Internal anterior fixators for pelvic ring injuries: Do monaxial pedicle screws provide more stiffness than polyaxial pedicle screws?

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.

Comparison of the two surgery methods combined with accelerated rehabilitation in the treatment of lateral compression type 1 pelvic fractures in the elderly

BACKGROUND

Treating lateral compression type 1 (LC1) pelvic ring injuries in older patients is controversial. This study evaluated surgical treatments combined with ERAS for treating LC1 pelvic fractures in the elderly.

METHODS

In this retrospective study, patients who underwent surgery with INFIX (supra-acetabular spinal pedicle screws, and a subcutaneous connecting rod; the experimental group) or superior pubic ramus cannulated screw (the control group) fixation of LC1 pelvic fracture from January 2019 to January 2022 were reviewed. Injury radiography and computed tomography were performed to determine the Young-Burgess classification. All patients performed standardized early rehabilitation exercises after surgery and were followed up for > 12 months. After surgery, the Matta score and the visual analog scale (VAS) were evaluated, and the postoperative weight-bearing time and the length of stay (LOS) were recorded. The Barthel index and the Majeed score were evaluated at 4 months after surgery and at the last follow-up.

RESULTS

Fifty-three patients were included. Thirty-two patients included in the experimental group had a mean age of 75.0 ± 6.2 (range, 66-86) years, and the other 21 patients in the control group had a mean age of 74.6 ± 4.6 (range, 68-83) years. The mean follow-up time was 13.1 ± 1.6 (range, 12-18) months in the experimental group and 13.4 ± 1.3 (range, 12-16) months in the control group. There were no significant differences in follow-up time between the groups (P > 0.05). The mean VAS score, time to weight-bearing, and LOS were 2.0 ± 0.7 (range, 1-3), 1.1 ± 0.3 (range, 1-2) d, and 5.8 ± 0.9 (range, 4-7) d in the experimental group and 2.3 ± 1.2 (range, 1-5), 2.5 ± 1.6 (range, 1-7) d, and 6.1 ± 1.6 (range, 5-11) d in the control group, respectively. Between the two groups, there was a significant difference in the postoperative time to weight-bearing (P < 0.05), while there was no significant difference in the LOS (P > 0.05). No bedrest-related complications occurred in either group. The Matta score was 90.6% in the experimental group and 90.4% in the control group (P > 0.05). At the 4-months follow-up, the experimental group had a better Barthel index and Majeed score compared with the control group, which were 86.1 ± 6.2 (range, 70-95) vs. 81.2 ± 4.1 (range, 75-90) and 86.3 ± 3.3 (range, 78-91) vs. 80.3 ± 3.9 (range, 76-86), respectively. The experimental group had better early rehabilitation effect than the control group. There was no significant difference in Barthel index and Majeed score between the two groups at the last follow-up (P > 0.05).

CONCLUSION

Both INFIX and intramedullary superior pubic ramus cannulated screws can successfully treat LC1 pelvic fractures and reduce bed rest complications among older patients.

Percutaneous Treatment of Locked Pubic Symphysis with the Anterior Subcutaneous Pelvic Fixator (INFIX): A Case Report

CASE

A 54-year-old woman was involved in a motor vehicle collision and sustained a lateral compression type 1 pelvic ring fracture with pubic symphyseal dislocation or a "locked pubic symphysis." Her injury failed to reduce with closed reduction maneuvers under anesthesia and necessitated a percutaneous reduction using a distraction force applied through supra-acetabular placed pedicle screws. This anterior subcutaneous internal pelvic fixator (INFIX) was also used to stabilize the injury.

CONCLUSION

This is the first reported case where a locked pubic symphysis, which failed standard closed reduction measures, was reduced and stabilized through a percutaneous technique, using the INFIX.

Outcomes and complications of the INFIX technique for unstable pelvic ring injuries with high-velocity trauma: a systematic review and meta-analysis

BACKGROUND

The pelvic INFIX technique has been proposed as a useful alternative to symphyseal plating for management of unstable pelvic ring injuries. The minimally invasive nature of the procedure, shorter operative time and less perioperative blood loss have been purported as potential advantages.

