Minimally invasive bilateral fixed angle locking fixation of the dorsal pelvic ring: clinical proof of concept and preliminary treatment results

PURPOSE

Dorsal pelvic ring fractures may result from high energy trauma in younger patients or from osteoporosis as fragility fractures in elderly patients. To date, no strong consensus exists on the best surgical technique to treat posterior pelvic ring injuries. The aim of this study was to evaluate the surgical performance of a new implant for angle-stable fixation of the posterior pelvic ring and patient outcome.

METHODS

In a prospective pilot study, 27 patients (age: 39-87 years) with posterior pelvic ring fractures classified according to the AO classification (n = 5) or to the fragility fractures of the pelvis (FFP) classification (n = 22) were treated using the new implant. During a follow-up period of 1 year, surgical parameters of the implantation technique, complication rate, morbidity, mortality, preservation of patient mobility, and social independence were evaluated.

RESULTS

No implant misplacement or failure was observed. Two patients developed symptomatic spinal canal stenosis at L4/L5 following mobilization. MRI diagnosis proved the implant was not responsible for the symptoms. In one case, an additional plate stabilization of a pubic ramus fracture was necessary 6 months later. There was no inpatient mortality. One patient died due to her underlying oncological disease within the first 3 months. The main outcome parameters were pain, mobility, preservation of independent living and employment.

CONCLUSION

Operative instrumentation of dorsal pelvic ring fractures should be stable enough to allow for immediate weight bearing. The new locking nail implant offers percutaneous reduction and fixation options and may decrease the generally observed rate of complications.

TRAIL REGISTRATION

German Clinical Trials Register ID: DRKS00023797, date of registration: 07.12.2020.

Fluoroscopy-guided vs. navigated iliosacral screw placement with intraoperative 3D scan or postoperative CT control: Impact of the clinical workflow on patients' radiation exposure: Radiation exposure of different workflows for iliosacral screw placement

INTRODUCTION

To guide iliosacral screws (ISS) and verify safe placement different techniques, e.g. Fluoroscopy-guided (FSG) or 3D navigation are known. However, higher radiation exposure for the conventional technique is a concern. It was the aim of this experimental study to evaluate radiation exposure for three clinical workflows.

METHODS

An anthropomorphic, cross sectional dosimetry phantom was equipped with metal oxide semiconductor field effect transistors to measure organ specific radiation exposure. The effective dose was calculated. Radiation exposure was measured for FSG placement of 2 transverse ISS based on clinical experience regarding fluoroscopy time (240s). Additional measurements were conducted to calculate the effective dose for an intraoperative 3D scan as used for navigated ISS (high-quality 3D), for intraoperative verification of proper guide wire placement (standard-quality 3D) and for postoperative CT, using three different protocols. The following workflows were compared: FSG including postoperative CT (FSG-CT, including 3 different protocols) vs. FSG with intraoperative 3D scan in standard quality (FSG-3D) vs. navigation including two intraoperative 3D scan for navigated ISS (NAV-3D).

RESULTS

The effective dose for FSG-CT ranged from 4.41 mSv to 5.27 mSv. FSG-3D resulted in a total of 4.93 mSv. For NAV-3D, the effective dose was the lowest (3.00 mSv). The effective dose of a high-quality 3D scan required for navigation was 1.94 mSv, compared to 1.06 mSv for a standard-quality 3D scan as used for control.

CONCLUSIONS

Intraoperative 3D scanning may be recommended, either combined with prior FSG ISS placement or following 3D navigation without increasing radiation exposure compared with alternative workflows with postoperative CT control.

Trans-sacral screw fixation of posterior pelvic ring injuries: review and expert opinion

Posterior pelvic ring injuries (i.e., sacro-iliac joint dislocations, fracture-dislocations, sacral fractures, pelvic non-unions/malunions) are challenging injury patterns which require a significant level of surgical training and technical expertise. The modality of surgical management depends on the specific injury patterns, including the specific bony fracture pattern, ilio-sacral joint involvement, and the soft tissue injury pattern. The workhorse for posterior pelvic ring stabilization has been cannulated iliosacral screws, however, trans-sacral screws may impart increased fixation strength. Depending on injury pattern and sacral anatomy, trans-sacral screws can potentially be more beneficial than iliosacral screws. In this article, the authors will briefly review pelvic mechanics and discuss their rationale for ilio-sacral and/or trans-sacral screw fixation.

The impact of the fluoroscopic view on radiation exposure in pelvic surgery: organ involvement, effective dose and the misleading concept of only measuring fluoroscopy time or the dose area product

INTRODUCTION

Minimally invasive fluoroscopy-guided screw fixation is an established technique to stabilize fractures of the posterior pelvic ring in orthopaedic surgery. However, safe placement of the screws may be associated with prolonged intervention time and extensive fluoroscopy is a concern. In the current literature, the dose area product (DAP) and fluoroscopy time are often used to describe radiation exposure of the patient. It was the aim of the study to compare DAP to organ doses and the effective dose for four standard views commonly used in pelvic surgery.

