Detection of Traumatic Ankle Arthrotomies: Computed Tomography Scan Versus Saline Load Test

OBJECTIVE

Periarticular wounds present a common diagnostic dilemma for emergency providers and orthopedic surgeons because traumatic arthrotomies (TA) often necessitate different management from superficial soft tissue wounds. Historically, TA have been diagnosed with the saline load test (SLT). Computed tomography (CT) scan has been studied as an alternative to SLT in diagnosing TA in several joints, but there are limited data specifically pertaining to the ankle. This study aimed to compare the ability of a CT scan to identify an ankle TA versus a traditional SLT. The hypothesis was that there would be no significant difference between a CT scan and SLT in diagnosing ankle TA in a cadaveric model.

METHODS

This cadaveric study used 10 thawed fresh-frozen cadaveric ankles. A baseline CT scan was performed to ensure no intra-articular air existed before simulated TA. After the baseline CT, a 1 cm TA was created in the anterolateral arthroscopy portal site location. The ankles then underwent a postarthrotomy CT scan to evaluate for the presence of intra-articular air. After the CT scan, a 30 mL SLT was performed using the anteromedial portal site location.

RESULTS

After arthrotomy, intra-articular air was visualized in 7 of 10 cadavers in the postarthrotomy CT scan. All the ankles had fluid extravasation during the SLT with <10 mL of saline. The sensitivity of the SLT for TA was 100% versus 70% for the CT scan.

CONCLUSIONS

The SLT was more sensitive in diagnosing 1-cm ankle TA than a CT scan in a cadaveric model.

Quantitative Analysis of Condition-based Limited Duty Duration of Musculoskeletal Conditions

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.

Biomechanical Analysis of Combined Medial Calcar and Lateral Locked Plating Versus Isolated Lateral Locked Plating of Proximal Humerus Fractures

OBJECTIVE

Medial calcar buttress plating combined with lateral locked plating is biomechanically tested against isolated lateral locked plating in synthetic humeri models for the treatment of proximal humerus fractures.

METHODS

Proximal humerus fractures (OTA/AO type 11-A2.1) were manufactured in 10 pairs of Sawbones humeri models (Sawbones, Pacific Research Laboratories, Vashon Island, WA). Specimen were randomly assigned and instrumented with either medial calcar buttress plating combined with lateral locked plating (CP) or isolated lateral locked plating (LP). Nondestructive torsional and axial load tests were performed to evaluate construct stiffness. Large-cycle axial tests were conducted followed by destructive ramp-to-failure tests. Cyclic stiffness was compared in both nondestructive and ultimate failure loads. Failure displacement was recorded and compared between groups.

RESULTS

The addition of medial calcar buttress plating to lateral locked plating constructs significantly increased the axial ( P < 0.01) and torsional ( P < 0.01) stiffness of the construct compared with isolated lateral locked plating by 95.56% and 37.46%, respectively. All models demonstrated greater axial stiffness ( P < 0.01) after 5000 cycles of axial compression, not dependent on the fixation method. During destructive testing, the CP construct withstood 45.35% larger load ( P < 0.01) and congruently exhibited 58% less humeral head displacement ( P = 0.02) before failure when compared with the LP construct.

CONCLUSION

This study demonstrates the biomechanical superiority of medial calcar buttress plating when combined with lateral locked plating as compared with isolated lateral locked plating of OTA/AO type 11-A2.1 proximal humerus in synthetic humeri models.

The effect of subtalar joint axis location on muscle moment arms

Most dynamic musculoskeletal models define the subtalar joint (STJ) as a one degree of freedom (DOF) hinge with a tri-planar axis. The orientation of this axis of rotation is often determined as a combination of inclination and deviation angles measured from the ground and midline of the foot, respectively. In defining the location of the axis, often the origin is found at the distal aspect of the heel instead of at the articulation of the talus and calcaneus. Key musculoskeletal modeling definitions, such as muscle moment arms, are dependent on the distance and relative location of muscle insertion to the axis of rotation. Since the axis orientation and origin location affect calculations of muscle moment arm and joint dynamics, there is much need for accurate characterization of the STJ axis to understand the STJ's role in dynamic weight-bearing motion. The purpose of this study is to explore how the STJ origin location and axis orientation affect muscle moment arms surrounding the ankle. Datasets from the Grand Knee Challenge, posted on the open-source SimTK website, were modeled using OpenSim. Modifying the location of the STJ axis from the original location closer to the articulation between the talus and calcaneus resulted in significant differences in STJ muscle moment arms and peak STJ moments. The findings of this study conclude that the location of the STJ axis origin needs to be considered and accurately defined, especially if the inclination/deviation angles of the rotational axis will be modified to represent a more subject-specific definition.