Archives of Orthopaedic and Traumatic Surgery

Arch Orthop Trauma Surg (1987) 106:89-93

© Springer-Verlag 1987

A Radiological Population Study on the Ossification of the Posterior Longitudinal Ligament in the Spine* K Ohtsukal , K Terayamal , M Yanagiharal , K Wadal , K Kasuga l , T Machida 2, and S Matsushima 2 'Department of Orthopaedic Surgery, Shinshu University School of Medicine, Asahi 3-1-1, Matsumoto, 390 Japan Saku Central Hospital, Usuda-machi, Nagano-prefecture, 384-03 Japan

2

Summary This paper reports the results of a radiological population study on the ossification of the posterior longitudinal ligament (OPLL) in both the cervical and the thoracic spine among Japanese The study was carried out in the Yachiho-mura district in the central part of Japan, where 5074 people were living X-ray examinations were made of 1058 of the people; there were 440 men and 618 women, 50 or more years of age. The roentgenograms showed 34 cases of OPLL in the cervical spine (3 2 %): 19 men (4 3%) and 15 women ( 2 4%) The condition was most frequently observed at the level of C-4 Radiological classification showed 18 cases of the segmental type, 11 of the continuous type, and five of a mixed type. There were eight cases of OPLL in the thoracic spine ( 0 8%), four in men ( 0 9 %) and four in women ( 0.6%) OPLL in the thoracic spine was most frequently observed at the midthoracic levels All eight cases showed a continuous type of ossification. There were three subjects with OPLL in both the cervical and the thoracic spine Therefore, the number of subjects with OPLL in either the cervical or the thoracic spine was 39 ( 3 7%) total.

Japanese we carried out a radiological study based on a fixed population sample. Patients and method This investigation of the spine was carried out among the inhabitants of the Yachiho-mura district, a mountain area situated in the central part of Japan The major occupation is farming The Community Health Care Division of Saku Central Hospital has been examining the people there annually in the framework of the Adult Health Study (AHS) for 25 years. In 1983 the study of the spine was added as a part of the AHS. The population in this area was 5074 (2486 male and 2588 female), among which there were 1897 individuals aged 50 years or more The team for this AHS included a physician, an orthopaedic surgeon, several nurses, and laboratory and X-ray technicians; at their disposal was a car equipped with an X-ray machine and a storage area for blood and urine samples We visited each village in the district and studied the people aged 50 years or more who were willing to undergo an examination of the spine The items included in the study were as follows: a lateral-view roentgenogram of the cervical and the thoracic spine; measurement of height, weight, and width of subcutaneous fat; and blood and urine samples The roentgenogram was taken indirectly on a 100 mm-square film, and it was subsequently projected on a 330 mm-square screen using a special

Table 1 Number of inhabitants who underwent X-ray examination of the cervical and thoracic spine

In order to clarify the true prevalence of OPLL in both the cervical and the thoracic spine among the Offprint requests to: Kuniyoshi Ohtsuka, M D , Department of Orthopaedic Surgery, Shinshu University School of Medicine, Asahi 3-1-1, Matsumoto, 390 Japan *This study was subsidized by the Japanese Ministry of Public Health and Welfare

Age

50-59

60-69

70-79

80 +

Men Women

197 262

117 219

101 118

Total

459

336

219

Total

Mean age

25 19

440 618

63 3 62 5

44

1058

62 8

90

K Ohtsuka et al : Ossification of Posterior Longitudinal Ligament of Spine

Table 2 Number of subjects with cervical OPLL Age Men Women Total

50-59

60-69

70-79

80 +

Total

7 5

7 8

4 1

1 1

19 15

(4 3 %) (2 4 %)

12

15

5

2

34

(3 2 %)

machine to detect unquestionable OPLL The blood and urine samples were sent to the laboratory of the AHS division. There were 1058 inhabitants (440 men and 618 women), mean age 63 years, range 50-89, who underwent this examination (Table 1).

Results No of cases

Fig 1 Number of cases of cervical OPLL at each level OPLL was most frequently observed at the level of C-4

0a

0

J 03 G Continyous type

Segmental type

The prevalence of cervical OPLL was 4 3 % ( 19 cases) in men, 2 4% ( 15) in women, and 3 2 % (34) in the total population studied The incidence was 2 6% ( 12 cases) for the sixth decade of life 4 5% ( 15 cases) for the seventh, 2 3% (five cases) for the eighth, and 4.5 % (two cases) for the ninth (Table 2) OPLL was most frequently observed at the level of C-4, i e , 25 cases (Fig 1). The varying pictures of OPLL on the roentgenograms were classified into four types: continuous, segmental, mixed, and circumscribed l23 l "Continuous" means that the OPLL spreads over two or more vertebrae in continuation; "segmental" means that

o Mixed type

Mixed type

Circumscribed type

Fig 2 Classification of ossification, showing lateral view of cervical spine l23 l

