Andreas Höch

Clinical implementation of finite element models in pelvic ring surgery for prediction of implant behavior: A case report

BACKGROUND Osteosyntheses to stabilize pelvic-ring fractures were developed for younger patients, and are not universally indicated for elderly people. We present the results of parallel-arranged numerical simulations of fixation treatment that an elderly patient with a bagatelle-injured pelvic ring fracture received using a patient-specific finite element model. METHODS The clinical course of an osteosynthetic stabilized pelvic ring fracture, based on an actual case, was numerically simulated using a patient-specific finite element model. FINDINGS A previously validated finite element model of a human pelvis was customized with computed tomography data from a patient with a stabilized pelvic-ring fracture. Numerical simulation was used to analyze primary stability. The clinical process, represented by radiologic examinations, was compared with the results from the finite element simulation. Implant loosening as well as newly-occurring fractures were shown to coincide with regions with the highest stress levels. INTERPRETATION The results from the patient-specific finite element model closely resembled the actual clinical course especially in terms of the location of high strain concentration and subsequent implant loosening. This indicates that patient-specific finite element models have a potential to play an important role in planning osteosynthesis according to biomechanical stability.

Outcome and 2-Year Survival Rate in Elderly Patients With Lateral Compression Fractures of the Pelvis:

Introduction: Osteoporotic pelvic ring fractures are a rising problem for surgeons in industrialized countries. There is no evidence-based treatment strategy especially for lateral compression (LC) fractures involving the sacrum. The aim of this study was to evaluate and compare outcome and survival rate of nonoperative and operative treatment strategies for lateral compression fractures. Patients and Methods: In a retrospective study, 128 patients (aged ≥65 years) with an Orthopedic Trauma Association (OTA) types B2.1 and B3.3 fracture were included and analyzed regarding demographic and treatment data and adverse events. After a follow-up period of at least 2-year survival rate, quality of life and pain were evaluated using the EuroQol-5D and Short Form–12 questionnaires and the visual analog scale. Results: Fifty patients (78.3 ± 7.6 years) obtained operative treatment and 77 patients (82.7 ± 7.9 years) obtained nonoperative treatment. One died within 24 hours after admission. High rates of complications occurred in both groups (operative group: 18% and nonoperative group: 8%). Eighteen percent (14 of the 77) of conservatively treated patients needed operative treatment after discharge due to worsening pain and mobilization. The 2-year follow-up showed a high overall mortality (30%), with a significant higher survival rate for operatively treated patients (2-year survival: operatively treated 82% vs conservative 61%). No difference was found in pain and quality of life. Discussion: Elderly patients display a high rate and variety of complications and mortality in the aftermath of lateral compression fractures of the pelvis. Although a significantly higher 2-year survival rate for operatively treated patients was found, this study cannot give proof of superior position for operative treatment. Due to lacking data for alternative treatment algorithms especially for fracture-related immobilized patients, we recommended operative treatment with the aim to reduce complications related to prolonged bed rest and ensure early mobilization.

Biomechanical analysis of stiffness and fracture displacement after using PMMA-augmented sacroiliac screw fixation for sacrum fractures

Abstract Cement augmentation of pedicle screws is the gold standard for the stabilization of osteoporotic fractures of the spine. In-screw cement augmentation, in which cement is injected through the cannula, is another option for fracture stabilization of fragility fractures of the sacrum. However, biomechanical superiority of this technique compared to conventional sacroiliac screw fixation has not been tested. The present study compares the stability of cement-augmented and non-cement-augmented sacroiliac screw fixation in osteoporotic sacrum fractures under cyclic loading. Eight human donor pelvises with intact ligaments and 5th lumbar vertebra were dissected. A vertical shear fracture was created as a combination of a sacrum fracture and cutting of the symphysis. Both sides were tested in a single-limb-stance setup with 10,000 loading cycles applied. Stiffness of the pelvis and displacement of the fracture were measured using a hydraulic testing machine and a 3D image correlation system. The augmented screw fixation failed in two of eight pelvises, and the non-augmented screws failed in three of eight pelvises. CT scans showed no leakage of cement. In-screw polymethylmethacrylate (PMMA) augmentation showed no advantage based on measured displacement of the sacrum fractures or stiffness for sacroiliac screw fixation of fragility fractures of the sacrum.

Ligament‐induced sacral fractures of the pelvis are possible

Pelvic ring stability is maintained passively by both the osseous and the ligamentous apparatus. Therapeutic approaches focus mainly on fracture patterns, so ligaments are often neglected. When they rupture along with the bone after pelvic ring fractures, disrupting stability, ligaments need to be considered during reconstruction and rehabilitation. Our aim was to determine the influence of ligaments on open‐book injury using two experimental models with body donors. Mechanisms of bone avulsion related to open‐book injury were investigated. Open‐book injuries were induced in human pelves and subsequently investigated by anatomical dissection and endoscopy. The findings were compared to CT and MRI scans of open‐book injuries. Relevant structures were further analyzed using plastinated cross‐sections of the posterior pelvic ring. A fragment of the distal sacrum was observed, related to open‐book injury. Two ligaments were found to be responsible for this avulsion phenomenon: the caudal portion of the anterior sacroiliac ligament and another ligament running along the ventral surface of the third sacral vertebra. The sacral fragment remained attached to the coxal bone by this second ligament after open‐book injury. These results were validated using plastination and the structures were identified. Pelvic ligaments are probably involved in sacral avulsion caused by lateral traction. Therefore, ligaments should to be taken into account in diagnosis of open‐book injury and subsequent therapy. Clin. Anat. 27:770–777, 2014.

