Fracture-dislocation is a serious type of thoracolumbar spine injury, often associated with spinal cord injury. Posterior decompression of the fresh fracture and 4 screws fixation of the short segment via the pedicle is the usual fixation method of choice for this type of injury. However, the spinal stability structure of this type of injury is severely damaged, and there is a large degree of unreliable internal fixation across the injured vertebrae, often with unsatisfactory repositioning or failure to achieve repositioning requirements and parallelogram effect. From July 2008 to November 2009, we treated 11 cases of fracture-dislocation type thoracolumbar spine injuries with 6 screws fixation of the pedicle (while fixation across the injured spine) and obtained good clinical results, which are reported below. Cai Xiaojun, Department of Orthopedics, Zunyi First People’s Hospital
General data This group of 11 cases, 9 male and 2 female, 24-48 years old, average 35.4 years old; 5 cases of high fall injury, 4 cases of coal mine collapse pressure smash injury, 2 cases of car accident. After admission, all cases took X-ray and CT examination of thoracic and lumbar spine, T111 cases, T122 cases, L14 cases, L23 cases, L51 cases. Fracture type: flexion-rotation fracture-dislocation in 7 cases, burst fracture-dislocation in 3 cases, and shear fracture-dislocation in 1 case. The degree of compression of the anterior edge of the injured vertebrae ranged from 40% to 85% mm (mean 65%), and the Cobb angle was 13° to 38° (mean 21°). The fracture block spinal canal encroachment rate: 1 case of total spinal canal encroachment, 2/37 cases of encroachment, 1/32 cases of encroachment, and <1/31 cases of encroachment. The degree of spinal cord function damage according to Frankel classification: 2 cases of grade A, 4 cases of grade B, 3 cases of grade C, 1 case of grade D, and 1 case of grade E. The admission time after injury was 1.5~14 hours, with an average of 4.6 hours; 9 cases were admitted within 8 hours after injury, and 5 cases with spinal cord damage were given high-dose methylprednisolone shock therapy (30 mg/kg intravenous drip within 30 min, and 5.4 mg/kg.h for 23 h after 30 min).
Surgical method Under general anesthesia, a posterior incision and repositioning, internal fixation with an arch nail system (with additional fixation of the injured vertebrae) + intervertebral or posterior lateral bone grafting (internal fixation was provided by Xinrong) were performed. After general anesthesia in the prone position, a posterior median incision was made to expose the fixed spinous processes, laminae, and small articular processes (7 cases of complete injury to the injured PLC), and pedicle screws were inserted into the healthy pedicles above and below the injured spine (screws could also be inserted after decompression was completed). The spinous process and lamina of the injured vertebra were completely resected, the spinous process and lamina of the upper healthy vertebra were resected in the lower 3/4 (the upper 1/4 was preserved), and the inferior articular process of the injured vertebra could be resected together with the injured vertebra if it was fractured. The vertebral canal is explored, and decompression is performed from the lateral front of the vertebral canal. The dislocated segment is removed, and the healthy pedicle screw is tried to be repositioned by lifting it, and the pedicle screw is implanted in the direction of the end plate diagonally from the nail entry point of the injured vertebral arch after eliminating the factors blocking the repositioning; a moderate pre-curved fixation rod is placed in the pedicle nail slot, and the slipped vertebral body is repositioned and fixed by the principle of three-point leverage, and bone grafting or titanium cage is placed in the injured vertebral space to support it; the repositioning, fixation, and bone grafting in the vertebral space are completed with the addition of transverse The connector was added and bone grafting was done on the posterior and lateral sides of the fixed vertebrae (including the small joint space, the lateral side of the small joint synapse and between the transverse processes). Negative pressure drainage tubes were routinely placed in the incision. Postoperative negative pressure drainage was removed at 48-72 h. Antibiotics were administered for 5-7 d, and stitches were removed 12 days after surgery.
