The Usefulness of Posterior Shiny Corner Lesions in the Early Diagnosis of Medial Meniscus Posterior Root Tears.

INTRODUCTION:  Posterior shiny corner lesions (PSCLs) have been reported to be useful for the early diagnosis of medial meniscus posterior root tears (MMPRTs) in surgical patients. However, the usefulness of PSCLs in outpatients, particularly regarding the optimal timing of magnetic resonance imaging (MRI) examinations after injury, remains unknown. We hypothesized that PSCLs would normally be observed in patients with MMPRTs within one month of injury. MATERIALS AND METHODS:  This study included 144 patients with knee pain who visited our hospital between January 2021 and May 2023. MRI findings within and after one month were examined. Fisher's exact test was performed for PSCLs, cleft signs, ghost signs, radial tear signs, bone cysts, and medial meniscus extrusion (MME), which are findings used for the diagnosis of MMPRTs. Time-dependent receiver operating characteristic (ROC) curve analysis was performed for each MRI finding. A binomial logistic regression analysis was performed for age, sex, PSCL, ghost sign, and MME. RESULTS: PSCLs were observed on 82.6% of the MRI scans within one month, but the positivity rate decreased after one month. After one month, a high percentage of patients had cleft signs and ghost signs. The results of a time-dependent ROC curve analysis showed that the PSCL had better diagnostic ability than the cleft sign, ghost sign, radial tear sign, and MME at a relatively early stage. Additionally, the area under the curve (AUC) of PSCL peaks around 35 days and then declines, reaching 0.8 or less around 40 days. On the other hand, the AUC of the cleft sign and ghost sign began to increase around 30 days after injury, and it exceeded 0.8 after approximately 100 days. The results of the binomial logistic regression analysis revealed significant PSCLs and ghost signs. Independent associations between the PSCL, or ghost sign, and the MMPRT were demonstrated. CONCLUSION:  This study suggests that PSCLs have a superior diagnostic capability for MMPRT during the early stages of injury compared with other MRI findings in outpatients. In particular, PSCLs have a high positivity rate within one month after injury and a high diagnostic capacity up to 40 days after injury.

Protective Effects of Extracorporeal Shockwave Therapy on the Degenerated Meniscus in a Rat Model.

BACKGROUND: Loss of meniscal function in association with degenerative changes affects the development and progression of knee osteoarthritis, for which there is currently no effective treatment. Extracorporeal shockwave therapy (ESWT) is an established treatment for musculoskeletal disorders. However, the therapeutic effect of ESWT on meniscal degeneration remains unclear. PURPOSE: To evaluate the therapeutic effect of ESWT on the degenerated meniscus in an anterior cruciate ligament transection (ACLT) model. STUDY DESIGN: Controlled laboratory study. METHODS: Twelve-week-old male Wistar rats were randomly assigned to 3 groups (normal, ESWT-, and ESWT+). Unilateral ACLT of the right knee was performed in the latter 2 groups. At 4 weeks after ACLT, the ESWT+ group received 800 shockwave impulses at an energy flux density of 0.22 mJ/mm2 in a single session. Histological changes were examined in the posterior portion of the medial meniscus after ESWT (n = 15 per group). Real-time polymerase chain reaction (PCR) was performed after ESWT (n = 5 per group) to analyze the expression of connective tissue growth factor/CCN family member 2 (CTGF/CCN2), sex determining region Y-box 9, vascular endothelial growth factor α, aggrecan, collagen type 1 alpha 2, and collagen type 2 alpha 1 (Col2α1). Immunohistochemistry was used to analyze the expression of CTGF/CCN2 and Ki-67 (n = 5 per group) after ESWT. RESULTS: The meniscal histopathological score at 4 weeks after ACLT was significantly higher than that in the normal group, and the score in the ESWT+ group was significantly lower than that in the ESWT- group at 4 and 12 weeks after ESWT. Real-time PCR revealed that the mRNA expression of CTGF/CCN2 and Col2α1 decreased 4 weeks after ACLT. In the ESWT+ group, real-time PCR revealed that the mRNA expression of CTGF/CCN2 increased 24 hours after ESWT, and the expression of Col2α1 increased 4 weeks after ESWT (all significant data were P < .05). The ratio of CTGF/CCN2-positive cells and Ki67-positive cells was significantly higher in the ESWT+ group after ESWT. CONCLUSION: The present study revealed that ESWT might suppress ACLT-induced meniscal degeneration by stimulating cartilage repair factors and inducing collagen type 2. CLINICAL RELEVANCE: ESWT can be an effective treatment to protect the degenerated meniscus in a rat model of ACLT.

