JSES International 5 (2021) 314e319 Contents lists available at ScienceDirect JSES International journal homepage: www.jsesinternational.org Coronal shear fractures of the capitellum and trochlea: interobserver variability in classifying the fracture and the need for a computed tomography scan for the correct surgical planning Claudia Lamas, MD, PhD *, Alex Grau, MD, Marta Almenara, MD, PhD, Luis Trigo, MD noma de Barcelona, Barcelona, Hand Unit and Upper Extremity, Department of Orthopaedic Surgery, Hospital de la Santa Creu i Sant Pau. Universitat Auto Spain a r t i c l e i n f o Background: To determine interobserver agreement in the classification by X-rays and by computed tomography (CT) scan of the coronal shear fractures of the capitellum and trochlea as well as the Keywords: agreement between these two tests. Coronal fracture Methods: Patients with coronal shear fractures of the capitellum who were managed at our center humeral fracture between January 2008 and December 2017 were included. This retrospective cohort study was carried capitellum out with the approval of the ethics committee of our institution (Nº: IIBSP-Cod-2019-02, Ref. 19/070). trochlea Clinical, radiographic, and elbow-specific outcomes, including the Mayo Elbow Performance Index, were elbow classification evaluated. Three observers analyzed the preoperative X-rays from all the cases. Each one of them independently classified the fractures according to the Bryan and Morrey classification (with the Level of evidence: Level IV; Case Series; modification of McKee et al). The interobserver agreement was calculated by Cohen kappa coefficient. Treatment Study The same methodology was used to analyze the CT scan. Thereafter, one single value was determined for each X-ray and CT scan, from the good interobserver agreements. Finally, the agreement between the global X-ray classification and the global CT scan classification was calculated using the agreement percentage and the Cohen kappa coefficient. Results: There were 3 males and 6 females, with a mean age of 47 years (range, 18-83). The mean follow- up period was 18 months (12-40). The average Mayo Elbow Performance Index score was 85 (range, 65- 100) points. The complications were nonunion in one patient (11 %), degenerative arthritis in 7 (78 %), joint step-off in 5 (55%), and heterotopic ossification in 7 (78%). The agreement analysis between the global X-ray classification and the global CT scan classification showed a 57.1% agreement, with a kappa coefficient of 0.167. These values imply the absence of agreement. Conclusion: Our results demostrated that simple X-rays do not allow for the adequate interpretation of distal humeral coronal plane fractures. Although an acceptable interobserver agreement was found, there is no agreement when the same fractures were analyzed by CT scan. The authors routinely recommend CT scan to assess the extent of the fracture and perform surgical planning. © 2020 The Author(s). Published by Elsevier Inc. on behalf of American Shoulder and Elbow Surgeons. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by- nc-nd/4.0/). Fractures of the capitellum compose 6% of distal humerus tissue injuries to the elbow occur frequently in capitellar frac- fractures and 1% of all elbow fractures.22 Distal humeral coronal tures.34 Rausch et al30 found injuries to the radial head in more than plane fractures may involve the capitellum alone; however, most 37% of all capitellar fractures. Lateral collateral ligament (LCL) extend medially to include a portion of the trochlea.13 Isolated injury may be seen in up to approximately 60% of patients with this fractures of the trochlea have been described but are especially type of fracture.9 Preoperative evaluation of the capitellum fracture rare9,14 (Fig. 1). Capitellum fractures are usually more complex than and its extension to the trochlea and presence or absence of pos- expected by analyzing plain radiographs. Associated bone and soft- terior condylar comminution is required to be able to perform surgical planning. This evaluation of the injury will allow planning of the surgical approach, the ability to perform an osteosynthesis This study was approved by the Ethical Committee of Hospital de la Santa Creu i versus a hemiarthroplasty and explain the prognosis of the injury Sant Pau (IIBSP-Cod-2019-02, Ref. 19/070). to the patient. Computed tomography (CT) scan is therefore regu- * Reprint request: Claudia Lamas, MD, PhD, C/ San Antoni M. Claret 167 (08025) larly recommended.27 However, objective data are needed to sup- Barcelona, Spain. E-mail address: clamasg@santpau.cat (C. Lamas). port this recommendation, and at this time, not all hospitals have a https://doi.org/10.1016/j.jseint.2020.10.015 2666-6383/© 2020 The Author(s). Published by Elsevier Inc. on behalf of American Shoulder and Elbow Surgeons. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). C. Lamas, A. Grau, M. Almenara et al. JSES International 5 (2021) 314e319 single value was determined for each X-ray and CT scan, from the good interobserver agreements. Statistical analysis was performed using IBM SPSS Statistics, version 24.0 (IBM, Armonk, NY, USA). Statistical data were evalu- ated by descriptive methods. For the results, differences between the two groups were compared by the t-test and Chi-square test. A p value of less than 0.05 was considered significant with a 95% confidence interval. The agreement between the global X-ray classification and the global CT scan classification was calculated using the agreement percentage and the Cohen kappa coefficient.10 The kappa coefficient provides infomation on interobserver and intraobserver reliability for each study variable.20 Kappa values have been assigned to subdivisions, with values of 0.00 to 0.20 indicating slight agreement; 0.21 to 0.40, fair agreement; 0.41 to 0.60, moderate agreement; 0.61 to 0.80, substantial agreement; and >¼ 0.81, almost perfect agreement. A kappa coefficient value lower than 0 indicates complete disagreement, and a value of 1, complete agreement. Results There were 3 males and 6 females, with a mean age of 47 years (range, 18-83). The mean follow-up period was 18 months (12-40). The trauma mechanism was a fall on an outstretched hand in 4 patients, traffic accident in 3, and direct blow to the elbow in 2. The nondominant, left side was injured in 8 of the cases. The mean time from admission to operation was 6 days, with a range of 1-22 days. According to the Bryan and Morrey classification (with the modi- fication of McKee et al),25 2 fractures were type I, one fracture was type II, and 6 fractures were type IV. The anterolateral approach which was described by Kaplan as Figure 1 Coronal section of the elbow in a specimen showing the anatomical characteristics of the capitellum and trochlea. the interval between extensor digitorum communis and extensor carpi radialis brevis was used in 3 cases. The lateral approach which was described by Kocher was used in 4 cases. The protocol to perform a three-dimensional (3D) CT scan or two- remaining 2 cases were managed by the posterior approach. The dimensional (2D) CT scan for this type of injury. The hypothesis technique was the posterior approach described by Bryan and of this study is that the classification of the capitellum and trochlear Morrey. In 5 patients (55.5%), we changed the surgical approach fractures only by plain radiography does not adequately agree with that we were going to perform in the initial surgical planning the classification obtained by a CT scan and underestimates the when verifying the severity of the fracture by CT scan. Eight pa- complexity of the fracture to carry out an adequate surgical plan- tients were treated by open reduction and internal fixation (ORIF) ning. The aim of the study is to determine interobserver agreement with Acutrak headless compression screws (Hillsboro, OR, USA) in the classification by X-rays and by CT scan of the coronal shear (Fig. 3). On the remaining patient, an excision of the osteochondral fractures according to the Bryan and Morrey classification (with the fragment was performed. Above-the-elbow splint was used for a modification of McKee et al)25,26 as well as the agreement between maximum period of 12 days postoperatively. The fractures were these two tests. united within 3 months in all the cases. The average MEPI score was 85 (range, 65-100) points, with 1 excellent, 4 good, and 4 fair Materials and methods results. The complications were nonunion in one patient (11%), degenerative arthritis in 7 (78%), joint step-off in 5 (55%), and Patients with distal humeral coronal plane fractures who were heterotopic ossification in 7 (78%). Avascular necrosis and implant managed at our center between January 2008 and December 2017 failure were not seen in any case. Among the 7 patients who were included. This retrospective cohort study was carried out developed degenerative arthritis, 3 were grade 1, 2 were grade 2, with the approvement of the ethics committee of our institution and 2 were grade 3, according to Broberg and Morrey classifica- (Protocol number: IIBSP-Cod-2019-02 Ref. 19/070). In this period, tion. There were 7 patients with heterotopic ossification. That