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PubMed2005

Combination of hook plate and tibial pro-fibular screw fixation of osteoporotic fractures: a clinical evaluation of operative strategy.

BACKGROUND: Internal fixation of osteoporotic ankle fractures is technically difficult and may fail because of unreliable purchase. This study was undertaken to determine if a combination of a hook plate and tibial pro-fibular screws can provide secure fixation until fracture union. METHODS: Thirty-one patients between the ages of 55 and 90 years had open reduction and internal fixation of ankle fractures between April, 2001, and April, 2003. Sixteen patients with an average age of 71.4 years had ankle fracture fixation with a combination of hook plate and tibial pro-fibular screws for the distal fibular fracture, and 15 patients with an average age of 71.9 years had fixation of their ankle fractures with standard fixation technique using AO/ASIF principles but no tibial pro-fibular screws. All patients were followed with clinical and radiologic assessment at 2 weeks, 6 weeks, and 12 weeks postoperatively. At an average of 15.8 months after injury, patients also completed a mailed questionnaire with the Olerud-Molander ankle score and the AOFAS ankle-hindfoot score for preoperative and postoperative status. RESULTS: All patients who had tibial pro-fibular screw fixation had fracture union without hardware failure or complications. In the standard fixation group two patients had wound breakdown and one had a valgus malunion with screw pull out. The AOFAS and Olerud-Molander scores for the standard open reduction and internal fixation were 57.3 and 82.8 before injury and 37 and 43.8 postoperatively, respectively. The AOFAS and Olerud-Molander scores for the hook plate and tibial pro-fibular fixation group were 55.9 and 81.3 before injury and 42.4 and 50.3 postoperatively, respectively. CONCLUSIONS: The combination of hook plate and tibial pro-fibular screws in osteoporotic ankle fractures in a series of patients has not been reported before. This novel technique provides stable fixation for osteoporotic ankle fractures in elderly patients until union is achieved with good clinical scores.

Aged↗

PubMed1999

A comparative study of various fixation methods for mandibular fracture.

BACKGROUND: Internal rigid fixation for mandibular fractures has been recognized as a reliable method for obtaining osteosynthesis. It may allow for early active physiotherapy and resumption of normal function. However, few studies have compared the various fixation methods. METHODS: From January 1993 through December 1997, 101 patients with mandibular fractures, who were selected for study, received treatment using various fixation methods at the Craniofacial Center, Chang Gung Memorial Hospital. The fixation methods included plate fixation in 44 patients, lag screw fixation in 30, combined plate and lag screw fixation in 15, and wire fixation in 12. Clinical data assessment was performed by reviewing hospital records. For assessment of the long-term surgical results, the patients were asked to complete a questionnaire including questions which specifically targeted history regarding occlusion, mastication, facial asymmetry, width of mouth opening, and general appearance. RESULTS: The outcome assessment showed statistically different results among the groups. The wire group required intermaxillary fixation more often and for a longer duration compared to the groups using plates and/or lag screws. The plate, lag screw, and combined plate and lag screw fixation groups had better total outcome scores, in particular for long-term dental occlusion and mastication function. CONCLUSION: This study shows that for mandible fractures, the more rigid types of fixation methods, i.e., plates and screws or lag screws, can offer better short and long-term outcomes.

Adolescent↗

PubMed1992

Open tibial shaft fractures: a comparative analysis of different methods of fixation in southwestern Greece.

A change in the method of managing open-grade-III tibial shaft fractures provided a new opportunity for a comparative study. One series of patients was treated exclusively by internal fixation and compared with another series treated with external fixation solely as well as with a series treated initially by external skeletal fixation and later by "Sarmiento walking plaster." The latter method was found to be a successful treatment and a good alternative to internal fixation for open grade-II and grade-III tibial shaft fractures when soft-tissue healing was completed. The supplementary use of the Sarmiento walking plaster had dramatically decreased the duration of hospital stay, saving the patient from an additional operation. There were no nonunions in this series. In open grade-I-II tibial shaft fractures, the deep infection rate in the cases in which internal fixation was used was significantly higher (5.4%), than that observed in the cases treated with external fixation, in which there was no deep infection. The nonunion rate was higher (22%) in the external fixation group compared with the internal fixation group (9%). The functional impairment of the ankle joint of the affected limb was less (15%) by using internal fixation than that of either the external fixation group (20%) or the group where the external fixation was changed to a Sarmiento walking plaster (35%).

