Cervical End-Range Joint Motion Does Not Indicate Maximum Cervical Joint Motion In Healthy Adults. An Observational Study

Abstract BackgroundIn clinical diagnosis, the largest motion associated with cervical range of motion is thought to be found at end-range and it is this perception that forms the basis for the interpretation of flexion/extension studies. There have however, been representative cases of joints producing their maximum motion before end-range, but this phenomenon is yet to be quantified. PurposeTo provide a quantitative assessment of the difference between maximum motion and end-range in healthy subjects. Secondarily to classify joints into type based on their motion and to assess the proportions of these joint types. Study designThis is an observational study. Subject sampleThirty three healthy subjects participated in the study. Outcome measuresMaximum motion, end-range motion and surplus motion in degrees were extracted from each cervical joint. MethodsThirty-three subjects performed one flexion and one extension motion excursion under video fluoroscopy. The motion excursions were divided into 10 percent epochs between the initial upright position and the end-range position, from which maximum motion, end-range and surplus motion were extracted. Surplus motion was then assessed in quartiles and joints were classified into type according to end-range. ResultsFor flexion 48.9% and for extension 47.2% of joints produced maximum motion before end-range (type Surplus). For flexion 45.9% and for extension 46.8% of joints produced maximum motion at end-range (type Classic) and 5.2% of joints in flexion and 6.1% of joints in extension concluded their motion anti-directionally (type Anti-directional). Mann-Whitney U tests produced significant results for C2/C3, C3/C4 and C4/C5 in flexion and C1/C2, C3/C4 and C6/C7 in extension when comparing end- range motion for type Classic and type Surplus. The average contributions to cervical range-of-motion (ROM) (C0 to C7) for flexion and extension were 60.23֯ and 67.86֯ for type Classic and 42.22֯ and 49.05֯ for type Surplus respectively. Thus, the average contribution to cervical ROM was larger for type Classic than for type Surplus. The average pro-directional surplus motion was 2.41֯ ± 2.12֯ with a range of range (0.07֯ -14.23֯) for flexion and 2.02֯ ± 1.70֯ with a range of 0.04°-6.97° for extension.ConclusionThis is the first study to categorise joints by type of motion. Type Surplus constituted approximately half of the joints analysed in this study. Therefore, end-range motion cannot be assumed to be a demonstration of a joint´s maximum motion.