Lazarević’s straight leg raising test
Dr. Lazar K. Lazarević was the founder of the Serbian neurology. He was the first Serbian neurologist who was perceived as an equal to the leading European and world scientists in this field.
The greatest contribution of L. Lazarević to medical science is his description of the straight leg raising test, used to diagnose lumbar root compression. An analysis of the historical events shows that he was actually the first to publish the description of this test, and to identify the stretching of the sciatic nerve as the cause of the pain. Although he was the first to describe this sign, he never claimed priority. All the medical students and practicing neurologists throughout the world remember Charles Lasègue (1816-1883) for straight-leg raising test, although Lasègue never published a description of this sign (1-12).
At the meetings of the Serbian Medical Association, Lazarević regularly submitted reports on his own observations and medical cases from his practice. The substance of Lazarević’s description of the straight leg raising test had been presented in a talk given at the 3rd meeting of the Serbian Medical Association in February 1880 to outstanding Serbian physicians. They decided to print this paper in the Serbian Archives of Medicine, journal of the Serbian Medical Association. The paper of Lazarević entitled “Ischiac postica Cotunnii- One contribution to its differential diagnosis” was published in Serbian language (in Cyrillic alphabet) in the Serbian Archives of Medicine in 1880 (13). The entire article is based on precise clinical observation and a thorough neurological examination of six patients from Lazarević’s medical practice. After four years, the paper was translated to German language and republished in Vienna in 1884 in Allgemeine Wiener medizinische Zeitung (14).*
*The full version of Lazarević’s article in German is available in the section Gallery: documents and publications.
At the beginning of his article “Ischiac postica Cotunnii- One contribution to its differential diagnosis” Lazarević writes: “At that point I noticed a certain symptom, which is in my opinion, of pathognomonic nature, and which has not been mentioned so far, although I was searching for it in every place possible, in case someone had noticed it and described it before me. I realized through my observations that this symptom is accompanying sciatica since it is usually possible to make the correct differential diagnosis on the basis of such a symptom (in each of my six cases). Therefore, the importance of this symptom is significant because there were no other symptoms revealed which could differentiate this disease at every stage and every time from muscular rheumatism, joint diseases, etc”. He also underlines that “little attention has been paid to a very characteristic walk of patients with sciatica. This walk is associated with the same causes as our symptom…” (13, 15)
Within the elaboration of previously described symptoms Lazarević points out: “Other symptoms are not reliable or appear only when the diagnosis from the disease course was already made… They can only confirm a diagnosis made on the basis of the disease course. So far, in my opinion, the diagnosis was only made in such a way… If the diagnosis wasn’t the most scientific and the most crucial component of the doctor’s procedure at the bedside of the patient, and if it was irrelevant whether it was made prior to or after the therapy, I wouldn’t give so much importance to the symptom which I intend to describe”.
After that, Lazarević relies on astute anatomical data and gives the nerve anatomy, nerve path and nerve branches. He points out: “This sign is correlated to the anatomical structure of the leg. Topography of the sciatic nerve is, in my opinion, explaining it entirely” (13).
- The stretching of the sciatic nerve produces the sciatic pain
Following the anatomic description of the sciatic nerve, Lazarević correctly explains that mechanism of pain occurrence during test performance is the stretching of the sciatic nerve and its roots. He states: “By putting pressure on the sciatic nerve (ischiadicus) we are mechanically stimulating other surrounding regions. The pain occurred in such a way that it could come from any other affected part. We have no way to press and squeeze the nerve, but we can stretch it. According to aforementioned anatomic correlations, the nerve will be most stretched when the knee is extended, the foot is dorsiflexed, and the entire leg is flexed on the abdomen”. He also states that some of the branches of the sciatic nerve will be “stretched like tamburitza strings… as soon as the leg is brought in the aforementioned position… the pain will occur, i.e. it will increase” (13, 15).
Dr. Lazarević in his paper of 1880 espoused the current explanation: that the sign is due to to stretching of the sciatic nerve and its roots. Unfortunately, this view is attributed to Lucien de Beurmann who wrote on the subject in 1884, four years after Lazarević (16). De Beurmann just bolstered a theory of Lazarević with cadaveric studies. He found that the sciatic nerve was significantly more stretched if the knee was extended rather than flexed.
- The maneuver that relaxes the sciatic nerve reduces the sciatic pain
Then, Lazarević explains maneuver that relaxes the nerve by shortening its course: “But thanks to the knowledge of anatomy we can perform other movements to stretch the muscles without nerves to a maximum or the movements which involve the motion of the joint without stretching the nerves. If we flex the knee, and subsequently flex the thigh, the nerve won’t be stretched. In this case, if we have pure sciatica, the pain will not occur or exacerbate in the sciatic nerve distribution… In this way, it is explained what we have seen in all six cases, i.e. that patients with sciatica avoid all movements which require the nerve stretching… Therefore, when patients on bed rest want to rise (to drink or eat, for example) they flex the knee of the affected leg…” (13, 15).
Today, leading articles and textbooks in clinical neuroscience have the same explanation of the mechanism that relaxes the nerve: “Flexion of the hip with the knee flexed relaxes the sciatic nerve and does not tug on the roots. Therefore, this maneuver relaxes the nerve and generally reduces the sciatic pain. When the straight-leg-raising test has produced the pain, it should be relieved abruptly by flexing the knee while the hip remains in flexion. This relaxes the stretch on the nerve” (1).
- Lazarević’s test/sign
Dr. Lazarević goes on to describe several maneuvers used to demonstrate his sign.
“In conclusion, we will report the examination of the patient suspected of sciatica.
If the patient is in standing position, he will be asked to flex his leg on the abdomen, maintaining full knee extension.
Or, the standing patient is asked to flex trunk forward, as much as possible, maintaining full knee extension.
If the patient is lying supine on the bed, we passively try to bring him in sitting position, holding his knees to prevent their flexing.
Or, if the patient is lying supine on the bed, with one hand we hold the knee of the affected leg in an extended position. Taking the heel with our other hand, we flex the leg on the abdomen” (13, 15).
Writing about one of his six patients, Lazarević repeats the fourth maneuver, giving a more detailed explanation. He even reports the recorded angle between the extended leg and abdomen when the pain occurs (indicating that test is positive): “The patient is placed on the bed in the supine position. We hold his knee with one hand, and taking the heel with our other hand, we try to flex the leg on the abdomen, but this evokes sharp pain accompanied by avoidance reaction in patient… When the patient feels the best (after 6-months treatment with electrical therapy), he can walk, dance or ride for hours. But, if we try to flex the leg on the abdomen with the knee extended, the pain occurs, and the angle between the extended leg and abdomen (because of pain) could not be less than 135˚. By flexing the knee, however, the patient is able to reach the chin with the knee, without any pain” (13, 15).
Subsequently, Lazarević explains another maneuver which is not different from Kernig’s sign, used primarily in the diagnosis of meningitis. He states: “All movements which are not stretching the nerve could be performed easier. For example, patients in the position with their knee flexed can touch abdominal muscles with their quadriceps femoris muscle, sometimes without any pain and always without significantly increased pain. But, if we try to extend their knee when the leg is in such position, patients immediately report pain and they are reflexively avoiding aforementioned movement”. Describing the case of another patient, Lazarević repeats this maneuver: “He endures when the knee is gradually (passively) brought into flexion, flexing simultaneously the thigh on the abdomen. If we now try to extend the leg at the knee, the patient reports intense pain and abruptly flexes the knee” (13, 15).
In these parts, Lazarević presented several maneuvers, which are now used as labels for various diagnostic categories. Unfortunately, maneuvers described by Lazarević are known by other names. The fourth maneuver, the straight leg raising test, is known as Lasègue sign/test/maneuver, whereas the second maneuver, the test of simple forward bending, is known as Thomayer’s test (15). One of Lazarević’s maneuver is equivalent to Kernig’s sign. Vladimir Kernig, a Russian physician published the description of the sign in 1882 in Russian journal, and he did it again in German in 1884 (17). Today, Kernig’s test is usually performed by attempting to extend the flexed knee of the supine patient after the thigh has been flexed on the pelvis. The procedure for demonstrating Kernig’s or Lazarević’s maneuver is identical, regardless of the pathological conditions responsible for them- e.g. meningitis or compression of the roots which form the sciatic nerve. Writing on this topic, Jane Orient emphasized (12): “Lasègue wrote a classic article on sciatica in 1864 without mentioning limitation of straight-leg-raising… The Kernig-Lasègue sign was first described in 1880 by a Yugoslav physician Lazarevic… In 1882, Kernig published the same test in a Russian journal… Up until this point, it is not clear whether any of the authors knew of each other’s work or whether they realized that they were all descrbing essentially the same sign”.
