Motion preservation for open book injuries of the pubic symphysis -a biomechanical cadaver study.

INTRODUCTION: Open book injuries are challenging injuries that oftentimes require surgical treatment. Currently, treatment is performed with symphyseal plating requiring extensive surgery and entirely limiting physiological movement of the symphyseal joint, frequently resulting in implant failure. Therefore, we investigated the biomechanical properties of a minimally invasive tape suture construct (modified SpeedBridge™) as an alternative stabilization technique for the treatment of open book injuries in human cadaver pelvic rings. MATERIALS AND METHODS: The symphysis of 9 human cadaver pelvises was dissected and dilated to 3 cm creating an open book injury. Next, the two osteosynthesis methods (plating, modified SpeedBridge™) were applied. All specimens then underwent cyclic horizontal and vertical loading, simulating biomechanical forces while sitting, standing and walking. For statistical analysis, 3D dislocation (mm) was calculated. RESULTS: Total displacement (mm) of the pubic symphysis displayed the following means and standard deviations: native group 1.34 ± 0.62 mm, open book group 3.01 ± 1.26 mm, tape group 1.94 ± 0.59 mm and plate group 1.37 ± 0.41 mm. Comparison between native and open book (p = 0.029), open book and plate (p = 0.004), open book and tape (p = 0.031), as well as tape and plate group (p = 0.002) showed significant differences. No significant differences were found when comparing the native and tape (p = 0.059), as well as the native and plate (p = 0.999) group. CONCLUSION: While both osteosynthesis techniques sufficiently stabilized the injury, symphyseal plating displayed the highest rigidity. The modified SpeedBridge™ as a tape suture construct provided statistically sufficient biomechanical stability while maintaining symphyseal micro mobility, consequently allowing ligamental healing of the injured joint without iatrogenic arthrodesis.

Uncemented hip revision cup as an alternative for T-type acetabular fractures: A cadaveric study.

BACKGROUND: The current rise in elderly patients with compromised bone quality complicates the surgical treatment of acetabular T-type fractures (AO type 62B2 fractures). There is on ongoing discussion about the treatment options, mostly consisting of an open reduction and internal fixation (ORIF) with or without primary or secondary total hip arthroplasty (THA). Yet, these patients are oftentimes unable to fulfil weight-bearing restrictions and mostly present with an unavailability of a stable anchor site. Consequently, this study investigates the feasibility of a cementless hip revision cup for acetabular T-type fractures and compares its biomechanical properties to ORIF. HYPOTHESIS: The cementless hip revision cup provides sufficient biomechanical stability under the simulation of full weight-bearing. PATIENTS AND METHODS: The study compared two groups of human cadaveric hip bones with T-type fractures, of whom 6 subjects were treated with ORIF (6 male; mean age: 62±17years; mean body weight: 75±15) versus 6 subjects treated with a cementless hip revision cup (2 male; 69±12 years; 73±15kg). The group-assignment was controlled for comparable BMD results (mean BMD: ORIF 110±37 mg Ca-Ha/mL versus hip revision cup 134±32 mg Ca-Ha/mL). To compare for biomechanical stability cyclic loading was applied measuring the force and dislocation of the fracture gap at standardized bone loci using an all-electric testing machine and a 3D-ultrasound measuring system. RESULTS: Comparing superior pubic ramus versus iliac wing (cementless hip revision cup versus ORIF [mean±standard deviation]: 5.8±2.0 versus 7.0±3.2; p=0.032) as well as sacral ala versus iliac wing (4.6±2.2 versus 6.4±3.7; p=0.002), the cementless revision cup achieved a significantly higher stability than the plate osteosynthesis. CONCLUSION: Revision cup and ORIF withstood biomechanical loading forces exceeding full weight-bearing in this biomechanical study. The results of our study suggest that the cementless hip revision cup might be promising alternative to the current standard care of ORIF with or without primary THA. LEVEL OF EVIDENCE: III; case control experimental study.

Micro-Structural and Biomechanical Evaluation of Bioresorbable and Conventional Bone Cements for Augmentation of the Proximal Femoral Nail.

