scapula fracture classification system - Kreiskrankenhaus Mechernich

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Classification of glenoid fractures 517 cases. The overall k coefficient was 0.79, and the surgeons’ pair-wise k (21 pairs) ranged from 0.66 to 0.93. The sample identifying the most likely ‘‘true’’ distribution included 46 cases (38%) with an F fracture, where the accuracy in identifying these fractures (diagnosis sensitivity) ranged from 91% to 99% (median, 95%). The surgeons’ accuracy in identifying the remaining 74 cases as non–articular segment fractures ranged from 86% to 98% (median, 93%). The 46 F fractures were further divided as follows: 1 F0 fracture, 38 F1 fractures, and 7 F2 fractures. Surgeons agreed on this subclassification in 72% of these cases (33), with an overall k coefficient of 0.64. The surgeons’ pair-wise k (21 pairs) ranged from 0.43 to 0.92 (median, 0.64). Surgeons were 86% to 100% accurate (median, 94%) in terms of classifying F1 fractures. The number of F2 fractures was considered too small for estimation of the surgeons’ classification accuracy with an adequate degree of precision; nevertheless, 4 surgeons correctly classified 6 of the 7 multifragmentary fractures, with a minimum of 4 of these fractures correctly classified among the other 3 surgeons. The only F0 fracture in the sample was correctly classified by 5 surgeons (Fig. 7), whereas the other 2 surgeons classified it as a simple fossa fracture (F1) or simple body fracture (B1). Surgeons attained full agreement in the classification of half of the 38 simple glenoid fossa (F1) fractures according to the higher level of the focused system (Figs. 3 and 4; Appendix I, available on the journal’s website at www. jshoulderelbow.org). The overall k coefficient was 0.66, with the surgeons’ pair-wise k ranging from 0.35 to 0.82 (median, 0.67) (Table I). The estimated distribution of cases within the sample included 14 F1(1) fractures, 7 F1(2) fractures, and 17 F1(3) fractures with category-specific k coefficients of 0.70, 0.65, and 0.62, respectively. There was no central fracture-dislocation among the 7 multifragmentary joint fractures (Fig. 6), and all were classified as having more than 2 fracture line exit points [code F2(4)] with full agreement among the surgeons. Classification session data supported the distinction of simple fossa fractures into 3 classes with the following proportions: 36%, 19%, and 45% (Table II). The largest group, representing transverse or short oblique fractures (class 3), was classified with 87% to 93% accuracy by 5 surgeons and 70% accuracy (median, 91%) for the other 2. The second largest fracture group represented anterior rim or oblique fractures (class 1), showing the highest classification accuracies from 85% to 98% among the surgeons (median, 91%). The posterior rim or oblique fractures (class 2) were classified with 80% to 96% accuracy by 4 surgeons and 64% to 69% accuracy by the other 3 (median, 80%). Incorrect classification of rim and oblique fractures as transverse and short oblique fracture types occurred more frequently, showing the higher ability to discern between anterior and posterior rim fractures. Further classification into the 3 subgroups of simple glenoid fossa fractures (ie, a, b, and c) showed a lower degree of interobserver reliability, with overall k coefficients of 0.46 and 0.39 based on the combined group of anterior and posterior fractures (Fig. 3; Appendix I, available on the journal’s website at www.jshoulderelbow.org) and the group of transverse fractures, respectively (Fig. 4, Table I). Surgeons’ pair-wise k coefficients ranged from 0.07 to 0.89 (median, 0.53) (anterior and posterior fractures) and from 0.03 to 0.88 (median, 0.36) (transverse fractures). After reviewing these results, members of the SCCG unanimously agreed that a revision of categories 1c and 2c was required and a final proposal was made, as presented in Figure 3. Discussion The SCCG was established to develop and validate a clinically useful comprehensive scapula classification system. In a first phase, special interest was targeted at testing its reliability to allow its integration in a clinical setting. This study focuses on glenoid fractures. In our series of scapula fractures, the involvement of articular segment fractures was estimated for 38% of the 120 cases. This incidence is much higher compared with data reported by Goss 15 suggesting that fractures of the glenoid cavity account for up to 10% of all scapula fractures. Ideberg et al 18 also reported involvement of the glenoid cavity in about 30% of scapula fractures, whichdsimilar to our own studydmight be due to the case selection process. Our scapular fracture cases were consecutively collected from 2 major level I trauma centers in the United States and central Europe regardless of their treatments. To achieve a precise diagnosis, both plain radiographs and CT scans were obtained. Obtaining the latter, especially in combination with 3D volume rendering, is believed to increase the accuracy in detecting glenoid fractures and, therefore, might also explain the higher proportion of glenoid fractures detected in our study compared with those from 3 more recent publications. 