Does Cement Augmentation of the Sacroiliac Screw Lead to Superior Biomechanical Results for Fixation of the Posterior Pelvic Ring? A Biomechanical Study

Evaluating the stability of external fixators following pelvic injury: A systematic review of biomechanical testing methods

INTRODUCTION

This systematic review aims to identify previously used techniques in biomechanics to assess pelvic instability following pelvic injury, focusing on external fixation constructs.

METHODS

A systematic literature search was conducted to include biomechanical studies and to exclude clinical trials.

RESULTS

Of an initial 4666 studies found, 38 met the inclusion criteria. 84% of the included studies were retrieved from PubMed, Scopus, and Web of Science. The studies analysed 106 postmortem specimens, 154 synthetic bones, and 103 computational models. Most specimens were male (97% synthetic, 70% postmortem specimens). Both the type of injury and the classification system employed varied across studies. About 82% of the injuries assessed were of type C. Two different fixators were tested for FFPII and type A injury, five for type B injury, and fifteen for type C injury. Large variability was observed for external fixation constructs concerning device type and configuration, pin size, and geometry. Biomechanical studies deployed various methods to assess injury displacement, deformation, stiffness, and motion. Thereby, loading protocols differed and inconsistent definitions of failure were determined. Measurement techniques applied in biomechanical test setups included strain gauges, force transducers, and motion tracking techniques.

DISCUSSION AND CONCLUSION

An ideal fixation method should be safe, stable, non-obstructive, and have low complication rates. Although biomechanical testing should ensure that the load applied during testing is representative of a physiological load, a high degree of variability was found in the current literature in both the loading and measurement equipment. The lack of a standardised test design for fixation constructs in pelvic injuries across the studies challenges comparisons between them. When interpreting the results of biomechanical studies, it seems crucial to consider the limitations in cross-study comparability, with implications on their applicability to the clinical setting.

Long-Term Follow-Up after Iliosacral Screw Fixation of Unstable Pelvic Ring Fractures

(1) Background: High-energy injuries of the pelvic ring are rare. The wide application of iliosacral screw fixation of the posterior pelvic ring is relatively new. The aim of the present study was to evaluate the long-term quality of life. (2) Methods: All patients treated with an iliosacral screw for a posterior pelvic ring stabilization after high-energy trauma at a level 1 trauma center between 2005 and 2015 were included. Pelvic ring injuries were classified according to the Tile classification adapted by AO/ASIF. The clinical evaluation included the patient-oriented questionnaires surveys of the Majeed Score, Iowa Pelvic Score (IPS), Work Ability Index (WAI), SF-36, EQ5D-5L. (3) Results: A total of 84 patients were included with a median follow-up of 130.1 months (IQR 95.0-162.0 months). The median ISS was 22.5 (IQR 16.0-29.0), mean Majeed Score 83.32 (SD ± 19.26), IPS 77.88 (SD ± 13.96), WAI 32.71 (SD ± 11.31), SF-36 PF 71.25 (SD ± 29.61) and EQ5D-5L 0.83 (SD ± 0.21). There was a notably difference between uni- and bilateral pelvic fractures (p = 0.033) as well as a correlation with the ISS (p = 0.043) with inferior functional outcome measured by IPS. (4) Conclusions: Long-term follow-up of iliosacral screw fixation of unstable pelvic ring fractures showed a good quality of life and functional outcome with equal EQ5D-5L results and inferior SF-36 physical functioning compared to the German population.

Cerclage augmentation of S1-S2 transsacral screw fixation in osteoporotic posterior pelvis ring injuries: A biomechanical feasibility study

Injuries of the posterior pelvic ring are predominantly associated with osteoporosis. Percutaneously placed screws transfixing the sacroiliac joint have become the gold standard for their treatment. However, screw cut-out, backing-out, and loosening are common complications. One promising option could be cerclage reinforcement of cannulated screw fixations. Therefore, the aim of this study was to evaluate the biomechanical feasibility of posterior pelvic ring injuries fixed with S1 and S2 transsacral screws augmented with cerclage. Twenty-four composite osteoporotic pelvises with posterior sacroiliac joint dislocation were stratified into four groups for S1-S2 transsacral fixation using either (1) fully threaded screws, (2) fully threaded screws with cable cerclage, (3) fully threaded screws with wire cerclage, or (4) partially threaded screws with wire cerclage. All specimens were biomechanically tested under progressively increasing cyclic loading until failure. Intersegmental movements were monitored by motion tracking. The transsacral partially threaded screw fixation with wire cerclage augmentation resulted in significantly less combined angular intersegmental movement in the transverse and coronal plane versus its fully threaded counterpart (p = 0.032), as well as in significantly less flexion versus all other fixations (p ≤ 0.029). Additional cerclage augmentation could be performed intraoperatively to improve the stability of posterior pelvic ring injuries treated with S1-S2 transsacral screw fixation. Further investigations should follow to consolidate the current results on real bones and possibly consider execution of a clinical study.

Analysis of the Spinopelvic Parameters in Patients with Fragility Fractures of the Pelvis

BACKGROUND

We investigated the spinopelvic parameters of lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT) and sacral slope (SS) in patients with fragility fractures of the pelvis (FFPs). We hypothesized that these parameters differ from asymptomatic patients.

