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 (with the exception of Morawietz et al.[4]) 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.[5]

Feldman criteria

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

Athanasou criterion

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

Morawietz criteria

  • 23 neutrophils / 10 HPF, where the field diameter = 0.625 mm.[4]

Notes:

  • The 0.625 mm field diameter is uncommon; it corresponds to a 25 mm eye piece with a 40x objective (25 mm/40 = 0.625 mm).
    • The PMNs/area is: 23 PMNs / (pi/4*0.625^2) = 7.49 PMNs/mm*mm
  • If one uses a 22 mm eye piece microscope and the 40x objective, the field diameter is 0.55 mm; thus, one would need to count PMNs in 12.91 HPFs ( 3.0680 mm*mm / 0.2376 mm*mm = 12.91 ) to get the same sample area.

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.[6]
  • May recur.
  • Described as (microscopically) indistinguishable from intramuscular myxoma.[7]

Gross

Features:

  • Close to large joints - classically around the knee.
    • >85% of cases around the knee in one large series.[6]

Microscopic

Features:[6]

  • Myxomatous stroma.
  • +/-Cystic changes.
  • Large nuclei with hyperchromasia and nuclear scalloping.[8]

DDx:

Images:

Morton neuroma

Ganglion cyst

Rheumatoid arthritis

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. //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. 4.0 4.1 Morawietz, L.; Tiddens, O.; Mueller, M.; Tohtz, S.; Gansukh, T.; Schroeder, JH.; Perka, C.; Krenn, V. (Jun 2009). "Twenty-three neutrophil granulocytes in 10 high-power fields is the best histopathological threshold to differentiate between aseptic and septic endoprosthesis loosening.". Histopathology 54 (7): 847-53. doi:10.1111/j.1365-2559.2009.03313.x. PMID 19635104.
  5. URL: http://path.upmc.edu/cases/case174.html. Accessed on: 8 January 2012.
  6. 6.0 6.1 6.2 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.
  7. 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.
  8. URL: http://path.upmc.edu/cases/case38/micro.html. Accessed on: 2 January 2011.