Retrograde lag screw placement in anterior acetabular column with regard to the anterior pelvic plane and midsagittal plane -- virtual mapping of 260 three-dimensional hemipelvises for quantitative anatomic analysis

Dependable Automated Approach for Measuring the Retrograde Superior Ramus Screw Corridor in Pelvic Fracture Fixation

BACKGROUND

Precise measurement of the intraosseous corridor within the superior pubic ramus is essential for the accurate percutaneous placement of a retrograde superior ramus screw (SRS). However, conventional manual measurement methods are often subjective, leading to variations in results among observers. Our goal was to develop an automated and dependable method for determining the retrograde SRS corridor.

METHODS

We developed an automated technique that utilized a computed tomography (CT) image-based search algorithm to identify the retrograde SRS corridor with the maximum diameter. We evaluated the reliability of this automated approach in comparison to a manual method using 17 pelves. Subsequently, we used both methods to measure the diameter, length, and orientation of the retrograde SRS corridor in 204 pelves in a Chinese population and assessed the intra- and interobserver agreement of each method by calculating the root-mean-square error (RMSE) and constructing Bland-Altman plots. We determined the screw applicability (percentages of hemipelves that could be treated with specific sizes of screws) for each method. Additionally, we investigated potential factors influencing the corridor, such as sex, age, height, and weight, through regression analysis.

RESULTS

The intra- and interobserver intraclass correlation coefficients (ICCs) for the automated method (0.998 and 0.995) were higher than those for the manual approach (0.925 and 0.918) in the assessment of the corridor diameter. Furthermore, the diameter identified by the automated method was notably larger than the diameter measured with the manual method, with a mean difference and RMSE of 0.9 mm and 1.1 mm, respectively. The automated method revealed a significantly smaller corridor diameter in females than in males (an average of 7.5 and 10.4 mm, respectively). Moreover, use of the automated method allowed 80.6% of the females to be managed with a 4.5-mm screw while a 6.5-mm screw could be utilized in 19.4%, surpassing the capabilities of the manual method. Female sex had the most substantial impact on corridor diameter (β = -0.583).

CONCLUSIONS

The automated method exhibited better reliability than the manual method in measuring the retrograde SRS corridor, and showed a larger corridor diameter for screw placement. Females had a significantly smaller corridor diameter than males. Given the intricate nature of the automated approach, which entails utilizing different software and interactive procedures, our current method is not readily applicable for traumatologists. We are working on developing integrated software with the goal of providing a more user-friendly solution for traumatologists in the near future.

LEVEL OF EVIDENCE

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

A standard canulated screw may not fit up to 1/3 of the patients treated percutaneously for anterior column acetabular fractures-A pilot study

A proper evaluation of the narrowings and length of the anterior acetabular column would offer better predictability and precision for implant insertion in the case of an acetabular fracture.

OBJECTIVE

To determine the diameter and length of the safety corridor of the anterior column of the acetabulum in patients with available pelvic computed tomography (CT), analyze the obtained measurements against those of a standard 6.5-mm implant, and verify possible sex differences regarding these measurements. A secondary aim was to develop a method for measurement of the anterior column of the acetabulum based on CT images.

MATERIALS AND METHODS

In 200 CT scans of hemipelvises we measured the diameter of two areas of narrowing and the length of the safety corridor of the anterior column. The images were submitted to multiplanar reformatting adjusted to a plane orthogonal to the bone corridor, drawn at the level of the superior pubic ramus.

RESULTS

Measurement #1 had a mean value of 8.12 (2.27) mm in the overall sample and median values of 9.03 (7.76-10.48) mm in men and 6.77 (5.44-7.19) mm in women. Measurement #2 had a mean value of 7.29 (2.19) mm and median values of 8.23 (7.18-9.82) mm in men and 5.9 (4.65-7.19) mm in women. Measurement #3 had a mean value of 109.53 (13.66) mm in the overall sample and median values of 117.17 (112.9-122.9) mm in men and 100.91 (90.95-111.17) mm in women (p<0.001 all three measurements). Measurement #1 was smaller than 6.5 mm in 22.5% of the patients (of whom 90% were women). Measurement #2 was smaller than 6.5 mm in 35% of the patients (of whom 80% were women).

CONCLUSIONS

This study proposed an anatomic evaluation of the anterior column of the acetabulum using conventional CT images The areas of narrowing in the anterior column had an average of 8.12 mm at the level of the pubic tubercle and 7.29 mm at the level of the acetabular fossa. The mean length of the safety corridor was 109.53 mm. In 35% of the cases, a 6.5 mm percutaneous screw would have violated the cortical bone of the safety corridor.