QUESTIONS/PURPOSES

This systematic review and meta-analysis were conducted to determine the outcomes and complications of the INFIX technique for unstable pelvic ring injuries.

METHODS

A systematic review of literature was performed on the PubMed, EMBASE and Scopus databases. Prospective and retrospective studies in all languages, whether comparative or non-comparative, pertaining to the use of INFIX in pelvic fractures were included. Studies which did not evaluate INFIX, case reports, conference abstracts and those with less than 10 cases were excluded. Cadaveric studies, technique papers and studies that did not describe the prespecified outcome measures were also excluded. Meta-analysis consisted of two different arms: a comparative arm, to compare INFIX to symphyseal plating, and a non-comparative meta-analysis arm, to determine pooled rates of outcomes and complications. Risk of bias was determined by the Methodological Index for Non-Randomised Studies (MINORS) tool.

RESULTS

A total of 22 studies were included in the systematic review, of which 7 were comparative and 15 were non-comparative. 746 patients were included for qualitative analysis and pooled analysis done for 589 patients. The average follow-up of these studies ranged from a minimum of 5.4 months to a maximum of 54 months. Comparative meta-analysis (n = 3 studies) of plating and INFIX showed significantly lesser blood loss (mean difference = 176.46 mL; 95% CI - 207.54 to - 145.38) and shorter operative time (mean difference = 26.43 min, 95% CI - 31.79 to - 21.07) with INFIX, but no significant difference in the overall complication rates (OR 1.59, 95% CI 0.83-3.05) and functional outcome scores (mean difference = - 2.51, 95% CI - 5.73 to 0.71). Pooled analysis showed overall good radiological (mean percentage of excellent to good reduction = 91.4%, 95% CI 0.860-0.969) and functional outcomes (mean Majeed score = 86.48, 95% CI 83.34-89.61) with INFIX. The most common complications were lateral femoral cutaneous nerve (LFCN) injury (overall rate 28%, 95% CI 15.1-41%) and heterotopic ossification (HO) (overall rate 9.4%, 95% CI 5.5-13.3%); rates of other complications were low. Significant heterogeneity was noted in the pooled analysis of blood loss, operative time, functional outcome, HO and LFCN injury. The overall strength of evidence was found to be weak.

CONCLUSION

The INFIX technique can be considered as a viable alternative to symphyseal plating for unstable pelvic ring injuries. It has the advantages of shorter operative times and less blood loss, along with comparable functional outcomes, when compared to plating. Overall, good functional outcomes can be expected. However, well-designed, multi-center randomized controlled trials are needed to conclusively prove the benefit of this technique.

Stability of internal versus external fixation in osteoporotic pelvic fractures - a biomechanical analysis

INTRODUCTION

Osteoporosis-related fragility fractures of the pelvic ring (FFP) differ fundamentally from pelvic fractures in younger patients. However, very little is known about biomechanical stability of different osteosynthesis procedures addressing the anterior pelvic ring in these fractures. The aim of this study was to compare standard external fixation with internal fixation using a novel screw-and-rod system in osteoporotic fractures of the pelvic ring in terms of stiffness, plastic deformation and maximum load under cyclic loading in a human cadaveric model.

MATERIALS AND METHODS

A total of 18 embalmed osteoporotic cadaver pelvis specimens were randomized based on the T-score into a group for external fixation and a group for internal fixation. FFP type-IIB fractures were created. In addition to the external or internal fixator, a cement-augmented sacroiliac screw was implanted. Afterwards, axial cyclic loading was performed in a testing setup simulating one-leg stand.

RESULTS

Mean plastic deformation and stiffness both were significantly better in the internal fixation group than in the external fixation group (plastic deformation: 0.37 mm (SD: 0.23) versus 0.71 mm (SD: 0.26), p = 0.011; stiffness: 43.69 N/mm (SD: 18.39) versus 26.52 N/mm (SD: 9.76), p = 0.029). Maximum load did not differ significantly between internal fixator (506.3 N; SD: 129.4) and external fixator (461.1 N; SD: 147.4) (p = 0.515).

CONCLUSIONS

Submuscular internal fixation might be an interesting alternative to external fixation in clinical practice because of better biomechanical properties as well as several advantages in clinical use.

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.

