Palpation and X-ray of the Upper Cervical Spine: A Reliability Study

ORIGINAL RESEARCH Palpation and X-ray of the Upper Cervical Spine: A Reliability Study John Hart D.C. 1 ABSTRACT Introduction: A complete examination of vertebral subluxation includes assessment of its neurological and misalignment components. A number of tests exist for determining alignment of vertebrae, and among these are palpation and x-ray. This study assesses the reliability of palpation and x-ray for determining vertebral alignment of the upper cervical spine. Methods: Thirty one patients, who were already scheduled for clinically necessary x-rays, were palpated by two independent examiners immediately following their x-rays. The radiographs were subsequently analyzed by two other examiners. Thirty-four palpation assessments and 30 x-ray assessments were analyzed for reliability using the kappa statistical test and percent agreement. Results: According to the kappa test, there were six x-ray assessments that had acceptable (.4 or greater) reliability. None of the palpation findings had acceptable reliability. Conclusion: Knowing which assessments have been shown to have acceptable reliability can help the chiropractor apply proper weight to the individual assessments, particularly when the assessments disagree. Determining which tests are reliable and which ones are not is important in contributing to the establishment of an evidence base for determining vertebral listings. More research is needed to verify the findings in this study. Key Words: X-ray, palpation, inter-examiner reliability. Introduction It is the objective of many chiropractors to locate and correct vertebral subluxations (VS). There are many methods for analyzing VS. For an adequate assessment of VS, its neurological and biomechanical (misalignment) components must be analyzed. 1 This study focuses on the biomechanical (vertebral listing ) aspect of VS. Obtaining a listing (direction of misalignment) is an important part of VS analysis. For example, if a subluxated vertebra was misaligned to the right, it would seem reasonable for the chiropractor to thrust from right to left, and not left to right. The writer has previously reported a case where a spinal thrust was unfortunately given in a direction that was not consistent with what the x-ray indicated, resulting in an adverse clinical event. 2 It is also important for the chiropractor to know whether a particular clinical assessment he or she uses is reliable. Assessments might contradict each other but more weight should be placed on the one that has been shown in previous research to be more reliable. Eriksen notes that there is very poor agreement between x-ray and non-x-ray methods of determining upper cervical misalignment. 3 Spano 4 found 6 out of 12 (50%) exact agreements for the atlas when comparing palpation to x-ray; when only atlas laterality was considered, there were 8 out of 12 (66%) agreements. When considering C2 spinous rotation, Spano found 9 out 12 (75%) agreements between x-ray and palpation. The present study is different from Eriksen and Spano inasmuch as the present study included two blinded examiners instead of one for both the x-ray and non-x-ray (palpation) methods. Another difference is that in the current study, palpation was performed immediately following the x-rays. There are a number of assessments for palpation x-ray assessments for upper cervical misalignment available to the chiropractor. For example, there are different palpation and x- ray assessments for atlas laterality. The reliability of both x- ray and palpation analyses has been the subject of previous 5 study. DeBoer et al found statistically significant agreement for lower cervical fixations, no agreement for the 1 Assistant Director of Research Sherman College of Straight Chiropractic Spartanburg, S.C. 29304 - jhart@sherman.edu J. Vertebral Subluxation Res. Oct. 25, 2006 1

