Biomechanical Testing of Two Devices for Internal Fixation of Fractured Ribs

A model for evaluating the biomechanics of rib fracture fixation

INTRODUCTION

High rates of morbidity and mortality following flail chest rib fractures are well publicized. Standard of care has been supportive mechanical ventilation, but serious complications have been reported. Internal rib fixation has shown improvements in pulmonary function, clinical outcomes, and decreased mortality. The goal of this study was to provide a model defining the biomechanical benefits of internal rib fixation.

METHODS

One human cadaver was prepared with an actuator providing anteroposterior forces to the thorax and rib motion sensors to define interfragmentary motion. Cadaveric model was validated using a prior study which defined costovertebral motion to create a protocol using similar technology and procedure. Ribs 4-6 were fixed with motion sensors anteriorly, laterally and posteriorly. Motion was recorded with ribs intact before osteotomizing each rib anteriorly and laterally. Flail chest motion was record with fractures subsequently plated and analyzed. Motion was recorded in the sagittal, coronal and transverse axes.

FINDINGS

Compared to the intact rib model, the flail chest model demonstrated an 11.3 times increase in sagittal plane motion, which was reduced to 2.1 times the intact model with rib plating. Coronal and sagittal plane models also saw increases of 9.7 and 5.1 times, respectively, with regards to flail chest motion. Both were reduced to 1.2 times the intact model after rib plating.

INTERPRETATION

This study allows quantification of altered ribcage biomechanics after flail chest injuries and suggests rib plating is useful in restoring biomechanics as well as contributing to improving pulmonary function and clinical outcomes.

Physical function and pain after surgical or conservative management of multiple rib fractures - a follow-up study

Background

There is scarce knowledge of physical function and pain due to multiple rib fractures following trauma. The purpose of this follow-up was to assess respiratory and physical function, pain, range of movement and kinesiophobia in patients with multiple rib fractures who had undergone stabilizing surgery and compare with conservatively managed patients.

Methods

A consecutive series of 31 patients with multiple rib fractures who had undergone stabilizing surgery were assessed >1 year after the trauma concerning respiratory and physical function, pain, range of movement in the shoulders and thorax, shoulder function and kinesiophobia. For comparison, 30 patients who were treated conservatively were evaluated with the same outcome measures.

Results

The results concerning pain, lung function, shoulder function and level of physical activity were similar in the two groups. The patients who had undergone surgery had a significantly larger range of motion in the thorax (p < 0.01) and less deterioration in two items in Disability Rating Index (sitting and standing bent over a sink) (p < 0.05).

Discussion

It is questionable whether the control group is representative since the majority of patients were invited but refused to participate in the follow-up. In addition, this study is too small to make a definitive conclusion if surgery is better than conservative treatment. But we see some indications, such as a tendency for decreased pain, better thoracic range of motion and physical function which would indicate that surgery is preferable. If operation technique could improve in the future with a less invasive approach, it would presumably decrease post-operative pain and the benefit of surgery would be greater than the morbidity of surgery.

Conclusions

Patients undergoing surgery have a similar long-term recovery to those who are treated conservatively except for a better range of motion in the thorax and fewer limitations in physical function. Surgery seems to be beneficial for some patients, the question remains which patients.

Trial registration

FoU i Sverige (R&D in Sweden), No 106121

Fixation of a human rib by an intramedullary telescoping splint anchored by bone cement

A novel concept for rib fixation is presented that involves the use of a bioresorbable polymer intramedullary telescoping splint. Bone cement is used to anchor each end of the splint inside the medullary canal on each side of the fracture site. In this manner, rib fixation is achieved without fixation device protrusion from the rib, making the splint completely intramedullary. Finite element analysis is used to demonstrate that such a splint/cement composite can preserve rib fixation subjected to cough-intensity force loadings. Computational fluid dynamics and porcine rib experiments were used to study the anchor formation process required to complete the fixation.

