Short summary

The number of severely obese patients who has knee replacement surgery is rising. Obesity increases the risk of the postoperative swelling. A complication that can cause pain and discomfort as well as complicate and prolong rehabilitation.

The aim of the present pilot study is to examine the effect of a compression stocking on postoperative swelling and pain among patients with a BMI over 30 kg/m², after total knee arthroplasty.

The hypothesis is that the use of a elastic compression stocking for 14 days postoperatively may reduce postoperative swelling by two centimeters.

The pilot study will furthermore provide useful information for feasibility which will be used to decide whether or not a larger study should be initiated.

Rationale

In Denmark approximately 9000 knee replacements were performed in 2015. Almost 7000 of the procedures performed were total knee arthroplasties.

A total knee arthroplasty is a common procedure performed as treatment for knee arthritis.

In 2015, 39,9 percent of the patients in Denmark who had knee replacement surgery were obese with a BMI  over 30 kg/m2.

The percentage of severely obese patients who has knee replacement surgery is rising and studies have shown that obesity increases the risk of postoperative complications.

A Danish cross-sectional study found that swelling with a prevalence of 90,7% was the most frequent patient-reported complication after knee arthroplasty.

A common postoperative complication after total knee arthroplasty and severe obesity increases the risk of postoperative swelling.

Postoperative swelling may impair movement of the knee, cause pain and discomfort as well as complicate and prolong rehabilitation.

Despite that, a BMI 30 kg/m2 causes more postoperative complications, obese experience the same quality of life and improvement of function after total knee arthroplasty as patients with a BMI  under 30 kg/m2 (3). The higher complication rate among the obese patients has socioeconomic consequences due to readmissions and unscheduled outpatient visits.

A study found that in the first 30 days postoperative after total knee arthroplasty 2,9 percent of the patients were readmitted. In 2015 7,3% of the patients who had primary knee replacement surgery in Denmark were readmitted within 30 days after the operation. Rossman et al. found that unscheduled outpatient visits 30 days postoperatively, were related swelling in the operated leg.                                                     

There is a need for further research on interventions that may prevent postoperative swelling after knee replacement surgery. A compression stocking is a feasible intervention.  A compression stocking is an effective treatment in the prevention of swelling. The stocking provides measured pressure against the leg, which helps the blood to move up toward the heart. By improving the blood flow, swelling is will be prevented and reduced.

A Danish randomized controlled study (RCT), that investigated the effect of a compression stocking when used for four weeks postoperatively found that the stocking didn´t have a clinical effect on postoperative swelling. However, the stocking were not applied before the day after the surgery, where seventy percent of the postoperative swelling already had occurred.

Therefore, it is relevant to investigate whether a compression stocking has an effect on postoperative swelling, when applied immediately after the operation has ended.

The aim of the present pilot study is to examine the effect of a compression stocking on postoperative swelling and pain among patients with a BMI  over 30 kg/m2, after total knee arthroplasty. The aim of the pilot study is furthermore to provide useful information for feasibility, which will be used to decide whether a larger RCT should be initiated. A future randomized controlled study that may contribute with new knowledge about the effect a compression stocking on postoperative swelling.

Description of the cohort

All patients will be recruited from Center for Planned Orthopaedic, Naestved Hospital, Denmark.

Inclusion criteria: planned for total knee arthroplasty, BMI over 30 kg/m2, aged 18 or older, speaks, reads and understands Danish and written informed consent.

Exclusion criteria: peripheral arterial disease, arterial insuffiency, no palpable pulse at the arteria dorsalis pedis, severe atherosclerosis, leg ulcers, skin disease, fragile "tissue paper" skin, neuropathy or other cause of sensory impairment, allergy to the stocking material, massive leg edema or pulmonary edema from congestive cardiac failure, deformity of the leg, or unusual leg shape or size preventing correct fit (of the stocking), or patient that cannot cooperate. For example does not understand the concept of Visual Analogue Scale (VAS) or is not able to use the compression stocking or pregnancy.

Patients who meet the inclusion criteria, and none of the exclusion criteria and wish to participate in the pilot study will be enrolled. Patients will be randomized to the intervention group or the control group. A web-based randomization program will perform block randomization on the day of admission before surgery.

Data and biological material

The intervention group will receive a thigh compression stocking (http://www.sw.dk/Struva-23), which is to be used for 24 hours a day for 14 days after surgery.

The control group will receive conventional treatment, a compression bandage applied straight after surgery and later removed on the night of the surgery.

Primary outcome measure is swelling of the knee. Secondary outcome measures are swelling of the calf, ankle and pain. Measurements will be taken on the day of admission before surgery and at days 1, 2 and 14 after surgery. All measurements of knee, calf and ankle will be taken in millimeters.

Assessment of pain will be measured using a 100-mm visual analogue scale at rest and when walking.

Feasibility outcome measures will be used to decide whether or not a larger study should be initiated. The predefined criteria are:

1. reduction of swelling over 1 cm in the intervention group compared to the control group
2. written consent
3. compression stocking used for 14 days

Predefined percentages for the tree criteria have been defined to indicate whether or not a larger study should be initiated.