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Fig. 1 MRI scans without contrast with sagittal (A) and coronal (B) views of the left knee of a 44-year-old woman, reveal a tibial plateau stress fracture. The patient presented with worsening medial-sided knee pain two weeks after running a 50-mile endurance race.
COURTESY OF KAREN M. SUTTON, MD

AAOS Now

Published 9/1/2019
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Terry Stanton

Sex-related Differences in Sports Medicine: Bone Health and Stress Fractures

During an Instructional Course Lecture presented at the American Orthopaedic Society for Sports Medicine Annual Meeting, panelists Mary K. Mulcahey, MD; Jo A. Hannafin, MD, PhD; Elizabeth A. Arendt, MD; and Karen M. Sutton, MD, discussed the influence of sex-related factors on treatment outcomes and return to play in sports medicine.

This article covers Dr. Sutton’s presentation on bone health and stress fractures, with particular attention given to female athletes. An article on page 12 covers the presentation by Dr. Mulcahey on sex differences with anterior cruciate ligament tears; the October issue of AAOS Now will cover the talks by Dr. Hannafin on shoulder injury and Dr. Arendt on patellofemoral injuries and issues.

Dr. Sutton, of Hospital for Special Surgery in New York, N.Y., described the female athlete triad, which involves:

  • low energy availability (LEA)
  • menstrual dysfunction
  • low bone mineral density (BMD)

LEA may occur with or without an accompanying eating disorder, Dr. Sutton explained. “They don’t have to come in and make you think, ‘This is someone with an extreme case of anorexia or bulimia.’ It actually may be an athlete who’s a midfielder in soccer and is running up and down the field, and they just happen to not be taking in the appropriate calories that they’re supposed to be taking.”

Menstrual function ranges from eumenorrhea to oligomenorrhea to amenorrhea, Dr. Sutton said. BMD ranges from normal to osteoporosis.

“I think we’re doing a little bit better of a job right now trying to figure out our athletes when they have low BMD, but it’s still challenging because most of the data [are] on women who are closer to about 60 to 80 years old,” Dr. Sutton said. “Even female athletes with apparently strong bone may suffer stress injuries when loading exceeds the bearing capacity. We are still working on a clear definition of adequate bone quality for higher levels of activity and sports participation. Sending some of these patients for a bone density scan is not always appropriate based on the incomplete data we have on female athletes.”

Dr. Sutton explained the concept of “relative energy deficiency in sports,” or RED-S. The syndrome may occur in male or female athletes, and although it may be of particular concern in females in regard to altered reproductive hormones and lower BMD, it may affect systems in both sexes, such as the metabolic, cardiovascular, gastrointestinal, and immune systems.

“If you are working with schools, colleges, or professional teams, you can talk about this as not just a female athlete issue but one that can affect the male athlete, too,” Dr. Sutton said.

Stress fracture

Bone stress injury (BSI), or stress fracture, occurs more often in female athletes versus male athletes. Common sites include the foot, tibia, fibula, pelvis, and sacrum. In pathophysiological terms, BSI occurs when bone is subjected to repetitive loads that exceed its capacity to repair itself, Dr. Sutton said. “Fortunately, bones aren’t like construction, where you are building a house and you rely on the original wood and nails to support it,” she explained. “Bone does tend to remodel, but sometimes it is not remodeling enough or it has increased osteoclastic activity. Then you start to see bone break down. If bone formation is inadequate, stress fractures may occur.”

BSI occurs on a spectrum, from stress reaction to stress fracture to complete fracture. “This is where collaborating with your radiologist and having terminology that works well with you is important,” Dr. Sutton said, noting that she has one main radiologist who reads most of her patients’ MRIs. “I am in sync with her semantics, where she’ll talk about a periosteal reaction or that there is a linear change in the bones seen on MRI. There’s a distinct difference when you’re talking to an athlete about a stress reaction of the periosteum versus if you are seeing an actual fracture there.”

Risk factors that are “extrinsic” include exercise volume, intensity, and type; surface; and footwear. “Work with your trainers and coaches on these factors,” Dr. Sutton advised. “I think it’s critical for these athletes. It’s tough in some of our younger athletes, but as you get to the college level, you should have appropriate footwear for the surface. For example, you may have a coach who makes the team run three miles around the trail, and they have to do that in their cleats. All the athletes should really come prepared with footwear for whatever the coach may have them do, including cleats, turf shoes, cross-trainers, and running shoes, so that they are always prepared. If they’re switching from a turf field to grass or from grass to turf, they’re not wearing over-aggressive cleats on a turf surface.”

