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Electrical studies as a prognostic factor in carpal tunnel syndrome
Letters to the Editor Darrach Procedure or Something Else? To the Editor: I would like to comment on "Salvage of the Failed Darrach Procedure" by Kleinman and Greenberg (Kleinman WB; Greenberg JA. J Hand Surg 1995; 20A:951-958). They show x-rays in which a considerable amount of the distal ulna has been removed. These illustrations do not reflect a Darrach procedure. The Darrach procedure has been variously described as excision of the distal 3 cm or 1 in. of the distal ulna. Showing these x-rays and calling this a Darrach procedure is an injustice to a surgical technique that provides excellent results when properly applied. Charles B. Clark, MD 10 Sierragate Plaza Roseville, CA 95678 In Reply: We are in complete agreement with Dr. Clark's statement regarding the efficacy of the Darrach distal ulna resection. This is an excellent operative procedure when indications are appropriate and when performed in a meticulous fashion requiring the utmost attention to detail. We are sure Dr. Clark is well aware that even when the Darrach procedure is performed correctly, there are patients who will develop impingement of the distal ulna against the ulnar border of the radius, usually when there is excessive bony resection. All of the patients in our series were referred to the Indiana Hand Center for care due to symptomatic impingement following distal ulna resection. The most common characteristic of patients in our series was excessive resection of the distal ulna to the proximal margin of the sigmoid notch. The x-ray illustration to which we believe Dr. Clark is referring (Fig. 3B) is an example of a preoperative x-ray of a patient in our study group. We do not advocate that amount of bony resection during a Darrach distal ulna resection, but in this instance, we intended to demonstrate preoperative x-rays of a patient suffering from a condition amenable to treatment using the technique about which we wrote. 930
The Journal of Hand Surgery
We hope this response clarifies our use of these particular x-rays and addresses the injustice that Dr. Clark believed that we were showing to a surgical technique also feel is appropriate when performed properly.
William B. Kleinman, AID Jeffrey A. Greenberg, AID Indiana Hand Center 8501 Harcourt Road P.O. Box 80434 Indianapolis, IN 46280-0434 Electrical Studies as a Prognostic Factor in Carpal Tunnel Syndrome To the Editor: We read with interest the study by Drs. Braun and Jackson regarding electrical studies as a prognostic factor in the carpal tunnel syndrome. 1 Their conclusions suggest that electrodiagnostic tests did not provide significant data for prediction of functional recovery or re-employment after carpal tunnel release. We believe that there are several aspects about this study that warrant further discussion: 1. Their criteria for "electrical abnormality" was "usually sensory latency over 3.5 ms." This definition of abnormality is not supported in the literatm'e, is outdated, and should not be considered the standard of practice. 2 More sensitive and specific techniques have been well established and would almost surely change interpretation of a significant number of subjects. Better criteria for abnormality would include: A. Comparison of median distal sensory latency to ulnar sensory distal latency. B. Comparison of median distal sensory latency to radial sensory distal sensory latency. C. Comparison of median midpalmar latency to ulnar midpalmar latency. D. Absolute median midpalmar latency.2 2. Descriptions of the electrodiagnostic techniques used are inadequate to make interpretations of distal latencies meaningful. The following information is missing:
A. Distance: The distance between stimulation and recording electrodes is a critical factor; a difference as small as 1 cm could change distal latency as much as 0.4 ms or 10%. 2
The Journal of Hand Surgery / Vol. 21A No. 5 September 1996
B. Temperature: Temperature of the hand greatly affects the distal sensory latency, with a difference of up to 0.2 ms in distal latency for every Celsius degree of cooling. If the temperature was not recorded and strictly controlled, the scientific value of the study is severely compromised, if not negated. C. Other: Other technical factors regarding electrodiagnosis were also inadequately described (ie, filter settings, laboratory normals, and other potentially confounding variables), z The issue of an arbitrary cutoff of normal versus abnormal at 3.5 ms is not supported by the literature, and the literature cited by the authors is based on data obtained prior to 1980. Thus, it is likely that many of the patients with distal latencies of greater than 3.5 ms would not meet electrodiagnostic criteria for median nerve compression. For example, if the ulnar and/or radial nerve distal sensory latency was slower than the median distal sensory latency, this would not suggest carpal tunnel syndrome. It is also probable that many patients with distal sensory latencies of less than 3.5 ms actually met electrodiagnostic criteria for median nerve compression if the midpalmar distal latency was slow, or if median distal sensory latency was significantly slower than the ulnar or radial distal sensory latency. 2 The authors also make it quite clear that they do not look at "incremental" variables; we agree with their conclusion that this may have limited the ability to detect prognostic information. Those of us who deal with electrodiagnosis and carpal tunnel syndrome are sensitisized to this issue. This reminds us of a previous similar study that was eventually retracted. 3 We appreciate that there are difficulties with interpretation of electrodiagnostic information and nerveconduction studies and are offering this input to assist in the interpretation of electrodiagnostic data. Proper collection and interpretation of electrodiagnostic data, as with all other tests, are necessary before outcome results can be counted as reliable.
