Clinical evaluation of repeat percutaneous vertebroplasty for symptomatic cemented vertebrae.

BACKGROUND: Percutaneous vertebroplasty (PV) with polymethylmethacrylate is widely used to treat osteoporotic vertebral compression fracture and satisfactory clinical outcomes have been reported in the literature. However, recurrent or persistent back pain after PV is not uncommon. Sometimes, the pain may result from pathogenesis within the previously treated vertebra. In this study, we evaluated the efficacy and safety of repeat PV for treating patients with recurrent back pain caused by the previously cemented vertebrae. METHODS: We retrospectively reviewed the medical records of 18 patients who underwent repeat PV to treat symptomatic cemented vertebrae. Patients were categorized into 3 groups based on clinical presentation and imaging studies: those with refracture (RF), residual vacuum (RV), and osteonecrosis (ON) along the bone-cement interface. A bipedicle approach was used for repeat PV in all patients. The visual analogue scale (VAS) and modified Brodsky criteria were used to evaluate clinical outcomes before and after surgery. The Kruskal-Wallis test, Wilcoxon signed-rank test, and Spearman correlation analyses were used to analyze patient surgical prognosis and radiologic findings. RESULTS: Nine patients were diagnosed with RF, 5 with RV, and 4 with ON. The average VAS score was 77.1 (range, 62-90) before repeat PV (80.1, 72.4, and 76.3 for the RF, RV, and ON groups, respectively) and 34.4 (range, 25-45) after repeat PV treatment (33.1, 36.8, and 34.3 for the RF, RV, and ON groups, respectively). The VAS score significantly decreased in all 3 groups. The vertebral body height was significantly restored by a mean of 13.9% across all groups (17.8%, 12.7%, and 6.8% in the RF, RV, and ON groups, respectively). Fifteen patients recovered from vertebral compression fracture and regained their preinjury activities of daily living. No surgery-related complications occurred except asymptomatic cement leakage in 5 patients. CONCLUSIONS: The results of this research demonstrate that repeat PV may be an effective method for relieving recurrent or persistent pain in patients with symptomatic cemented vertebrae, allowing them to regain functional activity.

Impact of cement leakage into disks on the development of adjacent vertebral compression fractures.

STUDY DESIGN: A retrospective study assessing new adjacent vertebral compression fracture (VCF) after percutaneous vertebroplasty (PV). OBJECTIVE: To evaluate the relationship between cement leakage into the disk during initial PV and development of subsequent new adjacent VCF. SUMMARY OF BACKGROUND DATA: Cement leakage outside the vertebral body during PV has been reported and usually responds to conservative treatment. Sometimes bone cement may leak into the intervertebral disk and result in painful new adjacent VCF that usually requires another PV for pain relief. METHODS: From January 2002 to December 2002, a total of 106 consecutive patients underwent PVs for osteoporotic VCFs. The risk of new fractures of adjacent vertebral bodies, the amount of cement injection, and the duration of development of new adjacent fractures in relation to cement leakage into the disk were retrospectively assessed and statistically compared. RESULTS: New adjacent VCFs occurred in 20 (18.9%) of 106 patients at 22 adjacent vertebral bodies after PVs during at least 24 months of follow-up. The difference in number of new adjacent fractures between both patients and vertebral bodies with cement leakage and those without leakage into the disk were statistically significant (P<0.001 and P<0.001). Amounts of cement injected and duration to development of new adjacent fractures differed between patients with or without cement leakage (P<0.001 and P=0.005, respectively). CONCLUSIONS: PV is a simple and effective, but not risk-free or complication-free procedure for the treatment of osteoporotic VCF. Patients undergoing PV should be informed of the possibility of new adjacent fractures and the higher risk if cement leaks into the disk.

Effects of liner stiffness for trans-tibial prosthesis: a finite element contact model.

The socket liner plays a crucial role in redistribution of the interface stresses between the stump and the socket, so that the peak interface stress could be reduced. However, how the peak stress is affected by various liner stiffnesses is still unknown, especially when the phenomenon of the stump slide within the socket is considered. This study employed nonlinear contact finite element analyses to study the biomechanical reaction of the stump sliding with particular attention to the liner stiffness effects of the trans-tibial prosthesis. To validate the finite element outcomes, experimental measurements of the interface stresses and sliding distance were further executed. The results showed that the biomechanical response of the stump sliding are highly nonlinear. With a less stiff liner, the slide distance of the stump would increase with a larger contact area. However, this increase in the contact area would not ensure a reduction in the peak interface stress and this is due to the combined effects of the non-uniform shape of the socket and the various sliding distances generated by the different liner stiffnesses.