Osteoporotic proximal femur fractures are on the rise due to demographic change. The most dominant surgical treatment option for per/subtrochanteric fractures is cephalomedullary nailing. As it has been shown to increase primary stability, cement augmentation has become increasingly popular in the treatment of osteoporotic per/subtrochanteric femur fractures. The ultimate goal is to achieve stable osteosynthesis, allowing for rapid full weight-bearing to reduce possible postoperative complications. In recent years, bioresorbable bone cements have been developed and are now mainly used to fill bone voids. The aim of this study was to evaluate the biomechanical stability as well as the micro-structural behaviour of bioresorbable bone cements compared to conventional polymethylmethacrylate (PMMA)-cements in a subtrochanteric femur fracture model. Biomechanical as well as micro-computed tomography morphology analysis revealed no significant differences in both bone cements, as they showed equal mechanical stability and tight interdigitation into the spongious bone of the femoral head. Given the positive risk/benefit ratio for bioresorbable bone cements, their utilisation should be evaluated in future clinical studies, making them a promising alternative to PMMA-bone cements.

Novel Tape Suture Osteosynthesis for Hyperextension Injuries of the Subaxial Cervical Spine: A Biomechanical Study.

BACKGROUND/AIM: Anterior tension band injuries are usually the result of high impact hyperextension trauma. Current surgical treatment includes anterior cervical discectomy and fusion bearing the risk of soft tissue irritation, degeneration of adjacent cervical segments, implant failure or iatrogenic spondylodesis. This study examined the biomechanical properties of tape suture constructs reenforcing ligamental stability for the treatment of Association of Osteosynthesis (AO) type B3 injuries compared to anterior fusion. MATERIALS AND METHODS: After creation of an AO type B3 injury in synthetic cervical segments (C5/6, Sawbone®), seven segments were treated with anterior fusion and seven with a tape suture construct, similar to the SpeedBridge™ (Arthrex®). Biomechanical testing was performed, simulating extension, flexion, lateral bending, and rotation. Dislocation (°) and corresponding force (N) were measured and compared. RESULTS: Anterior fusion displayed a mean range of extension, lateral bending, and rotation of 3.60° (SD 1.87°), 2.28° (SD 1.55°), and 2.81° (SD 0.78°), respectively. The tape suture showed a mean range of extension, lateral bending, and rotation of 4.24° (SD 0.81°) (p=0.146), 5.44° (SD 1.56°) (p=0.013), and 5.29° (SD 1.44°) (p<0.01), respectively. No specimen suffered from implant failure. CONCLUSION: The tape suture construct provides sufficient biomechanical stability for the treatment of AO type B3 injuries compared to anterior fusion. Regarding cervical extension, whose limitation is crucial for ligamental healing, the tape suture shows no significant inferiority. Yet, the tape suture approaches physiological mobility in the planes not affected by the injury. Consequently, the tape suture is a promising alternative preventing an iatrogenic spondylodesis.

Tape suture constructs for instabilities of the pubic symphysis: is the idea of motion preservation a suitable treatment option? A cadaver study.

INTRODUCTION: Current gold standard for the treatment of symphyseal disruptions includes anterior plating, almost entirely prohibiting symphyseal mobility and resulting in an iatrogenic arthrodesis followed by high rates of implant failure. Minimally invasive tape suture constructs have been found to maintain the micro mobility of ligamentous injuries, yet still providing sufficient biomechanical stability. Recently, this technique has been primarily investigated for symphyseal disruptions on synthetic pelvic models. Therefore, the aim of this study was to examine the feasibility of this novel flexible osteosynthesis on cadaveric pelvic models based on the following hypothesis: tape suture constructs ensure sufficient biomechanical stability without inhibiting micro mobility of the pubic symphysis for the treatment of symphyseal disruptions and maintain stability during long-term loading. MATERIALS AND METHODS: 9 cadaveric anterior pelvic rings were used in this study and a symphyseal disruption was created in every specimen. The specimens were then exposed to short- and long-term vertical and horizontal cyclic loading after treatment with a tape suture construct in criss-cross technique. The mean maximum displacement (mm) during cyclic loading and the corresponding stiffness (N/mm) were measured and compared. RESULTS: Regarding both displacement (mm) and corresponding stiffness (N/mm), the tape sutures displayed a significant difference between short- and long-term loading for cranial and caudal vertical loading (p < 0.01) but differences remained non-significant for horizontal loading (p > 0.05). No tape suture suffered from implant failure during long-term loading. CONCLUSIONS: The tape suture construct displayed sufficient biomechanical stability without exceeding the physiological mobility of 2 mm of the pubic symphysis; however, also maintained the desired micro mobility of the affected joint necessary to prevent an iatrogenic arthrodesis. Further, all tape sutures maintained stability throughout long-term loading.

