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Radiological changes of short and flat bones in primary hypertrophic osteoarthropathy
  1. Department of Rheumatology, Sisters of Mercy University Hospital, Zagreb, Croatia
  1. Professor I Jajić, Sisters of Mercy University Hospital, Department for Physical Med, Rehab and Rheum, Zagreb University School of Medicine, Vinogradska c 29, HR-10000, Zagreb,Croatia.

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Hypertrophic osteoarthropathy (HO) is defined as a syndrome characterised by finger clubbing and periostosis of long bones.1 It is classified into primary (PHO) and secondary hypertrophic osteoarthropathy (SHO).2

To establish the HO diagnosis, finger clubbing and periostosis of long bones must be present.2

Cases of PHO have not been frequently reported in the medical literature.3 HO cases have recently been more described, since HO was classified into the bone and cartilage group of diseases according to the international classification of rheumatic diseases.4

We formed a large group of patients in whom changes of flat bones were found. The analysis was based on a group of patients with PHO from 1970 to 1996. Over 26 years, a total of 76 patients was enrolled in the study. There were five female (6.5%) and 71 male (93.5) patients. Their age ranged from 18 to 64 years (mean age 43).

Radiological examination of short and flat bones (pelvis, vertebral column, ribs, sternum, clavicle, skull, hand, and foot) was performed in all the patients. A more or less pronounced periostosis of long bones was found in all the patients.

Periostitis was mainly evident in diaphysis, metaphysis and epiphysis with the irregular configuration of bones and extremities.

The localisation of periostosis was in calvaria, where the periostal reaction was present across the whole surface (figs 1 and 2).

Figure 1

Periostosis of calvaria.

Figure 2

Periostosis of calvaria (laterolateral view).

It was evident in the clavicular ribs (pelvis, os ilium, os ischii, foramen opturatum, pubic bone) (figs 3 and 4), radially in os navicularis carpi (fig 5), patella (fig 6), carpal bones (fig 6), and metatarsal bones (fig 7).

Figure 3

Periostosis in ilium to the left, foramen opturatum contralaterally, tuber ossis ischii and small trochanter.

Figure 4

Periostosis visible in the foramen opturatum to the right, and more pronounced osteoporosis is evident parallel with acetabulum and femur head.

Figure 5

Periostal layers in the distal part of radius, ulna, and metacarpal bones, and os naviculare.

Figure 6

Periostosis of tibia, fibula and patella (more pronounced in the left leg).

Figure 7

Periostal layers in the metacarpal bones.

In the terminal phalanges of fingers and toes, a clear acroosteolisis was found in 52 patients (78.4%) (fig 8).

Figure 8

Distal phalanges are rumpled. Periostosis is developed across the whole surface, and it is most pronounced in the basis of the distal phalange that tends to be connected to the one on the top. Acroosteolysis in the distal part of I, II, and IV phalange of the left foot and first four toes of the right foot.  

PHO is defined as a syndrome characterised by finger clubbing and periostosis of long bones.1 Data and this definition indicate that periostal reaction manifests very rarely in short and flat bones.1-3 5 In our study, the skeleton of 76 patients was radiologically examined and periostal reaction in short and flat bones found in 14 patients (18.5%). It was developed in many flat bones (calvaria, clavicula, scapula, pelvis - os ilium, os ischii, pubic bone, patella, small bones of the hand, foot and vertebral column skeleton).

Nevertheless, periostal reaction is not so pronounced in short and flat bones, as it is in long bones, and thus it should be “searched for”. It has been reported by only a few authors,3 while many others have not recorded it.6

Acroosteolysis is almost a regular phenomenon in terminal phalanges of the fingers and thumbs of hands and feet in cases when PHO was present for more than 10 years. Some authors have already described this, but in individual patients.7

In conclusion, it should be pointed out that periostal reaction can develop not only in long bones, but also in short and flat bones more often than it has been presumed.