The strength of iliosacral lag screws and transiliac bars in the fixation of vertically unstable pelvic injuries with sacral fractures

Biomechanical comparison of four triangular osteosynthesis fixations for unilateral vertical sacral fractures

To compare the stability and biomechanical characteristics of four commonly used triangular osteosynthesis techniques to treat unilateral vertical sacral fractures and provide a clinical application reference. Finite element models of Tile C-type pelvic ring injury (unilateral Denis II sacral fracture) were produced. In four models, sacral fractures were fixed with a combination of unilateral L5, unilateral L4, and L5 iliac lumbar fixation with lengthened or normal sacroiliac screws. The biomechanical properties of the four fixation models were measured and compared under bipedal stance and lumbar rotation. The fixation stability of the model with the lengthened sacroiliac screw was excellent, and the fracture end was stable. The stability of fixation using unilateral L4 and L5 segments was close to that of unilateral L5 segment fixation. Triangular osteosynthesis transverse stabilization devices using lengthened sacroiliac screws can increase the vertical stability of the sacrum after internal fixation and increase the stability of the fracture. When triangular osteosynthesis lumbar fixation segments were selected, simultaneous fixation of L4 and L5 segments versus only L5 segments did not significantly enhance the vertical stability of the sacrum or the stability of the fracture end.

Breakage risk of different sacroiliac screws in unilateral sacral fractures a finite element analysis

Objective

To compare the breakage risk of lengthened sacroiliac screws and ordinary sacroiliac screws to treat unilateral vertical sacral fractures and provide a reference for clinical application.

Methods

A finite element model of Tile C pelvic ring injury (unilateral type Denis II fracture of the sacrum) was produced. The sacral fractures were fixed with a lengthened sacroiliac screw and ordinary sacroiliac screw in 6 types of models. The maximal von Mises stresses and stress distributions of the two kinds of screws when standing on both feet were measured and compared.

Results

The maximal von Mises stress of the lengthened screw was less than that of the ordinary screw. Compared with ordinary screw, the stress distribution in the lengthened screw was more homogeneous.

Conclusions

The breakage risk of screws fixed in double segments is lower than that of screws fixed in single segments, the breakage risk of lengthened screws is lower than that of ordinary screws, and the breakage risk of screws fixed in S2 segments is lower than that of screws fixed in S1 segments.

Technical Note on Placement of Low-Profile Triangular Osteosynthesis for Unstable Posterior Pelvic Ring Injuries

SUMMARY

Triangular osteosynthesis is a technique used to stabilize posterior pelvic ring injuries. Conventional triangular fixation can be problematic for several reasons, including the need for advanced skill sets to place instrumentation, difficulty with pelvic reduction and placing the connecting construct, and prominent instrumentation. The purpose of this study is 2-fold: (1) to describe in detail a technique for lumbopelvic fixation using implants that are easy to connect, allow distraction for complex lumbosacral displacements, and are placed in a location minimizing soft tissue prominence and (2) to present our initial case series using this technique. We present a retrospective review of 18 consecutively treated patients with this technique. Inclusion criteria were patients with complete disruption through the sacrum or sacroiliac joint from blunt trauma (OTA/AO type C injuries). Outcomes included pelvic reduction/malreduction, wound healing, and complications. Fourteen patients underwent unilateral fixation (81%), and 4 patients underwent bilateral fixation (19%). All patients (18 of the 18) had a well-reduced pelvis after fixation. No patient (0%) required a return trip to the operating room for loss of reduction/malreduction, wound breakdown, or implant failure. This study presents an updated technique for a low-profile triangular osteosynthesis construct with straightforward application for unstable posterior pelvic ring injuries. This technique does not require rod bending, results in a consistently more recessed iliac screw and connecting rod, and can be used in a wide variety of unstable posterior pelvic ring injuries, including comminuted sacral fractures, L5/S1 facet fractures, and vertical shear injuries.

Safety and efficacy of 2D-fluoroscopy-based iliosacral screw osteosynthesis: results of a retrospective monocentric study

Introduction

Iliosacral screw osteosynthesis is a well-accepted procedure for stabilization of sacral fractures and iliosacral (fracture) dislocations.

Materials and Methods

In this monocentric study, safety and efficacy of conventional 2D-fluoroscopic-guided iliosacral screw insertion were evaluated.

Results

During a 10-year period (2005–2014), 98 patients between the age of 18 and 65 years received 207 iliosacral screws in 101 procedures. Average patient age was 43.2 years. There were 46 Type B and 40 Type C injuries in the AO/OTA classification, nine patients had a fragility fracture of the pelvis. In three patients, primary radiological data were missing. The indication for surgical treatment was a sacral fracture in 97 patients, a pure iliosacral dislocation in 37 patients and a fracture-dislocation in 31 patients. 70 procedures were performed with the patient in supine position, 31 with the patient in prone position. Surgery was done in a minimal-invasive technique in 76 patients, in 22 patients an open reduction was necessary before screw insertion. 81 patients received a unilateral, 17 patients a bilateral screw osteosynthesis. 199 screws were inserted in S1, only eight screws in S2. 65 patients received two screws unilaterally, ten patients two screws bilaterally. There were no vascular or neurologic complications. During in-hospital stay, there were seven complications, which needed 12 operative revisions: three wound infections, two hematomas, one screw malalignment and one early screw loosening. In 28 patients with 56 iliosacral screws, a pelvic CT-scan was performed during follow-up. A penetration of a cortical layer was diagnosed in 20 of these screws. All penetrations were seen in double screw osteosynthesis of S1. In none of the patients, complaints could be explained by the malalignment of these screws. Five operative revisions were performed during follow-up: two for screw loosening, two for fracture healing problems and one for screw malalignment. Metal removal was performed in 39 patients with 75 screws. 2D-fluoroscopic-guided iliosacral screw osteosynthesis is a safe and efficient procedure in clinical practice.

Discussion

A thorough preoperative evaluation of the morphology of the upper sacrum and careful operative procedure are indispensable. Fluoroscopic views in AP, lateral, inlet and outlet must allow recognition of all anatomical landmarks. The indication for double screw osteosynthesis in S1 should be taken with caution. Screw malalignments do not inevitably correlate with complaints.

Symptomatic Iliosacral Screw Removal After Pelvic Trauma-Incidence and Clinical Impact

OBJECTIVE

To calculate the incidence of symptomatic iliosacral (SI) screw removal following pelvic trauma and to determine the clinical impact of the secondary intervention.

DESIGN

Retrospective chart review.

SETTING

Level 1 and Level 2 trauma centers.

PATIENTS

Four hundred seventy-one consecutive patients undergoing percutaneous posterior pelvic fixation over 10 years, with 7 excluded for spinopelvic fixation,and 7 excluded due to age <16 year old.

INTERVENTION

Implant removal.

MAIN OUTCOME MEASUREMENT

Secondary intervention.

RESULTS

A total of 25/457 patients underwent screw removal (5.4%). Two patients were lost to follow-up, leaving 23 for analysis. There were 13 male patients and 10 female patients. There were 13 SI and 10 trans-sacral screws removed. Four screws were loose before removal (17%). Average time to screw removal was 10.7 months (4-26 minutes). Fifteen (83.3%) patients had subjective improvement, and 3 (16.7%) had no notable improvement.

