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Pull-out strength of screws from polymethylmethacrylate cement
N E Motzkin1, E Y Chao, K N An
1Department of Orthopaedics, Mayo Clinic, Rochester, Minnesota 55905.
The Journal of Bone and Joint Surgery. British Volume
|March 1, 1994
Summary
The best way to insert screws into polymethylmethacrylate (PMMA) cement for stronger fixation is using fluid or solid insertion methods. Screws inserted into curing PMMA were significantly weaker, compromising screw fixation.
Area of Science:
- Orthopedic Surgery
- Biomaterials Science
- Mechanical Engineering
Background:
- Polymethylmethacrylate (PMMA) cement is widely used in orthopedic surgery for prosthetic fixation.
- Ensuring optimal screw fixation within PMMA is crucial for long-term implant stability.
- The method of screw insertion into PMMA may significantly impact construct strength.
Purpose of the Study:
- To evaluate and compare the pull-out strength of screws inserted into PMMA using different methods.
- To determine the optimal insertion technique for enhancing screw-PMMA fixation.
Main Methods:
- Six groups of ten axial pull-out tests were conducted.
- Two screw sizes (3.5 and 4.5 mm AO cortical) were tested.
- Three insertion methods were employed: fluid PMMA, solid PMMA (drilling and tapping), and curing PMMA.
Main Results:
- No significant difference in pull-out strength was observed between screw sizes.
- Screws inserted into fluid or solid PMMA exhibited comparable pull-out strengths.
- Screws inserted into curing PMMA demonstrated significantly lower strength (71% of solid PMMA strength).
Conclusions:
- Screw insertion into curing PMMA results in substantially weaker fixation.
- Both fluid and solid PMMA insertion methods provide robust screw fixation.
- Surgeons can choose between fluid or solid insertion based on procedural needs and preference for optimal fixation.