Blocking screws for intramedullary nail guidance

Abstract

Intramedullary nails (IMNs) are commonly used for fracture fixation of the femur and tibia, and internal lengthening nails (ILNs) can be used for deformity correction and limb lengthening. While this form of fixation has demonstrated substantial success, one major limitation is imperfect reduction and malalignment, particularly when used for fractures or osteotomies in the metaphysis. One means of overcoming this challenge is through the use of blocking screws, given their ability to guide the path of the nail, decrease the width of the medullary canal, and maintain reduction. In this literature review, indications, techniques, outcomes, and complications are reported. Searches of PubMed and The Cochrane Collaboration were performed. Technique articles and single case reports were not reviewed. All other English studies reporting outcomes of IMN or ILN fixation of the femur or tibia with concomitant use of blocking screws were reviewed. Blocking screws have been used successfully in the lower extremity for both trauma and in deformity surgery. Key techniques are placing the screws in the concavity and perpendicular to the plane of deformity, with adequate distance from the planned path of the nail and from the fracture or osteotomy site. Current data suggest high rates of union with adequate alignment and a low complication rate, although most studies are small, retrospective case series. Blocking screws appear to be a reasonable strategy for achieving fixation in difficulty, metaphyseal segments. Further, well-designed prospective studies should be carried out to make more definitive conclusions.

Keywords

• blocking screw
• deformity
• femur
• fracture
• lengthening
• poller screw
• tibia