Removal of an iliosacral screw entrapping the L5 nerve root after failed posterior pelvic ring fixation: a case report

Complications of conventional percutaneous sacroiliac screw fixation of traumatic pelvic ring injuries: a systematic review and meta-analysis

OBJECTIVES

The objective of this review was to present a thorough overview of the complications associated with conventional percutaneous sacroiliac screw fixation to identify areas for improvement in surgical technique and patient selection.

METHODS

PubMed/Medline, Web of Science, Embase, Ovid, Cochrane library, and Google Scholar were systematically searched for original human studies reporting on complications of conventional percutaneous sacroiliac fixation in traumatic pelvic ring injuries from January 1, 2000, to April 30, 2022. The main meta-analysis was based on the random effect model to pool all complications reported in the included studies. The results were reported as weighted proportions with 95% confidence intervals. This review was conducted in line with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines.

RESULTS

A total of 56 studies with 3644 screws (2871 procedures) met the inclusion criteria, with a mean age of 40.5 years. The most frequently reported complications were screw malposition with a weighted proportion of 6% (95% CI: 5-9%) and involved 189 out of 3644 screws, persistent pain following the procedure with a weighted proportion of 3% (95% CI: 2-4%) and affected 98 out of 2871 patients, and nerve injury, which had a weighted proportion of 2% (95% CI: 1-3%) and was observed in 41 out of 2871 procedures. The L5 and S1 nerve roots were more frequently affected. Revision surgery was required for 184 out of 2871 patients with a weighted proportion of 5% (95% CI: 3-7%). The primary reason for the revision was persistent pain after the initial procedure, which affected 74 out of 184 patients, with a weighted proportion of 2.0% (95% CI: 1.2-2.8%).

CONCLUSIONS

This study showed that screw malposition, the need for revision surgery, persistent pain, and nerve injuries were the most frequent complications following conventional percutaneous sacroiliac screw fixation. However, these results must be interpreted in context due to confounding factors, including the lack of high-quality studies and the absence of uniformity in defining some complications across studies.

Determination of a neurologic safe zone for bicortical S1 pedicle screw placement

BACKGROUND CONTEXT

Lumbosacral fixation is commonly used for the management of lumbosacral instability. As the sacrum mainly consists of cancellous bone, bicortical fixation, in which the pedicle screw penetrates the anterior sacral cortex, can help increase the strength of fixation. However, this method carries a risk to the L5 nerves which lie anterior to the sacrum at this level.

PURPOSE

The goal of this study is to determine a safe zone for the placement of S1 pedicle screws to decrease the likelihood of L5 nerve injury.

STUDY DESIGN

Retrospective imaging review.

PATIENT SAMPLE

This study evaluated imaging data of patients who underwent lumbar spine magnetic resonance imaging (MRI) at our institute between September 1, 2020 and September 1, 2021.

OUTCOME MEASURES

T1-weighted axial MRIs were measured at the level of S1 pedicle screw placement. The space medial and lateral to the L5 nerve root on the anterior sacrum were measured and defined as safe zones. Additionally, the nerve width and sacral lengths were measured at this level.

METHODS

The distribution of the measurements were evaluated to determine a medial and lateral safe zone, as well as the average nerve width at the level of S1 pedicle screw placement. Correlation analysis was performed to determine a relationship between safe zone sizes and sacral size.

RESULTS

A total of 400 MRIs were analyzed. The average medial safe zone measured was 32.8 mm (95% CI: 32.2-33.4) with no nerves lying within 22.3 mm of the midline sacrum. The average lateral safe zone measured was 17.7 mm (95% CI: 17.1-18.2), with no nerves within 5.3 mm of the lateral border of the sacrum. The average nerve root width was 6.2 mm (95% CI: 6.13-6.34). An increased sacral length was associated with a larger medial (p<.001) and lateral (p<.001) safe zone.

CONCLUSIONS

Our study revealed lateral and medial safe zones for the placement of S1 pedicle screws to avoid iatrogenic nerve injury in a retrospective cohort of 400 patients. There were no L5 nerve roots found within 22.3 mm of the sacrum's mid-axis or within 5.3 mm of the sacrum's anterolateral border. These defined safe zones can be used during pedicle screw planning and placement to decrease the risk of injury to the L5 nerve root.

