Predictability of Magerl & McCormack's Load Sharing Classification on the Metal Failure after Pedicle Screw Fixation in the Thoracolumbar Spine Fracture / 대한척추외과학회지

STUDY DESIGN: A retrograde study of metal failures at thoracolumbar spinal fractures fixed using pedicle screws. OBJECTIVES: The predictability and usefulness of the McCormack's classifications for metal failures was compared with Magerl's classifications. SUMMARY OF LITERATURE REVIEW: The load sharing classification was introduced to predict metal failure after short-segmental pedicle screw fixation by McCormack. However, its reliability is uncertain. MATERIALS AND METHODS: From July 2000 to July 2003, this study examined the plain radiographs and CT images of 31 out of 46 patients who underwent posterior stabilization using pedicle screws for thoracolumbar fractures and could be followed up at least 1 year. Fractures were classified utilizing Denis's, Magerl's, and McCormack's systems. RESULTS: As a result of analysis of relation between metal failure and classification system by Magerl or McCormack, there was no significant difference in its distribution. There was no correlation between the fixation range and metal failures in type C3 fractures, but there was a correlation between short fixation and metal failures in rotational burst fractures in short fixation. CONCLUSIONS: In order to prevent metal failures after fixing thoracolumbar spinal fractures by pedicle screws, the stability should be evaluated using Magerl's classification and McCormack's total score. In addition, in cases of type C3 fractures according to the Magerl's classification, reconstructions should be carried out with a long segment fixation or anterior supporting bone grafts, particularly when McCormack's total score is greater than 7.

Metal Failure in patients with Short-segmental Pedicle Screw Fixation and Fusion for Degenerative Lumbar Disease: Comparison Monoaxial with Polyaxial Screw / 대한척추외과학회지

STUDY DESIGN: Retrospective study OBJECTIVE: To evaluate the factors affecting metal failure and screw loosening of short-segmental (1- or 2-segmental) monoaxial or polyaxial screw fixation for degenerative lumbar disease. SUMMARY OF LITERATURE REVIEW: There was a report on metal failure and screw loosening in short-segmental monoaxial and polyaxial screw fixation in degenerative lumbar disease. MATERIALS AND METHODS: This study examined 227 cases who underwent short-segmental transpedicular screw fixation and vertebral fusion for a degenerative lumbar. RESULTS: Metal failure of transpedicular screws was detected in 6 cases, 3 each in groups A and B. Screw loosening occurred in 16 and 43 cases in group A and B, respectively. Both groups had a similar incidence of spinal stenosis with instability and spondylolisthesis. The failure rate and screw loosening according to the fusion level was also similar. The failure and screw loosening rates was higher in the cases who did not undergo PLIF than in the cases who underwent PLIF but the difference was not statistically significant. CONCLUSION: The metal failure and screw loosening rates after transpedicular screw fixation and spinal fusion procedures for degenerative lumbar diseases using monoaxial screws and polyaxial screws were similar.

Mode of Fixation Failures of Dynamic Hip Screw with TSP in the Treatment of Unstable Proximal Femur Fracture: Biomechanical Analysis and a Report of 3 Cases / 대한정형외과학회잡지

There are few reports of the failure mode of a dynamic hip screw with a trochanteric stabilizing plate (TSP) in the treatment of unstable proximal femur fractures. We present 3 cases of fixation failure of a TSP used to treat unstable intertrochanteric fractures. All cases had the same type of failure mode, which represented a fatigue fracture of the distal screw at the junction of a plate and screw. Non-union occurred in 2 cases, and one case was an incidental finding 4 years after union. Biomechanical analysis and SEM (scanning electron micrograph) examination was also performed. Adding TSP to the plate might increase the level of shear stress and slip motion in the distal screw followed by a fatigue fracture. SEM of the surface of the broken screw revealed a multiple cycle and low stress fatigue fracture. Recommendations are made regarding the implant design and surgical technique.

Metal Failure of Pedicle Screw System / 대한척추외과학회지

STUDY DESIGN: The metal failure of pedicle screw system followed by posterolateral or posterior fusion used in variable cases(spine fracture, degenerative disorder of spine, deformity of spine) was analyzed retrospectively. PURPOSE: The goal of this study was to analyze frequency and clinical consequence of pedicle screw fixation system failure in the treatment of different etiology(spine fracture, degenerative disorder, deformity of spine) and to evaluate affected factors in metal failure. MATERIALS AND METHODS: We performed survivorship analysis on 442 patients treated with pedicle screw system from September 1990 to December 1999. The average follow-up period was 54 months(from 18 months to 129 months). As affected factors, some variables such as etiology, kinds of system and extent of fusion were subjected to analyzed their influence on metal failure. We also performed analysis about relationship between metal failure and clinical results. We defined the metal failure as 1) breakage of screw or rod 2) screw bending above 5 degrees 3) dissociation of rod-screw coupling system and 4) screw pull out from vertebral body or pedicle. RESULTS: We found out 33 cases of metal failure: among 2786 screws, 41 screws had a problem. The metal failure rate was different between each etiology ; 12 cases in fracture(10%), 21 cases in degenerative disorder(6.9%). There was also difference between a kinds of implants; 13 cases in side assembling type(5.4%), 20 cases in back open type(10.5%). However, there were no difference according to extent of fusion; 6 cases in one segment(6.9%), 21 cases in two segments(8.1%), 6 cases in more than three segments(6.3%). Among the overall patients with metal failure (33 cases), only eight patients were complaint significant symptoms. And three of this eight patients were improved after reoperation The mean interval to metal failure was 14.4 months from operation. CONCLUSION: The metal failure was more common in spine fracture(p0.05). And metal failure did not significantly affect the clinical results(p>0.05).

Metal Failure of the Internal Fixation Device for the Treatment of the Femur Fracture / 대한정형외과학회잡지

PURPOSE: Nonunion and metal failure as a complication may occur in femoral fractures, which are treated with plate and screw or intramedullary nail. The authors clinically reviewed metal failure patients from initial operation to rehabilitation program, and analyzed the cause of failure and attempted to establish more rational methods of management and prevention. MATERIALS AND METHODS: Seventeen patients of metal failure, treated at Kyungpook National University Hospital from 1989 to 1998, were included in this study. We studied the relationship between the initial site of fracture, type of fracture, time interval of metal failure, configuration of metal failure, probable cause of metal failure, and secondary reconstructive operation for metal failure. RESULTS: Dynamic compression plate was the most frequently (12cases) used implant. The most common site and type of fracture were proximal 1/3 of femoral shaft (8cases) and transverse fractures (11cases). As the configuration of metal failure, breakage of the plate or nail were more common at proximal or distal 1/3 of the shaft. There was no relationship between the time interval of metal failure and the initial site or type of fracture. The most probable cause of metal failure was improper rehabilitation in 6 cases (75%), other causes were another source of external force, inadequate bone support, improper choice of implant and infection. CONCLUSIONS: To prevent metal failure, we must preserve the periosteum and soft tissue, use bone-grafting at the time of treatment and employ cooperative rehabilitation therapy to implement gradual increasing non-weight bearing joint exercise, partial-and full-weight bearing excercise.