Iliac dysmorphism: defining radiographic characteristics and association with pelvic osseous corridor size

INTRODUCTION

Insertion of iliac wing implants requires understanding of the curvilinear shape of the ilium. This study serves to quantitatively identify the area of iliac inner-outer table convergence (IOTC), characterize the iliac wing osseous corridor, and define the gluteal pillar osseous corridor.

METHODS

Computed tomography scans of 100 male and 100 female hemipelves were evaluated. The iliac wing was studied using manual best-fit analysis of the bounds of the inner and outer cortices. The IOTC was defined as the location of the iliac wing with an intercortical width less than 5 mm. The shortest distance from the apex of the iliac crest to the superior border of the IOTC was defined as the iliac wing osseous corridor. Finally, the width of the gluteal pillar corridor from the gluteus medius tubercle to the ischial tuberosity was measured.

RESULTS

The IOTC is an elliptical area measuring 22.3 cm². All ilia had an area where the inner and outer cortices converged to an intercortical width of less than 5 mm; 48% converged to a single cortex. The shortest mean distance from the superior edge of the iliac crest to the beginning of the IOTC was 20.3 mm in men and 13.8 mm in women (p < 0.001). The gluteal pillar diameter averaged 5.3 mm in men and 4.3 mm in women (p < 0.001).

DISCUSSION

All ilia converge to a thin and frequently unicortical central region. A 4.5 mm iliac wing lag screw will not breach the cortex if it remains within 20 mm or 14 mm distal to the cranial aspect of the iliac crest in males and females, respectively. Not only is the gluteal pillar smaller than previously thought, in 41% of males and 73% of females, it is not be large enough for 5 mm implants.

CONCLUSION

This study quantitatively assesses the dimensions of the IOTC, the iliac crest osseous corridor, and the gluteal pillar. Overall, our findings provide improved understanding of the limits for implant use in the iliac wing as well as better appreciation of the complex osteology of the ilium. This will help surgeons to identify safe areas for implant placement and avoid inadvertent cortical penetration.

A computed tomography (CT) based morphometric study of superior pubic ramus anatomy among Arabs to determine safe intramedullary pubic rami screw insertion

PURPOSE

To assess the morphometric variables of the superior pubic ramus in an Arab/ Middle Eastern population to establish a safe pubic screw fixation technique.

METHODS

Cross-sectional retrospective analysis of computed tomography (CT) pelvic images. Morphometric data were extracted including; on pubic ramus length, insertion angles, potential danger zones and ramus diameters. The correlation between pubic rami diameter and patient demographics was also analyzed.

RESULTS

A total of 231 participants were included (45% female). The mean pubic ramus length was 104 mm in females and 127 mm in males. The narrowest canal diameters at the para-symphyseal area were; 7.35 mm (males) and 4.75 mm (females). The mediolateral insertion angle was 49.4° in females and 41.8° in males. The cephalic-caudal angle was 49.9° in males and 42.1° in females. The mean distance from the lateral ilium entry point to the joint articular surface was 23.5 mm in males and 19.9 mm in females. The symphysis pubis to tubercle exit point was higher in females than males (24.2 mm vs 16.6 mm, respectively). There was a significant positive correlation between age and pubic ramus diameters in all age groups.

CONCLUSION

The results from this study suggest that percutaneous pubic rami screw fixation using the standard 6.5 or 7.3 mm cannulated screw system may potentially be unsafe in female Arab patients. This subset of patients may require alternative non-cannulated screws (3.5-4.5 mm) or plate options. Further, female patients may have a higher risk of acetabular joint penetration, while males have a potentially higher risk of pudendal nerve injury.

Entry Point Variation in the Osseous Fixation Pathway of the Anterior Column of the Pelvis—A Three-Dimensional Analysis

Fractures of the superior pubic ramus can be treated with screw insertion into the osseous fixation pathway (OFP) of the anterior column (AC). The entry point determines whether the screw exits the OFP prematurely. This can be harmful when it enters the hip joint or damages soft tissues inside the lesser pelvis. The exact entry point varies between patients and can be difficult to ascertain on fluoroscopy during surgery. The aim of this study was to determine variation in the location of the entry point. A retrospective single center study was performed at a level 1 trauma center in the Netherlands. Nineteen adult patients were included with an undisplaced fracture of the superior pubic ramus on computer tomography (CT)-scan. Virtual three-dimensional (3D) models of the pelvises were created. Multiple screws were placed per AC and the models were superimposed. A total of 157 screws were placed, of which 109 did not exit the OFP prematurely. A universally reproducible entry point could not be identified. A typical crescent shaped region of entry points did exist and was located more laterally in females when compared to males. Three-dimensional virtual surgery planning can be helpful to identify the ideal entry points in each case.

