BioMed Research International

Review Article

Corrective Mechanism Aftermath Surgical Treatment of Spine Deformity due to Scoliosis: A Systematic Review of Finite Element Studies

Table 4

Data extraction on the effect of Cobb angles from the reviewed articles.


Authors	Category	Plane	Situation/ Zone	Cobb Angle		Outcome Measures	Parameter Output			Findings

Dumas et al. [10]	Simulation of clinical data and post-operative measurements comparison & rod rotation analysis	Lateral, Sagittal, Axial	Scheuermann hyper kyphosis Idiopathic scoliosis	50° 58°		Rod rotation (°)	Lateral rotation= - Sagittal rotation= Mean :4° = Max: 9° Axial rotation= - Lateral rotation= Mean :3° = Max: 7° Sagittal rotation = Mean :4° = Max: 9° Axial rotation = Mean :5° = Max: 11°			The surgeon's experience was consistent with models of two clinical situations of hypokyphosis and scoliosis. Follow-up: NM.
Abolaeha et al. [12]	Spinal growing rod analysis	Sagittal & Axial	Cycle of Adjustment period Initial 1^st growth 2^nd growth 3^rd growth 4^th growth	Before 37° 42° 40° 39° 49°	After 28° 34° 33° 37° 40°	Magnitude of force	Compressive force (N) 362N 669N 942N 1215N 1454N	Rod Displacement(mm) 5 10 17 20 30		The rod length was changed until the desired Cobb angle was achieved, which was decreased from an initial value of 37° to 28°. This necessitated a 5 mm lengthening of the rod, resulting in a correction force of 362 N. Follow-up: 2 years
Salmingo et al. [1]	The three-dimensional corrective forces analysis	Frontal (x-z plane)	Patient 1 Patient 2 Patient 3	Before 57° 59° 68°	After 13° 28° 18°	3D Forces(N), Stress, Strain Distribution	Only the rod geometry before and after the surgical treatment was used to analyse the distributions of forces that distorted the implant rod.			The highest force acting on each patient's screw ranged from 198 to 439 N. The force magnitude was clinically acceptable. The maximal forces were generated at each patient's lowest fixation level of vertebra. Follow-up: NM
Wang et al. [13]	The corrective forces & bone-screw forces analysis	Sagittal & Axial	NA	Sagittal curve: 5.3° Vertebral axial: 4°- 8°		Resultant Screw force(N)	TCF magnitudes vs resultant screw force magnitudes associated with monoaxial, dorsoaxial and polyaxial pedicle screw.			True corrective forces were 50±30N on average. For monoaxial, dorsoaxial and polyaxial screws, the average bone-screw forces were 229±140N, 141±99N, and 103±42N, respectively; the average EF magnitudes were 205±136N, 125±93N, & 65±39N respectively. Follow-up: NM.
Driscoll et al. [6]	The three-dimensional corrective force analysis	Transverse, Axial, & Sagittal	NA	Right thoracic: 73° Proximal thoracic: 42°		Screw pull-out force	T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 L1	0 1000N 350N 300N - 349N 0 0 300N - 349N <200N 350N >800N 0		Over the course of the surgical process simulation, stress in intervertebral discs discovered between instrumented vertebrae averaged 3.95MPa. Follow-up: NM
Salmingo et al. [2]	The three-dimensional corrective forces analysis	Sagittal	Patient 1 Patient 2 Patient 3 Patient 4 Patient 5 Patient 6	Before 76° 75° 57° 68° 83° 59°	After 27° 26° 13° 18° 14° 28°	Pull-out and push-in force	The screw density and implant implantation arrangement all contributed to a higher degree of correction. This shows that if more implants are put closer together, vertebrae can be easily altered.			Forces of correction are unrelated. Although increasing the number of implant screws reduced the magnitude of corrective forces, it did not result in a higher degree of correction. Follow-up: NM
Little et al.[3]	The three-dimensional corrective forces analysis	Coronal	Patient 1 Patient 2 Patient 3 Patient 4 Patient 5 Patient 6 Patient 7 Patient 8	Before 52° 51° 44° 53° 40° 42° 42° 53°	After 23° 18° 14° 25° 10° 7° 13° 34°	Degree of deformity correction, Compressive force profile	-3 -2 -1 0 1 2 3	400N 580N 675N 660N 550N 470N 320N		Endplate-to-endplate contact was seen on adjacent endplates of one or more intervertebral disc spaces in the instrumented curve after the surgical loading procedures, according to patient model predictions. Follow-up: NM
