Introduction: Operations inside the spinal canal are afflicted with a certain number of iatrogenic dural lesions. Incidence figures in the literature vary from 1 to 17% and are mainly based on retrospective studies. The Swedish Spine Register, SweSpine, provides a good possibility to study the incidence in a prospective patient material.

Patients and Methods: During 5 years more than 9 000 patients had surgical treatment for lumbar disc herniation or lumbar spinal stenosis and were registered according to the protocol of the Swedish Spine Register. One year follow-up data were present for 74 % of the patients. Pre- and postoperative data are entirely based on questionnaires answered by the patient whereas surgical data are completed by the surgeon. Complication and re-operation registration is included.

Mean patient age for LDH was 45 (12–88) years, for spinal stenosis 68 (27–93) years and 56% of the disc herniation patients and 43% of the spinal stenosis patients were males. Most common level for LDH operation was L5/S1 followed by L4/L5 and for spinal stenosis L4/L5 followed by L3/L4.

The one-year result was studied.

Results: The incidence of dural lesion in lumbar disc herniation surgery was 2.7% and in spinal stenosis decompression 7.3%. The risk for dural lesion was more than doubled in patients with previous surgery which, thus, was a significant but also the only risk factor. At one year after surgery the result was similar for patients with and without dural lesion when VAS pain, ODI, SF-36 and patient graded global assessment were studied. Correlation between previous surgery and inferior outcome was seen but was not affected by the dural lesion as such. Three and 5% respectively in the groups were subjected to repeat surgery before discharge from the hospital.

The lost-to follow-up group (26%) had similar pre-operative demographics and the same incidence of dural lesion as those followed-up.

Conclusion: In a large prospectively studied material, the incidence of dural lesion in lumbar disc herniation surgery was 2.7% and in decompressive spinal stenosis surgery 7.3%. Previous surgery was a significant risk factor for dural lesion. The dural lesion as such did not negatively influence the one-year outcome.

Lumbar spine surgery has been registered on a national basis in Sweden since 1993 but the register became widespread after 1998 when the protocol was made patient-based and a support function for participating units was created. The surgeon completes data on diagnosis, type of operation, implant, hospitalisation time and complications. All pre- and postoperative data are completed by the patients, including pain on the VAS scale, pain drawing, and the SF-36 and EuroQol questionnaires. Data are presented yearly in an aggregated form while individual departmental data are reported to the individual departments. A participation rate exceeding 85% of lumbar spine surgery in Sweden was calculated for 2002 and the one-year follow-up rate from the previous year was almost 85%. The national registration provides a basis for evidence based lumbar spine surgery, documenting indications for surgery, variation over time and region, complication reporting as well as patient reported outcomes. The mean reduction of VAS pain for the individual diagnoses (disc herniation, lateral and central spinal stenosis, spondylolisthesis and disc degenerative pain) demonstrates the outcomes of surgical treatment for these diagnoses to be favourable. Current projects are expansion of follow-up to 5 and 10 years postoperatively, the creation of a web based protocol version and the development of a cervical spine register.

Aim of many surgical operations on the spine is very often to achieve a solid fusion between two or more vertebrae (arthrodesis). Describing lumbar spine mobility radiographically has been determined to be very imprecise with measurement errors of three to six mm in the sagittal plane. Using roentgen stereophotogrammetric analysis (RSA) it is possible to perform clinical kinematic lumbar studies with high accuracy. Many experimental studies have presented basic data on the stabilising implant effect in human cadaver lumbar spines, but no study compared the in vivo stabilising effect in different types of implant.

The RSA was performed in a radiographic set-up with two 40° angulated roentgen tubes with simultaneous exposures. A combined reference plate and calibration device with 0.8 mm tantalum balls at known positions was situated between the patient and the uniplanar film cassette, enabling simultaneous calibration and patient examination. At each RSA the patients were examined in supine and erect positions without corset. The translatory movements, induced by the change in position, of the 0.8 mm tantalum balls implanted into the fused vertebrae were calculated by computed data processing. These translations visualised the movements of the most proximal vertebra of the fusion in relation to the most distal.

The present study has demonstrated the in vivo stability of lumbar fusion augmented with transpedicular screws to be adequate. Sagittal translation seems to be easier to elicit than movements along the other three-dimensional axes. A widely decompressed and destabilised vertebra without screw fixation increases the risk for persisting intervertebral translations. The RSA technique described seems to be a good way for comparing the in vivo behaviour of different implant systems