Comparative strength of three methods of fixation of transverse acetabular fractures

Independent volumetric internal fixation reduces posterior column acetabular fracture site motion as compared to plate/screw construct: A biomechanical analysis

Aims & objectives

To establish whether a suprapectineal pelvic reconstruction plate and posterior column screw (P&S) construct or a single 6.5-mm cannulated posterior column screw (PCS) construct demonstrates greater mechanical stability for fixation of acetabulum fractures involving the posterior column (PC). We hypothesized that the PCS construct would result in less fracture site motion.

Materials & methods

Twelve fourth-generation composite hemipelvi were utilized, 6 for each construct. The P&S construct consisted of a suprapectineal pelvic reconstruction plate with two 3.5-mm posterior column screws crossing the fracture site in lag-by-technique fashion and two screws anchoring the plate to the sciatic buttress. The PCS construct consisted of a single 6.5-mm partially threaded cannulated screw placed in an antegrade fashion. Both fixation models were cyclically loaded at 0.5 cycles/second at 400N and 800N, first in a sit-to-stand position that is expected during recovery, and subsequently in a squat-to-stand position to test overload conditions.

Results

Under sit-to-stand loading, the PCS construct resulted in less motion at the fracture site than the P&S construct (0.06 ± 0.02 mm vs 0.1 ± 0.02 mm at 400N, p = 0.02; 0.13 ± 0.03 mm vs 0.19 ± 0.04 mm at 800N, p = 0.03). The PCS construct also demonstrated less fracture site motion under squat-to-stand loading (0.22 ± 0.13 mm vs 1.9 ± 0.5 mm at 400N, p = < 0.001; 1.48 ± 0.44 mm vs 4.77 ± 0.3 mm at 800N, p = < 0.001). At 800 N, half of the repairs failed during squat-to-stand loading (2 PCS, 4 P&S).

Conclusion

Fixation of the posterior column of the acetabulum with a 6.5-mm cannulated screw demonstrated comparable fracture motion upon loading compared to the plate and screw construct.

Description of Standardized Planes and Angles for Percutaneous Supra-acetabular Screw Placement

BACKGROUND

Percutaneous screw fixation for pelvic fractures has become a minimally invasive alternative to an open operation. The complex anatomy of the pelvis renders this procedure challenging. The objective of this study was to assess standardized angles and dimensions of safety zones within a 3 D computed tomography model for optimal supra-acetabular screw placement.

METHODS

Computed tomography scans of 107 patients that suffered major trauma without showing any bone injury of the pelvis were collected. Using a software-based analysis, raw computed tomography data were transformed into 3 D models to set standardized landmarks and determine the possible insertion corridor.

RESULTS

Screws not exceeding a length of 97 mm in females and 106.4 mm in males were, in 95% of the evaluated cases, insertable without cortical bone penetration. The safety zone was 6.6 mm for females and 7.9 mm for males. Screws not exceeding these diameters were safely insertable in 95% of the cases. For the midsagittal plane, the angle was 36.4 ± 5.1 on the left and 34.7 ± 2.9 on the right (p = 0.008). For the anterior pelvic plane, the angle was 31.3 ± 4.5° on the left and 34.0 ± 4.8° on the right (p = 0.008).

CONCLUSIONS

Percutaneous fixation using supra-acetabular screws is a promising method to treat simple supra-acetabular fractures. These results may improve its safe utilization and could facilitate its broader clinical application.

Comparison between Novel Anatomical Locking Guide Plate and Conventional Locking Plate for Acetabular Fractures: A Finite Element Analysis

The treatment of complex acetabular fractures remains a complicated clinical challenge. Our self-designed novel anatomical locking guide plate (NALGP) has previously shown promising potential in T-shaped acetabular fractures (TAF), but a direct comparison with conventional fixations is yet to be made. The TAF model was established based on a volunteer's computer tomography data and then fixed with double column locking plates (DLP), a posterior column locking plate with anterior column screws (LPACS), and our NALGP. Forces of 200 N, 400 N, and 600 N were then loaded on the model vertically downward, respectively. The stress distribution and peaks and maximum displacements at three sites were assessed. We found that the stress area of all three plates was mainly concentrated around the fracture line, while only the matching screws of the NALGP showed no obvious stress concentration points. In addition, the NALGP and DLP showed significantly less fracture fragment displacement than the LPACS at the three main fracture sites. The NALGP was found to have less displacement than DLP at the posterior column and ischiopubic branch sites, especially under the higher loading forces of 400 N and 600 N. The fixation stability of the NALGP for TAF was similar to that of DLP but better than that of LPACS. Moreover, the NALGP and its matching screws have a more reasonable stress distribution under different loads of force and the same strength as the LPACS.

Antegrade Posterior Column Acetabulum Fracture Screw Fixation via Posterior Approach: A Biomechanical Comparative Study

Background and Objectives: Minimally invasive surgeries for acetabulum fracture fixation are gaining popularity due to their known advantages versus open reduction and internal fixation. Antegrade or retrograde screw fixation along the long axis of the posterior column of the acetabulum is increasingly applied in surgical practice. While there is sufficient justification in the literature for the application of the anterior approach, there is a deficit of reports related to the posterior approach. The aim of this study was to evaluate the biomechanical competence of posterior column acetabulum fracture fixation through antegrade screw placement using either a standard cannulated screw or a cannulated compression headless screw (CCHS) via posterior approach. Materials and Methods: Eight composite pelvises were used, and a posterior column acetabulum fracture according to the Letournel Classification was simulated on both their left and right sides via an osteotomy. The sixteen hemi-pelvic specimens were assigned to two groups (n = 8) for either posterior column standard screw (group PCSS) or posterior column CCHS (group PCCH) fixation. Biomechanical testing was performed by applying steadily increased cyclic load until failure. Interfragmentary movements were investigated by means of motion tracking. Results: Initial stiffness demonstrated significantly higher values in PCCH (163.1 ± 14.9 N/mm) versus PCSS (133.1 ± 27.5 N/mm), p = 0.024. Similarly, cycles and load at failure were significantly higher in PCCH (7176.7 ± 2057.0 and 917.7 ± 205.7 N) versus PCSS (3661.8 ± 1664.5 and 566.2 ± 166.5 N), p = 0.002. Conclusion: From a biomechanical perspective, CCHS fixation demonstrates superior stability and could be a valuable alternative option to the standard cannulated screw fixation of posterior column acetabulum fractures, thus increasing the confidence in postoperative full weight bearing for both the patient and treating surgeon. Whether uneventful immediate postoperative full weight bearing can be achieved with CCHS fixation should primarily be investigated in further human cadaveric studies with a larger sample size.

Comparison of Percutaneous Screw Fixation to Open Reduction and Internal Fixation in Acetabular Fractures: A Matched Pair Study Regarding the Short-Term Rate of Conversion to Total Hip Arthroplasty and Functional Outcomes

Closed reduction and percutaneous internal fixation (CRPIF) for acetabular fractures was introduced as a less invasive alternative to open reduction and internal fixation (ORIF) for moderately displaced fractures. Currently, comparisons of ORIF and CRPIF outcomes are rare. Twenty-three patients treated with CRPIF were matched with patients treated with ORIF based on sex, age, and fracture classification. Surgery-dependent and -independent factors of the in-hospital stay, the conversion rate to total hip arthroplasty (THA), and quality of life were assessed. The ORIF group had a higher preoperative fracture step (p = 0.04) and gull wing sign (p = 0.003) compared with the CRPIF group. Postoperatively, the gap and step size were not significantly different between the groups (p > 0.05). CRPIF required less time (p < 0.0001) and transfusions (p = 0.009) and showed fewer complications (p = 0.0287). Four patients were converted to THA (CRPIF, n = 1; ORIF, n = 3; p = 0.155) because of posttraumatic osteoarthritis. Functional outcomes and pain were similar in both groups (p > 0.05). The present study revealed less blood loss and a lesser extent of reduction in patients treated with CRPIF than in those treated with ORIF. The rates of conversion to THA and functional outcomes did not differ between CRPIF and ORIF. CRPIF appeared to be a valuable treatment option for selected patients.

The difference in the corridor of the antegrade posterior column screw according to the presence of pelvic dysmorphism

INTRODUCTION

Antegrade posterior column screw (aPCS) fixation via the anterior approach has been widely used for separated the posterior columns in acetabular fracture treatment. Although the relationship between pelvic dysmorphism and sacroiliac screws has been widely studied, no studies have reported on the clinical impact of pelvic dysmorphism on acetabular fractures. This study aimed to reveal the difference in the insertion angle and entry point of aPCS between the dysmorphic and normal pelvises.

