Minimally invasive approach with external fixator for intra-articular calcaneal fractures in children.

ABSTRACT: Calcaneal fractures are rare in pediatric population, with more displaced intra-articular fractures encountered due to the increasing number of high-energy trauma. Operative interventions are gaining popularity because of the unsatisfactory outcomes of traditional conservative methods. This study investigated the clinical outcomes of a minimally invasive technique using the sinus tarsi approach and external fixator in the treatment of intra-articular calcaneal fractures in pediatric patients.Patients who underwent open reduction between January 2010 and January 2018 at our institute were included in this study and reviewed retrospectively. Radiological and clinical parameters were all recorded and analyzed.Overall, 29 patients were included in the study, including 23 boys and 6 girls (10.2 ±â€Š2.2 years old). The average follow-up was 29.5 months postoperatively (range, 26-72 months). Bohler angle was 15.2 ±â€Š3.3° preoperatively, and 34.0 ±â€Š3.8° postoperatively (P < .001); Gissane angle was 101.8 ±â€Š6.2 degrees preoperatively, and 129.7 ±â€Š6.2° postoperatively (P < .001). The average length of incision was 3.4 ±â€Š0.7 cm. At the last follow-up, all patients showed satisfactory clinical outcomes and the score was 90.0 ±â€Š2.3 according to American Orthopedic Foot and Ankle Society Scale.Minimally invasive approach with external fixator is an effective method for treating displaced intra-articular calcaneal fractures in pediatric patients, with a lower incidence of wound-related complications and good cosmetic outcomes.

Distal third femoral shaft fractures in school-aged children: A comparative study of elastic stable intramedullary nail and external fixator.

Internal fixation such as elastic stable intramedullary(ESIN) nail and submuscular plate (SMP) is gaining popularity for femoral shaft fractures in school-aged children. However, external fixation (ExFix) might be a valuable option for the distal third femoral shaft fractures, where the fracture heals rapidly, but it is crucial to avoid angular malunion. This study aims to compare the clinical outcomes, postoperative complications of distal third femoral shaft fractures in school-aged children treated by ESIN versus ExFix.Patients aged 5 to 11 years with distal third femoral shaft fractures treated at our institute from January 2014 to January 2016 were included and categorized into ESIN (n = 33) and ExFix (n = 38) group. The preoperative data, including baseline information of the patients, radiographic parameters, and type of surgical procedure, were collected from the hospital database, and postoperative data, including complications, were collected during the follow-up visit.In all, 33 patients (average, 8.0 ±â€Š2.1 years, male 20, female 13) in the ESIN group and 38 patients (average, 8.3 ±â€Š2.3 years, male 23, female 15) in the ExFix group were included in this study. There was significantly less operative time for the ExFix group (45.4 ±â€Š7.8 min) as compared to the ESIN group (57.8 ±â€Š11.3 min) (P < .01), reduced estimated blood loss (EBL) in the ExFix group (9.9 ±â€Š3.5) as compared to the ESIN group (16.4 ±â€Š6.5) (P < .01). As for the frequency of fluoroscopy, there was a significant difference between the ExFix group (13.9 ±â€Š2.4) and the ESIN group (15.5 ±â€Š3.2) (P = .02). The rate of major complications was not significantly different between the 2 groups (P = .19). The rate of implant irritation was significantly higher in the ExFix group (28/38, 73.7%) than the ESIN group (12/33, 36.4%) (P < .01). The rate of surgical site infection (SSI) is significantly higher in the ExFix group (18/38, 47.4%)) than the ESIN group (1/33, 3%) (P < .01). The rate of scar concern was significantly higher in the ExFix (9/38, 23.7%) than the ESIN (2/33, 6.1%), (P = .04). According to the Flynn scoring system, 30(90.9%) patients in the ESIN group and 24(89.5%) patients in the ExFix group were rated as excellent. None of the patients had poor outcomes.Both ESIN and ExFix produced satisfactory outcomes in distal third femoral shaft fractures. ExFix remains a viable choice for selected cases, especially in resource-challenged and austere settings.

