Timing of Aquatic Therapy for Knee, Hip Arthroplasty Matters

Nancy A. Melville

December 22, 2011

December 22, 2011 — Initiating aquatic therapy just 6 days after total knee arthroplasty (TKA) improved patient-reported outcomes compared with starting therapy 14 days after surgery, according to a randomized controlled study published online December 21 in the Archives of Physical Medicine & Rehabilitation. In contrast, waiting until day 14 to start aquatic therapy was better for patients who had total hip arthroplasty (THA).

"Although the treatment differences did not achieve statistical 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," write study authors Thoralf R. Liebs, MD, from the Department of Orthopaedic Surgery, University of Schleswig-Holstein Medical Center, Kiel, Germany, and colleagues.

Aquatic therapy is useful for THA and TKA rehabilitation because it allows patients to exercise in an environment that relieves body weight while muscular strength is gradually restored. Patients do not usually start aquatic therapy until 14 days after surgery, to allow the wound to heal. However, Dr. Liebs and colleagues hypothesized that the clinical outcome could be improved if patients started therapy sooner.

To evaluate the effect of the timing of aquatic therapy after TKA or THA, the researchers randomly assigned patients undergoing primary THA (n = 280) or TKA (n = 185) to begin the therapy either 6 or 14 days after the surgery.

The patients included 156 men and 309 women with similar baseline characteristics. The therapy included 30-minute sessions given 3 times a week, up to the fifth postoperative week, for all patients. Pool exercises were designed to improve proprioception, coordination, and strengthening. Physical function, pain, and stiffness were evaluated 3, 6, 12, and 24 months after the surgery.

The primary outcome was self-reported improvement in physical function according to the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and the results were compared with previously published thresholds for minimal clinically important improvements. The 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.

Although there were no statistically significant differences in the total study population at follow-up, separate analyses of the TKA and THA patients showed early therapy had opposite effects in the 2 groups. All WOMAC subscales improved with early therapy in TKA patients compared with in TKA patients who started therapy at day 14. The effect sizes for physical function WOMAC subscales ranged from 0.22 to 0.39.

Among the THA patients, the later-therapy group had better outcomes, with WOMAC effects ranging from 0.01 to 0.19. However, those differences were not statistically significant.

"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," the authors write.

"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."

The authors speculate that one important explanation for the greater improvement with early aquatic therapy for TKA patients is a lower level of satisfaction that TKA patients typically have after the procedure compared with hip patients.

"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," the authors explain.

"After TKA, on the other hand, a significant higher number of patients is not satisfied, leaving room for the effect of additional interventions."

Another explanation could involve the physiology of the knee joint vs the hip, they add.

"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."

Additional studies are needed to better understand the issue, the authors conclude.

The authors have disclosed no relevant financial relationships.

Arch Phys Med Rehab. Published online December 21, 2011.

 

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