“Pagoda roof” of L5 spinous process with transverse processes and facet joints on either side of the spine
Similarly, the dancer with interspinous ligament sprain or interspinous bursitis may benefit from a diagnostic and therapeutic injection. Typically, the point of maximal discomfort can be localized by palpating the spinous processes and interspinous spaces to identify the level of the spine at which the dancer is experiencing pain. This injection can be done with the patient prone while lying on a pillow such that the spine is arched into flexion. This will separate the spinous processes, allowing for good visualization under ultrasound. The probe can be placed in the sagittal plane over the midline of the spine, exposing the spinous processes and the interspinous ligaments. For this injection an out-of-plane approach can typically be used to inject anesthetic and steroid just deep to the interspinous ligament. Again, immediately after the procedure, provocative maneuvers such as flexion or extension of the spine can be done to assess for anesthetic response to the injection.
The sacroiliac joint (SIJ) is not an uncommon cause of pain in the young dancer for several reasons. The young female often has more ligamentous laxity than males, and therefore potential instability in the SIJ. Furthermore, the sacrum is more vertical in the female than in the male, which also renders it more vulnerable to instability. Finally, dancers often sustain injuries to the spine, such as spondylolysis. In conditions of this kind the erector spinae, which are the primary stabilizers of the sacrum to pull it forward into a flexed and stable position , are inhibited and become weak.
Usually, rehabilitation of the stabilizing muscles is adequate to diminish pain. In some circumstances, however, it is useful from a diagnostic and therapeutic standpoint to perform a diagnostic injection. At times, pain may inhibit proper strengthening, and the corticosteroid may enhance the ability to perform physical therapy. The lower end of the SIJ is most suitable for injection. This is performed with the dancer prone. The posterior superior iliac spine is identified. In the thin dancer a high-frequency linear probe with virtual convexity demonstrates this nicely. The probe is held in an axial plane at the posterior superior iliac spine (PSIS) and slid caudally until the lowest end of the SIJ is seen. Then, from medial to lateral, the area is entered with a 22 spinal needle with an in-plane approach. Visualization of the inferior sacroiliac joint (ISIJ) allows for confirmation of proper placement once the entry has been accomplished. A combination of anesthetic and corticosteroid is used. Provocation maneuvers are performed before and after to assist in confirming the diagnosis of SIJ involvement.
Hip injuries account for 13.1% of all injuries in the young dancer and can be complex and difficult to treat . Once preliminary diagnostics have been completed, which may include physical examination, plain radiographs, and MRI, ultrasound can be used to examine the hip in both a static and dynamic manner (refer to the hip section in “Diagnostic Ultrasound Examination: Static/Dynamic” for further information on how to perform a static and dynamic examination of the hip). Ultrasound is also used to guide diagnostic and therapeutic injections.
It may be daunting to differentiate between intra-articular and extra-articular causes of the dancer’s hip pain. Micheli et al.  described three provocative maneuvers for isolating iliopsoas causes of pain. These include pain with passive hip flexion, resisted flexion/abduction/external rotation (FABER) of the hip, and hip extension/internal rotation. Additionally, a Ludloff’s test involves pain with resisted straight leg raise with the patient sitting at the edge of the bed and the hip flexed at 90°. Pain with this maneuver is felt to be specifically attributable to the psoas. During these maneuvers a pain score can be obtained from the patient pre- and post-injection. The comparison of “pre-” and “post-injection” scores can be used to identify the etiology of the dancer’s pain.
The two main injections used in the hip for both diagnostic and therapeutic value are an intra-articular injection and a psoas bursa injection. Past studies have discussed the use of fluoroscopic guidance of psoas injections ; however, more recently ultrasound has been shown to serve this purpose effectively [8, 9]. The psoas bursa injection can be performed in several different ways. Here we will discuss the two most commonly used in our clinical practice. The first method is to have the patient lying supine and placing the probe in the sagittal oblique plane over the hip to visualize the femoral head, neck, and acetabulum (Fig. 10.2). In this plane one can visualize the overlying hip capsule or synovial lining and just superficial to the capsule the psoas muscle/tendon. If the patient has psoas bursitis a hypoechoic, or black layer, will be seen just between the capsule of the hip and the psoas muscle/tendon, representing bursal fluid within the psoas bursa. The injection can then be performed in this plane with an in-plane approach, from distal to proximal, using a spinal needle to inject cortisone and anesthetic into the psoas bursa and the peritendon. The needle tip usually enters the bursa just above the femoral head (see Fig. 10.2). Fluid can be visualized both filling the bursa and washing up through the peritendinous layer. The other approach used for this injection involves obtaining a short axis or axial view of the psoas tendon, which can be done by placing the probe in the direct axial plane of the acetabulum and femoral head with the psoas tendon seen as a hyperechoic or round white structure typically lying in the gutter formed by the acetabulum and the femoral head. Again using an in-plane approach from lateral to medial, the spinal needle can be directed to just beneath the psoas tendon and cortisone and anesthetic can be injected into the pertendinous region as well as the bursa lying below the tendon.