Improving stability of atlantoaxial fusion: a biomechanical study.

PURPOSE: The incidence of atlanto-axial injuries is continuously increasing and often requires surgical treatment. Recently, Harati developed a new procedure combining polyaxial transarticular screws with polyaxial atlas massae lateralis screws via a rod system with promising clinical results, yet biomechanical data is lacking. This biomechanical study consequently aims to evaluate the properties of the Harati technique. METHODS: Two groups, each consisting of 7 cervical vertebral segments (C1/2), were formed and provided with a dens axis type 2 fracture according to Alonzo. One group was treated with the Harms and the other with the Harati technique. The specimen was loaded via a lever arm to simulate extension, flexion, lateral flexion and rotation. For statistical analysis, dislocation (°) was measured and compared. RESULTS: For extension and flexion, the Harati technique displayed a mean dislocation of 4.12° ± 2.36° and the Harms technique of 8.48° ± 1.49° (p < 0.01). For lateral flexion, the dislocation was 0.57° ± 0.30° for the Harati and 1.19° ± 0.25° for the Harms group (p < 0.01). The mean dislocation for rotation was 1.09° ± 0.48° for the Harati and 2.10° ± 0.31° for the Harms group (p < 0.01). No implant failure occurred. CONCLUSION: This study found a significant increase in biomechanical stability of the Harati technique when compared to the technique by Harms et al. Consequently, this novel technique can be regarded as a promising alternative for the treatment of atlanto-axial instabilities.

In vivo immunomodulation of IL6 signaling in a murine multiple trauma model.

A significant number of trauma patients die during the ICU phase of care because of a severe immune response. Interleukin-6 (IL6) plays a central role within that immune response, signaling through a membrane-bound (IL6-R) and a soluble IL6 receptor (sIL6-R). IL6 and the sIL6-R can form an agonistic IL6/sIL6-R-complex, activating numerous cells that are usually not IL6 responsive, a process called trans-signaling. We attempted to demonstrate that modulation of the IL6 signaling (classic signaling and trans-signaling) can attenuate the devastating immune response after trauma in a murine multiple trauma model. Mice were allocated to three study arms: sham, fracture or polytrauma. Half of the animals had the application of an IL6-R antibody following an intervention. After a pre-set time, blood samples were analysed for IL6 and sIL6-R serum levels, organs were analysed for neutrophil infiltration and end organ damage was evaluated. IL6 and sIL6-R showed a rapid peak after fracture, and much more markedly after polytrauma. These parameters were reduced significantly by globally blocking IL6 signaling via IL6-R antibody (Mab) application. Shock organ analysis also illustrated significant neutrophil infiltration following polytrauma, which was also abated via IL6-R Mab application. Furthermore, end organ damage was reduced by IL6-R Mab application. The study results prove the regulatory role of IL6 signaling pathways in polytrauma, with haemorrhagic shock being a major trigger of inflammatory response. Modulation of IL6 signaling shows promise in the prevention of adverse events like organ failure following major trauma and might be a target for in vivo immunomodulation to reduce mortality in severely injured patients, but further evaluation regarding classic IL6 signaling and IL6 trans-signaling is needed.

A Novel Device for Closed Reduction and Percutaneous Fixation of Thoracolumbar Fractures.

BACKGROUND/AIM: Open surgical reduction/fixation of thoracolumbar fractures results in significant soft-tissue trauma and related complications. Minimally-invasive technical developments could deliver similar radiological outcomes, while avoiding the related complications. We evaluated radiological and perioperative outcomes in thoracolumbar fractures by using a novel minimally-invasive device. PATIENTS AND METHODS: Twenty-six patients with 29 thoracolumbar fractures using the NForce device were analyzed. Postoperative reduction and alignment were assessed by radiographic measurement of the local kyphosis angle (LKA) up until a follow-up period of 9 months. RESULTS: Postoperative imaging revealed an average reduction of traumatic kyphosis of 8.25° (±7.72°) with an average postoperative LKA of 3.24° (±8.97°). The highest degree of reduction was 27.39°. The mean LKA had increased to 5.08° (±5.17°) at 3 months postoperative, 5.43° (±4.32°) at 6 months and 6.21° (±3.82°) at 9 months. CONCLUSION: The minimally invasive NForce system is effective in performing anatomic percutaneous reduction/fixation.

Novel minimally invasive tape suture osteosynthesis for instabilities of the pubic symphysis: a biomechanical study.

