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lnjuy Vol. 27, No. 3. pp. 195-197, 1996

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A comparison of isokinetics and muscle strength ratios following intra-articular and extra-articular reconstructions of the anterior cruciate ligament

0.0. A, Oni and E. Crowder The Glenfield Hospital, Leicester, and BUPA Hospital, Leicester, UK

A prospective, randomized clinical trial was conducted to compare an intru-articular with an extra-articular reconstruction of the anterior cruciate ligament. Isokinetic muscle testing was carried out 6 months to 2 years following operation using the Biodex isokinetic dynamometer. The extra-articular procedure resulted in a lower deficit for the peak quadriceps and hamstring torques and the range of motion. Copyright 0 1996 Elsevier Science Ltd. All rights reserved.

Injury, Vol. 27, No. 3, 195-197, 1996

Introduction The anterior cruciate ligament (ACL) prevents the anterior translation of the tibia on the femur as well as limiting tibia1 rotation1’2. Consequently, its absence results in antero- posterior instability and in the ‘pivot shift’ phenomenon3. These symptoms may be abolished by an intra-articular replacement of the ACL using a graft or by providing a checkrein/buttress extra-articularly4. In this study, both types of operations were compared head-to-head in a randomized prospective clinical trial using a dynamometer.

Materials and methods Patients The patients were part of a larger clinical study which started in 1990, and is still continuing, comparing a fascia lata tenodesis5 with a patellar tendon graft. Sixteen age- and sex-matched patients were selected from each group and evaluated 6 months to 2 years after operation. The operation was carried out for clinically manifested instab- ility in all cases.

The extra-articular procedure consisted of a distally based, 15 cm long and 5 cm wide, strip of fascia lata which was made into a tube and passed beneath the lateral collateral ligament (LCL) and then through an osseous tunnel in the lateral femoral condyle (LFC) and sutured back onto itself (Figure 1) with the knee at 60” of flexion and the foot maximally externally rotated. The intra- articular procedure consisted of a free graft obtained from the middle third of the patellar tendon which was then routed through trans-tibia1 and blind LFC tunnels and secured in place with interference screws and staples at the

tibia1 end (Figure 2). The new ligament was tightened with the knee in full extension and a notch-plasty was carried out as necessary.

Patients were allocated to treatment groups according to their year of birth: odd numbered years for the extra-articular procedure and even for the intra-articular procedure. The postoperative regimen was standardized: 3 weeks in a knee cylinder followed by a &month acceler- ated rehabilitation regimen designed for the study with the knee protected in a brace for the first 3 months.

Lateral collateral ligament

Figure 1. The fascia lata tenodesis: Le Maire procedure.

Figure 2. The patellar tendon substitution.

196 Injury: International Journal of the Care of the Injured Vol. 27, No. 3, 1996

Testing apparatus Testing and data collection were carried out at the BUPA Hospital Leicester, on the Biodex isokinetic dynamometer (Biodex Medical Systems, Shirley, NY) at velocities of 60”, 180” and 27O”/s. The involved and uninvolved knees of each patient were tested for flexion and extension using a standard protocol and with the range of motion (ROM) limits set at 0” and 90” of knee flexion.

Patients did a warm-up of 5 min on an exercise bike. Thereafter, they were seated for the examination and the stabilization and resistance pads were applied. At each speed, after four practice runs to familiarize the patients with the machine, four test efforts or consecutive sub- maximal repetitions of flexion/extension were carried out at 6O”/s; followed by four repetitions at 18O”/s and 20 repetitions at 27O”ls with rests of 30 s between bouts. All the tests were performed by one examiner.

Data analysis The following data were recorded for each patient: (a) personal details including height and weight; (b) extension and flexion repetitions, speed, peak torque, coefficient of variance, torque/body weight, maximum rep work, total work and average power; (c) flexors/extensors ratios; and (d) maximum and anatomical ROM.

In addition, graphical representations of peak torques and bar charts of peak torque, power and total work were automatically generated for the uninvolved and the involved knee at each speed.

The differences between the intra- and the extra- articular operations were analysed with respect to the percentage deficit in quadriceps and hamstring peak torques compared with the contralateral knee, the quadriceps/hamstring ratio and the percentage deficit in the ROM. The results for the patients in each operation group were pooled and the means were compared.

Results

At the time of testing, none of these selected patients had any symptoms referable to the operated knee and all the knees were clinically stable. There were three women in each group and the patients were aged between 19 and 43 years. All the patients had been injured during a sporting activity from 1 to 10 years before their operation.

