Pre-TKR isokinetic quadriceps strengthening has a positive effect which may diminish following the intervention despite pain and functional improvements: A case study

Abstract

We report a longitudinal survey of a 53-year-old man suffering from right knee osteoarthritis who has undergone total knee replacement (TKR). We aimed at evaluating the effect of a short preoperative isokinetic strengthening program on the functional status, pain, and quadriceps and hamstrings strength before and after TKR. The patient performed a 4-week (6 sessions) preoperative isokinetic strengthening program of the quadriceps and hamstrings. The findings for the concentric strength at 60 ${}^{\circ }$ /s, 6-minute walk test (6MWT), and Knee injury and Osteoarthritis Outcome Score (KOOS) were recorded. At baseline the patient presented with an overall KOOS score of 44%, a 6MWT of 444 m, a 63% and 21% strength deficits of the quadriceps and hamstrings, respectively. Following the strengthening program, the quadriceps strength of the operated limb improved ( $+$ 121 Nm; $+$ 83%), but the function as reflected by the KOOS score remained unchanged. Following the TKR, the concentric isokinetic strength of the quadriceps reappeared altered (63% of deficit) despite pain and functional improvements. This case report underlines the importance of functional evaluation rather than the maximal strength to assess the effectiveness of TKR. However, further studies are necessary to conceptualize the meaning of maximal strength measurement and the impact of associated deficits, if any.

1. Introduction

Knee osteoarthritis (OA) is a common degenerative musculoskeletal disease, associated with pain, stiffness, and loss of mobility. It affects 2% to 10% of men and 1.6% to 15% of women over 40 years old depending on the geographical area and definition of pathology [1]. According to a US study, 45% of adults over age 45 will show knee OA before the age of 85 [2].

Currently, there is no effective pharmacological treatment, but non-pharmacological treatments have been found effective [3]. The need for joint replacement surgery is frequent, and 86,000 knee replacements were performed in France in 2011 [4]. The frequency of joint replacement increased more than 33% between 2008 and 2013 [4], which is consistent with data from other knee arthroplasty registries in several Nordic and Anglo-Saxon countries.

In end-stage knee OA, total knee replacement (TKR) is an effective intervention to reduce pain and improve function for many patients. However, after TKR, some patients still experience pain, loss of function, deficient muscle strength or reduced walking speed.

Despite growing development of preoperative exercise programs, most studies show no difference between preoperative intervention and usual care in postoperative pain, function, and muscle strength [5, 6]. A recent (2018) meta-analysis concluded that preoperative training did not benefit functional recovery over the control treatment but that better studies with more patients seemed necessary before a definitive conclusion [7]. Indeed, only 9 randomized controlled trials were included in this meta-analysis, and the sample size of each study was small. Conversely, other studies, some of good quality (level of evidence I) support the interest in a program of preoperative exercises (especially designed to increase lower limb muscle strength) for patients with terminal OA to improve early post-operative results. These programs result in reduced length of hospital stay and faster physical and functional recovery (improved strength, range of motion and functional measures as well as reduced pain) in the early postoperative periods compared with control [8]. None of these studies used exercise programs tailored to patients’ phenotypes.

The great diversity of preoperative exercise protocols, both in terms of the type of exercises (aerobic/specific reinforcement, low/high intensity) and type of muscular reinforcement (isometric/isokinetic), as well as the period of intervention, may explain this great diversity in effect. For example, a meta-analysis suggested that an 8-week exercise period (including muscular strengthening exercise) seemed necessary to improve function and physical activity before TKR [9]. Moreover, it seems important to dissociate the content of these interventions: exercise (aerobic and specific reinforcement), self-management strategies, and associated interventions (occupational therapist, social worker).

We report a longitudinal study of a 53-year-old man with right knee OA who had to undergo TKR after failure of well-conducted medical and conventional physical therapies. His occupation involved significant physical activity but otherwise kept a sedentary lifestyle with few physical activities. This patient had grade 1 obesity (body mass index 30.8 kg/m ${}^2$ ). At the age of 43, he began presenting post-traumatic external tibiofemoral chondropathy (severely sprained knee and non-contact anterior cruciate ligament injuries), which required several successive surgical procedures: ligamentoplasty, meniscectomy, tibial osteotomy and 2 joint washes under arthroscopy. He also had clinically thigh-muscle weakness and amyotrophy. The treatment was initially medical for 10 years (several rounds of conventional physiotherapy including muscular strengthening program in private practice, regular physical activity, intra-articular injection of hyaluronic acid [8 times in single injection], orthotics), with limited effect on disability and muscle strength (assessed clinically and by isokinetic dynamometry). Because of the progressive pain and increasing functional limitation (especially descending stairs which was no longer possible in alternating steps due to increased pain), TKR was proposed. Faced with the failure of conventional physiotherapy and given the significant loss of quadriceps and hamstring strength, we proposed a preoperative isokinetic strengthening program which has been shown in some studies to be effective in knee OA patients improving muscle strength and health related quality of life [10].