was we treated 9 patients. Clinical, radiographic, and elbow-specific grade I in 4 patients, grade 2 in 2, and grade 3 in 1, according to outcomes, including the Mayo Elbow Performance Index (MEPI), Brooker classification applied to the elbow. Two of the nine pa- were evaluated. Broberg and Morrey System5 for grading degen- tients needed a second surgical intervention owing to elbow erative arthritis and Brooker System6 applied to the elbow for stiffness and free articular bodies. There was one concomitant classifying heterotopic ossification were used. All cases under- lateral epicondyle fracture. LCL injuries were seen in 3 patients went a preoperative CT scan. Three observers (two consultants with this type of fracture. There was no neurovascular lesion and one resident) analyzed the initial simple X-rays from all the associated with the injuries. At the end of the follow-up, all cases. Each one of them independently classified the fractures fractures were healed, there was no elbow instability or weakness, according to the Bryan and Morrey classification (with the and no infections developed. modification of McKee et al)26 (Fig. 2). The interobserver agree- In the interpretation of the radiograph, type I (complete cap- ment was calculated by Cohen kappa coefficient.10,20 The same itellar fracture) of the X-ray classification is the one that was most methodology was used to analyze the CT scan. Thereafter, one confused with type IV (capitelum fracture with extend to trochlea). 315 C. Lamas, A. Grau, M. Almenara et al. JSES International 5 (2021) 314e319 Figure 2 Coronal shear fractures of the capitellum and trochlea according to the Bryan and Morrey classification with the modification of McKee et al. Observer 1 agreed with its interpretation of the X-rays and CT scan Direct impacts on the flexed elbow have also been suggested as a on 7 of 9 X-rays (77.7%), observer 2 agreed on 4 of 9 X-rays (44.4%), mechanism as they have indirect impacts on the flexed elbow, and observer 3 agreed on 6 of 9 (66.6%). The Cohen kappa coeffi- when the radial head pushes the capitelum into a posterior posi- cient in the X-ray simple classification, which represents the tion.2,11 Alternatively, the fracture may occur after an episode of interobserver agreement, was between 0.449 and 0.757. According elbow instability and/or an LCL injury.9,34 In this injury, the cap- to the six categories of strength agreement of kappa by Landis and itellum and trochlea may be sheared off by the radial head and Koch,20 these values represent a moderate to substantial correla- coronoid after the reduction of a dislocation of the elbow.9 Brouwer tion. The CT scan percentage agreement was between 85.7% and et al7 reported that 33% of patients in their study sustained an 100%. The agreement analysis between the global X-ray classifica- elbow dislocation and/or a radial head fracture. An LCL injury or tion and the global CT scan classification showed a 57.1% agree- radial head fracture was reported in 57% of patients by Dubberley ment, with a kappa coefficient of -0.167. These values imply the et al.12 Radiographs showed a fracture of the capitellum alone or a absence of agreement. combined lesion with a trochlea fracture with anterosuperior dislocation of the fragment out of the ulnohumeral joint.3,27 For Discussion some authors, a classification system based on the radiographic patterns of these fractures is recommended.3,12 In the study pub- Most capitellum fractures are the result of a low-energy injury, lished by Jacquot et al, less than three-quarters of respondents such as a fall on the outstretched hand, with varying degrees of determined to correct AO classification based on the standard ra- elbow flexion.9,27 Biomechanical studies have yet to demostrate the diographs, and the level of experience had no influence on this mechanisms that cause coronal shear fractures of the distal hu- parameter. Reading the CT images resulted in correct fracture merus.9 Amis and Miller studied various mechanisms of injury for classification by 90% of the respondents who initially indicated the each of the common elbow fractures.2 The investigation was carried wrong fracture type.17 A recently introduced technique is 3D im- out with 40 specimens in which the elbow fractures were produced aging derived from 2D CT scans or obtained by modeling. This in a purpose-built impact-loading rig. There was one capitellar technique has been reported to improve intraobserver and inter- fracture caused by an indirect impact along the radius in full observer reliability in assessing distal humerus fracture