Matta's Arc: Relevant or Not?

Abstract

Matta's Roof Arc Angle (RAA) is utilised to evaluate the load-bearing dome in cases of acetabular fractures, assisting clinicians in making informed decisions regarding treatment options through the measurement of angular displacement. This assessment is crucial for the assessment of acetabular coverage and the stability of the femoral head, helping to determine whether surgical intervention or non-operative approaches are more suitable. Nevertheless, the variability of this method underscores the importance of incorporating additional criteria to ensure the best possible clinical outcomes for patients.

1. Introduction

Predicting the clinical prognosis following acetabular fractures has always been a key area of focus. Various factors, such as the type of fracture, level of displacement, comminution, and patient-specific conditions, play a crucial role in determining the outcomes.¹ In instances where fractures are managed non-operatively, the initial displacement holds significant importance, whereas in cases requiring surgery, the effectiveness of the reduction procedure is paramount.² Letournel and Judet's findings have illustrated a direct correlation between precise reduction and improved clinical results, underscoring the significance of achieving optimal reduction and ensuring stable fixation.^1,3

Matta and colleagues introduced the concept of radiographic roof arc angles (RAA) as a method to evaluate the weight-bearing dome of a fractured acetabulum. These measurements provide an estimation of the intact dome and offer insights into how the fracture lines intersect within the acetabulum. Fractures that displace the weight-bearing dome can elevate pressure on the joint cartilage, potentially leading to osteoarthritis, and often necessitate surgical treatment.^1,4

This discussion will explore the ongoing relevance of Matta's Arc in contemporary medical practice, emphasizing its importance in treatment strategies and patient outcomes in acetabular fracture management.

2. Matta's arc

Matta's Arc quantifies the angular displacement between a vertical reference line originating from the centre of the acetabulum and a line projecting towards the location of the fracture. This measurement evaluates the extent of acetabular containment and the stability of the femoral head, both crucial factors in guiding the treatment choice for acetabular fractures.⁵

The RAA is the angle between the vertical line drawn from the centre of the acetabulum through the acetabular dome and another line from the centre of the acetabulum to the fracture line through the acetabulum (Fig. 1). The measurement of the roof arc angle is conducted on three standard radiographic perspectives for a reduced out-of-traction hip: anteroposterior, obturator, and iliac oblique views. The recorded angles from these three views are analysed.⁵ The calculation of the Medial Roof Arc is performed on the Anteroposterior radiograph. The determination of the Anterior Roof Arc is executed on the Obturator Oblique radiographic view. The evaluation of the Posterior Roof Arc is carried out on the Iliac Oblique Radiographic View (Fig. 2(a)).

Fig. 1.

Roof Arc Angle Measurement

XY is a vertical line drawn from the centre of the acetabulum through the acetabular dome. YZ is the second line drawn from the centre of the acetabulum to the fracture line through the acetabulum.

Fig. 2.

Fig:2(a) Method of measurement of RAA on various views in an example case.

Fig:2(b) Follow-up Radiographs in the same patient at a recent follow-up of 12 months with complete radiographic union seen in all the Judet views of the right acetabulum with an excellent functional outcome.

Measuring the Roof Arc Angle (RAA) through Computed Tomography (CT) is a common practice in radiology. An important step in the process of measuring the roof arc is obtaining a CT scan slice located precisely 10 mm below the peak of the acetabulum, as it aids in determining the integrity of the dome. The presence or absence of fractures within this specific 10 mm region on the CT scan is crucial in determining the intactness of the dome.⁴

The quantification of the centrality of fracture lines within the dome is achieved through the roof arc score, which ranges from a maximum of 15 to a minimum of 01 (noted when the fracture line is observed in only one view with RAA >45°) (Table 1). This scoring system plays a crucial role in assessing the severity of the fracture and guiding the selection of the most suitable treatment approach.³

Table 1.

Roof arc score.

Roof Arc in each view (Degrees)	Roof Arc Score in each view
0 to 10	05
11 to 20	04
21 to 30	03
31to 45	04
>45	01

Maximum Score = 15.

Minimum score = 01 (Fracture line seen in only one view with RAA >45°).

