S2 iliosacral screw fixation for disruptions of the posterior pelvic ring: a report of 49 cases

A Quantitative Exposure Planning Tool for Surgical Approaches to the Sacroiliac Joint

OBJECTIVES

To aid in surgical planning by quantifying and comparing the osseous exposure between the anterior and posterior approaches to the sacroiliac joint.

METHODS

Anterior and posterior approaches were performed on 12 sacroiliac joints in 6 fresh-frozen torsos. Visual and palpable access to relevant surgical landmarks was recorded. Calibrated digital photographs were taken of each approach and analyzed using Image J.

RESULTS

The average surface areas of exposed bone were 44 and 33 cm for the anterior and posterior approaches, respectively. The anterior iliolumbar ligament footprint could be visualized in all anterior approaches, whereas the posterior aspect could be visualized in all but one posterior approach. The anterior approach provided visual and palpable access to the anterior superior edge of the sacroiliac joint in all specimens, the posterior superior edge in 75% of specimens, and the inferior margin in 25% and 50% of specimens, respectively. The inferior sacroiliac joint was easily visualized and palpated in all posterior approaches, although access to the anterior and posterior superior edges was more limited. The anterior S1 neuroforamen was not visualized with either approach and was more consistently palpated when going posterior (33% vs. 92%).

CONCLUSIONS

Both anterior and posterior approaches can be used for open reduction of pure sacroiliac dislocations, each with specific areas for assessing reduction. In light of current plate dimensions, fractures more than 2.5 cm lateral to the anterior iliolumbar ligament footprint are amenable to anterior plate fixation, whereas those more medial may be better addressed through a posterior approach.

Do Safe Radiographic Sacral Screw Pathways Exist in a Pediatric Patient Population and Do They Change With Age?

OBJECTIVES

Iliosacral screw pathways in the first (S1) and second (S2) sacral segments are commonly used for adult pelvic ring stabilization. We hypothesize that radiographically "safe" pathways exist in pediatric patients.

SETTING

Academic level I Trauma Center.

PATIENTS

All patients between ages 2 and 16 years with a computed tomography scan including the pelvis obtained over a 6-week period (174 children, mean age 10.8 ± 3.9 years; 90 boys, 84 girls).

INTERVENTION

The width and height at the "constriction point" in 3 safe screw pathways were measured bilaterally by 3 orthopaedists (resident, trauma fellow, trauma attending). Pathways corresponding to: (1) an "iliosacral" screw at S1, a "trans-sacral trans-iliac" (TSTI) screw at S1, and a TSTI screw at S2.

MAIN OUTCOME MEASUREMENTS

(1) Mean width and height of pathways, (2) interrater reliability coefficient, (3) availability of pathways greater than 7 mm, (4) growth of pathways with age, (5) sacral morphology.

RESULTS

The interrater reliability coefficient was above 0.917 for all measurements. Radiographically safe pathways were available for 99%, 51%, and 89% of children for iliosacral screws at S1 (width 16.4 ± 2.8 mm, height 15.1 ± 3.3 mm), TSTI screws at S1 (width 7.2 ± 4.9 mm, height 8.3 ± 5.6 mm), and TSTI at S2 (width 9.3 ± 2.2 mm, height 11.5 ± 2.7 mm), respectively.

CONCLUSIONS

Contrary to our hypothesis, almost all children aged 2-16 had a radiographically safe screw pathway for an iliosacral screw at S1, and most of the children had an available pathway for a TSTI screw at S2. However, only 51% had a pathway for a TSTI screw at S1.

Assessment of pelvic injuries treated with ilio-sacral screws: injury severity and accuracy of screw positioning

PURPOSE

The aim of this study was to analyse possible indicative parameters for percutaneous ilio-sacral stabilisation and to identify parameters associated with screw misplacement.

METHODS

Cohort study, level I trauma centre.

INCLUSION CRITERIA

(1) unstable pelvic injury, (2) percutaneous ilio-sacral screws placement.

EXCLUSION CRITERIA

(1) sacral dysmorphy, (2) failed closed reduction, (3) navigated techniques. Indicative parameters were age, gender, body mass index, number of screws, screw angulation, fracture type and injury severity. End points were ilio-sacral screw position and associated complications. Screw placement accuracy was graded as follows: grade 0, no perforation; grade 1, perforation <2 mm; grade 2, perforation from 2 to 4 mm; grade 3, ≥4 mm perforation.

RESULTS

Between March 2008 and March 2013, 102 (53 women) patients were included (mean age, 48.5 ± 21.4 years). The Injury Severity Score (ISS) and New Injury Severity Score (NISS) were 18.9 ± 9.9 and 22.3 ± 22.3, respectively. The positions of 137 ilio-sacral screws were analysed. Of all screws, 87.6 % (120) were placed satisfactory (<2 mm perforation). The incidence of screw misplacement was significantly higher in the case of two unilateral S1 screws compared with a single screw (failure rate: two unilateral screws 23.1 % vs single screw 7.0 %; p < 0.05). Screw perforation anterior to the lateral mass (in-out-in) represented the most frequent malposition. Revision was necessary in three cases due to malpositioning. Furthermore, no major complication occurred.

CONCLUSIONS

We conclude, that twofold ilio-sacral screw positioning from one side increases the risk for screw misplacement. In this case, alternative techniques like navigation should be considered. Anterior screw perforation represents a common problem with a high incidence and warrants particular attention.

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.

Investigation of bone quality of the first and second sacral segments amongst trauma patients: concerns about iliosacral screw fixation

Background

Iliosacral screw fixation has become a common method for surgical stabilization of acute disruptions of the pelvic ring. Placement of iliosacral screws into the first sacral (S1) body is the preferred method of fixation, but size limitations and sacral dysmorphism may preclude S1 fixation. In these clinical situations, fixation into the second sacral (S2) body has been recommended. The objective of this study was to evaluate the bone quality of the S1 compared to S2 in the described “safe zone” of iliosacral screw fixation in trauma patients.

