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Previous research indicates that positioning the neck inflexion when using cervical mechanical traction and astandard head halter will increase posterior interverte-bral separation (IVS). Cervical flexion is accomplishedby increasing the rope angle on the tractive device.1–5
When using a standard head halter, a 25°–30° rope angleis the most effective position to increase posterior IVSand open the foramen.6
Historically, a rope angle of 0° was associated withincreased radicular symptoms, such as pain, paresthesia,anesthesia, weakness, and loss of reflex.2 This result wasattributed to the tractive forces transmitted to the man-dible, forcing the neck into extension and decreasingposterior IVS.2,5 An increase in posterior IVS at a 0° ropeangle has been documented, however, the type of headhalter used was not described.7
Only 1 study investigating cervical traction angle andthe Saunders Cervical Traction Device (SCTD) (Chatta-nooga Corp., Chattanooga, TN) was found. Hsueh et al 8
investigated rope angles varying from 35° to 15° usingintermittent traction with a traction force of 15 kg. Theyconcluded that the posterior IVS increased with increas-ing rope angles. However, a 0° rope angle was not inves-tigated.
The purpose of the study was to determine whether arope angle of 0 or 30° achieves higher posterior andanterior IVS when using the SCTD. The study also inves-tigated if an increase in posterior IVS occurs at a 0° ropeangle during traction with the SCTD. A 30° rope anglewas selected because it represents the optimal angle toincrease posterior IVS when using a standard head hal-
ter.6 A 0° rope angle was chosen because of the lack of research investigating the SCTD and this angle of pull.
Materials and Methods
Computerized databases (EBSCOhost, ScienceDirect,PubMed, and APTA hookedonevidence) were searched with-out language restrictions from 1990 to 2004. Reference listsfrom all retrieved articles were also reviewed to identifyrelevant citations. A convenience sample of 20 young adults(15 women, 5 men) without a history of cervical dysfunc-tion, trauma, or pain was obtained. The physical character-istics are presented in Table 1. This investigation usedhealthy individuals and radiographic analysis to model pre-vious investigations.1,8–11 Before conducting the research,University human subject approval and participant consentswere obtained.
Static mechanical cervical traction was applied to each sub-ject using a SCTD and a Triton-700 series traction machine(Chattanooga Group Inc., Hixson, TN). A platform was con-structed to elevate the traction table and obtain a rope angle of 0°. Mounting the SCTD to the edge of the platform to preventthe sliding mechanism from interfering with the table elimi-nated undesirable friction (Figure 1).
Using a rope angle set at 0°, each subject was placed in theSCTD, and a cross-table lateral cervical spine radiograph was
obtained. The subject then underwent 2 minutes of static me-chanical traction using 11.34 kg of force. At 2 minutes of trac-
From the Department of Health Care Professions, College of AppliedSciences and Arts, Southern Illinois University, Carbondale, IL.Acknowledgment date: May 17, 2004. First revision date: February 24,2005. Second revision date: April 25, 2005. Acceptance date: July 7,2005.The device(s)/drug(s) is/are FDA-approvedor approved by correspond-ing national agency for this indication.Institutional funds were received in support of this work. No benefits inany form have been or will be received from a commercial party relateddirectly or indirectly to the subject of this manuscript.Address correspondence and reprint requests to H. Todd Vaughn, PT,MS, OCS, Physical Therapy Coordinator, Clinical Center 4602, South-ern Illinois University, Carbondale, IL 62901; E-mail address:[email protected]
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nificant difference between posterior IVS measurementsbefore and during traction for all cervical segments ex-cept C2–C3 (Table 4).
Discussion
Radiographic analysis on a healthy population has beenpreviously conducted to investigate rope angle and pos-terior IVS when using both the standard head halter and
SCTD.1,7–11 A 25°–30° rope angle is the most effectiveposition to increase posterior IVS when using the stan-dard head halter.6 A 0° rope angle has been associatedwith increased radicular symptoms.2 The rationale usedfor positioning the cervical spine in flexion and increas-ing the rope angle included: (1) minimizing friction be-tween the head and the treatment table, (2) decreasingcompression and irritation of the temporomandibularjoints, and (3) directing the tractive force away from themandible to prevent the neck from being forced intoextension and decreasing posterior IVS.1–3,6,11–16
A 30°–35° rope angle has been the most effective po-
sition to increase posterior IVS when using the SCTD,although, to our knowledge, a 0° rope angle has not beeninvestigated.8 The SCTD is a friction-free device thatdoes not require an increase in the rope angle to lift thehead off the table and negate friction. It has a V-shapedpad that fits against the back of the neck, just below theoccipital bone, designed to reduce stress on the temporo-mandibular joints.6 Tractive forces transmitted to theocciput are unlikely to force the neck into extension anddecrease posterior IVS.
The optimal tractive force to produce posterior IVS isbetween 11 and 21 kg when using the standard head
halter.1,4,6,9,11–13,17
Hsueh etal 8
reported that between 9and 12 kg of force is effective for increasing posterior IVS
when using the SCTD. Therefore, a tractive force of 11.34 kg was used in this study.
