Influence of flexible fixation for open book injury after pelvic trauma--a biomechanical study

Biomechanical in vitro analysis of a novel flexible implant for pubic symphysis disruption using an ultra-high molecular weight polyethylene fiber cord

BACKGROUND

Plate osteosynthesis depicts the gold standard to surgically treat pubic symphysis disruptions. However, high rates of implant failure after plate osteosynthesis are reported, probably because of the iatrogenic arthrodesis of this fibrocartilaginous joint. Therefore, flexible implants for treatment of pubic symphysis disruptions appear to be a sensible solution.

METHODS

In this biomechanical screening study, we designed and investigated a flexible implant, which consists of two plates connected with an ultra-high molecular weight polyethylene fiber cord. We mechanically tested eye splices as a possible fixation method of the cords by performing tensile load to failure tests. Afterwards, we developed a biomechanically appropriate plate design and cord routing between the plates. Finally, we biomechanically tested the flexible implant under tensile and shear loading until failure.

FINDINGS

When fixing a 1 mm ultra-high molecular weight polyethylene fiber cord with eye splices, a load at failure of 1570.74 N was detected under tensile loading. None of the eye splices failed but the cords itself ruptured. The load at failure of the designed cord routing in criss-cross technique and fixation within the plates amounts 4742.09 N under tensile and 2699.77 N under shear load.

INTERPRETATION

We developed a novel flexible implant for repair of pubic symphysis disruptions using ultra-high molecular weight polyethylene fiber cords connected to osteosynthesis plates. We identified eye splices as a mechanically optimal fixation method and proved that the ultra-high molecular weight polyethylene fiber cord routing and fixation of the flexible implant clearly withstands physiological forces acting on the pubic symphysis.

No clinical advantage of locking over nonlocking plate fixation of symphyseal disruptions

PURPOSE

although locking plates have led to important changes in fracture management, becoming important tools in the orthopedic surgeon's arsenal, the benefits of locking plates for traumatic diastasis of the pubic symphysis have not been established. This study was conducted to assess the quality of life in its different domains among patients with traumatic diastasis of the pubic symphysis managed either with locking or nonlocking plate.

METHODS

a prospective cohort study was undertaken at 3 level 1 trauma centres in Brazil. Patients presenting traumatic diastasis of the pubic symphysis treated with plate fixation with a minimum follow-up of 12 months were eligible for inclusion. Through a Pfannenstiel approach, the pubic symphysis was reduced and fixed with a superiorly positioned 4.5mm four to six hole reconstruction locked plate or 3.5mm four to six hole reconstruction nonlocked plate. Posterior injury was managed during the same procedure. Outcome measures were adequate healing of the pelvic injuries, return to pre-injury level on daily activities, and quality of life at the last follow-up visit. Complications and modes of failure were summarized and reviewed. Bivariate linear regression was used to assess individual factors affecting patients' health-related quality of life. A p value of <5% was considered significant.

RESULTS

a total of 31 adult patients (29 males and 2 females) were eligible for the study. Thirteen patients were managed with a reconstruction locked plate and 18 patients with a nonlocked reconstruction plate. Average postoperative follow-up time was 24 months. Adequate healing of the pelvic injuries was achieved in 61.5% of patients treated with locking plates and 94.4% of patients treated with nonlocking plates (p=0.003). Radiographic failure of fixation with minor complications occurred in 46.1% of patients after locked plating versus 11.1% of patients in the nonlocking plate group (p=0.0003). In bivariate analysis, abnormal gait (p=0.007) was associated with a reduced long-term quality of life as measured with the EQ-5D-3L.

CONCLUSION

internal fixation of traumatic diastasis of the pubic symphysis with locking plates has no clinical advantage when compared to nonlocked plating. Mechanical failure and inadequate healing are significantly increased after locked plating of the pubic symphysis. Therefore, we do not recommend routine use of locking plates for managing patients presenting traumatic diastasis of the pubic symphysis.

LEVEL OF EVIDENCE

II (prospective, cohort study).