Materials and methods

The pelvic computed tomography scans of 25 consecutive trauma patients, ages 18–49, at a level 1 trauma center were prospectively analyzed. Hounsfield units, a standardized computed tomography attenuation coefficient, was utilized to measure regional cancellous bone mineral density of the S1 and S2. No change in the clinical protocol or treatment occurred as a consequence of inclusion in this study.

Results

A statically significant difference in bone quality was found when comparing the first and second sacral segment (p = 0.0001). Age, gender, or smoking status did not independently affect bone quality.

Conclusion

In relatively young, otherwise healthy trauma patients there is a statistically significant difference in the bone density of the first sacral segment compared to the second sacral segment. This study highlights the need for future biomechanical studies to investigate whether this difference is clinically relevant. Due to the relative osteopenia in the second sacral segment, which may impact the quality of fixation, we feel this technique should be used with caution.

Level of evidence

III

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.

Biomorphometric analysis of ilio-sacro-iliacal corridors for an intra-osseous implant to fix posterior pelvic ring fractures

It is hypothesized that ilio-sacro-iliacal corridors for a new envisioned pelvic ring implant (trans-sacral nail with two iliacal bolts = ISI-nail: ilio-sacro-iliacal nail) exists on the level of S1- or S2-vertebra in each patient. The corridors of 84 healthy human pelves (42x ♂; 42x ♀, 18-85 years) were measured in high resolution CT scans using the Merlin Diagnostic Workcenter Software. Trans-sacral corridors (≥ 9 mm diameter) on the level of S1 and S2 were found in 62% and 54% of pelves with a mean length [mm ± SD] of 164 ± 12.9 and 142 ± 10.2. Corresponding iliac corridors were present in all specimens in caudally tilted axial planes of 37.8 ± 0.67° and 53.7 ± 0.94° in relation to the operating table plane and divergent angulations of 69.0 ± 0.49° and 70.1 ± 0.32° in relation to the sagittal midline plane. Sacral dysmorphism, with compensatory larger S2 corridors were prevalent in 24% of pelves; ilio-sacro-iliacal osseous corridors for the envisioned implant were found in 88% of pelves on the level of S1 or S2. In the remaining 12% with too narrow corridors for any trans-sacral implant (screws, bars, ISI nail) alternative fixation methods have to be considered. Expected advantages of the envisioned ISI nail compared to available fixation devices are discussed.

Transsacral screw safe zone size by sacral segmentation variations

Variations in sacral segmentation may preclude safe placement of transsacral screws for posterior pelvis fixation. We developed a novel automated 3D technique to determine the safe zone size for transsacral screws in the upper two sacral segments in 526 adult pelvis computed tomography scans. Safe zone sizes were then compared by gender and sacral segmentation variations (number of neuroforamen and the presence/absence of lumbosacral transitional vertebrae, ± LSTV). Ten millimeters was used as the safety threshold for a large screw. 3 (0.6%), 366 (70%), and 157 (30%) sacra had 3, 4, or 5 neuroforamen, respectively. Eighty-eight (17%) were +LSTV. Safe zone size depended on gender, number of neuroforamen in -LSTV sacra and presence of LSTV (p < 0.001) but not on the uni- or bilateral nature of the LSTV. 17% of -LSTV sacra were below the safety threshold in S1, 27% in S2, whereas 3% of +LSTV sacra were below in S1, 74% in S2. Of -LSTV sacra that cannot take an S1 screw safely, 77% can do so in S2, leaving only 4% of sacra that cannot accommodate a screw safely in either upper segment. The results demonstrate a predictable pattern of safe zone size based on gender and sacral segmentation variations.

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

BACKGROUND

Sacroiliac-percutaneous-screw-placement (SPSP) for unstable-posterior-pelvic-ring-injuries (UPPRI) might be associated with severe neurovascular complications because of screw-mal-position. The aim of the present study was to analysis the effectivity of computer-tomography-guided (CTG)-SPSP including accuracy of screw-placement, quality of injury-reduction and documentation of perioperative-complications. Additionally, procedure-dependent radiation-dose and outcome should be analysed.

METHODS

A consecutive cohort of 71 patients with UPPRI was operated by CTG-SPSP at a single trauma level 1 hospital. 136 sacroiliac screws were inserted to S1 and S2. Postoperatively, by the use of a computerised-radiologic-work-station all screws were visualised three-dimensionally. Their distancesmin to the sacral-borders in anterior-posterior and cranio-caudal direction as well as to the neuroforamen S1/S2 were determined. After CTG-SPSP, injury-dislocation in anterior-posterior and cranio-caudal direction was quantified. Local and general complications were documented during the 30-day-period. In 55 patients (77.5%) a follow-up-investigation (29.1±19.1 months) was performed.

RESULTS

132 screws (97.1%) were placed completely intraosseous, 3 screws (2.2%) perforated up to 1.0 mm (n(S1)=one screw; n(S2)=two screws), and one screw (0.7%) extended 2.2 mm into the S2-neuroforamen without contact to neural structures. Postoperative dislocationanterior-posterior was 1.3±0.9 mm and dislocationcranio-caudal 1.5±0.9 mm. No procedure-associated-complication was observed. Operation time showed a significant "learning curve" during the six-year study period (initially: 88.6±60.3 min; finally: 44.3±24.6 min). Perioperative effective-radiation-dose for patientsmale was 5.9±3.1 mSv and for patientsfemale 8.7±4.5 mSv. All injuries healed and 33 patients (46.5%) had metal removal after 11.0 (±4.9) months. Only two (5.0%) out of 40 patients complained persistent UPPRI-related pain so they were not able to restart work.