CONCLUSION

The incidence of symptomatic SI screws necessitating removal is low (5.4%). When removed, there is a high likelihood (83%) that the secondary intervention will result in subjective symptomatic improvement. Routine screw removal is unnecessary because most patients tolerate the implants without symptoms necessitating subsequent surgery.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Fixation Strategy Using Sequential Intraoperative Examination Under Anesthesia for Unstable Lateral Compression Pelvic Ring Injuries Reliably Predicts Union with Minimal Displacement

BACKGROUND

Examination under anesthesia (EUA) has been used to identify pelvic instability. Surgeons may utilize percutaneous methods for posterior and anterior pelvic ring stabilization. We developed an intraoperative strategy whereby posterior fixation is performed, with reassessment using sequential EUA to determine the need for anterior fixation. Our aim in the current study was to evaluate whether this strategy reliably results in union with minimal displacement.

METHODS

This was a multicenter retrospective study involving adult patients with closed lateral compression (LC) pelvic ring injuries treated during the period of 2013 to 2016. Included were patients who underwent percutaneous pelvic fixation based on sequential EUA. Data points included patient demographics, injury and fixation details, and displacement as observed on follow-up radiographs.

RESULTS

Complete documentation was available for 74 patients (mean age, 41 years). The mean duration of follow was 11 months. Fifty-three of the patients had LC-1 injuries, 19 had LC-2 injuries, and 2 had LC-3 injuries. Twenty-five (47.2%) of the 53 patients with LC-1 and 11 (57.9%) of the 19 patients with LC-2 injuries did not undergo anterior fixation on the basis of the algorithm. The 36 LC-1 or LC-2 patients who underwent combined anterior and posterior fixation had no measurable displacement at union. Of the 36 LC-1 or LC-2 patients with no anterior fixation, 27 with unilateral rami fractures had no measurable displacement at union. The remaining 9 LC-1 or LC-2 cases with no anterior fixation had bilateral superior and inferior rami fractures; each of these patients demonstrated displacement (mean, 7.5 mm; range, 5 to 12 mm) within 6 weeks of fixation that remained until union. All patients had protected weight-bearing for 12 weeks.

CONCLUSIONS

A fixation strategy based on sequential intraoperative EUA reliably results in union with minimal displacement for unstable LC pelvic ring injuries. Injuries requiring combined anterior and posterior fixation healed with no displacement. Those without anterior fixation and a unilateral ramus fracture healed with no displacement. In the presence of bilateral rami fractures, even with a negative finding on sequential EUA, the pelvis healed with 7.5 mm average displacement. Surgeons may consider anterior fixation to prevent this displacement.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Biomechanical evaluation of location and mode of failure in three screw fixations for a comminuted transforaminal sacral fracture model

Background

Pelvic ring–comminuted transforaminal sacral fracture injuries are rotationally and vertically unstable and have a high rate of failure.

Objective

Our study purpose was to use three-dimensional (3D) optical tracking to detect onset location of bone–implant interface failure and measure the distances and angles between screws and line of applied force for correlation to strength of pelvic fracture fixation techniques.

Methods

3D relative motion across sacral–rami fractures and screws relative to bone was measured with an optical tracking system. Synthetic pelves were used. Comminuted transforaminal sacral–rami fractures were modelled. Each pelvis was stabilised by either (1) two iliosacral screws in S1, (2) one transsacral screw in S1 and one iliosacral screw in S1 and (3) one trans-alar screw in S1 and one iliosacral screw in S1; groups 4–6 consisted of fixation groups with addition of anterior inferior iliac pelvic external fixator. Eighteen-instrumented pelvic models with right ilium fixed simulate single-leg stance. Load was applied to centre of S1 superior endplate. Five cycles of torque was initially applied, sequentially increased until permanent deformation occurred. Five cycles of axial load compression was next applied, sequentially increased until permanent deformation occurred, followed by axial loading to catastrophic failure. A Student t test was used to determine significance (p < 0.05).

Results

The model, protocol and 3D optical system have the ability to locate how sub-catastrophic failures initiate. Our results indicate failure of all screw-based constructs is due to localised bone failure (screw pull-in push-out at the ipsilateral ilium–screw interface, not in sacrum); thus, no difference was observed when not supplemented with external fixation.

Conclusion

Inclusion of external fixation improved resistance only to torsional loading.

Translational Potential of this Article

Patients with comminuted transforaminal sacral–ipsilateral rami fractures benefit from this fixation.

Symphyseal fixation in open book injuries cannot fully compensate anterior SI joint injury-A biomechanical study in a two-leg alternating load model

INTRODUCTION

In open book injuries type Tile B1.1 or B1.2 also classified as APC II (anteroposterior compression), it remains controversial, if a fixation of the anterior ring provides sufficient stability or a fixation of the posterior ring should be included. Therefore the relative motion at the sacroiliac joint was quantified in a two-leg alternating load biomechanical pelvis model in the intact, the injured and the restored pelvis.

METHODS

Fresh-frozen intact (I) pelvises (n = 6) were subjected to a non-destructive cyclic test under sinosuidal axial two-leg alternating load with progressively increasing amplitude. Afterwards an open book injury (J) including the anterior ligament complex of the left sacroiliac joint, the sacrospinal and sacrotuberal ligaments (Tile B1.1) was created and the specimens were retested. Finally, the symphysis was stabilized with a modular fixation system (1-, 2- or 4-rod configuration) (R) and specimens were cyclically retested. Relative motion at the sacroiliac joint was captured at both sacroiliac joints by motion tracking system at two load levels of 170 N and 340 N during all tests.

RESULTS

Relative sacroiliac joint movements at both load levels were significantly higher in the J-state compared to the I-state, excluding superoinferior translational movement. With exception of the anteroposterior translational movement at 340N, the relative sacroiliac joint movements after each of the three reconstructions (1-, 2-, 4-rod fixation) were significantly smaller compared to the J-state and did not differ significantly to the I-state, but stayed above the values of the latter. Relative movements did not differ significantly in a direct comparison between the 1-rod, 2-rod and 4-rod fixations.

CONCLUSION

Symphyseal locked plating significantly reduces relative movement of the sacroiliac joint in open book injuries type Tile B1.1 or B1.2 (APC II) but cannot fully restore the situation of the intact sacroiliac joint.

Internal fixation of S1-S3 iliosacral screws and pubic screw as the best configuration for unstable pelvic fracture with unilateral vertical sacral fracture (AO type C1.3)

BACKGROUND

Although internal fixation is the definitive treatment in unstable pelvic fractures with disruption of the anterior arch and a vertical fracture of the sacrum (AO type C1.3), there have been no agreement of the best technique of internal fixation yet. We aimed to derive comparable objective data on stiffness and load to failure in this type of fracture fixations.

METHODS

Synbone was modified into AO type C1.3 fracture model, while treatments were divided into six internal fixation treatment groups using tension band plate (TBP), symphysis pubis plate (SP) with iliosacral screw at S1 and S2 (IS S1-S2), pubic screw (PS) with iliosacral TBP, PS and IS S1-S2, SP and IS S1-S3, PS and S1-S3 and finally PS and IS S1-S3. Sensor was applied to detect the shifting and rotation of fracture fragments. Mechanical strength test conducted with the application of axial force on the sacrum vertebra (S1).

RESULTS

The highest translational stiffness was observed in the group IS S1-S3 + PS (830.36 N/mm, p = 0.031) and there was no difference on the rigidity of the rotation between the groups posterior fixation using IS S1-S2 and IS S1-S3 ( p = 0.51). Meanwhile the highest load to failure was found in group IS S1-S3 + PS (1522.20 N). PS provided advantages compared to the use of plate.

