Growing Without Pain: The Noninvasive Expandable Prosthesis is Boon for Children with Bone Cancer, as well as Their Surgeons!

Background: Orthopedic oncology has evolved over the past few decades to favor limb salvage over amputations. The noninvasive expandable prosthesis can be lengthened with an externally applied magnetic field eliminating the pain, stiffness, as well as the risk of infection. We present the largest series in Indian experience with this implant over the last 8 years while analyzing its benefit to the surgeons and the patients, but are we able to justify the cost effectiveness?

Materials and methods: Eighteen implants were used in 16 patients with nonmetastatic primary bone sarcoma from May 2006 to June 2015. All implants were manufactured by Stanmore implants worldwide based in London, UK. Lengthening was done in the outpatient department during the followup visits using an external electromagnetic coil. The function was assessed using the musculoskeletal tumor society (MSTS) score.

Results: The patients had a mean age of 10.25 years at the time of surgery. The mean followup was 49.56 months. Twelve patients are alive at a followup after surgery. The prostheses were lengthened by a mean of 31.64 mm and average lengthening per session was 4.18 mm. The mean MSTS score was 28.83. Two revisions for jammed mechanism and two patients had a successful two-stage revision for delayed infection.

Conclusion: The noninvasive expandable prosthesis is an ideal implant for children undergoing limb salvage surgery for bone sarcoma who are expected to have more than 3 cm of limb length discrepancy at maturity. The initial high cost compared to a minimally invasive expandable implant can be recovered as there is no additional cost of lengthening. The small amounts of lengthening at more frequent intervals is more physiological as compared with the minimally invasive type where more lengthening is done to minimize the number of procedures. While the functional and oncological outcomes are comparable, this implant allows limb lengths to be maintained without pain, functional compromise or risk of infection.