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.

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.

Does augmentation increase the pull-out force of symphyseal screws? A biomechanical cadaver study.

PURPOSE: Open reduction and internal fixation using anterior plate osteosynthesis currently represents the gold standard for the treatment of symphyseal disruptions. Since postoperative screw loosening with consequent implant failure is frequently observed, this study aims to evaluate if and to what extent augmentation can increase the pull-out force of symphyseal screws to improve the constructs stability. METHODS: Twelve human cadaveric anterior pelvic rings were separated at the symphyseal joint for bilateral testing, consequently achieving comparable sites. First, one non-augmented screw was drilled into the superior pubic ramus, whereas the contralateral side was primarily augmented. The screws were then withdrawn with a constant speed of 10 mm/min and the fixation strengths determined by the force (N) displacement (mm) curve. Finally, the primary non-augmented site was secondary augmented, representing revision surgery after initial implant failure, and the corresponding fixation strength was measured again. RESULTS: Augmentation compared to non-augmented screws displayed significantly higher pull-out forces with an increase in pull-out force by 377% for primary and 353% for secondary augmentation (p < 0.01). There was no significant difference in the pull-out force comparing primary and secondary augmentation (p = 0.74). CONCLUSIONS: Primary and secondary augmentation significantly increases the stability of symphyseal screws and, therefore, potentially decreases rates of implant failure.

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.

How relevant is lumbar bone mineral density for the stability of symphyseal implants? A biomechanical cadaver study.

PURPOSE: Osteoporotic bone tissue appears to be an important risk factor for implant loosening, compromising the stability of surgical implants. However, it is unclear whether lumbar measured bone mineral density (BMD) is of any predictive value for stability of surgical implants at the pubic symphysis. This study examines the fixation strength of cortical screws in human cadaver specimens with different BMDs. METHODS: The lumbar BMD of ten human specimens was measured using quantitative computed tomography (qCT). A cut-off BMD was set at 120 mg Ca-Ha/mL, dividing the specimens into two groups. One cortical screw was drilled into each superior pubic ramus. The screw was withdrawn in an axial direction with a steady speed and considered failed when a force decrease was detected. Required force (N) and pull-out distance (mm) were constantly tracked. RESULTS: The median peak force of group 1 was 231.88 N and 228.08 N in group 2. While BMD values differed significantly (p < 0.01), a comparison of peak forces between both groups showed no significant difference (p = 0.481). CONCLUSION: Higher lumbar BMD did not result in significantly higher pull-out forces at the symphysis. The high proportion of cortical bone near the symphyseal joint allows an increased contact of pubic screws and could explain sufficient fixation. This condition is not reflected by a compromised lumbar BMD in a qCT scan. Therefore, site-specific BMD measurement could improve individual fracture management.

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.

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.

Tape suture for stabilization of incomplete posterior pelvic ring fractures-biomechanical analysis of a new minimally invasive treatment for incomplete lateral compression pelvic ring fractures.

BACKGROUND: Incomplete lateral compression fractures (including AO Type B2.1) are among the most common pelvic ring injuries. Although the treatment of choice remains controversial, sacroiliac (SI) screws are commonly used for the operative treatment of incomplete lateral compression fractures of the pelvic ring. However, the disadvantages of SI screws include the risk of nerve root or blood vessel injury. Recently, tape sutures have been found useful as stabilizing material for the treatment of injuries of the syndesmosis, the rotator cuff and knee ligaments. In this current study, we aimed to test the biomechanical feasibility of tape sutures to stabilize the pelvis in the setting of AO Type B2.1 injury. METHODS: Six human cadaveric pelvises underwent cyclic loading to compare the biomechanical stability of different osteosynthesis methods in a B2.1 fracture model. The methods tested in this experiment were a FiberTape® suture and the currently established SI screw. A 3D ultrasound tracking system was used to measure fracture fragment motion. Linear regression was used to model displacement and stiffness at the posterior and anterior pelvic ring. RESULTS: At the posterior fracture site, the FiberTape® demonstrated similar displacement (2.2 ± 0.8 mm) and stiffness (52.2 ± 18.0 N/mm) compared to the sacroiliac screw (displacement 2.1 ± 0.6 mm, P >  0.999; stiffness 50.8 ± 13.0 N/mm, P > 0.999). Considering the anterior fracture site, the FiberTape® again demonstrated similar displacement (3.8 ± 1.3 mm) and stiffness (29.5 ± 9.0 N/mm) compared to the sacroiliac screw (displacement 2.9 ± 0.8 mm, P = 0.2196; stiffness 37.5 ± 11.5 N/mm, P = 0.0711). CONCLUSION: The newly presented osteosynthesis, the FiberTape®, shows promising results for the stabilization of the posterior pelvic ring in AO Type B2.1 lateral compression fractures compared to a sacroiliac screw osteosynthesis based on its minimal-invasiveness and the statistically similar biomechanical properties.