CONCLUSIONS

Group of PS and S1-S3 IS is the configuration of internal fixation with best translational and rotational stiffness and the largest load to failure compared to other techniques in AO type C1.3 fracture.

Does Lumbopelvic Fixation Add Stability? A Cadaveric Biomechanical Analysis of an Unstable Pelvic Fracture Model

OBJECTIVE

We sought to determine the role of lumbopelvic fixation (LPF) in the treatment of zone II sacral fractures with varying levels of sacral comminution combined with anterior pelvic ring (PR) instability. We also sought to determine the proximal extent of LPF necessary for adequate stabilization and the role of LPF in complex sacral fractures when only 1 transiliac-transsacral (TI-TS) screw is feasible.

MATERIALS AND METHODS

Fifteen L4 to pelvis fresh-frozen cadaveric specimens were tested intact in flexion-extension (FE) and axial rotation (AR) in a bilateral stance gliding hip model. Two comminution severities were simulated through the sacral foramen using an oscillating saw, with either a single vertical fracture (small gap, 1 mm) or 2 vertical fractures 10 mm apart with the intermediary bone removed (large gap). We assessed sacral fracture zone (SZ), PR, and total lumbopelvic (TL) stability during FE and AR. The following variables were tested: (1) presence of transverse cross-connector, (2) presence of anterior plate, (3) extent of LPF (L4 vs. L5), (4) fracture gap size (small vs. large), (5) number of TI-TS screws (1 vs. 2).

RESULTS

The transverse cross-connector and anterior plate significantly increased PR stability during AR (P = 0.02 and P = 0.01, respectively). Increased sacral comminution significantly affected SZ stability during FE (P = 0.01). Two versus 1 TI-TS screw in a large-gap model significantly affected TL stability (P = 0.04) and trended toward increased SZ stabilization during FE (P = 0.08). Addition of LPF (L4 and L5) significantly improved SZ and TL stability during AR and FE (P < 0.05). LPF in combination with TI-TS screws resulted in the least amount of motion across all 3 zones (SZ, PR, and TL) compared with all other constructs in both small-gap and large-gap models.

CONCLUSIONS

The role of LPF in the treatment of complex sacral fractures is supported, especially in the setting of sacral comminution. LPF with proximal fixation at L4 in a hybrid approach might be needed in highly comminuted cases and when only 1 TI-TS screw is feasible to obtain maximum biomechanical support across the fracture zone.

Mechanical comparison of iliosacral reconstruction techniques after sarcoma resection

BACKGROUND

Reconstruction of iliosacral defects following oncologic resection is a difficult clinical problem associated with a high incidence of failure. Technical approaches to this problem are heterogeneous and evidence supporting specific techniques is sparse. Maximizing construct stability may improve union rates and functional outcomes. The purpose of this study is to compare construct stiffness, load to failure, and mechanism of failure between two methods of iliosacral reconstruction in an ex-vivo model to determine if either is mechanically superior.

METHODS

Eight third-generation composite pelves reconstructed with a plate-and-screw technique were tested against seven pelves reconstructed with a minimal spinal instrumentation technique using axial loading in a double-leg stance model.

FINDINGS

The pelves from the plate group demonstrated higher stiffness in the direction of applied load (102.9 vs. 66.8N/mm; p=0.010) and endured a significantly larger maximum force (1416 vs. 1059N; p=0.015) than the rod group prior to failure. Subjectively, the rod-reconstructed pelves were noted to be rotationally unconstrained while pivoting around their single point-of fixation in each segment leading to earlier failure.

INTERPRETATION

Plate-reconstruction was mechanically superior to spinal instrumentation in the manner performed in this study. More than one point of fixation in each segment should be achieved to minimize the risk of rotational deformation.

The Effect of Transiliac-Transsacral Screw Fixation for Pelvic Ring Injuries on the Uninjured Sacroiliac Joint

OBJECTIVE

To evaluate the functional outcomes and pain in patients with unilateral posterior pelvic ring injuries treated with transiliac-transsacral screw fixation compared with unilateral iliosacral screw fixation.

DESIGN

Retrospective comparative study.

SETTING

Three academic level 1 trauma centers.

PATIENTS/PARTICIPANTS

From a group of 866 patients with pelvic ring injuries treated surgically, 86 patients with unilateral pelvic ring injuries treated with transiliac-transsacral screws and 97 patients treated with unilateral iliosacral screws were identified. Thirty-six patients treated with transiliac-transsacral fixation and 26 patients treated with unilateral iliosacral screws met the inclusion criteria and participated.

INTERVENTION

Patients were treated surgically for unstable pelvic ring injuries with either unilateral iliosacral screws or transiliac-transsacral screws at the discretion of the treating surgeon.

MAIN OUTCOME MEASUREMENT

Majeed Pelvic Score.

RESULTS

There was no significant difference in Majeed Pelvic Scores between patients treated with transiliac-transsacral screws and those treated with unilateral iliosacral screws (72.8 ± 23.7 vs. 70.4 ± 19.0, P = 0.66). There was no difference in side-specific Numeric Rating Scale pain scores between patients treated with transiliac-transsacral screws and those treated with unilateral iliosacral screws on the injured side (2.5 ± 3.1 vs. 2.0 ± 2.4, P = 0.46) or the uninjured side (1.7 ± 2.8 vs. 0.8 ± 1.7, P = 0.12). Mean follow-up was greater than 3 years with no difference between the groups (mean 1270 vs. 1242 days, P = 0.84).

CONCLUSIONS

Treatment of unilateral pelvic ring injuries with transiliac-transsacral screws does not adversely affect or improve patient outcomes or subjective pain scores when compared with those treated with unilateral iliosacral screws.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

The effect of implant placement on sacroiliac joint range of motion: posterior versus transarticular

STUDY DESIGN

A human cadaveric biomechanical study of 2 sacroiliac (SI) joint fusion implant placement techniques.

OBJECTIVE

To evaluate and compare the biomechanical properties of 2 implant placement techniques for SI joint fusion.

SUMMARY OF BACKGROUND DATA

Minimally invasive placement of SI joint fusion implants is a potential treatment of SI joint disruptions and degenerative sacroiliitis. Biomechanical studies of screw fixation within the sacrum have shown that placement and trajectory are important in the overall stability of the implant. Although clinical results have been promising, there is the possibility that a more optimal arrangement of implants may exist.

METHODS

Bilateral SI joints in 7 cadaveric lumbopelvic (L4-pelvis) specimens were tested using a single leg stance model. All joints were tested intact, pubic symphysis sectioned, and treated (3 SI joint fusion implants). The implants were laterally placed using either a posterior or transarticular placement technique. The posterior technique places the implants inline in the inlet view, parallel in the outlet view, and parallel to the posterior sacral body in the lateral view. The transarticular technique places all implants across the articular portion of the SI joint. For all conditions, the range of motion was tested in flexion-extension, lateral bending, and axial rotation.

RESULTS

The posterior technique significantly reduced the range of motion in flexion-extension, lateral bending, and axial rotation by 27% ± 24% (P = 0.024), 28% ± 26% (P = 0.028), and 32% ± 21% (P = 0.008), respectively. The transarticular technique significantly reduced the range of motion in flexion-extension, lateral bending, and axial rotation by 41% ± 31% (P = 0.013), 36% ± 38% (P = 0.049), and 36% ± 28% (P = 0.015), respectively. No significant differences were detected between the posterior and transarticular placement techniques (P > 0.25).