Fig 3 a Lateral X-ray view of cervical spine showing a continuous type of OPLL (arrows) in a man aged 68 years, who has no symptoms b Continuous type of OPLL observed on a lateral X-ray view of the thoracic spine (arrows) in a man without any symptoms

K Ohtsuka et al : Ossification of Posterior Longitudinal Ligament of Spine Table 3 Number of subjects with thoracic OPLL Age

50-59

60-69

70-79

80 +

Total

Men Women

1 0

3 1

0 1

0 2

4 4

(0 9 %) (0 6 %)

Total

1

4

1

2

8

(0 8 %)

No

91

seventh decade and one woman in the eighth Therefore, there were a total of 39 patients with OPLL in either the cervical or the thoracic spine ( 3 7%): 21 were men ( 4 8%) and 18 were women ( 2 9%) (see Table 4) As for the age distribution, 13 patients were in the sixth decade ( 2 8 %), 17 in the seventh ( 5 1%), five in the eighth ( 2 3%), and four in the ninth (9.1 %). The height, degree of obesity, thickness of subcutaneous fat, height loss in the past 25 years, blood cell counts, serum sugar levels at fasting, and calcium levels were examined for these 39 patients There were no significant differences in these data when compared with the results of another 1019 subjects without OPLL.

of

cas

6 5 4 3 2

Discussion 1 0

T

T2

T3

T4

T5

T6

T

T

T9

To T

T2

Fig 4 Number of cases of thoracic OPLL at each level All eight cases were the continuous type Thoracic OPLL was most frequently observed in the midthoracic area

Table 4 Number of subjects with OPLL in cervical and/or thoracic spine

Cervical (A)

Thoracic (B)

Both Total cervical A+B-C and thoracic (C)

Men Women

19 (4 3 %) 15 (2 4 %)

4 (0 9 %) 4 (0 6 %)

2 (0 5%) 1 (0 2 %)

21 (4 8%) 18 (2 9 %)

Total

34 (3 2 %)

8 (0 8 %)

3 (0 3%)

39 (3 7 %)

the OPLL is seen separately behind each vertebra; the mixed type consists of the continuous and the segmental type; the circumscribed type is bow-shaped ossification localized behind an intervertebral disk (Fig 2) There were 18 cases of the segmental type, 11 of the continuous, five of the mixed, and none of the circumscribed (Figs 2, 3a). The incidence of thoracic OPLL was 0 9% (four cases) in men, 0 6% (four cases) in women, and 0.8 % (eight cases) in total; there were one case in the sixth decade, four in the seventh, one in the eighth, and two in the ninth (Table 3) Thoracic OPLL was most frequently observed in the midthoracic area: there were six cases at the level of the T-6, five at T5, and four each at T-4 and T-7 (Fig 4) The thoracic OPLL was all of the continuous type, as shown in Fig 3 b The three patients with OPLL in both the cervical and the thoracic spine were two men in the

A large number of epidemiological studies on OPLL have been carried out in the past, mainly by Japanese scholars However, these studies are mostly radiographic investigations of the subjects who visited outpatient clinics or health check services l4, 7-12, 1618, 21, 25 l One exceptional study was made by Ikata et al l7l, on the incidence of OPLL among people with particular occupations in a limited area of Shikoku province, but the data on this population are therefore biased With the intention of knowing the real incidence of OPLL in Japan we made this survey of 1058 inhabitants of a certain district who were aged 50 years or more The results of this radiographic study showed that the incidence of OPLL in the cervical spine is roughly 3 2%; this is higher than the results of other authors l8, 11, 16l The subjects in our study were older than those in other series by 20 years This would suggest that aging plays a significant role in the development of the disorder. The results of the studies made by other authors using subjects at outpatient clinics or health-check services were modified in view of the age distribution beyond 50 years and were compared with ours, but no significant difference was revealed The results obtained in the surveys carried out by Kurokawa l10 l, Tetsuka l21 l, and Izawa et al l7 l in southeast Asian countries such as Taiwan, Korea, Hong Kong, and Singapore were compared with those on Japan and no difference was found in the incidence of OPLL of the cervical spine Statistical studies on the white race are very few Based on their investigations in the United States and West Germany, Yamauchi and his collaborators l8, 17, 25 l reported that the incidence of OPLL of the cervical spine in these nations is between 0 01 % and 0 1%, and therefore significantly lower than that in Japan On the other

