Differential Diagnosis
Given the patient’s history and physical exam, causes of both posterior
hip and low back pain must be considered.
The differential diagnosis of hip pain is broad and can be
compartmentalized into both intra-articular and extra-articular causes.
Intra-articular causes include a labral tear, femoroacetabular
impingement, and osteoarthritis. Extra-articular causes can be
subdivided by localization of the pain as either anterior, posterior, or
lateral. This patient presented with posterior hip pain. Causes of
posterior hip pain include sciatic nerve impingement, sacroiliac joint
pathology, tendinopathy, muscle strain, and referred pain from lumbar
spinal causes. Additionally, this patient has a history of bilateral
THA. Therefore, orthopaedic complications of THA, such as prothesis
wear, aseptic loosening, periprosthetic fracture, and leg length
discrepancy, must be considered in the differential diagnosis.
The differential diagnosis for low back pain includes lumbosacral muscle
strain, lumbar disc herniation, spondylosis, spinal stenosis, fracture,
and malignancy. A muscle strain presents following repetitive or
excessive use. On physical exam, pain is typically worse with movement,
range of motion is limited, and there is tenderness to palpation of the
muscles. Lumbar disc herniation occurs when an intervertebral disc
exerts pressure on a spinal nerve root causing pain and radiculopathy.
This typically presents with neurologic symptoms such as paresthesia,
sensory loss, decreased strength, and/or diminished reflexes.
Spondylosis, or the arthritic change of the spinal discs and facet
joints, presents as back pain with radiation to the buttock and/or thigh
along with neurologic deficits in the L5 – S1 spinal nerve root
distribution. Lumbar spinal stenosis is the narrowing of the spinal
canal, which presents as low back pain relieved by rest. Neurologic exam
may be normal or include decreased muscle strength or sensation.
Fracture can occur with significant trauma or as a result of a vertebral
compression. Physical exam may show focal tenderness on palpation and
history may include risk factors such as glucocorticoid use, increased
age, and osteoporosis.
Finally, non-orthopaedic causes of posterior hip and low back pain
include malignancy and AAA. Due to this patient’s age, malignancy must
be a consideration. Patient history may reveal previous malignancy,
unexplained weight loss, and/or constitutional symptoms. On physical
exam, we would expect focal tenderness to palpation. Additionally, given
the patient’s significant cardiac and vascular history, AAA cannot be
ruled out without imaging. Unruptured AAA can present as abdominal pain
radiating to the flank, back, or groin.
Given the acute nature of the patient’s pain, the HPI, and the findings
on physical exam, the leading diagnosis is posterior hip and low back
pain likely due to muscle strain and resultant inflammation. Due to the
patient’s history of bilateral THA, orthopaedic complications such as
prosthetic wear, aseptic loosening, periprosthetic fracture, and leg
length discrepancy should not be ruled out without further imaging. Both
malignancy and AAA are “Do Not Miss” differentials and must also be
ruled out with imaging.