Adolescent↗

PubMed1989

Plates versus external fixation in severe open tibial shaft fractures. A randomized trial.

A prospective study of 59 patients with Grade II or III open tibial shaft fractures compared internal and external fixation. Bony stabilization was with plating by AO principles or with external fixation with the one-half pin technique, prospectively randomized. In 12 cases, minimal internal fixation of the tibia and external fixation were combined. Definitive wound closure was delayed in all cases. Three free-flap transfers and two gastrocnemius myoplasties were done; vascular injury necessitated three early limb amputations. Fifty-six patients were followed for at least one year. Five plate fixations (19%) were complicated by severe osteomyelitis, and three plate fixations failed. Severe osteomyelitis occurred in one case (3%) treated with external fixation. Three pin-tract infections occurred. In two patients, a 10 degrees anteroposterior angulation occurred after external fixation removal. One patient healed with a 25 degrees external rotation deformity. At final follow-up evaluation, all tibial shaft fractures had healed. Knee and ankle ranges of motion were affected by ipsilateral femoral shaft fracture, knee injury, or ankle and foot trauma but not by the type of fixation. Both methods yielded excellent results, but the rate and extent of complications were lower with external fixation. Therefore, external fixation using the one-half pin technique should be regarded as a primary method of stabilization for Grades II and III open tibial shaft fractures.

Adolescent↗

PubMed1997

[Treatment of metaphyseal fractures of the tibia by the Ilizarov external fixator].

PURPOSE: This external fixation was used for 46 of 60 cases of proximal tibial metaphyseal fractures, over a 10 years period. The choice of an external fixation was determined by the poor reputation of internal fixation for even complex closed fractures. The reasons for the choice of the Ilizarov device were: the possibility of fitting the fixation pins close to the knee joint if necessary, the circular nature of the system, and finally the possibility of adding an intrafocal mounting (I.F.M.) which can bring the displaced bone fragments together using shaped blockstops pins. The program theoretically foresaw an initial sequence using external fixation until bone continuity was achieved, followed by a complementary plaster for one or two months. MATERIALS: 7 of the 46 fractures were lost for follow-up. Of the remaining 39 cases, there were 5 early complications: one knee septic arthritis which led to stop the method before the second month. Each of these 5 failures were due to improper use of the method. 34 cases have been followed for more than two years. RESULTS: 29 cases of consolidation of which 3 initial displacements were wrongly considered as acceptable. There was no case of displacement while the fixation was in place. There were 5 nonunions: 2 at the diaphyseal level in long metaphyso-diaphyseal fractures, 2 were comminutive metaphyseal fractures in which the fixation had been removed by error before the third month. With this fixation, neither the traumatic opening, nor the presence of a fibular fracture significantly affected consolidation. The healing period was however longer when the fracture was more extensive and comminutive. The bone gaps were treated by interfocal mounting (I.F.M.) but loss of bone stock persisted; they affected the occurrence of nonunion. CONCLUSION: Each failure of the method is explained by its improper use. The Ilizarov fixation is an excellent mechanical response to these fractures: on condition that the technical rules are respected, that an intrafocal mounting is used to remove interfragmentary gaps, and that the fixator is kept in place long enough, according to the size and comminutive nature of the fracture. This fixation is reliable in these conditions but does not compensate intrafocal bone loss exceeding 40 per cent of the metaphyseal bone mass.

Adult↗

PubMed1997

[Evaluation of AO kit screw fixation of medial condyle and epicondyle distal humeral epiphyseal fractures in children].

