Pain outcome and vertebral body height restoration in patients undergoing kyphoplasty.

Introduction: Kyphoplasty, a minimally invasive technique, has recently been developed to provide immediate pain relief, biomechanical stabilization, prevention of fracture progression, vertebral height restoration, and prevention or reversal of kyphosis to patients with osteoporotic vertebral compression fractures (VCF).

Materials and Methods: We retrospectively reviewed 24 patients treated with kyphoplasty. A total of 37 vertebral levels were augmented. Visual analog scale (VAS) scores were documented in the immediate pre- and postoperative period, as well as 4, 12, and 72 weeks after the procedure. Vertebral body height restoration was assessed on postoperative x-rays.

Results: Mean preoperative VAS score was 9.3 and improved to 5.4 in the immediate postoperative period. At 4, 12 and 72 weeks postoperatively, mean VAS scores were 5.1, 5.9, and 6.1 respectively. All patients returned to their daily activities within 24 hours. No significant restoration of vertebral body height was observed.

Conclusion: In regards to pain relief and postoperative functional outcome, kyphoplasty is a safe and effective treatment modality for osteoporotic VCFs, even when no significant restoration of vertebral body height is achieved.

Key Words: height restoration, pain, vertebral compression fracture

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Osteoporotic vertebral compression fractures (VCFs) constitute a significant cause of morbidity in the elderly, severely affecting quality of life. VCFs often result in chronic pain, depression, sleeping disorders, decreased pulmonary capacity due to kyphosis and malnutrition due to stomach compression. (1-4) Postmenopausal women are particularly vulnerable. It has been estimated that approximately 16% of postmenopausal women are affected (5); in women older than 80 years, this percentage increases to 40%. (4) In the United States alone, about 44 million people are considered to be at risk for developing osteoporotic VCFs. (6) The incidence of VCFs due to primary or secondary osteoporosis has been estimated to go up to 117/100,000 per year. (1)

Management of VCFs traditionally consisted of conservative pharmacological treatment with analgesic and anti-inflammatory drugs, bed rest, massage, heat therapy and occasionally, bracing. (6-8) Prolonged pain medication may, however, lead to gastrointestinal side effects and confusion, with increased fall risk, whereas bed rest and immobilization inevitably accelerate bone loss, enhancing the existing osteoporotic changes. Furthermore, bracing may restrict diaphragmatic movement and is very inconvenient for the patient. (6)

In an attempt to achieve immediate and long-lasting pain relief, a more aggressive treatment for VCFs was advocated. Vertebroplasty, a minimally invasive technique involving the high-force injection of low-viscosity polymethylmethacrylate (PMMA) was first described by Galibert et al (9) in 1987 for the management of vertebral body tumors, but was soon introduced in the treatment of VCFs, either due to osteoporosis or malignancy. Vertebroplasty has been documented to achieve stabilization of the fracture, prevention of fracture progression, vertebral height restoration, prevention or reversal of kyphosis and excellent immediate pain relief and early mobilization. (6,10-13) However, it has been associated with a relatively high incidence of cement extravasation to epidural or foraminal spaces, leading occasionally to nerve root compression. (2,6,14) Pulmonary embolism due to cement material has also been reported. (2,15) Moreover, vertebroplasty does not always restore vertebral body height or improve the kyphotic deformity (3,16) and compared with kyphoplasty, vertebral body height restoration and reversal of kyphosis rates appears to be inferior. (17,18)

Balloon kyphoplasty, another minimally invasive procedure, was developed in the last few years, aiming to address the shortcomings of vertebroplasty. This technique entails the percutaneous placement and inflation of a balloon in the vertebral body; low-force injection of high-viscosity PMMA follows. Kyphoplasty has been gaining increasing popularity among orthopaedic and neurologic surgeons. In 2003, 16,000 operations were performed, (14) and that number continues to grow.

We report our experience with the treatment of 24 consecutive patients with osteoporotic VCFs using kyphoplasty.

Materials and Methods

This is a retrospective clinical study, with certain limitations in regards to available patient data and the inherent biases of all retrospective studies. We studied 24 consecutive patients (16 female, 8 male) treated with balloon kyphoplasty for osteoporotic vertebral compression fractures. The average age was 72.6 years (range 48-87 yr). Surgical intervention was undertaken within 9 weeks from the onset of pain (range 4-9 wk). Thirteen patients had two vertebral levels treated, whereas eleven patients had single fractures. Overall, a total of 37 vertebral bodies (25 thoracic and 12 lumbar) were augmented. All patients had persistent focal pain that was not significantly alleviated by conservative treatment. Preoperative radiologic evaluation included magnetic resonance imaging (MRI) in all patients and occasionally, computed tomography (CT) with 3-D reconstruction.

