Distal locking of short cephalomedullary nails decreases varus collapse in unstable intertrochanteric fractures – a biomechanical analysis

IntroductionPeritrochanteric fractures are a growing problem and complications relating to operative fixation of these fracture, including varus collapse and screw cutout, are common in elderly osteoporotic patients. We hypothesize that unlocked nails will demonstrate increased varus collapse and inferior construct stiffness in specimens with increased diaphyseal medullary diameter.Materials and methodsSixteen non-cadaveric osteoporotic biomechanical femur specimens were utilized in this study, with eight specimens having an artificially large femoral canal to represent Dorr C femurs. All femurs were instrumented with a short cephalomedullary nail with and without distal cross-lock screw fixation and had an unstable intertrochanteric fracture created in a repeatable pattern. Specimens underwent cyclic compression to a maximal load of 1000N with segmental motion quantified through the use of visual tracking markers. Statistical comparisons were performed using one-way ANOVA with Tukey post-hoc analysis to determine differences between specific groups. Significance was defined as p<0.05.ResultsUnlocked short cephalomedullary nails showed increased varus collapse due to motion of the nail within the femoral canal in capacious femoral canals compared with narrow femoral canals and distally cross-locked nails. The coronal deformation of the wide canal unlocked group (17.9 ^o±2.6^o) was significantly greater in the varus direction than any other fixation under compressive load of 1000N. There was no significant difference in varus angulation between the wide canal or narrow canal locked groups (11.1^o±8.7^o vs. 8.2^o±1.7^o respectively, p=0.267). The narrow canal unlocked group (13.7^o±2.4^o) showed significantly greater varus angulation than the narrow canal locked (p=0.015). The wide canal unlocked group showed significantly greater varus angulation than the wide canal locked group (p=0.003). Motion between the femoral shaft and the cephalomedullary nail (toggling of the nail within the shaft) was significantly greater in narrow or wide canal unlocked specimens, 7.94^o±2.13^o and 10.2^o±1.7^o respectively, than in the narrow or wide canal locked specimens, 2.4^o±0.2^o and 4.2^o±0.5^o respectively (p<0.05)ConclusionUnlocked short intramedullary fixation for unstable peritrochanteric fractures results in increased varus collapse under axial compression. This study supports the use of distal cross-locking of short intramedullary fixation for unstable peritrochanteric fractures in patients with capacious femoral canals secondary to osteoporosis who might otherwise be as risk for varus collapse, device failure, and malunion.     

Biomechanical analysis of fracture fixation with external fixator in vivo

Objective: To investigate the different ways of measuring the main axial strain during treatment with an external fixator and to find the suitable compression loaded by the external fixator at an early stage. Methods: Eighteen healthy big-ear rabbits were randomly divided into two groups according to different measuring methods: Group A and Group B. In Group A, a strain gauge was affixed to the external tibial cortex with 502 glue, and in Group B, a bone cement-coated strain gauge was installed on the internal tibial cortex. Groups A and B were divided into two subgroups A1, A2 and B1, B2, respectively, according to the pressure of half of and the same as the body weight. A Z-shaped left mid-shaft tibial osteotomy was performed and fixed by an external fixator. Results: The sealer curves of Group A changed dramatically during the early stage. The trendlines of the internal and external cortex went consistently after reaching the stable stage while the latter strain value was higher than the former. The time for Group B reaching the stable stage was short, but its absolute strain value was less than that of Group A. Before they were pressed to the stable stage, the declined speed of Subgroup A1 was more slowly than that of Subgroup A2 while the results of Subgroups Bl and B2 were same. Group A had an ascending trend after it declined while Group B didn' t have. After they reached the stable stage, both Subgroups Al and A2 had a declining trend while Subgroup A2 was more quickly than Subgroup A1, Subgroup Bl was kept at a definite level while Subgroup B2 fluctuated. Conclusions: The axial strain under external fixator can be measured by bone cement coated-strain gauge in vivo. The data may suggest that half of the body weight load was suitable for external fixator.     

Biomechanical analysis of dual versus lateral locked plating in elderly bicondylar tibial plateau fractures: Does medial comminution matter?