Navigation Template Design and the Anatomic Measurement for Anterograde Transpubic Screws

OBJECTIVE

For pelvic ring fractures, screw fixation became a popular technique for its good biomechanical performance. The safe insertion of anterograde the transpubic screw is important for patients with anterior pelvic ring fractures. This paper is to research the anatomical parameters of the anterograde transpubic screw corridor and evaluate the safety of anterograde transpubic screw placement assisted by the assembled navigation template.

METHODS

Fifty subjects with normal pelvic, 25 men and 25 women, age from 20 to 60 were enrolled, and their ilium were 3D reconstructed. The ilium was divided into zone I, zone II and zone III. Zone I and zone III was defined as medial and lateral to the obturator foramen, respectively. Zone II is located between zones I and III. The corridor A is formed by zone I and zone II and corridor B is formed by zone I, zone II and zone III. The diameter and length of the inner circle, the distance from the center of the inner circle to the posterior superior and to the inferior iliac spine of corridor A and corridor B were measured, respectively. Nine patients with pelvic fractures underwent anterograde transpubic screw and transverse sacroiliac screw placement assisted by the assembled navigation template and were retrospectively analyzed. Operation time, blood loss, incision length and fluoroscopy times were recorded. Grading score and Matta score were evaluated after surgery.

RESULTS

In the 50 subjects, the diameter of corridor A was 11.16 ± 2.13 mm, and that of corridor B was 8.54 ± 1.52 mm. The length of corridor A was 86.39 ± 9.35 mm, and that of corridor B was 117.05 ± 5.91 mm. The surface distance from the screw entry point to the posterior superior iliac spine in corridor A was 109.31 ± 11.06 mm, and that in corridor B was 127.86 ± 8.23 mm. The surface distance from the screw entry point to the posterior inferior iliac spine in corridor A was 91.16 ± 10.34 mm, and that in corridor B was 106.92 ± 7.91 mm. A total of 18 sacroiliac transverse screws and 11 anterograde transpubic screws were inserted assisted by assembled navigation templates for nine patients. The average operation time was 108.75 ± 25.71 min, the blood loss was 141.11 ± 50.21 ml, the incision length was 14 ± 4.62 cm, and the intraoperative fluoroscopy was 17.89 ± 4.01 times.

CONCLUSION

Transpubic screw corridor can be obtained by 3D reconstruction. For the majority of patients, the anterograde pubic ramus corridor accommodated a 6.5 mm diameter screw. It is safe to use anterograde transpubic screw placement assisted by an assembled navigation template.

Application of a three-dimensional virtual model to study the effect of fluoroscopic angle on infra-acetabular corridor parameters and screw insertion rates

PURPOSE

To use three-dimensional (3D) virtual models to study how the parameters and insertion rates of the infra-acetabular corridor (IAC) change under different fluoroscopic angles.

METHODS

The pelvis computed tomography data of 187 patients are imported into Mimics software in DICOM format to generate a 3D model. The anterior pelvis plane is used as the reference plane to measure the diameter of the optimum IAC when the pelvis model is tilted forward by 5°, 15°, 25°, 35° and 45°. The diameter of at least 3.5 mm is defined as the cutoff for placing a 3.5 mm screw, the rate of infra-acetabular screw (IAS) insertion is calculated, and the mean length of the IAC and the mean tilt of the corridor axis in relation to the sagittal midline plane (SMP) are measured.

RESULTS

The similar diameters of the IAC can be found under fluoroscopy at 5°-35°, with the largest diameter of 4.08 ± 1.84 mm and the highest screw insertion rate of 60.42% at 15° and 25°, whereas the diameter and insertion rate are lowest at 45°. The corridor length increases with increasing fluoroscopic angle, and the angle of the corridor axis to the SMP decreases gradually.

CONCLUSION

The conventional fluoroscopic angle of the pelvic inlet is not suitable for the IAS insertion. The parameters of the IAC vary according to a certain rule under different fluoroscopic angles, so a surgeon can select the appropriate fluoroscopic angle in accordance with the type of fracture and the fracture line angle.

