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Original Research |
1 Department of Radiology, Virgen de la Arrixaca University Hospital, 30120-El
Palmar, Murcia, Spain.
2 Department of Radiation Protection, Virgen de la Arrixaca University Hospital,
Murcia, Spain.
3 Department of Orthopedic Surgery, Virgen de la Arrixaca University Hospital,
Murcia, Spain.
4 Department of Biostatistics, Murcia University, Murcia, Spain.
Received April 3, 2008;
accepted after revision June 2, 2008.
Address correspondence to J. D. Berná-Serna
(jdberna{at}um.es).
Abstract
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MATERIALS AND METHODS. Seventy-eight patients were divided into three groups of 26 each, according to the injection site selected: the upper third of the medial part of the humeral head, the lower third of the medial part of the humeral head, or the area between the middle and lower thirds of the glenohumeral joint. A marker plate with radiopaque coordinates was used in performing the technique. Radiologist time and exposure time were recorded, and the intensity of the patient's pain was measured using a Visual Analogue Scale (VAS). Groups were compared using variance analysis and the least significant difference method.
RESULTS. Shoulder arthrography was considered satisfactory for all three injection sites. Mean exposure time was 20.9 ± 7.8 (SD) milliseconds, and mean radiologist time was 6.4 ± 0.8 minutes. Mean pain intensity registered by the VAS was 1.7 ± 0.9, the lowest values tending to be those recorded by patients who received an injection in the upper third. Exposure and radiologist times were lower for these latter patients; differences between the upper third and the other two areas were statistically significant (p < 0.005).
CONCLUSION. The optimal injection site for anterior MR arthrography of the shoulder is the upper third of the humeral head, a simple, rapid procedure that is well tolerated by patients and reduces the radiation dose administered.
Keywords: arthrography • joint • shoulder
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One of the most difficult aspects of shoulder arthrography is determining the best place for injection. Although the most commonly used approach is the anterior, the exact site is still a topic of debate. One of the three following sites is usual: the upper third of the medial part of the humeral head, the lower third of the medial part of the humeral head, or the area between the middle and lower thirds of the glenohumeral joint that corresponds to the Schneider standard technique [2]. To our knowledge, no comparative study of the three areas has been performed to determine the optimal injection site for MR arthrography of the shoulder. Such was the aim of this study.
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Technique
The areas corresponding to the injection sites were defined by tracing a
notional horizontal line from the center of the sclerotic line corresponding
to the anatomic neck of the humeral head as far as the cortex of the humeral
head (Fig. 1). Injection sites
were the upper third of the medial part of the humeral head, the lower third
of the medial part of the humeral head, and the area between the middle and
lower thirds of the glenohumeral joint.
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Before arthrography was performed, a thick coating of 2 g of 5% EMLA cream (AstraZeneca; a 1:1 mixture of 2.5% lidocaine and 2.5% prilocaine) was applied to the skin corresponding to the glenohumeral joint area and covered with an occlusive dressing for 20–60 minutes (mean, 35 minutes). When the patient was in the fluoroscopy room, the anesthetic cream was removed with an alcohol swab before starting the examination.