METHODS

An anthropomorphic cross-sectional dosimetry phantom, representing the body of a male human (173 cm/73 kg), was equipped with metal-oxide-semiconductor field-effect transistors (MOSFET) in different organ locations to measure radiation exposure. Anteroposterior (APV), lateral (LV), outlet (OLV) and inlet (ILV) of the phantom were obtained with a mobile C-arm, and effective dose and organ doses were calculated. DAP was measured in the built-in ionisation chamber beyond the collimator of the C-arm. The measurements were repeated with a fat layer to simulate an obese patient.

RESULTS

Overall, the highest organ dose was measured in the stomach for ILV (0.918 mSv/min). Effective dose for ILV showed the highest values by far (1.85 mSv/min) and the lowest for LV (0.46 mSv/min). The DAP pattern was completely different to the effective dose with similar values for LV and ILV (12.2 and 12.3 µGy·m²/s). Adding a fat layer had no major effect on the measurements.

CONCLUSION

The exposure to radiation varies considerably between different orthopaedic standard views of the pelvis. About the fourfold amount of the effective dose was measured for ILV compared to LV. DAP and irradiation time do not respect either the body region in the field of radiation or the radiosensitivity of the affected organs. Thus, they do not allow a reliable interpretation of the radiation burden the patient is exposed to.

A systematic review of the transiliac internal fixator (TIFI) for posterior pelvic injuries

OBJECTIVE

To summarize the literature on transiliac internal fixator (TIFI) indications and outcomes for treating posterior pelvic ring injuries.

METHODS

We searched databases for original publications in journals. Biomechanical and clinical studies using a TIFI for posterior pelvic ring injuries were considered for inclusion. The dates of publications that were included ranged from January 2000 until December 2020.

RESULTS

A total of 13 articles were reviewed, including eight clinical studies and five biomechanical tests. We found only case series and no multicenter or randomized study. The clinical studies contained data for a total of 186 cases, including indications, treatments, complications, and outcomes, with a minimum follow-up time of 12 months. All studies reported superior results according to operation time, blood loss, complication, dislocation, and union. One biomechanical test evaluated inferior results.

CONCLUSIONS

The TIFI is a user-friendly and safe device to treat posterior pelvic injuries. It can also be used for acute, high-impact injuries, and fragility fractures. Nevertheless, there is no evidence concerning which types of pelvic fractures are most beneficial. Therefore, further biomechanical and clinical studies are necessary to resolve this question.

Corridor-diameter-dependent angular tolerance for safe transiliosacral screw placement: an anatomic study of 433 pelves

BACKGROUND

The purpose of this study was to determine the angular tolerance of the S1 and S2 segments to accommodate a transiliosacral screw across both sacroiliac joints.

HYPOTHESIS

We hypothesized that the angular tolerance for transiliosacral screw placement would be more constrained than the angular tolerance for iliosacral fixation in pelves where a safe osseous corridor was measured.

MATERIALS AND METHODS

The cortical boundaries of the S1 and S2 sacral segments in 433 pelvic CTs were digitally mapped. A straight-line path was placed within each osseous corridor and extended across both SI joints past the outer iliac cortices. The diameter of the path was increased until it breached the cortex, geometrically determining maximum diameter (Dmax). Angular tolerance for screw placement was calculated with trigonometric analysis of the Dmax value of the corridor, and the average distance from the termination of the osseous corridor to the site of percutaneous insertion. Gender, age, and BMI were evaluated as independent predictors using binomial logistic regression.

RESULTS

The transiliosacral angular tolerance for the S1 and S2 osseous corridors was 1.53 ± 0.57 degrees and 1.02 ± 0.33 degrees, respectively. 68.9% of S1 corridors and 81.1% of S2 corridors had a safe zone (corridor diameter ≥ 10 mm) for transiliosacral placement, 48.3% of the pelves had a safe zone for both corridors, while 5.1% had no safe zones. Females had a less frequent Dmax ≥ 10 mm at S1, 52% vs 67% (p = 0.001), and at S2, 64% vs 86% (p < 0.001).

DISCUSSION

In conclusion, the angular tolerance of 1.53 and 1.03 degrees for the S1 and S2 segments, respectively, creating a narrow interval for safe passage of the trans-iliac and trans-sacral, with approximately 31.1% of patients not having a viable corridor for screw passage. A correlation exist between S1 and S2 corridors with Dmax ≥ 10 mm and the resulting increase in angular tolerance for safe passage of a transilioscral screw.

LEVEL OF EVIDENCE IV

Level Retrospective Cohort.

