Percutaneous kyphon balloon kyphoplasty has achieved encouraging results in the treatment of osteoporotic compression fractures, both for correcting spinal deformities and relieving pain.1 Although kyphoplasty is a small invasion, the surgery itself has some defects such as more X-ray fluoroscopy time during the operation and accumulation of radiation dose causing harm to patients and operators, and the puncture is hard to achieve in a highly precise location.2 But those problems can be solved effectively with navigator guided puncture and kyphoplasty. The following is the summary of 38 cases treated successfully with the new puncture method in our hospital.
The percutaneous kyphon balloon kyphoplasty treating osteoporotic spinal compression fractures has been carried out in 59 cases since March 2003 in our hospital. From October 2005 to June 2007, 38 cases of spinal compression fractures were treated with C-arm navigator guided vertebral body kyphoplasty. Six males and 15 females aged from 60 to 78 comprised 21 conventional C-arm fluoroscopic kyphoplasty patients with an average age of 73.2 years (12 cases of thoracic fracture and 9 cases of lumbar fracture); 17 cases with one fractured vertebrae, 3 cases with two fractured vertebraes, and 1 case with three fractured vertebraes were included in this group. In the group with C-arm navigator guided kyphoplasty, 11 males and 27 females, aged from 61 to 85 years were included with an average age of 74.3 years. This group consisted of 23 cases of thoracic factures and 15 cases of lumbar fractures, among which 30 cases had one fractured vertebrae, 5 cases had two fractured vertebraes, and 3 cases had three fractured vertebraes. The fracture period of all cases before surgery in these two groups ranged from 5 to 35 days with an average period of 10.0 days. There were 45 cases with obvious traumatic history out of the rest 14 cases.
Patients were pronated after completion of general anesthesia with endotracheal intubation. One torus is placed respectively under the chest and the pelvis to over-extend the thoracic and lumber vertebraes to facilitate fracture reduction. A 1.5 cm incision was made from the processus spinosus adjacent to the fracture to reveal the supraspinal ligament, from both sides of which soft tissue is dissected by osteotome to reveal the processus spinosus. Fixation of the navigator reference frame and connection of both the frame and the C-arm X-ray machine to the navigator system was accomplished (Stethstation, Medtronic, U.S.A.).
X-ray antero -posterior (A-P) and lateral views were taken with the compressed vertebraes. The navigator system will collect and calibrate the images to form a virtual image with the virtual tools overlying on it, and then the puncture tool is registered. Under the guidance of A-P images on the navigator, we set the location of the pedicle of the vertebrae of the compressed vertebrae on the skin, then, move to the outside 1 cm and make an incision. A longitudinal incision about 0.5 cm is made through the skin. With the guide of the navigator, and along the pedicle, the soft tissue is punctured via skin with a needle with the bushing in a certain angle until touching the bone surface. Observe the location of transfixion pin in the virtual A-P and lateral views through the navigator, adjust the transfixion pin to the expected entry point, and then fix the bushing in case of movement and measure the prospective puncture depth (Figures 1 and 2). In this precise position, break the cortical bone with a transfixion pin and tap the needle down the center of the pedicle in the anterior-inferior direction of the vertebrae. Fix the bushing at the entry point and then pull out the transfixion pin which is replaced by an drill. With the guide of the navigator, confirm the precise angle and direction of pin performance, and make sure that the excavation tool is completely in the pedicle. Rotate the drill slowly down in the medial and inferior direction until 4 mm clearance is observed between its tip and the anterior border of the vertebrae in the lateral image. Fix the bushing at the entry point and then take off the excavation tool. Insert a thin guidewire and take out the bushing. Repeat the above steps to complete the puncture of the contralateral pedicle.
Insert the kyphon bushing to the pedicle along the thin guide pin. Make sure that under the monitor of the lateral view of the C-arm X-ray, the pointed end of the kyphon bushing is just 2 mm anterior of the posterior border of the vertebrae. Pull out the thin guide pin and use the kyphon drill bit and polishing tool along the bushing to expand the passage and make the passage wall smooth, based on the depth measured in advance. The following steps including expanding gradually and injecting bone cement are not different compared with conventional X-rayed kyphoplasty.
The day after operation, patients were encouraged to walk with braces. Patients took anti-osteoporotic agents such as Calcitonin or Fosamax for adjuvant therapy.
Comparisons were made for the number of X-ray fluoroscopy exposures and operative time of kyphoplasty for one fractured vertebrae between conventional and navigator guided groups. The accuracy of puncture could be evaluated indirectly by the leakage of bone cement with A-P and lateral X-ray views during the operation or 1 week after the surgery. Through the lateral X-ray views, the angle differences between the superior and inferior borders of the compression fracture vertebrae were used to calculate the rate of fracture reduction.
All data were expressed as mean±standard deviation. Data were compared between groups using analysis of variance (ANOVA). A P <0.05 was considered statistically significant.
The punctures of all 38 cases that were treated under the guidance of the C-arm navigator were confirmed within the expected range by X-ray fluoroscopy after the surgery. Two cases needed adjusting of the direction of the transfixion pin for entering working passages because of the departure to the cortical bone beside of the pedicle. Analyzing the bone cement filling, 29 cases had satisfactory results except for three with minimal leakage at anterior vertebrae, one with leakage behind the puncture point of the pedicle and five with minimal leakages through a fracture line of the end plate to the intervertebral space. In 21 conventional C-arm kyphoplasty cases, one had cerebrospinal fluid (CSF) leakage at T7 and the rest were without incidence and had the expected puncture results. However, in 7 cases, the puncture was adjusted several times in order to achieve satisfactory results. When we evaluated bone filling, there were 3 cases with leakages at the anterior border of the vertebrae, 2 with leakage at the posterior pedicle and 2 with leakage through end plates to the intervertebral space. In neither group were there any severe complications such as death or paraplegia.
