Anesthetic injection of the hip is one of the most commonly requested and performed articular injection procedures in the modern interventional musculoskeletal radiology practice. This is primarily due to the superior accuracy of the fluoroscopically guided needle positioning and the proximity of the joint to the femoral neurovascular structures. Verification of intra-articular needle positioning can also be difficult without fluoroscopy due to the depth of the joint capsule. Fluoroscopic guidance is therefore crucial to determine the proper needle approach and to verify intra-articular needle position. Although many techniques and approaches have been described, an anterolateral approach to the hip joint is preferred. This technique is both effective and safe due to the relative avoidance of the femoral neurovascular bundle.
All injection procedures should begin with a brief patient interview to elicit pertinent clinical history including contraindications for medications such as anticoagulants, medication allergies, and the patient's current pain level. A verbal pain scale from 0 through 10 (0, no pain; 10, worst imaginable pain) is useful for objective assessment (2).
The anterolateral approach to the hip joint is performed with the patient supine, utilizing single plane posterior-anterior (PA) fluoroscopy with the hip internally rotated. The skin overlying the greater trochanter of the femur is marked with an indelible marker prior to skin preparation and draping. Following local anesthesia, a 20 or 22 gauge spinal needle is directed in a posteromedial direction toward the femoral neck at or near its junction with the femoral head. The needle is advanced under fluoroscopic guidance until the cortex of the femoral neck is contacted. If under fluoroscopic monitoring, the needle tip passes medial to the femoral head-neck junction without cortical contact, a steeper entry angle is needed. The needle is then pulled back partially and redirected. If cortical contact is made significantly lateral to the head-neck junction, a shallower angle of the approach is needed and the needle tip can be "walked" medially along the femoral neck until the capsule is entered. After the desired needle tip position is obtained, a small amount of contrast should be injected to document capsular filling (Fig. 1). This should be followed immediately by injection of the desired anesthetic solution.
The injection solution depends on personal preference and availability of medications. The author prefers a mixture of equal parts of lidocaine (2%) and bupivicaine (0.75%). Steroid solutions may also be added for sustained anti-inflammatory effect if desired. It should be noted that some studies have found intra-articular steroid injections to be harmful in some
joints (3). Please see Chapter 2 for detailed information regarding the biochemistry of anesthetic agents for selective intra-articular injections.
After the procedure, a repeat pain level assessment is performed to gauge response to the injection. This is typically assessed following a short walk by the patient to assure adequate intra-articular anesthetic disbursement.
Procedural complications with this technique have been minimal in the author's experience. Obvious risks include bleeding from arterial puncture, joint or soft tissue infection, allergic reactions, and inadvertent femoral nerve anesthesia due to infiltration of the local anesthetic. These risks are reduced by a strict aseptic technique, careful needle positioning, and minimization of the overall procedure time. The risk of neurovascular injury is minimized by the anterolateral approach, which is especially helpful in obese patients in whom palpation and isolation of the femoral artery may be difficult. This approach also obviates the need for lateral fluoroscopy, which is variably employed during the lateral approach to the hip joint (4). Ultimately, the operator's familiarity and comfort level should dictate the selected approach to the hip.
Anesthetic agents can also be added to the contrast solution during arthrographic evaluation of the postarthroplasty hip to determine intra- or extra-articular origin of recurrent hip pain (5).
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