The present study included patients who underwent ACL reconstruction using autogenous tendons at our institute from August 2016 to August 2018. The inclusion criteria were as follows: a diagnosis of ACL rupture using preoperative imaging and physical examination; age, 18–50 years; unilateral ACL single bundle reconstruction performed for the first time; and postoperative rehabilitation training and follow-up performed by doctors. The exclusion criteria were knee joints with severe osteoarthritis (Kellgren − Lawrence grade ≥ III); confirmation of meniscal injury on MRI or arthroscopic exploration and suture requirement in addition to operation; confirmation of cartilage injury on arthroscopic exploration (Outerbridge grade ≥ III); and multiple ligament injury and infection.
Surgery was performed under general or epidural anesthesia. The patients were placed in the supine position; the lithotomy position was adopted for the healthy knee, while the affected knee drooped naturally. After ACL rupture was confirmed by anteromedial and anterolateral arthroscopic approaches, a 3-cm longitudinal skin incision was made approximately 2 cm medial to the tibial tubercle. Parts of the semitendinosus and gracilis tendons were cut and woven to prepare the tendon graft, with a diameter of 6–8 mm and length of 9–10 cm. According to the diameter of the graft, tibial and femoral tunnels were drilled into the tibial and femoral anatomical footprints of the ACL. The graft was pulled from the tibial tunnel to the femoral tunnel using the traction line, and the femoral end was fixed with an adjustable suspension titanium plate (DePuy Mitek Surgical Products, Inc. Raynham, MA, USA). The tibial end of the graft was then pulled with 20-N tension, and the joint was repeatedly flexed and extended 20 times. After confirming that there was no contact between the graft and the intercondylar fossa under arthroscopy, the tibial end was fixed with a compression screw with the knee in the extended position (DePuy Mitek Surgical Products, Inc. Raynham, MA, USA). The incision was closed; and the tension and fixation of the graft were reexplored.
After anesthesia recovery, the patients performed straight leg raises and ankle pump exercises in bed. Twenty-four hours later, they wore a knee brace to start active knee flexion and passive knee extension training. After 4–12 weeks of active knee flexion and passive knee extension training, the knee flexion angle gradually increased, reaching 90°–120°; the strength of the quadriceps femoris was increased by squatting. After 3–6 months, the knee joint had full range of motion, and weight-bearing walking could be continued according to the patient’s tolerance. The amount of activity was gradually increased to avoid fatigue and strenuous activities. At 6–9 months, they could gradually resume swimming, rope skipping, and jogging.
For efficacy evaluation, we performed 3.0 T MRI (scanning series: repetition time/echo time 3000/41 ms; field of view: 15 cm × 15 cm; matrix: 240 × 320; slice thickness: 3.0 mm; Magnetom, Verio, Siemens, Erlangen, Germany) at 3, 6, and 12 months postoperatively. All the images were imported into the RadiAnt DICOM viewer 5.0 (Medixant, Poznan, Poland), and the data were analyzed in the oblique-sagittal fat-suppressed middle-level imaging. The signal intensity was measured in the four regions: the femoral and the tibial ends of the graft, the quadriceps tendon, and the background (approximately 2 cm in front of the patellar tendon). The region of interest, which was also the area of the selected sites, was 0.2 cm2 (Fig. 1). The signal intensity of each site was then quantified and used in the SNQ value formula as follows: SNQ value = (signal intensity of ACL graft − signal intensity of quadriceps femoris tendon) / background signal intensity . The mean SNQ values of the femoral and tibial ends of the grafts were taken as the final SNQ values of the grafts. Two physicians participated in the MRI measurements of the grafts. Each physician independently measured the value of each region twice at an interval of 2 weeks to eliminate the memory effect. The average value of the measurements of the two physicians was then used to calculate the SNQ. The intra- and inter-observer reliability was calculated using the results of the measurements. The reliability was high when the intraclass correlation coefficient (ICC) was > 0.75, medium when the ICC was between 0.4 and 0.75, and low when the ICC was < 0.4. All statistical analyses were performed using SPSS software version 20.0 (IBM Corp., Armonk, New York, USA). Differences with p-values of < 0.05 were considered statistically significant.
The Lysholm score was used to assess the outcomes after the ACL injury. The Lysholm score ranges from 0 to 100 based on eight areas: pain, limping, stair climbing, locking, supporting, swelling, instability, and squatting.
The IKDC Subjective Assessment Form, the standardized international documentation system for knee surgery, consists of 18 questions that emphasize the effects of symptoms, activities of daily living, and physical activity on the knee. The form also assessed total knee function on a 0–100 conversion scale. A score of 100 indicates no symptoms and no restriction on activities of daily living or physical activity.
The Tegner score indicated the sport level of the patients, based on which they are graded on a scale of 0–10. Grade 0 represented sick leave/disability, and grade 10 represented ability to participate in national or international competitive sports activities. This evaluation table is widely used in the evaluation of the exercise capacity of patients with knee injuries.
SPSS version 20.0 (IBM Corp) was used for statistical analysis. The data are expressed as mean ± standard deviation. The data sets were compared using repeated-measures analysis of variance and Q test. Spearman’s correlation coefficient test was used to analyze the correlation between SNQ at 6 months and IKDC, Lysholm, and Tegner scores at 2 years postoperatively.