Published online before print November 16, 2007, 10.1148/radiol.2461070045
(Radiology 2008;246:193-197.)
© RSNA, 2007
Anterior Approach for Knee Arthrography: Tolerance Evaluation and Comparison of Two Routes1
Thomas Moser, MD,
Akli Moussaoui, MD,
Michel Dupuis, MD,
Valérie Douzal, MD, and
Jean-Claude Dosch, MD
1 From the Department of Radiology, Strasbourg University Hospital, 1 Place de l'Hôpital, 67000 Strasbourg, France. Received January 8, 2007; revision requested March 1; revision received March 14; accepted April 23; final version accepted July 2.
Address correspondence to T.M. (e-mail: thomas.moser{at}chru-strasbourg.fr).
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ABSTRACT
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Purpose: To prospectively evaluate patient tolerance and technical success of the anterior knee puncture approach for arthrography by using two different routes.
Materials and Methods: The study had Strasbourg University Hospital review board approval. Informed consent was obtained from all patients (and from their parents, if patients were minors). In 159 patients (89 male and 70 female; age range, 14–82 years; mean age, 44.3 years ± 16 [standard deviation]) referred for computed tomographic (CT) arthrography, anterior puncture of the knee was performed by using an anterolateral (n = 73) or anterior paramedian (n = 86) route. For each patient, body mass index, absolute pain on a visual analog scale, relative pain (compared with anticipatory pain), and history of previous knee arthrography were recorded. A score reflecting the technical success of the procedure was established by using a five-point scale. Factors influencing tolerance and technical success were analyzed with Pearson correlation coefficients. Student t and 
2 tests were used to compare the two routes.
Results: The anterior approach for knee arthrography was well tolerated (mean visual analog scale score, 12.9 ± 16.4) and technically successful (mean technical success score, 1.36 ± 0.84) in most cases. Absolute pain was not influenced by age, sex, or body mass index and was only weakly correlated (r = 0.33) with the technical success score. The technical success score weakly correlated (r = 0.23) with the body mass index. A slight but significant reduction in absolute (P < .05) and relative (P < .01) pain was observed for the anterolateral route compared with the anterior paramedian route, while no significant differences (P > .05) were found for other parameters, including the technical success score.
Conclusion: The anterior approach for knee arthrography is technically successful and well tolerated, particularly when an anterolateral route is used.
© RSNA, 2007
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INTRODUCTION
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Knee arthrography is currently considered a preliminary step for more sophisticated imaging techniques, such as multidetector computed tomographic (CT) arthrography and magnetic resonance (MR) arthrography. Evaluation of recurrent meniscal tears, osteochondral injuries, and articular loose bodies are existing indications for these techniques (1–3).
Different approaches for knee puncture have been described. The lateral patellofemoral approach is the one most commonly reported (4). With this technique, the knee is placed in slight flexion and the lateral aspect of the suprapatellar recess is punctured after lateral subluxation of the patella. In our experience, this approach is well suited for aspirating joint fluid but is often painful and sometimes unsuccessful when a knee without any effusion is punctured. Presence of lateral patellofemoral osteoarthritis and complete superior plica isolating the suprapatellar recess from the joint are other causes of unsuccessful arthrography. A medial patellofemoral approach has been advocated by other authors to overcome some of these drawbacks and may be easier to perform in patients with patellofemoral subluxation (4).
In our institution, we have extensive experience with an anterior approach similar to that used for knee arthroscopy. This approach has not received much attention in the literature, although Zurlo and colleagues (5) have described an anterior approach with lateral fluoroscopic guidance that differs substantially from our technique. Thus, the objective of our study was to prospectively evaluate patient tolerance and technical success of the anterior knee puncture approach for arthrography by using two different routes.
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MATERIALS AND METHODS
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Patients
Our study had Strasbourg University Hospital review board approval, and informed consent was obtained from all patients (and from their parents if patients were minors). During a 4-month period, 159 consecutive patients referred for internal derangement of the knee were enrolled. There were 89 male patients and 70 female patients, with an age range of 14–82 years (mean age, 44.3 years ± 16.0 [standard deviation]).
