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PubMed1997

Bioabsorbable pin fixation of intercarpal joints: an evaluation of fixation stiffness.

OBJECTIVE: Bioabsorbable pins made of poly-p-dioxanone (Johnson and Johnson Orthopaedics, Raynham, Massachusetts) were compared to steel pins in the fixation of the scapholunate and lunotriquetral intercarpal joints of the wrist. DESIGN: An in vitro experiment was performed using fresh-frozen cadaver wrists. BACKGROUND: In the surgical treatment of wrist ligament injuries, temporary intercarpal joint fixation is required. Although steel pins are currently used, there are several clinical problems associated with their use. These complications could potentially be reduced by using bioabsorbable fixation. METHODS: The carpal bones were mounted between sets of plates which were then attached to a materials testing machine. Two parallel pins were used for joint fixation; steel pin fixation was tested first in each joint. Seven scapholunate joints and seven lunotriquetral joints were each tested in three different modes: translation in two orthogonal directions, and rotation. RESULTS: Bioabsorbable pin fixation provided an average of 46% of the stiffness of steel pin fixation. CONCLUSIONS: Although bioabsorbable pin fixation was statistically less stiff than steel pin fixation, relatively high loads were required to induce significant intercarpal joint translation and rotation. RELEVANCE: The strength retention profile of poly-p-dioxanone pins and the quality of fixation demonstrated in this study indicate that these bioabsorbable pins could provide satisfactory fixation of the scapholunate and lunotriquetral joints in the treatment of partial injuries of the intercarpal ligaments.

Journal Article↗

PubMed1996

Comparison of screw post fixation and free bone block interference fixation for anterior cruciate ligament soft tissue grafts: biomechanical considerations.

Endoscopic (single-incision) anterior cruciate ligament (ACL) reconstruction with bone patellar tendon bone can usually be secured with interference screws on the femur and tibia. Infrequently, patella alta, which results in a longer tendinous component of the graft construct, can result in construct mismatch, resulting in a large portion of the tibial bone plug extruding from the tibial tunnel, requiring graft fixation with staples or a suture/screw and post technique. This study investigated the hypothesis that initial graft fixation could be enhanced if the bone plug was removed and press fit into the tibial tunnel and then secured with an interference screw in the scenario of graft construct mismatch. Initial biomechanical fixation strengths of bovine patellar tendon were compared using a screw and post suture fixation compared with a free bone plug, which was removed from the graft and sandwiched along with the soft tissue with an interference screw. Twenty-eight bovine knees were randomly divided into two groups. Graft fixation was performed with a free bone plug excised from the tibial tubercle portion of the bone tendon bone construct. Fixation was achieved with a cannulated 9-mm x 20-mm interference screw. Fixation was performed in group 2 patients with a Krackow suture of no. 5 Ticron secured over a screw and post. An Instron materials testing system was used and loading rates at 1 mm/sec until failure was performed. Statistically significant differences were noted for load to failure and stiffness (P < .001). Group 1 specimens' mean maximum load to failure was 669 N (range, 511 to 819 N), whereas the load to failure for group 2 patients was 374 N (range, 266 to 491 N). Group 1 stiffness was 90 N/mm (range, 50 to 122 N/m) compared with a mean stiffness of 24 N/m (range, 16 to 33 N/m) for group 2 knees. In our bovine model, free bone block interference fixation was stronger and stiffer than fixation using sutures tied over a post. This fixation method of securing a soft tissue graft with an interference screw warrants further clinical investigation and may offer an improvement to the alternative of suture/post fixation.

Animals↗

PubMed1996

Iris-fixated Worst claw versus sulcus-fixated posterior chamber lenses in the absence of capsular support.