Blood loss in the two groups was negligible. An average of 11.6±2.4 (8-18) times radiation exposures were needed in the C-arm navigator guided kyphoplasty. Conventional kyphoplasty required 19-30 radiation exposures, with an average of 24.7±3.2. A distinctive difference was shown in the number of X-ray exposures between the two methods (P <0.001). The average operative time for 30 cases, with one fracture lesion treated, with the C-arm navigator guided kyphoplasty was 67.8±10.0 minutes. For the average time to complete the 17 cases with one fracture lesion treated with conventional kyphoplasty was 112.1±10.5 minutes. There was a significant difference in the operative time between the two groups (P <0.001). In the C-arm navigator guided group, the angle of the superior and inferior border in the sagittal plane of the compression vertebrae was on an average of 17.9±7.8 degrees preoperatively and 5.2±2.7 degrees postoperatively, with a reduction of 70.9%. In the conventional group, the angle was on an average of 18.3±7.9 degrees preoperatively and 4.2±1.8 degrees postoperatively, with a reduction of 77.0%. No distinctive disparity existed (P >0.05).
There are few reports worldwide on navigated kyphoplasty treating osteoporotic spinal compression fracture. One relevant report showed that C-arm nagivated kyphoplasty would remarkably reduce operative time and X-ray exposure and enhance operative accuracy. However, it is not a direct comparison between C-arm navigator guided and conventional C-arm kyphoplasty.3 Our hospital developed vertebral body kyphoplasty guided by a navigator based on our abundant experience with navigator-guided vertebral column internal fixation. And we are skilled at placing the reference frame and registering tools during the surgery.
Dose and frequency of X-ray radiation during the operation
Multiple X-ray exposures are needed with the C-arm in different angles and directions to ensure the precision of puncture during traditional kyphoplasty. With the navigator, only two exposures are needed to obtain A-P and lateral views to create the navigator virtual simultaneous images. Consequently, the frequency and dose of X-ray are reduced and the risks of X-ray to the patients are also diminished. Increasing concerns are being raised as to the risks of X-ray radiation. It is reported that intra-operative X-ray does harm to skin, retina, thyroid gland and genital glands. It is found in this study that C-arm navigator guided kyphoplasty results in a substantial decrease in X-ray exposures compared to the traditional method, and thus decreases the operative time.
Many interruptions during the traditional kyphoplasty procedure are needed to adjust the pedicle entry point and the direction of puncture; because only one view can be obtained at one time of exposure with C-arm X-ray. Repeated fluoroscopy and the inability to monitor the real-time A-P and lateral views simultaneously could cause a decrease of puncture precision. What is more, repeated punctures could increase the risk of a mistake during the operation, aggravate the trauma, and prolong operative time. In this study, although the puncture results were generally satisfactory in conventional kyphoplasty, 7 cases had satisfactory puncture position only after several re-punctures and adjustments.
Two fluoroscopic views could be monitored at the same time, like using a G-arm X-ray machine. The real-time position and angle of the puncture instrument in the A-P view image and the lateral image could be displayed on the screen in real time, which increases puncture accuracy and decreases operating mistakes. Ohnsorge et al4 found in an in vitro experiment C-arm computer assisted kyphoplasty was superior to conventional kyphoplasty in both puncture angle and divergence. It is reported that the accuracy of internal fixation through the pedicle under the guidance of the navigator is much higher than the traditional C-arm X-rayed method.5 The location and puncture procedure in the percutaneous kyphoplasy is similar to the internal fixation through the pedicle, so it is obvious that C-arm navigator guided kyphoplasty could significantly increase the puncture accuracy.
Evaluation of postoperative imaging
In this study, the fracture reduction rate of conventional kyphoplasty and C-arm navigator guided kyphoplasty is 77.0% and 70.9%. There are no distinctive differences regarding fracture reduction rate and bone cement leaka ge between these two groups.
There are few hospitals now equipped with navigator instruments in China, and few doctors who have the necessary operator navigation techniques. Vertebral body kyphoplasty guided by navigator needs a few special navigation instruments as well as the navigator. For example, the transfixion pin with bushing is required. Minimal invasive technique is one of the important trends in surgery. Minimal invasion means not only minimal incision and less local tissue injury, but also less radiation exposure to the patient even to the operator during the whole diagnosis and treating procedure. C-arm navigator guided kyphon balloon kyphoplasty has advantages including reduced X-ray fluoroscopy time, shorter operative time and precise puncture, with the disadvantage of needing a small additional incision to expose the spinous process for the fixation of the navigator's reference frame.
1. Yang HL, Yuan HA, Chen L, Lu J, Ni CF, Tang TS. Kyphoplasty treating osteoporotic spinal compression fracture
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4. Ohnsorge JA, Siebert CH, Schkommodau E, Mahnken AH, Prescher A, Weisskopf M. Minimally-invasive computerassisted fluoroscopic navigation for kyphoplasty. Z Orthop Ihre Grenzgeb 2005; 143: 195-203.
5. Laine T, Schlenzka D, Mäkitalo K, Tallroth K, Nolte LP, Visarius H. Improved accuracy of pedicle screw insertion with computer-assisted surgery. A prospective clinical trial of 30 patients. Spine 1997; 22: 1254-1258.