Dual pedicle screws technique for revision surgery of adjacent segment degeneration after lumbar fusion surgery

English Keywords:Lumbar spine fusion  Adjacent segmental disease  Pedicle screw  Cortical bone trajectory

English Abstract:

  【Abstract】 Objectives: To investigate the feasibility and clinical efficacy of dual pedicle screws technique in revision for adjacent segment degeneration after lumbar fusion. Methods: From August 2016 to October 2018, 36 patients with adjacent segment disease(ASD) after previous thoracolumbar fusion were surgically treated in our department. The patients were divided into two groups according to the surgical procedures. Group A (Dual screws group): 12 patients (4 males and 8 females) with an average age of 66.2±4.2 years old (59-74); at 2 to 7 years after the first operation, with all ASD levels located in cephalic segments. First, the ASD segment was exposed, using Dual Screws(DS) technique, pedicle screw was implanted into the pedicle where there was already a pedicle screw, and the cephalad side of the ASD segment was inserted with cortical bone trajectory(CBT) screws. After decompression, short segmental fusion was performed. Group B(Control group): 24 patients (9 males and 15 females) with an average age of 64.0±7.7 years old (46-72); at 2 to 10 years after the first operation, with 19 ASD located in cephalic segments and 5 located in caudal segments. During the surgery, the previous surgical area was exposed and bilateral fixation rods were removed. The distal vertebral pedicles of ASD segment were inserted with screws using Magerl technique. Bilateral elongated rods were fixed after decompression of the responsible segment. The operation time, blood loss and postoperative complications were recorded. Pre- and postoperative ODI scores, low back pain VAS and leg pain VAS were also recorded. The position of internal fixation and intervertebral fusion were evaluated by X-ray and CT. The differences of clinical scores between and within each group were compared. Results: The ODI scores at pre-operation and final follow-up of group A were (82.5±16.7)% and (16.0±8.9)%, and that of group B were (78.0±14.6)% and (18.0±9.4)% respectively. The VAS back pain scores atpre-operation and final follow-up of group A were 8.3±3.5 and 1.7±0.9, and group B were 6.7±4.5 and 2.1±1.3 accordingly. The VAS leg pain at pre-operation and final follow-up of group A were 6.3±4.5 and 1.0±1.0, and group B were 7.8±3.4 and 2.3±2.4 accordingly. All patients were followed up for a average of 16.1±5.8 months(6-26 months). The ODI and VAS scores of the two groups were significantly improved after the revision(P<0.05). There was no significant difference in preoperative ODI score, VAS back pain score and VAS leg pain score between the two groups (P>0.05). There was no significant difference in preoperative and postoperative clinical scores and operation time between the two groups(P>0.05). The amount of intraoperative blood loss and the length of in-hospital time in group B were significantly greater than that in group A(P<0.05). There were no cases of surgical site infection and aggravated neurological symptoms in group A, while 1 case of intraoperative dural tear was repaired in group A. In group B, 5 cases of dural tear were repaired during operation or covered with subcutaneous fat, and 1 case of superficial wound infection was cured by dressing change. A total of 24 revision pedicle screws using dual pedicle screws technique were inserted, 18 of them were in good position, 4 screws penetrated the outer wall and 2 penetrated the inner wall of pedicles. However, there were no neurological injuries, no internal fixations loosing. In group B, 48 pedicle screws were inserted with no penetration and were all in good positions; at the final follow up, 8 cases of bony intervertebral fusion could be seen on CT scan in group A and 18 cases in group B. The average inclination angle of revision screws is 6.7°±6.6°(3°-16°). The average abduction angle was 10.3°±7.4°(0°-15°). Group B had no screw-related complications. Conclusions: The individualized dual pedicle screw fixation technique proposed a new minimally invasive alternative for surgical revision ASD after lumbar fusion. The clinical results of short-term follow-up were fairly good.