J Orthop Sci (1996) 1:171-177

Original articles

~ l o u r n a l of

th0paedic Science The Japanese Orthopaedic Association

Recovery of extensor muscle strength in athletes after anterior cruciate ligament reconstruction

SADAO NIGA ~, HARUYASU YAMAMOTO 2, and KOHTARO FURUYA 2

1 Department of Orthopaedic Surgery and Sports Medicine, Kawaguchi Kohgyo General Hospital, 1-18-15 Aoki, Kawaguchi, Saitama 332, Japan 2 Department of Orthopaedic Surgery, Tokyo Medical and Dental University, 1-15-45 Yushima, Bunkyo-ku, Tokyo 113, Japan

Abstract: We investigated the effects of the use of different autograft materials on the early postoperative recovery of extensor muscle strength after anterior cruciate ligament (ACL) reconstruction. Reconstruction was performed in 172 athletes with ACL-deficient knees; in 32, a quadriceps tendon- patellar tendon substitute (QTS) was used; in 79, semi- tendinosus and gracilis tendons (STG) were used; and in 61, a bone-patellar tendon-bone graft (BTB) was used. For QTS and STG autografts, a ligament augmentation device was used. Each group received the same accelerated rehabilitation program. Muscle strength was measured periodically 3-18 months after the operation, using a Cybex II dynamometer (Cybex Division of Lumex, Ronkonkoma, NY, USA). Knee extensor strength was evaluated, using the side-to-side ratio and the body weight ratio, to give a precise assessment of permissible sporting activity. After a period of 1 year, the percentage of athletes who recovered their extensor muscle strength at a level more than 80% of that in the uninvolved knee was 15.6% for those with QTS grafts, 41.0% for those with BTB grafts, and 77.9% for those with STG grafts (P < 0.001 between QTS and STG, P < 0.05 between QTS and BTB, and P < 0.001 between BTB and STG). The body weight ratio in men showed that, after reconstruction, recov- ery of extensor muscle strength sufficient for participation in vigorous sport required 6 months for STG grafts, 12 months for BTB grafts, and 18 months for QTS grafts.

Key words: extensor muscle strength, anterior cruciate liga- ment reconstruction, athlete, body weight ratio

Introduction

The goal of anterior cruciate l igament (ACL) recon- struction cannot be achieved without adequate recovery

Offprint requests" to: S. Niga Received for publication on Aug. 28, 1995; accepted on Dec. 15, 1995

of muscle strength, even if the knee has regained good stability and sufficient range of motion. This is espe- cially true for patients who desire to return to their previous level of sporting activity in the early postop- erative phase.

Muscle strength recovery after A C L reconstruction has been studied by various groups . 3'4'6'1~ Mar- der et al. 6 repor ted no postoperat ive (mean period, 29 months) difference in recovery of extensor muscle strength when patellar tendon autografts or flexor ten- don autografts were used. Rosenberg et al., 1~ in their postoperat ive study of patients with patellar tendon autografts, repor ted that, at 12-24 months, extensor muscle strength had recovered to 82% of the strength of the uninvolved knee. Yasuda et al. 16 repor ted that, with quadriceps tendon-patel lar tendon autografts, male patients showed 78% recovery of extensor muscle strength after 1 year, and female patients showed 66% recovery. These reports describe muscle strength recov- ery after long-term follow-up. Early postoperat ive re- covery differs with different tendon autografts, and this difference has not been fully clarified. We investigated the early postoperat ive recovery of extensor muscle strength and compared the results with different procedures.

We measured the extensor muscle strength periodi- cally after A C L reconstruction, carried out using three types of tendon autografts, in patients who had similar levels of sporting activity and who had undergone simi- lar rehabili tation in the early postoperat ive phase, and compared their recovery of extensor muscle strength after A C L reconstruction.