In the Pediatric Surgery Department of the Voivodeship Hospital in Koszalin the use of screw fixation claims to be the method od choice for treating the fractures of medial epicondyle and condyles of the distal humeral bone epiphysis in children, thus challenging Kirschner's wire fixation being commonly applied in these traumas, and in consequence making it necessary to compare the results obtained after resorting to each of these methods. The accomplished comparative study covered the total of 101 persons, aged from 5 to 28 years, over the period from 1 to 15 years (mean 6 years) after trauma, treated due to the above-mentioned injuries in the years 1976-1990, at this Department (86 persons), and in the years 1980-1990 at the Pediatric Surgery Clinic of the Pomeranian Medical Academy in Szczecin (15 persons) exclusively by means of Kirschner's wire fixation. In 64 patients screw fixation was implanted, and in 37-Kirschner's wire. The studied material was divided into 4 subgroups (Tab. 1) comprising respectively: 41 persons (subgroup A) after past fracture of medial epicondyle treated by screw fixation; 26 persons (subgroup A1) with past medial epicondyle fracture treated by Kirschner's wire fixation: 23 persons with past condyle fracture treated by screw fixation (subgroup B) and 11 persons after condyle fracture treated by Kirschner's wire fixation (subgroup B1). Three control groups were set up: control group I, showed normal reference values, represented the assessments of healthy ulnar joints contrasting with the previously inflicted injury in 101 persons of the studied group. The control group II, concerning the physical examinations, incorporated 43 persons burdened neither by past trauma, nor by any other lesions of the ulnar joints, randomly selected: 23 children, 12 under the care of their parents, and 11 persons of juvenile age, registered with the pediatric surgery or rehabilitation consulting centres in Koszalin. Control group III, concerned with correct radiologic measurements included 45 persons randomly selected, aged from 5 to 27 years in whom radiograms of their ulnar joints were made on indications not involving the trauma of the joint. The clinical evaluation took into account the anamnesis data, assessment of the ulnar joint shape, appearance of the postoperative scar, innervation status within the ulnar nerve range, measurements of the length of arm, its circumference, flexion and extension movement (with analysis of the range of movement) value of the angle of the arm axis deviation in relation to forearm axis, as well as muscle power. The radiographic evaluation encompassed the measurements of angles: humeral, ulnar, physiological valgity as well as diaphysio-epiphysial one, and moreover, the evaluation of the symphysis quality, outlines of distal epiphysis of the humeral bone and its bony structure. The mentioned parameters of the clinical evaluation, two of the parameters of the radiological evaluation, and also the final point estimation of the treatment results were subjected to statistical analysis by applying the analysis of variance, with the level of significance being accepted as p = 0.05. The noted results have shown that significant findings in the clinical evaluation were primarily the measurements of both the range of movements and the angle of the arm axis deviation, in relation to the forearm axis, while in the radiological evaluation-the symphysis quality estimation and occasionally occurring absence of correlation between the result of clinical evaluation and the radiological one (Fig. 1). Moreover, the recorded results pointed to the screw fixation as being more favourable, than Kirschner's wire fixation, method of treating the mentioned injuries in children (clinical and radiological data were favouring the screw fixation in fractures of medial epicondyle-whereas in condyle fractures-first of all the clinical data). (ABSTRACT TRUNCATED)

Adolescent↗

PubMed2006

Influence of bone quality on the strength of internal and external fixation of tibial plateau fractures.

