Assessment of Percutaneous Pedicle Screw Fixation in Management of Traumatic Thoracolumbar Spine Fractures ; Local Study at Suez Canal University Hospital

Background Data: Management of thoracolumbar fractures using the traditional posterior approach is associated with extensive paravertebral muscles damage and high postoperative morbidity. Minimally invasive percutaneous pedicle screw fixation is a highly valuable alternative for minimizing approach related morbidity. This technique ensures preservation of posterior musculature, less blood loss, less postoperative pain and shorter hospital stay. Purpose: To evaluate efficacy of percutaneous pedicle screw fixation in the treatment of traumatic thoracolumbar fractures. Study design: Descriptive cohort clinical case study. Patients and Methods: Thirty patients aged 18 to 50 years, with thoracolumbar fractures (AO types A1, A2 & A3) and neurologically intact underwent percutaneous pedicle screw fixation using


Introduction
The transition from the relatively stiff thoracic spine to the more dynamic lumbar spine subjects the thoracolumbar spine to significant biomechanical stress. 29This causes fractures of this region to be the commonest injury of the vertebral column, resembling nearly 60% of all traumatic spinal fractures. 10,18Injuries of the thoracolumbar spine ranges from compression fractures to flexion distraction injuries or fracture dislocation which can result in significant disability, deformity and neurological deficits. 12anagement of thoracolumbar fractures aims at stabilisation of the traumatized segments to achieve sound vertebral healing.This can be ascertained by using pedicle screw fixation that allows rigid stable constructs, earlier mobilization, and better deformity correction through providing three column spinal fixation. 10The efficacy and safety of traditional open techniques for pedicle screw placement has been well documented. 29However, open techniques require extensive paravertebral muscle dissection and retraction which results in muscle denervation, de-vascularization, and muscle atrophy. 8,9Add more, wide exposure and associated iatrogenic soft tissue injury increase intraoperative bleeding, increase the risk of infection, create significant postsurgical scarring, and can affect the stability of adjacent levels over the long term. 20Eventually, these shortcomings can affect the strength of back, prolong rehabilitation time, and induce chronic back pain which potentially delay the functional recovery. 28,14o minimize open approach-related morbidity, percutaneous pedicle screw fixation has been introduced as a novel technique of spinal fixation.Placement of pedicle screws percutaneously was first introduced by Magerl in 1977 as a temporary external spinal fixation to determine symptomatic disc levels before performing a spinal fusion. 13In 2001, Foley et al, 5 placed the first pre-curved rods onto percutaneously implanted pedicular screws in degenerative spinal disorder.The application of percutaneous pedicular fixation was initially limited to the lumbar spine. 2 later on, improvement in minimally invasive technologies has led to availability of more versatile instrumentations that can be used different regions or pathologies. 3,15he aim of the current study is to evaluate the efficacy and safety of percutaneous pedicle screw fixation in the management of relatively stable thoracolumbar fractures without neurologic compromise.

Patients and Methods
From March 2014 to March 2016, 30 patients suffered traumatic thoracolumbar fractures were involved in a prospective cohort study at Suez Canal university hospital.Inclusion criteria were; age between 18 and 50 years, and AO type A1, A2 or A3 thoracolumbar fracture without neurological deficit.We excluded patients with kyphotic deformity >45 o , obesity with BMI >30, or have bone disorders like osteoporosis or osteomalacia.Patients were treated with percutaneous pedicle screw fixation using the Medtronic Longitude II system under fluoroscopy.
Data included mechanism of injury, fracture type and level, pre and postoperative visual analogue scale evaluation for back pain, operative time and blood loss, complications and hospitalization time.Radiological parameters including the Cobb's angle of kyphosis, percentage of vertebral body height reduction, and percentage of anterior wedging of the fractured vertebral body were compared pre and postoperatively using plain radiographs.Accuracy of pedicle screw placement was evaluated using CT scan of the thoracolumbar spine in selected cases.Clinical outcome was assessed using modified Macnab criteria 11 at final follow up.

Results
The study included 21 (70%) males and 9 (30%) females.Their ages ranged from 18 to 50 years (mean 31 years).Falls were the mode of injury in 57%, followed by road traffic accidents in 43% of patients.Preoperatively, back pain scores on VAS ranged from 4 in 40% to 9 in 3.3% of patients (Mean 5±3.8 SD).(Figure 1) Level of fracture was D12 in 13, L1 in 7, D11 in 6, and L2 in 4 patients.Fracture type according to AO classification was A1 in 18, A2 in 7 and A3 in 5 patients.(Table 1) Preoperative radiographs revealed; a mean Cobb's angle of kyphosis 10.8 o and ranged from 5 o to 19.5 o .The percentage of mean vertebral body height reduction was 39.6% and ranged from 34% to 51%.The percentage of mean anterior wedging of the vertebral body was 35.6 % and ranged from 27% to 55%.All patients were treated using Medtronic Longitude II TM multi-level percutaneous fixation system.
A total number of 144 polyaxial pedicle screws were inserted under fluoroscopic guidance, with a mean of 4.6±0.81screws per patient (range from 4 to 8 screws).The mean operative time was 135 minutes (minimum of 125, maximum 240 minutes), and the mean intraoperative blood loss was 115 ml (minimum of 45, maximum of 200 ml).Early in the study, two percutaneous procedures were aborted and turned into open approach due to bad quality fluoroscopy, and both excluded from the study.The mean hospital stay was four days (min.2, max.11 days).Follow-up period ranged from 8 to 12 months.At final follow-up visit, back pain scores on VAS showed improvement with scores ranged from 1 (mild pain) to 5 (distressing pain) with a mean score of 2.8±1.Evaluation of patient satisfaction after surgery using Modified Macnab Criteria was excellent in 40%, good in 53% and fair in less than 7% of overall patients.(Figure 2) None of our patients exhibited poor recovery, wound infection or additional neurological deficit during follow-up.(Figure 3,4,5)