Anatomical Considerations in Percutaneous Fixation of the Pelvis and Acetabulum

Reduction and fixation techniques of the pelvis and acetabulum continue to evolve. There has been increased use of percutaneous and minimally invasive techniques in the past several decades. Although offering many advantages to traditional open techniques, percutaneous techniques still place nearby structures at risk, making a thorough understanding of the applied surgical anatomy essential.

Two-Dimensional Visualization of the Three-Dimensional Planned Sacroiliac Screw Corridor with the Slice Fusion Method

Insertion of sacro-iliac (SI) screws for stabilization of the posterior pelvic ring without intraoperative navigation or three-dimensional imaging can be challenging. The aim of this study was to develop a simple method to visualize the ideal SI screw corridor, on lateral two-dimensional images, corresponding to the lateral fluoroscopic view, used intraoperatively while screw insertion, to prevent neurovascular injury. We used multiplanar reconstructions of pre- and postoperative computed tomography scans (CT) to determine the position of the SI corridor. Then, we processed the dataset into a lateral two-dimensional slice fusion image (SFI) matching head and tip of the screw. Comparison of the preoperative SFI planning and the screw position in the postoperative SFI showed reproducible results. In conclusion, the slice fusion method is a simple technique for translation of three-dimensional planned SI screw positioning into a two-dimensional strict lateral fluoroscopic-like view.

Subacute Minimally Invasive Decompression of L5 and S1 Nerve Roots for Neurologic Deficit After Fixation of Unstable Pelvic Fracture: A Case Report and Review of the Literature

CASE

A 73-year-old man experienced immediate neurological decline after percutaneous transsacral screw fixation for a pelvic ring injury sustained after a 25-foot fall. Workup revealed well-positioned screws and compression of the right L5 and S1 nerve roots at the fracture site. Symptoms improved after direct decompression without screw revision.

CONCLUSION

The courses of the L5 and S1 nerve roots place them at risk of compression within the fracture during transsacral screw fixation. In highly comminuted fractures, avoidance of compression screws or use of intraoperative CT might prevent this complication. Direct nerve root decompression alone can be a successful treatment.

Does Implant Removal Across the Sacroiliac Joint Improve Pain and Outcomes?

OBJECTIVES

To determine if removal of previously inserted iliosacral screws improved posterior pelvic pain and Short Musculoskeletal Form Assessment (SMFA) scores.

DESIGN

Retrospective database review.

SETTING

Level-1 trauma center.

PATIENTS/INTERVENTION

Twenty-five patients who underwent iliosacral screw removal.

MAIN OUTCOME MEASURE

SMFA score.

RESULTS

Eighty-eight percent of patients stated that they were satisfied with the procedure and would undergo screw removal again. SMFA functional and bothersome scores decreased (improved) after the screw removal procedure, both at 3 months and at the final follow-up. Two-eight percent of the patients required narcotics before surgery compared with 8% after screw removal. No surgical complications occurred during screw removal.

CONCLUSION

A select group of patients who have symptomatic screws across the sacroiliac joint may benefit from elective screw removal.

LEVEL OF EVIDENCE

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

Percutaneous removal of sacroiliac screw following iatrogenic neurologic injury in posterior pelvic ring injury: A case report

INTRODUCTION

Percutaneous sacroiliac fixation is an effective minimally invasive method for posterior pelvic ring stabilization. Screw misplacement, and subsequent neurologic injury are two well described complications. Managing those complications however is under-reported.

CASE

A young female, sustained an unstable pelvic ring injury as a victim of motor vehicle collision. Following percutaneous sacroiliac screw fixation, she complained of L5 nerve root radiculopathy, and muscle weakness. Percutaneous removal of the screw after a wait period for fracture union resulted in immediate symptoms relief.

DISCUSSION

Safe sacroiliac screw placement is technically demanding requiring good understanding of sacral complex morphology and its anatomic variants. Risk of screw misplacement, and potential neurologic injury increases in dysmorphic sacra, or with inaccurate fracture reduction. Advances in intraoperative imaging modalities have been introduced in an attempt to improve accurate screw insertion. Literature is scarce with reports discussing removal of sacroiliac screw. Technique of screw retrieval is also controversial.

