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The Effect of Preoperative Exercise on Total Knee Replacement Outcomes

D'Lima, Darryl; Colwell, Clifford; Morris, Beverly; Hardwick, Mary; Kozin, Franklin

Clinical Orthopaedics and Related Research: May 1996 - Volume 326 - Issue - p 174-182
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This study compared the effects of preoperative physical therapy or general cardiovascular conditioning exercises with the routine procedure of no preoperative physical therapy on patients undergoing primary total knee replacement. Thirty patients were randomly assigned to 1 of 3 groups. Group 1 was the control group. Group 2 participated in a physical therapy program designed to strengthen the upper and lower limbs and improve knee range of motion. Group 3 participated in a cardiovascular conditioning program, consisting of arm ergometry, cycle ergometry, aquatic exercises, and aerobic activity. All patients were evaluated preoperatively and postoperatively using the Hospital for Special Surgery Knee Rating, the Arthritis Impact Measurement Scale, and the Quality of Well Being instrument. Both experimental groups tolerated their respective exercise protocols extremely well. All 3 groups showed significant improvement postoperatively as measured by the Hospital for Special Surgery Knee Rating, the Arthritis Impact Measurement Scale and the Quality of Well Being measurement scales. However, neither type of preoperative exercise added to the degree of improvement after surgery at any of the postoperative evaluations.

From the Division of Orthopaedics, Scripps Clinic and Research Foundation, La Jolla, CA.

Reprint requests to Clifford W. Colwell, Jr., MD, Head, Division of Orthopaedics, Scripps Clinic and Research Foundation, 10666 North Torrey Pines Rd, MS116, La Jolla, CA92037.

Received: June 12, 1995.

Revised: August 22, 1995; October 9, 1995.

Accepted: September 5, 1995.

Most studies evaluating total joint replacement emphasize design, material characteristics, fixation techniques, and wear phenomenon. Few evaluate the effects of conditioning and exercise programs.19 Approximately 35% of the population between the ages of 65 and 75 years experience limitation in activity.3 Although chronic diseases account for a portion of this inactivity, simple deconditioning causes a progressive decline of physical fitness in the elderly, even in the absence of disease. As a consequence of diminished exercise, an increasing number of the elderly will be living close to the threshold of physical inactivity, needing only a minor intercurrent illness to render them dependent.1,2 This study compared the effects of preoperative physical therapy or general cardiovascular conditioning exercises with the routine procedure of no preoperative physical therapy on patients over 55 years of age undergoing primary total knee replacement.

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MATERIALS AND METHODS

Consecutive patients scheduled for elective primary unilateral total knee replacement were screened for participation in this study following informed consent. The program was reviewed and approved by the institution's Investigational Review Board.

Eligibility requirements were age greater than 55 years, a primary diagnosis of osteoarthritis or rheumatoid arthritis, and residence within convenient distance of the facility. Only patients needing unilateral knee replacements were included. Exclusion criteria included cognitive, psychological, or language impairment. Patients had to be able to read and sign a consent form developed for seventh to ninth grade reading comprehension level. This was reviewed and approved by the Investigational Review Board. Patients with major cardiovascular impairment such as labile hypertension and unstable angina were excluded. Further screening by means of stress electrocardiogram was carried out if patients had borderline symptoms. Patients were also excluded if they had history of cerebral ischemia such as stroke or transient ischemic attacks.

All surgeries were performed by the senior author (C.W.C.) using the Press-Fit Condylar total knee system (Johnson & Johnson Orthopaedics, New Brunswick, NJ).

A computer generated randomization list was used to assign patients to 1 of the following treatment groups:

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Group 1 (Control): 10 Patients

These patients met with a physical therapist preoperatively for 45 minutes. Printed material that included the postoperative exercise regimen was provided. No recommendations for preoperative physical therapy or exercise were made. The existing routine postoperative protocol for total knee replacements included quadriceps and hamstring setting, straight leg raises, hamstring and heel cord stretching, knee strengthening, sitting and prone knee range of motion exercises, and routine precautions.

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Group 2 (Experimental Physical Therapy): 10 Patients

Patients participated in a 1-on-1 physical therapy training program to strengthen the upper and lower extremities and improve knee range of motion. This program included initial stretching of calf, hamstring, and quadriceps muscles, followed by isometric and isotonic strengthening exercises of the triceps surae, quadriceps, hamstrings, hip flexors, hip extensors, hip abductors, shoulder flexors, shoulder abductors, and triceps brachii. Weights were used as tolerated by the patient. Each session lasted for 45 minutes and was administered 3 times a week for a total of 18 exercise sessions. Patients were taught to use a graphed exercise program to meet a goal determined by the patient and therapist based on the patient's capabilities. The graph was used to record the number of repetitions. At each visit, the exercises were reviewed with the physical therapist to ascertain that they were performed properly. The graphed records were also reviewed with the patient. The number of repetitions was increased by 1 repetition every third day until the goal was reached.

