Workup of the Painful Total Hip Arthroplasty

Differentiating Hip Versus Spine Pathology

When a patient presents with pain following total hip arthroplasty (THA), it is essential to remember that pain patterns from lumbar spine disorders and hip pathology overlap. Overlapping pain patterns, coupled with the coexistence of lumbar spine disorders in 18% of patients undergoing THA, pose a challenge in the diagnosis of pain following THA. A thorough clinical history, physical exam, appropriate imaging, and diagnostic injections can help define the source of the patient’s pain.

Classically, radiculopathy is associated with pain that radiates past the knee, with intraarticular hip pain confined to the groin. Unfortunately, patients do not always present classically, with up to 47% of patients with hip arthritis indicated for THA reporting pain below the knee. Although groin pain has been reported to have a sensitivity of 84% and specificity of 70% for hip osteoarthritis, it is important to keep in mind that the following extraarticular sources can also generate groin pain: lumbar radiculopathy, facet syndrome, sacroiliac joint pain, and piriformis syndrome. A clear description of the pain distribution and exacerbating or alleviating factors will often steer diagnosis in the appropriate direction.

Spinal stenosis typically presents with neurogenic claudication described as back and bilateral lower extremity pain worsening with ambulation and improved with stooped posture or sitting. Physical exam findings in these patients are variable, with less than 20% of patients with spinal stenosis demonstrating a positive straight leg raise test or femoral tension sign. Rarely will the patient present with a neurologic deficit. These may include a positive Romberg test or weakness in coincident lower extremity distributions. Foraminal stenosis, specifically at L1 or L2, may result in groin pain. Foraminal stenosis due to a disc herniation or facet arthropathy typically worsens with increased lumbar lordosis in a standing position and improves with stooped posture or sitting. A thorough exam with vascular exam, reflexes, strength testing, sensation to pinprick, and pathologic reflexes, including clonus and Babinski sign, must be completed. Despite an exam, however, most physical tests to identify lumbar disc herniation and associated radiculopathy have low sensitivity and specificity.

Clinical history is invaluable when the possible etiology of pain is related to a patient’s prior hip arthroplasty. Pain in the groin or buttock can be related to acetabular-sided etiologies or infection while thigh pain is traditionally associated with femoral-sided loosening. Gait exam should evaluate for limb-length discrepancy and a Trendelenberg gait. In the acute perioperative period, the wound should be examined for any sign of infection. Later, the peri-incisional area should be evaluated for areas of erythema, warmth, or fluctuance. Active and passive range of motion should be assessed for pain and instability. Painful passive range of motion is concerning for infection, whereas apprehension is concerning for subtle instability.