Subjects and methods

The subjects were patients who underwent A C L recon- struction using either quadriceps tendon-patel lar ten- don autografts (QTS), semitendinosus tendon-gracilis

172 S. Niga et al.: Muscle strength after ACL operation

tendon autografts (STG), or bone-patellar tendon-bone autografts (BTB). Their clinical profiles are shown in Table 1. The three groups did not differ significantly with respect to male to female ratio (;(2 test), age at surgery (Student 's t-test), interval between injury and surgery (Student 's t-test), or preoperative Tegner activ- ity level (Tegner and Lysholm iS) (all patients had levels higher than 6) (Student's t-test). For QTS autografts, a section of the quadriceps tendon and prepatellar fascia and the middle third of the patellar tendon were col- lected, and the reconstruction was performed by open surgery. For STG autografts, the semitendinosus ten- don and gracilis tendon were collected using Tendon stripper (3 M, St. Paul, MN, USA) and an arthroscopic operation was performed. BTB autografting was per- formed by an arthroscopic technique, using the middle third of the patellar tendon with bone blocks. For the QTS and STG autografts, pediculated grafts were aug- mented with a ligament augmentation device (LAD) and fixed on the femoral side by double stapling through an over-the-top route with a bone trough. BTB grafts were not augmented with a LAD and were fixed with Kurosaka screws in both the tibial and femoral tunnels. QTS autografts were performed from 1987 to 1988, STG autografts from 1989 to 1991, and BTB autografts from 1992 to 1994.

In all patient groups, postoperative rehabilitation was conducted as summarized in Table 2. The early postop- erative rehabilitation program shown in Table 2 has been conducted at Kawaguchi Kohgyo General Hospi- tal since 1987. We began this study mainly because muscle strength recovery with QTS autografts was not sufficient with the postoperative accelerated rehabilita- tion. To elucidate the effect of each operation method on the clinical outcome, postoperative rehabilitation was conducted in the same way, regardless of the opera- tion method. Sporting activities, including running and sprinting, were permit ted incrementally according to

the recovery of knee extensor muscle strength. Move- ments such as landing on one leg after jumping, rapid pivoting, and activities involving violent body contact were prohibited for all patients for at least 6 months postoperatively.

The clinical outcome was evaluated subjectively by Lysholm and Gillquist scoring. 5 Physical examination included range of knee motion and the pivot shift test. Anterior translation was evaluated using a KT-1000 ar thrometer (MEDmetr ic Corp., San Diego, CA, USA) with maximum manual force.

Muscle strength was measured using the Cybex II dynamometer (Cybex Co., Division of Lumex, Ronkonkoma, NY, USA) 3, 6, 9, 12, 15, and 18 months postoperatively. Knee extension torque was measured in an isometric manner at 80 degrees flexion and 0 de- gree/s angular velocity.

The side-to-side ratio (involved/uninvolved • 100) and body weight ratio (Kigawa et al. 2) were used to determine the isometric extensor muscle strength. The side-to-side ratio is generally used for evaluating the muscle strength of the involved knee based on the strength of the uninvolved knee. Body weight ratio has

Table 2. Postoperative rehabilitation

Rehabilitation Time begun after operation

CPM Partial weight bearing Full weight bearing Walking up and down stairs Isokinetic exercise with

limitation of extension at 60 ~ knee flexion

Bicycle training Return to sporting activity

Within 1 week 1-2 Weeks 3-4 Weeks 4-5 Weeks 4 Weeks

4 Weeks According to recovery of knee

extensor muscle strength

CPM, continuous passive motion.

Table 1. Demographic data for patients in whom reconstruction was performed

QTS STG BTB

Total no. of operative procedures 32 79 Men 21 46 Women 11 33 Mean follow up (months) 42.5 26.3 Mean age at surgery (years) 20.8 23.2 Mean time from injury to surgery (months) 12.2 9.0 Mean pre-operative Tegner activity level 7.0 6.9 Medial menisectomy 8 11 Lateral menisectomy 4 20 Medial meniscal repair 0 7 Lateral meniscal repair 0 8 Medial collateral ligament repair 1 1

61 40 21 20.1 21.8 7.8 7.1

15 13 7

0

QTS, Quadricep tendon-pateUar tendon substitute; STG, semitendinosus and gracilis tendons; BTB, bone-patellar tendon-bone.

