Biomechanical comparison of kyphoplasty versus a titanium mesh implant with cement for stabilization of vertebral compression fractures.

ABSTRACT

STUDY DESIGN: In vitro biomechanical investigation. OBJECTIVE: To evaluate differences in biomechanical stability of vertebral compression fractures repaired using balloon kyphoplasty versus a titanium mesh implant. SUMMARY OF BACKGROUND DATA Vertebral compression fractures may be stabilized using an expandable balloon followed by cement injection. There are small but finite risks of endplate fracture and cement extravasation with this procedure. Alternative techniques may affect cement injection volumes, height maintenance, and biomechanical stability but require investigation. METHODS: Four male human cadaveric spines from T2 to L5 were used in this study. After determining bone mineral density, individual vertebral bodies were dissected and inspected for previous fractures or additional exclusion criteria. In the remaining vertebral bodies (n=48) anterior wedge fractures were created using a materials testing machine. Fractured vertebral bodies were systematically randomized to be repaired either with balloon kyphoplasty or with titanium mesh implant and polymethylmethacrylate bone cement, using image intensified fluoroscopy. Anterior vertebral body height (cm) was measured initially, after mechanically creating an anterior wedge fracture, after repairing the compression fracture with either technique, and after recompressing the vertebral body following a 24-hour cement polymerization period. Data for cement injection volume (mL) and height maintained following testing (cm) were compared between repair groups using a 1-way analysis of variance (P<0.05). Data for stiffness (N/mm), yield load (N), and ultimate load (N) were compared between intact bodies and repaired bodies using a 2-way analysis of variance (P<0.05). RESULTS: There was significantly less cement injected (P<0.001) and significantly greater height maintained (P<0.025) with the titanium implant group compared to the kyphoplasty group. There were no significant differences in biomechanical stability between the 2 groups (P>0.05). CONCLUSION: The titanium implant was biomechanically equivalent to the kyphoplasty repair while necessitating less cement and providing greater height maintenance in vitro. Improvements in pain and function could not be specifically addressed in this in vitro study and should be evaluated in a clinical case series.