CONCLUSIONS

The CTG-SPSP is a safe procedure for UPPRI-stabilisation especially in S1 but also in S2. Injury reduction was excellent and no procedure associated complications were observed.

Standardized posterior pelvic imaging: use of CT inlet and CT outlet for evaluation and management of pelvic ring injuries

OBJECTIVES

The null hypothesis of this study states that routine axial computed tomography (CT) images are obtained at a consistent and reproducible orientation relative to the sacrum. The secondary null hypothesis states that there is no difference in the measurement of the safe zone for placement of iliosacral screws when using routine axial CT images and standardized reconstructions in defined planes perpendicular and parallel to the sacrum.

DESIGN

Retrospective review.

SETTING

University Level 1 Trauma Center.

PATIENTS

Sixty-eight consecutive trauma patients evaluated with routine pelvic CT, without pelvic ring injury.

INTERVENTION

Retrospective radiographic review and measurement.

METHODS

Sixty-eight consecutive adult patients with routine axial pelvic CT scans, without injury to the pelvic ring, and obtained as part of a trauma evaluation were retrospectively identified. The orientation of the axial slices relative to the sacrum was measured for each patient and compared. The maximal cross-sectional distance at the smallest section of the sacral ala (safe zone) was measured using the routine axial CT images, and these measurements were compared with similar measurements taken on standardized images perpendicular (CT inlet) and parallel (CT outlet) to the body of the sacrum. Additional data referencing the orientation of multiple sacral radiographic landmarks were also collected.

RESULTS

The orientation of routine axial CT image planes relative to the sacrum spanned a wide range. The angle between the routine axial CT plane and the sacrum varied from 43.5 to 82.0 degrees (SD = 9 degrees). Significant differences were found in measured safe zones of routine axial CT images compared with standardized CT inlet and CT outlet images. Compared with CT inlet images, routine axial CT images underestimated safe zones for transverse sacral screws at both S1 (P < 0.01) and S2 (P < 0.01). When compared with CT outlet images, routine axial CT images overestimated safe zones for oblique sacroiliac screws (P < 0.01) and underestimated the safe zone for S2 transverse sacral style screws (P < 0.01). No significant differences in measured variables were found between genders and sacral morphology.

CONCLUSIONS

Our null hypotheses were rejected: routine axial CT images were found to be at widely ranging orientations relative to the sacrum, and standardized CT images (CT inlet and CT outlet) demonstrated statistically significant differences in measurements of safe zones compared with routine axial CT images. Furthermore, the CT inlet and CT outlet views provide additional information regarding sacral landmarks that could be useful for preoperative planning.

Anatomical conditions of the posterior pelvic ring regarding bisegmental transverse sacroiliac screw fixation: a 3D morphometric study of 125 pelvic CT datasets

INTRODUCTION

Sacroiliac (SI) screws are used for osteosynthesis in unstable posterior pelvic ring injuries. In the cases of "sacral dysplasia", in which the elevated upper sacrum does not allow a secure SI screw insertion into the S1 level, the S2 segment must be used to achieve stable fixation. The bone quality of the S2 segment is thinner compared to that of the S1 vertebra and may cause biomechanical weakness. An additional SI screw insertion into the S3 level may improve stability. With respect to the anatomical conditions of the posterior pelvic ring, there have been no anatomical investigations to date regarding SI screw placement into the third sacral segment.

MATERIALS AND METHODS

CT raw datasets from 125 patients (ø59 years, ø172 cm, ø76 kg) were post-processed using Amira 5.2 software to generate 3D pelvic models. A program code implemented in C++ computed a transverse bone corridor for the first, second and third sacral segments for a typical SI screw diameter of 7.3 mm. Volume, sagittal cross-section, iliac entrance area and length of the determined screw corridors were measured. A confidence interval of 95 % was assumed (p < 0.05).

RESULTS

The fully automatic computation revealed a possible transverse insertion for one 7.3-mm screw in the third sacral segment in 30 cases (24 %). The rate (60 %) of feasible S3 screw placements in the cases of sacral dysplasia (n = 25) is significantly higher compared to that (15 %) of "normal" sacra (n = 100). With regard to the existence of transverse iliosacroiliac corridors as a function of sacral position in between the adjacent iliac bone bilaterally, a new classification of three different shape conditions can be made: caudad, intermediate minor, intermediate major, and cephalad sacrum. Gender, age, body height and body weight had no statistically significant influence on either possible screw insertion or on the calculated data of the corridors (p > 0.05).

CONCLUSION

SI screw insertion into the third sacral level deserves discussion in the cases of sacral dysplasia. Biomechanical and practical utility must be verified.

Anatomic Determinants of Sacral Dysmorphism and Implications for Safe Iliosacral Screw Placement

BACKGROUND

Upper sacral segment dysplasia increases the risk of cortical perforation during iliosacral screw insertion. Dysmorphic sacra have narrow and angled upper osseous corridors. However, there is no validated definition of this anatomic variation. We hypothesized that pelves could be quantitatively grouped by anatomic measurements.

METHODS

One hundred and four computed tomography (CT) scans and virtual outlet views of uninjured pelves were analyzed for the presence of the five qualitative characteristics of upper sacral segment dysplasia. CT scans were reformatted to measure the cross-sectional area, angulation, and length of the osseous corridor. Principal components analysis was used to identify multivariable explanations of anatomic variability, and discriminant analysis was used to assess how well such combinations can classify dysmorphic pelves.

