What factors affect outcome after ACL injury?

There are numerous studies in the literature investigating factors of significance for outcome after anterior cruciate ligament (ACL) reconstruction. Physical factors, such as incidence of giving way, quadriceps muscle strength and number of additional knee injuries at the time of ACL reconstruction and subsequent arthroscopy, as well as psychosocial factors, for example fear of re-injury and health locus of control have been found to affect the outcome after ACL reconstruction. It is likely that a variety of interacting factors affect the outcome after ACL injury. Different variables are probably of importance for different time periods, i.e. short-, intermediate- and long-term outcome, after ACL injury. 

We have been working on a large prospective study at the Sports Surgery Clinic and results will be published very soon but in the paper I am discussing here..

The aim of this study was to investigate factors of significance for the intermediate outcome after ACL injury evaluated by the Knee injury and Osteoarthritis Outcome Score (KOOS). The factors examined in the study included gender, age, stable personality traits, associated meniscus and/or articular cartilage injuries, treatment (non-operative or reconstructive surgery), additional subsequent trauma to the ACL-injured knee, and activity level before injury. 

The subjects recruited from hospitals and sports medicine clinics in Stockholm, Sweden,  were between 18 and 50 years old and had sustained an ACL injury within the past 5 weeks. Twenty seven females and 30 males, mean age 32 ± 7.9 years, were included in the study; the median Tegner activity level before injury was 7 (range 5–9).

Within 5 weeks post injury, the subjects were requested to complete the Tegner score regarding activity level before injury. Furthermore, they completed the Swedish universities Scales of Personality (SSP). The SSP is a revised, updated and psychometrically evaluated version of the widely used Karolinska Scales of Personality (KSP). The inventory is designed to measure personality traits, i.e. stable personality characteristics not changing over time.

At follow-up, on average 5.6 ± 0.52 years after the ACL injury, the subjects were asked to complete the KOOS, a subjective score evaluating five areas i.e. pain, symptoms, activities of daily living (ADL), sport and recreational function and knee-related quality of life (QOL). The subjects were also requested to complete the Tegner score as well as a general questionnaire. In the general questionnaire the subjects were asked whether or not they had undergone ACL reconstruction and/or sustained any additional subsequent knee trauma for which they had received medical management. The analyses performed were based on 46 patients: 22 females and 24 males. Their mean age at inclusion was 32 ± 8.1 years.

At follow-up, on average 5.6 years after the ACL injury, the female subjects had lower ratings in the sport and recreational function domain of the KOOS than the males (P=0.04). However, there were no significant differences in the other subscores, pain, symptoms, ADL or QOL. Age did not influence the outcome evaluated with the KOOS at follow-up. The only personality variable that significantly correlated to the KOOS total score was the embitterment scale. However, this was only significant for the subscores pain and symptoms. Subjects with high ratings in these subscores were low in embitterment. 

At follow-up, 22 out of 46 subjects (48%) had undergone ACL reconstruction with either graft from patellar tendon (n=15) or hamstrings (n=7), on average 9 months after the ACL injury. Twenty-four subjects were conservatively treated. The subjects who had been treated non-operatively had a significantly (P=0.033) better outcome in the knee-related QOL domain of the KOOS than the patients who had undergone ACL reconstruction. There were no significant differences in the other subscores, pain, symptoms, ADL or sports. 

At follow-up, 11 out of 46 (24%) subjects had altogether sustained 20 additional subsequent traumas to their ACL-injured knee, requiring medical management. Their Tegner activity level before injury tended (P=0.056) to be higher compared with the subjects who did not sustain additional subsequent trauma. Additional subsequent trauma to the ACL-injured knee significantly (P=0.003) affected the outcome 5.6 years after ACL injury. The subjects who had sustained additional trauma subsequent to their ACL injury had a worse outcome according to the KOOS than the other subjects, a difference reflected in all the subscores pain, symptoms, ADL, sports and QOL. 

Activity level before injury did not affect the intermediate outcome. The median Tegner activity level of 7 (range 5–9) before injury had decreased to 6 (range 2–9) at follow-up. Even though the median Tegner activity level before injury was 7 in both treatment groups, the operatively treated subjects had a significantly higher activity level before the ACL injury than the conservatively treated subjects (P=0.010). 

The study shows that additional subsequent trauma to a previously ACL-injured knee is a risk factor for poor future outcome. The 11 subjects, who sustained at least one additional trauma, requiring medical management subsequent to their ACL injury, had a significantly worse outcome according to the KOOS than the other 35 subjects. They also had a tendency to have a higher activity level according to Tegner before their ACL injury.

Source:Swirtun LR and Renstrom P (2008) Factors affecting outcome after anterior cruciate ligament injury: a prospective study with a six-year follow-up. Scand J Med Sci Sports 18, 318–324.