Intra- and postoperative complications of navigated and conventional techniques in percutaneous iliosacral screw fixation after pelvic fractures: Results from the German Pelvic Trauma Registry

Background

Percutaneous iliosacral screw placement following pelvic trauma is a very demanding technique involving a high rate of screw malpositions possibly associated with the risk of neurological damage or inadequate stability. In the conventional technique, the screw's correct entry point and the small target corridor for the iliosacral screw may be difficult to visualise using an image intensifier. 2D and 3D navigation techniques may therefore be helpful tools.The aim of this multicentre study was to evaluate the intra- and postoperative complications after percutaneous screw implantation by classifying the fractures using data from a prospective pelvic trauma registry. The a priori hypothesis was that the navigation techniques have lower rates of intraoperative and postoperative complications.

Methods

This study is based on data from the prospective pelvic trauma registry introduced by the German Society of Traumatology and the German Section of the AO/ASIF International in 1991. The registry provides data on all patients with pelvic fractures treated between July 2008 and June 2011 at any one of the 23 Level I trauma centres contributing to the registry.

Results

A total of 2615 patients were identified. Out of these a further analysis was performed in 597 patients suffering injuries of the SI joint (187 × with surgical interventions) and 597 patients with sacral fractures (334 × with surgical interventions).The rate of intraoperative complications was not significantly different, with 10/114 patients undergoing navigated techniques (8.8%) and 14/239 patients in the conventional group (5.9%) for percutaneous screw implantation (p = 0.4242).Postoperative complications were analysed in 30/114 patients in the navigated group (26.3%) and in 70/239 patients (29.3%) in the conventional group (p = 0.6542). Patients who underwent no surgery had with 66/197 cases (33.5%) a relatively high rate of complications during their hospital stay. The rate of surgically-treated fractures was higher in the group with more unstable Type-C fractures, but the fracture classification had no significant influence on the rate of complications.

Discussion

In this prospective multicentre study, the 2D/3D navigation techniques revealed similar results for the rate of intraoperative and postoperative complications compared to the conventional technique. The rate of neurological complications was significantly higher in the navigated group.     

Supplemental S1 fixation for type C pelvic ring injuries: biomechanical study of a long iliosacral versus a transsacral screw

Background

A single iliosacral screw placed into the S1 vertebral body has been shown to be clinically unreliable for certain type C pelvic ring injuries. Insertion of a second supplemental iliosacral screw into the S1 or S2 vertebral body has been widely used. However, clinical fixation failures have been reported using this technique, and a supplemental long iliosacral or transsacral screw has been used. The purpose of this study was to compare the biomechanical effect of a supplemental S1 long iliosacral screw versus a transsacral screw in an unstable type C vertically oriented sacral fracture model.

Materials and methods

A type C pelvic ring injury was created in ten osteopenic/osteoporotic cadaver pelves by performing vertical osteotomies through zone 2 of the sacrum and the ipsilateral pubic rami. The sacrum was reduced maintaining a 2-mm fracture gap to simulate a closed-reduction model. All specimens were fixed using one 7.0-mm iliosacral screw into the S1 body. A supplemental long iliosacral screw was placed into the S1 body in five specimens. A supplemental transsacral S1 screw was placed in the other five. Each pelvis underwent 100,000 cycles at 250 N, followed by loading to failure. Vertical displacements at 25,000, 50,000, 75,000, and 100,000 cycles and failure force were recorded.

Results

Vertical displacement increased significantly (p < 0.05) within each group with each increase in the number of cycles. However, there was no statistically significant difference between groups in displacement or load to failure.

Conclusions

Although intuitively a transsacral screw may seem to be better than a long iliosacral screw in conveying additional stability to an unstable sacral fracture fixation construct, we were not able to identify any biomechanical advantage of one method over the other.

Level of evidence

Does not apply—biomechanical study.     

An evaluation of three-dimensional image–guided technologies in percutaneous pelvic and acetabular lag screw placement

Background

Percutaneous stabilization using three-dimensional (3D) navigation system is a promising treatment for pelvic and acetabular fractures. However, there are still some controversies regarding the use of 3D navigation to treat pelvic and acetabular fractures. The purpose of this study was to compare the Iso-C^3D fluoroscopic navigation, standard fluoroscopy, and two-dimensional (2D) fluoroscopic navigation in placing percutaneous lag screws in pelvic specimens to better understand the merits of 3D navigation techniques.