RESULTS

The prevalences of the five radiographic qualitative characteristics of upper sacral segment dysplasia, as determined by two reviewers, ranged from 28% to 53% in the cohort. The rates of agreement between the two reviewers ranged from 70% to 81%, and kappa coefficients ranged from 0.26 to 0.59. Cluster analysis revealed three pelvic phenotypes based on the maximal length of the osseous corridor in the upper two sacral segments. Forty-one percent of the pelves fell into the dysmorphic cluster. The five radiographic qualitative characteristics of dysmorphism were significantly more frequent (p < 0.007) in this cluster. A combination of upper sacral coronal and axial angulation effectively explained the variance in the data, and an inverse linear relationship between these angles and a long upper sacral segment corridor was identified. A sacral dysmorphism score was derived with the equation: (first sacral coronal angle) + 2(first sacral axial angle). An increase in the sacral dysmorphism score correlated with a lower likelihood of a safe transsacral first sacral corridor. No subjects with a sacral dysmorphism score >70 had a safe transsacral first sacral corridor.

CONCLUSIONS

Sacral dysmorphism was found in 41% of the pelves. The major determinants of sacral dysmorphism are upper sacral segment coronal and axial angulation. The sacral dysmorphism score quantifies dysmorphism and can be used in preoperative planning of iliosacral screw placement.

Radiographic displacement in pelvic ring disruption: reliability of 3 previously described measurement techniques

BACKGROUND

The literature on pelvic ring disruptions is based largely on nonstandardized and nonvalidated radiographic outcomes. A thorough review of the literature revealed only 3 described methods for measuring radiographic displacement and 1 frequently used grading system for displacement. We aimed to test the reliability of these previously published radiographic measurement methods and grading system.

METHODS

Five separate observers measured radiographic displacement on the standardized pre- and postoperative anteroposterior, inlet, and outlet views of 25 patients with surgically treated Tile B and C pelvic fractures. The readers measured their initial impression based on the Tornetta and Matta grading system (excellent, good, fair, and poor). Next, they measured displacement using the inlet and outlet ratio as described by Sagi, the cross measurement technique as described by Keshishyan, and the absolute displacement method (ADM) as described by Lefaivre. The millimeter measurement obtained by the ADM was converted using the Tornetta and Matta grading system. Each continuous measure was compared for interobserver reliability using intraclass correlations (ICCs), and the categorical outcomes were compared using a kappa statistic. Finally, the relationship of the initial impression to the grade as determined by the ADM was compared using kappa agreement.

RESULTS

The agreement among observers based on initial impression was poor (kappa statistic, 0.306) but was fair among those reductions that were excellent (κ = 0.495). Using the Sagi method, the reliability ICC was moderate for the postoperative inlet [0.515, 95% confidence interval (CI), 0.338-0.702] and outlet ratio (0.594, 95% CI, 0.423-0.760) but almost perfect in preoperative radiographs (inlet: 0.814, 95% CI, 0.703-0.901; outlet: 0.863, 95% CI, 0.775-0.929). The ICCs for all interpretations of the Keshishyan technique were excellent but were highest when considered as a ratio (preoperative: 0.938, 95% CI, 0.894-0.969; postoperative: 0.912, 95% CI, 0.850-0.955). Using the ADM, the location and film used for measurement had poor agreement, and the ICC for the measurement in millimeters was moderate (preoperative: 0.522, 95% CI, 0.342-0.708; postoperative: 0.432, 95% CI, 0.255-0.634) and the kappa agreement poor when converted using the Tornetta and Matta scale (κ = 0.2190). The agreement between the impression and the converted grade from the ADM was poor (κ = 0.2520).

CONCLUSIONS

Radiographic measurement in pelvic x-rays to date has been nonvalidated, and we found the interobserver reliability on common methods, including overall impression and absolute displacement in millimeters, to be poor. The inlet/outlet ratio as described by Sagi was reliable only with wide displacement. The cross measurement technique allows least observer choice and had excellent reliability but does not give a measurement that we can easily interpret based on convention in pelvic fracture description.

Intraoperative fluoroscopic evaluation of screw placement during pelvic and acetabular surgery

The surgical treatment of pelvic and acetabular fractures can be technically challenging. Various techniques are available for the reconstruction of pelvic and acetabular fractures. Less invasive percutaneous fracture stabilization techniques, with closed reduction or limited open reduction, have been developed and are gaining popularity in the management of pelvic and acetabular fractures. These techniques require knowledge and interpretation of various fluoroscopic images to ensure appropriate and safe screw placement. Given the anatomic complexity of the intrapelvic structures and the 2-dimensional nature of standard fluoroscopy, multiple images oriented in different planes are needed to assess the accuracy of guide wire and screw placement. This article reviews the fluoroscopic imaging of common screw orientations during pelvic and acetabular surgery.

Treatment of posterior pelvic ring disruptions using a minimally invasive adjustable plate

OBJECTIVE

Iliosacral (IS) screw fixation and posterior tension band plate (TBP) technique are two treatment alternatives for posterior pelvic ring injuries. However, IS screw fixation requires continuous fluoroscopic guidance for appropriate screw insertion and carries a risk of neurovascular injuries. TBP technique also has some disadvantages, including limited reduction potential, difficulty in precontouring the plate and a higher rate of symptomatic implants. To address these limitations, we introduced a minimally invasive adjustable plate (MIAP). This study aims to present the preliminary radiological and clinical results of posterior pelvic ring disruptions treated with MIAP.

METHODS

The MIAP conforms to the irregular shape of posterior pelvic ring and can be used without prebending. This plate has a role in reducing compressed or separated fractures/dislocations. Sixteen patients, including seven males and nine females, were treated with MIAP through a minimally invasive approach. The fracture patterns consisted of six Type B and ten Type C fractures according to OTA classification of fracture. Preoperative and postoperative radiography was taken to assess the fracture displacement and reduction quality. Postoperative rehabilitation programme was individualised and early exercise was encouraged. Patients were followed up and the functional outcome was evaluated based upon the scoring system proposed by Lindahl and associates.

