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Purpose This study aimed to identify independent predictive factors for return to sports (RTS) after anterior cruciate ligament (ACL) reconstruction in competitive-level athletes and to determine optimal cut-off values for these factors at 6 months after surgery. Methods A total of 124 competitive athletes (50 males and 74 females; mean age, 17.0 years; preinjury Tegner activity scale > 7) who underwent primary ACL reconstruction were enrolled. Assessments at 6 months after surgery consisted of knee functional tests [quadriceps index, hamstrings index, and single-leg hop for distance (SLH)] and 2 self-report questionnaires [IKDC subjective score and ACL-Return to Sport after Injury scale (ACL-RSI)]. At 1 year after surgery, athletes were classified into the RTS group ( n  = 101) or non-RTS group ( n  = 23) based on self-reported sports activities. After screening possible predictive factors of RTS, multivariate logistic regression and receiver operating characteristic curve analyses were performed to identify independent factors. Results Multivariate logistic regression analysis identified SLH (odds ratio, 2.861 per 10 unit increase; P  < 0.001) and ACL-RSI (odds ratio, 1.810 per 10 unit increase; P  = 0.001) at 6 months as independent predictors of RTS at 1 year after surgery. Optimal cut-off values of SLH and ACL-RSI were 81.3% (sensitivity = 0.891; specificity = 0.609) and 55 points (sensitivity = 0.693; specificity = 0.826), respectively. Conclusion In competitive athletes, SLH < 81% and ACL-RSI < 55 points at 6 months after surgery were associated with a greater risk of unsuccessful RTS at 1 year after surgery. SLH and ACL-RSI at 6 months could serve as screening tools to identify athletes who have difficulties with returning to sports after ACL reconstruction. Level of evidence III.

Purpose This study aimed to retrospectively compare the enlargement and migration of the femoral tunnel aperture after anatomic rectangular tunnel anterior cruciate ligament (ACL) reconstruction with a bone–patella tendon–bone (BTB) or hamstring tendon (HT) graft using three-dimensional (3-D) computer models. Methods Thirty-two patients who underwent ACL reconstruction and postoperative computed tomography (CT) at 3 weeks and 6 months were included in this study. Of these, 20 patients underwent ACL reconstruction with a BTB graft (BTBR group), and the remaining 12 with an HT graft (HTR group). The area of the femoral tunnel aperture was extracted and measured using a 3-D computer model generated from CT images. Changes in the area and migration direction of the femoral tunnel aperture during this period were compared between the two groups. Results In the HTR group, the area of the femoral tunnel aperture was significantly increased at 6 months compared to 3 weeks postoperatively ( P  < 0.05). The average area of the femoral tunnel aperture at 6 months postoperatively was larger by 16.0 ± 12.4% in the BTBR group and 41.9 ± 22.2% in the HTR group, relative to that measured at 3 weeks postoperatively ( P  < 0.05). The femoral tunnel aperture migrated in the anteroinferior direction in the HTR group, and only in the inferior direction in the BTBR group. Conclusions The femoral tunnel aperture in the HTR group was significantly more enlarged and more anteriorly located at 6 months after ACL reconstruction, compared to the BTBR group. Level of evidence IV.

Purpose In animal studies after ACL reconstruction (ACL-R) using the bone-patellar tendon-bone (BTB), the graft-healing pattern was found to depend on the relationship between bone plug and the tunnel wall. This difference of graft-healing pattern could influence the postoperative morphological changes of the tunnel. However, no study has assessed the relationship between bone plug position and the change of tunnel morphology. Therefore, the main purpose of this study was to investigate the relationship between the bone plug position within femoral or tibial tunnel and morphological changes of each tunnel aperture in ACL-R using computed tomography. Methods Subjects were 30 consecutive patients (six females and 24 males; mean age, 20.4 ± 5.4 years) who underwent primary ACL-R using BTB. The distance from the tunnel aperture to the tendon-bone junction (TBJ) at 2 weeks postoperatively, and tunnel aperture enlargement and tunnel wall migration from 2 weeks to 6 months postoperatively, were evaluated. Results The distance from the femoral tunnel aperture to the TBJ in most cases was less than 2 mm, whereas the TBJ was located within the tibial tunnel. Femoral tunnel aperture was significantly enlarged (17.0 ± 11.7%) distally, and the tibial tunnel aperture was significantly enlarged (19.6 ± 12.5%) posterolaterally. Only the position at distal portion of femoral bone plug was correlated with femoral tunnel aperture enlargement ( r  = 0.454, p  = 0.0015). Conclusion Both femoral and tibial tunnel aperture were significantly enlarged distally and posterolaterally 6 months postoperatively. Only correlation between the position at distal portion of femoral bone plug and femoral tunnel enlargement were found, suggesting the deep plug position in the tunnel is a risk factor for femoral tunnel enlargement, highlighting the importance of accurately locating the TBJ just at the femoral tunnel aperture. Another option is to deviate the harvest site in the patellar tendon to match the shape of the TBJ and the tunnel aperture. Level of evidence 4 (case series).