CONCLUSION

Posterior and transarticular placement of SI joint fusion implants stabilized the SI joint in flexion-extension, lateral bending, and axial rotation.

LEVEL OF EVIDENCE

N/A.

Standalone percutaneous transiliac plating of vertically unstable sacral fractures: outcomes, complications, and recommendations

PURPOSE

The aim of this study is to evaluate results of a standalone percutaneous posterior plating of the vertically unstable sacral fractures, to analyze the influencing factors, to discuss encountered complications, and to express the related recommendations.

METHODS

Forty two cases were included; all of them had type C vertical sacral fractures; and 16 cases had associated nerve roots injury. Subcutaneous 3.5-mm reconstruction plate was used in all cases, through vertical incisions in 28 cases and transverse incisions in 14 cases. Hannover pelvic outcome scoring system was implemented for results evaluation.

RESULTS

The mean follow-up period was 22.1 ± 7.5 months; the mean operative time was 43.3 ± 7 min; the mean surgical incision length was 4.6 ± 1.1 cm. 14 cases had excellent scores, 16 cases had good scores, 6 cases had fair scores, and 6 cases had poor scores. Younger age groups had significantly better outcome (P = 0.015), whereas the comminuted sacrum had significantly worse score (P = 0.041). Final residual posterior displacements significantly improved (P = 0.001) in comparison to the initial displacement. The nerve roots injury had final significant recovery (P = 0.012). Transverse skin incisions had subjectively significant satisfaction (P = 0.017).

CONCLUSIONS

Percutaneous 3.5-mm reconstruction plate is a good alternative to percutaneous iliosacral screws in vertically unstable sacral fractures; especially in the presence of contraindication to the latter. It is simple procedure with minimal incisions; short operative time; less radiological exposure; good mechanical stability; and less iatrogenic injuries.

Biomechanical study of four kinds of percutaneous screw fixation in two types of unilateral sacroiliac joint dislocation: a finite element analysis

OBJECTIVE

To compare the biomechanical stability of four different kinds of percutaneous screw fixation in two types of unilateral sacroiliac joint dislocation.

METHODS

Finite element models of unstable Tile type B and type C pelvic ring injuries were created in this study. Modelling was based on fixation with a single S1 screw (S1-1), single S2 screw (S2-1), two S1 screws (S1-2) and a combination of a single S1 and a single S2 screw (S1–S2). The biomechanical test of two types of pelvic instability (rotational or vertical) with four types of percutaneous fixation were compared. Displacement, flexion and lateral bend (in bilateral stance) were recorded and analyzed.

RESULTS

Maximal inferior translation (displacement) was found in the S2-1 group in type B and C dislocations which were 1.58 mm and 1.90 mm, respectively. Maximal flexion was found in the S2-1 group in type B and C dislocations which were 1.55° and 1.95°, respectively. The results show that the flexion from most significant angulation to least is S2-1, S1-1, S1-2, and S1–S2 in type B and C dislocations. All the fixations have minimal lateral bend.

CONCLUSION

Our findings suggest single screw S1 fixation should be adequate fixation for a type B dislocation. For type C dislocations, one might consider a two screw construct (S1–S2) to give added biomechanical stability if clinically indicated.

A biomechanical comparison of ipsilateral and contralateral pedicle screw placement for modified triangular osteosynthesis in unstable pelvic fractures

OBJECTIVES

Iliosacral fixation of unstable pelvic fractures does not produce enough stability to allow for immediate postoperative weight bearing. Triangular osteosynthesis creates additional resistance to vertical displacement and rotation. A disadvantage is the loss of the L5/S1 motion segment. We propose a modification of the standard triangular osteosynthesis construct in which the contralateral S1 pedicle is used. As the ipsilateral L5 pedicle is unavailable for fixation in a saw-bones composite pelvic model, we compared ipsilateral and contralateral S1 pedicle screw constructs. We hypothesized that ipsilateral and contralateral S1 pedicle screw constructs would demonstrate no difference in displacement or rotation.

METHODS

Seven saw bones pelvic models were tested. A 5-mm vertical fracture gap was created through the left sacrum while the pubic symphysis was completely dissociated. Each pelvis was tested sequentially in 4 triangular osteosynthesis configurations: ipsilateral S1 screw with anterior plate, contralateral S1 screw with anterior plate, contralateral S1 screw without anterior plate, and ipsilateral S1 screw without anterior plate. Specimens were cyclically loaded from 100-200 N at 0.25 Hz for 25 cycles and then loaded up to 300 N at 10 mm/min while displacement and rotation at the sacral and pubic fracture sites were measured.

RESULTS

There was no difference in any of the displacement measures between ipsilateral and contralateral constructs. When comparing rotation, the contralateral configuration experienced significantly less rotation than the ipsilateral configuration with and without the anterior plate applied.

CONCLUSIONS

Within the limitations of the current model, contralateral S1 constructs for modified triangular osteosynthesis were biomechanically equal to ipsilateral constructs in preventing displacement and superior in preventing rotation.

Transiliac-transsacral screws for posterior pelvic stabilization

Typical posterior pelvic fixation constructs use one or more large screws inserted from the lateral iliac cortex into the safe upper sacral ala or body. As a result of the deforming forces acting perpendicular to the implant axis, routine iliosacral screw fixation may not provide adequate stabilization, especially in certain unstable injuries. Longer iliosacral screws that traverse the entire upper sacrum and exit the contralateral iliac cortex may improve holding power and also stabilize concomitant contralateral posterior pelvic injuries. These transiliac-transsacral screws are reliably safe to insert using routine intraoperative fluoroscopy, and they provide durable fixation. These screws require careful preoperative planning and more precise technical attention during insertion because they pass through both sacral alar zones. Transiliac-transsacral screws may be particularly useful in the presence of osteoporosis, significant posterior pelvic instability including spinopelvic dissociation, patient obesity, anticipated noncompliant behavior, bilateral posterior pelvic injuries, and nonunion procedures.

Biomechanical testing of a concept of posterior pelvic reconstruction in rotationally and vertically unstable fractures

The purpose of this study was to assess the stability of a developmental pelvic reconstruction system which extends the concept of triangular osteosynthesis with fixation anterior to the lumbosacral pivot point. An unstable Tile type-C fracture, associated with a sacral transforaminal fracture, was created in synthetic pelves. The new concept was compared with three other constructs, including bilateral iliosacral screws, a tension band plate and a combined plate with screws. The pubic symphysis was plated in all cases. The pelvic ring was loaded to simulate single-stance posture in a cyclical manner until failure, defined as a displacement of 2 mm or 2°. The screws were the weakest construct, failing with a load of 50 N after 400 cycles, with maximal translation in the craniocaudal axis of 12 mm. A tension band plate resisted greater load but failure occurred at 100 N, with maximal rotational displacement around the mediolateral axis of 2.3°.

The combination of a plate and screws led to an improvement in stability at the 100 N load level, but rotational failure still occurred around the mediolateral axis. The pelvic reconstruction system was the most stable construct, with a maximal displacement of 2.1° of rotation around the mediolateral axis at a load of 500 N.