RESULTS

All posterior pelvic ring disruptions were reduced and fixed with MIAP. The average duration of surgery was 49 min, the average radiation exposure was 6s, and the average blood loss was 80 mL for the treatment of posterior pelvic ring injuries. Overall radiological results of the reduction were excellent in eleven patients and good in five. The patients were followed up for 30 months on average. All fractures healed. The functional outcome was excellent in ten patients, good in four and fair in two. There were no iatrogenic neurovascular injuries, implant failures, irritative symptoms or pressure sores due to subcutaneous implantation.

CONCLUSION

Favourable clinical and radiological outcomes can be achieved in treating posterior pelvic disruptions with MIAP. This plate is effective in view of its simplicity, less radiation exposure, safety, minimal invasion and stable fixation.

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.

Methodology and interpretation of radiographic outcomes in surgically treated pelvic fractures: a systematic review

OBJECTIVE

To identify and evaluate previously described methods for the measurement, and interpretation, of radiographic outcomes of operatively treated pelvic fractures.

DATA SOURCES

A systematic review of the available literature was performed using all major databases (MEDLINE, EMBASE, MEDLINE IN-PROGRESS, and Cochrane Central) in August 2009.

STUDY SELECTION

Inclusion criteria were case series, cohort studies, or clinical trials regarding orthopaedic treatment of acute traumatic pelvic ring fractures treated surgically in adults, with at least 12 weeks of radiographic follow-up. Exclusion criteria were case reports or case series of <10 patients, review articles, foreign language articles, and series where time frame of outcome measurement was not stated were excluded.

DATA EXTRACTION

Modality, and timeline, of the radiographic assessment was recorded. Next, the description of the method of radiographic measurement technique used was scrutinized for standardization. The interpretation of the radiographic measurement was evaluated, and any grading scale used was recorded. The interpretation of the quality of the radiographic result as described by each author was recorded. Finally, a qualitative methodological analysis was performed.

DATA SYNTHESIS

Number of standardized radiographic assessment techniques used (3 of 31) and interpretation scales used (13 of 31) were calculated. Nonweighted mean follow-up time (30.6 months) and overall positive radiographic outcomes were calculated (78.6% good or excellent).

CONCLUSIONS

Reporting of radiographic outcomes in pelvic fractures has been done using largely unstandardized and universally untested measurement techniques. The interpretations of these measurements are also inconsistent and untested. Substantive future research is needed in this area.

The lateral sacral triangle--a decision support for secure transverse sacroiliac screw insertion

Sacroiliac (SI) screw fixation represents an effective method to stabilise pelvic injuries. However, to date neither reliable radiological landmarks nor effective anatomical classifications of the sacrum exist. This study investigates the influence of variability in sacral shape on secure transverse SI-screw positioning. Furthermore, consistent correlations of these anatomical conditions are analysed with respect to standard planar pelvic views. For shape analysis, 80 human computed tomography data sets were segmented with the software Amira 4.2 to obtain 3D reconstructions. We identified anatomical conditions (ACs) according to the extent of the effect on the bony screw pathway. Subsequently, the pelvis was spatially aligned using representative bone protuberances in order to create standard Matta projections. In each view, the ACs were described in terms of distance from bone landmarks. Three-dimensional shape analysis revealed the height of the pedicular isthmus (PH) as the limiting variable for secure screw insertion. The lateral and outlet views allowed an orthogonal projection of PH. In the lateral view, the ratio of the lateral sacral triangle framed by the S1 body height and width showed a high correlation to PH (p = 0.0001). A boundary ratio of 1.5 represented a reliable variable to determine whether or not a screw can be inserted (positive predictive value: 97%). In the outlet view, the distance between the S1 endplate and the SI joint top level (EJ) strongly correlated with PH (p = 0.0001). With EJ 0 mm, screw insertion was possible in all cases (100%). SI-screw insertion requires a well-planned procedure. Orientation of the sacral pedicle is of extreme relevance. A narrow sacroiliac channel and high sacral shape variability limit secure screw placement. However, no determining parameters exist, allowing accurate prediction of secure screw insertion based on X-rays or fluoroscopy. The lateral sacral triangle in the lateral view represents a simple and accurate preoperative method of support for the surgeon's decision to undertake this procedure. No additional technical effort is necessary. A boundary ratio of 1.5 predicts a sufficient bone stock for at least one 7.3 mm screw. Furthermore, the evaluation of the outlet projection can be used to assess the safety of the operation. Basically, a preoperative lateral pelvic image should be mandatory.

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.

Minimally invasive stabilisation of posterior pelvic-ring instabilities with a transiliac locked compression plate

PURPOSE

Sacroiliac screw fixation is the method of choice for the definitive treatment of unstable posterior pelvic-ring injuries; however, this technique is demanding and associated with a high risk of iatrogenic neurovascular damage. This study evaluates whether minimally invasive transiliac locked compression plate stabilisation may be an alternative to sacroiliac screw fixation in unstable posterior pelvic-ring injuries.

METHODS

We performed a retrospective analysis of patients with unstable pelvic-ring injuries treated with a transiliac locked compression plate at a level I trauma centre. Outcome evaluation was assessed using the Pelvic Outcome Score and analysis of complications, intraoperative fluoroscopic time, and duration of the surgical procedure.

RESULTS

Twenty-one patients were available for follow-up after an average of 30 months. The main findings were as follows: Overall outcome for the Pelvic Outcome Score was excellent in 47.6% (ten patients), good in 19% (four patients), fair in 28.6% (six patients), and poor in 4.8% (one patient). Average operation time was 101 min and intraoperative fluoroscopic time averaged 74.2 s. No iatrogenic neurovascular injuries were observed.

CONCLUSION

Minimally invasive transiliac locked compression plate stabilisation may be a good alternative to sacral screw fixation because it is quick, safe and associated with a good functional outcome.

Prevalence of sacral dysmorphia in a prospective trauma population: Implications for a "safe" surgical corridor for sacro-iliac screw placement

Background

Percutaneous sacro-iliac (SI) screw fixation represents a widely used technique in the management of unstable posterior pelvic ring injuries and sacral fractures. The misplacement of SI-screws under fluoroscopic guidance represents a critical complication for these patients. This study was designed to determine the prevalence of sacral dysmorphia and the radiographic anatomy of surgical S1 and S2 corridors in a representative trauma population.

