SEATTLE – Correcting jumping and landing techniques may prevent lower-limb stress fractures in active young people, based on the results of a prospective study of 1,772 cadets at the United States Military Academy in West Point, N.Y.
Scores on the Landing Error Scoring System (LESS), which assesses 17 components of jumping and landing, were predictive of lower extremity stress fractures in the study, which was reported at the annual meeting of the American Orthopaedic Society for Sports Medicine.
Dr. Kenneth Cameron
Based on the results, freshman at West Point are now being screened for movement problems that are corrected when necessary. "We’ve seen a pretty impressive reduction – on average 30%-40% – in stress fractures, said lead investigator Kenneth Cameron, Ph.D., director of orthopedic research at Keller Army Community Hospital in West Point.
The reductions have not yet reached statistical significance because the program is fairly new, said Dr. Cameron, who added that the findings might prove useful for preventing post-traumatic osteoarthritis, anterior cruciate ligament tears, and other injuries.
For the study, cadets were instructed to jump off a 30-cm high box, then to leap as high as they could. Subjects were about 19 years old, on average, and had a body mass index of about 24 kg/m2 in men and 23 kg/m2 in women. The investigators videotaped the cadets and graded their movements using the LESS criteria.
Overall, there were 94 first-time fractures in the cohort, giving a cumulative incidence of 5.3%. Stress fractures were three times more likely in women, about one-third of the study population (incidence rate ratio = 2.86; 95% confidence interval, 1.88-4.34; P less than .001).
Controlling for sex and year of entry into the cohort, cadets who consistently landed flat footed or heel to toe were more than twice as likely (IRR = 2.32; 95% CI, 1.35-3.97; P = .002) to have a lower-extremity stress fracture during 4 years of follow-up. Similarly, a higher rate of stress fractures was noted in those who consistently landed asymmetrically (IRR = 2.53; 95% CI, 1.35-4.77; P = .004). Each additional movement error increased the incidence rate of lower-extremity stress fracture by 15% (IRR = 1.15; 95% CI, 1.02-1.31; P = .025).
"Typically, we don’t focus on changing movement patterns" when people have stress fractures, so most "move just as badly if not worse" and are at risk for another injury, he said. "Strength training isn’t enough; there’s a neuromuscular control issue, as well."
In stress fracture, "we see excessive motion in the frontal plane and transverse plane, and not much [side] plane motion. We also see hamstring and quadriceps weakness. Instead of flexing [the hip, knee, and ankle] to absorb force, [subjects] focus on compensatory movements," like internal rotation and abduction.
Hitting the floor with abnormal ankle flexion, stance width, and trunk flexion also increases the stress fracture risk.
The work was funded by the Department of Defense and National Institutes of Health, among others. Dr. Cameron had no relevant disclosures.