Background: Chronic neck pain was one of the most common clinical musculoskeletal injuries. Neck muscles played an important role in maintaining the dynamic stability of cervical
spine and preventing from injuries. This study investigated the correlation between the function of deep neck flexors (DNF) and the posture of shoulder and neck in patients with chronic neck pain and
provided an evidence for therapeutic exercise.
Methods: 39 patients were recruited as the experimental group (EG). The inclusion criteria: chronic neck pain repeatedly attacks for more than 3 months; non-severe neck symptoms (NDI
<15/50) to avoid exacerbation of pain when testing; no history of spinal surgery and trauma; no drugs; no rheumatism. 21 subjects with no neck pain as control group(CG). Participants underwent
postural screening to identify forward head and rounded shoulder. Posture was assessed using a digital camera. Forward head angle (FHA) measured from the vertical arterially to a line connecting the
tragus and the seventh cervical vertebra (C7) marker. Forward shoulder angle (FSA) for rounded shoulder measured from the vertical posteriorly to a line connecting the C7 marker and the acrominal
marker.Maximal isometric strength of neck retraction in neutral posture,45° rotation on left and right sides were measured by Multi-Cervical unit(MCU).Unit is a pound. DNF endurance test: Subjects
were in the supine position with knees flexed, cross hands on abdomen, keeping jaw backward and make head lift off the bed about 2.5 cm and maintain this posture. Testers ensured the height and record
the time in seconds. The independent samples T test was used to analyze the significance. Statistical significance was set a priori at ɑ<0.05 for all analyses. Pearson’s correlation coefficient was
used to investigate the relationship between posture and DNF strength. Statistical packages SPSS(19.0) was used for the analysis.
Results: The EG’ FHA(40.26±4.43°) was significantly bigger than the CG (35.95±3.57°) (p<0.01); The EG’ FSA(49.25±7.09°) was significantly bigger than the CG( 41.71±5.72°) ( p<0.01).
The EG's maximal isometric strength of neck retraction in neutral position was 11.97±5.05, the CG was 15.35±6.67 (p<0.05); In left rotating posture, the EG was 9.03±3.51, and the CG was 12.87±49
(p<0.01); In right rotating posture, the EG was 9.26±3.61, the CG was 12.96±57 (p<0.01).In endurance test, the EG was 44.92±23.89 and the CG was 66.21±30.03 (P<0.01).FHA was correlated with neck
retraction strength in neutrality (r=-0.084,p=0.524), left rotation (r=-0.216,p=0.097), right rotation(r=-0.129,p=0.327) and DNF endurance (r=-0.031,P=0.811).FSA was correlated with strength in
neutrality(r=-0.277,p=0.032), left(r=-0.391,p=0.002), right (r =-0.293,p=0.023) and DNF endurance( r=-0.282,p=0.029).
Conclusion: The patients with chronic neck pain always showed a poor posture in head and shoulder. Their strength indexes related with DNF would be worse than normal subjects; there
was strong correlation between the DNF strength and the abnormal shoulder position. Therefore, we suggest strength training of the DNF would be an important role to correct shoulder posture.