Biomechanical study of transsacral-transiliac screw fixation versus lumbopelvic fixation and bilateral triangular fixation for "H"- and "U"-type sacrum fractures with traumatic spondylopelvic dissociation: a finite element analysis study

Lumbopelvic Stabilization with Two Methods of Triangular Osteosynthesis: A Biomechanical Study

(1) Background: Pelvic fractures, and particularly instabilities of the dorsal pelvic ring, are becoming increasingly prevalent, particularly in orthogeriatric patients. Spino-pelvic triangular osteosynthesis is an effective approach to achieve sufficient stabilization in vertically unstable fractures. This study compares two types of osteosynthesis: the conventional one and a novel instrumentation where the iliosacral screw is placed through a fenestrated iliac screw. (2) Methods: Sixteen artificial osteoporotic L5+pelvis models with an unstable sacral fracture have been instrumented with either an iliac screw connected with a rod to a L5 pedicle screw and an iliosacral screw (TF) or a fenestrated ilium screw connected with a rod to a L5 pedicle screw and an iliosacral screw passing through the fenestra of the iliac screw (TFS). Biomechanical testing was performed using cyclic loading until failure. (3) Results: Both configurations yielded comparable results with regard to initial stiffness, implant loosening, and cycles to failure. The TFS exhibited markedly higher values for cycles to failure and markedly lower values for loosening. However, due to the characteristics of the artificial bone model, these findings were not significant. (4) Conclusions: The novel triangular fixation systems demonstrated comparable results to the standard triangular osteosynthesis configuration.

Lumbopelvic fixation in the treatment of spinopelvic dissociation: union, complications, and neurologic outcomes of a multicenter case series

PURPOSE

To review outcomes of spinopelvic dissociation treated with open lumbopelvic fixation.

METHODS

We reviewed all cases of spinopelvic dissociation treated at three Level-I trauma centers with open lumbopelvic fixation, including those with adjunctive percutaneous fixation. We collected demographic data, associated injuries, pre- and postoperative neurologic status, pre- and postoperative kyphosis, and Roy-Camille classification. Outcomes included presence of union, reoperation rates, and complications involving hardware or wound.

RESULTS

From an initial cohort of 260 patients with spinopelvic dissociation, forty patients fulfilled inclusion criteria with a median follow-up of 351 days. Ten patients (25%) had a combination of percutaneous iliosacral and open lumbopelvic repair. Average pre- and postoperative kyphosis was 30 degrees and 26 degrees, respectively. Twenty patients (50%) had neurologic deficit preoperatively, and eight (20%) were unknown or unable to be assessed. All patients presenting with bowel or bladder dysfunction (n = 12) underwent laminectomy at time of surgery, with 3 patients (25%) having continued dysfunction at final follow-up. Surgical site infection occurred in four cases (10%) and wound complications in two (5%). All cases (100%) went on to union and five patients (13%) required hardware removal.

CONCLUSION

Open lumbopelvic fixation resulted in a high union rate in the treatment of spinopelvic dissociation. Approximately 1 in 6 patients had a wound complication, the majority of which were surgical site infections. Bowel and bladder dysfunction at presentation were common with the majority of cases resolving by final follow-up when spinopelvic dissociation had been treated with decompression and stable fixation.

Posterior pelvic ring injuries, lumbosacral junction instabilities and stabilization techniques for spinopelvic dissociation: a narrative review

INTRODUCTION

From transiliac Harrington rods to minimally invasive (MIS) percutaneous 3D-navigated transsacral-transiliac screw (TTS) fixation, concepts of fixation methods in pelvic injuries with spinopelvic dissociation (SPD) are steadily redefined. This narrative review examines the literature of recent years regarding surgical treatment options and trends in SPD, outlining risks and benefits of each treatment option and addressing biomechanical aspects of sacral injuries and common classification systems.

MATERIALS AND METHODS

A literature search on the search across relevant online databases was conducted. As a scale for quality assessment, the SANRA-scoring system was taken into account.