Psoas bursa injection, with probe held in the sagittal oblique plane to visualize the acetabulum, femoral head-neck junction, and overlying psoas tendon. In this image, needle tip is at the level of the psoas bursa just beneath the tendon
The other commonly performed diagnostic and therapeutic procedure performed in the young dancer with hip pain is an intra-articular injection. This injection is typically used prior to surgery for either femoral acetabular impingement (FAI) or labral repair. Many dancers will have labral tears or other pathologic findings on MRI. However, this may not be the source of pain in all cases. One study showed that elite female ballet dancers with pathologic findings on MRI were symptomatic in less than two thirds of the cases . Another study demonstrated that in a group of professional ballet dancers 51% had labral pathology on MRI that was asymptomatic . A diagnostic and therapeutic intra-articular injection can be used to determine whether the dancer may benefit from surgical repair or if the etiology of their pain is due to other extra-articular sources.
The intra-articular injection is performed in a similar fashion to the psoas bursa injection described above with a sagittal oblique view. In this plane one can visualize the femoral head-neck junction, the overlying hip capsule, and the synovial lining. The probe is then slid back and forth medial to lateral to find the midpoint of the femoral head-neck junction. The injection can then be performed in this plane, using an in-plane approach, from distal to proximal. However, the needle is aimed at the femoral head-neck juncture in this case. (Fig. 10.3). Prior to injection of solution confirmation of intra-articular location can be achieved by turning the probe 90° into the axial plane to visualize the needle at the femoral head-neck junction beneath the capsule, or synovial lining. Once confirmation of intra-articular location is established the probe is turned back to the sagittal oblique plane and solution can be injected, watching for the fluid to fill the intra-articular space as the capsule fills.
Intra-articular hip injection with probe over the left hip in a sagittal oblique view to visualize the femoral head-neck junction and overlying hip capsule
After any of the above procedures are performed “post-injection” scores should be obtained to determine whether the injection did in fact target the etiology of the dancer’s pain. This information can then be used to guide further management.
Even more common than hip and spine injuries are knee injuries in the adolescent dancer, with a reported rate of 28.8% . The use of ultrasound to both diagnose and treat certain etiologies of knee pain in dancers has been slowly becoming more evidence based. In the section “Diagnostic Ultrasound Examination: Static/Dynamic,” we will discuss how to perform the static and dynamic knee examination. In this section we will discuss the interventional uses of ultrasound in the knee.
One source of knee pain commonly seen in the young dancer is medial plica syndrome. This is an area where injection under ultrasound guidance can be used to confirm the diagnosis and to treat the inflammation and improve pain. This injection is performed with the patient lying supine with the knee slightly bent to about 20° and the leg externally rotated to allow for the medial aspect of the knee to be easily accessed. The high-frequency, or linear, probe is placed in the axial plane, with the patella visualized on one side of the screen and the medial femoral condyle on the opposite side of the screen (Fig. 10.4). Using palpation to locate the plica and area of maximal pain, the probe can be slid distal and proximal until the plica is well visualized between the medial patellar facet and the medial femoral condyle. Then, using an out-of-plane approach, a needle can be dropped directly down adjacent to the plica and cortisone and anesthetic agent can be injected. Immediately after the injection the patient should perform previously determined provocative movements to assess for resolution of pain from the anesthetic portion of the injection.
Medial plica seen here with medial facet of the patella on the left and medial femoral condyle on the right, with hyperechoic area between representing plica
Similarly, young dancers may have medial knee pain due to Hoffa’s fat pad impingement. In this case injection can be performed with the patient supine with the knee flexed to 90° and the foot planted on the table. Then, placing the probe in the axial plane over the patellar tendon, the fat pad can be well visualized below the tendon. Depending on whether the dancer’s pain is more medial or lateral, a corresponding approach can be used to concentrate more of the injection at the area of increased discomfort. For medial sided pain a needle can be inserted using an in-plane approach, from medial to lateral, just deep to the patellar tendon, being careful to avoid injecting too closely to the tendon itself. Cortisone and anesthetic can then be injected directly into the fat pad. In some cases the dynamic examination of the patellar tendon’s relation to the fat pad is performed by flexing and extending the knee while directly observing the fat pad. It would be abnormal for the fat pad to adhere to the patellar tendon. When it does, a hydrodissection to loosen the fat pad from the tendon is required. This procedure can be performed with the patient in the same position as that used for the fat pad injection; however, this time as the tendon is visualized in the axial plane the probe is moved obliquely in a diagonal plane, pointing medial to lateral, from distal to proximal. Then, using an in-plane approach, the needle is placed just beneath the patellar tendon and superficial to Hoffa’s fat pad. Saline, anesthetic, or a combination of the two can be injected to hydrodissect the fat pad away from the tendon. (Cortisone is never used for this injection site.) This allows the tendon to glide more smoothly without impinging on the fat pad.