The percentage quadriceps and hamstring deficits when the involved knee was compared with the contralateral knee are shown in Figures3 and 4 respectively. At each speed, the tenodesis appears to produce significantly less deficits. Figure 5 shows the quadriceps/hamstring ratios.

Percentage quadriceps deficit

Figure 3. Percentage quadriceps deficit. n = uatellar.

25 Percentage hamstrings deficit

20

0 Peak torque 60 Peak torque 180 Peak torque 270

Figure 4. Percentage hamstring deficit. =Le Maire; n = patellar.

Quadriceps / hamstrings ratio

80

60

40

20

0 At 60 At 270

Figure 5. Quadriceps/hamstring ratio. =Le Maire; n = patellar.

Percentage range of motion deficit

Figure6. Percentage range of motion deficit. = Le Maire; n = patellar.

The ratio is similar to that obtained in normal knees6 at all speeds following tenodesis while the ratio is significantly abnormal at the higher speed following patellar recon- struction. As shown in Figure 6, the patellar reconstruction is associated with greater deficits in the ROM.

Discussion

The aim of ACL reconstruction is to return the knee to normality. Normal function requires coordinated and reciprocal interactions between various muscles. Conse- quently, muscle testing is a useful tool for evaluating the state of a knee and it may be carried out in a variety of ways. In manual testing, muscles are graded on a scale of 5 to 0, where the normal muscle is grade 5. In weight-lifting, muscles are graded according to the largest weight that can be lifted or according to the number of lifts that can be performed with a specified load. More recently, dynamo- meters have been introduced in an attempt to refine muscle testing7. These machines allow the strength (i.e. ability to

Oni and Crowder: Isokinetics and muscle strength ratios following reconstructionf of the ACL 197

develop tension, torque or force) and the functional capacity of muscles to be objectively measuredS.

Dynamometers provide variable but maximal resistance throughout the ROM while maintaining a constant velo- city which weight-lifting cannot do. A torque- displacement curve is generated from which a variety of information such as peak torque (i.e. highest point of the curve) and work (i.e. area under the curve) may be obtained’. By these means, the performance of muscle groups may be compared. These machines are capable of generating reliable and reproducible data and have the ability to discriminate between normal and abnormal function.

In this study, the quadriceps and hamstring muscles in the operated knee were shown to be generally weaker than those of the contralateral normal knee in this early postoperative period. The results also show that muscle strengths were generally higher following the extra- articular procedure and the patellar operation was more associated with knee stiffness. Whether these differences will be maintained in the long term is not clear and this is the subject of continuing investigation. The clinical impression of the authors is that patients recover more quickly with the extra-articular procedure. In general, our experience with this operation does not accord with the poor reputation of extra-articular procedures amongst some surgeon?.

References

1 Larson RL and Taillon M. Anterior cruciate ligament in&E- ciency: principles of treatment. J Am Acud Orfhop Surg 1994; 2: 26.

Shoemaker SC, Adams D, Daniel DM and Woo SL. Quadriceps/anterior cruciate graft interaction. An in vitro study of joint kinematics and anterior cruciate ligament tension. Clin Orfhop 19%; 294: 379. Galway HR, Beaupre A and Macintosh DL. Pivot shift: a clinical sign of symptomatic anterior cruciate insufficiency. ] Bone Joint Surg [BY] 1972; MB: 763. Matsumoto H and Seedhom BB. Treatment of pivot-shift. Intraarticular versus extraarticular or combined procedures. A biomechanical study. Clin Orfhop 1994; 299: 298. LeMaire M. Ruptures anciennes du ligament croise anterieur du genou. Frequence. Clinique. Traitement (46 cas). ] Chir (Paris) 1967; 93: 311. Holm I, Ludvigsen P and Steen H. Isokinetic hamstrings/ quadriceps ratios: normal values and reproducibility in sport students. Isokinef Exert Sci 1994; 4: 141. Almekinders LC and Oman J. Isokinetic muscle testing: is it clinically useful? ] Am Acud Orthop Surg 1994; 2: 221. Watkins MP and Harris BA. Evaluation of isokinetic muscle performance. Chn Sports Med 1983; 2: 37. Johnson RJ, Beynnon BD, Nichols CE and Renstrom PA. The treatment of injuries of the anterior cruciate ligament. J Bone Joint Surg [Am] 1992; 74A: 140.

Paper accepted 24 October 1995.

Requests for reprints should be addressed to: Mr 0. 0. A. Oni, Consultant Orthopaedic Surgeon, The Glenfield Hospital, Groby Road, Leicester LE3 9QP, UK.