The Natural History of ACL Tears
February 1, 2000 6 minutes read
The Natural History of ACL Tears
Abstract & Commentary
Synopsis: Over a 20-year period, most patients with ACL tears required further knee surgery, had progressive dissatisfaction with knee function, had knee problems affecting sports participation, and developed progressive arthritis.
Source: Maletius W, Messner K. Eighteen- to twenty-four-year follow-up after complete rupture of the anterior cruciate ligament. Am J Sports Med 1999;27(6):711-717.
Maletius and messner from sweden previously published their 20-year follow-up for partial anterior cruciate ligament (ACL) tears, noting most patients did well, and results did not deteriorate with time.1 Maletius and Messner, using the Swedish national registry, now present their 20-year follow-up of patients with complete ACL tears.
Shortly after the introduction of arthroscopy in 1971, 60 consecutive patients were diagnosed with complete ACL tears by arthroscopy and an exam under anesthesia within one week of injury. Three-quarters of patients also had major injury of the medial collateral ligament (MCL) (repaired in 43 of 46), and 23 of 60 had meniscal tears debrided. Almost all patients had a primary suture repair of the ACL, a procedure now known to fail and no longer performed. After surgery, patients were casted for 4-6 weeks followed by a nonstructured rehabilitation program.
Patients were evaluated at a mean of 12 and again at 20 years. Amazingly, all 56 living patients were contacted and interviewed at 20 years, and 54 were available for an exam and x-rays. At 20 years post-injury, Lysholm knee scores were spread over a broad range, with only 32% scoring in the excellent range. Although three-quarters of patients returned to their same level of sports participation immediately after rehabilitation of the initial injury, they could not sustain this level of competition. Tegner scores showed an anticipated decline with age (mean age of patients was 48 at 20-year evaluation), with only 23% of patients performing at or within one level of their preinjury activity level. More important, 73% of patients complained of problems with their knee during physical activities. Seventy-three percent of patients were satisfied with their knee function immediately after rehabilitation of the original injury; however, this declined to 23% by 20 years.
Although more than 80% of patients had unstable knees by Lachman examination, the mean side-to-side difference by arthrometry testing was only 3 mm. The major complaint for these patients was pain, rather than instability, at 20 years. Indeed, compared to values of an age-matched general population, the only disparities on the SF-36 Quality of Life Survey were for questions related to knee pain and function for the patients with ACL tears. During the entire follow-up period, 25 of 56 patients underwent additional surgery, and only 43% had intact menisci at 20 years. Radiographic examination showed arthritic changes that were progressive from the 12- to 20-year evaluations. Knees that had undergone meniscectomy statistically correlated with the most severe changes. In fact, only 13% of knees had normal x-rays at 20 years.
Comment and Expanded Review by David R. Diduch, MS, MD
Because of patient and physician selection bias, and difficulty tracking a young, mobile population, few long-term natural history studies exist for ACL tears. Maletius and Messner have now provided us with two excellent longitudinal studies for partial and complete ACL tears. The 20-year follow-up of all living patients is remarkable. Although they attempted primary suture repair in most patients, this has been shown to fail, so that we can basically view this study as a natural history of knees with ACL instability. The fact that most knees had an arthrotomy, and three-fourths had open MCL repairs, does confound the results somewhat due to associated morbidity. It also demonstrates the high degree of severity of the injuries these patients suffered. The morbidity due to the initial associated injuries may affect the degree of arthritis over time and further confound the results.
Their prior paper, regarding partial ACL tears (reviewed in Sports Medicine Reports, November 1999), demonstrated that most patients did well and that knee function, pain, and laxity changed little from the 12- to 20-year evaluations.1 However, this paper demonstrates that most patients with complete ACL tears did poorly over the long term. Three-fourths of patients complained of problems with their knee during activities, were dissatisfied with their knee function, and had a decline in Tegner activity score of at least two levels. The major complaint at 20 years for these patients was pain, rather than instability, with progressive arthritic changes noted radiographically.
Degenerative changes were most closely correlated with meniscectomies. This has been well demonstrated in numerous studies.2,3,4 Although no study has ever conclusively demonstrated that reconstructing the ACL prevents arthritis, many studies that look for statistical correlations find that preserving the meniscus correlates well with the lack of arthritic degeneration. Indirectly, this argues for reconstruction of an ACL tear for a young, active patient with instability. By restoring stability and preventing "giving way" episodes, the patient can preserve the meniscus and potentially avoid arthritic degeneration. In addition, meniscal tears may be repaired with healing rates of approximately 85% in conjunction with ACL reconstruction, compared to less than half that for ACL unstable knees.5 Although late degenerative changes may be due in part to the damage to the joint at the time of injury (perhaps reflected by the bone bruises we now see on MRI scans), little can be done to affect the natural sequelae of this initial damage.6 However, repairing the meniscus tear can help unload these chondral surfaces and secondarily prevent degeneration.
Certainly, a percentage of patients will do just fine despite an ACL tear without major instability, preserving their menisci and never developing arthritis. The challenge for us as caregivers is to predict which patients will do well and not benefit from a reconstruction at the outset. Another excellent natural history paper by Daniel and colleagues provides helpful guidelines.7 As they looked at many variables associated with ACL tears, two best correlated with the group of patients who tried unsuccessfully to manage with an ACL unstable knee and returned requesting surgery. These were the degree of laxity and the amount of participation in running, jumping, and pivoting sports prior to injury. More than 7 mm of side-to-side laxity by KT-1000 arthrometer testing or more than 200 hours of sports per year placed patients at least at a moderate risk for surgery. Combinations of the two resulted in a high risk to require surgery. A 7-mm side-to-side arthrometry test may also be viewed to represent "giving way" episodes with daily activities.
In counseling patients regarding reconstruction, I consider two other relative indications in light of these studies. Coexisting meniscal tears often are repairable, offering the opportunity to preserve the meniscus. Second, young patients have many years ahead, during which they may wish to be active.
Combining information from these studies, we can better counsel our patients regarding the decision to reconstruct the ACL. We can also begin to offer a more complete picture of the natural history of an unreconstructed knee. For many practical reasons I do not think we will ever see a truly prospective study with similar patient groups randomized to ACL reconstruction vs. nonoperative treatment. This study by Maletius and Messner, despite its shortcomings, is an excellent addition to the voluminous ACL literature.
References
1. Maletius W, Messner K. Eighteen- to twenty-five-year follow-up after acute partial anterior cruciate ligament rupture. Am J Sports Med 1999;27:455-459.
2. Noyes FR, et al. The symptomatic anterior cruciate-deficient knee. J Bone Joint Surg Am 1983;65:154-162.
3. Johnson RJ, et al. The treatment of injuries of the anterior cruciate ligament. J Bone Joint Surg Am 1992; 74:140-151.
4. Daniel DM, Fithian DC. Current concepts—Indications for ACL surgery. Arthroscopy 1994;10:434-441.
5. Belzer JP, Cannon WD. Meniscus tears: Treatment in the stable and unstable knee. JAAOS 1993;1(1):41-47.
6. Faber KJ, et al. Occult osteochondral lesions after anterior cruciate ligament rupture. Am J Sports Med 1999;27(4):489-494.
7. Daniel DM, et al. Fate of the ACL-injured patient. Am J Sports Med 1994;22:632-644.
The major complaint of patients followed for 20 years with an ACL unstable knee was:
a. pain.
b. instability.
c. giving way.
d. decreased sports participation.
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