General endotracheal anesthesia was employed in all procedures. Unilateral extrapedicular approach was performed on the thoracic levels and transpedicular approach on the lumbar levels. Intraoperative somatosensory-evoked potentials, motor-evoked potentials and electromyographic monitoring was routinely performed. Polymethylmethacrylate (PMMA) was injected under biplanar fluoroscopic guidance in all cases; a maximum amount of 3 mL of PMMA was used in each case.

VAS scores for the quantification of pain by the patients were obtained preoperatively, in the immediate postoperative period, and at 4, 12, and 72 weeks after the procedure. Restoration of vertebral body height was assessed on postoperative plain x-rays.

Results

All patients were discharged from the hospital within 24 hours and were able to resume their routine activities. All of our patients experienced significant pain relief postoperatively. The mean VAS score improved from 9.3 before surgery to 5.4 immediately after kyphoplasty was performed. The VAS score was 5.1 four weeks postoperatively, 5.9 at 12 weeks, and 6.1 at 72 weeks (Fig. 1). Two patients were lost to follow-up and their VAS scores at 72 weeks could not be obtained.

Although some degree of restoration of vertebral body height was obtained in our series, it did not reach a level of significance in any of our patients. Analytically, in 14 patients, no increase in the height of the vertebrae was noted, whereas in the 10 patients in whom some restoration was achieved, the increase did not exceed 20% (range 5-20%). Interestingly, no correlation was observed between pain relief and vertebral body height restoration in our current study.

We did not encounter any cement leakage or other major complications during the procedure.

Discussion

Kyphoplasty provides significant pain relief along with stabilization of the fracture, prevention of fracture progression, vertebral height restoration, and prevention or reversal of kyphosis. There is some variation in regards to pain relief, vertebral height restoration, prevention of kyphosis and return to premorbid functional status among different clinical series. (1-21) Pain relief following kyphoplasty is comparable to vertebroplasty, in the immediate and early postoperative period. (16-21) Garfin et al (22) reported in their review that 95% of patients experienced pain relief and 90% had functional improvement. Ledlie and Renfro (23) noted pain elimination in 73% of their patient cohort, and pain alleviation in 15%. Similar results have been reported by several other authors. (16,19,24) Furthermore, Dudeney et al (19) documented a statistically significant improvement in physical and social functioning, as well as vitality, in their group of patients who underwent kyphoplasty. Coumans et al, (16) in their well-organized prospective clinical trial, concluded that the vast majority of their treated patients experienced significant improvement not only in bodily pain and physical functioning, but in emotional and mental health as well. Our study provides further support for the efficacy of balloon kyphoplasty in pain improvement and a fast return to daily activities.

[FIGURE 1 OMITTED]

Cement leakage has been reported to occur less frequently with kyphoplasty than vertebroplasty. (3,10,24-27) It seems that the packing of the cancellous bone that surrounds the bone tap, in association with the higher viscosity of PMMA and the lower force injection, prevents the extravasation of cement. Lieberman et al (27) reported leakage of material in only 6 of 70 (8.6%) augmented levels; there was no development of any related clinical symptoms. Similarly, the incidence of cement extravasation in the cohort of Dudeney et al (19) was as low as 4%, and was asymptomatic in all cases. Consistent with the literature, no serious complications were noted in our patients.

In the first year following a VCF, there is a 5 to 25 times increased risk for a new VCF, most often in the vertebrae adjacent to the first VCF. (6) Furthermore, Kado et al (28) reported that mortality in women with one VCF increases by 23%, whereas when multiple VCFs are present the increase goes up to 34%. There is some controversy in the literature regarding the effect of kyphoplasty on the development of adjacent fractures. Rates of additional VCFs ranging from 3 to 29% have been reported. (29) Keller et al (30) concluded in their study, using a microstructural finite-element model of a vertebral motion, that cement repair strategy alters bone stress distributions in augmented and adjacent levels. Grafe et al (20) compared in their prospective study the incidence of fractures between two groups of patients, one treated with kyphoplasty and the other managed conservatively. They noted a significantly less risk for VCF in the group of patients that underwent kyphoplasty. Harrop et al (4) found that kyphoplasty does not lead to an increase in the risk for additional VCFs in patients with primary osteoporosis; this risk, however, seems increased when patients with steroid-induced osteoporosis undergo the procedure. The possible association between kyphoplasty and multiple vertebral fractures in patients with secondary osteoporosis was further supported by Donovan et al. (31) Contrariwise, Fribourg et al (29) stated that kyphoplasty leads to an increase in the incidence of adjacent VCFs even in patients with primary osteoporosis, compared with the natural history of the disease. The first two months after the procedure carried the highest risk. In our cohort, no additional fractures occurred during the entire follow-up period of 72 weeks.