METHODS

Patients diagnosed with unilateral acetabular fractures and who underwent pelvic computed tomography scans between 2013 and 2019 in two institutes were enrolled in this study. Patients were divided into the dysmorphic and control groups according to the sacral dysmorphic score, which predicts the presence of pelvic dysmorphism, and each group enrolled 130 patients. The semitransparent 3D hemipelvis model was reconstructed using a 3D reconstruction program. The sagittal and coronal angles of a virtual cylinder that fill the safe corridor of the column screw the most were measured. The surface area of the safe corridor and distance of the optimal entry point from the anterior border of the sacroiliac joint were analyzed. The measurements were compared between the dysmorphic and control groups.

RESULTS

The average sacral dysmorphic score in the normal and dysmorphic pelvis groups was 56.1 and 81.0, respectively. There were no significant differences in demographic data, including age, sex, height, weight, and body mass index, between the dysmorphic and control groups. There was a significant difference in the average sagittal insertion angle of PCs, which was 38.3° in the control group and 27.2° in the dysmorphic group (P < 0.001). The coronal insertion angles were not significantly different. The dysmorphic group presented longer straight distances (25.9 vs 24.8 mm, P = 0.026) and had a smaller aPCS surface area (685 vs 757 mm², P < 0.001) than the control group.

CONCLUSION

The present study describes a difference in the corridor of aPCS between the dysmorphic and normal pelvis. Insertion of aPCS in the dysmorphic pelvis requires a more acute angular trajectory in the sagittal plane than that in the normal pelvis.

Biomechanical analysis of fixation methods in acetabular fractures: a systematic review of test setups

Purpose

Optimal anatomical reduction and stable fixation of acetabular fractures are important in avoiding secondary dislocation and osteoarthritis. Biomechanical studies of treatment options of acetabular fractures aim to evaluate the biomechanical properties of different fixation methods. As the setup of the biomechanical test can influence the experimental results, this review aimed to analyze the characteristics, comparability and clinical implications of studies on biomechanical test setups and finite element analyses in the fixation of acetabular fractures.

Methods

A systematic literature research was conducted according to the PRISMA guidelines, using the PubMed/MEDLINE and Web of Science databases. 44 studies conducting biomechanical analyses of fixation of acetabular fractures were identified, which met the predefined inclusion and exclusion criteria and which were published in English between 2000 and April 16, 2021. The studies were analyzed with respect to distinct parameters, including fracture type, material of pelvis model, investigated fixation construct, loading direction, loading protocol, maximum loading force, outcome parameter and measurement method.

Results

In summary, there was no standardized test setup within the studies on fixation constructs for acetabular fractures. It is therefore difficult to compare the studies directly, as they employ a variety of different test parameters. Furthermore, the clinical implications of the biomechanical studies should be scrutinized, since several test parameters were not based on observations of the human physiology.

Conclusion

The limited comparability and restricted clinical implications should be kept in mind when interpreting the results of biomechanical studies and when designing test setups to evaluate fixation methods for acetabular fractures.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00068-022-01936-9.

Differences in fixation to young and elderly quadrilateral surfaces with anatomic quadrilateral surface plate (AQSP) based on cortical thickness morphological results

Aims

With relatively thinner cortical thickness, the management of acetabulum osteoporotic fractures in elderly patients is difficult. The aim of the research was to compare and present the morphological characteristics of the quadrilateral plate in young and elderly age groups, such as the area, and position distribution of the thin cortical thickness region, fracture lines maps, and propose a revised design plate for elderly patients based on these anatomic information.

Methods

As a retrospective research, acetabular fracture with one normal hemipelvises, including 110 men and 39 women, were collected to present the morphological characteristics of the quadrilateral region. The subjects were divided into three different age groups: Group I = 18–40 years (31.3 ± 6.6 years), Group II = 41–60 years (49.9 ± 5.3 years), and Group III ≥ 61 years (68.7 ± 6.8 years). The area of the quadrilateral surface, the area and position distribution of the thin cortical thickness region, the ratio and fracture lines maps were calculated and compared with Mimics in different groups.

Results

The thin cortical thickness/width region area (TCWRA) was significantly increased in Group III compared with Group I and Group II. The ratio of TCWRA accounted for in the quadrilateral region was also significantly increased in Group III (≥ 61 years) compared with Group I (P = 0.01) and Group II (P = 0.011). None of the subjects had a component involving the “A” zone, thirty-three thin cortical thickness regions were located in the “B” zone, and one hundred and sixteen involved both zones of the quadrilateral plate (“A + B” zone). Furthermore, there were a significant differences in the fracture line distributions in three age groups. More fracture lines of elderly patients were located at anterior part (B zone) compared with Group I and Group II.

Conclusions

It was identified the area of thin cortical thickness region increased as age grown, and fracture lines were inclined to be more distributed in “B” zone in elderly patients. To meet the demands of acetabular fixation in different age groups, cortical thickness changes in young and elderly individuals should be given special attention when the quadrilateral surface plate is designed.

Level of evidence Level IV, observational study.

The Short- and Mid-term Follow-Up of Single-Column Fixation in Transverse and Posterior Wall Acetabular Fractures

OBJECTIVE

To evaluate the radiological and clinical outcomes of the surgical treatment for transverse and posterior wall fractures using single-column posterior fixation.

METHODS

From January 2009 to January 2018, a total of 24 patients with transverse and posterior wall acetabular fractures in our center were included in this retrospective study, including 17 males and seven females with a mean age of 47 years and a minimum follow-up of 1 year. All cases were closed fractures. All fractures were fixed with single-column fixation via the Kocher-Langenbeck approach. Primary outcome measures, including quality of reduction and clinical outcomes, were recorded by an independent observer, who also noted secondary outcome measures, including time to surgery, surgical time, intraoperative blood loss, and postoperative complications.

RESULTS

Twenty-four patients (range, 26-74 years) included 17 males and seven females. There were 14 cases on the left side and 10 cases on the right side. The mean time from injury to surgery was 7.1 days. Mean intraoperative blood loss and surgical time were 405.4 mL and 135.8 min, respectively. The mean follow-up time was 29.5 months (range 12-96 months). All the acetabular fractures united within 5 months after surgery. The quality of reduction was graded as anatomical in 17 cases (70.8%), imperfect in three cases (12.5%), and poor in four cases (16.7%). According to grading system of Merle d' Aubigne and Postel, clinical outcomes at the final follow-up were excellent in 10 cases (41.7%), good in six cases (25.0%), fair in five cases (20.5%), and poor in three cases (12.5%). The excellent and good rate was 66.7%. There was a significant relation between the quality of reduction and clinical outcomes (P < 0.05). At follow-up, there were one case of sciatic nerve injury, one case of wound infection, two cases of deep vein thrombosis, two cases of avascular necrosis, three cases of heterotopic ossification, and five cases of postoperative traumatic arthritis. Three of these patients underwent reoperation, including one with heterotopic ossification affecting hip movement and two with femoral head necrosis.

CONCLUSIONS

Our study shows that single-column posterior fixation of transverse and posterior wall acetabular fracture through the Kocher-Langenbeck approach can obtain satisfactory radiological and clinical outcomes if there is adequate indirect reduction of the anterior column.

The largest secure corridor of the infra-acetabular screw-a 3-D axial perspective analysis

Background

The infra-acetabular screw which is placed from the pubis to the ischium can be used as a special positional screw of the posterior column of the acetabulum. This study was performed to simulate the surgical procedure and obtain the ideal insertion point, diameter, length and angle of the screw through the method of axial perspective in Chinese patients.

Methods

We randomly collected the pelvic computed tomography (CT) scans of 200 adults. DICOM-formatted CT-scan images were imported into Mimics software to establish the 3D digital model of the right semi-pelvic was established. A virtual cylinder representing the screw was placed from the pubis to the ischium to fix the posterior column. The largest secure diameter and length of the virtual screw were measured and the position of the insertion point and the directions of the screw were also researched.

Results

The screw insertion safe zone exhibits an irregular shape of “tear drop” in the reconstructed pelvic model. The mean maximum diameter of screws was 5.01 ± 1.28 mm, and the mean maximum length of screws was 93.99 ± 8.92 mm. The screw insertion corridor with the least diameter 3.5 mm was found in 94 of 100 males (94%) and 86 of 100 females (86%). We found gender-dependent differences for the mean maximum diameter and the maximum length of the screw. There was statistically significant difference between genders in the position of insertion point.

