Multicenter Randomized Controlled Trial Comparing Early Versus Late Aquatic Therapy After Total Hip or Knee Arthroplasty

Published:December 23, 2011DOI:https://doi.org/10.1016/j.apmr.2011.09.011

      Abstract

      Liebs TR, Herzberg W, Rüther W, Haasters J, Russlies M, Hassenpflug J, on behalf of the Multicenter Arthroplasty Aftercare Project. Multicenter randomized controlled trial comparing early versus late aquatic therapy after total hip or knee arthroplasty.

      Objective

      To evaluate if the timing of aquatic therapy influences clinical outcomes after total knee arthroplasty (TKA) or total hip arthroplasty (THA).

      Design

      Multicenter randomized controlled trial with 3-, 6-, 12-, and 24-month follow-up.

      Setting

      Two university hospitals, 1 municipal hospital, and 1 rural hospital.

      Participants

      Patients (N=465) undergoing primary THA (n=280) or TKA (n=185): 156 men, 309 women.

      Intervention

      Patients were randomly assigned to receive aquatic therapy (pool exercises aimed at training of proprioception, coordination, and strengthening) after 6 versus 14 days after THA or TKA.

      Main Outcome Measures

      Primary outcome was self-reported physical function as measured by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at 3-, 6-, 12-, and 24-months postoperatively. Results were compared with published thresholds for minimal clinically important improvements. Secondary outcomes included the Medical Outcomes Study 36-Item Short-Form Health Survey, Lequesne-Hip/Knee-Score, WOMAC-pain and stiffness scores, and patient satisfaction.

      Results

      Baseline characteristics of the 2 groups were similar. Analyzing the total study population did not result in statistically significant differences at all follow-ups. However, when performing subanalysis for THA and TKA, opposite effects of early aquatic therapy were seen between TKA and THA. After TKA all WOMAC subscales were superior in the early aquatic therapy group, with effect sizes of WOMAC physical function ranging from .22 to .39. After THA, however, all outcomes were superior in the late aquatic therapy group, with WOMAC effect sizes ranging from .01 to .19. However, the differences between treatment groups of these subanalyses were not statistically significant.

      Conclusions

      Early start of aquatic therapy had contrary effects after TKA when compared with THA and it influenced clinical outcomes after TKA. Although the treatment differences did not achieve statistically significance, the effect size for early aquatic therapy after TKA had the same magnitude as the effect size of nonsteroidal anti-inflammatory drugs in the treatment of osteoarthritis of the knee. However, the results of this study do not support the use of early aquatic therapy after THA. The timing of physiotherapeutic interventions has to be clearly defined when conducting studies to evaluate the effect of physiotherapeutic interventions after TKA and THA.

      Key Words

      List of Abbreviations:

      NSAID (nonsteroidal anti-inflammatory drug), RCT (randomized controlled trial), SF-36 (Medical Outcomes Study 36-Item Short-Form Health Survey), THA (total hip arthroplasty), TJA (total joint arthroplasty), TKA (total knee arthroplasty), WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index)
      DESPITE THE WIDESPREAD use of total hip arthroplasty (THA) and total knee arthroplasty (TKA), there is a notable lack of consensus regarding postoperative treatment.
      NIH Consensus Statement on Total Knee Replacement.
      • Enloe L.J.
      • Shields R.K.
      • Smith K.
      • Leo K.
      • Miller B.
      Total hip and knee replacement treatment programs: a report using consensus.
      • Duggal N.
      Improving orthopedic outcomes: focus on rehabilitation.
      • Youm T.
      • Maurer S.G.
      • Stuchin S.A.
      Postoperative management after total hip and knee arthroplasty.
      Given the 2-to-10-fold global increase in the incidence of arthroplasty in the last 10 to 20 years, it has been emphasized that the evaluation of rehabilitation of this patient group should be a priority.
      • Harmer A.R.
      • Naylor J.M.
      • Crosbie J.
      • Russell T.
      Land-based versus water-based rehabilitation following total knee replacement: a randomized, single-blind trial.
      In Europe, aquatic therapy, such as pool exercise, is commonly used in the aftercare of this patient group. Aquatic therapy, in general, has been reported to have a number of advantages
      • Ahlqvist J.
      Hydrotherapy has had and has a rationale.
      : the immersion in water relieves body-weight and allows patients to move their operated leg more easily, resulting in patients reporting a sense of pleasure while exercising in water.
      • Mannerkorpi K.
      • Nyberg B.
      • Ahlmen M.
      • Ekdahl C.
      Pool exercise combined with an education program for patients with fibromyalgia syndrome A prospective, randomized study.
      The viscous resistance of water protects the joint and leads to the development of increased muscular strength. By altering the movement velocity in water, different resistances can be achieved. The hydrostatic pressure supports reabsorption and gives the patient a sense of security while standing. Because pool exercises require continuous balance response, muscular coordination is improved.
      • Erler K.
      • Anders C.
      • Fehlberg G.
      • Neumann U.
      • Brucker L.
      • Scholle H.C.
      Objective assessment of results of special hydrotherapy in inpatient rehabilitation following knee prosthesis implantation.
      It has been argued that it may be “the combination of reduced gravity, hydrostatic force and warm water temperature”
      • Cochrane T.
      • Davey R.C.
      • Matthes Edwards S.M.
      Randomised controlled trial of the cost-effectiveness of water-based therapy for lower limb osteoarthritis.
      (p4) that contributes to pain relief in the joints.
      In a Cochrane review of aquatic therapy for osteoarthritis and rheumatoid arthritis, it was concluded that the scientific evidence for aquatic therapy was weak due to methodologic quality of the studies identified, but that most of the studies demonstrated positive findings.
      • Verhagen A.P.
      • de Vet H.C.
      • de Bie R.A.
      • Kessels A.G.
      • Boers M.
      • Knipschild P.G.
      Balneotherapy for rheumatoid arthritis and osteoarthritis.
      To our knowledge, 4 studies have evaluated the effect of aquatic therapy after arthroplasty. One study demonstrated that aquatic therapy improved muscular coordination and strength after TKA, as measured by electromyographic mapping, isokinetics, and ultrasound.
      • Erler K.
      • Anders C.
      • Fehlberg G.
      • Neumann U.
      • Brucker L.
      • Scholle H.C.
      Objective assessment of results of special hydrotherapy in inpatient rehabilitation following knee prosthesis implantation.
      Another study found comparable outcomes, including the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), up to 6 months after TKA between a land-based versus a water-based rehabilitation protocol.
      • Harmer A.R.
      • Naylor J.M.
      • Crosbie J.
      • Russell T.
      Land-based versus water-based rehabilitation following total knee replacement: a randomized, single-blind trial.
      Two other studies demonstrated improved patient reported outcomes, including the WOMAC, in patients who received aquatic therapy when compared with patients who received standard conventional gym treatment, after both THA
      • Giaquinto S.
      • Ciotola E.
      • Dall'armi V.
      • Margutti F.
      Hydrotherapy after total hip arthroplasty: a follow-up study.
      and TKA.
      • Giaquinto S.
      • Ciotola E.
      • Dall'armi V.
      • Margutti F.
      Hydrotherapy after total knee arthroplasty A follow-up study.
      These authors wrote that “the hydrotherapy benefits after THA appear so evident that it is hard to conceive a lack of their early implementation in a rehabilitation protocol…”
      • Giaquinto S.
      • Ciotola E.
      • Dall'armi V.
      • Margutti F.
      Hydrotherapy after total hip arthroplasty: a follow-up study.
      (p94) However, in these studies it remained unclear as to how early aquatic therapy should be initiated.
      We are aware of no studies that have evaluated the effect of the timing of an aquatic therapy rehabilitation intervention after TKA or THA. Usually aquatic therapy is started after wound healing, that is, not before the 14th postoperative day. We hypothesized that by starting the aquatic therapy earlier, the reported beneficial effects of aquatic therapy would improve the clinical outcome, as measured by the WOMAC physical function scale.
      For this reason we randomized patients into early versus late aquatic therapy, to evaluate if the timing of aquatic therapy influences patients' health-related quality of life and patient satisfaction after hip and knee arthroplasty. Early aquatic therapy in this context was defined as starting on postoperative day 6, while late aquatic therapy was defined as starting as before, that is, on postoperative day 14.

