Enhancing Post Operative Rehabilitation following Knee Arthroplasty – Physicool Study

Enhancing Post Operative Rehabilitation following Knee Arthroplasty Using a New Cryotherapy Product – a Prospective Study

Pavlou P. MBBS BSc(hons) FRCS (Tr&Orth) 1

Mumith A. MBBS BSc MRCS3

Barrett MD. MBBCh MRCS2

Thurston B. BMBCh1

Garrett SJW. BM MRCS FRCS(Tr&Orth) 1

  1. Department Of Trauma & Orthopaedics, Dorset County Hospital, Dorchester, UK.
  2. Department Of Trauma & Orthopaedics, Royal Hampshire County Hospital, Winchester, UK
  3. Department Of Trauma & Orthopaedics, St. Mary’s Hospital, Newport. IOW, UK

Neither the authors nor institution received industry support to conduct this study.

Correspondence: Mr Paul Pavlou  [email protected]

Aim: To compare a novel cooling product, PhysicoolTM, with a well-established cryotherapy system, CryocuffTM ; using pain scores, range of movement and cost as outcome measures in the early phase following total knee arthroplasty.

Method: We prospectively studied 90 consecutive patients undergoing unilateral total knee arthroplasty by a single surgeon. Following exclusions, 40 patients were recruited to each group. Visual analogue scale (VAS) for pain, and range of movement before and after application of cooling device was recorded at 24 and 48 hours after surgery.  The cost of treatment per patient was also calculated.

Results: Pain scores were significantly reduced in the PhysicoolTM group on day 1 post surgery (p=0.032) and day 2 (p= 0.0065) compared to the CryocuffTM group. A significant increase in range of movement was recorded in the PhysicoolTM group at 24 hours (p=0.00867) and at 48 hours (p= 0.00227) post surgery compared to the CryocuffTM group. The cost benefit of using PhysicoolTM over CrycocuffTM was approximately £25 per patient.

Conclusion: The PhysicoolTM system is a safe and effective cooling method for improving pain and range of movement in the early postoperative phase following total knee arthroplasty. Furthermore it offers substantial cost savings.

Key Words: Cryocuff, Cryotherapy, Pain, Physicool, Range of movement, Cost, TKA


Total Knee Arthroplasty (TKA) is one of the most successful operations in terms of patient reported quality of life outcomes and as a result approximately 89,000 procedures were performed in England and Wales in 201216. However, despite significant long term benefits in mobility, pain, function and health related quality of life, the initial rehabilitation following surgery remains challenging7,19.

Enhanced recovery programs have been used successfully to improve early pain management, range of movement, blood loss and hospital stay3,4,11,12,13. Cooling devices used as part of enhanced recovery programs have been shown to reduce pain, hasten discharge and promote greater movement in the early post operative phase following total knee arthroplasty9,10.

Cooling devices deliver localised cryotherapy which works by reducing intra-articular temperature and thus slowing the neuronal conduction of both C- and A- Delta – pain fibres.1,14,15 Small decreases in temperature have also been shown to reduce enzyme activity in inflammation and as a result reduce the inflammatory response15. Due to these molecular and cellular level actions, cryotherapy reduces localised swelling and perceived pain. In addition, a decrease in the measured blood loss has been shown following application of cryotherapy, presumably due to vasoconstriction in response to the reduced temperature17

There are a number of commercially available cryotherapy systems used following TKA. The most recent Cochrane review supported their safety and efficacy.2 However, concerns have been raised due to the potential inconvenience to patients and the cost effectiveness of these devices.

The aim of this study is to compare a novel cooling product, PhysicoolTM, with a well-established cooling system, CryocuffTM. The outcome measures were post-operative pain, improvement in range of movement and cost savings.  Both devices are used in our institution as part of our knee arthroplasty Enhanced Recovery Programme (ERP).


The CryocuffTM device consists of four elements: A cooling reservoir that is filled with water and ice, a compression cuff that wraps around the knee and is secured by VelcroTM straps with an aperture anteriorly for the patella, a connecting tube that exchanges water between the cuff and the reservoir and an insulation disc which helps keep the water and ice cold. Once the cuff has been applied and connected to the filled reservoir, the air vent on the reservoir is opened and is raised to no more than 15 inches above the knee for thirty seconds to fill the cuff. The air vent is then closed and the reservoir can be disconnected from the cuff. In order to re-circulate the water, the reservoir is reattached, lowered and warmed fluid is free to pass into the cooler where it can mix with the ice to be cooled. After a minute or two the filling process can be repeated. It is recommended that an initial fluid change be performed after 15 minutes and then hourly for up to 6 hours, without refilling the reservoir.

