Osteoporosis is a systemic disease characterized by deterioration of bone microarchitecture, decreased bone mineral density (BMD), and an increased risk of fractures.1 Lower limb amputation may negatively affect BMD and increase fracture risk.2,3 Many individuals with lower limb amputation experience significant BMD loss due to reduced mechanical loading on the bones following amputation.2

In individuals with amputation, BMD loss occurs mainly on the amputated side, whereas those having proximal-level amputation and delayed ambulation are at greater risk.2,4 Individuals who undergo transfemoral amputation (TFA) experience greater BMD loss than individuals undergoing transtibial amputation (TTA).4,5 Lower extremity amputations and especially TFAs, which carry an elevated risk of falls, lead to a decrease in hip BMD and increase the risk of hip fracture, which is an important problem for society, economy, and individuals. Therefore, it is important to evaluate BMD in these individuals and intervene in a timely manner.6,7

In individuals with TFA, residual limb length (RLL) is a factor affecting gait results and development of atrophy in hip joint muscles.8,9 An increased RLL provides a longer lever arm. Longer residual limbs can produce higher joint moments.9 Less muscle mass and muscle strength can reduce skeletal load, leading to poor bone health and an increased risk of osteoporosis. In addition to muscle mass, muscle strength is also an important determinant of bone health.10 Both bone microarchitecture and bone mass have been reported to be associated with muscle strength.1,11 During walking, individuals with unilateral amputation have greater muscle strength in the intact limb. The lower loading on the amputated limb may accelerate bone loss throughout the bone remodeling cycle, resulting in localized unloaded osteoporosis.3

To our knowledge, this is the first study to examine the relationship between BMD and muscle strength, RLL, and other factors in individuals with unilateral TFA. Many factors may affect BMD on the amputated side in individuals after amputation. The aim of this study was to determine the relationship between muscle strength on the amputated side, RLL and BMD in individuals with traumatic unilateral TFA and to identify other potentially related characteristics.