Methods

Fifty-four instrumentation procedures were performed in this study using six cadaveric pelvic specimens. Three groups were designated for different procedures and tests: group I, standard fluoroscopy; group II, 2D fluoroscopic navigation; and group III, Iso-C^3D fluoroscopic navigation. Nine screws were placed in each pelvis, including four screws placed bilaterally through the ilium into S1 and S2 vertebrae, four screws placed bilaterally through anterior and posterior columns of acetabulum, and one screw placed through the pubic symphysis. 3D fluoroscopic techniques were evaluated to determine the accuracy of screw position, instrumentation time, and fluoroscopic time. The data were statistically analyzed using SPSS 13.0.

Results

The malposition rate was 38.89%, 22.22%, and 0% in standard fluoroscopy, 2D fluoroscopic navigation, and Iso-C^3D fluoroscopic navigation groups, respectively. There was no significant difference between standard fluoroscopy and 2D fluoroscopic navigation. Compared with Iso-C^3D fluoroscopic navigation, there were significant differences (analysis of variance [ANOVA], P < 0.05). The mean instrumentation operating time using Iso-C^3D fluoroscopic navigation technique was 15.4 ± 4.5 min. There were significant differences compared with standard fluoroscopy (31.5 ± 6.2 min) and 2D fluoroscopic navigation (26.3 ± 7.5 min; ANOVA, post hoc Scheffe, P < 0.01). The mean fluoroscopic time of Iso-C^3D fluoroscopic navigation was 66 ± 4.8 min. Compared with standard fluoroscopy (132.8 ± 7.3 min) and 2D fluoroscopic navigation (47.7 ± 5.6 min), there were significant differences (ANOVA, post hoc least significant difference, P < 0.01).

Conclusions

In the present study, we compared Iso-C^3D fluoroscopic navigation, 2D fluoroscopic navigation, and standard fluoroscopy. Iso-C^3D fluoroscopic navigation showed a higher accuracy rate in positioning and a shorter instrumentation operating time. The fluoroscopic time was longer in Iso-C^3D fluoroscopic navigation than that in standard fluoroscopy, indicating that radiation exposure can be moderately reduced in Iso-C^3D fluoroscopic navigation operation, although the fluoroscopic time was the shortest in 2D fluoroscopic navigation.     

Risk of injury to the axillary nerve during antegrade proximal humeral blade nail fixation – An anatomical study

Introduction

The antegrade intramedullary Locking Blade Nail (Marquardt, Germany) is a device aimed at improving purchase in the humeral head and reducing varus displacement by providing medial buttress support and triangular stability within the humeral head. The aim of this study is to measure the relationship of the proximal fixation screws to the axillary nerve.

Methods

13 whole cadavers underwent insertion of an antegrade proximal humeral blade nail via a deltoid split approach to both shoulders. The anatomic proximity of the anterior branch of the axillary nerve to the screws was measured following soft tissue dissection and inspection of the nerve.

Results

The mean distance of the nerve from the anterolateral acromion was 62 mm (range 45–81 mm). The nerve lay closest to the distal blade fixation screw 4.9 mm (range 0–19 mm). In three cases the nerve lay directly underneath the washer and in all three cases there was macroscopic evidence of damage to the nerve. In 5 cases the nerve travelled obliquely in a cranial direction to lie 1.8 mm (range 0–3 mm) from the distal blade fixation screw, in 2 of these cases the nerve lay beneath the washer.

Conclusion

The anterior branch of the axillary nerve is placed at risk during insertion of the locking screws despite use of protection sleeves and trocars. We advocate that when using antegrade intramedullary nails that incorporate an inferomedial calcar screw an extended anterolateral acromial approach is undertaken.     