Obturator Oblique and Pubic Ramus Inlet Views Can Better Guide the Insertion of an Anterior Column Acetabular Screw

OBJECTIVE

The objective of the present paper was to investigate the value of obturator oblique and pubic ramus inlet views in guiding anterior column acetabular screw insertion.

METHODS

We collected pelvic CT scans at the diagnostic imaging center of our hospital between 2017 and 2019. Virtual three-dimensional (3D) models of the pelvis were created based on the CT scans. Then the transparency was adjusted to 30%. Two identical copies of the 3D model data were made. 3D model replications were divided into a control group and an experimental group. In the control group, the screw was inserted into the anterior acetabular column using obturator-outlet and iliac-inlet views. In the experimental group, the screw was guided under obturator oblique and pubic ramus inlet views. Based on whether the screw penetrated the hip joint and/or exited the pubic ramus, models were divided into three grades. Grade I: the screw travels completely within the anterior column bone corridor; Grade II: the screw exits the superior pubic ramus, but the length of the screw outside the channel does not exceed 1/2 of the anterior column; Grade III: the screw exits the superior pubic ramus and the length of the screw outside the corridor exceeds 1/2 of the anterior column. We compared the screw placement quality of the two groups and analyzed differences between genders. In addition, the distance between the screws and the acetabulum was recorded and compared among the two groups.

RESULTS

A total of 110 hemipelves were selected, including those of 80 men and 30 women, with an average age of 46.76 ± 14.26 years. In the control group, the screw quality of 64 models (58.2%) was Grade I. In the experimental group, 94 models (85.5%) had Grade I screw placement quality. Grade II screw placement quality accounted for 18.2% of the control group and 7.3% of the experimental group. In the control and the experimental groups, there were 26 and 8 cases with Grade III screw placement quality, respectively. The quality of screw placement in the experimental group was significantly better than that in control group, and the difference between the two groups was statistically significant (P < 0.01). The distance between the screw and the acetabulum in the control group and experimental group was 0.92 ± 0.49 mm and 2.78 ± 1.15 mm, respectively. The difference between the two groups was statistically significant.

CONCLUSION

Anterior column acetabular screws can be inserted successfully and more accurately using the obturator oblique and pubic ramus inlet views.

Fracture characteristics and outcomes of acetabular fracture management with minimally invasive approach and percutaneous fixation

PURPOSE

The aim was to assess acetabular fracture outcomes of percutaneous fixation (PF) with or without minimally invasive surgery (MIS).

METHODS

Between July 2011 and October 2016, acetabular fractures fixed with PF with or without MIS were included. Data collected are demographics, mechanism of injury, associated injuries, time to surgery, American Society of Anesthesiologists grade, fracture characteristics, surgical techniques, fracture reduction, secondary osteoarthritis (OA), revision surgery, patient survival and complications.

RESULTS

Of 26 patients with a mean age of 56 years (19-86) (22 males and 4 females), 11 were < 50 years age (U50) and 15 were > 50 years (A50). Most common pattern was anterior column with posterior hemi-transverse. Three out of 11 U50 were minimally displaced and had PF only; the rest had MIS and PF. All had good fracture reduction, but 2 had secondary OA at follow-up but no further surgery. Eight out of 26 had secondary OA but only 3 needed surgery. Three (A50 with PF) with fair/poor reduction (deemed unfit for open reduction) had secondary OA but no further intervention. Three more (A50 with MIS + PF) had secondary OA treated with primary total hip replacement (THR). Complications were as follows: one foot drop recovered after immediate repositioning of screw, one cardiac event and one pulmonary embolism.

CONCLUSION

Fracture mal-reduction predicts secondary OA, but good fracture reduction does not prevent secondary OA. MIS and PF in elderly are useful even with suboptimal reduction as it sets the bed for a non-complex THR. Despite MIS surgery, medical complications are potentially significant.

Infra-acetabular screw exited between ischial tuberosity and ischial spine is more suitable for Asian population: a 3D morphometric study

Background

Recently, the infra-acetabular screw has been proposed for use in treatment of acetabular fractures as a part of a periacetabular fixation frame. Biomechanical studies have shown that an additional infra-acetabular screw placement can enhance the fixation strength of acetabular fracture internal fixation. Currently, the reported exit point of the infra-acetabular screw has been located at the ischial tuberosity (Screw I). However, our significant experience in placement of the infra-acetabular screw has suggested that when the exit point is located between the ischial tuberosity and the ischial spine (Screw II), the placement of a 3.5 mm infra-acetabular screw may be easier for some patients. We conducted this study in order to determine the anatomical differences between the two different IACs.