Conclusions

In this study, we suggest an individual preoperative 3D reconstruction simulation to develop better screw placement plans, which provides a valuable guideline for seeking the largest secure corridor of infra-acetabular screw. Further biomechanical studies are needed to verify the function of the screw.

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.

Comparative study of anatomical locking plate and reconstruction plate in treating acetabular fractures

PURPOSE

This study aims to compare the effectiveness of anatomic locking plate and reconstruction plate used in treating acetabular fractures.

METHODS

From January 2009 to January 2016, patients with acetabular fractures were included in this retrospective study. We grouped the patients into two groups based on the internal fixation: reconstruction plate group (RPG) and anatomic locking plate group (ALPG). The operation time, blood loss, intra-operative screw penetration, and plate breakage were compared between the two groups. The intra-operative fluoroscopic images were used to evaluate the fixation location. The quality of reduction and radiological grading were assessed according to the criteria developed by Matta. The clinical assessment was based on the Merle d'Aubigne-Postel score.

RESULTS

Eighty-three patients were included in this study and were followed up for an average of 35 months (range, 25 to 42 months). Thirty-five patients were treated with the anatomical locking plate, and 48 patients were treated with the reconstruction plate. The mean surgical time was significantly shorter (P < 0.0001) in ALPG patients than in RPG patients, and the intra-operative blood loss was significantly lower (P = 0.008). The rates of intra-operative screw penetration or plate breakage in the ALPG (0/35) are significantly lower than that in the RPG (7/48) (P = 0.018). Post-operative Matta score (P = 0.905), Merle d'Aubigne-Postel score (P = 0.957), and overall complication rates (P = 0.391) were not significantly different among the groups.

CONCLUSION

Patients treated by anatomical locking plate had shorter operation time, less bleeding, and lower rate screw perforation compared to patients treated by reconstruction plate. Anatomical locking plate is a better choice for acetabulum fractures, especially complicated fractures.

Biomechanical analysis of fixation methods for acetabular fractures: A review

Acetabular fractures are known as one of the most frequent types of pelvic fractures with growing frequency among elderly people. Because of this, it is important to establish the methods of repair that will produce optimal outcomes for fracture healing and joint remobilization. Open reduction and internal fixation are considered as the "gold standard" of acetabular fracture repair; however, to the best of authors' knowledge, there is no systematic review comparing different repair methods from biomechanical point of view. As such, in this review paper, we summarize the results of English language literature biomechanically focused on acetabular fracture fixation methods in the last thirty years with the aim to create a reference for clinical decision making. The selected literature within the review is broken down into categories based on type of fracture, i.e., simple or complex, and then further grouped based on fracture line orientation. Clinical recommendations and future research possibilities are also provided.

A novel Patient-Specific Three-Dimensional Printing Template Based on External Fixation for Pelvic Screw Insertion

PURPOSE

To investigate the clinical effect of novel patient-specific 3D printing templates based on external fixation for pelvic screw insertion compared with the fluoro-navigation technique.

MATERIALS AND METHODS

We retrospectively studied 18 pelvic fracture patients from July 2017 to July 2018. For analysis, patients were divided into two groups: the template group (15 screws in 8 patients) and the fluoro-navigation group (22 screws in 10 patients). The screw insertion time, radiation exposure time, and accuracy of the screw insertion as evaluated by postoperative CT scans were analyzed.

RESULTS

In the template group, the average screw insertion time (11.5 ± 2.3 min/screw) was significantly 50.6% less than that in the fluoro-navigation group (23.3 ± 3.1 min/screw; P < 0.05). The average time of X-ray exposure in the template group (11.5 ± 3.9 s/screw) was also significantly 39.8% less than in the fluoro-navigation group (19.1 ± 2.5 s/screw; P < 0.05). In the template group, the mean deviation distance and angle between the actual and planned screw position was 2.6 ± 0.2 mm and 2 ± 0.3°.

CONCLUSIONS

The patient-specific template based on external fixation can guide the insertion of the pelvic screw accurately and safely while significantly reducing operation and radiation exposure time.

Biomechanical Comparison of Different Fixation Techniques for Typical Acetabular Fractures in the Elderly: The Role of Special Quadrilateral Surface Buttress Plates

BACKGROUND

Anterior column-posterior hemitransverse fractures are prevalent in the elderly and are often associated with quadrilateral surface (QLS) comminution. Several special QLS buttress plates have been introduced, but evidence of their comparability with traditional fixation devices is lacking. This biomechanical study aimed to compare special QLS buttress plates with traditional fixation devices.

METHODS

Anterior column-posterior hemitransverse fractures with an isolated QLS fragment were created on 24 composite hemipelves and were allocated to 4 fixation groups: (1) infrapectineal QLS buttress plate, (2) suprapectineal QLS buttress plate, (3) suprapectineal reconstruction plate with 3 periarticular long screws, and (4) infrapectineal reconstruction plate with 3 periarticular long screws. Specimens were loaded to simulate partial weight-bearing (35 to 350 N) or full weight-bearing (75 to 750 N). A testing machine was synchronized with a 3-dimensional video tracking system to optically track displacement at the points of interest and to calculate construct stiffness. The fixation systems were compared using the Kruskal-Wallis and Mann-Whitney U tests.

RESULTS

The experimental results of the partial and full weight-bearing simulations were surprisingly similar. During 40 loading cycles, the maximum displacement on the 6 predetermined points did not exceed 1.1 mm. Multiple-group comparisons of relative displacements of each predetermined measurement point did not differ significantly (p > 0.05). The suprapectineal reconstruction plate with 3 periarticular long screws demonstrated the greatest construct stiffness and significantly greater stiffness than the infrapectineal plate with long screws (p < 0.017). However, no significant difference (p > 0.017) in stiffness was identified between the infrapectineal QLS buttress plate and the suprapectineal reconstruction plate with long screws.

CONCLUSIONS

The suprapectineal pelvic brim plate with 3 periarticular long screws remains the gold standard to treat anterior column-posterior hemitransverse fractures. The special infrapectineal QLS buttress plate provides stiffness and stability comparable with those of standard fixation. However, moving the pelvic brim plate from the suprapectineal border to the infrapectineal border is not recommended for anterior column-posterior hemitransverse fractures because it significantly decreases fixation stiffness.

CLINICAL RELEVANCE

Special QLS buttress plates may be an alternative fixation method for anterior column-posterior hemitransverse acetabular fractures in the elderly, especially when a less invasive anterior intrapelvic approach is selected.

Biomechanical analysis of transverse acetabular fracture fixation in the elderly via the posterior versus the anterior approach with and without a total hip arthroplasty

This study provides the first biomechanical comparison of the fixation constructs that can be created to treat transverse acetabular fractures when using the “gold-standard” posterior versus the anterior approach with and without a total hip arthroplasty in the elderly. Synthetic hemipelvises partially simulating osteoporosis (n = 24) were osteotomized to create a transverse acetabular fracture and then repaired using plates/screws, lag screws, and total hip arthroplasty acetabular components in one of four ways: posterior approach (n = 6), posterior approach plus a total hip arthroplasty acetabular component (n = 6), anterior approach (n = 6), and anterior approach plus a total hip arthroplasty acetabular component (n = 6). All specimens were biomechanically tested. No differences existed between groups for stiffness (range, 324.6–387.3 N/mm, p = 0.629), clinical failure load at 5 mm of femoral head displacement (range, 1630.1–2203.9 N, p = 0.072), or interfragmentary gapping (range, 0.67–1.33 mm, p = 0.359). Adding a total hip arthroplasty acetabular component increased ultimate mechanical failure load for posterior (2904.4 vs. 3652.3 N, p = 0.005) and anterior (3204.9 vs. 4396.0 N, p = 0.000) approaches. Adding a total hip arthroplasty acetabular component also substantially reduced interfragmentary sliding for posterior (3.08 vs. 0.50 mm, p = 0.002) and anterior (2.17 vs. 0.29 mm, p = 0.024) approaches. Consequently, the anterior approach with a total hip arthroplasty may provide the best biomechanical stability for elderly patients, since this fixation group had the highest mechanical failure load and least interfragmentary sliding, while providing equivalent stiffness, clinical failure load, and gapping compared to other surgical options.

