OPBSPathologyVigorita chapter 19
Routine orthopaedic operations send bone, soft tissue, fluid and implants to the laboratory. Knowing what each specimen can show, and how to send it, avoids missed tumours, infection and metabolic bone disease.
Must Know
- Arthroplasty specimens usually confirm the diagnosis but can reveal inflammatory arthritis, osteonecrosis or malignancy.
- Surgeon and histology diagnoses differed in 18.4 percent of hip and 9.4 percent of knee arthroplasties in one study.
- Sample synovium for inflammation, the cartilage bone junction for tidemarks and subchondral bone, marrow for haematopoiesis, and any gross lesion.
- In suspected tumour, send the blood clot. Tumour cells keep their morphology best in clot.
- Reamings are poor diagnostic material because reaming destroys architecture.
- Formal biopsy gives the best chance of diagnosis when pathological fracture is suspected.
- Surgical handling of bone can cause crush artefact.
- Increased osteoclasts, woven bone or irregular cement lines in any bone specimen point to metabolic disease such as Paget disease or hyperparathyroidism.
- Marked lymphoplasmacytic synovitis is not seen in osteoarthritis or trauma. Treat it as inflammatory arthropathy until proven otherwise.
- Elderly femoral fractures may hide osteomalacia, best shown on undecalcified sections.
- Atypical fractures on bisphosphonates justify examining the fracture fragments.
What Each Specimen Can Show
| Specimen | Pathologist looks for |
|---|---|
| Primary hip or knee arthroplasty | Synovitis type, tidemarks, subchondral bone, cysts, osteonecrosis, marrow |
| Revision arthroplasty tissue | Neutrophils per high power field, wear debris, type of inflammatory cell |
| Fracture fixation fragments and clot | Tumour type, callus stage, osteomalacia |
| Kyphoplasty bone | Lesion type, fracture repair, marrow cellularity |
| Loose bodies | Fibrinous or cartilaginous. Cartilaginous ones are primary (neoplastic) or secondary (reactive) |
| Disc | Cystic, mucinous and calcific change, notochordal remnants |
| Spinal fusion after BMP | Adverse BMP effects |
| Toe or foot amputation | Necrosis at the viable margin, organisms, fungi |
| Synovial fluid | Crystals, cell count, culture |
| Carpal tunnel tenosynovium | Grade of subsynovial neovascularity |
| Dupuytren cord | Myofibroblast proliferation, cellularity grade |
| Removed hardware | Gross inspection, culture if infected |
More on periprosthetic tissue and implants
- Sample several soft tissue sites so neutrophil numbers are reliable.
- Report the neutrophil number with the objective lens used, for example 7 per ×40 field.
- Metal debris turns tissue grey or black. Cement and polyethylene debris lighten it.
- Polarised light shows wear debris best.
- Describe the reaction as lymphocytic, histiocytic or foreign body giant cell, and quantify the debris.
- Polyethylene wears mostly by abrasion from third bodies and provokes a histiocytic osteolytic response.
- PMMA anchors implants as a grout and has no adhesive action.
- Silicone small joint implants can cause synovitis.
- Titanium forms an adherent oxide layer and resists corrosion, but wears poorly as a bearing.
More on other specimens
- Degenerate disc can show reactive chondrocyte proliferation that mimics a cartilage neoplasm.
- Fibrinous loose bodies suggest trauma or rheumatoid arthritis.
- Meniscal shavings are examined for degeneration.
- Deep bone and tissue scrapings give the most accurate cultures in foot infection.
- Silver methenamine or PAS stains show fungi.
- Urate crystals are yellow when parallel to the red compensator axis and blue when perpendicular.
- Marrow biopsy for a haematological disorder is best taken from the iliac crest.
- Soft tissue masses over 5 cm, deep to fascia or heterogeneous on MRI raise concern for sarcoma.
- Malignant excisions need margin assessment. Benign lesions are sampled serially to exclude malignancy.
Numbers to Remember
- Diagnostic discrepancy. 18.4 percent hip and 9.4 percent knee arthroplasty.
- Soft tissue mass concern. Over 5 cm or deep to fascia.
- Neutrophil report. Number per high power field with the lens power stated.
Memory Aids
- Clot keeps cells. Always send the clot when tumour is possible.
- Grey is metal, pale is plastic. Debris colour hints at its source.
Exam Traps
- Reamings rarely give a diagnosis. A formal biopsy is better.
- Lymphoplasmacytic synovitis points away from osteoarthritis.
- Reactive disc chondrocyte clusters are not chondrosarcoma.
- A neutrophil number means little without the field magnification.
- Woven bone or excess osteoclasts in a routine specimen is abnormal even without a named disease.
Source
Breceda AP, Bryk E. Commonly Performed Orthopaedic Procedures. In. Vigorita VJ, Ghelman B, Mintz D. Orthopaedic Pathology. 3rd ed. Philadelphia, Wolters Kluwer, 2016. Chapter 19.
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 17 October 2026.