Methods

The raw datasets were reconstructed into 3D models using the software MIMICS. Then, the models, in the STL format model, were imported into the software Geomagic Studio to delete the inner triangular patches. Additionally, the STL format image processed by Geomagic Studio was imported again into MIMICS. Finally, we used an axial perspective based on 3D models in order to study the anatomical parameters of the two infra-acetabular screw corridors with different exit points. Hence, we placed the largest diameter virtual screw in the two different screw corridors. The data obtained from this study presents the maximum diameter, length, direction, and distances between the entry point and center of IPE.

Results

In 65.31% males and 40.54% females, we found a screw I corridor with a diameter of at least 5 mm, while a screw II corridor was present in 77.55% in males and 62.16% in females. Compared to screw I, the length of screw II is reduced, the angle with the coronal plane is significantly reduced, and the angle with the transverse plane is significantly increased.

Conclusions

For East Asians, changing the exit point of the infra-acetabular screw can increase the scope of infra-acetabular screw use, especially for females.

Morphometric analysis of the anterior column of the acetabulum and safety of intramedullary screw fixation for its fractures in Indian population: a preliminary report

INTRODUCTION

Morphometric variations of the anterior column of the acetabulum have been described in the literature for its complex structure, which can influence the safe containment of intramedullary screw for fixation of its fractures. The purpose of this CT-based study is to present a preliminary report on the morphometric variations and safety of intramedullary screw fixation of the anterior column of the acetabulum in the Indian population.

METHODS

CT-based data from 102 uninjured pelves were retrospectively analyzed in iPlanⓇ BrainLab AG, Feldkirchen, Germany. Narrowest zones around acetabulum and superior pubic ramus were measured. We calculated the axis of the anterior column of the acetabulum by joining the centres of these narrowest zones. Standard screws trajectories were directed along this axis. Screw length up to the first cortical perforation, the distance of the exit point from the pubic symphysis, and the length of the anterior column up to the pubic tubercle were measured.

RESULTS

The osseous corridor of the anterior column of acetabulum had variable cross-section along its length with two constriction zones, first in the acetabular region and second in the superior pubic ramus. Only 54% of our cases allowed safe applicability of 6.5-mm-diameter screw trajectories with safety margin of 2 mm on either side of the screw. Significant morphometric and screw applicability-related differences were observed among male and female cases with males having a wider osseous corridor in general. Elimination of safety margin results in a significant increase in the screw applicability.

CONCLUSION

The osseous corridor of the anterior column varies in its dimensions from individual to individual. Standard screws of 6.5-mm and 7.3-mm diameters may not be safe for intramedullary screw fixation in every patient and carry a risk of cortical violation when a 2 mm of width around the screw is considered as a safety margin. However, with a precise screw placement within the extents of the cortices of the anterior column, 6.5-mm screws can be applied in most of the female cases and 7.3-mm screws can be applied in most of the male cases for anterior column fixation.

Recommendations for iliosacral screw placement in dysmorphic sacrum based on modified in-out-in corridors

(1) Can iliosacral osseous corridor diameters in sacral dysmorphism be enlarged by in-out-in screw placement at the posterior iliosacral recessus? (2) Are lumbosacral transitional vertebra (LSTV) the anatomical cause for sacral dysmorphism? (3) Are there sex-specific differences in sacral dysmorphism? 594 multislice CT scans were screened for sacral dysmorphism and 55 data-sets selected. Each pelvis was segmented manually and cylindrical iliosacral corridors (on the level of S1 and S2 vertebra) were semi-automatically determined. Corridor trajectories, -diameters and -lengths were measured. LSTV (Castellvi-type IIIb and IV) were found in 3 of 55 pelves and these lumbosacral variations are therefore not the anatomical basis for sacral dysmorphism. The prevalence of transsacral osseous corridors with diameters of <7.5 mm in axial CT images correlates with qualitative and quantitative criteria of sacral dysmorphism. Enlarging the osseous corridor diameters by penetration of the posterior iliosacral recessus increase the safe corridor diameters (females versus males) by 26% versus 15% at the level of S1- and 50% versus 48% at the level of S2-vertebra. Sex-specific differences for both corridors (osseous and in-out-in) were only found for the osseous corridor diameters at the level of S1 vertebra, being smaller in females (females versus males: 13.3 ± 3.6 mm versus 15.5 ± 3.8 mm, p = 0.04). Dysmorphic sacra can be reliably detected on standard axial CT slice images. Modified in-out-in corridors on the level of S1-vertebra allow screw placement in all patients, but is still demanding compared to non-dysmorphic sacra, due to the oblique corridor axis. Recommendations for intraoperative orientation for oblique screw placement are defined. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Percutaneous fixation of acetabular fractures

