Semi-automated finite element analyses of surgically treated acetabular fractures to investigate the biomechanical behaviour of patient-specific compared to conventional implants.

BACKGROUND: In acetabular fracture surgery, understanding the biomechanical behaviour of fractures and implants is beneficial for clinical decision-making about implant selection and postoperative (early) weightbearing protocols. This study outlines a novel approach for creating finite element models (FEA) from actual clinical cases. Our objectives were to (1) create a detailed semi-automatic three-dimensional FEA of a patient with a transverse posterior wall acetabular fracture and (2) biomechanically compare patient-specific implants with manually bent off-the-shelf implants. METHODS: A computational study was performed in which we developed three finite element models. The models were derived from clinical imaging data of a 20-year-old male with a transverse posterior wall acetabular fracture treated with a patient-specific implant. This implant was designed to fit the patient's anatomy and fracture configuration, allowing for optimal placement and predetermined screw trajectories. The three FEA models included an intact hemipelvis for baseline comparison, one with a fracture fixated with a patient-specific implant, and another with a conventional implant. Two loading conditions were investigated: standing up and peak walking forces. Von Mises stress and displacement patterns in bone, implants and screws were analysed to assess the biomechanical behaviour of fracture fixation with either a patient-specific versus a conventional implant. RESULTS: The finite element models demonstrated that for a transverse posterior wall type fracture, a patient-specific implant resulted in lower peak stresses in the bone (30 MPa and 56 MPa) in standing-up and peak walking scenario, respectively, compared to the conventional implant model (46 MPa and 90 MPa). The results suggested that patient-specific implant could safely withstand standing-up and walking after surgery, with maximum von Mises stresses in the implant of 156 MPa and 371 MPa, respectively. The results from the conventional implant indicate a likelihood of implant failure, with von Mises stresses in the implant (499 MPa and 1000 MPa) exceeding the yield stress of stainless steel. CONCLUSION: This study presents a workflow for conducting finite element analysis of real clinical cases in acetabular fracture surgery. This concept of personalized biomechanical fracture and implant assessment can eventually be applied in clinical settings to guide implant selection, compare conventional implants with innovative patient-specific ones, optimizing implant designs (including shape, size, materials, screw positions), and determine whether immediate full weight-bearing can be safely permitted.

What is the long-term clinical outcome after fragility fractures of the pelvis? - A CT-based cross-sectional study.

BACKGROUND: Recently, Rommens and Hoffman introduced a CT-based classification system for fragility fractures of the pelvis (FFP). Although fracture characteristics have been described, the relationship with clinical outcome is lacking. The purpose of this study was to get insight into the type of treatment and subsequent clinical outcome after all types of FFP. METHODS: A cross-sectional cohort study was performed including all elderly patients (≥ 65 years) with a CT-diagnosed FFP, between 2007-2019 in two level 1 trauma centers. Data regarding treatment, mortality and clinical outcome was gathered from the electronic patient files. Patients were asked to complete patient-reported outcome measures (PROMs) regarding physical functioning (SMFA) and quality of life (EQ-5D). Additionally, a standardized multidisciplinary treatment algorithm was constructed. RESULTS: A total of 187 patients were diagnosed with an FFP of whom 117 patients were available for follow-up analysis and 58 patients responded. FFP type I was most common (60%), followed by type II (27%), type III (8%) and type IV (5%). Almost all injuries were treated non-operatively (98%). Mobility at six weeks ranged from 50% (type III) to 80% type II). Mortality at 1 year was respectively 16% (type I and II), 47% (type III) and 13% (type IV). Physical functioning (SMFA function index) ranged from 62 (type III and IV) to 69 (type II) and was significantly decreased (P=<0.001) compared to the age-matched general population. Quality of life was also significantly decreased, ranging from 0.26 (type III) to 0.69 (type IV). CONCLUSIONS: FFP type I and II are most common. Treatment is mainly non-operative, resulting in good mobility after six weeks, especially for patients with FFP type I and II. Mortality rates at one year were substantial in all patients. Physical functioning and quality of life was about 20-30% decreased compared to the general population.

The accuracy of gap and step-off measurements in acetabular fracture treatment.

