资料来源： 刘艳、 宝、 MBBCh、 急诊医学、 耶鲁大学医学院、 纽黑文，康涅狄格州美国
肩关节前脱位是最常见的关节脱位，见于紧急设置之一。在肩关节前脱位，肱骨头被流离失所出来盂肱关节在肩胛盂，造成损失的手臂和肩膀的其余部分的衔接。这可能导致跌倒被绑架、 扩展和外部旋转的手臂，如在自行车或运行的事故。有时前肩关节脱位可以是由于轻微外伤或甚至导致从翻滚在床上与外部旋转和拉伸的架空手臂。
肩关节前脱位是痛苦的伤害。病人不能积极绑架、 加合物或内部旋转的肩。减少肩是镇痛的最佳形式和，当然，有必要恢复上肢功能。虽然它是目前的做法，要求病人接受肩膀复位过程中的程序性镇静，镇静剂有严重副作用 （心脏和呼吸抑郁），和需要长时间停留在应急部门 (ED)，专门负责护理人员、 多个射线照相和咨询服务。
关节内注射治疗局部麻醉，如利多卡因，提供显著的疼痛缓解肩关节脱位复位过程中患者。它是技术上简单的过程，不需要长 ED 停留或大医院的资源。可以增强关节内麻醉的成功进一步通过执行床边超声引导下的程序，它允许实时可视化的针尖达到相应的区域。
For shoulder dislocation, intra-articular injection of lidocaine as analgesia (and subsequent reduction) avoids the cardiopulmonary depression and side effects associated with procedural sedation. Intra-articular injection of lidocaine is a safe procedure since the administrated dosages are below the levels that cause cardiotoxicity. In addition, the direct injection into the joint space decreases the risk of systemic infection, and the risk of septic arthritis is mitigated by sterile precautions.
One of the main reasons for not achieving adequate analgesia is not accessing the joint capsule due to inadequate needle length in obese patients or those with large musculature. Regular needles may be too short to pierce through the subcutaneous tissue in these patients, and the procedure may require a longer 22-gauge spinal needle. In addition, the inserted needle might be abutting a bony prominence due to inappropriate trajectory of the needle insertion, and the operator report meeting resistance during the procedure. Performing the intra-articular injection under ultrasound guidance helps to determine the appropriate pathway to the joint capsule. The ultrasound allows visualization of the hemarthrosis of the joint capsule and confirmation of needle entry, resulting in aspiration and injection of the appropriate area and increasing success of the procedure.
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!
