Prior to reading, please check out Case Report: Female Runner with Bilateral Knee Pain, Part 1.
The patient described was a friend that I evaluated after her symptoms continued to worsen, even after over a month of physical therapy and a cortisone shot. Following my initial evaluation, I instructed and prescribed a home exercise program (HEP) that targeted the ‘weak’ hip musculature and altered biomechanics, especially evident during running. I also recommended holding back on her current training program until her symptoms were under control. Once under control, a proper well progressed aerobic training program would be initiated.
A few weeks following the evaluation, she returned to her physician who ordered an MRI to rule out any significant underlying pathology. The MRI report was negative for any significant meniscal or articular cartilage pathology. However, the report did find substantial Bilateral Femoral Shaft Stress Fractures, which were not picked up on the initial x-ray report!
According to Monteleone et al and Matheson et al, femoral shaft stress fractures make up only 5-7% of all stress fractures. They also found that the overall incidence of bilateral stress fractures is ~16.6% of all cases, but I have to imagine there is an even smaller population suffering from fractures to the femoral shaft. Not only is this a rare pathology, but it is an equally difficult injury to diagnose. Harrast et al report that the referral pattern is highly variable, potentially affecting the groin, thigh, and/or knee regions. Additionally, palpation of the affected area is unreliable due to the amount of soft-tissue that overlies the femoral shaft. This is almost always caught as a diagnosis of exclusion or as a result of failed conservative treatment. The difficulty in diagnosis does not stop at the physical examination as initial radiological testing only has a sensitivity of 15-35%. This injury is typically not found until symptoms continue to worsen and an MRI is ordered (sensitivity of 100%, specificity of 85%). So, just because the x-ray report is negative does not mean it should be ruled out as a potential causative factor.
So, what causes a femoral shaft stress fracture?
A biomechanical study published by Edwards et al found that the largest bending moments about the A-P axes of the proximal femur occur during the impact phase of loading response. The direction of this bending moment in addition to the axially oriented compressive force would place the largest stress on the medial aspect of the femur. This stress may become even more pronounced during training after the hip abductors (resist the AP bending moment) begin to fatigue or are already weak prior to activity.
Obviously, this is not a typical case, but what could have been done to arrive at this conclusion from day one?
Johnson et al investigated the utility of a new (at the time) clinical test to aid in the early diagnosis of femoral stress fractures. The fulcrum test is conducted with the patient seated with legs dangling over the edge of the table. The therapist’s arm is positioned under the thigh and is used as a fulcrum as gentle inferiorly directed pressure is applied to the anterior knee by the opposite hand, just proximal to the patella. A positive finding is a sharp pain produced at the site of potential fracture (video demonstration provided below). Unfortunately this was a case series and only mentioned the use of the test, but did not provide data on specificity, sensitivity, or positive predictive value, nor has there been a study done to determine these values since. Speaking in terms of biomechanical/pathological plausibility, this test does seem to be worth incorporating in individuals who have a suspected femoral stress fracture, but there is currently no evidence to support its widespread use. Additionally, Clement et al found that approximately 70% of individuals with a femoral stress fracture will complain of anterior thigh pain during the single-leg hop test (video demonstration provided below). These additional clinical tests could have increased the likelihood of early detection, but the ability to consistently catch this injury remains allusive.
This case shows us that we, as healthcare providers, must continually assess and reassess our patients. If our conservative measures are not improving or are potentially worsening symptoms, a change needs to be made. The plan of care provided was appropriate for the patient’s clinical presentation, but unfortunately it was not as simple as it originally seemed. Sometimes, a patient’s pain is secondary to serious pathology and without reassessment, it would have never been found and appropriate treatment would not have been provided.
Now that a diagnosis is firmly in place, where would you go from here?
(Video Credit: DPT2012diffd)
(Video Credit: Brian Schiff)