The assessment of gaps and steps in acetabular fractures is challenging. Data from various imaging techniques to enable accurate quantification of acetabular fracture displacement are limited. The aim of this study was to assess the accuracy of pelvic radiographs, intraoperative fluoroscopy, and computed tomography (CT) in detecting gaps and step-offs in acetabular fractures. Sixty patients, surgically treated for acetabular fractures, were included. Five observers (5400 measurements) measured the gaps and step-offs on radiographs and CT scans. Intraoperative fluoroscopy images were reassessed for the presence of gaps and/or step-offs. Preoperatively, 25% of the gaps and 40% of the step-offs were undetected on radiographs compared to CT. Postoperatively, 52% of the gaps and 80% of the step-offs were missed on radiographs compared to CT. Radiograph analysis led to a significantly smaller gap and step-off compared to the CT measurements, an underestimation by a factor of two. Approximately 70% of the residual gaps and step-offs was not detected using intraoperative fluoroscopy. Gaps and step-offs that exceed the critical cut-off indicating worse prognosis often remained undetected on radiographs compared to CT scans. Less-experienced observers tend to overestimate gaps and step-offs compared to the more-experienced observers. In acetabular fracture treatment, gaps and step-offs were often undetected and underestimated on radiographs and intraoperative fluoroscopy in comparison with CT scans. This means that CT is superior to radiographs in detecting acetabular fracture displacement, which is clinically relevant for patient counselling regarding treatment decisions and prognosis.

Quantitative 3D measurements of tibial plateau fractures.

Fracture gap and step-off measurements on 2DCT-slices probably underestimate the complex multi-directional features of tibial plateau fractures. Our aim was to develop a quantitative 3D-CT (Q3DCT) fracture analysis of these injuries. CT-based 3D models were created for 10 patients with a tibial plateau fracture. Several 3D measures (gap area, articular surface involvement, 3D displacement) were developed and tested. Gaps and step-offs were measured in 2D and 3D. All measurements were repeated by six observers and the reproducibility was determined by intra-class correlation coefficients. Q3DCT measurements demonstrated a median gap of 5.3 mm, step-off of 5.2 mm, gap area of 235 mm2, articular surface involvement of 33% and 3D displacement of 6.1 mm. The inter-rater reliability was higher in the Q3DCT than in the 2DCT measurements for both the gap (0.96 vs. 0.81) and step-off (0.63 vs. 0.32). Q3DCT measurements showed excellent reliability (ICC of 0.94 for gap area, 1 for articular surface involvement and 0.99 for 3D displacement). Q3DCT fracture analysis of tibial plateau fractures is feasible and shows excellent reliability. 3D measurements could be used together with the current classification systems to quantify the true extent of these complex multi-directional fractures in a standardized way.

Introduction of a three-dimensional computed tomography measurement method for acetabular fractures.

INTRODUCTION: Acetabular fractures consist of complex fracture patterns whereby bone fragments are displaced in different directions. Two-dimensional computed tomography (2DCT) gap and step-off measurements tend to underestimate the multidirectional features of these fractures. The aim was to develop a three-dimensional computed tomography (3DCT) measurement method for acetabular fractures and validate whether this method will provide an observer independent fracture characterization. MATERIALS AND METHODS: Sixty patients, operated for an acetabular fracture between 2007 and 2018, were included. The displacement was measured on the pre- and postoperative CT scans. Pre- and postoperative CT-based 3D models were made for each patient. Multiple 3D measurements, namely the 3D step-off, gap and the total gap area were introduced to quantify the preoperative and postoperative displacement. The Wilcoxon signed rank analysis was used to compare the 2DCT and 3DCT measurements. RESULTS: The preoperative displacement was significantly underestimated by 2DCT measurements in comparison with 3DCT measurements (2D vs. 3D; step-off 8 vs. 16 mm with P < 0.001; gap 19 vs. 21 mm with P = 0.001). The same applies to the postoperative residual displacement (2D vs. 3D; step-off 0 vs. 6 mm; gap 3 vs. 8 mm; P < 0.001). The total gap area, defined as the surface area between all fracture lines in the 3D model, was measured for each patient, resulting in a median value of 722 mm2 preoperatively and 168 mm2 postoperatively, with excellent inter- and intra-rater reliability. CONCLUSION: 2DCT measurements tend to underestimate the initial and residual displacement in complex acetabular fractures. A 3DCT analysis of these injuries was developed to overcome this and should be used in addition to the Judet/Letournel and AO/OTA classification systems, in order to provide an observer independent quantifiable fracture description and accurate assessment of the fracture reduction.

Long-term physical functioning and quality of life after pelvic ring injuries.

BACKGROUND: Pelvic ring injuries are serious injuries, often associated with substantial morbidity and mortality rates. The long-term consequences of these injuries might affect the patients' personal life. Our aim was to assess the long-term effects of pelvic ring injuries on physical functioning and quality of life (QoL) using validated patient-reported outcome measures (PROMs) and comparing these results to normative data from the general population. PATIENTS AND METHODS: A retrospective cohort study was conducted on adults treated for pelvic ring injuries between 2007 and 2016. Demographics, fracture type, injury mechanism, treatment and complications were recorded. PROMs questionnaires concerning physical functioning (SMFA) and quality of life (EQ-5D) were used. Patients were divided according to their age (18-30, 31-64, 65 and older) and fracture type (Tile/AO type A, B or C). Differences in SMFA and EQ-5D scores of the operatively and non-operatively treated patients and between the study population and general population were analyzed. RESULTS: A total of 413 patients were identified of which 279 were eligible for follow-up. One-hundred and ninety-two (69%) patients responded with a mean follow-up of 4.4 years. Patients reported a median score of 13.9 on the SMFA function index, 16.7 on the bother index, 12.5 on the lower extremity, 18.8 on the activities of daily living and 23.4 on the emotion subscale. A median EQ-5D score of 0.8 was reported. There was no difference in physical functioning and QoL between operatively and non-operatively treated patients. Comparison of these results to normative data of the general population revealed a significant (P < 0.05) decrease in physical functioning and QoL in patients with all types of pelvic ring injuries. CONCLUSION: Long-term physical functioning and QoL in patients who had sustained a pelvic ring injury seems fair, although significantly decreased in comparison with their peers from the general population.

