Components of bone cement, such as benzoyl peroxide, may rarely cause allergic complications. However, because of the irritant potential of these substances, careful performance, reading and interpretation of the patch tests is required.

A hook-screw has been devised to link the vertebral arch and superior articular process across the defect of a spondylolysis. This method of direct repair overcomes the difficulty of fixation in dysplasia of the arch and avoids crossing the defect with a screw. Compression and a bone graft are applied to the defect to obtain union. This procedure has been used in 33 patients followed for an average period of 3.5 years, and has given satisfactory relief of back pain in 79% and radiographic fusion in 73%, with better results in patients under 20 years of age. Associated degeneration and instability of the disc spaces should be assessed before operation by magnetic resonance imaging so that a standard intervertebral fusion can be used if indicated rather than this direct approach to the lysis. The technical problems encountered and the recent addition of a compression spring to the hook-screw are described. R~sum~. En 1984 l' un de nous (E. M) a publi6 une nouvelle m#thode de fixation de la spondylolyse au moyen d'une vis ?t crochet. Contrairement ?t la m#thode d6crite par Buck, cette vis ne p6nbtre pas la spondylolyse et ne comble pas la lacune, mais elle permet de la remplir avec de l'os spongieux et d' appliquer une bonne compression. On peut 6galement utiliser cette vis dans les dysplasies de l'arc vertebral. Nous pr6sentons les r6sultats des 33 premiers cas, avec un recul moyen de 3. 7 ans. L'Ctge moyen au moment de l'op6ration ~tait de 23 ans. 16 malades avaient moins de 20 ans, 17 6taient plus ag6s. Le r6sultat subjectif a 6tg satisfaisant dans 78. 8% des cas. Le r6sultat radiologique #tait satisfaisant (fusion nette) dans 72.7% des cas. Les r6sultats des plus Reprint requests to: E Hefti jeunes #taient meilleurs que ceux des plus Ctgbs. Chez les patients de plus de 16 ans nous demandons une IRM de la colonne lombaire de routine avant l'op6ration. En cas de spondylolyse douloureuse, si l'on ne trouve pas de d6g6n6rescence discale, la fixation par vis ?t crochet est indiqu6e. Mais si l'on constate une d6shydratation du disque intervert6-bral, une spondylod@se du segment en question est le traitement de choix.

No abstract

This is a follow up study of 61 patients with a 'failed back surgery syndrome' (FBSS). The mean follow up time is 5.4 years after the first operation on the lumbar spine. The diagnosis before the first operation was in 35 patients an entrapment disease (disc herniation or stenosis of the spinal canal), in 25 patients a segmental instability and once a deformity. The reason for the development of a 'failed back surgery syndrome' was in 18% a perioperative complication, in 24% a late unhappy consequence of the operation, in 40% an assessment- or treatment error. In 18% we were not able to figure out any reason for the failure. The correlating diagnosis were: postoperative infections 3, hematoma 1, disc herniation or instability on a second level 12, a second disc herniation at the same level 3, scarring or arachnoiditis 2, instability 18, lateral spinal stenosis 10. We emphasize the importance to distinguish between a clinical relevant and irrelevant diagnosis and to use special tests for this differentiation.