Assessing lower extremity loading during activities of daily living using continuous-scale physical functional performance 10 and wireless sensor insoles: a comparative study between younger and older adults

The optimal weight-bearing and mobilization protocol for postoperative rehabilitation of the lower extremity, especially in patients with fragility fractures, has been a topic of ongoing debate. While some experts suggest protocols that involve immediate mobilization and weight-bearing, others argue for more cautious approaches, such as bed-to-wheelchair mobilization. However, limited evidence exists to conclusively determine which approach is superior [1, 2]. A contributing factor to this controversy may be the limited knowledge about the exact load placed on the leg during activities of daily living (ADL). While previous research has focused on measuring weight-bearing using methods such as force plates, pressure sensors, and motion capture systems [3‐5], these have primarily been limited to static situations, such as standing or sitting still, and laboratory settings. The utilization of wireless sensor insoles to measure ground reaction forces (GRFs) during ADLs represents a promising new approach for gaining a better understanding of lower extremity loading in ADLs. These insoles are equipped with capacitive pressure sensors that measure plantar pressures. This ensures the calculation of applied ground reaction forces during stance and provides simple spatiotemporal gait parameters [6]. Some studies have utilized wireless sensor insoles to measure weight bearing during specific activities, such as walking or stair climbing, but there is limited research that has used these sensors to measure weight bearing during a broader range of activities [7, 8].

The Continuous-Scale Physical Functional Performance (CS-PFP) test offers the possibility to assess an individual's physical performance [9]. The short form of the test, the CS-PFP 10, includes 10 tasks that evaluate various aspects of functional mobility such as stair climbing, carrying groceries, and walking on different surfaces [10]. The present study aimed to investigate GRFs of the lower extremity during ADLs using the CS-PFP 10 test and wireless sensor insoles.

The analysis of the PFP-10 test showed that the group with younger participants had significantly higher scores compared to the older group, with a mean total score of 78.2 (SD 5.4) compared to 57.1 (SD 9.0), respectively (Fig. 1). The UBS subscore was highest in the young group (94.0, SD 6.6), while the older group did best in UBF (75.6 SD 9.4). Both groups had the lowest subscore in LBS, with the younger group scoring 73.2 (SD 7.3) and the older group significantly lower at 49.1 (SD 10.7) (Fig. 2).

Three older participants in our study scored below 47 on the CS-PFP 10 test, indicating dependence on activities of daily living. Nevertheless, we included them in our analysis of lower extremity loading as they reported being independent in ADLs, with no assistance required from third parties.

This study aimed to use the CS PFP-10 test to compare the lower extremity force during ADLs between healthy young and older participants. This study is the first to investigate the lower extremity load during ADLs in both age groups using the CS-PFP 10 test.

There is currently a lack of a systematic approach to personalizing postoperative rehabilitation protocols for old patients after fracture fixation, as discussed in previous research [2]. The ideal rehabilitation protocol should balance the need to protect those who cannot comply with weight-bearing restrictions while also assisting others in mobilization with partial weight-bearing and minimizing the risk of inadvertent overloading. In clinical practice, various considerations influence surgeons when determining weight-bearing restrictions in older adults. These factors include fracture type, comminution, bone quality, the accuracy of reduction, implant positioning and stability, as well as patient-specific factors such as the ability to adhere to postoperative weight-bearing restrictions. There is also a potential “cost–benefit ratio” to consider when deciding on these restrictions, particularly in patients who are unable to comply with partial weight-bearing instructions [20]. Overloading the osteosynthetic construct before fracture healing may result in failure, requiring revision surgery with significant morbidity in older patients. Unstable trochanteric fractures, especially in the presence of poor bone quality and suboptimal fracture fixation, have been associated with failure rates of over 50% [21]. Accordingly, no clear consensus exists on optimal aftercare for unstable trochanteric fractures treated with intramedullary nailing [2]. On the other hand, prolonged immobilization can have several detrimental effects. It can lead to muscle disuse and atrophy, resulting in muscle weakness, loss of muscle mass, and decreased functional capacity [22]. Immobilization can also cause joint stiffness and contractures, limiting the range of motion and impairing joint function, leading to decreased mobility and difficulties with ADLs [23]. Additionally, immobilization can accelerate bone loss, increasing the risk of osteoporosis and fractures, further compromising the healing process and functional recovery [24]. Therefore, early weight bearing and minimizing immobilization are beneficial to preserve muscle strength, joint function, bone density, and overall functional recovery in older adults.

