The Pros and Cons of Spinal Fusion: What are the indications to fuse?
Chronic back pain is common, affecting one in eight Australians. It is more common in the second part of life. It may be related to work, sport, injury, or disease. It is worsened by age, lack of fitness, extra weight and smoking. It is characterized by episodes of exacerbations and remissions and can be severe at times. It has a negative effect on quality of life and prevents patients from working and socializing.
Chronic back pain may be associated by leg pain. It may be referred from abdominal organs, such as an aortic aneurism or from renal stones. Rarely it is caused by tumours or infection. Beware of so called Red Flags, which are constitutional symptoms such as night sweats or weight loss and may indicate sinister pathology.
Patients may need investigations with MRI, CT scan, bone scan, dynamic x-rays, and blood tests. Whilst the MRI is very sensitive, it does not show pain and may overread some changes. It is estimated that at least 20% or asymptomatic people have a black disc on MRI.
Most patients with chronic back pain improve with physical therapy and reassurance. Some require lifestyle changes. Some need medications or injections. Surgery is only rarely needed.
Spinal fusion is an un-physiological treatment, as we stiffen one or more motion segments. We get bones to grow together, with or without implants. The principles are the same in the cervical, the thoracic and the lumbar spine. The incidence of spinal fusions has continued to grow exponentially, being most common in the elderly.
The indications for spinal fusion are controversial. Some patients with severe or with progressive deformity require corrective surgery. Some patients with instability, such as a fracture or a spondylolisthesis require stabilization. Some patients with nerve compression or with mechanical back pain benefit from fusion surgery. Sometimes one has to operate because of previous surgery. Contraindications may be co-morbidities, osteoporosis, psychological issues or smoking, which inhibits wound healing and bony fusion.
There are techniques to achieve a fusion, with or without implants. Most common are constructs with pedicle screws and interbody cages to give anterior column support. Surgery takes between 2 to 4 hours and requires a general anaesthetic. X-ray guidance or computer navigation is necessary. Either autologous bone graft, allograft, or synthetic graft can be used to achieve a fusion.
Rehabilitation progresses gradually. Early mobilization is followed ROM and non-impact exercises. Hydrotherapy is useful and is core strengthening and strengthening of the legs to get the patients up and about.
Spinal fusion surgery is complex and there are several complications intra-operatively, early and late. These include damage to neural structures, dural tears, bleeding and blood clots, infection, failure to fuse and failure of implants.
The outcomes of spinal fusions are variable. There are many studies, but there is no high-level evidence to support fusions for simple back pain. It is difficult to define success and there is a high rate of potential complications. There is evidence of the benefits of spinal fusion for patients with fractures, tumours, instability and deformity, but much less so for patients with chronic back pain.
Ideally patients should be offered a multi-disciplinary approach, involving the GP, the physiotherapist, perhaps a psychologist, work and lifestyle changes. Weight loss should be considered. If surgery is considered, the patient needs to understand the pros and cons and the potential complications of an operation.
With careful selection, good preparation, careful surgery, and good rehabilitation, many patients can be helped with spinal fusion.