The objective of surgery for acetabular fractures is to achieve precise reduction to restore joint congruence, fix internal bone fragments, avoid displacement of the fracture and allow rapid rehabilitation.Open reduction and internal fixation is the benchmark method for displaced acetabular fractures, but open reductions can increase morbidity, causing neurovascular injury, blood loss, heterotopic bone formation, infection and poor wound healing.An anatomical reduction with a gap of 2 mm or less is a predictor of good joint function and reduced risk of post-traumatic osteoarthritis.The percutaneous approach is associated with fewer complications than open techniques, but acetabular geometry makes percutaneous screw insertion a challenging procedure.The percutaneous technique is recommended for non-displaced or slightly displaced fractures, and in obese, osteoporotic and elderly patients who cannot receive total joint arthroplasty.We recommend the use of intramedullary cannulated screws.Fracture reductions are achieved by manual traction of the affected bones. If some fracture displacement remains, accessory windows can be used to introduce a ball spike pusher, a hook or a Steinmann pin which can be used as a joystick to rotate the fracture.In this paper, we describe the accessory windows for the anterior column, the quadrilateral plate and the posterior column. We detail the position, direction and kind of screws used to stabilize the anterior and posterior columns. Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170054.

[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.

[Management of complex acetabulum fractures and their consequences]

In the structure of pelvic bone injuries, acetabular fractures are the most complex type and, according to different authors, account for up to 20% [1]. The severity of these injuries is confirmed by the fact that early descriptions of acetabular fracture were based only on the results of autopsies of patients who had suffered a combined injury. Thus, as early as 1788, Callisen reported an acetabular fracture, but without a detailed description of the nature of the injury. In 1909, Schroeder provided a detailed report of 49 cases of acetabular fractures reported in the literature. Most of them were described during autopsies of patients who died from complications associated with hemorrhagic shock or the onset of sepsis [2]. Fractures of the acetabulum in most observations are the result of high-energy impacts, usually as a result of traffic accidents; therefore, the mechanism of injury determines the combined and multiple nature of the injuries in the victims. A significant proportion of acetabular fractures (up to 60%) are accompanied by fragment displacement and dislocation of the femoral head, in which the most severe tissue changes occur [3].

Anterograde Fixation Module for Posterior Acetabular Column Fracture: Computer-Assisted Determination of Optimal Entry Point, Angle, and Length for Screw Insertion

BACKGROUND The aim of this study was to provide valid data for a plate-screw fixation model for fractured posterior-anterior columns of the acetabulum. MATERIAL AND METHODS Nineteen cadaveric bony hemi-pelvis specimens were obtained and 50 healthy adults were enrolled. The modified Stoppa approach and computed tomography (CT) imaging were used to collect the measured parameter data of the module. RESULTS The measured parameter data were as follows: OP, 0.96±0.32 cm in females and 0.92±0.16 cm in males (P>0.05); PI, 0.98±0.28 cm in females, and 0.75±0.23 cm in males (P>0.05); Ðϴ, 59.68°±6.28° in females and 56.75°±3.22° in males (P>0.05); and Ðφ, 41.27°±2.76° in females and 34.31°±2.78° in males (P<0.05). The corresponding CT image data were as follows: PI, 1.08±0.22 cm in females and 0.85±0.27 cm in males (P>0.05); OP, 1.06±0.29 cm in females and 1.12±0.24 cm in males (P>0.05); Ðϴ, 55.33°±4.00° in females and 55. 50°±3.43° in males (P>0.05); and Ðφ was 39.21°±2.45°in females and 35.58°±2.31°in males (P<0.05). No significant difference with respect to sex and side existed between specimens and healthy adults (P>0.05). CONCLUSIONS The measured parameter data obtained in healthy adults and cadaveric specimens provided an anatomic basis for the designation of the guide module, and thus confirmed the accuracy and safety of screw placement in fractured columns of the acetabulum.

