Range of motion in reconstruction situations following corpectomy in the lumbar spine: a question of bone mineral density?
METHODS
In vitro biomechanical study to evaluate the stability of different types of instrumentation in the lumbar spine following corpectomy in relation to bone mineral density (BMD).


OBJECTIVE
To investigate the relation between the stability of a spinal instrumentation and BMD. To determine a threshold value of BMD allowing a single ventral instrumentation following corpectomy in the lumbar spine.


BACKGROUND
Some in vitro studies determined the biomechanical properties of different spinal instrumentations in various spinal injury models. To the authors' knowledge, there are no published data available concerning stabilization in relation to BMD. A guideline for the treatment of a corpectomy depending on BMD would be helpful in order to choose the appropriate surgical method.


METHODS
Twenty-four fresh frozen human lumbar cadaveric spine specimens L1-L3 were used for testing of biomechanical properties. Plain radiographs were taken. BMD was determined using quantitative computed tomography (QCT). Testing in a 6 df loading device included native specimens and specimens after corpectomy of L2, restoration of the defect with a titanium cage, and two reconstruction situations: single ventral and additional dorsal instrumentation. Load-displacement curves and range of motion parameters were recorded and correlated with BMD.


RESULTS
A significant (P < 0.05) influence of BMD on range of motion was found. Single ventral instrumentation was critical concerning axial rotation. Combined dorsoventral instrumentation offered sufficient stability. The threshold value for use of single ventral instrumentation is a BMD > or = 0.22 g/cm.


CONCLUSIONS
Single ventral instrumentation can provide sufficient stability following corpectomy in the lumbar spine under the condition of a high BMD. Determination of BMD and the use of this guideline provides a valid tool for surgical planning.
Knöller
Stefan M
SM
Department of Orthopaedic Surgery, University of Freiburg, Freiburg, Germany. knoeller@ch11.ukl.uni-freiburg.de
Meyer
Georg
G
Eckhardt
Christina
C
Lill
Christoph A
CA
Schneider
Erich
E
Linke
Berend
B
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D001863:Bone Screws; D005260:Female; D006801:Humans; D016268:Internal Fixators; D007593:Joint Instability; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000378:metabolism / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D019651:Plastic Surgery Procedures / Q000295:instrumentation / Q000379:methods*; D012399:Rotation; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D014057:Tomography, X-Ray Computed; D016474:Weight-Bearing