Lumbar Fusion Techniques

PLIF / Posterior Lumbar Interbody Fusion






1.  Wide laminotomy 

- resection flavum, significant cranial lamina

- preserve if possible the posterior elements

- spinous processes, supra and interspinous ligaments

- these provide tension stability

- resect medial two thirds of superior facet /  lower one third inferior facet


2.  Resect disc

- retract dura and traversing nerve root medially

- distract disc space with lamina spreader

- disc space retractors (insert wedge, then turn on side) 

- remove end plates


3.  Insert interbody device 

- carbon or titanium cages

- wedge shaped

- allows correction of sagittal deformity

- allows restoration of disc height

- immediate stability

- facilitates fusion

- usually contain morcellised allograft / BMP

- check under II that interbody device not too posterior


4.  Stabilise with pedicle screws



- dural tears

- nerve palsy

- hard ware failure

- psedoarthrosis


ALIF / Anterior Lumbar Interbody Fusion


Surgical Technique L2 - L5


Patient supine, stand on right

- find level with II

- make incision through skin and subcutaneous fat

- divide external and intenal obliques and transversus

- mobilise peritoneum around, until see psoas


All dissection with swabs on sticks or peanuts

- ureter lifted up with peritoneum

- diva retractors for bowel, as per general surgery

- self retainers attached to side of bed


Common iliac artery and vein on medial psoas

- mobilise vessels medially, psoas laterally

- will see large sympathetic trunk, mobilise either way (don't damage to avoid retrograde ejaculation)

- may need to divide iliolumbar vein


Identify disc

- check level again with needle


Steinman type pins in vertebral body to keep back bowel


Divide ALL (can keep as layer, especially in Disc replacement)

- remove entire disc

- knife, rongeurs, normal and ring curettes 


Distract disc space

- special lamina spreaders

- disc distractors (wedges inserted then turn on side i.e. 10 - 14 mm)

- pins in bodies above and below and add distracting device as per cervical fusion


Remove end plate to bleeding bone


Interbody cage

- trial for height, depth and angle

- i.e. 6o 10 mm

- check II to make sure not too far back

- insert real prosthesis

- augment with plate


Surgical Technique L5/S1 Fusion


Access between vessels

- much easier than going to the lateral side of one and mobilising it medially

- identify sacral promontory, big angle as sacrum dives away

- use pins and retractors as before


Resect disc and minimal end plate

- just to bleeding bone for fusion

- not too much so bone is soft and cage or disc subsides


Trial for height & angle, II for depth

- insert cage

- these made of plastic with same modulus as bone

- doesn't compress but at same time doesn't subside into bone

- cage is radiolucent except for small opacities to see on x-ray

- cage has cental hole

- fill with synthetic bone graft, mixed with patient's blood and rolled as sushi in BMP membrane

- insert cage, can put more synthetic BG/BMP around it

- check II, ensure not too posterior

- application of anterior plate and screws


Pedicle Screws





- superior to sublaminar wires or hooks

- purchase in all 3 columns

- cross-linkage and converging screws enhances pullout strength



- essential to have fit & fill of pedicle

- bone mineral density of vital importance with pedicle screws

- minor osteoporosis OK

- marked osteoporosis hooks as good as screws

- bicortical fixation improves strength but only safe in S1

- pedicle screws not safe in S2 at all

- if fracture pedicle greatly reduces strength of construct




To place screw through centre of pedicles 

- parallel to upper end plate or slightly angled downward

- screws also converge towards midline

- up to 20% depending on spinal level

- this is to ensure do not penetrate lateral wall of vertebral body



- II facilitates insertion

- can use computer navigation


Entry Points


1.  Thoracic spine

- entry just below rim of upper facet near base of TP

- angle 7-10o towards midline & 10-20o caudally


2.  Lumbar Spine

- entry at junction TP & superior facet

- angle: screws converge 5o at TLJ and increase 10-15o as one progresses from L2-L5


3.  Sacrum

- S1 only safe level

- line tangential to lateral border superior articular facet &

- line along inferior border of superior articular facet

- angle: screws converge towards midline / aim at anterior corner of promontorium




Osteotome away facet joint

- reveal cancellous bone

- entry with curved awl

- ball tip guide, bone on all 4 sides, check II

- pass tap

- insert screw (6.5, 5.5, 4.5, 30 - 40 mm long)

- usually poly-axial heads




Union rate >90%


Screw misplacement 4%


Nerve and spinal injury 1-20%

- most misplaced screws don't cause neural injury

- higher risks with power over hand preparation


Infection 1.1-4.2%

- usually can leave metal in situ with early washout & debridement


Screw breakage 2-60%