Joints

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Schematic of a synovial joint. (WC/OpenStax College)

Joints are important for locomotion. This article collects tidbits about their pathology.

A general differential diagnosis for joints is dealt with in the cartilage article.

Septic arthritis

Septic joint redirects here.

General

  • Uncommon.
  • May be treated in a one-stage or two-stage procedure.[1]

Microscopic

Features:

Note:

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RIGHT FEMORAL HEAD AND SURROUNDING TISSUE, REMOVAL:
- OSTEOMYELITIS, ACUTE.
- OSTEONECROSIS, FOCAL.
- DEGENERATIVE JOINT DISEASE.
- SOFT TISSUE WITH FOCAL NECROSIS AND COCCI MICROORGANISMS, CORRELATION
  WITH MICROBIOLOGY SUGGESTED.
- NEGATIVE FOR MALIGNANCY.

Prosthetic joint infection

General

  • Bits of tissue come for frozen section to r/o infection.
  • The interface membrane (not the pseudocapsule) should be sampled to obtain a high sensitivity.[2]

Microscopic

Features:

  • Neutrophils - key feature.

Notes:

  • Various criteria for the number of neutrophils exist (see below).[3]
    • The definitions suffer from HPFitis.
  • Finding of plasma cells and lymphocytes is not contributory for the diagnosis of infection.[3]
  • Granulomatous inflammation that isn't of a foreign-body type should get the usual work-up.[4]

Feldman criteria

  • >= Five neutrophils / HPF (x400) assessed in at least five separate microscopic fields.[3][2]

Athanasou criterion

  • >= Ten neutrophils / ten HPF (x400).[3]

A comparison of the criteria

A study by Bori et al.[3] compared the criteria of Feldman and Athanasou:

Measure Feldman Athanasou
Sensitivity 29% 71%
Specificity 100% 64%

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Tissue from Left Hip, Revision Arthroplasty:
- Connective tissue with focally increased neutrophils (at least 
  11 neutrophils/HPF).
- Negative for microorganisms with routine stains.
- NEGATIVE for malignancy.

Comment:
The findings raise the possibility of a joint infection; correlation with 
cultures is required.

1 HPF = 0.2376 mm*mm.

Block letters

HEMATOMA, RIGHT HIP, IRRIGATION AFTER HIP REPLACEMENT/TISSUE REMOVAL:
- FIBROADIPOSE TISSUE WITH POSTSURGICAL CHANGES INCLUDING:
-- FOREIGN-BODY TYPE MULTINUCLEATED GIANT CELLS AND FOREIGN MATERIAL.
-- GRANULATION TISSUE.
-- FAT NECROSIS (FOCAL).
- FIBRIN, BLOOD.
- NEUTROPHILS IN BLOOD VESSEL WALLS/PERIVASCULAR (FOCAL), SEE COMMENT.
- NEGATIVE FOR MICROORGANISMS WITH ROUTINE STAIN.

COMMENT:
Up to 17 neutrophils per high power field (0.55 mm field diameter) are seen.

FEMUR, LEFT, BIOPSY:
- BONE MARROW WITH A PATCHY MILD FOCAL PROMINENCE OF PLASMA CELLS AND NEUTROPHILS.
- FIBROUS TISSUE WITH HEMOSIDERIN, ISOLATED NEUTROPHILS AND RARE
MACROPHAGES.
- BONE FRAGMENTS.
- NEGATIVE FOR MICROABSCESS FORMATION.
- NEGATIVE FOR MICROORGANISMS WITH ROUTINE STAINS.

BONE AND SOFT TISSUE, LEFT HIP, EXCISION:
- FIBROADIPOSE TISSUE, SKELETAL MUSCLE AND FRAGMENTS OF BONE WITH SURGICAL CHANGES.
- NEGATIVE FOR MICROABSCESS FORMATION.
- NEGATIVE FOR MICROORGANISMS WITH ROUTINE STAINS.

Juxta-articular myxoma

  • Abbreviated JAM.

General

  • Classically present as a mass or with pain.[5]
  • May recur.
  • Described as (microscopically) indistinguishable from intramuscular myxoma.[6]

Gross

Features:

  • Close to large joints - classically around the knee.
    • >85% of cases around the knee in one large series.[5]

Microscopic

Features:[5]

  • Myxomatous stroma.
  • +/-Cystic changes.
  • Large nuclei with hyperchromasia and nuclear scalloping.[7]

DDx:

Images:

Morton neuroma

Main article: Morton neuroma

Ganglion cyst

Main article: Ganglion cyst

Rheumatoid arthritis

Main article: Rheumatoid arthritis

Acute synovitis

Main article: Acute synovitis

See also

References

  1. ↑ Chen CE, Wang JW, Juhn RJ (October 2008). "Total hip arthroplasty for primary septic arthritis of the hip in adults". Int Orthop 32 (5): 573–80. doi:10.1007/s00264-007-0366-1. PMC 2551720. PMID 17483946. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2551720/.
  2. ↑ 2.0 2.1 Bori, G.; Muñoz-Mahamud, E.; Garcia, S.; Mallofre, C.; Gallart, X.; Bosch, J.; Garcia, E.; Riba, J. et al. (Apr 2011). "Interface membrane is the best sample for histological study to diagnose prosthetic joint infection.". Mod Pathol 24 (4): 579-84. doi:10.1038/modpathol.2010.219. PMID 21131917.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Bori, G.; Soriano, A.; García, S.; Mallofré, C.; Riba, J.; Mensa, J. (Jun 2007). "Usefulness of histological analysis for predicting the presence of microorganisms at the time of reimplantation after hip resection arthroplasty for the treatment of infection.". J Bone Joint Surg Am 89 (6): 1232-7. doi:10.2106/JBJS.F.00741. PMID 17545426.
  4. ↑ URL: http://path.upmc.edu/cases/case174.html. Accessed on: 8 January 2012.
  5. ↑ 5.0 5.1 5.2 Meis, JM.; Enzinger, FM. (Jun 1992). "Juxta-articular myxoma: a clinical and pathologic study of 65 cases.". Hum Pathol 23 (6): 639-46. PMID 1592386.
  6. ↑ Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 624. ISBN 978-0781765275.
  7. ↑ URL: http://path.upmc.edu/cases/case38/micro.html. Accessed on: 2 January 2011.
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