Cut Cortical Screw Purchase in Diaphyseal Bone: A Biomedical Study

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Materials Science

Background:

• During fracture osteosynthesis, surgeons sometimes cut and reinsert screws that are too long to minimize waste.
• The impact of this practice on screw purchase, a critical factor in fracture fixation, is not well understood.

Purpose of the Study:

• To determine if cutting excess length from a screw affects its purchase in bone.
• To evaluate this practice in both normal and osteoporotic bone models.

Main Methods:

• Maximal insertion torque (MIT) was measured for 3.5 mm stainless steel cortical screws.
• Tests were conducted on normal and osteoporotic bone models under three conditions: long screw (LS) insertion, LS removal followed by normal screw (NS) insertion, and LS removal followed by cut screw (CS) insertion.

Main Results:

• In normal bone, mean MIT was highest for LS insertion (546 N-cm), followed by NS (496 N-cm) and CS (465 N-cm).
• In osteoporotic bone, mean MIT was 110 N-cm for LS, 98 N-cm for NS, and 101 N-cm for CS.
• No significant difference in MIT was found between CS and NS reinsertions in osteoporotic bone models.

Conclusions:

• Cutting excess length from a screw does not decrease its purchase.
• Reinserting a shortened screw is a viable cost-saving strategy in osteosynthesis.
• This practice does not compromise fracture fixation, regardless of bone density.