Osteoporosis, Surgery, and the Aging Spine

As throughout the developed world, the median age of the population of the US is increasing: whereas in 1970 it was approximately 27 years of age, it is expected to be nearer 40 years of age by 2025. As a result, we are likely to see an increase in the amount of surgery being performed in the elderly, who have increased comorbidity; significant alterations in thinking and procedural matters in dealing with surgery will be required.

Osteoporosis is assumed to be primarily a disease of females, although it does occur in males. At age 75, 40% of the population will have osteoporosis, of which 50% will sustain a fracture, the spine being the most common location. A peak bone mass generally occurs at approximately age 30 and then decreases significantly in the female population as menopause occurs. As bone mass decreases, the risk of fracture increases.

It is estimated that 30–35 million people in the US are at risk for osteoporotic fractures, and approximately 700,000 vertebral fractures occur per year, of which more than 200,000 are refractory to narcotics and 150,000 require admission to hospital.

The problem is not benign. In 1995, the costs were estimated to be greater than US$13.8 billion annually. It is anticipated that by 2050 this cost will be greater than US$60 billion.

There are many myths and legends with reference to osteoporotic fractures. The myths are that these fractures do not disable people, do not hurt much, will heal with rest, and result in few long-term problems.

However, if one looks at the reality, first that fractures do not hurt, why are there more than 150,000 hospital admissions and more than 200,000 people requiring narcotics? There is no doubt that 60% of people feel better within six months. However, bed rest is far from recommended, as 10% of bone mass can be lost within two weeks. With one thoracic fracture, thoracic kyphosis may be increased by an average of 12º. Respiratory functional capacity may be decreased by 9%. The risk of further fracture is increased by 500%. In a study of osteoporotic fractures in 9,000 women of greater than 65 years of age—of whom 1,915 had fractures at baseline—who were followed for more than eight years, adjusting for age and comorbidities of smoking, any fractures resulted in an approximately 23% increase in mortality, and severe fractures resulted in a 37% increase. There is an increased risk for pulmonary death in this population of 300%.

Fracture Types
The majority of compression fractures are a result of axial compression. Other fracture types are wedge fractures involving the anterior column, biconcave fractures, and crush or burst fractures with failure of the anterior middle columns. These crush factors may be true burst fractures and have implications for stability and altered neurological function.

The use of magnetic resonance imaging (MRI) has greatly enhanced the ability to assess these fractures from the points of view of both soft tissue problems and possible neurological compression, as well as being able to differentiate between old and new fractures.

Treatment of Compression Fractures
A patient must be assessed carefully, including a careful neurological examination, and assessment for a deformity, posture, osteoporotic risk, and bone mineral density. Current treatment options include prevention, which may include specifically exercise, drug therapy, calcium supplementation, and vitamin D. The diphosphonates are often used. Bracing has proved generally to be of little value in the presence of kyphosis. Surgical repair in the past has been restricted for neurological problems and more recently for chronic pain and deformity.

Standard treatment, such as analgesics, have problems and the deformity remains with potentially continued pain and a mechanical environment that may lead to further fracture. Prevention does not reverse severe cases and symptomatic control with analgesics and braces does not correct deformity and pain. Surgical repair can be fraught with failures of fixation, is invasive, and has a high potential of morbidity. Delayed collapse of osteoporotic fractures may occur and be progressive. This is often secondary to avascular necrosis of the bone. As a result, females with compression fractures should be followed for a minimum of one year.

Although neurological compromise is uncommon, it is not as uncommon as initially thought. There are no good population data. Four hundred and ninety-seven fractures submitted with variable compression factors; 10 had significant involvement requiring surgery.¹