Bone Abstracts

Lack of extension of the knee and fixed flexion of the knee may occur in patients with arthrogryposis, rheumatoid arthritis, achondroplasia, osteogenesis imperfecta, cerebral palsy and other conditions. They develop a crouch gait and this is an energy non-efficient condition that causes a compensatory flexion deformity of the hip and lumbar lordosis. Recommended treatments have included bracing, physical therapy, posterior release, distal femoral osteotomy or progressive distraction with external fixation; but these treatments often fails. We studied 11 patients (12 knees) with: arthrogryposis (7), achondroplasia (1), osteogenesis imperfecta (1), postaxial hypoplasia and short femur (1), rheumatoid arthritis (2) and 1 knee with cerebral palsy and hemiplegic pattern. The average age was 6 years (3–13) and the average lack of extension was 40° (20°–60°). Clinical assessment included measurement of knee range motion, gait evaluation, and screening for concomitant deformities. We found three patterns: Type 1: fixed flexion with limitation of flexion and extension; Type 2: lack of extension but normal flexion; and Type 3, pro-curvatum deformity of the distal femur with lack of extension. One patient had previous treatment with staples that failed because of forward migration and five patients had been treated previously with custom plates (without hinges), in these cases we observed that the correction stops when the screws impinge the plate and lock. These six patients where treated changing the staple or the plate to a Hinge Plate. 82% of the knees had a full correction in 14 months, the rest are progressing. We do not find loosening of the screws or migration. We observed in some cases that after the screws impinged the plate the hinge started to move. We observed that guided growth is effective with the Hinge Plates.

Declaration of interest: M Galban is unpaid consultant for Pega Medical, Inc.