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PubMed1995

Resorbable device for fracture fixation: in vivo degradation and mechanical behaviour.

The availability of a high molecular weight poly(L-lactide), with supposed good mechanical properties, encouraged us to carry out an in vivo experimental study to evaluate the degradation rate and accompanying loss of strength during interaction with bone. Small cylindrical PLLA rods were manufactured by compression moulding. Thirty-six male New Zealand rabbits (b.w. 3 kg), randomly divided into six groups of six animals each, were submitted to implantation of the rods under general anaesthesia (phi 3 x 7 mm rods in the lateral condylic region of the right femur and phi 3 x 50 mm rods in the intracondylic channel of the left femur). The animals were then sacrificed at the end of each experimental time (4, 8, 12, 24, 52, 64 weeks), hence the femurs were explanted. Histology showed no inflammatory cells with fragmentation or resorption of bone trabeculae. Mechanical studies showed a decrease in mechanical properties and flexional stiffness, and the absence of evident material resorption. Finally, the properties of this newly developed resorbable device, when confirmed, seem to justify future clinical introduction of this synthetic material.

Animals↗
PubMedDate not supplied

Radioanatomical measurements of the medullary cavity of the humerus in Kuwait: ethnic differences and clinical implications for fracture fixation.

OBJECTIVE: To compare the difference in diameter of the medullary cavity of the humerus in Arab and South Asian patients in Kuwait. SUBJECTS AND METHODS: In 46 patients (29 Arab, 17 South Asian) treated at Al-Razi Hospital, Kuwait, for diaphyseal fracture of the humerus, the medullary cavity of the humerus on the radiographs of the uninjured (contralateral side) was examined. Bone density was also measured. Statistical significance was calculated by parametric and nonparametric test using SPSS package. RESULTS: South Asians had a significantly narrower medullary cavity (p < 0.05) and higher cortical indices (p < 0.05) than Arabs, and also a narrower external diameter of the humerus at levels 5 and 6 (p < 0.05). CONCLUSION: In cases of fracture of the humerus, radiographic measurements of the diameter of the medullary cavity of the uninjured side were essential in selecting the appropriate fixation device.

Adult↗
PubMed2004

New implant designs for fracture fixation in osteoporotic bone.

Screws are one of the limiting factors for fixation of implants, particularly in poor bone quality. A class of new implants with an implant-bone-interface optimized regarding load transition by increasing the peripheral area might improve the anchorage of implants in osteoporotic bone. However, the shape of these implants requires new technologies for insertion. The goal of the work presented here was to analyze the relevant parameters regarding implant geometry and to demonstrate the effect of new procedures for their insertion. The investigation was divided into three parts: 1) implant design optimisation, 2) efficiency of cortical bone ablation, and 3) implant insertion technology. Finite element analysis (FEA) was performed to investigate the influence of the number of lobes, the radius of the outer curvature and additional milling to remove any sharp changes of section around the lobe. Opening of the cortical bone with an Er:YAG laser was studied using calf cortex from 2 to 7 mm thickness. The effect of a) pulse energy and pulse duration, b) cortical thickness, c) wet or dry boundary conditions on volume and geometry of ablated bone, time required to penetrate the cortical bone and local bone tissue damage was quantified. Pneumatic and ultrasound based insertion were compared in the third experiment. The cortical bone was prepared in the following ways: a) no opening, b) predrilling of three holes (1 mm diameter each) and c) exact pre-cutting of the whole contour. Increasing the radius of the outer curvature from 2 to 5 mm reduces the peak stresses during loading in all planes in the implant as well as in the adjacent cortical bone by about 30-40%. An increase in the number of lobes from two to three decreases the mean peak stress by about 46% (alpha < 0.001) and the range between the minimal and maximal peak stresses for different loading directions by about 83%. Penetration of cortical bone with an Er:YAG laser was possible up to a cortical thickness of 6 mm with fewer than 100 pulses. The ablation rate per pulse increased more with increasing duration than with increasing energy. Signs of bone damage such as melting were only visible when high pulse energies and durations were used. Insertion of the prototype was possible with all devices, but only when the whole contour was cut out of the cortical bone. However, the use of the ultrasound vibrator led to heating up of the tissue fluid and subsequently to water evaporation and tissue damage. Insertion of the prototype was possible with both pneumatic vibrators, but only when the whole contour was cut out of the cortical bone. New implant designs may lead to reduced stress peaks in the surrounding bone and might be inserted with the help of new insertion technologies, namely laser cutting of cortical bone and pneumatic vibration. Further studies are required to optimize these technologies prior to clinical use.

Animals↗
PubMed1990

Femoral neck fracture fixation. Comparison of a sliding screw with lag screws.

