ABSTRACT
INTRODUCTION: Understanding the real shape of the undersurface of the acromion prior to acromioplasty is indispensable. Today, Supraspinatus outlet view (SSOV) is a standard view used to determine the shape of the anterior acromion. Three types of acromial undersurface were described by Bigliani and Morrison. The purpose of this study was to find out whether the real acromial type can be visualized on X-ray SSOV and compare the shape of the anterior undersurface of the acromion visualized on SSOV, with the shape revealed on 2D CT reconstructions. METHODS: The SSOV X-rays and CT scans of 30 consecutive patients suffering from rotator cuff dysfunction were retrospectively analyzed. The shape of the acromion visualized on plain X-rays was classified according to Bigliani and Morrison classification system. Two-dimensional CT reconstructions were performed, reproducing the lateral, middle, and medial sections of the acromion. The acromial type that was visualized on each of those reconstructions was separately classified according to the Bigliani and Morrison system. A complete profile of the acromial undersurface was constructed from the integration of acromial types seen on each CT section. The acromial morphology seen on X-rays and CTs was compared. RESULTS: A total of 30 patients comprised the study cohort; mean age was 57 (STD = 8.5) years. Three Type I, 22 Type II, and 5 Type III acromions were visualized on the SSOV X-rays. CT reconstructions revealed seven different morphological acromial profiles (I,I,I; I,II,II; I,II,III, etc.), which we divided into 3 groups: (1) Uniform (30%), (2) Internally curved (20%), and (3) Internally hooked (50%). The acromial type visualized on X-ray correlated with the acromial type on at least one CT section in all of the cases. In the case of uniform acromial profile, there is a full correlation between the acromial type visualized on X-rays and the type visualized on CT. In non-uniform profiles, there was an incomplete correlation between the types of the acromion visualized on SSOV and CT. SSOV X-rays correlated with or underestimated, but never overestimated, the acromial morphological type. DISCUSSION: The curved or hooked portion of the acromial undersurface is not always visualized on the SSOV. On X-rays, the middle and lateral sections are seen more accurate than the medial section. CONCLUSION: Surgeons should be aware that SSOV X-rays may underestimate the true type of the acromial undersurface.
Subject(s)
Acromion/anatomy & histology , Acromion/diagnostic imaging , Rotator Cuff/diagnostic imaging , Aged , Female , Humans , Male , Middle Aged , Tomography, X-Ray ComputedABSTRACT
OBJECTIVE: The objective of this study was to describe and validate a simple method to quantitatively calculate the missing area of the anterior part of the glenoid in anterior glenohumeral instability. MATERIALS AND METHODS: The calculations were developed from three-dimensional (3D)-reconstructed computerized tomography en face images of the glenoid with "subtraction" of the humeral head in 13 consecutive cases with known anterior glenohumeral joint instability diagnosed by history and clinical examination. The inferior portion of the glenoid was approximated to a true circle whose center was determined by means of a femoral head gauge. The eroded anterior area was calculated as the ratio between the depth (a perpendicular line from the center of the circle to the eroded edge of the anterior glenoid) and the radius of the inferior glenoid circle. This data was then compared to the results obtained by two additional different methods: direct computerized measurements of the missing area and direct computerized measurement of the ratio between the radius and depth, on two dimensional computed tomography (CT) en face view reconstructions of the glenoid. RESULTS: We provide a function that correlates the ratio between depth and radius of the inferior glenoid circle and the area of the missing anterior glenoid. The results obtained by three different methods were comparable. Simple trigonometric calculations showed that a 5% area defect corresponds to 0.8 (12.5%) of the radius of the inferior glenoid, while a 20% area defect corresponds to 0.5 (50%) of the same radius (Table 1). Table 1 Results according to each different method Patient Sex Side CA1 MA1 PAM1 R2 D2 PAM2 R3 D3 PAM3 1 M R 738 19.1 2.58 15.1 13.4 2.45 16 14 2.6 2 M R 462.6 30.5 6.59 11.9 9.7 4.83 16 10 12.97 3 F L 359 24.5 6.82 17 11.8 9.86 11.8 17 9.86 4 M L 522 59.4 11.37 12.7 9.1 8.95 16 10 12.97 5 M L 670 93.1 13.89 13.6 7.6 16.84 16 9 16.31 6 M R 659 137.5 20.8 14.3 7.1 20.10 20 8 25.23 7 M L 520 137 26.34 11.6 5.1 23.49 16 8 19.55 AVG 12.63 12.36 14.21 SD 8.46 7.92 7.20 CA1 Area of circle directly measured by MPR software, MA1 missing area of circle measured by MPR software, PAM1 calculated (100 x MA1/CA1) percentage area missing for method 1, R2 radius of the circle measured by MPR software, D2 depth from the missing edge to the center of the circle measured by MPR software, PAM2 calculated Percentage area missing from R2 and D2 using the function "q" (Appendix), R3 radius of the circle measured with a femoral gauge, D3 depth from the missing edge to the center of the circle measured with a femoral gauge, PAM3 calculated Percentage area missing from R3 and D3 using the function "q" (Appendix), AVG average, SD standard deviation CONCLUSION: Using this simple method and the function provided, the eroded area of the anterior part of the glenoid in anterior glenohumeral instability can be calculated preoperatively using a 3D CT reconstruction of the glenoid with "subtraction" of the humeral head, obviating the need for sophisticated software to obtain this critical information for preoperative decision making.
