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Some muscle strains turn out to be stress fractures

 •  • by Paul Ingraham
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Weekly nuggets of pain science news and insight, usually 100-300 words, with the occasional longer post. The blog is the “director’s commentary” on the core content of a library of major articles and books about common painful problems and popular treatments. See the blog archives or updates for the whole site.

The main symptom of a muscle strain is pain in a specific spot or area of muscle tissue… but there are other conditions that can cause pain like that. For instance, groin or high thigh pain in athletes is often a muscle strain, but not always. If it’s just not getting better (or actually getting worse), it could also be a femoral or pelvic stress fracture — especially in women, but sometimes in men as well.

Some stress fractures, especially in the hip, are devilishly good at mimicking common muscle strains, especially in runners, and one of the strongest clues is pain that surges with weight-bearing. If bearing weight is unbearable, think stress fracture. Kiel et al:

“Stress fractures of the pelvis can be vague clinically and mimic other causes of groin and hip pain, for example, adductor strain, osteitis pubis, or sacroiliitis. The most common location is the ischiopubic ramus and sacrum. These injuries are seen most commonly in runners. … Femoral neck stress fractures make up approximately 11% of stress injuries in athletes. The patient complains of hip or groin pain which is worse with weight bearing and range of motion especially internal rotation.”

How a typical femoral neck stress fracture looks on MRI — that dark line on the underside of the neck.

But by far the simplest way to eliminate a fracture? Just take a peak inside with the magic machines! MRI are very “sensitive” and “specific” for signs of stress fractures: if it shows one, it’s definitely for real; if not, it’s probably doesn’t exist. Schneiders et al:

“The gold standard for stress fracture diagnosis is either triple-phase technetium-99m bone scan (scintigraphy) or MRI. Scintigraphy is able to diagnose stress fractures by identifying areas of increased uptake of the radioisotope and has a reported sensitivity of 100% and specificity of 76%. MRI has been shown to have comparable sensitivity and superior specificity to scintigraphy for assessment of bone pathology. Although MRI is less invasive and provides greater anatomic detail than scintigraphy, it is more costly. Of further concern is the accessibility of these procedures to many patients.”

“Triple-phase technetium-99m” sounds a lot like Star Trek technobabble. 😄

Bone scintigraphy is out because of “low specificity, high dosage of ionizing radiation, and other limitations” (Wright).

And X-ray isn’t great for stress fractures: it tends to miss them in the early stages.

This is a small excerpt from an update to my muscle strain book … which keeps evolving, to my surprise. It amuses me that I once thought the topic was simple. Literally nothing in this business is simple.