The middle layer of lumbar fascia can transmit tensile forces capable of fracturing the lumbar transverse processes: an experimental study.
BACKGROUND
Transversus abdominis and its aponeurotic attachment to the lumbar transverse processes via the middle layer of lumbar fascia are of proposed clinical and biomechanical importance. Moderate traction on these structures (simulating submaximal contraction of transversus abdominis) is reported to influence segmental motion, but their tensile capacity is unknown and the effects of sudden, maximal traction on these attachments and the transverse processes are uncertain.


METHODS
In 15 embalmed cadaver abdomens, the middle layer of lumbar fascia was isolated, gripped and rapid tension applied in either a lateral or posteroanterior direction (simulating forces that may produce avulsion and traumatic fractures). Peak forces prior to tissue failure were recorded and the gross effects of traction documented.


RESULTS
Lumbar transverse process fractures were produced in all specimens; by transverse traction in 50% of tests and posteroanterior force in 80%. In the remainder the middle layer of lumbar fascia was torn. Mean transverse and posteroanterior peak forces reached in the middle layer of lumbar fascia prior to failure were 82 N (range 20-190 N) and 47 N (range 25-70 N), respectively.


CONCLUSIONS
The middle layer of lumbar fascia can transmit substantial tensile forces to lumbar vertebrae, capable of transverse process fracture under experimental conditions. Tensile capacity is likely to be even greater in-vivo. This suggests transversus abdominis and the middle layer of lumbar fascia can strongly influence vertebral motion, should be incorporated in biomechanical models of the spine and considered as potential contributors to transverse process fractures by avulsion.
Barker
Priscilla J
PJ
Department of Anatomy & Cell Biology, The University of Melbourne, Parkville, Victoria 3010, Australia. p.barker@unimelb.edu.au
Freeman
Ashley D
AD
Urquhart
Donna M
DM
Anderson
Colin R
CR
Briggs
Christopher A
CA
D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D005205:Fascia / Q000502:physiology*; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology*; D008161:Lumbosacral Region / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009133:Muscular Atrophy / Q000473:pathology; D013131:Spine; D013314:Stress, Mechanical; D013718:Tensile Strength