Comparison of anterograde versus retrograde percutaneous screw fixation of anterior column acetabular fractures

Acetabular posterior column screws via an anterior approach

Screw fixation of acetabular column fractures is a well-established alternative option to plate fixation providing comparable biomechanical strength and requiring less surgical exposure. For displaced acetabular fractures involving both columns open reduction and plate fixation of one column in combination with a column-crossing screw fixation of the opposite column via a single approach is a viable treatment option. Preoperative planning of posterior column screws (PCS) via an anterior approach is mandatory to assess the eligibility of the fracture for this technique and to plan the entry point and the screw trajectory. The intraoperative application requires fluoroscopic guidance using several views. A single view showing an extraarticular screw position is adequate to rule out hip joint penetration. The fluoroscopic assessment of cortical perforation of the posterior column requires several oblique views such as lateral oblique views, obturator oblique views and axial views of the posterior column or alternatively intraoperative CT scans. The application of PCS via an anterior approach is a technically demanding procedure, that allows for a relevant reduction of approach-related morbidity, surgical time and blood loss by using a single approach.

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.

Accuracy of Patient-Specific Drilling Guides in Acetabular Fracture Surgery: A Human Cadaver Study

Due to the complex anatomical shape of the pelvis, screw placement can be challenging in acetabular fracture surgery. This study aims to assess the accuracy of screw placement using patient-specific surgical drilling guides applied to pre-contoured conventional implants in acetabular fracture surgery. CT scans were made of four human cadavers to create 3D models of each (unfractured) pelvis. Implants were pre-contoured on 3D printed pelvic models and optically scanned. Following virtual preoperative planning, surgical drilling guides were designed to fit on top of the implant and were 3D printed. The differences between the pre-planned and actual screw directions (degrees) and screw entry points (mm) were assessed from the pre- and postoperative CT-scans. The median difference between the planned and actual screw direction was 5.9° (IQR: 4–8°) for the in-plate screws and 7.6° (IQR: 6–10°) for the infra-acetabular and column screws. The median entry point differences were 3.6 (IQR: 2–5) mm for the in-plate screws and 2.6 (IQR: 2–3) mm for the infra-acetabular and column screws. No screws penetrated into the hip joint or caused soft tissue injuries. Three-dimensional preoperative planning in combination with surgical guides that envelope pre-contoured conventional implants result in accurate screw placement during acetabular fracture surgery.

[Digital study of the ideal position of lag screw internal fixation in the anterior column of the acetabulum]

Objective

To find the ideal position of lag screw internal fixation in the anterior column of acetabulum by digital technology, and measure its related parameters, so as to improve the accuracy of lag screw implantation.

Methods

The CT scan data of 266 semi-pelvic raw in 133 cases (78 males and 55 females, aged 18-65 years old with an average age of 42 years) were collected between January 2019 and January 2020 to compose three-dimensional models. According to the relationship between the peripheral bone cortex of the anatomical channel and the lag screw, a new standard for the ideal position of lag screw fixation in the anterior column of acetabulum was proposed to simulate the implantation of the screw. After the screw was in the ideal position, the following indicators were measured: the maximum allowable diameter of the virtual screw (the diameter of the cylinder up to the new standard, R), the length (the distance between the center of the nail point on both sides, L); the position of the retrograde nail point (the interval between the nail insertion points and the midpoint of the pubic symphysis and the pubic tubercle, respectively, D1 and D2) and the position of the antegrade nail insertion point (the distance between the nail insertion point and the anterior superior iliac spine, the major ischial notch, and the vertical distance between the nail insertion point and the apex of the posterior upper edge of the acetabulum, respectively, D3, D4, D5); and the direction of the virtual screw at the ideal position (the angle between the screw and the horizontal plane, sagittal plane, and coronal plane, respectively, ∠β, ∠γ, ∠δ) were calculated.

Results

The maximum allowable diameter of virtual screws was 5.70-14.10 mm for males, with an average of 9.25 mm; for females, it was 4.40-10.40 mm with an average of 7.29 mm. The antegrade insertion point of the anteroposterior acetabular lag screw was located at 2.0-2.5 cm above the apex of the acetabulum, which was almost the same distance from the anterior superior iliac spine and the ischial notch, about 5 cm; the insertion point of the retrograde implant was located at the pubic bone 2.5-3.0 cm below the nodule. When the acetabular anterior column screw was in the ideal position, there was no significant difference in the comparison of ∠β and ∠γ between the male and the female ( P>0.05), and the differences in the other indicators were significant ( P<0.05). Except for D4 and ∠β showing no significant difference between the left and right sides ( P>0.05), the differences in the other indicators were significant ( P<0.05).

Conclusion

In the bony channel of the anterior column of the acetabulum, all males can accommodate screws with a diameter of <5.70 mm, and females can accommodate screws with a diameter of <4.40 mm. The anterograde or retrograde screw insertion points are different for male and female. The use of digital technology to individually measure the appropriate screw parameters can improve the accuracy and stability of the lag screw internal fixation for acetabular anterior column fractures.

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.

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.