Rationale for more consistent choice of surgical approaches for acetabular fractures

OBJECTIVES

All acetabular fractures are difficult to treat surgically, but there are four types involving two columns that are particularly challenging. The choice of surgical approach is crucial. The purpose of the study was to determine and evaluate the factors influencing the choice of surgical approach for two-column acetabular fractures. We hypothesised that more accurate preoperative planning, sophisticated technical capabilities, and evolution of surgeon experience will result in more consistent use of non-extensile single surgical approaches. We also evaluated the outcomes of surgical treatment and the correlation with the surgical approach used.

DESIGN

Retrospective cohort study.

PATIENTS AND METHODS

A total of 156 patients with 157 acetabular fractures involving two columns (Letournel T-types and both-column) treated surgically in a 25-year period (1988-2013) were included in the study. The acetabular fractures in this study were divided into two groups according to the date of surgery: 81 in Group 1 (1998-2002) and 76 in Group 2 (2003-2013). All fractures were classified preoperatively according to the Judet and Letournel classification system and Matta's categorisation of surgical approach. Four surgical approaches were used: single Kocher-Langenbeck (KL), single ilioinguinal (II), combined Kocher-Langenbeck and ilioinguinal (KL+II), and extended iliofemoral (EIF). The efficacy of the surgical approach utilised was assessed using three parameters: anatomical reduction, surgical time and intraoperative complications.

RESULTS

There was no statistical difference between Group 1 and Group 2 in the distribution of T-type (p=0.424) and both-column (p=0.425) fractures. In Group 2 more acetabular fractures were treated through single non-extensile approaches compared with Group 1 (90.8% vs. 54.3%, p<0.001). Increase in single approach surgery resulted in shorter mean surgical time (p<0.001) and significant increase in anatomical reduction (p=0.039). The frequency of intraoperative complications was not statistically different (p=0.07) between the two groups, but there was a trend to fewer complications in Group 2.

CONCLUSIONS

The surgical approaches chosen for acetabular fractures that involve two columns (Letournel T-types and both-column) should become more consistent. The results of this study indicate that the majority of such acetabular fractures can be treated successfully through single surgical approaches.

Virtual mapping of 260 three-dimensional hemipelvises to analyse gender-specific differences in minimally invasive retrograde lag screw placement in the posterior acetabular column using the anterior pelvic and midsagittal plane as reference

BACKGROUND

Due to complex pelvic geometry, percutaneous screw placement in the posterior acetabular column can pose a major challenge even for experienced surgeons.

METHODS

The present study examined the preformed bone stock of the posterior acetabular column in 260 hemipelvises. Retrograde posterior column screws were virtually implanted using iPlan CMF (BrainLAB AG, Feldkirchen, Germany); maximal implant length, maximal implant diameter and angles between the screw trajectories and the reference planes anterior pelvic plane as well as the midsagittal plane were assessed for gender-specific differences.

RESULTS

The virtual analysis of the preformed bone stock column showed two constrictions of crucial clinical importance. These were located 49.6 ± 3.4 (41.0-60.2) mm (inferior margin of acetabulum) and 77.0 ± 5.6 (66.5-95.3) mm (centre of acetabulum) from the entry point of the implant in men and respectively 43.7 ± 2.3 (38.3-49.3) mm as well as 71.2 ± 3.5 (63.5-79.99) mm in women (men vs. women: p < 0.001). The entry point of the retrograde posterior column screw was located dorsal from the transition of the lower margin of the ischial tuberosity to ramus inferior pointing to the medial margin of the ischial tuberosity. In female patients, the entry point was located significantly closer to the medial margin of the ischial tuberosity. However, 7.3 mm screws can generally be used in men and women. The angle between the screw trajectory and the anterior pelvic plane in sagittal section was 14.0 ± 4.9 (2.5-28.6) °, the angle between the screw trajectory and the midsagittal plane in axial section was 31.1 ± 12.8 (1.5-77.9) ° and the angle between the screw trajectory and the midsagittal plane in coronal section was 8.4 ± 3.8 (1.5-20.0) °. For all angles, significant gender-specific differences were found (p < 0.001).

CONCLUSION

Therefore, the anterior pelvic plane as well as the midsagittal plane can facilitate intraoperative orientation for retrograde posterior column screw placement considering gender-specific differences in preformed bone corridor, implant length as well as angles formed between screw trajectory and these reference planes.