92

K Ohtsuka et al : Ossification of Posterior Longitudinal Ligament of Spine

hand, Terayama et al l20 l studied 1258 outpatients in Italy and found OPLL of the cervical spine in 22 subjects ( 1 7 %) They reported that this incidence was not significantly different from that in Japan. Among the Japanese OPLL was regarded as a rare disease in the past, but recently this disorder has attracted more attention and the many studies have shown that the incidence of OPLL in the cervical spine in Japan is approximately 1%-3 % It is anticipated that more attention will be paid to the disorder in Europe and America in the future, and that the results of more statistical studies will make the real incidence among the white race clear. There are only a few reports of epidemiological studies on the incidence of OPLL in the thoracic spine in Japan Ono et al l13 l examined the lateralview chest roentgenograms of 8610 subjects who had been exposed to the atomic bomb and found that the incidence of thoracic OPLL was 0 56 % Ikata et al. l5 l investigated 729 subjects including farmers, factory workers, and car drivers, and found the incidence of OPLL in the thoracic spine to be 0 3 % The population survey made by us of 1058 subjects revealed the incidence to be 0 8 % On the basis of these results it can be concluded that the incidence of thoracic OPLL is very much lower than that of cervical OPLL, and probably lower than 1 % in Japan We found, as did many other authors, that the ossification develops most frequently in the midthoracic spine l 1, 6, 22, 24l Harada et al l3l studied 511 diabetic patients and found cervical OPLL in 15,9 % of them They inferred that although diabetes is not a cause of OPLL development, the combination of the aging process and diabetes could facilitate ossification The present study did not reveal any definite correlation between OPLL and diabetes The etiology of OPLL is still obscure; however, it is possibly related to both local and systemic factors One of the findings suggesting a local factor is that the ossified foci often grow rapidly after patients undergo decompressive laminectomy This would suggest that surgical invasion could cause some biological reaction in loco and that postoperative structural changes of the cervical column could hasten the progress of pathological ossification It has been found that cervical OPLL shows a preference for the C-5 vertebra, one of the most mobile portions l19l although in the present study C-4 was the most frequently involved segment This would suggest the possibility of incessantly inflicted stresses on the posterior longitudinal ligament inducing the development of OPLL There are two systemic factors, one of which is the clear evidence of a high familial incidence The incidence of OPLL among blood relatives of a patient is about 30%, which is significantly higher than that among

the general population The other fact is that patients with OPLL frequently show concomitant ossification of the anterior longitudinal ligament (OALL), the ligamenta flava (OLF), and the supraspinous ligament (OSSL), as well as of the ligamentous insertions to such bones as the pelvis, knee, calcaneus, and elbow, i e , conditions similar to Forestier's l2l ankylosing hyperostosis of the spine, or to the diffuse idiopathic skeletal hyperostosis (DISH) described by Resnik et al l14, 15 l OPLL can be regarded as a local appearance of DISH, and this would suggest the necessity for epidemiological surveys on OALL, OLF, and OSSL as well.

References 1 Akiyama N, Ohnari K, Kitao S, Tsuchiya T (1981) Ossification of the posterior longitudinal ligament of the thoracic spine; radiological study (in Japanese) Orthop Surg (Tokyo) 32:1029-1039 2 Forestier J, Rotes-Querol J (1950) Senile ankylosing hyperostosis of the spine Ann Rheum Dis 9:321-330 3 Harada S, Tohno S, Kawagishi T, Ohmi Y (1981) The ossification of the posterior longitudinal ligament of the cervical spine in diabetes International Congress Series No 581: Diabetic neuropathy, Tokyo, September 18 and 19 4 Hasue M, Kikuchi S, Fujiwara M, Skuyama Y, Sakomoto T, Miura H, Kawasaki S (1980) Roentgenographic analysis of ossification of the spinal ligaments; with special reference to the findings of the whole spine (in Japanese) Orthop Surg (Tokyo) 31:1179-1186 5 Ikata T, Takeuchi R, Takada K and Yamaoka K (1980) Epidemiological study on ossification of the spinal ligaments (in Japanese) In: Tsuyama N (ed) Disease designations by Ministry of Public Health and Welfare Report of the proceedings of studies of the Research Committee on Ossification of the Posterior Longitudinal Ligament, 1979. Ministry of Public Health and Welfare, Tokyo, pp 9-16 6 Imai K, Kakonami Y, Nakahara S, Nishihara S, Kodama H, Okamoto Y, Murakawa H, Fujiwara I, Ono K, Monzen T (1977) Clinical study of ossification of the posterior longitudinal ligament of the thoracic spine (in Japanese) Clin Orthop Surg (Tokyo) 12:340-344 7 Izawa K (1980) Comparative roentgenographical study on the incidence of ossification of the posterior longitudinal ligament and other degenerative changes of the cervical spine among Japanese, Koreans, Americans and Germans. J Jpn Orthop Assoc 54:461-474 8 Izawa K, Yamauchi Y, Itoh K (1979) Radiographic survey of cervical diseases among Koreans, especially on ossification of the posterior longitudinal ligament (in Japanese). Orthop Traum Surg (Tokyo) 22: 645-651 9 Kurihara A, Kataoka O, Maeda M, Kawai K (1978) Clinical picture and course of ossification of the posterior longitudinal ligament of the cervical spine (in Japanese). Orthop Surg (Tokyo) 29:745-751 10 Kurokawa T (1978) The incidence of ossification of the posterior longitudinal ligament of the cervical spine in Taiwan, Hong Kong and Singapore (in Japanese) In: Tsuyama N (ed) Disease designations by Ministry of Public