2. Evaluation and strength conditioning

We aimed to evaluate the effect of a short preoperative isokinetic strengthening program on functional status, pain, and muscle strength assessed before and after TKR in this patient. Repeated measures followed the International Classification of Functioning, Disability and Health core assessment set, isokinetic quadriceps concentric strength (60 ${}^{\circ }$ /s), 6-min walk test (6MWT), and Knee injury and Osteoarthritis Outcome Score (KOOS). Isokinetic quadriceps strength was evaluated using a Cybex HumacNorm ${}^{\mathrm{TM}}$ in concentric mode. Patient was installed in a sitting position according to the manufacturer’s recommendations, using the upper tibial pad dedicated to knee instability. Knee range of motion (RoM) for the eva-luation was 0 ${}^{\circ }$ (full extension) to 90 ${}^{\circ }$ of flexion. The tests included 3 series of 5 concentric repetitions at 60 ${}^{\circ }$ /s. Between each series, 30 s of rest were allowed. The best result was retained as the peak moment value. To ensure standard testing conditions (1) a familiarization bout was integrated, (2) standardized verbal encouragements were given and (3) comparison of the strength curves was performed for ensuring a reasonable extent of overlapping. We also carried out a gait analysis of using a back and forth 7.01-m computerized walking carpet (GaitRite ${}^{\mathrm{\circledR }}$ ). Parameters recorded included speed, cadence of walking and length of step and stride.

The patient performed a preoperative isokinetic strengthening program of the quadriceps-hamstrings couple on a Cybex HumacNorm ${}^{\mathrm{TM}}$ : 5 repetitions (concentric mode at 60 ${}^{\circ }$ /s)/set x gradually increasing the number of sets from 6 to 12 (20 seconds inter-set time rest) $\times$ 2 days/Week $\times$ 4 Weeks.

The TKR involved also tibial tuberosity realignment. The intervention was performed without any complications (Fig. 2B) and allowed for walking without weight-bearing restriction. In view of the tibial tuberosity realignment, postoperative rehabilitation was initially limited because of use of a functional knee brace with knee range of motion restriction from 0 ${}^{\circ }$ to 60 ${}^{\circ }$ for 2 months postoperatively. On day 5 after surgery, the knee range of motion reached 0–60 ${}^{\circ }$ and the patient performed a conventional rehabilitation program: initially focused on functional exercises to improve transfer, walking and stair negotiation performance. Quadriceps and hamstrings muscle strength was first conditioned in closed kinetic chain due to tibial tuberosity realignment, followed progressively by open kinetic chain strengthening exercises using for instance isometric and isotonic contractions.

3. Results

At baseline, active and passive RoM were 0–90 ${}^{\circ }$ and 0–100 ${}^{\circ }$ respectively. The overall KOOS score was 44% (58.3% pain and 58.8% function), with a 6MWT of 444 m, 63% deficit of quadriceps concentric muscle strength (66 Nm operative vs 179 Nm non-operative limb) and 21% deficit of hamstrings concentric muscle strength (52 Nm operative vs 65 Nm non-operative limb). Radiographic evaluation established Kellgren and Lawrence stage 4 knee OA (predominantly in the lateral compartment) with joint space greatly reduced and the presence of several bone remodeling events (large osteophytes). Evaluation of static lower-limb alignment with the EOS®system showed a right knee valgus of 12 ${}^{\circ }$ (Fig. 1).

Figure 1.

Static lower-limb alignment evaluation with the EOS ${}^{\mathrm{\circledR }}$ system. Front view standing upright.

After the strengthening program (but before the intervention) quadriceps strength of the compromised limb (assessed under identically as at baseline) almost doubled (to 121 Nm; $+$ 83%) but function with the KOOS score remained unchanged: 44% (58.3% pain and 58.8% function).

Figure 2.

Radiography after total knee replacement (TKR). A. Static lower-limb alignment evaluation with the EOS ${}^{\mathrm{\circledR }}$ system, front and side view standing upright; B. Radiography of the right knee immediately post-TKR, front and side view lying down; C. Radiography of the right knee at 1 year post-TKR: front, side and patellofemoral view standing upright.

