The prognostic significance of radiologically detected knee joint effusions in the absence of associated fracture

Artificial intelligence for detection of effusion and lipo-hemarthrosis in X-rays and CT of the knee

BACKGROUND

Traumatic knee injuries are challenging to diagnose accurately through radiography and to a lesser extent, through CT, with fractures sometimes overlooked. Ancillary signs like joint effusion or lipo-hemarthrosis are indicative of fractures, suggesting the need for further imaging. Artificial Intelligence (AI) can automate image analysis, improving diagnostic accuracy and help prioritizing clinically important X-ray or CT studies.

OBJECTIVE

To develop and evaluate an AI algorithm for detecting effusion of any kind in knee X-rays and selected CT images and distinguishing between simple effusion and lipo-hemarthrosis indicative of intra-articular fractures.

METHODS

This retrospective study analyzed post traumatic knee imaging from January 2016 to February 2023, categorizing images into lipo-hemarthrosis, simple effusion, or normal. It utilized the FishNet-150 algorithm for image classification, with class activation maps highlighting decision-influential regions. The AI's diagnostic accuracy was validated against a gold standard, based on the evaluations made by a radiologist with at least four years of experience.

RESULTS

Analysis included CT images from 515 patients and X-rays from 637 post traumatic patients, identifying lipo-hemarthrosis, simple effusion, and normal findings. The AI showed an AUC of 0.81 for detecting any effusion, 0.78 for simple effusion, and 0.83 for lipo-hemarthrosis in X-rays; and 0.89, 0.89, and 0.91, respectively, in CTs.

CONCLUSION

The AI algorithm effectively detects knee effusion and differentiates between simple effusion and lipo-hemarthrosis in post-traumatic patients for both X-rays and selected CT images further studies are needed to validate these results.

Examination of joint space by magnetic resonance imaging in anatomically normal knees

The medical and lateral knee joint spaces of 184 patients who had anatomically normal knees were measured by using magnetic resonance imaging (MRI) method. The findings were compared according to age, sex, height, and body mass index changes of the individuals and the mean values of medial and lateral knee joint spaces were calculated in every group. The results show that in an anatomically normal population, all the individuals have larger lateral knee joint spaces than medial knee joint spaces. The patients lose knee joint space regularly with increasing age. Children have larger knee joint spaces than adults. Men have larger knee joint spaces than women. The knee joint space size of the patients increase regularly with increasing height up to 180 cm. The patients, who are taller than 180 cm do not show any marked difference in joint space size, when compared with the patients whose heights differ in between 171-180 cm. Knee joint space size is not related to the body mass index of the individual.

Use of radiography in acute knee injuries: need for clinical decision rules

OBJECTIVES

To study: 1) the efficiency of the current use of radiography in acute knee injuries, 2) the judgments and attitudes of experienced clinicians in their use of knee radiography, and 3) the potential for decision rules to improve efficiency.

METHODS

This two-stage study of adults with acute knee injuries involved: 1) a retrospective review of all 1,967 patients seen over a 12-month period in the EDs of one community and two teaching hospital, and 2) a prospective survey of another 1,040 patients seen by attending emergency physicians. The prospective survey assessed each clinician's estimate of the probability of a knee or patella fracture; 120 patients were independently assessed by two physicians.

RESULTS

Of the 1,967 patients seen in the first stage, 74.1% underwent radiography but only 5.2% were found to have fractures. Of the 1,727 knee and patella radiographic series ordered, 92.4% were negative for fracture. In the second stage, experienced physicians predicted the probability of fracture to be 0 or 0.1 for 75.6% of the patients. The kappa value for this response was 0.51 (95% CI 0.34 to 0.68). The physicians also indicated that they would have been comfortable or very comfortable in not ordering radiography for 55.5% of the patients. The area under the receiver operating characteristics curve for the physicians' prediction of fracture was 0.87 (95% CI 0.82 to 0.91), reflecting good discrimination between fracture and nonfracture cases. Likelihood ratios for the physicians' prediction ranged from 0.09 at the 0 level to 42.9 at the 0.9-1.0 level.

CONCLUSIONS

Emergency physicians order radiography for most patients with acute knee injuries, even though they can accurately discriminate between fracture and nonfracture cases and expect most of the radiographs to be normal. These findings suggest great potential for more efficient use of knee radiography, possibly through the use of a clinical decision rule.

Clinical decision rules discriminate between fractures and nonfractures in acute isolated knee trauma

STUDY OBJECTIVE

To develop criteria that optimize clinical decisionmaking in the use of radiography after isolated knee trauma in adults.

DESIGN

A prospective survey of emergency department patients over a 7-month period. Standardized data forms were completed by emergency physicians, residents, and certified physician assistants.

SETTING

A large suburban community teaching hospital.

PARTICIPANTS

Two hundred forty-two patients older than 17 years with isolated knee injuries sustained less than 24 hours previously.

RESULTS

We constructed a clinical decision model, calculating sensitivity, specificity, and odds ratios. Twenty-eight patients (11.6%) had fractures, with the patella the most commonly fractured osseous structure. Patients able to walk without limping had not experienced a fracture, nor had patients with twist injuries without effusion. Sensitivity of this model for detecting fracture was 1.0 (99% confidence interval, .97 to 1.0), and specificity was .337 (99% confidence interval, .26 to .42).

CONCLUSION

Clinical decision rules are effective in detecting knee fractures with 100% sensitivity and with sufficient specificity to eliminate 29% of knee radiographs in the ED. These findings require prospective validation.

Derivation of a decision rule for the use of radiography in acute knee injuries

STUDY OBJECTIVE

To derive a highly sensitive decision rule for the selective use of radiography in acute knee injuries.

DESIGN

Prospectively administered survey.

SETTING

Emergency departments of two university hospitals.

PARTICIPANTS

Convenience sample of 1,047 adults with acute knee injuries.

RESULTS

Attending emergency physicians assessed each patient for 23 standardized clinical findings, which were recorded on data collection forms. A total of 127 patients was examined independently by two physicians to determine interobserver agreement. The outcome measure was fracture of the knee. Any patients who did not have ED radiography underwent a structured telephone interview to determine the possibility of a missed fracture. Those variables found to be both reliable (highest kappa values) and strongly associated with a fracture (highest chi 2 values) were further analyzed by a recursive-partitioning multivariate technique. The derived decision rule included the following variables: (1) age 55 years or older, (2) tenderness at the head of the fibula, (3) isolated tenderness of the patella, (4) inability to flex to 90 degrees, and (5) inability to bear weight both immediately and in the ED (four steps). The presence of one or more of these findings would have identified the 68 fractures in the study population with a sensitivity of 1.0 (95% confidence interval [Cl], .95 to 1.0) and a specificity of .54 (95% Cl, .51 to .57). Application of the rule would have led to a 28.0% relative reduction in the use of radiography from 68.6% to 49.4% in the study population.

CONCLUSION

A practical, highly sensitive, and reliable decision rule for the use of radiography in acute knee injuries has been derived. Clinical application should await prospective validation of the rule.