We studied the influence of different parameters of bone quality on the fixation strength of bicondylar tibial plateau fractures and examined the relationship between these parameters. Bone quality was measured in the plateau of 16 cadaveric tibias using three modalities: dual-energy X-ray absorptiometry (DXA), peripheral quantitative computer tomography (pQCT), and spectral analysis of digitized radiographs (SADR). The tibias were divided into two groups by the median bone mineral density (BMD) and randomized to receive either dual plating or external fixator for the stabilization of a standardized bicondylar tibial fracture. The fixed fractures were subjected to axial compression until failure. DXA BMD correlated most significantly with the failure load (r>or=0.79, p<0.001), followed by the pQCT parameters of cancellous bone (0.52>or=r>or=0.73, p<0.01). Similar strong correlations were also evident in both fixation methods. For parameters derived from SADR, only those including both longitudinal and transverse trabecular orientations had modest correlation with the fixation strength (0.53>or=r>or=0.71, p<0.01). The failure loads of the two fixation techniques were not significantly different (mean+/-SD=3522+/-1386 N and 3710+/-1356 N, respectively, p=0.78). However, BMD in the dual-plating group influenced the failure load significantly (p=0.03), whereas in the external fixation group this was less evident (p=0.100). The majority of bone quality parameters that correlated with fixation strength were also strongly correlated with each other, particularly the BMDs measured by DXA and pQCT. This is the first study that relates fixation strength of bicondylar tibial plateau fractures to bone quality assessed at the same anatomical site. BMD around the fracture site had the best correlation with the failure load regardless of the fixation technique. The two fixation methods tested performed equally well, and the choice between them depends on the soft tissue condition and surgeon preference.

Biomechanical Phenomena↗

PubMed2007

The use of rigid internal fixation in the surgical management of cervical spondylosis.

In the surgical management of cervical spondylosis, the application of rigid internal fixation can enhance the immediate stability of the cervical spine. The sophistication of such internal fixation systems and the indications for their use are continuously evolving. A sound understanding of regional anatomy, biomechanics, and kinematics within the cervical spine is essential for the safe and effective application of internal fixation. Numerous options currently exist for anterior cervical plating systems; some lock the screws to the plate rigidly (constrained), whereas others allow for some rotational or translational motion between the screw and plate (semiconstrained). The role of anterior fixation in single and multilevel fusions is still the subject of some controversy. Long anterior cervical reconstructions may require additional posterior fixation to reliably promote fusion. Rigid fixation in the posterior cervical spine can be achieved with lateral mass screws or pedicle screws. Although lateral mass screws provide excellent fixation within the subaxial cervical spine, the regional anatomy of C2 and C7 often make it difficult to place such screws, and pedicle screws at these levels are advocated. Pedicle screws achieve fixation into both the anterior and posterior column and are arguably the most stable form of rigid internal fixation within the cervical spine. Familiarity with these internal fixation techniques can be an extremely valuable tool for the spine surgeon managing these degenerative disorders of the cervical spine.

Cervical Vertebrae↗

PubMed1998

[Resilience of tibial transplant fixation for replacement of the anterior cruciate ligament. Interference screws vs. staples].

The endoscopic single incision technique for ACL reconstruction with a femoral half-tunnel may lead to a graft/tunnel mismatch and subsequent protrusion of the block from the tibial tunnel. The typical tibial fixation with an interference screw is not possible in these cases. Fixation with staples in a bony groove inferior to the tunnel outlet can be used as an alternative technique. Current literature does not provide biomechanical data of both fixation techniques in a human model. This study was performed to evaluate primary biomechanical parameters of this technique compared to a standard interference screw fixation of the block. 55 fresh-frozen human cadaver knee joints of a younger age (mean age: 44 years) were used. Grafts were harvested from the patellar tendon midportion with bone blocks of 25 mm length and 9 mm width. A 10 mm tibial tunnel was drilled from the anteromedial cortex to the center of the tibial insertion of the ACL. 3 different sizes of interference screws (7 x 30, 9 x 20 and 9 x 30 mm) were chosen as a standard control procedure (n = 40). For tibial bone-block fixation the graft was placed through the tunnel, the screw was then inserted on the cancellous or the cortical surface respectively. 15 knees were used for staple fixation. A groove was created inferior to the tunnel outlet with a chisel. The bone block was fixed in this groove with 2 barbed stainless steel staples. Tensile testing in both of the groups was carried out under axial load parallel to the tibial tunnel in a Zwick-testing-machine with a velocity of 1 mm/sec. Dislocation of the graft and stiffness were calculated at 175 N load. Maximum load to failure using interference screws varied between 506 and 758 N. Load to failure using staples was 588 N. Dislocation of the graft ranged between 3.6 and 4.7 mm for interference screw fixation and was 4.2 mm for staples. With both fixation techniques, the recorded failure loads were sufficient to withstand the graft loads which are to be expected during the rehabilitation period. Staple fixation of the bone block outside of the tunnel resulted in fixation strength comparable to interference screw fixation.

