Ultrasound of the Week: Hip Pain

Authors: Julian Moncada, MD, & Meghan Nagam

Edited by Christopher Parker, DO, and Molly Hartrich, MD

Here's the story:

A 66-year-old female presented to the emergency departement (ED) after a mechanical fall at home with severe, 9/10, right hip pain. She denied hitting her head but fell on her right hip and heard a popping sound. She was able to pull herself up and sit on her walker and could bear weight but could not ambulate.

Vital signs were 98.4ºF, HR 145, BP 123/80, RR 22, O2 sat 100% on RA. On physical exam, there was tenderness over right buttock with mild swelling, no deformity of hip or leg, and her right leg was in external rotation with exquisite pain with movement. There was no ecchymosis or erythema over right lower extremity or buttock. The distal pulses were intact and patient was able to wiggle toes, but the remainder of motor exam was limited due to pain. The patient's sensation to light tough was grossly intact in all nerve distributions.

Plain radiographs of the right hip and pelvis were taken, along with point-of-care ultrasound (POCUS) of the right hip.

How do the x-ray images compare to the ultrasound images and clips? What is the suspected diagnosis?

Figure 1a. X-ray of right hip and pelvis, anterior-posterior view

Figure 1b. X-ray of right hip and pelvis, lateral view

Figure 2. POCUS image of right hip, sagittal view

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ANSWER:

Radiographs of the right hip and pelvis were negative for fracture. There were no displaced osseous fragments or cortical disruption of the femur. The femoral head was well situated within the acetabulum. The pelvis, including the superior and inferior rami, the acetabulum, and sacroiliac joints, was intact.

Bedside ultrasound demonstrated a nearly anechoic fluid collection with questionable cortical step-off at the femoral neck (Figure 3). This suggested acute hematoma, which is consistent with an acute intertrochanteric fracture of the right hip. Due to these findings, computer tomography (CT) of the hip was ordered, which revealed a nondisplaced intertrochanteric fracture, with the fracture line extending from the greater to the lesser trochanter (Figure 4).

Figure 3. POCUS image of right hip showing anechoic region adjacent to the femoral neck (arrow), with cortical irregularity suspected to be artifact (star), sagittal view. Femoral head (FH); femoral neck (FN).

Figure 4. CT image of right hip showing nondisplaced intertrochanteric fracture (arrow).

PEARLS & CONCLUSION

Plain radiograph is the initial imaging modality for evaluating for fracture in the ED. However, x-ray is not always able to detect all fractures and can be inconclusive. The prevalence of occult hip fracture found after an unremarkable x-ray is approximately 4-14%. [1,2] CT and magnetic resonance imaging (MRI) are commonly used to evaluate for fractures if suspicion is high, but radiographs are negative. [3] However, these modalities are expensive, cause delays in care, and may not be readily available at community hospitals.

POCUS is useful in detecting fracture lines in certain locations, specifically long bones, as well as joint effusions, bursal effusions, and peri-trochanteric edema. [3,4] In one small study of patients with hip pain after low energy trauma with nondiagnostic hip radiographs, POCUS interpreted by radiologists has a sensitivity of 100% and specificity of 65% for diagnosing hip fracture (NPV 100%, PPV 59%). [4] A fracture line was seen in only 20% of cases. In the present case, the cortical irregularity of the femoral neck on ultrasound did not align with the fracture line on CT, suggesting it most likely to be artifact (Figure 3). This emphasizes the importance of scanning the contralateral hip to evaluate for symmetry. In addition, maintain a high level of suspicion for fracture with post-traumatic soft tissue abnormalities, such as the joint effusion seen with this patient. Soft tissue abnormalities, including unilateral hip effusions, hematomas, or fluid collections around the greater trochanter, are reported to be 100% sensitive for diagnosing hip fractures with ultrasound. [4]

ED physicians have been found to accurately evaluate long bone fractures using POCUS. A negative POCUS exam for a suspected fracture in addition to a thorough physical exam is associated with decreased probability of long bone fracture. [5}

POCUS has demonstrated ability to help with diagnosis of joint effusions, tendon ruptures, and occult fractures. [6] Utilization of POCUS could help expedite a patient's care and prevent misses in occult hip fracture.

CASE CONCLUSION:

The patient was given adequate analgesia and admitted to the hospital with orthopedic surgery on consult. She underwent an open reduction internal fixation for repair of her right intertrochanteric fracture.

References:

  1. Dominguez, S., Liu, P., Roberts, C., Mandell, M., & Richman, P. B. (2005). Prevalence of traumatic hip and pelvic fractures in patients with suspected hip fracture and negative initial standard radiographs--a study of emergency department patients. Academic emergency medicine : official journal of the Society for Academic Emergency Medicine, 12(4), 366–369.

  2. Kirby, M. W., & Spritzer, C. (2010). Radiographic detection of hip and pelvic fractures in the emergency department. American Journal of Roentgenology, 194(4), 1054-1060.

  3. 1. Caroselli C, Zaccaria E, Blaivas M, Dib G, Fiorentino R, Longo D. (2020). A pilot prospective study to validate point-of-care ultrasound in comparison to x-ray examination in detecting fractures. Ultrasound Med Biol, 46(1),11-19.

  4. Safran, O., Goldman, V., Applbaum, Y., Milgrom, C., Bloom, R., Peyser, A., & Kisselgoff, D. (2009). Posttraumatic painful hip: sonography as a screening test for occult hip fractures. Journal of Ultrasound in Medicine, 28(11), 1447-1452.

  5. Oluku, J., Stagl, A., Cheema, K.S., El-Raheb, K., Beese, R. (2021). The role of point of care ultrasound (PoCUS) in orthopaedic emergency diagnostics. Cureus, 13(1).

  6. Waterbrook, A.L., Adhikari, S., Stolz, U., Adrion, C. (2013). The accuracy of point-of-care ultrasound to diagnose long bone fractures in the ED. The American Journal of Emergency Medicine, 31(9),1352-56.