Quantitative Analysis of Condition-based Limited Duty Duration of Musculoskeletal Conditions
Authors: Smith Christopher S , Yoon Laura , Zuppke Julia N , Zundel Mike 
Published: February 2024

ABSTRACT

Introduction
Musculoskeletal injuries affect nearly a million service members annually within the DoD, ultimately costing the U.S. Military half a billion dollars in direct patient costs and a significant loss to fleet readiness as many members are assigned days on limited duty (LIMDU) until they are deemed medically fit to return to duty (RTD). The new approach implemented by Navy Medicine in 2022, called “condition-based LIMDU,” aims to drastically impact the time in which Sailors and Marines spend under a provider’s care by assigning LIMDU days based on a standardized set of guidelines. This study provides a quantitative analysis on LIMDU duration, before and after implementation of the new condition-based LIMDU paradigm, to increase the understanding on the effectiveness and impact to fleet readiness and to assess the accuracy of suggested patient outcome timelines.

Materials and Methods
De-identified and aggregated data were obtained from the Naval Medical Forces Atlantic’s (NMFL) LIMDU Sailor and Marine Readiness Tracker System (SMART) program for all active duty military patients with ICD-10 code for musculoskeletal conditions. Only closed LIMDU cases in which active duty patients were given a final status of RTD were included. This study analyzed top musculoskeletal ICD-10 codes, optimum period (weeks), maximum period (weeks), and average days on LIMDU assigned at NMFL centers (medical and non-medical) for fiscal years 2021 (FY21) and 2022 (FY22). As well as descriptive statistics, t-test analysis was used to test if there was a difference between FY21 and FY22 and at what point the difference was no longer significant. Critical value method was then used to compare the top five most common musculoskeletal injuries to determine the accuracy of recommended LIMDU days to actual average assigned LIMDU per injury type. A color-coded compliance chart was created based on the results.

Results
The results showed that for RTD population, the implementation of condition-based LIMDU significantly decreased average days assigned on LIMDU by 33%. In fact, there is a 35-day (5-week) difference before we can confidently say that the difference between FY21 and FY22 is no longer statistically significant. This significant decrease in LIMDU days, before and after implementation, is a trend consistent at both medical and non-medical NMFL centers; however, medical centers reported significantly more assigned LIMDU days for both years. The five most common injuries of FY21 and FY22 were low back pain, pain in shoulder, pain in hip, pain in knee, and pain in ankle. Before implementation, all five of these injury types far exceeded the recommended amount of LIMDU days. With the new condition-based LIMDU paradigm, the average assigned LIMDU days for pain in hip, pain in knee, and pain in ankle were all found to be in compliance with the recommended LIMDU days within a 99% confidence level.

Conclusions
The new condition-based LIMDU paradigm is successful in its aim to improve fleet readiness by returning Sailors and Marines to full duty status significantly faster. Regular assessment of ICD-10 diagnosis codes and update to recommended LIMDU assignment timelines should be conducted to maximize the effectiveness and accuracy for all medical conditions.