Accuracy of screw fixation using the O-arm<Superscript>®</Superscript> and StealthStation<Superscript>®</Superscript> navigation system for unstable pelvic ring fractures

Purpose

Screw fixation for unstable pelvic ring fractures is generally performed using the C-arm. However, some studies reported erroneous piercing with screws, nerve injuries, and vessel injuries. Recent studies have reported the efficacy of screw fixations using navigation systems. The purpose of this retrospective study was to investigate the accuracy of screw fixation using the O-arm^® imaging system and StealthStation^® navigation system for unstable pelvic ring fractures.

Methods

The participants were 10 patients with unstable pelvic ring fractures, who underwent screw fixations using the O-arm StealthStation navigation system (nine cases with iliosacral screw and one case with lateral compression screw). We investigated operation duration, bleeding during operation, the presence of complications during operation, and the presence of cortical bone perforation by the screws based on postoperative CT scan images. We also measured the difference in screw tip positions between intraoperative navigation screen shot images and postoperative CT scan images.

Results

The average operation duration was 71 min, average bleeding was 12 ml, and there were no nerve or vessel injuries during the operation. There was no cortical bone perforation by the screws. The average difference between intraoperative navigation images and postoperative CT images was 2.5 ± 0.9 mm, for all 18 screws used in this study.

Conclusion

Our results suggest that the O-arm StealthStation navigation system provides accurate screw fixation for unstable pelvic ring fractures.

     

Percutaneous iliosacral screwing in pelvic ring injury using three-dimensional fluoroscopy

Background

Iliosacral screw fixation is a popular technique for treatment of unstable pelvic injuries involving the posterior ring. However, screw malposition may result in dangerous complications involving injury to adjacent neurovascular structures. This study was conducted in order to evaluate the results and efficacy of using three-dimensional fluoroscopy in the performance of iliosacral screw fixation.

Methods

Twenty-nine patients (31 cases, two bilateral) who suffered injury to the pelvic ring requiring surgical treatment were included in this study. According to the Association for Osteosynthesis-Orthopaedic Trauma Association (AO-OTA) classification, there were 14 patients with type B, 13 patients with type C, and 2 patients with a bilateral sacral fracture. The mean age of patients was 39 years. Once the guide pin had been inserted, its safety was confirmed using three-dimensional fluoroscopy; screw fixation was then performed. Eighteen patients underwent percutaneous iliosacral screw fixation and anterior fixation, while 11 patents underwent screw fixation only. Postoperative computed tomography (CT) was performed for evaluation of the screw position, including any invasion into the sacral foramen or canal and neurovascular injury. The perforation of the screw was divided according to the location (sacral zones I, II, and III) and the degree (grade 0, no perforation; grade 1, perforation <2 mm; grade 2, perforation between 2 and 4 mm; grade 3, perforation >4 mm).

Results

The mean operation time was 35.6 min, and the mean radiation exposure time was 85.9 s. For accurate location of the guide pin, one patient underwent three-dimensional reconstruction twice. None of the patients required reoperation or suffered any neurovascular injury. Although seven cases involved perforation, all were less than 2 mm (grade 0: 24 cases, grade 1: 7 cases).

Conclusions

When performing percutaneous iliosacral screw fixation in a patient with an unstable pelvic ring injury, use of three-dimensional fluoroscopy may allow for accurate location of the screw and result in fewer complications.     

Augmented Reality: A New Tool To Improve Surgical Accuracy during Laparoscopic Partial Nephrectomy? Preliminary In Vitro and In Vivo Results

Background

Use of an augmented reality (AR)–based soft tissue navigation system in urologic laparoscopic surgery is an evolving technique.

Objective

To evaluate a novel soft tissue navigation system developed to enhance the surgeon's perception and to provide decision-making guidance directly before initiation of kidney resection for laparoscopic partial nephrectomy (LPN).

Design, setting, and participants

Custom-designed navigation aids, a mobile C-arm capable of cone-beam imaging, and a standard personal computer were used. The feasibility and reproducibility of inside-out tracking principles were evaluated in a porcine model with an artificially created intraparenchymal tumor in vitro. The same algorithm was then incorporated into clinical practice during LPN.

Interventions

Evaluation of a fully automated inside-out tracking system was repeated in exactly the same way for 10 different porcine renal units. Additionally, 10 patients underwent retroperitoneal LPNs under manual AR guidance by one surgeon.

