Cooling of the Knee After Total Knee Arthroplasty

Postoperative pain, swelling, blood loss, and delayed functional recovery are common challenges after total knee arthroplasty (TKA). Cryotherapy has been proposed as a simple, non-invasive adjunct therapy to reduce these postoperative problems. However, published evidence is inconsistent because of differences in cooling devices, application duration, and study methodology.

This randomized controlled clinical trial aims to evaluate the clinical effectiveness of a standardized cooling protocol using a Cool Down liquid bandage compared with ice package cooling and a standard postoperative protocol without cooling in patients undergoing primary TKA. All patients receive the same implant design and standardized surgical and perioperative management.

Patients are randomized into three parallel groups: Cool Down liquid bandage cooling, ice package cooling, or no cooling. Cooling is initiated 24 hours postoperatively and continues for two weeks, three times daily. Passive knee motion using a continuous passive motion (CPM) machine is applied in all groups according to the same rehabilitation protocol.

The primary outcome is postoperative pain intensity measured by the Visual Analog Scale (VAS) at 48 hours after surgery. Secondary outcomes include opioid consumption expressed in morphine milligram equivalents (MME), changes in hemoglobin and erythrocyte levels, knee range of motion, knee swelling, and length of hospital stay.

The study is designed to clarify whether standardized postoperative knee cooling provides measurable clinical benefits and may help define evidence-based postoperative care pathways after total knee replacement.

• Cool Down Liquid with Bandage ( CoolDown, CH) (Device): The CoolDown Bandage is intended for postoperative local cooling and is capable of reducing skin and subcutaneous tissue temperature by approximately 7°C. Its proposed clinical benefits include reduction of postoperative pain, swelling, surgical-site bleeding, and opioid consumption. The bandage is designed to be applied directly over the surgical field for 2 hours per session, three times daily, allowing for prolonged and controlled cooling. This represents a significant advantage compared with conventional cryotherapy using ice packs, where the recommended application duration is typically limited to 10 minutes per session, three times daily, due to risks of cold-related tissue injury.This treatment should be started 24 hours after surgery.
• Ice package cooling system (Other): * Application of an ice package over the operated knee * Cooling initiated 24 hours after surgery * Cooling performed for 2 weeks postoperatively * Frequency: 3 times daily * Duration: 10 minutes per session * Cooling combined with passive knee motion using a continuous passive motion (CPM) machine according to the standard rehabilitation protocol
• Standard Postoperative Protocol Without Cooling (Other): * Standard postoperative care without cooling * Passive knee motion using a CPM machine according to the same standard rehabilitation protocol

Primary outcomes

• Visual Analog Scale [From 24 hours to 14 days postoperatively (assessed at 24, 36, and 48 hours and at postoperative days 5, 7, and 14]: VAS (Visual Analog Scale) is a simple and widely used tool for measuring subjective pain intensity. It consists of a straight horizontal line, usually 10 cm long, with endpoints representing: 0 = no pain 10 = worst pain imaginable The patient marks a point on the line that best corresponds to their current pain level. The distance from the "no pain" end to the patient's mark is measured in centimeters or millimeters to quantify pain intensity.

Secondary outcomes

• Total opioid consumption [from 48 hours to 2 weeks postoperatively]: Total opioid consumption during hospitalization and up to 2 weeks postoperatively was quantified and standardized by conversion to morphine milligram equivalents (MME). MME represents a normalized measure of opioid exposure that accounts for differences in potency among various opioid agents. All administered and prescribed opioid doses were converted to their equianalgesic morphine dose using established opioid conversion tables, allowing direct comparison of cumulative opioid use across patients and treatment groupsAfter discharge, patients were instructed to prospectively record all analgesic medications consumed, including drug name, dosage, and frequency, in standardized medication diaries. Diary entries were reviewed during the 2-week postoperative follow-up visit and cross-checked with prescription records to ensure accuracy
• Changes in hemoglobin (Hgb) and erythrocyte (Er) levels [Assessed on postoperative day 1 and postoperative day 3]: Serial measurements of hemoglobin (Hgb) and erythrocyte (Er) levels will be performed preoperatively and on postoperative days 1 and 3 to evaluate perioperative blood loss, hemodilution, and early hematologic recovery. The way how we desribe changes for this measure:Preoperative values (baseline) Represent the patient's starting hematologic status. Important for identifying preexisting anemia and estimating transfusion risk. Postoperative Day 1 (POD1) Typically shows the largest decrease in Hgb and Er. Reflects: Intraoperative blood loss Early postoperative bleeding Hemodilution due to IV fluids A sharp drop suggests significant perioperative blood loss. Postoperative Day 3 (POD3) Values often stabilize or partially recover. Reflects: Physiological compensation Mobilization of extravascular fluid Early erythropoietic response (though true RBC production takes longer) Continued decline may indicate ongoing bleeding or complications.
• Active knee range of motion (ROM) [Discharge day and 2 weeks postoperatively]: Active knee range of motion (ROM), defined as the maximal voluntary knee flexion and extension, was assessed using a handheld universal goniometer at discharge and at 2 weeks postoperatively, providing an objective measure of early postoperative functional outcomes.
• Knee swelling measured by circumferential knee measurements [Assessed at 48 hours, 7 days, and 14 days postoperatively]: Postoperative knee swelling was evaluated by standardized circumferential measurements taken with a flexible tape measure at predefined anatomical landmarks at 48 hours, 7 days, and 2 weeks after surgery, allowing objective assessment of periarticular edema.
• Length of hospital stay [days from surgery to discharge]: Hospital length of stay will be calculated as the total number of days from the day of surgery to the day of discharge and will be used as an indicator of early postoperative recovery, complication burden, and efficiency of perioperative care.

Sex: All

Inclusion Criteria:

* • Adults undergoing primary total knee arthroplasty

  * Use of a primary knee prosthesis of identical design in all patients
  * Body mass index (BMI) < 35 kg/m²
  * Ability to understand the study protocol and comply with postoperative instructions
  * Absence of diagnosed mental disease

Exclusion Criteria:

* • Unregulated or poorly controlled diabetes mellitus

  * Rheumatoid arthritis or other inflammatory arthropathies
  * Presence of mental disease impairing cooperation or protocol adherence

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