RESULTS

Sacral Isler type 1 injuries of the LPJ in U- and H-type fractures are frequently treated with stand-alone TTS. Fractures with higher instability (Isler types 2 and 3) require unilateral or bilateral LPF, subject to side involvement, as a buttressing construct, or triangular fixation as additional compression and neutralization, determined by fracture radiation. A more comprehensive classification from which to derive stabilization options is provided by the 2023 301SPD classification. MIS techniques are on the rise and offer shorter OR time, less blood loss, fewer infections, and fewer wound complications. It is advisable to implement MIS techniques as much as possible, as long as decompression is not required and closed fracture reduction succeeds satisfactorily.

CONCLUSION

SPD is characteristic of severe injuries, mostly in polytraumatized patients. The complication rates are decreasing due to the increasing adaptation of MIS techniques.

Patient-specific bone material modelling can improve the predicted biomechanical outcomes of sacral fracture fixation techniques: A comparative finite element study

OBJECTIVE

To evaluate and compare the biomechanical efficacy of six iliosacral screw fixation techniques for treating unilateral AO Type B2 (Denis Type II) sacral fractures using literature-based and QCT-based bone material properties in finite element (FE) models.

METHODS

Two FE models of the intact pelvis were constructed: the literature-based model (LBM) with bone material properties taken from the literature, and the patient-specific model (PSM) with QCT-derived bone material properties. Unilateral transforaminal sacral fracture was modelled to assess different fixation techniques: iliosacral screw (ISS) at the first sacral vertebra (S1) (ISS1), ISS at the second sacral vertebra (S2) (ISS2), ISS at S1 and S2 (ISS12), transverse iliosacral screws (TISS) at S1 (TISS1), TISS at S2 (TISS2), and TISS at S1 and S2 (TISS12). A 600 N vertical load with both acetabula fixed was applied. Vertical stiffness (VS), relative interfragmentary displacement (RID), and the von Mises stress values in the screws and fracture interface were analysed.

RESULTS

The lowest and highest normalised VS was given by ISS1 and TISS12 techniques for LBM and PSM, with 137 % and 149 %, and 375 % and 472 %, respectively. In comparison with the LBM, the patient-specific bone modelling increased the maximum screw stress values by 19.3, 16.3, 27.8, 2.3, 24.4 and 7.8 % for ISS1, ISS2, ISS12, TISS1, TISS2 and TISS12, respectively. The maximum RID values were between 0.10 mm and 0.47 mm for all fixation techniques in both models. The maximum von Mises stress results on the fracture interface show a substantial difference between the two models, as PSM (mean ± SD of 15.76 ± 8.26 MPa) gave lower stress values for all fixation techniques than LBM (mean ± SD of 28.95 ± 6.91 MPa).

CONCLUSION

The differences in stress distribution underline the importance of considering locally defined bone material properties when investigating internal mechanical parameters. Based on the results, all techniques demonstrated clinically sufficient stability, with TISS12 being superior from a biomechanical standpoint. Both LBM and PSM models indicated a consistent trend in ranking the fixation techniques based on stability. However, long-term clinical trials are recommended to confirm the findings of the study.

Sacroiliac versus transiliac-transsacral screw osteosynthesis in osteoporotic pelvic fractures: a biomechanical comparison

INTRODUCTION

Pelvic fractures were often associated with high-energy trauma in young patients, but data show a significant increase in osteoporotic pelvic fractures in old age due to the progressive demographic change. There is an ongoing discussion about the best fixation techniques, which are ranging from lumbopelvic fixation to sacral bars or long transiliac-transsacral (TITS) screws. This study analyzes TITS screw osteosynthesis and sacroiliac screw osteosynthesis (SI), according to biomechanical criteria of fracture stability in osteoporotic human pelvic cadavers ex vivo.

METHODS

Ten osteoporotic cadaveric pelvises were randomized into two groups of 5 pelvises each. An FFP-IIc fracture was initially placed unilaterally and subsequently surgically treated with a navigated SI screw or a TITS screw. The fractured side was loaded in a one-leg stance test setup until failure. Interfragmentary movements were assessed by means of optical motion tracking.