The rigidity of a sliding compression screw and three cannulated lag screws in the treatment of subcapital fractures was compared in five pairs of female cadaver femora. There were no significant differences between the compressive strength, bone density, cortical thickness or Singh index of the bones in each pair. A subcapital fracture was standardised using a perpendicular saw cut across the femoral neck. A uniaxial 'load test system' with force and length measurement facilities was used to mimic cyclical stressing applied in vivo at a frequency of 0.5 Hz from 0 to 3 times body-weight. There was no significant difference between the fixation afforded by the sliding compression screw and three lag screws. Bone quality was the single most important factor in the stability of the bone implant unit.

Aged↗
PubMed2005

Olecranon fracture fixation utilizing a bioabsorbable tension band construct: analysis of stability with motion in a cadaveric model.

This study was performed to determine if tension band suturing with bioabsorbable materials can maintain fracture (osteotomy) reduction when subjected to an early motion protocol. Olecranon osteotomies were created in 13 cadaveric upper extremities and then sequentially fixed with axial Kirschner wires, and tension band wiring/suturing utilizing: musical #1 PDS (Ethicon Inc., Somerville, New Jersey, USA), musical #1 Panacryl (Ethicon Inc.), musical #2 Panacryl (Ethicon Inc.), and 18 gauge surgical wire. Specimens were cycled through a range of motion in a continuous passive motion machine. Specimens fixed with K-wires only, musical #1PDS and musical #1 Panacryl tension band suturing failed to maintain osteotomy reduction. Only surgical steel and musical #2 Panacryl maintained osteotomy reduction; both were superior to the other fixation methods (P<0.001). The musical #2 Panacryl suture is an excellent choice for a tension band suture construct; it retains 80% of its breaking strength at 3 months, is fully absorbed, and maintains osteotomy reduction throughout a passive motion protocol.

Absorbable Implants↗
PubMed1997

A biomechanical study on five unilateral external fracture fixation devices.

OBJECTIVE: This study examines plastic, slip and fatigue failures in external fixator frames. DESIGN: Failure was examined in five commonly used unilateral external fixators using experimental models that simulated both stable and unstable diaphyseal fractures. BACKGROUND: Plastic failure arises from permanent deformation of a frame initiated by bending of frame components, while slip failure arises from slip at clamping interfaces. Such failure may lead to refracture or to malalignment of the bone (transverse or angular). Fatigue failure arises from the loosening or wear of components under long-term cyclic loading; this can lead to variable interfragmentary displacement and impairment of fracture stability. METHODS: Axial loads were measured at which plastic or slip failure occurred, as were changes in interfragmentary motion due to 10 000 load cycles simulating walking activity. RESULTS: In four fixators, plastic or slip failure initiated bone malalignment at only 50% of average adult weight bearing (650 N). Additionally, in three fixators a third screw at the clamp centre was found to reduce retention of the two adjacent screws, causing premature slip failure. Evidence of fatigue was found in all the fixators after only 10 000 load cycles. In one fixator, the amplitude of elastic interfragmentary motion increased progressively by 30% transversely, 15% angularly and 100% torsionally. In another fixator it increased by 10% in all directions while the column was locked (non-dynamizing), and it increased a further 10% while it was unlocked and able to slide telescopically (dynamizing). Clamp slip occurred at the column of a third fixator almost immediately after commencing the cyclic loading. CONCLUSION: Plastic or slip failure of frames may occur prematurely during routine weight-bearing on unstable fractures, and frame fatigue may affect long-term interfragmentary stability.

Journal Article↗
PubMed2006

A new and effective tension-band braided polyester suture technique for transverse patellar fracture fixation.

OBJECTIVES: Concerning the tension-band principle of internal fixation, this study aims to establish whether any difference in interfragmentary gap exists after bone-reducing forceps are released, when a recommended suture-knot technique and a new technique are tested in vitro on a purpose built machine that features a model of a transverse fracture of the patella. In addition, a standard tension-band wiring technique has also been tested as one form of control. BACKGROUND: Satisfactory compression at a fracture site reduces the risk of failure of fixation, loss of reduction (interfragmentary gap >2mm) and subsequent risks of malunion, delayed union, and ultimately non-union from excessive movement. Stainless-steel wire can provide a stable rigid construct but is associated with complications. Tension-band fixation employing a braided polyester non-absorbable suture provides a less rigid construct. However, satisfactory clinical results and fewer complications are reported. The method by which a suture is tied has an effect on initial compression provided the fracture is reduced. However, it also has an effect on the degree of fracture gap once it is subject to biomechanical distraction. METHODS: By measuring the output of a strain gauge Wheatstone bridge of a purpose built rig that had been calibrated against fracture gap and compression force, the various tension-band fixation techniques as discussed above were evaluated. RESULTS: The tension-band suture technique examined in this work (the modified Wagoner's Hitch) has been evaluated. It has quantitatively shown less fracture gap than other recognised tension-band suture and wire techniques. The results exhibit statistical significance (p<0.001). CONCLUSIONS: This evaluation study has produced quantitative and comparable data of fracture gap as observed with the model of a transverse patella fracture, for both new and established surgical techniques. The contribution this study has made to the knowledge of the subject is that a testing device similar to the one in this study may be useful in the future for conducting preliminary studies of new or established tension-band techniques. The proposed tension-band suture method tested in this dissertation provided statistically significant quantitative data, which may after further work, support its use as an alternative method in the clinical setting.