- The control test
Then, Lazarević describes the control test to make a differential diagnosis between sciatica and hip disorder. He underlines that the control test has to be negative in patients with sciatica: “If during these maneuvers the patient begins to feel the pain or if the persisting pain exacerbates, then, in order to rule out muscle or joint disorder, we flex the leg at the knee, and subsequently, in the flexed hip joint we assess passive motions. Now, if the pain is completely absent, or if the persistent pain is not exacerbated, we should, without any further examination, diagnose ischias postica” (13, 15).
Unfortunately, some authors describe this control test by Lazarević as Lasègue’s Differential test, although Lasègue never published a description of the control test. In addition, Lazarević’s control test is equivalent to Patrick’s test (passive flexion, abduction, external rotation and extension in the hip joint), which elicits pain in hip disease, but not in sciatica.
At the end of his paper Lazarević concludes: “I made the diagnosis of sciatica, in this way, immediately upon the examination and I wasn’t mistaken. Similarly, once or twice before I excluded sciatica applying the same principle and I was right. What I saw on the one hand and what I thought looking at the anatomical scheme, on the other hand encouraged me to report the whole issue to my colleagues, wishing that they pay attention to it, which it is completely worth of, in my opinion”.
- Lasègue and Forst
It is a strange irony that test to which his name is attached was not described by Charles Lasègue. His reference volume, “Consideration on Sciatica”, published in 1864, is frequently quoted as the first description of the test and the sign of Lasègue, although its description is not mentioned in this paper (18). As Robert Wartenberg pointed out: “It is apparent that the authors of leading textbooks of neurology which cited this article as the source of the Lasègue sign had never read it” (8, 9). In this paper on sciatica, Lasègue analyzed then-current theories of sciatica and his own clinical observations. He divided the pain of sciatica into two broad varieties, benign and a serious form. In this article Lasègue mentioned “traction” of the nerve, but he did not describe the sign anywhere.
Remarkably, Lasègue stated in his paper of 1864 that any sort of passive flexion or extension of the affected leg is possible without increase of pain. This incorrect observation from Lasègue is quite opposite to the mechanism of the straight-leg raising test, to which his name is attached. In the straight-leg raising test, the increase in sciatic pain is caused by flexing of the extended leg on the abdomen. The steps are unknown by which Lasègue came to modify his incorrect views on the features of sciatic pain, published in his paper of 1864.
In 1881, one year after the full and clear description of the test given by Lazar K. Lazarević, the straight-leg raising test was described by Lasègue’s student J.J. Forst (19). According to a biographical note of Pierre Astruc, Lasègue conceived the straight-leg raising test when he had to answer the question posed by Inspector-General of how to discern between patients with real sciatic pain and malingers (10). When he watched his son-in-law tuning his violin, it occurred to him that the fibers of the sciatic nerve, stretched by leg raising, are extended in the same way as the strings are stretched over the bridge of the violin. However, in Forst‘s thesis of 1881, both Lasègue and Forst wrongly concluded that pain produced by passive elevation of the knee-extended leg originates from pressure of the posterior thigh muscles upon the sciatic nerve.
Forst wrote: “We suppose that the sharp pain experienced by the patient can be ascribed to the compression of the nerve by the muscle bulk: this is also opinion of our teacher professor Lasègue” (19). Forst’s explanation is apparently not in agreement with the anecdote of the violin (2). If this biographical note is true, it is not clear when and why Lasègue modified his first views on the features of sciatic pain and wrongly concluded in Forst’s thesis that pain is due to sciatic compression by the muscle mass (12).
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