Biomechanical aspects of pelvic ring reconstruction techniques: Evidence today

Despite the remarkable advances achieved within the boundaries of the new discipline of Pelvic surgery, pelvic ring disruptions remain challenging and complex problems in orthopaedics. The long-term complications related to reconstruction techniques of these injuries have motivated researchers and surgeons to explore various alternative treatment modalities. Several biomechanical studies have addressed these issues. We performed a medline search including studies published during the last 30 years. Our search yielded 114 studies, 39 of which met the pre-specified inclusion criteria and were further critically analysed and discussed regarding the biomechanical aspects of pelvic ring reconstruction techniques. Based on observational approach and evaluation of the studies specific keypoints are highlighted comprising the clinical translation of the biomechanical supported findings.

[Biomechanical principles for treatment of osteoporotic fractures of the pelvis]

Fractures of the pelvis are of increasing interest, especially in older patients due to the often concomitant osteoporosis. The low bone quality can be a problem in several fixation situations. In this review the present and relevant literature on biomechanical data of unstable pelvic ring injuries and all biomechanical data dealing with osteosynthesis for acetabular fractures are discussed.

Locked plates reduce displacement of vertically unstable pelvic fractures in a Mechanical Testing Model

BACKGROUND

The purpose of this study is to compare a locked screw construct to a single iliosacral screw for fixation of a vertically unstable pelvic ring injury in a transforaminal sacral fracture model.

METHODS

Orthopaedic Trauma Association type 61-C1.3a2c5 fractures were created in 10 fresh frozen cadaveric pelvis specimens. Specimens were divided into two groups of five. In both groups, the anterior ring was stabilized with a six-hole 3.5-mm reconstruction plate. In the locked plate (LP) group, the posterior injury was stabilized using a two-hole locking plate with one solid 5.0-mm locking iliosacral screw directed onto the S1 body and a second locking screw directed into the lateral sacral ala. In the iliosacral screw group, the posterior injury was stabilized using a single cannulated 7.3-mm screw. Testing was conducted on a Materials Testing System. Values for displacement and rotation were recorded. Each pelvis was axially loaded with a compressive sine wave from 175 N to 350 N for 10,000 cycles to simulate limited weight bearing, with data recorded at 1,000 cycle increments.

RESULTS

Two specimens in the iliosacral screw group displaced more than 1 cm during the first 1,000 cycles. These two specimens displayed gross fracture motion in all planes. All five specimens in the LP group completed 10,000 cycles of testing with less than 1 cm of displacement. A vector displacement calculation from the plane displacement data revealed that the LP group had significantly less displacement (median 1.9 mm) than the specimens in the iliosacral group (median 6.7 mm; p = 0.008) after 10,000 cycles.

CONCLUSIONS

A two-hole plate locked head screw construct resulted in less displacement than a single iliosacral screw in a transforaminal sacral fracture model.

Severe Pelvic Bleeding: The Role of Primary Internal Fixation

Pelvic ring injuries form part of the spectrum of polytraumaandmust be considered a potentially lethal injury with mortality rates of 10-20%. The stabilization of the unstable pelvic ring in acute resuscitation of multiply injured patients is now conventional wisdom.We aimed: (1) to design a new iliosacral (IS) screw, (2) to prove the clinical advantages of this new implant, and (3) to work out the optimal surgical strategy using this implant. Taking the demands of the above mentioned data into account, a 10 mm 2.8 mm-cannulated iliosacral screw seemed to be optimal for the special requirements. Before industrial production, finite element analysis (FEA) was performed to find out whether these screws would be enough to stabilize the posterior pelvic ring alone or not. Clinical experience led to the modification of the set of instruments, which finally yielded handy tools and implants. Building further on the surgical skills and experiences gained (by the surgeons and the O.R. personnel), we increased our capacity to perform more and more immediate pelvic fixations. Emergency pelvic stabilizationswere performed in patientswith pelvic injuries who had hemodynamic instability, despite immediate shockmanagement during the diagnostic period. During thelast eleven years, 244 patientswith Tile B3 and Cpelvic injuries have been stabilized with 10-mm diameter cannulated IS screws percutaneously posteriorly. Fortyeight hemodynamically unstable patientswere stabilized in the first 2 h with iliosacral screw fixation. The percutaneous pelvic ring stabilization with 10-mm cannulated screws provedstrongenoughin bothersome casesaswell.

Pelvic ring fractures internal fixation: iliosacral screws versus sacroiliac hinge fixation

INTRODUCTION

Pelvic ring fractures are severe injuries whose functional results depend on the quality of reduction. Numerous internal fixation alternatives have been described, but the biomechanical studies comparing them remain rare.

HYPOTHESIS

This study compared the biomechanical behavior of iliosacral screws (ISS) with sacroiliac hinge type fixation (SIF) following unstable pelvic ring fractures fixation.

MATERIALS AND METHODS

A lesion simulating sacroiliac disruption and pubic disruption was created on 14 cadaver pelves. After randomization, the fractures were internally fixed using an anterior plate associated with either an ISS or an SIF. The specimens were then submitted to forces applied vertically at the coxofemoral joints. Relative movements in vertical translation and in rotation between the iliac wing and the sacrum, as well as the stiffness and the forces at failure of the assemblies were measured and compared.

RESULTS

The mean age of the bodies was 66 years (+/-8). No significant difference was demonstrated between the groups in terms of residual motion and stiffness in both vertical and rotational displacement. The results showed a slight residual mobility in rotation of the hemipelvis. The SIFs presented greater, although non significant resistance to failure. No fixation, however, restituted stiffness comparable to a healthy pelvis.

DISCUSSION

The results of this study show that a Tile C.1.2-type injury to the pelvic ring can be treated as effectively with ISS or SIF when combined anterior and posterior fixations are performed. SIF therefore seems reliable and its continued use is justified. The long-term clinical outcomes should nevertheless be evaluated, notably on the younger population, more often affected by this type of injury.

A comprehensive analysis with minimum 1-year follow-up of vertically unstable transforaminal sacral fractures treated with triangular osteosynthesis

PURPOSE

To analyze the radiographic, clinical, and functional results of triangular osteosynthesis constructs for the treatment of vertically unstable comminuted transforaminal sacral fractures.

SETTING

Level I trauma center.

METHODS

During a 3-year period (July 1, 2003 to June 30, 2006), 58 patients with vertically unstable pelvic injuries were treated with triangular osteosynthesis fixation by a single surgeon at a single institution. Patients were followed-up prospectively as a single cohort, with institutional review board approval. Inclusion criteria for this study were skeletally mature patients with a vertically unstable pelvic ring injury associated with a comminuted transforaminal sacral fracture. Minimum follow-up, both clinically and radiographically, was 1 year. Computed tomography scan was performed on all patients at 6 months to assess healing of the fracture. If the fracture healed, the fixation was removed. Functional outcome was assessed using the Short Form 36, version 2, and short version of Musculoskeletal Functional Assessment questionnaires at 6 months (before fixation removal) and 12 months.

RESULTS

Forty of 58 patients with an average age of 39 years were available for a minimum of 1-year follow-up. Wound complications requiring surgical debridement occurred in 5 patients (13%), all of whom had severe soft tissue wounds with internal degloving. Two patients required removal of infected fixation. Iatrogenic L5 nerve injury occurred in 5 patients (13%). Ten patients (25%) had a delayed union on computed tomography scans, and 3 patients had a nonunion as a result of residual fracture gap and incomplete reduction. Six patients (15%) were found to have pronounced tilting of the L5 vertebral body (scoliosis) and distraction of the L5/S1 facet joint ipsilateral to the fixation. This did not correct with removal of the fixation. Failure of the triangular osteosynthesis construct resulting in malunion occurred in 2 patients (5%). All but 2 patients (95%) complained of painful and prominent implants. Functional outcome scoring showed that patients continued to function below the population mean at 1 year but continued to improve, particularly with function and daily activity. Ninety-seven percent of patients returned to some form of work or schooling.