      Methods

      We conducted a multicenter randomized controlled trial (RCT) comparing the clinical outcomes of patients who had been randomly assigned to receive aquatic therapy after 6 versus 14 days after THA or TKA. The study protocol was approved by the local ethics committee, and all participants provided written informed consent prior to participation in this study. A data and safety monitoring board monitored the study.

       Participants

      All patients who were scheduled to receive unilateral hip or knee replacement surgery at participating centers on an elective basis after diagnosis of osteoarthritis were candidates for inclusion in the study between August 16, 2003 and December 31, 2004. Exclusion criteria were: (1) a history of septic arthritis, (2) hip or knee fracture, (3) intraoperative complications, (4) revision arthroplasty, (5) rheumatoid arthritis, (6) amputations, (7) malignancy, and (8) inability to complete the questionnaires because of cognitive or language difficulties.
      Information about the study was handed out to participants on the day of admission to the hospital. Eligible patients were identified by the admitting physicians and were approached to participate in the trial by either the admitting physician or a study coordinator. Patients providing written informed consent were then enrolled in the trial.
      Participating centers are all located in the northernmost state of Germany. These are 2 orthopedic departments of university hospitals, 1 department of surgery at a municipal hospital, and 1 department of orthopedics at a rural hospital.

       Randomization Scheme

      All patients had an equal probability of assignment to the groups. External randomization was achieved by means of computer-generated lists (Microsoft Excela) in blocks of 20, stratified by participating hospital. At the time of enrollment of each participant, the coordinating center was notified via telefax, where the study nurse added them to the list in sequential order. After surgery, the result of the randomization was faxed back to the participating hospital, thereby avoiding that the study participants or surgeon knew of the randomization results beforehand (allocation concealment).
      • Moher D.
      • Schulz K.F.
      • Altman D.G.
      The CONSORT statement: revised recommendations for improving the quality of reports of parallel-group randomised trials.
      The method of generation of the randomization lists was unknown to the participating hospitals. Due to the nature of the intervention, blinding of the study participants and physiotherapists was not possible.

       Intervention

      Participants were randomized into 2 groups: 1 group received aquatic therapy as pool exercise after the completion of wound healing on the 14th postoperative day, while the other group received this aquatic therapy beginning on the 6th postoperative day with the wound covered with a waterproof adhesive dressing (Op-Siteb). In both groups the aquatic therapy was performed for 30 minutes for 3 times a week up to the 5th postoperative week. In both groups the pool exercises aimed at training of proprioception, coordination, and strengthening, with the aid of float cuffs, training kickboards, and bar floats.
      • Erler K.
      • Anders C.
      • Fehlberg G.
      • Neumann U.
      • Brucker L.
      • Scholle H.C.
      Objective assessment of results of special hydrotherapy in inpatient rehabilitation following knee prosthesis implantation.
      Apart from the interventions, both groups participated in a standard postsurgery program of daily physiotherapy, consisting of range of motion activities, exercises for improvement of muscle tension, venous return, balance, coordination and gait, and instruction in activities of daily living, including transfers, walking, and negotiation of stairs and uneven surfaces. In patients with knee replacement surgery, continuous passive motion machines were used on a daily basis after removal of suction drains. All patients were given analgesics according to a standard scheme.
      Special attention was given so that all therapies, with the exception of the timing of aquatic therapy, were not affected by the study. At the beginning of the study, all hospital physiotherapists were informed in detail about the study.