Minimally invasive screw fixation is as stable as anterior plating in acetabular T-Type fractures - a biomechanical study.

INTRODUCTION: Operative treatments of T-type acetabular fractures are challenging surgical procedures. Open reduction and internal fixation is the standard method for the operative management of these fractures, however this is associated with high blood loss, long hospital stay and longer rehabilitation. Anterior subcutaneous pelvic fixation (internal fixation=INFIX) and retrograde pubic screw fixation have shown promising results in minimally invasive treatment of pelvic ring fractures. For T-type acetabular fractures, however, minimally invasive treatment concepts are still rare. Therefore we performed a mechanical in vitro study to: - investigate the potential favorability of minimally invasive treatment options over the already established open anterior locking plate osteosynthesis of acetabular T-fractures regarding biomechanical stability and post-surgical stiffness; - explore the biomechanical feasibility of the INFIX; - assess its potential ability to reduce the anterior acetabular column. HYPOTHESIS: A minimally invasive treatment of acetabular T-type fractures is biomechanically equivalent to an open anterior plate osteosynthesis. METHODS: Twenty-four synthetic hemipelvis specimens with a T-type acetabular fracture were divided in four groups. A posterior column screw was placed in every pelvis of every group. The anterior column was fixed with: - anterior column screw; - anterior column screw incl. INFIX; - INFIX alone; - 14-hole angular stable locking plate (standard fixation method). Displacement of the anterior column was reduced in group 2+3 using the INFIX. All specimens were cyclically loaded with 200N until a maximum of 600N. Movement/displacement of the fracture fragments were detected with a 3D-ultrasound measuring system. Displacement (mm) and Stiffness (N/mm) of the construction were analyzed. RESULTS: Statistical assessment showed no significant differences between the four fixation types (p>0.05). The 14-whole locking plate (group 4) displayed the overall highest stability with a displacement of 1.3±0.04mm and stiffness of 76.3±2.4N/mm. Anterior screw fixation (group 1) proved to be the minimally invasive fixation method with the least displacement and highest stiffness (1.5±0.2mm, 68.3±6.8N/mm). The combination of an INFIX and an anterior column screw (group 2), showed a mean stiffness of 62.1±6.0N/mm and a mean displacement of 1.7±0.2mm. INFIX only (group 3) presented a displacement of 1.6±0.1mm and a stiffness of 64.5±4.5N/mm. DISCUSSION: Minimally invasive fixation techniques for T-type acetabular fractures show promising biomechanical stability in non- or slightly displaced fractures. Furthermore, INFIX could be a feasible tool for the reduction of the anterior acetabular column. LEVEL OF EVIDENCE: III, case control prospective experimental study.

Sacroiliac Coalition: First Description and Report of a Successful Resection.

Study Design Case report. Objective This report describes the first case of a sacroiliac coalition, its clinical features, the diagnostic difficulties, and the surgical treatment chosen in this case. Methods A 33-year-old man presented to our outpatient clinics complaining of severe left-sided low back pain with an intermitted nondermatomal radiation into the left thigh. The only abnormality on a pelvic radiograph was a coin-size, faint hyperdensity, which was almost overlooked. Subsequent computed tomography (CT) and magnetic resonance imaging (MRI) confirmed two bridging bone spurs on the anterior surface of the left joint with a fibrous interruption at the apex. After the conservative treatment failed, a surgical treatment was offered to the patient. The coalition was resected via an anterior retroperitoneal approach and through the tissue plane between the psoas and the iliacus muscles. A histopathologic examination was performed and confirmed the diagnosis of a coalition. Results The patient's pain resolved immediately after surgery. After 8 months, a follow-up CT scan showed complete removal of the coalition without any signs of recurrence, and at 12 months' follow-up, the patient remained pain-free. Conclusions This is the first published case of a sacroiliac coalition. The only sign of this rare condition on the plain radiographs was very easy to miss. As has been discussed in the literature, CT and MRI are important in the differential diagnostics of such lesions. The histopathologic findings included that of a fibrous bar, confirming the diagnosis, which is further corroborated by the complete resolution of the symptoms.

