Tendon Sheath and Insertion Injections

Published on 06/06/2015 by admin

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12 Tendon Sheath and Insertion Injections

Steve R. Geiringer, MD, Ted A. Lennard, MD

Tendons are impressively strong structures that link muscles to bone. They function to transmit the force of muscular contraction to a bone, thereby moving a joint or helping to immobilize a body part. Their microscopic organization is thoroughly described elsewhere.¹^–³

The organizational unit in a tendon is the collagen fibril, which collectively forms fascicles, which as a group compose the tendon itself.⁴ Some tendons, especially long ones, are guided and lubricated along their paths by sheaths (Fig. 12-1) (e.g., biceps brachii, (Fig. 12-2) extensor pollicis brevis, and abductor pollicis longus).

Figure 12-1 Drawing demonstrating a flexor tendon (A) within its sheath. The paratendinous septum is reflected (B).

Figure 12-2 Biceps brachii long head tendon ultrasound evaluation. A, Transverse imaging view over the biceps groove. Note transverse humeral ligament (arrowheads) and tendon. (arrows) B, Longitudinal imaging view of the biceps tendon in the anterior arm (arrows).

(From Jacobson J: Fundamentals of Musculoskeletal Ultrasound, Saunders, 2007, p 42.)

A prototypical muscle consists of the muscle belly centrally, two musculotendinous junctions, and tendinous insertions into bone at the points of anatomic origin and insertion.⁵ Some muscles, such as the extensor carpi radialis longus and brevis at the elbow, attach directly into bone (Figs. 12-3), an arrangement that may be more susceptible to injury.⁶

Figure 12-3 Common forearm extensor tendon at the lateral epicondyle—ultrasound evaluation. A, Longitudinal imaging of the common extensor tendon (arrows) and radial head (R). B, Longitudinal imaging of the common extensor tendon (arrowheads) demonstrating tendinosis (arrows) as hypoechoic swelling. L, Lateral epicondyle; R,radius.

(From Jacobson J: Fundamentals of Musculoskeletal Ultrasound, Saunders, 2007, pp 110, 124.)

Much is known about a tendon’s response to laceration and operative repair,² although this clinical situation is not frequently encountered. Less is understood about the more common and clinically relevant overuse tendinitis. A tendon and its sheath (if present) will undergo a typical inflammatory response to acute or chronic overuse injury, followed by a regenerative repair process.^2,^7,⁸ The distinction between an overload type of acute injury and a chronic overuse mechanism will aid in successful rehabilitation of tendinitis.⁹

Corticosteroid Injections

Cortisone and its derivatives are known to reduce or prevent inflammation. Numerous corticosteroid preparations are available for local injection ¹⁰ (see Chapter 2 on medications). The injectable corticosteroids are suspensions of insoluble particles, and therefore, the antiinflammatory effect is profound only where the material is deposited.¹¹ The ability of corticosteroids to control inflammation makes them a valuable adjunct in treating tendon injuries because they do not alter the underlying process that leads to inflammation.¹⁰

Efficacy

As with many other physical medicine treatment modalities, well-designed scientific studies regarding the usefulness of corticosteroid injections are rare. These injections should be considered when, in the practitioner’s judgment, the recognized antiinflammatory effect of local corticosteroid placement may be beneficial for the conditions of tendinitis, enthesitis, or tenosynovitis, and no harm will likely result.

McWhorter and colleagues injected hydrocortisone acetate into rat Achilles peritenons that had been previously injured.³ There were no deleterious effects of one, three, or even five injections, measured biomechanically (tension to failure) or histologically (light microscopy), compared to controls. This finding should reassure physicians that they are not doing harm with properly placed steroid injections. A 30-year literature review identified eight prospective, placebo-controlled studies of steroid injection treatment for sports-related tendinitis.¹² Three of the studies showed beneficial effects of injections at clinical follow-up. A meta-analysis of properly designed investigations of steroid injection for Achilles tendinitis found no beneficial effects,¹³ although very few studies qualified as rigorous. Adverse side effects occurred with a 1% incidence. No “proof” of the usefulness or uselessness of this treatment modality exists.