S. Niga et al.: Muscle strength after ACL operation 173

not generally been used for evaluating muscle strength; however, using the body weight ratio enables independ- ent evaluation of the muscle strength of the uninvolved and involved knees. The body weight ratio refers to the force produced at the ankle by knee motion and is obtained by dividing the peak torque by the body weight and the length of the lower leg (measured from the center of rotation of the knee to the ankle). Kigawa et al. 2 measured the body weight ratios of isometric extensor muscle strength in 600 healthy students at a physical education university and showed that the body weight ratio of male students (n = 484) was 1.03 _+ 0.19 and that of female students (n = 116) was 0.85 _+ 0.19 (sex-related difference; P < 0.01). Kigawa also con- ducted a follow-up study on the body weight ratios of isometric extensor muscle strength in patients with lower limb disorders. Based on the results of the study, Kigawa established standards for the evaluation of weight-bearing ability for athletic activities. The stand- ards showed that gait disorder occurred in patients with a body weight ratio of 0.4 or less, running disorder occurred in those with a body weight ratio of 0.6 or less, and a body weight ratio of 0.8 or more was required for a subject to be able to practice and participate in athletic competitions without any trouble. This evaluation re- flects the patient's recovery of weight-bearing ability for sports, and we found it helpful clinically. The evaluation is also very useful in designing postoperative athletic programs for individual patients. Sporting activities af- ter reconstruction were conducted according to the re- covery of body weight ratio of extensor muscle strength. Patients with a body weight ratio of isometric extensor muscle strength of 0.4 were permitted to walk and climb stairs without an ACL brace, and, at a body weight ratio of more than 0.6, they were permit ted to run and to participate in other recreational sports. Patients with a body weight ratio of more than 0.8 were permit ted intense movement, including sprinting, turning, and jumping, and participation in competitive sports.

Statistical analysis

We compared the incidence of postoperative extension and flexion loss and positive pivot shift between the two groups, i.e., QTS Men and STG Men, using the ?(2 test for independence with correction using Fisher's exact probability test. Also, Lysholm scores or KT-1000 as- sessment of involved-uninvolved postoperative differ- ences were compared between the two groups, using Student's t-test with Welch's correction. Comparisons of side-to-side ratio and body weight ratio of isometric extensor muscle strength were made for the three groups (i.e., QTS, STG, and BTB) at corresponding points in time using two-way ANOVA. One-way A N O V A and Scheffe's post hoc test were used for com- paring the side-to-side ratio and body weight ratio of isometric extensor muscle strength for the three groups at the same time after operation. The percentage of athletes who recovered 80% or more of their side-to- side ratio of isometric extensor muscle strength was compared in the two groups (i.e., QTS and STG) 1 year after the operation, using the •2 test. Differences were considered significant when P < 0.05.

Results

Table 3 shows the Lysholm scores, the range of motion, and the knee instability measured at the patient's last examination. For Lysholm scores, no significant inter- group difference was observed, in men; in women, scores in the STG graft group were significantly lower than those in the BTB graft group. The three groups did not differ significantly with respect to the percentage of patients having an extension limit greater than 5 degrees, a flexion limit greater than 10 degrees, or a positive pivot shift. KT-1000 arthrometer assessment of knee instability showed no significant inter-group dif- ference in men; however, there was a significant inter-

Table 3. Results of reconstruction

QTS STG BTB

Men Women Men Women Men Women

Lysholm score 98.1 + 2.5 97.6 • 3.7 Extension loss (>5 degrees) 1 (4.8%) 1 (9.1%) Flexion loss (>10 degrees) 0 (0%) 0 (0%) Positive pivot shift 2 (9.5%) 2 (18.2%) KT-1000 involved-uninvolved 2.2 _+ 2.8 2.9 • 2.0

differences (manual maximum)

97.5 --+ 3.7 95.6 • 4.9* 97.5 • 3.0 98.4 • 2.4 1 (2.2%) 0 (0%) 1 (2.5%) 0 (0%) 1 (2.2%) 1 (3.0%) 3 (7.5%) 0 (0%) 9 (20.0%) 11 (33.3%) 6 (15.0%) 4 (19.0%) 1.2 --+ 2.1 3.1 -+ 2.6* 0.9 + 2.1 1.3 • 2.2

*P < 0.05, STG women vs BTB women (Student's t-test).