RESULTS

No significant difference in axial stiffness were found between the SI and the TITS screws (21.2 ± 4.9 N and 18.4 ± 4.1 N, p = 0.662). However, there was a significantly higher stability of the fracture treatment in the cohort with TITS-screws for gap angle, flexion, vertical movement and overall stability. The most significant difference in the cycle interval was between 6.000 and 10.000 for the gap angle (1.62 ± 0.25° versus 4.60 ± 0.65°, p = 0.0001), for flexion (4.15 ± 0.39 mm versus 7.60 ± 0.81 mm, p = 0.0016), interval 11.000-15.000 for vertical shear movement (7.34 ± 0.51 mm versus 13.99 ± 0.97 mm, p < 0.0001) and total displacement (8.28 ± 0.66 mm versus 15.53 ± 1.07 mm, p < 0.0001) for the TITS and the SI screws.

CONCLUSIONS

The results of this biomechanical study suggest a clear trend towards greater fracture stability of the TITS screw with significantly reduced interfragmentary movement. The application of a TITS screw for the treatment of the osteoporotic pelvic ring fracture may be prioritized to ensure the best possible patient care.

Surgical Management of Unstable U-Shaped Sacral Fractures and Tile C Pelvic Ring Disruptions: Institutional Experience in Light of a Narrative Literature Review

Unstable U-shaped sacral fractures and vertical shear Tile C pelvic ring disruptions are characterized by rare lesions occurring in patients with severe trauma. Because the initial damage-control resuscitation primarily aims to stop life-threatening bleeding, emergency treatment often includes an anterior external pelvic fixator. Delayed surgery is mandatory to allow early mobilization, reduce mortality, and improve functional outcomes. Regarding U-shaped sacral fractures, although Roy-Camille type 1 U-shaped sacral fractures can be treated with iliosacral screws, types 2 (posteriorly displaced, equivalent to AO Spine C3) and 3 (anteriorly displaced, equivalent to AO Spine C3) fractures require spinopelvic triangular fixation. Besides, proper reduction of type 2 and some type 3 sacral fractures is mandatory to prevent wound complications. In patients with neurological deficits, the need for sacral laminectomy is left at the discretion of the surgeon, given the indirect decompression already obtained with fracture reduction. Tile C pelvic disruptions with posterior ring injury located lateral to the sacral foramen can be treated with either iliosacral screws or triangular spinopelvic fixation, combined with anterior pelvic fixation. Conversely, Tile C pelvic disruptions with posterior ring injury located at, or medial, to the sacral foramen (Denis zone II or III) induce vertical lumbosacral instability and thus require spinopelvic triangular fixation with anterior pelvic osteosynthesis. Although minimally invasive techniques have been developed, open surgeries are still required for inexperienced operators and in case of major displacement. The complication rate reaches approximately 33.33% of the cases, and complications include hardware malposition, wound infection or dehiscence, hardware prominence, and sometimes hardware failure.

[Sacral H-shaped fractures between traumatic, insufficiency and fatigue fractures : Similarities, differences and controversies]

In the basic entirety of stress fractures, insufficiency fractures are defined as fractures caused by prolonged normal or physiological loading of a bone with insufficient elastic resistance. This clearly distinguishes it from fatigue fractures, in which excessive loads are continuously applied to a bone with normal elastic resistance. According to Pentecost (1964) both entities of stress fracture result from "the inherent inability of the bone to withstand stress applied without violence in a rhythmical, repeated, subthreshold manner". This distinguishes them from acute traumatic fractures. In the clinical routine these differences are not always so clearly presented. The example of the H‑shaped sacral fracture is used to illustrate the relevance of a clear terminology. In this context, current controversies in the treatment of sacral insufficiency fractures are discussed.