The Anterior Subcutaneous Pelvic Ring Fixator: No Biomechanical Advantages Compared with External Fixation

BACKGROUND

Subcutaneous fixation of the anterior pelvic ring is an emerging surgical technique for trauma patients. The aim of this study was to biomechanically evaluate 2 internal fixation devices for stabilizing a disrupted pelvic ring and compare them with traditional external fixation.

METHODS

Thirty-six synthetic pelvises with a simulated unstable ring fracture (anteroposterior compression type III) were divided into 3 groups. Group A underwent fixation with a supra-acetabular external fixator; group B, with an internal fixator using the USS II polyaxial system; and group C, with an internal fixator using the Click'X polyaxial system. Biomechanical testing included measurement of peak-to-peak displacement at 300, 400, and 500 N; total displacement; plastic deformation; stiffness; and fracture-line displacement.

RESULTS

Statistical analysis of all measured parameters revealed no significant differences among the groups. However, vertical displacement of the preshaped connecting rod within the screw heads occurred as a result of inadequate stability of the internal fixation at the rod-screw interface.

CONCLUSIONS

Although internal fixator devices are placed close to the bone and should therefore maintain greater stiffness, our data did not support the hypothesis of superior stability. Special attention is required when using a curved connecting rod as the rod is easily displaced, placing relevant anatomical structures at risk. These devices require further refinement to avoid potential patient injury.

Fixation of Anterior Pelvic Ring Injuries

Treatment of anterior pelvic ring injuries involves both acute stabilization during the initial resuscitation and definitive fixation. Definitive management has evolved substantially over the past 40 years with improved patient mobilization and long-term outcomes. Although its use has recently declined, external fixation remains a favorable option in certain situations. Symphyseal plating is the preferred technique for stabilization of symphyseal diastasis because of superior stability and low morbidity. Ramus screws can be effective for simple ramus fractures but require a careful technique because of the proximity of neurovascular structures. The subcutaneous internal fixator provides a good option for obese patients in whom external fixation would be poorly tolerated. Regardless of fixation strategy, posterior ring reduction and stabilization is crucial.

Safe Supra-Acetabular Pin Insertion in Relation to Intraosseous Depth

In pelvic fractures, dysfunction of the pelvic ring is often stabilized with supra-acetabular pin insertion. In existing literature, there are heterogeneous indications on proper pins selection and inclinations. Therefore, this study aimed to quantify the narrowing of safe pin corridors in the transverse and sagittal planes with increments of intraosseous screw depths. A computer algorithm created cross-sections over three-dimensional pelvic reconstructions at sagittal inclinations from 45° cranial to 45° caudal in 5° increments. Templates of screw depths spanning 60-120 mm in 15 mm increments were disposed in the transverse plane from 45° medial to 45° lateral. Each intraosseous screw depth and transverse angle were evaluated for intraosseous containment to evaluate ranges narrowing with increasing screw depths. The 60-mm depth resulted in the largest sagittal range (60.9° ± 6.9°) and transverse range (27.5° ± 4.1°) at 30° caudal. Increasing depths by 15 mm resulted in ranges being significantly different from one another (p < 0.01). The sagittal plane of 20° cranial had the highest frequency of insertion for all depths, while transverse ranges were narrowed (p < 0.01). Bisecting angles were similar for sagittal planes 20° cranial to 30° caudal with an average of 27.9° ± 1.2° (p ≥ 0.115). In conclusion, while 60 mm depths can be inserted with the highest discretion, 15 mm increments in depth significantly reduce safe ranges. Screws depths above 90 mm have low frequencies of insertion, should be inserted more cranially and must be considered prone to breaching. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1790-1797, 2019.