PURPOSE: To evaluate visual outcomes and complications of iris-fixated intraocular lenses (IOLs) (lobster-claw) and sutured sulcus-fixated posterior chamber (PC) IOLs in primary and secondary implantation. SETTING: Eye Department, University Hospital "La Fe", Valencia, Spain. METHODS: This retrospective study reviewed 47 patients who had primary implantation of an iris-fixated (n = 34) or sulcus-fixated (n = 13) IOL and 54 patients who had secondary implantation of an iris-fixated (n = 41) or sulcus-fixated (n = 13) IOL. RESULTS: Visual acuity in the primary implantation group was similar with both lens types. Overall, 54.0% had a postoperative acuity of 20/40 or better. In eyes without pre-existing pathology, 60.0% with an iris-fixated IOL and 54.6% with a sutured PC IOL had this level of postoperative acuity (P = .768). In the secondary implantation group, the percentage of patients with a postoperative visual acuity of 20/40 or better was significantly higher in iris-fixated IOL eyes (78.0%) than in sulcus-fixated PC IOL eyes (46.2%) (P < .05). In eyes without pre-existing pathology, the difference was maintained. No intraoperative complications directly associated with iris-fixated lens implantation occurred. The incidence of postoperative complications common to either IOL type in primary and secondary implantation did not differ significantly. The incidence of retinal complications was higher in eyes that had primary implantation of either lens type, although the differences between both lenses in either primary or secondary implantation were not significant. CONCLUSION: The good visual outcomes and low incidence of intraoperative and postoperative complications in eyes with iris-fixated IOLs indicate that these lenses should be considered an alternative to sutured PC IOLs in eyes in which capsular support is inadequate or absent.

Adolescent↗

PubMed2001

The EndoPearl device increases fixation strength and eliminates construct slippage of hamstring tendon grafts with interference screw fixation.

PURPOSE: The EndoPearl (Linvatec, Largo, FL), a biodegradable device to augment the femoral interference screw fixation of hamstring tendon grafts has been developed. The first objective of this study was to compare the initial fixation strength of quadrupled hamstring tendons and biodegradable interference screw fixation with and without the application of the EndoPearl device. The second objective was to determine the influence of the EndoPearl device on the fatigue behavior under incremental cyclic loading conditions in a simulation of critical fixation conditions. TYPE OF STUDY: Biomechanical study. METHODS: Fresh human hamstring tendons were harvested and grafts were fixed with biodegradable poly-L-lactide interference screws. Twenty proximal calf tibias were used to compare the initial fixation strength of the study and the control group. In the study group, the EndoPearl device was secured to the graft using two No. 5 Ethibond sutures (Ethicon, Somerville, NJ). Specimens were loaded until failure in a materials testing machine. For cyclic testing, human hamstring tendons and 20 distal porcine femurs were used. Critical graft fixation conditions were simulated by increasing tunnel diameter 2 mm over the graft diameter. Grafts were loaded progressively in increments of 100 N until failure; 100 cycles were applied per load increment. RESULTS: Graft fixation with the additional EndoPearl device had a significantly higher maximum load to failure (658.9 +/- 118.1 N v 385.9 +/- 185.6 N, P =.003) and stiffness (41.7 +/- 11 N/mm v 25.7 +/- 8.5 N/mm). Graft fixation with the EndoPearl device sustained a significant higher total number of cycles (388.5 +/- 125.6) compared with the control group (152.8 +/- 144.9, P =.002). CONCLUSIONS: We demonstrated that the augmentation of a hamstring tendon graft with the EndoPearl device increases interference screw fixation strength significantly. Under dynamic loading conditions, specimens of the study group sustained substantially higher loads and a larger number of cycles, which indicates a greater resistance to graft slippage. The application of the EndoPearl device may also allow for a secure soft-tissue graft fixation with interference screws in cases of critical fixation conditions.

Absorbable Implants↗

PubMed1999

Biomechanical evaluation of a newly developed monocortical expansion screw for use in anterior internal fixation of the cervical spine. In vitro comparison with two established internal fixation systems.