       Outcomes

      The primary outcome was self-reported physical function 3-, 6-, 12-, and 24-months postoperatively. This was measured by means of the WOMAC,
      • Bellamy N.
      • Buchanan W.W.
      • Goldsmith C.H.
      • Campbell J.
      • Stitt L.W.
      Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee.
      using a validated translated version.
      • Stucki G.
      • Meier D.
      • Stucki S.
      • et al.
      Evaluation of a German version of WOMAC (Western Ontario and McMaster Universities) Arthrosis Index.
      Secondary outcomes consisted of leg specific stiffness and pain, both measured by the WOMAC; the physical component summary of the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36),
      • Bullinger M.
      German translation and psychometric testing of the SF-36 Health Survey: preliminary results from the IQOLA Project International Quality of Life Assessment.
      • Ware Jr, J.E.
      • Kosinski M.
      • Bayliss M.S.
      • McHorney C.A.
      • Rogers W.H.
      • Raczek A.
      Comparison of methods for the scoring and statistical analysis of SF-36 health profile and summary measures: summary of results from the Medical Outcomes Study.
      the Lequesne-Hip/Knee-Score,
      • Lequesne M.G.
      • Mery C.
      • Samson M.
      • Gerard P.
      Indexes of severity for osteoarthritis of the hip and knee Validation−value in comparison with other assessment tests.
      and a question on patient satisfaction.
      • Katz J.N.
      • Phillips C.B.
      • Poss R.
      • et al.
      The validity and reliability of a Total Hip Arthroplasty Outcome Evaluation Questionnaire.
      For the WOMAC, responses were recorded on a visual analog scale with terminal descriptors. Scores were added for each category and standardized to a score of 0 to 100, with higher scores indicating more pain, more stiffness, or more dysfunction.
      All patients were asked to answer the questionnaire at the time of hospital admission. During hospital stay, the study nurse visited the patient to ensure that the questionnaire was filled in completely.
      After 3, 6, 12, and 24 months, participants were mailed a questionnaire with a prepaid return envelope. Nonresponding participants were reminded by mail up to 3 times at intervals of 2 weeks. Participants still not responding were contacted by telephone to determine the reason for not responding.
      Data were entered into a database (Microsoft Accessa) at the coordinating center. There were no changes to trial outcomes after the trial commenced.

       Minimal Clinically Important Improvements

      The interpretation of the results of RCTs has emphasized statistical significance rather than clinical importance.
      • Chan K.B.
      • Man-Son-Hing M.
      • Molnar F.J.
      • Laupacis A.
      How well is the clinical importance of study results reported? An assessment of randomized controlled trials.
      The lack of emphasis on clinical importance has been reported to lead to frequent misconceptions and disagreement regarding the interpretation of the results of clinical trials and a tendency to equate statistical significance with clinical importance.
      • Chan K.B.
      • Man-Son-Hing M.
      • Molnar F.J.
      • Laupacis A.
      How well is the clinical importance of study results reported? An assessment of randomized controlled trials.
      In some instances, statistically significant results may not be clinically important and, conversely, statistically insignificant results do not rule out completely the possibility of clinically important effects.
      • Chan K.B.
      • Man-Son-Hing M.
      • Molnar F.J.
      • Laupacis A.
      How well is the clinical importance of study results reported? An assessment of randomized controlled trials.
      To allow readers to interpret the clinical importance of trial results from their own perspective, the concept of the minimal clinically important difference has been introduced.
      • Chan K.B.
      • Man-Son-Hing M.
      • Molnar F.J.
      • Laupacis A.
      How well is the clinical importance of study results reported? An assessment of randomized controlled trials.
      The minimal clinically important difference is defined as the “smallest treatment effect that would result in a change in patient management, given its side effects, costs and inconveniences.”
      • Chan K.B.
      • Man-Son-Hing M.
      • Molnar F.J.
      • Laupacis A.
      How well is the clinical importance of study results reported? An assessment of randomized controlled trials.
      (p1197)
      To assess whether the statistical significant differences observed in the present study represent clinically meaningful change, we compared the observed differences of the primary outcome to previously published thresholds for the minimal clinically important improvements that were stratified to the severity of the disease.
      • Tubach F.
      • Ravaud P.
      • Baron G.
      • et al.
      Evaluation of clinically relevant changes in patient reported outcomes in knee and hip osteoarthritis: the minimal clinically important improvement.
      These thresholds are 5.3 WOMAC function units for knee osteoarthritis, stratified for a WOMAC function score of 35.3 or less; and 2.6 WOMAC function units for hip osteoarthritis, stratified for a WOMAC function score of 38.2 or less.
      • Tubach F.
      • Ravaud P.
      • Baron G.
      • et al.
      Evaluation of clinically relevant changes in patient reported outcomes in knee and hip osteoarthritis: the minimal clinically important improvement.

       Power Analysis

      For the power analysis we chose an effect size d of .30, and a significance level of .05. Based on the .80 power to detect a significant difference (P=.05, 2-sided), 176 patients were required for each study group. Because we expected a loss to follow-up of about 25% to 30%, we increased the number of recruited patients accordingly.
      Because it was unknown whether the effect of the timing of aquatic therapy would differ between patients with knee and hip arthroplasty, we prespecified separate analyses for these groups.

       Statistical Analysis

      All analyses were conducted according to the intention-to-treat principle. Baseline data were examined for differences. Continuous follow-up data were initially tested for normative distribution with the Kolmogorov-Smirnov test. Because many of them deviated from such a pattern, the nonparametric Mann-Whitney U test was used to determine differences between groups. Categorical data (patient satisfaction) were compared using chi-square tests. All P values are 2-tailed; no corrections were made for multiple comparisons. Effect sizes d,
      • Altman D.G.
      • Schulz K.F.
      • Moher D.
      • et al.
      The revised CONSORT statement for reporting randomized trials: explanation and elaboration.
      as the standardized differences between 2 groups, were calculated as described by Cohen.
      • Cohen J.
      Statistical power analysis for the behavioral sciences.
      Statistical analysis was performed using SPSS.c

