Overuse-related instability of the elbow: the role of CT-arthrography

Semiquantitative index of symptomatic minor instability of the lateral elbow at CT arthrography (SMILE index): clinical applicability and reproducibility study

OBJECTIVE

To assess the applicability of a semiquantitative index for symptomatic minor instability of the lateral elbow (SMILE).

MATERIALS AND METHODS

CT arthrograms of consecutive patients with lateral elbow pain who underwent ultrasound-guided CT arthrography at our orthopedic center between April 2019 and May 2022 were included. Images were acquired at 100 kVp and 80 mAs. An expert radiologist (R1) and a radiology resident (R2) retrospectively performed an independent, blinded evaluation of the arthrograms to assess the presence of imaging findings suggestive of elbow instability. The SMILE index (0-8) was obtained adding (I) radial head chondromalacia (0 - 1); (II) humeral capitellum chondromalacia (0 - 1); (III) humeral trochlear ridge chondromalacia (0 - 1); (IV) annular ligament laxity (0 - 2); (V) synovial thickening (0 - 1); (VI) humeroradial joint asymmetry (0 - 1); and (VII) capsular tear (0 - 1). R1 repeated the assessment after 14 days. Cohen's weighted κ statistic and raw concordance were used to appraise reproducibility.

RESULTS

Eighty patients (median age 49 years, interquartile range 40-53 years, 49, 61% males) underwent CT arthrography at our center, and 10 (12%) of them underwent bilateral elbow examination, leading to 90 included CT arthrograms. Median SMILE index was 4 (IQR: 2-5) for R1, 4 (IQR: 2-5) for R2, and 4 (IQR: 2-5) for the second assessment by R1. Intra-reader agreement was excellent (κ = 0.94, concordance 87%), while inter-reader agreement was substantial (κ = 0.75, concordance 67%).

CONCLUSION

The proposed SMILE index showed good reproducibility; further studies are warranted to correlate our index with clinical and surgical data.

CLINICAL RELEVANCE STATEMENT

Our scoring system allows a standardized evaluation of patients with lateral elbow pain and instability suitable for application into clinical practice, complementing the orthopedic surgeon's clinical diagnosis with imaging findings that may aid treatment choices.

KEY POINTS

• Lateral elbow pain is often interpreted clinically as lateral epicondylitis, but it can also encompass intra-articular pathology. • The proposed arthrographic index allows comprehensive quantification of lateral elbow pathology with good reproducibility and application times. • Our index provides the orthopedic surgeon with information regarding intra-articular findings, aiding treatment choices.

Anterior radial head subluxation in primary elbow osteoarthritis

PURPOSE

To investigate elbows with primary osteoarthritis (OA) for the presence of anterior radial head subluxation.

METHODS

A total of 71 patients with elbow osteoarthritis and 45 with lateral epicondylitis were initially identified. The baseline characteristics and preoperative elbow X-rays of consecutive patients that had been clinically confirmed with elbow OA or lateral epicondylitis between March 2011 and January 2020 were then retrospectively reviewed. The radiocapitellar ratio (RCR; the ratio of the displacement of the radial head about the diameter of the capitulum) was calculated using lateral views. These RCR values were compared between the OA and lateral epicondylitis cases.

RESULT

A significant increase was detected in RCR values between patients in elbow OA and the control group (13.2% (± 10.6) vs -1.2% (± 6.8), P<0.001). Based on receiver operating characteristic curves, RCR values had an excellent area under the curve (0.89) for the detection of elbow OA (Youden index, 0.69; sensitivity, 89%; specificity, 80%). Based on the ROC curve, the cutoff value of RCR was 0.04. Patients with RCR ≥ 0.04 had a significantly higher proportion of cases with elbow OA (risk ratio, 31.50 [95% CI, 11.17-88.82]) than those with RCR ˂ 0.04 (P ˂ 0.001).

CONCLUSION

Radial head subluxation is a radiographic finding associated with elbow OA and RCR ≥ 0.04 could be used as an aetiological factor for elbow OA diagnosis.