Discussion
Pedicle screw fixation procedures are reliable methods of spinal stabilisation for a wide variety of spinal disorders.However, conventional posterior instrumentations are commonly associated with some drawbacks including extensive muscle dissection and denervation, greater blood loss, considerable postoperative pain, and sometimes functional impairment. 6,19ecently, various minimally invasive techniques with percutaneous transpedicular screw fixation were introduced, especially for lumbar and thoracolumbar disorders to minimize the open approach-related drawbacks. 7,26In this study, we performed percutaneous pedicle screw fixation using polyaxial screws without fusion for patients presented with AO type A thoracolumbar fractures and neurologically intact.Fixation alone can be considered for fractures with temporary bone instability and high power of spontaneous healing after immobilization as it provides pain relief, corrects the deformation and avoids any additional displacements. 3,16n a randomized study compared pedicle instrumentation with and without fusion, Wang et al, 27 demonstrated better results in the group without fusion.On the other side, other studies 4,16 showed that pedicle fixation with fusion seems better for highly comminuted fractures and fractures with significant anterior vertebral wedging.Our average intraoperative blood loss was 115 ml which is consistent with previous studies that reported average intraoperative blood loss ranged from 88 ml to 194 ml, 16,29 while the average operative time was 135 minutes which is little longer than the average operative times reported in previous studies (87 min to 120 min), 17,29 but it improved later with the progression of our learning curve.Postoperatively, all patients required supplementary analgesics, but none of them required narcotics.The majority of our patients exhibited an improvement of back pain according to the VAS with a pain reduction from 5±3.8 preoperatively to 2.8±1.3 at final follow up.Wang et al, 24 16 who performed percutaneous pedicle fixation of thoracolumbar fractures without neurological deficits and reported a final mean Cobb's angle of 8.9°.In current study, 144 screws were inserted in 30 patients.The rate of pedicular cortical breach was 11.8%, but all were of mild to moderate degree.None of the misplaced screws resulted in neurological injury or required revision.Schizas et al, 22 reported a screw perforation rate of 23% in 60 percutaneous screws inserted under fluoroscopy.In another study comprised 115 percutaneous screws, Ringel et al, 21 reported a cortical breach rate of 13% with need for revision surgery for 9 misplaced screws.Percutaneous pedicle fixation entails a precise screw placement which requires a high quality intra-operative imaging that unfortunately increases operating time, and surgeon/patient exposure to ionizing radiation. 3n 2016 in a similar study by Abdelbaky A, 1 stated that Mean operative time was 110 minute.Mean days of hospitalization was 3.Only 7% of pedicle screws had a less than 2 mm pedicle breach with no neurological deficit.Taha H, 23 Stated that the average time of hospitalization was 3 days with no necessary oral analgesia on discharge in 63% of cases.The mean of VAS post-operative was 1.6 in the follow up.After 6 months from surgery all patients showed perfect vertebral reconstruction with improved vertebral body angle and Cobb's angle where vertebral body angle changed from 10.4 degrees to 6.2 degrees post-operatively and Cobb's angle ranged from 4.9 degrees to -6.3 degrees.Screw accuracy in pedicle showed a 5.4% misplaced screws.
In a comparative prospect between open versus minimal invasive percutaneous fixation technique, Wang et al, 25 it showed nearly similar results related to percutaneous fixation and it is better than traditional open technique related to surgical time, blood loss, hospital stay and use of narcotics post-operative.While there is no significant difference related to infection rate and screw positioning.For clinical outcome evaluation, we used Modified Macnab Criteria with an overall patient satisfaction rate of 93% (40% excellent recovery, 53% good recovery) which is comparable with the results published by Wang et al with a reported satisfaction rate of 88.2% (52% excellent, 35% good).

Conclusion
The data reported in this study suggest that percutaneous pedicle screw fixation suggest is a safe and reliable alternative to open surgery in the management of type A thoracolumbar fractures not associated with neurologic compromise.Much radiation exposure represents a limitation.However, the technique is better or comparable in terms of post operative pain, deformity correction, complication rate and return to the activities of daily living with the advantage of being minimally invasive.

Figure 2 Figure 5 .
Figure 2. Patient Satisfaction According to Modified MacNab Criteria

Figure 3 .
Figure 3. Illustrative patient aged 25 years old male, Presented with AO type A3 fracture of L1, without neurological deficit.(A) Axial view of CT spine (B) Sagittal view of CT spine.A

Table 2 .
Radiological Evaluation Pre-and Post-operative Parameters.

Table 1 .
Demographics of the Study Population.
published an average postoperative VAS score of 2.2±0.8 for open fixation group and 1.5±0.9 for percutaneous fixation group which impacted on earlier mobilization, shorter recovery time, shortened hospital stay, and reduced hospital costs for percutaneous fixation group.The final Cobb's angle of kyphosis averaged 5.6 o which is comparable to the results reported by Palmisani et al, 17 in a study comprised 51 patients with thoracolumbar fractures treated by percutaneous pedicular fixation and a final mean Cobb's angle of 7.8 o , and the results published by Ni W et al,