CONCLUSIONS

Triangular osteosynthesis fixation is a reliable form of fixation that allows early full weight-bearing at 6 weeks while preventing loss of reduction in comminuted vertical shear transforaminal sacral fractures. For this study group, operative reduction was maintained until healing in 95% of patients. However, the 1-year follow-up shows a substantial rate of potential technical problems and complications. Of primary concern were the asymmetric L5 tilting with L5-S1 facet joint distraction and the need for a second surgery in all patients to remove painful fixation. Iatrogenic nerve injury occurred in 5 patients (13%) and is thought to arise secondary to fracture manipulation and reduction. We recommend selective use of this technique for comminuted transforaminal sacral fractures in situations only where reliable iliosacral or trans-sacral screw fixation is not obtainable.

Outcome and complications of posterior transiliac plating for vertically unstable sacral fractures

Vertically unstable sacral fractures often make it difficult to achieve rigid fixation and there is no consensus on the optimal fixation technique for these injuries. The purpose of this study was to evaluate complication rate and short-term outcome of vertically unstable sacral fractures treated by posterior transiliac plate fixation. We performed a retrospective review of prospectively collected data of patients who underwent posterior transiliac plating for sacral fractures at two institutions. All patients were treated with the standard posterior approach using a 4.5-mm reconstruction plate and followed for at least 12 months. Patients' demographics, Majeed functional questionnaire surveys, and radiographic outcomes were collected. There were 19 patients with a mean age of 37.5-years. The mean follow-up was 26.3 months. The most frequent mechanism of injury was a fall from a height. According to the AO/OTA classification, there were 10 C1, 6 C2, and 3 C3, which were classified as 2 Denis I, 20 Denis II, and 2 Denis III, including 5 bilateral sacral fractures. Neurological deficit at the initial examination was recorded in 10 patients. The mean ISS was 20.7 and the mean timing of the internal fixation was 6.4 days. Anterior internal fixation of pelvic ring was added in eight patients. A Morel-Lavallee lesion was identified in 5 patients during the operation. Reductions were graded as nine excellent, seven good, and three fair according to the method of Tornetta. There were two postoperative surgical wound infections, both occurring in patients with a Morel-Lavallee lesion. All the sacral fractures united eventually and no implant failure occurred, though there were two patients with a small loss of reduction (<5mm) over the follow-up period. A total of 18 patients completed the functional assessment with a mean score of 78.5 points. Posterior plate fixation of vertically unstable sacral fractures is effective in maintaining fracture reduction even in the presence of significant posterior comminution. We caution its use in the presence of a known Morel-Lavallee lesion, as this may increase the wound complication and infection risk.

Reduction of displaced pelvic ring disruptions using a pelvic reduction frame

The need for reduction in displaced pelvic ring disruptions is well established, but actual techniques to perform this difficult task are evolving. Reduction is often difficult, especially if minimally invasive techniques are used. This pelvic reduction frame (Starr Frame LLC, Richardson, TX) provides stabilization of the intact hemipelvis to the operating table and facilitates multiplanar reduction of the injured hemipelvis with the use and manipulation of external fixator pins. With the pelvis reduced and locked on the frame, the surgeon is free to place, or teach, fixation in a controlled manner. This lessens the usual assistance, training, and hardware placement difficulties associated with the surgical treatment of these injuries. The basic surgical technique and 2 cases of acute fracture treatment are presented.

Minimally invasive transiliac plate osteosynthesis for type C injuries of the pelvic ring: a clinical and radiological follow-up

OBJECTIVE

To evaluate radiological and functional outcome in patients treated with minimally invasive transiliac plate osteosynthesis for unstable pelvic injuries.

DESIGN

Retrospective analysis of a prospective treatment protocol in a consecutive patient series.

SETTING

Level 1 trauma center.

PATIENTS

Between January 1998 and December 2005, 31 patients with type C injuries of the pelvic ring were treated with minimally invasive transiliac plate osteosynthesis. According to the AO classification, 16 patients had a C1-injury, 9 had a C2 fracture, and 6 patients sustained a C3 injury of the pelvic ring. Anterior-posterior, inlet, and outlet radiographs were obtained preoperatively, immediately postoperatively, and during follow-up. Clinical outcome was determined according to the Hannover pelvic outcome score.

INTERVENTION

Posterior plate osteosynthesis for type C injuries of the pelvic ring.

MAIN OUTCOME MEASUREMENT

Preoperative and postoperative dislocation of the posterior pelvic ring, loss of reduction, implant failure, implant removal, clinical results of the pelvic injury and general limitations following the trauma.

RESULTS

Maximum average dislocation of the posterior pelvic ring was 16.1 mm preoperatively; postoperatively, it was 6.1 mm. A total of 23 patients (74.2%) could be followed up after an average of 20 months (range 7-57 months). Seven patients underwent follow-up treatment at other hospitals closer to their respective residences, whereas 1 patient passed away in the early postoperative phase due to multiorgan failure. Loss of reduction occurred in 2 cases. The clinical outcome regarding the pelvis was very good in 8 cases, good in 9 cases, fair in 4 cases, and poor in 2 cases. Social reintegration according to the Hannover pelvic outcome score was complete in 9 cases, poor in 10 cases, and incomplete in 10 cases.

CONCLUSION

Posterior plate osteosynthesis is a sufficiently stable method for the treatment of unstable pelvic ring injuries with a low risk of iatrogenic nervous tissue and vascular lesions. The disadvantages are limited reduction possibilities, the necessity of bilateral bridging of the sacroiliac joint in a unilateral injury, as well as a higher rate of symptomatic hardware.

Biomechanical evaluation of conventional internal contemporary spinal fixation techniques used for stabilization of complete sacroiliac joint separation: a 3-dimensional unilaterally isolated experimental stiffness study

STUDY DESIGN

Comparative 3-dimensional biomechanical testing.

OBJECTIVE

To compare 5 fixation techniques, 3 using screws or screw and plates and 2 spinal, used for stabilization of complete unilateral sacroiliac dislocation in composite models.

SUMMARY OF BACKGROUND DATA

Harrington compression rods have been used for posterior iliosacral stabilization. Recently, the use of compact spinal instrumentation has been introduced for stabilization of iliosacral joint separation to achieve immediate and permanent stability, allowing early mobilization. To the authors' knowledge, no comparative mechanical studies between commonly used internal fixation techniques and contemporary spinal instrumentation have been performed.