Postoperative Medial Tilting of the Joint Line and Preoperative Kinematics Influence Postoperative Medial Pivot Pattern Reproduction in Total Knee Arthroplasty.

Background: Reproducing the medial pivot pattern after total knee arthroplasty (TKA) is known to improve patient satisfaction. However, the factors affecting the postoperative medial pivot pattern in TKA are controversial. The purpose of this study was to examine the factors affecting the postoperative medial pivot pattern in posterior-stabilized TKA. Methods: This study involved 30 cases with knee osteoarthritis who underwent primary posterior-stabilized TKA. The preoperative and postoperative kinematics were measured using a computed tomography-free navigation system, and the patients were divided into the following 2 groups: the medial pivot pattern (MP) group and non-medial pivot pattern (non-MP) group. In addition, we measured each of the following angles on X-ray films (preoperative and postoperative femorotibial angle, hip-knee-ankle angle, mechanical lateral distal femoral angle, medial proximal tibial angle). We examine the factors affecting the postoperative medial pivot pattern. Results: There were 14 cases in the MP group and 16 cases in the non-MP group at the preoperative knee kinematic assessment and 17 cases in the MP group and 13 cases in the non-MP group at the postoperative knee kinematic assessment. The preoperative kinematic pattern was conserved after the surgery at a rate of 76.7%. The postoperative MP-group showed a significantly smaller preoperative femorotibial angle and hip-knee-ankle and a significantly smaller postoperative mechanical lateral distal femoral angle and medial proximal tibial angle in comparison to the postoperative non-MP group. Conclusions: Preoperative kinematics and postoperative mechanical lateral distal femoral angle and medial proximal tibial angle may be important factors that affect the postoperative medial pivot pattern.

Insufficient restoration of meniscal extrusion by transtibial pullout repair for medial meniscus posterior root tears.

PURPOSE: The long-term changes in the dynamics of the medial meniscus after transtibial pullout repair for medial meniscus posterior root tears (MMPRTs) are not completely understood. Thus, the aim of this study was to investigate the effects of transtibial pullout repair on MMPRTs and whether the effects would be sustained. METHODS: Nineteen knees with MMPRTs that were treated by trans-tibial pullout repair were enrolled in this study. Medial meniscus extrusion (MME) was measured by ultrasonography during knee extension (no weight-bearing with the knee at 0° extension: NW0°) and 90° flexion (no weight-bearing with the knee at 90° flexion: NW90°) with the patient in the supine position and with full weight-bearing (FW0°) preoperatively and at 3 and 12 months postoperatively. The clinical outcomes were assessed using the Knee Injury and Osteoarthritis Outcome Score, Lysholm score, and International Knee Documentation Committee score. RESULTS: The difference in MME with NW0° was not statistically significant between the preoperative (3.4 ± 1.0 mm) and 12-month postoperative (3.7 ± 0.6 mm) time points. The MME with NW90° at 3 (2.1 ± 0.7 mm) and 12 months (2.9 ± 0.6 mm) postoperatively were significantly lower than the preoperative values (3.4 ± 0.8 mm) (P < 0.05). However, the value significantly increased from 3 to 12 months postoperatively (P < 0.05). The MME with FW0° at 12 months postoperatively (4.3 ± 0.6 mm) was significantly larger than that at pre-operatively (3.6 ± 0.9 mm) (P < 0.05). All the patients' clinical conditions were significantly improved at 12 months postoperatively when compared to their preoperative clinical conditions. CONCLUSION: Surgery did not reduce the extrusion in the no weight-bearing and weight-bearing positions at knee extension, and these values increased in the postoperative period. In addition, while the surgery reduced the extrusion in the knee flexion position, the restoration achieved by the surgery was not sustained in the long term. LEVEL OF EVIDENCE: Level IV.

Deep Infrapatellar Bursitis in Preadolescent Baseball Players: A Cross-Sectional Study.

