[Ventral intercorporeal traction spondylodesis of the lumbar spine]

Interkorporelle Metallimplantate („Cages“) bei lumbalen Spondylodesen

Over the last 15 years, interbody metal implants have become commonly used worldwide for lumbar interbody fusion. The so called "cages" are made of metal or absorbable materials. By using different surgical techniques, they can be implanted either regularly or via endoscopy. The published results on surgical techniques using cages for the lumbar spine show, in most cases and with or without additional instrumentation, rates of fusion of more than 90%. It seems that the use of osteoinductive substances (especially BMP) leads to even better results. Dorsoventral fusion with internal fixation and bone show the same rate of consolidation, but the advantages of cages are primarily in the maintenance of the distraction and the possibility of a single surgical procedure without additional instrumentation (including endoscopy), and in a lower donor side morbidity.

Experimental anterior spine fusion using bovine bone morphogenetic protein: a study in rabbits

We developed an experimental model to study the merit of bovine bone morphogenic protein (bBMP) injection into the intervertebral disc to induce anterior interbody fusion. A total of 24 rabbits, divided into three groups of 8 animals each, were used. One hundred and fifty microg of partially purified bBMP was employed in the first group and 10 microg bBMP in the second group. In the control group, a sham operation was performed. The animals were followed radiographically at weekly intervals and animals were killed 3, 6, and 12 weeks postoperatively. After sacrifice, a mechanical and histologic evaluation of fusion was performed. Results of radiographic and histologic evaluation showed bone formation, which had resulted in the bridging of adjacent endplates, in the 150-microg group. In the 10-microg group, new bone formation was less extensive. In the control group, intradiscal bone formation was seen in only 1 animal. Range of motion measurements on flexion/extension films showed significantly decreased motion in segments that were fused with 150-microg of BMP. This study demonstrated the utility of an experimental model which allowed investigation of how anterior spine fusion may be further studied. Intradiscal injection of BMP could ultimately play a role in the development of minimally invasive techniques for anterior spinal fusion.

Surgical management of severe spondylolisthesis in children and adolescents. Anterior fusion in situ versus anterior spondylodesis with posterior transpedicular instrumentation and reduction

STUDY DESIGN

A clinical and radiologic retrospective follow-up examination of patients treated surgically for severe juvenile spondylolisthesis.

OBJECTIVE

To compare two different surgical techniques in the management of severe (degree of slip > 30%) juvenile spondylolisthesis (anterior spondylodesis in situ versus combined anterior spondylodesis and posterior transpedicular instrumentation including reduction of the slipping vertebra) to determine if the advantages of the repositioning of the slipping vertebra and a decreased number of pseudarthroses because of the transpedicular instrumentation lead to clinical improvement despite showing better alignment radiologically.

METHODS

This study included 59 children and adolescents with severe spondylolisthesis of L5 who were treated surgically at the authors' orthopedic department between 1980 and 1992. Twenty-nine children received anterior spondylodesis (AS group), and 30 children received, in addition, a posterior reduction and transpedicular instrumentation (posteroanterior spondylodesis, PAS group).

RESULTS

Distribution of age, gender, preoperative clinical symptoms, and preoperative radiologic classification of the spondylolisthesis were comparable in both groups (average degree of slip for the AS group, 66%; that for the PAS group, 75%; angle of slip, 28 degrees and 36 degrees, respectively; sacral inclination, 31 degrees and 25 degrees, respectively). The postoperative follow-up period of the AS group lasted 125 +/- 22 months, considerably longer than that of the PAS group at 67 +/- 20 months. At the time of the follow-up assessment, the PAS group showed a reduced rate of pseudarthrosis (7% versus 24%), a reduced degree of slip (36% versus 59%), and a reduced lumbosacral kyphosis (14 degrees versus 26 degrees) in comparison with the AS group. The transpedicular instrumentation decreased the fusion time of osseous consolidation of the spondylodesis markedly (7 months versus 17 months, on average). Adverse effects and rate of complications were equal in both groups. The results failed to show any differences in favor of either of the two surgical techniques used either subjectively to the patient or objectively by means of clinical examination.

CONCLUSION

Anterior spondylodesis including posterior instrumentation and reduction was superior to the simple anterior fusion in situ for normalization of the lumbosacral profile and osseous consolidation of the spondylodesis. This result was not reflected in the clinical evaluation.