Injury

Volume 52, Issue 8, August 2021, Pages 2104-2110
Injury

Size and location of posterior wall fragment on CT can predict hip instability in a cadaveric model

https://doi.org/10.1016/j.injury.2021.03.041Get rights and content

Highlights

  • •
    A fracture size of 15% and fracture angle of 40° were stable on EUA
  • •
    All fracture sizes above 15% and fracture angles greater than 40 degrees were unstable on EUA
  • •
    The use of CT to evaluate posterior wall acetabulum fractures could be a beneficial tool to aid providers in determining need for EUA

Purpose

Previous research has been unable to elucidate the exact factors that contribute to hip instability in the setting of posterior wall acetabular fractures. The purpose of this study was to determine the influence of posterior wall fracture fragment size and fracture angle on the stability of the hip joint in a cadaveric model.

Methods

Six fresh human cadavers (12 hips) were used. Specimens underwent pre-procedure CT evaluation and were then randomized to one of three groups: posterior wall fragment size (FS) of 15%, 20% and 25%. Osteotomies were performed starting at a fracture angle (FA) of 40°. The specimens underwent an exam under anesthesia (EUA). If the hip remained stable, the fracture angle was increased in 20° increments and re-tested until it became unstable.

Results

In the group with a FS of 15%, all hips were stable with a FA of 40°. Increasing the FA to 60° caused all hips to be unstable (subluxation or dislocation). In the group with a FS of 20% and 25%, all hips were unstable with a FA of 40°.

Conclusion

In all specimens, a FS of 15% and FA of 40° were stable on EUA. Varying combinations of increasing FS size and increasing FA were all unstable. This study provides data for a CT-based measurement to predict hip instability in the setting of posterior wall acetabular fractures based on FS and FA. More research is required to validate this data in a clinical setting.

Introduction

Posterior wall fractures are the most common types of acetabular fractures [1]. The main goal of treatment is to restore hip joint congruency and stability. Judet and Letournel showed that reduction of the articular surface decreased the incidence of post-traumatic arthritis [2,3]. The Letournel classification remains the most commonly used tool for the management of acetabular fractures. However, the concept of hip stability, especially in relation to posterior wall fractures, is poorly captured. In addition, the ability of two-dimensional (2D) imaging to assess a three-dimensional (3D) structure is somewhat limited. Controversy persists regarding the reliability of radiological studies to assess the stability of the hip joint in the setting of posterior wall fractures ([4,5]).
Recently, computed tomography (CT) based measurements of acetabular fracture fragment size have been applied to attempt to predict the stability of the hip joint and inform the need for surgical fixation [6], [7], [8]. Despite these efforts, dynamic stress examination under anesthesia (EUA) remains the gold standard in assessing hip joint stability [9,10].
The purpose of this descriptive cadaveric study was to test the effect of fracture fragment size and fracture angle (using CT measurements) on hip joint stability in isolated posterior wall acetabular fractures (OTA 62.1.1) [11].

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Section snippets

Materials and Methods

Local Institutional Ethical Committee Board approval was obtained. The study specimens included six fresh human cadavers ([12] hips), which included 4 males and 2 females with a mean age of 58 years (range 49-72). The donors were confirmed to have had no prior deformity, joint stiffness, or previous surgery to either hip.

Results

Table 1 lists the results of stress examination of the 12 hips. All specimens in the small fragment size group (FS 15%) were stable at 40° osteotomy angle. Increasing the angle to 60° rendered all hips unstable (25% dislocated, 75% subluxated) in ADIR. With an 80° osteotomy angle, 75% dislocated in the ADIR position. In the intermediate fragment size group (FS 20%), all four hips were unstable with a 40° osteotomy angle (100% subluxation in ADIR). With a 60° osteotomy angle, there was a 100%

Discussion

Posterior wall acetabulum fractures represent a spectrum of injury. There are multiple treatment options, and one major indication for surgical reduction and fixation is instability of the hip joint. The purpose of this study was to determine what effect the posterior wall fragment size and fracture angle had on hip joint stability.
In this cadaveric study, both the angle of the fracture and fragment size were found to play a role in hip stability in the setting of posterior wall acetabulum

Declaration of Competing Interest

Theerachai Apivatthakakul has received funding from the Endowment Fund, Faculty of Medicine and partially support by Chiang Mai University. The rest of the authors have nothing to disclose.

Acknowledgements and funding information

N/A.

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