Background: Deep infrapatellar bursitis (DIB) has been detected in cases of Osgood-Schlatter disease (OSD). However, the clinical implications of DIB in the apophyseal stage, during the period when OSD has not yet developed, remain unclear. Purpose: To investigate the factors related to DIB in the apophyseal stage in preadolescent baseball players. Study Design: Cross-sectional study, Level of evidence, 3. Methods: The study participants were junior baseball players who participated in a medical checkup in 2020. We included knees in the apophyseal stage evaluated using ultrasonography, and classified them into the bursitis and no-bursitis groups using color-enhanced Doppler ultrasonography. We also investigated bone lesions of the tibial tuberosity, determined by fragmentation of the bone and irregularity of the ossification center. Demographic data, practice duration, pressure pain on tuberosity, pain while playing baseball (visual analog scale), heel-buttock distance (HBD), straight-leg raise angle, and range of hip internal and external rotation were evaluated. Group comparisons were performed using the Mann-Whitney U test and Fisher exact test, and a logistic regression analysis was performed. Results: A total of 261 knees (139 male players; age 10.5 ± 1.1 years) were included, 30 in the bursitis group and 231 in the no-bursitis group. Bone lesions were present in 4 knees in the bursitis group and in 32 knees in the no-bursitis group; there was no significant relationship between the presence of bone lesions and bursitis. Compared with the no-bursitis group, the bursitis group had a significantly longer practice duration (12.9 ± 3.3 vs 15.2 ± 3.8 hours/week, respectively; P = .003) and larger HBD (0.5 ± 1.3 vs 1.4 ± 2.4 cm, respectively; P = .003). The logistic regression analysis showed that practice duration (P = .001) and HBD (P = .004) were significantly related to the presence of bursitis. Conclusion: DIB in the apophyseal stage was related to practice duration and thigh muscle tightness. These findings may help predict overload and thigh muscle tightness at a very early stage.

Medial meniscus extrusion as a predictor for a poor prognosis in patients with spontaneous osteonecrosis of the knee.

BACKGROUND: Risk factors for the progression of spontaneous osteonecrosis of the knee (SONK) remain unclear. The purpose of this study was to investigate the association between magnetic resonance imaging (MRI) findings of the meniscus and the prognosis of SONK. METHODS: A total of 78 consecutive patients (female 85%; mean age 75.6 ± 7.2 years old) diagnosed with SONK were included. Of these, 30 patients did not receive surgery within 1 year from the onset of SONK (conservative group), while the remaining 48 patients underwent unicompartmental knee arthroplasty due to worsening of symptoms (UKA group). Using MRI findings obtained within 3 months of the onset, we compared the types of meniscus tear and medial meniscus extrusion between the conservative group and UKA group. We performed a receiver operating characteristics (ROC) analysis to estimate the cut-off value. RESULTS: Patients in the UKA group showed greater medial meniscus extrusion (absolute value, 4.2 mm ± 1.9 vs. 2.8 mm ± 1.2, P = 0.001; relative percentage of extrusion (RPE), 45.7% ± 21.5 vs. 30.7% ± 12.9, P = 0.001) and a higher prevalence of radial tear (P = 0.021) than those in the conservative group. In the multivariate analysis, RPE remained a relevant independent factor (P = 0.035) for future UKA. An ROC analysis found that the cut-off point of RPE was 33% (sensitivity, 81.2%; specificity, 63.3%). CONCLUSION: RPE was a predictor of the prognosis of patients who underwent UKA within 1 year after the onset of SONK. Our results suggest that patients with RPE ≥ 33% are at high risk for progression.

Hallux valgus deformity and postural sway: a cross-sectional study.