Contraindications, Complications, and Side Effects

The lack of a specific diagnosis is the single largest contraindication to a local corticosteroid injection. If the diagnosis is clear and the antiinflammatory effect of a corticosteroid may facilitate the rehabilitation process, injection can be considered.¹⁰

Repeated injections to the same area must be avoided, particularly into joints. Alterations in articular cartilage have been documented with repeated administration,¹⁴ possibly resulting in joint damage and weakened ligaments.¹⁵ A widely recognized complication of steroid injection is tendon rupture, a negative outcome that appears to be decreasing in frequency because it is now well understood. Achilles and other tendon ruptures have been reported,¹⁶^–²⁶ and deposition of injected material directly into any tendon substance is contraindicated. One report links the effect of repeated steroid injections to rupture of the plantar fascia.²⁷

Some experimental findings have suggested that corticosteroid administration led to smaller, weaker tendons as a side effect.²⁸ A more common side effect is subcutaneous atrophy, especially at the knee and lateral elbow and more frequently with the use of triamcinolone.¹⁰ Theoretically, atrophy of the specialized fat pads of the heel following steroid injection for plantar fasciitis may lead to a significant disability in an athlete, due to the loss of cushioning effect.

Alternatives to Corticosteroids

In recent years alternatives to corticosteroids have emerged for the treatment of chronic localized musculotendinous pain. These treatments include percutaneous tenotomies and platelet rich plasma (PRP) injections.

Percutaneous tenotomies have been described for treatment of chronic lateral epicondylitis and plantar fasciitis.^18,²⁹ These injections are performed with large bore needles (18 or 20 gauge) under ultrasound guidance. The needle tip is used to repeatedly fenestrate the affected tissue under local anesthetic. The bony surface (i.e., epicondyle) can be abraded and calcifications may be fragmented. This technique is thought to be a safe and effective alternative to corticosteroid injections.^18,²⁹

Platelet rich plasma injections use concentrated platelets from autologous blood to stimulate a healing response in damaged tissue. Blood is drawn from the patient and placed in a centrifuge. The concentrated platelets are removed and reinjected directly into the patient’s abnormal musculotendinous tissue or ligament usually under ultrasound guidance. These concentrated platelets produce growth factors that include platelet derived growth factor (PDGF), vascular endothelial growth factor (VEGF), and transforming growth factor-beta (TGF-β). These compounds are instrumental in attracting cells that promote healing by stimulating neovascularization and cellular reproduction.^4,^5,^7,³⁰ The efficacy of PRP injections and appropriate clinical indications (when and where it should be used) are currently being researched and yet to be definitively determined. Initial results of clinical studies appear promising.^13,^31,³²

Methods of Injection

Tendon and tendon sheath injections are office procedures, typically performed under clean or sterile conditions. The corticosteroid of choice is often combined with a local anesthetic, the latter helping to confirm the proper location of the deposited material. Diagnostic ultrasound has been advocated to guide injections near the heel when guidance by palpation alone fails.³³

Immobilization of the treated structure usually is not needed following injection, although vigorous use of weight-bearing tendons (Achilles, patellar) should be avoided for 48 hours. Ice application may help when the local anesthesia fades, along with other physical medicine modalities as indicated by the particular condition present, usually starting after 48 hours.

If an initial corticosteroid injection proves useful, one or two repeat injections separated by a few weeks or more may be considered. Numerous injections over time should not be considered the sole or primary treatment.

Indications

Diagnosis

Corticosteroid or local anesthetic injections should not be used routinely to arrive at diagnoses pertinent to the musculoskeletal system. The range of physical examination techniques used by the physician is described elsewhere ³⁴ and, in most cases, will suffice at pinpointing the specific cause of pain. The distinction between the conditions of subacromial bursitis and rotator cuff tendinitis can be clarified with injection,¹⁰ but even in this case the physical examination and subsequent rehabilitation program deservedly receive most of the attention.

Treatment

In most instances, the literature supports an adjunctive, not primary, role for injections in the treatment of tendon and tendon sheath injuries.^10,²⁰ When the doctor and patient decide to proceed with injection, the control of inflammation that is obtained should be used to facilitate the prescribed rehabilitation program, rather than being the only treatment. The area of exception to this generalization is the wrist and hand (to be discussed in detail later).

Upper Extremity Injections

The literature supports the use of corticosteroid injections as a primary treatment for stenosing flexor tenosynovitis in the hand, known as trigger thumb or trigger digit.^30,³⁵^–⁴¹ In this setting, injection has been shown to be as effective as operative release of the tendon sheath and to have fewer complications.⁴² Injection has been employed successfully into the hands of patients with diabetes mellitus and trigger digit, but the success rate may be reduced.^43,⁴⁴ Instillation of the material directly into the tendon sheath has no apparent benefit over subcutaneous placement.⁴⁵ Multiple pulley rupture¹⁷ and flexor digitorum profundus and superficialis tendon rupture¹⁶ has been reported as a complication from this injection. As with other soft tissue injections, a physician treating trigger finger with instillation of corticosteroid needs to maintain expertise by performing this procedure at least several times yearly.