An increase in posterior IVS occurs during the firstfew seconds of traction.10,14 No difference in posteriorIVS has been observed between intermittent and statictraction.18 Two minutes of static traction was used inthis study based on the findings of Colachis and
Strohm.10
Increasing the rope angle and flexing the cervical spinemay produce undesirable effects to the foramen and softtissue. The intervertebral foramina enlarge with flexionand narrow with extension.2,12,19 However, researchsuggests that flexing the cervical spine beyond thestraight position (reversal of the lordosis) decreases thespace available for the spinal nerves within the interver-tebral foramen.20 As the rope angle increases, the myo-electric activity of the cervical musculature during trac-tion also increases.21,22 Muscle contraction could negatethe effect of traction and cause a narrowing of the foram-
ina.11,18
Subjects with neck pain, positioned at a 0° ropeangle, recorded no myoelectric activity as measured byelectromyogram.22
Traction has been applied clinically to relieve symp-toms related to cervical radiculopathy.17 The proposedclinical indication for static cervical traction is the pres-ence of a nuclear disc protrusion.23,24 The most commoncause of cervical radiculopathy is disc herniations.25 Cer-vical disc herniations are most often found at the levels of C4 –C5 and C5–C6.26 The basic pathology in disc herni-ation is the compression and/or irritation of the nerveroot by the herniated nucleus pulposus.27,28 The ratio-
nale for using cervical mechanical traction when treatingcervical radiculopathy is to increase posterior IVS andenlarge the intervertebral foramen to decrease compres-sive or irritative forces on the nerve roots.26,29 Interver-tebral disc space widening allows for increased IVS and isone of the most important effects of cervical traction.8,26
Disc pressure decreases as the IVS increases with spinaltraction.30 A decrease in discal pressure creates a vacuumeffect that allows for the regression of a herniated disc.26
Recent publications describing the effect of tractionon spinal structures used computerized tomography andmagnetic resonance imaging. Sari etal 26 showed by com-puterized tomography that static cervical traction in pa-tients with cervical herniated disc increases interverte-bral disc space and stretches the posterior longitudinalligament. The reported result was effective regression of herniated disc volume by 30.3%. In a prospective case-series study, following intermittent cervical traction withthe SCTD, magnetic resonance imaging showed a re-duced size of disc material in patients with a disc herni-ation.31 Good-to-excellent outcomes can be accom-plished with nonoperative treatment.32,33 Case studieshave shown successful treatment of cervical disc hernia-tion and radiculopathy with cervical mechanical trac-tion.34,35
Previous research focused primarily on increasingposterior IVS. Little consideration has been given to an-
Table 3. Posterior IVS During Traction Measurements With the SCTD at 0° and 30°
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terior IVS. During cervical flexion, the intervertebral discspace narrows anteriorly and widens posteriorly, causingthe anterior intervertebral space to decrease and the pos-terior to increase. In extension, the situation is re-versed.1,7,9,10,16,20,36 A posterior directed force on thenucleus pulposus occurs with cervical flexion. Flexionmay aggravate an existing tear in the anulus fibrosis and
cause further extrusion of a herniated nucleus pulpo-sus.37–39 In a more recent case study using the SCTD, apatientdiagnosed with a herniated disc at C6–C7 did nottolerate rope angles higher than 20°, secondary to anincrease in symptoms.40
A primary limitation to this study involves the conve-nience sample of asymptomatic subjects. Research con-ducted on an asymptomatic population has limitations inthat symptoms could not be assessed before, during, andafter traction. Further research is warranted on subjectswith known cervical spondylosis and disc herniation todetermine treatment effect and outcomes. The findings
may be most applicable for the treatment of cervical discherniations, in which anterior compression and in-creased intradiscal pressure is to be avoided. Second, theaverage age of the subjects was 22.6 years, which maynot adequately represent the population of adults withcervical dysfunctions. A final limitation is the small num-ber of subjects19 involved in this study.
Conclusion
The results of this study suggest that a 0° rope angle canproduce a statistically significant increase in anterior
IVS, when compared to the more conventional 30° angleof rope pull. Although there was a significant increase inposterior IVS (except C2–C3) at 0° of traction, the com-parative difference between 0° and 30° was not signifi-cant. Cervical traction has not been studied in enoughdetail to assess its efficacy.41 It is recommended that clin-ical research, using the SCTD at a rope angle of 0°, beconducted on a large population of symptomatic subjectsof various ages to substantiate clinical outcomes.
Key Points
● The relationship of traction rope angle and IVSwas investigated using cervical radiographic mea-surements.● To our knowledge, no previous research hasbeen identified investigating the SCTD and a 0°rope angle.● A rope angle of 0° produced higher anterior IVSthan 30° at all cervical segments during tractionusing the SCTD.● There was no statistically significant differencein posterior IVS comparing traction angles of 0°and 30°.●
An increase in posterior IVS occurred with theSCTD at a 0° rope angle.
Acknowledgment
The authors thank Mr. Bret Simon for his assistance inthe statistical analysis portion of the manuscript.
References
1. Colachis SC Jr, Strohm BR. A study of tractive forces and angle of pull on
vertebral interspaces in the cervical spine. Arch Phys Med Rehabil 1965;46:
820–30.2. Crue BL Jr. Importance of flexion in cervical traction for radiculitis. U S
Armed Forces Med J 1957;8:374–80.
3. Stoddard A. Traction for cervical nerve root irritation. Physiotherapy 1954;