References 1. Braun RM, Jackson WJ. Electrical studies as a prognostic factor in the surgical treatment of carpal tunnel syndrome. J Hand Surg 1994; 19A:893-900. 2. AAEM Quality Assurance Committee (Jablecki CK, Andary MT, So YT, Wilkins DE, Williams FH). Literature review of the usefulness of nerve conduction studies and electromyography for the evaluation of patient with carpal tunnel syndrome. Muscle Nerve 1993;16:1390-1414,. 3. Louis DS, Hankin FM. Symptomatic relief following carpal tunnel decompression with normal electroneuromyographic
931
studies (retracted by Hankin and Louis in two subsequent issues, Orthopedics 1988;11:532 and Orthopedics 1988 11:1244). Orthopedics 1987;10:434-436.
Michael T. Andary, MD Department of Physical Medicine and Rehabilitation Michigan State University B401 West Fee Hall East Lansing, MI 48824-1316 Steve Geiringer, MD Wayne State University
In Reply: Several readers have written to me regarding the type of electrical studies that were performed. It is obvious that there are many techniques that are available to electrodiagnostic physicians, just as there are many surgical techniques available to surgeons. Our article clearly states that we accepted the impression of the neurologist or electrodiagnostic specialist in declaring that a result was abnormal. We did not question the method that was used, nor did we specify that a specific electrodiagnostic protocol had to be followed. I do not tell neurologists how to perform electrodiagnostic studies, and fortunately, they do not tell me what operations to p e r f o r m - - m o s t of the time. We noted that the most simple abnormality was a delay in sensory latency. In some of our patients, this was a single finding. Others had more pronounced changes. Some neurologists are more complete in their testing than others who feel that they have made the diagnosis and that it is unreasonable to perform further tests. In any event, if our etectrodiagnostic consultants said that the result was abnormal, we accepted it at face value. Our results indicate that patients with normal, abnormal, and untested clinical states have the same prognosis. This does not negate the value of electrodiagnostic testing. It does indicate that, in our series of cases, we were able to make a clinical diagnosis that carried the same prognosis as for those patients who underwent electrodiagnostic studies. We have said no more or less about this method. We continue to recommend that all of our elective surgery candidates present for electrodiagnostic studies for the evaluation and treatment of carpal tunnel syndrome.
Richard M. Braun, MD 6699 Alvarado Road, #2302 San Diego, CA 92120
The Journal of Hand Surgery
We hope this response clarifies our use of these particular x-rays and addresses the injustice that Dr. Clark believed that we were showing to a surgical technique also feel is appropriate when performed properly.