mid-cervicals, and intermediate agreement for the upper cervical spine. In a study involving two physiotherapists, Strender et al found an acceptable kappa score (>.4) for only one out of the five palpation assessments for pain. 6 Agreement is good if there is a prominent fixation is present (i.e., congenitally blocked vertebrae). 7 Consistent with muscle palpation theory, a tight muscle could indicate an action the body is taking in 4, 8-9 attempting to correct a subluxation. For example, the theory holds that a tight inter-transversarri muscle between C1 and C2 would indicate that the body is attempting to correct the malposition of the transverses found with atlas laterality. For x-ray, Sigler and Howe 10 found that an upper cervical x- ray marking system was unreliable but Jackson et al found that such measurements were reliable. 11 The present study focuses on the biomechanical, (listing) aspect of the vertebral subluxation as this relates to two popular methods of determining listings: x-ray and palpation. The purpose of this study is to determine how well examiners agree using these assessments. Methods The study was approved by the Sherman College Research Committee. Thirty-one patients, who were already scheduled for clinically necessary x-ray procedures as part of their regular care plan, were recruited from the College s Health Center to participate in this study. The patient was asked to read and sign a consent form. The examiners were selected via the convenience sample method and consisted primarily of licensed chiropractors but also included experienced chiropractic interns. Consequently, there were varying levels of experience for both palpation and x-ray examiners. For example, one of the x-ray examiners had not used the base posterior radiograph in his practice and was given a mini-course on its analysis by the author. Each examiner was blinded to all other examiner findings. The author was an x-ray examiner who also assessed the agreement scores (on a 3 x 3 computer table in Excel [Microsoft Corp., Redmond, WA]). The statistical tests, kappa and percent agreement were used and acceptable levels were set minimally at.4 for kappa 12 and.65 for percent agreement. 13-14 Palpation Immediately following the x-rays, the patient's upper cervical spine was palpated. The first examiner placed his or her findings in a sealed envelope. A second examiner then performed the second palpation exam and placed these findings in a sealed envelope. Table 3 lists the palpation assessments that were studied while Figure 5 shows some of the muscles that were used. The primary approach was focused on muscle palpation which assessed the tightness or lack thereof for the muscles listed in Table 3. Static (boney) palpation was also studied, although this approach was used for 17 of the 31 patients (Table 3). X-ray Figures 1-4 show the x-ray views that were used with some of the assessment landmarks identified. Table 2 lists all x-ray assessments that were studied. Additional details of the x-ray assessments can be found in Remier, 15 Strazewski, 16 and Kuhta. 17 Line analysis (versus visual analysis) was emphasized in this study. The patient was x-rayed in the seated position using the following four-view series: 1. AP open mouth 2. Lateral cervical 3. Either a base posterior or a vertex 4. Nasium Explanations of the x-ray assessments are provided in Appendix A. Results Final Atlas Listings For final atlas listings, palpation examiners agreed with each other in 12 out 31 cases (38.7%) for atlas laterality only compared to 19 out of 31 (61.2%) cases for the x-ray examiners. There were five cases (out of 31 = 16.1%) where all four examiners (two palpation examiners and two x-ray examiners) agreed on atlas laterality (Table 1). For atlas tilt (2 nd letter in the atlas listing), the palpation examiners agreed in 24 out of 31 cases (74.4%) compared to 18 out of 31 (58.0%) for the x-ray examiners. Nine out of 31 cases (29.0%) showed agreement the four examiners for atlas tilt (Table 1). Axis Listings The palpation examiners agreed with each other on C2 body (dens) laterality in eight out of 31 cases (25.8%) compared to 19 out of 31 (61.2%) cases for the x-ray examiners (includes three cases where both examiners either could not see the structures or did not arrive at a finding). For axis spinous rotation, the palpation examiners agreed in 13 out of the 31 cases (41.9%) compared to 17 out of 31 (54.7%) cases for the x-ray examiners. Inter-examiner Reliability There were six x-ray assessments (out of 30 =20%) that had acceptable kappa scores (.4 or greater), and these were: 1) atlas tilt on the lateral view according to the interspace, 2) atlas tilt on the lateral view according to the V space, 3) axis body laterality according to VML-O, 4) axis body laterality according to VML-M, 5) final axis body laterality, and 6) axis relative to C3 on lateral view. (Table 4). Acceptable kappa scores were not found in any of the following: palpation assessments, nasium view assessments, and base posterior assessments. J. Vertebral Subluxation Res. Oct. 25, 2006 2