Abe et al. [14]	The corrective force estimation	NM	NA	Thoracic: 53°- 74°		Push out or push in forces	Convex	F1 F2 F3 F4 F5 F6 F7	113N 31N 48N 55N 52N 34N 123N	The concave side corrective force is four times greater than in convex side. Follow-up: NM
							Concave	F1 F2 F3 F4 F5 F6 F7	424N 105N 169N 218N 214N 142N 466N
							Flexion	L2-L3 L3-L4 L4-L5	3.28°-.4° 3.06°-1° 3.58°-1°	Axial compression- The rod was the part that was subjected to the most stress Flexion- the stress was centred on proximal pedicle screws. Extension and lateral bending- an osteotomized L1 vertebra bore the greatest stress on the model. Follow-up: NM
							Extension	L2-L3 L3-L4 L4-L5	2.3°-3.3° 1.18°-2.3° 2.56°-4°
Wang et al. [15]	The stress-strain analysis	Coronal	NA	Thoracolumbar: 53°		The ranges of motion (ROM)	Lateral Bending	L2-L3 L3-L4 L4-L5	3.31°-5.0° 3.33°-4.3° 2.08°-4.01°
Clin et al. [16]	Pedicle screw design & Load-Sharing Capacity analysis	Transverse & coronal	NA	Thoracic: 53°-85°		Derotation force, axial torque	The average post-instrumentation force sustained by high and low-density implant patterns with varied pedicle screw design configurations was recorded, as well as the peak force experienced during surgery simulation.			Increased degrees of freedom in the screw head limit the screw's ability to cure coronal deformity while lowering bone-screw forces. Follow-up: 10 years
Balamurugan et al. [17]	Effect on spine deformity correction	NM	NA	NM		Stress distribution	T5 T6 T7 T8 L1 L2 L3 L4 L5	<0.5MPa <0.5MPa MPa 300 – 349MPa 0-0.5MPa 0.5-1MPa >1.5MPa >1.5MPs >1.5MPa		After surgery, the stress concentration is highest near the end of the lumber area. Follow-up: NM
Guan et al. [18]	The three-dimensional corrective forces analysis	Coronal, sagittal and horizontal	(i) Forward bend (ii) Stretch (iii) Side bender (iv) Twists	Thoracic: 14°-36° Lumbar: 10°-17°		Stress	As the 3D corrective forces increased, the cobb angle of the thoracolumbar section reduced, as did the rotation angle of the vertebra. The combined force correction effects were higher.			The objective functions were each lowered by 58%, 52%, and 63 percent. On the convex side of the highest displacement of the vertebral body, the optimal corrective forces point was found. Follow-up: NM
Zhang et al.[9]	Stress distribution	Coronal, sagittal and frontal	NA	Frontal: 43° Lumbar: 45°		Stress distribution	Stress is concentrated on the lumbar vertebral body during flexion loading, with an unequal stress distribution on the left anterior side of the vertebral body (concave side). Stress in the lumbar spine is localised primarily at the pedicle of the vertebral arch and the lamina of the vertebral arch during extension load.			Under all loads, the range of motion (ROM) is reduced. Flexion loads cause a greater distribution of vertebral concave stress. The stress is concentrated in the L3 vertebral arch. Follow-up: NM
He at al. [11]	The three-dimensional corrective forces analysis	Coronal, sagittal and horizontal	NA	NM		Stress shielding rate	FEA analysis of the new improved spinal correction system ISCS to determine its stability and biomechanical features, as well as a comparison of the ISCS to the pedicle screw and rod system (PSRS).			Maximum stress L2 vertebral body & L1/2 and L2/3 discs in PSRS were smaller than in ISCS. PSRS and ISCS have identical maximum stress in lateral bending and axial rotation directions. Follow-up: NM
Chen at al [19]	The pedicle screw placement strategies	Sagittal	(a) All segments have pedicle screws placed. (b) Pedicle screws were implanted in all of the concave side's segments, with interval screws inserted in the convex side. (c) Both side alternate screws (d) instruments on both sides of the interval screws (e) interval and alternate screws instrumentation in each side	Thoracic: 43°		Interaction force	113N 113N 289N 172N 172N			Densities of pedicle screws and screw-placement techniques have little influences in the curve correction. Strategy E has better biomechanics properties for surgery. Follow-up: NM