CT-guided sacroiliac percutaneous screw placement in unstable posterior pelvic ring injuries: accuracy of screw position, injury reduction and complications in 71 patients with 136 screws.

BACKGROUND: Sacroiliac-percutaneous-screw-placement (SPSP) for unstable-posterior-pelvic-ring-injuries (UPPRI) might be associated with severe neurovascular complications because of screw-mal-position. The aim of the present study was to analysis the effectivity of computer-tomography-guided (CTG)-SPSP including accuracy of screw-placement, quality of injury-reduction and documentation of perioperative-complications. Additionally, procedure-dependent radiation-dose and outcome should be analysed. METHODS: A consecutive cohort of 71 patients with UPPRI was operated by CTG-SPSP at a single trauma level 1 hospital. 136 sacroiliac screws were inserted to S1 and S2. Postoperatively, by the use of a computerised-radiologic-work-station all screws were visualised three-dimensionally. Their distancesmin to the sacral-borders in anterior-posterior and cranio-caudal direction as well as to the neuroforamen S1/S2 were determined. After CTG-SPSP, injury-dislocation in anterior-posterior and cranio-caudal direction was quantified. Local and general complications were documented during the 30-day-period. In 55 patients (77.5%) a follow-up-investigation (29.1±19.1 months) was performed. RESULTS: 132 screws (97.1%) were placed completely intraosseous, 3 screws (2.2%) perforated up to 1.0 mm (n(S1)=one screw; n(S2)=two screws), and one screw (0.7%) extended 2.2 mm into the S2-neuroforamen without contact to neural structures. Postoperative dislocationanterior-posterior was 1.3±0.9 mm and dislocationcranio-caudal 1.5±0.9 mm. No procedure-associated-complication was observed. Operation time showed a significant "learning curve" during the six-year study period (initially: 88.6±60.3 min; finally: 44.3±24.6 min). Perioperative effective-radiation-dose for patientsmale was 5.9±3.1 mSv and for patientsfemale 8.7±4.5 mSv. All injuries healed and 33 patients (46.5%) had metal removal after 11.0 (±4.9) months. Only two (5.0%) out of 40 patients complained persistent UPPRI-related pain so they were not able to restart work. CONCLUSIONS: The CTG-SPSP is a safe procedure for UPPRI-stabilisation especially in S1 but also in S2. Injury reduction was excellent and no procedure associated complications were observed.

Hydroxyapatite-coated pins versus titanium alloy pins in external fixation at the wrist: a controlled cohort study.

BACKGROUND: The purpose of this study was to analyze whether the prevalence of pin-related complications can be reduced by the use of hydroxyapatite (HA)-coated pins in external fixators applied for unstable wrist fractures. METHODS: Forty patients (160 pins) were randomized for standard uniplanar fixator treatment with the use of identically designed pins either composed of titanium-alloy (Ti6Al4V) (n = 20) or coated by HA (n = 20). Each pin site was clinically evaluated with regard to erythema, drainage, pain value, and radiologically assessed concerning loosening at T1 (mean, 9 days), T2 (mean, 43 days), and T3 (mean, 56 days). In case of pin-track complication, the patient was followed continuously. The need for antibiotics or additional surgery was documented. Bone mineral density was analyzed by Dual Energy X-ray Absorptiometry. At fixator removal (T2), the pin-extraction strength was measured by the use of a digital-torque-wrench. RESULTS: Two minor pin-track infections requiring oral antibiotics occurred in the HA-pin group (2.7%) (p > 0.05). The vast majority of clinical pin-site parameters were comparable in both groups. At the end of the fixator therapy, there were 16 loose pins (n(Ti6AL4V-group) = 10; n(HA-group) = 6). The rate of loose pins was correlated to patient's age (p < 0.05) but not to bone mineral density values or the occurrence of pin-site infection. Finally, no significant difference between the two groups was detected with regard to the prevalence of clinical relevant pin-site complications (p = 0.80). CONCLUSIONS: In external fixation of the wrist, the use of HA-coated pins yields no clinical advantages: there is a trend toward a superior pin-bone anchorage, but a tendency of increased susceptibility for minor pin-track infections.

