1. In the lumbar spinal canal of the achondroplast there is decreased cross-sectional area. In addition the intervertebral foramina are narrow. These changes result in reduced area for the dural sac and exiting spinal nerves. 2. There is associated thoracolumbar kyphosis and a lumbosacral hyperlordosis. These sagittal plane changes result in increased tension on the dural sac and nerves. 3. With aging there is disc degeneration with disc space narrowing and osteophyte formation. In addition facet hypertrophy with osteophyte formation are common. These degenerative changes further reduce the size of an already compromised spinal canal and intervertebral foramina. The above understanding of the normal spinal and anatomy in the achondroplast, and the added effects of aging allow the surgeon to plan a logical treatment regimen for neurological problems in the achondroplast. Fig. 6. Cross-section at the di sc level of an achondroplast (A) and an age matched non-achondroplast (B). The cross-sectional area of the spinal canal is reduced in the achondroplast, with a reduction in the antero posterior canal (C vs. C 1 ). There is facet hyper trophy extending into the nerve root canal and into the spinal canal lateral recess (B vs. B 1 ). In ad dition the nerve root canal is markedly reduced in-the achondroplast (D vs. D1 ). (Reprinted with permis sion, as of Fig. 5). 225 REFERENCES 1. R. J. Eulert, Scoliosis and kyphosis in dwarfing conditions, Arch. Orthop.Traum. Surg.102:45 (1983).

Inhalt
Genetics, Ultrastructure and Cartilage Histochemistry.- The natural history of achondroplasia.- Birth prevalence and mutation rate of achondroplasia in the Italian Multicentre Monitoring System for Birth Defects.- Premutation in achondroplasia.- Achondroplasia: a clinician's viewpoint.- Radiologic features of achondroplasia.- Osteogenesis imperfecta: a model for the analysis of inborn errors of connective tissue.- Molecular genetic studies in achondroplasia.- Molecular studies in achondroplasia using Col2Al probes.- Histochemical and ultrastructural study of the growth plate in achondroplasia.- Gene expression in the early mouse embryo and cultured cells.- Growth plate cartilage studies in achondroplasia.- Achondroplastic mice: morphological investigations of epiphyseal cartilage and bone.- Collagen distribution of endochondral cartilage obtained in vitro from differentiated cells.- Clinical Findings, Growth Disordres, and Anaesthesiological Problems.- The skull in achondroplasia.- Bone formation in achondroplasia.- Clinical variability in achondroplasia.- GH therapy in two patients with osteochondrpdisplasia.- Achondroplasia: an altered GH control in post-receptorial chondrocyte cell sites?.- Audiologic findings in achondroplasia.- Otologic impairments in achondroplasia: a nosologic assessment.- Neurological considerations in achondroplasia.- Hypochondroplasia: radiological diagnosis and differential diagnosis.- Anaesthesia in achondroplastic dwarves.- Mesomelic dwarfism: Campailla-Martinelli type.- Acromesomelic dwarfism: Maroteaux-Martinelli-Campailla type.- The unreliability of metacarpo-phalangeal-profile (MPP) in the diagnosis of achondroplasia.- Evaluation of hearing in achondroplastic patients.- Spinal Disorders.- Orthopedic aspects of achondroplasia inchildren.- Cervicomedullary cord conpression in young children with achondroplasia: value of comprehensive neurologic and respiratory evaluation.- Surgical management of cervico-medullary compression in achondroplastic patients.- Cervical abnormalities in osteochondrodysplasia.- Anatomy of the lumbar spinal canal.- Anatomy of the lumbar spine in achondroplasia.- Thoracolumbar kyphosis and lumbosacral hyperlordosis in achondroplastic children.- Surgical treatment of kyphosis in achondroplasia.- Extended laminectomy for spinal stenosis in achondroplasia.- The subarachnoid fluid space in achondroplastic spinal stenosis: the surgical implication.- Treatment of kyphosis and lumbar stenosis in achondroplasia.- Relevant principles in the management of spinal disorders in achondroplasia.- Spinal disorders: Kyphosis and lumbar stenosis.- Kyphosis and lumbar stenosis in achondroplasia.- Orthotic correction of sitting abnormality in achondroplastic children.- Techniques and Results in Extensive Limb Lengthening (ELL).- The possibilities offered by our method for lengthening various segments in upper and lower limbs.- Neurological complications arising in bilateral lengthening of the tibiae in an achondroplastic subject.- Techniques and results in extensive limb lengthening.- Lengthening of the lower limbs in achondroplastics.- Lengthening of the lower limbs and correction of lumbar hyperlordosis in achondroplasia.- Biomechanical problems, axial deviation and functional recovery in extensive limb lengthening.- Strategies for limb lengthening in achondroplasia using the Ilizarov method.- Auxological results or surgical correction of hypometries in congenital osteodysplasia.- An analysis of referrals to a regional leg-lengthening service, with special reference to achondroplasia.- Techniques and complications in extensive limb lengthening.- Instability of external fixators: evaluation of the problem and suggestions for a solution.- Characteristics of the Variodyne external fixator.- Social and Psychological Implications.- The experience and expectations of achondroplastic subjects during the period of surgical lengthening.- The psychodynamics of achondroplasia.- Social implications of achondroplasia a public health view.- Social implications of achondroplasia a public health review.- Surgical lengthening of limbs in achondroplastic children: a medical and psycho-social programme to select and treat patients.- Contributors.- Author Index.