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Greater Assurance In Cemented Endoprosthetics
Author: Dr. Thomas Niemann, Accente Communication GmbH
Secure and reliable anchoring of the endoprosthesis in the bone guarantees a long life span and good functionality for the prosthesis. Cement-free anchoring of prostheses is usually preferable for younger patients, whereas fixation with bone cement is most common for older patients.
The manufacturing process for bone cement is complicated and requires high precision. Even the slightest deviations in the cement quality, cement mixture and application change the properties and have a significant impact on the mechanical stability of the prosthesis.
Clinical observations document service life with PALACOS®
Decades of trials in Scandinavia show how important cement quality is for service life. In the so-called ‘Sweden study’, more than 200,000 first implantations of artificial joints were recorded from 1976 onwards. 1 The parameters registered included the bone cement used. The lowest risk of revisions was found when PALACOS® was used both with, and without an antibiotic (Gentamicin). Compared with other bone cements, the risk of loosening or infection was up to 50% lower with PALACOS® cement.1 The Norwegian Hip Register also shows a decisive effect of cement quality on the service life.2
Antibiotics: Prophylaxis with a therapeutic effect
Since the 1970s, the addition of Gentamicin to PALACOS® has been an approach proven in practice to protect against infections in joint replacement operations. The rate of infections dropped from 7% to less than 1%.3 “The local application in bone cement can achieve a far higher level of effectiveness in the region of the wound than the administration of antibiotics in tablet form or by injection”, Klaus-Dieter Kühn, Head of Division, Heraeus Medical GmbH is convinced.
In an evaluation of the Norwegian Hip Register of 22,170 artificial joints, it transpires that patients who only received a systematic antibiotic have a 1.4 fold higher risk of revision.4 “The risk of an infection-related revision is 1.8 times higher for bone cements not containing antibiotics”.
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| Fig. 1: Spectrum of activity of the antibiotics gentamicin and clindamycin (mod. after Förster et al. 1988). |
Septic revisions
The operative approach towards of aseptic prosthesis loosening is a one-stage revision and largely corresponds to the initial implant apart from the treatment of bone defects. Usually a bone cement containing antibiotic is used for infection prophylaxis.
In the case of septic prosthesis loosening, a two-stage revision is currently standard. Besides removing the implanted material and excision of the necrotic bone tissue, comprehensive debridement of the bone bed is also undertaken. The prosthesis is preferably anchored with bone cement with combined antibiotic. COPAL® is the name of the Heraeus revision cement and contains effective protection of Gentamicin and Clindamycin.
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| Fig. 2: Post-Operative X-Ray of a PALACOS-cemented total hip replacement. |
COPAL® - The bone cement with two antibiotics
Studies have revealed: Significantly more Gentamicin is released in the presence of Clindamycin than without a second antibiotic.5 The synergetic mixture of Gentamicin and Clindamycin offers very good protection through the combined higher rate of release of the active substances from the bone cement. That makes COPAL® with its dual protection of Clindamycin and Gentamicin so effective.
Consistent quality and effectiveness for local antibiosis
But only a homogenous cement matrix ensures a continuous release of antibiotics. Cements with a manual mixture cannot reliably fulfil this requirement. “If industrially manufactured antibiotic bone cements are available these are preferable to manually mixed cements on account of their method of manufacture”.3 This not only ensures constant quality and effectiveness, but also the product liability lies with Heraeus – to the relief of the doctor or pharmacist.
References
- Malchau H et al: Prognosis of Total Hip Replacement; Dep. of Orthopedics Univ. Göteborg, Sweden 2002
- Espehaug B et al The type of cement and failure of total hip replacements. J Bone Joint Surg (Br) 2002; 84-B: 832-38
- Lars Frommelt, Klaus-Dieter Kühn: The Well-Cemented Total Hip Arthroplasty. Springer 2005: p.91.
- Engesaeter LB, et al: Antibiotic prophylaxis in total hip prothesis; Acta Orthop Scand 2003; 74 ):644 – 651
- Kühn KD: Bone Cements, Springer, Berlin, Heidelberg, Tokyo, 2000, p.253-62.
Manufacturer’s details for reproduction
Heraeus Medical GmbH, Philipp-Reis-Strasse 8/13; D-61273 Wehrheim
Web: www.palacos.org
The Role Of Post-operative Autologous Blood Transfusion In Protecting Future Blood Stocks
Authors: Dr David Coates, Consultant Anaesthetist, St Mary’s Nuffield Hospital, Bristol
Craig Mustoe, Product Manager, Summit Medical Ltd
Donor blood is in short supply. Despite awareness drives from the National Blood Service aimed at encouraging more people to donate, the risk of a shortage continues to loom. Under normal circumstances, where supply meets demand, enough blood is available to satisfy requirements and it is fair to say that normal circumstances, for the most part, tend to prevail. However, the question that raises concerns is what happens when the normal becomes abnormal and, most importantly, how will allocation of blood be prioritised in the event of a shortage?
The Integrated Blood Shortage Plan was implemented in 2005 by the Chief Medical Officer’s Blood Transfusion Committee with a view to answering this question by developing a national framework for the management of both acute and chronic blood shortages. This has strong links to a previous publication circulated by the Department of Heath in 2002 called Better Blood Transfusion 2 (BBT2). The purpose of BBT2 was to ensure that there were sufficient mechanisms in hospital trusts to guarantee the most appropriate use of blood and to ensure that patients were provided with better information about blood transfusion. Key elements of both documents aim to reduce the unnecessary use of banked blood with the objective of avoiding a shortage, and also to provide a clear plan of action, including effective prioritisation of blood, should a shortage occur.
The implications, for current transfusion requirements, of an acute or chronic shortage could be quite different and resulting challenges may need to be managed differently. For instance, an acute shortage of blood caused by a flu epidemic, or similar situation, which temporarily prevents donors from attending donor sessions may be enough to require action. However, couple this with a greater demand for blood due to an unforeseen incident requiring immediate allocation and a more critical acute shortage may occur. Management of such an event could include immediate awareness campaigns encouraging people to donate and may also be donor driven with donors themselves volunteering additional blood in order to provide assistance. Situations such as this have occurred when the need for blood is a particularly public event, such as in the aftermath of 9/11 and the London bombings in July 2005.
Legislative Measures
Additionally, there is a risk of surgical cancellations being employed in order to help manage shortages. Indeed, in June 2005, hospitals in Ireland were called upon to cancel all elective surgery over a period of 4 days due to a shortage of blood. Legislative reasons were cited as one of the driving forces behind these cancellations and it is such reasons that could lead to the acute shortages of today becoming the chronic shortages of tomorrow. More recently (June 2007), it was identified that only 3 days stock of some blood groups were available in Scotland.
UK legislation set in 2004 prevents anyone who has received a blood transfusion since 1st Jan 1980 from donating blood due to the risk of transmission of vCJD. In Ireland, the legislation extended to anyone who had lived in the UK for a year or more between 1980 and 1996. In the UK, the legislation resulted in a reduction in the donor pool of around 55,000 donors. This has undoubtedly had a significant impact on the current and future availability of blood. On top of this, the much discussed implementation of a vCJD screening test has led to fears of more donors refusing to continue making donations due to concerns surrounding the potential socioeconomic effects of an individual knowing, and in some cases having to declare (for example for the purposes of life assurance) that they are a carrier. With these issues plus the fact that fewer younger people are donating, increasing the average age of donors, there are, unsurprisingly, continued concerns about the potential for chronic supply problems.
The key to success surely lies with avoidance of the necessity to manage such a shortage by focussing on preventative measures. In the face of such potential adversity, it becomes even more important to ensure compliance with BBT2 to ensure that banked blood is only being used when it is really needed and to implement methods that may help to reduce transfusion requirements in order to avoid surgical cancellations and, in the worst case, the need to prioritise blood allocation in emergencies. With Better Blood Transfusion 3 due for publication imminently, there is likely to be renewed interest and action in the blood transfusion arena and a continued drive towards further improvements.
Avoiding the unnecessary use of blood through post-operative ABT
So, how can the unnecessary use of blood be avoided? In the first instance, elective surgery can be targeted because the ability to be able to plan carefully can lead to an understanding of the likely volume of blood loss and allow for the use of methods to reduce banked blood use. Around 6% of blood transfusions in the UK are administered to patients undergoing elective hip and knee replacement surgery 1. With around 2 million units of red cells being issued per year in the UK 2 the total requirement for hip and knee replacements is around 120,000 units. With donors eligible to donate approximately every 16 weeks, this represents an annual donor capacity of around 40,000 donors and could, therefore, provide a valuable resource for transfusion in areas where alternative measures are not indicated.
One increasingly important method of reducing the need for transfusion is post-operative autologous blood transfusion (ABT). This is a simple method requiring the placement of a wound drain at the surgical site which is in turn connected to a collection device that provides a vacuum for suction of blood from the wound. The blood is then returned to the patient post-operatively through filtration. The filtration capability of the device is ultimately important as blood collected from orthopaedic surgery can contain undesirable materials such as bone and bone cement fragments, activated white cells, complement proteins and fat particles, the re-infusion of which could lead to clinical complications. Such devices have been in use in the UK for around 20 years and have an excellent track record for reducing the need for homologous transfusion.
Historically, the use of these devices has been focussed on total knee replacement (TKR) surgery - the use of a tourniquet rendering the vast majority of the blood loss post-operative. There have been many instances where a reduction in the transfusion requirements has been demonstrated 3,4,5 and, on top of avoiding additional risks 6,7, has contributed to other benefits such as reduced patient length of hospital stay 3, reduction in infective episodes 3 and a reduction in the risk of transfusion transmitted infections such as HIV, Hepatitis and vCJD 7. Indeed, a number of studies recommend the routine use of ABT when performing TKR 4,8,9.
With the pressure always on to further reduce transfusion requirement, the use of post-operative ABT systems has also extended to total hip arthroplasty (THA) with total hip replacement (THR) being the most common surgical indication for transfusion accounting for 4.6% of all blood used 1.
Although perhaps not used as widely as with TKR, post-operative ABT has mainly been used on revision hips as the expected blood loss post-operatively warrants caution and transfusion rates can be quite high. However, progress is also being made with the use of these devices in primary hips and significant reductions in the requirement for banked blood have been shown 10.
In order to ensure that the most appropriate transfusion alternatives are available, and particularly if using post-operative ABT, it is advisable to reduce the intra-operative blood loss as far as possible. There are various methods for the reduction of intra-operative blood loss that are currently employed in THA and successful implementation of these can result in an increase in the proportion of total blood loss that occurs post-operatively. This means that any transfusion requirement is likely to be more closely related to post-operative blood loss than blood lost intra-operatively making post-operative ABT the most appropriate autologous solution.
The following case studies demonstrate how appropriate patient management can help to reduce blood transfusion requirements in primary THA.
Case 1: Queen’s Medical Centre (QMC), Nottingham
Malcolm Chambers (Transfusion Practitioner / Autotransfusion course co-ordinator, QMC) presented the findings of a transfusion audit at the AfPP Congress in 2006. The audit was aimed at determining the best process of care for patients undergoing THR in order to minimise post-operative transfusion requirement. QMC adopted a 3 stage approach considering blood conservation activities in the pre-operative, intra-operative and post-operative settings. These included pre-assessment of patients in outpatient clinics in order to maximise haemoglobin levels prior to surgery. Patients not meeting the minimum criteria were referred back to their GP in order to receive the necessary treatment for anaemia. Intra-operatively, cell salvage was employed along with, if indicated, the use of antifibrinolytic drugs. This was followed by the use of post-operative ABT. The process of patient care was designed such that it met the requirements of the individual patient based on pre-assessed clinical indicators.
The move to this approach came about as a result of the transfusion audit which showed that 43.5% of Primary Total Hip Replacements (PTHR) patients were being transfused with 35.3% receiving two or more units. 10.5% of patients were transfused intra-operatively with 100% transfused post-operatively. Of those transfused post-operatively, 36.1% had lost 400-600ml of blood after completion of surgery. Since full implementation, the blood ordering schedule has changed from a 4 unit cross match in PTHR (6 unit cross match for revisions) to group and save only in PTHR and a 2 unit cross match for revisions due to confidence in the ability of post-operative ABT to reduce homologous transfusion requirements.
Case 2: St Mary’s Nuffield, Bristol
Dr David Coates (Consultant Anaesthetist, St Mary’s Nuffield) presented information regarding the use of post-operative ABT use in THA at the AfPP Congress in 2005. The findings of an audit showed transfusion rates of 40% with routine cross-matching for every patient. The use of hypotensive anaesthesia in order to reduce intra-operative blood loss has meant that post-operative ABT has become an important part of the transfusion reduction programme and enabled St Mary’s to come away from the more complex intra-operative machines 11. Since implementing a protocol including post-operative ABT for use in THA, transfusion rates have dropped to 5% and routine cross-matching no longer takes place. Cross-matching adds expense to the transfusion process and will now only take place if the patient arrives for surgery with a clinically low Hb level, or if the routine group and save identifies unusual antibody presence.
More recently, Dr Coates has noted that, although transfusion requirement has dropped at St Mary’s Nuffield in Bristol, there are still many locations throughout the UK where potentially avoidable transfusions are still taking place and where, therefore, significant improvements in transfusion practice could be achieved with the right protocols in place.
Future considerations affecting the UK blood supply
The advantage of focussing on elective orthopaedic procedures is twofold. Firstly, 6% of all blood used is accounted for by hip and knee replacements and the nature of elective surgery means that careful planning can help reduce the requirement for banked blood. There have been many other reasons to consider the need to plan including donor shortages and inherent risks associated with the use of donor blood and, as time goes on, further implications continue to arise.
The inclusion of prion filtration in the routine processing of donated blood, aimed at reducing the risk of transmission of vCJD, is imminent, with fears of additional cost burden on hospitals performing transfusions. The vCJD screening test which is largely anticipated, but as yet with no clear timetable for implementation, has led to fears that the donor pool could reduce by up to 50% due to paranoia over potential social implications for known carriers. Indeed, current donors struck from the register due to increased risk may have previous transfusions traced back through the transfusion history in order to identify recipients who may, therefore, also be at risk. This method of managing risk and attempting to cut vCJD off at the source could have the knock on effect of removal of further potential donors from the donor pool.
With these changes in the logistics of blood donation and the consideration of potentially adverse clinical implications, a counter change is required in transfusion practice to ensure that the availability of blood for patients who have a genuine and unavoidable requirement for blood is unchanged. If the blood required cannot be made available through donation, then it must be made available through appropriate use programmes and alternative methods.
Better Blood Transfusion 2 has provided a platform for significant improvements in blood transfusion practice and, undoubtedly, there has been a reduction in the inappropriate use of blood. Indeed, in 2005-6, there was a 4.4% reduction in red cells issued over the previous year 2 providing a good indicator that appropriate use programmes are working. Better Blood Transfusion 3 is due for publication this year and will undoubtedly maintain emphasis on the need to reduce inappropriate blood use and should build on the momentum gained through previous publications. It is, however, ultimately down to actions in the clinical arena to ensure successful implementation of protocols in line with requirements. So, by understanding current usage and through the use of resources empowered to focus on blood transfusion practice, further improvements are possible. And let’s not forget that success stories do exist and significant improvements have been made so sharing of knowledge and experience could result in rapid action. A symptomatic blood shortage looms closer and the quicker we act, the more likely we are to avoid what is often billed as “the inevitable”.
References
- A W Wells, P J Mounter, C E Chapman, D Stainsby, J P Wallis. Where does blood go? Prospective observational study of red cell transfusion in north England. BMJ 2002;325:803 (12 October)
- Blood Stocks Management Scheme annual report 2005-2006
- Newman JH, Bowlers M, Murphy J. The clinical advantages of autologous transfusion - A randomized controlled study after knee replacement. The Journal of Bone and Joint Surgery (Br) 1997 Vol. 79B pages 630-632
- Gannon DM, Lombardi AV, Mallory TH, Vaughan BK, Finney CR, Niemcryk S. An evaluation of the efficacy of post-operative blood salvage after total joint arthroplasty. The Journal of Arthroplasty, Vol. 1, No. 2, June 1991, pp 109-114
- Majkowski RS, Currie IC, Newman JH. Post-operative collection and reinfusion of autologous blood in total knee arthroplasty. Annals of the Royal College of Surgeons of England, Vol. 73, No. 6, Nov 1991, pp 381-384
- G. Senthil Kumar, O.A. Von Arx, J.L. Pozo. Rate of blood loss over 48 hours following total knee replacement. The Knee 12 (2005) 307-309
- William L. Healy et al. Evaluation of autologous shed blood for Autotransfusion after orthopaedic surgery. Clinical Orthopaedics and Related Research number 299, pp. 53-59, 1994
- Thomas Apostolou, Elias Fotiadis, Efthimios Samoladas, Anastasios Christodoulou, Panagiotis Akritopoulos, Ioannis Notaras. Allogenic versus autologous transfusions: Comparison of results following primary total knee replacement. Orthopaedics Vol. 30 No. 3 March 2007
- Hand GC, Henderson M, Mace P, Sherif N, Newman JH, Goldie DJ: Methyl methacrylate levels in unwashed salvage blood following unilateral total knee arthroplasty. Journal of Arthroplasty 1998 Aug; 13 (5) : 576-9
- David Grosvenor, Varish Goyal, Stuart Goodman. Efficacy of post- operative blood salvage following total hip arthroplasty in patients with and without deposited autologous units. Journal of Bone and Joint Surgery. 82:951 (2000)
- Utilising post-operative autologous blood transfusion following total hip arthroplasty. Dr David Coates. Clinical Services Journal, March 2006
Radiofrequency ProbesAuthors: Mr Ashok Rampurada MBBS, MRCS Ed Miss Lizzie Neville and Mr Ford Qureshi FRCS (Tr & Ortho.) - www.shoulderelbowsolutions.com
Introduction
Many instruments have been developed for modification and resection of soft tissue in knee, shoulder, elbow and ankle procedures. Thermal ablation has been the standard surgical technique for removing and treating damaged tissues. Thermal ablation has been studied in many other forms including standard electrosurgical tools, microwave, laser, high-intensity focused ultrasound and cryotherapy. All these methods of tissue decomposition have evolved to address the problems associated with high heat and potential damage to the surrounding tissue. Bipolar radiofrequency (RF) thermal ablation, known as coblation, has emerged as the most popular technology compared to other types of tissue ablation.
| Conventional Monopolar RF Electrosurgery |
RF Thermal Ablation |
Coblation |
| Interface of electrode-tissue is in excess of 400 °C, rapid tissue heating |
Usually below 100°C |
Interface temperature is between 40-70°C. |
| Deep thermal penetration, causing serious collateral tissue damage. |
Depth of heat penetration depends on heat transfer. Collateral damage is minimal if temperature of target is carefully monitored |
Localized effect; minimal thermal penetration thus minimal collateral damage. |
| Tissue along the probe’s way is cut. |
Part of the tissue between the active and ground electrodes is ablated due to heat. |
Tissue removal due to molecules disintegrating. By-products removed by suction |
History of RF ablation
During the early 20th century Ham radio operators found that radio waves caused heating that led to skin burn. In 1928, Harvey Gushing and W. T. Bovie made the first AC generator radiofrequency prototype to coagulate blood in vessels during surgery. In the 1960’s RF ablation was experimented upon different organs. In the 1970’s advances in modulation of RF waveforms led to successful RF ablation in neurosurgery and dermatologic applications. In the mid 1980’s RF ablation was first implemented for the control of cardiac arrhythmias and in 1997 coblation technique was patented.
Mechanism
RF thermal ablation is a hyperthermic process that is the use of high temperatures to cause tissue necrosis. The same frequency can be used to cut tissue (RF electrosurgery) and to seal vessels. The main differences between RF electrosurgery and RF thermal ablation is that RF electrosurgery uses high voltage and power as compared to RF ablation.
When the temperature reaches around 48°C, the RF thermal heat causes cellular depolarization. Ablation starts with heat-caused pore formation and an increase of membrane fluidity leading to an overwhelming number of calcium ions and depolarization. This effect is reversible around 48 °C with irreversible loss of tissue electrical conductivity at temperatures greater than 50°C. At 62°C creatine kinase activity decreases in addition to nuclear damage and denaturation of cystoskeletal proteins (Zipes, 2002).
The dead cells that have undergone thermal injury through this process are replaced by fibrosis and scar tissue. Over time the treated tissue will shrink due to collagen denaturation and the healing process begins. The cause of shrinkage is believed to be due to the unwinding of the triple helix of collagen.
Cobalation
When there is a very high voltage difference across two conductive materials placed in close proximity an arc is created. When there is an electrolytic solution present in the gap between the active and return electrode, a high electric field intensity caused by the high voltage difference can vaporize the electrically conducting fluid between the distal tip of electrode and the target ablation site. This causes ionization within the vaporized layer creating a plasma layer. When the electrolytic solution is isotonic saline, there are ions like sodium present due to vaporization. Later, the ionization induces the discharge of high energy electrons and/or photons from the plasma layer into the target site. These ions have enough energy to cause disintegration of organic material within the tissue.
Both ablation and coagulation in Coblation are performed in the temperature range of 40 to 70 °C. In comparison, RF electro surgery can have temperatures in excess of 400 °C. It is possible to keep the temperature in Coblation low since the current is localized near the active and return electrodes and not flowing into the tissue directly. The differences between radiofrequency and coblation surgery are shown in the following table.
Application
RF ablation is commonly used in bone, liver, kidney, lung, heart, breast, lymph nodes, nerve ganglia, and soft tissue. It has been used to treat a variety of solid tumours, including breast and prostate although it is more common in the treatment of hepatic tumours. Within the heart it is used to destroy abnormal electrical pathways in heart tissue, such as recurrent atrial fibrillation and other types of supraventricular tachycardia. RF ablation has also shown some success in initial experiments for the treatment of Obstructive Sleep Apnea (OSA).
RF coblation is used in Orthopaedic surgery for the debridement of soft tissues in knee, shoulder, elbow and ankle in orthopaedic procedures, and is used as an alternative to standard electro surgical techniques for removing and treating damaged tissues. Coblation devices are used intra-operatively to assist with haemostasis in surgery, and recently have been used to remove soft tissue in tendinopathies, particularly in sports injuries. The procedure uses a cold ablation technique, where a precisely controlled amount of radiofrequency energy is delivered that stimulates a healing response in the tissue.
The coblation is contraindicated in procedures where a conductive irrigant (e.g. Normal saline) is not used, and in patients with cardiac pacemakers or other electronic device implants.
Discussion
Most instruments used for modification and resection of soft tissues such as lasers and electrosurgical devices use heat-driven processes to remove or cut tissue, which routinely induce char (carbonisation of the tissue) at the surface. In contrast, Coblation based technology uses radiofrequency energy that is coupled with saline to cool the tissue, allowing for more precise procedures than would be performed with traditional surgical tools. Instead of exploding tissue structures under high temperatures, Coblation gently dissolves target tissue, thus minimising collateral damage to surrounding tissue, and preserving the anatomical structure of the tissue, whilst stimulating a healing response.
Several studies have confirmed that Coblation-treated tissue exhibits a rapid and effective healing response. The studies have demonstrated that because the procedure is carried out under much lower temperatures, patients treated with Coblation devices appear to recover significantly faster and with less pain than patients treated with conventional therapies.
One study compared the supraspinatus tendons from eight patients suffering with rotator cuff tears to six healthy tendons. It was found that the altered tendons exhibited a lack of vascularity, expressed by lower levels of angiogenic markers. These results confirmed that injured tendon tissue is associated with hypovascularity.
A controlled study performed on seventeen white rabbits in New Zealand studied the effects on local vascularity and healing response of bipolar radiofrequency microdebridement in normal Achilles tendons. This study demonstrated that Coblation stimulation increases the tissue vascularity as well as improving the organisation of fibroblastic cells thus promoting a healing response in the affected tendon. Studies such as these have suggested that, in addition to ablation, Coblation therapy also induces a healing response by improving vascularity. This is achieved through the production of VEGF (an angiogenic marker), the creation of local micro-vessels and an increase in local perfusion.
Conclusion
Radio frequency probes are valuable tools in orthopaedic surgery particularly in soft tissue resection. Coblation technology will further help in reducing collateral damage to surrounding tissue during arthroscopic surgeries. Larger-scale studies providing evidence for the efficacy of the Topaz Coblation radiofrequency probe are currently lacking. From early low power studies and case reports it is clear that this method of treatment involves a less invasive and less traumatic approach, and a shorter recovery time. At least in the short-term, this microdebridement system is beneficial.
References
- Bertone A, Lipson D, Kamei J et al. Effective Bone Haemostasis and Healing Radiofrequency and Conductive Fluid. Clinical orthopaedics and related research. 2006; 446: 278-285.
- Bortnick DP; Plastic Surgery Educational Foundation DATA Committee. Coblation: an emerging technology and new technique for soft tissue surgery. Plast Reconstr Surg. 2001; 107(2):614-615.
- Cook, JL, Kuroki K, Kenter K, et al. Bipolar and monopolar radiofrequency treatment of osteoarthritic knee articular cartilage: acute and temporal effects on cartilage compressive stiffness, permeability, cell synthesis, and extracellular matrix composition. J Knee Surg. 2004; 17(2):99-108.
- Khan AM, Fanton GS. Thermal energy in the knee. Techniques in knee surgery. 2004; 3(3):180-186.
- Kyes K. Radiofrequency Innovations. Orthopaedic Technology Review. Sept 2006.
- Levine MJ, Shaffer B. Basic science applications of thermal energy in arthroscopic surgery. Sports Med Arthro Rev. 2005; 13(4):186-192.
- Owens BD, Stickles BJ, Balikian P, Busconi BD. Prospective analysis of radiofrequency versus mechanical debridement of isolated patellar chondral lesions. Arthroscopy. 2002; 18(2):151-155.
- Sherk HH, Vangsness CT, Thabit G 3rd, Jackson RW. Electromagnetic surgical devices in orthopaedics. Lasers and radiofrequency. J Bone Joint Surg. 2002; 84-A(4):675-681.
- Tasto JP, Cummings J, Medlock V, et al. Microtenotomy using a radiofrequency probe to treat lateral epicondylitis. Arthroscopy. 2005; 21(7):851-860.
- Zipes, D. P., Haissaguerre, M. 2002. Catheter Ablation of Arrhythmias. New York: Futura Publishing.
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