Matta's Arc assesses the extent of intact roof in the three standard radiographic views and the intersection of central/peripheral lines at the acetabulum. It aids in determining whether the remaining intact acetabulum is adequate to maintain a stable and congruent relationship with the femoral head, thus assessing sufficient acetabular coverage and femoral head stability.^1,2,4

According to Matta et al., a crucial threshold for a roof arc is 45°. A measurement below 45° in all views indicates a dome fracture, typically necessitating surgical intervention.¹ Conversely, a measurement exceeding 45° suggests preservation of the weight-bearing dome, often allowing for non-surgical management. While variations exist in studies, all indicate a threshold above 45° .⁵Achieving anatomical reduction, as per Matta's criteria, is essential for preventing complications such as post-traumatic osteoarthritis and ensuring enduring joint stability.^1,6

3. Example case study (Fig. 2):

A case of a 40-year-old male involved in a road traffic accident exemplifies the application of roof arc measurements in guiding treatment. Fifteen days post-injury, his acetabular fracture was evaluated using roof arc angles: Medial Roof Angle (69°), Anterior Roof Angle (65°), and Posterior Roof Angle (63°), with a Roof Arc Score of 3. (Fig. 2(a)). These measurements indicated stable fracture characteristics and conservative management was chosen. After three months of adhering to the treatment protocol, the patient fully recovered, demonstrating the effectiveness of roof arc assessments in treatment planning. (Fig. 2(b)).

4. Can RAA be a fixed number?

The Roof Arc Angle (RAA), initially characterized by Joel Matta, serves as a critical metric for assessing whether an acetabular fracture implicates the weight-bearing dome of the acetabulum. Traditionally, it was believed that a 45-degree arc corresponded to approximately 10 mm of roof arc width; however, contemporary research has called this assumption into question. Current studies demonstrate that the mean width associated with a 45-degree arc is approximately 25.95 mm, indicating considerable variability influenced by the individual anatomical characteristics of patients, particularly the dimensions of the acetabulum. Typically, smaller acetabula display reduced RAAs, whereas larger acetabula are associated with heightened values. This variability implies that the RAA cannot be universally standardized to a specific numerical value across the patient population.^7,8

Consequently, the previously accepted measurement of 10 mm for a 45-degree arc may not accurately represent the complexities of acetabular anatomy, necessitating modifications in surgical approaches and fracture management strategies. Individualized measurements, derived from radiographic imaging or CT scans, are now preferred for enhanced precision in fracture assessment and surgical planning. These insights emphasize the necessity of tailoring roof arc width calculations to the distinct anatomical features of each patient, particularly in the context of acetabular fracture.^7,8

5. Discussion

The use of Matta's Arc and the roof arc score is critical in deciding treatment approaches for acetabular fractures, but these tools should not be used in isolation. The notable variability in roof arc measurements, particularly between plain X-rays and CT-scans, highlights the importance of patient-specific assessments. CT scans provide greater accuracy in evaluating dome involvement and detecting subtle fractures that may not be visible on X-rays. Additionally, other factors such as fracture gaps or steps can affect joint stability and influence treatment decisions. Even with favorable roof arc angles, the presence of a significant gap or step may require surgical intervention to restore joint congruity. By integrating roof arc measurements with CT findings, fracture characteristics, overall patient health status, underlying comorbidities and the timing of the injury, clinicians can develop more tailored treatment strategies. The case study underscores how these measurements can effectively guide conservative management and lead to successful outcomes, further supporting the need for comprehensive, individualized care.

6. Conclusion

Matta's Arc, combined with other clinical data, remains a fundamental tool in evaluating acetabular fractures. Its proper utilization, alongside patient-specific assessments, enables clinicians to determine the appropriate course of action, whether surgical or conservative, improving patient outcomes and reducing complications.

Credit author statement

Dr Aditya L. Kekatpure: Conceptualization, Methodology, Draft Preparation.

Dr Aashay L. Kekatpure: Data curation, Writing.

Dr Pradip Nemade: Reviewing and Editing.

Declaration of generative AI and AI-assisted technologies in the writing process

During the preparation of this work the author(s) used SciSpace and ChatGpt 4o to improve language and readability. After using this tool/service, the author(s) reviewed and edited the content as needed and take(s) full responsibility for the content of the publication.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.