STUDY DESIGN: The primary biomechanical stability of anterior internal fixation of the cervical spine obtained with a new monocortical expansion screw in vitro was evaluated. OBJECTIVES: To determine whether the anterior internal fixation of the spine obtained with the new monocortical expansion screw provides biomechanical stability comparable with that obtained with bicortical fixation. SUMMARY OF BACKGROUND DATA: The anterior plate instrumentation used with bicortical screw fixation in the cervical spine provides a primary stability superior to that associated with monocortical screw fixation. However, bicortical screws have the potential to perforate the posterior cortex. Therefore, monocortical instrumentation systems were developed, but without the biomechanical stability associated with bicortical systems. A new expansion screw for monocortical fixation was developed to improve biomechanical stability of monocortical systems. METHODS: Three different internal fixation systems were compared in this study: 1) H-plate with AO 3.5-mm bicortical screws, 2) cervical spine locking plate with monocortical screws, and 3) H-plate with the new monocortical expansion screws. Eight fresh human cadaver spine segments from C4 to C7 were tested in flexion-extension, axial rotation, and lateral bending using pure moments of +/- 2.5 Nm without axial preload. Five conditions were investigated consecutively: 1) intact spine; 2) uninstrumented spine with the segment C5-C6 destabilized; 3-5) instrumentation of the segment C5-C6 with the three implants mentioned above after removal of the disc and insertion of an interbody spacer. RESULTS: Between bicortical and monocortical expansion screw H-plate fixation, no significant differences were observed in all load cases concerning range of motion and neutral zone. The neutral zone and range of motion were significantly larger for the cervical spine locking plate than for bicortical and monocortical expansion screw fixation in all load cases, except neutral zone for axial rotation versus bicortical screw fixation. The instrumented cases only had a significantly lower range of motion and neutral zone than the intact cases in extension-flexion, whereas for lateral bending and axial rotation no significant differences could be observed. Because the experimental design precluded any cyclic testing, the data represent only the primary stability of the implants. CONCLUSIONS: In anterior instrumentation of the cervical spine using a H-plate, the new monocortical expansion screw provides the same biomechanical stability as the bicortical 3.5-mm AO screw and a significantly better biomechanical stability than the cervical spine locking plate. Therefore, the expansion screw may be an alternative to the bicortical fixation and does not involve the risk of penetration of the posterior vertebral body cortex.

Aged↗

PubMed2004

A new technique: in vitro suture anchor fixation has superior yield strength to bone tunnel fixation for distal biceps tendon repair.

BACKGROUND: Suture anchor and bone tunnel fixations are used for distal biceps tendon repairs and have not been compared. HYPOTHESIS: Suture anchor fixation is equal or superior to bone tunnel fixation. STUDY DESIGN: Randomized controlled in vitro study. METHODS: A new fixation technique was compared to traditional bone tunnel fixation of distal biceps tendon ruptures between randomly selected sides of nine matched-pair, fresh-frozen elbow specimens from cadaveric donors (mean age = 74.7 years). Bone densities were determined. The distal biceps tendon was attached to the actuator of a servohydraulic load frame and loaded to tensile failure at a constant rate of 4 mm/sec. Bone density, sex, age, side, tuberosity area, repair, failure type, repair stiffness, and yield strength were compared. RESULTS: Superior yield strength of suture anchor fixation (263 N) compared to bone tunnel fixation (203 N) (P = 0.0233) were demonstrated. When suture anchor fixation failure (1 of 9) occurred, the matched pair also failed. CONCLUSION: Suture anchor fixation offers an equal if not superior alternative to bone tunnel fixation for repair of the distal biceps tendon in the specimens tested. CLINICAL RELEVANCE: Suture anchor fixation may be used for distal biceps tendon repairs.

Age Factors↗

PubMed2002

A biomechanical comparison of fragment-specific fixation and augmented external fixation for intra-articular distal radius fractures.