      Results

       Participants

      In total, 502 patients were candidates for participation in the study. Of these, a total of 465 underwent randomization. The recruitment process and participant flow, including losses and exclusions after randomization, are outlined in figure 1.
      Figure thumbnail gr1
      Fig 1Consolidated Standards of Reporting Trials participant flow chart. Abbreviations: BKA, below knee amputation; CVA, cerebrovascular accident; F-U, follow-up; POD, postoperative day.
      No statistically significant pretreatment differences existed among the study groups (table 1), suggesting that the randomization procedures produced well balanced and comparable groups at baseline.
      Table 1Baseline Characteristics
      Hip ArthroplastyKnee Arthroplasty
      CharacteristicEarly Aquatic Therapy (n=138)Late Aquatic Therapy (n=142)Early Aquatic Therapy (n=87)Late Aquatic Therapy (n=98)
      Age (y)66.7±10.369.1±9.868.5±8.670.9±7.5
      Body mass index
      low asterisk Body mass index is the weight in kilograms divided by the square of the height in meters.
      27.6±4.426.8±4.629.3±5.029.3±4.6
      Sex ratio (men:women)50:8854:8826:6126:72
      WOMAC physical function score
      Range from 0 to 100 with lower scores representing better quality of life.
      57.3±21.454.8±22.753.1±24.850.2±24.4
      WOMAC pain score
      Range from 0 to 100 with lower scores representing better quality of life.
      54.8±23.252.4±25.153.1±24.850.2±24.6
      WOMAC stiffness score
      Range from 0 to 100 with lower scores representing better quality of life.
      57.7±25.652.0±27.651.4±31.748.6±31.5
      SF-36, physical component summary
      Higher scores representing better quality of life.
      28.1±6.726.8±8.229.0±7.928.5±6.5
      SF-36, mental component summary
      Higher scores representing better quality of life.
      47.7±12.550.4±11.449.4±12.046.9±12.6
      Lequesne-Hip/Knee-Score
      § Lower scores representing better quality of life.
      11.9±3.211.6±3.111.0±3.111.4±3.0
      Number of comorbidities
       None15 (51.7%)14 (48.3%)10 (38.5%)16 (61.5%)
       One45 (48.9%)47 (51.1%)18 (43.9%)23 (56.1%)
       Two or more78 (49.1%)81 (50.9%)59 (50.0%)59 (50.0%)
      Additional limitation due to
       Contralateral same great joint33 (55.9%)26 (44.1%)32 (42.1%)44 (57.9%)
       Ipsilateral adjacent great joint22 (40.7%)32 (59.3%)7 (53.8%)6 (46.2%)
       Contralateral adjacent great joint17 (45.9%)20 (54.1%)3 (60.0%)2 (40.0%)
       Low back pain53 (49.5%)54 (50.5%)35 (53.0%)31 (47.0%)
       Upper extremities6 (30.0%)14 (70.0%)9 (40.9%)13 (59.1%)
       Feet10 (47.6%)11 (52.4%)11 (64.7%)6 (35.3%)
      Diagnosis
       Osteoarthritis131 (49.1%)136 (50.9%)86 (47.3%)96 (52.7%)
       Femoral head necrosis/Ahlbäck's disease7 (53.8%)6 (46.2%)1 (NA)2 (NA)
      NOTE. Values are mean ± SD or as otherwise indicated.
      Abbreviation: NA, not applicable.
      low asterisk Body mass index is the weight in kilograms divided by the square of the height in meters.
      Range from 0 to 100 with lower scores representing better quality of life.
      Higher scores representing better quality of life.
      § Lower scores representing better quality of life.
      Overall, 417 patients completed the postal questionnaire at 3 months, resulting in a follow-up rate of 90%. The follow-up rate dropped to 85% at 6-month, 79% at 12-month, and to 74% at 24-month follow-up. There was no significant association between patients who did not respond to the follow-up questionnaire and patient baseline characteristics.

       Follow-Up (Hip Arthroplasty)

