Researchers studied 22 teenagers who broke their hip bones (femoral neck fractures) and found something surprising: teens with lower body weight were more likely to get these injuries from minor accidents, while heavier teens only got them from major trauma. This is unusual because most research focuses on overweight people getting fractures. The study suggests that being underweight might weaken bones in ways we don’t fully understand yet. However, the study was small, so more research is needed to confirm whether low body weight really does increase fracture risk in teenagers.

The Quick Take

  • What they studied: Whether teenagers with different body weights have different risks of breaking their hip bones, and whether the type of accident that caused the break matters
  • Who participated: 22 teenagers aged 10 and older who came to a major trauma hospital with broken hip bones. The researchers looked at their weight and height measurements to categorize them as underweight, normal weight, overweight, or obese
  • Key finding: Among teens who broke their hips from minor accidents (like falls from standing height), 30.77% were underweight. In contrast, none of the teens who broke their hips from major accidents (like car crashes) were underweight. This difference was statistically significant (p < 0.05), meaning it’s unlikely to be due to chance
  • What it means for you: If you’re a teenager on the lighter side, you might want to be extra careful about falls and minor injuries, and talk to your doctor about bone health. However, this is based on a small study, so don’t panic—more research is needed to understand this connection fully

The Research Details

This was a small research study that looked back at medical records of 22 teenagers who had already broken their hip bones and received surgery at a major trauma center. The researchers measured each teenager’s body mass index (BMI)—a number based on height and weight—and sorted them into five categories: underweight, normal weight, overweight, moderately obese, and extremely obese. They also divided the teenagers into two groups based on how serious their accident was: low-energy trauma (like falls from standing height) and high-energy trauma (like car accidents or falls from high places). Then they compared the two groups to see if body weight differences were related to fracture type.

The researchers used statistical tests (t-tests and chi-square tests) to determine whether the differences they found between groups were real or just due to chance. This approach allowed them to look for patterns in existing data without randomly assigning people to different conditions.

Hip fractures in teenagers are rare but very serious because they can cause permanent damage like avascular necrosis (when bone tissue dies from lack of blood supply) or uneven leg lengths. Understanding who is at higher risk helps doctors identify vulnerable teenagers and potentially prevent these injuries. Most previous research focused on overweight people getting fractures, so this finding about underweight teenagers is new and unexpected

This study has several important limitations to consider: it’s very small (only 22 teenagers), it looked at past cases rather than following teenagers forward in time, and it was done at just one hospital so the results might not apply everywhere. The study lost track of 2 patients, which further reduced the sample size. Because the study is small, the findings are preliminary and need to be confirmed by larger, more detailed research before doctors should change their recommendations

What the Results Show

The main finding was a striking difference in body weight between the two trauma groups. Among the 13 teenagers who broke their hips from low-energy trauma (minor accidents), 4 teenagers (about 31%) were underweight. In contrast, none of the 9 teenagers who broke their hips from high-energy trauma (major accidents) were underweight. The average BMI percentile was significantly different between the two groups (p < 0.05), meaning this difference is unlikely to be due to random chance.

The study also found that 7 of the 20 fractures were nondisplaced (the bone pieces stayed roughly in place), while 13 were displaced (the bone pieces moved out of alignment and needed to be repositioned). This matters because displaced fractures are generally more serious and harder to treat.

Complication rates were concerning: avascular necrosis (bone tissue death) occurred in 4 cases, and limb length discrepancy (one leg becoming shorter than the other) occurred in 3 cases. These are exactly the serious complications that doctors worry about with hip fractures in young people.

The study found that underweight teenagers were more likely to experience low-energy fractures, suggesting their bones might be more fragile or vulnerable to injury from everyday accidents. The fact that none of the high-energy trauma cases involved underweight teenagers suggests that major accidents can break anyone’s hip, regardless of body weight, but minor accidents seem to preferentially affect underweight teens. The high rate of complications (avascular necrosis and limb length problems) in this small group highlights why these fractures are so serious and need careful treatment

This finding is surprising because most previous research has focused on obesity and fracture risk, or on vitamin D deficiency and young-onset osteoporosis. Very little research has specifically examined whether being underweight increases fracture risk in teenagers. This study suggests that the relationship between body weight and bone strength in adolescents might be more complex than previously thought, with both extremes (very low and very high weight) potentially causing problems

The study is quite small with only 22 teenagers, which limits how much we can trust the findings. It’s a retrospective study, meaning researchers looked back at past cases rather than following teenagers forward over time, so they couldn’t control for other factors that might affect bone strength like nutrition, exercise, or family history. The study was done at one hospital, so the results might not apply to teenagers in other regions or populations. Two patients were lost to follow-up, further reducing the sample size. The study doesn’t explain why underweight teenagers might have weaker bones—it just shows the association. Finally, with such a small sample, the findings could be due to chance or other unmeasured factors

The Bottom Line

Based on this preliminary research, teenagers who are underweight should consider: (1) talking to their doctor about bone health and whether they need extra calcium or vitamin D, (2) being extra cautious about falls and minor injuries, and (3) engaging in weight-bearing exercise like walking, running, or sports to strengthen bones. However, these recommendations are based on a very small study, so discuss them with your doctor before making major changes. The confidence level is LOW because the study is small and needs to be repeated with larger groups

Teenagers who are underweight, their parents, and their doctors should pay attention to this research. Coaches and physical education teachers might also want to be aware that underweight athletes could be at higher risk for serious hip injuries. However, this doesn’t mean overweight teenagers should ignore bone health—they have different risk factors. Anyone with concerns about their bone strength should talk to their doctor regardless of body weight

If you’re underweight and make changes to improve bone health (like adding more calcium and vitamin D, exercising regularly, or gaining weight if appropriate), it typically takes several months to see improvements in bone strength. You won’t feel bones getting stronger, but your doctor can monitor bone health through physical exams and, if needed, special imaging tests. The goal is prevention—avoiding fractures in the first place—rather than seeing quick improvements

Want to Apply This Research?

  • Track weekly falls, trips, or minor injuries (even if they don’t result in fractures) along with your body weight and BMI percentile. Note the type of activity when injury occurred (sports, daily activities, accidents) to identify patterns and high-risk situations
  • Set a goal to engage in 30 minutes of weight-bearing exercise at least 4 days per week (walking, running, dancing, sports, or strength training). Log your exercise type and duration. Also track calcium and vitamin D intake through food or supplements to ensure adequate nutrition for bone health
  • Monthly check-ins on body weight and BMI percentile, quarterly reviews of injury frequency and type, and semi-annual conversations with your doctor about bone health. If you’re underweight, work with your healthcare provider to develop a safe plan for appropriate weight gain if needed, and monitor whether injury frequency changes over time

This research is preliminary and based on a small study of only 22 teenagers. The findings have not been confirmed by larger studies and should not be used to diagnose or treat any condition. If you are a teenager concerned about bone health, fracture risk, or if you have experienced a fall or injury, please consult with your doctor or a pediatric orthopedic specialist. This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions you may have regarding your health or the health of your child.