The biomechanical stability of an internal fixation system that uses low-profile modular implants to stabilize individual fracture components was studied in a validated cadaver fracture model that incorporated physiologic muscle forces and wrist motion. Fragment-specific fixation with immediate range of motion was compared with static augmented external fixation in simulated, unstable 3- and 4-part intra-articular distal radius fractures (n = 20). Fixation was applied and specimens were loaded via their major wrist tendons. Because the wrist joint was not constrained in the internal fixation group, full wrist motion occurred during load application in these specimens. A 3-dimensional motion tracking system calculated individual fracture fragment motion in both groups. In the 3-part fracture pattern fragment-specific fixation showed comparable stability to static augmented external fixation despite the full wrist range of motion that occurred during application of load in these specimens. In the 4-part fracture pattern fragment-specific fixation was shown to be significantly more stable when compared with static augmented external fixation in 4 of 6 axes of motion. Our findings confirm the stability of this low-profile plating system and support the consideration of early wrist motion when treating complex, intra-articular distal radius fractures with fragment-specific fixation.

Biomechanical Phenomena↗

PubMed2005

The effect of transfixion wire number and spacing between two levels of fixation on the stiffness of proximal tibial external fixation.

OBJECTIVES: Anatomic constraints about the proximal tibia limit the ability to insert wires at the biomechanically optimum angle of 90 degrees, thus diminishing the potential stability of external fixators used for proximal tibial fractures. To overcome this problem, surgeons use more than 2 wires at a single level of fixation or a second level of fixation. This study evaluated the effect of transfixion wire number and placement of a second level of fixation on the stiffness of proximal tibial external fixation. METHODS: A fiberglass tibia fixed into an idealized ring external frame was tested. Load-deformation behavior was compared among the different wire numbers (1 level with 2, 3, 4, and 5 wires) and placement of a second level of fixation (2 wires first level and 1 wire second level, and 2 wires first level and 2 wires second level) at 2, 3, 4, 5, 6, 7, 8, 9, and 10 cm distance from the first level of fixation. Identical loading conditions of central axial compression, medial compression-bending, posterior compression-bending, posteromedial compression-bending, and torsion were used. Stiffness values were calculated from the load-displacement and the torque-angle curves. RESULTS: An increase in wire number at 1 level led to an overall increase in stiffness, whereas the addition of a second level of fixation and increased spread between these 2 levels increased bending stiffness. CONCLUSIONS: The addition of a second level of external fixation of the proximal tibia fragment with maximum possible distance between the 2 levels increases bending stiffness, whereas increasing the number of transfixion wires increases overall stiffness. Axial and torsional stiffness is proportional to the total number of wires regardless of the number of levels of fixation.

Biomechanical Phenomena↗

PubMed2005

Fixation stiffness of Dynafix unilateral external fixator in neutral and non-neutral configurations.

A primary function of external fixator is to stabilize the fracture site after fracture reduction. Conventional fracture reduction method would result in fixator configurations deviated from its neutral configuration. How the non-neutral configurations would affect the biomechanical performance of unilateral external fixators is still not well-documented. We developed a finite element model to predict the fixation stiffness of the Dynafix unilateral external fixator at arbitrary configurations under compression, torsion, three-point, and four-point bending. Experimental testing was done to validate the model using six Dynafix unilateral external fixators in neutral and particular non-neutral configurations. Effects of loading directions on bending stiffness were also studied. It appeared that the model succeeded in revealing the relative stiffness of the neutral and non-neutral configuration in all the loading conditions. Our results also demonstrated that bending stiffness could vary substantially for different loading directions and the principle loading directions could be very different for different fixator configurations. Therefore, a more logical way to compare the bending stiffness is to identify the principle loading directions of each fixator configuration and used their maximum and minimum bending stiffness as comparison criteria. Given that fixator configurations could substantially change the stiffness properties of the bone-fixator system, computer simulation with finite element modeling of this kind will provide useful clinical information on the rigidity of certain configurations in stabilizing the fracture site for bone healing.

