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Published on: February 10, 2014
Improved extraction torque of hydroxyapatite-coated pedicle screws
B Sandén1, C Olerud, C Johansson
1Department of Orthopaedic Surgery, Uppsala University Hospital, Sweden. bengt.sanden@ortopedi.uu.se
Summary
Hydroxyapatite coating significantly enhances pedicle screw fixation in spinal instrumentation. This biomaterial coating improves screw anchorage, reducing loosening and increasing extraction torque compared to standard screws.
Area of Science:
- Biomaterials Science
- Orthopedic Surgery
- Spinal Instrumentation
Background:
- Pedicle screw loosening is a common complication in spinal instrumentation.
- Hydroxyapatite coating is known to improve metal implant fixation.
- The effect of hydroxyapatite on pedicle screw anchorage was previously undescribed.
Purpose of the Study:
- To evaluate the effect of hydroxyapatite coating on the anchorage and stability of pedicle screws.
- To compare insertion and extraction torque of hydroxyapatite-coated versus standard pedicle screws.
Main Methods:
- Seven patients underwent spinal instrumentation with four stainless steel pedicle screws each.
- Hydroxyapatite-coated screws were used in either the upper or lower instrumented levels.
- Insertion torque was measured, and extraction torque was measured after 10-22 months in four cases.
Main Results:
- Mean insertion torque was significantly higher for hydroxyapatite-coated screws (107 Ncm) than standard screws (76 Ncm).
- Extraction torque for coated screws exceeded 600 Ncm in three cases, while conventional screws were loose (< 5 Ncm).
- Significant differences in extraction torque were observed, with coated screws demonstrating vastly superior purchase.
Conclusions:
- Hydroxyapatite coating effectively improves pedicle screw purchase and stability.
- Fully coated screws provide excellent anchorage but may pose extraction challenges.
- Modifying the coated area could optimize enhanced purchase while facilitating easier extraction.