Results Eleven cases were followed up for 6~45 months, with a mean of 18.6 months. x-ray showed healing of the intervertebral and posterior lateral implants in 10 cases, with a mean healing time of 8.5 months; the vertebral sequence recovered well, with the preoperative height of the anterior margin of the injured vertebra 40%~85% mm (mean 65%) recovering to 92%~98.8% (mean 95.6%), and the Cobb angle preoperatively 13°~38° (mean 21°) The spinal cord damage function was restored to different degrees in 10 cases. 2 cases of Frankel grade A were restored to grade B in 1 case and grade C in 1 case; 4 cases of grade B, no change in 2 cases and restored to grade C in 2 cases; 3 cases of grade C, restored to grade D in 2 cases and grade E in 1 case; 1 case of grade D was restored to normal. There were no complications such as internal fixation fracture, loosening, nail extraction and spinal curvature.
Discussion The thoracolumbar fracture-dislocation has huge injury violence, complex injury mechanism, and is often accompanied by more serious spinal cord, conus and cauda equina damage, and posterior surgical decompression with pedicle screw repositioning and fixation is the mainstream treatment at present. Previously, we used Dick nail, SF nail, AF nail, 4 nail bar system and other fixation existed some complications, such as unsatisfactory reset, unreliable fixation, parallelogram effect of fixed nail, loss of height of the anterior edge of the injured vertebra during postoperative follow-up, fracture and loosening of internal fixation, and spinal curvature phenomenon. Proper orthosis of thoracolumbar segment fractures according to biomechanical principles relies on three aspects [1], namely (1) bracing and bone graft support on the ventral side to restore the height and load-bearing capacity of the anterior column; (2) compression on the dorsal side and fixation by the short segmental pedicle system to provide a good biomechanical environment and promote fusion by strengthening the tension band mechanism of the spine based on the integrity of the anterior column; (3) posterior protrusion at the The top of the deformity (generally the injured vertebrae) is directly pushed, and the forward extrusion makes the dorsally displaced injured vertebrae reset forward and reconstruct the anatomical sequence. For this reason, we changed the previous 4-nail fixation of spinal fracture-dislocation to 6-nail fixation, i.e., increased nailing of the injured vertebra, which does not contradict the principle of fixation of thoracolumbar fracture-dislocation, but rather increases spinal stability.
Dick et al [2] conducted an in vitro biomechanical study of internal spinal fixation as early as 1994, in which six- and four-nail fixation was performed on a bovine lumbar spine model, and found that six-nail fixation had significant advantages: a 160% increase in axial load-bearing capacity, a 48% increase in flexion resistance, and a 38% increase in torsion resistance. This indicates that axial load, flexion and extension, and torsional stability can be increased after fixation of the injured spine. Yuan Qiang et al [3] applied the “structural mechanics solver” for structural mechanics analysis and concluded that fixation of the injured spine has the following advantages: (1) provides good three-point fixation and reduces the suspension effect of the internal fixation system, thus reducing the formation of kyphosis; (2) reduces the parallelogram effect and enhances stability; (3) avoids the strain on the normal intervertebral disc, which is beneficial to the stability of the injured spine. Shen et al [4] concluded that the screwed-in screws in the injured vertebrae could act as a forward pushing force during repositioning and fixation, and the “three-point fixation” facilitated the correction of the Cobb angle. In our 11 cases of thoracolumbar fracture-dislocation with increased nail fixation of the injured spine, we eliminated the concerns of unsatisfactory repositioning and unreliable fixation, and there was no parallelogram effect or broken nails and rods in all cases during the follow-up, and there was no significant loss of anterior margin height and Cobb angle after surgical correction, and no case of spinal curvature. Thus, internal fixation of the pedicle in the injured spine is significantly superior for restoring vertebral height and correcting subluxation, while increasing the ability to maintain stability postoperatively.
For the technique of nailing the injured spine, we have learned in 11 cases of nailing the injured spine that the operation of this technique is not difficult, but the key lies in the nailing of burst fractures and dislocated injured spine. In this group, 3 cases of burst fracture-dislocation, 2 cases of bilateral arch fracture, intraoperative displacement of both sides of the arch, 3 side of the arch from the body or the base of the fracture, nail implantation to remove one side of the fracture of the loose arch and 2 side of the broken arch can not be reused, if the arch of the vertebral body can be intact through the arch of the nail implantation to the vertebral body, the tail of the implanted injured spinal screw as far as possible with the tail of the upper and lower arch screws in a coronal level, which is conducive to nail rod fixation after This helps to maintain the restriction and pushing effect on the injured vertebra after fixation.
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