Measurements

The navigation errors and image-acquisition times were determined in vitro. The mean operative time, time to locate the tumor, and positive surgical margin were assessed in vivo.

Results and limitations

The system was able to navigate and superpose the virtually created images and real-time images with an error margin of only 0.5 mm, and fully automated initial image acquisition took 40 ms. The mean operative time was 165 min (range: 135–195 min), and mean time to locate the tumor was 20 min (range: 13–27 min). None of the cases required conversion to open surgery. Definitive histology revealed tumor-free margins in all 10 cases.

Conclusions

This novel AR tracking system proved to be functional with a reasonable margin of error and image-to-image registration time. Mounting the pre- or intraoperative imaging properties on real-time videoendoscopic images in a real-time manner will simplify and increase the precision of laparoscopic procedures.     

Trans-iliosacral plating for vertically unstable fractures of sacral spine associated with spinopelvic dissociation: A cadaveric study

Background:

The treatment algorithm for sacral fracture associated with vertical shear pelvic fracture has not emerged. Our aim was to study a new approach of fixation for comminuted and vertically unstable fracture pattern with spinopelvic dissociation to overcome inconsistent outcome and avoid complications associated with fixations. We propose fixation with well-contoured thick reconstruction plate spreading across sacrum from one iliac bone to another with fixation points in iliac wing, sacral ala and sacral pedicle on either side. Present biomechanical study tests the four fixation pattern to compare their stiffness to vertical compressive forces.

Materials and Methods:

Dissection was performed on human cadavers through posterior midline paraspinal approach elevating erector spinae from insertion with two flaps. Feasibility of surgical exposure and placement of contoured plate for fixation was evaluated. Ten age and sex matched computed tomography scans of pelvis with both hips were obtained. Reconstructions were performed with advantage windows 4.2 (GE Light Speed QX/I, General Electric, Milwaukee, WI, USA). Using the annotation tools, direct digital CT measurement (0.6 mm increments) of three linear parameters was carried out. Readings were recorded at S2 sacral level. Pelvic CT scans were extensively studied for entry point, trajectory and estimated length for screw placement in S2 pedicle, sacral ala and iliac wing. Readings were recorded for desired angulation of screw in iliac wing ala of sacrum and sacral pedicle with respect to midline. The readings were analyzed by the values of mean and standard deviation. Biomechanical efficacy of fixation methods was studied separately on synthetic bone. Four fixation patterns given below were tested to compare their stiffness to vertical compressive forces: 1) Single S1 iliosacral screw (7.5 mm cancellous screw), 2) Two S1 and S2 iliosacral screws, 3) Isolated trans-iliosacral plate, 4) Trans-iliosacral plate + single S1 iliosacral screw.

Statistical Analysis:

Mean of desired angulation for inserting screws and percentage of displacement on biomechanical testing was evaluated.

Results:

Mean angulations for inserting sacral pedicel were 12.3° (SD 2.7°) convergent to midline and divergent of 14° (SD 2.3°) for sacral ala screw and 23° (SD 4.9°) for iliac wing screw. All screws needed to be inserted at an angle of 90° to sacral dorsum to avoid violation of root canals. Cross headed displacement across fracture site was measured and plotted against the applied vertical shear load of 300 N in five cycles each for all the four configurations. Also, the force required for cross headed displacement of 2.5 mm and 5 mm was recorded for all configurations. Transmitted load across both ischial tuberosities was measured to resolve unequal distribution of forces. Taking one screw construct (configuration 1) as standard base reference, trans-iliosacral plate construct (configuration 3) showed equal rigidity to standard reference. Two screw construct (configuration 2) was 12% stronger and trans-iliosacral plate (configuration 4) with screw was 9% stronger at 2.5 mm displacing on 300 N force, while it showed 30% and 6%, respectively, at 5 mm cross-headed displacement.