174 S. Niga et al.: Muscle strength after ACL operation

group difference for women, anterior translation in the STG group being larger than that in the BTB group.

The body weight ratios of isometric extensor muscle strength for the uninvolved knee 18 months after recon- struction for men were: 1.02 + 0.23 for QTS, 1.01 _+ 0.20 for BTB, and 1.02 _+ 0.22 for STG; for women, the values were: 0.81 _+ 0.23 for QTS, 0.83 _+ 0.16 for BTB, and 0.82 _+ 0.19 for STG. For the uninvolved knees, there was a significant difference between men and women who underwent the same surgical procedure (Student's t-test; QTS men vs QTS women, P < 0.05; BTB men vs BTB women, P < 0.01; STG men vs STG women, P < 0.001), although no significant differ- ence was observed for the three procedures for the same sex.

No significant sex-related differences were observed in any group in the recovery of the side-to-side ratio of isometric extensor muscle strength at any assessment time: There was a significant difference in the recovery of the side-to-side ratio among the three groups (as a whole, i.e., including men and women) at corresponding points in time (P < 0.000l) (Fig. 1). The side-to-side ratio findings indicate that extensor muscle strength re- covery after STG was better than that after BTB (P < 0.0001), which, in turn, was better than that after QTS (P < 0.0001) at corresponding points in time.

The percentage of patients with a side-to-side ratio of more than 80% within 1 year was 15.6% in the QTS group, 41.0% in the BTB group, and 77.9% in the STG group (Fig. 2). There were significant differences be- tween BTB and QTS (P < 0.05), STG and BTB (P < 0.001), and QTS and STG (P < 0.001).

In men, there was a significant difference among the three groups in recovery of the body weight ratio of the involved knee at corresponding points in time (P < 0.001) (Fig. 3). Recovery of the body weight ratio of the involved knee after BTB was significantly greater than that after QTS (P < 0.05) and was significantly less than that after STG (P < 0.005) at corresponding points in time. The body weight ratio of the involved knee after STG was significantly greater than that after QTS at the corresponding point in time (P < 0.0001). The time required to achieve sufficient muscle strength in the involved knee for running and participation in other recreational sports (body weight ratio 0.6) was 3 months for the STG group, 3-6 months for the BTB group, and 6-9 months for the QTS group. The time required to achieve sufficient muscle strength in the involved knee for vigorous sports, including jumping, turning, and sprinting (body weight ratio 0.8) was 6 months after reconstruction for the STG group, 12 months for the BTB group, and 18 months for the QTS group.

side to side ratio %

100

80

4 0 - -

2O

g-~f 0

3 6 9

!

12

I

15

Fig. 1. Side-to-side ratio at peak torque of isometric extensor muscle strength in men and women. Two-way ANOVA, P < 0.0001 among the three groups, i.e., bone-patellar tendon- bone (BTB), semitendinosus and gracilis tendons (STG), and quadriceps tendon-patellar tendon substitute (QTS). P < 0.0001 between BTB (white columns) and STG (gray col- umns); P < 0.0001 between BTB and QTS (black columns); P < 0.0001 between STG and QTS. One-way ANOVA, P <

I

J

t I

1 8 Months

0.0001 (3, 6, 9, 12, 15 months); P < 0.001 (18 months) among the three groups. Scheffe's method, P < 0.001 (3, 12 months); P < 0.0001 (6 months); P < 0.01 (9, 15 months); P = 0.05 (18 months) between BTB and STG. P < 0.01 (3, 6, 12 months); P < 0.001 (9, 15 months); P = 0.13 (18 months) between BTB and QTS. P < 0.000l (3, 6, 9, 12, 15 months); P < 0.001 (18 months) between STG and QTS

