Minimally invasive lumbopelvic instrumentation for traumatic sacrolisthesis in an elderly patient

A Case Series That Supports the Application of the S2AI Technique for Fractures and Failures After Lumbosacral Fusion

BACKGROUND

Sacral fractures and failures are uncommon after lumbosacral fusion but have received increasing attention in the surgical literature. They can be difficult to diagnose, making timely treatment difficult. No consensus has been reached on the characteristics of these complications or on optimal treatment.

QUESTIONS/PURPOSES

The goal of this retrospective case series is to contribute additional cases of these uncommon complications of lumbosacral fusion to the surgical literature to help clinicians to anticipate, diagnose, characterize, manage, and treat sacral fractures and failures after lumbosacral fusion.

METHODS

The medical records of five patients who experienced a sacral fracture or failure after lumbosacral fusion between January 2012 and November 2017 were identified and reviewed retrospectively. Records were reviewed for age, sex, clinical presentation, previous management, outpatient clinical records, imaging, and post-operative course.

RESULTS

Four patients in the series experienced a sacral fracture and one experienced hardware failure. All patients presented with elevated pain and underwent revision surgery. Radiographic detection of the fracture or failure occurred at a mean of 11.2 weeks (range, 3 to 24 weeks) after initial surgery, and the mean age of patients was 68.2 years (range, 63 to 80 years). Of the five patients, four were female; two had been diagnosed with osteoporosis and two with osteopenia. In our case series, the S2-alar-iliac (S2AI) technique was used with success in all five cases.

CONCLUSION

Fractures and failures after lumbosacral fusion can be difficult to diagnose because of delayed presentation, nonspecific presenting symptoms, and a lack of identifiable mechanism. A high index of suspicion is required to detect these uncommon complications, and patients have responded well to both conservative and surgical treatments.

Morphometric measurement and applicable feature analysis of sacral alar-iliac screw fixation using forward engineering

PURPOSE

To evaluate S1AI-S4AI screw channels with three-dimensional digital technology simulation analysis and to study the feasibility and applicable features of sacral alar-iliac screw fixation in adults.

MATERIALS AND METHODS

Forty (20 men and 20 women) normal adult's pelvic CT scan data sets were selected to reconstruct the three-dimensional pelvic model. The ideal S1AI-S4AI screw channels were simulated, followed by precise measurement of their parameters.

RESULTS

The results showed that there were no significant differences in the transverse angles, sagittal angles, radiuses of the maximal inscribed circles, or lengths of the screw channels in S1AI-S2AI screws between genders (P > 0.05). In contrast, the radiuses of the maximal inscribed circles on the left and right, respectively, were 5.93 ± 1.02 mm and 5.92 ± 1.04 mm in males and 4.64 ± 0.98 mm and 4.59 ± 0.95 mm in females, and there was a significant difference in S3AI screws between genders (P < 0.05). With a radius of 2.50 mm considered to be standard, there were 25 cases (62.5%) with an S4AI screw channel radius ≤ 2.50 mm in 40 adults, and 15 cases (37.5%; 9 males and 6 females) with a radius > 2.50 mm. Furthermore, the transverse angles, the sagittal angles, the lengths of the screw channels, and the radiuses of the maximal inscribed circles were significantly different between genders in 15 cases (P < 0.05).

CONCLUSION

Only one maximum ideal screw can be placed on one side at a time. With a radius of 2.50 mm considered to be standard, it is feasible to place S1AI-S3AI screws with a radius > 2.50 mm in the entire adult population and S4AI screws with a radius > 2.50 mm in some of the adult population. Furthermore, preoperative three-dimensional reconstruction and three-matic research software can effectively simulate the sacral alar-iliac screw channels, and they can provide accurate data for clinical applications.

Minimally Invasive Fixation for Spinopelvic Dissociation: Percutaneous Triangular Osteosynthesis with S2 Alar-Iliac and Iliosacral Screws: A Case Report

CASE

Traumatic U- and H-type sacral fractures are often unstable, causing spinopelvic dissociation. We describe a minimally invasive approach that allows percutaneous spinopelvic fixation of unstable H-type sacral fractures using a triangular osteosynthesis construct with S2 alar-iliac screws. We present the case of a patient with traumatic lumbopelvic dissociation who underwent percutaneous S2 alar-iliac and iliosacral screw fixation.

CONCLUSIONS

Combined percutaneous S2 alar-iliac and iliosacral screw fixation is a safe option for spinopelvic fixation and avoids the soft-tissue compromise of open approaches. The triangular osteosynthesis construct provides adequate pelvic anchor points to allow immediate weight-bearing.

Neurological Outcome After Traumatic Transverse Sacral Fractures: A Systematic Review of 521 Patients Reported in the Literature

BACKGROUND

The purpose of this study was to determine the neurological outcome after transverse sacral fractures in patients with neurological impairment.

METHODS

A systematic review of the English, French, German, and Dutch literature was conducted. All study designs, including retrospective cohort studies and case reports, describing transverse sacral fractures were included. Two authors independently extracted the predefined data and scored the neurological impairment according to the Gibbons classification after the trauma and at the time of follow-up. The neurological outcomes were pooled according to the Gibbons classification.

RESULTS

No randomized controlled trials or prospective case series were found. A total of 139 articles were included, consisting of 81 case reports and 58 retrospective case series involving 521 patients. Regardless of the type of management, neurological recovery of at least 1 Gibbons category was reported in 62% of these patients. A comparison of the neurological outcome of nonoperatively treated patients and surgically treated patients showed similar neurological recovery rates. For the surgically treated patients, fixation of the fracture resulted in a better neurological improvement compared with an isolated decompression.