Antegrade versus retrograde screw fixation of anterior column acetabular fractures: a biomechanical in vitro study

BACKGROUND

To compare the mechanical strength of antegrade versus retrograde lag screw fixation of anterior column acetabular fractures.

METHODS

Standardised anterior column fractures were created in synthetic pelvis models and stabilised by either antegrade (ANTE, n = 4) or retrograde (RETRO, n = 4) anterior column screw fixation. In a validated setup, a cyclic loading protocol was applied with increasing axial force (750 cycles, 250-750 N) followed by load to failure. Construct survival, energy absorbed, construct stiffness, and load to failure were assessed. Descriptive and opto-metric methods were used to describe the mode of failure.

RESULTS

All constructs failed with loads below 1500 N. With regard to energy absorbed until failure, the ANTE group resisted to 3.763 × 10⁵ N*cycles (range 3.760 × 10⁵-3.763 × 10⁵) and the RETRO group to 3.762 × 10⁵ N*cycles (range 3.761 × 10⁵-3.765 × 10⁵; p = 1.0). The load to failure was 1254 N (range 977-1299) in the ANTE group and 1234 N (range 1087-1456) in the RETRO group (p = 1.0). Construct stiffness with 250 N was not different between the two groups (ANTE 192 N/mm vs. RETRO 215 N/mm, p = 0.486). In all samples, the mode of failure was a transiliac fracture with screw breakout due to rotation of the pubic fragment around the axis of the screw with a range of rotational motion [ROM] during cyclic testing of 0.96° in one ANTE sample and 0.82° in one RETRO sample for 750 N, and ROM at failure of 2.53° in one ANTE sample and 2.23° in one RETRO sample. There was some plastic deformation of the screws in all cases but no breakage.

CONCLUSIONS

In this in vitro mechanical study, antegrade screw fixation of an anterior column acetabular fracture was not different in construct survival, load to failure, stiffness, and mode of failure when compared to retrograde screw fixation.

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.

Ilioinguinal approach versus Stoppa approach for open reduction and internal fixation in the treatment of displaced acetabular fractures: A systematic review and meta-analysis

PURPOSE

To compare the efficacy and safety of open reduction and internal fixation through ilioinguinal approach and Stoppa approach for the treatment of displaced acetabular fractures.

METHODS

Case-controlled trials (CCTs) published from January 2010 to August 2015 that compared the ilioinguinal approach and Stoppa approach in the management of displaced acetabular fractures were retrieved from the databases of Cochrane Library, Pubmed, CNKI, and so on. Methodological quality of the trials was critically assessed. Statistical software RevMan 5.0 was used for data analysis.

RESULTS

Eight articles were included in the meta-analysis. Through comparing the efficacy and safety of ilioinguinal approach and Stoppa approach in the treatment of displaced acetabular fracture, statistical significance was found in the average operation time [WMD = 68.29, 95% CI (10.52, 126.05), p < 0.05] and the median intraoperative blood loss [WMD = 142.26, 95% CI (9.30, 275.23), p < 0.05]. However, there existed no statistical significance in the fracture end reset satisfaction rate [RR = 0.63, 95% CI (0.17, 2.37), p > 0.05], the early complications rate [RR = 0.89, 95% CI (0.33, 2.40), p > 0.05], the late complications rate [RR = 0.91, 95% CI (0.27, 3.01), p > 0.05], and Harris hip score good function rate [RR = 0.52, 95% CI (0.25, 1.10), p > 0.05].

CONCLUSION

Though both techniques can obtain satisfactory clinical functions in the treatment of displaced acetabular fractures, Stoppa approach is superior to the ilioinguinal approach in terms of operation time and intraoperative blood loss.

The Retrograde-Antegrade-Retrograde Technique for Successful Placement of a Retrograde Superior Ramus Screw

Stabilization of pelvic ring injuries and certain acetabular fractures using percutaneous techniques is becoming increasingly more common. Intramedullary superior ramus screw fixation is beneficial in both injury types. While implants can be placed in an antegrade or retrograde direction, parasymphyseal ramus fractures benefit from retrograde implant insertion. In some patients, the parabolic osseous anatomy or obstructing soft tissues of the anterior pelvis or thigh can prevent appropriate hand and instrumentation positioning for appropriate retrograde ramus screw insertion through the entire osseous fixation pathway. Instead of abandoning medullary fixation, we propose a technique utilizing cannulated screws to successfully place retrograde screws in this distinct clinical scenario.

A radiographic simulation study of fixed superior pubic ramus fractures with retrograde screw insertion

OBJECTIVES

The study's aim is to calculate the parameters for retrograde insertion points for fixed superior pubic ramus fractures.

METHODS

From the pubic symphysis, diameter and length of the screw were measured, as well as the angle between the screw axis and the 3 planes.

RESULTS

When the diameter was fixed at 4.5 mm, the maximum lengths were 125 mm and 119 mm.

CONCLUSIONS

When the fracture occurs in Zone I, the penetration point could be selected in the pubic symphysis pubis angle to ensure that medial fracture fragments have sufficient screw channel length.