Arthrography
A pamphlet describing the procedure was mailed, along with the appointment letter, to all patients 1–2 weeks before the procedure. Patients were placed supine on the fluoroscopy table with a pillow under their heads and a bolster under the knee to be injected. The knee was sterilely prepared and punctured by one of five musculoskeletal radiologists by using an anterior approach and anteroposterior fluoroscopic guidance. The anterior approach for knee arthrography has been used for 30 years in our department (instead of the lateral patellofemoral approach). We did not use local anesthesia for the procedure.
An anterior paramedian route (Fig 1a) was used in 86 patients by three musculoskeletal radiologists with 10 (A.M.), 10 (V.D.), and 30 (M.D.) years of experience in knee arthrography. The knee was flexed at 60°. A 20-gauge 45-mm intravenous cannula (Insyte-W; Becton Dickinson, Franklin Lakes, NJ) was introduced just lateral to the patellar ligament and was directed upward and slightly medially toward the femoral notch. This needle gauge was chosen so as to be able to aspirate any potential joint effusion. In our experience, anteroposterior fluoroscopy was sufficient to confirm adequate intraarticular position of the needle, by means of contrast medium flowing away from the needle tip when the first drops were gently injected (Fig 1b). If contrast medium pooling was noted around the tip, the needle was considered to be in an extraarticular position and was immediately repositioned. Lateral fluoroscopy was never used because it requires mobilization of the patient.
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Figure 1a: Anterior paramedian route for knee arthrography. (a) Diagram of needle path on an anteroposterior view. (b) Anteroposterior fluoroscopic image shows confirmation of correct needle positioning.
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Figure 1b: Anterior paramedian route for knee arthrography. (a) Diagram of needle path on an anteroposterior view. (b) Anteroposterior fluoroscopic image shows confirmation of correct needle positioning.
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An anterolateral route (Fig 2a) was employed in 73 patients by two other radiologists: one resident (T.M.) with no prior experience and a radiologist (J.C.D.) with 30 years of experience in knee arthrography. This route was a refinement of the above technique aiming to use a shorter needle and to prevent extraarticular injection. This technique was developed by the senior radiologist (J.C.D.), and it was used for 7 years and taught to the younger radiologist. The knee was flexed at 90°. The arthrographer's thumb was placed over the anterolateral aspect of the lateral tibial plateau to locate the joint space. A 21 -gauge 40-mm needle (Microlance 3; Becton Dickinson) was introduced horizontally immediately above the palpating thumb, thus preventing inadvertent puncture of the lateral meniscus. The needle was directed posteriorly and slightly medially to ensure contact with the articular portion of the femoral condyle (Fig 2b). This contact with the femoral condyle's cartilage was absolutely nonpainful. Correct position of the needle was confirmed with injection of contrast medium at anteroposterior or slightly caudocranially angulated fluoroscopy (Fig 2c).
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Figure 2a: Anterolateral approach for knee arthrography. (a) Diagram of needle path on an anteroposterior view. To ensure articular position, the needle tip should reach a portion of the femoral condyle covered with cartilage. (b) Image shows knee position and entry point determined by palpation. (c) Anteroposterior fluoroscopic image shows confirmation of correct needle positioning.
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Figure 2b: Anterolateral approach for knee arthrography. (a) Diagram of needle path on an anteroposterior view. To ensure articular position, the needle tip should reach a portion of the femoral condyle covered with cartilage. (b) Image shows knee position and entry point determined by palpation. (c) Anteroposterior fluoroscopic image shows confirmation of correct needle positioning.
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Figure 2c: Anterolateral approach for knee arthrography. (a) Diagram of needle path on an anteroposterior view. To ensure articular position, the needle tip should reach a portion of the femoral condyle covered with cartilage. (b) Image shows knee position and entry point determined by palpation. (c) Anteroposterior fluoroscopic image shows confirmation of correct needle positioning.
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The allocation of patients to each technique depended on which radiologist performed the procedure, as each radiologist used his or her preferred technique (route) as described.