INTRODUCTION: Open book fractures are challenging injuries oftentimes requiring surgical treatment. The current treatment of choice is symphyseal plating, which requires extensive surgery and entirely limits physiological movement of the symphyseal joint, frequently resulting in implant failure. Therefore, we investigated the biomechanical properties of a semi-rigid implant (modified SpeedBridge™) as a minimally invasive tape suture construct for the treatment of open book fractures and evaluated the superiority of two techniques of implementation: criss-cross vs. triangle technique. MATERIALS AND METHODS: Nine synthetic symphyseal joints were dissected creating an open book fracture. The different osteosynthesis methods (plating, modified SpeedBridge™ in criss-cross/triangle technique) were then applied. All constructs underwent horizontal and vertical loading, simulating biomechanical forces while sitting, standing and walking. For statistical analysis, dislocation (mm) and stiffness (N/mm) were calculated. RESULTS: Symphyseal plating for the treatment of open book fractures proved to be a rigid osteosynthesis significantly limiting the physiological mobility of the symphyseal joint (dislocation: 0.08 ± 0.01 mm) compared to the tape sutures (dislocation: triangle technique 0.27 ± 0.07 mm, criss-cross technique 0.23 ± 0.05 mm) regarding horizontal tension (p < 0.01). Both modified SpeedBridge™ techniques showed sufficient biomechanical stability without one being superior to the other (p > 0.05 in all directions). Considering vertical loading, no statistical difference was found between all osteosynthesis methods (caudal: p = 0.41; cranial: p = 0.61). CONCLUSIONS: Symphyseal plating proved to be the osteosynthesis method with the highest rigidity. The modified SpeedBridge™ as a semi-rigid suture construct provided statistically sufficient biomechanical stability while maintaining a minimum of symphyseal movement, consequently allowing ligamental healing of the injured joint without iatrogenic arthrodesis. Furthermore, both the criss-cross and the triangle technique displayed significant biomechanical stability without one method being superior.

Cementless hip revision cup for the primary fixation of osteoporotic acetabular fractures in geriatric patients.

BACKGROUND: Elderly patients suffering from hip fractures are usually not able to fulfil postoperative weight-bearing restrictions. Therefore, the operative fixation construct has to be as stable as possible. Aim of the present study was to determine (1) whether a therapeutic advantage could be achieved when using hip arthroplasty to treat acetabular fractures in geriatric patients; (2) whether an acetabular revision cup would be suitable for achieving fast postoperative mobilization and full weight-bearing; and (3) when a treatment with an uncemented hip revision cup for the primary fixation of osteoporotic acetabular fractures in geriatric patients is indicated. MATERIALS AND METHODS: The functional outcome of THA using a reconstruction cup for an acetabular fracture was evaluated in ten patients using standardized scoring instruments. In addition, an analysis of the preexisting literature referring to total hip replacement in geriatric acetabular fractures was conducted and an algorithm for standardizing the treatment approach for geriatric patients with acetabular fractures was developed. RESULTS: The mean EQ-5D-3L quality of life score 0.7. The mean VAS Score was 58.2. The average Barthel Index was 80.0 points [range: 0-100]. The mean HHS was 72.0 points, while the MHH Score yielded an average of 63.4 points. The average AP Score was 7.5. The literature analysis showed that total hip arthroplasty could be a feasible option for geriatric acetabular fractures. CONCLUSION: Primary hip arthroplasty using uncemented revision cup fixed with angular stable screws showed good results and is a feasible treatment option of acetabular fractures in geriatric patients. The approach is especially beneficial in patients with poor bone stock and allows postoperative full weight-bearing. The presented treatment algorithm could be a useful tool for identifying the most appropriate treatment option. LEVEL OF EVIDENCE: IIb.

Resomer C212© in vertebroplasty or kyphoplasty: A feasibility study on artificial bones with biomechanical and thermal evaluation.