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Group 3 (Experimental Cardiovascular Conditioning): 10 Patients

The patients initially were tested by an exercise physiologist on the Monark 881E Arm Ergometer and the Monark 818 Cycle Ergometer (Quinton, Seattle, WA). This included timed tests with measurement of resting, peak, and ending heart rate and blood pressure to establish endurance and predictable workload. A cardiovascular conditioning program was designed for each patient to improve fitness within their physical limitations and to maintain heart rate in the training range by the formula: Training Heart Rate Range = Resting Heart Rate + 0.4 to 0.7 Heart Rate Reserve9 (where Heart Rate Reserve = Maximum Heart Rate - Resting Heart Rate). This consisted of 3 exercise sessions per week for a total of 18 sessions, each lasting 45 minutes. Twelve of these sessions emphasized arm ergometry and cycle ergometry on the Cybex Aerobic Ergometer and the Cybex Upper Body Ergometer (Cybex, Ronkonkoma, NY), and included light stretching, muscle toning, and aerobic activity. The remaining 6 sessions consisted of aquatic exercises. Heart rate was monitored throughout all the sessions, and blood pressure was monitored throughout each ergometry session.

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Measurement Instruments

All patients were evaluated at 6 weeks preoperative, 1 week preoperative, 3 weeks postoperative, 12 weeks postoperative, 24 weeks postoperative, and 48 weeks postoperative.

Three tools were used for this evaluation, 1 of which was the Hospital for Special Surgery Knee Rating. This rating scale is a functional assessment developed by Insall et al5 (Hospital for Special Surgery, New York). This includes assessment of pain, function, range of motion, muscle strength, flexion deformity, and instability, with an overall rating given as a total score. Pain is measured on a scale of 0 to 30, with no pain measured as 30. Total function is measured on a scale of 0 to 52, with full function measured as 52. The range of the total score is 0 to 100, with 100 being a perfect score.

The second tool used was the Arthritis Impact Measurement Scale, which is a health index instrument designed by Meenan et al14 (Boston University Multipurpose Arthritis Center). The Arthritis Impact Measurement Scale is an arthritis specific instrument which has been used extensively on both rheumatoid arthritis and osteoarthritis patients.15 This is a multidimensional measure which gives 3 summary ratings of pain, psychological status, and lower extremity function, as well as an overall health status rating given as the total score.13 The range of the score in each category is from 0 to 10, with 0 being a perfect score and 10 being the worst score.

The third tool used was the Quality of Well Being, which is a general health status measure developed by Kaplan and colleagues.7 This instrument was not designed specifically for orthopaedic patients; however, it has been used by Liang et al to measure the benefits in patients undergoing total joint replacement and has been shown to be adequately sensitive.11 The Quality of Well Being addresses 5 areas of health status: general symptoms, physical activity, mobility, social activity, and global health. Because the Quality of Well Being is not disease- or organ-specific, it can take into account the broad impact of a disease and/or intervention.16 However, it does not attempt to quantify pain. The range of the total score is from 0.00 to 1.00, with 1 being a perfect score.

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Statistical Analysis

This study was designed to detect an increase of at least 10 points in the postoperative Hospital for Special Surgery Knee Rating and a reduction in the duration of hospital stay by at least 1 day, given an α of 0.05 and a power of 80%. Data analysis was performed on a Sun computer system (Sun Microsystems, Inc., Mountain View, CA) using Prophet statistical program (Release 3.2) (Bolt Beranek and Newman, Inc., Cambridge, MA). Repeated measures analysis of variance testing was performed on different scores for each patient; student's 1-tailed t-test was performed on scores between the control group and each of the 2 treatment groups.

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RESULTS

No significant differences were observed in age, length of hospital stay, or rate of complications between the 3 groups (Table 1). The preoperative diagnosis was osteoarthritis in 25 patients and rheumatoid arthritis in 5 patients. There were 2 postoperative complications in each group: Group 1 had a patient who had a deep surgical infection and a patient with intestinal pseudoobstruction; Group 2 had a patient with atrial fibrillation and a patient with paroxysmal tachycardia; Group 3 had a patient with sleep apnea and a patient who had restricted range of motion which was manipulated 8 weeks after surgery.

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Pain

It is interesting to note that the average pain scores as measured by the Hospital for Special Surgery Knee Rating showed an increase in pain for groups 1 (control) and 3 (cardiovascular conditioning) during the preoperative period (6 weeks preoperative and 1 week preoperative evaluation), whereas group 2 (physical therapy) showed a minor decrease (Fig 1). The major portion of pain relief occurred in the immediate postoperative period. Group 1 showed the greatest improvement within 3 weeks of surgery, with Groups 2 and 3 taking 12 to 24 weeks to reach comparable levels. However, final pain scores were higher at 48 weeks for Groups 2 and 3 than Group 1, although this was not statistically significant.

