5.2 Orthopedic Instruments: Total Joints

Arthroplasty Is a Measuring Operation

A joint replacement is a sequence of precise cuts and precise sizes. Almost every instrument in a total joint tray exists to guide a cut, measure a size, prepare a surface, trial a fit, or seat an implant. That is why arthroplasty instrumentation is far more system-specific than any other orthopedic tray: the guides and trials only make sense with the implants they were designed for.

---

Total Knee Arthroplasty (TKA) Instrumentation

Total Hip Arthroplasty (THA) Instrumentation

---

Trials Versus Implants

This distinction is a genuine patient-safety issue and a favourite exam point.

• A trial is a reusable, non-implantable component used to test size and fit intraoperatively. It is processed with the instruments, and it is often colour-anodized or marked "TRIAL" precisely so it is not confused with an implant.
• An implant is the sterile device that stays in the patient. Implants have their own handling, documentation, lot-tracking, and sterilization requirements (Chapter 9), including the rule that implants are not processed by immediate-use steam sterilization except in a documented emergency, and that an implant load carries a biological indicator in a process challenge device.

A trial released into the implant caddy — or an implant used as a trial — is a serious event. Assemblers verify trial and implant positions against the count sheet and never intermix the two.

---

The Two Dominant Inspection Concerns

1. Cutting guides and jigs

The saw blade runs in a slot in the cutting block. As the block ages, the slot widens and the pin holes elongate. The result is a block that still looks perfect but no longer constrains the blade, so the resection wanders and the component sits malaligned.

Inspection therefore covers:

• Slot edges — sharp-edged, parallel, not belled or burred
• Pin holes — round, not oval, not enlarged
• Any bend, twist, or crack in the block body
• Legible size and left/right markings
• Mating fit with the alignment handle or tower

A guide showing slot wear is a vendor service or replacement item; it cannot be corrected in-house.

2. Broaches, rasps and reamers

These carry aggressive cutting teeth that pack with bone slurry, marrow, and fat. They are among the hardest instruments in the department to clean, and they are frequently cited in cleaning-verification failures.

Expectations:

• Prompt point-of-use moisture retention; dried marrow in a broach tooth pattern is very difficult to remove
• Dedicated brushing of each tooth row, and brushing of any cannulation
• Verification with a cleaning-verification test or visual inspection under magnification
• Inspection for chipped, rounded, or missing teeth — a dull reamer burnishes rather than cuts
• Inspection of the driver connection (Hudson, trinkle, or system-specific) for wear and free engagement

---

System Discipline

Total joint instruments are system- and generation-specific. A cutting block from one manufacturer's implant line does not produce a correct cut for another's, and even within a manufacturer, a guide from an earlier generation may not match the current implant geometry. Instruments must therefore be kept in their own case, matched against the system-specific count sheet, and never "borrowed" from an adjacent tray to fill a gap. Where the set is a vendor loaner, the whole loaner workflow in Chapter 9 applies.

Modularity and the Real Cost of a Missing Size

Arthroplasty instrumentation is built as a system: a family of sizes that step through the anatomical range, with each trial, broach, cutting block, and reamer keyed to a specific implant size. That structure creates a failure mode that does not exist for general sets. A total knee tray missing the size-4 femoral trial is not a tray that is slightly incomplete; it is a tray that cannot be used if the patient measures size 4, and the discovery happens with the joint open.

This is why arthroplasty count sheets itemise every size individually, why the trays are usually numbered and processed as a matched group rather than as independent boxes, and why the specialist's count must be against the sheet, size by size, rather than a visual impression of fullness. When a size is genuinely missing, the set is held and the vendor or the OR is notified before the case — never sent with a note.

Cemented and Cementless Technique

The fixation method changes the instrument list, and the exam may test the association.

Cemented arthroplasty requires bone cement mixing and delivery equipment, a cement restrictor and its inserter, cement removal instruments such as osteotomes and curettes for revision, and pulsatile lavage for cleaning the bone bed. Cementless (press-fit) arthroplasty relies on precise bone preparation for an interference fit, so the broaches, rasps, and reamers carry the load and their cutting-tooth condition is directly clinically significant.

Revision sets add extraction instruments, flexible reamers, and cement-removal osteotomes, and they are typically loaner sets, which brings the whole loaner workflow with them.

Why Cutting Teeth Are the Priority Inspection

Broaches, rasps, reamers, and saw blades cut bone, and dull cutting surfaces do not simply work more slowly — they generate heat, produce an oversized or ragged cut, and compromise the press fit the implant depends on.

Inspect every cutting tooth under magnification along the whole working surface, looking for rounding, chipping, and packed bone debris in the flutes. Retained bone and marrow in reamer flutes and broach teeth is both a cleaning failure and a cutting failure, and these items frequently require dedicated brushes and manual attention before any automated cycle.

Cutting guides and jigs must be checked for slot integrity and flatness: a slot worn oversize lets the saw blade wander, and a bent jig transfers its error directly into the bone cut.