Implant placement increases bone remodeling transiently in a rat model.

Area of Science:

• Orthopedic Surgery
• Biomaterials Science
• Bone Physiology

Background:

• Bone remodeling is crucial for bone health and response to orthopedic implants.
• Ovariectomy (ovx) in rats mimics postmenopausal bone loss, a common comorbidity affecting implant outcomes.
• Understanding implant-bone interactions is vital for improving implant longevity and patient recovery.

Purpose of the Study:

• To investigate the effects of intramedullary femoral implant placement on bone remodeling.
• To compare bone response in sham ovariectomy (sham-ovx) and ovariectomy (ovx) rat models.
• To evaluate the temporal changes in bone formation and volume around implants.

Main Methods:

• 88 female Sprague-Dawley rats underwent sham-ovx or ovx.
• Bilateral intramedullary femoral implants were placed in 71 rats, with follow-ups at 4, 8, and 12 weeks.
• Microcomputed tomography and histomorphometry were used to assess bone volume, architecture, and remodeling parameters.

Main Results:

• Implant placement did not alter bone volume compared to baseline controls in either sham-ovx or ovx groups.
• Significant increases in mineralizing surface, mineral apposition rate, and bone formation rate were observed at trabecular and endocortical surfaces within 4-8 weeks.
• Periosteal bone formation also increased at 4 weeks post-implantation, returning to baseline by 8 weeks.

Conclusions:

• Intramedullary implant placement induces a transient increase in bone remodeling activity around the implant.
• This localized bone formation response occurs without affecting overall bone volume in both sham-ovx and ovx models.
• The findings suggest that implants stimulate a temporary bone remodeling response that resolves over time.