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Results for “FRACTURE FIXATION”

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PubMed1985

Fracture fixation by using vibration absorbers.

During recent years, increasing attention has been focused on the importance of cyclic stresses or bone microstructure and bone/implant interaction. Use of rigid fixation often leads to loosening and reduction of the bone cortex strength under the rigid plate. This presentation discusses a new approach to the design of shock-absorbing bone fixation devices along with the supporting clinical experience. Even though this discussion concerns only preliminary results, it should stimulate orthopaedic researchers to think about alternative approaches for developing internal fixation devices.

Bone Screws↗
PubMed1996

Augmentation of femoral neck fracture fixation with an injectable calcium-phosphate bone mineral cement.

The first goal of this study was to determine if augmentation with an injectable, in situ setting, calcium-phosphate cement that is capable of being remodeled and was designed to mimic bone mineral significantly improved the strength and stiffness of fixation in a cadaveric femoral neck fracture model. The second goal was to determine if greater increases in fixation strength were achieved as the bone density of the specimen decreased. Sixteen pairs of fresh cadaveric human femora with a mean age of 70.9 years (SD = 17.2 years) were utilized. The bone density of the femoral neck was measured with dual-energy x-ray absorptiometry. The femoral head was impacted vertically with the femoral shaft fixed in 12 degrees of adduction using a materials testing machine to create a fully displaced fracture. Following fracture, 30% inferior comminution was created in each specimen. One randomly chosen femur from each pair underwent anatomic reduction and fixation with three cannulated cancellous bone screws, 7 mm in diameter, in an inverted triangle configuration. The contralateral femur underwent the same fixation augmented with calcium-phosphate cement. Specimens were preconditioned followed by 1.000 cycles to one body weight (611.6 N) at 0.5 Hz to simulate single-limb stance loading. The stiffness in the first cycle was observed to be significantly greater in cement-augmented specimens compared with unaugmented controls (p < 0.05). After cycling, each specimen was loaded at 10 mm/min until complete displacement of the fracture surface and failure of fixation occurred. Specimens augmented with bone mineral cement failed at a mean of 4,573 N (SD = 1,243 N); this was significantly greater (p < 0.01) than the mean for controls (3,092 N, SD = 1,258 N). The relative improvement in fixation strength (augmented/control x 100%) was not inversely correlated to femoral neck bone density (p = 0.25, R2 = 0.09), was weakly correlated to the volume of cement injected (p = 0.07, R2 = 0.22), and was inversely related to the fixation failure load of the control specimen (p = 0.001, R2 = 0.54). There was a mean relative improvement in fixation strength of 169.6% (SD = 77.5). These findings suggest that calcium-phosphate cement provides initial beneficial augmentation to fixation of femoral neck fractures.

Adult↗
PubMed1993

A biomechanical study of odontoid fractures and fracture fixation.

The purpose of this study was to measure the stability of the odontoid process after fracture and subsequent screw fixation. To accomplish this, we mechanically reproduced Type II and Type III odontoid fractures on isolated C2 vertebrae by varying the direction of load. These fractures were subsequently stabilized with a single 3.5 mm screw and retested for multidirectional stability and load to failure. Reduced and instrumented specimens were found to have a stiffness equivalent to one half of that of the unfractured odontoid. Load to failure was also slightly less than one half of the original fracture force (average 160 lb). Screw failure was by a cut-out mechanism in all Type III fractures and by bending of the screw in all Type III fractures. Our findings, in conjunction with the existing literature, strongly suggest that Type III fractures result from extension forces, whereas Type II fractures result from lateral or oblique loading forces. Single screw fixation of an odontoid fracture will provide stability equal to approximately one half that of the unfractured bone.

Aged↗
PubMedDate not supplied

Bone fracture fixation.

This article reviews the anatomy, physiology and biomechanics of bone and describes various types of fractures. It discusses the comparative advantages of different imaging techniques for fracture diagnosis and the radiographic characteristics of some common fractures. The article concludes with a description of fixation techniques and the role of imaging after treatment.

Biomechanical Phenomena↗
PubMed2002

Biomechanical evaluation of proximal humeral fracture fixation supplemented with calcium phosphate cement.