CONCLUSION

This case addresses management of an iatrogenic neurologic complication following percutaneous sacroiliac screw fixation. Our experience showed that, percutaneous retrieval of an intact misplaced sacroiliac screw is achievable, resulting in complete resolution of neurologic symptoms.

Rate of intraoperative problems during sacroiliac screw removal: expect the unexpected

BACKGROUND

The indications for sacroiliac screw (SI) removal have been under debate. Data on complication rates of SI screw removal is missing in the current literature. The objective of this study was to compare the rate of intra- and perioperative problems and complications during SI screw removal to those with SI screw fixation.

METHODS

A retrospective observational study with two interventions in the same cohort was performed. Consecutive patients who underwent both sacroiliac screw fixation for an isolated fracture of the pelvic ring and removal of the same implants between November 2008 and September 2015 (n = 19; age 57.3, SD 16.1 years) were included. Intraoperative technical problems, postoperative complications, duration of surgery, and radiation dose were analysed.

RESULTS

Intraoperative technical problems occurred in 1/19 patients (5%) during SI screw fixation and in 7/19 cases (37%) during SI screw removal (p = .021). Postoperative complications were seen in 3/19 patients after SI screw fixation and in 1/19 patients after SI screw removal (p = 0.128). The surgical time needed per screw was longer for screw removal than for implantation (p = .005). The amount of radiation used for the whole intervention (p = .845) and per screw (p = .845) did not differ among the two interventions.

CONCLUSIONS

Intraoperative technical problems were more frequent with SI screw removal than with SI screw fixation. Most of the intraoperative technical problems in this study were implant-related. They resulted in more surgical time needed per screw removed but similar radiation time.

Sacral Dysmorphism and its Implication on the Size of the Sacroiliac Joint Surface

STUDY DESIGN

This is a retrospective data analysis.

OBJECTIVE

The aim of this study was to analyze the prevalence of sacral dysmorphism and its correlation to the size of the sacroiliac joint (SIJ) surface based on computed tomography (CT) scans.

SUMMARY OF BACKGROUND DATA

Sacroiliac screw fixation is a widely accepted technique for stabilization of posterior pelvic ring injuries. Safe sacral screw placement may be impaired by sacral dysmorphism. The prevalence and impact of sacral dysmorphism on the size of the SIJ surface is unknown.

MATERIALS AND METHODS

In total, 269 CT scans were evaluated for the presence of the 5 signs of sacral dysmorphism (mammillary bodies, tongue-in-groove, residual upper sacral disk space, colinearity, and dysmorphic sacral neural foramina). The size of the SIJ surface was calculated by measuring the sacral joint line of the SIJ on each axial CT slice. Logistic regression analyses were conducted to reveal sex-related or age-related differences and correlations between the presence of the dysmorphic signs and the size of the SIJ surface.

RESULTS

Prevalence rates of the dysmorphic signs ranged from 5% (colinearity) to 70% (residual sacral disk space). Only 15% did not show any sign of sacral dysmorphism. The average size of the SIJ surface was 7.36 cm; it was significantly larger in male (8.46 cm) than in female (6.11 cm) patients (P<0.001). The presence of tongue-in-groove morphology was associated with a significantly larger SIJ surface (P<0.001), the presence of a residual upper sacral disk space with a significantly smaller joint surface (P=0.006).

CONCLUSIONS

The prevalence of sacral dysmorphism is remarkably high in a normal population and it is questionable if the respective signs should be called dysmorphic after all. The possibility of a smaller joint surface in female patients and patients with a residual upper sacral disk space should be considered in the planning of iliosacral screw placement.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Percutaneous screw fixation of the iliosacral joint: A case-based preoperative planning approach reduces operating time and radiation exposure

INTRODUCTION

A preoperative planning approach for percutaneous screw fixation of the iliosacral joint provides specific entry points (EPs) and aiming points (APs) of intraosseous screw pathways (as defined by CT scans) for lateral fluoroscopic projections used intraoperatively. The potential to achieve the recommended EPs and APs, to obtain an ideal screw position (perpendicular to the iliosacral joint), to avoid occurrence of extraosseous screw misplacement, to reduce the operating time and the radiation exposure by utilizing this planning approach have not been described yet.

METHODS

On preoperative CT scans of eight human cadaveric specimen individual EPs and APs were identified and transferred to the lateral fluoroscopic projection using a coordinate system with the zero-point in the center of the posterior cortex of the S1 vertebral body (x-axis parallel to upper S1 endplate). Distances were expressed in relation to the anteroposterior distance of the S1 upper endplate (in%). In each specimen on one side a screw was placed with provided EP and AP (New Technique) whereas at the contralateral side a screw was placed without given EP and AP (Conventional Technique). Both techniques were compared using postoperative CT scans to assess distances between predefined EPs and APs and the actually obtained EPs and APs, screw angulations in relation to the iliosacral joint in coronal and axial planes and the occurrence of any extraosseous screw misplacement. The "operating time (OT)" and the "time under fluoroscopy (TUF)" were recorded. Statistical analysis was performed by the Wilcoxon signed-rank test.

RESULTS

EPs were realized significantly more accurate using the new technique in vertical direction. The screw positions in relation to the iliosacral joint showed no significant difference between both techniques. Both techniques had one aberrantly placed screw outside the safe corridor. The (mean±SD) "OT" and the (mean±SD) "TUF" were significantly decreased using the new technique compared to the conventional technique (OT: 7.6±2min versus 13.1±5.8min, p=0.012; TUF: 1.5±0.8min versus 2.2±1.1min).

CONCLUSION

The presented preoperative planning approach increases the accuracy in percutaneous screw fixation of the iliosacral joint, reduces operating time and minimizes radiation exposure to patient and staff.

A simple approach for the preoperative assessment of sacral morphology for percutaneous SI screw fixation

BACKGROUND

Percutaneous sacroiliac screw fixation under fluoroscopic control is an effective method for posterior pelvic ring stabilization. However, sacral dysmorphism has a high risk of L5 nerve injury. This study describes a simple method for the preoperative assessment of the sacral morphology using CT scans with widely available tools.

MATERIALS AND METHODS

CT scans of 1000 patients were analyzed. True inlet, outlet, and lateral views of the sacrum were obtained using a two-dimensional reconstruction tool to align the sacrum in a reproducible manner. Corridor morphology in the inlet view was measured to calculate different morphological types: (1) Ascending type, (2) Horizontal type, and (3) Descending type. In a second step, the corridor was analyzed for the presence of an anterior indentation of the sacrum between the SI joint and the midsagittal plane with proximity to the nerve root L5, which, therefore, may be harmed during screw misplacement.

RESULTS

A notch was found in the majority of cases with relative frequencies ranging from 69 % (upper quartile of S1) to 95 % (upper quartile of S2). Descending types were, by far, the most frequent corridor type with one exception: In the upper quartile of S1, the ascending type was the most frequent corridor (71 %). Horizontal types were less frequent with a relative incidence between 2 and 14 %.

DISCUSSION

This study should increase the awareness for sacral dysmorphism, emphasize the importance of a preoperative assessment of the osseous corridor, and provide a simple method for the preoperative assessment with widely available tools.

Evaluation of Partial Cut-out of Sacroiliac Screws From the Sacral Ala Slope via Pelvic Inlet and Outlet View

STUDY DESIGN

An anatomic and radiographic study of placement of sacroiliac screws.

OBJECTIVE

The aim of this study was to quantitatively assess the risk of partial cut-out of sacroiliac screws from the sacral ala slope via inlet and outlet view.

SUMMARY OF BACKGROUND DATA

The partial cut-out of sacroiliac screws from the superior surface of sacral ala can jeopardize the L5 nerve root, which is difficult to identify on the pelvic inlet and outlet views.

