A comprehensive in vivo kinematic, quantitative MRI and functional evaluation following ACL reconstruction — A comparison between mini-two incision and anteromedial portal femoral tunnel drilling
Introduction
Anterior cruciate ligament (ACL) tears are one of the most common knee ligament injuries that require surgical reconstruction [1]. The development of post-traumatic medial compartment arthritis is well-documented regardless of treatment, with several studies reporting increased rates of degenerative changes after ACL reconstruction [2], [3], [4], [5], [6]. There has been an increased emphasis on utilizing new methods to position the femoral tunnel in order to improve the current trend of achieving less than satisfactory mid-term and long-term results after ACL reconstruction.
The Anteromedial Portal Technique (AM) has gained popularity as it allows for all-inside placement of the femoral tunnel, independent of tibial tunnel placement. Potential pitfalls still remain with this method [7]. The tunnel length and orientation are dependent on the flexion angle of the knee at the time of drilling, and the knee must be hyperflexed past 100° of flexion to achieve an acceptable tunnel position and length, which frequently limits optimal visualization of the femoral ACL footprint while drilling [8]. There is also a risk of lateral cortex disruption while placing the femoral tunnel, since the endpoint of reaming is not well-defined [7]. A short femoral tunnel and damage to the articular cartilage are other potential downsides [7], [9].
A Mini-two Incision Technique (MT) has been developed to allow for a more reliable placement of the femoral tunnel [7]. The MT utilizes a one to two centimeters incision over the lateral femur to limit trauma to the soft tissue and iliotibial band [7]. The femoral tunnel is then drilled from the inside–out with a retrograde drill under arthroscopic visualization, which can lead to a reliable and anatomic position of the femoral tunnel [7]. Ultimate tunnel length is calculated prior to drilling, and a cadaveric study has shown that the tunnel created with this method is on average significantly longer than the tunnel drilled through the anteromedial portal [9]. This procedure is performed with the knee at 90° of flexion, which allows for improved identification of anatomic landmarks.
Advanced imaging methodologies can provide an early assessment of knee function through information on progressive cartilage degradation and abnormal kinematics. In particular, the T1ρ relaxation time, which describes spin–lattice relaxation in a rotating spatial frame, can provide detailed information on the extracellular matrix of cartilage [10]. This parameter reflects the proteoglycan content of cartilage and can detect early changes in the cartilage matrix prior to the development of radiographic abnormalities [11]. Kinematic MR imaging reconstructs static images in different positions to understand the complex rotational and translational movements of the knee [12], [13]. Accelerated medial compartment degenerative changes are commonly encountered after ACL injury, and quantitative MR imaging provides a focused assessment of abnormalities.
The purpose of this study is to evaluate MR-based in vivo kinematics, early cartilage degeneration, as measured by T1ρ values, and patient reported outcomes between the MT reconstruction and the AM reconstruction. We hypothesized that both the MT and AM reconstructions would restore normal knee kinematics and produce similar patient reported outcomes. The primary outcome was a dynamic anterior tibial translation. Additionally, we hypothesized that both surgical techniques would lead to similar cartilage health as compared with healthy control patients.
Section snippets
Subjects
A total of 20 patients were recruited for participation, with 10 patients undergoing ACL reconstruction with the MT method and 10 patients with the AM technique, with data collected 12 months after ACL reconstruction. Quantitative cartilage imaging was obtained from both knees for a matched group of 10 control subjects who had no history of previous knee injury. Patient demographics for each of the groups are displayed in Table 1. Inclusion criteria were an acute, isolated ACL injury requiring
Results
Demographic results for the MT, AM, and Control groups are shown in Table 1. There was no significant difference between the groups with respect to patient age, height, weight, or body mass index. All the patients underwent ACL reconstruction with a soft-tissue graft, with a similar number of autografts and allografts. The time of image acquisition was significantly later for the MT group, though this difference is likely not clinically significant.
The dynamic tibiofemoral kinematics showed no
Discussion
The AM and MT methods for ACL reconstruction have both been proposed in order to allow for a more anatomic ACL reconstruction. The results of this study suggest possible clinical differences between the two cohorts using the different techniques. We originally hypothesized that both techniques would lead to the restoration of kinematic parameters that are similar to the patient's contralateral knee and there would be no evidence of early cartilage degeneration.
The MT group showed significant
Conclusion
In conclusion, this study reports the one year results of two different surgical reconstruction techniques following ACL injury, with an observed difference in kinematic outcomes and early cartilage matrix alteration following the mini-two incision ACL reconstruction. Further investigations are needed to evaluate the effects of femoral tunnel placement and orientation on the tibial position, as well as on early cartilage changes and long-term functional outcomes.
Acknowledgments
Funding for this project was provided by grants from the Orthopaedic Research and Education Foundation (OREF #12-034) and the National Institutes of Health/National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIH/NIAMS P50 AR060752).
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