Methods

Prospective observational cohort study on a consecutive series of 344 skeletally mature trauma patients of both genders enrolled between January 1, 2007, to September 30, 2007, at a single academic level 1 trauma center. Inclusion criteria included a pelvic CT scan as part of the initial diagnostic trauma work-up. The prevalence of sacral dysmorphia was determined by plain radiographic pelvic films and CT scan analysis. The anatomy of sacral corridors was analyzed on 3 mm reconstruction sections derived from multislice CT scan, in the axial, coronal, and sagittal plane. "Safe" potential surgical corridors at S1 and S2 were calculated based on these measurements.

Results

Radiographic evidence of sacral dysmorphia was detected in 49 patients (14.5%). The prevalence of sacral dysmorphia was not significantly different between male and female patients (12.2% vs. 19.2%; P = 0.069). In contrast, significant gender-related differences were detected with regard to radiographic analysis of surgical corridors for SI-screw placement, with female trauma patients (n = 99) having significantly narrower corridors at S1 and S2 in all evaluated planes (axial, coronal, sagittal), compared to male counterparts (n = 245; P < 0.01). In addition, the mean S2 body height was higher in dysmorphic compared to normal sacra, albeit without statistical significance (P = 0.06), implying S2 as a safe surgical corridor of choice in patients with sacral dysmorphia.

Conclusions

These findings emphasize a high prevalence of sacral dysmorphia in a representative trauma population and imply a higher risk of SI-screw misplacement in female patients. Preoperative planning for percutaneous SI-screw fixation for unstable pelvic and sacral fractures must include a detailed CT scan analysis to determine the safety of surgical corridors.

Quantification of the upper and second sacral segment safe zones in normal and dysmorphic sacra

OBJECTIVES

To quantify the obliquity and dimensions of the upper and second sacral segment iliosacral screw safe zones and to determine the differences between normal and dysmorphic sacral morphology.

DESIGN

Retrospective cohort.

SETTING

University Level I trauma center.

PATIENTS/PARTICIPANTS

Fifty patients with pelvic computed tomography scans.

INTERVENTION

All sacra were characterized as normal or dysmorphic based on plain pelvic radiographs and previously described criteria. Multiple computed tomography scan reconstructions were viewed and manipulated simultaneously with 6 degrees of freedom to allow for custom visualization in any plane.

MAIN OUTCOME MEASUREMENTS

In each patient, a unique reconstruction plane was created perpendicular to the safe zone axis. The narrowest safe zone cross-sectional area was measured. Next, on simulated pelvic outlet and inlet views, safe zone obliquity and width were measured. Finally, the space available for a transverse screw was assessed. Measurements were performed for both upper and second sacral segment. Values for normal and dysmorphic safe zones were compared.

RESULTS

Sacral dysmorphism was identified in 22 patients. In these sacra, the upper sacral segment safe zone cross-section was 36% smaller than in normal sacra (P < 0.001). No transverse screws could be placed, but accommodating for the caudal to cranial obliquity (30° versus 21° in normals, P < 0.001) and posterior to anterior obliquity (15% versus 4% in normals, P < 0.001) of the safe zone, an iliosacral screw at least 75 mm in length could be placed safely in 91% of patients. A transverse screw could be placed in 75% of normal sacra. In the second segment safe zone, the cross-sectional area was more than twice as large in dysmorphic sacra compared to normals (220 mm versus 109 mm, P < 0.001). The obliquity was not different on either the inlet or outlet views between groups. A transverse screw could be placed at this level in 95% of those with dysmorphic sacra and in only 50% of normal sacra.

CONCLUSIONS

Sacral dysmorphism occurred in 44% of patients in this consecutive series. Many anatomic differences were consistently found between the two morphologies with clinical relevance to iliosacral screw placement. Specifically, the dysmorphic upper sacral segment safe zone is significantly smaller and more obliquely oriented but is still large enough to accommodate an iliosacral screw in nearly all patients. The second sacral segment safe zone is approximately transversely oriented in both sacral types but is more than twice as large in dysmorphic sacra. This segment may be a primary fixation opportunity in patients with sacral dysmorphism.

Locked transsacral screw fixation of bilateral injuries of the posterior pelvic ring: initial clinical series

OBJECTIVES

The purpose of this study was to evaluate the clinical safety and efficacy of using a cannulated transsacral screw having a novel locking capability for pelvic fracture fixation.

DESIGN

Retrospective analysis of a treatment protocol, patient series.

SETTING

Level I trauma center.

PATIENTS

Beginning in 2001, 10 patients with bilateral injury to the posterior pelvic ring were treated using a cannulated transsacral screw having a novel locking capability. Patients ranged in age from 21 to 64 years. Follow-up averaged 2 years (range, 1-5 years). Preoperative and postoperative radiographic evaluation included anteroposterior, inlet and outlet pelvic x-rays, and two-dimensional computerized tomography with 3-mm slice thickness. Candidates for this fixation required adequate space estimated on computerized tomography across either the first or second sacral body.

INTERVENTION

Locked transsacral screw fixation of bilateral injuries of the posterior pelvic ring consisting of a long 7.0-mm cannulated screw inserted over a washer from the near ilium, across one sacroiliac joint, through the body of the sacrum, and across the other sacroiliac joint, exiting the far iliac cortex. A self-locking nut was placed on the distal end of the screw.

MAIN OUTCOME MEASUREMENTS

Intraoperative iatrogenic nerve root injuries, postoperative screw position, and maintenance of the fixation construct until fracture healing.