      After hip arthroplasty, all mean WOMAC subscales at all follow-up intervals were better in the group starting aquatic therapy after wound-healing. This effect was not statistically significant for any of the outcomes at any time, however (table 2).
      Table 2Outcomes 3, 6, 12, and 24 Months After Total Joint Arthroplasty
      Hip ArthroplastyKnee Arthroplasty
      CharacteristicEarly Aquatic TherapySELate Aquatic TherapySEPEffect Size (d)Early Aquatic TherapySELate Aquatic TherapySEPEffect Size (d)
      WOMAC function score
      low asterisk Range from 0 to 100 with lower scores representing better quality of life.
       3-mo F/U21.2±18.91.820.9±17.91.6.7980.0121.9±19.42.226.8±20.72.3.0980.24
       6-mo F/U19.0±19.11.915.9±14.41.3.5200.1918.2±15.11.822.1±21.12.4.4530.22
       12-mo F/U17.1±19.51.915.5±16.01.5.9230.0917.1±16.72.121.4±21.32.5.2910.22
       24-mo F/U15.6±18.11.814.1±14.51.4.8250.0913.8±13.61.720.7±21.32.6.1170.39
      WOMAC pain score
      low asterisk Range from 0 to 100 with lower scores representing better quality of life.
       3-mo F/U13.7±15.31.413.1±14.61.3.9260.0420.1±20.02.322.5±21.72.3.3900.12
       6-mo F/U14.0±18.21.810.1±12.31.1.4980.2514.7±14.91.718.0±20.12.2.4230.19
       12-mo F/U13.1±19.21.910.4±15.11.4.5820.1613.2±15.01.817.4±22.42.6.3340.22
       24-mo F/U12.2±17.21.79.9±14.41.4.8390.159.6±11.91.515.2±19.22.3.0970.35
      WOMAC stiffness score
      low asterisk Range from 0 to 100 with lower scores representing better quality of life.
       3-mo F/U27.1±22.32.125.2±22.82.2.4500.0829.6±25.02.931.4±25.12.7.5220.07
       6-mo F/U24.0±23.42.322.4±19.91.8.9640.0823.6±21.42.525.9±26.52.9.8540.09
       12-mo F/U23.1±25.02.619.4±20.11.9.5890.1625.4±24.12.924.6±24.22.8.8710.03
       24-mo F/U20.8±23.42.316.9±18.21.7.5520.1915.2±14.11.720.4±21.72.6.3470.28
      SF-36, PCS
      Higher scores representing better quality of life.
       3-mo F/U38.6±10.41.039.3±9.70.9.4470.0737.8±8.00.936.0±8.20.9.1080.21
       6-mo F/U43.4±10.11.043.0±9.90.9.7910.0540.1±8.61.039.9±9.11.0.9540.02
       12-mo F/U43.9±10.71.144.9±9.40.9.6970.1042.0±8.91.140.9±9.91.2.4950.12
       24-mo F/U45.1±11.11.145.2±9.70.9.8080.0143.9±9.41.241.0±9.71.2.1310.31
      Lequesne-Hip/Knee-Score
      Lower scores representing better quality of life.
       3-mo F/U7.9±4.30.47.9±4.10.4.9790.009.1±3.30.49.8±3.60.4.3150.20
       6-mo F/U6.7±4.00.46.8±3.90.4.9110.028.1±3.80.48.4±4.00.4.6180.08
       12-mo F/U6.6±4.40.46.0±3.90.4.3570.167.3±3.50.48.2±4.20.5.2430.24
       24-mo F/U5.6±3.80.45.8±4.20.4.9090.046.8±3.80.57.4±3.80.5.3610.15
      NOTE. Data are mean ± SD unless otherwise indicated. All P values are based on the Mann-Whitney U test.
      Abbreviations: PCS, Physical Component Summary; F/U, follow-up.
      low asterisk Range from 0 to 100 with lower scores representing better quality of life.
      Higher scores representing better quality of life.
      Lower scores representing better quality of life.
      The effect sizes for the primary outcome ranged from .01 (3-mo follow-up, absolute difference=.30; P=.80) to .19 (6-mo follow-up, absolute difference=3.1; P=.52). Using the SF-36, the Lequesne-Hip/Knee-Score, and patient satisfaction, no differences could be detected between study groups at all follow-up intervals (see Table 2, Table 3, Fig 2, Fig 3) .
      Table 3Patient Satisfaction by Timing of Aquatic Therapy
      Hip ArthroplastyKnee Arthroplasty
      CharacteristicEarly Aquatic Therapy n (%)Late Aquatic Therapy n (%)Relative Risk
      The relative risk of answering “very satisfied” when late aquatic therapy had been performed.
      95% Confidence IntervalPEarly Aquatic Therapy n (%)Late Aquatic Therapy n (%)Relative Risk95% Confidence IntervalP
      Patient satisfaction
      low asterisk Percentage of patients that answered very satisfied to the question “How satisfied are you with the results of your joint replacement surgery?” Other possible answers were: somewhat satisfied, somewhat dissatisfied, very dissatisfied.
       3-Month F/U95 (85%)107 (82%)0.7980.40–1.57.51455 (71%)61 (70%)0.9380.48–1.84.854
       6-Month F/U92 (84%)112 (90%)1.6860.78–3.62.17858 (77%)61 (73%)0.8130.39–1.68.576
       12-Month F/U88 (88%)105 (88%)1.0230.79–2.35.95752 (75%)54 (72%)0.8410.40–1.77.613
       24-Month F/U88 (88%)97 (88%)1.0170.44–2.35.96851 (77%)51 (74%)0.8330.38–1.83.840
      Abbreviation: F/U, follow-up.
      low asterisk Percentage of patients that answered very satisfied to the question “How satisfied are you with the results of your joint replacement surgery?” Other possible answers were: somewhat satisfied, somewhat dissatisfied, very dissatisfied.
      The relative risk of answering “very satisfied” when late aquatic therapy had been performed.
      Figure thumbnail gr2
      Fig 2Physical function as measured with the WOMAC 3, 6, 12, and 24 months after early versus late aquatic therapy. Vertical bars represent SE. Abbreviations: ES, effect size; F/U, follow-up.
      Figure thumbnail gr3
      Fig 3Patient satisfaction 3, 6, 12, and 24 months after early versus late aquatic therapy. Abbreviation: F/U, follow-up. *RR: relative risk (95% confidence interval). Percentage of participants who answered “very satisfied” to the question: “How satisfied are you with the results of your joint replacement surgery?” (very satisfied, somewhat satisfied, somewhat dissatisfied, very dissatisfied).

       Follow-Up (Knee Arthroplasty)

      After knee arthroplasty, however, all mean outcomes were better in the early aquatic therapy group at 3-, 6-, 12-, and 24-month follow-up. The only exception to this finding was a slightly better WOMAC stiffness score for the late aquatic therapy group at 12-month follow-up (effect size=.03). All these effects were not statistically significant, however (see Table 2, Table 3, Fig 2, Fig 3).
      The effect sizes for the primary outcome WOMAC physical function ranged from .22 at 6-month follow-up (absolute difference=3.9; P=.45) to .39 at 24-month follow-up (absolute difference=6.9; P=.12).

       Adverse Effects

      After knee arthroplasty, 5 patients of the early aquatic therapy group (because of limited range of motion of knee [n=2], intraarticular effusion of knee, diabetes, cerebrovascular accident) and 1 of the late aquatic therapy group (because of limited range of motion of knee) were readmitted to the hospital within 3 months. Of these, the first 3 of the early aquatic therapy group and 1 of the late aquatic therapy group could be directly or indirectly related to the intervention.
      After hip arthroplasty, 10 patients of the early aquatic therapy group (because of dislocation of hip, wound dehiscence, thrombosis [n=2], intestinal perforation, shunt revision, supervision after fall, abscess, appendicitis, pneumonia) and 4 of the late aquatic therapy group (because of dislocation of hip, wound dehiscence, pulmonary embolism, pulmonary edema) were readmitted to the hospital within 3 months. Of these, the first 2 adverse effects of the early aquatic therapy group and the first 2 of the late aquatic therapy group could be directly or indirectly related to the intervention.