BACKGROUND: Hallux valgus deformity has been reported to be associated with increased postural sway. However, the direction and magnitude of postural sway associated with hallux valgus remain inconclusive. We assessed the association between hallux valgus deformity and postural sway using a force plate. METHODS: The subjects were 169 healthy volunteers, > 40 years old (63 males, 106 females, average age: 66.0 ± 12.4 years old), who took part in an annual medical examination. We investigated the photographic hallux valgus angle (°), total trajectory length of the gravity center fluctuation (mm), area of the center of pressure (mm2), mediolateral and anteroposterior postural sway (mm) in a standing position with 2-legged stance and eyes open, hallux pain (Numerical Rating Scale), trunk and lower limb muscle mass (kg). We classified the subjects into a hallux valgus group (n = 44, photographic hallux valgus angle of 1 or both feet ≥ 20°) and a no hallux valgus group (n = 125, photographic hallux valgus angle of both feet < 20°) and analyzed the relationship between hallux valgus and postural sway. RESULTS: The anteroposterior postural sway in the hallux valgus group (6.5 ± 2.8) was significantly greater than in the no hallux valgus group (5.4 ± 2.2, p = 0.014), and the lower limb muscle mass in the hallux valgus group (12.4 ± 2.2) was significantly smaller than in the no hallux valgus group (13.5 ± 3.2, p = 0.016). The total value of the photographic hallux valgus angle on both feet was positively correlated with the anteroposterior postural sway (p = 0.021) and negatively correlated with the lower limb muscle mass (p = 0.038). The presence of hallux valgus (p = 0.024) and photographic hallux valgus angle (p = 0.008) were independently related to the magnitude of anteroposterior postural sway. CONCLUSIONS: Hallux valgus deformity and its severity were positively associated with the magnitude of the anteroposterior postural sway. TRIAL REGISTRATION: 2017 - 135. Registered 22 August 2017.

Sagittal Inclination Angle of Graft Is Associated With Knee Stability After Anatomic Anterior Cruciate Ligament Reconstruction.

PURPOSE: To evaluate whether the sagittal inclination angle (SIA) of a graft is associated with postoperative knee stability after anatomic anterior cruciate ligament (ACL) reconstruction. METHODS: All patients who had undergone anatomic ACL reconstruction between April 2014 and September 2015 in addition to volunteers with no history of knee injury were eligible for inclusion in this study. The patients were evaluated by magnetic resonance imaging of the knee in full extension at 1 year after surgery, as were volunteers. The posterior tibial slope (PTS) angle and the SIA of the intact ACL and reconstructed graft were measured relative to each medial and lateral tibial plateau. The patients were examined for knee stability by the side-to-side difference in the anterior tibial translation on stress radiographs at minimum 2-year follow-up. RESULTS: We included 43 patients (26 male, 17 female, mean age 32.8 ± 14.8 years) and 12 volunteers (7 male, 5 female, mean age 28.7 ± 3.1 years) as normal controls. The mean follow-up duration was 29.8 ± 3.6 months. The mean PTS angle and mean SIA in the patients did not significantly differ from those of the intact ACL. The PTS angle in the patients was not significantly correlated with postoperative side-to-side difference in the anterior tibial translation. However, the graft SIA was significantly correlated with the postoperative anterior tibial translation (medial SIA; r = 0.42, P = .005, lateral SIA; r = 0.52, P < .001). CONCLUSIONS: Even if anatomically reconstructed, the graft SIA in reference to the tibial plateau at full knee extension is variable and is associated with postoperative knee stability. The larger graft SIA was correlated with graft laxity after anatomic ACL reconstruction. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Patient-reported evaluation on giving way is important for return to preinjury activity level after Anterior Cruciate Ligament reconstruction.

PURPOSE: The present study evaluated the rate of returning to the preinjury level of competitive sports after ACLR and influential factors. METHODS: After excluding composite ligament injury cases, 96 patients with a Tegner activity score of ≥ 6 who were managed between April 2015 and March 2016 and had been followed for ≥ 2 years were included in the present study. The patients were evaluated for instability, and the following data were collected: second-look arthroscopy findings, muscle strength, and International Knee Documentation Committee (IKDC) subjective score (follow-up rate: 88.1%). RESULTS: The rate of returning to the preinjury level of competitive sports was 62/96 (64.6%). Only the total IKDC subjective score (odds ratio, 1.052; 95% confidence interval 1.004-1.102; p = 0.035) and the subjectively evaluated item about giving way (odds ratio, 1.762; 95% confidence interval 1.066-2.911; p = 0.027) were independently associated with the returning to the preinjury level of competitive sports after ACLR in the logistic regression analysis. CONCLUSION: The rate of returning to the preinjury level of competitive sports after ACLR was 64.6%, even if a good knee stability and healing status of the sutured meniscus were acquired after ACLR. The IKDC subjective score, especially the item about giving way, was significantly associated with the returning to the preinjury level of competitive sports. The factors assessed by patient-reported evaluations concerning giving way that may be related to functional performance, including brain activity, are important to consider to improve the rate of returning to the preinjury level of competitive sports. LEVEL OF EVIDENCE: III.

