Intra-articular hip injection is an established diagnostic and therapeutic procedure in the management of hip pathologies.1,2 Despite its frequent use, wide variation exists in the technique of hip injection.3,4 Improper injection can lead to erroneous diagnosis, inappropriate management and can damage the labrum and neurovascular structures.5

PRINCIPLES Avoid damage to neurovascular bundle. Pearl: the neurovascular bundle runs obliquely from mid inguinal point toward the adductor hiatus. Tip: draw a vertical line from tip of anterior superior iliac spine along the axis of limb—the point of entry of the needle should be lateral to this line (Fig. 1). We prefer a needle trajectory along the neck of femur with an inclination angle of approximately 45 degrees to the horizontal. The proximal-distal entry point is decided based on the above and confirmed with the help of image intensifier. Avoid damage to labrum and femoral head. Pearl: the labrum produces a seal around the femoral head and separates the central compartment from the peripheral compartment. Tip: hip injections are preferably given into the peripheral compartment. Attempting to inject into the central compartment in an undistracted hip joint can potentially damage the labrum or femoral head (Figs. 2, 3). Avoid erroneous injection into psoas sheath/extracapsular tissues. Pearl: psoas tendon runs over the anterior wall of the acetabulum before inserting into the lesser trochanter. When the patient is supine and the hip is in neutral position, the tendon is firmly opposed to the anterior capsule and there is very little space between the capsule and the femoral neck (Fig. 4). Tip: the hip needs to be flexed to relax the anterior capsule, iliofemoral ligament and psoas tendon. We routinely place a pillow beneath the ipsilateral knee to achieve about 10 degrees of flexion at both hip and knee. This maneuverer increases the joint space as well (Fig. 1). The limb is kept in appropriate rotation (neutral/internal rotation) so that the full profile of neck is visible. The needle should be directed along the neck and aimed at its middle third. If the needle is directed far medially, it will enter the psoas sheath whereas a far lateral injection might be extracapsular. Once the anterior capsule is crossed, the surgeon will be able to feel a give way and the tip of the needle can be felt against the anterior femoral neck. It is a good practice to confirm the position of the needle with either a contrast/air arthrogram (Figs. 5, 6). The surgeon should now be able to administer the injection without much resistance. Pitfall: in a severely arthritic hip, the capsule could be scarred and the surgeon may feel some resistance initially while administering the injection. However, the pressure of the injection would release some of the adhesions and there will be a sensation of give way if the needle is in the correct position. If significant resistance is felt during injection, then the position of the needle should be reconfirmed before proceeding further. Reduce patient discomfort. Pearl: some patients experience sudden loss of consciousness and fall in blood pressure.6 This can be due to pain shock, vasovagal syncope secondary to sudden rise in intra-articular pressure or anaphylaxis to any of the drugs/contrast material. Tip: always confirm allergies before the procedure. The potential needle track and skin entry site could be infiltrated with 1% Lignocainene. Always warn the patient before the procedure that he/she would still be able to feel the needle passing through the tissues and a pressure sensation would be felt towards the end of procedure due to volume expansion within the joint. It is a good practice to keep all the emergency resuscitation equipment and trained personnel at standby and secure an intravenous line before the procedure. FIGURE 1:

Picture depicting the setup for hip injection. Note the vertical line from tip of snterior superior iliac spine and pillow beneath the knee.

FIGURE 2:

Incorrect technique of injection trying to access the central compartment.

FIGURE 3:

Damage to femoral head due to previous hip injection by suboptimal technique (picture taken during subsequent hip arthroscopy).

FIGURE 4:

Far medial injection without hip flexion getting into psoas bursa.

FIGURE 5:

Perfect contrast arthrogram of hip obtained by correct injection technique.

FIGURE 6:

Air arthrogram of hip.

DISCUSSION

Erroneous hip injection is not just wastage of resources but also reduces the patient’s confidence in the treatment. In our tertiary referral hip service, it is not uncommon for us to find suboptimal techniques being employed for hip injection as depicted in Figure 2. Despite an extensive literature search, we could not find any technique description stressing the importance of the above mentioned principles.

REFERENCES 1. Bursa GT. Diagnostic and therapeutic injection of the hip and knee. Am Fam Physician. 2003;67:2147–2152. 2. Crawford RW, Gie GA, Ling RSM, et al. Diagnostic value of intra-articular anaesthetic in primary osteoarthritis of the hip. J Bone Joint Surg Br. 1998;80:279–281. 3. Kurup H, Ward P. Do we need radiological guidance for hip joint injections? Acta Orthop Belg. 2010;76:205–207. 4. Diraçoğlu D, Alptekin K, Dikici F, et al. Evaluation of needle positioning during blind intra-articular hip injections for osteoarthritis: fluoroscopy versus arthrography. Arch Phys Med Rehabil. 2009;90:2112–2115. 5. Leopold SS, Battista V, Oliverio JA. Safety and efficacy of intraarticular hip injection using anatomic landmarks. Clin Orthop. 2001;391:192–197. 6. Aliabadi P, Baker ND, Jaramillo D. Hip arthrography, aspiration, block, and bursography. Radiol Clin North Am. 1998;36:673–690.