2,8,21 In an earlier evaluation session using only radiographs for 33 cases, 8 cases (24%) were diagnosed with glenoid involvement. The misdiagnosis of glenoid fractures may lead to either joint instability or joint incongruence, with the potential consequence of secondary arthrosis, so it is mandatory to identify these fractures precisely. We strongly recommend performing a CT scan routinely in all cases of scapular fractures. Using the entire scapula classification system provided by the SCCG, the involved shoulder surgeons were extremely accurate (>90%) in identifying all fractures involving the articular segment (code F). According to the focused classification system, the incidence of anterior rim fractures was 2 times higher compared with posterior fractures in our series. Single transverse or short oblique fractures were slightly more frequent compared with anterior rim fractures. Multifragmentary fractures with central fracture-dislocation were rare; this type of fracture pattern was not found in any of the 120 cases. The use of the
518 M. Jaeger et al. Figure 7 Fracture of the articular segment not involving the glenoid fossa (F0). Ó 2012, Jaeger et al. Table I Coding agreement and reliability for glenoid fossa fractures according to focused system Fracture subsets Categories) No. of cases y Full agreement k Coefficient Overall Pair-wise (21 pairs) Minimum Median Maximum Simple fossa (F1) 50% 0.66 0.35 0.67 0.82 1 14 0.70 2 7 0.65 3 17 0.62 Multifragmentary fossa (F2) 4/5 7/0 100% F1(1) and F1(2) combined a/b/c 4/9/8 24% 0.46 0.07 0.53 0.89 F1(3) a/b/c 3/8/6 29% 0.39 0.03 0.36 0.88 ) The categories of 1 to 5 represent the following: 1, anterior simple rim or oblique fracture; 2, posterior simple rim or oblique fracture; 3, simple transverse or short oblique fracture; 4, multifragmentary fossa with more than 2 fracture line exit points; and 5, multifragmentary fossa with central fracture-dislocation (no exit line through the rim). y Estimated by latent class analysis and the distribution of the surgeons’ codes. detailed subclassification seems to be reproducible with high accuracy (>80%) in all categories of F1 (1, 2, and 3). A more detailed description of rim fractures with respect to their location to the equator becomes less reliable and is most pronounced when differentiating short oblique fractures [F1(3)]. This cannot be done without a CT scan and was still not highly reliable with 3D volume rendering. One reason for this outcome might be the method used in this study. To provide the same data for all participating surgeons, 1 shoulder surgeon performed the volume rendering of all CT scans. The result was presented to the surgeons as a movie sequence in a 360 horizontal and 360 vertical rotation; this setting was chosen based on common practice (usually of the radiologist) in presenting these types of data for further evaluation. Subsequently, the other shoulder surgeons did not perform their own 3D analysis, that is, they were unable to rotate or focus the 3D scans according to their own needs, and as such, their accuracy may have been limited. On the other hand, these results highlight the difficulty in distinguishing fractures bordering between 2 categories. Because the distribution of all glenoid fractures can be considered a continuum of possible patterns, any category is inherently associated with some level of imprecision for adjacent fracture pathologies. Former scapula classifications, especially of the glenoid, were conducted based on the assessment of plain radiographs. 5,15,24 All of them were published without further reliability assessment. To our knowledge, this is the first study providing an evaluation of classification reliability and accuracy. Armitage et al 3 recently provided a frequency map of surgically treated scapula fractures. To our knowledge, this was the first article until now describing the use of 3D CT volume rendering to enhance the mapping of scapula fractures. In contrast to our study, Armitage et al
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scapula fracture classification system - Kreiskrankenhaus Mechernich

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