Biceps Tendon Sheath Injection

Anatomy and Physiology

The long head biceps muscle has a proximal insertion at the shoulder, where the tendon is intra-articular, originating on the supraglenoid tubercle and superior glenoid labrum. It exits the glenohumeral joint at the level of the humeral head near the rotator cuff attachments on the humerus, entering the bicipital groove. It is held within the proximal bicipital groove by the coracohumeral and transverse humeral ligaments as well as fibers of the subscapularis tendon.

In most patients, there are distinct attachments of the long and short heads of the biceps tendon on the radial tuberosity. The distal biceps tendons traverse the elbow joint and attach to the radial tuberosity. The long head normally constitutes the more proximal insertion on the radial tuberosity and the short head the more distal. Therefore, it is possible to have an isolated tear of either the long or short head.

At the distal biceps myotendinous junction, there is a broad aponeurosis known as the lacertus fibrosus (also called the bicipital aponeurosis), which circumferentially covers the flexor muscle attachments as well as the median nerve and brachial artery. This aponeurosis originates at the distal biceps tendon and inserts onto the radial tuberosity and proximal ulna. It is held in place by multiple strong fascial connections and serves as a protective covering for the neurovascular structures that course beneath. In most cases, the lacertus fibrosus prevents a torn biceps tendon from retracting more than a few centimeters proximal to the elbow joint; however, if the lacertus fibrosus is also injured, the tendon retraction may be more severe, making surgical repair more difficult.

Indications

Ultrasound has uses in a wide range of musculoskeletal procedures, including joint or bursa aspiration to evaluate for infection or crystalline deposition disease; joint or bursa injection, such as an arthrogram or steroid injection; tendon sheath injection; tendinosis therapy, such as dry needling; platelet-rich plasma injection; and percutaneous biopsy. Injections into a joint, bursa, or tendon sheath can be both therapeutic (pain relief) and diagnostic, allowing the referring provider to assess the patient’s pathology based on their pain response post-treatment.[11][12] 

Shoulder pain can be complex and multifactorial. Clinicians use a combination of physical examination, history, and imaging to establish a differential diagnosis.[13][14] In some cases, MRI may identify multiple abnormal findings, and injections may help elucidate their clinical significance. For example, the MRI examination may identify a superior labral tear and biceps tendinosis in addition to a rotator cuff tear, but the physical examination is most consistent with rotator cuff pathology. The orthopedist may request a biceps tendon injection to determine if a biceps tenodesis at the time of rotator cuff repair is indicated.[6][15][16]

Contraindications

Absolute contraindications to corticosteroid injections include local infection and bacteremia. If the infusion is intra-articular, absolute contraindications would also include septic arthrosis and intra-articular fracture. In the setting of biceps tendon sheath injection, it should be noted that the biceps tendon sheath communicates with the glenohumeral joint. Therefore, medication injected into the biceps tendon sheath also extends to the joint. If the clinical indication is to assess for septic arthrosis or tenosynovitis, one must carefully evaluate the overlying soft tissues for signs of cellulitis. It is crucial to avoid contamination of the joint or tendon sheath by placing the needle through infected soft tissue before accessing the joint. Relative contraindications include local or juxta-articular osteoporosis, coagulopathy, or recent injection or multiple frequent injections, defined as 3 or more injections over the last year or within the prior 6 weeks.[17]

Equipment

Several varieties of steroids are available on the market today, including methylprednisolone acetate, triamcinolone, betamethasone acetate with betamethasone sodium phosphate, and dexamethasone sodium phosphate, each with its own strengths and weaknesses. The most commonly used steroids in the United States include methylprednisolone, triamcinolone hexacetonide, triamcinolone acetonide, and betamethasone.[18]

Of note, the equivalent potency of betamethasone and dexamethasone sodium phosphate is approximately 5 times that of the others. Solubility also varies between the steroid formulations. For example, the acetate portion of betamethasone is insoluble, while the sodium phosphate portion of betamethasone and dexamethasone sodium phosphate is freely water-soluble. Particle size varies from 0.5 micrometers for dexamethasone to over 500 micrometers for methylprednisolone acetate, and triamcinolone exhibits extensive particle aggregation, requiring meticulous mixing of the solution before injection.