RESULTS

There were no iatrogenic nerve injuries. Satisfactory screw position was documented on the postoperative computerized tomography in all cases. Fixation failure did not occur and satisfactory pelvic ring position was maintained in all cases.

CONCLUSIONS

Locked transsacral screw fixation is a safe and effective technique that should be added to our surgical armamentarium. Indications include bilateral posterior injury as well as any situation in which routine transsacral screw fixation might otherwise be considered such as the presence of pelvic osteopenia or insufficient space for a second point of posterior fixation.

Radiographic quantification and analysis of dysmorphic upper sacral osseous anatomy and associated iliosacral screw insertions

OBJECTIVE

To quantify upper sacral dysmorphic osseous anatomy and assess its impact on second sacral segment iliosacral screw insertion.

DESIGN

Retrospective evaluation of a prospective trauma database.

SETTING

Regional Level I trauma center.

PATIENTS

Twenty-four patients with unstable posterior pelvic ring disruptions and sacral dysmorphism were evaluated radiographically and second segment (S2) screws were placed using a standard technique.

MAIN OUTCOME MEASUREMENTS

The sacral osseous pathway limits were measured using preoperative pelvic computed tomography at the upper and second sacral segments. The S2 screw location relative to the sacral nerve root tunnels and the maximum possible screw lengths for both S1 and S2 screws were evaluated with postoperative pelvic computed tomography. The S2 screw positions were graded as intraosseous, juxtaforaminal, or extruded. Preoperative and postoperative peripheral neurologic examinations were documented.

RESULTS

The dysmorphic S1 width available for screw insertion averaged 13.2 mm. The S2 pathway width averaged 15.2 mm. The maximum potential screw length for the dysmorphic S1 averaged 100.8 mm and for S2 measured 151.9 mm. Twenty of 24 patients with S2 screws were intraosseous and in four patients were juxtaforaminal. There were no extruded screws. There were no neurologic injuries.

CONCLUSIONS

Dysmorphic S1 segments are anatomically competent for routine screw fixation. The S2 segment provides a larger osseous site for screw insertion than S1 in dysmorphic sacrums. Significantly longer screws are possible in S2 compared with the dysmorphic S1 segment. S2 iliosacral screws can be safely and accurately accomplished using a standard technique in patients with unstable posterior pelvic ring disruptions and sacral dysmorphism. Safe screw insertions avoid iatrogenic nerve root injuries.

2D-fluoroscopic navigated percutaneous screw fixation of pelvic ring injuries--a case series

BACKGROUND

Screw fixation of pelvic ring fractures is a common, but demanding procedure and navigation techniques were introduced to increase the precision of screw placement. The purpose of this case series was the evaluation of screw misplacement rate and functional outcome of percutaneous screw fixation of pelvic ring disruptions using a 2D navigation system.

METHODS

Between August 2004 and December 2007, 44 of 442 patients with pelvic injuries were included for closed reduction and percutaneous screw fixation of disrupted pelvic ring lesions using an optoelectronic 2D-fluoroscopic based navigation system. Operating and fluoroscopy time were measured, as well as peri- and postoperative complications documented. Screw position was assessed by postoperative CT scans. Quality of live was evaluated by SF 36-questionnaire in 40 of 44 patients at mean follow up 15.5 +/- 1.2 month.

RESULTS

56 iliosacral- and 29 ramus pubic-screws were inserted (mean operation time per screw 62 +/- 4 minutes, mean fluoroscopy time per screw 123 +/- 12 seconds). In post-operative CT-scans the screw position was assessed and graded as follows: I. secure positioning, completely in the cancellous bone (80%); II. secure positioning, but contacting cortical bone structures (14%); III. malplaced positioning, penetrating the cortical bone (6%). The malplacements predominantly occurred in bilateral overlapping screw fixation. No wound infection or iatrogenic neurovascular damage were observed. Four re-operations were performed, two of them due to implant-misplacement and two of them due to implant-failure.

CONCLUSION

2D-fluoroscopic navigation is a safe tool providing high accuracy of percutaneous screw placement for pelvic ring fractures, but in cases of a bilateral iliosacral screw fixation an increased risk for screw misplacement was observed. If additional ramus pubic screw fixations are performed, the retrograde inserted screws have to pass the iliopubic eminence to prevent an axial screw loosening.

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.

Accuracy of minimally invasive navigated acetabular and iliosacral fracture stabilization using a targeting and noninvasive registration device

BACKGROUND

To assess the feasibility and accuracy of guide pin (GP) placement using a combined noninvasive patient immobilization and stereotactic targeting system in computer-assisted percutaneous pelvic fracture stabilization.

METHODS

A total of 12 patients with negligible dislocated unstable pelvic fractures were enrolled in this study, performed between February 2002 and October 2005. Our original plans included 13 GP placements in the iliosacral area (SF) and 8 in the acetabular (AF) area. Patients were bedded on a noninvasive dual-vacuum immobilization device. Interventions were planned on a navigation system using intraoperatively acquired CT data. Radiodense markers glued to the skin and the immobilization device provided synchronization between virtual data set and real anatomical situation. A stereotactic targeting device was used for stabilization of GP tracking. GP positions were verified intraoperatively by CT, followed by fracture stabilization with cannulated screws.

RESULTS

Mean GP placement accuracy according to plan: (1) SF-cohort: 2.8 mm (SD 2.0 mm, range 0.5-9.0 mm) at the bony entry point and 3.8 mm (SD 2.3 mm, range 0.6-9.5 mm) at the target point. (2) AF-cohort: 3.0 mm (SD 0.9 mm, range 1.6-4.9 mm) at the bony entry point and 3.9 mm (SD 1.9 mm, range 1.6-7.5 mm) at the target point. GP placement succeeded optimally in 11 out of 13 cases in the SF-cohort, and 6 out of 8 cases in the AF-cohort. The individual average dose-length product (DLP) per successful finished procedure was 1,576 mGy x cm (SD 812 mGy x cm, range 561-2,739 mGy x cm).