BACKGROUND: Proximal humeral fractures are common injuries, and numerous surgical methods have been described for their treatment. The biomechanical characteristics of various internal fixation devices that are used to treat these fractures have not been extensively studied, nor has the potential beneficial effect of calcium phosphate cement supplementation. METHODS: We used a cadaveric three-part proximal humeral osteotomy model to perform a biomechanical evaluation of three types of internal fixation devices: a cloverleaf plate, an angled blade-plate, and Kirschner wires. The effect of supplementing the fixation with SRS (Skeletal Repair System) calcium phosphate cement was evaluated as well. Eighteen pairs of fresh-frozen humeri were obtained, and the bone-mineral density of each specimen was measured. In each pair, one specimen was secured with internal fixation alone and the contralateral specimen was secured with internal fixation combined with calcium phosphate cement. The specimens were tested cyclically in abduction and in external rotation for 250 cycles to evaluate interfragmentary motion. The specimens were then loaded to failure in external rotation to measure torsional load to failure and torsional stiffness. RESULTS: Overall, there were no significant differences between the specimens treated with the blade and cloverleaf plates, whereas the specimens treated with Kirschner wires demonstrated more interfragmentary motion, less stiffness, and lower torque to failure. In general, supplementation with calcium phosphate cement led to significant improvements in the mechanical performance of all three forms of internal fixation as demonstrated by a significant decrease in interfragmentary motion, a significant increase in torque to failure, and a significant increase in torsional stiffness. The addition of calcium phosphate cement increased the stiffness of even the most osteoporotic specimens to levels that were higher than those of the most osteodense specimens that had been treated with internal fixation alone. CONCLUSION: The initial biomechanical properties of internal fixation as measured with use of a proximal humeral osteotomy model and three methods of fixation were significantly improved by the addition of calcium phosphate cement.

Aged↗
PubMedDate not supplied

Randomized prospective study of humeral shaft fracture fixation: intramedullary nails versus plates.

OBJECTIVES: To compare the clinical and radiographic results for locked intramedullary (IM) nails and plates used in the treatment of humeral diaphyseal fractures. DESIGN: Prospective randomization by sealed-envelope technique of eighty-four patients into two study groups: those treated by intramedullary nailing (IMN group; n = 38) and those treated by compression plating (PLT group; n = 46). SETTING: Patients admitted consecutively to a university-affiliated Level I trauma center. PATIENT/PARTICIPANTS: All skeletally mature patients admitted to Harborview Medical Center with acute humeral shaft fractures requiring surgical stabilization. Fractures of the diaphysis were defined as being at least three centimeters distal to the surgical neck and at least five centimeters proximal to the olecranon fossa. INTERVENTION: Treatment with locking antegrade intramedullary humeral nails (Russell-Taylor design [Smith and Nephew Richards]) or with 4.5-millimeter dynamic compression and limited contact dynamic compression plates (AO design [Synthes]). MAIN OUTCOME MEASUREMENTS: Clinical outcome measurements included fracture healing, radial nerve recovery, infection, and elbow and shoulder discomfort. Radiographic measurements included fracture alignment, time to healing, delayed union, and nonunion. RESULTS: Follow-up averaged thirteen months. Forty-two fractures (93 percent) in the PLT group were healed by sixteen weeks versus thirty-three fractures (87 percent) in the IMN group (p = 0.70). Shoulder pain and a decrement in shoulder range of motion (ROM) were significant associations with IMN (p = 0.007 for both variables) but not with PLT. A decrement in elbow ROM was significantly associated with PLT (p = 0.03), especially for fractures of the distal third of the diaphysis, whereas elbow pain was not (p = 0.123). The sum of other complications demonstrated nearly equal prevalence for both treatment groups. CONCLUSIONS: For patients requiring surgical treatment of a humeral shaft fracture, intramedullary nailing and compression plating both provide predictable methods for achieving fracture stabilization and ultimate healing.

Adolescent↗
PubMed1995

Biomechanical study on femoral neck fracture fixation in relation to bone mineral density.

Twenty pairs of fresh-frozen cadaveric femurs were used in the study. The left femurs were used as control for the mechanical testings and bone mineral content scans, the right femurs were divided into two experimental groups, i.e. 'fractured' group and 'healed' group. In the 'fractured' group, twelve right femurs were osteotomized at the plane perpendicular to the femoral neck shaft axis, through the mid-cervical area of the femoral neck. The artificially created fractures were fixed with the AO dynamic hip screw system using a 4-hole plate and a compression screw. In the 'healed' group, the dynamic hip screws were applied to eight intact right femurs to simulate healed fractures. Bone mineral density scans and mechanical testings were performed on all the femurs. Good correlation was observed between bone mineral density and femoral neck strength in the control group. There was a decrease of 43.5% in strength in the 'fractured' group when compared to the control group. However, in the 'healed' group the failure load was found to be 15.2% lower than the control group. The femoral fixation strength in the 'fractured' and 'healed' groups had good correlation with the bone mineral density. RELEVANCE--:Results from this study indicated that bone mineral density is an important predictive factor in fracture fixation failure. Therefore it may be appropriate to consider the bone mineral density of a patient with proximal femoral fracture treated with fixation devices, as a criterion in prescribing a more protective postoperative management, with respect to weight bearing protocol.

Journal Article↗