Computer Simulation↗

PubMed2000

Comparison of rat retinal fixation techniques: chemical fixation and microwave irradiation.

In histological studies using retinas, eyes are commonly fixed with aldehyde derivatives administered by immersion or perfusion. However, the histology of rat retinas chemically fixed as a whole eye is typically inferior to the histology of retinas that are immediately fixed after acute dissection from the rest of the eye. Chemical fixation without dissection often results in neuronal swelling resembling excitotoxic damage induced by ischemia because the retina is protected by the sclera and is thus poorly accessible to immersion or perfusion fixation techniques. In order for the acute dissection technique to work properly, it must be completed in a timely manner, which may be difficult under some circumstances. Microwave irradiation is an alternative method for fixing tissues that are inaccessable to chemicals. We examined the effectiveness of microwave irradiation of the whole eye as a substitute for acute retinal dissection. To study the feasibility of microwave methods, we compared retinal morphology using microwave irradiation to morphology using conventional immersion fixation methods. Eyes were removed from rats, placed in a container with 2 or 20 ml artificial cerebrospinal fluid (aCSF) and irradiated with a household microwave oven. For morphological comparison, control eyes were immersed in a chemical fixative containing 1% paraformaldehyde and 1.5% glutaraldehyde. All eyes were embedded in araldite for evaluation by light microscopy. Retinal segments acutely isolated before immersion fixation revealed intact histology whereas retinal segments exposed to 60 min of simulated ischemia showed severe neuronal degeneration. Using an immersion technique, the retinas of chemically fixed whole eyes showed neuronal swelling similar to excitotoxic ischemic damage, suggesting that conventional immersion methods provide poor whole eye fixation. The neuronal degeneration observed with conventional immersion fixation was not found in retinas of whole eyes fixed with 20 sec of microwave irradiation. During microwave irradiation the temperature in the bathing aCSF rose to 55-72 degrees C. In some eyes, overcooking produced chromatin clumping and a small loss of contrast in staining. Although nuclear clumping and diminished staining occasionally result from overcooking, ischemic damage is well controlled with microwave fixation of enucleated eyes. When the optimal conditions are defined, microwave fixation may be preferable for retinal histology if chemical fixation following acute dissection is not feasible.

Animals↗

PubMed1984

Healing of rabbit tibial fractures using external fixation. Effects of removal of the fixation device.

Bone healing after external fixation of rabbit tibial osteotomies was studied in order to throw light on the problem of the optimal time for removal of external fixation. The animals were divided into various groups according to different periods of time for removal of external fixation and sacrifice. The strength and stiffness of the healing bones at 12 weeks were greater in tibiae where the external fixator was removed at 4, 6 or 9 weeks than in those with the continuous presence of the fixator for 12 weeks. Although fixation is essential in the early healing period, it seems that bone healing is stimulated by the removal of the fixation after a certain period of time. The optimum time for removal of external fixation in the rabbit tibia was at 6 weeks of healing, when the bone had regained normal stiffness and about 50 per cent of normal strength. The clinical relevance of this investigation is that it might be rational to remove the external fixator before bone healing has been completed. If it is felt that healing is not secure when the fixator is removed, a tibial brace might subsequently be used for a short period.

Animals↗

PubMed2006

The fixation strength of hydroxyapatite-coated Schanz screws and standard stainless steel Schanz screws in lower extremity lengthening : a comparison based on a new torque value index: the fixation index.