Clinical benefit of hydroxyapatite-coated pins compared with stainless steel pins in external fixation at the wrist: a randomised prospective study.

BACKGROUND: The purpose of this study was to determine the clinical benefit of hydroxyapatite (HA)-coated pins compared with standard stainless steel pins in external fixators applied for unstable fractures of the distal radius. METHODS: A total of 40 patients (160 pins) with unstable wrist fractures were randomised for uniplanar fixator treatment with the use of identically designed, commercially available pins either composed of stainless steel (steel group) (n = 20) or coated by hydroxyapatite (HA group) (n = 20). Each pin site was clinically evaluated concerning erythema and grade of drainage as well as pain intensity (numeric rating scale (NRS) 0­10) and, additionally, radiological assessment was performed concerning pin-loosening/infection as well as fracture healing at T1 (Ø18 days), T2 (Ø44 days) and T3 (Ø65 days). In case of pintrack complication, the patient was followed continuously. The need for intensified pin-site care, oral or intravenous antibiotic medication, re-admission for additional surgery and premature fixator removal was documented. Bone mineral density (BMD) was determined by dual energy X-ray absorptiometry. At fixator removal (T2), the pin-extraction strength was measured by the use of an electronic torque wrench. RESULTS: Two pin-track infections requiring daily pin-site care and oral antibiotics occurred in the HA group (2.6%) compared with four in the steel group (5.3%) (p = 0.601) and although a trend towards a superior performance of HA pins was detectable, the majority of clinical pin-site-parameters were comparable in both groups. At the end of the fixator therapy, the HA group showed a non-significant lower rate of loose pins (n(steel group) = 9; n(HA group) = 6; p = 0.864) and both hydroxyapatite-coated pins showed at the radius a significantly stronger pin-bone bonding measured by the torque wrench (p(proximal radius pin) = 0.007; p(distal radius pin) = 0.031). Except for elderly patients of the steel group (p = 0.018), all demographic-, health- and injury-related data including BMD were not correlated to any type of pin-site complication in both groups (p > 0.05). Since all fracture healed uneventfully without any type of additional surgery, the number of patients suffering clinically relevant pin-related complications showed no significant difference between both groups (p = 0.707). CONCLUSIONS: The use of HA-coated pins compared with standard stainless-steel pins in external fixation for unstable wrist fractures yields only a trend towards a superior clinical outcome.

Genetically engineered attenuated measles virus specifically infects and kills primary multiple myeloma cells.

The applicability of cytoreductive treatment of malignant diseases using recombinant viruses strongly depends on specific recognition of surface receptors to target exclusively neoplastic cells. A recently generated monoclonal antibody (mAb), Wue-1, specifically detects CD138(+) multiple myeloma (MM) cells. In this study, a haemagglutinin (H) protein that was receptor-blinded (i.e. did not bind to CD46 and CD150) was genetically re-engineered by fusing it to a single-chain antibody fragment (scFv) derived from the Wue-1 mAb open reading frame (scFv-Wue), resulting in the recombinant retargeted measles virus (MV)-Wue. MV-Wue efficiently targeted and fully replicated in primary MM cells, reaching titres similar to those seen with non-retargeted viruses. In agreement with its altered receptor specificity, infection of target cells was no longer dependent on CD150 or CD46, but was restricted to cells that had been labelled with Wue-1 mAb. Importantly, infection with MV-Wue rapidly induced apoptosis in CD138(+) malignant plasma cell targets. MV-Wue is the first fully retargeted MV using the restricted interaction between Wue-1 mAb and primary MM cells specifically to infect, replicate in and deplete malignant plasma cells.