A novel anatomically pre-contoured side-specific titanium plate versus the reconstruction plate for quadrilateral plate fractures of the acetabulum: a propensity-matched cohort study

Background

Surgical treatment of acetabular fractures involving a quadrilateral plate is a challenge to orthopedic surgeons. We have developed a novel fixation technique using a specially shaped reconstruction plate combined with several buttress screws of a quadrilateral plate which was also called a dynamic anterior plate-screw system for quadrilateral plate (DAPSQ) to treat acetabular fractures involving quadrilateral plate since 2005 (RP group). And the long-term follow-up results have confirmed the effectiveness and safety of this technique. After 2016, standardized titanium plate (STP group) of DAPSQ have been designed and applied. The aim of the study was to compare the clinical efficacy of anatomical plate and the reconstruction plate of DAPSQ in the treatment of quadrilateral plate fractures.

Methods

We led a propensity-matched cohort study of quadrilateral plate fractures. Twenty-two patients were included in the STP group during the inclusion period (2016–2018) and were matched to 22 cases in our database of the RP group (2008–2016). The primary outcome measures were the quality of reduction and functional outcomes. Intraoperative conditions were also compared.

Results

Of these 22 consecutive patients in the STP group, the mean age was 46.7 years and the most common fracture pattern was a both-column fracture (12 cases, 54.5%) according to Letournel-Judet classification. The mean follow-up period was 23.1 months (range 12–37). There were no significant differences between the two groups with regard to the quality of reduction using the Matta radiological criteria and functional outcomes evaluated by the modified Merle d’Aubigné score (P > 0.05). Compared with the RP group, the STP group had a shorter operation time (245.1 min vs. 286.8 min, P = 0.020), less intraoperative blood loss (1136.4 mL vs. 1777.3 mL, P = 0.014), and transfusion (780.9 vs. 1256.8 mL, P = 0.035). The complication rate was 18.2% in the STP group, and there was no significant difference compared with the RP group (36.4%) (P > 0.05). None of the cases in the two groups had quadrilateral screws entering the hip or implant failure.

Conclusions

The fixation of standardized titanium plate in quadrilateral plate fractures showed a similar result to the reconstruction plate, in terms of quality of reduction and functional outcome. The standardized titanium plate of DAPSQ has the advantages of a short operation time, less intraoperative bleeding, and blood transfusion, and it is worth further promotion and research.

Minimally invasive surgical treatment of minimally displaced acetabular fractures does not improve pain, mobility or quality of life compared to conservative treatment: a matched-pair analysis of 50 patients

Background

Currently available procedures for the treatment of minimally displaced acetabular fractures include conservative treatment and minimally invasive percutaneous screw fixation. Screw fixation of acetabular fractures allows patients’ early full-weight bearing due to improved biomechanic stability. Can the range of motion, pain and mobility and quality of life in patients with acetabular fractures be improved by minimally invasive screw fixation, compared to conservative treatment in the long term?

Methods

Patients treated for a minimally displaced acetabular fracture, either conservatively or by closed reduction percutaneous screw fixation, in the period from 2001 to 2013 were included in this retrospective study. Minimal displacement was considered to be less than 5 mm. As well as the collection and analysis of baseline data, Harris Hip Score, Merle d’Aubigné score and Short Form 12 (SF-12) questionnaire data were recorded in the context of a clinical study. To better account for confounding factors, patients of each group were matched. The matched-pair criteria included age, BMI, Letournel fracture classification and the presence of associated injuries.

Results

Twenty-five patients from each group were matched. On the Harris Hip Score, conservatively treated patients obtained 96 points (52–100, SD 17) vs. 89 points (45–100, SD 17, p = 0.624). On the Merle d’Aubigné score, conservatively treated patients obtained 17 points (10–18, SD 2) vs. 17 points (11–18, SD 2, p = 0.342).

Patients with acetabular fractures treated by minimally invasive screw fixation did not result in improved quality of life, measured by SF-12 questionnaire, compared to conservatively treated patients (PCS 47, SD 9 vs. 44, SD 10; p = 0.294 and MCS 51, SD 7 vs. 53, SD 7; p = 0.795).

Conclusions

The clinical results of the two groups revealed no statistically significant differences. From the data, it cannot be deduced that minimally invasive surgical therapy is superior to conservative treatment of minimally displaced acetabular fractures. Prospective randomised studies are recommended to allow reliable evaluation of both treatment options.

Trial registration

Retrospectively registered

Precontoured Quadrilateral Surface Acetabular Plate Fixation Demonstrates Increased Stability When Compared With Pelvic Reconstruction Plates: A Biomechanical Study

OBJECTIVE

To compare the stability of 3 fixation strategies for a transverse acetabular fracture: a reconstruction plate with anterior and posterior column screws (group A); an infrapectineal precontoured quadrilateral surface buttress (iPQSB) plate alone (group B); and an anterior column lag-screw and iPQSB plate (group C).

METHODS

A transverse acetabular fracture was created in 18 synthetic hemipelvises. Six were fixed by each of the 3 methods described. Specimens underwent cyclic axial compressive loading to 1700N for 42,000 cycles while anterior and posterior column displacements were measured, followed 4800N for 50 cycles. Displacement and stiffness data were analyzed with analysis of variance and Tukey HSD. A Cox proportional hazards regression model was used to determine survival rate. P values < 0.05 were considered significant.

RESULTS

Group C had significantly less posterior column displacement (0.16 ± 0.06 mm) compared with group B (0.38 ± 0.37 mm, P < 0.0001) and group A (0.38 ± 0.37 mm, P < 0.0001). In addition, group A had significantly more anterior column displacement (0.28 ± 0.11 mm) than group B (0.22 ± 0.14 mm, P = 0.0310) and group C (0.18 ± 0.09 mm, P = 0.0001). Group C was 10.5% stiffer than group A (P = 0.0037). Group B had a 7.27x greater rate of failure than group C (95% confidence interval, 1.6-33.2).

DISCUSSION AND CONCLUSION

Under anatomical loading, iPQSB plates with anterior column lag-screw fixation demonstrate increased stability in a synthetic bone transverse acetabular fracture model. Based on our data, we support additional evaluation of early weight-bearing after transverse acetabular fracture fixation in patients with healthy bone when an anterior column screw-iPQSB plate construct is used.

Precontoured buttress plate vs reconstruction plate for acetabulum posterior wall fractures: A biomechanical study

BACKGROUND

The purpose of open reduction and internal fixation of acetabulum posterior wall fractures is to restore anatomical structure and stability of the hip joint, in order to start weight bearing as soon as possible and prevent hip arthrosis; restoration of the anatomy should preserve function of the joint as well. Although “special shaped precontoured plates” have been developed in recent years for surgical treatment of this region, studies comparing the traditional plates with the newly designed precontoured plates are lacking.

AIM

To evaluate the biomechanical properties of precontoured anatomic buttress and conventional curved reconstruction plates (CCRPs) for posterior wall acetabulum fracture treatment.

METHODS

Twelve pelvis models were created for testing plate treatment of fracture in the posterior wall of the acetabulum. These 12 pelvis models were used to create 24 hemipelvis models (experimental) by cutting from the sagittal plane and passing over the center of gravity, after which the posterior wall acetabular fractures (of similar type and size) were created. In these experimental models, the right acetabulum was fixed with a 5-hole CCRP, while the left was fixed with a precontoured anatomic buttress plate (PABP). Samples were placed through the test device and were subjected to static load testing, with a constant testing velocity of 2 mm/min until the load reached 2.3 kN or the acetabular fixation failed. Dynamic tests were also performed with sinusoidal wave load, with a maximal load of 2.3 kN and a load ratio of 0.1.

RESULTS

The average stiffness values were 460.83 ± 95.47 N/mm for the PABP and 291.99 ± 118.58 N/mm for the 5-hole CCRP. The precontoured anatomic acetabulum buttress plates had significantly higher rigidity than the CCRPs (P = 0.022). There was a statistically significant difference between the unloaded and 2.3 kN-loaded values of AL (posterosuperior fracture line vertical to the ground surface) and CL (posteroinferior fracture line vertical to the ground surface) parameters for both the PABPs and the 5-hole CCRPs (P = 0.036 and P = 0.045, respectively). According to the static tests, the amount of total displacement was significantly less in the PABPs than in the CCRPs. Comparative analysis of the displacement in the BL (posterior wall fracture line horizontal to the ground) parameter yielded no statistically significant differences between the PABP and the 5-hole CCRPs (P = 0.261).

