SPECIAL FEATURES INDEX OF JOURNAL This index will help

SPECIAL FEATURES INDEX OF JOURNAL This index will help readers locate special features. Always refer to the most recent issue for an up-to-date index because predicted schedules may change. Annual Conference Call for papers (Research, Theory, and Special Interest) June to November Conference registration, hotel reservations, general information March, April Preliminary program February to April Proceedings November Program participants, abstracts, intermediate program, general information and commercial exhibits May Association Committees, Task Forces, and Section Chairmen November Association Membership Coupon January, April, August Board of Directors and APTA Staff

January, March, May, September

Bylaws

October

Combined Sections Meeting Preliminary program, registration, and information October to January Exhibitors January Educational Programs and State Board Examinations Index to Journal

April, October

December

Instructions to Authors Alternate months starting February Membership Qualifications Membership Statistics

October November

Nominees for National Office Obituaries

March July

Publications/ Audiovisuals February, April, July, September, November Section Membership February Application June, September Theses and Dissertations Titles WCPT Reports

280

January As available

tween points G and D was determined using equation (3). I apologize for any lack of clarity there may have been on this point. 2. Regarding the opinion of poor correlation between radiographic and surface measurements, I think it is a dangerous generalization for Stokes and Moreland to make based on their limited application of the method. I believe their finding a low reliability could be the result of methodological inadequacies in their study. This measurement is complex, however, because there are several factors interacting. Perhaps there are other factors that play a role in addition to the ones I have mentioned. Demonstrating the reliability of this method of measurement also calls for large amounts of data that, unfortunately, are not available. As I stated in my article, further studies based on larger samples are needed to test the reliability of the methods used in our preliminary study. 3. With regard to the similarities between our measurements of the spinal curvature and Kamal's measurements,2 some similarities do exist, as would be expected.3 To say, however, that our studies are identical is not correct. 4.1 agree with Stokes and Moreland's comment about variability with repeated measurements, as I noted in my article when discussing the limitations of the study. I recognize that both intertherapist and intratherapist variability will occur. I further recognize that there will be variability in locating points of maximum and minimum asymmetry. Sources of variability described by Cox include the observer, the condition being measured, and the measuring technique.4 Observers can bring biases to a situation and can vary in their abilities of mental concentration and visual acuity, which may lead to measurement error. It is believed that additional experience increases the rate of interobserver agreement among physical therapists engaged in moire topographic analysis.5 Measuring the condition without using positioning and reflective dots as reference points and measuring when location of the central axis and the levels of maximum and minimum asymmetry are inconsistent both could account for the variability Stokes and Moreland noted in their trial. Therapists from Egypt and Saudi Arabia with whom I have worked have responded well to this measurement method, finding it a repeatable and valuable frame of reference for planning and evaluating treatment programs because it allows comparable measurements of the same patient over a period of time. Moire topographic measurements of the angle of spinal curvature

have been taught easily and applied reliably.6 Many questions still must be addressed before we can begin to accept moire topography as a replacement for roentgenography. We need, for instance, to know more about the role of positioning in the process. We also need to know more about the accuracy of roentgenographic curve measurement, which is accepted today, for lack of an alternative method.7 In taking more than one theoretical perspective and using more than one form of data, we have the variety that can lead to a deeper understanding of the measurement of spinal curvature. MOHSEN M. EL-SAYYAD, P H D Associate Professor and Director Physical Therapy Laboratory PO Box 344 Madinah Menawwara, Saudi Arabia REFERENCES 1. Hefti FL, Hartzell CH, Pizzutillo PD, et al: Dot pattern analysis for back shape measurement in scoliosis. In Drerup B, Frobin E, Hierholzer E (eds): Moire Fringe Topography and Spinal Deformity. Proceedings of the Second International Symposium. Stuttgart, Federal Republic of Germany, Gustav Fischer Verlag, 1983, pp 189-197 2. Kamal SA: Determination of degree of correction of spinal deformity by moiré topographs. In Drerup B, Frobin E, Hierholzer E (eds): Moiré Fringe Topography and Spinal Deformity. Proceedings of the Second International Symposium. Stuttgart, Federal Republic of Germany, Gustav Fischer Verlag, 1983, pp 117-126 3. El-Sayyad MM, Kamal SA: Cobb's angle measurement by moire topographs. In: Proceedings of the Thirty-Fourth Annual Conference on Engineering in Medicine and Biology. Houston, TX, September 23, 1981, p 311 4. Cox K: Planning clinical experiments. Springfield, IL, Charles C Thomas, Publisher, 1968 5. Ruggerone M, Austin JH: Moiré topography in scoliosis: Correlations with vertebral lateral curvature as determined by radiography. Phys Ther 66:1072-1077, 1986 6. El-Sayyad MM, Sabry I: Accuracy of moire topography. Journal of the Egyptian Association of Physical Medicine and Rehabilitation 10:11-16,1983 7. Csongradi JJ, Bleck EE: Moiré topography: Use in scoliosis observation. In Drerup B, Frobin E, Hierholzer E (eds): Moire Fringe Topography and Spinal Deformity. Proceedings of the Second International Symposium. Stuttgart, Federal Republic of Germany, Gustav Fischer Verlag, 1983, pp 141-147

