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Competing Interests: POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

Implantable intramedullary nail lengthening devices (e.g., PRECICE 2 system) have been proposed as alternative method to external fixation for lower limb lengthening surgery. The aim of this study was to analyse our outcomes and complications using the PRECICE 2 (P2) nail system and review them in light of the existing literature. A retrospective multicentre study was conducted on patients <18 years, who were treated for limb lengthening using the P2 system. The inclusion criteria were a limb length discrepancy ≥ 30 mm and a follow-up ≥6 months after the end of treatment. A total of 26 (15 males) patients were included, average age was 14.7 ± 2.3 years; 26 nails (21 femur, 5 tibia) were implanted. The average goal lengthening was 49.4 ± 12.4 mm, while average achieved lengthening was 44.4 ± 11.6 mm. Average distraction and consolidation indexes were 11.9 ± 2.1 days/cm and 25.1 ± 8.1 days/cm, respectively. Nail accuracy and reliability were 91.1% and 88.5%, respectively. A total of five problems (joint contractures), one obstacle (femur fracture) and three complications (hip joint subluxation, deep infection and nail running back) were encountered. The P2 nail system is a valid alternative to external fixator for limb lengthening in young patients with no significant angular or rotation deformities. Our study confirms a favourable complication rate and available evidence from literature suggests a lower complication rate than external fixator systems. Nevertheless, surgeons should keep a watchful eye on risk of joint subluxation and mechanical complications with intramedullary lengthening.

Over the past 5 years, published literature regarding treatment of pediatric limb deformity and limb length discrepancy demonstrates much interest in better understanding, categorizing and treating these challenging problems. Many studies explore expanding and refining indications for traditional treatment methods like guided growth techniques. Other studies have evaluated the results of new techniques such as lengthening via mechanized intramedullary nails. Additionally, series comparing older and newer techniques such as lengthening with external devices versus mechanized nails are becoming increasingly available.

The ability to correct limb deformities is one of the core elements of pediatric orthopedics. The term, orthopedics, is derived from the Greek language and means straightening (ortho) children (paidos). New advances in the evaluation and management of children with limb alignment or limb length issues are constantly appearing. This review highlights some of the recent technologies that have been developed to improve the care of these children., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Secondary limb lengthening after intercalary bone resection in pediatric patients is still challenging. After the resection, a free fibula autograft can be used to reconstruct the osseous gap. However, in particular in young pediatric patients, insufficient growth of the epiphyseal plate after transplantation may lead to a significant limb-length discrepancy (LLD). In this case, the autograft was used for limb lengthening. We report on the lengthening of a humerus regenerate after fibula autograft transplantation into a humeral defect in a pediatric/young adolescent patient. Because of LLD, she underwent callus distraction of the humerus regenerate after transplantation of a fibula autograft using a unilateral external fixator device. An 18-year-old female patient with status postintercalary proliferating chondroma resection (at the age of 7 years) required treatment for correction of a 13 cm humerus shortening. She reported no pain, had no functional limitations, and had a full range of motion of the shoulder and elbow joint. She complained about her short humerus and overall body scheme. A unilateral external fixator device for callus distraction was applied to the transplanted humerus regenerate after free fibula autograft transplantation. Bone lengthening was performed by distraction (2×0.5 mm/day). After 62 days and a lengthening of 6 cm in total, bone distraction was stopped mainly to avoid any complication. At this time, there was no limitation in the range of motion. No nerve palsy or other problems occurred at any time of the distraction. In pediatric patients, the transplantation of a fibula autograft is a well-established option to bridge an osseous gap after intercalary bone resection. This case report shows that even the humerus regenerate after fibula autograft transplantation has excellent potential for callotasis and bone remodeling and therefore bone lengthening in patients with LLD is an option even after transplantation of an autograft. This method provides a new therapeutic option for patients with LLD after fibula transplantation.

Limb lengthening is now an accepted practice in orthopaedic surgery. The principles of distraction osteogenesis have become well established with the use of external fixators, utilizing both monolateral and ring fixators. Corticotomy technique, frame stability, lengthening rate and rhythm all contribute to the formation of bone regenerate and tissues. Complications are however common including pin-site infection, soft tissue tethering from the pins and wires resulting in pain, regenerate deformity from soft tissue forces or fracture following frame removal and patient intolerance of the frames during treatment. Surgical techniques have changed to try and minimise these complications. The use of intramedullary nails have been used in conjunction with an external fixator or inserted after lengthening has been achieved, to reduce fixator time and prevent regenerate deformity. Implant innovation has led to the production of intramedullary lengthening nails. The initial devices used ratchet mechanisms with rotation of the bone fragments to achieve lengthening (Bliskunov, Albizzia and ISKD). More accurate control of lengthening and a reduction in pain, resulting from the manual rotation of the leg required to achieve the ratchet progression, was achieved by the use of a transcutaneous electrical conduit powered by external high frequency electrical energy (Fitbone). The most recent implant uses an external remote controller which contains two neodymium magnets. These are placed over the nail on the skin and rotate which in turn rotates a third magnet within the intramedullary nail (Precice). This magnet rotation is converted by a motor to extend or retract the extendible rod. There are multiple nail sizes and lengths available, and early results have shown accurate control with few complications. With such promising outcomes the use of this lengthening intramedullary nail is now recommended as the implant of choice in femoral lengthening. This article is an historical account of the intramedullary device and the impact on limb lengthening., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Leg lengthening has been performed since early in this century. The first successful lengthening was reported in 1905. Leg lengthening evolved from forced lengthening of the bone during anaesthesia, through use of cortical bone grafts, plate and screws to callus distraction (callotasis). Development of external fixators and evolution of biological concepts of bone regeneration has been important. In 1951 Ilizarov developed his apparatus. Ilizarov pioneered the biology of bone and soft-tissue regeneration. He performs a percutaneous subperiosteal corticotomy and waits five to seven days prior to distraction with a rate of 0.25 mm of length four times each day. The method has increased the opportunities in reconstructive bone surgery. The technique is difficult with many problems and obstacles which can be overcome.

The procedure and the external fixator for lengthening long bones was developed by G.A. Ilizarov in the late 1960's. This technique has, despite its proven abilities for leg lengthening and correction of angular deformities, some considerable disadvantages for the patients. Discomfort, infections and restricted weight bearing are some reasons for the development of a completely intramedullary device for leg lengthening. The device developed at the Laboratory of Biomechanical Engineering, University of Twente, is a telescopic intramedullary nail with a maximum diameter of 13 mm, which can be lengthened with 0.5 mm steps induced by a shape memory alloy actuator. The electrical energy for the actuator is supplied from outside the body by inductive coupling of two solenoid coils. Internally, the electrical energy is transformed to thermal energy by Thermofoils and Peltier-elements.

Leg lengthening has been a procedure of last resort because of its high complication rate and significant morbidity with a relatively long period of disability during the process even when no complications occur. The new techniques of lengthening hold promise that orthopedists will be able to achieve more length with fewer complications. It is interesting to note, however, that, while it is the technology of these techniques that has stimulated the greatest enthusiasm, it is the biologic principles that are likely to offer the greatest ultimate benefit. The modern era of leg lengthening has therefore brought two things: new technical versatility to correct complex and coexisting deformities and new concepts of the biology of lengthening that are not device specific and can be applied with most lengthening devices.