CONCLUSION

PABP provides more stable fixation in acetabulum posterior wall fractures than 5-hole CCRP, allowing for proximal or distal fracture line screw application without reshaping.

Biomechanical Evaluation of a New Fixation Type in 3D-Printed Periacetabular Implants using a Finite Element Simulation

Pelvic implants require complex geometrical shapes to reconstruct unusual areas of bone defects, as well as a high mechanical strength in order to endure high compressive loads. The electron beam melting (EBM) method is capable of directly fabricating complex metallic structures and shapes based on digital models. Fixation design is important during the 3D printing of pelvic implants, given that the fixation secures the pelvic implants to the remaining bones, while also bearing large amounts of the loads placed on the bone. In this study, a horseshoe-shaped plate fixation with a bridge component between two straight plates is designed to enhance the mechanical stability of pelvic implants. The aim of this study is to investigate the biomechanics of the horseshoe-shaped plate fixation in a 3D-printed pelvic implant using a finite element (FE) simulation. First, computed tomography (CT) scans were acquired from a patient with periacetabular bone tumors. Second, 3D FE implant models were created using the patient’s Digital Imaging and Communications in Medicine (DICOM) data. Third, a FE simulation was conducted and the stress distribution between a conventional straight-type plate model, and the horseshoe-shaped plate model was compared. In both of the models, high-stress regions were observed at the iliac fixation area. In contrast, minimal stress regions were located at the pubic ramus and ischium fixation area. The key finding of this study was that the maximal stress of the horseshoe-shaped plate model (38.6 MPa) was 21% lower than that of the straight-type plate model (48.9 MPa) in the iliac fixation area. The clinical potential for the application of the horseshoe-shaped plate fixation model to the pelvic implant has been demonstrated, although this is a pilot study.

Single versus double column fixation in transverse fractures of the acetabulum: A randomised controlled trial

INTRODUCTION

Biomechanical studies have compared fixation methods in transverse acetabular fractures, yet there is not enough clinical data to suggest an optimal fixation method. The aim of this randomized controlled trail was to compare fracture stability in posterior plating alone versus posterior plating and anterior column lag-screw fixation in treatment of transverse and transverse with posterior wall acetabular fractures.

METHODS

Thirty patients were randomized to one of two groups, either posterior fixation alone (single column group), or posterior plating and anterior fixation with percutaneous anterior column screw (double column group). Patients were followed up with serial radiographic assessments documenting any loss of reduction, utilizing Matta's radiological criteria, measuring the roof arc angles and by measuring any change in the femoral head offset.

RESULTS

Fifteen patients were randomized to each group. Mean patient age was 31 years, mean follow up period was 19 months (range 12-24). There was no significant differences between the two groups with regards the quality of post-operative reduction, blood loss, hospital stay and functional score using the modified Merle D'Aubinge and Postel score. The operative time was significantly longer in the double column fixation group (130 min versus 104 min). There was no loss of reduction observed in either of the two groups.

CONCLUSION

Single poster column fixation in transverse and transverse posterior wall fractures showed similar result to double column fixation, in terms of fractures stability in the follow up period, quality of reduction and early functional outcome.

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.

Posterior column acetabular fracture fixation using a W-shaped angular plate: A biomechanical analysis

Objective

The purpose of this study was to compare the stability and feasibility of four fixation constructs in a posterior column acetabular fracture: one reconstruction plate, one reconstruction plate and lag screw, two reconstruction plates, and a W-shaped acetabular angular plate.

Methods

Twenty embalmed cadaveric pelvises with a posterior column acetabular fractures were allocated to one of four groups: 1) a reconstruction plate, 2) a reconstruction plate with a posterior column lag screw, 3) double reconstruction plates, and 4) a W-shaped acetabular angular plate. These constructs were mechanically loaded on a testing machine, and construct stiffness values were measured. Strain gauges were utilized to measure the mechanical behavior in the condition of compressive force.

Results

Final stiffness was not different between the two reconstruction plates (445.81±98.30 N/mm) and the W-shaped acetabular angular plate (447.43±98.45 N/mm, p = 0.524), both of which were superior to a single reconstruction plate (248.90±61.95 N/mm) and a combined plate and lag screw (326.41±94.34 N/mm). Following the fixation of the W-shaped acetabular angular plate, the strain distribution was similar to the intact condition around the acetabulum. The parameters of the W-shaped acetabular angular plate that were observed at the superior region of the acetabulum were less than those of a single reconstruction plate (p<0.05), a single reconstruction plate with lag screw (p<0.05), and two reconstruction plates (p<0.05).

Conclusions

The novel W-shaped acetabular angular plate fixation technique was able to provide the biomechanically stiffest construct for stabilization of a posterior column acetabular fracture; it also resulted in a partial restoration of joint loading parameters toward the intact state.

Treatment of Transverse with or without Posterior Wall Fractures of Acetabulum Using a Modified Smith-Petersen Combined with Kocher-Langenbeck Approach

BACKGROUND The aim of this study was to explore the surgical treatment of transverse with or without posterior wall fractures of the acetabulum. MATERIAL AND METHODS We surgically treated 21 consecutive cases of pure transverse (7 cases) and with posterior wall (14 cases) fractures of the acetabulum. The anterior column fractures were firstly reduced, temporarily fixed through a modified Smith-Petersen small incision, and finally fixed after the fixation of the posterior column and wall fractures, which were reduced and fixed through a Kocher-Langenbeck approach. The operative time, intra-operative blood loss, quality of reduction (Matta criteria), perioperative complications, osseous union, subsequent complications, and hip function evaluation were recorded. RESULTS The mean operative time was 198.1 min and the mean intra-operative blood loss was 938.1 ml. Anatomic reduction of the anterior column was obtained in 20 cases and was imperfect in 1 case. All posterior column and wall fractures were anatomically reduced. We followed up 18 cases for a mean duration of 16.3 (8-30) months. All the fractures achieved osseous union. The mean Harris score was 85.1 points, with an excellent result in 7 cases, good in 8, fair in 2, and poor in 1. According to modified Merle d' Aubigne and Postel score system, the results were excellent in 2 cases, good in 15, and poor in 1. Avascular necrosis of the femoral head occurred in 1 case, heterotopic ossification in 3 cases, and numbness of the anterolateral thigh in 6 cases. CONCLUSIONS For transverse with or without posterior wall fractures of the acetabulum, reduction and fixation of anterior and posterior column should be done in sequence, and a modified Smith-Petersen small incision might be a good choice in reduction and fixation of the anterior column because it possesses advantages of direct visualization and minimal invasion.

Definition of a safe zone for antegrade lag screw fixation of fracture of posterior column of the acetabulum by 3D technology

The objective of this study was to define a safe zone for antegrade lag screw fixation of fracture of posterior column of the acetabulum using a novel 3D technology. Pelvic CT data of 59 human subjects were obtained to reconstruct three-dimensional (3D) models. The transparency of 3D models was then downgraded along the axial perspective (the view perpendicular to the cross section of the posterior column axis) to find the largest translucent area. The outline of the largest translucent area was drawn on the iliac fossa. The line segments of OA, AB, OC, CD, the angles of OAB and OCD that delineate the safe zone (ABDC) were precisely measured. The resultant line segments OA, AB, OC, CD, and angles OAB and OCD were 28.46mm(13.15-44.97mm), 45.89mm (34.21-62.85mm), 36.34mm (18.68-55.56mm), 53.08mm (38.72-75.79mm), 37.44° (24.32-54.96°) and 55.78° (43.97-79.35°) respectively. This study demonstrates that computer-assisted 3D modelling techniques can aid in the precise definition of the safe zone for antegrade insertion of posterior column lag screws. A full-length lag screw can be inserted into the zone (ABDC), permitting a larger operational error.

A novel navigation template for fixation of acetabular posterior column fractures with antegrade lag screws: design and application

PURPOSE

To test whether a novel guide template we designed can facilitate accurate insertion of antegrade lag screws in the fixation of acetabular posterior column fractures.

METHODS

We created virtual three-dimensional reconstruction models of the pelvis from CT scan data obtained from 96 adult patients without any bony problems. A virtual cylindrical implant was placed along the longitudinal axis of the acetabular posterior column passing through the ischial tuberosity. The diameter of cylindrical implant was augmented to 6.5 mm, and the direction was adjusted until the optimal screw path was found using the reverse engineering technique. The orifice of this cylinder from the iliac fossa was determined as the entry point for the antegrade lag screw. The anatomical parameters of the screw entry path were measured and saved in .stl format. The guide template was designed according to the acetabular morphology and the measured anatomical parameters before it was put into manufacture of a solid template with the rapid prototyping technique. The feasibility and accuracy of the guide template were tested in cadaveric pelvises. Finally, the guide template was used in real surgery for five patients. Furthermore, the time required for surgery was recorded.

