Subsidence of polyetheretherketone intervertebral cages in minimally invasive lateral retroperitoneal transpsoas lumbar interbody fusion.
METHODS
A retrospective review.


OBJECTIVE
The objective is to evaluate subsidence related to minimally invasive lateral retroperitoneal lumbar interbody fusion by reviewing our experience with this procedure.


BACKGROUND
Polyetheretherketone intervertebral cages of different lengths, widths, and heights filled with various allograft types are commonly used as spacers in lumbar fusions. Subsidence is a potential complication. To date, there are no published reports specifically addressing subsidence, because it relates to a series of patients undergoing minimally invasive lateral retroperitoneal transpsoas lumbar interbody fusion.


METHODS
An institutional review board-approved, retrospective review of a prospectively collected database was conducted. One hundred forty consecutive patients who underwent this procedure between L1 and L5 during a 2-year period were included. All patients had T scores of -2.5 or more. Postoperative radiographs during routine follow-ups were reviewed for subsidence, defined as any violation of the vertebral end plate.


RESULTS
Radiographical subsidence occurred in 14.3% (20 of 140), whereas clinical subsidence occurred in 2.1%. Subsidence occurred in 8.8% (21 of 238) of levels fused. Construct length had a significant positive correlation with increasing subsidence rates. Subsidence rates decreased progressively with lower levels in the lumbar spine, but had a higher than expected rate at L4-L5. Subsidence rates of 14.1% (19 of 135) and 1.9% (2 of 103) were associated with 18-and 22-mm-wide cages, respectively. No significant trends were observed with cage lengths. Supplemental lateral plates had a higher rate of subsidence than bilateral pedicle screws. Subsidence occurred at the superior end plate 70% of the time.


CONCLUSIONS
The use of wider intervertebral cages leads to a significantly lower rate of subsidence, but a longer cage does not necessarily offer a similar advantage. Wide cages are protective against subsidence, and the widest cages should be used whenever feasible for interbody fusion in the lumbar spine to protect indirect compression and promote arthrodesis.
Department of Neurosurgery and Brain Repair, University of South Florida, Tampa, FL 33606, USA. tienvle@me.com
Tien V
TV
Le
Ali A
AA
Baaj
Elias
E
Dakwar
Clinton J
CJ
Burkett
Gisela
G
Murray
Donald A
DA
Smith
Juan S
JS
Uribe
D000368:Aged; D001577:Benzophenones; D005260:Female; D006801:Humans; D016268:Internal Fixators; D007659:Ketones; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data; D011092:Polyethylene Glycols; D011108:Polymers; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000209:etiology; D016658:Psoas Muscles / Q000601:surgery; D011859:Radiography; D012187:Retroperitoneal Space / Q000601:surgery; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*
D001577:Benzophenones; D007659:Ketones; D011108:Polymers; C063834:polyetheretherketone; D011092:Polyethylene Glycols