In all cases, a volume of 10 mL iopamidol (Iopamiron; Schering, Lyz-les Lannois, France) with an iodine concentration of 370 mg/mL was injected. After mobilization of the joint, radiographs were obtained in posteroanterior, lateral, and skyline views. Patients were then immediately directed to the CT suite for CT arthrography.
For each procedure, a technical success score was self-reported by the radiologist and was documented by using a five-point scale: score of 1, no needle repositioning, smooth injection; 2, slight needle repositioning, smooth injection; 3, multiple needle repositioning, or difficult injection; 4, extraarticular injection of a small volume (1–5 mL); and 5, extraarticular injection of a large volume (>5 mL). All procedures were satisfactorily completed with no adverse effects or complications.
Patient Tolerance
After completion of the CT arthrography examination, patients were asked to anonymously fill out a form recording the following details: height, weight, absolute pain during the procedure (measured in millimeters on a visual analog scale), relative pain (lower than, identical to, or worse than anticipatory pain), and history of previous knee arthrography.
Height and weight were used to estimate the body mass index, which reflects general adiposity. Obesity was defined as a body mass index of 30 kg/m2 or greater (6).
Statistical Analysis
Descriptive statistics were obtained for all parameters.
The relationship between absolute pain, technical success, age, and body mass index were investigated by using Pearson correlation coefficients. The strength of the relationship between two parameters was considered important for r values ranging between 0.8 and 1.0, moderate for r values ranging between 0.5 and 0.8, and weak for r values ranging between 0.2 and 0.5.
Results were then compared for the two groups, corresponding to the anterolateral and anterior paramedian routes, by using the Student t test (age, body mass index, absolute pain, and technical success) or 2 test (sex, relative pain, and history of previous knee arthrography). Additionally, we compared absolute pain and technical success among different radiologists of each group to detect intragroup variation. Differences were considered statistically significant for a P value of less than .05. Tests were performed by using R software (version 2.2.0; R Foundation for Statistical Computing, Vienna, Austria).
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RESULTS
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In one patient with a large joint effusion (over 150 mL), the anterolateral route was inadequate in completely aspirating the joint fluid, and a lateral patellofemoral approach was successfully used.
The technical success score was 1.36 ± 0.84, and both absolute pain (mean visual analog scale score, 12.9 ± 16.4) and relative pain (lower pain, 68%; worse pain, 18%; and identical pain, 14%) were minimal with the anterior approach for knee arthrography (both anterior paramedian and anterolateral routes combined).
Absolute pain was not influenced by age (r = –0.01), sex (P = .10), body mass index (r = 0.01), or history of previous knee arthrography (P = .57). However, absolute pain was weakly correlated (r = 0.33) with the technical success score, which in turn was weakly correlated with the body mass index (r = 0.23).
When the anterior paramedian and anterolateral routes were considered separately, there was no significant difference among radiologists of the same group for absolute pain experienced by the patient (P > .05). A slight but significant difference (P = .01) for the technical success score was observed between the radiologists using the anterior paramedian route. Absolute pain was significantly lower for the anterolateral route than for the paramedian route (P < .05). Relative pain was more frequently lower (P < .01) and less frequently equal (P < .05) for the anterolateral route in comparison with the paramedian route (Table).
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DISCUSSION
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Our study findings demonstrate that the anterior approach for knee arthrography is well tolerated and technically successful, whether a paramedian or an anterolateral route is used. Not much attention has been accorded to the discomfort resulting from knee arthrography, and we were unable to find studies reporting the tolerance of the classical lateral patellofemoral puncture. Authors of a few studies have investigated the respective roles of air, carbon dioxide (double-contrast arthrography) (7), or ionic or nonionic contrast media (8) in the pathogenesis of pain after knee and shoulder arthrography. Pain attributed to the puncture itself has never been precisely quantified, to our knowledge. In fact, as suggested by our results, this pain appears to be generally minimal and in most cases lower than the anticipatory pain. Findings of recent studies on MR arthrography of the shoulder have also demonstrated that articular puncture represents only a minor discomfort compared with the MR procedure itself (9–11).