BACKGROUND: Vertebroplasty and kyphoplasty are now well-established methods for treating compression fractures of vertebral bodies (AO type A) as well as vertebral body metastases [1, 2, 3]. However, polymethylmethacrylate (PMMA) augmented vertebrae show fractures of subsequent vertebral bodies due to the increased stability of the augmented vertebral body [4]. Resorbable cements are currently only used experimentally. Many commercially available resorbable calcium phosphate cements do not exhibit sufficient biomechanical stability to treat vertebral body fractures [5]. Resomer C212© (Evonik Industries AG, Essen, Germany) is a slow resorbable poly-ε-caprolactone that has low melting temperatures and good biomechanical properties. OBJECTIVE: This is a feasibility study on how the poly-ε-caprolactone Resomer C212© can be used for kypho- or vertebroplasty, what temperatures are used in the argumentation and how differences in load capacity are measurable compared to conventional PMMA cement. METHODS: 23 Sawbones© blocks (7.5 Open Cell Foam, SKU: 1522-09, laminated on both sides, 4 × 4 × 2.9 cm, Sawbones, Vashon Island, USA) were divided into three groups: 7 without augmentation, 8 augmented with PMMA cement Traumacem V+© (DePuy Synthes, West Chester, USA) and 8 augmented with Resomer C212©. Temperature measurements were made in a 37∘C water bath centrally in the block and on the top and bottom plates. This was followed by a maximum load of up to 2000 N using a universal testing machine (Instron E 10000, Instron Industrial Products, Grove City, USA). RESULTS: In the Resomer C212© test group, the maximum average increase in temperature was 4.15 ± 4.72∘C central, 0.3 ± 0.31∘C at the top and 0.78 ± 1.27∘C at the base. In the cement test group, the average increase in temperature was 9.80 ± 10.65∘C centrally in the test block, 1.50 ± 0.73∘C at the top plate and 1.42 ± 0.66∘C and the base plate. In the axial compression test, the 7 non-kyphoplasted test blocks showed a first loading peak on average at 275.23 ± 80.98 N, a rigidity of 238.47 ± 71.01 N/mm2. In the Traumacem V+© group, the mean peak load was 313.72 ± 46.26 N and rigidity was 353.45 ± 77.23 N/mm2. The Resomer C212© group achieved a peak load of 311.74 ± 52.05 N and a stiffness of 311.30 ± 126.63 N/mm2. A compression to 50% could not be seen in any test block under the load of 2000 N. At 2000 N, Traumacem V+©'s average height reduction was 9.26 ± 2.16 mm and Resomer C212© was 10.93 ± 0.81 mm. CONCLUSIONS: It has been shown that the application of Resomer C212© in kyphoplasty or vertebroplasty is well feasible. Thermal analysis showed significantly lower temperatures and shorter temperature application in the Resomer C212© group. In the biomechanical load up to 2000 N no significant differences could be observed between the individual groups.

Biomechanical stability of sacroiliac screw osteosynthesis with and without cement augmentation.

BACKGROUND: Percutaneous sacroiliac (SI) screw fixation is the standard operative treatment of traumatic disruptions to the posterior pelvic ring. The technique offers good outcomes and early postoperative mobilization, which is vital in elderly patients with fragility fractures of the pelvis. While a double-screw technique has been shown to provide optimal biomechanical stability compared to a single-screw construct, anatomic variations and patient-specific characteristics may prevent the safe insertion of two SI screws. We aimed to determine whether cement augmentation of a single SI screw would provide biomechanical stability comparable to that of the double-screw technique. METHODS: Three sacroiliac screw osteosynthesis configurations were tested on 10 human cadaveric pelvis specimens: a single cannulated screw; two cannulated screws; and a single, cement-augmented cannulated screw. Displacement and stiffness of the anterior and posterior pelvic ring after fixation with each technique were measured under axial load. Results where compared using linear regression and paired t-tests. RESULTS: A single uncemented screw offered significantly worse stability in the anterior pelvis compared to a double-screw technique (P < 0.05) and to a single cement-augmented screw technique (P < 0.05). There was no significant difference in anterior pelvic ring stability between the single cement-augmented screw technique and the double-screw technique (P > 0.05). There was no significant difference in the stability of the posterior pelvic ring between the three techniques (P > 0.05). CONCLUSIONS: A single cement-augmented cannulated sacroiliac screw provides biomechanical stability similar to that of a non-augmented double-screw technique in the treatment of posterior pelvic ring fractures.

Load-Bearing Detection with Insole-Force Sensors Provides New Treatment Insights in Fragility Fractures of the Pelvis.

