Extramedullary Motorized Lengthening of the Femur in Young Children

Mark T. Dahl, Stewart G. Morrison, Jennifer C. Laine, Susan A. Novotny, Andrew G. Georgiadis

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1 Scopus citations

Abstract

Background:Limb lengthening by distraction osteogenesis is now achievable via motorized intramedullary devices, mitigating many complications of lengthening by external fixation. In young patients, antegrade intramedullary nailing of the femur risks avascular necrosis of the femoral head. A method of extramedullary placement of a motorized expandable intramedullary nail has been employed by the senior author to safely achieve femoral lengthening without the use of an external fixator in young patients.Methods:Eleven skeletally immature patients with lower limb length discrepancy were reviewed who underwent extramedullary placement of a magnetic, expandable intramedullary nail for lengthening of the femur. Surgical details, lengthening parameters, and complications were reviewed and classified according to the modified Clavien-Dindo Classification.Results:Average lengthening was 32.3 mm (range: 27 to 40 mm) comprising an average 14.8% of femoral segment length. The average lengthening duration was 6.3 weeks, and average full weight-bearing began at 12.6 weeks. All but 1 patient underwent early removal of the device at an average of 4.5 months, and 5 had immediate plating of the femur. Complications rates were comparable to other methods of femoral lengthening, including varus or procurvatum through the regenerate, and unplanned reoperation in 3 of 11 cases. Preoperative considerations included careful planning of implant length due to short femoral segments and protection of the knee joint from contracture or iatrogenic instability.Conclusions:Extramedullary placement of a magnetic expandable intramedullary lengthening nail can achieve lengthening of the femur without the use of external fixation. Considerations with this technique include careful planning of implant length relative to trochanteric-physeal distance, protection against knee subluxation during lengthening, and mitigating deformity of the regenerate. Off-label, extramedullary use of these devices can be considered to decrease the burdens of external fixation in young children. The technique begs the advent of future all-internal technology specifically designed for safe limb lengthening in this age group.Level of Evidence:Level IV - retrospective case series.

Original languageEnglish (US)
Pages (from-to)E978-E983
JournalJournal of Pediatric Orthopaedics
Volume40
Issue number10
DOIs
StatePublished - Nov 1 2020

Bibliographical note

Funding Information:
From the *Department of Orthopaedic Surgery, Gillette Children’s Specialty Healthcare, St. Paul; †Department of Orthopaedic Surgery, University of Minnesota; and ‡University of Minnesota Rehabilitation Science Graduate Program, Minneapolis, MN. The technique described involved off-label use of existing devices. A.G.G. and M.T.D.: conception and design, overall responsibility. A.G.G., J.C.L., S.A.N., S.G.M., M.T.D.: analysis and interpretation, writing the article, and critical revision of the article. A.G.G.: data collection and statistical analysis. A.G.G., S.G.M, M.T.D.: final approval of the article. No authors received financial support for this investigation. M.T.D. (senior author) is a paid consultant for NuVasive and a con-sultant for Stryker Trauma. The remaining authors declare no con-flicts of interest. Reprints: Andrew G. Georgiadis, MD, Department of Orthopaedic Surgery, Gillette Children’s Specialty Healthcare, 200 University Avenue East, St. Paul, MN 55101. E-mail: andrew.g.georgiadis@gmail.com. Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website, www. pedorthopaedics.com. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/BPO.0000000000001593

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