Conclusions:

Trans-iliosacral plating is feasible anatomically, biomechanically and radiologically for sacral fractures associated with vertical shear pelvic fractures. Low profile of plate reduces the risk of hardware prominence and decreases the need for implant removal. Also, the fixation pattern of plate allows to spare mobile lumbosacral junction which is an important segment for spinal mobility. Biomechanical studies revealed that rigidity offered by plate for cross headed displacement across fracture site is equal to sacroiliac screws and further rigidity of construct can be increased with addition of one more screw. There is need for precountered thicker plate in future.     

Navigation of vertebro-pelvic fixations based on CT-fluoro matching

Different navigation procedures (based on 2D-, 3D-fluoroscopy or CT modalities) with their respective limitations are established in orthopedic surgery. The hypothesis is that intraoperative matching of different modalities (fluoro and CT) increases the precision of navigated screw placement and reduces the fluoroscopy time. Vertical unstable pelvic ring fractures of 12 patients were treated with vertebro-pelvic fixations (6 in the standard technique and 6 using the fluoro-CT navigation). An optimal osseous corridor could be determined by the navigation procedure increasing the overall precision of screw placement (no misplacement in the second group as compared to one malplaced pedicle screw in the standard group). The achieved screw lengths were [(mean ± SE) 78 ± 5 vs. 53 ± 4 mm, p < 0.001). Less invasive open approaches and a reduction of fluoroscopy time (time per screw in seconds: 121 vs. 62 s) were observed. CT-fluoro-matched navigation improves the intraoperative visualization of osseous structures and increases the precision of screw placement with less radiation exposure.     

Applied anatomy of the calcaneocuboid articular surface for internal fixation of calcaneal fractures

Background

Many types of steel plates are used for internal fixation of calcaneal fractures through extensive lateral approach. The fixation screw at the anterior calcaneal process must be placed into the dense compression trabeculae located directly under the calcaneocuboid articular surface to achieve a stable fixation.

Methods

The transverse diameter and inner tilt angle of the calcaneocuboid articular surface were measured and the inner structures near the calcaneocuboid articular surface were observed in forty adult calcaneus bone specimens to provide an anatomical basis for internal fixation of calcaneal fractures.

Results

The transverse diameter was 22.67 ± 2.14 mm and the inner tilt angle was 60.4 ± 7.1°.

Conclusion

Screws should be implanted under the calcaneocuboid articular surface and the length and direction of the screw should be selected according to the transverse diameter of the calcaneal articular surface and the inner tilt angle, respectively.     

Locked versus standard unlocked plating of the symphysis pubis in a Type-C pelvic injury: A cadaver biomechanical study

Introduction

The benefits of locked plating for pubic symphyseal disruption have not been established. The purpose of this biomechanical study was to determine whether locked plating offers any advantage over conventional unlocked plating of the pubic symphysis in the vertically unstable, Type-C pelvic injury.

Methods

In each of eight embalmed cadaver pelvis specimens, sectioning of the pubic symphysis in conjunction with a unilateral release of the sacroiliac, sacrospinous, and sacrotuberous ligaments and pelvic floor was performed to simulate a vertically unstable Type-C (Orthopaedic Trauma Association 61-C1.2) pelvic injury. The disrupted SI joint was then reduced and fixed using two 6.5 mm cannulated screws inserted into the S1 body. Using a six-hole 3.5 mm plate specifically designed for the symphysis pubis having both locked and unlocked capability, four pelvises were fixed with locked screws and four pelvises were fixed with standard unlocked bicortical screws. Both groups were similar based on a dual-emission X-ray absorptiometry evaluation (P = 0.69). Each pelvis was then mounted on a servohydraulic materials-testing apparatus using a bilateral stance model to mainly stress the symphyseal fixation and was cycled up to 1 million cycles or failure, whichever occurred first.

Results

Five specimens experienced failure at the jig mounting/S1 vertebral body interface, occurring between 360,000 and 715,000 cycles. Frank failure of the anterior or posterior instrumentation did not occur. However, end-trialing diastasis of the initial pubic symphysis reduction was found in all pelvises. There were no differences between the groups with respect to this loss of symphyseal reduction (P = 0.69) or average cycles to failure (P = 1.0).

Conclusion

Pubic symphyseal locked plating does not appear to offer any advantage over standard unlocked plating for a Type-C (OTA 61-C1.2) pelvic ring injury.     