Bone Wires↗
PubMed1992

Femoral neck fracture fixation with hook-pins. 2-year results and learning curve in 626 prospective cases.

We performed a prospective 2-year follow-up study of 626 consecutive femoral neck fractures treated with closed reduction and hook-pin fixation in all cases. The woman:man ratio was 2.9:1, the displaced:undisplaced fracture ratio 2.6:1. Mean patient age was 78 (18-100) years. The first 476 fractures were operated on by one of six surgeons with special interest in the technique, while the remaining operations were performed by any of the 35 surgeons in the department, all specialists in orthopedic surgery. Mortality within two years was 31 percent. Healing complications (redisplacement, nonunion or segmental femoral head collapse) in the total material/survivors only were for undisplaced fractures 5/7 percent, for displaced fractures 30/41 percent and for the total material 23/32 percent. According to life-table analysis, the complication rate in the total material at two years was 24 percent. The rate of secondary arthroplasty for healing complications was 13/19 percent. For displaced fractures, as well as for the total material, the group of specially interested surgeons had better results than the department as a whole.

Adolescent↗
PubMed2007

Biomechanical analysis of distal femur fracture fixation: fixed-angle screw-plate construct versus condylar blade plate.

OBJECTIVE: The objective of this study is to establish the relative strength of fixation of a locking distal femoral plate compared with the condylar blade plate. METHODS: Eight matched pairs of fresh-frozen cadaveric femurs were selected and evaluated for bone density. A gap osteotomy model was used to simulate an OTA/AO A3 comminuted distal femur fracture. One femur of each pair was fixed with the blade plate; the other, with a locking plate. After 100 N preload and 10,000 cycles between 100 N and 1000 N, total displacement of each specimen was assessed. After completion of cyclic loading, maximum load to failure was tested. RESULTS: Significantly greater subsidence (total axial displacement) occurred with the blade plate (1.70 +/- 0.45 mm; range, 1.21-2.48 mm) than with the locking plate fixation (1.04 +/- 0.33 mm; range, 0.67-1.60 mm) after cyclic loading (P = 0.03). In load-to-failure testing, force absorbed by the locking plate before failure (9085 +/- 1585 N; range, 7269-11,850 N) was significantly greater than the load tolerated by the blade plate construct (5591 +/- 945 N; range, 3546-6684 N; P = 0.001). Variability in bone mineral density did not affect the findings (fixed angle distal femoral plate r = 0.1563; condylar blade plate r = 0.0796). CONCLUSIONS: The locking screw-plate construct proved stronger than the blade plate in both cyclic loading and ultimate strength in biomechanical testing of a simulated A3 distal femur fracture. Although differences were small, the biomechanical performance of the locking plate construct over the blade plate may lend credence to use of the locking plate versus the blade plate in the fixation of comminuted distal femur fractures.

Biomechanical Phenomena↗
PubMed2003

Calcium sulfate used as bone graft substitute in acetabular fracture fixation.

The purpose of this study was to determine the natural history of calcium sulfate pellets implanted during acetabular fracture surgery. The study group consisted of patients sustaining an acetabular fracture with intraarticular comminution or marginal impaction or both in whom calcium sulfate pellets were implanted in lieu of autologous bone graft. Between 1997 and 1999, 32 fractures were treated. Followup adequate to delineate pellet outcome, including radiographs and computed tomography, was obtained in 31 patients. Evaluation of plain radiographs showed that the calcium sulfate pellets became undifferentiated from the surrounding bone at an average of 7 weeks postoperatively. In no case was a residual bony deficit seen. Computed tomography analysis showed that in 22 patients, the pellets essentially had been (> 90%) replaced by bone and in four patients, the majority (> 50%-90%) of the pellets had been replaced by bone. However, in five patients, less than 50% of the pellets had been replaced by bone, including one showing no bony replacement. The common finding in patients with an extensive residual deficit was direct communication of the pellets with the joint space shown on the postoperative computed tomography scan. Patients with the best results had complete containment of the pellets within bone. Therefore, it seems that implanted calcium sulfate pellets in contact with joint synovial fluid are at risk for resorption without significant bony response. If calcium sulfate pellets are to be implanted in a periarticular location, complete bony containment is desirable. Evaluation of the periacetabular bony response requires computed tomography scans, as plain radiographs are inadequate for this purpose.

