Risk stratification scoring system for femoral neck bony stress injuries in military recruits: a pilot study

Bony stress injury (BSI) is an overuse injury through excessive repetitive loads on normal healthy bone that commonly affects military recruits. Confirmation of diagnosis often requires costly investigations such as MRI, and there is a need for better prior screening procedures. This study aimed to assess a clinical risk assessment tool 'Hip1' for its utility to screen and identify BSI for further detailed confirmatory investigation.

A retrospective cohort study using the Defence Medical Information Capability Programme, identifying all patients potentially presenting with BSI from clinical codes between 1 January 2021 and 31 December 2022 inclusive. All records were reviewed to determine if a 'Hip1' score had been performed by either a doctor or physiotherapist, and related to further investigations (X-ray and/or MRI reports) and patient outcomes.

47/213 patients were eligible. In the high-risk group (n=23), the mean Hip1 score was 7.4±1.7 versus the low-risk group (n=24), with a mean Hip1 score of 3.1±0.73. Nine patients from the high-risk group had a positive diagnosis of a BSI with a mean Hip1 score of 7.7±1.7. All patients in the low-risk group had a negative diagnosis and returned to training. Comparison between positive and negative cohorts gave the Hip1 score a sensitivity of 100% (95% CI 66.4% to 100%), specificity of 63.2% (95% CI 45.9% to 78.2%), positive predictive value of 39.1% (95% CI 29.8% to 49.3%) and negative predictive value of 100% (95% CI, N/A). Patients with a score of ≥5 were more likely to have a BSI than those with a score of ≤4 (p<0.05).

The Hip1 clinical scoring system showed high sensitivity with a very high negative predictive value to exclude those subjects that did not have a BSI; therefore, reducing unnecessary investigation, while directing the diagnostic resources to those who were most likely to require them.