Introduction:. Non-invasive extendible endoprostheses (NIEE) were primarily developed for salvage after musculo-skeletal tumour surgery in the immature skeleton. However, they may also have a unique application to manage complex limb reconstruction in revision surgery to address limb-length inequality in the mature skeleton. The aim of this study is to present the minimum 2 –year results of using non-invasive extendible endoprostheses for complex lower limb reconstruction. Methods:. Between 2004 and 2013, 21 patients were treated with 23 NIEE. The indication for surgery was salvage of infected prosthesis following primary tumor resection in 6 cases, aseptic prosthesis failure after primary tumour resection in 5 cases, aseptic non-tumor prosthesis failure in 1 case, infected non-tumor prosthesis in 8 cases and symptomatic non-union of graft reconstruction in 3 cases. There were 14 male and 7 female patients with a mean age of 49.8 years (range 19–81). Results:. The mean length gained was 41.5 mm (range 0 to 90) requiring a mean of 7 (0–25) lengthening episodes performed in the outpatient department. 4 cases required revision surgery for persistent infection. These had multiple previous surgeries and inadequate soft tissue coverage. There were also 2 early dislocations in one patient treated successfully with lengthening and 1 failure to achieve desired length. The Mean Musculoskeletal Tumour Society rating score was 19. Conclusion:. The use of NIEE is associated with good functional outcome and offers yet another way of limb salvage. A modest complication rate is noted in this series, which reflects the complexity of these cases

Introduction. Following bone tumour resection, lower limb reconstruction results in leg-length discrepancy in skeletally immature patients. Previously, minimally invasive endoprostheses have been associated with a high risk of complications including joint stiffness, nerve injury, aseptic loosening and infection. The purpose of this study was to examine the outcome of the Stanmore non-invasive extendible endoprostheses used in our institution between 2002 and 2009 and compare them with implants used in the past. Methods. Fifty-five children with a mean age of 11.4 years (5 to 16) underwent limb reconstruction with thirty-three distal femoral, two total femoral, eight proximal femoral and twelve proximal tibial implants. Forty-six endoprostheses were lengthened in clinic without anaesthesia using the principle of electromagnetic induction. Patients were assessed using the Musculoskeletal Tumour Society Score (MSTS) and the Toronto Extremity Salvage Score (TESS). Results. Ten children (18.2%) died of disseminated disease. One child underwent amputation for infected prosthesis. Forty-four patients were reviewed after a mean follow-up of 41 months (16 to 98). The mean MSTS score was 80.7% (26.7-100) and the TESS score was 92.3% (55.2-99). There was no local tumour recurrence. Complications developed in sixteen patients (29.1%). Seven patients (12.7%) underwent ten revision procedures. The mean length gained per patient was 38.6mm (3.5 to 161.5) requiring a mean of 11.3 (1-40) extensions. Ten component exchanges were performed in nine patients (16.4%) after attaining the maximum lengthening capacity of the implant. Eleven patients (20%) were skeletally mature at follow-up, of which ten had equal leg-lengths and nine had full range of hip and knee movement. Overall our outcomes compared favourably with minimal endoprostheses and other non-invasive designs. Discussion. This is the largest reported series of non-invasive extendible endoprostheses, demonstrating good functional outcome with prevention of limb-length discrepancy at skeletal maturity

We have compared the cost:benefit ratio of the new type of non invasive extendable prostheses with the old type which required lengthening under general anaesthetic with an invasive procedure. Over the past four years we have inserted 27 non invasive endoprostheses (cost £14,000). Two have failed to lengthen due to problems with the inbuilt motor. So far there have been no infections, no loosenings and no patient has required revision. The lengthenings are painless and take half an hour. In the past 25 years we inserted 175 extendable endoprostheses (cost £7,000). All lengthenings were performed under a general anaesthetic. The risk of infection was initially 20% at ten years but had decreased to 8%. Pain and stiffness arose in about 10% requiring physiotherapy or occasionally manipulation under anaesthetic. Assuming the following costs (current NHS cost) are accurate and appropriate, then the non invasive extendable prosthesis becomes cost effective when Cost EPR < Cost old EPR + (Additional risk physio(P) x cost) + (additional cost x number of lengthenings (L)) + (additional cost of revision for infection x risk of infection (R)). 14000 < 7000 + (300 x P) + (1500 x L) + (20000 x R). Assuming a 10% need for physiotherapy, four lengthenings and a 10% risk of infection gives: 14000 < 7000 + (30) +(6000) + (2000) = 15030. Given the high complication rate of the old type of extendable procedure and assuming there are few if any with the non invasive type, then the non-invasive endoprostheses becomes cost effective if more than three lengthenings are required. They are certainly more popular with parents and children alike!

Introduction: Since 1975, 6 types of extendable endo-prostheses have been developed at Biomedical Engineering, UCL, and Stanmore Implants Worldwide in conjunction with the surgeons at this centre. Aims: To establish whether developments in design have had the desired effect of improving both implant survivorship and functional outcome. Methods: This was a retrospective study using case notes, hospital databases and a radiological review, combined with contemporary functional outcome assessments (MSTS, TESS, SF36). Results: 161 consecutive prostheses in 138 paediatric patients, between the years of 1983 – 2005, were implanted for primary bone tumours. Mean age was 10.3 (3 – 18), 81 were males and 57 females. There were 136 primary procedures and 25 revisions. 6 prostheses that used ball bearings to achieve length (designed in 1981) were implanted, 3 (50 %) were revised due to mechanical failure. 19 prostheses that utilised external C-washes (1998) to achieve length were implanted, 6 (32 %) were revised, half of these for mechanical failure. Of the 98 minimally invasive prostheses (1992) that utilized an Allan key and screw-jack mechanism to lengthen, 14 (14 %) were revised, half of these for infection. 17 non-invasive extendable endoprostheses (2001) that are lengthened by electromagnetic coupling have been implanted so far. There has only been 1 (6 %) revision. This was due to full extension being reached. Conclusions: Design improvements in growing endoprostheses since 1983 have led to improved survivorship. Initially this led to a reduction in mechanical failure and latterly to a reduction in infection, as indications for revision. Key Words: Bone tumour, children, endoprosthesis, survivorship