Extracorporeal Shockwave Therapy Accelerates the Healing of a Meniscal Tear in the Avascular Region in a Rat Model.

BACKGROUND: The treatment of meniscal tears in the avascular region remains a clinical challenge. Extracorporeal shockwave therapy (ESWT) is a minimally invasive, safe, and effective therapy for various orthopaedic disorders. However, the therapeutic effect of ESWT on meniscal tears has not been reported. PURPOSE: To evaluate the therapeutic effect of ESWT in the treatment of meniscal tears. STUDY DESIGN: Controlled laboratory study. METHODS: Twelve-week-old male Wistar rats were divided into 3 groups (normal, ESWT-, and ESWT+). The authors made a full-thickness 2-mm longitudinal tear in the avascular region of the anterior horn in the latter 2 groups. At 1 week after surgery, the ESWT+ group received 800 impulses of shockwave at 0.22-mJ/mm2 energy flux density in a single session. The authors performed a histological examination to evaluate meniscal healing (n = 10 for each group) and immunohistochemistry to analyze the expression of bromodeoxyuridine (BrdU; n = 5 for each group) and CCN family member 2/connective tissue growth factor (CCN2/CTGF; n = 5 for each group) at 2, 4, and 8 weeks after ESWT. The mRNA levels of CCN2, SOX 9, VEGF-a, aggrecan, Col1a2, and Col2a1 at the site of the meniscal tear at 4 weeks after ESWT were quantitatively evaluated by a real-time polymerase chain reaction (n = 5 for each group). RESULTS: The meniscus healing scores in the ESWT+ group were significantly higher than those in the ESWT- group at 4 weeks and 8 weeks. The ratio of BrdU-positive cells was the highest in the ESWT+ group at all observation periods. The ratio of CCN2-positive cells was highest in the ESWT+ group at 4 and 8 weeks. In the ESWT+ group, real-time polymerase chain reaction revealed that the levels of CCN2, SOX9, aggrecan, and Col2a1 were upregulated (All significant data were P < .05). CONCLUSION: ESWT promoted the healing of meniscal tears in the avascular area. ESWT stimulated proliferation of meniscal cells and the upregulation of cartilage-repairing factors such as CCN2, with the upregulation of cartilage-specific extracellular matrix expression. CLINICAL RELEVANCE: ESWT may be an effective therapeutic option that promotes meniscal healing in the avascular region.

Relationship Between Lower Limb Tightness and Practice Time Among Adolescent Baseball Players With Symptomatic Osgood-Schlatter Disease.

BACKGROUND: Osgood-Schlatter disease (OSD) is characterized by traction apophysitis of the tibial tuberosity. Few studies on symptomatic and asymptomatic OSD have correlated findings with clinical examination. PURPOSE: To investigate the relationship between lower limb tightness and practice time among adolescent baseball players with symptomatic OSD. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: The study participants were 402 male baseball players (N = 804 knees) with a mean ± SD age of 10.9 ± 1.5 years (range, 7-14 years). Participant age, height, body weight, body mass index, practice time per week, range of motion of the hip and ankle joints, heel-buttock distance (HBD), and straight-legged raise angle were evaluated. Tibial tuberosity development, as assessed with ultrasonography, was classified into 4 stages: cartilaginous, apophyseal, epiphyseal, and bony. Knees that were classified as apophyseal or epiphyseal were investigated. Participants were divided into 3 groups: non-OSD, asymptomatic OSD, and symptomatic OSD. RESULTS: Of 400 knees in the apophyseal and epiphyseal stages, 23 knees had asymptomatic OSD, and 11 had symptomatic OSD. Players with symptomatic OSD practiced for significantly longer than the non-OSD group (P = .001) and asymptomatic OSD group (P = .001). Players with symptomatic OSD also had a larger HBD (P = .006) and smaller range of motion regarding internal rotation of hip (P = .023) and dorsiflexion of the ankle (P = .013) than the non-OSD group. CONCLUSION: Players with symptomatic OSD had longer practice times than the non-OSD and asymptomatic OSD players. Symptomatic OSD was also associated with tightness of the lower limbs as assessed by the HBD and range of motion in the hip and ankle joints.

