A prospective evaluation of a test for lateral meniscus tears

Transcription

1 Knee Surg, Sports Traumatol, Arthroscopy (1996) 4 : Springer-Verlag 1996 P. P. Mariani E. Adriani G. Maresca C. G. Mazzola A prospective evaluation of a test for lateral meniscus tears Received: 8 December 1995 Accepted: 12 March P. P. Mariani (~) 9 G. Maresca 1 ~ Orthopaedic Clinic University "La Sapienza", Piazzale Aldo Moro, 5, Rome, Italy E. Adriani Ospedale Sandro Petrini, USL Roma B, Via dei Monti Tiburtini, Rome, Italy C. G. Mazzola Ospedale Civile di Lavagna, Via Don Bobbio, 25 Lavagna (Genova), Italy Abstract A test for diagnosing lesions to the lateral meniscus is described. Due to our inability to find its description in the literature we called it 'dynamic test'. The accuracy of this test was assessed in 421 knees. The test was compared against arthroscopic findings in all cases. Inter-rater reliability was also estimated among three observers, who were shown to have a K coefficient ranging from 0.61 to In a series of healthy subjects, the test was positive in eight normal knees (9.4%), but none of these false-posi- tives was unanimously identified by more than one rater. This manipulative test was very accurate: sensitivity 85%, specificity 90.3%, positive predictive value 73.2%, negative predictive value 95% prevalence 23.7% and accuracy 89%. Thus, the test seems to be a tool that can improve the diagnostic accuracy of meniscal lesions. An important feature of this test is that it can be performed in patients with acute injuries. Key words Lateral meniscus test 9 Diagnostic knee Introduction The clinical diagnosis of meniscal tears may be difficult even for experienced surgeons to make. Several tests have been described for the diagnosis of meniscal disorders, and their accuracy and reliability have been assessed by many authors [1, 3-7, 8, 11, 12] with varying results. The most common test, the McMurray test, is reported to have a sensitivity ranging from 16% [7] to 62% [11] and a specificity from 41.7% [11] to 98% [7]. Most of the diagnostic errors in these studies were associated with the lateral meniscus. For several years we have diagnosed lesions to the lateral meniscus using a tool we call the 'dynamic test'. Due to our inability to find any description of this manoeuvre in the literature we will go on calling it this way in this study. The purpose of this study was to determine prospectively the sensitivity and specificity of this test, using arthroscopic findings as the gold standard. A preliminary study was carried out to assess inter-rater reliability and the test's positivity in healthy controls. Materials and methods We carried out two preliminary studies to assess the agreement between the examiners (interobserver reliability) and the frequency of a positive dynamic test in healthy controls. The first of the preliminary studies was carried out over a period of 3 months, during which three examiners (A: Ezio Adriani, B: Gaetano Maresca, and C: Claudio Guido Mazzola) concurrently but individually examined 54 patients scheduled for arthroscopic surgery for various disorders. The data obtained from the examiners were used to estimate the interobserver reliability by the Kappa coefficient [6, 13]. The Kappa coefficient is defined according to the equation (Table 1): K = observed proportion of agreement - expected proportion in agreement 1 - expected proportion in agreement The observed proportion of agreement is defined as the sum of the cases in which two raters are in agreement as to the positivity or negativity of the test divided by the total number of cases (A + D A + D. - - m the example given in Table 1). The expected proportion of agreement is based on the expected values calculated in the same way as those used in a chi-square test.

