A CASE SERIES REVIEW OF THE ORTHOPAEDIC PROBLEMS ASSOCIATED WITH PSEUDOACHONDROPLASIA

Purpose To define the orthopaedic problems associated with pseudoachondroplasia (PSACH) and their functional impact. Methods We reviewed the medical records of 12 consecutive patients presenting to our unit. Radiographic analysis of deformity included assessment of mechanical axis and dysplasia at hip, knee and ankle measured by acetabular index (AI), Reimer9s migration percentage (MP), neck-shaft angle, distal lateral femoral (aDFLA) and proximal (mMPTA) and distal tibial angles. The paediatric/adolescent PODCI questionnaires and the SF36 were used to assess quality of life issues. Results 12 patients (9 female) were reviewed at median age 18yrs (range 12-43yrs). Most symptoms related to walking tolerance, joint discomfort and deformity: 9 patients had genu varum, 7 tibial torsion, 2 patella instability and 3 significant low back pain. All patients had hip dysplasia. 10 had medial displacement of the mechanical axis, with a mean mDFLA 105 deg (88 -128) and mMPTA 75deg (51-90). 2 patients have been treated only with growth hormone; 10 patients have undergone a total of 9 distal femoral, 19 proximal tibial and 2 supramalleolar osteotomies. 6 procedures were performed using an external fixator. 7 limb segments have been treated by guided growth and in all these cases alignment has improved. One patient has had bilateral hip arthroplasties (age 29), a second patient has had bilateral patellectomies. These 10 patients have undergone a mean 3.8 operative procedures on a mean 2.4 occasions. Patients scored less well than their peer groups in all domains of the PODCI assessment. All have maintained some independent mobility. Conclusions PSACH is a severe skeletal dysplasia with deformity at all levels of the lower limb affecting patient satisfaction and quality of life. Knee deformities are those which most frequently require surgical intervention. Significance The genetic defect in PSACH differs from that in achondroplasia, joint degeneration is more common and maintenance of limb alignment is essential.