Panjabi set out a conceptual model in which spinal stability depends on three interacting subsystems, and described how the system responds to dysfunction, adapts and enhances stability.
Conceptual paper from Yale University, built on earlier in vitro biomechanical studies.
Methods
Scope
Conceptual model of spinal stability drawn from earlier biomechanical work
Topics
Passive, active and neural subsystems
Neutral zone and ligament feedback
Responses to subsystem dysfunction
Adaptation with aging
Stability enhancement for anticipated loads
Key Points
In this model, dysfunction of one component may be met by immediate compensation that preserves normal function, by long‑term adaptation that keeps function but alters the system, or by injury that ends in overall dysfunction such as low back pain.
Panjabi hypothesized that ligament deformation, not ligament force, is the more useful feedback signal for stability, because forces stay small through the neutral zone while deformations are large.
Muscle firing with the wrong force or wrong timing may explain acute low back pain that starts with negligible loads, such as picking a sheet of paper off the floor.
Increased spinal stiffness with age from osteophytes, and possibly facet hypertrophy, may be the passive subsystem compensating for declining muscle strength.
In anticipation of extra load or an awkward posture, neural control may change how muscles are recruited, raising stability for a time above normal needs.
Board pearl
Panjabi's stabilizing system has three subsystems: passive (vertebrae, facet joints, discs, ligaments, capsules), active (muscles and tendons) and neural (nerves and CNS, which direct the active subsystem).
Authors' conclusion
It is conceptualized that the first response results in normal function, the second results in normal function but with an altered spinal stabilizing system, and the third leads to overall system dysfunction, producing, for example, low back pain.
Panjabi set out a conceptual model in which spinal stability depends on three interacting subsystems, and described how the system responds to dysfunction, adapts and enhances stability.
Conceptual paper from Yale University, built on earlier in vitro biomechanical studies.
Methods
Scope
Conceptual model of spinal stability drawn from earlier biomechanical work
Topics
Passive, active and neural subsystems
Neutral zone and ligament feedback
Responses to subsystem dysfunction
Adaptation with aging
Stability enhancement for anticipated loads
Key Points
In this model, dysfunction of one component may be met by immediate compensation that preserves normal function, by long‑term adaptation that keeps function but alters the system, or by injury that ends in overall dysfunction such as low back pain.
Panjabi hypothesized that ligament deformation, not ligament force, is the more useful feedback signal for stability, because forces stay small through the neutral zone while deformations are large.
Muscle firing with the wrong force or wrong timing may explain acute low back pain that starts with negligible loads, such as picking a sheet of paper off the floor.
Increased spinal stiffness with age from osteophytes, and possibly facet hypertrophy, may be the passive subsystem compensating for declining muscle strength.
In anticipation of extra load or an awkward posture, neural control may change how muscles are recruited, raising stability for a time above normal needs.
Board pearl
Panjabi's stabilizing system has three subsystems: passive (vertebrae, facet joints, discs, ligaments, capsules), active (muscles and tendons) and neural (nerves and CNS, which direct the active subsystem).
Authors' conclusion
It is conceptualized that the first response results in normal function, the second results in normal function but with an altered spinal stabilizing system, and the third leads to overall system dysfunction, producing, for example, low back pain.