RESULTS

Under the guide of this navigation template, antegrade lag screws were successfully placed in the posterior column of the acetabulum in the cadaveric test. And five lag screws were successfully placed in five patients. The mean time of antegrade lag screw insertion required 5.8 (3-10) min.

CONCLUSIONS

Antegrade lag screws can be more accurately put into the posterior column of the acetabulum with the help of this navigation template.

Axial perspective to find the largest intraosseous space available for percutaneous screw fixation of fractures of the acetabular anterior column

OBJECTIVE

To find the largest screw path in the acetabular anterior column using a novel method of axial perspective and test the clinical feasibility of the anterior column axial view projection.

METHODS

3D models with the inner triangular patches deleted were created from the pelvic CT scan data of 58 normal pelvises. The transparency of each 3D model was downgraded at the axial perspective (the view perpendicular to the cross section of the anterior column axis) so that a translucent area was seen clearly. The orientations of each 3D model were adjusted until a triangle-like translucent area that could accommodate the largest virtual screw (Screw I) was present and then an ellipse-like translucent area that could accommodate the two largest virtual screws (Screw II) was present. The maximum diameter, direction of Screw I and the maximum diameter Screw II were measured. Clinical feasibility of the axial view projection was next tested in five cadaveric specimens.

RESULTS

The mean maximum diameters of Screw I and Screw II were 11.20 ± 1.73 (7.80-14.60 mm) and 8.71 ± 0.91 (6.60-10.60 mm), respectively. The angles of Screw I to the transverse, coronal and sagittal planes were 41.16° ± 4.59°, 18.18° ± 1.15° and 44.33° ± 4.31°, respectively. Translucent areas were successfully observed in all the cadaveric hemi-pelves and guide pins were successfully inserted in all the cadaveric hemi-pelves with the assistance of the anterior column axial view projection without cortex penetration or joint violation.

CONCLUSIONS

The acetabular anterior column could safely accommodate not only one 7.3-mm screw, but also two 6.5-mm screws. The anterior column axial projection may be clinically feasible.

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.

Are quadrilateral surface buttress plates comparable to traditional forms of transverse acetabular fracture fixation?

BACKGROUND

Several construct options exist for transverse acetabular fracture fixation. Accepted techniques use a combination of column plates and lag screws. Quadrilateral surface buttress plates have been introduced as potential fixation options, but as a result of their novelty, biomechanical data regarding their stabilizing effects are nonexistent. Therefore, we aimed to determine if this fixation method confers similar stability to traditional forms of fixation.

QUESTIONS/PURPOSES

We biomechanically compared two acetabular fixation plates with quadrilateral surface buttressing with traditional forms of fixation using lag screws and column plates.

METHODS

Thirty-five synthetic hemipelves with a transverse transtectal acetabular fracture were allocated to one of five groups: anterior column plate+posterior column lag screw, posterior column plate+anterior column lag screw, anterior and posterior column lag screws only, infrapectineal plate+anterior column plate, and suprapectineal plate alone. Specimens were loaded for 1500 cycles up to 2.5x body weight and stiffness was calculated. Thereafter, constructs were destructively loaded and failure loads were recorded.

RESULTS

After 1500 cycles, final stiffness was not different with the numbers available between the infrapectineal (568±43 N/mm) and suprapectineal groups (602±87 N/mm, p=0.988). Both quadrilateral plates were significantly stiffer than the posterior column buttress plate with supplemental lag screw fixation group (311±99 N/mm, p<0.006). No difference in stiffness was identified with the numbers available between the quadrilateral surface plating groups and the lag screw group (423±219 N/mm, p>0.223). The infrapectineal group failed at the highest loads (5.4±0.6 kN) and this was significant relative to the suprapectineal (4.4±0.3 kN; p=0.023), lag screw (2.9±0.8 kN; p<0.001), and anterior buttress plate with posterior column lag screw (4.0±0.6 kN; p=0.001) groups.

CONCLUSIONS

Quadrilateral surface buttress plates spanning the posterior and anterior columns are biomechanically comparable and, in some cases, superior to traditional forms of fixation in this synthetic hemipelvis model.

CLINICAL RELEVANCE

Quadrilateral surface buttress plates may present a viable alternative for the treatment of transtectal transverse acetabular fractures. Clinical studies are required to fully define the use of this new form of fixation for such fractures when accessed through the anterior intrapelvic approach.

Biomechanical comparison of different stabilization constructs for unstable posterior wall fractures of acetabulum. A cadaveric study

PURPOSE

Operative treatment of unstable posterior wall fractures of acetabulum has been widely recommended. This laboratory study was undertaken to evaluate static fixation strength of three common fixation constructs: interfragmentary screws alone, in combination with conventional reconstruction plate, or locking reconstruction plate.

METHODS

Six formalin-preserved cadaveric pelvises were used for this investigation. A posterior wall fracture was created along an arc of 40-90 degree about the acetabular rim. Three groups of different fixation constructs (two interfragmentary screws alone; two interfragmentary screws and a conventional reconstruction plate; two interfragmentary screws and a locking reconstruction) were compared. Pelvises were axial loaded with six cycles of 1500 N. Dislocation of superior and inferior fracture site was analysed with a multidirectional ultrasonic measuring system.

RESULTS

No statistically significant difference was found at each of the superior and inferior fracture sites between the three types of fixation. In each group, the vector dislocation at superior fracture site was significantly larger than inferior one.

CONCLUSIONS

All those three described fixation constructs can provide sufficient stability for posterior acetabular fractures and allow early mobilization under experimental conditions. Higher posterior acetabular fracture line, transecting the weight-bearing surface, may indicate a substantial increase in instability, and need more stable pattern of fixation.

An evaluation of three-dimensional image-guided technologies in percutaneous pelvic and acetabular lag screw placement

BACKGROUND

Percutaneous stabilization using three-dimensional (3D) navigation system is a promising treatment for pelvic and acetabular fractures. However, there are still some controversies regarding the use of 3D navigation to treat pelvic and acetabular fractures. The purpose of this study was to compare the Iso-C(3D) fluoroscopic navigation, standard fluoroscopy, and two-dimensional (2D) fluoroscopic navigation in placing percutaneous lag screws in pelvic specimens to better understand the merits of 3D navigation techniques.

METHODS

Fifty-four instrumentation procedures were performed in this study using six cadaveric pelvic specimens. Three groups were designated for different procedures and tests: group I, standard fluoroscopy; group II, 2D fluoroscopic navigation; and group III, Iso-C(3D) fluoroscopic navigation. Nine screws were placed in each pelvis, including four screws placed bilaterally through the ilium into S1 and S2 vertebrae, four screws placed bilaterally through anterior and posterior columns of acetabulum, and one screw placed through the pubic symphysis. 3D fluoroscopic techniques were evaluated to determine the accuracy of screw position, instrumentation time, and fluoroscopic time. The data were statistically analyzed using SPSS 13.0.

RESULTS

The malposition rate was 38.89%, 22.22%, and 0% in standard fluoroscopy, 2D fluoroscopic navigation, and Iso-C(3D) fluoroscopic navigation groups, respectively. There was no significant difference between standard fluoroscopy and 2D fluoroscopic navigation. Compared with Iso-C(3D) fluoroscopic navigation, there were significant differences (analysis of variance [ANOVA], P < 0.05). The mean instrumentation operating time using Iso-C(3D) fluoroscopic navigation technique was 15.4 ± 4.5 min. There were significant differences compared with standard fluoroscopy (31.5 ± 6.2 min) and 2D fluoroscopic navigation (26.3 ± 7.5 min; ANOVA, post hoc Scheffe, P < 0.01). The mean fluoroscopic time of Iso-C(3D) fluoroscopic navigation was 66 ± 4.8 min. Compared with standard fluoroscopy (132.8 ± 7.3 min) and 2D fluoroscopic navigation (47.7 ± 5.6 min), there were significant differences (ANOVA, post hoc least significant difference, P < 0.01).

