Introduction: Non-invasive expandable prostheses for limb salvage tumour surgery was first used in 2002 and has now been implanted in a series of 40 skeletally immature patients.

Method: Our review of these includes 24 distal femoral replacements, 5 proximal femoral replacements, 3 total femoral replacements and 8 proximal tibial replacements. These were used to treat 31 osteosarcomas, 7 Ewing’s sarcomas, 1 chondrosarcoma and 1 aneurysmal bone cyst. Patients had a mean age of 11.7 years (7–16). Follow-up extended to 88 months with a mean of 26.3 months.

Results: There has been 1 failure of the prosthesis gearbox which required revision surgery. 4 of the prostheses reached their maximum length and were successfully re-operated to exchange components of the prosthesis and resume lengthening. 3 patients had disseminated meta-static disease (1 being present before primary surgery) and another developed infection of the prosthesis that required an above-knee amputation. There have been 233 lengthenings overall with 1 patient requiring reversal on one occasion due to intractable pain; this pain rescinded 30 minutes after lengthening was reduced by 10mm. Otherwise lengthening was well tolerated despite the significant growth of the limbs: mean 21.2mm (0.5–84mm). At latest follow-up the mean Musculoskeletal Tumour Society score was 75% (26–93%).

Discussion: The results achieved are equivalent to our series of minimally invasive growers which require repeated surgery. Our non-invasive growing prostheses remain reliable and negate the need for recurrent operations, thus resulting in low infection rates. Our results remain encouraging up to 7 years after first use, maintaining leg-length equality and function.

Four patients who developed malignant synovial tumours are described; one with chondromatosis developed a synovial chondrosarcoma and three with pigmented villonodular synovitis developed malignant change. The relevant literature is discussed.