Intraoperative three-dimensional fluoroscopy assessment of iliosacral screws and lumbopelvic implants stabilizing fractures of the os sacrum

Introduction  

Percutaneous iliosacral screw fixation of unstable sacrum fractures has gained popularity since its introduction in the 1990s. The combination with lumbopelvic implants allows the application even in situations of higher instability. Both manual and navigated screw insertion in the sacrum and vertebra bodies shows unchanged relevant malpositions. The current standard to control the screw position is postoperative computed tomography. The study presents the results of assessment of these implants by intraoperative three-dimensional fluoroscopy.     

Combined Ultrasmall Superparamagnetic Particles of Iron Oxide–Enhanced and Diffusion-Weighted Magnetic Resonance Imaging Reliably Detect Pelvic Lymph Node Metastases in Normal-Sized Nodes of Bladder and Prostate Cancer Patients

Background

Lymph node staging of bladder or prostate cancer using conventional imaging is limited. Newer approaches such as ultrasmall superparamagnetic particles of iron oxide (USPIO) and diffusion-weighted magnetic resonance imaging (DW-MRI) have inconsistent diagnostic accuracy and are difficult to interpret.

Objective

To assess whether combined USPIO and DW-MRI (USPIO–DW-MRI) improves staging of normal-sized lymph nodes in bladder and/or prostate cancer patients.

Design, setting, and participants

Twenty-one consecutive patients with bladder and/or prostate cancer were enrolled between May and October 2008. One patient was excluded secondary to bone metastases detected on DW-MRI with subsequent abstention from surgery.

Intervention

Patients preoperatively underwent 3-T MRI before and after administration of lymphotropic USPIO using conventional MRI sequences combined with DW-MRI. Surgery consisted of extended pelvic lymphadenectomy and resection of primary tumors.

Measurements

Diagnostic accuracies of the new combined USPIO–DW-MRI approach compared with the “classic” reading method evaluating USPIO images without and with DW-MRI versus histopathology were evaluated. Duration of the two reading methods was noted for each patient.

Results and limitations

Diagnostic accuracy (90% per patient or per pelvic side) was comparable for the classic and the USPIO–DW-MRI reading method, while time of analysis with 80 min (range 45–180 min) for the classic and 13 min (range 5–90 min) for the USPIO–DW-MRI method was significantly shorter (p < 0.0001). Interobserver agreement (three blinded readers) was high with a kappa value of 0.75 and 0.84, respectively. Histopathological analysis showed metastases in 26 of 802 analyzed lymph nodes (3.2%). Of these, 24 nodes (92%) were correctly diagnosed as positive on USPIO–DW-MRI. In two patients, one micrometastasis each (1.0 × 0.2 mm; 0.7 × 0.4 mm) was missed in all imaging studies.

Conclusions

USPIO–DW-MRI is a fast and accurate method for detecting pelvic lymph node metastases, even in normal-sized nodes of bladder or prostate cancer patients.     

Emergency stabilization of the pelvic ring: Clinical comparison between three different techniques

Background

Emergency devices for pelvic ring stabilization include circumferential sheets, pelvic binders, and c-clamps. Our knowledge of the outcome of these techniques is currently based on limited information.

Methods

Using the dataset of the German Pelvic Trauma Registry, demographic and injury-associated characteristics as well as the outcome of pelvic fracture patients after sheet, binder, and c-clamp treatment was compared. Outcome parameters included transfusion requirement of packed red blood cells, length of hospital stay, mortality, and incidence of lethal pelvic bleeding.

Results

Two hundred seven of 6137 (3.4%) patients documented in the German Pelvic Trauma Registry between April 30th 2004 and January 19th 2012 were treated by sheets, binders, or c-clamps. In most cases, c-clamps (69%) were used, followed by sheets (16%), and binders (15%). The median age was significantly lower in patients treated with binders than in patients treated with sheets or c-clamps (26 vs. 47 vs. 42 years, p = 0.01). Sheet wrapping was associated with a significantly higher incidence of lethal pelvic bleeding compared to binder or c-clamp stabilization (23% vs. 4% vs. 8%). No significant differences between the study groups were found in sex, fracture type, blood haemoglobin concentration, arterial blood pressure, Injury Severity Score, the incidence of additional pelvic packing and arterial embolization, need of red blood cell transfusion, length of hospitalisation, and mortality.