CONCLUSIONS

In the present study, we compared Iso-C(3D) fluoroscopic navigation, 2D fluoroscopic navigation, and standard fluoroscopy. Iso-C(3D) fluoroscopic navigation showed a higher accuracy rate in positioning and a shorter instrumentation operating time. The fluoroscopic time was longer in Iso-C(3D) fluoroscopic navigation than that in standard fluoroscopy, indicating that radiation exposure can be moderately reduced in Iso-C(3D) fluoroscopic navigation operation, although the fluoroscopic time was the shortest in 2D fluoroscopic navigation.

Quadrilateral plate fractures of the acetabulum: an update

Acetabular fractures with quadrilateral plate involvement form a heterogeneous group of fractures, which are not specifically defined by any current classification system. Their incidence is increasing due to the rising number of elderly osteoporotic fractures. They have always been notoriously difficult fractures to treat. We present a systematic review of conservative and operative management and their respective outcomes over the last century.

Screw placement in percutaneous acetabular surgery: gender differences of anatomical landmarks in a cadaveric study

PURPOSE

Percutaneous reduction and periarticular screw implantation techniques have been successfully introduced in acetabular surgery. The advantages of this less invasive approach are attenuated by higher risks of screw misplacement. Anatomical landmarks are strongly needed to prevent malplacement. This cadaver study was designed to identify reliable anatomical osseous landmarks in the pelvic region for screw placement in acetabular surgery. Gender differences were specifically addressed.

METHODS

Twenty-seven embalmed cadaveric hemipelvic specimens (13 male, 14 female) were used. After soft-tissue removal, anterior and posterior column acetabular screw placement was conducted by one orthopaedic trauma surgeon under direct vision. Each column was addressed by antegrade and retrograde screw insertion. Radiographic verification of ideal screw placement was followed by assessment of the distance from the different entry points to adjoining anatomical osseous structures.

RESULTS

For anterior column screw positioning, the posterior superior iliac spine (PSIS), posterior inferior iliac spine (PIIS), iliopectineal eminence and centre of the symphysis were most reliable regarding gender differences. For posterior column screw positioning, the distance to the anterior superior iliac spine (ASIS) and the ischial tuberosity showed the lowest deviation between the different gender specimens. Highest gender differences were seen in relation to the cranial rim of the superior pubic ramus in retrograde anterior column screw positioning (p = 0.002). Most landmarks could be targeted within a 2.5-cm range in all specimens.

CONCLUSIONS

The findings emphasise the relevance of osseous landmarks in acetabular surgery. By adhering to easily identifiable structures, screw placement can be safely performed. Significant gender differences must be taken into consideration during preoperative planning.

Cerclage wiring in displaced associated anterior column and posterior hemi-transverse acetabular fractures

PURPOSE

The effects of cerclage wiring in the open reduction and internal fixation of displaced associated anterior column and posterior hemi-transverse acetabular fractures were evaluated.

METHODS

This is a retrospectively clinical study of such cases where the main surgical strategy was open reduction and internal fixation with cerclage wire and reconstruction plates. Data on 12 cases treated between 1992 and 2011 were collected. The mean follow-up period was 32 (12-132) months.

RESULTS

Reduction with a fracture gap of less than 2 mm without articular stepping and solid union was achieved in all 12 cases. Postoperative complication developed in one case of symptomatic arthritis. Excluding the case with symptomatic arthritis, the other cases had good to excellent final D'Aubigne and Postel functional results.

CONCLUSIONS

Cerclage wiring is very useful and effective in the reduction and fixation of displaced associated anterior column and posterior hemi-transverse acetabular fractures, and supplemental fixation with reconstruction plates and screws is necessary.

Single column locking plate fixation is inadequate in two column acetabular fractures. A biomechanical analysis

Background

The objective of this study was to determine whether one can achieve stable fixation of a two column (transverse) acetabular fracture by only fixing a single column with a locking plate and unicortical locking screws. We hypothesized that a locking plate applied to the anterior column of a transverse acetabular fracture would create a construct that is more rigid than a non-locking plate, and that this construct would be biomechanically comparable to two column fixation.

Methods

Using urethane foam models of the pelvis, we simulated transverse acetabular fractures and stabilized them with 1) an anterior column plate with bicortical screws, 2) an anterior locking plate with unicortical screws, 3) an anterior plate and posterior column lag screw, and 4) a posterior plate with an anterior column lag screw. These constructs were mechanically loaded on a servohydraulic material testing machine. Construct stiffness and fracture displacement were measured.

Result and Discussion

We found that two column fixation is 54% stiffer than a single column fixation with a conventional plate with bicortical screws. There was no significant difference between fixation with an anterior column locking plate with unicortical screws and an anterior plate with posterior column lag screw. We detected a non-significant trend towards more stiffness for the anterior locking plate compared to the anterior non-locking plate.

Conclusion

In conclusion, a locking plate construct of the anterior column provides less stability than a traditional both column construct with posterior plate and anterior column lag screw. However, the locking construct offers greater strength than a non-locking, bicortical construct, which in addition often requires extensive contouring and its application is oftentimes accompanied by the risk of neurovascular damage.

Accuracy of minimally invasive navigated acetabular and iliosacral fracture stabilization using a targeting and noninvasive registration device

BACKGROUND

To assess the feasibility and accuracy of guide pin (GP) placement using a combined noninvasive patient immobilization and stereotactic targeting system in computer-assisted percutaneous pelvic fracture stabilization.

METHODS

A total of 12 patients with negligible dislocated unstable pelvic fractures were enrolled in this study, performed between February 2002 and October 2005. Our original plans included 13 GP placements in the iliosacral area (SF) and 8 in the acetabular (AF) area. Patients were bedded on a noninvasive dual-vacuum immobilization device. Interventions were planned on a navigation system using intraoperatively acquired CT data. Radiodense markers glued to the skin and the immobilization device provided synchronization between virtual data set and real anatomical situation. A stereotactic targeting device was used for stabilization of GP tracking. GP positions were verified intraoperatively by CT, followed by fracture stabilization with cannulated screws.

RESULTS

Mean GP placement accuracy according to plan: (1) SF-cohort: 2.8 mm (SD 2.0 mm, range 0.5-9.0 mm) at the bony entry point and 3.8 mm (SD 2.3 mm, range 0.6-9.5 mm) at the target point. (2) AF-cohort: 3.0 mm (SD 0.9 mm, range 1.6-4.9 mm) at the bony entry point and 3.9 mm (SD 1.9 mm, range 1.6-7.5 mm) at the target point. GP placement succeeded optimally in 11 out of 13 cases in the SF-cohort, and 6 out of 8 cases in the AF-cohort. The individual average dose-length product (DLP) per successful finished procedure was 1,576 mGy x cm (SD 812 mGy x cm, range 561-2,739 mGy x cm).

CONCLUSION

Our findings substantiate application of the noninvasive patient immobilization and stereotactic targeting system as effective in computer-assited percutaneous stabilization of sacral bone fractures/SI joint disruptions and coronally oriented acetabular dome fractures. We recommend according to the ALARA (as low as reasonable achievable) principle: first, the kV and mAs values have to be reduced. Second, the scanned volume has to be strictly limited to the area of interest. Third, the number of control CTs have to be minimized. Also, the IsoC might be a better choice for implant tracking below 12 cm to reduce the radiation dose to the minimum. We believe that for all high-precise GP placements in the acetabular column area, further improvements in GP guidance (inhibiting pin tip slipping and detecting intraosseous GP deflection) are necessary.

Quantitative anatomic basis of antegrade lag screw placement in posterior column of acetabulum

BACKGROUND

Lag screw fixation has been recommended for treatment of acetabular and pelvic fracture for several years. The aim of the present study was to determine the projection of the axis of the posterior column on the inner table of the iliac wing in the supra-acetabular region.

METHODS

Thirty adult dried bony hemipelves specimens and other five intact adult dried pelvic specimens were included in this study. The projection point of the axis of the posterior column of the acetabulum was determined on the inner table of the iliac wing of the hemipelves specimens. The perpendicular distance from the optimal entry point to the linea terminalis of pelvis was measured and recorded as the lateral distance. The same measurement along the linea terminalis from the optimal entry point to the junction between the anterior border of iliosacral articulation and the linea terminalis of pelvis was made and recorded as the posterior distance. The depth of the anchor path and the corresponding average retroversion angulation and extraversion angulation were also measured. According to the results acquired from this study, a series of 6.5 mm lag screws were inserted into the posterior column of each side of the other five intact specimens, respectively, to evaluate the position of the screws. The data were expressed as mean +/- SD and analyzed by using the descriptive methods with SPSS 10.0.