The relationship between the clinical results and the remnant type following anterior cruciate ligament reconstruction using a hamstring tendon.

PURPOSE: The aim of the present study was to investigate the correlations among the preoperative and postoperative knee laxity, the clinical results, and the type of remnant tissue following the anterior cruciate ligament (ACL) reconstruction. METHODS: One hundred ninety-two patients (male, n = 101; female, n = 91; mean age, 27.1 years) with ACL-deficient knees who had undergone double-bundle reconstruction were included. The time between injury and surgery (TBIS) was 34.7 weeks (range, 1-504 weeks). The subjects were divided into four groups according to the Crain's classifications and factors such as the age at surgery, gender, TBIS, side-to-side difference (SSD), Tegner activity score (TAS), and Lysholm score were compared. RESULTS: The percentage of patients with ACL remnant pattern types 1, 2, 3, 4 was 19% (37 knees), 52% (101 knees), 9% (19 knees), and 18% (35 knees), respectively. The TBIS of the patients with Crain type 4 was significantly longer in comparison to the other groups ( p < 0.01). A significant difference was observed in the preoperative SSD of the Crain type 3 and Crain type 4 (6.2 ± 3.4 mm, 9.3 ± 3.6, respectively) groups. The TBIS in patients with Crain type 4 was significantly longer in comparison to the other groups ( p < 0.01). There were no significant differences between the groups in terms of the postoperative SSD, TAS, or Lysholm score. CONCLUSION: This study suggests that a Crain type 3 remnant was associated with a significantly lower preoperative SSD. In addition, the TBIS in patients with Crain type 4 was found to be significantly longer in comparison to the other groups. LEVEL OF EVIDENCE: Level III, case-control study.

The Effect of Remnant Tissue Preservation in Anatomic Double-Bundle ACL Reconstruction on Knee Stability and Graft Maturation.

Several investigators have developed anterior cruciate ligament reconstructions (ACLR) with remnant tissue preservation (RTP) and have reported better clinical outcomes. However, the effects of RTP remain controversial. To date, no reports have compared both clinical and radiological outcomes of anatomic double-bundle ACLR using the hamstring tendon and outside-in technique with/without RTP. This article evaluates the effectiveness of RTP in ACLR on knee stability and graft maturation. In total, 75 patients with unilateral ACL injury who had undergone anatomic double-bundle ACLR using autografted hamstring tendon either with RTP (Group P, n = 43) or without (Group N, n = 32) were enrolled. Clinical scores, pre- and postoperative side-to-side differences (SSDs) obtained using Telos, radiological evaluations of the grafted tendon using the signal/noise quotient (SNQ) measured using magnetic resonance imaging, and arthroscopic evaluations of the grafted tendon were retrospectively compared between the groups. Postoperative SSDs were smaller in the Group P (0.78 ± 1.90 mm) than in the Group N (1.29 ± 2.18 mm); however, this difference was not significant. Comparing two subgroups of the Group P, the SSD was significantly smaller in those with sufficient remnant coverage (-0.56 ± 1.38 mm) than in those without (1.48 ± 1.77 mm) (p = 0.019), as well as in the Group N patients (p = 0.019). The degree of synovial coverage of the anteromedial (p = 0.0064) and posterolateral (p = 0.032) bundle grafted tendon at the time of second-look arthroscopy was significantly better in the Group P than in the Group N. SNQ values of ACL grafted tendon at proximal (p = 0.049), middle, and distal (p = 0.039) one-third in Group P were better than those in Group N. RTP may enhance synovial coverage and maturation of the grafted tendon. Sufficient remnant tissue coverage may contribute to better knee stability. This is a Level III, retrospective comparative study.

The remnant preservation technique reduces the amount of bone tunnel enlargement following anterior cruciate ligament reconstruction.