Given the amount of rotational force placed on the knee of the young dancer, meniscus injuries can occur. Typically, in young dancers with a moderate to large tear, surgical meniscal repair is recommended, given their age and ability to heal well after a repair. Minor tears or small areas of degeneration seen on either MRI or ultrasound examination, on the other hand, have recently been found to respond well to ultrasound-guided needle fenestration of the meniscus followed by injection with autologous growth factors such as platelet-rich plasma (PRP) or whole blood. Our early experience with this has been encouraging. Further studies in this area are needed. The procedure is performed with the patient in the supine and slightly decubitus position. The high-frequency linear probe is placed in the coronal plane to visualize images of the affected meniscus (medial or lateral). The probe is slid from posterior to anterior to visualize the meniscus between the femoral condyle superiorly and the tibial plateau inferiorly. Using an out-of-plane approach, a 22 to 25-gauge needle is used to make 8–10 fenestrations into the meniscus, injecting small amounts of PRP with each fenestration. The needle is then inserted just between the meniscus and the meniscofemoral ligament if that area is affected, and PRP can be injected between these layers. The patient is then placed in a hinged knee brace with specific limitation in flexion and extension, depending on which horn of the meniscus was fenestrated. Typically, we use a long-hinged knee brace for 2 weeks locked from 0 to 30° of flexion, then 2 weeks at 0–60°, and then progress to full ROM. During this time the patient is also started on physical therapy, consisting of mostly isometric exercises for the first 2 weeks and progressing through increased range of motion as the brace range is increased.
Patellar tendinopathy can be very difficult to resolve, especially once degenerative changes have occurred. When a hypoechoic area has been identified and all conservative management has been exhausted, needle tenotomy with whole blood injection can be performed. This is done with the dancer lying in the supine position, the knee bent to between 45 and 90° of flexion, and the foot placed on the table. A high-frequency linear probe is placed in the axial view to visualize the hypoechoic area of tendon degeneration, typically seen near the proximal insertion at the distal pole of the patella (Fig. 10.5a, b). Using an out-of-plane approach, a 22-gauge needle is inserted through the tendon into the area of degeneration (Fig. 10.5c). Depending on the extent of injury, a number of fenestrations are made to include the entire width and depth of the affected area. Typically, small aliquots of whole blood or PRP are injected with each fenestration. After the procedure is performed the dancer is placed in a knee immobilizer for a few days to control pain, but then mobilized using isometrics and biking for the next 2 weeks. During the third and fourth weeks dynamic exercises, both open and closed chain, and added resistance on the stationary bike can be initiated. Eccentrics are added gradually.
a Long axis view of patellar tendon (probe held in direct sagittal plane) with hypoechoic area of degenerative tendon on insertion into patella. b Short axis view of patellar tendon (probe held in direct axial plane) with hypoechoic area of degeneration, which correlates with area as shown in Fig. 10.5a. c Long axis view with needle in degenerative area during needle tenotomy
Dance is often performed in the plantar flexed position and can lead to impingement of both soft tissue and bony structures, particularly in the posterior ankle between the tibia and calcaneus. Some dancers will have a prominent Stieda process of the posterior talus, while others will have a discrete os trigonum. These conditions are reported to occur in up to 14% of the general population, and when present they are bilateral in 50% of patients . We have a clinical impression that the incidence of os trigonum in dancers is much greater than that of the general population. Diagnosis can be made with a plain lateral radiograph with the dancer in full plantar flexion (en pointe). Ultrasound can be used in this case to perform guided diagnostic injection to confirm the source of pain and help with surgical planning. For this injection the patient is normally lying prone with the foot hanging just off the end of the table. The high-frequency, or linear, probe is placed in the sagittal plane in line with the Achilles tendon and slid out to the lateral ankle. As the Achilles goes out of view, the stedia process or os trigonum comes into view, with the calcaneus distal to that. It is sometimes difficult to differentiate between a prominent stieda process and os trigonum with ultrasound, as the bone has acoustic shadowing that may make it difficult to identify. A needle can then be inserted in the in-plane or out-of-plane approach down to the level of the stieda process/os trigonum, and cortisone and anesthetic solution can be injected to encompass the object in question and any surrounding soft tissue while avoiding any vascular or tendon structures. Immediately after this injection is performed provocative movements can be initiated, typically forced plantar flexion, to assess for resolution of pain.