There were two palpation assessments (out of 34 = 5.8%) and three x-ray assessments (out of 30 = 10%) that had acceptable percent agreements (Tables 2 and 3). Discussion Variable reliability of clinical tests is nothing new in health care, including chiropractic health care. Knowing which assessments have been shown to have acceptable reliability and which ones have not will assist the chiropractor in applying appropriate weight to the various assessments, particularly when different assessments disagree regarding the direction of misalignment. There are three possible limitations to this study. First, the study included examiners with different levels of experience and expertise. This may however be a strength of the study because in the real world, different doctors are going to have different levels of experience and expertise. Second, the findings may not be easily generalized due to the lack of random selection of the examiners (they were selected by the convenience sample method). Third, the percent agreement statistic is a weaker than the kappa statistic 18-19 and therefore the kappa findings should be given more weight. Further research is needed to verify the findings of this study. Conclusions This study identified both reliable and unreliable assessments for upper cervical listing analysis. According to the kappa statistic, only a small number of (x-ray) assessments showed acceptable reliability. Knowing which assessments are reliable and which ones are not will help the chiropractor weigh each assessment appropriately, particularly when assessments contradict each other. Future studies should: a) Determine which assessments for listings (palpation and x-ray), if any, have a significant correlation with the successful correction of the neurological interference component of vertebral subluxation, and b) emphasize the visual method to see if this improves reliability. Acknowledgements Gratitude is given to the following colleagues who assisted in this study: Kesnold Baptiste, DC (examiner) Ralph Boone, PhD, DC (consultant) Coleman Carrington, DC (examiner) Joseph J. Donofrio, DC (examiner) William Fehl, DC (examiner) Janice Fordree, DC (examiner) Jerry Gardner, DC (examiner) Robert Irwin, DC (examiner) Kyle Martin, DC (examiner) Tyler Mason, DC (examiner) Ed Owens, MS, DC (data analysis assistance) John Reizer, DC (examiner) Kim Sanders, DC (examiner) Shane Walker, DC (examiner) References 1. Council on Chiropractic Practice. Vertebral Subluxation in Chiropractic Practice. 1998, p. 59. 2. Hart JF. Manipulation-induced subluxation and associated cardiac arrythmia. Digest of Chiropractic Economics. 1991 (January/February), pp. 68-69. 3. Erickson K. Comparison between upper cervical x- ray listings and technique analyses utilizing a computerized database. Chiropractic Research Journal 1996; 3(2):21. 4. Spano N. Static palpation of muscle imbalance as compared to radiographic evaluation of C1. Journal of Straight Chiropractic 1995; 1(1):24-27. 5. Deboer KF et al. Reliability study of detection of somatic dysfunctions in the cervical spine. Journal of Manipulative and Physiological Therapeutics 1985;8(1):9-16). 6. Strender LE, Lundin M, Katarina N. Inter-examiner reliability in physical examination of the neck. Journal of Manipulative and Physiological Therapeutics 1997;20(8):516-520. 7. Humphreys BK, Delahaye M, Peterson CK. An investigation into the validity of cervical spine motion palpation using subjects with congenital block vertebrae as a 'gold standard'. BMC Musculoskelet Disord 2004; 15, 5:19. 8. Gates, D. Spinal Palpation. 1995. 9. Donofrio, J. Palpation II (Class Notes). Sherman College of Straight Chiropractic. 10. Sigler DC, Howe JW. Inter-and intraexaminer reliability of the upper cervical x-ray marking system. Journal of Manipulative and Physiological Therapeutics 1985; 8:75-80. 11. Jackson BL et al. Inter-and intra-examiner reliability of the upper cervical x-ray marking system: a second look. Journal of Manipulative and Physiological Therapeutics 1987; 10(4):157-163. 12. Agreement between Categorical Measurements: Kappa Statistics. Retrieve 9-26-06 at: http://www.dmi.columbia.edu/homepages/chuangj/ka ppa/ 13. Revonsuo A, Valli K. Dreaming and Consciousness: Testing the Threat Simulation Theory of the Function of Dreaming. Retrieved 9-26-06 at: http://psyche.cs.monash.edu.au/v6/psyche-6-08- revonsuo.html 14. Hume C, Ball K, Salmon J. Development and reliability of a self-report questionnaire to examine children's perceptions of the physical activity environment at home and in the neighbourhood. Int J Behav Nutr Phys Act. 2006; 3: 16. Retrieve 9-27-06 at: http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid= 1550247 15. Remier, PA. Modern X-ray Practice and Chiropractic Spinography. Davenport, IA: Palmer School of Chiropractic, 1947. 16. Strazewski J. Essentials of Toggle Recoil (HIO). [2 nd Edition]. Davenport, IA: John Strazewski, 1998. 17. Kuhta, P. Radiographic Analysis 612 (Class Notes). Sherman College of Straight Chiropractic. J. Vertebral Subluxation Res. Oct. 25, 2006 3