2 23 Table 1 Example of the data table for comparing two observers using the K test (the expected values are shown in brackets; A and D = no. of cases with agreement between two observers; B and C = no. of cases without agreement between two observers) Observer X Observer Y A B E [E*G/] [ E* H/] (A + B ) C D F [ F*G /] [ F* H/] ( C + D ) G H (A+C) (B+D) In Table 1 the expected values are shown in brackets. Thus, substituting the formula we have: of the visit. In this manner, we examined 85 'normal' knees; 15 knees were excluded from the series because a previous trauma was identified upon examination. After this screening, we set up the protocol for selecting the patients to submit to examination and surgery. We adopted the following exclusion criteria: (1) previous lateral meniscectomy; (2) patients with synovial disease; (3) patients with acute capsuligamentous injury or chronic posterolateral instability. Using the criteria, we enrolled 405 consecutive patients awaiting elective arthroscopic surgery. The examiner was blind to the patient's preoperative diagnosis. The data were archived in a database and subsequently used to evaluate the sensitivity, specificity, and the positive and negative predictive values, according to the following formulas (Table 2). Prevalence : ( + False negative ) ( ) (A+C) K= + Sensitivity : o. meniscal tears ( + False negative ) (A) (A+C) The Kappa coefficient can be negative or positive; its value is 0 when agreement occurs only at the chance-expected level, and 1.0 when agreement is perfect. In our preliminary study the Kappa coefficient was evaluated by comparing all three observers. The second preliminary study included the examination of 50 young subjects (normal controls; mean age 25 years, range years) who came to our attention for a problem related to the upper extremities, who had no previous history of surgery or trauma to the knees, and who in any case had no knee symptoms at the time Specificity : o. healthy meniscal ( + False positive ) (D) Table 2 The typical 2 x 2 contingency table Dynamic Torn Healthy test meniscus meniscus A B s False positives C D False negatives s A+C B+D o. meniscal tears o. healthy menisci [100 x (A)/(A+C)] [100 x (D)/(B + D)] [100 x (A)/(A+B)] Sensitivity Specificity PVP 85% 90.3% 73.2% [100 x (A + D)/] Accuracy 89% A+B o. positives 116 C+D o. negatives [100 x (D)/(C + D)] PV 95%

3 24 predictive value : PVP predictive value : PV Accuracy: [ o. positive ] ( + False positive ) (a) (A+B) [ o. negative ] ( + False negative) (D) (C+D) o. true ( + ) (A+D) () In all, 405 consecutive patients underwent arthroscopic examination by the senior author who was blinded to the test results. Bilateral arthroscopy was performed in 16 patients, giving a total of 421 knees examined. The patients, 243 men and 162 women, ranged in age from 14 to 77 years (mean 34 years). The right side was affected in 246 cases (58.43%). The dynamic test The patient is examined in the supine position, the leg positioned with the hip abducted 60 ~, flexed and rotated externally by about l# Fig. 1 The dynamic test 45 ~, the knee bent about 90 ~, and the lateral border of the foot resting on the examination bed. In this position the femur is rotated externally, whereas the tibia is rotated internally (Fig. 1). The knee is in a varus position due to the effects of gravity. As examiner's index finger palpates the lateral joint line, tenderness may be elicited in this position, even though this is not pathognomonic for the test. By keeping pressure on the outer rim, the examiner progressively adducts the hip, while keeping the degree of flexion of the knee the same. During the manoeuvre, the knee varus is reduced and at the same time the femur is rotated internally. The meniscus is thus squeezed between the femur and the tibia, and pushed outwardly against the pressure of the examining finger. The test is considered positive if (1) any pain that may be present due to the pressure of the finger increases during the manouvre or (2) a sharp pain is felt when the final position is reached. Results The interobserver reliability using the dynamic test on 54 patient is reported in Table 3, which compares the contingency tables of examiners A, B and C. The K coefficient was calculated from the values in the table; in summary, it provided the following indications: Comparison between A and B (Table 3 a): K = (A + D/) - [(E*G/) / 1 - [(E*G/) K = ( /54) - [(15"17/54) + (39*37/54)/54] / 1 - [(15"17/54) + (39*37/54)/54] K = ( /54) / 1 - ( /54) K = ( ) / (1-0.58); K = 0.3/0.42 [K = 0.71] Comparison between A and C (Table 3 b): K = (A + D/) -/(E'G/) / 1 - [E*G/) K -- ( /54) - [(15"16/54) + (39*36/54)/54] / 1 - [(15"16/54) + (39*36/54)/54] K = ( /54) / 1 - ( /54) K = ( ) / (1-0.59); K = 0.35/0.41 [K--0.S5] Comparison between B and C (Table 3 c): K = (A + D/) - [(E*G/) / 1 - [(E*G/) K = ( /54) - [(17"16/54) + (37*38/54] / 1 - [(17"16/54) + (37*38/54)/54] K = ( /54) / 1 - ( /54) K = ( ) / (1-0.57); K = 0.26/0.43 [K = 0.61] The second preliminary study examined 85 healthy knees; only 8 knees gave a positive test, but in no case did all three raters agree that the test was positive. A test was rated as positive by examiners A and B in one case and examiners A and C in two cases; tests were positive only for rater A in one case, only for rater B in two cases and only for rater C in an additional two cases.