Management of C0 Sacral Fractures Based on the AO Spine Sacral Injury Classification: A Narrative Review

The Arbeitsgemeinschaft fur Osteosynthese fragen Spine Sacral Injury Classification hierarchically separates fractures based on their injury severity with A-type fractures representing less severe injuries and C-type fractures representing the most severe fracture types. C0 fractures represent moderately severe injuries and have historically been referred to as nondisplaced "U-type" fractures. Injury management of these fractures can be controversial. Therefore, the purpose of this narrative review is to first discuss the Arbeitsgemeinschaft fur Osteosynthese fragen Spine Sacral Injury Classification System and describe the different fracture types and classification modifiers, with particular emphasis on C0 fracture types. The narrative review will then focus on the epidemiology and etiology of C0 fractures with subsequent discussion focused on the clinical presentation for patients with these injuries. Next, we will describe the imaging findings associated with these injuries and discuss the injury management of these injuries with particular emphasis on operative management. Finally, we will outline the outcomes and complications that can be expected during the treatment of these injuries.

Spinopelvic dissociation: extended definition, physical examination, classification, and therapy

BACKGROUND

Spinopelvic dissociation (SPD) is generally caused by high-energy injury mechanisms, and, in the absence of timely diagnosis and treatment, it can lead to chronic pain and progressive deformity. However, SPD is difficult to manage because of its rarity and complexity. In this study, we re-defined SPD according to the mechanism of injuries and biomechanical characteristics of the posterior pelvic ring and developed new classification criteria and treatment principles based on the classification for SPD.

METHODS

Between June 2015 and September 2020, 30 patients with SPD which were selected from 138 patients with pelvic fractures were enrolled. Physical examination was performed, classification criteria (301 SPD classification) were developed, and specific treatment standards were established according to the classifications.

RESULTS

The injury mechanisms and co-existing injuries did not significantly differ between the classical SPD patients and expanded SPD patients. The 301 SPD classification criteria covered all the patients. Fixation by biplanar penetration screws was used in 7 patients, 11 patients received fixation by uniplanar penetration screws, 6 patients used sacroiliac compression screws, 3 patients received uniplanar screws combined with sacroiliac compression screws, and open spondylopelvic fixation was used in only 3 patients. According to the Matta criteria, 19, 7, and 4 patients achieved excellent, good, and fair reduction. The Majeed function score of the patients ranged from 9 to 96 points, and the mean score was 72.9 ± 24.6 points.

CONCLUSION

The expanded definition for SPD is particularly significant for definite diagnosis and prevention of missing diagnosis, based on which the 301SPD classification criteria can more systemically guide the clinical treatment of SPD, increase the treatment efficacy, and reduce surgical trauma. Chinese Clinical Trial Registry: ChiCTR-IPR-16009340.

Effective treatment of highest instability in a subacute fragility fracture of the pelvis (FFP IV) using a cement augmented transsacral screw only

The highest instability in fragility fractures of the pelvis (FFP) is noted in presence of H-, U-type sacral fractures. Suggested surgical treatment options include uni- or bilateral sacroiliac or transsacral screw fixation at different levels or in combination, as well as lumbopelvic and bilateral triangular lumbopelvic stabilization. However, distinct treatment recommendations for this subset of injuries are scarce. We present a case sustaining rapid FFP crescendo instability following initial conservative treatment of a FFP type II injury resulting in a U-type spinopelvic dissociation. Fixation using one percutaneous cement augmented transsacral S1 screw resulted in perpetual clinical improvements in pain and mobility in presence of radiologic fracture consolidation.

Causes of Increased Use of Closed Reduction and Internal Fixation for High-Energy-Related Traumatic Sacral Fractures

BACKGROUND

Reasons for the increased use of closed reduction and internal fixation (CRIF) for traumatic sacral fractures (SFs) are unclear in the literature. Therefore, we aimed to report the annual changes in the number of patients, mechanisms of injury, fracture patterns, and fixation methods.

METHODS

In this retrospective study, we extracted data of 271 patients (mean age, 37.5 years) from the trauma register over an 8-year period. Annual records regarding the number of patients, injury mechanisms, fracture types, and treatment options were statistically analyzed to examine the interactions among these factors.