18. Hunt RJ. Percent agreement, Pearson's correlation, and kappa as measures of inter-examiner reliability. J Dent Res. 1986 Feb;65(2):128-30. 19. Percent Agreement (%agree). Retrieved 9-26-06 at: http://tagotoweb.adfg.state.ak.us/adu/percentagree ment.asp 20. From: Family Practice Notebook. Retrieved 4-1-06 at: http://images.google.com/imgres?imgurl=http://www.fpnotebook.com/necklateralmuscles.jpg&imgrefurl =http://www.fpnotebook.com/ort65.htm&h=541& w=750&sz=89&tbnid=jvoyummjcv7-3m:&tbnh=100&tbnw=140&hl=en&start=1&prev=/i mages%3fq%3dmuscles%2bof%2bthe%2bneck%2 6svnum%3D10%26hl%3Den%26lr%3D with permission. Tyler Ma J. Vertebral Subluxation Res. Oct. 25, 2006 4

Table 1 Final Listings For Both X-ray and Palpation 1 X-ray Palpation Examiner #1 Examiner #2 Examiner #1 Examiner #2 Case # Atlas C2 Atlas C2 Atlas C2 Atlas C2 1 ASL CPBL AIRP SPBL ASRa PR ASRA ESR 2 ASRP ESR ASRP ESR ASR ESR AILP CPBL 3 ASL ESL ASLA ----- ASLP PL ASLA SPBR 4 AIR ESR AIRA ESR AIRP PL ASLA PL 5 ASRP ESR ASLA --- ASLA CPBR ASLP CPBL 6 ASRP ESRBR ASRA CPBR ASR PR ASRA CPBL 7 ASLP CPBL ASLP CPBL ASRP CPBL ASRA BR 8 AILP BL AILP ESL-SL ASR PR ASLA ESL 9 A--(LP) PR AILP PR AIRP BR ASLP ESR 10 AIRP ---- AIRP ESR-BR ---- ---- ASRa CPBR 11 ASRP ESR AIRP ESR ASLA CPBR ASLP SPBR 12 ASLA ESL-BL AILP ---- AIRA ESL ASLP ---- 13 AIRA BPSR AILA ESR-SR ASRP CPBR ASRP CPBR 14 AI--- CPBL AIR CPBL ASRA SPBR ASL CPBL 15 ASLa ----- ASL ----- ASLa PL ASLA ESL 16 AS--- ----- ASL ----- ASLA SPBL ASRP PR 17 AILA ----- AIRP ----- ASL PL ASLA CPBL 18 ASLP PR ASLP ESR-SR ASRP BR LP PRs 19 ASRA ---- ASLP ESL-SL ASL ESL ASRA PR 20 ASRA BR ASRP ESR ASRP ESR ASL CPBR 21 AIRP ESR AIRP ESR ASLA ESR ----- PR 22 A--LP ---- AILP BL ASLP CPBL ASRP ESR 23 AIRP ---- ASR ESL-BL ASLA PL ASRP SPBL 24 A---R BR ASRP BR ASR CPBR ASL CPBL J. Vertebral Subluxation Res. Oct. 25, 2006 5

25 ASRP CPBL AILP ESL ASR ESL ASLA BPSL 26 A-RP CPBR ASRP BPSL ASRA SPBR ASR CPBR 27 AIRP ESR-SR ASRA ESR-SR ASRP ESR ASR CPBL 28 ASRP --- ASLA ESL-SL ASRP BR ASRP CPBR 29 AS-(LP) ESL AILP ESL-SL ASRP ESR ASR CPBR 30 ASLA BR ASRP CPBR ASL CPBR ASR PL 31 A-RP PL AIRP ---- ASL ESL ASR CPBR 1. Inter-examiner similarities are in bold. Inter-method similarities are underlined. --- = examiners could not see structures on this view or arrived at no finding. In case #9, no tilt or laterality for atlas was found but rotation on the left side was found. A small a with ASLa = small amount of anterior rotation. CPBR has a spinous left and that is why case #31 has the axis listings underlined. J. Vertebral Subluxation Res. Oct 25, 2006 6

