Journal Article

Which Radiographic Parameters Are Linked to Failure of a Dynamic Spinal Implant?

Rohlmann, Antonius, Groß, Christian, Hoff, Eike, Putzier, Michael, Strube, Patrick

2012

Overview

Background Knowledge about factors leading to failure of posterior dynamic stabilization implants is essential to design future implants and establish surgical indications. Therefore, we analyzed an implant for single-level or hybrid configuration (adjacent to spondylodesis), which was recalled due to high failure rates. Questions/purposes We asked: (1) Were postoperative radiographic changes linked to implant failure? (2) Were radiographic parameters different between the two configurations? And (3) was implant failure related to inferior clinical scores? Methods The implant was used in 18 patients with lumbar single-level spinal stenosis or with (recurrent) disc herniation and concurrent degenerative disc disease and in 22 patients with an initially degenerated segment adjacent and superior to a fusion site. We prospectively obtained preoperative and postoperative (immediate, 6-, 12- and 24-month) clinical and radiographic evaluations; 37 of the 40 patients completed the 24-month followup. Using plain and extension-flexion radiographs, we compared implant failure rates and their association with postoperative implant translation, anterior and posterior disc height, and ROM for each configuration and between configurations. We assessed associations between clinical scores (VAS pain scores for back and leg, Oswestry Disability Index) and implant failure. Results Implant failure occurred in 10 of the 37 implants and corresponded to greater posterior disc height (single-level only) and implant translation. Adjacent-segment ROM increases and posterior disc height decreases over time were greater with the hybrid configuration. Implant failure rate related to higher Oswestry Disability Index (single-level only) and higher back pain scores. Conclusions Implant translation is associated with failure likely due to insufficient resistance to shear forces. Load transfer may cause progressive degeneration in the dynamic and adjacent segments, especially in the hybrid configuration. Level of Evidence Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

• Publisher: Springer-Verlag,Lippincott Williams & Wilkins Ovid Technologies
• Subject: Adult / Analysis of Variance / Biomechanical Phenomena / Conservative Orthopedics / Device Removal / Disability Evaluation / Equipment Failure Analysis / Female / Germany / Humans / Intervertebral Disc Degeneration - diagnostic imaging / Intervertebral Disc Degeneration - physiopathology / Intervertebral Disc Degeneration - surgery / Intervertebral Disc Displacement - diagnostic imaging / Intervertebral Disc Displacement - physiopathology / Intervertebral Disc Displacement - surgery / Lumbar Vertebrae - diagnostic imaging / Lumbar Vertebrae - physiopathology / Lumbar Vertebrae - surgery / Male / Medical Device Recalls / Medicine / Medicine & Public Health / Middle Aged / Orthopedics / Prospective Studies / Prosthesis Design / Prosthesis Failure / Radiography / Range of Motion, Articular / Reoperation / Severity of Illness Index / Spinal Fusion - adverse effects / Spinal Fusion - instrumentation / Spinal Stenosis - diagnostic imaging / Spinal Stenosis - physiopathology / Spinal Stenosis - surgery / Sports Medicine / Stress, Mechanical / Surgery / Surgical Orthopedics / Symposium: Retrieval Studies / Time Factors / Treatment Failure