Difference in Knee Joint Loading Metrics Following ACL Repair versus ACL Reconstruction

Abstract

Research Question: Do individuals who undergo a primary anterior cruciate ligament (ACL) repair (ACL-r) versus standard ACL reconstruction (ACL-R) have differences in knee joint loading metrics?

Background and Significance: injuries are one of the most common knee injuries in athletes and the general population. At this time, ACL injuries are most often treated with ACL reconstruction and even with the great advances made in technology and physician expertise, the outcomes of ACL reconstruction on joint health is bleak. Those that undergo ACL-R may result in or expedite the arthritic process and lead to articular cartilage lesions. This is hypothesized to take place due to a variety of factors, including prolonged underloading of the knee joint following surgery. Recent studies have shown that ACL-r may provide some type to the cartilage and possibly slow the effects of joint degeneration. This is said to be due to decreased surgical trauma associated with preservation of the native ACL ligament. ACL-r has been shown to benefit lower extremity and knee biomechanics and proprioception. This data is based off of older ACL-r methods and there is limited data on newer ACL-r techniques and the effect on knee joint loading. Therefore, this study is being conducted to assess the difference in knee joint loading metrics between individuals who have undergone primary ACL-r and those following standard ACL-R with a patella bone-tendon-bone autograft.

Materials and Methods: A total of 30 participants were enrolled in this study. The ACL-r group [n: 15, age(yrs): 38.8±13.9, Ht(cm): 173.4±10.0, Wt(kg): 77.9±17.5] sustained a proximal ACL disruption (Sherman Classification Type 1 or 2) that was amendable to repair, while the ACL-R group [n: 15, age(yrs): 25.60±1.7, Ht(cm): 173.5±10.3, Wt(kg): 75.4±15.6] underwent primary reconstruction with a patella bone-tendon-bone autograft. At 12 weeks post-operation, participants in both groups completed the International Knee Documentation Committee (IKDC) questionnaire and underwent biomechanical testing. Total knee joint power measured as eccentric loading (contraction) during the descent phase of the squat and bilateral peak knee extension were calculated using the average of the middle three of five repetitions of testing on both the surgical and non-surgical limb. Three months after surgery, participants also completed a quadriceps strength test on both limbs on an isokinetic dynamometer 60 °/sec. The average peak torque of five repetitions was used to calculate the limb symmetry index (LSI). To examine differences between groups, separate ANOVAS were performed for each biomechanical variable.

Results: The ACL-r had a significantly greater peak knee extension moment (ACL-r: 78.46±5.79%; ACL-R: 56.86±5.79%; p=0.019, ¿p2=.186) , as well as total knee joint power (ACL-r: 72.47±7.39%; ACL-R: 39.70±7.39%, p=0.006, ¿p2=.245) than the ACL-R group. The ACL-r group also had a significantly greater quadriceps LSI than the ACL-R group (ACL-r: 66.318±4.61%, ACL-R: 48.03±4.61%, p=0.013, ¿p2=.206).

Conclusion: Individuals who underwent ACL-r demonstrated increased knee joint loading symmetry during a single leg squat test, as well as greater quadriceps strength symmetry at 12 weeks post-operation as compared to those who underwent ACL-R.