Table 2 Percentage Agreements and Kappa Scores for All Palpation Assessments 1 Atlas Factor Percent agreement Kappa N Muscle 1. Atlas laterality - levator scapula.51.17 31 2. Atlas laterality - superior oblique.26-0.07 30 3. Atlas laterality - transversarri.56.2 30 4. Atlas anteriority - superior oblique.5.26 30 5. Atlas anteriority - inferior oblique.2-0.36 30 6. Atlas anteriority - splenius cerv..46.2 30 7. Atlas anteriority - SCM.22-0.21 31 8. Atlas posteriority- splenius capitus.33-0.08 30 9. Atlas posteriority - spinalis capitus.36.09 30 10. Atlas posteriority - RCP major.4.1 30 11. Atlas superiority RCP minor.56.08 30 12. Axis (C2) body laterality - scalenus medius.3-0.10 30 13. Axis body laterality - splenius cerv..36-0.10 30 14. Axis spinous laterality - inferior oblique.19-0.30 31 15. Axis spinous laterality - RCP major.43.15 30 16. Atlas tilt in muscle listing.76.02 30 17. Atlas laterality in muscle listing.48.06 31 18. Atlas rotation in muscle listing.45.13 31 19. Axis body in muscle listing.29-0.07 31 20. Axis spinous in muscle listing.35.03 31 Static (Boney) 21. Atlas TP more prominent per static.29-0.04 17 22. Atlas side of post. rotation per static.52.2 17 23. Atlas high TP per static.17-0.25 17 24. Atlas final laterality per static.35-0.06 31 25. Atlas final rotation per static.32-0.03 31 26. Axis (C2) more prominent body per static.11-0.18 17 27. Axis spinous laterality per static.58.38 17 28. Axis final static body laterality.16-0.27 30 29. Axis final static spinous laterality.48.22 31 FINAL ATLAS LISTING 30. Tilt.77-0.08 31 31. Laterality.41-0.09 31 32. Rotation.35.03 31 FINAL AXIS LISTING 33. Body.25-0.14 31 34. Spinous.38.04 31 1 Po = percent agreement. Acceptable values in bold. Two out of 35 palpation assessments had acceptable Po agreements. There were no assessments that had acceptable kappa scores. The different number of patients (30 versus 31) is due to examiners omitting to record the finding for the assessment. Positive kappa = agreement and negative kappa = disagreement. J. Vertebral Subluxation Res. Oct 25, 2006 7

Table 3 Percentage Agreements and Kappa Scores for All X-ray Assessments 1 Atlas Factor Po Kappa N APOM 1. Atlas closed wedge.32-0.01 31 2. Atlas long A-O articulation.58.36 31 3. Atlas horizontal measurement (VML-O).51.25 31 4. Atlas horizontal measurement (VML-M)*.48.2 31 5. Atlas overlap.58.36 31 6. Atlas laterality conclusion.61.38 31 NASIUM 7. Atlas closed wedge.34-0.00 29 8. Atlas long A-O articulation.13-0.29 29 9. Atlas horizontal measurement (VML-O).27-0.15 29 10. Atlas horizontal measurement (VML-M).31-0.06 29 11. Atlas overlap.34.06 29 12. Atlas laterality conclusion.44.07 29 BASE POSTERIOR/VERTEX 13. Atlas laterality.6.37 30 14. Atlas rotation.53.22 30 LATERAL CERVICAL 15. Atlas tilt per interspace.67.43 31 16. Atlas tilt per V.64.41 31 17. Atlas tilt per line.58.24 31 18. Atlas tilt conclusion for lat. Cerv view.54.27 31 FINAL ATLAS LISTING 19. Tilt.61.34 31 20. Laterality.61.30 31 21. Rotation.54.21 31 22. Side of head rotation per APOM view.48.2 31 J. Vertebral Subluxation Res. Oct. 25, 2006 8

