Spontaneous psoas haematoma secondary to antiplatelet therapy: a rare cause of atraumatic hip pain

Abstract

A 92-year-old woman with previous total hip replacement presented with sudden onset of atraumatic hip pain and inability to weight bear. In the absence of radiographic signs of fracture, loosening or biochemical evidence of infection a CT scan of the pelvis and hips was performed, which showed psoas thickening. MRI identified two separate collections related to the psoas and greater trochanteric regions. Ultrasound-guided aspiration was performed to rule out infection and demonstrated a haematoma. In contrast to previously reported cases caused by anticoagulant therapy or inherited coagulopathy, this case was secondary to single antiplatelet agent treatment alone. In the increasingly co-morbid ageing population with associated polypharmacy, aspirin is a common primary and secondary prevention treatment. In patients with atraumatic hip pain, spontaneous psoas haematoma due to antiplatelet therapy should be considered and investigated appropriately.

Background

Total hip replacement (THR) is the second most common arthroplasty procedure performed in the UK.¹ Dislocation, periprosthetic fracture and infection are all recognised complications of hip replacement that present acutely with hip pain.

Spontaneous Iliopsoas haematomas are rare retrofascial haematomas with only a handful of cases reported in the literature. They usually present with sudden and severe hip pain, back pain and rarely lumbar radiculopathy due to femoral nerve compression.^{2 3} They are often associated with therapeutic anticoagulation or bleeding disorders.^{4 5}

With an ageing and increasingly co-morbid population, it is common for elderly patients with polypharmacy to be on antiplatelet or anticoagulant medication. Spontaneous Iliopsoas haematomas have been reported in warfarinised patients but not due to antiplatelet therapy in absence of other related co-morbidities.⁶ This case highlights spontaneous atraumatic iliopsoas haematoma secondary to antiplatelet treatment as a rare cause of hip pain. The diagnosis should be considered alongside more common causes of hip pain in the elderly patient with previous hip replacement presenting with atraumatic hip pain.

Treatment remains controversial and should be suitably adapted to the individual case, taking into account the cause, haemodynamic status and haematoma volume. It has been recommended that medical management should be used initially with surgical intervention reserved for cases of haemodynamic instability and those involving femoral nerve palsy.^7–9

Case presentation

A 92-year-old woman was attended by paramedics following sudden onset ‘agonising’ pain in her right thigh. She had first started to notice the pain 2 weeks ago, when the pain was much less severe and originated in the lower back. Previously, the pain had improved with oral analgesia. The pain was centred in the right groin and radiated to the lateral thigh. She described no recent falls or injuries to the hip and was systemically well. Past medical history included osteoporosis, hypothyroidism, previous thoraco/lumbar vertebral crush fractures, a hiatus hernia, a right-sided THR 6 years ago and transient ischaemic attacks treated with aspirin for secondary prevention. She was cognitively intact, living independently with family assistance and mobile with the aid of a stick.

Examination revealed normal bedside observations, inability to mobilise, limited ability to straight leg raise and significant pain on axial loading and with all passive movements of the right hip. There was no neurovascular deficit.

Radiographs of the pelvis and right femur were interpreted as normal. Initial haematological markers were within normal limits with a haemoglobin (Hb) of 136 g/L, platelet count of 230×10⁹/L and white blood cell count (WBC) of 9.7×10⁹/L. Due to her pain and inability to mobilise, she was admitted under the medical team for analgesia and physiotherapy. She was referred to orthopaedics for further investigation with persistent, unexplained hip pain.

Investigations

Orthopaedic review of her radiographs demonstrated a right-sided uncemented THR but no obvious periprosthetic fracture, dislocation or signs of component loosening (figure 1). An undisplaced old right-sided inferior pubic rami fracture was seen but this did not correspond to her current symptoms. Routine blood tests were repeated with Hb 129 g/L, WBC 8.9×10⁹/L and a C reactive protein of 28 mg/L. The working differential diagnosis of occult periprosthetic fracture, component loosening and infection were all considered.

Figure 1.

A-P pelvis radiograph demonstrating a right uncemented THR with an old inferior pubic rami fracture. THR, total hip replacement.