A lot of focus has been given in the literature regarding the vertebral body height restoration achieved by kyphoplasty, especially compared with vertebroplasty. (17,18) Vertebral body height restoration is considered to aid in the correction of the kyphotic deformity, with positive effects on the functional outcome of the patients. Theodorou et al (32) reported a 65.7% restoration of midline vertebral body height with a subsequent 62.4% [+ or -] 16.7% improvement in kyphosis. Similarly, Lieberman et al (27) observed that 70% of the operated vertebrae showed, on average, a 47% midline height restoration. Comparable results have been reported by several authors. (19,32) Garfin et al (22) reported in their review article that kyphoplasty achieves substantial restoration of vertebral body height and about 50% correction of the kyphotic deformity, when performed within 3 months from the onset of pain. Berlemann et al (33) further outlined the significance of early intervention for reduction of the deformity. They observed, however, no correlation between the amount of reduction and pain relief.

In our cohort, the majority of our patients experienced no restoration of vertebral body height and in those cases where some restoration was accomplished, the amount was less than 20%. This vertebral body height restoration rate is definitely lower than those reported in other clinical series. (17,18,21) This finding might be explained by the fact that most of the patients included in our current series were evaluated approximately two months after the onset of their symptomatology. This somewhat prolonged compression of the involved bone trabeculae could result in an irreversible alteration of the bone microarchitecture with a subsequent inability to restore height during kyphoplasty. Furthermore, in the few patients where some degree of restoration was observed, there did not seem to be any significance in regards to the patients' daily activities and pain. The long-lasting pain-alleviating effect of kyphoplasty in our series might imply that significant improvement in the quality of life and in the functional level of the patients can be accomplished even without considerable restoration of vertebral body height.

Concern has been raised lately by the possible effects of radiation from fluoroscopic exposure to patients, fluoroscopy operators and operating room personnel. Seibert (34) emphasizes the importance of educating operators on the optimal use of fluoroscopy in regards to radiation exposure to themselves and to the patients and encourages medical physicists to establish strict guidelines for the use of fluoroscopic machinery, especially in light of the expanding utilization of both vertebroplasty and kyphoplasty. Persinakis et al (35) reported that the mean fluoroscopy time for kyphoplasty is 10.1 minutes [+ or -] 2.2; if that period is extended or the source of radiation-to-skin distance is less than 35 cm, injuries to the skin might occur.

Conclusion

In terms of pain relief and functional outcome, kyphoplasty is a safe and effective treatment option for osteoporotic VCFs. Significant and long-lasting pain improvement, as well as a return to premorbid levels of daily activities are accomplished, even in the absence of substantial restoration of vertebral body height. However, the relatively recent introduction of this procedure in clinical practice requires that large, multicenter, randomized clinical trials be performed for evaluation of the long-term effects of kyphoplasty, as well as of the actual significance of height restoration for clinical outcome.

References

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Theofilos G. Machinis, MD, Kostas N. Fountas, MD, PHD, Carlos H. Feltes, MD, Kim W. Johnston, MD, and Joe S. Robinson, MD, FACS 

From the Department of Neurosurgery, The Medical Center of Central Georgia, Macon, GA.

Reprint requests to Kostas N. Fountas, MD, PhD, 840 Pine Street, Suite 880, Macon, GA 31201. Email: [e-mail]

Accepted January 6, 2006.

RELATED ARTICLE: Key Points

* Kyphoplasty is an effective treatment for osteoporotic vertebral compression fractures, resulting in immediate and long-lasting pain relief.

* A desirable functional outcome and significant improvement in the quality of life may be achieved, even when no restoration of vertebral body height can be obtained.

* Kyphoplasty is a safe procedure, with only minimal associated complications.