INTRODUCTION: Lengthening procedures are often complicated by loosening of pins. It has been reported that coating with hydroxyapatite improves fixation and reduces the rate of pin-track infection. MATERIALS AND METHODS: We compared 47 hydroxyapatite-coated Schanz screws (HA screws) in 12 monolateral fixators mounted at the University Hospital Hamburg-Eppendorf with 45 standard stainless steel screws in 9 monolateral fixators mounted at the St Josefs-Hospital Wiesbaden by measuring the insertion and extraction torque values. The average implantation period was 7 months for the hydroxyapatite-coated screws and 5.4 months for the uncoated screws. We established the quotient of the maximum extraction torque over insertion torque which shows the change in the fixation strength with respect to time, the fixation index. It eliminates the influence of the varying pin-bone contact. RESULTS: There was no significant difference in the rate of infection. In the Schanz screws without signs of infection the index was 1.92 for the HA screws and 0.76 for the stainless steel screws (P = 0.0002) giving evidence of the improvement of the fixation by the coating. CONCLUSION: HA coating resulted in improved fixation of Schanz screws in bone and may be useful in prolonged external fixation of the lower leg. The fixation index proved to be a simple tool for the evaluation of the fixation strength of Schanz screws.

Bone Lengthening↗

PubMed2004

Medial rectus pulley posterior fixation is as effective as scleral posterior fixation for acquired esotropia with a high AC/A ratio.

PURPOSE: To compare traditional medial rectus (MR) scleral posterior fixation versus MR pulley posterior fixation without scleral sutures for the treatment of acquired esotropia (ET) with a high accommodative convergence over accommodation (AC/A) ratio. DESIGN: Nonrandomized interventional case series. METHODS: Medical records were retrospectively reviewed for twenty-two patients who underwent bilateral MR posterior fixation for acquired ET with a high AC/A ratio, with or without associated MR recessions. The main outcome measure was the reduction in distance-near disparity created by MR scleral posterior fixation compared with MR pulley posterior fixation. RESULTS: Nine patients underwent MR scleral posterior fixation surgery, seven in combination with MR recessions for distance ET. Postoperatively, the distance-near disparity decreased an average of 11.8 prism diopters, stereoacuity improved in six patients, and eight patients no longer needed bifocals. Thirteen patients underwent MR pulley posterior fixation surgery, 10 in combination with MR recessions for distance ET. Postoperatively the distance-near disparity decreased an average of 14.4 prism diopters, stereoacuity improved in eight patients, and 12 patients no longer required bifocals. Statistically, the two procedures were equivalent. One patient in each group was undercorrected at near only, with the residual near ET controlled with bifocals. One patient who underwent MR pulley posterior fixation combined with large MR recessions was overcorrected at distance only. CONCLUSION: Traditional MR scleral posterior fixation and MR pulley posterior fixation are equally effective in treating acquired ET with a high AC/A ratio.

Accommodation, Ocular↗

PubMed1999

Update on fixation of rigid and foldable posterior chamber intraocular lenses. Part II: Choosing the correct haptic fixation and intraocular lens design to help eradicate posterior capsule opacification.

PURPOSE: Posterior capsule opacification (PCO) is one of the most common complications of cataract surgery, and there is an urgent need to reduce its incidence. Its main treatment, neodymium:YAG (Nd:YAG) laser posterior capsulotomy, may be associated with significant morbidity and is expensive. In this study, the authors ascertain the effect of posterior chamber intraocular lens (PC-IOL) fixation and various IOL designs (rigid polymethyl methacrylate [PMMA] optic and small-incision foldable designs) on the pathogenesis of PCO. DESIGN: Prospective analysis of pseudophakic eyes obtained postmortem. PARTICIPANTS: A total of 3493 eyes with PC-IOLs obtained postmortem and received between 1984 and 1998. METHODS: Miyake-Apple posterior photographic technique. MAIN OUTCOME MEASURES: Peripheral Soemmering's ring, central PCO in the visual axis, and eyes that have had Nd:YAG laser posterior capsulotomy were analyzed and scored, and these findings were correlated with the type of fixation and IOL design. RESULTS: The degree of formation of peripheral Soemmering's ring was not influenced by IOL fixation. The acrylic design revealed relatively low Soemmering's ring scores. In contrast, central PCO and Nd:YAG laser capsulotomy scores were consistently influenced by fixation. The scores were significantly lower in eyes with in-the-bag fixation. The bag-bag fixated acrylic-PMMA design and the three modern silicone IOL designs analyzed in this study had less central PCO and lower posterior capsulotomy scores than did the PMMA IOLs. CONCLUSIONS: The formation of peripheral PCO (the Soemmering's ring), the precursor of clinically significant, vision-threatening PCO, is not significantly influenced by the haptic fixation pattern. It is much more dependent on the quality and thoroughness of surgical cortical cleanup. Reduction of Soemmering's ring is an important goal because the retained regenerative cortical cells within this lesion are the cells of origin of PCO. The acrylic IOL design was associated with a lessor amount of peripheral Soemmering's ring as compared with all other designs. In sharp contrast to peripheral PCO, fixation of the IOL was a highly significant factor affecting the formation and quantity of central PCO-the clinically significant opacity behind the IOL optic, measured in this series either by scoring an intact retro-optical membrane or by documenting the presence of a Nd:YAG laser posterior capsulotomy orifice. The quantity of central PCO was consistently much lower in eyes with in-the-bag fixated IOLs compared with lenses with one or both haptics out of the bag. This is best explained by the fact that secure in-the-bag fixation positions the IOL optic in the best possible position to create a barrier effect. The lowest PCO rates were generally noted with the acrylic and modern silicone IOL designs.