Adult↗

PubMed2004

The load of an implanted graft during and after fixation in anterior cruciate ligament reconstruction.

Although the importance of initial graft load has been discussed in the literature, it has not been confirmed whether a surgeon can provide the desired load to an implanted graft in anterior cruciate ligament reconstruction. The purpose of this study was to compare the set force (initial load given to the graft before fixation) and residual load in the implanted graft using three different fixation techniques. A total of ninety porcine knees were tested using bone-patellar tendon-bone autograft. Each bone-tendon-bone autograft was fixed to the tibia with either the interference-fit screw, fixation post, or button technique. Graft load was monitored during fixation procedures, and for 10 min after fixation. Residual graft load with each fixation technique exhibited unique features. Highest graft load was obtained by the interference-screw fixation technique; however, the graft was usually over-loaded beyond the intended set force with this technique. In the fixation-post technique, the load of the graft increased while the screw was retightened. The graft load in the button-fixation technique was low, probably due to slight slippage of the button. When the graft was fixed under maximum manual tension, the graft loads at completion of fixation for the interference fit screw, fixation post, and button techniques were 116.3, 54.2, and 25.9 N respectively.

Animals↗

PubMed2001

Outcomes of laparoscopic herniorrhaphy without fixation of mesh to the abdominal wall.

BACKGROUND: Recently there has been interest in performing laparoscopic herniorrhaphies without the use of staples or tacks to fix the mesh. Although mesh fixation has been linked to an increased incidence of nerve injury and involves increased operative costs, many surgeons feel that fixation is necessary to reduce the risk of hernia recurrence. This study evaluates the outcomes of laparoscopic herniorrhapies performed with and without mesh fixation at our institution. METHODS: We retrospectively evaluated our last 172 laparoscopic herniorrhaphies, which span a period of conversion from staple fixation to nonfixation of total extraperitoneal herniorrhaphies using systematic chart review and follow-up self-administered questionnaires. The outcomes assessed were the incidences of postoperative neuralgia and hernia recurrence. Adjustment for important prognostic factors was achieved using Cox regression for estimating the risk of recurrence, and multiple logistic regression for estimating the risk of neuropathic complications. RESULTS: Of 172 laparoscopic herniorrhaphies performed in 129 patients since July 1993, 105 were accomplished without mesh fixation, and 67 were performed with fixation of mesh to the abdominal wall. There were no significant differences in demographics between the two groups. A trend toward a higher incidence of neuropathic complications was observed in the mesh-fixation group (risk ratio [RR], 2.2; 95% CI, 0.5-10). A nonsignificant increased risk of hernia recurrence with fixation of mesh was observed (4.2 vs 1.6 per 100 hernia-years at risk; RR, 2.3; 95% CI, 0.4-13.10), but this finding may be associated with a selection bias with regard to giant hernia defects. CONCLUSIONS: Our data suggest that mesh fixation to the abdominal wall may be avoided in total extraperitoneal repairs without increasing the risk of hernia recurrence and neuropathic complications. The increased risk of recurrence observed with mesh fixation possibly results from selection bias. Large randomized controlled studies are needed to determine whether mesh fixation is truly related to neuropathic complications and the incidence of recurrence.

Adult↗

PubMed2002

Temporary external pedicular fixation versus definitive bony fusion: a prospective comparative study on pain relief and function.