character- extension and one caused by direct impact to the end of the distal istics without improving determination of the fracture type in most humerus with the elbow at 90º flexion. The most common fracture widely accepted classification systems.8,11,17 A 3D CT scan recon- is a coronal plane to the anterior surface of the humeral shaft, struction better outlines the fracture and the loss of radiocapitellar producing a hemispheral fragment which is often displaced prox- alignment.26 CT improves diagnostic accuracy and, in some cases, imally.2 This is usually ascribed to a fall onto the outstretched hand, changes the surgical strategy.38 CT did not improve interobserver the radial head acting like piston shearing off the capitellum.2,11 agreement. Intraobserver agreement was improved by 3D CT but 316 C. Lamas, A. Grau, M. Almenara et al. JSES International 5 (2021) 314e319 Figure 3 Distal humerus coronal fracture. (A and B) Preoperative radiographs. (C and D) A 3-dimensional computed tomography reconstruction. (E and F) An X-ray image in profile and anteroposterior views shows the fracture fixation. not by 2D CT.17 For Doornberg et al,11 3D CT scans are easier to described another classification. Type I fracture involves the cap- interpret than 2D CT scans and are helpful in the anticipation of itellum with or without extension to the lateral trochlear ridge (ie, important fracture characteristics and preoperative planning of the Bryan-Morrey type I equivalent) and may be treated with ORIF operative treatment of fractures of the distal part of the humerus. through a muscle-splitting approach. Type II fracture involves the capitellum and trochlea as a single fragment (ie, McKee type IV). Fracture classification Access to the medial side of the joint may require a more extensile approach. Type III fracture involves the capitellum and trochlea as 2 Several classification systems for coronal shear fractures of the independent fragments. Fractures demonstrating posterior condylar distal humerus have been described.12,24,26 Bryan and Morrey pro- comminution are denoted with a B modifier.9,12 The presence of posed a classification based on 3 types of capitellum fractures. A type posterior condylar comminution was found to influence surgeon I (Hahn-Steinthal) lesion involves a fracture isolated to the capitellum selection of the fixation method as well as outcome.12,33 with attached subchondral bone; type II fractures (Kocher-Lorenz) The Orthopedic Trauma Association classification defines partial are those involving primarily the articular cartilage overlying the articular fractures of the distal humerus as type 13-B. A partial capitellum; type III (Broberg-Morrey) lesions are defined as articular fracture in the coronal plane is subclassified as 13-B3. comminuted capitellum fractures. A type IV lesion (McKee) was later Fractures involving the capitellum are further subdivided as added to the classification scheme and involves a capitellum fracture involving only the capitellum (13-B3.1), the trochlea (13-B3.2), or that extends medially into the trochlea.9,13,26,34 Dubberley et al12 both (13-B3.3).24 317 C. Lamas, A. Grau, M. Almenara et al. JSES International 5 (2021) 314e319 Surgical approach Although an acceptable interobserver agreement was found, there is no agreement when the same fractures were analyzed by a CT Several surgical approaches have been described.9,26 The scan. The authors routinely recommend a CT scan in distal humeral optimal choice depends on fracture characteristics and associated coronal plane fractures as the assessment of fracture extension and periarticular injuries. The deep exposure to the lateral elbow is comminution by plain x-ray is particularly deceptive in this region. simplified in situations whereby the LCL has been disrupted or the lateral epicondyle has been fractured.4,9 If the LCL complex remains Disclaimer intact, the exposure is through the Kocher interval, between the anconeus and extensor carpi ulnaris. To improve visualization of The authors, their immediate families, and any research foun- the anterior compartment, a Kocher interval may be extended dations with which they are affiliated have not received any proximally to release an inferior portion of the extensor digitorum financial payments or other benefits from any commercial entity communis muscle. Capitellum fractures extending into the trochlea related to the subject of this article. may not be adequately accessed using laterally based extensile No funding was disclosed by the author(s). maneuvers. 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