Trans-obturator cable fixation of open book pelvic injuries

Operative treatment of ruptured pubic symphysis by plating is often accompanied by complications. Trans-obturator cable fixation might be a more reliable technique; however, have not yet been tested for stabilization of ruptured pubic symphysis. This study compares symphyseal trans-obturator cable fixation versus plating through biomechanical testing and evaluates safety in a cadaver experiment. APC type II injuries were generated in synthetic pelvic models and subsequently separated into three different groups. The anterior pelvic ring was fixed using a four-hole steel plate in Group A, a stainless steel cable in Group B, and a titan band in Group C. Biomechanical testing was conducted by a single-leg-stance model using a material testing machine under physiological load levels. A cadaver study was carried out to analyze the trans-obturator surgical approach. Peak-to-peak displacement, total displacement, plastic deformation and stiffness revealed a tendency for higher stability for trans-obturator cable/band fixation but no statistical difference to plating was detected. The cadaver study revealed a safe zone for cable passage with sufficient distance to the obturator canal. Trans-obturator cable fixation has the potential to become an alternative for symphyseal fixation with less complications.

The role of anterior supra-acetabular external fixator as definitive treatment for anterior ring fixation in unstable pelvic fractures

PURPOSE

Management of anterior ring injuries is still a matter of discussion, and there are only few studies reporting anterior external fixator as definitive treatment for unstable pelvic injuries. This study aimed to describe the clinical and radiological outcomes of a consecutive series of mechanically unstable pelvic injuries that were treated with definitive anterior supra-acetabular external fixator for the anterior ring, and to identify risk factors for failure.

METHODS

We included a consecutive series of patients with unstable pelvic ring fractures who underwent anterior supra-acetabular external fixation for definitive treatment, between January 2012 and January 2020. All demographics, associated injuries and procedures, injury mechanism, and complications were analysed. Pelvic fracture was classified based on Orthopaedic Trauma Association/Tile AO (OTA/AO) and Young-Burgess classifications. Complications associated with the external fixator were revised. All patients were functionally evaluated at final follow-up and asked to report their clinical outcomes using the Majeed score.

RESULTS

A total of 47 patients were included, of which 25 were females. The median age was 44 years (interquartile range 23-59). Median follow-up duration was 14 months (interquartile range 6-31). The most frequent aetiology was motor vehicle accident (35), followed by fall from height (8). All fractures required posterior pelvic ring fixation. The median time during which patients had external fixation in situ was 11 weeks (interquartile range 9-13). All patients achieved healing of pelvic fracture at median time of 10 weeks (interquartile range 8-12). At final follow-up, the median displacement of the anterior pelvis was 6 mm (interquartile range 0-11). Superficial infection was the most common complication (n = 7). No washout procedures were needed. No major complication was reported. No patient required reoperation for anterior ring fracture. The median Majeed score was 88 points (range 60-95; interquartile range 80-90) at final follow-up.

CONCLUSION

Our findings suggest that the use of supra-acetabular external fixator is safe and effective for definitive treatment of the anterior ring in unstable pelvic fractures. It is a method with high proportion of excellent results, regardless of the type of fracture. The rate of complications is low, and it does not compromise functional results.

A novel internal fixation method for open book injuries of the pubic symphysis- A biomechanical analysis

BACKGROUND

Pelvic fractures in adults are common injuries and account for up to 3.64% of all fractures. Usually, the treatment of open book injuries (Types B1.1 and B1.2 AO-Classification) is open reduction and plate stabilization using dynamic compression plates, with or without interlocking screws. These implants seem to enhance the outcome of such injuries, but also variety of complications occurs. To reduce complications and achieve appropriate reduction and stabilization, this study compared established stabilization techniques to a novel minimally invasive internal fixation method using an internal fixator system that is already being utilized for spinal fractures.

METHODS

This study was performed on 32 composite pelvises in a bilateral stance biomechanical model. The pelvises were variously stabilized with an internal fixator, a 4.5 mm dynamic compression plate and a 3.5 mm symphyseal locking dynamic compression plate. The contact area and loading forces were assessed by a sensor film inside the symphyseal gap.