Dosage varies based on the chosen steroid and the location treated, with small joints (metacarpophalangeal, facet, acromioclavicular) receiving higher amounts, and medium-sized joints (elbow, wrist) and larger joints (knee, shoulder, hip, ankle) receiving higher amounts. For example, while a large joint might require 40 to 80mg of methylprednisolone acetate, that same joint would only require 8 to 15 mg of dexamethasone sodium phosphate. Similarly, a small joint might require 4 to 10 mg of methylprednisolone acetate, while that same joint would only require 0.8 to 2 mg of dexamethasone sodium phosphate. Some examples of steroid mixtures used for biceps tendon sheath injection at our institution include 3.75 mg dexamethasone mixed with 2 ml 1% lidocaine or 1ml betamethasone (6 mg/ml) mixed with 2 ml 1% lidocaine.[19]

Before injecting the steroid, a local anesthetic is provided to the skin and superficial soft tissues using 1% lidocaine. Although around 5 to 7 mL is the typical amount for local anesthesia, it bears mentioning that the maximum safe dosage for lidocaine in the United States is 300 mg, which equates to 30 mL of 1% lidocaine.[18] Bupivacaine is an alternative medication that can be useful for anesthesia. Its long duration of action is advantageous, but it has shown the highest toxicity to chondrocytes of the local anesthetics. It should never be used for intraarticular injections.[11][12][18][20][21]

Preparation

As with every image-guided procedure, planning begins with reviewing the patient’s history, clinical indication, and relevant prior imaging, including plain film, ultrasound, CT, and MRI. After reviewing the history and available imaging, a decision should be made on whether the requested procedure is medically indicated and the best available to address the clinical concern. All medications should be reviewed, with specific attention to anticoagulation therapy, blood thinners (including fish oil and vitamin E), and aspirin. Risks and benefits of continuing or discontinuing anticoagulation should be considered on a case-by-case basis and may involve discussion with the prescribing provider.[5][22] Additionally, one needs to review the patient’s allergies to ensure there are no prior reactions to any planned medications, including skin-cleansing agents and adhesives.

Once the requested procedure is determined to be clinically indicated, the patient should be made aware of the risks, benefits, and alternatives. While nearly all musculoskeletal injections are considered low risk, some potential risks of ultrasound-guided procedures include pain, infection, bleeding, damage to nearby structures, allergic reaction, steroid flare, and failure to address the clinical concern (eg, failure to relieve pain). Additionally, if steroids are inadvertently injected into the subcutaneous soft tissues, atrophy of the subcutaneous fat or skin discoloration can occur. Although extremely rare, it has been documented in the literature that steroid injections can weaken tendons; thus, there is a theoretical risk of tendon rupture.[18] Once this discussion is completed and all the patient’s questions are answered to their satisfaction, written consent must be obtained. If the procedure is performed for pain relief, pre- and post-procedural pain levels should also be recorded to document an objective measure of symptomatic relief. Following the procedure and before releasing the patient from the radiology department, the patient is given return precautions, including signs of a post-procedural infection such as worsening pain beyond baseline, redness, swelling, and/or fever. Although exceedingly rare, an intraarticular joint infection would require urgent medical attention. Thus, patients are instructed to seek care at an urgent care center or the emergency department if symptoms occur outside normal business hours.