CONCLUSIONS

This review could not provide evidence of improved neurological recovery after surgical treatment compared with nonoperative treatment. When surgical treatment was considered, there was a low level of evidence that fixation of the fracture results in better neurological improvement compared with isolated decompression.

LEVEL OF EVIDENCE

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

S2 Alar Iliac Fixation in Long Segment Constructs, a Two- to Five-Year Follow-up

STUDY DESIGN

Retrospective review of patients having undergone S2 alar-iliac (S2AI) fixation for long fusions with a minimum two-year follow-up.

OBJECTIVES

To report on fusion rates, complications, technique-specific complications of patients having undergone S2AI fixation.

SUMMARY OF BACKGROUND DATA

Sacropelvic fixation continues to be a challenge when performing long fusions to the pelvis. S2AI screws have been found to provide solid biomechanical fixation and have been found to have good clinical results in short-term follow-up for pediatric and adult patients.

METHODS

Cases were retrospectively reviewed in patients who had placement of S2AI screws for long fusions with at least a two-year follow-up. Demographic data, complications, and reoperations were reviewed. Complications were broken into minor and major categories similar to previous series on pelvic fixation.

RESULTS

There were 86 cases identified. Minor and major complications occurred in 29% and 24% of patients, respectively, with the majority of minor complications being intraoperative dural tears. Revision surgery for all causes was performed in 23% of the cohort. Fusion rate at L5-S1 for patients without preoperative pseudarthrosis was 95.3%. Preoperative L5-S1 pseudoarthrosis was identified in 20 patients, 17 (95%) of these went onto fusion after one surgery. There was evidence of S2AI screw lucency in 10.4% of cases. However, the majority of these were asymptomatic.

CONCLUSIONS

Sacropelvic fixation using the S2AI technique provides safe, durable fixation with low rates of technique-specific complications and limited need for hardware removal. Complication rates in this series were similar to other series on long fusions to the pelvis. Additionally, fusion rates were high at L5-S1 for both patients with and without preoperative L5-S1 pseudarthrosis. It appears that the S2AI technique is a powerful option for patients with previous L5-S1 pseudarthrosis.

LEVEL OF EVIDENCE

Level III.

Freehand S2 Alar-Iliac Screw Placement Using K-Wire and Cannulated Screw : Technical Case Series

Objective

Among the various sacropelvic fixation methods, S2 alar-iliac (S2AI) screw fixation has several advantages compared to conventional iliac wing screw. However, the placement of S2AI screw still remains a challenge. The purpose of this study was to describe a novel technique of free hand S2AI screw insertion using a K-wire and cannulated screw, and to evaluate the accuracy of the technique.

Methods

S2AI screw was inserted by free hand technique in sixteen consecutive patients without any fluoroscopic guidance. The gearshift was advanced to make a pilot hole passing through the sacroiliac joint and directing the anterior inferior iliac spine. A K-wire was placed through the pilot hole. After introducing a cannulated tapper along with the K-wire, a cannulated S2AI screw was installed over the K-wire.

Results

Thirty-three S2AI screws were placed in sixteen consecutive patients. Thirty-two screws were cannulated screws, and one screw was a conventional non-cannulated screw. Thirty out of 32 (93.8%) cannulated screws were accurately positioned, whereas two cannulated screws and one non-cannulated screw violated lateral cortex of the ilium.

Conclusion

The technique using K-wire and cannulated screw can provide accurate placement of free hand S2AI screw.

Biomechanical evaluation of S2 alar-iliac screws: effect of length and quad-cortical purchase as compared with iliac fixation

STUDY DESIGN

A biomechanical study conducted on cadaveric specimens.

OBJECTIVE

(1) To compare the biomechanical strength of the S2 alar-iliac (S2AI) screw to traditional iliac fixation and (2) to examine the effect of length and trajectory on the S2AI screw.

SUMMARY OF BACKGROUND DATA

A recent technique to attain spinal fixation distal to S1 pedicle screws is the S2AI screw using either an open or a percutaneous approach with an altered S2 alar screw trajectory to obtain purchase in the ilium. A novel modification of the S2AI screw is placement with bicortical purchase in the ilium (quad-cortical screw). This may allow for a shorter-length screw with equivalent biomechanics.

METHODS

Seven human cadaveric spines (L2-Pelvis) were fixed at L2 proximally and the pubis distally. Pedicle screws were placed from L3-S1 with S2AI screw lengths of 65-mm, 80-mm, or 90-mm iliac screws. S2AI screws were tested with and without quad-cortical purchase. Each specimen was tested on the 6 degrees of freedom spine simulator. A load control protocol with an unconstrained pure moment of 10 Nm was used in flexion-extension, lateral bending, and axial rotation for a total of 3 load/unload cycles. The range of motion was normalized to the intact cadaveric spine (100%).

RESULTS

All the instrumented constructs significantly reduced range of motion compared with the intact spine. The L3-S1 construct was statistically significantly less stable than all instrumented constructs in flexion-extension. There was statistically no significant difference between the S2AI screws of all lengths and the iliac screw constructs with offset connectors.

CONCLUSION

S2AI screws are biomechanically as stable as the test constructs using iliac screws in all loading modes. Sixty-five-millimeter S2AI screws were biomechanically equivalent to 90-mm iliac screws and 80-mm S2AI screws. Quad-cortical purchase did not statistically significantly improve the biomechanical strength of S2AI screws.

LEVEL OF EVIDENCE

N/A.