      Discussion

      This is the first study, to our knowledge, to examine the influence of the timing of a single rehabilitation intervention, here the timing of aquatic therapy after hip and knee joint replacement surgery, on physical function, pain, joint stiffness, and quality of life. These dimensions of health-related quality of life are recommended as a rationale for the implementation of the most adequate standard of care.
      • Ethgen O.
      • Bruyère O.
      • Richy F.
      • Dardennes C.
      • Reginster J.Y.
      Health-related quality of life in total hip and total knee arthroplasty A qualitative and systematic review of the literature.
      This randomized study showed that the use of early aquatic therapy has opposite effects in terms of health-related quality of life after THA when compared with TKA. After TKA, early aquatic therapy led to clinically important improved patient outcomes when compared with late aquatic therapy. After hip arthroplasty, on the other hand, the results of this study indicate that early aquatic therapy should be avoided.
      In addressing the clinical importance, commonly comparing effect sizes
      • Matthews J.N.
      • Altman D.G.
      Statistics notes Interaction 2: compare effect sizes not P values.
      is recommended, especially in systematic reviews and meta-analyses.
      • Liberati A.
      • Altman D.G.
      • Tetzlaff J.
      • et al.
      The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate healthcare interventions: explanation and elaboration.
      • Moher D.
      • Cook D.J.
      • Eastwood S.
      • Olkin I.
      • Rennie D.
      • Stroup D.F.
      Improving the quality of reports of meta-analyses of randomised controlled trials: the QUOROM statement Quality of Reporting of Meta-analyses.
      The effect sizes of the primary outcome for our intervention ranged from .01 to .19 after hip arthroplasty and ranged from .22 to .39 for knee arthroplasty. Therefore, these effect sizes for the intervention are rather consistent after knee arthroplasty, but inconsistent after hip arthroplasty. The effect sizes after knee arthroplasty exceeded the pooled effect size of .20 that was obtained from a meta-analysis of randomized placebo controlled trials for reduction in functional disability by nonsteroidal anti-inflammatory drugs (NSAIDs) in osteoarthritis of the knee.
      • Bjordal J.M.
      • Ljunggren A.E.
      • Klovning A.
      • Slordal L.
      Non-steroidal anti-inflammatory drugs, including cyclo-oxygenase-2 inhibitors, in osteoarthritic knee pain: meta-analysis of randomised placebo controlled trials.
      Therefore, the effect size of early aquatic therapy after knee arthroplasty is in the same range as the effect size of NSAIDs in osteoarthritis of the knee.
      The clinical importance of our findings is supported by the concept of the minimal clinically important improvements,
      • Tubach F.
      • Ravaud P.
      • Baron G.
      • et al.
      Evaluation of clinically relevant changes in patient reported outcomes in knee and hip osteoarthritis: the minimal clinically important improvement.
      because the published specific threshold of 5.3 WOMAC function units for the primary outcome is exceeded in our study (6.9 WOMAC function units at 24-mo follow-up).
      As baseline data showed that patients were homogeneous between the groups, there is no evidence that factors other than the timing of aquatic therapy could have influenced the outcomes. However, several patients after THA were randomized to early aquatic therapy, but did not receive early aquatic therapy for various patient specific reasons. This noncompliance with assigned therapy may mean that the conducted intention-to-treat analysis underestimates the real treatment effect.
      • Altman D.G.
      • Schulz K.F.
      • Moher D.
      • et al.
      The revised CONSORT statement for reporting randomized trials: explanation and elaboration.
      According to a recent review,
      • Ethgen O.
      • Bruyère O.
      • Richy F.
      • Dardennes C.
      • Reginster J.Y.
      Health-related quality of life in total hip and total knee arthroplasty A qualitative and systematic review of the literature.
      age, sex, operated joint, primary or revision surgery, comorbidities, and baseline characteristics are known to influence the health-related quality of life after total joint arthroplasty (TJA). All these factors cannot be influenced by the physician. On the other hand, studies in which patients were randomized to different prosthetic types have failed to demonstrate a significant effect of different surgical procedures on health-related quality of life.
      • Ethgen O.
      • Bruyère O.
      • Richy F.
      • Dardennes C.
      • Reginster J.Y.
      Health-related quality of life in total hip and total knee arthroplasty A qualitative and systematic review of the literature.
      Also, there appears to be no effect of inpatient compared with home-based rehabilitation.
      • Mahomed N.N.
      • Davis A.M.
      • Hawker G.
      • et al.
      Inpatient compared with home-based rehabilitation following primary unilateral total hip or knee replacement: a randomized controlled trial.
      Recently, an association of hospital and surgeon procedure volume with patient centered outcomes has been described.
      • Katz J.N.
      • Mahomed N.N.
      • Baron J.A.
      • et al.
      Association of hospital and surgeon procedure volume with patient-centered outcomes of total knee replacement in a population-based cohort of patients age 65 years and older.
      Therefore, this is one of the few studies demonstrating a clinically important effect on the health-related quality of life after TKA by a factor that can be influenced by health care professionals, apart from procedure volume.
      Looking at these findings, it should be noted that the intervention was simple to administer, requiring only limited extra input from health care professionals.
      We chose 3 and 6 months as the appropriate study interval because the most improvement in postoperative physical health takes place during this time.
      • Ethgen O.
      • Bruyère O.
      • Richy F.
      • Dardennes C.
      • Reginster J.Y.
      Health-related quality of life in total hip and total knee arthroplasty A qualitative and systematic review of the literature.
      We added a 12- and 24-month study interval to standardize our research with that of other authors who have analyzed health-related quality of life after TJA.
      • Ethgen O.
      • Bruyère O.
      • Richy F.
      • Dardennes C.
      • Reginster J.Y.
      Health-related quality of life in total hip and total knee arthroplasty A qualitative and systematic review of the literature.
      Similarly to other studies concerned with health-related quality of life,
      • Ethgen O.
      • Bruyère O.
      • Richy F.
      • Dardennes C.
      • Reginster J.Y.
      Health-related quality of life in total hip and total knee arthroplasty A qualitative and systematic review of the literature.
      the current study was not designed to analyze long-term implant failure. This issue has been extensively addressed previously.
      • Finerman G.A.
      • Dorey F.J.
      • Grigoris P.
      • McKellop H.A.
      Total hip arthroplasty outcomes.
      We hypothesize that the weak effect of the timing of aquatic therapy after THA is due to the ceiling effect of that procedure, with a high rate of patient satisfaction and improvement of health-related quality of life due to THA alone, thereby leaving only a limited space for improvement by additional interventions. After TKA, on the other hand, a significantly higher number of patients is not satisfied,
      • Ranawat C.S.
      • Ranawat A.S.
      • Mehta A.
      Total knee arthroplasty rehabilitation protocol: what makes the difference?.
      leaving room for the effect of additional interventions.
      We assume that, apart from the known advantages of aquatic therapy, the hydrostatic force of water immersion reduces effusion of the operated knee joint. Because the joint capsule is closed after TKA, the reduction of effusion leads to less pain inhibition, and leading to an advantage in functional recovery. As the joint capsule is not closed during THA, this mechanism does not apply to THA.
      The present study has several strengths. It is an RCT in a multicenter setting, performed at university, rural, and municipal hospitals, ensuring a high external validity. Furthermore, this setting provided a broader coverage of surgical experience levels when compared with a mono-center study. We also used the WOMAC as the primary outcome score, which is recommended in this setting.
      NIH Consensus Statement on Total Knee Replacement.

