The patient history and clinical evaluation
The patient was a 74-year-old woman who lived in the rural areas of North China. She was thin and 154 cm in height. She complained that she could not lie flat on a bed, with an aching back while trying to stand erect or walk for a long time. She endured this chronic illness and fell into despondency due to failure of long-term conservative treatment.
Physical examination showed that she had severe kyphosis and limited motion of the spine. The strength and sensation of the lower limbs were normal, and the physiological reflex was present. Her physical condition was acceptable, and no obvious contraindication was found.
The clinical outcome was evaluated using the Oswestry Disability Index (ODI) and back pain evaluated by the Visual Analog Scale method (VAS score): 0 represented no pain and 10 reflected the most unbearable pain preoperatively and at finial follow-up. Maximal ambulation distance without pain was also recorded.
Standing 36-inch posterior-anterior (PA) and lateral views were used to evaluate global spinal balance and pelvic parameters before and after surgery. This included coronal balance (C7-CSVL, horizontal distance between a line drawn vertically through the center of the sacrum (CSVL), and a plumb line dropped from the C7 centroid), coronal Cobb angle (the coronal cobb angle from the upper-end vertebra to lower-end vertebra ), thoracic kyphosis (TK, the sagittal cobb angle from the upper endplate of T5 to the lower endplate of T12 ), lumbar lordosis (LL, the sagittal cobb angle from the upper endplate of L1 to the upper endplate of S1), and global kyphosis (GK, the sagittal cobb angle from the upper endplate of upper end vertebra to the lower endplate of lower end vertebra), sacral slope (SS, the angle between the horizontal and the sacral plate), pelvic tilt (PT, the angle between the vertical and the line through the midpoint of the sacral plate to femoral heads axis), pelvic incidence (PI, the angle subtended by a perpendicular from the upper endplate of S1 and a line connecting the center of the femoral head to the center of the upper endplate of S1), sagittal vertical axis (SVA, the horizontal offset from the posterior-superior corner of S1 to the vertebral body of C7). Sagittal and coronal imbalance was defined as an imbalance greater than 5 cm. By convention, a C7PL that falls anterior or posterior to the posterior superior sacrum is designated as positive or negative, respectively.
Additional radiographs that provided important information to evaluate spinal deformity included standing dynamic radiographs and supine side-bending radiographs (Fig. 1). Computed tomography (CT) images were also obtained to verify deformity structures pre-operation and to evaluate the degrees of the extent of bone resection and fusion situation at final follow-up (Fig. 2). Pre-operative magnetic resonance imaging (MRI) showed normal nerve structure and no prominent variation in the planned osteotomy site.
The surgical procedure.
After informed consent was obtained, the patient was placed prone on the operating table and underwent general endotracheal anesthesia. Intraoperative neurophysiologic monitoring was performed throughout the procedure. The back was prepared and draped in the routine sterile fashion. The reference frame was attached to the spinous process of the T5 vertebra and surgical instruments were registered. The navigation probe located the right outer edge of the L2 facet joint on the skin surface (convex side). A longitudinal incision about 3 cm was made and the skin, subcutaneous tissue and deep fascia were sequentially cut off. An expandable tubular retractor was used with the retractor system fixed to the table using an articulating arm (Fig. 3,4). After blunt separation of muscle space with the index finger, sequentially larger tubular retractors were placed to allow a working portal.
Residual soft tissue at the base of the tube was removed to expose the pars, partial laminae and facet joint of the L2 vertebra (Fig. 3). The first step was to resect the inferior process of L1 and superior articular process of L2 using piezosurgery and osteotomes alternatively to try to preserve as much bone pieces as possible. Subsequently, then a partial removal of the laminae and removal of the ligamentum was performed to expose the L2 right nerve root and dura sac. The second step was to detach the transverse processes from the pedicle and then resect the pedicle stump on right side flush with the vertebral body as verified by the navigation probe. Third, the lateral vertebral cortex and the posterior wall of the vertebral body underneath the posterior vertebral cortex were resected as much as possible with piezosurgery and osteotomes alternatively (Fig. 4). The same step was performed on the left side, but the resection of the lamina and vertebral body of this side was less than that of the right side. A fixed tubular retractor was also used on this side. (Fig. 5). Once the posterior wall of the L2 vertebral body was thin enough, a substantial reverse-angled curette was placed between the anterior dura and the posterior vertebral cortex and subsequently pushed anteriorly to create a greenstick fracture of the posterior vertebral cortex. The fractured posterior cortex was then removed.
Percutaneously placed pedicle screws were inserted on both sides from T9 to L5 (except L2) assisted by navigation. On the left side, and a temporary rod was passed underneath the fascia and then secured to the connecting rod with the set screws (Fig. 6). The posterior elements (spinous process and ligaments) were completely resected using Leksell rongeurs and piezosurgery alternatively. The spinal canal was then enlarged centrally somewhat more with the use of a Kerrsion rongeur.
Contoured rods with a natural lumbar lordosis and an appropriate kyphosis at the thoracolumbar junction were passed freehand through all the extenders, and then sequentially reduced into the tulip of the screw head with the extenders. Significant compressive forces had to be applied to achieve proper osteotomy closure, which was confirmed by radiography and palpation while viewed through the tubular retractor. The rod was held in a strict sagittal plane as the reduction was achieved. The extenders were removed after the rod was locked in position with top locking screws. The wound was irrigated with saline. The facet joints were decorticated via osteotomy, and copious amounts of decorticated local bone autograft were then placed in each facet-pars complex. A sub-fascial drainage was placed through a separate stab incision and the wound was closed in layers.
The patient began to ambulate three days after the operation and exercised in the stage of recovery. She was discharged from the hospital without complications and advised to come back to the hospital for a check at regular intervals. At the same time, anti-osteoporosis treatment was given.