For an ideal osteochondral repair, it is important to facilitate zonal restoration of the subchondral bone and the cartilage, layer by layer. Specifically, restoration of the osteochondral junction and secure integration with adjacent cartilage could be considered key factors. The purpose of the present study was to investigate the feasibility of a combined material comprising a scaffold-free tissue-engineered construct (TEC) derived from synovial mesenchymal stem cells (MSCs) and a hydroxyapatite (HA) artificial bone using a rabbit osteochondral defect model. Osteochondral defects were created on the femoral groove of skeletally mature rabbits. The TEC and HA artificial bone were hybridized to develop a combined implant just before use, which was then implanted into defects (N=23). In the control group, HA alone was implanted (N=18). Histological evaluation and micro-indentation testing was performed for the evaluation of repair tissue. Normal knees were used as an additional control group for biomechanical testing (N=5). At hybridization, the TEC rapidly attached onto the surface of HA artificial bone block, which was implantable to osteochondral defects. Osteochondral defects treated with the combined implants exhibited more rapid subchondral bone repair coupled with the development of cartilaginous tissue with good tissue integration to the adjacent host cartilage when assessed at 6 months post implantation. Conversely, the control group exhibited delayed subchondral bone repair. In addition, the repair cartilaginous tissue in this group had poor integration to adjacent cartilage and contained clustered chondrocytes, suggesting an early osteoarthritis (OA)-like degenerative change at 6 months post implantation. Biomechanically, the osteochondral repair tissue treated with the combined implants at 6 months restored tissue stiffness, similar to normal osteochondral tissue. The combined implants significantly accelerated and improved osteochondral repair. Specifically, earlier restoration of subchondral bone, as well as good tissue integration of repair cartilage to adjacent host tissue could be clinically relevant in terms of the acceleration of postoperative rehabilitation and longer-term durability of repaired articular surface in patients with osteochondral lesions, including those with OA. In addition, the combined implant could be considered a promising MSC-based bio-implant with regard to safety and cost-effectiveness, considering that the TEC is a scaffold-free implant and HA artificial bone has been widely used in clinical practice.

Purpose The purpose of the study was to evaluate the entire course of ACL grafts on coronal oblique MR images, focusing on differences in graft morphology and graft-to-tunnel healing among single-bundle (SB), double-bundle (DB), and triple-bundle (TB) reconstructions. Methods Eighty-three patients underwent anatomical ACL reconstruction using the semitendinosus tendon. SB reconstruction was performed on 20 patients, DB on 29 patients, and TB on 34 patients. The anteromedial-bundle (AMB) and posterolateral-bundle (PLB) images were extracted from coronal oblique images of grafts at 6 months to visualize their entire course. Signal intensity of grafts was measured independently in three regions: (1) intra-femoral tunnel region, (2) intra-articular region, and (3) intra-tibial tunnel region, followed by calculation of the signal-to-noise quotient (SNQ). To evaluate graft-to-tunnel healing, T2-weighted images were examined for the presence of a high signal-intensity lesion between the graft and bone tunnel around the tunnel aperture. Results AMB images showed that SB graft was thick throughout the entire course, while DB graft was thinner than SB graft. TB graft showed a fan shape approaching the tibial tunnels. The SNQ in the femoral tunnel of SB graft was significantly lower than in the DB and TB grafts. High signal-intensity lesions were frequently observed around the femoral tunnel aperture in PLB images of DB and TB grafts compared to SB grafts. Conclusion Gross morphology of TB grafts resembled that of the natural ACL. However, the graft-to-tunnel healing around the femoral tunnel seemed to be insufficient in PLB images of DB and TB compared to SB grafts. Level of evidence III.