S. Niga et al.: Muscle strength after ACL operation 175

o,

100

80

60

40

20

0 QTS BTB STG

Fig. 2, Percentage of athletes who recovered more than 80% (black columns) or less than 70% (gray columns) of the side- to-side ratio of isometric extensor muscle strength 1 year post- operation. The percentage of athletes who recovered more than 80% of the side-to-side ratio of isometric extensor mus- cle strength was 15.6% for QTS, 41.0% for BTB, and 77.9% for STG. There was a significant difference between BTB and QTS (* P < 0.05), between STG and BTB (** P < 0.001), and between QTS and STG (*** P < 0.001). The percentage of athletes who recovered less than 70% of the value was 56.3% for QTS, 34.4% for BTB, and 7.8% for STG. White columns, Percentage of athletes who recovered 70%-79% of the side- to-side rate of isometric extensor muscle strength

For women, the body weight ratio showed a pattern similar to that in men (Fig. 4), although there were significant sex-related differences in the recovery of body weight ratio at all times of assessment. There was a significant difference among the three groups in the recovery of the body weight ratio of the involved knee at corresponding points in time (P < 0.01) (Fig. 4). The recovery of the body weight ratio of the involved knee after QTS was significantly lower than that after BTB (P < 0.05) and was significantly less than that after STG (P < 0.01) at corresponding points in time. The body weight ratio of the involved knee after STG was higher than that after BTB at corresponding points in time, but the difference was not significant (P = 0.09). The time required to achieve sufficient muscle strength in the involved knee for running and for participation in other recreational sports (body weight ratio 0.6) was 6 months in the STG group, 9 months in the BTB group, and 18

Body weight ratio

1.2

0.8

0.6

0 .4

0 ' 2 t

0 i

T

J I I I I

3 6 9 12 15 18 Monks

Fig. 3. Body weight ratio of isometric extensor muscle strength of the involved knee in men. Two-way ANOVA, P < 0.001 among the three groups; P < 0.005 between BTB (cir- cles) and STG (squares); P < 0.05 between BTB and QTS (dots); P < 0.0001 between STG and QTS. One-way ANOVA, P < 0.0001 (3, 6 months); P < 0.01 (9, 12, 15 months); P < 0.05 (18 months) among the three groups. Scheffe's method, P < 0.001 (3 months); P < 0.01 (6 months); NS (9, 12, 15, 18 months) between BTB and STG. P < 0.01 (3 months); P = 0.10 (6 months); NS (9, 12, 15, 18 months) between BTB and QTS. P < 0.0001 (3, 6, 9 months); P < 0.01 (12, 15 months); P < 0.05 (18 months) between STG and QTS

months in the QTS group. Only a few women were able to participate in competitive sports safely (body weight ratio 0.8) after reconstruction.

Discussion

In previous studies, 3,4,6a~ muscle strength analy- sis was often performed in terms of the side-to-side ratio at peak torque. This parameter cannot be used independently to assess the strength of the involved and uninvolved knees, and is vulnerable to vari- ability in the strength of the uninvolved knee. The body weight ratio independently expresses the muscle strength of the involved and uninvolved knees. In pa- tients with high side-to-side ratio in extension torque and low body weight ratio of the uninvolved knee, the extension strength of the uninvolved knee was weak. Such patients could not participate in sporting activities safely at a vigorous level due to the insufficient muscle strength of the uninvolved knee. In patients with low side-to-side ratio in extension torque and very high muscle strength in the uninvolved knee, the body weight ratio of the involved knee was high and the

176 S. Niga et al.: Muscle strength after ACL operation

Body weight ratio

1-

0.8

0.6

0.4

0.2

0

. . . .

I I I I I I

3 6 9 12 15 18 vlonths

Fig. 4. Body weight ratio of isometric extensor muscle strength of the involved knee in women. Two-way ANOVA, P < 0.01 among the three groups. P = 0.09 between BTB and STG; P < 0.05 between BTB and QTS; P < 0.01 between STG and QTS. One-way ANOVA, P < 0.01 (3, 9, 12, 15 months); P < 0.0001 (6 months); P < 0.05 (18 months) among the three groups. Scheffe's method, NS (3, 6, 9, 12, 15, 18 months) between BTB and STG. P = 0.08 (3 months); P < 0.01 (6 months); P - 0.09 (9 months); P = 0.07 (12 months); NS (15, 18 months) between BTB and QTS. P < 0.01 (3, 9, 12, 15 months); P < 0.0001 (6 months); P < 0.05 (18 months) be- tween STG and QTS. Symbols, As in Fig. 3

