Discussion
Our case report demonstrates an incidental finding of a large, unruptured AAA during a workup for a chief concern of posterior right hip and low back pain. Unruptured AAA are typically asymptomatic. Occasionally, unruptured AAA can become symptomatic and mimic MSK pain in the flank, back, and/or groin. In the orthopaedic clinic, an AAA is not high on the differential for a patient presenting with posterior hip and low back pain. In our case, the patient presented to an orthopaedic-only urgent care. In this setting, any non-MSK pathology is usually not considered. However, there is crucial information in the patient’s history and physical exam that should steer the provider away from an MSK etiology and towards the diagnosis of an unruptured AAA.
With a chief concern of posterior hip and low back pain in a patient with a history of bilateral THA, the initial assumption would be muscle strain or a complication related to the patient’s prostheses. There are aspects of the patient’s physical exam that align with this orthopaedic etiology. First, the patient ambulated with a painful right leg and their gait was antalgic. Additionally, there was reproducible tenderness on the posterior aspect of the right lumbosacral junction. Reproducible pain is a commonly known sign of MSK pathology. However, this physical exam finding is not specific for MSK etiologies and cannot rule out other causes.
Contrarily, there were important aspects in the HPI and physical exam findings that point away from MSK pathology. First, the patient denied any trauma, injury, or falls. Mechanism of injury (MOI) is a vital component of orthopaedic assessment. With no known MOI, certain injuries such as muscle strain or periprosthetic fractures are lower on the differential. However, non-traumatic causes such as infection and osteolysis must still be considered. An important note from the patient’s physical exam was the finding that range of motion was fully intact with no discomfort. Again, this points away from MSK pathology.
The patient’s past medical history is, perhaps, the most important consideration that would direct a provider towards the diagnosis of an AAA. The patient’s history is significant for hypertension, hyperlipidemia, CAD, T2DM, and PAD; all of which are high risk factors for the development of an AAA. Further, the patient is > 65 years old and male. Both are also risk factors for an AAA. The patient’s significant cardiac and vascular history, in conjunction with the HPI and negative findings on orthopaedic physical exam, should logically lead a provider towards a non-orthopaedic etiology and raise suspicion for an AAA.
Hip and back pain are an atypical, but known, presentation for an AAA. This clinical scenario is similar to other cases described in the literature. Smith et al. reported a 66-year-old male patient with an 8-month history of progressive left hip pain who was incidentally found to have an unruptured AAA. Baskaran et al. described a 58-year-old patient with a 6-month history of progressively worsening left hip pain associated with unintentional weight loss of 38 kg and tender bilateral testicular swelling. These two cases demonstrated chronic hip pain, unlike the patient in our report who presented with a 3-day history of pain. A complaint of chronic pain is more typical of a symptomatic unruptured AAA, due to the insidious growth of the dilatation. Our case is unique in this regard. Furthermore, low back pain has been a well-documented presentation of an unruptured AAA in several case reports.
Our case report emphasizes the necessity of extracting a thorough HPI and performing a holistic physical exam in the orthopaedic clinic. Orthopaedic providers should consider an unruptured AAA as an atypical differential diagnosis when a patient presents with hip and/or low back pain. There should be a particularly high index of suspicion for an AAA in the context of a significant cardiac and vascular history, associated risk factors (i.e., smoking, T2DM, atherosclerosis, hypertension, etc.), and negative orthopaedic findings on physical exam. Awareness and education of this presentation is crucial for avoiding a missed diagnosis. A missed diagnosis of an unruptured AAA may put the patient at risk of catastrophic rupture and subsequent death.
Orthopaedic surgery is a field that tends to have a myopic approach to patient care. With increasingly advanced subspecialties, orthopaedic surgeons are highly skilled in their respective disciplines. Inadvertently, differential diagnoses that are typically outside the field of practice may not be considered. However, it is important for orthopaedic providers to be well-rounded in all aspects of patient care and perform holistic investigations when assessing a patient.
This case report has limited generalizability, as it discusses a single case. However, it highlights important aspects of patient care and can be used as a teaching tool to advocate for holistic practices in the orthopaedic clinic.