BACKGROUND: Due to an aging society, more and more surgeons are confronted with fragility fractures of the pelvis (FFPs). The aim of treatment of such patients should be the quickest possible mobilization with full weight-bearing. Up to now however, there are no data on loading of the lower extremities in patients suffering FFPs. We hypothesized to find differences in loading of the lower limbs. METHODS: 22 patients with a mean age of 84.1 years were included. During gait analysis with insole-force sensors, loading on the lower extremities was recorded during early mobilization after index fracture. RESULTS: Especially the average peak force showed differences in loading, as the affected limb was loaded significantly less {59.78% (SD ± 16.15%) of the bodyweight vs. 73.22% (SD ± 14.84%) (p = <0.001, effect size r = 0.58)}. Furthermore, differences in loading in between the fracture patterns of FFPs were observed. CONCLUSION: This study shows that it is possible to reliably detect the extremity load, with the help of an insole device, in patients presenting with fragility fractures of the pelvis. There is great potential to improve the choice and time of treatment with insole-force sensors in FFPs in future.

The T-pod is as stable as supraacetabular fixation using 1 or 2 Schanz screws in partially unstable pelvic fractures: a biomechanical study.

INTRODUCTION: Unstable fractures of the pelvis remain the predominant cause of severe hemorrhage, shock and early death in severely injured patients. The use of pelvic binders has become increasingly popular, particularly in the preclinical setting. There is currently insufficient evidence available about the stability of the pelvic binder versus supraacetabular fixation using 1 or 2 Schanz screws. We aimed to analyze the stability of the pelvic binder and supraacetabular fixateurs using either 1 or 2 Schanz screws in a cadaver model of an induced pelvic B-type fracture. MATERIALS AND METHODS: The study was undertaken in 7 human fresh-frozen cadaveric pelvises with induced AO-type B fractures. Three stabilization techniques were compared: T-POD (pelvic bandage), supraacetabular external fixator with 1 pin on each side and external fixator with 2 pins on each side. Stability and stiffness were analyzed in a biomechanical testing machine using a 5-step protocol with static and dynamic loading, dislocation data were retrieved by ultrasound sensors at the fracture sites. RESULTS: No significant differences in fracture fragment displacement were detected when using either the T-POD, a 1-pin external fixator or a 2-pin external fixator (P > 0.05). The average difference in displacement between the three methods was < 1 mm. CONCLUSIONS: Pelvic binders are suitable for reduction of pelvic B-type fractures. They provide stability comparable to that of supraacetabular fixators, independently of whether 1 or 2 Schanz screws per side are used. Pelvic binders provide sufficient biomechanical stability for transferring patients without the need to first replace them with surgically applied external fixators. However, soft tissue irritation has to be taken into consideration and prolonged wear should be avoided. LEVEL OF EVIDENCE: Level III.

Intraoperative use of cortical step sign and diameter difference sign: Accuracy, inter-rater agreement and influence of surgical experience in subtrochanteric transverse fractures.

BACKGROUND: The cortical step sign (CSS) and diameter difference sign (DDS) are radiographic tools for torsional alignment control in intramedullary nailing. They have been found to be highly relevant in objective radiographic measurements, but for intraoperative visual identification they lack sufficient evidence yet. The aim of this experimental study was to evaluate their (1) accuracy, (2) inter-rater agreement, (3) predictors of correct identification for clinically relevant maltorsion (CRM: ≥15°), and (4) positive and negative predictive values. HYPOTHESIS: Sensitivity and specificity of CSS and DDS in visual identification of CRM are comparable to those in objective measurement. MATERIAL AND METHODS: Six observers of three different levels of surgical experience evaluated 50 a.p. and 50 lateral views of subtrochanteric fractures of cadaveric specimens with internal/external maltorsion from 0° to 30° to assess for CSS, DDS, and CRM. (1) Sensitivity and specificity were evaluated. Percentage agreement and Cohen's Kappa were used to evaluate accuracy as agreement with measured/true values and (2) inter-rater agreement. To determine (3) significant predictors of correct identification of the CSS, DDS, and CRM, a mixed-effects logistic model was constructed, and (4) predictive values were calculated. RESULTS: (1) Sensitivities of CSS and DDS for CRM (0.99±0.03 and 0.88±0.06) were close to those in objective measurement (1.00 and 0.90). So were specificities (0.25±0.08 and 0.47±0.17 vs. 0.32 and 0.47). Agreement percentage for CSS was high (90-94%, kappa 0.40-0.69), for DDS and CRM it was slightly lower (74-82%, kappa 0.34-0.57 and 62-76%, kappa 0.26-0.49). (2) Inter-rater agreement also showed the highest values for CSS (88-96%, kappa 0.51-0.73) with slightly lower values for DDS (74-84%, kappa 0.36-0.63) and CRM (62-84%, kappa 0.21-0.68). (3) Training level and the magnitude of maltorsion were found the most relevant predictors of a correct identification of CSS/DDS/CRM. (4) DDS showed a higher positive predictive value (73.1%), CSS a higher negative predictive value (93.5%). DISCUSSION: We found visual identification of CSS and DDS to be almost as accurate as objective measurement in the detection of CRM. Estimation of maltorsion is not sufficiently reliable, but a negative CSS excludes a CRM with high probability. Both signs should be applied by experienced surgeons. LEVEL OF EVIDENCE: Level III, experimental setting, non-randomised experimental trial.

