300 Injury (1992)23,(5), 300-302 Printed in Great Britain

Changing prevalence of osteomalacia in hip fractures in southeast Scotland over a Xl-year period

C. M. Robinson’, M. M. McQueen’, E. F. Wheelwright’, D. L. Gardner2 and D. M. Salter’ ‘Department of Orthopaedics, Princess Margaret Rose Orthopaedic Hospital, Edinburgh, UK and 2Department of Pathology, University of Edinburgh, Edinburgh, UK

In a randomized study of 81 patients with fresh hip fractures who underwenf bone biopsy af fhe fime of surgery there was no hisfologically detecfable osfeomalacia. This represented a fall in prevalence since a similar study LO years previously had shown a IZ per cent incidence in fhe same populafion. The implications for roufine histological screening ana’ measurement of serum bone biochemisfy in pafients with hip fractures is discussed. The majority of patients in the sfudy group had histologically detectable osfeoporosis suggesfing that fhis was an important factor in the aetiology of femoral neck fractures.

Introduction

In 1969 Chalmers et al. reported that osteomalacia detect- able on bone biopsy coupled with clinical or radiographic correlates was present in 12 per cent of patients with femoral neck fractures seen in Edinburgh hospitals. Other studies performed around this time seem to confirm the association of osteomalacia with these fractures (Jenkins et al., 1973; Aaron et al., 1974; Hoikka et al., 1982). However, more recent studies in the last 10 years (Campbell et al., 1984; Wilton et al., 1987a) have suggested a much lower preva- lence of the disease in the elderly population and only 2 per cent prevalence in a large series of over 1000 patients with hip fractures. This study aims to clarify whether the apparent disparity is merely a reflection of regional differences or whether there has been a true decrease in the prevalence of osteomalacia in patients with hip fractures by examining the same regional population as in the original 1969 paper with a duplicate study 20 years on.

70 per cent alcohol and undecalcified plastic embedded 10pm sections prepared and stained using von Kossa’s method with red counterstaining for osteoid. Individual sections were examined for osteoid and trabecular bone under an eyepiece graticule counting adjacent fields until a regression to a ‘normal value’ was achieved. Values for mean trabecular bone volume, osteoid area as a percentage of total trabecular area (‘osteoid volume’) and osteoid surface extent as a percentage of trabecular surface (‘osteoid surface’) were derived as described by Revel1 (1983). There is variation between individual authors and between different labora- tories as to the range of ‘normal’ values for the above indices and also the values at which osteomalacia can confidently be diagnosed. For the purposes of this study age/sex matched trabecular bone volumes quoted by Melsen et al. (1978) and Courpron et al. (1966) were used for comparison and an osteoid volume of greater than 5 per cent with an osteoid surface of greater than 25 per cent used to indicate significant hyperosteoidosis usually attributed to osteo- malacia.

As in the previous study corrected calcium, phosphate and alkaline phosphatase were measured in all patients at the time of admission.

Results

The mean trabecular bone volume was low (Figwe I) compared with normal values quoted by Melsen et al.

Methods

As far as possible the methods used in the original study were duplicated. Over an lb-month period 81 patients with subcapital or intertrochanteric fractures who were able to give formal consent underwent vertical bone biopsy at the time of surgery for their fractures. The mean age of subjects was 81 years (range 61-95 years, standard deviation 12.2, with sex ratio of M : F I : 7.5). There was an equal prevalence of subcapital and intertrochanteric fractures and these were all low-energy injuries as a result of falls at home or in residential care. The biopsy specimen was initially fixed in

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Figure 1. Distribution of mean trabecular bone volumes (MTBV) within the study group.

Robinson et al.: Osteomalacia in hip fractures 301

Table I. Measured indices of osteomalacia compared with quoted ‘normal’ values

Osteoid volume

Osteoid surface

No. of cases

measured

81

81

Mean and SD

(W

0.97+1.18

14.48+6.72

Highest measurement

6)

4.3

24.5

‘Normal’ measurement

< 5% (Wilton et al.. 1987a) ~6% (Chalmers et al.. 1969) ~25% (Wilton et al., 1987a)

Table II. Various serum biochemical values within study group

Measurement Mean and SD Norma/ value

No. of cases less than or greater than (*) normal

Corrected calcium Inorganic phosphate Alkaline phosphatase Calcium/phosphate product

2.16 + 0.20 mmol/l 2.12-2.62 mmol/l 18 (22%) 0.93 + 0.25 mmol/l 0.8-l .4 mmol/l 25 (31%) 85+4Oiu/l 30-l 10 iu/l 14‘ (17%) 2.12 + 0.30 1.7-3.67 19 (23%)

(1978) and Courpron et al. (1966) for this age group, confirming that the majority of the fractures occur in osteoporotic bone. Indeed, in only 19 sections (23 per cent) did the trabecular bone volume exceed 15 per cent (the generally accepted ‘normal’ value for this age group).