[Minimally invasive stabilization of sacral fractures]

BACKGROUND

Sacral fractures can be of traumatic origin and can also occur as insufficiency fractures. While the therapeutic target of mechanically stable insufficiency fractures is mainly pain relief, mechanically unstable insufficiency fractures and traumatic sacral fractures following high-energy trauma require biomechanical stabilization. Various surgical strategies are available for this, whereby minimally invasive techniques are now preferred whenever possible.

OBJECTIVE

This article presents the clinical challenges and options for minimally invasive treatment of sacral fractures.

MATERIAL AND METHODS

Selected important study data are discussed and our own treatment approach is presented.

RESULTS

The most important minimally invasive techniques for operative treatment of sacral fractures are presented: sacroiliac screw osteosynthesis, lumbopelvic stabilization and sacroplasty. The selection of the surgical technique should be made on an individual basis. While sacroiliac screw osteosynthesis is the international gold standard, diverse authors have also published minimally invasive techniques for lumbopelvic stabilization. The latter enables a higher mechanical stability. In contrast, sacroplasty should only be used as an alternative treatment in insufficiency fractures. Comparative studies of the described techniques are still missing.

CONCLUSION

All surgical options have their indications. Nevertheless, the biomechanical stability which can be achieved differs widely. Therefore, an exact analysis should be carried out of what is necessary with respect to reduction and retention and what should be achieved when treating sacral fractures.

Outcome of pubic rami fractures with or without concomitant involvement of the posterior ring in elderly patients

INTRODUCTION

Pubic rami fractures are common fractures in a growing osteoporotic geriatric population. Concomitant posterior ring fractures (cPRF) are often found when properly looked for. The pain and consequent immobilization leaves this vulnerable patient group at risk for complications. Conservative therapy is usually sufficient, but with cPRF's surgery can be indicated. Although previous studies have pointed out that mortality rates are high, longer term morbidity outcomes are lacking. This study aims to further establish the longer term consequences of these fractures. Risk factors will be identified for complications, also addressing the possible differences between patients with or without a cPRF.

METHOD

Retrospective analysis of patients aged over 65 years sustaining a pubic rami fracture in the North-West Hospital Group Alkmaar combined with a survey to establish risk factors for morbidity and mortality after 6 months' post trauma. Multiple logistic regression analysis was used to identify risk factors.

RESULTS

117 patients matched inclusion criteria with a median age of 83 and of which 86% was female. 23 cPRF's were identified. Significant deterioration in ambulation and independency was found. 34% was institutionalized at discharge. 49% lost their independent mobility status and 40% of the patients did not experience a full recovery. One-year mortality rate was 23%. Patients with a cPRF had a significant higher complication rate (44 vs 18% p = 0.02), but mortality and other morbidity outcomes did not statistically differ. The strongest predictor for 1-year mortality was complications during admission and a dependent ambulatory status (OR 5.2 and 4.1 respectively).

CONCLUSION

Pubic fractures with or without involvement of the posterior pelvic ring in patients aged over 65 have a significant impact on mobility and independency. Mortality rates are similar to hip fracture patients. Careful evaluation of every patient's mobility status is necessary to identify patients at risk for complications and determine their future health care needs. Future studies are needed to achieve consensus on diagnostic and treatment protocols and identify ways to decrease the significant impact of this injury.

Assessment of the Breakaway Torque at the Posterior Pelvic Ring in Human Cadavers

Purpose: To enhance the diminished screw purchase in cancellous, osteoporotic bone following the fixation of posterior pelvic ring injuries by iliosacral screws an increased bone-implant contact area using modificated screws, techniques or bone cement may become necessary. The aim of the study was to identify sites within the pathway of iliosacral screws requiring modifications of the local bone or the design of instrumentations placed at this site. Materials and Methods: The breakaway torque was measured mechanically at the iliosacral joint (“ISJ”), the sacral lateral mass (“SLM”) and the center of the S1 (“CS1”), at a superior and an inferior site under fluoroscopic control on five human cadaveric specimens (3 female; mean age 87 years, range: 76–99) using the DensiProbe™Spine device. Results: The measured median (range) breakaway torque was 0.63 Nm (0.31–2.52) at the “iliosacral joint”, 0.14 Nm (0.05–1.22) at the “sacral lateral mass”, 0.57 Nm (0.05–1.42) at the “S1 center.” The “sacral lateral mass” breakaway torque was lower than compared to that at the “iliosacral joint” (p < .001) or “S1 center” (p < .001). The median (range) breakaway torque measured at all superior measurement points was 0.52 Nm (0.10–2.52), and 0.48 Nm (0.05–1.18) at all inferior sites. The observed difference was statistically significant (p < .05). Conclusions: The lateral mass of the sacrum provides the lowest bone quality for implant anchorage. Iliosacral screws should be placed as superior as safely possible, should bridge the iliosacral joint and may allow for cement application at the lateral mass of the sacrum through perforations.