Acrylic Resins↗

PubMed2003

Rigid fixation of the calvaria in craniosynostosis without using "rigid" fixation.

Early observations of intracranial translocation of metal wires, plates, and screws used for infant skull surgery have led some surgeons to investigate alternative forms of fixation. The purpose of this study was to review a series of infants and children in whom absorbable suture fixation was used as the sole method of fixation in cranial vault remodeling. Standard osteotomies were successfully modified to permit the use of this less rigid form of fixation. Over a 6-year period, 142 cranial vault procedures were performed, primarily for craniosynostosis, using absorbable sutures (2-0 polydioxanone). Patients who did not have absorbable suture fixation, or who had a combination of absorbable sutures with another form of fixation, were excluded from this review. Records were reviewed for results (assessed by both the treating surgeon and an independent anthropologist) and for complications. The average age of patients was 2 years, 7 months (range, 1 month to 16 years). The clinical results were judged as follows: grade I (excellent), 49 percent; grade II (minor imperfections), 48 percent; grade III (small surgical procedure needed), 2 percent; and grade IV (complete reoperation required), 1 percent. Anthropologic results were similarly distributed: excellent, 36 percent; good, 56 percent; fair, 8 percent; and poor, 0 percent. Those 3 to 8 percent of patients who were found to have the poorest results were all noted to have syndromes, and it appeared that an inherent lack of growth was the primary basis for the low score. There were no deaths or major complications in this series of patients. The smaller complications identified were infections [four cases (2.8 percent)] and transient cerebrospinal fluid leak [two cases (1.4 percent)]. The most important factor in determining whether absorbable suture fixation was sufficient was the size of a preexisting calvarial defect. Although concerns have been raised about a possible link between absorbable suture fixation and subsequent poor reossification, no such association was noted in this review. The primary disadvantage of using absorbable sutures was the lack of rigidity provided. Advantages included lower costs, speed of application, and the absence of observed intracranial translocation. In conclusion, the use of absorbable suture fixation (with modifications in osteotomy design) was associated with both acceptable aesthetic outcomes and low complication rates. Craniofacial surgeons may wish to consider the use of absorbable sutures as another option for bone fixation in treatment of craniosynostosis.

Absorption↗

PubMed2001

Proposed technique for evaluation of endotracheal tube fixation and comparison of four fixation methods.