A Novel Biodegradable Polycaprolactone Fixator for Osteosynthesis Surgery of Rib Fracture: In Vitro and in Vivo Study

Osteosynthesis surgery for rib fractures is controversial and challenging. This study developed a noval poly(ε-caprolactone) (PCL)-based biodegradable “cable-tie” fixator for osteosynthesis surgery for rib fractures. A biodegradable fixator specifically for fractured ribs was designed and fabricated by a micro-injection molding machine in our laboratory. The fixator has three belts that could be passed through matching holes individually. The locking mechanism allows the belt movement to move in only one direction. To examine the in vitro biomechanical performance, ribs 3–7 from four fresh New Zealand rabbits were employed. The load to failure and stress-strain curve was compared in the three-point bending test among native ribs, titanium plate-fixed ribs, and PCL fixator-fixed ribs. In the in vivo animal study, the sixth ribs of New Zealand rabbits were osteotomized and osteosynthesis surgery was performed using the PCL fixator. Outcomes were assessed by monthly X-ray examinations, a final micro-computed tomography (CT) scan, and histological analysis. The experimental results suggested that the ribs fixed with the PCL fixator were significantly less stiff than those fixed with titanium plates (p < 0.05). All ribs fixed with the PCL fixators exhibited union. The bridging callus was confirmed by gross, radiographic micro-three-dimensional (3D) CT, and histological examinations. In addition, there was no significant inflammatory response of the osteotomized ribs or the PCL-rib interface during application. The novel PCL fixator developed in this work achieves satisfactory results in osteosynthesis surgery for rib fractures, and may provide potential applications in other orthopedic surgeries.

Management of pulmonary contusion and flail chest: an Eastern Association for the Surgery of Trauma practice management guideline

BACKGROUND

Despite the prevalence and recognized association of pulmonary contusion and flail chest (PC-FC) as a combined, complex injury pattern with interrelated pathophysiology, the mortality and morbidity of this entity have not improved during the last three decades. The purpose of this updated EAST practice management guideline was to present evidence-based recommendations for the treatment of PC-FC.

METHODS

A query was conducted of MEDLINE, Embase, PubMed and Cochrane databases for the period from January 1966 through June 30, 2011. All evidence was reviewed and graded by two members of the guideline committee. Guideline formulation was performed by committee consensus.

RESULTS

Of the 215 articles identified in the search, 129 were deemed appropriate for review, grading, and inclusion in the guideline. This practice management guideline has a total of six Level 2 and eight Level 3 recommendations.

CONCLUSION

Patients with PC-FC should not be excessively fluid restricted but should be resuscitated to maintain signs of adequate tissue perfusion. Obligatory mechanical ventilation in the absence of respiratory failure should be avoided. The use of optimal analgesia and aggressive chest physiotherapy should be applied to minimize the likelihood of respiratory failure. Epidural catheter is the preferred mode of analgesia delivery in severe flail chest injury. Paravertebral analgesia may be equivalent to epidural analgesia and may be appropriate in certain situations when epidural is contraindicated.A trial of mask continuous positive airway pressure should be considered in alert patients with marginal respiratory status. Patients requiring mechanical ventilation should be supported in a manner based on institutional and physician preference and separated from the ventilator at the earliest possible time. Positive end-expiratory pressure or continuous positive airway pressure should be provided. High-frequency oscillatory ventilation should be considered for patients failing conventional ventilatory modes. Independent lung ventilation may also be considered in severe unilateral pulmonary contusion when shunt cannot be otherwise corrected.Surgical fixation of flail chest may be considered in cases of severe flail chest failing to wean from the ventilator or when thoracotomy is required for other reasons. Self-activating multidisciplinary protocols for the treatment of chest wall injuries may improve outcome and should be considered where feasible.Steroids should not be used in the therapy of pulmonary contusion. Diuretics may be used in the setting of hydrostatic fluid overload in hemodynamically stable patients or in the setting of known concurrent congestive heart failure.