How is the outcome of the Limb Preservation System™ for reconstruction of hip and knee?

BACKGROUND

Despite tremendous advantages in the development and application of megaprostheses in tumour and revision surgery, complications are still not infrequently observed. Only two studies investigating the outcome of the LPS™ system in the proximal femur and distal femur/proximal tibia have been published thus far. Herein, mid-term implant survival rates one of the largest cohort of patients treated with the LPS™-system are presented aiming tp answer: 1) How is the outcome of the LPS™ system in the proximal femur and distal femur/proximal tibia? 2) Which factors are associated with altered implant survival? 3) What is the cumulative risk of complications according to Henderson?

HYPOTHESIS: The LPS™-system is associated with high complication rates that depend on implant site, with infections being most common.

PATIENTS AND

METHODS

Fifty-seven patients who received the LPS™-system at the proximal femur (n=31), distal femur (n=21) and proximal tibia (n=5) between 2004 and 2010 for oncological (n=40) or non-oncological (n=17) causes, were retrospectively included. Median follow-up was 5.0 years (range, 0-12.4 years). Complications were classified according to Henderson into instability/soft tissue failure (type 1), aseptic loosening (type 2), structural failure (type 3), periprosthetic infection (type 4), tumour progression (type 5). Competing-risk-analyses were applied to estimate implant survival with death as the competing event.

RESULTS

Twenty-six patients (45.6%) developed a complication, of whom 9 (29.0%) had a proximal femoral and 17 (65.4%) a distal femoral/proximal tibial implant. Type 4 complications were most common (n=11), followed by type 3 (n=6, including 2 yoke-fractures), type 1 and 2 (n=4 each), and type 5 (n=1). The only factor associated with the development of complications in the multivariate model was a distal femoral/proximal tibial implant (hazard-ratio: 7.418, 95% confidence-interval: 2.193-26.096, p=0.001), irrespective of reason for reconstruction and use of muscular flaps. The cumulative-incidence of failure including all complications was 34.3%, 40.7% and 67.1% at 3, 5 and 10 years, respectively.

DISCUSSION: The LPS™-system may be used for proximal femoral reconstructions both in the oncological and non-oncological setting. Rates of complications are higher in our cohort than reported in literature for other, comparable, megaprosthesis systems. Especially in the distal femur/proximal tibia, complication rates were high, partially attributable to the former implant design leading to fractures of the yoke-mechanism. As the implant has been remodelled after these issues became evident, there is no objection to use this megaprosthesis system today.

LEVEL OF EVIDENCE: IV, Observational Study.