Involucrum

An involucrum (plural involucra) is a layer of new bone growth outside existing bone.

There are two main contexts:

In pyogenic osteomyelitis where it is a layer of living bone that has formed about dead bone.^[1] It can be identified by radiographically (i.e., with x-rays).
In cetaceans such as whales, it is a thick covering of bone over the middle-ear space.^[2]^[3]

References

^ Pineda, Carlos; Espinosa, Rolando; Pena, Angelica (May 2009). "Radiographic Imaging in Osteomyelitis: The Role of Plain Radiography, Computed Tomography, Ultrasonography, Magnetic Resonance Imaging, and Scintigraphy". Semin Plast Surg. 23 (2): 080–089. doi:10.1055/s-0029-1214160. PMC 2884903. PMID 20567730.
^ "Science Word of the Day: Involucrum". National Geographic. 2015-01-05. Archived from the original on October 30, 2018. Retrieved 29 October 2018.
^ Switek, Brian (1 December 2010). "How Did Whales Evolve?". Smithsonian. Retrieved 30 October 2018.

Bone and joint disease

Bone

Inflammation

endocrine:	Osteitis fibrosa cystica Brown tumor
infection:	Osteomyelitis Sequestrum Involucrum Sesamoiditis Brodie abscess Periostitis Vertebral osteomyelitis

Other

Chondritis	Costochondritis Relapsing polychondritis
Other	Slipping rib syndrome Tietze syndrome

Combined

leg:	hip Legg–Calvé–Perthes disease tibia Osgood–Schlatter disease Blount's disease foot Köhler disease Sever's disease
spine	Scheuermann's disease
arm:	wrist Kienböck's disease elbow Panner disease