K Ohtsuka et al : Ossification of Posterior Longitudinal Ligament of Spine

11

12 13

14 15 16

17

18

Health and Welfare Report of the proceedings of studies of the Research Committee on Ossification of the Posterior Longitudinal Ligament, 1977 Ministry of Public Health and Welfare, Tokyo, pp 26-28 Ohtani K (1980) Epidemiological study on ossification of the posterior longitudinal ligament in the cervical spine in Yaeyama District (in Japanese) In: Tsuyama N (ed) Disease designations by Ministry of Public Health and Welfare Report of the proceedings of studies of the Research Committee on Ossification of the Posterior Longitudinal Ligament, 1979 Ministry of Public Health and Welfare, Tokyo, pp 17-18 Okamoto Y (1967) Ossification of the posterior longitudinal ligament of cervical spine with or without myelopathy. J Jpn Orthop Assoc 40: 1349-1360 Ono M, Russel WJ, Kudo S, Kuroiwa Y, Takamori N, Motomura S, Murakami J (1982) Ossification of the thoracic posterior longitudinal ligament in a fixed population. Neuroradiology 143: 469-474 Resnik D, Niwayama G (1981) Diagnosis of bone and joint disorders, vol 2 Saunders, Philadelphia, p 1416 Resnik D, Shaul SR, Robins JM ( 1975) Diffuse idiopathic skeletal hyperostosis (DISH): Forestier's disease with extraspinal manifestations Radiology 115:513-524 Sakou T, Morimoto N (1982) Epidemiological study on ossification of the posterior longitudinal ligament in the Islands of Kagoshima Prefecture (in Japanese) In: Terayama K (ed) Disease designations by Ministry of Public Health and Welfare Report of the proceedings of studies of the Research Committee on Ossification of the Ligaments in the Spine, 1981 Ministry of Public Health and Welfare, Tokyo, pp 20-23 Sasaki K, Yamauchi Y, Izawa K (1980) Radiographic survey of cervical diseases among Germans, especially on ossification of the posterior longitudinal ligament (in Japanese) Orthop Surg (Tokyo) 31:585-590 Shinoda Y, Hanzawa S, Nonaka K and Ohwada O (1971) Ossification of the posterior longitudinal ligament in the cervical spine (in Japanese) Orthop Surgery (Tokyo) 22: 383-391

93

19 Terayama K (1976) Ossification of the posterior longitudinal ligament (in Japanese) J Jpn Orthop Assoc 50:415442 20 Terayama K, Ohtsuka K, Merlini L, Gui L (1984) A report of roentgenographic survey on ossification of the posterior longitudinal ligament in the cervical spines in Bologna: a study of 1258 subjects of the out-patient clinic (in Japanese) In: Terayama K (ed) Disease designations by Ministry of Public Health and Welfare Report of the proceedings of studies of the Research Committee on Ossification of the Ligaments in the Spine, 1983 Ministry of Public Health and Welfare, Tokyo, pp 55-62 21 Tetsuka A (1980) Epidemiological study on ossification of the cervical spine in Taiwan (in Japanese) In: Tsuyama N (ed) Disease designations by Ministry of Public Health and Welfare Report of the proceedings of studies of the Research Committee on Ossification of the Posterior Longitudinal Ligament, 1979 Ministry of Public Health and Welfare, Tokyo, pp 26-27 22 Tsuchiya T, Imai K, Yamanouchi T, Nobuhara S, Yamaguchi S and Kato Y (1975) Ossification of the posterior longitudinal ligament in the thoracic spine (in Japanese). Orthop Surg (Tokyo) 26:667-672 23 Tsuyama N (1981) The ossification of the posterior longitudinal ligament of the spine (OPLL) J Jpn Orthop Assoc 55:425-440 24 Tsuyama N, Kurokawa T (1977) Ossification of the posterior longitudinal ligament in the thoracic and lumbar spine. Statistical report of ossification of the posterior longitudinal ligament for all of Japan (in Japanese) Clin Orthop Surg (Tokyo) 12:337-339 25 Yamauchi Y, Izawa K, Fujiwara M (1977) Radiological investigation of the posterior longitudinal ligament of the cervical spine in American subjects (in Japanese) Orthop Surg (Tokyo) 28: 757-765

Received January 4, 1986