The Anterior Subcutaneous Pelvic Ring Fixator: No Biomechanical Advantages Compared with External Fixation.

BACKGROUND: Subcutaneous fixation of the anterior pelvic ring is an emerging surgical technique for trauma patients. The aim of this study was to biomechanically evaluate 2 internal fixation devices for stabilizing a disrupted pelvic ring and compare them with traditional external fixation. METHODS: Thirty-six synthetic pelvises with a simulated unstable ring fracture (anteroposterior compression type III) were divided into 3 groups. Group A underwent fixation with a supra-acetabular external fixator; group B, with an internal fixator using the USS II polyaxial system; and group C, with an internal fixator using the Click'X polyaxial system. Biomechanical testing included measurement of peak-to-peak displacement at 300, 400, and 500 N; total displacement; plastic deformation; stiffness; and fracture-line displacement. RESULTS: Statistical analysis of all measured parameters revealed no significant differences among the groups. However, vertical displacement of the preshaped connecting rod within the screw heads occurred as a result of inadequate stability of the internal fixation at the rod-screw interface. CONCLUSIONS: Although internal fixator devices are placed close to the bone and should therefore maintain greater stiffness, our data did not support the hypothesis of superior stability. Special attention is required when using a curved connecting rod as the rod is easily displaced, placing relevant anatomical structures at risk. These devices require further refinement to avoid potential patient injury.

Simultaneous lateral column shortening along with differential distraction by Joshi's external stabilization system for rigid neglected clubfoot correction.

Correction of rigid clubfoot in an older child by gradual differential distraction using the Ilizarov's device or Joshi's external stabilization system (JESS) is a time-consuming procedure. We simultaneously combined the lateral column shortening by cuboid wedge resection along with the differential distraction by application of JESS fixator for the treatment of severe, rigid, neglected, or relapsed congenital talipes equinovarus (CTEV) foot deformity in 30 feet in 18 children with mean age of 5.3 years and mean follow-up of 27.6 months. The mean pretreatment Pirani score was 5.3 which improved to mean Pirani score after treatment of 1.4. Excellent results were obtained in 22 (71.33%) feet, good results in four (13.33%) feet, and poor results in four (13.33%) feet. The average period for distraction in our series was 6.3 weeks, and total average period of fixator in place was 11.2 weeks. To conclude, lateral column shortening with JESS application simultaneously gives early good to excellent short-term results, and the combination of techniques permits rapid correction of deformity, and thus reducing the time for which the fixator is in place and hence has better acceptance by the patient.

Standards for external fixation application: national survey under the auspices of the German Trauma Society.

INTRODUCTION: External fixation is widely accepted as a provisional or sometimes definitive treatment for long-bone fractures. Indications include but are not limited to damage control surgery in poly-traumatized patients as well as provisional bridging to definite treatment with soft tissue at risk. As little is known about surgeon's habits in applying this treatment strategy, we performed a national survey. METHODS: We utilized the member database of the German Trauma Society (DGU). The questionnaire encompassed 15 questions that addresses topics including participants' position, experience, workplace, and questions regarding specifics of external fixation application in different anatomical regions. Furthermore, we compared differences between trauma centre levels and surgeon-related factors. RESULTS: The participants predominantly worked in level 1 trauma centres (42.7%) and were employed as attendings (54.7%). There was widespread consensus for planning and intra-operative radiographical control of external fixation. Surgeons appointed at a level I trauma centre preferred significantly more often supra-acetabular pin placement in external fixation of the pelvis rather than the utilization of iliac pins (75.8%, p = 0.0001). Moreover, they were more likely to favor a mini-open approach to insert humeral pins (42.4%, p = 0.003). Overall, blunt dissection and mini-open approaches seemed equally popular (38.2 and 34.1%). Department chairmen indicated more often than their colleagues to follow written pin-care protocols for minimization of infection (16.7%, p = 0.003). CONCLUSION: Despite the fact that external fixation usage is widespread and well established among trauma surgeons in Germany, there are substantial differences in the method of application.

A web-based survey to identify current practice in skeletal pin site management.

Infections associated with percutaneous pins and wires are common complications which can have a significant impact on patient outcomes. A survey was undertaken to identify current practice and gain insight into variations of clinical practice. Invitations were sent by email to complete an electronic questionnaire using SurveyMonkey. The survey was left open for 100 days. The single largest group of respondents (37.4%, n = 120) cleansed pin sites daily, with significant differences identified between medical and nursing professions (P = 0.02), and country of practice (P < 0.001). Significant differences were also identified in the use of different cleansing solutions between medical and nursing professions (P < 0.001) and country (P < 0.001). The majority group preferences were saline 30% (n = 96) and alcoholic chlorhexidine 29.6% (n = 95). Pin site crusts were routinely removed by 57.9% (n = 186). Pin sites were left exposed by 50.3% (n = 160). Dry gauze was identified as the most common dressing used to dress pin sites, however, substantial variation was identified in the types of dressings used. Compression was not routinely applied to pin sites by 51.6% (n = 165). There remains considerable diversity of practice when caring for pin sites. Further research is required to identify the most effective methods in preventing pin site infection.

The effect of 'Out of hours surgery Service' in Israel on hip fracture fixation outcomes: a retrospective analysis.

BACKGROUND: 'Out of Hours Surgery Service' (OHSS) was implemented in Israel, amongst other reasons, in order to reduce the time interval between hospital admission and surgery and consequently improve outcomes. The OHSS is currently operated in the public hospitals in Israel. In this study we compared the data of patients before and after OHSS implementation to determine its efficacy in improving patient care. METHODS: This is a retrospective observational study of 792 adult patients who underwent hip fracture surgery between 2002 and 2007 in a single hospital. The study population included two groups: patients that were operated before the implementation of the OHSS (2002-2004) and after the implementation of the OHSS (2005-2007). Data regarding all patients was collected using the institution's computer program. The following variables were analyzed: patients' demographics, time interval from hospitalization to surgery, causes for delaying surgery, post-operative length of hospitalization and mortality. RESULTS: Patients in the post-OHSS group had more illnesses and higher ASA classification than those in the pre-OHSS group. The post-OHSS group had a significantly decreased length of stay in the hospital before and after the surgery. After adjusting for ASA score and age, the post-OHSS group was found to have decreased post-operative hospitalization and lower post-operative mortality. Surgery was delayed in pre-OHSS period mainly due to operating rooms unavailability. CONCLUSION: Implementation of OHSS facilitated operating room availability, thus early operation and reduced post-operative mortality. In accordance with other studies, patient's outcome is greatly influenced by the time from admission to hip fracture surgery.

The Effect of Insertion Technique on Temperatures for Standard and Self-Drilling External Fixation Pins.

OBJECTIVES: No studies have assessed the effects of parameters associated with insertion temperature in modern self-drilling external fixation pins. The current study assessed how varying the presence of irrigation, insertion speed, and force impacted the insertion temperatures of 2 types of standard and self-drilling external fixation half pins. METHODS: Seventy tests were conducted with 10 trials for 4 conditions on self-drilling pins, and 3 conditions for standard pins. Each test used a thermocouple inside the pin to measure temperature rise during insertion. RESULTS: Adding irrigation to the standard pin insertion significantly lowered the maximum temperature (P <0.001). Lowering the applied force for the standard pin did not have a significant change in temperature rise. Applying irrigation during the self-drilling pin tests dropped average rise in temperature from 151.3 ± 21.6°C to 124.1 ± 15.3°C (P = 0.005). When the self-drilling pin insertion was decreased considerably from 360 to 60 rpm, the temperature decreased significantly from 151.3 ± 21.6°C to 109.6 ± 14.0°C (P <0.001). When the force applied increased significantly, the corresponding self-drilling pin temperature increase was not significant. CONCLUSIONS: The standard pin had lower peak temperatures than the self-drilling pin for all conditions. Moreover, slowing down the insertion speed and adding irrigation helped mitigate the temperature increase of both pin types during insertion.

Improving Spanning-Knee External Fixator Stiffness: A Biomechanical Study.

The purpose of this study was to test and compare external fixator construct stiffness using pin-to-bar clamps or multipin clamps across 2 external fixation systems. Constructs were tested with 8-mm and 11-mm-diameter bar systems and pin-to-bar or multipin clamps. Three construct designs were tested: construct 1 with a single crossbar and pin-to-bar clamps, construct 2 with 2 crossbars and pin-to-bar clamps, and construct 3 with 2 crossbars and multipin clamps. The stiffness of each construct (N = 24) was tested using anterior-posterior bending. Two crossbars and pin-to-bar clamps resulted in the highest mean stiffness. Constructs with a single crossbar and pin-to-bar clamps had a similar average stiffness compared with constructs with 2 crossbars and multipin clamps. Pin-to-bar clamps with 2 crossbars result in stronger spanning-knee external fixators than constructs using multipin clamps.

In vitro biomechanical testing of different configurations of acrylic external skeletal fixator constructs.

OBJECTIVE: To evaluate the in vitro biomechanical properties of four different configurations of acrylic external skeletal fixator constructs. MATERIALS AND METHODS: Simulated bone constructs were prepared using two segments of 20 mm ultra-high-density polyethylene rods with a gap of 5 mm. The full pins (1.5 mm) were passed through the proximal and distal segments of ultra-high-density polyethylene rods, in the same plane, parallel to each other in configuration U, and were crossed in the M1, M2 and C configurations at a 90° angle to each other. Configuration U was a single bilateral uniplanar construct, M1 was a double orthogonal bilateral construct, M2 was a double orthogonal bilateral construct with proximal and distal connecting articulations, and C was a double orthogonal bilateral construct with proximal and distal circumferential articulations. Temporary scaffolds of different external skeletal fixator configurations were constructed using commercially available polyvinyl chloride pipes (20 mm) connected and secured to the fixation pins at a fixed distance from the rods. Acrylic powder (polymer) mixed with liquid (monomer) was poured into the pipes and allowed to solidify to form the side bars and rings. The external skeletal fixator constructs were then subjected to axial compression, cranio-caudal three-point bending and torsion (n = 4 each) using a universal testing machine. Mechanical parameters, namely stress, strain, modulus of elasticity, stiffness and bending moment of fixator constructs, were determined from load-displacement curves. RESULTS: Configuration U was the weakest and configuration C was the strongest under all the testing modes. Under compression, the M1, M2 and C configurations were similar. Under bending, a significant difference was observed among the uniplanar, multiplanar and circular configurations with no difference between M1 and M2. However, under torsion, all the external skeletal fixator configurations differed significantly. CLINICAL SIGNIFICANCE: The freeform external skeletal fixator using acrylic as a replacement for a metallic bar may be useful to treat bone fractures and luxations in small animals, as it is mechanically strong, lightweight, economical, and pins can be passed from any direction depending upon the clinical situation.

Axial stiffness and ring deformation of complete and incomplete single ring circular external skeletal fixator constructs.

OBJECTIVE: To compare the axial stiffness, maximum axial displacement, and ring deformation during axial loading of single complete and incomplete circular (ring) external skeletal fixator constructs. SAMPLE: 32 groups of single ring constructs (5 constructs/group). PROCEDURES: Single ring constructs assembled with 2 divergent 1.6-mm-diameter Kirschner wires were used to stabilize a 60-mm-long segment of 16-mm-diameter acetyl resin rod. Construct variables included ring type (complete or incomplete), ring diameter (50, 66, 84, or 118 mm), and fixation wire tension (0, 30, 60, or 90 kg). Axial loading was performed with a materials testing system. Construct secant stiffness and maximum displacement were calculated from the load-displacement curves generated for each construct. Ring deformation was calculated by comparing ring diameter during and after construct loading to ring diameter prior to testing. RESULTS: Complete ring constructs had greater axial stiffness than did the 66-, 84-, and 118-mm-diameter incomplete ring constructs. As fixation wire tension increased, construct stiffness increased in the 66-, 84-, and 118-mm-diameter incomplete ring constructs. Maximum axial displacement decreased with increasing fixation wire tension, and complete ring constructs allowed less displacement than did incomplete ring constructs. Incomplete rings were deformed by wire tensioning and construct loading. CONCLUSIONS AND CLINICAL RELEVANCE: Mechanical performance of the 66-, 84-, and 118-mm-diameter incomplete ring constructs improved when wire tension was applied, but these constructs were not as stiff as and allowed greater displacement than did complete ring constructs of comparable diameter. For clinical practice, tensioning the wires placed on 84- and 118-mm-diameter incomplete rings to 60 kg is recommended.

Biomechanical stability of a supra-acetabular pedicle screw internal fixation device (INFIX) vs external fixation and plates for vertically unstable pelvic fractures.

BACKGROUND: We have recently developed a subcutaneous anterior pelvic fixation technique (INFIX). This internal fixator permits patients to sit, roll over in bed and lie on their sides without the cumbersome external appliances or their complications. The purpose of this study was to evaluate the biomechanical stability of this novel supraacetabular pedicle screw internal fixation construct (INFIX) and compare it to standard internal fixation and external fixation techniques in a single stance pelvic fracture model. METHODS: Nine synthetic pelves with a simulated anterior posterior compression type III injury were placed into three groups (External Fixator, INFIX and Internal Fixation). Displacement, total axial stiffness, and the stiffness at the pubic symphysis and SI joint were calculated. Displacement and stiffness were compared by ANOVA with a Bonferroni adjustment for multiple comparisons RESULTS: The mean displacement at the pubic symphysis was 20, 9 and 0.8 mm for external fixation, INFIX and internal fixation, respectively. Plate fixation was significantly stiffer than the INFIX and external Fixator (P = 0.01) at the symphysis pubis. The INFIX device was significantly stiffer than external fixation (P = 0.017) at the symphysis pubis. There was no significant difference in SI joint displacement between any of the groups. CONCLUSIONS: Anterior plate fixation is stiffer than both the INFIX and external fixation in single stance pelvic fracture model. The INFIX was stiffer than external fixation for both overall axial stiffness, and stiffness at the pubic symphysis. Combined with the presumed benefit of minimizing the complications associated with external fixation, the INFIX may be a more preferable option for temporary anterior pelvic fixation in situations where external fixation may have otherwise been used.

Design, characterisation and in vivo testing of a new, adjustable stiffness, external fixator for the rat femur.

Very little is known about the influence of the mechanical environment on the healing of large segmental defects. This partly reflects the lack of standardised, well characterised technologies to enable such studies. Here we report the design, construction and characterisation of a novel external fixator for use in conjunction with rat femoral defects. This device not only imposes a predetermined axial stiffness on the lesion, but also enables the stiffness to be changed during the healing process. The main frame of the fixator consists of polyethylethylketone with titanium alloy mounting pins. The stiffness of the fixator is determined by interchangeable connection elements of different thicknesses. Fixators were shown to stabilise 5 mm femoral defects in rats in vivo for at least 8 weeks during unrestricted cage activity. No distortion or infections, including pin infections, were noted. The healing process was simulated in vitro by inserting into a 5 mm femoral defect, materials whose Young's moduli approximated those of the different tissues present in regenerating bone. These studies confirmed that, although the external fixator is the major determinant of axial stiffness during the early phase of healing, the regenerate within the lesion subsequently dominates this property. There is much clinical interest in altering the mechanics of the defect to enhance bone healing. Our data suggest that, if alteration of the mechanical environment is to be used to modulate the healing of large segmental defects, this needs to be performed before the tissue properties become dominant.

Management of chronic atlantoaxial rotatory fixation.

STUDY DESIGN: Retrospective case series of chronic atlantoaxial rotatory fixation (AARF) treated by a novel closed reduction method (remodeling therapy) and review of the literature. OBJECTIVE: To describe clinical features of chronic AARF and the rationale of the remodeling therapy. SUMMARY OF BACKGROUND DATA: Treatment strategy for chronic recurrent AARF remains controversial. Posterior C1-C2 arthrodesis has been widely used for recurrent unstable AARFs after the closed reduction, and a variety of posterior fusion techniques have been advocated. In contrast, several investigators reported a chronic AARF case treated by a simple traction or closed reduction followed by cervical immobilization. Previously, we have found that a deformity of the superior C2 facet joint (C2 facet deformity) on three dimensional computed tomography (3D CT) reconstructions is a risk factor for recurrent subluxation. In addition, the remodeling of this C2 facet deformity by careful closed manipulation followed by halo fixation (remodeling therapy) could prevent the recurrence of subluxation. METHODS: Twelve children with chronic AARF who sustained torticollis for an average of 4.4 months after the onset were referred to our clinic. The mean age at the initial visit was 7.8 years. All patients underwent the remodeling therapy as reported previously. Radiographic findings and clinical courses were retrospectively reviewed. Treatment methodology, pearls, and pitfalls of the remodeling therapy were discussed with review of the literature. RESULTS: 3D CT images before reduction revealed persistent atlantoaxial subluxation and the C2 facet deformity in the dislocated side in all cases. Follow-up 3D CT scans demonstrated the remodeling of the C2 facet deformity at an average of 2.4 months after successful reduction of subluxation. Neither recurrence of symptoms nor subluxation was observed at a mean follow-up of 42 months in any case. The cervical range of motion was 73.9° at the dislocated and 83.5° at the contra-dislocated side from the midline. CONCLUSION: Chronic irreducible and recurrent unstable AARF should be initially managed by remodeling therapy using the facet deformity sign as a clinical index, if the C1 and C2 have not been osseously fused.

The impact of halo-gravity traction on curve rigidity and pulmonary function in the treatment of severe and rigid scoliosis and kyphoscoliosis: a clinical study and narrative review of the literature.

INTRODUCTION: The treatment of rigid and severe scoliosis and kyphoscoliosis is a surgical challenge. Presurgical halo-gravity traction (HGT) achieves an increase in curve flexibility, a reduction in neurologic risks through gradual traction on a chronically tethered cord and an improvement in preoperative pulmonary function. However, little is known with respect to the ideal indications for HGT, its appropriate duration, or its efficacy in the treatment of rigid deformities. MATERIALS AND METHODS: To investigate the use of HGT in severe deformities, we performed a retrospective review of 45 patients who had severe and rigid scoliosis or kyphoscoliosis. The analysis focused on the impact of HGT on curve flexibility, pulmonary function tests (PFTs), complications and surgical outcomes in a single spine centre. RESULTS: PFTs were used to assess the predicted forced vital capacity (FVC%). The mean age of the sample was 24±14 years. 39 patients had rigid kyphoscoliosis, and 6 had scoliosis. The mean apical rotation was 3.6°±1.4°, according to the Nash and Moe grading system. The curve apices were mainly in the thoracic spine. HGT was used preoperatively in all the patients. The mean preoperative scoliosis was 106.1°±34.5°, and the mean kyphosis was 90.7°±29.7°. The instrumentation used included hybrids and pedicle screw-based constructs. In 18 patients (40%), a posterior concave thoracoplasty was performed. Preoperative PFT data were obtained for all the patients, and 24 patients had ≥3 assessments during the HGT. The difference between the first and the final PFTs during the HGT averaged 7.0±8.2% (p<.001). Concerning the evolution of pulmonary function, 30 patients had complete data sets, with the final PFT performed, on average, 24 months after the index surgery. The mean preoperative FVC% in these patients was 47.2±18%, and the FVC% at follow-up was 44.5±17% (a difference that did not reach statistical significance). The preoperative FVC% was highly predictive of the follow-up FVC% and the response during HGT. The mean flexibility of the scoliosis curve during HGT was only 14.8±11.4%, which was not significantly different from the flexibility measures achieved on bending radiographs or Cotrel traction radiographs. In rigid curves, the Cobb angle difference between the first and final radiographs during HGT was only 8°±9° for scoliosis and 7°±12° for kyphosis. Concerning surgical outcomes, 13 patients (28.9%) experienced minor and 15 (33.3%) experienced major complications. No permanent neurologic deficits or deaths occurred. Additional surgery was indicated in 12 patients (26.7%), including 7 rib-hump resections. At the final evaluation, 69% of the patients had improved coronal balance, and at a mean follow-up of 33±23.3 months, 39 patients (86.7%) were either satisfied or very satisfied with the overall outcome. CONCLUSION: The improvement of pulmonary function and the restoration of sagittal and coronal balance are the main goals in the treatment of severe and rigid scoliosis and kyphoscoliosis. A review of the literature showed that HGT is a useful tool for selected patients. Preoperative HGT is indicated in severe curves with moderate to severe pulmonary compromise. HGT should not be expected to significantly improve severe curves without a prior anterior and/or posterior release. The data presented in this study can be used in future studies to compare the surgical and pulmonary outcomes of severe and rigid deformities.

