Joints

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

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.[1]

Microscopic

Features:

  • Neutrophils - key feature.

Notes:

  • Various criteria for the number of neutrophils exist (see below).[2]
    • The definitions suffer from HPFitis.
  • Finding of plasma cells and lymphocytes is not contributory for the diagnosis of infection.[2]
  • Granulomatous inflammation that isn't of a foreign-body type should get the usual work-up.[3]

Feldman criteria

  • >= Five neutrophils / HPF (x400) in at least five separate microscopic fields.[2][1]

Athanasou criterion

  • >= Ten neutrophils / ten HPF (x400).[2]

Juxta-articular myxoma

  • Abbreviated JAM.

General

  • Classically present as a mass or with pain.[4]
  • May recur.
  • Described as (microscopically) indistinguishable from intramuscular myxoma.[5]

Gross

Features:

  • Close to large joints - classically around the knee.
    • >85% of cases around the knee in one large series.[4]

Microscopic

Features:[4]

  • Myxomatous stroma.
  • +/-Cystic changes.
  • Large nuclei with hyperchromasia and nuclear scalloping.[6]

DDx:

Images:

Morton neuroma

Ganglion cyst

General

  • Very common.
    • Most common tumour of the hand.[7]
  • Classically on the wrist.[8]

Microscopic

Features:[7]

  • Empty space(s); usually multiple.
  • Fibrotic wall.
  • No epithelial lining.†


† The entity is really a pseudocyst.[7]

DDx:

Images:

Rheumatoid arthritis

See also

References

  1. 1.0 1.1 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.
  2. 2.0 2.1 2.2 2.3 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.
  3. URL: http://path.upmc.edu/cases/case174.html. Accessed on: 8 January 2012.
  4. 4.0 4.1 4.2 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.
  5. 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.
  6. URL: http://path.upmc.edu/cases/case38/micro.html. Accessed on: 2 January 2011.
  7. 7.0 7.1 7.2 URL: http://emedicine.medscape.com/article/1253223-overview]. Accessed on: 8 February 2012. Cite error: Invalid <ref> tag; name "emed_gc" defined multiple times with different content
  8. Hasham, S.; Burke, FD. (May 2007). "Diagnosis and treatment of swellings in the hand.". Postgrad Med J 83 (979): 296-300. doi:10.1136/pgmj.2005.043992. PMID 17488856.