patients were able to participate in sporting activities safely at a vigorous level. In this study, significant sex- related differences were observed in the recovery of the body weight ratio of isometric extensor muscle strength of the involved knee, although no significant sex-related differences were seen in the recovery of the side-to-side ratio of isometric extensor muscle strength. Maugham et al. 7 reported no significant sex-related differences in the ratio of muscle strength to cross-sectional area of the muscle. Therefore , since the weight of muscle per body weight was lower in women than in men, we con- sider that the body weight ratio of muscle strength was lower in women than in men. Evaluation with the body weight ratio is more useful for evaluating each patient than the side-to-side ratio. For comparing groups using the body weight ratio of the involved knee, however, values vary widely and standard deviations tend to be large. Because of the large differences in the body weight ratios of the uninvolved knee, the body weight ratios of the involved knee could vary widely.

The currently used accelerated rehabilitation, re- ported by Shelbourne and Nitz, 13 appears to provide solutions (shortening of time of immobilization, early

recovery of range of motion, and early weight bearing) to most of the problems encountered in past rehabilita- tion procedures after A CL reconstruction. We consider that the poor muscle strength recovery despite acceler- ated rehabilitation is due to defects in the reconstruc- tion procedure, including the sacrifice of part of the tendon in collecting the autograft.

The results of this study showed that recovery of extensor muscle strength after reconstruction using QTS grafts was less favorable than the recovery with the other two reconstruction procedures, and the insuffi- cient body weight ratios of many patients who under- went reconstruction with QTS grafts prevented them from returning to sporting activities even 1 year postoperatively. Accordingly, reconstruction with QTS grafts should not be performed on athletes. Yasuda et al. 16 evaluated the clinical outcome of reconstruction with QTS grafts and reported insufficient postoperative recovery of extensor muscle strength.

Recovery of extensor muscle strength after recon- struction with the BTB grafts was bet ter than that with the QTS grafts, but less favorable than that with the STG grafts in the early postoperative phase. In men, the mean time required to achieve sufficient muscle strength for intense movement in the involved knee was within 1 year after reconstruction with the BTB graft.

Recovery of extensor muscle strength after recon- struction with the STG graft was bet ter than that with the other two types of grafts. In men, after reconstruc- tion with the STG graft, the mean body weight ratio had recovered sufficiently for running within 3 months and for intense movement, including sprinting, within 6 months.

In this study, the QTS and STG grafts were aug- mented with a LAD. Previous studies of the use of the LA D 1,<9,n have reported no significant difference in clinical outcome, including muscle strength recovery, between A CL reconstruction with and without the use of a LAD, for quadriceps tendon-patellar tendon autografts, 8 patellar tendon allografts, 9 semitendinosus- gracilis tendon autografts, n or bone-patellar tendon- bone autografts. 1 The use of the LA D in this study also does not seem to have had any substantial effect on postoperative muscle strength recovery.

In terms of muscle strength recovery, A CL recon- struction using autografts from the hamstring is more advantageous than reconstruction using autografts from the extensor apparatus, since the autografts from the hamstring have less effect on the recovery of extensor muscle strength and pose a smaller burden to the pa- tient in increasing muscle strength during rehabilitation. The less favorable recovery after QTS grafts than after BTB grafts indicates that the impairment of recovery after quadriceps tendon grafting was more severe than that after pateltar tendon grafting.

S. Niga et al.: Muscle strength after A C L operat ion 177

Acknowledgments. T h e a u t h o r s t h a n k A . H o s h i n o

M . D . , S. H a y a s h i M . D . , a n d T. M i z u t a M . D . f o r t h e i r

h e l p in t h e s tudy.

N o b e n e f i t s o f a n y k i n d h a v e b e e n r e c e i v e d o r wi l l be

r e c e i v e d f r o m c o m m e r c i a l p a r t i e s r e l a t e d d i r e c t l y o r

i n d i r e c t l y to t h e sub j ec t o f th is ar t ic le .

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