Purpose Medial patellofemoral ligament (MPFL) reconstruction has been performed to treat recurrent patellar dislocation. However, the effects on patellar tracking have not been well documented, particularly in patients. The purpose of this study is to compare patellar tracking pattern and chondral status at MPFL reconstruction with those at second-look arthroscopy. Methods Between 1999 and 2008, 71 patients with recurrent patellar dislocation underwent MPFL reconstruction using a double-looped semitendinosus tendon. Of these, 25 knees in 24 patients underwent second-look arthroscopy (at 6–26 months after initial surgery), forming the subject for the present study. No other surgical procedures such as tibial tuberosity transfer, lateral release, or osteotomy were performed in any patients. To assess the patellar tracking pattern, the position of the patella on femoral groove was evaluated arthroscopically during passive knee motion through lateral suprapatellar portal. Results Before MPFL reconstruction, the patella in all patients was shifted laterally throughout the entire range of knee motion. Immediately after MPFL reconstruction, patellar malalignment was corrected in all cases. On second-look arthroscopy, two different patellar tracking patterns were observed. In 9 knees, the patella was located on the center of the femoral groove throughout the range of motion. Meanwhile, in the remaining 16 knees, the patella was shifted laterally at knee extension and migrated to the center of femoral groove with increased knee flexion. No significant deteriorations in chondral status were seen on second-look arthroscopy. Conclusion The present study revealed that not all improved patellar trackings after MPFL reconstruction remained intact at follow-up. Chondral status in patellofemoral joint was not aggravated by MPFL reconstruction. Level of evidence Therapeutic studies, Level IV.

Background: Accumulating evidence suggests that long-term anterior cruciate ligament (ACL) deficiency can give rise to an abnormal tibiofemoral relationship and subsequent intra-articular lesions. However, the effects of chronic ACL deficiency (ACLD) on early graft failure after anatomic reconstruction remain unclear. Hypothesis: We hypothesized that patients with long-term ACLD lasting more than 5 years would have a greater rate of early graft failure due to insufficient intraoperative reduction of the tibia and that the preoperative and immediately postoperative abnormal tibiofemoral relationship in the sagittal plane, such as anterior tibial subluxation (ATS), would correlate with the graft status on postoperative magnetic resonance imaging (MRI). Study Design: Cohort study; Level of evidence, 3. Methods: A total of 358 patients who had undergone anatomic ACL reconstruction with hamstring grafts were divided into 5 groups based on chronicity of ACLD: (1) 0 to 6 months, (2) 6 months to 1 year, (3) 1 to 2 years, (4) 2 to 5 years, and (5) longer than 5 years. Preoperatively and immediately postoperatively, lateral radiographs in full extension were taken in all patients to evaluate the tibiofemoral relationship, specifically with regard to ATS, space for the ACL (sACL), and extension angle. All patients underwent MRI at 6 months to reveal graft status. Groups with a high rate of graft failure were further analyzed to compare demographic and radiographic factors between the intact and failure subgroups, followed by multivariate logistic regression analysis to identify predisposing factors. Results: Graft failure without trauma was observed in 4 (1.8%), 0 (0%), 1 (3.7%), 3 (9.7%), and 8 patients (17.7%) in groups 1, 2, 3, 4, and 5, respectively. Of the 76 patients in groups 4 and 5, significant differences were noted between the failure and intact subgroups in preoperative ATS (4.9 vs 2.4 mm, respectively; P < .01), side-to-side differences in sACL (sACL-SSD) (4.7 vs 1.9 mm, respectively; P < .01), extension deficit (4.4° vs 1.3°, respectively; P < .01), and chondral lesions (P = .02), while postoperative ATS and sACL-SSD showed no differences. Multivariate logistic regression analysis revealed that of these factors, preoperative sACL-SSD could be a risk factor for early graft failure (odds ratio, 3.2; 95% CI, 1.37-7.46). Conclusion Early graft failure at 6 months increased in patients with ACLD longer than 2 years. In this population, preoperative sACL-SSD was the most significant risk factor for early graft failure on MRI. However, immediately postoperative radiographic measurements had no effect on graft failure rates.

Purpose The purpose of this study was to investigate the tibiofemoral relationship sequentially before and after anatomic triple-bundle (TB) anterior cruciate ligament (ACL) reconstruction in the same patients. Methods Nine patients with complete unilateral ACL rupture participated in this study. Anatomic TB ACL reconstruction was performed using autogenous semitendinosus tendon grafts. Computed tomography images were obtained before surgery as well as 3 weeks and 6 months afterwards. During image acquisition, the patient’s knees were fully extended in the supine position. Using three-dimensional computer models, anterior–posterior and medial–lateral displacement of the tibia relative to the femur were evaluated for each period, as were internal–external and varus–valgus rotation, followed by calculation of side-to-side differences in parameters. As the control group, 7 healthy volunteers were evaluated. Results The tibia was located anteriorly by 1.4 ± 0.9 mm and rotated internally by 2.1 ± 1.7° before surgery, while the tibia was located posteriorly by 2.0 ± 1.2 mm and rotated externally by 3.4 ± 3.5° 3 weeks after surgery. Six months after surgery, there was no significant difference between the patient and control groups. Conclusions The anteriorly located and internally rotated tibia in ACL-deficient knees was over-constrained (posterior displacement and external rotation) 3 weeks after anatomic TB ACL reconstruction, but returned to the normal position 6 months afterwards. Therefore, anatomic tunnel placement, appropriate initial tension, and moderate rehabilitation can be the key for return to the normal tibiofemoral relationship after ACL reconstruction. Level of evidence Therapeutic study, Level IV.

Purpose The purpose of this study was to identify the optimal material and implantation method for subchondral bone repair. Methods Four osteochondral defects in a femoral groove were created in both knees of 12 pigs, and the total number of defects was 96. Eight defects were left empty (empty group). Beta-tricalcium phosphate (β-TCP) bone substitutes with 75 and 67 % porosity were implanted in 30 and 29 defects, respectively (β-TCP75 and β-TCP67 groups). Hydroxyapatite (HA) bone substitutes with 75 % porosity were filled in 29 defects (HA group). Bone substitutes were implanted at 0, 2, or 4 mm below the subchondral bone plate (SBP). The reparative tissue was assessed using microfocus computed tomography and histology 3 months after implantation. Results Regardless of the kind of bone substitutes, the defects were filled almost completely after implanting them at the level of the SBP, while the defects remained after implanting them at 2 or 4 mm below the SBP. Reparative tissue of the β-TCP75 group was similar to the normal cancellous bone, while that of the β-TCP67 or HA group was not. Conclusions Subchondral bone defects were filled almost completely only when bone substitutes were implanted at the level of the SBP. The reparative tissue after implanting the β-TCP bone substitutes with 75 % porosity was the most similar to the normal cancellous bone. Therefore, implanting the β-TCP bone substitutes with 75 % porosity at the level of the SBP could be recommended as a treatment method for subchondral bone repair in osteochondral defects. Level of evidence I.

Most patients with recurrent patellar dislocation show cartilage damage in the patellofemoral joint. Medial patellofemoral ligament reconstruction has become one of the most important surgical techniques for treating recurrent patellar dislocation. However, patellofemoral chondral status after this reconstruction has not been elucidated. The purpose of this study was to investigate the effects of medial patellofemoral ligament reconstruction on articular cartilage in the patellofemoral joint by comparing the arthroscopic chondral status at the time of reconstruction with that at second-look arthroscopy. Participants in the present study comprised 31 patients (22 females, 9 males; 32 knees) who underwent second-look arthroscopy at a median of 12 months (range 6–40 months) after dual tunnel medial patellofemoral ligament reconstruction using a double-looped autologous semitendinosus tendon graft. Median age at the time of initial surgery was 20 years (range 13–43 years). The patellofemoral joint was divided into six portions, comprising the medial facet of the patella, central ridge, lateral facet of the patella, anterior medial femoral condyle, femoral groove, and anterior lateral femoral condyle. Chondral status in each portion according to the International Cartilage Repair Society classification was retrospectively evaluated at the time of initial surgery and second-look arthroscopy. Before medial patellofemoral ligament reconstruction, chondral lesions were observed in the patellofemoral joint in 31 knees (97 %). At the central ridge of the patella, chondral damage was observed in 22 knees (69 %) at initial surgery and damaged cartilages showed recovery in 6 knees. No significant difference in the alteration of chondral status was seen for the medial facet, lateral facet of the patella, anterior medial femoral condyle, femoral groove, and anterior lateral femoral condyle. According to short-term results, the patellofemoral chondral status after medial patellofemoral ligament reconstruction was not altered at second-look arthroscopy in most part of patellofemoral joint. At the central ridge of the patella, significant improvement of the International Cartilage Repair Society grading was observed.