Conclusions

The data suggest that emergency stabilization of the pelvic ring by binders and c-clamps is associated with a lower incidence of lethal pelvic bleeding compared to sheet wrapping.

Level of evidence

Level III.     

Influence of plate–bone contact on cyclically loaded conically coupled locking plate failure

Introduction

The maintenance of friction between locking plates and bone is not essential, so that they can be applied with a gap between the plate and underlying bone. We hypothesised that the presence of a gap under a locking plate with a conical coupling mechanism would reduce fixation stability or allow uncoupling of the locking screws from the plate.

Materials and methods

Locking plates with two conically coupled locking screws were applied to 6 pairs of adult canine femora. One of each pair had plate to bone contact and the contralateral construct had a 2 mm plate to bone gap. Constructs were cyclically loaded in cantilever bending with 10 percent incremental increases every 1000 cycles at 2 Hz, starting at 250 N. The constructs were fatigued to failure. To evaluate fatigue life of the conical coupling, testing was repeated with aluminium tubing replacing the bone, to eliminate screw–bone cutout failure.

Results

The mean sustained loads and cycles to failure in the contact group (420.80, standard error [SE] 14.97 N; 7612.00, SE 574.70 cycles) were significantly greater than in the gap group (337.50, SE 14.97 N; 4252.00, SE 574.70 cycles), (p < 0.001). Failure mode of all bone constructs was via screw cutout from the bone. Aluminium tubing constructs failed via screw or plate fatigue and breaking, with one construct having elevation of the plate over the screw head.

Discussion and conclusions

Elevation of locking plates with a conical coupling system by 2 mm from the bone reduced construct fatigue life but did not result in screw head uncoupling from the plate.     

Simultaneous anterior and posterior compression of the pelvic ring with external fixation using a pre-tensed curved bar: A biomechanical study

Introduction

External fixators continue to be essential tools in the urgent treatment of pelvic fractures for compression and stabilization of the pelvic ring. Current systems fail to produce simultaneous anterior and posterior compression. A modified application of an existing curved bar fixator is proposed using a specifically designed tensioner to pre-tense the bar prior to its connection to Schanz screws. Subsequent pre-tension release and elastic recovery of the bar could potentially compress the pelvis. The aim of this work was to determine if the modified application could produce greater simultaneous compression across the sacroiliac joint and the symphysis of an unstable fractured pelvis than the standard application without pretension.

Materials and methods

Six synthetic pelvis models with symphyseal and unilateral sacroiliac joints disruptions, simulating a Tile type C pelvic ring fracture, were used. Each specimen was stabilized using two 5 mm × 250 mm supra-acetabular Schanz pins, a couple of open adjustable clamps and a semicircular carbon fibre rod applied without and with pre-tension. Two distances from bar to bone and three levels of pretension were compared. Each pelvis was tested with the six possible parameter combinations. Compressive forces at the disrupted joints were measured using pressure sensitive film sensors.

Results

The modified application produced forces significantly higher than the minimal compression achieved with standard application. At the sacroiliac joint, after pre-tension release, mean compressive forces measured ranged from 28.7 to 85.6 N. The closest bar-to-bone distance always produced a significantly higher force; similarly, a significant increase in compression was found as the pre-tension level rose. At the symphysis, mean compressive forces between 35.3 N and 49.0 N were determined. No significant variations were seen with changes of any of the two factors analyzed

Conclusions

To pre-tense a semi-circular bar before its use for external fixation of the fractured pelvis, is an effective means of applying compression simultaneously through the sacroiliac joint and the symphysis. The proposed method generates the highest compressive forces at the sacroiliac joint when the rod is subject to the highest pre-tension level not producing subluxation and is subsequently positioned as close as possible to the bone depending on patient's condition.     

How bilateral iliolumbar fusion increases the stability of horizontal osteosynthesis in unstable pelvic ring injuries?