3D printing method for next-day acetabular fracture surgery using a surface filtering pipeline: feasibility and 1-year clinical results.

INTRODUCTION: In orthopedic surgery, 3D printing is a technology with promising medical applications. Publications show promising results in acetabular fracture surgery over the last years using 3D printing. However, only little information about the workflow and circumstances of how to properly derive the 3D printed fracture model out of a CT scan is published. MATERIALS AND METHODS: We conducted a retrospective analysis of patients with acetabular fractures in a level 1 trauma center. DICOM data were preoperatively used in a series of patients with acetabular fractures. The 3D mesh models were created using 3D Slicer (https://www.slicer.org) with a newly introduced surface filtering method. The models were printed using PLA material with FDM printer. After reduction in the printed model, the acetabular reconstruction plate was bent preoperatively and sterilized. A clinical follow-up after 12 months in average was conducted with the patients. RESULTS: In total, 12 patients included. Mean printing time was 8:40 h. The calculated mean printing time without applying the surface filter was 25:26 h. This concludes an average printing time reduction of 65%. Mean operation time was 3:16 h, and mean blood loss was 853 ml. Model creation time was about 11 min, and mean printing time of the 3D model was 8:40 h, preoperative model reduction time was 5 min on average, and preoperative bending of the plate took about 10 min. After 12 months, patients underwent a structured follow-up. Harris Hip Score was 75.7 points, the Modified Harris Hip Score 71.6 points and the Merle d'Aubigne Score 11.1 points on average. CONCLUSIONS: We presented the first clinical practical technique to use 3D printing in acetabular fracture surgery. By introducing a new surface filtering pipeline, we reduced printing time and cost compared to the current literature and the state of the art. Low costs and easy handling of the 3D printing workflow make it usable in nearly every hospital setting for acetabular fracture surgery.

Biomechanical comparison of minimally invasive treatment options for Type C unstable fractures of the pelvic ring.

BACKGROUND: The definite treatment of pelvic C fractures presents a widely discussed issue and undergoes continuous evolution. While the stabilization of the posterior ring has been studied extensively, the fixation of the anterior pelvic ring continuous to be rarely investigated. The importance of the simultaneous stabilization however lays in the earlier mobilization and prevention of long-term damage to the pelvis. Therefore we investigated four combinations of minimally invasive fixation techniques for unstable type C1-3 pelvic injuries and aimed to answer the following research questions: (1) what combination of fixation methods yields the highest stiffness and the least displacement? (2) Is the combination of a single sacroiliac screw (SI-screw) with a transiliac internal fixator (TIFI) a reasonable alternative to two SI-screws? (3) Is a modified unilateral anterior fixation comparable to a retrograde transpubic screw? HYPOTHESIS: Minimally invasive fixation techniques provide sufficient biomechanical stability for type C pelvic fractures. METHODS: Thirty synthetic full pelvises were divided into 5 groups, of which 4 groups were assigned a different osteosynthesis method and one was an intact pelvis used as reference (group 1: internal fixator+2 sacroiliac screws, group 2: internal fixator+transiliac internal fixator+1 sacroiliac screw, group 3: retrograde transpubic screw+2 sacroiliac screws, group 4: retrograde transpubic screw+transiliac internal fixator+1 sacroiliac screw). The pelvises underwent a protocol of cyclic loading between 100N and 200N, during which they were subjected to compression loads while the position of the fracture fragments was measured every 30 milliseconds. Displacement and stiffness were calculated for statistical analysis. RESULTS: The minimally invasive fixation methods investigated in this study all provide sufficient biomechanical stability without one method being superior to the others (p [anterior displacement]=0.61 and p [posterior displacement]=0.88). Group 3 was allowed the least displacement (1.8±0.2mm for anterior and posterior fracture) for the treatment of a C1.3 fracture. The other fixation methods displayed the following dislocations (mm) of the anterior pelvic ring: group 1: 1.9±0.3, group 2: 2.1±0.4, group 4: 2.0±0.5. Posteriorly, the displacements (mm) were the following: group 1: 1.8±0.6, group 2: 1.9±0.2, group 4: 2.0±0.5. DISCUSSION: The minimally invasive fixation methods investigated in this study all provide sufficient biomechanical stability without one method being superior to the others since differences were not significant regarding anterior and posterior displacements. Even if not significantly, we could reveal that out of all the methods tested the combination of 2 SI-screws with a retrograde transpubic screw (group 3) displayed the least displacement and highest stiffness. These techniques could therefore potentially improve patient's clinical outcome by reducing the surgical invasiveness and procedure time while providing sufficient biomechanical stability. LEVEL OF EVIDENCE: III, comparative in vitro study.