ObjectiveTo assess dual plating versus lateral locked plate fixation of bicondylar tibial plateau fractures in an elderly cadaveric model with and without medial bone lossParticipants10 pairs of elderly (range 78–93 years of age) fresh frozen tibias.InterventionBicondylar tibial plateau fractures were created reproducing AO/OTA 41 C1 (without medial bone loss) and C2 fractures (with medial bone loss). Cadavers were randomized to 4 different groups. Groups 1 and 2 were 41 C1 fractures and fixated with either dual or lateral plating, respectively. Groups 3 and 4 were fixated in a similar fashion with medial metaphyseal bone loss (41 C2 fracture) with dual plating Group 3 and lateral plating group 4. Lateral plating consisted of a 3.5 mm 5-hole lateral plate (ALPS, ZimmerBiomet) with 6 bicortical locking screws proximally and two diaphyseal screws. Dual plating groups underwent lateral plating and additional 3.5 mm 5-hole posteromedial 1/3 tubular plate (ZimmerBiomet) placed at the apex of the fracture with two shaft screws and one unicortical screw proximally. Specimens were tested in a Mechanical Testing System (MTS) machine loading both condyles.Outcome measurementsSpecimens were loaded to 300 N and coronal alignment obtained. Specimens were then cycled from 100 N to 700 N for 5000 cycles at 2 Hz. Average axial displacement, maximal displacement, average force and coronal alignment after 5000 cycles were recorded. Lastly, force to failure was recorded at 100 N/sec.ResultsMean axial displacement was 4.21 mm ranging from 3.12 mm in group 1 to 5.92 mm in group 4 (P = 0.51). Failure force averaged 3340 N ranging from 4342 N in group 1 to 2433 N in group 4 (P = 0.36). Maximal displacement ranged from 3.69 mm in group 1 to 7.37 mm in group 4 (P = 0.21). Change in coronal alignment ranged from 0.98° in group 1 to 1.97° in group 4 (P = 0.45). No statistically significant difference was noted between all four groups for all data points.ConclusionThe results of this study demonstrate that a lateral locked plate may offer an alternative means of fixation in AO/OTA 41 C1 and C2 fractures.     

Use of Ganga Hospital Open Injury Severity Scoring for determination of salvage versus amputation in open type IIIB injuries of lower limbs in children—An analysis of 52 type IIIB open fractures

Introduction and aimsOpen injuries in children are rare compared to adults. In children with major open injuries, there is no specific scoring system to guide when to amputate or salvage the limb. The use of available adult scoring systems may lead to errors in management. The role of Ganga Hospital Open Injury Severity Scoring (GHOISS) for open injuries in adults is well established and its applicability for pediatric open injuries has not been studied. This study was done to analyse the usefulness of GHOISS in pediatric open injuries and to compare it with MESS(Mangled Extremity Severity Score).MethodsAll children (0–18 years) who were admitted with Open type IIIB injuries of lower limbs between January 2008 and March 2015 were included. MESS and GHOISS were calculated for all the patients. There were 50 children with 52 type IIIB Open injuries of which 39 had open tibial fractures and 13 had open femur fractures.ResultsOut of 52 type IIIB open injuries, 48 were salvaged and 4 were amputated. A MESS score of 7 and above had sensitivity of 25% for amputation while GHOISS of 17 and above was found to be more accurate for determining amputation with sensitivity of 75% and specificity of 93.75%.ConclusionGHOISS is a reliable predictor of injury severity in type IIIB open fractures in children and can be used as a guide for decision-making. The use of MESS score in children has a lower predictive value compared to GHOISS in deciding amputation versus salvage. A GHOISS of 17 or more has the highest sensitivity and specificity to predict amputation.     

Correlative analysis of the results of surgical treatment of thoracolumbar injuries with long Texas Scottish rite hospital construct: is the use of pedicle screws versus hooks advantageous in the lumbar spine?

This is a prospective, randomized study to compare the efficacy of two similar "long-segment" Texas Scottish Rite Hospital instrumentations with the use of hooks in the thoracic spine and pedicle screws versus laminar hook claw in the lumbar spine for thoracolumbar A3, B, and C injuries. Forty consecutive patients with such thoracolumbar fractures (T11-L1) associated with spinal canal encroachment underwent early operative postural reduction and stabilization. The patients were randomly sampled into two groups: Twenty patients received hooks in "claw configuration" in both the thoracic and the lumbar spine (group A), and 20 patients received hooks in the thoracic vertebrae and pedicle screws in the lumbar vertebrae (group B). Pre- and postoperative plain roentgenograms and computed tomography scans were used to evaluate any changes in Gardner post-traumatic kyphotic deformity, anterior and posterior vertebral body height at the fracture level, and spinal canal clearance (SCC). All patients were followed for an average period of 52 months (range 42-71 months). The correction of anterior vertebral body height was significantly more (P < 0.01) in the spines of group B (33%) than in group A (16%), with a subsequent 11% loss of correction at the latest evaluation in group A and no loss of correction in group B. There were no significant differences in the changes of posterior vertebral body height and Gardner angle between the two groups. The SCC was significantly more (P < 0.05) immediately postoperatively in the spine of group B (32%) than in group A (19%). In the latest evaluation, there was a 9% loss of the immediately postoperatively achieved SCC in group A, while SCC was furthermore increased at 10.5% in group B. All patients with incomplete neurologic lesions in groups A and B were postoperatively improved at 1.1 and 1.7 levels, respectively. There were two hook dislodgements in the thoracic spine, one in each group, while there was no screw failure in group B. There was neither pseudarthrosis nor neurologic deterioration following surgery. Visual Analog Pain Scale and Short Form-36 scores were equally improved and did not differ between the two groups. The use of pedicle screws in the lumbar spine to stabilize the lowermost end of a long rigid construct applied for A3, B, and C thoracolumbar injuries was advantageous when compared with that using hook claws in the lumbar spine because the constructs with screws restored and maintained the fractured anterior vertebral body height better than the hooks without subsequent loss of correction and safeguarded postoperatively a continuous SCC at the injury level.