Retrospective interobserver agreement on diagnoses of 4th and 5th carpometacarpal fracture-dislocation and hamate fracture in plain X-ray - Is CT essential after ulnar carpometacarpal pain?

OBJECTIVE: To determine interobserver agreement and reliability of different radiological parameters in the assessment of fracture-dislocation of the 4th and 5th carpometacarpal joints (FD CMC 4-5) and associated hamate fracture on radiographs. MATERIALS AND METHODS: A retrospective, consecutive case series of 53 patients diagnosed with FD CMC 4-5. Emergency room diagnostic radiology images were reviewed by four independent observers. The reviews included assessment of radiological patterns and parameters in relation to CMC fracture-dislocations and associated injuries previously described in the literature, to analyze their diagnostic power (specificity and sensitivity) and reproducibility (interobserver reliability). RESULTS: Among 53 patients, mean age 35.3 years, dislocation of the 5th CMC joint was present in 32/53 (60%) of patients, mostly (11/32 [34%]) associated with 4th CMC dislocation and base of 4th and 5th metacarpal fracture. The most common presentation of hamate fracture, in 4/18 (22%), was associated with combined 4th and 5th CMC dislocation and base of metacarpal fracture. Computed tomography (CT) was performed in 23 patients. Performing CT scan was significantly associated with hamate fracture diagnosis (p < 0.001). Interobserver agreement was slight (0-0.641) for most of the parameters and diagnoses. Sensitivity ranged from 0 to 0.61. Overall, the described parameters had low sensitivity. CONCLUSION: Radiological parameters described for assessment of fracture-dislocation of the 4th and 5th CMC joints and associated hamate fracture have a slight interobserver agreement index in plain X-ray and low sensitivity for diagnostic assessment. These results suggest the need for emergency medicine diagnostic protocols that include CT scan for such injuries. GOV IDENTIFIER: NCT04668794.