Tested postoperatively at 3, 9 and 17 months, quadriceps strength amounted to 50, 65, and 104 Nm, respectively (versus 178, 171 and 165 Nm for the non-operative limb). On average therefore, knee extension strength deficiency was a significant 57% throughout the follow-up time but significantly stood at 37% at 17 m. Hamstring bilateral values were, at 3, 9 and 17 months, 52, 58 and 62 Nm (operated side) versus 65, 53 and 79 Nm (non-operative limb), Thus, knee flexion deficiency stood on average at 11% and although at 17 m it amounted to 22%, on the whole there was marginal deficiency at worst [11, 12]. The 6MWT was 295, 540, 565 and 575 m at 1, 3, 9 and 17 months, respectively. The KOOS score was 81% (80.6% pain and 91.2% function) at 3 months, 83.9% (83.3% pain, 91.2% function) at 9 months and 85% (83.4% pain, 91.3% function) at 17 months.

Radiography performed 2 months after the TKR revealed a tricompartmental prosthesis in place, no evidence of loosening and satisfactory ossification of the tibial tuberosity (Fig. 2C). Static lower-limb alignment evaluation performed with the EOS ${}^{\mathrm{\circledR }}$ system revealed a left pelvic tilt in relation to inequality of functional length of the lower limbs because of a difference of 15 mm at the expense of the left side. The global angular deviation measured 2 ${}^{\circ }$ to the right and 0 ${}^{\circ }$ to the left in valgus. There was a right flessum at 3 ${}^{\circ }$ and a left flessum at 0 ${}^{\circ }$ (Fig. 2A).

Despite substantial persistent amyotrophy of approximately 4 cm (with thigh perimeter at 49, 50 and 52 cm on the right limb against 51, 57 and 58 cm on the left at 5, 10 and 15 cm above-patellar respectively), the patient was very satisfied with the care that allowed for walking “without any restriction” and a “faster walking speed”, measured with the GAITRite ${}^{\mathrm{\circledR }}$ system and showing a speed increase from 114.5 cm/s initially to 152 cm/s at 17 months postoperatively; values for other spatio-temporal parameters were also improved and were comparable to non-symptomatic people of the same age and gender.

Quadriceps isokinetic strength was improved after a short preoperative isokinetic strengthening program, but postoperative quadriceps strength deficit remained despite pain and functional improvements. Preoperatively, this patient underwent quite an intensive strength enhancement program using isokinetic dynamometer and so it is not surprising to find a strength improvement in the same measurement modality. However, function and pain were not related to this improvement according to the KOOS score. A possible explanation could be that the main postoperative objective was on function rather than on quadriceps strengthening. Thus, the extent to which quadriceps strength enhancement is transferrable to functional or pain improvements is still open, a point raised by Husby et al. in their study [13]. On the other hand, hamstrings isokinetic strength was practically normalized concordant with literature showing predominant quadriceps deficit in OA and post TKR patient [14]. In this particular case, tibial tuberosity realignment could explain the more pronounced deficiency in quadriceps.

The fact that the functional status and the isokinetic strength are not related is not obvious, especially as both are frequently considered to be closely complementary constructs. Further, several randomized control trials or clinical control trials used isokinetic muscle strength as a primary criterion for assessing the efficacy of rehabilitation outcomes in TKR [12, 15]. Our case deviates from this schema possibly due to of the lack of post-operative quadriceps strengthening. This observation is consistent with Cavanellas et al. study who have indicated that traditional rehabilitation programs were not sufficient in terms of quadriceps strength restoration [14].

This case report suggests the potential interest of focusing on functional evaluation rather than maximal strength to assess the effectiveness of TKR. However, it should be emphasized that without an adequate level of strength, good functioning may not be possible. Moreover, in situations where the integrity of the knee is threatened (e.g. perturbations) quadriceps strength and the speed with which it may be recruited, could be crucial.

Thus, further studies are needed to determine the significance of attaining maximal strength (which in fact relates to the strength level of the sound side) and to the impact of such deficit. The usefulness of a pre- and post-operative isokinetic strengthening program remains undetermined but could be of interest in preparing younger individuals with knee OA with high expectations regarding functional improvement after TKR.

Author contributions

CONCEPTION: Vivien Reynaud, Lech Dobija and Emmanuel Coudeyre.

PERFORMANCE OF WORK: Vivien Reynaud, Lech Dobija, Pierre-Louis Fournier and Charlotte Lanhers.

INTERPRETATION OR ANALYSIS OF DATA: Vivien Reynaud, Lech Dobija and Charlotte Lanhers.

PREPARATION OF THE MANUSCRIPT: Vivien Reynaud and Lech Dobija.

REVISION FOR IMPORTANT INTELLECTUAL CONTENT: Vivien Reynaud, Lech Dobija and Charlotte Lanhers.

SUPERVISION: Emmanuel Coudeyre.

Ethical considerations

Because patients’ data were retrospectively retrieved for the purpose of the present study, a formal approval by an institutional review board is not required according to the Jardé Law of March 5, 2012 and its application decree (No. 2016-1537) relating to research involving the human person in France. We still proceeded to a reinforced information with explanatory mail and form to the patient and retrieved his signature of an information and non-opposition form.

Funding

The authors report no funding.