PURPOSE: The aim of the present study was to investigate the correlation between postoperative tunnel enlargement after ACLR and remnant tissue preservation using the hamstring tendon. METHODS: One hundred and ninety-two subjects (male, n = 101; female, n = 91; mean age 27.1) who had undergone double-bundle ACL reconstruction were included in the present study. The patients were divided into two groups: the remnant tissue preservation group (Group R) and the non-remnant tissue preservation group (Group N). Computed tomographic scans of the operated knee were obtained at 2 weeks and 6 months after surgery. The area of the tunnel aperture for the anteromedial femoral tunnel (FAMT), posterolateral femoral tunnel (FPLT), anteromedial tibial tunnel (TAMT), and posterolateral tibial tunnel (TPLT) was measured. The area at 2 weeks after ACLR was subtracted from the area at 6 months after ACLR and then divided by the area at 2 weeks after ACLR. The differences in the outcomes and characteristics of the two groups were evaluated. RESULTS: Seventy-seven knees were classified into Group R, and 115 knees were classified into Group N. The age, gender, and body mass index did not differ to a statistically significant extent. The percentages of FAMT and TAMT enlargement in Group R were significantly smaller in comparison with Group N (P = 0.003 and P = 0.03, respectively). The percentage of FPLT and TPLT enlargement in the two groups did not differ to a statistically significant extent. CONCLUSION: The remnant-preserving technique reduces the amount of bone tunnel enlargement. The present findings indicate the advantages of the remnant-preserving ACLR technique, and therefore the remnant-preserving technique should be recommended. LEVEL OF EVIDENCE: II.

Evaluation of muscle activity just after straight leg raising exercise by using 18FDG-PET.

BACKGROUND: Exercise therapy is one of the recognized treatment methods for knee osteoarthritis (KOA). One such exercise technique, straight leg raising (SLR), is widely known as a home exercise method for strengthening the quadriceps femoris muscle. However, whether this exercise truly strengthens the quadriceps is not known. The objective of the present study was to investigate which lower limb muscle is stimulated and shows increased activity with SLR. METHODS: A total of 14 lower limbs in seven healthy adult male volunteers (mean age: 31.3 ± 2.2 years) were investigated. Participants were asked to perform SLR and subsequently underwent FDG-PET/CT examination for evaluation of the muscles of the entire lower limb. The maximum standardized uptake value (SUVmax) of each muscle (iliacus, psoas major, gluteus maximus, gluteus medius, gluteus minimus, vastus medialis, vastus intermedius, vastus lateralis, rectus femoris, biceps femoris, semimembranosus, semitendinosus, adductor, sartorius, gracilis, tibialis anterior, tibialis posterior, soleus, medial head of gastrocnemius, and lateral head of gastrocnemius) was measured in four cross-sections: at the trunk, pelvis, thigh, and lower leg. RESULTS: SUVmax was significantly greater in: iliacus and adductor compared to vastus medialis, vastus lateralis, biceps, semitendinosus, gracilis, tibialis anterior, and gastrocnemius; psoas major compared to all muscles except for gluteus minimus and adductor; gluteus minimus compared to all muscles except for iliacus, psoas major, gluteus medius, and adductor; and gluteus medius compared to semitendinosus and gracilis. CONCLUSIONS: After SLR, SUVmax was significantly greater in iliacus, psoas major, gluteus minimus, gluteus medius, and adductor compared to some of the other muscles. Performing SLR increased glucose metabolism of the above muscles in particular, and this may have increased their activity levels.

Patient age as a preoperative factor associated with tunnel enlargement following double-bundle anterior cruciate ligament reconstruction using hamstring tendon autografts.