METHODS

Fifteen identical composite models of the left hemipelvis and sacrum were used to simulate consistently the "worst-case scenario" of complete unilateral sacroiliac dislocation. Subgroups of 3 models each were used to apply 5 (A-E) alternative fixation iliosacral joint fixation techniques: 1 multiaxial 7.5 mm Cotrel-Dubousset screw inserted in the posterior superior iliac spine and connected with a long Cotrel-Dubousset horizontal rod with 6.5 mm multiaxial Cotrel-Dubousset screws inserted bilaterally in the S1 pedicles (technique A); 1 multiaxial 7.5 mm Cotrel-Dubousset titanium pedicle screw inserted in the posterior superior iliac spine and connected with a short horizontal Cotrel-Dubousset-rod to a 6.5 mm multiaxial Cotrel-Dubousset-screw inserted to the ipsilateral S1 pedicle (technique B); 1, 6.5 mm cancellous AO-screw (technique C); 2, 6.5 mm cancellous AO screws (technique D); and 2 dynamic stainless steel compression plates (technique E) placed anteriorly. Constructs were biomechanically tested. The ilium was unilaterally rigidly fixed, the sacrum was put horizontal in the mediolateral direction with a forward tilt of 30 degrees (close to physiologic conditions) in the sagittal plane, and a vertical quasi-static compressive load ranging from 0 to 500 N was applied on the endplate of S1, reproducing a "worst case" loading scenario. Construct stiffness, frontal plus sagittal kinematics, and iliosacral joint gap size for all 5 techniques were measured.

RESULTS

The construct stiffness (N/mm +/- standard deviation) ranged for model: A, 121 +/- 18; B, 78 +/- 10; C, 168 +/- 13; D, 193 +/- 42; and E, 145 +/- 4. All other parameters exhibited minor variations between the different techniques of fixation: at the 400 N load level, the maximum iliosacral gap globally ranged 0.9-2.8 mm, the maximum mediolateral sacral tilt ranged 1.3-2.4 degrees, and the maximum anteroposterior sacral tilt ranged 0.6-3.0 degrees.

CONCLUSIONS

The iliosacral fixation with 2 6.5 mm AO-cancellous screws for complete sacroiliac dislocation demonstrated the highest stiffness and the short spinal instrumentation the poorest stiffness. All other fixation techniques could be generally considered of equivalent stability value.

Contemporary management of pelvic fractures

BACKGROUND

Pelvic fractures occur when there is high kinetic energy transfer to the patient such as would be expected in motor vehicle crashes, auto-pedestrian collisions, motorcycle crashes, falls, and crush injuries. High-force impact implies an increased risk for associated injuries to accompany the pelvic fracture, as well as significant mortality and morbidity risks. Choosing the optimum course of diagnosis and treatment for these patients can be challenging. The purpose of this review is to supply a contemporary view of the diagnosis and therapy of patients with this important group of injuries.

METHODS

A comprehensive review of the medical literature, focusing on publications produced in the last 10 years, was undertaken. The principal sources were found in surgical, orthopedic, and radiographic journals.

CONCLUSIONS

The central challenge for the clinician evaluating and managing a patient with a pelvic fracture is to determine the most immediate threat to life and control this threat. Treatment approaches will vary depending on whether the main threat arises from pelvic fracture hemorrhage, associated injuries, or both simultaneously. Functional outcomes in the long-term depend on the quality of the rigid fixation of the fracture, as well as associated pelvic neural and visceral injuries.

Cyclic loading of sacroiliac screws in Tile C pelvic fractures

BACKGROUND

To investigate the stiffness and strength of completely unstable pelvic fractures fixated both anteriorly and posteriorly under cyclic loading conditions, the authors conducted a randomized, comparative, cadaveric study.

METHODS

In 12 specimens, a Tile C1 pelvic fracture was created. The authors compared the intact situation to anterior plate fixation combined with one or two sacroiliac screws. In 2,000 measurements, each pelvis was loaded with a maximum of 400 N. The translation and rotation stiffness of the fixations were measured using a three-dimensional video system. Furthermore, the load to failure and the number of cycles before failure were determined.

RESULTS

Both translation and rotation stiffness of the intact pelvis were superior to the fixated pelvis. No difference in stiffness was found between the techniques with one or two sacroiliac screws. However, a significantly higher load to failure and significantly more loading cycles before failure could be achieved using two sacroiliac screws compared with one screw.

CONCLUSION

Although the combination of anterior plate fixation combined with two sacroiliac screws is not as stable as the intact pelvis, in this study, embalmed aged pelves could be loaded repeatedly with physiologic forces. Given the fact that the average trauma patient is younger and given the fact that the quality (or grip) of the fixation was a significant covariable for longer endurance of the fixation, this suggests that direct postoperative weight bearing could be possible if these results are confirmed in further research.

Standard multiplanar fluoroscopy versus a fluoroscopically based navigation system for the percutaneous insertion of iliosacral screws: a cadaver model

OBJECTIVES

To compare the safety and efficiency of standard multiplanar fluoroscopy (StdFluoro) and virtual fluoroscopy (VirtualFluoro) for use in the percutaneous insertion of iliosacral screws.

DESIGN

: Human cadaver study comparing 2 imaging modalities during iliosacral screw insertion; imaging randomized from side to side.

SETTING

Bioskills laboratory in a medical school.

PARTICIPANTS

Twenty-nine embalmed whole human cadavers without prior hip or pelvic surgery.

INTERVENTION

Iliosacral screws were inserted into the S1 bodies using a percutaneous insertion technique. Screws were inserted on one side using StdFluoro, and on the other side, screws were placed using VirtualFluoro.

MAIN OUTCOME MEASUREMENTS

Time necessary for imaging preparation, screw insertion, and actual fluoroscopy were recorded. Accuracy and safety of screw placement was assessed using computed tomography and an anatomic dissection of the pelvis.

RESULTS

: Fifty-six of 58 iliosacral screws were placed within the desired bony corridor of the posterior pelvis. One screw placed using each method was inserted erroneously, but both were relatively minor deviations. There were no obvious injuries to major vessels or nerve roots. The total surgical time required for preparation of imaging and screw insertion averaged 7.3 minutes using StdFluoro and 6.7 minutes using VirtualFluoro (P = 0.4). Although the time necessary for screw insertion using VirtualFluoro averaged only 3.5 minutes, compared to 7.0 minutes for StdFluoro (P < 0.05), this time savings was offset by that required for application and calibration of tracking devices when using VirtualFluoro. The average fluoroscopy time using StdFluoro method was 26 seconds, whereas that for the VirtualFluoro was only 6 seconds (P < 0.01).

CONCLUSIONS

Most of the percutaneous iliosacral screws were safely inserted using StdFluoro and VirtualFluoro, and total surgical times were similar using both methods. As VirtualFluoro continues to evolve, improved efficiency in operative times may be expected. Currently, the most beneficial aspect of using VirtualFluoro during the insertion of percutaneous iliosacral screws appears to be significantly decreased use of fluoroscopy when compared to StdFluoro.

Treatment of Unstable Pelvic Fractures: Use of a Transiliac Sacral Rod for Posterior Lesions and an External Fixator for Anterior Lesions

BACKGROUND

This study sought to define the role of transiliac sacral rods used in combination with an external fixator for the management of unstable pelvic fractures.

METHODS

This retrospective study evaluated cases in which the surgical strategy was open reduction and internal fixation of posterior lesions with two transiliac sacral rods and closed reduction and external fixation of anterior lesions with an AO external fixator. The data for 65 cases were analyzed. Comprehensive Classification (AO) identified 42 C1 cases, 21 C2, cases and 2 C3 cases. Fractures with iliac bone involvement that impeded the application of an external fixator or transiliac sacral rods were excluded. The follow-up period was 85 months (range, 24-140 months).