The wide dispersion of visual analog scale scores in our study could be accounted for by the large variability of pain sensation among patients. This finding gives limited value to the measure of absolute pain in our study. It also suggests that the pain experienced by a given patient cannot be accurately predicted on the basis of age, sex, and previous history of knee arthrography. We do not use local anesthesia for knee arthrography because the injection of local anesthetic itself is painful. Technical success scores could not account for the significant difference in pain scores between the two groups. A potential explanation for the difference could be that the anterior paramedian route systematically transgresses the infrapatellar (Hoffa) fat pad, which has a rich nerve supply (12). The fat pad is only minimally crossed with the anterolateral route, which could account for the difference in pain between the two groups (Fig 3). Although not demonstrated in our study, we have noted that extraarticular injection of contrast medium within the Hoffa fat pad is usually painful.
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Figure 3: Anterior paramedian (yellow arrow) and anterolateral (green arrow) routes on a transverse CT section. Note the anterolateral route only minimally transgresses the infrapatellar (Hoffa) fat pad (white dotted line). The patellar ligament (green), as well as the cruciate ligaments (green) and their synovial fold (orange dotted line), should be avoided.
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It is also worth noting that obesity, which is frequently associated with knee joint disorders, did not alter the technical success of our technique. There is less soft tissue at the puncture site for an anterior approach than for a patellofemoral approach. Further, soft-tissue thickness is minimal for the anterolateral route on a 90° flexed knee, thus allowing puncturing with a shorter and thinner-gauge needle.
Our study had limitations. The first was the absence of comparison to the classical patellofemoral approach. The patellofemoral approach (either lateral or medial) has not been used for a long time and has been successfully replaced by the anterior paramedian approach in our department. More recently, we became fully aware of the different advantages offered by the anterolateral route through using it and teaching it to our residents. There is essentially no learning curve since comparable results were obtained by a senior musculoskeletal radiologist and a radiology resident in our study.
Another potential limitation of this study is the difference in needle size between the two groups, which may partly explain the difference in pain scores. However in our opinion, advantages of the anterolateral route over the anterior paramedian route reside not only in its better tolerance but in the ability to obtain adequate needle positioning without the need for fluoroscopic guidance. Contact with the articular portion of the lateral femoral condyle provides a reliable clue for intraarticular position. We recommend that a smooth and nonpainful articular injection is a prerequisite with this blind technique. If not, needle repositioning or test injection of saline or anesthetic should be performed. The advantage of a blind anterolateral puncture can be extrapolated to MR arthrography, where a fluoroscopy suite may not be readily available and/or injection of iodinated contrast medium is to be avoided. On the other hand, we do not recommend omitting fluoroscopic control when using the anterior paramedian route because no bone contact is used for establishing the intraarticular position of the needle tip. Hence if the procedure is performed blindly the needle tip can be located either too anteriorly in the Hoffa fat pad or too posteriorly within the cruciate ligaments. Furthermore, it is possible for the needle to freely cross the condylar notch to reach the popliteal vessels and result in an intravascular injection. Hence, we do not recommend performing the anterior paramedian route anymore and advocate the anterolateral route, which we believe much safer.
In conclusion, we used two different routes for knee arthrography with an anterior approach. Although the technical success score and tolerance were excellent for both, we recommend using the anterolateral route for reasons already noted.
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ADVANCES IN KNOWLEDGE
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- The anterior approach for knee arthrography is an alternative to the classic patellofemoral approach.
- The anterior approach can be performed by using either a paramedian or preferably an anterolateral route.
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IMPLICATION FOR PATIENT CARE
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- The anterior approach for knee arthrography is technically successful and minimally painful.
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ACKNOWLEDGMENTS
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We thank the radiographers of our radiology department for their contribution to our study.
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FOOTNOTES
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Guarantors of integrity of entire study, T.M., J.C.D.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approval, all authors; literature research, T.M., J.C.D.; clinical studies, all authors; statistical analysis, T.M.; and manuscript editing, T.M., J.C.D.
Authors stated no financial relationship to disclose.
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References
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ABSTRACT
INTRODUCTION