       Study Limitations

      Although the study has several strengths, there are limitations. First, we conducted separate analysis of knee and hip arthroplasty, because it was unknown beforehand if the effect of the intervention would differ between these patient groups. These separate analyses, however, resulted in a smaller number of patients for the subanalyses with the subanalyses being underpowered. These underpowered subanalyses have increased probability of failing to demonstrate statistically significant differences, as in our study.
      Second, while this study has a 90% follow-up rate at 3 months and 85% at 6 months, the follow-up rate dropped to 79% at 12 months and to 74% at 24 months. Because the results of the 24-month follow-up are quite similar to the results of the 3 earlier follow-ups, it appears unlikely that a more complete 24-month follow-up would have altered the study result.
      Third, although the eligibility criteria were fairly broad, the trial was restricted to patients undergoing unilateral primary total joint replacement. Therefore, our results cannot be transferred to patients undergoing revision or bilateral total joint replacement.
      Fourth, in our study the study nurse visited the patient after randomization to ensure that the questionnaire was filled in completely. Because this study nurse also handled the randomization lists, it could be argued that the nurse as an outcome assessor was not blinded to the randomization result. However, given the large number of patients involved in the study it is unlikely that the nurse remembered the randomization status when checking the preoperative questionnaire for completeness. In addition, in most cases the number of questions not already filled in by the participant was very small, leaving only limited room for the study nurse to possibly influence the questionnaire result. Besides, by this mechanism the nurse could have only affected the baseline measure. The study nurse could not have influenced the postoperative outcome, because a mail-in questionnaire was used for that purpose. Moreover, the nurse was not aware of which questions were to be used as an outcome measure. The calculation of outcomes measures was performed by the authors. Therefore, it appears unlikely that the nurse as an outcome assessor could have influenced the study results.
      Fifth, we have compared early versus late beginning of aquatic therapy after TKA and THA. We did not compare aquatic therapy with no aquatic therapy or other types of physical therapy for a number of reasons: beneficial effects of aquatic therapy have been reported in three
      • Erler K.
      • Anders C.
      • Fehlberg G.
      • Neumann U.
      • Brucker L.
      • Scholle H.C.
      Objective assessment of results of special hydrotherapy in inpatient rehabilitation following knee prosthesis implantation.
      • Giaquinto S.
      • Ciotola E.
      • Dall'armi V.
      • Margutti F.
      Hydrotherapy after total hip arthroplasty: a follow-up study.
      • Giaquinto S.
      • Ciotola E.
      • Dall'armi V.
      • Margutti F.
      Hydrotherapy after total knee arthroplasty A follow-up study.
      of the four reports
      • Harmer A.R.
      • Naylor J.M.
      • Crosbie J.
      • Russell T.
      Land-based versus water-based rehabilitation following total knee replacement: a randomized, single-blind trial.
      • Erler K.
      • Anders C.
      • Fehlberg G.
      • Neumann U.
      • Brucker L.
      • Scholle H.C.
      Objective assessment of results of special hydrotherapy in inpatient rehabilitation following knee prosthesis implantation.
      • Giaquinto S.
      • Ciotola E.
      • Dall'armi V.
      • Margutti F.
      Hydrotherapy after total hip arthroplasty: a follow-up study.
      • Giaquinto S.
      • Ciotola E.
      • Dall'armi V.
      • Margutti F.
      Hydrotherapy after total knee arthroplasty A follow-up study.
      dealing with aquatic therapy after TKA or THA. Withholding a group from aquatic therapy could lead to an unacceptable reduction of compliance, because patients in our country expect aquatic therapy after total joint arthroplasty. For this reason we randomized patients to early versus late aquatic therapy, assuming that the beneficial effects of aquatic therapy would improve the clinical outcome if started sooner after surgery.

      Conclusions

      The present study demonstrates that the timing of physiotherapy measures, such as aquatic therapy, has clinically relevant effects after knee arthroplasty. Although not statistically significant, the effect size of the timing of the intervention is clinically relevant after knee arthroplasty because it is in the same range as NSAIDs in the treatment of osteoarthritis of the knee. However, the results of this study do not support the use of early administration of aquatic therapy after hip arthroplasty.
      Therefore, further research is warranted to identify the optimal time frame for the start of aquatic therapy after TKA in order to exploit the potential of aquatic therapy for improving clinical outcome after TKA. Most importantly, however, this study demonstrates that the timing of physiotherapeutic interventions has opposite effects after TKA when compared with THA and therefore the timing of physiotherapeutic interventions has to be carefully planned if studies are performed to evaluate the effect of physiotherapeutic rehabilitation after TKA and THA.
      • a
        Microsoft Inc, One Microsoft Way, Redmond, WA 98052.
      • b
        Smith & Nephew, 15 Adam St, London WC2N 6LA, UK.
      • c
        SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606.