Stenosing tenosynovitis of the first dorsal wrist compartment also is known as de Quervain syndrome. This compartment typically transmits the tendons of both the abductor pollicis longus (APL) and extensor pollicis brevis (EPB). However, anatomic studies have demonstrated that multiple APL slips are common, as are two subcompartments.³⁹ Interestingly, although one or more injections are usually successful in treating de Quervain syndrome nonoperatively,^22,⁴⁶ patients requiring subsequent operative release have been found to have two subcompartments in greater than expected frequency.^22,⁴⁶ Trigger digit and de Quervain syndrome, therefore, are usually treated successfully nonoperatively, and corticosteroid injection is the primary component of the management (Fig. 12-4).

Figure 12-4 Injection technique for first dorsal compartment stenosing tenosynovitis (de Quervain syndrome). The needle is parallel to the tendon.

The use of corticosteroid injection for lateral epicondylitis (tennis elbow) appears widespread (Fig. 12-5), although carefully controlled studies to confirm its efficacy are absent from the literature.⁴⁷ One prospective investigation found that corticosteroid injection was more effective in controlling symptoms 8 weeks after injury than anesthetic alone, but the benefit disappeared by 24 weeks.²⁹ This may be explained by the finding that the histology of tennis elbow is noninflammatory.⁴⁸ A prospective chart review found that injection alone was effective in 91% of patients within 1 week, but was associated with a 51% recurrence after 3 months. Initially, a standard physical therapy regimen led to improvement in only 74%, but the recurrence rate dropped to 5%.⁴⁹ In the typical clinical setting, of course, injection(s) and physical therapy are often combined with careful consideration of the intrinsic and extrinsic biomechanical factors that may be contributors.^9,⁵⁰

Figure 12-5 Injection technique for lateral epicondylitis. The needle tip is placed into the point of maximum tenderness at the edge of the bone.

No recent studies have examined the use of corticosteroid injections in the treatment of biceps brachii tendinitis. In this area, care should be taken to deposit the suspension to bathe the tendon sheath rather than into the body of the tendon itself (Fig. 12-6). Additionally, heavy lifting or vigorous exercise of the arm should be restricted for 48 to 72 hours following injection.

Figure 12-6 Injection technique for long head of biceps brachii. The needle is directed parallel to the tendon.

Corticosteroid injection has been found to be effective for rotator cuff tendinitis—at least for the first several weeks. In one study, injection was superior to placebo and to oral antiinflammatory medication over the course of 4 weeks.⁵¹ No more than three injections are recommended.¹⁰ The technique itself is detailed elsewhere.¹¹ After corticosteroid injection for treatment of rotator cuff tendinitis, heavy lifting and excessive overhead work are to be avoided for at least 2 days.

Lower Extremity Injections

The literature contains relatively few references to corticosteroid injections of the lower limb for tendon or tendon sheath injuries. In this arena, as in much of musculoskeletal medicine, the practitioner must rely on anecdotal evidence, clinical experience and judgment, and trial and error when choosing a course of treatment.

Although it is not a true tendinitis, plantar fasciitis is commonly treated with steroid injection(s) (Fig. 12-7). If used, they must be considered complementary to a complete rehabilitation program that includes flexibility training and correction of any contributing intrinsic or extrinsic biomechanical factors.¹⁰ If lipoatrophy occurs in the fat pad of the heel secondary to corticosteroid deposition, true disability in the active individual may result. Cosmesis is less of a problem because of the location.

Figure 12-7 Injection technique for plantar fasciitis. The needle tip is advanced to the insertion of the plantar fascia adjacent to the bone.

Most physicians are aware of possible tendon rupture if corticosteroid is injected directly into the Achilles tendon.^34,^52,⁵³ On the other hand, the Achilles sheath can be injected,¹¹ often with a good therapeutic result. One double-blind, randomized, controlled study found no advantage of Achilles tendon sheath injections when compared with standard physical therapy measures.⁵⁴

Iliotibial band tendinitis, refractory to other measures, sometimes responds to corticosteroid injection. The material is placed around the insertion of the iliotibial band at the proximal, lateral tibia, or, depending on the site of symptoms, where it passes over the prominence of the lateral femoral condyle.¹⁰ Iliopsoas tendinitis has been similarly treated,⁵⁵ with up to 2 years of symptomatic relief. The quadriceps (infrapatellar) tendon can be injected for cases of tendinitis,¹¹ but because this is a weight-bearing structure, many practitioners avoid this procedure for fear of rupture.