Hamid Namazi,MD
Assistant professor Of Orthopaedic Surgery Department

Mohammad Jafar Emami,MD
Associate Professor Of Orthopaedic Surgery Department

Ahmad Ensafdaran,MD
Assistant Professor Of Orthopaedic Surgery Department

Department of Orthopaedic surgery Shiraz University of Medical Sciences

Correspondence:
Dr. M.J. Emami
Department of Orthopaedic Surgery
Chamran Hospital
Shiraz- IRAN
Fax: +98 711-6231409
Tel: =+98 711-6246093- 6231410
Box: 71345
E- mail: namazih@sums.ac.ir

Introduction

The incidence of hip fracture has increased in recent years. Approximately 40 percent of women will experience one or more fractures after the age of 50⁽¹⁾. At 50 years of age for women the lifetime risk of hip fracture is 17.5%⁽²⁾. Mortality rate of hip fracture is 15-20% as compared to 0.92% mortality of other orthopaedic problems⁽³⁾. Patients with hip fracture have risk of complications such as deep vein thrombosis, bed sores, UTI, etc⁽⁴⁾. Osteoporosis is the single most important risk factor⁽⁵⁾. There are several techniques such as Radiographic absorptiometry, Dual-energy X-ray absorptiometry, Quantitative CT, Ultrasonography, etc, that detect osteoporosis but Dual-energy X-ray absorptiometry is the current gold standard method^{(6, 7)}. We have conducted this study to detect the severity of osteoporosis and to determine the level of bone mineral density that guides us to start preventive therapy of hip fractures.

Patients and Methods

This is a prospective study in which hip bone mineral density was measured by Dual-energy x-ray absorptiometry in 100 patients (50 men, 50 women) who had hip fracture after minor trauma. All 100 patients were evaluated by Dual -energy X-ray absorptiometry within 2 weeks after fracture. The age of patients was between 50 and 90 years. Bone mineral density measurement was done on the side that had no fracture.
The control group consisted of 100 persons (50 men, 50 women) between 50 and 90 years old in whom bone mineral density of hip was measured by Dual-energy x-ray absorptiometry.

We excluded the following patients1-Patients with metabolic bone diseases.
2-Patients who had old fracture of more than 2 weeks duration.
3-Patients who had previous osteoporosis due to drug consumption.
4-Patients who had major trauma.
5-Patients who had a history of previous fracture or surgery on the other hip.
Each person had three sets of data:

Bone Mineral density (BMD), T- score, Z- score
1- BMD that is mineral content of bone and recorded in gr/cm2
2- T-score that compares BMD of each person with young person.
3-Z-score that compares BMD of each person with age- matched persons.
After collection of all data, by comparing the patient group with the control group, T- test analysis was done and then results were reported.

Results

The mean age in the patient group was 70 years (S.D: 10.3) and in the control group was 68 years (SD: 8.82). The statistical analysis revealed no difference between the two groups in terms of age ( P.value=0.342). The mean bone mineral density in the patient group was significantly lower than the control group, being 0.6333 gr/cm² (min: 0.345, max: 1, S.D:0.126) versus 0.7589 gr/cm² (min: 0.441, max: 1.099, SD: 0.144) (P.value=0) (Table 1). The mean T score in the patient group was significantly lower than the control group, being - 2.986 (min: 1.2, max: 4.7, S.D: 1.109) versus - 1.98(min: 0.1, max: 4.5, S.D: 1.17) (P. value= 0) (Table 2). The mean Z- score in the patient group was significantly lower than the control group, being-1.218 (S.D: 0.769) versus- 0.652 (S.D: 0.983) (P.value= 0.002) (Table 3).

Discussion

Because the number of hip fractures are projected to increase, osteoporosis will become an increasing burden on the health care system, in addition to causing pain, disability and reducing quality of life⁽⁸⁾. Perhaps the major value of bone densitometry in current orthopaedic practice is identification of the patients with osteoporosis who are at increased risk for fracture⁽⁹⁾.

Whether osteoporosis is more prevalent in patients with hip fracture than age and sex-matched groups has remained controversial. Makin in 1987 could not confirm that the degree of osteoporosis is related to the incidence of femoral neck fractures. He concluded that the incidence of proximal femoral fractures is related to other factors in addition to the degree of osteoporosis⁽¹⁰⁾. In a few studies osteoporosis has not been shown to be more prevalent in those with hip fractures than in age -matched controls⁽¹¹⁾. But Atkin in 1984 demonstrated that patients with hip fractures often have bone that is more osteoporotic than that of age and sex- matched control subjects⁽¹²⁾. Barth and colleagues measured osteon dimensions and numbers in cortical bone specimens obtained from the medial femoral cortex in patients treated with hemiarthroplasty for femoral neck fracture. They compared these measurements to those of 12 age-matched cadavers without fractures. There were fewer osteons per unit area and the osteon haversian canals were larger in the fracture group than in the control group⁽¹³⁾. In our study we found that the patients with hip fracture often have bone that is more osteoporotic than the age- and sex- matched control group (BMD). In the patient group it was 0.1256 gr/cm2 lower than the control group). 0.6333 gr/cm² is the level of hip bone mineral density that has an essential risk for hip fracture and needs an aggressive prophylactic therapy for osteoporosis. Also it enables us to find out whether after treatment, the patient has any improvement in bone mass or not. So the physician can effectively follow the effect of treatment and also the duration of prophylaxis needed.

Conclusion

This study shows that hip fracture is strongly associated with osteoporosis and the level of femoral neck bone density that has significant risk for hip fracture is 0.6333 gr/cm². Therefore, we recommend that prophylactic treatment be started for every person screened by DXA who has bone mineral density below 0.6333 gr/cm ². Also regular follow up by DXA is needed until BMD reaches at least above 0.6333 gr/cm².

References