BKW Ng, VWY Hung, JCY Cheng, TP Lam

Abstract

Achondroplasia and hypochondroplasia limb lengthening has become better accepted over last thirty years. We studied our experience on all limb lengthening for short stature over the last ten years. We reviewed patient records, X-rays and Dual Energy X-ray Absorptiometry (DEXA) scans to evaluate the changes in body proportion after limb lengthening and the complications. Fourteen patients with 14 tibial, five femoral and two humeral lengthening procedures were included in this study. Average age at first lengthening procedure was 12.2 (9.6-14.4) years. The average height gained from tibial lengthening alone was 10.47 (2.8-16.3) cm. The average height gained from tibial and femoral lengthening was 19.4 (14.7-25.3) cm. The average humeral length gained was 11 (10.5-11.5) cm. All humeral and femoral lengthenings were performed with the Orthofix uniplanar fixator. In femoral lengthening, mild varus deformity occurred in all patients. Mild pin deformity occurred in all patients. Revisions were not required. More rigid pins are required for femoral lengthening. Tibial lengthenings were accomplished with three different types of fixators. Most complications were encountered in tibial lengthenings. Premature fusion occurred in three patients. One procurvatum and five valgus deformity occurred. Revision to multiplanar construct eliminated deformity. Body proportion has improved between upper and lower segments. Sitting to Standing height ratio decreased from 0.64 (0.59-0.74) to 0.58 (0.54-0.61). Armspan to Standing height ratio worsened from 0.92 before lengthening to 0.84 at follow up and did not have any significant functional effect. The ratios for an achondroplasia patient is 0.72 and 0.84 respectively. Callotasis BMD rises to 40% of original bone indicates premature fusion.