Fluoroscopic Marker-Based Guidance System Improves Gamma Lag Screw Placement During Nailing of Intertrochanteric Fractures: A Randomized Controlled Trial.

OBJECTIVES: To determine whether a fluoroscopy-based navigation system would improve tip-apex distance (TAD) compared with the conventional technique. DESIGN: Randomized controlled trial. SETTING: Level 1 trauma center. PATIENTS: A total of 161 patients were screened for inclusion in the study. After meeting inclusion and exclusion criteria, 31 patients were randomized (n = 18 navigated vs. n = 13 control group), with the patient blinded to the result. INTERVENTION: Fluoroscopy-based navigated guidance of lag screw length and position. MAIN OUTCOME MEASURES: Average TAD and the proportion of TAD over 25 mm. RESULTS: TAD was lower in the navigated group compared with the control group (mean = 17.5 vs. 24.2 mm; P = 0.0018). No navigated cases exceeded the 25 mm TAD threshold, compared with 39% of conventional cases (P = 0.0076). Navigation resulted in fewer drilling attempts compared with the conventional technique (median = 1 vs. 4 attempts; P < 0.0001). We detected no significant differences in operation time or total number of fluoroscopic images (P > 0.05). CONCLUSIONS: Fluoroscopy-based computer navigated Gamma nailing for intertrochanteric fractures improved TAD and reduced the number of drilling attempts without increasing operation time compared with the conventional fluoroscopy-guided technique in a teaching hospital setting. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Modified less invasive anterior subcutaneous fixator for unstable Tile-C-pelvic ring fractures: a biomechanical study.

BACKGROUND: Operative procedures for unstable pelvic ring fractures remain controversially discussed. Minimally invasive treatment options for pelvic ring fractures have several benefits for the patient. But they can also provide disadvantages. Anterior subcutaneous pelvic fixation (INFIX) has shown promising biomechanical results in pelvic ring fractures, but there is a high complication rate of nerve injuries. An additional screw to the INFIX seems to be more stable. The aim of this study is to compare biomechanical stability of a new modified unilateral INFIX fixing the unilateral injured pelvic ring with the standard INFIX. METHODS: 24 composite synthetic full pelvises were used in this study. 4 groups each with a number of six pelvic specimens were randomly assigned. A C1.3-type pelvic fracture was made with an osteotomy of the sacrum and an osteotomy of the anterior pelvic ring. Fracture fixation was performed within the four groups: (1) unilateral INFIX, (2) "extended" unilateral INFIX + additional pubic ramus pedicle screw, (3) bilateral INFIX, (4) "extended" bilateral INFIX + additional pubic ramus pedicle screw. All specimens were cyclic loaded with 200 N until maximum of 300 N. Distance/dislocation of the fracture fragments were detected with 3D-ultrasound measuring system. Stiffness was calculated. RESULTS: Extended unilateral INFIX showed the lowest mean dislocation. Lowest rotational stability was displayed by the standard bilateral INFIX. A significant difference (P = 0.04) was shown between the extended unilateral INFIX and the "standard" bilateral INFIX in terms of rotational stability. Extended unilateral INFIX showed significantly improved stability of anterior fracture dislocation (P = 0.01) and unilateral INFIX showed the highest rotational stiffness. Anterior fixation stiffness of the unilateral INFIX was significantly improved using an additional symphysis/pubic ramus screw (P = 0.002). CONCLUSION: Extended unilateral INFIX (+ additional pubic ramus pedicle screw) is a feasible minimally invasive treatment for anterior pelvic ring fractures. Higher stability and lower probability of bilateral nerve damage is provided by the extended unilateral INFIX compared to the standard bilateral INFIX.