McCormack (1994) — The load sharing classification of spine fractures.

The Load Sharing Classification of Spine Fractures.

·Spine·1994·910 citations·Spine

Retrospective study of 28 patients with three-column thoracic/thoracolumbar fractures treated with short-segment VSP pedicle screw instrumentation, asking: can preoperative imaging predict which fractures will cause screw breakage? The authors develop and validate a 3-parameter CT- and radiograph-based scoring system to answer that question.

Study Snapshot

Design

Retrospective cohort

Setting: Single center, University of Missouri

Objective

Whether load sharing classification predicts pedicle screw breakage after short-segment spine fracture fixation

Outcome(s)

Screw breakage at minimum 3-year follow-up

Subjects

28 patients, three-column thoracic/thoracolumbar fractures

Short-segment VSP pedicle screws + plates + autograft fusion

Inclusion

Three-column spinal fracture or fracture-dislocation
Treated with short-segment VSP pedicle screw fixation
Surgery within 2 weeks of injury

Follow-up

Minimum 3 years (mean 4 years)

Key Findings

The Load Sharing Classification scores three CT/radiograph parameters on a 1–3 point scale — total range 3–9 points:
Vertebral body comminution (sagittal CT): ≤30% = 1 pt, 30–60% = 2 pts, >60% = 3 pts
Fragment apposition (axial CT): 0–1 mm = 1 pt, ≥2 mm in <50% cross-section = 2 pts, ≥2 mm in >50% cross-section = 3 pts
Kyphosis correction (plain films): ≤3° = 1 pt, 4–9° = 2 pts, ≥10° = 3 pts
A score of ≥7 identified every screw failure in the series — all 10 fractures fell in this range, five at the maximum score of 9; adding anterior strut reconstruction for this group eliminated implant failures from 1988 onward
A score of ≤6 predicted hardware survival — zero screw fractures occurred in the 18 patients with lower scores at minimum 3-year follow-up
Hardware failure was clinically silent in 9 of 10 cases — fractures were minimally displaced and invisible on plain radiographs, discovered only at implant removal, underscoring that absence of symptoms does not confirm implant integrity

Clinical Relevance

When planning posterior short-segment pedicle screw fixation for a thoracolumbar fracture, calculate the LSC score preoperatively: a score ≤6 supports posterior fixation alone, while a score ≥7 indicates the anterior column cannot share load and anterior reconstruction (vertebrectomy + strut graft) should be added to prevent hardware failure.

Supplemental

The Load Sharing Classification of Spine Fractures.

McCormack, Gaines, et al.·Spine·1994·910 citations·Spine

The Load Sharing Classification of Spine Fractures.

Study Snapshot

Key Findings

Clinical Relevance

Related Articles

The Load Sharing Classification of Spine Fractures.

Study Snapshot

Key Findings

Clinical Relevance

Related Articles

The Load Sharing Classification of Spine Fractures.

Study Snapshot

Key Findings

Clinical Relevance

Related Articles

The Load Sharing Classification of Spine Fractures.

Study Snapshot

Key Findings

Clinical Relevance

Related Articles