Reoperation for Spinal Restenosis in Achondroplasia *Michael C. Ain, Ilhan Elmaci, †Orest Hurko, Richard E. Clatterbuck, ‡Roland R. Lee, and Daniele Rigamonti Departments of Neurosurgery; †Neurology, Medicine, Pediatrics, and the Center for Medical Genetics; *Orthopedic Surgery; and ‡Radiology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, U.S.A. Summary: The characteristics of spinal restenosis in achondroplasia and its treatment are evaluated in this study. Radiologic and surgical findings were correlated to establish the causes of achondroplastic spinal restenosis and the benefits of its therapy. Eight patients (five men, three women) with spinal restenotic complications of achondroplasia were studied. The most common neurological sign of recurrent stenosis was impaired motor function. The mean interval between the most recent surgeries was 8.2 years (9.5 years for surgeries at the same levels). The most common causes of recurrent stenosis were facet hypertrophy and disk disease. The complications were a dural tear and cerebellar hemorrhage in one patient and transient neurological deterioration in another. One patient died after operation. Restenosis can occur many years after original decom- pression in the achondroplastic spine, and repeated operation can successfully lessen pain and neurological symptoms in most patients. Key Words: Achondroplasia—Laminec- tomy—Spinal stenosis—Reoperation and achondroplasia. Achondroplasia is one of the most common skeletal dysplasias, an autosomal-dominant condition resulting from a characteristic mutation in the gene encoding fibro- blast growth factor receptor 3 (21). The incidence of achondroplasia is 17 to 29 per million (10,16), and at least 80% of cases are new mutations (7). Dwarfism, macro- cephaly, rhizomelic shortening of the extremities, and other skeletal abnormalities (7,10,17,20,26) characterize achondroplasia. Neurological problems such as hydro- cephalus, upper cervical cord compression, and spinal ste- nosis are frequent in achondroplasia (1,3–6,10). Intellec- tual function is normal (7). It is well known that persons with achondroplasia have a spinal canal narrowed by shortened pedicles and de- creased interpedicular distance (5,11,12). Many studies have shown a reduction in size of the entire spinal canal, caudal tapering, and stenosis of the foramina (5,22,27,29). Spinal stenosis usually is not a problem before late ado- lescence (7,9). As the patient with achondroplasia ages, the stenosis is aggravated by hypertrophy of the ligamen- tum flavum and degenerative spondylosis (2,18). A wide spectrum of neurological signs and symptoms ranges from low back pain and neurogenic claudication to complete paraplegia or quadriplegia (10,14,23). Approximately 20% to 30% of persons with achondroplasia have symp- toms of spinal stenosis and nearly 10% require therapy (7). Spinal decompression is widely accepted as the treat- ment of choice. We report a series of eight patients with achondroplasia who underwent repeated operation and repeated achon- droplastic spinal decompression at a level that previously was decompressed. PATIENTS AND METHODS From 1994 to 1996, eight patients with achondroplasia who had clinically significant signs of restenosis at levels previously decompressed were operated on by the senior neurosurgeon (author D.R.). These eight patients account for 4.3% of all patients with achondroplasia operated on for spinal stenosis at the Johns Hopkins Hospital during the last 20 years (patients who had repeated operations at Received April 21, 1999; accepted September 27, 1999. Address correspondence and reprint requests to Dr. D. Rigamonti, 600 N. Wolfe Street, Meyer 5-181, The Johns Hopkins Hospital, Department of Neurological Surgery, Baltimore, MD 21287-7581, U.S.A. Journal of Spinal Disorders Vol. 13, No. 2, pp. 168–173 © 2000 Lippincott Williams & Wilkins, Inc., Philadelphia 168