METHODS

Computed tomography images of 60 patients without pelvic ring deformity or injury were used to measure the width (on inlet view) and height (on outlet view) of the sacral ala. The angle of the sacral ala slope was measured on lateral view. According to the measured parameters, the theoretical safe trajectories of screw placement were calculated using inverse trigonometric functions. Under fluoroscopic guidance, a sacroiliac screw was placed close to the midline on both inlet and outlet views, including posterosuperior, posteroinferior, anterosuperior, and anteroinferior regions to the midline. The incidence of screw partial cut-out from the superior surface of sacral ala was identified.

RESULTS

The measured widths and heights of the sacral alas were 28.1 ± 2.8 and 29.8 ± 3.1 mm, respectively. The average angle between the superior aspect of the S1 vertebral body and the superior aspect of the sacral ala was 37.2 ± 2.5 degrees. The rate of partial cut-out of the screws from the superior surface of sacral ala slope was 12.5% (5/40) in posterosuperior, 0% (0/40) in posteroinferior, 70% (28/40) in anterosuperior, and 20% (8/40) in anteroinferior.

CONCLUSION

To avoid the risk of partial cut-out from sacroiliac screw placement, more precise description should be added to the conventional description: the sacroiliac screws should be placed at the inferior half portion on outlet view and at the posterior half portion on inlet view.

LEVEL OF EVIDENCE

4.

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.

The percutaneous stabilisation of the sacroiliac joint with hollow modular anchorage screws: a prospective outcome study

PURPOSE

The use of percutaneous iliosacral screw fixation as a treatment of sacroiliac joint pain has been reported to be successful. This study was a prospective single surgeon series to evaluate the short-term outcomes of patients who underwent percutaneous sacroiliac joint stabilisation.

METHODS

Between July 2004 and February 2011, 73 patients underwent percutaneous sacroiliac joint fusion in our unit. All patients completed a short form (SF)-36 questionnaire, visual analogue pain score and Majeed scoring questionnaire prior to treatment and at last follow-up.

RESULTS

55 patients (9 male and 46 female) completed follow-up. The average follow-up period was for 36.18 months (range 12-84). The mean preoperative SF-36 scores were 26.59 for physical health and 40.38 for mental health. The mean postoperative SF-36 scores were 42.93 for physical health and 52.77 for mental health. The mean visual analogue pain scores were 8.1 preoperative and 4.5 postoperative. The mean pelvic specific scoring were 36.9 preoperative and 64.78 postoperative. We noted that patients who had previous instrumented spinal surgery did significantly worse than those who had not. We had two nerve root-related complications.

CONCLUSION

We conclude that in selected patient group who respond positively to CT-guided injection, a percutaneous SI joint stabilisation is beneficial in effecting pain relief and functional improvement.

[Hardware removal after pelvic ring injury]

BACKGROUND

Pelvic ring fractures are considered as rare injuries. Minimally invasive sacroiliac screw fixation has been used increasingly in recent years as an operative strategy for the treatment of these injuries, if the dorsal pelvic ring needed to be addressed. Treatment options for the anterior pelvic ring comprise plates, screws or external fixation.

METHOD

Based on the limited number of publications on this subject and our own experience with 80 patients who suffered pelvic ring B- or C-type injuries during a period of 8 years we are able to show that the indication for hardware removal in the pelvic ring should be strictly defined.

RESULTS

In some cases like external fixation, implant-associated infection, malpositioning, allergic implant reaction, critical soft tissue covering, palpable hardware and consolidated juvenile fractures implant removal is certainly indicated. In patients without symptoms and in patients with trauma-associated symptoms which are not definitely associated with the hardware, the removal should be only indicated after thorough consideration of the risks versus the benefits and additionally by taking the initial injury pattern into account. If despite all these objections the hardware removal has been indicated it should always be considered that hardware removal may be challenging with several possible severe complications.

Ureteral injury after percutaneous iliosacral fixation: a case report and literature review

We report a case of right ureter injury in an 11-year-old girl after a percutaneous iliosacral screwing with non-computer-assisted fluoroscopic guidance. The indication was a pelvic ring fracture, C1-1 in the Tile modified AO classification (J Am Acad Orthop Surg. 1996;4:143-151). The mechanism was a ski accident. A percutaneous iliosacral screwing was performed to stabilize the right iliac wing fracture. Twelve days after the initial trauma, a right ureter tear was highlighted, just opposite the fourth lumbar vertebra. Uneventful spontaneous healing of the ureteral injury site occurred following double J-stent catheterization.

