Background
Pedicle subtraction osteotomy is one of the most common spinal osteotomies used for correcting kyphotic deformities. The main disadvantage of this osteotomy is the complete dissociation between the vertebral body and the posterior elements, which creates an anterior displacement of the involved segment. There is also a reduction of the vertical dimension of the neural foramen. A new modification is to perform partial subtraction to avoid both complications.
Purpose
The aim of the study was to introduce a new modification of the traditional pedicle subtraction osteotomy, in which we perform partial pedicle osteotomy, preserving the inferior third of the pedicle. This allows smoother correction of the deformity, minimizes the injury or irritation to the nerve root below this pedicle, and decreases the incidence of subluxation and dorsal impingement. As the correction occurs with theoretically smaller wedges, better closure and union of the osteotomy site is expected.
Patients and methods
Our study included 33 patients with sagittal plan deformity (16 patients with ankylosing spondylitis, eight with old fractures, five with congenital kyphosis, and four with postlaminectomy kyphosis after cord tumor resection). All patients were treated by our modifications of the pedicle subtraction osteotomy technique. Radiographic analysis included assessment of kyphosis by the regional Cobb angle and the C7 sagittal plumb line in preplain and postplain radiographs. Clinically, the patients were assessed by the Oswestry functional score.
Results
Our series included 23 men and 10 women. The mean age of the group was 42.3 years. The vertical plumb line distance from the first sacral segment improved to 3.4 cm compared with a mean of 9.3 preoperatively. The degree of correction for single osteotomy was a mean of 22.41. The intervertebral foramen below the osteotomized pedicle showed an unchanged vertical dimension after the osteotomy. Complications included four patients with dural tears, one with massive bleeding (2500 ml), three with superficial wound infection, and one patient with transient postoperative paraparesis. There was no single case of root injury. The mean follow-up period of the patients was 27.4 months. At the end of the follow-up period, radiological examination showed a loss of correction of a mean of 21 with no appearance of pseudoarthrosis or metal failure. According to the Oswestry disability score, 88% of patients were able to return to normal to moderate daily activities confidently and with overall satisfaction.
Conclusion
Although our new technique is technically demanding, it has a lower rate of neurological complication, with better chances of union compared with traditional osteotomy.