A non-contrast CT scan of the pelvis and hips was arranged to rule out periprosthetic fracture or component loosening. CT demonstrated no evidence of component loosening or periprosthetic fracture but an old right inferior pubic ramus fracture was identified. Remarkably, the CT revealed marked thickening of the right iliopsoas that was suspicious of infection but not associated with obvious focal collection (figure 2).

Figure 2.

Axial section from pelvis CT demonstrating marked thickening of the right iliopsoas muscle.

Blood cultures were taken and an MRI study of the pelvis and hips was arranged. The MRI demonstrated a collection deep to psoas extending distally along the psoas tendon toward the lesser trochanteric insertion suggestive of a haematoma measuring at its maximum dimensions 12.3 cm cranial–caudal, 4.6 cm medial–lateral and 2.1 cm anterior–posterior (figure 3). A second, separate collection was identified overlying the right greater trochanter measuring at its maximum dimensions 7.4 cm cranial–caudal, 2.7 cm medial–lateral and 6.2 cm anterior–posterior. Both collections were extra-articular.

Figure 3.

Coronal section from T1 sequence MRI pelvis demonstrating collections related to the right psoas and right greater trochanter.

Treatment

An ultrasound-guided aspiration of both collections was performed to differentiate between infection and haemorrhage. Blood stained fluid suggestive of haematoma was aspirated from both collections and sent for urgent microscopy and culture. This demonstrated 3+ of red cells, no white cells, no crystals and a negative Gram-stain. Culture demonstrated no growth of organisms at 48 hours.

The patient was treated conservatively with analgesia and her mobility progressed with inpatient physiotherapy. Her aspirin was withheld for a period of 7 days and mechanical rather than chemical thromboembolic prophylaxis was utilised.

Outcome and follow-up

The patient underwent a period of inpatient rehabilitation with both occupational and physiotherapy input to ensure optimisation of her mobility and a safe discharge.

Discussion

Atraumatic hip pain following THR is most commonly due to dislocation, component loosening or infection. As the main hip flexor, pathology of the iliopsoas can mimic these presentations with hip pain and reduced mobility. Psoas impingement following hip replacement is a recognised cause of ongoing pain and iliopsoas haematoma has been linked to impingement from acetabular component malposition.¹⁰

Although rare, spontaneous haematoma of the iliopsoas has been reported in patients with varying forms of anticoagulation, those with hereditary coagulopathies and due to liver failure.3 4 6–13 In severe coagulopathy and trauma, psoas haemorrhage can cause significant morbidity and has been reported to cause haemodynamic instability due to haemorrhagic shock.⁸

This case is unique because it identifies low-dose aspirin as the sole risk factor for developing a spontaneous iliopsoas haematoma. In contrast, previous cases have been reported in patients with significant risk factors for coagulopathy. For example, in the literature, Iliopsoas haematomas have been attributed to causes ranging from idiopathic thrombocytopenia and von Willebrand disease to cardiopulmonary bypass for open heart surgery and most commonly warfarin anticoagulant therapy.^{4–8 11} In contrast, low-dose aspirin would previously have been regarded as low risk for developing a complication as significant as a spontaneous psoas haematoma.

In the elderly population where patients are often medicated with antiplatelet therapy for secondary prevention of cardiovascular pathology, this case highlights the importance of considering spontaneous iliopsoas haematoma as a diagnosis in cases of sudden onset of atraumatic hip pain.

Patient’s perspective.

I have suffered pain for many years from my hips but have always managed to walk about. I don’t like this bed-bound business, its just not me. What I really want to be able to do is get to the toilet to keep my dignity. At the moment I can’t sleep with the pain unless I’m taking pain relief and I can’t walk by myself. I have been told that there is nothing to do other than pain relief and physiotherapy, which is a shame as I just want to get home as quickly as possible.

Learning points.

• Spontaneous psoas haematoma should be considered as a cause for atraumatic hip pain in patients on antiplatelet therapy.

• Common presentation includes hip pain, lower back pain and may include femoral neuropathy or haemodynamic instability.

• Appropriate radiological and biochemical investigations should be performed for all patients with atraumatic hip pain.

• Antiplatelet agents for secondary prevention are not without systemic complications in the elderly population.