The PhysicoolTM system safely employs the cooling effects of latent heat evaporation rather than traditional direct external cooling. It utilises a cotton bandage soaked in an ethanol based solution. A pre-soaked bandage, stored in resealable foil pouch is wrapped around the knee on top of a waterproof dressing and secured with the pre-attached self-grip strap. The cooling effect lasts for approximately 2 hours, by which time the bandage will have become dry.  It can either be recharged by spraying the cooling fluid directly to the bandage in situ or it can be re-rolled and placed in the re-sealable bag with additional cooling solution.



We performed a prospective audit to evaluate PhysicoolTM , a novel cryotherapy device against CryocuffTM in patients undergoing primary total knee arthroplasty by a single surgeon (SG) using his default surgical technique. All patients were operated on in one hospital between March 2011 and February 2012.

During this period all patients were managed as part of a protocol driven Enhanced Recovery Program. Pre-operative information leaflets including expected length of stay were routinely used. Patients were pre-assessed prior to surgery and attended on the day of their operation to a dedicated admission unit. Patients received either spinal or general anaesthesia depending on their preference and clinical indications. Thigh tourniquets were in place for the entire procedure in all patients. The Triathlon Knee® (Stryker, ???location USA) system was used in all patients through a medial para-patellar approach. Local anaesthetic infiltration using standardised volume, concentration and technique was routinely used. A retransfusion drain was inserted prior to closure and removed on the first post-operative day.  An integrated care pathway was used to record a patient’s progress throughout the admission and post-operative rehabilitaion was standardised.

Power Calculation

Following a pilot study, a power calculation revealed that 40 patients in each group would be sufficient to show a significant difference in outcomes.

Patient Selection

Ninety consecutive patients were entered into the study. Consent was obtained from all patients and their rights were protected at all times. Exclusion criteria included any patients who had cryotherapy discontinued for any reason, any wound complications and any patients with incomplete data sets.

Ten patients were excluded in accordance with the exclusion criteria, leaving 80 patients; 40 patients in each group. The two groups were well matched. There was no significant difference in age or sex in either group (Table 1)

Outcome measures

Primary outcome measures were pain and range of movement (ROM). Pain was assessed using a visual analogue scale (VAS) and range of movement using a goniometer. Scores and ROM were recorded before and thirty minutes after application of the cooling device on the first and second post-operative day. The patients were often discharged home on the third post operative day.

Data Collection

Data collection was performed by physiotherapists. All data for each patient was recorded on a custom designed data collection form. The patient hospital number was recorded on the cover sheet with subsequent pages for recording pain and ROM for each post-operative day. Although all physiotherapists were appropriately trained and briefed on the methodologies of the study, these were also detailed within this tool. Data was kept in a secure location throughout the study period.

The devices were assigned on the first post-operative day.  Both devices were applied in the first instance by a physiotherapist. Following this, the patient was responsible for re-application of the device, unless they were unable to do so.

In the cryocuffTM group, ice and water changes were performed by physiotherapists or nursing staff. The physicoolTM group recharged the bandage themselves when they perceived the cooling benefit to have diminished,


All methodology and data collection was approved and conformed to the Hospital Trust audit protocols.



The data sets from the two independent groups were compared using Student’s t-test statistical analysis. Graphpad Prism® Version 5 (Graphpad Software, San Diego, California) was used to analyse the data. A p-value<0.05 was considered statistically significant.


Range of movement: On day 1 the improvement in range of movement in the CryocuffTM group was 12 degrees compared to 20 degrees in the PhysicoolTM group. This was statistically significant (p = 0.00867) (Figure 1)

On day 2, the improvement in the CryocuffTM group was 9 degrees compared to 16 degrees in the PhysicoolTM group. This was statistically significant (p = 0.00227) (Figure 2)

Pain: On day 1 the improvement in pain score in the CryocuffTM group was 1.2 compared to 1.7 in the PhysicoolTM group. This was statistically significant (p = 0.03218) (Figure 3)

On day 2 the improvement in the CryocuffTM group was 0.8 compared to 1.7 in the PhysicoolTM group. This was statistically significant (p = 0.00065) (Figure 4)

Cost: The cost of a PhysicoolTM pre-soaked bandage and sufficient additional cooling fluid is £21. The cost of a CryocuffTM is £44, excluding the cost of water and ice production, which is difficult to quantify. The cooling reservoirs cost £80 each, and are replaced as required. Patients are not able to take them home with them due to the cost.

Cost savings of approximately £23 per patient were estimated accounting for the cost of disposables, replacement cooling reservoirs and ice. This equates to a potential saving of £8050 per year based on 350 Total Knee Arthroplasties performed annually.


A recent Cochrane meta-analysis concluded that potential benefits of cryotherapy on postoperative pain and range of motion may be too small to justify its use, when balanced against potential inconveniences and expense of using cryotherapy2. With increasing constraints on resources and pressure on hospital beds our department has successfully introduced enhanced recovery to reduce the length of inpatient stay without an increase in readmission rate.

The CryocuffTM system of cryotherapy, whilst used successfully in our department’s Enhanced Recovery Program, is not without its limitations. The bulkiness of the cuff limits full knee flexion. The lack of constant flow compared to more technologically advanced but expensive cooling devices may limit its effectiveness of cooling, and regular ice and water changes are labour intensive. The ice reservoirs are expensive and designed to be reusable, it is therefore impractical for patients to take them home.  Currently we do not have an option for patients to purchase the reservoirs.

In view of these factors we wanted to find a cooling product, which addressed the shortfalls of the CryocuffTM system, without increasing cost. The PhysicoolTM system is easy to apply and recharge.  Owing to its lack of bulk it does not limit knee flexion whilst in-situ on the limb. Furthermore it remains effective once taken home by the patient for continued use. No complications were associated with the use of PhysicoolTM either in our study or in the literature.

Our results show that the PhysicoolTM system was significantly better at providing pain relief and improving ROM compared to the Cryocuff TM system on both the first and second post operative days. We believe this difference continues following discharge from hospital. In addition, using the PhysicoolTM system provides a modest cost saving of £23 per patient, which multiplied by 350 knee replacements over the course of a year would save £8050 in an averaged size department.


There are some limitations associated with our study design. We accept that this was not a randomised blinded study and therefore results are susceptible to bias. In view of the nature of the cryotherapy devices, patient blinding is not feasible. It may, however, have been possible to blind assessors, though due to resource and time limitations this was not included in our methodology.

Whilst there was no control group it was felt that sufficient evidence exists to support the efficacy of cryotherapy versus placebo for the outcome measures we examined. Previous work has shown CryocuffTM to be superior to compression bandages and external ice at reducing pain and improving early range of movement.6,20,21

Furthermore, we did not examine analgesic requirements between the two groups, although previous meta-analysis has shown a reduction in analgesia requirement with cryotherapy5.

Pain scores and range of movement data were only recorded for the first two post-operative days. The mean length of stay of TKA patients in our department is 4.2 days, with a significant number of patients being discharged on the 3rd post-operative day. As no provision for measurement following patient discharge was made we felt a shorter follow up was preferable to multiple incomplete data sets.

We used VAS as it provides a simple and validated scoring system18. Intra-observer variability was controlled by having the same physiotherapist recording pre and post cryotherapy measurements with a goniometer; however, no mechanisms were put in place to control inter-observer variability.

Some patients reported that the cooling fluid soaked bandage caused dampness on bed sheets and clothing, and some found the odour of the cooling fluid unpleasant.  Application of the device can be challenging for those with poor manual dexterity.


This study clearly demonstrates the superiority of the physicoolTM cryotherapy system over that of the CryoCuffTM method for patients undergoing total knee arthroplasty when considering pain scores, range of movement and cost in the early post-operative period.

In addition to the acute post-operative phase of knee arthroplasty, cryotherapy has been used successfully following several arthroscopic procedures, particularly cruciate ligament reconstruction22. It has been used to reduce both the recovery time from traumatic injuries and in the treatment of chronic sporting injuries. It would seem likely that the advantage of PhysicoolTM over CryocuffTM would be similar in these situations, so this study could prompt the exploration of the use of the PhysicoolTM system in a wide range of operative and non-operative scenarios.


This study shows that the PhysicoolTM system is a viable alternative to other available cooling methods.  It is relatively inexpensive and easy for the majority of patients to apply.

It allows patients to mobilise without removing the device and can be used following discharge.

This is the first study demonstrating that the PhysicoolTM system improves pain and range of movement in the acute post-operative phase following TKA. We have shown it to be more effective in reducing pain and in increasing range of movement of the knee and also more cost effective compared to the CryocuffTM system.


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