Document Title: Halbrecht-AJSM-Jul05.shtml
Article Title: Long-term Failure of Thermal Shrinkage for Laxity of the Anterior Cruciate Ligament
Author: Jeffrey Halbrecht, MD
Publication: American Journal of Sports Medicine, Baltimore, Maryland
Date: July 2005
Volume 33, pages 990-995
Keywords: Thermal shrinkage, extremely high failure rate, anterior cruciate ligament, ACL, partial tearing, stretched graft, ACL graft failure.

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Comments: 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.

ABSTRACT

Background: Appropriate treatment for anterior cruciate ligament laxity, owing to partial tears of the native ligament or lax reconstruction, is unclear. Studies suggest that a significant percentage of these untreated tears may progress to complete tears or the patient may develop additional injuries to the meniscus or articular cartilage. Shrinkage of the ligament or graft using thermal energy has been proposed as a solution for this problem.

Purpose: To evaluate the long-term results using thermal energy to shrink laxity of the anterior cruciate ligament.

Study Design: Case series; Level of evidence, 4.

Methods: Nineteen patients with partial tears of the anterior cruciate ligament (n = 14) or stretched anterior cruciate ligament grafts (n = 5) underwent thermal shrinkage treatment. Fourteen were available for follow-up at 1 and 5 years. At 1 year, there were 12 partial tears and 2 grafts available for evaluation. At 5 years, there were 10 partial tears and 4 grafts. Preoperative, postoperative, and intraoperative stability testing was performed using the KT-1000 arthrometer. Clinical results were evaluated using the Cincinnati and Lysholm scoring systems.

Results: Intraoperative shrinkage averaged 2.12 mm (17%, P < .0001). At 1 year, 12 of the 14 patients remained stable (86%) with a negative Lachman test result and mean KT-1000 arthrometer maximum side-to-side score of 1.29 mm (P < .001). The 2 failed shrinkages were partial tears of the native anterior cruciate ligament. For these 12 patients, Cincinnati scores improved from 53 to 89 (P < .0001), and Lysholm scores improved from 55 to 89 (P < .0003). At 5-year follow-up, 11 of 13 patients had gone on to complete failure (85%, P < .002; 8/9 partial tears and 3/4 grafts).

Conclusion: Thermal shrinkage provides short-term benefit in the treatment of anterior cruciate ligament laxity but leads to catastrophic failure in the majority of patients at long-term follow-up. We can no longer recommend this procedure for the treatment of anterior cruciate ligament laxity.

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