Inter- and intraobserver reliability of morphological Mutch classification for greater tuberosity fractures of the proximal humerus: A comparison of x-ray, two-, and three-dimensional CT imaging

Classification and measurement of displacement of isolated greater tuberosity fractures: Intra and interobserver reliability

Background

Literature demonstrates variability in the amount of displacement of isolated greater tuberosity (GT) fractures and measurement techniques that orthopaedic surgeons deem warrant surgical intervention. This study aims to assess the intra and interobserver reliability for classifying and measuring the displacement amount for isolated GT fractures.

Methods

Eight surgeons, consisting of four shoulder specialists and four trainee surgeons, reviewed 25 plain radiographs on two separate occasions, 3 months apart. They were required to morphologically classify the GT fracture, measure the displacement distance on anteroposterior and axillary views, calculate the GT displacement ratio, and state whether they would offer surgical treatment.

Results

There was a lack of good reliability for the classification of the depression and avulsion fracture types. There was good intraobserver but poor interobserver consistency in classifying the split-type fractures. The measurement of the displacement distance showed good intraobserver reliability, but not as good interobserver agreement. Also, the displacement ratio calculated revealed poor consistency. We found good agreement between and within the raters for the treatment decision. No significant difference was noted when comparing the senior surgeons to the junior surgeons.

Conclusions

This study has revealed ongoing inconsistency in the classification and measurement of isolated GT fractures.

Isolated fracture of the greater tuberosity: prediction of superior and posterior fracture displacement on plain radiographs

BACKGROUND

Isolated fractures of the greater tuberosity represent up to 20% of all proximal humeral fractures. Conservative and surgical treatment strategies are reported. Fracture displacement on radiographs is a key factor in treatment decisions, but the accuracy of measurement methods can limit this process. This study aimed to (Aim I) assess the inter- and intraobserver reliability of established radiographic measurements of fracture displacement and (Aims II/III) determine if these measurements can predict superior, posterior, or combined superior + posterior fracture displacement quantified on computed tomography (CT) scans in a patient cohort.

METHODS

Forty-nine cases of isolated greater tuberosity fractures with complete radiographs and CT scans were analyzed. (Aim I) Displacement was measured on radiographs in millimeters as superior ("sup") and lateral ("lat") displacement, along with Mutch's superior ratio ("sGT"), anterior/posterior ratio ("apGT"), and Nyffeler's impingement index ("I-Ind"). Reliability was assessed by 3 independent observers. (Aim II) A humerus saw-bone model with predefined superior, posterior, and combined fracture displacements was used to validate a CT-based measurement technique. (Aim III) This CT-based method was applied to patient CT scans, and linear regression was used to test if radiographic measurements predicted the CT-measured displacements.

RESULTS

(Aim I) Inter- and intraobserver reliability was excellent for "I-Ind" (inter 0.98/intra 0.94), good-excellent for "lat" (0.82/0.76) and "sGT" (0.75/0.94), and moderate for "sup" (0.73/0.66) and "apGT" (0.64/0.49). (Aim II) The CT-based technique accurately measured superior (R2 = 0.99), posterior (R2 = 0.99), and combined (R2 = 0.99) displacement. (Aim III) Patient CT scans showed mean displacement of 3.3 ± 2.5 mm superior, 8.4 ± 5.6 mm posterior, and 11.6 ± 7 mm combined. Superior displacement correlated with "sup" (P < .001), posterior with "lat" (P < .001), "apGT" (P = .004), "I-Ind" (P = .048), and combined displacement with "lat" (P < .001) and 'apGT' (P = .006). In fractures displaced ≥5 mm, "sup" (P = .002) correlated with superior, 'lat' (P = .003) and "I-Ind" (P = .049) with posterior, and "lat" (P < .001) with combined displacement.

CONCLUSIONS

The CT-based technique accurately measured fragment displacement in the saw-bone model. For fractures with ≥5 mm displacement, "lat" was the best predictor of combined displacement (interobserver reliability: 0.82-0.94). However, in the reported cohort, "lat" underestimated the "true" fragment displacement. Therefore, in "lat" measurements ≥ 3 mm, a CT scan for quantification of fragment displacement should be considered. However, these findings must be confirmed in bigger patient populations before clinical translation.

Validation of the modified AO sternum classification system

INTRODUCTION

The Arbeitsgemeinschaft für Osteosynthesefragen (AO) foundation along with the Orthopaedic. Trauma Association (OTA) introduced a new classification for sternal fractures in 2018 aiming to provide greater uniformity and clinical utility for the surgical community. A previous validation study identified some critical issues such as the differentiation between type A and B fractures and localization of the fracture either in the manubrium or in the body. Due to the moderate agreement in inter- and intra-observer variability, some modifications were proposed in order to improve the performance of the classification. The aim of this study was to re-assess the inter- and intra-observer variability after adding modifications to the classification. Our hypothesis was that a significative improvement of inter- and intra-observer variability could be achieved.

MATERIAL AND METHODS

Twenty computed tomography (CT) scans of patients with sternal fractures were analyzed by six. Junior and six senior surgeons independently. Two assessments were performed with an interval of 6 weeks. The kappa (K) value was calculated in order to assess inter- and intra-observer variability.

RESULTS

The overall mean kappa value for inter-observer variability improved from 0.364 to 0.468 (p < 0.001). Inter-observer variability mean for location was 0.573 (SD 0.221) and for type was 0.441 (SD: 0.181). Intra-observer variability showed a mean of 0.703 (SD: 0.153) with a statistic significant improvement when compared to the previous study (mean 0.414, SD: 0.256, p < 0.001).

CONCLUSIONS

By modifying the AO/OTA classification of sternal fractures, the inter- and intra-observer variability improved and now shows moderate to substantial agreement.