Acetabulum↗
PubMed2000

Extramedullary fixation implants for extracapsular hip fractures.

BACKGROUND: Extramedullary fixation of hip fractures refers to the application of a plate and screws to the lateral side of the proximal femur. OBJECTIVES: To compare different types of extramedullary fixation implants for the surgical treatment of extracapsular hip fracture in adults. SEARCH STRATEGY: We searched the Cochrane Musculoskeletal Injuries Group trials register and reference lists of relevant articles. Date of the most recent search: March 1998. SELECTION CRITERIA: All randomised or quasi-randomised trials comparing extramedullary implants used in the fixation of extracapsular hip fracture in adults. DATA COLLECTION AND ANALYSIS: All three reviewers independently assessed trial quality, using a ten item scale, and extracted data. Additional information was sought from all trialists. Wherever appropriate and possible, results of outcome measures were pooled by comparison. MAIN RESULTS: The methodological quality of all six included trials was poor and in no trial was there clear concealment of allocation. Three trials involving 355 patients compared a fixed nail plate (Jewett or McLaughlin) with the sliding hip screw (SHS). The limited data presented indicated an increased risk of fixation failure outcomes for fixed nail plates. One trial involving 233 patients compared the RAB plate (a fixed angle blade plate with an oblique connecting strut) with the SHS. In this trial both implants had a high incidence of fixation failure. There was a tendency to a lower incidence of cut-out, re-operation, fixation failure, leg shortening, varus deformity and mortality for the RAB plate. None of the differences in these outcomes were statistically significant. One trial involving 100 patients compared the Pugh nail and the SHS. There was no significant difference between implants for the outcome measures reported. One trial involving 176 patients with 182 fractures, compared the Medoff plate with the SHS. A significantly higher mean operative blood loss and longer mean operative time were reported for the Medoff plate. There was however a tendency to a lower risk of fixation failure for unstable trochanteric fractures fixed with the Medoff plate. REVIEWER'S CONCLUSIONS: The fixed nail plate was demonstrated to have to an increased risk of implant breakage and fixation failure in comparison to the SHS. Although the lack of evidence from randomised trials for other outcomes means that a firm conclusion of overall superiority of the SHS cannot be made, the increased fixation failure rate is a major consideration and indicates that the SHS is preferable. Insufficient information is available to draw firm conclusions of the clinical significance of differences between the SHS and either the RAB plate, the Pugh nail or the Medoff plate.

Bone Plates↗
PubMedDate not supplied

The comparative strength of laryngeal fracture fixation.

PURPOSE: To assess the fixation strength provided by miniplate fixation, wire-tube batten fixation, and wire fixation alone in repair of thyroid cartilage. MATERIALS AND METHODS: Segments 2.5-cm wide x 1-cm long were cut from three fresh, frozen, human cadaveric larynges from an 83-year-old man, a 58-year-old woman, and an unknown cadaver. A vertical fracture was induced and repaired with one of three randomly assigned fixation techniques (n=10 in each fixation group). The repaired cartilage was placed in an Instron Universal Testing Device (Boston, MA) and subjected to a three-point bending test. Load to failure was recorded on an analogue graph. RESULTS: All reconstruction techniques significantly differed from each other, with miniplate fixation providing a stronger repair than wire tube batten (P < .05), wire tube batten providing a stronger repair than wire alone (P < .01), and miniplate providing a stronger repair than wire alone (P < .001). CONCLUSION: In experimentally induced fractures of the human larynx, miniplate fixation consistently yielded the strongest repair. Although both miniplate and wire batten produced excellent anatomic reaction, we feel that miniplate fixation was easier to perform.

Aged↗
PubMed1987

Resorbable materials of poly(L-lactide). VI. Plates and screws for internal fracture fixation.

Poly(L-lactide) (PLLA) with an extremely high molecular weight (Mv up to 1 X 10(6)) was synthesized at a low catalyst concentration (0.015 wt%) and temperatures between 100-110 degrees C. Besides good mechanical properties the as-polymerized PLLA exhibited a microporous structure. Plates and screws of this material were used for the treatment of mandibular fractures, both in dogs and in sheep. Bone healing was uneventful and proceeded without callus formation or signs of inflammation. Fracture healing was accompanied by a progressive degradation of the microporous implants of PLLA.

Animals↗