Axis (C2) (APOM) 23. Axis body laterality (VML-O).67.51 31 24. Axis body laterality (VML-M)*.64.47 31 25. Axis spinous laterality (VML-O).54.29 31 26. Axis spinous laterality (VML-M).61.39 31 27. Does head rotation confound axis spinous rotation?.58.30 31 28. Axis relative to C3 on lateral view.67.48 31 FINAL AXIS LISTING 29. Body laterality.64.46 31 30. Spinous laterality.54.3 31 1 Acceptable scores are in bold. Po = percent agreement. Acceptable level for Po is.65 and for Kappa,.4. Acceptable values in bold. Three out of 30 x-ray assessments had acceptable Po agreement scores for inter-examiner agreement while six of the 30 had acceptable kappa scores. The different number of patients (29 versus 30 versus 31) is due to inability of examiners to read the film in those instances. Positive kappa = agreement and negative kappa = disagreement. Kappa scores for determining atlas laterality almost reached the acceptable level (of.4) on the AP open mouth and base posterior views but were weak for the nasium view (Table 3). Consequently, the AP open mouth and base posterior views appear to be more reliable than the nasium view for determining atlas laterality. Table 4 Assessments with Acceptable Reliability 1 Assessment and view Kappa score 1. Atlas tilt on the lateral view according to the interspace on the lateral view.43 2. Atlas tilt on the lateral view according to the V space on the lateral view.41 3. Axis relative to C3 on the lateral view.48 4. Axis body laterality according to VML-O on the APOM view.51 5. Axis body laterality according to VML-M on the APOM view.47 6. Final axis body laterality on the APOM view.46 1. Kappa score of at least.4. J. Vertebral Subluxation Res. Oct. 25, 2006 9

Fig. 1. AP Open Mouth Radiograph 1 1 Upper set of arrows point to MITs and lower set point to junction of posterior arch and lateral mass. From the author s collections Fig. 2. Lateral Cervical Radiograph. 1 1 Vertical line represents tall space that suggests an inferior tilted atlas when anterior tubercle is the reference point. From the author s collections J. Vertebral Subluxation Res. Oct. 25, 2006 10

Fig. 3. Base Posterior Radiograph. 1 1 Upper set of arrows are pointed at Duff s Vs (ossification centers of the occipital bone and lower set point at transverse foramen of atlas. The atlas has rotated anterior on the left (posterior on the right). From the author s collections. Fig. 4. Nasium Radiograph 1 1 Arrow points to area where A-O overlap would be assessed. Courtesy of Dr. Perry Rush J. Vertebral Subluxation Res. Oct. 25, 2006 11

Fig. 5. Muscles of the Neck. From Family Practice Notebook. 21 with permission. J. Vertebral Subluxation Res. Oct. 25, 2006 12