Axial view of acetabular anterior column: a new X-ray projection of percutaneous screw placement

INTRODUCTION

To search for a new radiographic view/projection of the acetabular anterior column to provide a safe guide for percutaneous screw placement for acetabular fractures.

MATERIALS AND METHODS

Eight pelvic specimens taken from normal adult cadavers were positioned in a supine position on the operating table. First, the ipsilateral ilium-oblique view of the observed side was obtained on C-arm fluoroscopy by tilting the C-arm approximately 35° toward the contralateral hip joint. Then, the tilting angle of the C-arm was changed gradually until an oval track image (acetabular anterior column axial view) appeared. The oval shadow was clear only in one position as the angle of the C-arm was changed toward the caudal side of the operating table. A guide pin was put on the skin of the cadaver, and the location and tilting direction of the guide pin were adjusted under C-arm fluoroscopy until the pin's shadow became a point in the center of the oval track. Then, the guide pin was inserted into the bone using a battery-powered drill. The degree of inclination of the guide pin in the cadaver in the frontal and sagittal planes was measured using computed tomography (CT).

RESULTS

Axial views of the anterior column were found successfully in all of the pelvic specimens, and the guide pins were inserted accurately into the acetabular anterior column under C-arm fluoroscopic guidance. On the CT-reconstructed image, the average degree of angle between the guide pin and the sagittal plane was 33.6° (range 29.6°-36.5°). The average angle between the guide pin and the transverse plane was 59.1° (range 56.4°-63.2°).

CONCLUSION

This axial view of the acetabular anterior column is a novel X-ray projection which provides an optimal method for guiding percutaneous insertion of anterior column screws for acetabular fractures.

Sex-specific differences of the infraacetabular corridor: a biomorphometric CT-based analysis on a database of 523 pelves

BACKGROUND

An infraacetabular screw path facilitates the closure of a periacetabular fixation frame to increase the plate fixation strength in acetabular fractures up to 50%. Knowledge of the variance in corridor sizes and axes has substantial surgical relevance for safe screw placement.

QUESTIONS/PURPOSES

(1) What proportion of healthy pelvis specimens have an infraacetabular corridor that is 5 mm or larger in diameter? (2) Does a universal corridor axis and specific screw entry point exist? (3) Are there sex-specific differences in the infraacetabular corridor size or axis and are these correlated with anthropometric parameters like age, body weight and height, or the acetabular diameter?

METHODS

A template pelvis with a mean shape from 523 segmented pelvis specimens was generated using a CT-based advanced image analyzing system. Each individual pelvis was registered to the template using a free-form registration algorithm. Feasible surface regions for the entry and exit points of the infraacetabular corridor were marked on the template and automatically mapped to the individual samples to perform a measurement of the maximum sizes and axes of the infraacetabular corridor on each specimen. A minimum corridor diameter of at least 5 mm was defined as a cutoff for placing a 3.5-mm cortical screw in clinical settings.

RESULTS

In 484 of 523 pelves (93%), an infraacetabular corridor with a diameter of at least 5 mm was found. Using the mean axis angulations (54.8° [95% confidence interval {CI}, 0.6] from anterocranial to posterocaudal in relation to the anterior pelvic plane and 1.5° [95% CI, 0.4] from anteromedial to posterolateral in relation to the sagittal midline plane), a sufficient osseous corridor was present in 64% of pelves. Allowing adjustment of the three-dimensional axis by another 5° included an additional 25% of pelves. All corridor parameters were different between females and males (corridor diameter, 6.9 [95% CI, 0.2] versus 7.7 [95% CI, 0.2] mm; p<0.001; corridor length, 96.2 [95% CI, 0.7] versus 106.4 [95% CI, 0.6] mm; p<0.001; anterior pelvic plane angle, 54.0° [95% CI, 0.9] versus 55.3° [95% CI, 0.8]; p<0.01; sagittal midline plane angle, 4.3° [95% CI, 0.6] versus -0.3° [95% CI, 0.5]; p<0.001).

CONCLUSION

This study provided reference values for placement of a 3.5-mm cortical screw in the infraacetabular osseous corridor in 90% of female and 94% of male pelves. Based on the sex-related differences in corridor axes, the mean screw trajectory is approximately parallel to the sagittal midline plane in males but has to be tilted from medial to lateral in females. Considering the narrow corridor diameters, we suggest an individual preoperative CT scan analysis for fine adjustments in each patient.