Abstract We report on a 9-year-old boy who has type II autosomal dominant osteopetrosis associated with a chronic grade II slipped capital femoral epiphysis. He was treated with a single cannulated screw. This rare association has been reported only once. Keywords Osteopetrosis · Slipped capital femoral epiphysis · In-situ pinning Introduction Osteopetrosis, first described by Albers-Schonberg in 1904 and then by Karschner in 1926, is a rare bone dys- plasia characterized by functional deficiency of osteo- clasts leading to failure of bone resorption and persistence of calcified chondroid and primitive bone. At least 20 dif- ferent types of osteopetrosis have been described in ani- mals and humans [8]. The main human variants were cat- egorized as malignant autosomal recessive infantile form, milder autosomal recessive intermediate form, and benign autosomal dominant form [1, 3, 8]. The autosomal domi- nant form (ADO) was further subdivided into two forms by Bollerslev and Mosekilde [3] based on radiological variations. A third form was suggested later by Kovacs et al. [5]. The congenital (malignant) type appears at birth or in infancy as marrow dysfunction and pancytopenia result- ing from obliteration of marrow with primitive bone. Spontaneous bruising, abnormal bleeding, severe anemia, failure to thrive, hepatosplenomegaly, delayed dentition, caries in the teeth, palsies of the cranial nerves due to im- pingement in the foramina, pathologic fractures, and os- teomyelitis of the mandible are the common presenting symptoms. Death usually occurs because of sepsis and he- morrhage in the first decade [1, 8]. The ADO tarda type may remain clinically silent and asymptomatic or present with fracture (especially in type II), coxa vara, limb deformity, and osteoarthrosis. This form is compatible with normal physical activity and life span. Mild anemia, cranial nerve palsies, stomatologic problems may also occur. A liability to spondylolysis was also reported [7]. Atypical cases that do not fall into either the congeni- tal or tarda categories have been grouped as an intermedi- ate form. This form is also autosomal recessive. The radiological features include increased opacity of bones, obliteration of the medullary cavity, and in ade- quately penetrated films transverse, sometimes longitudi- nal striations. Endobone or the ‘os-in-os’ pattern which is pathognomonic for osteopetrosis, splaying of the meta- physes with enlargement of the ends of the diaphysis (Er- lenmeyer flask appearance), ‘sandwich’ appearance of vertebrae in the lateral projection (rugger jersey spine), in- creased density and sclerosis in the skull base, and usually absence of mastoid air cells and paranasal sinuses are the other features [1, 2, 3, 8]. The radiological differentiation of autosomal dominant types according to Kovacs et al. [5] is shown in Table 1. This subdivision is important from an orthopedic point of view since ADO type II pa- tients are regarded as having an increased risk of frac- Hakan Kinik · Onur Polat · Yusuf Yildiz · Ertan Mergen Slipped capital femoral epiphysis in osteopetrosis: an unusual case Arch Orthop Trauma Surg (2002) 122 : 302–305 DOI 10.1007/s00402-002-0391-x Received: 22 June 2001 / Published online: 13 February 2002 CASE REPORT H. Kinik · O. Polat · Y. Yildiz · E. Mergen Ankara University Ibn-ï Sina Hospital, Department of Orthopedics & Traumatology, Ankara, Turkey H. Kinik (✉) Mesa Koru Sitesi, Fulya Blok No: 44, Çayyolu, 06530, Ankara, Turkey e-mail: kinik@dialup.ankara.edu.tr, Fax: +90-312-3112522 © Springer-Verlag 2002 Table 1 Radiographic differentiation of autosomal dominant os- teopetrosis subtypes (modified after Kovacs et al. [5]) Radiographic findings Type I Type II Type III Generalized osteosclerosis + + + Calvarial sclerosis + – + Skull base sclerosis – + – ‘Rugger jersey’ spine – + – Pelvic ‘endobones’ – + +