Screws are put in pedicles during the surgery. The pedicles are pieces of bone varying in diameter from about 3½ mm up to about 15 mm depending on the size of the patient. Screws vary in width from about 3½ mm up to 6½ mm.
When screws are inserted, it is usual to perform some form of imaging. This allows the surgeon to identify which levels the screws are being put in and the position of the screws. Misplaced screws can cause a neurological problem and very rarely a misplaced screw can risk a vascular problem. During insertion of the screws the tract that the screw follows is felt to try and identify any potential misplacement.
There is always a small risk of infection, the risk in an adolescent idiopathic (low risk) is 1-2%. The risk in neuromuscular cases can be much higher and in revision or growing rod lengthening cases can be higher still. Metalwork is normally left in situ once the spine has fused. Studies show that about 90% of patients do not need their metal removed in the longer term.
Traditionally, scoliosis surgeons are orthopaedic surgeons. Most scoliosis surgeons do nothing but spinal surgery, though occasionally they also have trauma commitments. One or two surgeons would call themselves paediatric orthopaedic surgeons rather than spinal surgeons, so they will do hips as well as spines in children. One or two scoliosis surgeons are primary neurosurgeons but their main interest tends to be the degenerative scoliosis rather than the paediatric scoliosis.
Surgical Risks in Degenerative Scoliosis
Because patients develop co-morbidities as they get older, the risks to patients in treating degenerative scoliosis is much higher. Firstly, there are general risks such as wound healing which is more of a problem in 70 year olds than in children. Because the wounds do not heal as well, there is a higher risk of wound breakdown and wound infection. There are then other co-morbidities such as problems related to heart and lungs, and a risk of stroke.
In children’s scoliosis surgery, the risk of DVT and pulmonary embolus is virtually unheard of, whereas the risks in degenerative scoliosis are high with a pulmonary embolus rate being significant, despite prophylactic treatment.
In general, in children’s scoliosis surgery, the risk of death only relates to the risks related to the other co-morbidities of the syndromes they have. In adult degenerative scoliosis surgery, however, there is a risk of death due to stroke, pulmonary embolus, etc. This all needs to be fully discussed. Scoliosis surgery in later life never improves quantity of life, can improve quality of life but equally when things go wrong, they can significantly reduce quality of life. The risks related to paralysis, blindness, etc are all similar to children’s scoliosis surgery.
Intra operative navigation to try and prevent screw misplacement is on its way. This can be combined with robotic modules, which may reduce length of time and may increase the accuracy of the surgery. Such devices, however, rely on the intra operative CT scanning or pre-operative CT scanning.
Genetic engineering may help prevent scoliosis or prevent the diseases associated with scoliosis.
Other growth guidance systems similar to vertebral body tethering will probably be developed.
Because intensive care units are becoming more skilled at preserving children’s lives, the number of patients with unusual scoliosis associated with syndromes has increased. There are therefore increasing numbers of children coming through with curves, who would not have survived ten or twenty years ago, who are now presenting needing surgery. This increases the demand on intensive care units. These patients tend to have a higher complication rate because of their co-morbidities.