A quantitative definition of scaphoid union: determining the inter-rater reliability of two techniques

Abstract

BackgroundDespite extensive literature supporting the use of computerized tomography (CT) scans in evaluating scaphoid fractures, there has not been a consensus on the methodology for defining and quantifying union. The purpose of this study was to test the inter-observer reliability of two methods of quantifying scaphoid union.MethodsThe CT scans of 50 non-operatively treated scaphoid fractures were reviewed by four blinded observers. Each was asked to classify union into one of three categories, united, partially united, or tenuously united, based on their general impression. Each reviewer then carefully analyzed each CT slice and quantified union based on two methods, the mean percentage union and the weighted mean percentage union. The estimated percentage of scaphoid union for each scan was recorded, and inter-observer reliability for both methods was assessed using a Bland-Altman plot to calculate the 95% limits of agreement. Kappa statistic was used to measure the degree of agreement for the categorical assessment of union.ResultsThere was very little difference in the percentage of union calculated between the two methods (mean difference between the two methods was 1.2 ± 4.1%), with each reviewer demonstrating excellent agreement between the two methods based on the Bland-Altman plot. The kappa score indicated very good agreement (Ƙ = 0.80) between the consultant hand surgeon and the musculoskeletal radiologist, and good agreement (Ƙ = 0.62) between the consultant hand surgeon and the hand fellow for the categorical assessment of union.ConclusionsThis study describes two methods of quantifying and defining scaphoid union, both with a high inter-rater reliability. This indicates that either method can be reliably used, making it an important tool for both for clinical use and research purposes in future studies of scaphoid fractures, particularly those which are using union or time to union as their endpoint.Level of evidenceDiagnostic, level III

Proximal Pole Scaphoid Fractures: A Computed Tomographic Assessment of Outcomes

“…We were able to identify a few risk factors that were associated with a significantly greater time to union (fracture comminution, cystic resorption, and translation of fracture fragments). These factors were found to increase union times in other studies evaluating union times in scaphoid fractures 21 and are more easily identified on CT than plain radiography.…”

Comparison of Computed Tomography Scan and Plain Radiograph for the Assessment of Postoperative union in Patients Treated for Scaphoid Nonunion

“…Each reviewer reported the mean percentage of union and the weighted mean percentage of the union and then the inter-observer reliability of scores was assessed. The results revealed high inter-rater reliability among the observers, suggesting CT as a reliable method for the evaluation of scaphoid union [12].…”

Simultaneous Fractures of the Ipsilateral Scaphoid and Distal Radius

“…We judged the scaphoid to be healed if bridging bone was appreciated > 50 across the fracture, no cystic changes or sclerosis was present at the fracture site, and no hardware loosening was visible. This is a potential weakness of these studies, since CT is considered the most reliable way to characterize the healing status of a scaphoid fracture, [23][24][25][26][27] and it is not possible to definitively state that a scaphoid fracture is healed at 6 weeks without advanced imaging. However, it is not routine to obtain a CT scan when plain radiographs strongly indicate healing (►Fig.…”