低減肩関節脱臼肩関節内注射

Intra-articular injection with a local anesthetic offers significant pain relief in patients with shoulder dislocation.

The dislodgment of humerus from the scapula is a painful injury that leads to loss of active abduction… adduction… and internal rotation. Reduction is the best form of analgesia, and of course, is necessary to restore of arm function. But the procedure for this restoration can be extremely painful. Therefore, before attempting the repair, injecting a local anesthetic into the intra-articular space decreases pain perception and eliminates the need for complete sedation for the reduction process.

This video will illustrate the intra-articular injection procedure performed in the absence and presence of ultrasound guidance.

Before going into the details of the procedure, let’s briefly review the types and etiology of shoulder dislocation.

The anatomy of the shoulder joint provides both extensive range of motion and considerable instability, making shoulder dislocation one of the most common joint disarticulations seen in emergency settings. The three major types of shoulder dislocations are: anterior, posterior, and inferior. Anterior shoulder dislocation is most typical accounting for almost 95% of the cases. This could be further classified into four types: subcoracoid, subglenoid, subclavicular, and intrathoracic. Of all the anterior shoulder dislocation cases, 75% are subcoracoid, and about 20% are subglenoid, leaving 5% for the other two types combined.

With this knowledge, let’s review how to perform intra-articular injection technique in the absence of ultrasound guidance.

After performing the physical exam and analyzing the X-ray confirming anterior joint dislocation, gather all the equipment needed for the procedure. These include: betadine solution, sterile gloves, 1% lidocaine, 20 ml syringe, 20 gauge 3.5 cm needle, gauze, tape, and a sterile tray to place the equipment.

Next, place the patient in a sitting or semi-recumbent position, as these positions are typically tolerable in case an anterior shoulder dislocation. Once the patient is as comfortable as injury allows, palpate the surface landmarks of the posterior acromion and the coracoid, and look for the newly formed lateral sulcus, which is an abnormal finding in presence of an empty glenoid fossa associated with anterior shoulder dislocation. Press into the shoulder from the posterolateral or lateral side and the sulcus will be evident by finger intrusion into the space or depression of the skin. This will be the insertion site for the injection. Mark this site with a skin marker. Next, apply antiseptic solution generously over the site in sterile fashion. Following that, prepare a syringe with 10-20 mL of 1% lidocaine, and attach an appropriate needle.

At this point, don sterile gloves, and palpate the anticipated insertion site again to confirm the point of entry. Now insert a small wheal of subcutaneous lidocaine to anesthetize the skin. Thendirect the needle about 2 cm inferior and lateral to the acromion in the lateral sulcus, toward the shoulder joint. Proceed deeper slowly, injecting a small amount of lidocaine into the tract of subcutaneous tissue and muscle.Aspirate intermittently, and when you have broached the injured joint capsule, serosanguinous fluid will be seen in the syringe.

At this point, slowly inject the remaining lidocaine. If the needle has been inserted all the way in but no blood has been aspirated, this means that either you are not in the correct space, or the needle is not long enough. Do not inject more lidocaine, as it will not be effective. If this happens, you can attempt to repeat the procedure using a longer needle — sometimes this procedure requires a spinal needle — or use of ultrasound guidance as described in the next section.

Now let’s review the same procedure under ultrasound guidance. 

The linear probe is more suitable for a thin person, and the curvilinear probe is apt for a larger person. Place the probe in the transverse plane across the dorsal aspect of the affected shoulder. In a normal shoulder, the humeral head will be in contact with the glenoid and ultrasound imaging will reveal both structures adjacent to each other in the same imaging plane. In case of anterior displacement, look for of the humeral head away from the glenoid. In the evacuated glenoid fossa in between the glenoid and the humerus, you will see clot formation, or hemarthrosis.

Like before, sterilize the lateral shoulder using an antiseptic, prepare the syringe and don sterile gloves. Now under ultrasound guidance, inject a superficial wheal of lidocaine to anesthetize the skin at the insertion site on the lateral or posterolateral aspect of the shoulder. Proceed deeper slowly, injecting a small amount of lidocaine into the subcutaneous tissue and muscle. Follow the needle tip on the ultrasound screen as it enters in an “in plane” approach — meaning that the direction of the needle insertion is parallel to or “in plane” with the direction of probe orientation. Direct the needle tip towards the blood clot in the empty glenoid fossa. When the needle tip is seen within the joint capsule, aspirate. Blood in syringe would confirm that the location is accurate. Now inject 10-20 mL of lidocaine into the joint space. This will be visible as a “swirling” motion on the ultrasound screen.

Wait 10-15 minutes and assess the effect of intra-articular anesthesia by asking the patient if their pain has decreased. If an adequate level of anesthesia has been achieved, proceed with shoulder reduction. Lastly, confirm correct humeral head placement in line with the glenoid by ultrasound.

“One of the main reasons for not achieving an adequate analgesia using this procedure is, not accessing the joint capsule due to inadequate needle length in the patients with large musculature or obese individuals. Regular needles may be too short to pierce through the subcutaneous tissue, and the procedure may require a longer 22 gauge spinal needle in these patients.”

“The other complication is that the author may report meeting resistance during the procedure. This may be due to inappropriate trajectory of the needle insertion causing it to abut against the bony prominence. This can be avoided by performing the injection under the ultrasound guidance, which helps to determine the appropriate pathway and increases the success of the procedure.”

You’ve just watched JoVE’s illustration of intra-articular injection for reduction following anterior shoulder dislocation. You should now understand the anatomy of an evacuated glenoid fossa, mechanics of the intra-articular injection, and the advantages of using ultrasound for this procedure. As always, thanks for watching!