Differential Diagnosis
Question: Now that you have taken the patient’s history, what are the top two diagnoses in your differential from this list and why?
Differential Diagnosis Discussion
Avascular necrosis and osteoarthritis are probably highest on the list, given his age, comorbid conditions and presenting symptoms.
- Osteoporosis: Osteoporosis is not associated with pain unless there is a fracture.
- Hip Osteoarthritis: This would be in your top 3 as osteoarthritis is common as people get older, is associated with pain with range of motion, but more so with weight bearing. Pain is often relieved with sitting.
- Avascular Necrosis: definitely. Avascular necrosis, also known as osteonecrosis, is more common in HIV-infected patients, and this would be a classic presentation of this disease.
- Trochanteric Bursitis: This usually presents as unilateral hip pain, although bilateral is possible and patients often point to their outer hip as the source of pain. Range of motion is typically not limited nor is it very painful if at all.
- Muscle Strain: This has been going on for too long to believe it is just a muscle strain especially as he is not exercising, so there is no risk of re-injury.
- Ligament Sprain: Same as the sprain.
- Hip fracture: There is no history of trauma and a spontaneous fracture in a middle aged male would be very unusual unless he had significant osteoporosis due to medications.
Question: What is the next best step?
Option 1: Reassure the patient that the pain is likely due to a muscle strain, which will resolve on its own.
Option 2: Prescribe oxycodone XR, and start at a dose of 30mg PO q12, starting at a relatively high dose due to the pt’s history of substance abuse and likely tolerance to opioids.
Option 3: Prescribe a low dose Fentanyl patch (12mcg), because transdermal therapy is more difficult to abuse.
Option 4: Order bilateral hip x-rays, and if normal, order bilateral hip magnetic resonance imaging (MRI) scans.
Discussion of Answer Choices
Option 1: This is not the best next step.
It unlikely that a simple muscle strain would last for 3 months. Given the persistence and severity of the patient’s symptoms, it is essential to investigate their etiology. In particular, this patient has several risk factors for hip osteonecrosis, including having HIV infection, taking fluticasone and ritonavir concurrently, and having recently taken a course of steroids. Other intraarticular hip pathologies, such as osteoarthritis, are also possible, although less likely given his age and lack of history of trauma to the joint. When possible, it is important to identify the etiology and mechanism for patients’ pain. Although it is not always possible to radiographically pinpoint the source of the patient’s pain, when the source is identified, disease-directed therapy can be considered.
Option 2: This is not the best next step.
Although opioids will likely be an important part of this patient’s management, it is not appropriate to start opioids at a high dose. Although the patient does have a history of substance abuse and may require higher doses than patients without substance abuse, this is not the case in all patients. Starting at such a high dose of a long-acting opioid places this patient at serious risk of opioids overdose and is unsafe. Patients should always be initiated on a starting dose of short-acting opioids (in this case, oxycodone 5-10 mg) and titrated up.
Option 3: This is not the best next step.
There is no evidence that transdermal therapy is safer or has less abuse potential than other opioid formulations. To the contrary, several case reports of patients orally ingesting or injecting transdermal patches have been reported in the literature.
Option 4: This is the best next step.
This patient has several risk factors for hip osteonecrosis, including having HIV infection, taking fluticasone and ritonavir concurrently, and taking a recent course of steroids. Plain radiographs of the hip may not be sensitive enough to detect early osteonecrosis. Therefore, if the plain radiograph is negative, MRI is the preferred imaging modality. Other intraarticular hip pathologies, such as osteoarthritis, are also possible. When possible, it is important to identify the etiology and mechanism for patients’ pain. Although it is not always possible to radiographically pinpoint the source of the patient’s pain, when the source is identified, disease-directed therapy can be considered.