Temporary external pedicular fixation is used as a prognostic instrument when treating degenerative conditions with spinal fusion. We studied the validity of the method and whether a functional test could improve the prognostic value of such fixation. Twenty-six patients with long-standing lumbar pain had an external temporary fixation. Pain levels were registered before fixation on a visual analogue scale at rest, as a mean for the previous week, and at seven different standardized activities. Walking capacity and walking speed for a standardized distance were also measured. Identical evaluations were then repeated during the external fixation and 1 year after definitive fusion. Based on the outcome of the temporary fixation, 20 patients were recommended for definitive surgical fusion. In six cases, the option of fusion surgery was rejected due to an unfavourable pain response or insufficient pain relief during the test fixation period, and this group was not further followed within the study. One year after surgery, 14 of 20 patients reported a good outcome. Solid bony fusion assessed by conventional radiography was seen in 19 patients. One patient with a poor clinical outcome had a pseudarthrosis. The mean values for pain level at rest, during last week and at the seven different activities in the functional test tended to decrease after fusion compared to the situation with temporary external fixation. In no activity did the external fixator overestimate the mean positive pain-relieving effect after definitive fusion. The walking capacity significantly increased, while the walking speed did not alter at the three different measurements. We conclude that with a good outcome ratio of 14 patients out of 19 having a solid fusion, the external frame improved patient selection and can be used as a valid prognostic instrument. The pain relief and function after definitive fusion can not be quantified by the external fixation, probably due to the fact that the stabilisation with an external frame is partial. The value of the functional test design presented is moderate, and an outcome evaluation comprising pain relief at rest and mean pain level during a week in fixation seems adequate.

Activities of Daily Living↗

PubMed2001

Effect of implant lengthening and mode of fixation on knee laxity after ACL reconstruction with an artificial ligament: a cadaveric study.

An "apparent" lengthening of the ligament implant, which causes an increase in knee laxity after the reconstruction of the anterior cruciate ligament (ACL) may be due to either slippage of the implant from under the fixation devices, or tunnel migration (due to bone resorption). These two mechanisms are related to the initial ligament placement, implant tensioning, and fixation modes. This cadaveric study simulates, in a controlled experimental situation, the postoperative lengthening of artificial ACL implants, and seeks to quantify the consequent increase in joint laxity. Eight cadaveric right knees, in which the Leeds-Keio artificial ligament was implanted, were tested in a specially constructed apparatus, which allowed the knee joint six degrees of freedom. In each of the tested joints the laxity was measured under several test conditions for two final fixation modes of the implant. The difference between the fixation modes was the application (as in mode B) or not (as in mode A), of a posteriorly directed force of 50 N on the tibia, at the moment of final fixation of the ligament. In both cases a tensile load of 50 N was maintained along the implant. All measurements were taken at flexion angles of 20 degrees and 90 degrees and with controlled implant lengthening of up to 3 mm in 0.5-mm increments. After implantation, adopting fixation mode B resulted in the knee exhibiting an anterior laxity considerably less than the original physiological laxity, compared with that measured after using fixation mode A. Thus at 20 degrees of knee flexion, under an anterior load of 100 N applied on the tibia, adopting fixation mode B, the joint laxity was 2.8 mm smaller than the natural laxity, whereas, for fixation mode A, it was 1.4 mm larger. At 90 degrees of knee flexion, the situation was similar, but with smaller differences. However, the situation was overturned as the implant length was increased. Thus, at 20 degrees of knee flexion, when the implant was lengthened in a range of 1--2 mm, the laxity observed with fixation mode B was similar to that recorded when the ACL was intact, whereas the laxity observed with fixation mode A was about 3--4 mm greater. Similar data were observed at 90 degrees of knee flexion. It appears that fixing the implant finally by applying a tensile load on it while simultaneously pushing the tibia posteriorly could be an effective measure against the possible return of joint laxity.

Adult↗

PubMed2005

Iliac fixation length and resistance to in-vivo stent-graft displacement.