BACKGROUND: The fixation of an endotracheal tube must be rapid in conditions involving numerous casualties, such as a chemical warfare (CW) situation. The tube also should be fixed and strong to prevent unplanned extubations. METHODS: We developed a technique for the evaluation of fixation methods. This technique was used to evaluate four methods. Three commercial fixators were compared with the fixation method used today in the Israeli Defense Forces (IDF) and commonly used in different out-of-hospital settings. The exercises were performed on adult intubation mannequins with and without CW protective gear. The fixations were timed, and their quality was evaluated by the participants and inspectors. RESULTS: The time score for the method used today in the IDF was significantly higher compared with the commercial fixation methods. The quality scores for the Thomas fixator and the IDF method were significantly higher than for the fixators by VBM and Rusch. The CW protective gear significantly prolonged the time but did not affect the quality of the fixation. CONCLUSIONS: With this technique, a good estimation of the time and quality of fixation can be achieved.

Adhesives↗

PubMed1997

Biomechanical comparison of intramedullary and percutaneous pin fixation for proximal humeral fracture fixation.

OBJECTIVES: The purpose of this study was to investigate the mechanical strength and durability of intramedullary nailing (IM) and percutaneous pinning (PP) for fixation of three-part proximal humeral fractures using a cadaveric model. DESIGN: Three-part surgical neck fractures were created in paired embalmed cadaveric humeri. Fractures were fixed with IM and PP fixation. The fixation stiffness and durability was assessed under cyclic rotational loading (infraspinatus) ramping from 0.1 to 1.25 Newton-meters for 10,000 cycles. The specimen were then torsionally loaded to failure. SETTING: Mechanical testing was performed using a servohydraulic test system (MTS, Minneapolis, MN, U.S.A.). INTERVENTION: PP fixations were accomplished using standard multiplane techniques. IM fixation was attained using an 11.0-millimeter-diameter curved rod interlocked proximally with three splayed 5.0-millimeter cancellous screws and distally with three 3.5-millimeter cortical screws. MAIN OUTCOME MEASUREMENTS: During cyclic loading the reconstruction stiffness, angular migration, and angular displacement per cycle were measured and compared between fixation methods. The ultimate torque at failure, absolute angular migration, and reconstruction stiffness during failure were recorded and compared between fixation methods during destructive testing. RESULTS: The intramedullary device had greater stiffness and less angular displacement of fragments during cyclic loading. When loading the reconstructions to failure, the intramedullary device proved to have greater failure torques, stiffness, energy absorbed, and angular displacement before failure. CONCLUSIONS: This biomechanical study showed that the IM device provided a stronger, more stable, and durable fixation option than did PP fixation for large-fragment multipart proximal humeral fractures with minimal comminution.

Biomechanical Phenomena↗

PubMed1994

[External fixator: surgical technique, pinless fixator, change in procedure].

External Fixation-Technique: The advantages of external over internal fixation are as follows: a) endosteal and periosteal blood supply is undisturbed, b) "low-tech" equipment may be used, c) secondary adjustments are possible and d) easy implant removal. These benefits however are outweighed by the main disadvantages of long term external fixation i.e. pin complications and delayed union of fractures. Better understanding of postoperative management and careful application of screws of improved design will lead to better results. Today's standard applications of external fixation for tibial fractures is a unilateral fixator, using Schanz screws. The pin-bone interface is the most critical site of all external fixation. By avoiding heat necrosis (low temperature drilling) and preventing micro motion at the pin-bone interface (by applying bending- or more recently radial-preload), pin complications such as infection and loosening can be reduced. Two Schanz screws are inserted into each main fragment and are connected with one short tube per fragment. The fracture is then reduced by using these tubes as handles. After reduction a third tube connects the first two by means of two tube-to-tube clamps. This type of fixation will easily allow for three dimensional secondary corrections of alignment. Approximately three weeks following the injury some motion at the fracture site will stimulate callus formation. This can be achieved by destabilisation, dynamisation or "active stimulation" of the fracture site [2]. Pinless fixator: The pinless external fixator holds the fragments firmly with pointed clamps that penetrate about one millimeter into cortical bone without entering and contaminating the medullary canal.(ABSTRACT TRUNCATED AT 250 WORDS)

Equipment Design↗