A Case of Pedicle Screw Loosening Treated by Modified Transpedicular Screw Augmentation with Polymethylmethacrylate

We report a case of pedicle screw loosening treated by modified transpedicular screw augmentation technique using polymethylmethacrylate (PMMA), which used the anchoring effect of hardened PMMA. A 56-year-old man who had an L3/4/5 fusion operation 3 years ago complained of continuous low back pain after this operation. The computerized tomography showed a radiolucent halo around the pedicle screw at L5. We augmented the L5 pedicle screw with modified pedicle screw augmentation technique using PMMA and performed an L3/4/5 pedicle screw fixation without hook or operation field extension. This modified technique is a kind of transpedicular stiffness augmentation using PMMA for the dead space around the loosed screw. After filling the dead space with 1-2 cc of PMMA, we inserted a small screw. Once the PMMA hardened, we removed the small screw and inserted a thicker screw along the existing screw threading to improve the pedicle screws' pullout strength. At 10 months' follow-up, x-ray showed strong fusion of L3/4/5. The visual analogue scale (VAS) of his back pain was improved from 9 to 5. This modified transpedicular screw augmentation with PMMA using anchoring effect is a simple and effective surgical technique for pedicle screw loosening. However, clinical analyses of long-term follow-up and biomechanical studies are needed.

Instrument Failure in Anterior Cervical Plate Fixation

OBJECTIVE: Anterior cervical fusion is widely used with many kinds of plate systems. The purpose of this study is to evaluate the rate and influencing factor of instrument failure. METHODS: The authors reviewed 101 consecutive patients who underwent anterior interbody fusion used Caspar, PCB(Cervical Plate Cage System), Orion and Atlantis plate system during the period of January 1991 to December 2000. The cases of trauma were 49, tumor 2 and degenerative disorder 50. The average length of follow up was 12.2 months. RESULTS: There were 10 cases of instrument related complications and 18 cases of non-instrument related complications. Among 10 cases of instrument related complication, eight patients showed screw loosening and two patients showed bone graft displacement. The nine cases of hardware failure occurred within 3 months. The rate of instrument failure was higher in trauma, unlocking plate and multi-level than non-trauma, locking plate and one-level. There were no injuries to tracheoesophageal or neurovascular structures as a results of instrument failure. CONCLUSION: We conclude that anterior cervical plating can be carried out with acceptable complication rate. The incidence of prominent instrument failure that endangers tracheoesophageal structures is minimal.

Instrument-Related Complications Following Lumbar Transpedicular Screw Fixation

OBJECTIVE: Transpedicular screw fixation systems are coming into wide use as an effective adjunct to lumbar spinal fusion procedures. However, there are some problems concerning hardware failure. In this report, we present an analysis of instrument-related complications following lumbar transpedicular screw fixation. METHODS: Lumbar spinal fusion using a transpedicular screw has been performed between 1995 and 2000 in 298 patients. We retrospectively investigated the complications related to screws and/or rods, which have been used in lumbar spinal fusions. RESULTS: The 262 patients(87.9%) who had undergone the surgery were satisfied with the results of their operations. The wound infection rate was 4.0%(n=12). Neural injuries occurred in 4 patients(1.3%); one patient was related to decompressive procedure and the others were related to instrumentation. The unsatisfactory screw placement occurred in 3.8%(60 of 1,582 screws placed). Forty-nine screws(81.7%) were misplaced in lateral direction in a total of 60 unsatisfactorily placed screws. Screw fractures occurred in 5(1.7%) patients, and the overall fracture rate was 0.3%(5 of 1,582 screws placed). Rod fractures occurred in 3(1.0%) patients and the overall fracture rate was 0.5%(3 of 596 rods placed). The breakage was usually apparent in the late stage of the clinical course, as seen on follow-up radiographs. CONCLUSION: We believe that failure of arthrodesis and multilevel fusion are the predisposing factors of instrument failure. The authors conclude that to minimize the complications following transpedicular screw fixation, it would be necessary to make a precise insertion of the transpedicular screw with adequate bone fusion.