Bone is one of the most biologically unique tissues in the human body. What distinguishes bone from most other tissues is that, when injured, it heals by regeneration of its original tissue as opposed to the formation of scar. Recognizing this phenomenon, surgeons as early as the turn of the nineteenth century initiated efforts to lengthen limbs by performing osteotomies and initiating distraction immediately. They had various degrees of success. By the middle of the twentieth century, this technique had been refined thanks to the pioneering work of Dr. Gavril Ilizarov, who recognized the importance of a latency period and the rate and rhythm of the distraction. Ilizarov devoted his life to the research and advancement of a minimally invasive procedure that could be used to treat limb-length deformities and injuries by stimulating the formation of new bone. While Ilizarov and others continued to refine these techniques for clinical use, clinician-scientists recognized that the ability to regenerate tissue through slow, steady, and rhythmic distraction at the site of an osteotomy could yield substantial new knowledge in the field of bone repair and regeneration. Following this recognition, experimental studies demonstrated that the process of distraction osteogenesis is driven by the formation of new blood vessels; thus, angiogenesis precedes osteogenesis.
In the August 2015 issue of JBJS Reviews, Compton et al. discuss the potential biological basis for the phenomenon of distraction osteogenesis and recognize the importance of angiogenesis. Vascular endothelial growth factor (VEGF) has been shown to be one of the most essential and important growth factors in the development of bone regeneration and is regulated by its upstream promoter, hypoxia-inducible factor-1 alpha (HIF-1-α). Further research is needed to fully understand the role of specific molecules and genetic mechanisms in the development of regenerate bone.
In another article in the August 2015 JBJS Reviews, Christopher Iobst notes that limb lengthening as a technique has many advantages, yet the surgeon needs to be vigilant about potential lengthening complications such as joint contractures, joint subluxation, and fractures. While an exciting field, the primary goal of limb lengthening is to produce healthy regenerate bone of the desired length without these complications. In addition, the experience should be as easy and comfortable as possible for the patient. A comprehensive and accurate assessment of limb deformities is essential for successful treatment. In order to accomplish this goal, the concept of preparatory operative treatment has been introduced. Such treatment involves preparing the limb for lengthening by first stabilizing the adjacent joints and removing known soft-tissue constraints. Soft-tissue constraints such as the iliotibial band also may need to be addressed at the time of lengthening. Similar preparation has been outlined prior to lengthening in patients with fibular hemimelia. This stepwise and comprehensive approach is vital to the success of the lengthening.
Iobst also explains how patient selection for limb lengthening is extremely important. Lengthening can be a long and stressful process, and a preoperative assessment of the patient’s psychosocial situation is recommended before the lengthening is started. Advances in limb lengthening techniques involving combinations of external and internal fixation and internal fixation alone with intramedullary rods are presented. Completely internal lengthening nails may have potential advantages over combinations with external fixation, including elimination of pin-track infections and a lower risk of neurovascular injury.
These two articles addressing the scientific and clinical aspects of limb lengthening offer a comprehensive review of this fascinating and important topic. I hope you enjoy reading them!
Thomas A. Einhorn, MD
Editor, JBJS Reviews