These osteoporotic burst fractures had relatively acute findings on MRI or CT images. Patients complained of initially experiencing difficulty in daily activities and walking and having severe tenderness around the vertebral fracture site. The patients were very old and had severe osteoporosis (under -4.6 bone mineral density [BMD] T score), along with other medical comorbidities. They were treated with bed rest, analgesics, and braces over the course of 4 weeks. However, they still complained of back pain after conservative treatment. We assumed that the incidence of cement leakage would be greater before the 4-week mark, and the optimal time to correct kyphotic deformity was considered to be 4 weeks after burst fracture.

Our control group consists of 33 cases of conservative treatment and 13 cases of posterior instrumentation and bone fusion (conservative treatment group: age range 64~88 years; mean age, 80 years; and under -4.7 BMD T score; posterior surgery group: age range 60 to 81 years; mean age, 74 years; and under -4.2 BMD T score). These patients were also followed for over 1 year. There were no statistical differences between the study group and the control group with respect to age and BMD (p=0.153). We retrospectively compared the percutaneous balloon KP group with the control group. We performed 5 thoracic and 8 lumbar procedures (Table 1). Five patients had diabetes, and three patients had cardiovascular disease. Moreover, one patient had chronic obstructive pulmonary disease. Both diabetes and cardiovascular disease were observed in three patients. Preoperative BMD revealed the presence of osteoporosis in 12 patients (T score range, -6.2 to -4.6; mean T score -4.9) (Table 2).

After skin infiltration with local anesthesia, a 1 cm paramedian incision was made. On anteroposterior fluoroscopy, an 11-gauge bone biopsy needle was centered over the pedicle at the 10 o'clock (left pedicle) and 2 o'clock (right pedicle) positions. The needle was medialized through the cylinder of the pedicle to reach the middle of the vertebral body. A guide pin was passed through the biopsy needle into the vertebral body. The needle was then removed, and the access portal was expanded with larger cannulae. Through this cannula, an inflatable balloon was advanced. Once both balloons had been inserted, they were sequentially inflated until the fracture was realigned or maximal inflation pressure (220 psi) had been reached. The balloons were then removed, and the bone was stabilized with polymethyl methacrylate.

The reductions in pain from baseline to the third day and to 3 months post-operative were statistically significant (VAS scores: pre-operative, 8.3±0.4; 3 days post-operative, 3.9±0.2; 3 months post-operative, 3.2±0.17; 1 year post-operative, 3.1±0.17). The average VAS score decreased by 5.2±0.3. Every patient was capable of walking autonomously one day after KP. After conservative treatment, the VAS score decreased by 3.4±0.2 (VAS score: pre-operative, 7.9±0.4; after 3 months, 4.8±0.18; after 1 year, 4.5±0.17). Hence, there was a statistically significant difference between the KP and conservative treatment groups with regard to improvement in the VAS score (p=0.012). After posterior instrumentation and fusion, the VAS score decreased by 5.3±0.3 (VAS score: pre-operative, 8.5±0.5; 3 days post-operative, 3.5±0.21; 3 months post-operative, 3.4±0.2; 1 year post-operative, 3.2±0.19). Hence, there was no statistically significant difference between the KP and open posterior surgery groups with regard to improvement in VAS score (p=0.125).

The initial Chen and Lee semi-quantitative scale was grade 3 or 4 in all patients. In the KP group, 12 patients (100%) improved to grade 0 at final follow-up. In the conservative treatment group, 12 patients (36.5%) improved to grade 0, 18 patients (54.5%) improved to grade 1, and 3 patients (9%) improved to grade 2 at final follow-up. In the posterior instrumentation and fusion group, 13 patients (100%) improved to grade 0 at final follow-up.

KP, as well as vertebroplasty, offers significant pain relief and fracture stabilization. The application of percutaneous vertebroplasty as a minimally invasive procedure is popular and pervasive. Nevertheless, the danger of cement leakage into the posterior spinal canal has precluded percutaneous vertebroplasty as a treatment for burst fractures. In 2004, however, Chen and Lee¹, reported a clinically satisfactory result by performing percutaneous vertebroplasty in six stable burst fractures without osteoporosis. Although cement leakage into the adjacent intervertebral disc space occurred in four instances (66.7%), it did not cause the neurological symptoms associated with cement leakage into the posterior spinal canal. Despite its evident benefits with regard to pain relief and vertebral stabilization, vertebroplasty is not as effective in correcting kyphotic deformities. Balloon KP was developed in order to compensate for vertebroplasty's disadvantages in correcting kyphotic deformities. Balloon KP minimizes the possibility of cement leakage. Hence, we performed balloon KP for the treatment of osteoporotic burst fractures.

Balloon KP was developed by applying Dr. Mark Reiley's balloon tamp in percutaneous vertebroplasty^2,3. The balloon tamp was developed by Reiley in 1997, with the goal of restoring vertebral body height and reducing kyphosis. KP involves the inflation of a balloon tamp before injection of bone cement in the compressed vertebral body, in an effort to reduce kyphotic deformity. Shindle et al.⁴, reported that balloon KP enhances the height reduction >4.5-fold over the positioning maneuver alone and accounts for over 80% of the ultimate reduction. Because KP enables the injection of bone cement at low pressure, the procedure minimizes the possibility of cement leakage^5-7.

Reportedly, the complication rate following balloon KP is similar to that seen in vertebroplasty. Complications deriving from vertebroplasty as a treatment for osteoporotic burst fracture occur in less than 1% of patients when the procedure is performed by an experienced surgeon. The complication rate stemming from vertebral pathologic compression fractures is 5~10%. Although complications occur slightly more frequently in KP than in vertebroplasty, we believe that such results derive from KP's relative dearth of recognition. However, according to Orlando, the complication rate with respect to symptomatic cement extravasation may be lower in KP than in vertebroplasty². We observed only one instance of cement leakage in this study. We attribute our success to 4 weeks of conservative treatment prior to the procedure and our decision to perform KP in stable burst fractures. Hulme et al.⁸, reported the following distribution of cement extravasation in vertebroplasty: epidural, 32%; paraspinal, 32.5%; intradiscal, 30.5%; pulmonary, 1.7%; and foraminal, 3.3%. He further reported the following distribution of cement extravasation in KP: epidural, 11%; paraspinal, 48%; intradiscal, 38%; pulmonary, 1.5%; and foraminal, 1.5%. In most cases (vertebroplasty, 96%; KP, 89%), symptoms do not accompany cement extravasation. Intradiscal cement leakage, which occurs relatively frequently, may cause mechanical overload to the disc and/or to the adjacent vertebrae. Lin et al.⁹, reported that 58% of vertebral bodies adjacent to a disc with cement leakage fractured during the follow-up period, compared with 12% of vertebral bodies adjacent to a disc without cement leakage after vertebroplasty. We only observed complications accompanying cement leakage in a single case.

Frail older patients have poor tolerance for the bed rest required in non-operative management and the physiologic stress engendered by an open stabilization procedure¹⁰. Indications for open surgery are rare and include major neurologic injury and mechanical instability. Anterior decompression is an effective method; however, the morbidity rate and the risk of spinal deterioration in instrumentation and fusion are very high in senile patients. Posterior decompression and stabilization are perhaps better tolerated by older patients. The pedicles remain stronger than the vertebral bodies, but implant loosening remains a problem¹⁰.

Nevertheless, balloon KP is somewhat beneficial for strengthening the spinal wall. Because KP enables the injection of bone cement at low pressure, the procedure further diminishes the possibility of cement leakage^5-7.