Anterior subcutaneous internal fixator (INFIX) versus plate fixation for pelvic anterior ring fracture

The aim of this study was to compare the clinical outcomes in patients with unstable anterior pelvic ring fractures after treatment with anterior subcutaneous internal fixator (INFIX) or plate fixation. We performed a retrospective study from August 2015 to October 2017. A consecutive series of 74 patients who underwent surgical treatment of their anterior pelvic ring (35 treated with INFIX and 39 treated with plates) were studied. Data collected included patients’ demographic data, injury severity score (ISS), AO/OTA classification, injury mechanism, time to surgery, procedure time, and blood loss. The quality of postoperative reduction were assessed by postoperative radiographs using the Tornetta and Matta method. Functional outcome was evaluated using Majeed scoring system. In the INFIX group, ten patients developed LFCN paralysis, one patient suffered from superficial infection. Three screw loosening cases and two wound infection cases occurred in the plate group. INFIX is relatively minimally invasive and time-saving than the reconstruction plate in the treatment of anterior pelvic ring fracture. However, plate fixation increases the rate of anatomic reduction of the pelvic anterior ring fracture. Plates also provide a higher functional outcome compared with INFIX. INFIX is especially suitable in patients with urological injury, which can also decrease the wound infection rate.

A biomechanical study comparing minimally invasive anterior pelvic ring fixation techniques to external fixation

INTRODUCTION

INFIX and Pelvic Bridge are two new minimally invasive surgical techniques for unstable pelvic ring injuries, and they have demonstrated early clinical success in small, single-center case-series. The primary objective of this study is to gather evidence speaking to the biomechanical stability of internal bridging methods relative to external fixation, with the expectation of biomechanical equivalence.

METHODS

Ten human cadaveric pelvic specimens were dissected free of all skin, fat, organs, and musculature and were prepared with a partially unstable pelvic ring injury (OTA/AO 61-B). The specimens were randomized to two groups and were repaired and tested with anterior pelvic external fixation (APEF) and INFIX sequentially, or APEF and Pelvic Bridge sequentially. Testing was performed with each specimen mounted onto a servo-hydraulic testing frame with axial compression applied to the superior base of the sacrum under five axial loading/unloading sinusoidal cycles between 10 N and 1000 N at 0.1 Hz. Relative translational motion and rotation across the osteotomy site was reported as our primary outcome measures. Outcome measures were further analyzed using a Wilcoxon signed-rank test to determine differences between non-parametric data sets with significance defined as a p value < 0.05.

RESULTS

We found no statistical difference in translation (p = 0.237, 0.228) or rotation (p = 0.278, 0.873) at the fracture site when comparing both new constructs to external fixation. Under the imposed loading protocol, no episodes of implant failure or failure at the bone-implant interface occurred.

DISCUSSION

Our study provides the biomechanical foundation necessary to support future clinical trial implementation for pelvic fracture patients. While biomechanical stability of these newer, subcutaneous techniques is equivalent to APEF, the surgeon must take into account their technical abilities and knowledge of pelvic anatomy, patient-specific factors including body habitus, and the potential complications associated with each implant and the ability to avoid them.

Complications Following Internal Fixator in the Treatment of Pelvic Fracture

The aim of this systematic review was to investigate the incidence of complications of the internal fixator in the treatment of anterior pelvic ring injury. The literature was comprehensively searched from 1980 to January 2017 to identify potential studies. Six studies involving 272 cases of anterior pelvic ring injury treated with the internal fixator were included in this meta-analysis. The rates of wound infection, heterotopic ossification, nerve paresthesia, pain, and fracture dislocation were 5.7%, 35.1%, 28.2%, 3.7%, and 3.0%, respectively. This new technique should be prudently used to treat pelvic fractures. [Orthopedics. 2019; 42(1):e7-e13.].

Minimally invasive treatment for anterior pelvic ring injuries with modified pedicle screw-rod fixation: a retrospective study

Background

Pelvic ring injuries constitute only 2 to 8% of all fractures; however, they occur in 20% of polytrauma patients. High-energy pelvic fractures often result in mechanical instability of the pelvic ring. Successful treatment of unstable pelvic ring fractures remains a challenge for orthopedic surgeons. This study presents a novel internal fixation method for stabilizing unstable anterior pelvic ring fractures using a minimally invasive modified pedicle screw-rod fixation (MPSRF) technique.

Methods

This retrospective study included six patients with unstable pelvic ring injuries who underwent MPSRF, with or without posterior fixation. Intraoperative parameters such as blood loss, operative time, complications, and quality of reduction (Matta criteria) were recorded and evaluated by a blinded reviewer.