RESULTS

All the fractures/dislocations healed well. The complications involved 17 cases (26.2%) of persistent posterior pain, 16 cases (24.6%) of irreversible neurologic deficit, 2 cases (3.1%) of posterior wound infection, 3 cases (4.6%) of pin tract infection, and 4 cases (6.2%) of irreversible urologic deficit. The functional results showed that the surgical results were satisfactory in 42 cases (64.6%) and unsatisfactory in 23 cases (35.4%).

CONCLUSIONS

For type C pelvic fractures without significant iliac bone involvement, surgical management with posterior transiliac fixation using sacral rods and anterior external fixation yields good radiologic results. The functional results correlated primarily with avoidance of complications and not necessarily with the radiologic results.

Biomechanical analysis of fixation for vertically unstable sacroiliac dislocations with iliosacral screws and symphyseal plating

OBJECTIVES

To examine the effects of various iliosacral screw configurations with and without symphyseal plating on sacroiliac (SI) motion and hemipelvis stability in the vertically unstable pelvic model.

DESIGN

Biomechanical, human cadaver.

SETTING

Level 1 trauma center.

INTERVENTION

Hemipelvis and SI motion were analyzed on a Materials Testing System before and after creation of a vertically unstable APC III pelvic injury. Posterior fixation constructs consisted of iliosacral screws: (1). one into S1, (2). two into S1, or (3). one into S1 and one into S2. Results were obtained for all posterior constructs with and without a two-hole symphyseal plate.

MAIN OUTCOME MEASUREMENT

Hemipelvis and SI motion with axial loading.

RESULTS

There was no statistically significant difference between one or two iliosacral screws when hemipelvis rotational or linear displacement was examined at the SI joint. The two-hole symphyseal plate significantly increased the stability of the fixation construct in resisting linear displacement in all three planes. Without the symphyseal plate, an abnormal loading response was seen at the SI joint, resulting in paradoxical posterior translation and sagittal plane rotation. The addition of the plate restored the normal response, and anterior rotation and translation were observed as in the intact state.

CONCLUSIONS

Anterior symphyseal plating for the vertically unstable hemipelvis significantly increases the stability of the fixation construct and restores the normal response of the hemipelvis to axial loading. A significant benefit to supplementary iliosacral screws in addition to a properly placed S1 iliosacral screw was not shown.

Biomechanical comparison of posterior pelvic ring fixation

OBJECTIVE

To determine relative stiffness of various methods of posterior pelvic ring internal fixation.

DESIGN

Simulated single leg stance loading of OTA 61-Cl.2, a2 fracture model (unilateral sacroiliac joint disruption and pubic symphysis diastasis).

SETTING

Orthopaedic biomechanic laboratory.

OUTCOME VARIABLES

Pubic symphysis gapping, sacroiliac joint gapping, hemipelvis coronal plane rotation.

METHODS

Nine different posterior pelvic ring fixation methods were tested on each of six hard plastic pelvic models. Pubic symphysis was plated. The pelvic ring was loaded to 1000N.

RESULTS

All data were normalized to values obtained with posterior fixation with a single iliosacral screw. The types of fixation could be grouped into three categories based on relative stiffness of fixation: For sacroiliac joint gapping, group 1-fixation stiffness 0.8 and above (least stiff) includes a single iliosacral screw (conditions A and J), an isolated tension band plate (condition F), and two sacral bars (condition H); group 2-fixation stiffness 0.6 to 0.8 (intermediate stiffness) includes a tension band plate and an iliosacral screw (condition E), one or two sacral bars in combination with an iliosacral screw (conditions G and I); group 3-fixation stiffness 0.6 and below (greatest stiffness) includes two anterior sacroiliac plates (condition D), two iliosacral screws (condition B), and two anterior sacroiliac plates and an iliosacral screw (condition C). For sacroiliac joint rotation, group 1-fixation stiffness 0.8 and above includes a single iliosacral screw (conditions A and J), two anterior sacroiliac plates (condition D), a tension band plate in isolation or in combination with an iliosacral screw (conditions E and F), and two sacral bars (condition H); group 2-fixation stiffness 0.6 to 0.8 (intermediate level of instability) includes either one or two sacral bars in combination with an iliosacral screw (conditions G and I); group 3-fixation stiffness 0.6 and below (stiffest fixation) consists of two iliosacral screws (condition B) and two anterior sacroiliac plates and an iliosacral screw (condition C).

DISCUSSION

Under conditions of maximal instability with similar material properties between specimens, differences in stiffness of posterior pelvic ring fixation can be demonstrated. The choice of which method to use is multifactorial.

Electromyography monitoring for percutaneous placement of iliosacral screws

OBJECTIVE

To report our experience with the use of continuous electromyography (EMG) for placement of iliosacral screws.

DATA SOURCES

Concurrently acquired data as well as patient charts, intraoperative EMG records, x-rays, and pelvic computed tomography (CT) scans.

DESIGN

The monitored group of twenty-nine patients was studied prospectively. The control group consisted of twenty-two patients studied retrospectively.

SETTING

Level One trauma center.

METHODS

Continuous electromyograms were recorded for twenty-nine patients and compared with those from a group of twenty-two antecedent patients who were not monitored. The primary parameter of interest of this study was the presence or absence of neurologic change after iliosacral screw placement. This information was obtained prospectively in the study group and by retrospective review in the historical control.

RESULTS

Four patients in the control group had postoperative and/or sensory motor changes prompting a postoperative CT scan; in each of these patients, a misdirected screw was identified and subsequently removed in a second procedure. There were no neurologic changes subsequent to placement in the twenty-nine patients who were monitored (7.5 percent versus 0 percent; p = 0.029, Fisher's exact test). All monitored patients had postoperative CT scans and showed the screw in a safe position with no significant violations of the S1 tunnel.

CONCLUSION

Continuous EMG monitoring during iliosacral screw placement may be a useful neuroprotective tool.

Effect of pin location on stability of pelvic external fixation

Pelvic external fixators allow two locations of pin purchase: anterosuperior (into the iliac crest) and anteroinferior (into the supraacetabular dense bone, between the anterior superior and anterior inferior iliac spine). The purpose of this study was to compare the stability of these two methods of fixation on Tile Type B1 (open book) and C (unstable) pelvic injuries. Five unembalmed cadaveric pelves (mean age, 68 years; four males and one female) were loaded vertically in a servohydraulic testing machine in a standing posture. The AO tubular system and Orthofix were used. On each pelvis, a Type B1 injury was simulated. Each external fixator was applied in each location in random order. Cyclic loads were applied through the sacral body to a maximum of approximately 200 N while force and displacement of the pelvic ring were recorded digitally. Sacroiliac joint motion was quantified tridimensionally with displacement transducers, mounted on the sacrum and contacting a target fixed to the posterior superior iliac spine. A Type C injury was created and augmented with two iliosacral lag screws, and the tests were repeated. For the Type B1 injuries with anteroinferior pin purchase, the mean stiffness was 201.2 N/mm for the AO frame and 203.2 N/mm for the Orthofix. For the anterosuperior frames the mean stiffness was 143.9 N/mm for the AO frame and 163.3 N/mm for the Orthofix. For Type B1 and Type C injuries, the anteroinferior location of pin purchase resulted in significantly reduced sacroiliac joint separation. There were no significant differences between the frame types. Dissection of the preinserted anatomic specimen revealed no evidence of injury to the lateral femoral cutaneous nerve after blunt dissection and drilling with protective drill sleeves. It is concluded that the anteroinferior location of external fixation pins is a safe technique with the potential for increased stability of fixation.