Patients were placed in a supine position on the fluoroscopy table (Siregraph CF, Siemens Medical Solutions) with the shoulder in external rotation; in patients in whom this position caused discomfort, the shoulder was placed in neutral rotation. Rigorous aseptic measures were applied. The intraarticular contrast material was injected following the arthrography technique described in detail previously [12], using a marker plate with radiopaque coordinates to select the injection site without the need for fluoroscopic guidance. The adhesive marker plate was placed on an area of skin over the shoulder and a spot radiograph was obtained to determine the injection site (Fig. 2A). When the injection was to the upper or lower third of the humeral head, we took care that the injection site selected was close to the glenohumeral joint. A 22-gauge, 1.5-inch (4-mm) spinal needle was used for injections to the upper third and lower third of the medial part of the humeral head, and a 22-gauge, 3.5-inch (88-mm) spinal needle was used for injections to the glenohumeral space. The needle insertion was performed in an anteroposterior direction, progressively and slowly, until the needle came into contact with the humeral head (for the upper third or lower third of the medial part of the humeral head) or until a change in resistance was perceived (for the glenohumeral joint). A spot radiograph was then obtained to confirm the localization of the tip of the needle (Fig. 2B). Next, a small test injection of anesthetic was performed [10]. If the needle is in the articular space, there will be little resistance to the injection; a small quantity of iodinated contrast material must be injected to verify intraarticular needle placement (Fig. 2C). Between 0.5 and 4 mL of gadopentetate dimeglumine (Magnevist, Bayer HealthCare [formerly Schering]) was diluted in 100 mL of sterile saline. The solution was slowly injected until the joint capsule was appropriately distended. After the needle was removed, a dressing was placed over the injection site.
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Radiologist times—that is, the time elapsing from positioning of the adhesive marker plate on the shoulder to withdrawal of the needle—were recorded for each procedure by a radiography technician. Exposure time was recorded by a radiophysicist. Both technician and radiophysicist were blinded to the arthrographic approach and were unaware of the injection site used during the procedure.
Pain intensity was registered using a Visual Analogue Scale (VAS) of 0–10, in which 0 meant no pain and 10, the worst possible pain. We also used a verbal scale for pain from 0 (no pain) to 5 (worst possible pain). In every case, MRI was evaluated for extraarticular contrast material and for any possible distortion of the anatomic intraarticular structures resulting from the injection (i.e., injection into the biceps tendon).
Statistical Analysis
For statistical analysis of the data, the SPSS software package, version
14.0 (SPSS for Windows, 2006) was used. A descriptive statistical analysis of
each variable was made, giving the frequency of distribution. For quantitative
variables, the usual parameters were also calculated: mean; SD; and standard
errors of the mean, maximum, and minimum. The relationship between qualitative
variables was obtained using Pearson's chi-square test, and the quantitative
variables were analyzed using Pearson's lineal correlation coefficient.
Analysis of variance was used to compare groups, complemented by comparing mean pairs using the least significant difference. Differences were considered statistically significant at p < 0.05.
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The mean volume of contrast material injected was 14.9 ± 6.2 (SD) mL (range, 9–20 mL). Mean exposure time was 20.9 ± 7.8 milliseconds (range, 11.2–29 milliseconds) and mean radiologist time was 6.4 ± 0.8 minutes (range, 5–8 minutes). Mean pain intensity registered by the VAS was 1.7 ± 0.9 (range, 0–3), and the mean pain registered on a verbal scale was as follows: 10 patients (12.8%) gave a score of 0 (no pain); 40 (51.3%), a score of 1 (slight pain); and 28 (35.9%), a score of 2 (discomfort). A significant degree of correlation was seen between the verbal scale and the VAS (r = 0.858, p < 0.0005). When the VAS was used to evaluate the pain of the 39 arthrographic examinations performed by the resident in training, the mean was 1.6 ± 0.9 (range, 0–3), and the mean for the corresponding score for the examinations performed by the experienced radiologist was 1.7 ± 0.9 (range, 0–3). No differences were observed in arthrographic technique times between the experienced radiologist and the resident.
An association was seen between the injections in the lower third of the humeral head and those performed in the glenohumeral space: Both showed higher pain intensities on the verbal and VAS scales than the injections in the upper third of the humeral head. Significant correlations were recorded between VAS and exposure time (r = 0.387, p < 0.001), VAS and radiologist time (r = 0.383, p < 0.001), and exposure time and radiologist time (r = 0.724, p < 0.0005).