Results

In the present clinical series, the mean operative times and mean blood loss for unilateral versus bilateral anterior ring fixations were 176.0 min versus 295.6 min, and 153.3 mL versus 550.0 mL, respectively. No iatrogenic neuropraxia of the lateral femoral cutaneous nerve or femoral nerve palsy occurred. The reduction quality, graded by the Matta criteria, was excellent in five patients and good in one patient.

Conclusions

There were no infections, delayed unions, nonunions, or loss of reductions during the follow-up period. Only one patient suffered from a broken rod at 4 months postoperatively. The modified technique represents a novel, minimally invasive procedure for the treatment of anterior pelvic ring fractures and offers a reliable and effective alternative to currently available surgical techniques.

Anterior Subcutaneous Internal Pelvic Fixation/INFIX: A Systemic Review

INTRODUCTION

The purpose of this article is to review the available literature on anterior subcutaneous internal pelvic fixation (ASIPF) to identify indications, clinical and radiographic outcomes, and compare these with alternative fixation methods.

METHODS

Using the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines, a systematic search on PubMed and Google Scholar was performed. Articles included were in the English language or English translations and published between 2007 and 2018. Studies included were appraised with narrative data synthesis.

RESULTS

Twenty-five articles with 496 patients were included. These included 17 case series, with 3 case reports reporting adverse events.

CONCLUSIONS

ASIPF and the appropriate posterior fixation resulted in healing of pelvic ring injuries in 99.5% of cases. Indications include unstable pelvic ring injuries with the appropriate posterior fixation. Radiographic parameters and outcome measures were infrequently reported. ASIPF is a valuable tool for reduction and fixation in unstable pelvic ring injuries. Complications include lateral femoral cutaneous nerve irritation (26.3%); heterotopic ossification (36%); infection (3%); and femoral nerve palsy (1%), which is likely related to placing the bar and screws too deep.

Robot-assisted percutaneous screw placement combined with pelvic internal fixator for minimally invasive treatment of unstable pelvic ring fractures

Purpose

The purpose of this study was to investigate the safety and efficacy of the combination of robot‐assisted percutaneous screw placement and pelvic internal fixator (INFIX) for minimally invasive treatment of unstable anterior and posterior pelvic ring injuries.

Methods

From September 2016 to June 2017, twenty‐four patients with unstable anterior and posterior pelvic ring injuries were treated with TiRobot‐assisted percutaneous sacroiliac cannulated screw fixation on the posterior pelvic ring combined with robot‐assisted pedicle screw placement in the anterior inferior iliac spine along with INFIX on the anterior pelvic ring. The results of the treatment, including surgery duration, fluoroscopy frequency, total drilling, amount of blood loss, fracture healing time, and postoperative functional outcomes were recorded and compared with another 21 similar patients who underwent conventional manual positioning surgery.

Results

The TiRobot group incurred significantly shorter duration of surgery; less fluoroscopy frequency, intraoperative bleeding, and total drilling than in the conventional group (P < 0.05). Postoperative radiological follow‐up showed that all screws were in the safe area and no screw penetrated the cortex. All wounds healed by primary intention and no iatrogenic damage to the blood vessels, nerves, and organs occurred. Patients showed good tolerance to INFIX and reported no discomfort. The mean follow‐up duration was 5.4 months; the fractures were all healed, no loss of reduction occurred, and the mean Majeed score at the last follow‐up did not show any difference.

Conclusion

TiRobot‐assisted percutaneous screw placement combined with INFIX for the anterior and posterior pelvic ring injuries is accurate, safe, less invasive, and shows satisfactory efficacy, suggesting it is a better method for minimally invasive treatment of unstable pelvic ring fractures.