Fig. 1 MRI scans without contrast with sagittal (A) and coronal (B) views of the left knee of a 44-year-old woman, reveal a tibial plateau stress fracture. The patient presented with worsening medial-sided knee pain two weeks after running a 50-mile endurance race.
COURTESY OF KAREN M. SUTTON, MD
Karen M. Sutton, MD, and other panelists, spoke about the influence of sex-related factors on treatmentoutcomes and return to play in sports medicine at the American Orthopaedic Society for Sports MedicineAnnual Meeting in Boston.PHOTO
COURTESY OF TERRY STANTON

She recalled a situation with a collegiate athletic program: A new shoe sponsor was selected, and “The women playing field sports could only request cleats or turf shoes. In our discussions with our athletic director, we said, ‘At this time, they all need to have both the cleats and the turf shoes. Otherwise, we need to explore different brands.’”

Intrinsic factors for BSI include biomechanics, muscle strength, balance, and limb alignment. “There are medical and psychological factors that occur with this injury, too, including poor nutrition, menstrual dysfunction, low BMD, and low body mass index, as well as eating disorders,” Dr. Sutton said. “Having a sport psychologist on your team is important.”

BSI in trabecular bone and multiple injuries should trigger evaluation for underlying medical abnormalities. “Have the endocrinologist work closely with you in some of these high-risk athletes,” Dr. Sutton advised. “If they’re suffering from femoral neck stress fractures, sacral or calcaneal stress fractures, these need to be treated as concerning stress fractures.”

High-risk fractures

Stress fractures at high risk for complication include those of the femoral neck, patella, anterior tibia, medial malleolus, talus, navicular, proximal fifth metatarsal, and sesamoids. Femoral neck fractures, with a prevalence of 5 percent of BSIs, may be seen especially in young, active female runners, along with endurance athletes and members of the military. Most injuries are seen on the compression side, “But always be aware and look at the images yourself if it’s called ‘just a stress fracture’; you really want to visualize that and make sure it’s not on that tension side, because then you’re going to be treating it differently,” Dr. Sutton said.

Tension-side fractures are usually on the superior-lateral neck and call for immediate restricted weight-bearing and surgery with percutaneous screw fixation. Such injuries are considered high-risk due to the potential for displacement, Dr. Sutton said, and displaced fractures require urgent surgical intervention.

Risk factors include sudden reduction in weight and lower-extremity muscle mass, combined with daily training, decreased femoral BMD, gluteus medius weakness, and coxa vara. “This is where your performance team can come in as well, and these athletes—female and male—should not shy away from the weight room. It’s always important [that] we check in regularly with our performance team just to see what they’re doing. Are they ramping up? Are they changing some of their routines?”

The patella is involved in 1 percent of stress injuries. When the injury is limited to a stress response with no fracture, rest until the patient is symptom-free is appropriate, Dr. Sutton said.

Incomplete or nondisplaced fractures may be managed nonoperatively with extension immobilization and partial weight-bearing for four to six weeks. “If conservative management fails, that’s when you want to look into the surgical intervention,” Dr. Sutton said. High-demand athletes requiring a rapid return to play may benefit from early surgical intervention, and displaced fractures “obviously require surgical intervention.”

Dr. Sutton also addressed fractures to the tibia, the most common type of BSI, which often occur posteromedially in runners. If nonoperative measures fail, then surgical intervention is warranted, with tibial intramedullary nailing as an option.

The tarsal navicular represents 14 percent to 25 percent of all stress injuries, as typically seen in young male athletes doing explosive sprinting, rapid cutting, and jumping in track and field, football, and basketball. “We’ll place the patient in nonweight bearing for at least six weeks,” Dr. Sutton said. “Initial surgical fixation is commonly considered in elite athletes. The return to play is 16.4 weeks with surgery versus 21.7 weeks with nonoperative treatment.”

Finally, proximal fifth metatarsal BSI is seen most often in soccer, basketball, and football, with offensive linemen most at risk. One trial of nonoperative care with nonweight-bearing cast immobilization for six weeks versus early intramedullary screw surgical fixation found a 4.6 nonunion rate and 6.9 percent refracture rate with surgery compared to 7.1 percent and 17.9 percent, respectively, with conservative treatment; return to play was 13.8 weeks with surgery versus 19.2 weeks with conservative treatment.

Terry Stanton is the senior science writer for AAOS Now. He can be reached at tstanton@aaos.org.