[Nora's lesion. Discussion of a rare bone proliferation]

First presentation of a Nora-lesion of the talus in a paraossal fasciitis

Nora-Lesion is a proliferation that normally develops out of an intact corticalis. The entity of this fibroostotic pseudotumor, as discussed in literature, is triggered from repeating trauma or reactive periosteitis. In the literature, there are more than 200 cases defined as Nora lesion. In the daily routine of medical offices or ambulances, the Nora- Lesion should be established as a differential diagnosis for a swelling of the foot. Our case report of a 49-year-old patient is the worldwide first description of a Nora lesion of the talus, as well as secondary of the calcaneus. In the immense differential diagnosis discussion for bony pathologies of the hindfoot the Nora-lesion should be now added.

[Bizarre parosteal osteochondromatous proliferation of the metatarsal bone]

A bizarre parosteal osteochondromatous proliferation (BPOP), also known as a Nora lesion, is a rare benign bone formation. It emanates mainly from the intact cortex of the metaphysis of short tubular bones (hands or feet). Conventional radiographs should be complemented using cross-sectional imaging modalities (CT/MRI). In the absence of symptoms a non-operative regime with radiological and clinical controls is possible. If symptomatic, excision biopsy is the treatment of choice, though a high recurrence rate has been reported. Histopathological examination confirms the diagnosis and typically shows an endochondral ossification zone and an unusually mineralized cartilaginous matrix referred to as "blue bone".

Differential diagnosis of BPOP arising in relation to patella

INTRODUCTION

Solitary exostosis is common at the metaphysis of long bones, and rarely may it develop in the lower pole of the patella. Usually it stops growing after skeletal maturity unless complicated. When the growth continues after skeletal maturity, other rare possibilities need to be considered such as bizarre parosteal osteochondromatous proliferation (BPOP). Though solitary exostosis is common at the metaphysis of long bones, very rarely it also develops in lower pole of the patella. Usually they stop growing after skeletal maturity unless complicated. When it starts after skeletal maturity and continues to grow, other rare possibilities like bizarre parostealosteochondromatousproliferation (BPOP) are to be thought of.

CASE REPORT

21 years male student presented with anterior midline painless progressive swelling over right knee joint of one year duration which was hard, non-tender, fixed to patella but mobile with patella. X ray showed midline heterogeneously radio-opaque swelling attached to inferolateral aspect of the anterior surface of patella. Patellar out line is fully maintained except the narrow site of tumour attachment. After exposing through midline incision, the swelling was found to incorporate the patellar tendon completely and an anterior vertical midline cleavage was found. The mass was deliberately detached along the cleavage and from intact patellar tendon. Almost full range of knee movement is obtained in operation table. Immediate post operative 10° quadriceps lag was corrected with quadriceps setting exercises in two weeks time. Histopathological examination demonstrated thin layer of cartilage cover, irregular lamellar bone in deeper zone and spindle cells between them without cytoplasmic atypia. Plenty of cartilage cells in different stages of maturation are seen without column formation. Marrow elements are absent. Periosteum could not be demonstrated and there was no other evidence of malignancy. Features simulate 'bizarre parosteal osteochondromatous proliferation'. There is no recurrence in five years of follow up.

CONCLUSION

When exostosis like lesions arise from unusual site and at an unusual age group, other rare conditions need to be investigated. Though the final diagnosis of BPOP is obtained after careful histo-pathological examination, the clinico-radiological findings are also relevant. As literature search indicates, this is possibly second incidence where BPOP arised from sesamoid bone and first from patella.