Complications Associated With Pelvic External Fixation

An external fixator is an essential tool for treating unstable pelvic ring injuries but its use carries risks, including pin-site infections and injury to the lateral femoral cutaneous nerve (LFCN). Surgeons currently lack data regarding these risks for patient counseling. This study aimed to identify the incidence of and risk factors for superficial and deep pin-site infection and LFCN damage. Fifty-two patients who underwent pelvic external fixation with anterior pin placement as part of definitive treatment for unstable pelvic ring disruption were retrospectively evaluated to identify factors associated with the development of infection. Ten (19%) patients developed superficial pin-site infections, with none developing a deep infection. Five were treated with oral antibiotics alone, 5 with additional intravenous antibiotics, and 1 underwent superficial surgical debridement at the time of external fixator removal. Three (6%) patients had temporary symptoms consistent with irritation to their LFCN that all resolved by 3 months. One (2%) patient had residual mild and intermittent LFCN dysesthesias at the 6-month follow-up. Adjusted logistic regression models identified no specific factors that were associated with increased risk of infection. The incidence of superficial infections related to pelvic external fixation was 19%, which can usually be treated with antibiotics with low risk of deep infection. In addition, there remains a low risk of long-term LFCN damage. Patients should be counseled on these risks during the perioperative period. [Orthopedics. 2017; 40(6):e959-e963.].

Minimally invasive treatment of unstable pelvic ring injuries with modified pedicle screw-rod fixator

Objective

To evaluate the clinical application of the minimally invasive modified pedicle screw–rod fixator for unstable pelvic ring injuries, including its feasibility, merits, and limitations.

Methods

Twenty-three patients (13 males, 10 females; average age, 36.3 years) with unstable pelvic ring injuries underwent anterior fixation using a modified pedicle screw–rod fixator with or without posterior fixation using a transiliac internal fixator. The clinical findings were assessed using Majeed scores. The quality of reduction was evaluated using the Matta criteria.

Results

Clinical results at 1 year postoperatively were excellent in 14 patients, good in 7, and fair in 2. The two patients with fair results had intermittent pain at the sacroiliac joint because of the posterior implant. One woman complained of persistent pain at the pubic tubercle during sexual intercourse. Iatrogenic neuropraxia of the unilateral lateral femoral cutaneous nerve occurred in three patients. Unilateral femoral nerve palsy occurred in one patient. The quality of fracture reduction was excellent in 12 patients, good in 8, and fair in 3. Heterotopic ossification occurred in eight patients; all were asymptomatic.

Conclusions

Minimally invasive modified pedicle screw-rod fixation is an effective alternative treatment for pelvic ring injuries.

Modified pedicle screw-rod fixation as a minimally invasive treatment for anterior pelvic ring injuries: an initial case series

Background

Unstable pelvic ring injuries often involve high mortality and morbidity. This study was aimed to evaluate the modified minimally invasive pedicle screw–rod fixation for anterior pelvic ring injuries, in the respects of its feasibility, merits, and limitations.

Methods

Twenty-three patients with unstable pelvic ring injuries underwent the modified anterior pedicle screw–rod fixation, with or without posterior fixation. The clinical outcomes were assessed using Majeed scores, and the quality of reduction was evaluated according to the criteria of Matta.

Results

Majeed scores showed that the clinical outcomes at postoperatively 1 year were excellent in 14 patients, good in 7, and fair in 2. One woman complained of persistent pain at the pubic tubercle during sexual intercourse. Iatrogenic neuropraxia of the unilateral lateral femoral cutaneous nerve occurred in 3 patients. Unilateral femoral nerve palsy occurred in 1 patient. The reduction was found to be excellent in 12 patients, good in 8, and fair in 3. Heterotopic ossification occurred in 8 patients, all being asymptomatic.

Conclusions

The modified pedicle screw–rod fixation with the minimally invasive technique offered an effective alternative for unstable anterior pelvic ring injuries.

Midterm Radiographic and Functional Outcomes of the Anterior Subcutaneous Internal Pelvic Fixator (INFIX) for Pelvic Ring Injuries

OBJECTIVE

To describe our experience using the anterior internal pelvic fixator (INFIX) for treating pelvic ring injuries.

DESIGN

Case Series.

SETTING

Level 1 Trauma Center.

PATIENTS

Eighty-three patients with pelvic ring injuries were treated with INFIX. Follow-up average was 35 months (range 12-80.33).

INTERVENTION

Surgical treatment of pelvic ring injuries included reduction, appropriate posterior fixation, and INFIX placement.

OUTCOME MEASUREMENTS

Reduction using the pelvic deformity index and pubic symphysis widening, Majeed functional scores, complications; infection, implant failure, heterotopic ossification (HO), nerve injury, and pain.