FINDINGS

This study showed significantly greater reduction and loading capabilities of the internal fixator compared to the other implants (p < 0.05). There was also significantly greater contact area with the use of an internal fixator compared to the other implants (p < 0.05). The 3.5 mm interlocking plate showed significantly greater contact area compared to the 4.5 mm plate (p < 0.05).

INTERPRETATION

The internal fixator that is already proven in spinal surgery is biomechanically superior to conventional implants used in pelvic surgery. The contact area analysis furthermore showed a more physiological loading pattern, which can improve ligamentous healing in a clinical context.

Stabilization of a Type B1.1 Injury in a Morbidly Obese Patient Using an Internal Fixator in a Minimally Invasive Technique: A Case Report

CASE

In this case report, we present a novel stabilization technique of the pubic symphysis using an internal spinal fixator in a 78-year-old morbidly obese woman having a pelvic disruption type B1.1 (AO classification). We treated the disruption using an internal fixator to reduce the extent of the incision and soft-tissue damage.

CONCLUSIONS

The use of an internal fixator, known from percutaneous spinal fixation, for the stabilization of the pubic symphysis in cases of disruption ("open book" injuries) may be an alternative to the standard plate fixation as a novel minimally invasive stabilization technique.

EASY (endoscopic approach to the symphysis): a new minimally invasive approach for the plate osteosynthesis of the symphysis and the anterior pelvic ring-a cadaver study and first clinical results

BACKGROUND

Minimally invasive surgical approaches to reduce approach-associated morbidity are an interdisciplinary goal in surgery. In principle, the endoscopic approach for the extraperitoneal repair of groin hernias is the minimally invasive variant of the modified Stoppa-approach, which is used for the treatment of pelvic ring injuries in traumatology.

METHOD

Anatomical feasibility study regarding the plate osteosynthesis of the anterior pelvic ring via a minimally invasive variant of the modified Stoppa-approach.

RESULTS

We present the minimally invasive variant of the modified Stoppa-approach in a human cadaver step by step, both photographically and radiologically. Feasibility of the plate osteosynthesis of the symphysis is presented in a patient with open book injury via the minimally invasive approach using standard laparoscopic instruments.

CONCLUSION

The plate osteosynthesis of the anterior pelvic ring via the minimally invasive variant of the modified Stoppa-approach is feasible with existing standard laparoscopic instruments.

Biomechanics of unilateral and bilateral sacroiliac joint stabilization: laboratory investigation

OBJECTIVE Bilateral symptoms have been reported in 8%-35% of patients with sacroiliac (SI) joint dysfunction. Stabilization of a single SI joint may significantly alter the stresses on the contralateral SI joint. If the contralateral SI joint stresses are significantly increased, degeneration may occur; alternatively, if the stresses are significantly reduced, bilateral stabilization may be unnecessary for patients with bilateral symptoms. The biomechanical effects of 1) unilateral stabilization on the contralateral SI joint and 2) bilateral stabilization on both SI joints are currently unknown. The objectives of this study were to characterize bilateral SI joint range of motion (ROM) and evaluate and compare the biomechanical effects of unilateral and bilateral implant placement for SI joint fusion. METHODS A lumbopelvic model (L5-pelvis) was used to test the ROM of both SI joints in 8 cadavers. A single-leg stance setup was used to load the lumbar spine and measure the ROM of each SI joint in flexion-extension, lateral bending, and axial rotation. Both joints were tested 1) while intact, 2) after unilateral stabilization, and 3) after bilateral stabilization. Stabilization consisted of lateral transiliac placement of 3 triangular titanium plasma-sprayed (TPS) implants. RESULTS Intact testing showed that during single-leg stance the contralateral SI joint had less ROM in flexion-extension (27%), lateral bending (32%), and axial rotation (69%) than the loaded joint. Unilateral stabilization resulted in significant reduction of flexion-extension ROM (46%) on the treated side; no significant ROM changes were observed for the nontreated side. Bilateral stabilization resulted in significant reduction of flexion-extension ROM of the primary (45%) and secondary (75%) SI joints. CONCLUSIONS This study demonstrated that during single-leg loading the ROMs for the stance (loaded) and swing (unloaded) SI joints are significantly different. Unilateral stabilization for SI joint dysfunction significantly reduces the ROM of the treated side, but does not significantly reduce the ROM of the nontreated contralateral SI joint. Bilateral stabilization is necessary to significantly reduce the ROM for both SI joints.

