Knee Surg, Sports Traumatol, Arthrosc (2001) 9 : 211–216
KNEE
DOI 10.1007/s001670100196
Alexander L. Boerboom At L. Hof Jan P.K. Halbertsma Jos J.A.M. van Raaij Willem Schenk Ron L. Diercks Jim R. van Horn
Received: 17 July 2000 Accepted: 28 December 2000 Published online: 1 March 2001 © Springer-Verlag 2001 A. L. Boerboom (✉) · W. Schenk · R. L. Diercks · J.R. van Horn Department of Orthopedics, University Hospital Groningen, P.O. Box 30001, 9700 RB Groningen, The Netherlands e-mail:
[email protected], Tel.: +31-50-3612802, Fax: +31-50-3611737 A.L. Hof · J.P.K. Halbertsma Department of Rehabilitation/Laboratory of Human Movement Analysis, University Hospital Groningen, P.O. Box 30001, 9700 RB Groningen, The Netherlands J.J.A.M. van Raaij Department of Orthopedics, Martini Hospital, P.O. Box 30033, 9700 RM Groningen, The Netherlands
Atypical hamstrings electromyographic activity as a compensatory mechanism in anterior cruciate ligament deficiency
Abstract Anterior cruciate ligament (ACL) deficiency may cause functional instability of the knee (noncopers), while other patients compensate and perform at the same level as before injury (copers). This pilot study investigated whether there is a compensatory electromyographic (EMG) activity of the hamstrings in copers, noncopers and control patients. Ten patients with an ACL deficiency were equally divided into two groups of copers and noncopers. All patients underwent gait analysis with EMG of six muscles around the knee. Ten healthy young men formed the control group. In contrast to noncopers, copers showed an atypical semitendinosus activity during stance phase; the corresponding trend was found in biceps femoris activity. There was no
Introduction Persistent functional instability after conservative treatment of an anterior cruciate ligament (ACL) rupture can be an indication for a reconstruction. There are no predictive values which can help in deciding whether and when to stabilize an ACL-deficient knee [22, 23]. Only after a period of conservative treatment it becomes clear whether a patient is improving and is able to perform actively in sports (“coper”) or cannot compensate for the ACL deficiency (“noncoper”). In some cases it is more difficult to ascertain whether a patient is a coper or a noncoper, as he accepts his situation by performing on a much lower level of sports and activities (“adapter”) [10, 27]. If
difference between copers and controls in knee extension during stance phase. The noncopers had less knee extension. Atypical hamstring muscle activity may thus be a compensatory mechanism by which copers enable themselves to perform on a normal level. Keywords Gait analysis · Anterior cruciate ligament deficiency · Electromyography · Hamstrings · Compensatory mechanism
the decision on operation is postponed, the patient is at risk of reinjury with additional damage, which may worsen the final prognosis. Gait analysis and electromyography (EMG) are nowadays well accepted as quantitative methods in research on the functional outcome of knee arthroplasty. These techniques can also be used in measuring the functioning of an ACL-deficient patient before or after treatment [3]. The absence of the ACL permits anterior subluxation of the tibia, which can be counteracted by the posteriorly located hamstring muscles. Normally there is a fixed pattern of muscle activity of the quadriceps and hamstrings [8, 9]. Nonstandard activity of the hamstrings during the gait cycle does not have to be abnormal or pathological but may be a result of adaptation in cases of ACL deficiency. Theo-
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retically this should also be possible for other posterior muscles acting across the knee, i.e., the gastrocnemius. The goal of this pilot study was to determine the EMG pattern of muscles around the knee in relation to the functional outcome of the conservative treatment after ACL rupture. We present a quantitative parameter that can be used to differentiate copers from noncopers.
Materials and methods Ten patients were selected for this study. All had been treated conservatively after an ACL rupture, which was confirmed by physical examination and arthroscopy. The conservative treatment consisted of functional training and muscle exercises. Five patients were copers, acting at the same level of sports and daily activities (level I of the International Knee Documentation Committee, IKDC, score [11, 12, 17, 19]) as before the injury. The group of noncopers consisted of five patients with functional instability; these patients acted at a lower level (four patients at level III and one patient at level II) while they were all on level I before injury. The copers consisted of five men and the noncopers of three men and two women. All had a unilateral ACL deficiency with a normal contralateral knee. From all patients the IKDC grades of the four major headings were determined: subjective assessment, symptoms, range of motion, and stability. Gait was analyzed and EMG of the injured leg was recorded simultaneously with angles of both knees using Penny and Giles goniometers. Standing with straight legs was the position in which 0° of flexion was determined. Surface EMGs were recorded by KLab SPA-10 preamplifiers from the vastus medialis and lateralis, biceps femoris, semitendinosus, gastrocnemius medialis and lateralis muscles. Electrode placements were in accordance with the recommendations of Perotto [24]. Surface EMGs were band-pass filtered 20 Hz–10 kHz, rectified, and smoothed with a 25 Hz third order Butterworth filter. Smoothed rectified EMGs were A/D converted at 100 Hz. The sampled data were linearly interpolated to 100 points per stride, triggered by heel contact of the leg of interest. The recorded steps were screened to exclude those with obvious artifacts or incorrect foot contacts. Average walking speed was assessed from the interval between passing two light beams at both ends of the walkway, 7 m apart. The following activities were carried out: walking at normal, slower, and faster than normal speed. The results of the two groups were compared with a control group of ten healthy young men without a history of knee injury. Their median age was 22 years (range 18–24). These persons performed the same trials with identical EMG measurements. Only their right knee served as control for the injured knee of the patients. Statistical analysis was performed using the Wilcoxon twosample test; P