      References

      1. NIH Consensus Statement on Total Knee Replacement.
        NIH Consens State Sci Statements. 2003; 20: 1-32
        • Enloe L.J.
        • Shields R.K.
        • Smith K.
        • Leo K.
        • Miller B.
        Total hip and knee replacement treatment programs: a report using consensus.
        J Orthop Sports Phys Ther. 1996; 23: 3-11
        • Duggal N.
        Improving orthopedic outcomes: focus on rehabilitation.
        Orthopedics. 2007; 30 (341): 339
        • Youm T.
        • Maurer S.G.
        • Stuchin S.A.
        Postoperative management after total hip and knee arthroplasty.
        J Arthroplasty. 2005; 20: 322-324
        • Harmer A.R.
        • Naylor J.M.
        • Crosbie J.
        • Russell T.
        Land-based versus water-based rehabilitation following total knee replacement: a randomized, single-blind trial.
        Arthritis Rheum. 2009; 61: 184-191
        • Ahlqvist J.
        Hydrotherapy has had and has a rationale.
        Rheumatology (Oxford). 2002; 41: 1070-1071
        • Mannerkorpi K.
        • Nyberg B.
        • Ahlmen M.
        • Ekdahl C.
        Pool exercise combined with an education program for patients with fibromyalgia syndrome.
        J Rheumatol. 2000; 27: 2473-2481
        • Erler K.
        • Anders C.
        • Fehlberg G.
        • Neumann U.
        • Brucker L.
        • Scholle H.C.
        Objective assessment of results of special hydrotherapy in inpatient rehabilitation following knee prosthesis implantation.
        Z Orthop Ihre Grenzgeb. 2001; 139 ([German]): 352-358
        • Cochrane T.
        • Davey R.C.
        • Matthes Edwards S.M.
        Randomised controlled trial of the cost-effectiveness of water-based therapy for lower limb osteoarthritis.
        Health Technol Assess. 2005; 9 (iii-xi, 1-114)
        • Verhagen A.P.
        • de Vet H.C.
        • de Bie R.A.
        • Kessels A.G.
        • Boers M.
        • Knipschild P.G.
        Balneotherapy for rheumatoid arthritis and osteoarthritis.
        Cochrane Database Syst Rev. 2000; (CD000518)
        • Giaquinto S.
        • Ciotola E.
        • Dall'armi V.
        • Margutti F.
        Hydrotherapy after total hip arthroplasty: a follow-up study.
        Arch Gerontol Geriatr. 2010; 50: 92-95
        • Giaquinto S.
        • Ciotola E.
        • Dall'armi V.
        • Margutti F.
        Hydrotherapy after total knee arthroplasty.
        Arch Gerontol Geriatr. 2010; 51: 59-63
        • Moher D.
        • Schulz K.F.
        • Altman D.G.
        The CONSORT statement: revised recommendations for improving the quality of reports of parallel-group randomised trials.
        Lancet. 2001; 357: 1191-1194
        • Bellamy N.
        • Buchanan W.W.
        • Goldsmith C.H.
        • Campbell J.
        • Stitt L.W.
        Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee.
        J Rheumatol. 1988; 15: 1833-1840
        • Stucki G.
        • Meier D.
        • Stucki S.
        • et al.
        Evaluation of a German version of WOMAC (Western Ontario and McMaster Universities) Arthrosis Index.
        Z Rheumatol. 1996; 55 ([German]): 40-49
        • Bullinger M.
        German translation and psychometric testing of the SF-36 Health Survey: preliminary results from the IQOLA Project.
        Soc Sci Med. 1995; 41: 1359-1366
        • Ware Jr, J.E.
        • Kosinski M.
        • Bayliss M.S.
        • McHorney C.A.
        • Rogers W.H.
        • Raczek A.
        Comparison of methods for the scoring and statistical analysis of SF-36 health profile and summary measures: summary of results from the Medical Outcomes Study.
        Med Care. 1995; 33: AS264-AS279
        • Lequesne M.G.
        • Mery C.
        • Samson M.
        • Gerard P.
        Indexes of severity for osteoarthritis of the hip and knee.
        Scand J Rheumatol Suppl. 1987; 65: 85-89
        • Katz J.N.
        • Phillips C.B.
        • Poss R.
        • et al.
        The validity and reliability of a Total Hip Arthroplasty Outcome Evaluation Questionnaire.
        J Bone Joint Surg Am. 1995; 77: 1528-1534
        • Chan K.B.
        • Man-Son-Hing M.
        • Molnar F.J.
        • Laupacis A.
        How well is the clinical importance of study results reported?.
        CMAJ. 2001; 165: 1197-1202
        • Tubach F.
        • Ravaud P.
        • Baron G.
        • et al.
        Evaluation of clinically relevant changes in patient reported outcomes in knee and hip osteoarthritis: the minimal clinically important improvement.
        Ann Rheum Dis. 2005; 64: 29-33
        • Altman D.G.
        • Schulz K.F.
        • Moher D.
        • et al.
        The revised CONSORT statement for reporting randomized trials: explanation and elaboration.
        Ann Intern Med. 2001; 134: 663-694
        • Cohen J.
        Statistical power analysis for the behavioral sciences.
        2nd ed. Lawrence Erlbaum Associates, Hillsdale1988
        • Ethgen O.
        • Bruyère O.
        • Richy F.
        • Dardennes C.
        • Reginster J.Y.
        Health-related quality of life in total hip and total knee arthroplasty.
        J Bone Joint Surg Am. 2004; 86-A: 963-974
        • Matthews J.N.
        • Altman D.G.
        Statistics notes.
        BMJ. 1996; 313: 808
        • Liberati A.
        • Altman D.G.
        • Tetzlaff J.
        • et al.
        The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate healthcare interventions: explanation and elaboration.
        BMJ. 2009; 339: b2700
        • Moher D.
        • Cook D.J.
        • Eastwood S.
        • Olkin I.
        • Rennie D.
        • Stroup D.F.
        Improving the quality of reports of meta-analyses of randomised controlled trials: the QUOROM statement.
        Lancet. 1999; 354: 1896-1900
        • Bjordal J.M.
        • Ljunggren A.E.
        • Klovning A.
        • Slordal L.
        Non-steroidal anti-inflammatory drugs, including cyclo-oxygenase-2 inhibitors, in osteoarthritic knee pain: meta-analysis of randomised placebo controlled trials.
        BMJ. 2004; 329: 1317
        • Mahomed N.N.
        • Davis A.M.
        • Hawker G.
        • et al.
        Inpatient compared with home-based rehabilitation following primary unilateral total hip or knee replacement: a randomized controlled trial.
        J Bone Joint Surg Am. 2008; 90: 1673-1680
        • Katz J.N.
        • Mahomed N.N.
        • Baron J.A.
        • et al.
        Association of hospital and surgeon procedure volume with patient-centered outcomes of total knee replacement in a population-based cohort of patients age 65 years and older.
        Arthritis Rheum. 2007; 56: 568-574
        • Finerman G.A.
        • Dorey F.J.
        • Grigoris P.
        • McKellop H.A.
        Total hip arthroplasty outcomes.
        Churchill Livingstone, Secaucus1998
        • Ranawat C.S.
        • Ranawat A.S.
        • Mehta A.
        Total knee arthroplasty rehabilitation protocol: what makes the difference?.
        J Arthroplasty. 2003; 18: 27-30