Interferential Current News To the Editor: In response to Dr. Hansjuergen's Letter to the Editor (PHYSICAL THERAPY

66:1003, 1986), I concur that the concept of interferential current (IC) has been exploited and misused and that true IC requires two output circuits that differ somewhat in carrier frequencies. I, however, do not agree with the rest of his statements. PHYSICAL THERAPY

First, creation of IC from two crossing currents is not unique to the biological medium and can be created in water medium or electronically inside the stimulator (premodulation). The net electrophysiological effects most likely are identical. Second, the claim that only the use of "medium" frequency (4,000 to 10,000 Hz) lowers skin resistance has been proven false. The lowering of skin resistance depends not only on the frequency, but also on the phase duration and the voltage.1 The phase duration of an IC at 4,000 Hz is 125 sec; thus, when the phase duration is 125 µsec, any transcutaneous electrical nerve stimulation device will provide the same low skin resistance as will an IC.2 In fact, skin resistance under the high voltage TENS units is less than half of that obtained with IC (B.L. Plevney and P.B. Nutter, unpublished data, October 1981). Third, I challenge the statement that IC can guarantee depth of penetration. Among the factors that determine current penetration is the heterogeneous conductivity of the various tissues, including the highly resistive bones, ligaments, and capsules. Skin resistance, electrode size, and electrode placement also affect currentflowand penetration.

Volume 67 / Number 2, February 1987

Depth of penetration, therefore, is not dependent on a "patent by Nemectron Corporation." Because of the nonhomogeneous conductivity of the various tissues, the path of current flow through a patient virtually is impossible to predict. It is very unlikely that the current will flow in a straight line as commercial pictures attempt to illustrate. Even in a homogeneous water medium, the interference may take place in many areas in the conductive medium, including under the electrodes.3 Consequently, the statement that interference effect is not generated under the electrode is incorrect and conclusions relative to the superiority of IC in pain-blocking effect are not supported. Within the limits of current knowledge and reported clinical results,4,5 an IC stimulator is simply a redundant TENS unit. It uses a different and inefficient electronic approach to obtain the same electrophysiological responses. All the clinical benefits that can be obtained with IC likely are obtainable with a simple battery-operated TENS unit that is much more cost-effective than an interferential stimulator. If the companies and therapists who promote interferential current are convinced that they have a superior stimulator, then the time is

long overdue for them to provide objective clinical data that support such superiority. Commercial claims that are not documented either in electrophysiological knowledge or in objective reporting of clinical results must be rejected by the professional therapist. GAD ALON, PHD Assistant Professor Dept of Physical Therapy Univ ofMaryland 32 S Greene St Baltimore, MD 21201

REFERENCES 1. Lane JF: Electrical impedances of superficial limb tissues: Epidermis, dermis and muscle sheath. Ann NY Acad Sci 170:813-823, 1973 2. Alon G: Electrical stimulators: Let's eliminate the confusion! Teleconference Videotape. Chattanooga, TN, Chattanooga Corporation, 1985 3. Treffene RJ: Interferential fields in a fluid medium. Australian Journal of Physiotherapy 29:209-216, 1983 4. Taylor MK, Newton RA: The effects of interferential current stimulation for the treatment of subjects with recurrent jaw pain. Abstract. Phys Ther 66:774-775, 1986 5. Strauss GR, DeDomenico G: Torque production in human upper and lower limb muscles with voluntary and electrically stimulated contractions. Australian Journal of Physiotherapy 32:38-49, 1986

281