gms | German Medical Science

Objective: Nowadays many types of spinal lumbar fixation are available; far now the most used method is still the well established pedicle screw technique, whose trajectory is lateral-to-medial. Since April 2014 we have used a new technique with a different trajectory in fifteen consecutive cases of mono or bisegmental degenerative lumbar disease.

Method: From April to October 2014 we performed fifteen consecutive surgeries for mono or bisegmental degenerative lumbar disease using this new screw trajectory; spondylolistesis and ADS (Adult Degenerative Scoliosis) were not considered as candidates due to the higher correction needed. A total amount of 62 screws have been placed. In 4 cases a bone decompression alone was necessary. The other 11 patients underwent an interboby fusion. This new trajectory, the so-called “cortical bone screw”, involves, as starting point, the medial aspect of the pars interarticularis and a caudo-cephalad and medial-to-lateral direction. Given this direction we used screws whose lenght was 30-35 mm and whose diameter was 4,5-5,5 mm (to avoid the breakage of the lateral wall of the vertebra and of the pedicle respectively). In all cases needing a fusion, this was obtained positioning interbody grafts (PEEK implants) via a posterior or transforaminal approach.

Results: Considering only screws placement, the average operative time was 26 minutes/screw and blood loss was lower than 20 cc/screw. Recovery time varied from 2 days to 5 days. No complications occured during the surgery and before discharging the patients. No reintervention was needed for screw misplacement. In all cases clinical scores were found considerely improved 1 month after the surgery(ODI, VAS back and leg, EuroQoL-5D).

Conclusions: Some recent biomechanical studies have found that the pullout strenght of these screws is equivalent to the traditional pedicle screws and even superior in case of osteoporotic vertebras where the cortical bone density remains higher than that in cancellous bone. Moreover, since the more medial insertion point, less muscular retraction is needed. Finally, this new pedicle trajectory seems to have a safer profile reducing the risk of neurovascular injury compared to the traditional pedicle insertion technique. Thus, in our experience, the cortical bone trajectory is a real effective alternative to the traditional pedicle screw for the treatment of short lumbar degenerative disease. Longer follow-up evaluation is needed to confirm these early results.