ABSTRACT
As an effective implant for bone fracture, bone screws are widely used in clinic. Based on the clinical application of bone screws, this study summarized different kinds of bone screws according to their structures and materials, analyzed 3 kinds of common screw failure (loosening, breaking, corrosion) and the influencing factors. The common testing methods of screws were summarized, especially the key points and difficulties during the testing process for bone screws were analyzed, which was important for improving the design of product, selection of materials and development of in vitro testing technology. The development trend for testing method of bone screws was prospected as well.
ABSTRACT
STUDY DESIGN: It is a multicenter, controlled case study review of a big scale of pedicle-screw procedures from January 2000 to June 2010. The outcomes were compared to those with no implant failure. PURPOSE: The purpose of this study was to review retrospectively the outcome of 100 patients with implant failure in comparison to 100 control-patients, and to study the causes of failure and its prevention. OVERVIEW OF LITERATURE: Transpedicular fixation is associated with risks of hardware failure, such as screw/rod breakage and/or loosening at the screw-rod interface and difficulties in the system assembly, which remain a significant clinical problem. Removal or revision of the spinal hardware is often required. METHODS: Two hundred patients (88 women, 112 men) were divided into 2 major groups, with 100 patients in group I (implant failure group G1) and 100 patients in group II (successful fusion, control group G2). We subdivided the study groups into two subgroups: subgroup a (single-level instrumented group) and subgroup b (multilevel instrumented group). The implant status was assessed based on intraoperative and follow-up radiographs. RESULTS: Implant failure in general was present in 36% in G1a, and in 64% in G1b, and types of implant failure included screw fracture (34%), rod fracture (24%), rod loosening (22%), screw loosening (16%), and failure of both rod and screw (4%). Most of the failures (90%) occurred within 6 months after surgery, with no reported cases 1 year postoperatively. CONCLUSIONS: We tried to address the problem and study the causes of failure, and proposed solutions for its prevention.
Subject(s)
Female , Humans , Follow-Up Studies , Retrospective StudiesABSTRACT
STUDY DESIGN: This is a retrospective study. OBJECTIVES: To identify complications of long segment fusion with pedicular screw fixation of lumbosacral spine and analyze causative factors of complications. SUMMARY OF LITERATURE REVIEW: An unexpected high rate of complication has been observed in pedicle screw fixations used in long segment fusion for degenerative lumbar diseases. Adjacent problem, fixation problem due to osteoporosis, insufficient bone stock may cause implant failure and pseudarthrosis. MATERIALS AND METHODS: From January 1991 to March 1998, 62 patients underwent long segment fusion more than 3 segments for degenerative lumbar diseases, such as degenerative spinal stenosis, associated spondylolisthesis, spinal deformity(kyphoscoliosis), etc. 50 of them followed for more than one year after operation, average follow up period was 21.9 months(range: 12 to 58 months). 17 of them were male and 33 were female and average age was 59.76 years(range : 50 to 76 years). In all cases, pedicle screw fixation was performed with or without additional anterior/posterior lumbar interbody fusion. The number of fused segment was 25 three levels, 14 four levels, 6 five levels, 5 more than six levels. RESULTS: Problem in implant was noted in 19 patients, of which 16(33 screws) showed screw loosening and 3(4 screws) showed screw breakage. 25 of 33 loosened screws were in most distal segment and 21 of them were sacral screws. All the screw breakages developed in sacrum. The problem of screw was associated with the number of fused segment(p=0.009) and sagittal imbalance(p=0.043). Pseudarthrosis rate was 20%(10 patients) and was associated with screw failure(p=0.030). On clinical results, 66% of good to excellent results were obtained, and revision rate of complicated cases was 24%. CONCLUSIONS: In long segment fusion of degenerative lumbar spine, we need to restore more adequate sagittal balance, and need additional sacral fixation and anterior fusion to avoid implant failure and pseudarthrosis.