The CS-PFP-10 is a widely accepted and validated tool for assessing an individual's ability to perform ADLs. Its tasks are standardized with precise specifications, making it a valuable tool for cross-laboratory comparisons. Previous studies have utilized the CS-PFP-10 to evaluate patients with various medical conditions, including chronic obstructive pulmonary disease and heart failure, as well as to investigate the relationship between functional performance and the risk of falls [25‐27]. In our study, all young participants scored > 57, indicative of physical reserve and independent living status [28]. The results of our study demonstrate that older participants had significantly lower scores on both the total CS-PFP 10 score and all subcategories compared to their younger counterparts. Notably, three older participants scored below 47 on the CS-PFP 10 test, indicating a lower physical reserve and a dependent living status. Due to their self-reported independence, we included them in our analysis. We acknowledge that the use of subjective self-reported values rather than objective measurement tools such as the Short-Form Health Survey Physical Function scale may have limitations. Nevertheless, other measurements of cognitive function, weakness, and frailty did not reveal any significant difference between younger and older participants.

To accurately measure load bearing during ADLs, we utilized a wireless sensor insole (Open Go, Moticon, Germany), which has already been clinically validated [6]. This innovative technology has been utilized in various clinical studies, including those focused on gait analysis in older patients and also in Parkinson's patients [29] as well as analyzing pathological gait patterns after talus fractures [30]. Studies have shown that using sensors and providing biofeedback can improve adherence to weight-bearing restrictions [31, 32]. This adherence is crucial for successful post-surgical outcomes. Additionally, wireless sensor insoles can be particularly useful for patients in remote areas, allowing healthcare professionals to monitor adherence to weight-bearing instructions in telehealth settings [33]. To the best of our knowledge, this is the first study to use this technology for measurements of ADLs. In this study, we specifically directed our attention to ADLs rather than focusing on exercises typically performed in a rehabilitation setting. The rationale behind this choice was to investigate ADLs in order to refine post-surgical protocols not only within a rehabilitation environment but also in the patients' home and daily lives. Exercises often involve higher magnitudes of load and repetitive loading patterns compared to ADLs [34]. These exercises are designed to intentionally apply controlled loads to target specific muscle groups or achieve specific fitness goals. On the other hand, ADLs encompass a broader range of movements and loading patterns that may be less predictable or repetitive in nature.

Our results identified two tasks with a high load on the lower limb (> 1.5 BW) in all participants, regardless of age. Stair climbing (CS-PFP 10 task 9) and a 6-min walk (CS-PFP 10 task 10) resulted in the highest loads on the lower limb. We found a significant difference in maximum total forces between younger and older participants in the 6-min walk test (CS-PFP 10 task 10). However, there was no significant difference in the mean total force on the lower extremity load. The literature suggests that older individuals tend to adopt a more cautious gait [35]. Other studies have shown that age-related decline in muscular capabilities at the ankle may contribute to decreased walking performance in older adults [36]. Moreover, reduced overall muscular strength could negatively affect gait performance [37].

In conclusion, the utilization of the sensor insole provided valuable insight into the accurate and reliable measurement of lower extremity loading during various ADLs. The study results emphasize the significance of recognizing the high load on lower extremities during ADLs, regardless of age. For patients with weight-bearing restrictions, tasks such as stair climbing, and endurance walking require special attention due to the high loading. Future studies should investigate the impact of specific comorbidities on lower extremity force during ADLs in older adults. Overall, these findings highlight the potential for this technology to be used in clinical settings to evaluate lower extremity loading during ADLs and develop targeted interventions to improve physical function and independence.