4 25 Table 3a Comparison between observers A and B with the K test Observer A Observer B [4.72] [10.28] (A + B) [12.28] [26.72] (C + D) Table 3 b Comparison between observers A and C with the K test ObsetwerA Observer C [4.44] [10.55] (A + B) [11.55] [27.44] (C + D) Table 3 e Comparison between observers B and C with the K test Observer B Observer C [5.03] [11.96] (A + B) [10.96] [26.03] (C + D) In 421 subjects submitted to arthroscopy, a lateral meniscal tear was found in 100 patients. Fifty-eight percent of these cases had associated an anterior cruciate ligament tear. The type of lesions included longitudinal tears (24%), radial tears (36%), horizontal tears (13%) and complex (horizontal and/or longitudinal) tears (27%). In four patients a cyst of the lateral meniscus was present. Examination of 421 knees compared in terms of the arthroscopic findings gave the results shown in the 2 2 contingency table (Table 2). We had 85 true-positives and 31 false-positives, 290 true-negatives and 15 false-negatives. Table 2 demonstrates the clinical accuracy of the dynamic test in a population about to undergo operation with 85% sensitivity and 90.3% specificity. The positive pre- dictive value was 73.2%, and the negative predictive value was 95%, with a prevalence of 23.7% and accuracy of 89%. Discussion Occasionally, the patient's description of his (or her) symptoms suffices to make a diagnosis of a meniscal lesion, but often only a very thorough evaluation of all symptoms and tests allows us to solve the diagnostic problem. As stated by Barry et al. [2], it is often the combination of symptoms and clinical signs that leads to the correct diagnosis. A history of locking is of great diagnostic significance for a bucket-handle tear of the meniscus with displacement of the fragment. But this classical presentation of locking is very rarely produced by the first injury, and other causes, such as muscle contractures or joint effusion, can produce the same limitation of motion. A great number of special diagnostic signs have been described for the diagnosis of a meniscal lesion. Most depend on the presence of a point of tenderness in the articular joint line and/or the presence of an audible 'snap' or 'click'. Flexion and extension of the knee with internal or external rotation displaces the fragment of the meniscus and can enhance these symptoms. Tenderness localized at the joint line is one of the most valuable diagnostic signs [1, 2, 9-11], but it is positive in only 60%-80% of cases [12]. The Apley test, one of the best-known and reliable signs, is positive in only 40%-60% of meniscal lesions [1, 2, 9-11]. Anderson and Lipscomb [1] evaluated the sensitivity and specificity of the McMurray test and found it positive in only 68% of the cases. Most diagnostic errors were associated with lateral meniscus lesions [1, 4, 5, 7]. Evans et al. [7] have recently shown a 50% sensitivity of the McMurray test for the lateral meniscus, with a very low positive predictive value (29%). Anatomical differences are one of the reasons behind the greater difficulty in diagnosing lesions of the lateral meniscus. In fact, as is widely known, the lateral meniscus, unlike the medial, has no firm tibial or femoral peripheral attachments and is relatively more mobile. The menisci are displaced differently by knee motion, and the lateral meniscus has a greater displacement than the medial. This observation accounts for its lower risk of tear. When the different manipulative tests are performed, knee motion displaces the menisci and produces abnormal traction stresses on the capsule and synovium, accounting for pain if there is a mobile fragment. Therefore, some diagnostic tests may be less accurate for lateral than medial meniscus tears. For example, with the knee rotated internally, a thud on the lateral joint line elicited by the Mc- Murray test is heard only seldomly and is not significant. The only specific test for a lateral meniscus tear described in the literature is Cabot's sign [3, 11], a well-