Symphyseal fixation in open book injuries cannot fully compensate anterior SI joint injury-A biomechanical study in a two-leg alternating load model

INTRODUCTION

In open book injuries type Tile B1.1 or B1.2 also classified as APC II (anteroposterior compression), it remains controversial, if a fixation of the anterior ring provides sufficient stability or a fixation of the posterior ring should be included. Therefore the relative motion at the sacroiliac joint was quantified in a two-leg alternating load biomechanical pelvis model in the intact, the injured and the restored pelvis.

METHODS

Fresh-frozen intact (I) pelvises (n = 6) were subjected to a non-destructive cyclic test under sinosuidal axial two-leg alternating load with progressively increasing amplitude. Afterwards an open book injury (J) including the anterior ligament complex of the left sacroiliac joint, the sacrospinal and sacrotuberal ligaments (Tile B1.1) was created and the specimens were retested. Finally, the symphysis was stabilized with a modular fixation system (1-, 2- or 4-rod configuration) (R) and specimens were cyclically retested. Relative motion at the sacroiliac joint was captured at both sacroiliac joints by motion tracking system at two load levels of 170 N and 340 N during all tests.

RESULTS

Relative sacroiliac joint movements at both load levels were significantly higher in the J-state compared to the I-state, excluding superoinferior translational movement. With exception of the anteroposterior translational movement at 340N, the relative sacroiliac joint movements after each of the three reconstructions (1-, 2-, 4-rod fixation) were significantly smaller compared to the J-state and did not differ significantly to the I-state, but stayed above the values of the latter. Relative movements did not differ significantly in a direct comparison between the 1-rod, 2-rod and 4-rod fixations.

CONCLUSION

Symphyseal locked plating significantly reduces relative movement of the sacroiliac joint in open book injuries type Tile B1.1 or B1.2 (APC II) but cannot fully restore the situation of the intact sacroiliac joint.

Defining the pubic symphysis angle with respect to the coronal plane - Clinical and biomechanical considerations

BACKGROUND

Fixation strength of constructs placed across the pubic symphysis after injury is dependent on screw length, maximisation of which requires knowledge of the bony anatomy. The aim of this study was to describe the ideal angle of drilling to achieve maximal safe screw placement within the pubic body. Furthermore, the influences of age and gender on the skeletal topography were investigated.

METHODS

Three hundred CT scans of patients without pelvic injury were analysed to record the angle of the pubic body (APB) with respect to the coronal plane, and the depth of the pubic body (DPB) in the sagittal plane.

RESULTS

Mean APB and DPB were 54.69° and 55.35mm, respectively. Females had a significantly higher mean APB than males (57.29° vs. 52.41°; p<0.001), whereas males had a significant larger mean DPB (59.13mm vs. 51.03mm; p<0.001). Age had no effect on the mean APB. Mean width of the pubic body at the base was 9.38mm.

CONCLUSION

The anatomy of this region is reliable in terms of angles and sizes; a drill angle of 55° with respect to the operating table will allow maximal screw length, which should be in the region of 55mm. The mean width of the pubic body should allow for placement of a 3.5 or 4.5mm diameter screw.

Reduced rates of non-union with modified periacetabular osteotomy using peracetic-acid sterilized cancellous allografts

The objective of the present study was to analyze the clinical and radiological results of periacetabular osteotomies (PAO) using Kirschner wire fixation and an allogeneic cancellous bone graft. This retrospective cohort study included 73 patients (85 PAOs). The allografts were processed from distal femur of cadaveric donors, defatted, sterilized with a peracetic-acid ethanol solution and freeze-dried. The clinical outcome, as measured by the Harris Hip Scores (HHS), the complication rate and the acetabular correction, as measured by radiological parameters, were compared. The postoperative femoral head coverage and HSS were significantly improved. Major complications occurred in five cases (6 %), but in no case did we observe a non-union or a graft-associated adverse effect. Fixation of the acetabular fragment with Kirschner wires in combination with an allogeneic cancellous bone graft is a safe method, with a low complication rate, no loss of correction and can prevent the occurrence of non-union with a high degree of probability.

The Effect of Implant Failure After Symphyseal Plating on Functional Outcome and General Health

OBJECTIVES

To relate the incidence of implant failure after internal anterior fixation of the pelvic ring to functional outcome and the health-related quality of life in patients.

DESIGN

Retrospective chart and radiographic review.

SETTING

Level I Trauma center.

METHODS

We retrospectively identified all patients who were treated with symphyseal plating for traumatic symphyseal diastasis between January 2003 and December 2013. Patients were asked to complete 2 questionnaires, the SF-36 and the Majeed score. A retrospective chart and radiographic control review were performed on all patients. The following data were collected: demographic data and details regarding the pelvic surgery. Computed tomograms were used to determine fracture classification and quality of reduction. Conventional radiographic follow-up were used to detect implant failure.

RESULTS

A total of 37 patients enrolled the study. Implant failure occurred in 11 (30%) patients resulting in the identification of 2 groups, "implant failure" (n = 11) and "intact implants" (n = 26). The baseline characteristics were equal in both groups. The analysis of the questionnaires revealed that the SF-36 score was not significantly different in any of the dimensions between the both groups. Patients in the implant failure group scored higher on all of the Majeed items, including the total Majeed score, but the difference did not reach statistical significance of P < 0.05.

CONCLUSIONS

Our study showed comparable results regarding the general health measured by the SF-36 for both groups and higher Majeed scores for patients with implant failure compared with patients with intact implants.

LEVEL OF EVIDENCE

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

Comparison of Biomechanical Characteristics and Pelvic Ring Stability Using Different Fixation Methods to Treat Pubic Symphysis Diastasis: A Finite Element Study

The intention of this study was to compare the biomechanical characteristics using 5 internal fixation methods used clinically to stabilize a pubic symphysis diastasis (PSD, Tile type B1).A 3-dimensional finite element model of PSD was simulated using 5 implants, including single superior plate (Single-Plate), superior and anterior plate (Dual-Plate), single cannulated screw (Single-Screw), crossed dual cannulated screws (Cross-Screw), and parallel dual cannulated screws (Para-Screw). Three loads were distributed in all models, including dual-leg standing, single-leg stance, and rotation. To evaluate the biomechanical properties, the construct stiffness, the stress distribution, and the von Misses stress were recorded and analyzed. To evaluate pelvic ring stability, the micromotion of the pubic symphysis and iliosacral joint was analyzed.Disruption of pubic symphysis dramatically decreased the pelvic ring stability. Cross-screw and Para-Screw showed higher stiffness than other methods. All implants endured the maximum von Misses stress under single-leg stance. For Plate-Screw system, the maximum stress occurred at a place where it strides over pubic symphysis and adjacent Plate-Screw interface. The single implant and Para-Screw had a tendency to fail. Para-Screw showed the best fixation effect under dual-leg conditions. Cross-screw showed superior antishearing force capacity under single-leg stance. Dual-Plate provided maximum antihorizontal rotation. Para-Screw provided the maximum stabilization for the posterior pelvic ring.This study showed the biomechanical advantages of dual-implant for PSD only from the finite element view. The Para-Screw provided high construct stiffness under 3 load conditions. The single implant and Para-Screw had a tendency to fail. The better anterior and posterior pelvic stabilization were obtained by the dual-implant fixation than other methods. Therefore, the Cross-Screw and Dual-Plate fixation methods should be preferred in the treatment of pubic symphysis from the finite element view.