Fast Track Recovery Knee Arthroplasty Project

OBJECTIVES

The purpose of this prospective, randomized, single-blind, comparative and controlled clinical study was to evaluate a new cryotherapy device, the cTreatment® system (Waegener®, Belgium) consisting of the Cryoceutical Treatment Server 100 series (CTS) and the Cryoceutical Treatment Pad (cPad®), in comparison to the standard cooling protocol, which was the cold packs (cold/hot pack, Dahlhausen®) currently used at the Department of Orthopaedic Surgery of the Medical University of Graz, Austria, in patients undergoing primary and unilateral TKA surgery. It was particularly focused on the device's efficiency in terms of eventual improvements in the patient's postoperative rehabilitation and mobilisation, such as positive alterations of knee ROM and NRS pain scale, which were set as primary objectives. Further contributing elements, such as alterations of the analgesic consumption, knee girth and the device's safety were set as secondary objectives.

METHODS

Subjects between 18 and 90 suffering from severe degeneratively or traumatically caused gonarthritis or gonarthrosis of the knee joint scheduled for endoprothetic treatment with TKA could be included when giving their informed consent. Exclusion criteria particularly included, on the one side, reasons, which might interfere with the patients' statistical comparability regarding the outcome, such as severe pre-existing local and systemic conditions others than gonarthritis and foregone surgical interventions others than arthroscopy. On the other side it contained conditions, which would interfere with the planned study design, for instance, the standardized medication and PCA and long cooling intervals during hospitalisation.

After giving their written consent they were further randomized to the cryotherapy group, receiving the cTreatment®, or the standard group, receiving cold pack application. Therefore a web-based programme, the "Randomizer", was used (23), considering the patient's sex and scheduled design type of endoprostheses to be implanted, which was either the PFC® or the LCS® (both from DePuy®, Warsaw, IN, USA) endoprosthesis.

After being randomized to the therapy group patients were assigned to the locally applied cryotherapy treatment by use of the cTreatment® system until the end of the clinical study, which was set for POD six. That implied the first cooling session to the extent of one hour already preoperatively on the first preoperative day (PreOD), which coincidently was the day of admission throughout all cases. Furthermore, the subjects received cryotherapy immediately after TKA in the postanaesthesia care unit for six hours in total. During the in-patient setting until POD six the cTreatment® was applied each day for four hours in total, divided into two hours in the morning and two hours in the afternoon. Also there was the option to use the cTreatment® in terms of additional analgesia in the evening for up to four hours on each POD.

PreOD 1 TKA POD 1 POD 2 POD 3 POD 4 POD 5 POD 6

• 1 h pre-OP 6 h post-OP 4 h optional 2 h morning 2 h afternoon 4 h optional 2 h morning 2 h afternoon 4 h optional 2 h morning 2 h afternoon 4 h optional 2 h morning 2 h afternoon 4 h optional 2 h morning 2 h afternoon 4 h optional 2 h morning 2 h afternoon 4 h optional Table 1: cTreatment® protocol in therapy group

According to the manufacturer, the CTS is a class IIa medical device, which thermodynamically exchanges heat controlled by a built-in computer. It is able to regulate both the flow rate and the fluid's temperature reaching the cPad®. The CTS is operated by use of a touch screen, which allows to start, pause, resume and stop a cooling session. According to the instruction manual the cPad®, which is connected to the Server with flexible tubes using anti-reflux design, is made of flexible Polyurethane, latex free and hypoallergenic. Using hook and loop fasteners it is easy to wrap around the knee ensuring a maximum of contact surface.

The control group was treated abiding by the standard cryotherapy regimen at the Department of Orthopaedic Surgery including the usage of common cold packs (cold/hot pack, Dahlhausen®). They did not receive any cryotherapy before the surgical intervention corresponding to the standard regimen. After TKA cold packs were applied three times per day for 20 minutes each throughout the whole trial. In the context of blinding, the cold packs were placed beneath the applied cPads® in subjects randomized to the standard group, in order to account for a subjectively experienced cold as the CTS was turned off. Besides that, the study setting was identical in both groups.

For the purpose of a better comparability all participating patients received general anaesthesia and a postoperative analgetic therapy based on patient controlled analgesia (PCA), which was filled with diluted hydromorphone, accounting for 0,2 mg hydromorphone per single dose. In addition to that, exclusively Novalgin® 4 x 1 g was administered as a non-opiate analgesic. The PCA was removed after 72 hours postoperative.

The performed physical measurements consisted of the quantification of the knee girth and the ROM of the treated knee joint. The measurements concerning the knee girth were performed at three different levels, at middle-patella, 7 centimetres proximal of the patellar base and 7 centimetres distal of the apex patellae. The ROM was evaluated by use of a hand-held goniometer and the patient being in a supine position. Among the non-physical evaluations was verbally assessing the subjectively experienced pain intensity by use of the eleven-point numeric rating scale (NRS) pain score, about which each patients was told that zero was equal to "no pain at all" and ten was equal to "strongest pain imaginable". The NRS was always evaluated for the state of absolute rest and the state of motion. In this relation the more objectively evaluable analgesics consumption was recorded. Therefore the total hydromorphone usage administered by use of PCA after 72 hours was noted. The physical examinations of the knee joint's ROM and girth and the NRS score evaluation were performed on admission day and POD two, four and six. In the course of the regular change of dressings during the medical rounds the surgical area was exactly examined for potential cold-induced local alterations. In this context, it was particularly searched for signs of frostbite, nerve palsy, inhibited wound healing, deep vein thrombosis and infection. In case of occurrence, the patients had also been told to immediately call attention to eventual adverse effects related to the cold therapy, which they were preliminarily informed about.

IBM® SPSS® Statistics software version 20 was used in order to perform all statistical analyses. In this regard descriptive statistics were conducted using basic calculations of means, standard deviations, ranges, minima and maxima. For the comparisons between the two study groups on admission day, POD two, four and six measured data was first checked for the existence of normal distribution by use of Shapiro-Wilk and Kolmogorov- Smirnov tests. In case of normal distribution, the independent-samples t-test as parametric test was performed. If a normal distribution did not exist, the Wilcoxon-Mann-Whitney test as non-parametric test was performed in order to obtain values of significance regarding between-group distinctions. Throughout the statistical analyses, the level of significance, respectively the P-value was defined as ≤ 0,05.