Technique or Treatment

Optimal positioning can be patient-dependent; however, most patients are positioned supine with the arm externally rotated. The transducer is placed on the skin perpendicular to the axis of the biceps tendon (see Image. Patient Positioning). This results in an image in which the bicipital groove appears as a semicircular trough, with the tendon appearing circular or oval (see Image: Ultrasound Appearance). The approach is from lateral to medial with an in-plane technique. The patient’s skin is marked at the planned injection site. The skin is then prepped and draped in a sterile fashion. A sterile ultrasound probe cover is placed on the selected probe. The subcutaneous soft tissues are then infiltrated with 1% lidocaine as the needle is advanced towards the biceps tendon under ultrasound guidance. Optimally, one should enter the tendon sheath in an area where the bicipital groove is shallow, allowing the needle to be positioned somewhat parallel to the transducer. The more parallel the needle is to the transducer, the more clearly it can be visualized on ultrasound. A steeper approach leads to decreased reflection of sound waves returning to the transducer and poorer visualization. If the needle tip is positioned superficial to the tendon, the subdeltoid bursa can fill with fluid mimicking the tendon sheath; thus, the ideal positioning is beneath the tendon to avoid this pitfall (see Image. Biceps Tendon Sheath Injection).

The in-plane technique, in which the needle is parallel to the transducer, provides improved visualization of the entire needle and reduces the risk of damage to surrounding structures. If using an out-of-plane technique, one would only see a small portion of the needle, making it difficult to appreciate the needle tip's position (see Image: Ultrasound Techniques). Some options to increase needle visibility include beam steering, heel-toe maneuver, using a larger-gauge needle, and entering the skin farther from the target, which allows for a more parallel orientation but a longer needle path.[23][24]

Given the superficial nature of the biceps tendon, the use of a higher frequency ultrasound transducer (10 to 15 MHz) allows for better near-field resolution. The probe should be maintained perpendicular to the tendon to maximize the reflection of sound beams and reduce anisotropy, which can result in poor tendon visualization.

Complications

Potential complications include pain, infection, bleeding, damage to nearby structures, allergic reaction, and non-therapeutic results. Complications specific to steroid use include septic arthritis, post-injection flare, local tissue atrophy, skin discoloration, tendon rupture, cartilage damage, avascular necrosis, flushing, and increased blood glucose level. If inadvertently injected intravascularly, there can be severe CNS and cardiac effects, particularly with insoluble, particulate formulations such as triamcinolone, which can embolize and lead to stroke.[18] As mentioned previously, the maximum safe dose of lidocaine in the ultrasound is 300 mg or 30 ml of 1% lidocaine. Above this threshold, there is a risk of CNS, cardiac, and skeletal muscle toxicity. Local anesthetics are toxic to chondrocytes in both animal studies and in vitro studies using human chondrocytes; bupivacaine is the most chondrotoxic, and ropivacaine the least. Lidocaine is most often used because it is the least expensive and most readily available.[20][21]

Enhancing Healthcare Team Outcomes

As mentioned above, shoulder pain is often multifactorial in etiology. Often, the radiologist and orthopedist work together to determine the underlying cause of a patient’s pain. A patient typically presents initially to their primary care provider, and if clinically indicated, they may be referred to an orthopedic specialist for further evaluation. Considering the patient’s history and physical exam findings, further evaluation with diagnostic imaging is sometimes indicated to evaluate for underlying pathology. It is not uncommon for imaging evaluation, such as MRI, to demonstrate multiple abnormalities, any of which could be causing the patient’s pain. In these cases, it can help perform a diagnostic and sometimes therapeutic injection to help clarify the clinical significance of the imaging findings. If a patient experiences pain relief after a targeted injection, it can be inferred that the treated area was a pain generator. Alternatively, if the patient does not have pain relief, one can infer that this area was not a pain generator. The patient’s response is clinically important as it can guide what surgical procedures, if any, may be offered for symptomatic relief. It can also help a patient avoid unnecessary surgical procedures. Orthopedic nurses set up the procedure, assist during the procedure, and provide patient instruction. Physical therapy may be needed to assist with post-procedure recovery exercises and to strengthen the muscles around the shoulder joint. These disciplines need to function as an interprofessional team to achieve optimal patient outcomes from this procedure.