Table 1 shows several parameters related to the injection sites. Statistically significant differences (p < 0.005) were observed between radiologist time and pain felt during arthrography and between the injection sites (the upper third vs the other two sites). Lower values were associated with the upper third site. With respect to total exposure time, statistically significant differences (p < 0.005) were observed between the upper third and lower third injection sites, and between the lower third injection site and the glenohumeral space site.
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Many of these structures are concentrated around the anteroinferior aspect of the articulation, the inferior glenohumeral ligament complex, and the anterior labrum. When the Schneider technique is used, the needle traverses the subscapularis muscle or tendon and can traverse the inferior glenohumeral ligament and anteroinferior labrum and penetrate the subcoracoid bursa; there is a risk of causing distortion of these structures and creating confusing findings on MR arthrography [8]. Moreover, when the inferomedial third of the humeral head is the site chosen for injection, the needle traverses the subscapularis tendon and avoids the inferior glenohumeral ligament and the anteroinferior labrum. Regarding the injection site corresponding to the supero medial third of the humeral head, the injection is performed in the rotator cuff interval, a triangular space located between the supraspinatus and subscapularis tendons [11]; the needle can traverse the coracohumeral ligament but accessing the superior glenohumeral ligament is difficult. Another structure traversing this space is the long head of the biceps tendon, which during the procedure can be cleared laterally by external rotation of the arm. Furthermore, when the rotator cuff interval is used, perforation of the anterosuperior labrum, anteroinferior labrum, and inferior glenohumeral ligament is avoided. Thus, when injections are performed over the humeral head in either the inferomedial or the superomedial space, the stabilizing structures of the shoulder can be avoided.
We agree with other reports [11, 12] that the anterior approach is safe and nontraumatic, especially when the injection involves the upper third of the humeral head. In addition, by performing the injection in the rotator cuff interval, the subcoracoid bursa, which can be penetrated when the conventional technique is used, can be avoided.
In our study, we used short spinal needles for both the upper and lower third sites because these are easier to use than the long spinal needles necessary for the glenohumeral space; we thus avoided possible movement of the needle when inserted into soft tissue. The use of longer needles for the upper and lower thirds of the humeral head is recommended only in the case of obese patients or those with voluminous soft tissue on the shoulder. We used an adhesive marker plate with radiopaque coordinates to select the different injection points for performing shoulder arthrography without the need for fluoroscopic guidance. This method protects the radiologist from radiation and minimizes patient exposure, especially when using the upper third of the humeral head for arthrography. We have observed that when the upper third of the humeral head is used, injection of a small quantity of iodinated contrast material is sufficient to rapidly establish that the needle is correctly inserted into the articular space because the material is evenly distributed. When the lower third of the humeral head or the glenohumeral space is used, it is sometimes necessary to inject more contrast material to confirm that the needle is correctly placed; this requires an additional spot radiograph, more time is needed for the procedure, and the patient undergoes greater exposure.
Because no significant differences were observed between the experienced radiologist and the resident, we tend to prefer the upper third of the humeral head as the injection site, with the lower third of the humeral head as the second best. The glenohumeral space is considered the most difficult to use, especially by inexperienced operators.
In the 78 patients in the present study, the MRI findings were evaluated and no diagnostic dilemmas based on the site of injection arose because no qualitative dif ferences were observed. No distortion of the anterosuperior labrum, superior glenohum eral ligament, or coracohumeral ligament was observed in the patients in whom the injection site was in the space correspond ing to the rotator cuff interval. In only two cases of injections performed in the gleno humeral articular space was reposition ing of the needle necessary to achieve adequate distribution of contrast material in the articular space. In both of these cases, extraarticular contrast material was observed. On the basis of our results, we recommend the use of the superomedial third of the humeral head for the performance of shoulder arthrography.
The results of this study show that for MR arthrography examinations of the shoulder, contrast injection into the upper third of the humeral head is best tolerated by patients. In addition, the time required by the radiologist and patient exposure to radiation are both reduced. Injection in this site is also simpler and more rapid to perform in comparison with the other two sites analyzed in this study.
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