PURPOSE: Migration of endovascular stent grafts has been related to the security of proximal device fixation to the aortic neck. This study evaluated the importance of iliac fixation in preventing longitudinal in vivo device displacement of a modular, externally supported stent graft. METHODS: Experimental ovine infrarenal aneurysms (n = 8) were treated with a fully supported, modular, bifurcated stent graft (AneuRx, Medtronic, Santa Rosa, Calif). Minimum iliac fixation length (1 cm) was used in four animals and iliac extender modules were used to achieve maximum iliac fixation in four animals. Suture anastomosis of bifurcated polyester grafts to the infrarenal aorta served as controls (n = 8). Aortic grafts were displaced in vivo by applying downward traction to a guidewire that was passed over the iliac flow divider and brought out both femoral arteries. The displacement force needed to initiate stent-graft migration was recorded and compared with the force needed to disrupt the sutured anastomosis. RESULTS: There was no difference in animal weight (88.8 +/- 2.5 kg vs 87.5 +/- 2.9 kg), aortic neck diameter (12.7 +/- 0.9 mm vs 13.4 +/- 1.1 mm), aortic neck length (23.2 +/- 0.9 mm vs 21.8 +/- 2.4 mm), experimental aneurysm size (24.7 +/- 1.1 mm vs 24.2 +/- 2.0 mm), or iliac artery diameter (9.0 +/- 1.5 mm vs 9.3 +/- 0.5 mm) among the groups. Iliac fixation length was 31.0 +/- 0.3 mm in the maximum iliac fixation group and 11 +/- 0.25 mm in the minimum fixation group (P < .0001). Peak displacement force to initiate migration was 30.2 +/- 5.5 N (range, 25 to 38) in animals with maximum iliac fixation compared with 18.1 +/- 3.7 N (range, 13 to 21) in those with minimum fixation (P = .01). The force needed to disrupt the control surgical anastomosis was 40.6 +/- 7.5 N (range, 31 to 50) (P < .01). CONCLUSIONS: Maximizing iliac fixation length increases the longitudinal in vivo force needed to displace a fully supported stent graft by 67%. This suggests that increasing iliac fixation length may reduce the long-term risk of migration in patients undergoing endovascular aneurysm repair.

Anastomosis, Surgical↗

PubMed2005

Investigation of a hybrid method of soft tissue graft fixation for anterior cruciate ligament reconstruction.

To increase knee stability following anterior cruciate ligament (ACL) reconstruction, development of increasingly stronger and stiffer fixation is required. This study assessed the initial pullout force, stiffness of fixation, and failure modes for a novel hybrid fixation method combining periosteal and direct fixation using porcine femoral bone. A soft tissue graft was secured by combining both an interference screw and an EndoButton (Smith and Nephew Endoscopy, Andover, MA). The results were compared with the traditional direct fixation method using a titanium interference screw. Twenty porcine hindlimbs were divided into two groups. Specimens were loaded in line with the bone tunnel on a materials testing machine. Maximum pullout force of the hybrid fixation (588+/-37 N) was significantly greater than with an interference screw alone (516+/-37 N). The stiffness of the hybrid fixation (52.1+/-12.8 N/mm) was similar to that of screw fixation (56.5+/-10.2 N/mm). Graft pullout was predominant for screw fixation, whereas a combination of graft pullout and graft failure was seen for hybrid fixation. These results indicate that initial pullout force of soft tissue grafts can be increased by using the suggested novel hybrid fixation method.

Animals↗

PubMed1996

Interaction of selection and recombination in the fixation of negative-epistatic genes.