RESULTS

The number of patients with SFs increased significantly each year. The rate of admission to the intensive care unit after resuscitation was high (64.9%). Arbeitsgemeinschaft für Osteosynthesefragen (AO) type C pelvic ring injury (PRI), Dennis zone II injury, Roy-Camille type 2 injury, and U/H-type injury were the most common fracture types. Trans-iliac trans-sacral screws were mainly used in AO type B PRI, and their use significantly increased each year. For AO type C PRI, open reduction and internal fixation (ORIF) with rigid fixation was the main treatment, and the use of CRIF with iliosacral screws decreased each year. Stepwise statistical analysis revealed that the increase in AO type B PRI and ORIF for anterior PRI were the factors contributing to the increased use of CRIF for SFs.

CONCLUSIONS

While the use of osteosynthesis for SFs is increasing, an increased use of CRIF for traumatic SFs has also been observed in clinical practice. This increase can be attributed to the increase in AO type B PRIs and ORIF for anterior PRIs.

The surgical management of highly unstable fragility fractures of the sacrum with spinopelvic dissociation: A case series and proposal of a surgical treatment algorithm

INTRODUCTION

U- and H-shaped fragility fractures of the sacrum (FFP IVb) are unstable fractures. Non-operative treatment may be associated with impaired walking abilities, chronic pain and the potential loss of independency. However, different treatment options are still controversially debated. The aim of surgical treatment includes sufficient fracture stability for immediate full weight bearing and good pain control postoperatively. A new surgical treatment algorithm was developed. This algorithm was evaluated in a cohort of geriatric patients with FFP type IVb regarding surgical complications and patient-related outcome.

METHODS

Retrospective case series. Patients ≥65 years, admitted with FFP IVb between 01/2017 and 12/2020 were included. Pelvic CT was performed and the surgical technique was chosen according to the proposed surgical treatment algorithm. For this algorithm, the technique of fracture stabilisation was adapted to sacral anatomy and the specific fracture pattern to minimize the impact of surgery and postoperative complications without compromising a sufficient fracture stability. Pain levels, complications and surgical revisions were recorded. Level of independency, walking abilities and -aids were compared 3- and 12- months postoperatively to the pre-injury situation.

RESULTS

Twenty-three patients were included. Outcome parameters could be obtained in 20 patients (85%) after three months and in 18 patients (78%) patients one year postoperatively. All patients were treated according to the algorithm. Sixteen patients received two transilio-transsacral screws (TI-TSS), whereas either lumbopelvic fixation (LPF) combined with a TI-TSS or bilateral ilio-sacral screws (ISS) was performed four times. Three patients underwent bilateral ISS into S1 with one TI-TSS into S2. Three days postoperatively, median pain VAS was 2 (0-8) compared to 7 (4-10) before surgery. One loosened TI-TSS was removed six weeks postoperatively. Three-month mortality was 14% (n=3). At one-year follow-up, all patients regained their pre-injury level of walking abilities.

CONCLUSIONS

Restoration of walking abilities, preservation of independency and efficient pain control can be achieved with surgical fixation of FFP type IVb fractures. With the proposed surgical algorithm, the fixation techniques are adapted to the fracture pattern to minimize the surgical burden.

LEVEL OF EVIDENCE

IV.

Future Directions in Patellofemoral Imaging and 3D Modeling

PURPOSE OF REVIEW

Patellofemoral instability involves complex, three-dimensional pathological anatomy. However, current clinical evaluation and diagnosis relies on attempting to capture the pathology through numerous two-dimensional measurements. This current review focuses on recent advancements in patellofemoral imaging and three-dimensional modeling.

RECENT FINDINGS

Several studies have demonstrated the utility of dynamic imaging modalities. Specifically, radiographic patellar tracking correlates with symptomatic instability, and quadriceps activation and weightbearing alter patellar kinematics. Further advancements include the study of three-dimensional models. Automation of commonly utilized measurements such as tibial tubercle-trochlear groove (TT-TG) distance has the potential to resolve issues with inter-rater reliability and fluctuation with knee flexion or tibial rotation. Future directions include development of robust computational models (e.g., finite element analysis) capable of incorporating patient-specific data for surgical planning purposes. While several studies have utilized novel dynamic imaging and modeling techniques to enhance our understanding of patellofemoral joint mechanics, these methods have yet to find a definitive clinical utility. Further investigation is required to develop practical implementation into clinical workflow.