The low mean osteoid volume and osteoid surface extent (Table 1) suggest a low incidence of osteomalacia, the highest recorded volume being an osteoid value of 4.6 and surface extent of 24.5, which are well below the values at which a diagnosis of osteomalacia could be made. In the majority of biopsies there was little osteoid apparent.

A low serum calcium was present in 18 cases (22 per cent), low phosphate in 25 cases (31 per cent) and elevated alkaline phosphatase in 14 cases (17 per cent). In the 14 patients with elevated alkaline phosphatase only four had other abnormal live function tests. As in the previous study the calcium/ phosphate product (Table II) was also computed as this was thought to have a predictive value for osteomalacia, but values lower than the reference level were found in 19 cases (23 per cent). There was, however, no evidence of any positive or negative correlation between the three measured values or the calcium/phosphate product and the osteoid volumes or surface extent. The combination of a low calcium and high alkaline phosphatase has also been quoted as being of a predictive value in identifying patients at risk of osteomalacia (Wilton et al., 1987b), and this combination was found in only three cases (4 per cent).

Discussion

The results indicate that there has been a decline in the prevalence of osteomalacia in the study population with femoral neck fractures over the last 20 years. The highest observed osteoid volume was 4.3, this being well below the 6 per cent cut-off used in the original study (Chalmers et al., 1969) and the 5 per cent value quoted by Wilton et al. (1987a). Our study is therefore in concordance with the most recent studies which suggest that osteomalacia is at present not a significant causative factor in hip fractures, and therefore routine biopsy for screening purposes does not appear justified. The reason for the fall in prevalence of

osteomalacia over the last 20 years is unclear from the

present study, but improved nutrition coupled with a rise in the incidence of osteoporotic hip fractures (Wallace, 1983) are probably implicated.

The present study also suggests that the values of serum calcium, phosphate, alkaline phosphatase and calcium phos- phate product are insensitive in screening for osteomalacia, being abnormal in up to one-quarter of cases with no histologically detectable hyperosteoidosis. The combina- tion of low calcium and high alkaline phosphatase has been suggested recently as a more sensitive predictor of osteo- malacia and this was found in only 4 per cent of patients in the present study. The finding of a low mean trabecular bone volume in the majority of cases supports the theory that osteoporosis is the major aetiological factor involved in femoral neck fractures.

References

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Campbell G. A., Komm J. R., Hosking B. J. et al. (1984) How common is osteomalacia in the elderly? Lancef 2, 386.

Chalmers J., Barclay A., Davison A. M. et al. (1969) Quantitative measurements of osteoid in health and disease. Clin. Orthop. Rel.

Res. 63, 196. Courpron I’., Meunier P., Bressot C. et al. (1966) Amount of bone

in iliac crest biopsy. Significance of the trabecular bone volume. Its values in normal and in pathological conditions. In: Meunier P. J. (ed.) Bone Hisfomorphomefry. 2nd Int. Workshop. Armar

Montagu, Paris, 39. Hoikka V., Aluaua E. M., Savolainen K. et al. (1982) Osteomalacia

in fractures of the proximal femur. Acfu Orfhop. Scmd. 53,255. Jenkins P. N. R., Roberts J. G., Webster D. et al. (1973)

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Microbial. Stand. 86, 70.

302 Injury: the British Journal of Accident Surgery (1992) Vol. 23/No. 5

Revel1 P. A., (1983) Histomorphometry of bone 1. C/in. Puthol. 36, 1323.

Paper accepted 4 November 1991.

Wallace W. A. (1983) The increasing incidence of fractures of the proximal femur: an orthopaedic epidemic. Lar~cef 1, 1413.

Wilton T. J., Hosking D. J., Pawley E. et al. (1987a) Osteomalacia and femoral neck fractures. J. Bone joint Surg. 69B, 388.

Wilton T. J., Hosking D. J., Pawley E. et al. (1987b) Screening for osteomalacia in elderly patients with femoral neck fractures.

]. Bone ]oinf Surg. 69B, 765.

Requests for reprints should be addressed to: Mr C. M. Robinson FRCS, Orthopaedic Registrar, Princess Margaret Rose Orthopaedic