Abstract
Background
Extendable partial femoral replacements (EPFR) permit limb salvage in children with bone tumours in proximity to the physis. Older designs were extended through large incisions or minimally invasive surgery. Modern EPFR are lengthened non-invasively. Lengthening improves functional score (Futani, 2006) but has been associated with complications including infection (Jeys, 2005). This study is the first to look specifically at the relationship between EPFR lengthening and complications.
Method
Retrospective review of 51 paediatric (<16 years) oncology patients undergoing primary (1 °) EPFR (minimally/noninvasive) between 06/1994 and 01/2006. Exclusions: 1 patient with 5cm extension without medical intervention and 5 patients with incomplete data.
Results
There was a negative relationship between age at 1 ° operation and EPFR lengthening (p = 0.03).
Mean lengthening for all (including revision) EPFR was 3cm (range 0–13.05). 28 (64%) patients were lengthened a mean 4.8cm at a mean 7 procedures each. 18 were not lengthened, of which 12 were deceased at last followup and 1 had undergone amputation. Lengthening of secondary prostheses contributed a mean 3.7cm to limb length. 2 tertiary implants were lengthened noninvasively by 1.2cm (3 lengthenings) and 1.275cm (5 lengthenings).
16 of 21 failed 1 ° femoral components had been lengthened. The 21 implants underwent a mean 4.2 lengthenings in comparison to mean 1.3 lengthenings in the 28 that did not fail.
Number of 1 ° prosthetic lengthenings was positively related to risk of component failure (p = 0.035) and total number of complications (p = 0.049). Complication rate was also related to total lengthening of 1 ° prosthesis (in cm) (p = 0.004).
There was a statistically insignificant (p = 0.059) trend towards increased infection rate with higher number of minimally invasive lengthening procedures.
Complications were commoner in those undergoing lengthening (mean 3 vs 1.75 in non-lengthened prostheses). Number of lengthenings correlated with number of complications (p = 0.001).
Total lengthening of distal EPFR correlated with incidence of knee fixed flexion deformity (FFD)(p = 0.034). Median lengthening was 3cm in those with FFD and 0cm in those without (p = 0.019).
Open lengthening procedures caused 6 complications: 2 deep & 3 superficial infections and recurrent subluxation requiring acetabuloplasty in a proximal replacement.
Summary/Conclusions
The inverse relationship between age at 1 ° operation and lengthening is expected if the aim of offsetting limb length discrepancy during growth is being achieved.
Lengthening is associated with increased complications (particularly infection and FFD) and femoral component failure, suggesting that lengthening procedures are implicated in the cause of some complications. 5 infective complications after lengthening were theoretically avoidable if noninvasive growers were used.