In-screw polymethylmethacrylate-augmented sacroiliac screw for the treatment of fragility fractures of the pelvis: a prospective, observational study with 1-year follow-up

BackgroundThe incidence of pelvic ring fractures in the elderly significantly increased. Because of persistent pain and immobilization associated with this injury, surgical treatment is recommended. To minimise comorbidities and surgical risk, percutaneous techniques are becoming more relevant. In-screw cement augmentation of sacroiliac screw fixation is a promising procedure; however, clinical follow-up data remain scarce. This study investigated the safety and possible complications of the procedure along with a 1-year follow-up.MethodsThirty-four patients (treated with 43 screws) were prospectively included. Data on patients’ age and sex, the mechanism of accident, fracture pattern, duration of hospital stay, surgery and adverse events were recorded. Data were obtained postoperatively on the reduction of pain and complications, such as infection, cement leakage and neurological deficits, and at 1-year follow-up on pain, quality of life according to the 12-Item Short Form Survey and mobility. Implant failure was defined as retraction or dislocation of screws and was also documented.ResultsScrew-related complications occurred with 2 of 43 screws. None of these complications were related to cement augmentation. In-hospital adverse events occurred in 6 of 34 patients. Postoperative pain, measured by the visual analogue scale, was significantly reduced from 6.7 ± 1.4 preoperatively to 2.7 ± 1.0 postoperatively (p < 0.001). Although patients complained of pain at the 1-year follow-up, they reported a significant decline compared with pain at admission (3.4 ± 2.3; p < 0.001). Results on the quality of life were comparable with those for the age- and gender matched German population. All patients were mobile, and no implant failure was detected.ConclusionsThe results indicate that in-screw augmented sacroiliac screw fixation for fragility fractures of the pelvis is a safe technique. Pain was significantly reduced immediately after surgery compared to the preoperative state. Furthermore, significant pain reduction after one year compared to the preoperative state and quality of life was comparable to the age- and gender- matched German population. Thus, we recommend in-screw augmentation for screw fixation for sacral fragility fractures of the pelvis following failed conservative treatment.

Effects of Cutting the Sacrospinous and Sacrotuberous Ligaments: Effects of Cutting the Sacrospinous and Sacrotuberous Ligaments

The sacrospinous (SS) and sacrotuberous (ST) ligaments form a complex at the posterior pelvis, with an assumed role as functional stabilizers. Experimental and clinical research has yielded controversial results regarding their function, both proving and disproving their role as pelvic stabilizers. These findings have implications for strategies for treating pelvic injury and pain syndromes. The aim of the present simulation study was to assess the influence of altered ligament function on pelvis motion. A finite elements computer model was used. The two‐leg stance was simulated, with the load of body weight applied via the fifth lumbar vertebra and both femora, allowing for nutation of the sacroiliac joint. The in‐silico kinematics were validated with in‐vitro experiments using the same scenario of load application following SS and ST transection in six human cadavers. Modeling of partial or complete ligament failure caused significant increases in pelvis motion. This effect was most pronounced if the SS and ST were affected with 164% and 182%, followed by the sacroiliac and iliolumbar ligaments with 123% and 147%, and the pubic ligaments with 113% and 119%, for partial and complete disruption, respectively. Simultaneous ligament transection multiplied the effects on pelvis motion by up to 490%. Unilateral ligament injury altered the motion at the pelvis contralaterally. The experiments presented here provide strong evidence for the stabilizing role of the SS and ST. A fortiori, the instability resulting from partial or complete SS and ST injury merits consideration in treatment strategies involving these ligaments as important stabilizers. Clin. Anat. 32:231–237, 2019.

Corrigendum to “Development of a Patient-Specific Finite Element Model for Predicting Implant Failure in Pelvic Ring Fracture Fixation”

[This corrects the article DOI: 10.1155/2017/9403821.].

Severe cardiac trauma or myocardial ischemia? Pitfalls of polytrauma treatment in patients with ST-elevation after blunt chest trauma.

Introduction Thoracic injuries are the third most common injuries in polytrauma patients. The mechanism of injury and the clinical presentation are crucially important for adequate emergency treatment. Presentation of case Here we present a case of a 37-year-old male who was admitted to our level-1 trauma center after motor vehicle accident. The emergency physician on scene presented the patient with a myocardial infarction. During initial clinical trauma assessment the patient developed circulatory insufficiency so that cardiopulmonary resuscitation was necessary. Considering the preclinical and clinical course it was decided to proceed with thrombolysis. Despite consistently sufficient resuscitation measures circulatory function was not restored and the patient remained in asystole and passed away. Discussion The initial assessment showed cardiopulmonary instability. After applying thrombolysis a therapeutic point of no return was reached because surgical intervention was impossible but autopsy findings showed severe myocardial and pulmonary contusions likely due to shear forces. Conclusion This case outlines the importance of understanding the key mechanism of injury and the importance of communication at each stage of healthcare transfer. A transesophageal echocardiography can help to identify injuries after myocardial contusion.