CONCLUSION

Our findings substantiate application of the noninvasive patient immobilization and stereotactic targeting system as effective in computer-assited percutaneous stabilization of sacral bone fractures/SI joint disruptions and coronally oriented acetabular dome fractures. We recommend according to the ALARA (as low as reasonable achievable) principle: first, the kV and mAs values have to be reduced. Second, the scanned volume has to be strictly limited to the area of interest. Third, the number of control CTs have to be minimized. Also, the IsoC might be a better choice for implant tracking below 12 cm to reduce the radiation dose to the minimum. We believe that for all high-precise GP placements in the acetabular column area, further improvements in GP guidance (inhibiting pin tip slipping and detecting intraosseous GP deflection) are necessary.

Early experience with reduction of displaced disruption of the pelvic ring using a pelvic reduction frame

We describe our early operative experience with a new pelvic reduction frame and the standard of reduction of fractures of the pelvic ring which we achieved in the first 35 consecutive patients, with 34 acute fractures and one nonunion. The pre-operative and immediate post-operative radiographs were measured, using two methods, to find the maximum radiological displacement of the fracture and the quality of the reduction according to the criteria of Tornetta and Matta. There were 19 vertical shear fractures and 16 compression injuries. The mean age of the patients was 33.5 years (10 to 59) and mean delay to surgery was 4.6 days (0 to 16) in the 34 acute injuries. The mean operative time in isolated procedures was 103.4 minutes (SD 6.5). All but one patient had iliosacral screws implanted, 18 had screws in the anterior column, six had plates at the symphysis pubis and 12 had anterior external fixators. The mean maximum horizontal or vertical displacement was improved from 30.8 mm (SD 2.7) to a mean of 7.1 mm (SD 0.7). The reduction was assessed as excellent in ten patients, good in 18, and fair in the remainder. There was no significant influence on the quality of the reduction caused by obesity (p = 0.34), the type of fracture (p = 0.41) or delay to surgery (p = 0.83). The frame was shown to be effective, allowing the surgeon to obtain a satisfactory reduction and fixation of acute displaced disruptions of the pelvic ring.

Treatment of posterior pelvic ring injuries with minimally invasive percutaneous plate osteosynthesis

From January 2004 to July 2007, 21 patients with injuries at the posterior pelvic ring were treated with locking compression plate osteosynthesis through a minimally invasive approach and followed up for a mean of 12.2 months. Preoperative and postoperative radiography was conducted to assess the reduction and union. The mean operation time was 60 minutes (range: 40-80). Intraoperative blood loss was 50-150 ml. All patients achieved union at the final follow-up. The overall radiological results were excellent or good in 17 patients (85%). The functional outcome was excellent or good in 18 patients (90%). There was no iatrogenic nerve injury, deep infection or failure of fixation. We believe that fixation with a locking compression plate is an effective method for the treatment of injuries of the posterior pelvic ring in view of its convenience, minimal traumatic invasion and lower morbidity.

[Bony sacroiliac corridor. A virtual volume model for the accurate insertion of transarticular screws]

BACKGROUND

Minimally invasive sacroiliac (SI) screw fixation carries a high risk for implant malposition. Only idealised shape conceptions of the safe bony corridor exist.

METHODS

Two SI corridor models were generated based on a 3D CT reconstruction of a human pelvis. Therefore two penetration depths of the screws into the sacrum were defined.

RESULTS

By inserting screws into the centre of the first sacral body an osseous volume of 121 cm3 and an iliac entrance area of 53 cm2 were utilizable. Screw positioning beyond the opposite sacral isthmus leads to a reduction of the bony volume to 72 cm3 (60%) and a decrease of the iliac screw entrance to 20 cm2 (38%).

CONCLUSION

The computed realistic 3D models provide exact references to confining bone structures for safe screw positions. The implementation of a software algorithm for fully automated calculation of such volumes based on fluoroscopic or CT images could enhance the performance of computer-assisted navigation systems.

A biomechanical comparison of lateral and posterior approaches to sacroplasty

STUDY DESIGN

Biomechanical cadaveric bench study.

OBJECTIVE

To measure the augmentation effect and extravasation risk of posterior and lateral approaches to sacroplasty.

SUMMARY OF BACKGROUND DATA

The biomechanical stabilizing effect of sacroplasty is unknown.

METHODS

Using a sacral insufficiency fracture model, we performed sacroplasty in 15 osteoporotic cadaveric pelves. Five served as controls, and 10 were each injected with 4 mL of a polymethylmethacrylate cement (5 via a posterior approach, 5 via a lateral approach). Cement extravasation was assessed using computed tomography. Restored strength and stiffness were defined as the ratios of treatment to initial strength and to stiffness, respectively. Between-group differences in restoration parameters were checked for significance (P < 0.05) using an analysis of variance followed by Tukey's test.

RESULTS

We found no significant differences between groups in terms of restored strength ( approximately 61%) and stiffness ( approximately 77%). Both injection methods produced extravasation into the anterior sacrum, the posterior sacrum, the sacroiliac joint, and the neural foramens.

CONCLUSION

Sacroplasty with 4 mL of cement does not restore the strength or stiffness of the sacrum in a cadaveric model, regardless of the approach used.

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.

Percutaneous fixation of the pelvic ring: an update

With the development of systems of trauma care the management of pelvic disruption has evolved and has become increasingly refined. The goal is to achieve an anatomical reduction and stable fixation of the fracture. This requires adequate visualisation for reduction of the fracture and the placement of fixation. Despite the advances in surgical approach and technique, the functional outcomes do not always produce the desired result. New methods of percutaneous treatment in conjunction with innovative computer-based imaging have evolved in an attempt to overcome the existing difficulties. This paper presents an overview of the technical aspects of percutaneous surgery of the pelvis and acetabulum.