Bone island and hand involvement - A short review

Abstract

Bone island or enostosis is an enigmatic lesion affecting the skeleton system. As these anomalies have limited clinical implications owing to an asymptomatic course with most cases diagnosed incidentally, the exact etiopathogenesis is not clearly understood. A lot has been studied regarding radiological features and morphology despite scarce clinical cases and relevant studies. More research is warranted to provide in-depth details of these lesions that has potential to enlighten us with newer aspects of bone metabolism and properties. These lesions might just not be an aberration and may offer important clues about bone behavior and morphogenesis. Bone islands, when in large number, are associated with equally fascinating disorder called osteopoikilosis. This review, however, does not include osteopoikilosis on purpose. Hand involvement, although rarer, has been described and a short review is attempted to acknowledge that apart from relevant facts on diagnosis and management.

Atypical Enostoses—Series of Ten Cases and Literature Review

“…Although the exact etiology is unknown, some authors hypothesize that BI arise due to misplaced hamartomatous cortical bone that failed to resorb during endochondral ossification [ 2 , 14 ]. The presence of numerous enostoses usually simply represents the condition osteopoikilosis (autosomal dominant; multiple BI; seen in two of the current cases) but rarely they may be associated with osteopathia striata (Voorhoeve’s disease), melorheostosis (unknown etiology; typified by candle wax dripping appearance of extra bone on the surface), Gardner’s syndrome (autosomal dominant; osteopoikilosis or multiple osteomas with colonic polyposis and sometimes extra-abdominal desmoid tumors and/or sebaceous cysts; the syndrome occurring in one of the current cases), Buschke-Ollendorff syndrome (autosomal dominant; osteopoikilosis and cutaneous nevi) and Gunal-Seber-Basaran syndrome (autosomal dominant; osteopoikilosis and dacrocystitis) [ 6 , 11 , 15 , 16 , 17 , 18 ].…”

“…Enostoses are typically discovered incidentally on imaging. Plain radiographs display a homogenously dense, oval, round or oblong shaped sclerotic focus in the cancellous bone with peripheral radiating bony spicules (“rose thorn,” “thorny radiations” or “spokes”) that blend with the surrounding normal trabeculae [ 1 , 6 ]. On CT scan, enostoses appear as a low attenuation focus without central radiolucency and the typical peripheral radiating spicules.…”

“…BI have a predilection for the pelvis, femur and ribs but have also been documented in the mandible, spine, carpal and tarsal bones, among other sites [ 6 , 10 , 14 , 22 ]. In the cases presented, sclerotic appearing enostoses were found in the pelvis, proximal and distal femur and spine in accordance with the literature.…”

“…Small, asymptomatic enostoses are managed conservatively by observation with periodic imaging. However, atypical features of enostosis such as pain, increased uptake on bone scintigraphy and enlargement mimic characteristics of active benign or malignant bone lesions, creating a differential diagnosis including osteoid osteoma, osteoblastoma, low-grade central osteosarcoma and metastatic carcinoma [ 6 ]. Atypical enostoses may pose a diagnostic challenge, potentially requiring biopsy to determine the diagnosis, as was done in seven of our cases.…”

“…Enostosis, also known as bone island (BI), is a common benign osseous lesion that consists of a focus of compact (cortical) bone within cancellous (spongy) bone [ 1 , 2 ]. Characteristically, enostoses are asymptomatic, “cold” on bone scintigraphy and stable metabolically with scarce evidence of documented growth [ 2 , 3 , 4 , 5 , 6 ]. However, when enostoses display atypical features of pain, increased radiotracer uptake, and/or enlargement, they can be difficult to differentiate from more sinister bony lesions such as osteoblastic metastasis, low-grade central osteosarcoma, osteoid osteoma and osteoblastoma.…”