We investigated the interaction of recombination and selection on the process of fixation of two linked loci with epistatic interactions in fitness. We consider both the probability of fixation of newly arising mutants (the static model) and the time to fixation under continued mutation (the dynamic model). Our results show that the fixation of a new advantageous combination is facilitated by higher fitness of the advantageous genotype and by weaker selection against the intermediate deleterious genotypes. Fixation occurs more rapidly when the recombination rates are small, except when selection against intermediate genotypes is weak and selection in favour of the double mutant is very strong. In these cases fixation is more rapid when the recombinant rate is large. Mutations of strong effects, deleterious when alone but beneficial when coupled, are fixed more easily than mutations of intermediate effects, at least for large recombination rates. Among the possible pathways the process of fixation might follow, independent substitutions lead to the fixation of the double mutant only when selection is weak. The relative importance of the other pathways depends on the interaction between recombination and selection. The coupled-gamete pathway (i.e. when the population waits until the double mutant appears and then drives it to fixation) is more important as selection intensity increases and the recombination rate is reduced. For all recombination rates, asymmetries in fitness of the intermediate genotypes increase the rate at which fixations occur. Finally, throughout the fixation process, the population will be monomorphic at least at one of the two loci for most of the time, which implies that there would be little opportunity to detect the presence of negative epistasis even if it were important for occasional evolutionary transitions.

Alleles↗

PubMed1996

Effect of intraocular lens fixation on acute intraocular pressure rise after neodymium-YAG laser capsulotomy.

Neodymium-YAG laser posterior capsulotomy is associated in some cases with an acute rise in the intraocular pressure (IOP), possibly caused by blockage of the trabecular meshwork by debris. To test the hypothesis that the IOP rise is preventable if fixation of the intraocular lens (IOL) in the capsular bag is ensured, we conducted a study comparing IOP changes at 1, 2, 3 and 24 hours after Nd:YAG capsulotomy between eyes with capsular bag-fixated, one haptic in the bag (haptic in/out) and cillary sulcus-fixated IOLs. Analysis of variance for repeated measures showed that after capsulotomy there were significant increases in IOP from baseline (p < 0.05) in both the sulcus-fixated (1, 2 and 3 hours) and haptic in/out groups (2 and 3 hours), while IOPs in the bag-fixated group did not show any significant increase. The increases in IOP in the sulcus-fixated group at 1, 2 and 3 hours after capsulotomy were significantly higher than the IOP changes at the corresponding periods in the other two groups (Kruskal-Wallis test, p < 0.01). The mean maximum IOP rise in the sulcus-fixated group (11.33 +/- 7.85 mmHg) was significantly higher than that in the haptic in/out group (3.89 +/- 7.14 mmHg) and the bag-fixated group (1.10 +/- 2.71 mmHg), while there was no difference between the latter two groups. In 57.5% of the sulcus-fixated group, 5% of the haptic in/out group and none of the eyes of the bag-fixated group the IOP rise was more than 10 mmHg. A significantly larger proportion of sulcus-fixated eyes had anterior chamber cells and capsular debris after capsulotomy (chi 2 test, p < 0.001). In the haptic in/out group significant correlation (-0.56, p = 0.009) between IOP rise at 1 hour and the percentage enclosure of the IOL by the anterior capsule was demonstrated. There was no significant difference in maximum IOP rise between glaucomatous and non-glaucomatous eyes (Mann-Whitney U-test, p = 0.49).

Acute Disease↗

PubMed2003

Biomechanical analysis of five fixation techniques used in glenohumeral arthrodesis.

BACKGROUND: The purpose of the present study is to compare five fixation techniques in shoulder fusion. The most common complications resulting from shoulder fusion, non-union and unacceptable arm position, might reflect a failure to achieve rigid fixation during the surgical procedure. METHODS: Twenty-five shoulder fusions were carried out on human cadaveric specimens using the following techniques: screw fixation, external fixation, external fixation supplemented with screw fixation, single plate fixation and double plate fixation. Each specimen was tested on a servohydraulic machine to determine stiffness. RESULTS: There was a statistically significant difference in bending and torsional stiffness between all five fixation techniques. Normalized bending (B) and torsional stiffness (T), in descending order, were: double plate (B = 1.00, T = 1.00), single plate (B = 0.77, T = 0.89), external fixation with screws (B = 0.68, T = 0.74), external fixation alone (B = 0.40, T = 0.53), and screws alone (B = 0.13, T = 0.26). CONCLUSION: The risk of the most common complications resulting from shoulder fusion might be minimized if these biomechanical findings are applied to surgical decision making.

Aged↗