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Total Function

Groups 1 and 2 demonstrated a decrease in total function during the preoperative period as measured by the Hospital for Special Surgery Knee Rating, with group 3 showing a modest rise (Fig 2). However, in the immediate postoperative period both exercise groups showed a steeper decline in function than the control group. The final scores at 48 weeks did not show any significant difference between the 3 groups.

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Total Score

The mean total scores of the Hospital for Special Surgery Knee Rating dropped dramatically in the immediate postoperative period for patients in the exercise groups (2 and 3) due to the decline in function overshadowing the pain relief (Fig 3). However, the control group showed no such drop. The final score at 48 weeks was similar in all 3 groups.

Because the patients with rheumatoid arthritis were not equally distributed among the different groups, they were also analyzed separately to determine their outcomes as a group. Their evaluations at different time points are summarized in Table 2. In addition, their mean total Hospital for Special Surgery Knee Rating scores are compared with those of all patients in Figure 4, and were found to be similar.

An attempt was made to compare the Arthritis Impact Measurement Scale and the Quality of Well Being scores with each other and with the Hospital for Special Surgery Knee Rating. Since the numerical scoring systems are different, the total scores of each measurement instrument were calculated as the percentage improvement over the original preoperative score (Figs 5-7). Although the Arthritis Impact Measurement Scale was not originally designed to measure surgical outcomes, it is remarkably sensitive to the postoperative improvement. The Quality of Well Being measures general quality of life and is not orthopaedically oriented, but it too showed significant postoperative improvement, confirming Liang et al's results.11 This suggests that the results of questionnaires that are subjective or self rated are similar to traditional evaluation systems such as the Hospital for Special Surgery Knee Rating. Currently, measurements are taken using the SF-36 Health Survey (New England Medical Center Hospitals, Inc., Boston, MA) and the WOMAC (Western Ontario and McMaster University) Osteoarthritis Index, which are validated outcome assessment instruments recommended by the American Association of Hip and Knee Surgeons.

This population (all over 55 years) tolerated both the preoperative physical therapy and cardiovascular conditioning programs remarkably well without adverse events that were directly related to these programs.

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DISCUSSION

Although there have been several articles that have compared different physical therapy regimens for cardiothoracic and general surgery,4,6,17 there have been few controlled trials that have evaluated the potential benefits of preoperative physical therapy for joint replacement patients. Recently, Wijgman et al reported the results of a study involving patients subjected to preoperative physical therapy before total hip replacement in 1994.20 The patients who had received preoperative physical therapy had a higher Harris Hip Score over the control group on day 14 and on the day of discharge. However, there was no difference in the time taken to begin standing, walking, climbing stairs, or the duration of hospital stay between the 2 groups. The conclusion reached was that preoperative physical therapy and instruction are not useful for patients undergoing total hip replacement.

In 1993 Weidenheilm et al18 and Mattsson12 did a similar study on patients scheduled for unicompartmental knee arthroplasty. Before surgery, the patients who had received preoperative physiotherapy did show a slight improvement in pain, subjective stability of the knee during walking, and an improvement in gait speeds over the control group. However, 3 months after surgery there was no significant difference between the 2 groups. In fact, the experimental group showed a decrease in muscle strength, while the patients in the control group showed no change.

The present study also did not find any statistically significant difference in the postoperative course among the different groups. One possible explanation for this finding is that these patients with chronic joint disease are resistant to a few weeks of physical therapy, or that age and overall health status prevents them from obtaining any major benefit. Another explanation could be that total knee replacement surgery provides such a dramatic improvement in symptoms that it overshadows the relatively smaller benefit of perioperative exercise. This is supported by Liang et al who reported no significant change in outcome of total joint replacement surgery when the hours of postoperative exercise therapy were reduced by about 30%.10

A third reason could be that surgery itself deconditions the function of the extremity with loss of any preoperative improvement. Karumo et al performed preoperative and postoperative biopsies on patients who underwent meniscectomies and found that the extent of physiotherapy (routine, as against intensive exercise) did not significantly modify the results.8 They also noted that quadriceps atrophy actually increased after meniscectomy, and this was more marked in patients who had a better preoperative status. This may explain the temporary decrease in function score after surgery for the exercise groups in the present study, in contrast with the control group.

While it seems reasonable to believe that patients undergoing total knee replacement would benefit from preoperative strengthening exercises, there is no evidence to support this assumption. Preoperative physical therapy is not an effective method of improving outcome or shortening hospital stay in patients undergoing total knee replacement.

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Acknowledgments

The authors thank Richard T. Cotton, MA, Joan C. Hackett, MA, and Margaret Chivers, MCSP, for their contribution in developing and implementing the exercise programs.

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References

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