Bone loss at the distal femur and proximal tibia in persons with spinal cord injury: imaging approaches, risk of fracture, and potential treatment options

Abstract

Persons with spinal cord injury (SCI) undergo immediate unloading of the skeleton and, as a result, have severe bone loss below the level of lesion associated with increased risk of long-bone fractures. The pattern of bone loss in individuals with SCI differs from other forms of secondary osteoporosis because the skeleton above the level of lesion remains unaffected, while marked bone loss occurs in the regions of neurological impairment. Striking demineralization of the trabecular epiphyses of the distal femur (supracondylar) and proximal tibia occurs, with the knee region being highly vulnerable to fracture because many accidents occur while sitting in a wheelchair, making the knee region the first point of contact to any applied force. To quantify bone mineral density (BMD) at the knee, dual energy x-ray absorptiometry (DXA) and/or computed tomography (CT) bone densitometry are routinely employed in the clinical and research settings. A detailed review of imaging methods to acquire and quantify BMD at the distal femur and proximal tibia has not been performed to date but, if available, would serve as a reference for clinicians and researchers. This article will discuss the risk of fracture at the knee in persons with SCI, imaging methods to acquire and quantify BMD at the distal femur and proximal tibia, and treatment options available for prophylaxis against or reversal of osteoporosis in individuals with SCI.

Locomotor training with adjuvant testosterone preserves cancellous bone and promotes muscle plasticity in male rats after severe spinal cord injury

“…Bone loss, muscle loss, and impaired muscle contractile properties are hallmarks of SCI (Biering-Sorensen et al, 2009) that contribute to the high fracture risk in this population (Cirnigliaro et al, 2017). Reduced weight bearing and low testosterone (Abilmona et al, 2018) are factors that influence these bone and muscle deficits, suggesting that combinatory therapies addressing both impairments may enhance musculoskeletal recovery after motor-incomplete SCI (Otzel, Lee, et al, 2018).…”

“…Bone outcomes were evaluated at the distal femur or proximal tibia because these skeletal sites display dramatic bone loss and are the most prone to fracture in persons with SCI (Cirnigliaro et al, ). Muscle outcomes were evaluated in the soleus because it is mostly composed of type I fibers that exhibit significant atrophy (Phillips et al, ) and a phenotypic slow‐oxidative to fast‐glycolytic fiber‐type transition in response to disuse and because the rat soleus is recruited during locomotion and standing (Jayaraman et al, ; Liu et al, , ; Stevens et al, ).…”

“…However, after more severe SCI, humans (Behrman, Ardolino, & Harkema, ) and animal models (Battistuzzo, Callister, Callister, & Galea, ) exhibit only minimal muscular improvement and negligible recovery of over‐ground walking ability in response to bodyweight‐supported TM training. Similarly, the effectiveness of TM training and of other reloading strategies in regenerating bone after SCI remains contentious (Panisset, Galea, & El‐Ansary, ), especially at the sites most prone to fracture (i.e., distal femur and proximal tibia) in this population (Cirnigliaro et al, ). These results suggest that alternative regenerative rehabilitation strategies are needed to enhance musculoskeletal recovery after more severe SCI (Leon & Dy, ).…”

Fatigue in complete spinal cord injury and implications on total delay

“…This causes greater susceptibility to bone fractures, mostly in long bones . The risk of fractures increases considerably in the knee joint due to the demineralization of the epiphysis of the trabecular bones, distal femur, and proximal tibia . To avoid bone fracture, we developed the F ms protocol for this study, which was effective for ensuring the integrity of the knee joint of all participants during the essay.…”

“…Regarding the control of variables in experiments with SCI, the main studies indicate the intensity of electrical stimulation but do not report the control of the intensity level of force production. A hypothesis for this could be the high risk of bone fractures …”