Analysis of injected cement volume and clinical outcomes following kyphoplasty for vertebral compression fractures

INTRODUCTION

Many studies have shown the effectiveness of kyphoplasty in restoring vertebral height and relieving pain.[4-6,8] Kyphoplasty involves placing a balloon into the vertebral body and creating a void within that body that can then be filled cement injected under lower pressures, to reduce the risk of cement leakage.[7]

Here, we uniquely correlated cement volumes injected with pain, disability, and quality of life indices in those undergoing percutaneous kyphoplasty for the treatment of vertebral compression fractures.

MATERIALS AND METHODS

Patient selection

This retrospective series of 136 consecutive patients undergoing kyphoplasty for vertebral compression fractures was approved by an IRB. Two neurosurgeons treated 230 vertebral fractures with kyphoplasty in these 136 patients [Table 1]. All had cement injected bilaterally utilizing an average total cement injected volume of 5.44 cc ± 1.35 cc (range 2–9 cc), and these injection volumes were correlated with outcomes.

Table 1:: Demographics by cancer status, n=136.

Statistical analysis

Mean pain VAS, EQ5D scores, and RMDI scores were recorded preoperatively and postoperatively. Pearson’s correlations and linear regression models were derived for the association of total cement volume and vertebral height restoration with patient outcomes [Tables 2-5]. Statistical analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC).

Table 2:: Pearson’s correlations for VAS, RMDI, and EQ-5D improvement.

Table 3:: Multiple linear regression modeling VAS improvement as outcome, n=136.

Table 4:: Multiple linear regression modeling RMDI improvement as outcome, n=136.

Table 5:: Multiple linear regression modeling EQ-5D improvement as outcome, n=136.

RESULTS

All patients had reduced pain (n = 136; 100.0%), most had reduced disability (n = 134; 98.5%), and most exhibited an improved quality of life (n = 135; 99.3%). The average improvement in VAS, RMDI, and EQ5D scores for all patients was −6.8, +8.3, and +0.41, respectively [Table 2]. Eighty-eight (64.7%) patients reported preoperative narcotic use; this decreased to 24 (17.6%) postoperatively. No correlations or associations were found between total cement volume injected and outcomes utilizing VAS, RMDI, and EQ5D scores [Table 2]. There was little relationship between total cement volume injected and outcome measures using the Pearson’s correlation [Table 2]. Linear regression models also revealed little evidence for age, gender, body mass index, or total cement volume as predictors of clinical improvement [Tables 3-5].

DISCUSSION

The biomechanical literature suggests that cement-filling volumes may play an important role in vertebral augmentation and its effectiveness in relieving pain.[1-3] However, adequate clinical data regarding optimal filling volumes are scarce, as most series are small, and results are mixed. Röder et al., in a study of 276 patients, found that cement volume was a significant predictor for pain relief in kyphoplasty and recommended utilizing cement volumes of >4.5 cc.[2] In a biomechanical analysis, Rotter et al. reported that injecting only 10% of the vertebral volume when performing bilateral kyphoplasty was insufficient in stabilized fractured vertebra/ relieving pain.[3] Rather, Molloy et al. found that kyphoplasty injected cement volumes of 16–30% were warranted.[1,3] Notably, neither study correlated the volume of injected cement during kyphoplasty with quality of life metrics.

CONCLUSION

All patients improved on all outcome scales (e.g., VAS, RMDI, and EQ5D) regardless of the injected cement volume following kyphoplasty.