December 12, 2008 — Patients with anterior cruciate ligament (ACL) injuries may not need surgery, according to the results of a study reported in the December 15 issue of Arthritis Care & Research. At 2 to 5 years after injury, muscle strength and function were similar in patients treated with training and surgical reconstruction or training only.

“…ACL injuries are associated with the development of osteoarthritis (OA) in the long term, leading to pain, functional limitations, and decline in quality of life in the young or middle-aged adult,” write Eva Ageberg, PT, PhD, from Lund University in Lund, Sweden, and colleagues. “There is no evidence to suggest that reconstruction of the ACL prevents or reduces the rate of early-onset OA. On the contrary, the prevalence of OA may be even higher in patients with reconstructed ACL than in those with nonreconstructed ACL.”

Because the role of reconstructive surgery in restoring muscle function is unclear, the goal of this study was to evaluate muscle strength and functional performance in patients with ACL injury with or without surgical reconstruction 2 to 5 years after injury.

Of 121 patients with ACL injury enrolled in a randomized controlled trial comparing training and surgical reconstruction vs training only, 54 underwent follow-up evaluation 2 to 5 years after injury.

Mean age at follow-up was 30 years (age range, 20 – 39 years), 28% were women, and mean duration of follow-up was 3 ± 0.9 years.

Evaluation included reliable, valid single tests and test batteries for strength (knee extension, knee flexion, leg press) and hop performance (vertical jump, 1-leg hop, side hop). Analysis of variance for comparisons between groups was performed with the Limb Symmetry Index (injured leg divided by uninjured and multiplied by 100), with a Limb Symmetry Index of more than 90% considered normal.

The surgical and nonsurgical treatment groups did not differ in muscle strength or functional performance. Muscle function was normal in 44% to 89% of subjects on the single tests and in 44% to 56% in the test batteries.

Limitations of the study include lack of evidence as to whether surgical or nonsurgical treatment is best for these patients in overall outcome.

“The lack of differences between patients treated with training and surgical reconstruction or training only indicates that reconstructive surgery is not a prerequisite for restoring muscle function,” the study authors write. “Abnormal muscle function, found in approximately one-third or more of the patients, may be a predictor of future knee OA.”

The Swedish National Centre for Research in Sports, the Swedish Research Council, the Swedish Rheumatism Association, Region Skåne, the Local Research and Development Council of Göteborg and Southern Bohuslän, and the Faculty of Medicine, Lund University, supported this study. The original KANON study, from which patients were included, was also supported by Pfizer Global Research, Thelma Zoegas Fund, the Swedish National Centre for Research in Sports, and the Stig & Ragna Gorthon Research Fund.

Arthritis Care Res. 2008;59:1773-1779.

Learning Objectives for This Educational Activity

Upon completion of this activity, participants will be able to:

  1. Compare muscle strength and functional performance in patients with anterior cruciate ligament injury after surgical reconstruction with training and training only.
  2. Describe the proportion of patients who recover muscle strength and performance 2 to 5 years after anterior cruciate ligament injury.

Clinical Context

ACL injuries are associated with the development of OA in the long term, leading to pain, functional limitation, and decline in quality of life, and loss of muscle function is a predictor of OA in patients with ACL injury. Although surgical reconstruction is widely used in the United States and Sweden, it is not clear that reconstruction is associated with improved outcomes in the medium (2 – 5 years) to long term.

This is a cross-sectional cohort study conducted within another study, the Knee, Anterior cruciate ligament, NON-surgical versus surgical treatment (KANON), a randomized clinical trial examining the outcomes of reconstructive surgery with training vs training alone after ACL injury. The purpose of this study was to examine the impact of the 2 interventions on muscle strength and functional performance 2 to 5 years after the injury.

Study Highlights

  • 54 patients from the 121 in the KANON study were included in this observational study.
  • Patients were aged 18 to 35 years with a complete ACL rupture less than 4 weeks old and a moderate to high baseline activity level.
  • Both groups (with and without reconstruction) underwent a moderately aggressive training program supervised by physical therapists, which lasted 4 months.
  • The training program included a set of prespecified goals for range of motion, muscle function, and performance.
  • Excluded were patients who were pregnant or used crutches within 3 months of the assessment.
  • 54 patients (15 women) were included in the assessment of muscle strength and functional performance at a mean of 3 years after the ACL injury.
  • 36 were in the surgical reconstruction group, and 18 did not undergo reconstruction.
  • The patients rated their knee symptoms on the Swedish version of the Knee Injury and Osteoarthritis Outcome Score with 42 questions and 5 subscales, with a range of 0 (worst) to 100 (best).
  • Patients were asked to continue their usual activities of daily living before testing.
  • Before testing, patients completed a warm-up consisting of 5 minutes of stationary cycling, 2 sets of 10 squats, 2 sets of toe rises, 10 jumps on both legs, and 5 jumps on the left and right legs.
  • Muscle strength was assessed with 3 hop tests.
  • The hop tests consisted of the vertical jump (knee bent, upward jump to maximal height), 1-leg hop for distance (same foot for takeoff and landing, with hands behind the back), and the side hop (side to side jump with hands behind back).
  • Functional performance was assessed with a battery of 3 muscle power tests of the lower extremity.
  • The tests were chosen for the quadriceps (knee extension power test), hamstrings (knee flexion power test), and lower extremity muscle with use of leg press.
  • Before each test, patients completed 10 repetitions at submaximal weight, followed by 5 repetitions using a higher submaximal weight, and practice trials were performed before testing.
  • The Limb Symmetry Index value, consisting of injured leg divided by noninjured leg multiplied by 100, and absolute values were used for comparisons between groups.
  • There were no differences between the surgical and nonsurgical groups in muscle strength or functional performance.
  • Between 44% and 89% of patients had normal muscle function in single tests.
  • Between 44% and 56% of patients had normal function for the test batteries.
  • In the single tests, two thirds of patients had recovered normal muscle function and one third had not recovered muscle strength.
  • In the test batteries, only half had recovered normal function.
  • The authors concluded that reconstructive surgery for ACL injury was not associated with a higher rate of return to muscle function or functional performance at 2 to 5 years after injury.
  • They also noted that ACL injury was associated with a high rate of no recovery of muscle function at 2 to 5 years, and this could predict future OA.

Pearls for Practice

  • Patients with ACL injury who undergo training with and without surgical reconstruction have similar muscle strength and functional performance at 2 to 5 years after injury.
  • ACL injury is associated with reduced muscle strength and lower limb performance 2 to 5 years after injury.

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