The design, production and clinical application of 3D patient-specific implants with drilling guides for acetabular surgery.

An innovative procedure for the development of 3D patient-specific implants with drilling guides for acetabular fracture surgery is presented. By using CT data and 3D surgical planning software, a virtual model of the fractured pelvis was created. During this process the fracture was virtually reduced. Based on the reduced fracture model, patient-specific titanium plates including polyamide drilling guides were designed, 3D printed and milled for intra-operative use. One of the advantages of this procedure is that the personalised plates could be tailored to both the shape of the pelvis and the type of fracture. The optimal screw directions and sizes were predetermined in the 3D model. The virtual plan was translated towards the surgical procedure by using the surgical guides and patient-specific osteosynthesis. Besides the description of the newly developed multi-disciplinary workflow, a clinical case example is presented to demonstrate that this technique is feasible and promising for the operative treatment of complex acetabular fractures.

Delayed presentation of diaphragmatic rupture after blast injury.

A diaphragmatic injury is usually associated with injury to thoracic or abdominal organs due to blunt or penetrating trauma, and is uncommon after blast injury. We describe a patient with respiratory distress due to herniation of the stomach into the chest through a diaphragmatic injury, sustained 1 year previously when he suffered a blast injury while on deployed military operations, but without obvious visceral injury at that time. At emergency laparotomy there was a gastric perforation which was exteriorised as a gastrostomy and the diaphragmatic rupture closed. Postoperative pneumonia and pelvic abscess were both treated successfully and he left the hospital in good condition. Delayed treatment of traumatic diaphragmatic injury leads to an increased risk for herniation and/or strangulation of abdominal organs, which can be life-threatening. Recognising the symptoms indicating diaphragmatic injury is especially important in cases in which the relationship to previous trauma is less clear.

Knee disarticulation: survival, wound healing and ambulation. A historic cohort study.

The aim of this study was to analyze survival, wound healing and ambulation after knee disarticulation (KD). A historic cohort study using medical records and nursing home records was performed. Data included demographics, reason for amputation, concomitant diseases, survival, wound healing, re-amputation and ambulation. Data of 80 patients (71 unilateral and nine bilateral amputees) were available for evaluation. Median follow-up was 9.9 years (IQR: 4.1; 14.3 years). Mean age of amputation was 76.9 (+/- 9.6) years. Reason for amputation was gangrene in 72 patients. Most common concomitant (96%) disease was peripheral arterial disease (PAD). Survival after 1, 6 and 12 months was 87%, 65% and 52%, respectively. Delayed wound healing occurred in 42% (n = 16) of the patients with two or three concomitant diseases and in 15% (n = 6) of the patients with no or one concomitant disease. Trans-femoral re-amputation was performed in nine (12%) patients. Of the 61 discharged KD amputees, 36 (59%) were provided with a prosthesis. Eventually 21 (34%) patients became household walkers.

[Abdominal pain and transit disorders following a laparoscopic procedure: be alert to a trocar hernia]. / Buikpijn en passagestoornissen na een laparoscopische ingreep: denk aan een trocart-hernia.

Three patients, three women aged 40, 64 and 75, suffered from a trocar hernia, a specific complication of laparoscopic surgery. This type of hernia may result in small bowel obstruction and normally appears within two weeks after laparoscopy. The usual presentation is that of abdominal pain with nausea and vomiting. Trocar herniation implicates the necessity of reposition and might result in bowel resection with prolonged hospital stay. The advice for prevention is to use a trocar with a diameter as small as possible, as the chance of a hernia occurring increases withthe use of larger trocars. Fascial closure is advised for trocars to mm and larger. With a growing number of procedures being performed laparoscopically, the importance of recognizing and preventing this complication is evident. Three cases illustrate the importance of early recognition of small bowel obstruction resulting from trocar herniation.

[Diagnostic image (376). A man with a tumour in the anal seam]. / Diagnose in beeld (376). Een man met een zwelling in de bilnaad.

A 50-year-old man presented with a sacral tumour due to a sacrococcygeal chordoma.