How does McCormack load sharing classification determine level of spine fixation?

Asked by Anonymous 

McCormack load sharing classification takes into account, 3 different factors: 

1. Apposition
2. Comminution
3. Deformity correction

Score	1point	2 points	3 points
Comminution/Sagittal collapse	30%	30-60%	>60%
Apposition of fragments	1 mm	2 mm	> 2 mm
Deformity (kyphosis) correction	</= 3 degrees	4-9 degrees	>/= 10 degrees
Total	3 points	6 points	9 points

Source: McCormack T, Karaikovic E, Gaines RW. The load sharing classification of spine fractures

Interpretation:

1. Score <6: Short segment posterior stabilization
2. Score >6 without translation: Anterior instrument and strut graft
3. Score >6 with fracture dislocation: Staged surgery; posterior short segment posterior stabilization followed by anterior column support OR Long segment posterior stabilization

Long-Segment Posterior Fixation (LSPF) at least two levels above and below the fractured vertebra allows for a stronger construct, though limits flexibility at the fractured level and is more extensile and may be associated with higher intraoperative blood loss and length of operation. Short-segment fixation has largely replaced long-fixation in the management of burst fractures. However, instrument failure and recurrence of kyphosis are reported if short-segment posterior fixation.