title: Precision of the PRECICE internal bone lengthening nail.
abstract: BACKGROUND
  Previous designs of internal bone lengthening devices have been fraught with imprecise distraction, resulting in nerve injuries, joint contractures, nonunions, and other complications. Recently, a magnet-operated PRECICE nail (Ellipse Technologies, Inc, Irvine, CA, USA) was approved by the FDA; however, its clinical efficacy is unknown.
  
  
  OBJECTIVE
  We evaluated this nail in terms of (1) accuracy and precision of distraction, (2) effects on bone alignment, (3) effects on adjacent-joint ROM, and (4) frequency of implant-related and non-implant-related complications.
  
  
  METHODS
  We reviewed medical and radiographic records of 24 patients who underwent femoral and/or tibial lengthening procedures using the PRECICE nail from August 2012 to July 2013 for conditions of varied etiology, the most common being congenital limb length discrepancy, posttraumatic growth arrest, and fracture malunion. This group represented 29% of patients (24 of 82) who underwent a limb lengthening procedure for a similar diagnosis during the review period. At each postoperative visit, the accuracy and precision of distraction, bone alignment, joint ROM, and any complications were recorded by the senior surgeon (SRR). Accuracy reflected how close the measured lengthening was to the prescribed distraction at each postoperative visit, while precision reflected how close the repeated measurements were to each other over the course of total lengthening period. No patients were lost to followup. Minimum followup from surgery was 3 weeks (mean, 14 weeks; range, 3-29 weeks).
  
  
  RESULTS
  Mean total lengthening was 35 mm (range, 14-65 mm), with an accuracy of 96% and precision of 86%. All patients achieved target lengthening with minimal unintentional effects on bone alignment. The knee and ankle ROM were minimally affected. Of the complications requiring return to the operating room for an additional surgical procedure, there was one (4%) implant failure caused by a nonfunctional distraction mechanism and six (24%) non-implant-related complications, including premature consolidation in one patient (4%), delayed bone healing in two (8%), delayed equinus contracture in two (8%), and toe clawing in one (4%).
  
  
  CONCLUSIONS
  We conclude that this internal lengthening nail is a valid option to achieve accurate and precise limb lengthening to treat a variety of conditions with limb shortening or length discrepancy. Randomized, larger-sample, long-term studies are required to further confirm clinical efficacy of these devices, monitor for any late failures and complications, and compare with other internal lengthening devices with different mechanisms of operation.
  
  
  METHODS
  Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Limb Lengthening and Complex Reconstruction Service, Hospital for Special Surgery, New York, NY, 10021, USA.
authors.forename: Yatin M
authors.initials: YM
authors.lastname: Kirane
authors.forename: Austin T
authors.initials: AT
authors.lastname: Fragomen
authors.forename: S Robert
authors.initials: SR
authors.lastname: Rozbruch
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D001858:Bone Nails; D005260:Female; D005269:Femur / Q000002:abnormalities / Q000000981:diagnostic imaging / Q000293:injuries / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D007596:Joints / Q000503:physiopathology; D007870:Leg Length Inequality / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000601:surgery*; D059346:Magnets; D008297:Male; D008875:Middle Aged; D019857:Osteogenesis, Distraction / Q000009:adverse effects / Q000295:instrumentation*; D011183:Postoperative Complications / Q000209:etiology; D011474:Prosthesis Design; D011859:Radiography; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D013977:Tibia / Q000002:abnormalities / Q000000981:diagnostic imaging / Q000293:injuries / Q000503:physiopathology / Q000601:surgery*; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult