Primary Closure of External Fixator Pin Sites Is Safe After Orthopaedic Trauma Surgery.

OBJECTIVES: To determine if rates of pin site infection and surgical site infection among patients managed with primary closure after external fixator removal were similar to those allowed to heal secondarily. DESIGN: Retrospective cohort. SETTING: Urban/Suburban Academic Level I Trauma Center. PATIENT SELECTION CRITERIA: Patients who had received a lower extremity external fixator for provisional management before definitive fixation of lower extremity fractures were included with pin site wounds closed primarily or allowed to heal by secondary intention. OUTCOME MEASURES AND COMPARISONS: The rate of pin tract infection and surgical site infection following primary closure of external fixator pin sites relative to patients whose pin sites were allowed to heal through secondary intention. RESULTS: In total, 256 patients were evaluated: 143 patients (406 pin sites) in the primary closure group and 113 patients (340 in sites) in the secondary closure group. The average age was 49 ± 16 years. Sixty-five percent of included patients were male. There was no difference in pin tract infections between cohorts (primary = 0.5%, secondary = 1.5%, P = 0.26). External fixator duration in the primary closure group was 11.5 ± 8.4 days and 13.0 ± 8.1 days in the secondary closure group (P = 0.15). There was a greater rate of surgical site infections in the secondary intention cohort (15.9% vs. 7.7%, P = 0.047). CONCLUSIONS: There was no difference in pin site infection rate after primary pin site closure relative to patients who were allowed to heal through secondary intention. Furthermore, there was a lower rate of surgical site infection after primary closure. These results challenge the dogma of secondary closure for ex fix pin sites, suggesting that debridement and primary closure is a safe option for management of external fixator pin sites and may impart benefit in decreasing infection risk. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

[Design and Testing of a Pressure Measurement and Adjustment Device for Fracture Ends].

Objective: To design and test a device which is capable of accurately measuring and dynamically adjusting the axial pressure at the fracture end in real-time. Methods: Upon completion of the design, the pressure measurement and adjustment device was implemented in a canine tibial fracture external fixation model. A pressure sensor was mounted at the fracture end, and the displayed values of the pressure sensor were used as the standard for comparison. The relationship between the displayed values of the measurement and adjustment device and the pressure sensor under identical conditions was examined. Results: The device was utilized in external fixation models of tibial fractures in five beagles. A linear correlation was observed between the displayed values of the device and the pressure sensor at the fracture end. The measurement values from the device could be transformed into fracture end pressure through the application of coefficients, thereby facilitating accurate measurement and dynamic adjustment of the fracture end pressure. Conclusion: The pressure measurement and adjustment device at the fracture end is easy to operate, enabling precise measurement and dynamic regulation of the pressure at the fracture end. It is well-suited for animal experiments aimed at investigating the impact of axial compression on fracture healing, demonstrating promising potential for experimental applications.

3D printing feasibility of a controlled dynamization device for external circular fixation.

AIM: to assess the small-scale 3D printing feasibility and cost estimation of a device for controlled dynamization. MATERIALS AND METHOD: The two-part device previously developed by our research group was printed with a carbon fiber-reinforced nylon filament (Gen3 CarbonX™ PA6+CF, 3DXTECH Additive Manufacturing) by a professional 3D printer (FUNMAT HT, Intamsys). Electricity, material, and labor costs for production in a Brazilian city in the Santa Catarina state were calculated. RESULTS: The devices for controlled dynamization were successfully printed in accordance with the planned design and dimensions. Six out of 38 printed devices presented defects in the bolt hole and were discarded. The average printing time per device was 1.9 h. The average electricity, material, and labor costs per printed device were respectively US$0.71, US$13.55, and US$3.04. The total production cost per device reaches approximately US$20 by adding the average cost of defective devices (15 %). CONCLUSION: 3D printing of the controlled dynamization device is feasible and its cost seems affordable to most healthcare services, which could optimize the consolidation of diaphyseal fractures and reduce treatment time for patients.

In vivo axial load-share ratio measurement using a novel hexapod system for safe external fixator removal.

BACKGROUND: External fixation is widely used in the treatment of traumatic fractures; however, orthopedic surgeons encounter challenges in deciding the optimal time for fixator removal. The axial load-share ratio (LS) of the fixator is a quantitative index to evaluate the stiffness of callus healing. This paper introduces an innovative method for measuring the LS and assesses the method's feasibility and efficacy. Based on a novel hexapod LS-measurement system, the proposed method is to improve the convenience and precision of measuring LS in vivo, hence facilitating the safe removal of external fixators. METHODS: A novel hexapod system is introduced, including its composition, theoretical model, and method for LS measurement. We conducted a retrospective study on 82 patients with tibial fractures treated by the Taylor Spatial Frame in our hospital from September 2018 to June 2020, of which 35 took LS measurements with our novel method (Group I), and 47 were with the traditional method (Group II). The external fixator was removed when the measurement outcome (LS < 10%) was consistent with the surgeon's diagnosis based on the clinical and radiological assessment (bone union achieved). RESULTS: No significant difference was found in the fracture healing time (mean 25.3 weeks vs. 24.9 weeks, P > 0.05), frame-wearing duration (mean 25.5 weeks vs. 25.8 weeks, P > 0.05), or LS measurement frequency (mean 1.1 times vs. 1.2 times, P > 0.05). The measurement system installation time in Group I was significantly shorter compared to Group II (mean 14.8 min vs. 81.3 min, P < 0.001). The LS value of the first measurement in Group I was lower than that of Group II (mean 5.1% vs. 6.9%, P = 0.011). In Group I, the refracture rate was 0, but in Group II it was 4.3% (2/47, P > 0.05). CONCLUSION: The novel hexapod LS-measurement system and involved method demonstrated enhanced convenience and precision in measuring the LS of the external fixator in vivo. The LS measurement indicates the callus stiffness of fracture healing, and is applicable to evaluate the safety of removing the fixator. Consequently, it is highly recommended for widespread adoption in clinical practice.

A new ring fixator system for automated bone fixation.

BACKGROUND: In the field of orthopaedics, external fixators are commonly employed for treating extremity fractures and deformities. Computer-assisted systems offer a promising and less error-prone treatment alternative to manual fixation by utilising a software to plan treatments based on radiological and clinical data. Nevertheless, existing computer-assisted systems have limitations and constraints. METHODS: This work represents the culmination of a project aimed at developing a new automatised fixation system and a corresponding software to minimise human intervention and associated errors, and the developed system incorporates enhanced functionalities and has fewer constraints compared to existing systems. RESULTS: The automatised fixation system and its graphical user interface (GUI) demonstrate promising results in terms of accuracy, efficiency, and reliability. CONCLUSION: The developed fixation system and its accompanying GUI represent an improvement in computer-assisted fixation systems. Future research may focus on further refining the system and conducting clinical trials.

Audio Distraction for Traction Pin Insertion: A Prospective Randomized Controlled Study.

BACKGROUND: Insertion of a skeletal traction pin in the distal femur or proximal tibia can be a painful and unpleasant experience for patients with a lower-extremity fracture. The purpose of this study was to determine whether providing patients with audio distraction (AD) during traction pin insertion can help to improve the patient-reported and the physician-reported experience and decrease pain and/or anxiety during the procedure. METHODS: A prospective randomized controlled trial was conducted at 2 level-I trauma centers. Patients ≥18 years of age who were conscious and oriented and had a medical need for skeletal traction were included. Patients were randomized to receive AD or not receive AD during the procedure. All other procedure protocols were standardized and were the same for both groups. Surveys were completed by the patient and the physician immediately following the procedure. Patients rated their overall experience, pain, and anxiety during the procedure, and physicians rated the difficulty of the procedure, both on a 1-to-10 Likert scale. RESULTS: A total of 54 patients met the inclusion criteria. Twenty-eight received AD and 26 did not. Femoral fractures were the most common injury (33 of 55, 60.0%). Baseline demographic characteristics did not differ between the 2 groups. The overall patient-reported procedure experience was similar between the AD and no-AD groups (3.9 ± 2.9 [95% confidence interval (CI), 3.1 to 4.7] versus 3.5 ± 2.2 [95% CI, 2.9 to 4.1], respectively; p = 0.55), as was pain (5.3 ± 3.2 [95% CI, 4.4 to 6.2] versus 6.1 ± 2.4 [95% CI, 5.4 to 6.8]; p = 0.28). However, anxiety levels were lower in the AD group (4.8 ± 3.3 [95% CI, 3.9 to 5.7] versus 7.1 ± 2.8 [95% CI, 6.3 to 7.9]; p = 0.007). Physician-reported procedure difficulty was similar between the groups (2.6 ± 2.0 [95% CI, 2.1 to 3.1] versus 2.8 ± 1.7 [95% CI, 2.3 to 3.3]; p = 0.69). CONCLUSIONS: AD is a practical, low-cost intervention that may reduce patient anxiety during lower-extremity skeletal traction pin insertion. LEVEL OF EVIDENCE: Therapeutic Level I . See Instructions for Authors for a complete description of levels of evidence.

[Basic principles of surgical treatment of distal radius fractures]. / Grundprinzipien der operativen Versorgung der distalen Radiusfraktur.

Distal radius fractures are one of the most frequent fractures of the upper extremities. The decision for conservative or surgical treatment is made after appropriate diagnostics using conventional radiographic and usually computed tomography imaging examinations. If the indications for surgical treatment are present, various options for reduction and fixation are available. The spectrum ranges from closed to open procedures up to accompanying arthroscopic support. Appropriate preoperative patient education about the procedure and the planned postinterventional treatment is essential. The goal of treatment is to restore wrist function while maintaining mobility and strength with a low risk of complications. All surgical procedures share the principle of reduction to restore anatomical relationship followed by fixation. Closed procedures include fixation with Kirschner wires and the construction of an external fixator. Volar locking plate osteosynthesis has become established in recent years as the method of choice for the majority of the fractures to be treated. For special fracture patterns and the treatment of accompanying injuries, arthroscopic support can be indicated. There is no uniform consensus on the best choice of procedure. This article discusses the possible procedures including the approaches, fixation techniques and specific follow-up treatment.

Biomechanical comparative study on external fixators of new configurations in the treatment of Tile C pelvic injury.

To compare the biomechanical properties of several anterior pelvic ring external fixators with two new configurations in the treatment of Tile C pelvic fractures, in order to evaluate the effectiveness of the new configurations and provide a reference for their clinical application. A finite element model of a Tile C pelvic ring injury (unilateral longitudinal sacral fracture and ipsilateral pubic fracture) was constructed. The pelvis was fixed with iliac crest external fixator (IC), anterior inferior iliac spine external fixator (AIIS), combination of IC and AIIS, combination of anterior superior iliac spine external fixator (ASIS) and AIIS, and S1 sacroiliac screw in 5 types of models. The stability indices of the anterior and posterior pelvic rings under vertical longitudinal load, left-right compression load and anterior-posterior shear load were quantified and compared. In the simulated bipedal standing position, the results of the vertical displacement of the midpoint on the upper surface of the sacrum are consistent with the displacement of the posterior rotation angle, and the order from largest to smallest is IC, AIIS, ASIS + AIIS, IC + AIIS and S1 screw. The longitudinal displacement of IC is greater than that of the other models. The displacements of ASIS + AIIS and IC + AIIS are similar and the latter is smaller. In the simulated semi-recumbent position, the vertical displacement and posterior rotation angle displacement of the midpoint on the upper surface of the sacrum are also consistent, ranking from large to small: IC, AIIS, ASIS + AIIS, IC + AIIS and S1 screw. Under the simulated left-right compression load state, the lateral displacements of the highest point of the lateral sacral fracture end are consistent with the highest point of the lateral pubic fracture end, and the order from large to small is S1 screw, IC, AIIS, ASIS + AIIS and IC + AIIS, among which the displacements of S1 screw and IC are larger, and the displacements of ASIS + AIIS and IC + AIIS are similar and smaller than those of other models. The displacements of IC + AIIS are smaller than those of ASIS + AIIS. Under the simulated anterior-posterior shear load condition, the posterior displacements of the highest point of the lateral sacral fracture end and the highest point of the lateral pubic fracture end are also consistent, ranking from large to small: IC, AIIS, ASIS + AIIS, IC + AIIS and S1 screw. Among them, the displacements of IC and AIIS are larger. The displacements of ASIS + AIIS and IC + AIIS are similar and the latter are smaller. For the unstable pelvic injury represented by Tile C pelvic fracture, the biomechanical various stabilities of the combination of IC and AIIS are superior to those of the external fixators of conventional configurations. The biomechanical stabilities of the combination of ASIS and AIIS are also better than those of the external fixators of conventional configurations, and slightly worse than those of the combination of IC and AIIS. Compared with sacroiliac screw and conventional external fixators, the lateral stabilities of IC + AIIS and ASIS + AIIS are particularly prominent.

Five-Year Follow-Up of Surgery vs Functional Bracing for Closed Displaced Humeral Shaft Fractures.

This study compares outcomes of surgery and functional bracing for closed humeral shaft fractures after 5 years of follow-up.

Safety and effectiveness of the three-dimensional-printed guide plate-assisted rotation axis positioning of a hinged external fixator for the elbow.

PURPOSE: We aimed to evaluate the safety and effectiveness of three-dimensional (3D)-printed guide plates for assisting in the positioning of the rotation axis of an elbow-hinged external fixator. METHODS: Terrible triad (TT) patients, who were screened using the predefined inclusion and exclusion criteria, underwent installation of a hinged external fixator on the basis of internal fixation; 3D-printed guide plates, generated from the patient's imaging data, assisted in positioning the rotation axis. All patients received the same peri-operative management and were followed up at six, 12, 24, and 48 weeks postoperatively. The duration of positioning pin placement, the number of fluoroscopies, pin placement success rate, types and incidence of post-operative complications, and the Mayo elbow performance score (MEPS) of the diseased elbow and range of motion (ROM) of both elbows were assessed. RESULTS: In 25 patients who completed the follow-up, the average time required for positioning pin placement was 329.32 ± 42.38 s (263-443 s), the average number of fluoroscopies was 2.32 ± 0.48 times (2-3 times), and the pin placement success rate was 100%. At the last follow-up, the mean MEPS of the diseased elbow was 97.50 ± 6.92 (75-100), with an excellent and good rate of 100%, and all patients demonstrated stable concentric reduction. The average range of flexion and extension was 135.08° ± 17.10° (77-146°), while the average range of rotation was 169.21° ± 18.14° (108-180°). No significant difference was observed in the average ROM between the both elbows (P > 0.05). Eight (32%) patients developed post-operative complications, including elbow stiffness due to heterotopic ossification in three (12%) patients, all of whom did not require secondary intervention. CONCLUSION: Utilizing 3D-printed guide plates for positioning the rotation axis of an elbow-hinged external fixator significantly reduced intra-operative positioning pin placement time and the number of fluoroscopies with excellent positioning results. Satisfactory results were also obtained in terms of post-operative complications, elbow ROM, and functional scores.

The therapeutic value of vacuum external fixation in polytrauma patients with multiple ribs fracture.

BACKGROUND: Multiple displaced rib fractures often result in a poor prognosis. Open reduction and internal fixation has been shown to provide benefits for patients with displaced rib fractures and flail chest. Nevertheless, for patients who are unwilling or unsuitable for surgery, the therapeutic options are limited. We developed a novel plastic vacuum device for rib fractures external stabilization. This study aims to compare the therapeutic efficacy of this device against a traditional chest strap in polytrauma patients with multiple rib fractures. METHODS: A retrospective investigation was conducted on polytrauma patients with multiple rib fractures admitted to our trauma center between March 2020 and March 2023. Patients were categorized into two groups: vacuum external fixation and chest strap. Comparative analysis was conducted on baseline parameters, injury characteristics, and clinical outcomes between the two groups. RESULTS: In this study, 54 patients were included, with 28 receiving chest strap and 26 undergoing vacuum external fixation. Results showed that, at 3 days and 7 days postintervention, the vacuum external fixation group had significantly lower visual analog scale scores during deep breathing and coughing (P < .05). Vacuum external fixation also reduced pleural drainage duration and volume, as well as lowered the risk of pneumonia and other complications (P < .05). Furthermore, the vacuum external fixation group demonstrated notable improvements in vital capacity, tidal volume, blood-gas test results, and a shorter hospital length of stay. CONCLUSIONS: According to the study findings, vacuum external fixation appears to offer benefits to patients with multiple rib fractures, potentially reducing the risk of complications and improving overall clinical outcomes.

[A retrospective study on manual reduction combined with Chinese Orthopaedic ankle external fixator in the treatment of trimalleolar fracture].

OBJECTIVE: To evaluate the needle puncture safety and clinical efficacy of manual reduction combined with external fixation of ankle frame in the treatment of trimalleolar fracture under the guidance of Chinese Osteosynthesis (CO) theory. METHODS: The clinical data of 118 patients with trimalleolar fractures admitted from December 2010 to December 2021 were retrospectively analyzed. Fifty-three patients were treated with manual reduction combined with external fixation of ankle frame(observation group). Sixty-five patients were treated with open reduction and internal fixation with plate and screws(control group). The operation time, hospitalization days, non-weight-bearing time of the affected limb, clinical healing time of fracture, incidence of complications, visual analogue scale (VAS) before and 1 month after operation, and American Orthopedic Foot and Ankle Society(AOFAS) score of ankle joint before and 1 year after operation were compared between the two groups. RESULTS: Patients in both groups were followed up for more than 1 year. All patients were followed up, and the duration ranged from 14 to 70 months, with an average of(35.28±14.66) months. There were statistically significant in operation time, hospitalization days, non-load-bearing time of affected limbs, clinical healing time of fractures and VAS score one month after operation between the two groups. One month after operation, the VAS score of the observation group was lower than that of the control group(t=3.343, P=0.001). The operation time of the observation group was significantly shorter than that of the control group(t=9.091, P=0.000). The hospitalization days in the observation group were significantly less than those in the control group(t=5.034, P=0.000). The non-load-bearing time of the affected limb in the observation group was significantly shorter than that in the control group(t=11.960, P=0.000). The clinical healing time of fracture in the observation group was significantly shorter than that in the control group(t=4.007, P=0.000). There was no significant difference in AOFAS score between the two groups one year after operation(t=0.417, P=0.678). In the observation group, there were 2 cases of pinhole infection and 3 cases of loss of reduction less than 2 mm. There were 3 cases of surgical incision infection in the control group. There was no significant difference in the incidence of complications between the two groups(χ2=0.446, P=0.504). CONCLUSION: Manual reduction combined with external fixation is safe and effective in the treatment of trimalleolar fracture under the guidance of CO theory, and the function of ankle joint recovers well after operation. This therapy has good clinical value.

A Modified Technique of Percutaneous Fixation of Displaced Pediatric Lateral Humeral Condyle Elbow Fractures (aka the Martini Technique): A Brief Case Series.

Displaced lateral humeral condyle (LHC) fractures have routinely been treated with open reduction, which has known postoperative complications. Recent reports show that closed reduction and percutaneous pinning (CRPP) is a valid treatment. Five pediatric patients with displaced LHC fractures were included in a retrospective case series. Closed reductions (CRs) were facilitated by Kirschner wire placement into the capitellum through a toothed drill guide. The Kirschner wire and drill guide were used like a joystick to manipulate the fragment and maintain reduction for placement of additional Kirschner wires. Patient records were used to determine the number of patients diagnosed with LHC fractures between 2011 to 2022 among six pediatric orthopaedic surgeons at one institution along with the treatment and associated complications. Satisfactory reduction of displaced LHC fractures was achieved with CRPP in all patients with no complications using the "martini" modification. Of 26 LHC fractures, 16 were treated with CRPP/CRPS and 10 with open reduction and percutaneous pinning/open reduction and internal fixation, with four converted from CR to OR. Complications included one superficial infection in the CR group and four stiff elbows and one nonunion in the OR group option for LHC fractures. CRPP is an effective treatment option with a decreased risk of complications. Our modified reduction technique may help improve the success and results of closed treatment of LHC fractures.

Clinical Results of Closed Reduction and Percutaneous Pinning for Gartland Type II Flexion-Type Supracondylar Humeral Fractures in Children: Report of Three Cases.

Supracondylar humerus fractures are the most common upper limb injury in children, but the incidence of flexion-type fractures is relatively low. Herein, we report the clinical results for three children with Gartland type II flexion-type supracondylar humeral fractures treated by closed reduction and percutaneous pinning. From April 2004 to March 2020, 102 children with supracondylar humeral fractures underwent surgery at our hospital and related institutions. Four had a flexion-type supracondylar humeral fracture (3.9%). Three patients (1 boy and 2 girls) with Gartland type II flexion-type supracondylar humeral fractures were followed for more than 12 months. The patients were treated by closed reduction and percutaneous pinning. Age was 7-13 years at the time of injury, and the duration of postoperative follow-up was 12-16 months. In one case, ulnar nerve paresis was observed as a preoperative complication. After performing closed reduction, percutaneous Kirschner wire cross-fixation was performed. Subsequently, long upper limb cast fixation was carried out for 4 weeks postoperatively. One patient developed preoperative nerve paralysis but recovered in approximately 3 months, without postoperative complications such as infection, nerve paralysis, or cubitus varus or valgus deformity. Flynn's criteria results were excellent for two patients and good for one patient. To maintain anatomical reduction of the fracture fragment, closed reduction using a traction table and percutaneous steel wire fixation are useful for treating flexion-type supracondylar humerus fractures in children with Gartland type II fractures.

Accuracy of osseointegrated screw-bone construct stiffness and peri-implant loading predicted by homogenized FE models relative to micro-FE models.

Computational predictions of stiffness and peri-implant loading of screw-bone constructs are highly relevant to investigate and improve bone fracture fixations. Homogenized finite element (hFE) models have been used for this purpose in the past, but their accuracy has been questioned given the numerous simplifications, such as neglecting screw threads and modelling the trabecular bone structure as a continuum. This study aimed to investigate the accuracy of hFE models of an osseointegrated screw-bone construct when compared to micro-FE models considering the simplified screw geometry and different trabecular bone material models. Micro-FE and hFE models were created from 15 cylindrical bone samples with a virtually inserted, osseointegrated screw (fully bonded interface). Micro-FE models were created including the screw with threads (=reference models) and without threads to quantify the error due to screw geometry simplification. In the hFE models, the screws were modelled without threads and four different trabecular bone material models were used, including orthotropic and isotropic material derived from homogenization with kinematic uniform boundary conditions (KUBC), as well as from periodicity-compatible mixed uniform boundary conditions (PMUBC). Three load cases were simulated (pullout, shear in two directions) and errors in the construct stiffness and the volume average strain energy density (SED) in the peri-implant region were evaluated relative to the micro-FE model with a threaded screw. The pooled error caused by only omitting screw threads was low (max: 8.0%) compared to the pooled error additionally including homogenized trabecular bone material (max: 92.2%). Stiffness was predicted most accurately using PMUBC-derived orthotropic material (error: -0.7 ± 8.0%) and least accurately using KUBC-derived isotropic material (error: +23.1 ± 24.4%). Peri-implant SED averages were generally well correlated (R2 ≥ 0.76), but slightly over- or underestimated by the hFE models and SED distributions were qualitatively different between hFE and micro-FE models. This study suggests that osseointegrated screw-bone construct stiffness can be predicted accurately using hFE models when compared to micro-FE models and that volume average peri-implant SEDs are well correlated. However, the hFE models are highly sensitive to the choice of trabecular bone material properties. PMUBC-derived isotropic material properties represented the best trade-off between model accuracy and complexity in this study.

Biomechanical Study of Intramedullary Versus Extramedullary Implants for Four Types of Subtrochanteric Femoral Fracture.

OBJECTIVES: To compare the biomechanical performance of proximal femoral nail anti-rotation (PFNA), the "upside-down" less invasive plating system (LISS), and proximal femoral locking plate (PFLP) in fixing different fracture models of subtrochanteric fractures. METHODS: Thirty composite femurs were divided into three equal groups (PFNA, PFLP, and reverse LISS). The implant-femur constructs were tested under axial compression load (0-1400 N) from models I to IV, which represented the Seinsheimer type I subtrochanteric fracture, type IIIa subtrochanteric fracture with the posteromedial fragment reduced; type IIIa subtrochanteric fracture with the posteromedial fragment lost; and type IV subtrochanteric fracture, respectively. Axial stiffness was analyzed for each group. Each group was then divided into two subgroups, one of which underwent torsional and axial compression failure testing, while the other subgroup underwent axial compression fatigue testing. The torsional stiffness, failure load, and cycles to failure were analyzed. RESULTS: PFNA had the highest axial stiffness (F = 761.265, p < 0.0001) and failure load (F = 48.801, p < 0.0001) in model IV. The axial stiffness and failure load of the PFLP were significantly higher than those of the LISS (p < 0.0001, p = 0.001). However, no significant difference in axial stiffness was found between models I to III (model I: F = 2.439, p = 0.106; model II: F = 2.745, p = 0.082; model III: F = 0.852, p = 0.438) or torsional stiffness in model IV (F = 1.784, p = 0.187). In fatigue testing, PFNA did not suffer from construct failure after 90,000 cycles of axial compression. PFLP and LISS were damaged within 14,000 cycles, although LISS withstood more cycles than PFLP (t = 3.328, p = 0.01). CONCLUSION: The axial stiffness of the three implants was similar in models I to III. The biomechanical properties of PFNA were the best of the three implants in terms of axial stiffness, failure load, and fatigue testing cycles in model IV. The axial stiffness and failure load of the PFLP were better than those of the reverse LISS, but PFLP had fewer cycles in the fatigue tests than the reverse LISS.

Effects of the number and the position of transfixation pins in acrylic connecting bars.

Acrylic columns are commonly used in external skeletal fixators, especially for fracture management or trans-articular fixations. To the authors' knowledge, there are no studies demonstrating if the number or position of the transfixation pins influence the ultimate strength and stiffness of the acrylic column. The objective of this study was to evaluate the effects of the number and position of transfixation pins (concentric versus eccentric) on the strength and stiffness of acrylic columns placed in axial compression. We hypothesized that strength and stiffness of acrylic columns under axial compression would not be affected by the number or position of the transfixation pins through the column. Three different groups of 12 acrylic columns were constructed with 4, 6, and 8 pins. In each group, 6 columns were constructed with the pins placed concentrically and the remaining 6 columns with the pins placed eccentrically. Each column was then placed under axial compression using a biomechanical testing machine. No significant differences were observed in ultimate strength regarding the number or position of transfixation pins (P = 0.83 and P = 0.27, respectively). However, stiffness was significantly decreased for columns with 4 eccentric pins compared with columns with 6 and 8 eccentric pins (P < 0.01) and with columns with 4 concentric pins (P < 0.001). Although the effects of transfixation pins on the rigidity of acrylic columns do not appear to be clinically significant, these tests were performed only in compression and results might differ if complete external fixator systems are used with different models of testing. Future studies are recommended.

Les colonnes d'acrylique sont couramment utilisées dans les fixateurs externes, notamment pour la gestion des fractures ou les fixations transarticulaires. Selon les auteurs, aucune étude ne démontre si le nombre ou le positionnement des broches de transfixation influence la résistance ultime et la rigidité de la colonne d'acrylique. Les objectifs de cette étude étaient d'évaluer l'effet du nombre et du positionnement des broches de transfixation (concentriques versus excentriques) sur la résistance et la rigidité des colonnes d'acryliques placées en compression axiale. Nous avons émis l'hypothèse que la résistance et la rigidité des colonnes d'acryliques en compression axiale ne seraient pas affectées par le nombre ou le positionnement des broches de transfixation à travers la colonne. Trois groupes différents de douze colonnes acryliques ont été construits avec quatre, six, et huit broches. Dans chaque groupe, six colonnes ont été construites avec les broches placées concentriquement et les six colonnes restantes avec les broches placées de manière excentrique. Chaque colonne a ensuite été placée sous compression axiale à l'aide d'une machine de tests biomécaniques. Aucune différence significative n'a été observée pour la résistance ultime selon le nombre ou le positionnement des broches de transfixation (P = 0,83 et P = 0,27, respectivement). Cependant, la rigidité a été significativement diminuée pour les colonnes avec quatre broches excentriques par rapport aux colonnes avec six et huit broches excentriques (P < 0,01) et avec les colonnes avec quatre broches concentriques (P < 0,001). Bien que les effets des broches de transfixation sur la rigidité des colonnes acryliques ne semblent pas être cliniquement significatifs, ces tests ont été effectués uniquement en compression et les résultats pourraient différer si des systèmes complets de fixateurs externes sont utilisés avec différents modèles de test. De futures études sont recommandées.(Traduit par les auteurs).

Three-dimensional volume-rendered computed tomography application for follow-up fracture healing and volume measurements pre-surgical rib fixation and post-surgical rib fixation.

BACKGROUND: Surgical rib fixation (SRF) is being used increasingly in trauma centers for stabilization of chest wall injuries, in line with new and evolving surgical techniques. Our institution has developed a pathway for the management of chest wall injuries and SRF, which includes a follow-up low-volume, noncontrast computed tomography (CT) scan at 12 months. METHODS: This study was a single-center retrospective study conducted on 25 consecutive patients who underwent SRF between February 2019 and February 2020. All CT measurements were done by a CT radiographer under the supervision of a board-certified radiologist and included the use of three-dimensional volume-rendered images. RESULTS: There were no patients with SRF who experienced hardware failure at 12 months in either flail or nonflail groups. For fractured ribs treated with SRF, complete or partial union occurred in 75 of 76 ribs plated (98.7%). The median ratio for improvement in lung volumes was 1.71 for flail SRF and 1.69 for nonflail SRF in our study. CONCLUSION: Three-dimensional volume-rendered CT at 12 months post-SRF showed good alignment (no hardware failure) and fracture healing of fixed ribs in both flail and nonflail groups. Lung volumes also improved pre-SRF and post-SRF for both flail and nonflail patients. More studies are needed to define how the pattern of rib fracture healing of fixed and nonfixed ribs affects lung volumes. LEVEL OF EVIDENCE: Therapeutic, Level V.