5 26 known sign in European countries. Pain is elicited during extension of the affected knee with the leg crossed over the contralateral limb; while palpating the lateral joint line with the thumb, the knee is extended against the resistance of the examiner's hand. In positive cases, pain or a sensation of painful resistance is elicited from the patient. The accuracy and reliability of Cabot's test have not yet been rated or reported. A disadvantage of this test is that it cannot be performed in acute cases due to the flexion in which the knee is held. In the dynamic test, the knee is always held at the same degree of flexion, and the pain is elicited only by means of varus stress and internal rotation of the femur. During the manoeuvre, a compressive force is transmitted through the lateral meniscus that is trapped between the femur and the tibia with tension on its capsular attachment. Since the knee does not need to be flexed or extended, the test may also be performed in acute cases or in the presence of a locked joint. The results of our evaluation of this test were highly encouraging: sensitivity 85%, specificity 90.3%, positive predictive value 73.2%, negative predictive value 95%, prevalence 23.7% and accuracy 89%. Moreover, test reliability indicates a high level of agreement among the different examiners (K value ranging from and 0.85). Indeed, our diagnoses of lateral meniscus lesions are better than those reported in the literature. One of the reasons may stern from the different exclusion criteria adopted in this study. In fact, we excluded all cases with recent capsuloligamentous injury or history of inflammatory synovial disease, conditions that may be a source of spontaneous or elicited pain at the synovial meniscal attachment. It is generally accepted that any meniscal test may be considered pathognomonic for a specific tear, and all tests have their diagnostic limitations. It is very important to perform several of the multitude of tests that are available before passing judgement as to a meniscal tear. The dynamic test, with its reliability; may become an adjunct diagnostic tool that used together with other well-known tests may help improve our diagnostic accuracy for lateral meniscus disorders. References 1. Anderson AF, Lipscomb AB (1986) Clinical diagnosis of meniscal tears. Description of a new manipulative test. Am J Sports Med 14: Barry OCD, McManus F, McCauley P (1983) Clinical assessment of suspected meniscal tears. Ir J Med Sci 152: Cabot JR (1954) Biomecanica de la rodilla. Rev Esp Reumatisma 8 : Corea JR, Moussa M, A10thman A (1994) McMurray's test tested. Knee Surg Sports Traumatol Arthroscopy 2 : Daniel D, Daniels E, Aronson D (1982) The diagnosis of meniscus pathology. Clin Orthop 163 : De Lee JC, Drez D (1994) Orthopaedic sports medicine. Principles and practice, vol 1, chapter 5. Saunders, Philadelphia 7.Evans PJ, Bell D, Frank C (1993) Prospective evaluation of the McMurray test. Am J Sports Med 21 : Fowler PJ, Lubliner JA (1989) The predictive value of five clinical signs in the evaluation of meniscal pathology. Arthroscopy 5 : Hede A, Hejgaard (1981) Menisklaseionens diagnostik. Ugeskrlaeger 143 : Medler RC, Mandiberg JJ, Lyne DE (1980) Meniscectomies in children. Am J Sports Med 8 : oble J, Erat K (1980) In defence of the meniscus. J Bone Joint Surg [Br] 62: Strobel M, Stedtfeld HW (1990) Diagnostic evaluation of the knee, chapter 4. Springer, Berlin Heidelberg ew York 13.Thompson WD, Walter SD (1988) A reappraisal of the Kappa coefficient. J Clin Epidemiol 41: