For a brief overview of knee anatomy, physiology, and biomechanics, please click here.

Monopolar Radiofrequency Treatment of Partial-Thickness Cartilage Defects in the Sheep Knee Joint Leads to Extended Cartilage Injury, Max J. Kääb et al.; American Journal of Sports Medicine, Baltimore; October 2005, Vol 33, pages 1472-1478. The authors found that cartilage thermal shrinkage (just as it is harmful in the context of damaged knee ligaments) has no place in the realm of articular-cartilage defect repairs. They note that radiofrequency-induced damage can still be detected at 6 months post-operative; this damage probably persists well beyond this time frame. The authors found that irregular fronds of articular cartilage, a hallmark of chondromalacia, are aesthetically unpleasing but often represent viable articular cartilage. Reshaping everything with a thermal wand may make it look nicer, but will destroy its viability. (Doctors who still believe in the orthopedic use of thermal shrinkage might do well to be reminded that the thin layer of articular cartilage which covers the articulating bony surfaces is very different from the flat tar-and-gravel roofs typically found on commercial office buildings. Tar-and-gravel roofs can, in certain circumstances, be repaired by heating and smoothing out of the tar. Radiofrequency thermal shrinkage of cartilage attempts to do exactly this, yet with cartilage inside the human body. It does not work! So, the doctor might wish to consider donating his/her themal-shrinkage wand to a local roofing company.)

A Systematic Review of Prolotherapy for Chronic Musculoskeletal Pain (Critical Review), David Rabago et al.; Clinical Journal of Sports Medicine; September 2005, Volume 15(5), pages 376-80. Comments: Prolotherapy entails injecting irritating substances with the goal of causing cell proliferation. Although this study does not delve into prolotherapy for knee-ligament injuries in particular, it is apparent that prolotherapy is inappropriate for such injuries. Sue Barber-Westin, a seasoned knee researcher known internationally, has discussed this article in posting 249914.

Long-term Failure of Thermal Shrinkage for Laxity of the Anterior Cruciate Ligament , Jeffrey Halbrecht; American Journal of Sports Medicine, Baltimore; July 2005, Vol 33, pages 990-995. This article makes it abundantly and unequivocally clear that thermal shrinkage has no place in treatment of any type of ACL injury. The staggeringly high failure rate of the procedure should come as a warning to any orthopedist who still thinks that a thermal-shrinkage wand is a magical panacea for partial ACL tears, stretched-out ACL grafts (which may have stretched due to improper placement of the bone tunnels, hence surgeon error), or reinjured ACLs. The fact that ACL thermal shrinkage has a horrifically high failure rate is to be expected, given the underlying biomechanics of the knee (i.e. the huge torques exerted at the knee due to the very long lever arms of the leg bones, the enormously high dynamic loadings on the knee, and the absence of native bone stability) as well as the microscale biomechanics and histology of the ligament itself. The damage done by thermal shrinkage actually makes the shrunken structure more prone to future problems, and it kills nerve endings, denatures proteins, damages blood vessels and harms cells in general. The short-term shortening of the treated ligament tends to deceive the person into thinking the knee is normal, whereupon the person returns to pre-injury activities (even after a protracted rehabilitation period) and reinjures the knee (each knee-instability event can bring new bone-bruising and meniscal tearing)...therefore very likely ending up with a worse situation than what was the case prior to the thermal shrinkage. (This article also notes that partial ACL tears affecting more than 50% of the ACL's cross-sectional area are very likely to soon progress to complete tearing. This is to be expected, given that from structural engineering we know that tensile stress is inversely proportional to intact cross-sectional area. The authors note that minor partial tears can remain in this condition [i.e. without worsening] for many years, especially if the person is careful to avoid ACL-demanding activities.) The authors also note that thermal shrinkage, which initially appeared to be very promising for shoulder stabilization, is now also considered a poor choice in this realm too. In short, it is now safe to say that thermal shrinkage has no place in orthopedics at all.

The effect of electrothermal shrinkage on the biomechanical properties of the anterior cruciate ligament: An experimental study, Eiji Kondo et al.; Arthroscopy: The Journal of Arthroscopic & Related Surgery; April 2005, Volume 21, pp 448-456. Comments: This razor-sharp study makes it abundantly and unequivocally clear that thermal shrinkage (as done by radiofrequency, laser, or other means) has no place in the treatment of ACL injuries such as partial tearing. Thermal shrinkage was found to cause an extremely pernicious and nefarious weakening of the ligament, thus greatly heightening the worry of catastrophic injuries due to gross-knee-instability events. A procedure that was initially thought to be harmless and worth a try now turns out to be extremely dangerous and foolhardy to apply.

Critical Review of Prolotherapy for Osteoarthritis, Low Back Pain, and other Musculoskeletal Conditions: A Physiatric Perspective, Sunny R. Kim et al.; American Journal of Physical Medicine and Rehabilitation, Lippincott Williams and Wilkins; May 2004, Volume 83(5), pp 379-389. Comments: Prolotherapy, also known as sclerotherapy, essentially entails injecting irritating substances with the intent of causing cell proliferation. Serious concerns arise, especially in the context of dealing with knee-ligament injuries. These issues have been discussed in considerable detail on Bob's ACL WWWBoard. Sue Barber-Westin, an experienced clinical knee researcher of international renown, has commented on this article in posting 215494.

Does Immobilization After Radiofrequency-Induced Shrinkage Influence the Biomechanical Properties of Collagenous Tissue? An In Vivo Rabbit Study, Wolfgang Pötzl et al.; American Journal of Sports Medicine, Baltimore; April 2004, Vol 32/4, pages 681-687. Comments: This study looks at thermal shrinkage from a tissue viewpoint, and uses the patellar tendon of the rabbit. Granted, while much experience with thermal shrinkage has been gained in the context of shoulders, this article reveals that there is still much to worry about with regards to the use of thermal shrinkage for ACLs. The authors note that even with carefully done six-week immobilization periods, the treated rabbit tendons failed to completely recover their normal biomechanical properties. Also, it must be remembered that the knee of a rabbit is not subjected to proportionally the same physiological loadings as the human knee. Most notably, the human knee must deal with lever arms (tibia and femur) that are proportionally much longer than their counterparts in the diminutive rabbit; furthermore, humans are bipedal and rabbits are quadrupedal. This means that the thermal-shrinkage-related worries raised by this study are greatly amplified when human knees are being considered.

Prolotherapy Injections, Saline Injections, and Exercises for Chronic Low-Back Pain: A Randomized Trial, Michael J. Yelland et al.; Spine, Lippincott Williams and Wilkins Incorporated; January 2004, Volume 29(1), pp 9-16. Comments: Yelland et al. found that prolotherapy is no better at relieving low-back pain than simply injecting a saline (salt-water) solution; both bring a relief in pain but nothing substantive in terms of actual injury healing. Please note that with regards to treating knee-ligament injuries, prolotherapy brings a lot of very serious concerns, given the enormous biomechanical stresses that the knee is subjected too. The knee is the most vulnerable-to-injury joint in the entire body, primarily because it bears weight (i.e. dynamic loadings, not just the static weight of the body) and because it is situated at the interface of the body's two longest lever arms (tibia and femur, each of which is several times as long as any household wrench). It is both inappropriate and extremely risky to expect any injected substance to engender any type of useful knee-ligament healing, particularly in the context of the cruciate ligaments (ACL and PCL). By delaying pursuit of meaningful knee-injury treatments such as tendon-graft ACL reconstruction, prolotherapy introduces the danger of returning to knee-demanding activities with an inherently unstable knee (and therefore having the knee give way catastrophically and incur additional, permanent, and cumulative damage to articular cartilage and menisci...thereby heightening the already worrisome spectre of premature osteoarthritic degeneration). The best that can be expected with prolotherapy injections into knees is simply scarring throughout the joint space (and this in itself can be very troubling).

Radiofrequency electrothermal shrinkage of the anterior cruciate ligament, Thomas R. Carter; The American Journal of Sports Medicine, Baltimore; March-April 2002, Vol 30/2, p. 221. Comments: In this carefully-done study, Carter et al find that thermal shrinkage does not bring good results for ACLs. They conclude that the procedure is inappropriate for treating chronically lax or previously reconstructed ACLs. The mean follow-up period in this study was 20.5 months (excepting cases in which failure occurred sooner). At the time this article was submitted for printing, thermal shrinkage had failed in 11 of 18 patients, hence an aggregate failure rate of 61% overall. This translates into a staggering 86% failure rate for the people who had previously undergone reconstruction on the ACL, and a nonetheless-worrisome 45% failure rate with the patients for whom the thermal shrinkage was used as a first-time treatment (e.g. for partial ACL tearing). A major reason for the understandably disappointing performance of ACL thermal shrinkage is embodied in the enormously long lever arms of the tibia and femur, which make it impossible to completely shield the treated ACL from physiological loadings during the rehab period (even if a full-leg cast is used). Also notable is the thermal damage done to the highly biomechanically optimized helical-parallel-aligned collagen tensile-fibre structure of the ACL, along with heat-related (searing) damage to the ligament cells in general. Clearly, thermal shrinkage has no place in the realm of knee-ligament treatment. Doctors who are still using this procedure for ACLs might do well to think of the old adage: "when all you have is a hammer, everything starts to look like a nail". It should be kept in mind that, in general, stretching seems to occur more commonly with reconstructed ACLs (as compared to with original ACLs), whereas partial rending seems more common with original ACLs than with reconstructed ones; however, both stretching and tearing modes of injury occur in both original and reconstructed ACLs. (Carter found that the type of ACL damage [i.e. stretching versus tearing] did not correlate to the thermal-shrinkage failure rate.) Also, note that partial tearing in particular brings a weakening of the ligament, in accordance with the fact that tensile stress is defined as force divided by cross-sectional area...and so a halving of a ligament (i.e. 50% partial tear) immediately brings a doubling of stress in the remaining intact portion. The fact that thermal shrinkage does absolutely nothing to alleviate this unfavourable state of affairs means that the procedure is inherently just as worthless for people with nonreconstructed partly-torn ACLs as it is for people with reconstructed-but-stretched ACLs. Finally, note that the use of ACL thermal shrinkage, if it manages to bring a fleeting reduction in ACL laxity, may encourage the person to return to knee-demanding sports...whereupon the ACL can be expected to fail catastrophically, thereby resulting in almost-certain damage to the menisci and articular cartilage. So, the false hope of ACL thermal shrinkage could best be described as a bitter disappointment. For severely partly-torn ACLs (herein defined as being badly torn to the extent that the knee is rendered unstable or has manifested itself as unstable during the initial tearing event, and assuming that conservative treatment is infeasible), the best solution is standard tendon-graft reconstruction. (For first-time ACL reconstructions, the failure rates of patellar-tendon and hamstring autografting are 5% and 10%, respectively.) For unsuccessfully-grafted ACLs (i.e. the graft has failed to revascularize and reinnervate, or it has failed via stretching-out or tearing), the best solution clearly remains revision reconstruction (for which the failure rate is roughly 25%).

Creep Behavior of a Rabbit Model of Ligament Laxity after Electrothermal Shrinkage In Vivo , Andrew L. Wallace et al.; American Journal of Sports Medicine, Baltimore; January-February 2002, Vol 30/1, p. 98-102. Comments: This is an interesting article from the viewpoint of fundamental research in the realm of thermal shrinkage. Note that because thermal shrinkage is also used for shoulders, this article initially discusses this application...although the study entailed thermal shrinkage of the MCLs of rabbits, and thus is very much knee-relevant. The article provides grounds for serious concern regarding the use of thermal shrinkage for knee ligaments, specifically with regards to stretching-out of tissue and failure of the tissue to fully regain the tensile strength that is the hallmark of normal collagen. Wallace notes that the "risk of early failure or development of recurrent laxity in the first few weeks after thermal shrinkage is significant", and recommends further research with regards to rehabilitation and mobilization. Careful reading of this article (along with subsequent pondering and critical analysis) reveals that the issue of low-load viscoelastic behaviour, hence creep (manifested as stretching-out) of the treated ligament, remains a concern long after the first few weeks mentioned in the foregoing quote. Additionally, please keep in mind that the knee of a rabbit is not exposed to proportionally the same physiological loadings as the human knee. Consider that the human knee is situated at the interface of two lever arms (tibia and femur) that are proportionally much longer than their counterparts in the rabbit; furthermore, humans walk on only two legs and yet rabbits have four legs at their disposal. These factors mean that the thermal-shrinkage-related worries raised by this study are greatly amplified when human knees are being considered.

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