Overview
ISO 5835:1991 specifies dimensions and tolerances for metal bone screws used in surgery that have a hexagonal drive connection, spherical under‑surface of head, and asymmetrical thread. The standard defines two thread series - shallow (HA) for cortical screws and deep (HB) for cancellous/spongiosa screws - and gives the identification code, dimensional tables and figures, and limits for thread profile variation. Marking and packaging requirements are referenced to ISO 6018. Informative annexes provide an example of a combined screw (Annex A), an interrelationship map with related implant and tool standards (Annex B), and a bibliography (Annex C).
Key topics and requirements
- Scope: Dimensions and tolerances for HA (shallow) and HB (deep) asymmetrical threads; all dimensions in millimetres.
- Thread coding: Use code HA for shallow (cortical) and HB for deep (cancellous) screws.
- Design detail control: Drive connection, under‑surface head shape and thread form are critical interfaces with plates and instruments; no variation is permitted in these areas.
- Dimensional data: HA series defined in figures 1–2 and tables 1–2; HB series in figures 3–4 and tables 3–4.
- Thread profile variation limits (recommended):
- HA 1.5 and HA 2: maximum deviation 0.050 mm from theoretical profile
- HA 2.7 to HA 5: maximum deviation 0.075 mm
- HB series: maximum deviation 0.075 mm
- Pitch note: Example difference - HA 4 pitch is 1.5 mm while HB 4 is 1.75 mm.
- Marking & packaging: To be in accordance with ISO 6018.
- Mechanical requirements and tests: Referenced to ISO 6475 (mechanical requirements and test methods for asymmetrical‑thread bone screws).
Applications and users
ISO 5835 is essential for:
- Orthopaedic implant manufacturers designing and producing metal bone screws to ensure dimensional interchangeability and fit with plates and tools.
- Surgical instrument makers (hexagon keys, drivers, taps, drills, countersinks) to match drive connections and head geometry.
- Quality assurance and regulatory teams verifying dimensional tolerances, thread profiles and packaging/marking compliance.
- Procurement and hospital device committees assessing compatibility and standard compliance of supplied screws and plates.
Practical uses include design validation, production inspection, acceptance testing, and ensuring compatibility between screws, bone plates and driving tools.
Related standards
- ISO 6475 - mechanical requirements and test methods for asymmetrical thread screws
- ISO 6018 - marking, packaging and labelling of orthopaedic implants
- ISO 5836 / ISO 9269 - related plate hole/slot and under‑surface forms
- ISO 8319‑1 / ISO 8319‑2 - drive connections, keys and screwdrivers
- ISO 9268 - screws with conical under‑surface (for comparison and combined designs)
Keywords: ISO 5835, metal bone screws, hexagonal drive, spherical under‑surface, asymmetrical thread, dimensions, tolerances, HA, HB, orthopaedic implants.