intraosseous ganglion cyst ( igc ) is a benign , no neoplastic bone lesion with histological similarity to the soft tissue ganglion cyst.1 , 2 intraosseous ganglion contains mucoid viscous material with no epithelial or synovial lining .
the radiolucent carpal lesions are usually symptom - free found incidentally on radiographs of the wrist performed for other reasons .
detecting a single radiolucent lesion in the lunate accompanied by pain is rare , and detecting a pathological fracture of the lunate revealing an intraosseous ganglion cyst is exceptional . isolated rare cases of intraosseous ganglion cysts in the carpal bones have been reported , most commonly in the lunate and the scaphoid.5 , 6 , 7 , 8 , 9 their etiology remains largely unknown ; however trauma , herniation of the joint capsule , mucoid degeneration , intramedullary metaplasia of mesenchymal cells , and congenital rests of synovial producing cells have been suggested to play a part .
we report a case of a pathological fracture of the lunate revealing an intraosseous ganglion cyst .
a 42-year - old female , with a history of right distal radius fracture , presented with right wrist pain following a fall on the palm of the right hand .
clinical study revealed a moderate swelling over the mid - section of the palmar face and pain through extreme ranges of motion of the wrist .
radiographic studies of the right wrist revealed a round - shaped defect with a fracture of the lunate ( fig .  1 ) .
ct scan confirmed a cystic lesion of the lunate and was able to localize the lesion and the fracture precisely ( fig .  2 ) .
the patient was operated upon using anterior surgical approach with a medial palmar extension ; both the lunate and the distal radius were exposed for harvesting vascularized bone .
a soft - tissue ganglion cyst communicating with the lunate intraosseous ganglion cyst was identified through a defect on the anterior side of the lunate . through the cortical defect
the cavity was rinsed with saline solution and packed using a vascularized bone graft based on the volar carpal artery , e.g. kuhlman 's vascularized radial bone graft ( fig .  3 ) .
after closing the joint capsule , the subcutaneous and cutaneous tissues , a removable wrist cast was applied for six weeks .
the content of the cyst was described anatomopathologically as a cystic formation with walls constituted by flattened , synovial - like , fibro - connective tissue cells with no true epithelial lining .
after a ten - month follow - up period she was completely relieved of pain without any limitation of the wrist motion .
in 1956 , hicks described radiolucencies with a sclerotic margin within bones as  synovial bone cysts  . in 1966 crabbe first used the term  intraosseous ganglion  .
synonymous terms include synovial bone cyst , ganglionic cystic defect of bone , subchondral bone cyst and juxta - articular bone cyst .
radiolucent carpal bone lesions are usually symptom - free found incidentally on radiographs of the wrist performed for other reasons .
their differential diagnosis includes igc , osteoarthritic cyst , post - traumatic cyst , simple bone cysts , and aneurysmal bone cyst .
when they present themselves as painful wrist , kienbock 's disease , osteoid osteoma and osteoblastoma should be included in a differential diagnosis list .
ganglia in the lunate is mostly located near the radiocarpal joint in the proximal part of the bone , and in the majority of cases turned toward the scaphoid .
most intraosseous ganglions in the scaphoid are located in the proximal portion near the lunate because about 70% of hand tissue - ganglia arise from the posterior side of the scapho - lunate joint.12 , 13 a lesion was classified as an intraosseous ganglion when histopathology was identical to soft - tissue ganglion cysts .
the wall of the cysts consists of fibrous , collagenous fibers similar to flattened histiocytes , partly mucoid - degenerated without epithelial cells and without synovial lining .
the cyst wall in general is surrounded by sclerotic bone with necrotic and regenerated  bone tissue.6 , 14 the causes of both soft tissue and intraosseous ganglion remain unsettled .
there seem to be two fundamental types of intraosseous ganglia : one originating by penetration of an extra - osseous ganglion into the underlying bone , the other being idiopathic .
erosion of an extraosseous ganglion through bone is the generally agreed - on mechanism for the penetrating type .
it seems that idiopathic type of ganglion cyst originates from modified mesenchymal or synovial cells at the capsule  synovial interface in response to repeated minor injury , explaining high prevalence of ganglion cyst in the scapho - lunate site where the motion and force is concentrated .
. then proliferation of fibroblasts and histocytes and production of hyaluronic acid with mucoid degeneration during tissue revitalization occur to form a cyst .
surgical treatment is indicated if the igc is symptomatic or if its size is growing in imaging findings .
growing igc can result in traumatic and collapsing fracture in the lunate with serious complications .
when igc has been completely stopped growing and there is no cortical defects or collapsing fractures , regular follow - up with radiography is recommended .
increased uptake in lunate area in a painful wrist indicates surgical treatment.17 , 18 treatment of igc consists in the curettage of the cyst , injection of saline solution and packing the cavity with cancellous bone graft . in our case an anterior approach was preferred and a kuhlman 's vascularized radial bone grafting was performed because of the palmar localization of the ganglion cyst within the lunate bone .
in addition to this approach , a dorsal approach or some alternative surgical techniques such as excision of the lunate , dorsal flap arthroplasty , prosthetic replacement , radiocarpal or intercarpal fusion are also used .
an igc should be suspected when patients present with pain or swelling of the wrist following a trauma along with a cyst with fine marginal sclerosis close to the scapholunate joint .
although ct scan shows the bony architecture , mri may better demarcate the tissues surrounding the bones . in conclusion ,
this case shows an unusual presentation of an intraosseous ganglion cyst of the lunate revealed by a pathological fracture . surgical treatment provided excellent outcome .
 intraosseous ganglion cyst of the carpal bones represents a rare cause of wrist pain . 
 we report a case of a 42 year - old , right - handed female , who presented with pain of the right wrist following a fall on the palm of the hand . clinical study revealed a moderate swelling over the mid - section of the palmar face and pain through extreme ranges of motion of the wrist . 
 plain radiographs and ct - scan of the wrist have revealed an intraosseous ganglion cyst of the lunate bone . curetting - filling by kuhlman 's vascularized radial bone graft allowed a good functional recovery . 
 the clinical , radiological and therapeutic aspects are discussed . 