Cement augmentation as revision strategy for loosened thick-diameter non-fenestrated iliac screws - A biomechanical analysis

[Translated article] Spinopelvic dissociation: Current concepts

INTRODUCTION

Spinopelvic dissociation is an uncommon injury, but, at the same time, very serious, since it can associate important complications with high morbidity and mortality. Its low frequency means that the experience of the specialists who have to deal with it is often very limited.

OBJECTIVE

To analyze the treatment indications based in classifications and surgery techniques.

METHOD

A search for scientific articles from high-impact journals was performed through international databases, such as Pubmed, Cochrane Library, Scopus, Science Direct and OVID.

CONCLUSIONS

The management of the injury we are analyzing represents a challenge. The diagnosis is carried out through a meticulous anamnesis and physical examination, supported by imaging tests, where tomography acquires special relevance. The treatment is fundamentally surgical, reserved the conservative option for a few cases. Triangular fixation is nowadays considered the treatment of choice.

Spinopelvic dissociation: Current concepts

INTRODUCTION

Spinopelvic dissociation is an uncommon injury, but, at the same time, very serious, since it can associate important complications with high morbidity and mortality. Its low frequency means that the experience of the specialists who have to deal with it is often very limited.

OBJECTIVE

To analyze the treatment indications based in classifications and surgery techniques.

METHOD

A search for scientific articles from high-impact journals was performed through international databases, such as Pubmed, Cochrane Library, Scopus, Science Direct and OVID.

CONCLUSIONS

The management of the injury we are analyzing represents a challenge. The diagnosis is carried out through a meticulous anamnesis and physical examination, supported by imaging tests, where tomography acquires special relevance. The treatment is fundamentally surgical, reserved the conservative option for a few cases. Triangular fixation is nowadays considered the treatment of choice.

When spinal instrumentation revision is not an option: Salvage vertebral augmentation with polymethylmethacrylate for mechanical complications: A systematic review

Intoduction

Mechanical complications from spinal fusion including implant loosening or junctional failure result in poor outcomes, particularly in osteoporotic patients. While the use of percutaneous vertebral augmentation with polymethylmethacrylate (PMMA) has been studied for augmentation of junctional levels to offset against kyphosis and failure, its deployment around existing loose screws or in failing surrounding bone as a salvage percutaneous procedure has been described in small case series and merits review.

Research Question

How effective and safe is the use of PMMA as a salvage procedure for mechanical complications in failed spinal fusion?.

Materials and Methods

Systematic search of online databases for clinical studies using this technique.

Results

11 studies were identified, only consisting of two case reports and nine case series. Consistent improvements were observed in pre- to post-operative VAS and with sustained improvements at final follow-up. The extra- or para-pedicular approach was the most frequent access trajectory. Most studies cited difficulties with visibility on fluoroscopy, using navigation or oblique views as a solution for this.

Discussion and Conclusions

Percutaneous cementation at a failing screw-bone interface stabilises further micromotion with reductions in back pain. This rarely used technique is manifested by a low but increasing number of reported cases. The technique warrants further evaluation and is best performed within a multidisciplinary setting at a specialist centre. Notwithstanding that underlying pathology may not be addressed, awareness of this technique may allow an effective and safe salvage solution with minimal morbidity for older sicker patients.

Pull-out strength evaluation of cement augmented iliac screws in osteoporotic spino-pelvic fixation

INTRODUCTION

Spino-pelvic fixation has been widely accepted for surgical treatment of sacral tumor, scoliosis surgery and pelvic fractures. Cement augmentation of screws is an option to improve implant stability in osteoporotic bone quality. Aim of the present study is to compare iliac screw fixation without cement fixation and two cement application options in a biomechanical testing.

HYPOTHESIS

Cement augmentation of iliac screws leads to superior pull-out strength.

MATERIAL AND METHODS

Thirty female and osteoporotic human iliac bones were used. Three operation treatment groups were generated: Screw fixation (cannulated screws) without cement augmentation [Operation treatment (OT) A], screw fixation with cement augmentation before screw placement (cannulated screws) (OT B) and screw fixation with perforated screws and cement augmentation after screw placement (OTC). Pull-out tests were performed with a rate of 6mm/min. A load versus displacement curve was generated. Maximum pull-out force (N) was measured in the load-displacement curve.

RESULTS

Paired group 1 (OT A vs. OT B): Screw fixation without cement augmentation: 592.6N±335.07 and screw fixation with cement augmentation before screw placement: 996N±287.43 (p=0.0042). Paired group 2 (OT A vs. OT C): screw fixation without cement augmentation: 716.2N±385.86 and fenestrated screw fixation with cement augmentation after screw placement: 1324.88N±398.76 (p=0.0489). Paired group 3 (OT B vs. OT C): Screw fixation with cement augmentation before screw placement: 1077.2±486.66 and fenestrated screw fixation with cement augmentation after screw placement: 1298.2N±726.19 (p=0.3286).

DISCUSSION

Regarding iliac screw fixation for spino-pelvic ostesynthesis in osteoporotic bone, cement augmentation is significantly superior to solid iliac screw fixation respecting pull-out-strength. Nevertheless, further biomechanical studies are needed to verify these findings.

LEVEL OF EVIDENCE

Not applicable; biomechanical cadaver study.

[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.