of translaminar fixation with a 4.5-mm-diameter screw. Biomechanical tests for torsion and flexion-extension were performed on 8 fresh human cadaveric lumbar spines before and after modeling for bilateral spondylolytic defects. Three pars repair techniques were tested at each level and in the following sequence: pedicle screw–cable, pedicle screw–rod–hook, and pedicle screw–intralaminar screw. Results The majority of laminae can accept 4.5 × 25-mm screws. The cable construct allowed the greatest motion and least stability across the defect in all biomechanical tests. The hook and laminar screw constructs performed similarly in all tests and exhibited no significant difference in stiffness. Conclusions A surgically placed intralaminar screw construct may be a safe and effective alternative to current pars repair methods.

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BIOMECHANICS OF A NEW TECHNIQUE FOR FLEXOR TENDON TENORRAPHY OF THE HAND

British Journal of Surgery ◽

10.1093/bjs/znab160.003 ◽

2021 ◽

Vol 108 (Supplement_3) ◽

Author(s):

S García Cabeza ◽

M Lara Guerrero ◽

F Salinas Ramila ◽

G J Martínez Magide ◽

S Carnero López ◽

...

Keyword(s):

Tensile Strength ◽

Ultimate Tensile Strength ◽

Flexor Tendon ◽

Testing Machine ◽

Conventional Technique ◽

Biomechanical Analysis ◽

New Technique ◽

Flexor Digitorum Profundus ◽

A New Technique ◽

Breaking Time

Abstract INTRODUCTION The present study compares ultimate tensile strength, gap strength (2, 4, 6 mm), distortion time and breaking time in a new flexor tendon suture, to a conventional technique. MATERIAL AND METHODS The flexor digitorum profundus tendons of 40 porcine forelimbs were repaired. The biomechanical analysis was carried out in a universal testing machine applying a constant speed. Tenotomy gap, the force applied and the rupture point were analysed. RESULTS The ultimate tensile strength, and 4 and 6 mm gap strength were significantly higher with the new technique compared with the conventional 4-strand cruciate technique. CONCLUSIONS The new technique is a higher provider of repair strength during early active mobilization when compared with the conventional 4-strand cruciate technique. These findings suggest that this new suture can be considered a biomechanically favourable technique for the repair of flexor tendon lacerations.

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