Appendix A Description of X-ray Assessments Assessments for the AP Open Mouth Radiograph for C1 (atlas) Atlas wedge: Assessed by constructing a horizontal line connecting the medial inferior tips of the occipital condyles (MITs) and another horizontal line connecting like points on the atlas. The theory is that when atlas misaligns laterally, it glides superior on the occipital condyle on the side of atlas laterality. Atlas-occipital (A-O) articulation: Assessed by measuring the distance between the following two points: The MIT of the occipital condyle and the lateral superior tip of the articulating atlas lateral mass. Atlas vertical median line perpendicular to the ocular orbit points line (VML-O): Assessed by constructing a vertical line drawn through the neural canal that bisects the distance between the MITS of the occiput condyles, and is parallel to a horizontal line that connects like points in the skull (i.e. in the ocular orbits). A measurement is then made from this vertical median line (VML) to like points on the atlas. The greater distance, if any, indicates the side of laterality according to this assessment. Atlas: vertical median line perpendicular to the MIT line (VML-M): Assessed in the same manner as VML-O except that VML is constructed perpendicular to a line that connects the MITs. Atlas overlap: Assessed by observing which side, if any, the superior lateral tip of the atlas lateral mass extends beyond the lateral aspect of the articulating occipital condyle. The theory is that the atlas lateral mass will extend beyond the condyle on the side of laterality. Atlas laterality conclusion: Arrived at by considering the above assessments for laterality. Assessments for Lateral Cervical Radiograph Atlas Atlas tilt per insterspace: Primarily a visual comparison of the interspaces above and below the posterior arch/ tubercle of atlas. The theory is that the atlas arch should be about halfway between the bony structure above and below the arch / tubercle of atlas. V space: Primarily a visual observation of the space anterior to the dens of axis and posterior to the anterior tubercle of atlas. The borders of this space should be parallel if the atlas is in normal alignment. Atlas line analysis: Assessed by constructing a line on the occiput where the condyles seem to meet the skull, and comparing this line to a line on the atlas that is constructed through the anterior and posterior tubercles. Normally the atlas should sit on a 4-degree angle relative to the aforementioned skull line. Atlas tilt conclusion: Arrived at by considering the above assessments for tilt on this view. Atlas tilt: This part of the listing was basically derived from the conclusion found on the lateral cervical. Atlas laterality: This aspect of the misalignment was derived from conclusions from the three views above (AP open mouth, nasium, and base posterior). When the views/findings conflicted, the laterality was determined by the greater number of indicators, the visibility quality of the particular finding, or both. Atlas rotation: Derived from the base posterior finding. This finding is reflected with a fourth letter on the atlas listing, i.e., the P in ASRP. Assessments for the Base Posterior Radiograph (atlas only) Atlas laterality: Assessed by bisecting a line that connects Duff's V (occipital condyle ossification center - one for each condyle) and drawing the vertical line through the neural canal parallel to the V line. The greater distance measured out to the atlas transverse foramen is the side of laterality according to this assessment. Atlas rotation: The Duff's V line is compared a line connecting the transverse foramen. The side of convergence, if any, is considered the side of anterior rotation; the side of divergence, if any, would be considered the side of posterior rotation. J. Vertebral Subluxation Res. Oct. 25, 2006 13

Assessments for Nasium (atlas only) These assessments were assessed in the same way as for the AP open mouth. Final Atlas Listing The atlas listing used in this study was based on the Palmer listing system. For example, an ASRP means C1 has misaligned superior (determined on the lateral - anterior tubercle angled up, posterior tubercle down), to the right (determined on AP open mouth, nasium and base posterior views as previously described) in relation to the occiput, and the side of laterality (right in this example) shows the right transverse process has rotated posteriorly relative to the occiput (determined primarily from the base posterior view). Assessments for C2 on the APOM Radiograph Side of head rotation: This is a factor to consider when determining C2 spinous rotation. It is also considered when assessing the size of the lateral masses (i.e., the side closer to the film will appear smaller, assuming the two lateral masses are anatomically the same size). Head rotation was assessed by comparing like structures on both sides of the skull (i.e., the frontal process of the zygomatic bone) and comparing the distance of these structures to the edge of the skull. Does head rotation confound C2 spinous rotation finding? This question is related to the previous question (of head rotation) and if present, could cause erroneous interpretations for C2 spinous rotation finding. For example, extreme left head rotation would most likely cause a right spinous finding on the radiograph. In this example, head rotation would interfere with the accuracy of the analysis. However, if the C2 spinous was found to be left of the median line with left head rotation, then it was analyzed to most likely be left-rotated spinous, since the left head rotation would tend to move the C2 spinous to the right. C2 body laterality and spinous rotation: Achieved by measuring from the VML to: a) the left and right lateral edges of the dens or body for determining body (dens) laterality, and b) to the center of the spinous for determining spinous rotation. Both VML-O and VML-M were used as reference lines. C2 relative to C3 on the lateral cervical: Determined by assessing the posterior body margins of C2 relative to C3. Final C2 listing Body laterality: Determined from VML-O. Spinous laterality/rotation: Determined from VML-O. For final x-ray listings, both visual and line analysis was considered but a heavier weight was placed on line analysis. J. Vertebral Subluxation Res. Oct. 25, 2006 14