RESULTS

All patients healed in an appropriate time frame (full weight bearing 12 weeks postoperation). The average pelvic deformity index reduction (injury = 0.0420 ± 0.0412, latest FU = 0.0254 ± 0.0243) was 39.58%. The average reduction of pubic symphysis injuries was 56.92%. The average Majeed score of patients at latest follow-up was 78.77 (range 47-100). Complications were 3 infections, 1 case of implant failure, 2 cases implantation too deep, 7 cases of lateral femoral cutaneous nerve irritation, and 3 cases of pain associated with the device. HO was seen in >50% of the patients, correlated with increased age (P < 0.007), injury severity score (P < 0.05) but only 1 case was symptomatic.

CONCLUSIONS

The pelvic injuries had good functional and radiological outcomes with INFIX and the appropriate posterior fixation. The downside is removal requiring a second anesthetic, there is a learning curve, HO often occurs, the lateral femoral cutaneous nerve may get irritated which often resolves once the implants are removed. Surgery-specific implants need to be developed.

LEVEL OF EVIDENCE

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

[Percutaneous internal fixation of pelvic fractures. German version]

BACKGROUND

Percutaneous internal fixation of pelvic fractures is increasing in popularity with multiple new techniques reported.

OBJECTIVES

The purpose of this article is to outline the imaging, indication, planning, equipment, surgical technique and complications of these methods.

METHODS

A review of the literature is provided and the techniques for anterior and posterior pelvic stabilization are discussed.

RESULTS

High-quality preoperative CT scans are essential in planning for this technique. The anterior internal fixator ("InFix") is an effective method for stabilizing the anterior ring and should be usually used in conjunction with posterior fixation. Good technique avoids neurovascular injury, which can be a devastating complication. The retrograde anterior column screw (RACS) is a technique that can be used in most patients, although in smaller patients smaller screw diameters may be needed. The entry point for the screw is more lateral in women than men. Iliosacral screws (ISS) are an effective method of posterior stabilization and can be placed using 2D or 3D fluoroscopy, computer navigation or CT navigation.

CONCLUSION

Percutaneous fixation of pelvic fractures requires high-quality imaging and can be aided by computer navigation. Safe techniques are reproducible; however, not all patients and fracture patterns can be treated using these techniques.

Biomechanical characteristics of fixation methods for floating pubic symphysis

Background

Floating pubic symphysis (FPS) is a relatively rare injury caused by high-energy mechanisms. There are several fixation methods used to treat FPS, including external fixation, subcutaneous fixation, internal fixation, and percutaneous cannulated screw fixation. To choose the appropriate fixation, it is necessary to study the biomechanical performance of these different methods. The goal of this study was to compare the biomechanical characteristics of six methods by finite element analysis.

Methods

A three-dimensional finite element model of FPS was simulated. Six methods were used in the FPS model, including external fixation (Ext), subcutaneous rod fixation (Sub-rod), subcutaneous plate fixation (Sub-plate), superior pectineal plate fixation (Int-sup), infrapectineal plate fixation (Int-ifa), and cannulated screw fixation (Int-scr). Compressive and rotational loads were then applied in all models. Biomechanical characteristics that were recorded and analyzed included construct stiffness, micromotion of the fracture gaps, von Mises stress, and stress distribution.

Results

The construct stiffness of the anterior pelvic ring was decreased dramatically when FPS occurred. Compressive stiffness was restored by the three internal fixation and Sub-rod methods. Unfortunately, rotational stiffness was not restored satisfactorily by the six methods. For micromotion of the fracture gaps, the displacement was reduced significantly by the Int-sup and Int-ifa methods under compression. The internal fixation methods and Sub-plate method performed well under rotation. The maximum von Mises stress of the implants was not large. For the plate-screw system, the maximum von Mises stress occurred over the region of the fracture and plate-screw joints. The maximum von Mises stress appeared on the rod-screw and screw-bone interfaces for the rod-screw system.

Conclusions

The present study showed the biomechanical advantages of internal fixation methods for FPS from a finite element view. Superior stabilization of the anterior pelvic ring and fracture gaps was obtained by internal fixation. Subcutaneous fixation had satisfactory outcomes as well. Sub-rod fixation offered good anti-compression, while the Sub-plate fixation provided favorable anti-rotational capacity.