Chronic anterior tibial stress fractures in athletes: No crack but intense remodeling

Abstract

Purpose Delayed healing of anterior tibial stress fractures in athletes is related to high tensional forces acting across a putative fracture gap. These forces lead to crack propagation and create strains that exceed tissue differentiation thresholds for new bone to form in the gap. The “dreaded black line” is a radiographic hallmark sign of stress fractures considered to represent a transverse fracture gap. However, whether a fracture gap truly exists at the microscopic level remains unclear. The aim of this study was to describe the area of the “dreaded black line” microscopically and to identify signs of delayed healing. Methods Between 2011 and 2016, we included seven athletes with chronic anterior mid‐shaft tibial stress fractures. The fracture site was excised as a cylindrical biopsy. The biopsy was evaluated with micro‐CT and histology. The formation of new bone in the defect was evaluated radiographically. Results The “dreaded black line” seen on pre‐operative radiographs in all patients could not be seen on the microscopic level. Instead, the area of the putative crack showed widened resorption cavities, lined with active osteoblasts, and surrounded by immature bone. This area of intense remodeling seemed to create a false impression of a fracture line on radiographs. Complete cortical continuity was restored at the biopsy site at median 8 months (range 6‐13 months). Conclusion Tibial stress fractures in athletes normally show no fracture defect, but a region of increased remodeling. The healing process is already ongoing but seems mechanically insufficient.

Effects of Low Energy Availability on Bone Health in Endurance Athletes and High-Impact Exercise as A Potential Countermeasure: A Narrative Review

“…The relationships between acute changes in markers of bone formation and resorption in response to LEA and longterm bone health are unclear. Sustained and localized acceleration of bone remodeling may play a role in the pathogenesis of bone stress injury in athletes [82,83]. However, bone (re)modeling markers are typically measured systemically and, therefore, any change in the balance of such markers does not necessarily reflect a change in bone remodeling at a specific site.…”

Radiological evaluation of pseudofracture after the administration of asfotase alfa in an adult with benign prenatal hypophosphatasia: A case report

“…However, only a small number of studies have reported the clinical course of pseudofracture healing in response to asfotase alfa in adult patients with infantile-, pediatric- or adult-onset HPP. The pseudofracture typically developed in the immaturely mineralized bone tissue, and the detailed evaluation of the pseudofracture in pediatric-onset HPP under treatment with asfotase alfa, using three-dimensional cone-beam computed tomography, indicated the pathophysiologic changes of the remineralization in the osteoid tissue ( Schilcher et al, 2019 ; Stürznickel et al, 2021 ). Rolvien et al assessed the healing course of fracture in adults with infantile-onset HPP under treatment with asfotase alfa by several modalities, including physical function tests, magnetic resonance imaging (MRI), and dual-energy X-ray absorptiometry ( Rolvien et al, 2019 ).…”

Pathophysiology of Demineralization, Part II: Enamel White Spots, Cavitated Caries, and Bone Infection

“…More persistent ROD associated with deep penetration of the cortical bone along phalanges is like cavitated caries. In addition, noncavitated caries are morphologically similar to resorption cavities during bone remodeling [2,3,30] or the osseous radiolucencies defined as traumatic cysts [31].…”

“…From a physiologic perspective, WSLs are localized pathologic processes (caries) that may or may not be active [83]. From an osseous perspective, a WSL is analogous to some manifestations of negative calcium balance, i.e., accelerated bone remodeling [30] or relatively quiescent bone cysts [31]. It is clear that bones and teeth are susceptible to severe destruction in the presence of sustained demineralization.…”