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Anterolateral Route Less Painful for Knee Arthrography

January 22, 2008
Written by: , Filed in: Musculoskeletal Radiology
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Background
Knee arthrography is used in conjunction with CT and MRI in the evaluation of recurrent meniscal tears, osteochondral injuries, and intra-articular loose bodies.

In the presence of a knee joint effusion, the lateral patellofemoral approach is often used but can be painful and unsuccessful if no fluid is present. The authors of this paper use an anterior approach, similar to arthroscopy.

The objective of a recent study was to assess patient tolerance and technical success of 2 different approaches of anterior knee arthrography.

The study has concluded that the anterolateral route for knee arthrography is recommended, as it is slightly less painful and can be performed without fluoroscopy.

Participants
159 patients who underwent arthrography.

Methodology
73 patients had an anterolateral approach with the knee in 90-degree flexion. The joint space was palpated with the thumb, and a 40-mm 21.5-gauge needle was inserted horizontally immediately above the palpating thumb and directed posteriorly and slightly medially to obtain contact with the femoral condyle. Needle position was confirmed with injection of intra-articular contrast material.

The anterior paramedian approach was used in 86 patients, with the knee in 60-degree flexion. A 20-gauge 45-mm IV cannula was used and inserted just lateral to the patella tendon and directed upward and slightly medially toward the femoral notch.

If contrast was pooling around the needle tip, the needle was extra-articular and was then further advanced. For each procedure, a technical success score was self-reported by the radiologist and documented using a 5-point scale.

After the procedure, patients completed a questionnaire regarding absolute pain, anticipated pain, height, weight, and prior experience with arthrography.

Results
All procedures were satisfactorily completed and had no adverse effects or complications. One patient had a large effusion, and the anterolateral route was inadequate for aspirating the joint fluid. A lateral patellofemoral approach was then used.

The technical success score was 1.36 +/- 0.84, and both absolute and relative pain were minimal with the anterior approach for both approaches. Absolute pain weakly correlated with the technical success score (r = 0.33), which in turn weakly correlated with body mass index (r = 0.23).

Absolute pain was significantly lower for the anterolateral route than for the paramedian route (P <0.05). Relative pain was less frequently equal (P <0.05) and more frequently lower (P <0.01) for the anterolateral route.

Reviewer’s Comments
The difference in pain scores may be caused by the needle coursing through Hoffa’s fat pad with the anteromedian approach. The fat pad is known to have a rich nerve supply.

Obesity did not adversely affect success of the procedure.

A limitation of this study is lack of direct comparison to the standard patellofemoral approach, as it was not used any longer in this institution.

The difference in needle size may partially explain the difference in pain scores.

An advantage of the anterolateral route over the paramedian route was that it does not require fluoroscopy to confirm adequate needle position.

Author: Cornelia Wenokor, MD

Reference:
Moser T, Moussaoui A, et al. Anterior Approach for Knee Arthrography: Tolerance Evaluation and Comparison of Two Routes.
Radiology; 2008; 246 (January): 193-197

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