Can the carbon fiber rods for the Hoffmann II external fixation system be reused?

The Hoffman II External Fixator is the external fixation system used by the United States Army during Operation Iraqi Freedom (OIF) and Operation Enduring Freedom (OEF). To our knowledge, there have been no studies comparing the bending strength or stiffness of new to used or reprocessed rods. The purpose of our study was to determine if there was any difference in bending strength or stiffness of these rods. Used rods were obtained from soldiers serving in OIF/OEF. The bending strength and stiffness of these rods was determined using 4-point bending. The location of rod failure was noted. Testing conditions simulated those utilized by the manufacturer for release of new rods. There was no statistically significant difference in bending strength. There was a 6% difference in bending stiffness between new and used rods. Thirteen total used/refurbished rods broke at locations of previous clamping, the remainder breaking at one of the loading points on the testing jig. The difference in bending stiffness among new, reprocessed, and used rods was only 6%. The clinical significance of this is unknown. There was no difference amongst the groups in bending strength. Rods recovered from soldiers serving in OIF/OEF appear to be safe for reuse.

The influence of a weight-bearing platform on the mechanical behavior of two Ilizarov ring fixators: tensioned wires vs. half-pins.

BACKGROUND: A weight-bearing platform applied at the distal end of an Ilizarov external frame allows patients with hindfoot transfixations, foot deformities or plantar skin lesions to bear weight. This leads to an indirect loading of the fracture or osteotomy site. However, the effect on the fracture/osteotomy site's motion or compressive loads is unknown. The aim of this study was to analyze the mechanical effects of a weight-bearing platform on the traditional all-wire, four-ring frame in comparison to a two-ring frame consisting of half-pins. METHODS: Two frame configurations, with either anatomically positioned wires or half-pins, were analyzed with and without a weight-bearing platform applied underneath the distal ring. Composite tibiae with a mid-diaphyseal osteotomy of 3.5 mm were used in all the experiments. An axial load was applied with the use of a universal test machine (UTS®). Interfragmentary movements, the relative movements of bone fragments and movements between rings were recorded using displacement transducers. Compressive loads at the osteotomy site were recorded with loading cells. RESULTS: Indirect loading with a weight-bearing platform altered the force transmission through the osteotomy. Indirect loading of the tibiae decreased the extent of the axial micro-motion by 50% under the applied weight load when compared to direct weight loading (p < 0.05). The half pin frame was 25% stiffer than the wire frame under both direct and indirect loading of the tibiae (p < 0.05). Compressive loads under indirect loading were reduced by 67% in the wire frame and by 57% in the half-pin frames compared to direct loading of the bones (p < 0.05). While axial loading in the wire frames resulted in plain axial movements at the site of the osteotomy, it was coupled with translational movements and angular displacements in the half pin mountings. This effect was more apparent in the case of indirect loading. CONCLUSIONS: A weight-bearing platform has substantial influence on the biomechanical performance of an Ilizarov external fixator. Half-pins induce greater stiffness to the Ilizarov external fixator and allow the usage of only one ring per bone segment, but shear stresses at the osteotomy under axial loading should be considered. The results allow an estimation of the size and direction of interfragmentary movements based on the extent of weight bearing.