METHODS

All patients treated for FFPs in a center of maximal care of the German Spine Society (DWG) between 2017 and 2021 were included. The inclusion criteria were age ≥ 60 years and the availability of a standing lateral radiograph of the spine and pelvis in which the spine from T12 to S1 and both femoral heads were visible. The baseline characteristics and study parameters were calculated and compared with databases of asymptomatic patients. The two-sample t-Test was performed with p < 0.05.

RESULTS

The study population (n = 57) consisted of 49 female patients. The mean age was 81.0 years. The mean LL was 47.9°, the mean PT was 29.4°, the mean SS was 34.2° and the mean PI was 64.4°. The mean value of LLI was 0.7. LL, LLI and SS were significantly reduced, and PI and PT were significantly increased compared to asymptomatic patients.

CONCLUSIONS

The spinopelvic parameters in patients with FFPs differ significantly from asymptomatic patients. In patients with FFPs, LL, LLI and SS are significantly reduced, and PI and PT are significantly increased. The sagittal spinopelvic balance is abnormal in patients with FFPs.

Comparative outcome of different treatment options for fragility fractures of the sacrum

BACKGROUND

Fragility fractures of the sacrum (FFS) have been detected more and more frequently in recent times, and the incidence will continue to increase due to increasing life expectancy. The aim of this study was to compare the clinical outcome of conservative, interventional and surgical treatment of FFS.

METHODS

Retrospectively, 292 patients (276 women, 16 men) with confirmed FFS were followed up over a period of 2 years. The age of the women was Ø 81.2 (58 - 99) and that of the men Ø 78.1 (76 - 85) years. The pain was quantified using a VAS. Fractures were classified in accordance with the Rommens and Hofmann and with the Denis classification using conventional X-rays, CT and MRI. A QCT of the lumbar spine was performed to quantify bone mineral density. Concomitant diseases of every patient were recorded. An interdisciplinary case conference determined the individual treatment concept considering the age, type of fracture, pain level and comorbidities with classification into conservative, interventional (any type of sacroplasty) or surgical treatment. Over the course pain and independence were measured, complications and patient satisfaction were documented. A vitamin D determination was done, and existing comorbidities were included.

RESULTS

Patients with a pain level of ≤5 benefited from the conservative therapy measures, with pain levels > 5 significantly delaying the development of mobility. After sacroplasty, the pain reduced significantly, which caused a rapid improvement in mobility without any significant difference being found between vertebro- (VSP), balloon (BSP), radiofrequency (RFS) and cement sacroplasty (CSP). In terms of pain reduction and mobilization, the surgical treated patients benefited from osteosynthesis, although more complex fracture types with lumbopelvic stabilization took longer. Overall, there were no deaths during the hospital stay. Mortality after 12 months was 21.7% for the conservative, 8.4% for the interventional and 13.6% for the surgical therapy group; the differences are significant. For patients in the conservative therapy group who were difficult to mobilize due to pain, the mortality increased to 24.3%. Over 24 months, patients achieved the best independence after sacroplasty. At 12 and 24 months, subjective satisfaction with the therapies was best after sacroplasty, followed by osteosynthesis and conservative measures. All patients had a pronounced vitamin D deficiency and manifest osteoporosis. Cardiovascular pathologies were the main concomitant diseases.

CONCLUSIONS

Patients with FFS with a low level of pain benefit from conservative therapy measures, whereby complications and mortality increase significantly in the case of persistent immobilizing pain. Patients with an unacceptable level of pain resulting from non-dislocated fractures benefit significantly from sacroplasty. Patients with unstable and displaced fractures (Rommens and Hofmann type III and IV) should be operated on promptly. Different techniques are available for sacroplasty and osteosynthesis, which lead to an improvement of independence and a reduction in mortality.

[Cement augmentation in pelvic ring fractures]

Cement augmentation of sacroiliac (SI) screws in the posterior pelvic ring has been shown to provide greater biomechanical stability in cadaveric studies. Pelvic ring fractures are relatively rare compared to the total number of fractures. Nevertheless, the 1‑year mortality rate of up to 27% is very high, especially for geriatric pelvic ring fractures and is also largely associated with reduced mobility due to the fracture. The primary goal of treatment is therefore the restoration of patient mobility. This requires the achievement of sufficient stability of the pelvic ring. As osteoporosis is often a causative factor for the pelvic ring fracture, a more stable anchoring of the implants in the osteoporotic bone can be achieved by cement augmentation. This article presents the possibilities of cement augmentation of the pelvic ring and describes the technique of cement-augmented SI screws.

[Cement augmentation and bone graft substitutes-Materials and biomechanics]

BACKGROUND

Materials with different characteristics are used for cement augmentation and as bone graft substitutes.

OBJECTIVE

Cement augmentation and bone graft substitutes are the subject of current research. The evaluation of new knowledge allows its specific application.

MATERIAL AND METHODS

Selective literature search and outline of experimental research results on cement augmentation and bone graft substitutes.

RESULTS

Augmentation and bone graft substitutes are essential components of current trauma surgical procedures. Despite intensive research all materials have specific disadvantages. Cement augmentation of implants enhances not only the anchorage but also influences the failure mode.

CONCLUSION

Cement augmentation has large potential especially in osteoporotic bone. In load-bearing regions acrylic-based cements remain the standard of choice. Ceramic cements are preferred in non-load-bearing areas. Their combination with resorbable metals offers still largely unexplored potential. Virtual biomechanics can help improve the targeted application of cement augmentation.