Minimally invasive fluoro-navigation screw fixation for the treatment of pelvic ring injuries

Intensive use of intraoperative fluoroscopy is mandatory to achieve good accuracy and avoid neural or vascular injury and may prolong surgical time and increase exposure-related hazards. New methods of percutaneous treatment in conjunction with innovative fluoroscopy-based computerized navigation have evolved in an attempt to overcome the existing difficulties. This report described our experience in applying fluoroscopic surgical navigation technique and evaluated its clinical application to pelvic ring injuries, including its feasibility, merits and limitations. Twenty-two patients with pelvic ring injuries were treated with percutaneous pubic ramus screw and sacroiliac screw techniques under the guidance of a fluoroscopy-based navigation system. A total of forty-four screws were inserted, including twenty-seven pubic ramus screws and seventeen sacroiliac screws. The average operation time and the average fluoroscopy time per screw were 23.6 minutes and 22.2 seconds respectively. Compared to the final position of the screw, the average deviated distance of wire tip was 2.8 mm and the average trajectory difference was 2.6°. A ventral cortex perforation of the sacrum was found in one sacroiliac screw without any clinical symptoms. No superficial or deep infection occurred. No patient sustained recognized neurologic, vascular, or urologic injury as a result of percutaneous screw fixation of pubic ramus fractures, sacroiliac disruptions, or sacral fractures. Our results showed that fluoroscopy-based navigation technique for the pelvic ring injuries could become a safe and effective alterative method for the treatment of pelvic ring injuries in some selected patients.

Successful laparoscopic exploration and screw extraction for intractable pain after anterior iliosacral arthrodesis

We report on the case of a patient suffering from L5 radicular pain after previous anterior sacroiliac arthrodesis using 2, 4-hole plates. Technical investigations indicated loosening and migration of a screw from the upper sacroiliac plate, irritating the L5 nerve root. The problem was managed by removal of the screw using an anterior transperitoneal laparoscopic approach.

The upper sacral nerve root tunnel: an anatomic and clinical study

OBJECTIVES

To radiographically demonstrate the upper sacral nerve root tunnel (USNRT) in both cadaveric specimens and a clinical cohort and to quantify its clinical relevance.

SETTING

Level 1 trauma center and anatomy laboratory.

PATIENTS AND PARTICIPANTS

Eleven cadaveric pelves and 23 consecutive patients who underwent fluoroscopically assisted iliosacral screw insertions.

INTERVENTIONS

Cadaveric pelves were fluoroscopically imaged using standard pelvic inlet, outlet, and true lateral sacral views. The course of the USNRT pathway was identified. Then, these tunnels were filled completely with a semisolid radio-opaque agent. The specimens were reimaged after the contrast injection. Clinically, 23 consecutive patients with unstable posterior pelvic ring disruptions were treated using fluoroscopically assisted percutaneous iliosacral screws based on these predictable radiographic landmarks. A total of 44 iliosacral screws were inserted.

MAIN OUTCOME MEASUREMENTS

For the cadaveric portion, the images with contrast were used to identify the USNRTs. For the clinical study, tunnel visualization was determined on all views intraoperatively. Screw placement was documented by postoperative pelvic plain radiographs and computed tomography scan.

RESULTS

In the cadaveric specimens, the contrast agent consistently demonstrated the USNRTs on all 3 pelvic radiographic views. In the clinical series, the USNRTs were well visualized on the pelvic outlet image in all 23 patients (100%). Using the inlet image, the USNRTs were visualized in only 5 of 23 patients (21%). On the true lateral sacral views, the USNRTs were seen in 21 of 23 patients (91%). Using these USNRT radiographic landmarks, no iliosacral screw was extraosseous.

CONCLUSIONS

The USNRTs have a consistent radiographic appearance that is best seen on the pelvic outlet and true lateral sacral views, but their course is best understood when seen on all 3 views. Awareness and understanding of the USNRT, its course, and its radiographic landmarks allow the surgeon to avoid tunnel intrusion by an iliosacral screw.