Objective

In type C pelvic ring injuries, the operative stabilization of the posterior ring is absolutely indicated. There exist four different types of operative methods: iliosacral screw fixation, transsacral plate synthesis, ventral plate fixation (primarily for sacroiliac luxations), and local plate synthesis performed on the dorsal cortex of the sacrum. In our current article, we analyzed the stability of fixation methods used together with bilateral iliolumbar techniques.

Methods

We analyzed a finite element pelvic model attached to lumbar 4–5 vertebrae. By imitating a standing position on two feet, we measured the differences in tension and displacement in T1 and T2 thoracic vertebrae fractures with and without iliolumbar fusion in cases of iliosacral screw fixation, transsacral plate synthesis and KFI-H (small fragment-H) plate synthesis.

Results

The osteosynthesises reinforced via Galveston technique were rather stable; the amount of displacement measured in the fracture gap was significantly less than in the cases without iliolumbar fusion. The tension in the implants were below the allowed values, therefore they were capable of withstanding the imposed loads without permanent deformation.

Conclusions

In unilateral pelvis injuries, if a non-weight bearing status cannot be achieved on the injured side, unilateral iliolumbar fusion reinforcement is justified, since the contralateral lower limb must also be non-weight bearing due to the pelvis injury itself. In the case of the most unstable sacrum fracture—“jumper’s fracture”, bilateral iliolumbar fusion is necessary, in which case the patient will be able to bear weight during the early postoperative period.     

Comparing the predictive value of the pelvic ring injury classification systems by Tile and by Young and Burgess

Introduction

Radiology-based classifications of pelvic ring injuries and their relevance for the prognosis of morbidity and mortality are disputed in the literature. The purpose of this study was to evaluate potential differences between the pelvic ring injury classification systems by Tile and by Young and Burgess with regard to their predictive value on mortality, transfusion/infusion requirement and concomitant injuries.

Patients and methods

Two-hundred-and-eighty-five consecutive patients with pelvic ring fractures were analyzed for mortality within 30 days after admission, number of blood units and total volume of fluid infused during the first 24 h after trauma, the Abbreviated Injury Severity (AIS) scores for head, chest, spine, abdomen and extremities as a function of the Tile and the Young–Burgess classifications.

Results

There was no significant relationship between occurrence of death and fracture pattern but a significant relationship between fracture pattern and need for blood units/total fluid volume for Tile (p < .001/p < .001) and Young–Burgess (p < .001/p < .001). In both classifications, open book fractures were associated with more fluid requirement and more severe injuries of the abdomen, spine and extremities (p < .05). When divided into the larger subgroups “partially stable” and “unstable”, unstable fractures were associated with a higher mortality rate in the Young–Burgess system (p = .036). In both classifications, patients with unstable fractures required significantly more blood transfusions (p < .001) and total fluid infusion (p < .001) and higher AIS scores.

Conclusions

In this first direct comparison of both classifications, we found no clinical relevant differences with regard to their predictive value on mortality, transfusion/infusion requirement and concomitant injuries.     

Technik der perkutanen SI-Verschraubung mit Unterstützung durch konventionellen C-Bogen

Background

During percutaneous iliosacral screw fixation, fluoroscopy with a conventional C-arm X-ray unit is still the standard procedure for intraoperative orientation. Lateral sacral images in combination with the inlet and outlet view are always necessary. Nevertheless, the complex pelvic anatomy makes it difficult to prevent malpositioning of screws.

Operative technique

Defining the correct entry into the bone is the decisive step for ideal screw placement. The better this is defined, the larger safety margins will be concerning cortical perforation by the screws. In the lateral view, an entry ventral to the sacral canal has to be avoided as well as an entry into the cranial half of the first sacral vertebra. To improve the surgeon’s three-dimensional orientation with the help of his personal experience and two-dimensional images, it is recommended to place the tip of the screws in the center of the sacrum (in AP view) whenever possible. Routinely performed postoperative CT imaging of 24 screws, consecutively implanted according to the standards described, revealed no case of malpositioning.

Conclusion

Standard X-ray views in combination with standardized aiming of screw entry position and final screw thread position enable the surgeon to find the “safe zone” for iliosacral screw insertion and to prevent iliosacral screw malpositioning with high accuracy.