RESULTS

The average length of lag screw was 104.8 +/- 4.2 mm. The average lateral distance was 16.8 +/- 2.1 mm. The average posterior distance was 23.5 +/- 3.4 mm. The corresponding average retroversion angulation and extraversion angulation were 57 degrees 36' +/- 4 degrees 28' and 119 degrees 18' +/- 2 degrees 32', respectively. The insertion of the single 6.5 mm lag screw of adequate length was possible in the posterior column along its anchor path and no accidental extraosseous or intraarticular screw placement had occurred.

CONCLUSIONS

The present study describes a safe anchor path of antegrade lag screw fixation in the posterior column. Insertion of the lag screws of adequate length is possible in the posterior column along its functional axis.

Differences of percutaneous retrograde screw fixation of anterior column acetabular fractures between male and female: a study of 164 virtual three-dimensional models

INTRODUCTION

Percutaneous retrograde screw fixation of the anterior column has been recommended for the treatment of minimally displaced acetabular fractures. However, proper placement of the screw in anterior column is challenging because of its unique anatomy. There are few anatomic studies on this technique, and the differences between male and female have never been reported.

METHODS

We created virtual three-dimensional reconstruction models of the pelvis from CT scan data obtained from 82 adult patients without any bony problems. Virtual cylindrical implants were placed intraosseously both in left and right anterior column. The maximum diameter, length and optimal direction of the virtual cylindrical implant were determined for the screw. The perpendicular distance from the insertion point (P) of virtual cylindrical implant to the pubic symphysis (A) and the rim of superior ramus of pubis (B) were measured respectively. In the same model, cross-sections of the anterior column were created and the diameters of them were measured.

RESULTS

164 (80 males and 84 females) hemipelvis models were obtained. The mean maximum diameter and length of virtual cylindrical implant were 8.16+/-1.21 mm (range: 5.60-10.80 mm) and 109.39+/-8.95 mm respectively. The angles of the virtual cylindrical implant to transverse, coronal and sagittal planes were 39.66+/-3.92 degrees , 20.81+/-4.58 degrees and 42.66+/-3.23 degrees respectively. The distance of PA and PB were 18.42+/-4.82 mm and 17.76+/-2.63 mm. Both the differences of the diameter and length of the virtual cylindrical implant, and the distance of PA between the male and female were of statistical significance (p<0.00001). The mean minimum cross-sectional diameter of anterior column was larger than the mean diameter of the virtual cylindrical implant.

CONCLUSIONS

The anterior column of a male will accommodate a 6.5mm lag screw very well, but it does not fit all the females. The same direction of screw can be used in both male and female, but the insertion points of the screw are different. In addition, the determination of the size of the screw used for the anterior column cannot be based solely on the measurement of cross-sectional diameter and the virtual three-dimensional reconstruction model might be useful in preoperative planning.

Operative treatment of transverse acetabular fractures: is it really necessary to fix both columns?

OBJECTIVE

we prospectively evaluated clinical and radiographic outcomes in patients with displaced combined transverse-posterior wall acetabular fractures managed at our Institution over a period of seven years by posterolateral single approach, direct posterior wall and posterior column reduction and plating, and indirect reduction of anterior column controlled by fluoroscopic images with or without lag-screw fixation. The aim was to identify if the obtained immediate postoperative Matta radiographic roof-arc angles after fracture reduction and fixation alters in the postoperative period when comparing posterior plating alone versus posterior plate and anterior column lag-screw fixation.

PATIENTS AND METHODS

35 skeletally mature patients (31 male and four female, with mean age of 39.9 years old [range, 23.3 to 66.7 y/o]) with combined transverse-posterior wall acetabular fractures surgically treated by a posterolateral single approach were enrolled in this prospective investigation. Nineteen patients had associated orthopaedic injuries. The first part of the acetabular fracture management was similar to all patients and consisted in anatomical reduction and fixation of the transverse posterior component followed by anatomical reduction and fixation of the posterior wall component. The transverse anterior component reduction was controlled by fluoroscopic images (anteroposterior (AP), iliac oblique, and obturator oblique views) and digital palpation through the greater sciatic notch. Fifteen of the 35 patients had an additional lag-screw fixation from the posterior to the anterior columns with an extra-long small-fragment cortical screw. AP and Judet oblique radiographic views were taken at the end of the procedure and roof-arc angles were measured. Clinical results were assigned according to the grading system of Merle D'Aubigne and Postel as modified by Matta et al. Radiographic roof-arc angles were checked and compared between the two groups of patients to the same data collected both at the time of the surgical procedure and at three months postoperatively. Statistical analysis was done by either using chi-square (clinical outcome) and Mann-Whitney (roentgenographic outcome) tests, with a level of significance of alpha = 5%.

RESULTS

at final follow-up examination 18 to 84 months postoperatively (mean, 46.8 months), the clinical results were considered satisfactory in 31 (88.6%) patients (excellent in nine (25.7%) and good in 22 (62.9%) patients). There was no difference between patients with (n = 15) and without (n = 20) fixation of the transverse anterior component of the acetabular fracture (p = 0.67). Radiographic roof-arc angles measured at discharge, at three months postoperatively and at the last follow-up consultation didn't changed significantly (p > 0.05). There was no statistically significant difference between patients treated with (n = 15) and without (n = 20) fixation of the anterior component of the transverse acetabular fracture in terms of medial displacement of the femoral head.

CONCLUSION

the authors suggest that associated transverse-posterior wall acetabular fractures can be managed by a single posterior approach. Direct reduction and fixation of the posterior wall and column components is an adequate option for these injuries. If there is adequate indirect reduction of the anterior column, as checked by digital palpation and fluoroscopy, we feel that it is not necessary to fix the anterior column component of the transverse acetabular fracture.

Results after operative treatment of transverse acetabular fractures

BACKGROUND

Treatment of the transverse acetabular fracture is known to have worse results than other fracture types, although this fracture belongs to the elementary fracture group. The operative results of the transverse acetabular fracture, however, have not been well documented. To determine the results and factors that affect the choice of operative treatment for transverse acetabular fractures, we retrospectively reviewed 15 cases of transverse fracture.

METHODS

A total of 15 patients had a transverse fracture, with an average follow-up period of 43 months; there were 8 patients with and 7 without a posterior wall fracture. There were 11 men and 4 women, with a mean age of 46.6 years. In seven cases there was also comminution of the weight-bearing dome. The surgical approaches used were the anterior ilioinguinal approach in 4 patients, the posterior approach in 10 patients, and the combined approach in 1 patient. Postoperative radiographic results were evaluated by Matta's criteria. Final clinical results were evaluated by a modified Merle d'Aubigne scoring system.

RESULTS

All of the fractures healed. The average time for fracture healing was 17.5 weeks. Postoperative radiology revealed six cases of anatomical reduction, five cases of imperfect reduction, and four cases of poor reduction. According to the clinical results, nine patients had satisfactory results (three excellent, six good), and six had unsatisfactory results (three fair, three poor). Regarding complications, there were four cases of traumatic osteoarthritis and three of heterotopic ossification. The patients with an anatomical reduction had a higher satisfactory result rate. Comminution of the transverse fracture seemed to have an adverse influence on the postoperative radiologic result as well as a correlation with the development of traumatic arthritis.

CONCLUSIONS

Transverse acetabular fractures, if not reduced anatomically, may have a tendency toward traumatic osteoarthritis and poor clinical outcome. Comminution of the dome may portend poor results.

Non-union of acetabular fractures

Non-unions of acetabulum are rare. Seven cases of acetabular non-unions are reported in this retrospective study. Five out of our seven patients had either transverse or associated transverse with posterior wall fractures. All patients had surgical stabilisation of their index fractures. A diagnosis of non-union was made at an average of 5.8 months from the original injury based on clinical and radiological features. Five of the six patients who underwent re-stabilisation and bone grafting of the non-union healed where as the remaining one did not heal after two attempts at re-stabilisation and was treated with excision arthroplasty. Two of the healed five, subsequently developed osteoarthritis and had total hip arthroplasty where as one patient had already developed degeneration of his hip at the time of diagnosis and hence treated with total hip arthroplasty. Analysis of the non-unions confirmed that fixation was unstable in all with residual displacement seen in two of them. In conclusion acetabular fracture non-union appear to be associated with transverse fractures and unstable fixation.