William B. Kleinman, AID Jeffrey A. Greenberg, AID Indiana Hand Center 8501 Harcourt Road P.O. Box 80434 Indianapolis, IN 46280-0434 Electrical Studies as a Prognostic Factor in Carpal Tunnel Syndrome To the Editor: We read with interest the study by Drs. Braun and Jackson regarding electrical studies as a prognostic factor in the carpal tunnel syndrome. 1 Their conclusions suggest that electrodiagnostic tests did not provide significant data for prediction of functional recovery or re-employment after carpal tunnel release. We believe that there are several aspects about this study that warrant further discussion: 1. Their criteria for "electrical abnormality" was "usually sensory latency over 3.5 ms." This definition of abnormality is not supported in the literatm'e, is outdated, and should not be considered the standard of practice. 2 More sensitive and specific techniques have been well established and would almost surely change interpretation of a significant number of subjects. Better criteria for abnormality would include: A. Comparison of median distal sensory latency to ulnar sensory distal latency. B. Comparison of median distal sensory latency to radial sensory distal sensory latency. C. Comparison of median midpalmar latency to ulnar midpalmar latency. D. Absolute median midpalmar latency.2 2. Descriptions of the electrodiagnostic techniques used are inadequate to make interpretations of distal latencies meaningful. The following information is missing:
A. Distance: The distance between stimulation and recording electrodes is a critical factor; a difference as small as 1 cm could change distal latency as much as 0.4 ms or 10%. 2
The Journal of Hand Surgery / Vol. 21A No. 5 September 1996
B. Temperature: Temperature of the hand greatly affects the distal sensory latency, with a difference of up to 0.2 ms in distal latency for every Celsius degree of cooling. If the temperature was not recorded and strictly controlled, the scientific value of the study is severely compromised, if not negated. C. Other: Other technical factors regarding electrodiagnosis were also inadequately described (ie, filter settings, laboratory normals, and other potentially confounding variables), z The issue of an arbitrary cutoff of normal versus abnormal at 3.5 ms is not supported by the literature, and the literature cited by the authors is based on data obtained prior to 1980. Thus, it is likely that many of the patients with distal latencies of greater than 3.5 ms would not meet electrodiagnostic criteria for median nerve compression. For example, if the ulnar and/or radial nerve distal sensory latency was slower than the median distal sensory latency, this would not suggest carpal tunnel syndrome. It is also probable that many patients with distal sensory latencies of less than 3.5 ms actually met electrodiagnostic criteria for median nerve compression if the midpalmar distal latency was slow, or if median distal sensory latency was significantly slower than the ulnar or radial distal sensory latency. 2 The authors also make it quite clear that they do not look at "incremental" variables; we agree with their conclusion that this may have limited the ability to detect prognostic information. Those of us who deal with electrodiagnosis and carpal tunnel syndrome are sensitisized to this issue. This reminds us of a previous similar study that was eventually retracted. 3 We appreciate that there are difficulties with interpretation of electrodiagnostic information and nerveconduction studies and are offering this input to assist in the interpretation of electrodiagnostic data. Proper collection and interpretation of electrodiagnostic data, as with all other tests, are necessary before outcome results can be counted as reliable.
References 1. Braun RM, Jackson WJ. Electrical studies as a prognostic factor in the surgical treatment of carpal tunnel syndrome. J Hand Surg 1994; 19A:893-900. 2. AAEM Quality Assurance Committee (Jablecki CK, Andary MT, So YT, Wilkins DE, Williams FH). Literature review of the usefulness of nerve conduction studies and electromyography for the evaluation of patient with carpal tunnel syndrome. Muscle Nerve 1993;16:1390-1414,. 3. Louis DS, Hankin FM. Symptomatic relief following carpal tunnel decompression with normal electroneuromyographic
931
studies (retracted by Hankin and Louis in two subsequent issues, Orthopedics 1988;11:532 and Orthopedics 1988 11:1244). Orthopedics 1987;10:434-436.
Michael T. Andary, MD Department of Physical Medicine and Rehabilitation Michigan State University B401 West Fee Hall East Lansing, MI 48824-1316 Steve Geiringer, MD Wayne State University
In Reply: Several readers have written to me regarding the type of electrical studies that were performed. It is obvious that there are many techniques that are available to electrodiagnostic physicians, just as there are many surgical techniques available to surgeons. Our article clearly states that we accepted the impression of the neurologist or electrodiagnostic specialist in declaring that a result was abnormal. We did not question the method that was used, nor did we specify that a specific electrodiagnostic protocol had to be followed. I do not tell neurologists how to perform electrodiagnostic studies, and fortunately, they do not tell me what operations to p e r f o r m - - m o s t of the time. We noted that the most simple abnormality was a delay in sensory latency. In some of our patients, this was a single finding. Others had more pronounced changes. Some neurologists are more complete in their testing than others who feel that they have made the diagnosis and that it is unreasonable to perform further tests. In any event, if our etectrodiagnostic consultants said that the result was abnormal, we accepted it at face value. Our results indicate that patients with normal, abnormal, and untested clinical states have the same prognosis. This does not negate the value of electrodiagnostic testing. It does indicate that, in our series of cases, we were able to make a clinical diagnosis that carried the same prognosis as for those patients who underwent electrodiagnostic studies. We have said no more or less about this method. We continue to recommend that all of our elective surgery candidates present for electrodiagnostic studies for the evaluation and treatment of carpal tunnel syndrome.
Richard M. Braun, MD 6699 Alvarado Road, #2302 San Diego, CA 92120