Aims

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.

The August 2013 Children’s orthopaedics Roundup³⁶⁰ looks at: a multilevel approach to equinus gait; whether screening leads to needless intervention; salvage of subcapital slipped epiphysis; growing prostheses for children’s oncology; flexible nailing revisited; ultrasound and the pink pulseless hand; and slipping forearm fractures.

Introduction. Historically, amputation or rotationplasty were the treatment of choice in skeletally immature patients. The introduction of expandable endoprostheses in the late 1980s offered the advantages of limb-salvage and limb length equality at skeletal maturity and a promising alternative with improved cosmetic results and immediate weight bearing. Objective. to describe the Rizzoli experience in reconstruction with three different types of expandable prostheses in growing children with malignant bone tumors of the femur, assess the outcome of limb salvage in these patients, analyze survival and complications related to these prostheses used over time. Materials and Methods. Between 1996 and 2010, 39 expandable implants were used in 32 children (16 boys and 16 girls; mean age, 9 years at initial surgery) with bone sarcomas of the femur treated with limb salvage using expandable prostheses. The most common diagnosis was osteoblastic osteosarcoma; all children were classified as having a stage IIB lesion and had preoperative and postoperative chemotherapy. The minimally invasive Kotz Growing prosthesis was used in 17 cases (10 primary implant and 7 revision after failure of non-invasive Repiphysis®), the non-invasive Repiphysis® in 15 cases and Stanmore® expandable prostheses in 7 cases. The mean follow-up was 48 months. Functional evaluation and survival analysis of the children and implants were performed. Results. The rate of implant-related complications was 51.3%; 9 prostheses (23%) were revised because of aseptic loosening, infection and breakage. The mean total lengthening was 26 mm (4 to 165 mm) achieved by 78 procedures (2.4 procedures/patient). Three of the nine children who reached skeletal maturity had limb length equality and six discrepancy of 15–30 mm. The survival of the children was 94% and 76% at 24 and 72 months. The survival of the primary prostheses was 90% and 70% at 24 and 72 months. Survival was significantly higher only for the Kotz compared to the Repiphysis® prostheses (p= 0.026). The mean MSTS score was excellent (79%) without a significant difference between the type of prostheses (p= 0.934). Conclusions. In the growing children expandable prostheses are viable reconstruction options with good and excellent oncological and functional outcome, and limb-length equality at skeletal maturity. Mechanical failures including aseptic loosening and breakage, dysfunction of the expansion mechanism, contractures especially around the knee, dislocation and infection were the most common; some designs have been associated with an unacceptably high inherent risk of complications. However, the non-invasive systems are associated with high complications and failure rates. Early experience is promising, but further study is warranted to determine long-term structural integrity of these newer designs

Introduction: The non-invasive growing prosthesis continues to be used successfully for the treatment of limb salvage operations in tumour patients. We report our continued experience in 17 skeletally immature patients with osteosarcoma of the distal femur.

Methods: Patients had a mean age of 10.2 years (range 6 to 15) at the time of surgery. The endoprosthesis was lengthened at appropriate intervals in outpatient clinics without anaesthesia using the principle of electromagnetic induction.

Results: The mean follow-up was 28 months (range 2 to 55). The prostheses were lengthened by a mean of 47.4 mm (range 0.5 to 208) and maintained a mean knee flexion of 110 degrees (range 90 to 120 degrees).

Complications developed in seven patients: two implants failed requiring revision, one peri-prosthetic fracture occurred, one developed a flexion deformity of 25 degrees at the knee joint, which was subsequently overcome and three died of disseminated disease.

Discussion: The medium term results from patients treated with this device have continued to show a promising outcome. Four patients successfully completed desired lengthening, six patients are continuing with ongoing lengthening. The implant avoids multiple surgical procedures, general anaesthesia and assists in maintaining leg-length equality.

Introduction and Aims: Limb salvage surgery for the pediatric patient poses unique surgical challenges for the orthopaedic oncologist. In the past, surgeons have advocated amputation or rotationplasty as treatment for the skeletally immature child with a malignant bone tumor that involves a major growth plate and has an expected limb length discrepancy.

Method: The Repiphysis is a non-invasively expandable prosthesis. Applications for the knee joint are approved and other joints are pending. The expansion principle involves energy stored in a spring compressed by a locking system. Lengthenings are achieved via exposure to an electromagnetic field that allows controlled release of the spring and can be done without general anesthesia. Numerous small expansions (5–10mm) keep pace as the child grows. Between 1998–2002, 25 prostheses [knee (19), shoulder (five), hip (one)] were implanted in 21 patients. Most were implanted at the time of tumor resection and nine were revisions from previous reconstruction or fusion.

Results: Ninety lengthenings were performed with all but two on an outpatient basis. An average of 5mm was obtained per lengthening (range 1–35mm). The average follow-up was 25 months (range 12–48 months) and the latest Musculoskeletal Tumor Society functional scores averaged 87%. Eight revisions were required for mechanical problems or stem loosening. There was one amputation caused by post-operative arterial thrombosis.

Conclusion: This unique prosthesis offers many benefits in maintaining limb-length equality in growing patients. We are optimistic that this technology will prove beneficial to patients with malignant bone tumors as well as patients requiring serial limb lengthening or those with spinal deformities.

Growing prostheses have been utilised in the United Kingdom since the late 1970s. Various mechanisms have been tried, but to date all have required some form of surgical intervention. This has led to multiple hospital admissions and a large amount of resources, both in theatre time and rehabilitation. Over the last ten years the Department of Bio-Medical Engineering at University College, London, together with the Royal National Orthopaedic Hospital, Stanmore, have developed a prosthesis which does not require surgical intervention to elongate. The total cost of the development has been something in the order of £350,000.00. The design features are the power worm screw mechanism where one turn equals 1 mm of elongation, but attached to this mechanism is an epicyclic gearbox, which has been reduced in size so that it can fit in to the body of the prosthesis. The speed reduction achieved by the gear box is 13061 to 1. The mechanism is capable of withstanding an axial load of 1,350 newtons. When an external magnetic field is applied an external coil speed of 3,000 revs per minute leads to a lengthening of 0.23 mm per minute. To date the prosthesis has been inserted in three patients ages 11, 12 and 13. All were suffering from osteosarcoma of the distal femur and had previously received neo-adjuvant chemotherapy. Early elongation had been achieved in all patients without any major discomfort and without the need for either analgesia or inpatient admission. There had been no loss of range of movement in the early post-lengthening period.

This new prosthesis represents a significant advance in the management of skeletal sarcomas in children.