title: What is the morbidity of a non-invasive growing prosthesis?
abstract: OBJECTIVE
  Extendible endoprostheses have been available for more than 30 years and have become more sophisticated with time. The latest generation is 'non-invasive' and can be lengthened with an external magnetic force. Early results have shown a worryingly high rate of complications such as infection. This study investigates the incidence of complications and the need for further surgery in a cohort of patients with a non-invasive growing endoprosthesis.
  
  
  METHODS
  Between 2003 and June 2014, 50 children (51 prostheses) had a non-invasive growing prosthesis implanted for a primary bone sarcoma. The minimum follow-up was 24 months for those who survived. Their mean age was 10.4 years (6 to 14). The incidence of complications and further surgery was documented.
  
  
  RESULTS
  The mean follow-up was 64 months (20 to 145). The overall survivorship of the patients was 84% at three years and 70% at five years. Revision-free survival was 81.7% at three years and 61.6% at five years with competing risk analysis. Deep infection occurred in 19.6% of implants at a mean of 12.5 months (0 to 55). Other complications were a failure of the lengthening mechanism in five prostheses (9.8%) and breakage of the implant in two (3.9%). Overall, there were 53 additional operations (0 to 5 per patient). A total of seven patients (14%) underwent amputation, three for local recurrence and four for infection. Their mean limb length discrepancy was 4.3 mm (0 to 25) and mean Musculoskeletal Tumor Society Score functional score was 26.5 (18 to 30) at the final follow-up.
  
  
  CONCLUSIONS
  When compared with previously published early results, this mid-term series has shown continued good functional outcomes and compensation for leg-length discrepancy. Infection is still the most common complication: post-operative wound healing problems, central line infection and proximal tibial location are the main risk factors. Cite this article: Bone Joint J 2016;98-B:1697-1703.
authors.affiliation: Medical University of Graz, Auenbruggerplatz 5, 8036 Graz, Austria.
authors.forename: M M
authors.initials: MM
authors.lastname: Gilg
authors.affiliation: The Royal Orthopaedic Hospital, Bristol Road South, Birmingham, B31 2AP, UK.
authors.forename: C L
authors.initials: CL
authors.lastname: Gaston
authors.affiliation: The Royal Orthopaedic Hospital, Bristol Road South, Birmingham, B31 2AP, UK.
authors.forename: M C
authors.initials: MC
authors.lastname: Parry
authors.affiliation: The Royal Orthopaedic Hospital, Bristol Road South, Birmingham, B31 2AP, UK.
authors.forename: L
authors.initials: L
authors.lastname: Jeys
authors.affiliation: The Royal Orthopaedic Hospital, Bristol Road South, Birmingham, B31 2AP, UK.
authors.forename: A
authors.initials: A
authors.lastname: Abudu
authors.affiliation: The Royal Orthopaedic Hospital, Bristol Road South, Birmingham, B31 2AP, UK.
authors.forename: R M
authors.initials: RM
authors.lastname: Tillman
authors.affiliation: The Royal Orthopaedic Hospital, Bristol Road South, Birmingham, B31 2AP, UK.
authors.forename: S R
authors.initials: SR
authors.lastname: Carter
authors.affiliation: The Royal Orthopaedic Hospital, Bristol Road South, Birmingham, B31 2AP, UK.
authors.forename: R J
authors.initials: RJ
authors.lastname: Grimer
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D001852:Bone Lengthening / Q000295:instrumentation* / Q000379:methods; D001859:Bone Neoplasms / Q000473:pathology / Q000601:surgery*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D057068:Periprosthetic Fractures / Q000209:etiology; D019736:Prostheses and Implants / Q000009:adverse effects; D011474:Prosthesis Design; D011475:Prosthesis Failure; D019919:Prosthesis Implantation / Q000009:adverse effects* / Q000379:methods; D016459:Prosthesis-Related Infections / Q000209:etiology; D012086:Reoperation / Q000379:methods; D012509:Sarcoma / Q000473:pathology / Q000601:surgery*; D017678:Sex Distribution
keywords: Extendible prosthesis; Growing prosthesis; Leg length discrepancy; Non-invasive; Sarcoma