PURPOSE: A few studies have detected associations of post-operative tunnel enlargement with sex, age, and the timing of anterior cruciate ligament reconstruction (ACLR). The aim of the present study was to investigate the correlation between post-operative tunnel enlargement following ACLR using hamstring tendon autografts and preoperative factors. The authors hypothesized that tunnel enlargement is associated with age in patients undergoing ACLR. METHODS: One hundred and six patients (male, n = 57; female, n = 49; mean age, 26.9 years) who underwent double-bundle ACL reconstruction were included in the present study. The time between injury and surgery was 26.3 ± 71.4 weeks. Computed tomographic scans of the operated knee were obtained at 2 weeks and 6 months after surgery. The area of the tunnel aperture was measured for the femoral anteromedial tunnel (FAMT), femoral posterolateral tunnel (FPLT), tibial anteromedial tunnel (TAMT), and tibial posterolateral tunnel. The percentage of tunnel area enlargement was defined as the area at 2 weeks after ACLR subtracted from the area at 6 months after ACLR and then divided by the area at 2 weeks after ACLR. Spearman's correlation coefficient was calculated for each factor. The patients were divided into two groups based on age. Patients aged <40 and ≥40 years were assigned to Groups A and B, respectively. The differences in the outcomes and characteristics of the two groups were evaluated. RESULTS: The percentage of enlargement of the FAMT, FPLT, and TAMT was correlated with patient age (r = 0.31, p = 0.001; r = 0.24, p = 0.012; and r = 0.30, p = 0.002, respectively). In total, 87 and 19 knees were classified into Groups A and B, respectively, based on patient age. The percentage of enlargement of the FAMT was significantly higher in Group B than A (78 vs. 60%, respectively; p = 0.01). The percentage of enlargement of the TAMT was significantly higher in Group B than A (53 vs. 36%, respectively; p = 0.03). CONCLUSION: The percentage of enlargement of the FAMT and TAMT was associated with patient age. These findings suggest the need to consider the possibility of tunnel enlargement when double-bundle ACLR is performed for patients aged >40 years. Age was a preoperative factor associated with tunnel enlargement. LEVEL OF EVIDENCE: III.

Shear wave velocity measurement of upper trapezius muscle by color Doppler shear wave imaging.

PURPOSE: Skeletal muscle stiffness is thought to be the result of increased tissue hardness, but measurement accuracy has been dependent on operator technique. We have proposed a novel shear wave real-time imaging method (color Doppler shear wave imaging: CD SWI) with continuous shear waves excited from the tissue surface by a mechanical vibrator. METHODS: Using the method, shear wave velocity was measured for the upper trapezius muscle. Adaptive shear wave velocity measurement by means of quality estimation of shear wave wavefront was adopted. We recruited 23 male volunteers with no history of orthopedic disease and recorded shear wave propagation to assess the intra- and inter-observer reliability. For intra-observer reliability, one observer took two measurements separated by a time delay, and the intra-class correlation coefficient (ICC) was calculated (1,1). For inter-observer reliability, ICC (2,1) was calculated from both observers' measurements. RESULTS: Mean propagation speed was 3.75 ± 0.47 (first) and 3.71 ± 0.49 m/s (second) for Observer A (ICC (1,1) = 0.91 [95% CI 0.76-0.96]) and 3.80 ± 0.53 m/s for Observer B (ICC (2,1) = 0.83 [95% CI 0.56-0.94]). CONCLUSIONS: This result suggests that our technique is satisfactorily reliable and has potential for future application in various fields, such as evaluation of muscle condition or the effects of rehabilitation.

Factors affecting knee laxity following anterior cruciate ligament reconstruction using a hamstring tendon.

BACKGROUND: The aim of the present study was to investigate the correlation between the pre-operative and intraoperative factors that predict postoperative knee laxity following anterior cruciate ligament (ACL) reconstruction using a hamstring tendon. METHODS: The subjects included 108 patients (male, n=49; female, n=59) with ACL-deficient knees who had undergone double-bundle reconstruction. The median time between injury and surgery (TBIS) was 27.5weeks (range one to 504). The patients were divided into two groups according to the side-to-side difference (SSD) in anterior translation on a stress radiograph one year after undergoing the operation (Group A: SSD of <3mm and Group B: SSD of ≥3mm) and were compared regarding such factors as age at surgery, sex, body mass index, pivot shift test, TBIS, pre-operative laxity, concomitant ligament, meniscus, and articular cartilage injury. A logistic regression analysis was performed to identify the factors associated with knee laxity. RESULTS: The postoperative SSD values after one year were correlated with the TBIS (r=0.28; P<0.01). Eighty-one and 27 knees were classified into Groups A and B, respectively, based on the SSD at one year after surgery. The TBIS in Group B (60.2weeks) was significantly longer than that in Group A (16.6weeks; P<0.01). A logistic regression analysis showed that there was a significant association between the TBIS and postoperative knee laxity (P<0.01; odds ratio 1.013; 95% CI 1.002-1.023). CONCLUSION: Increased knee laxity was associated with the time between injury and surgery.

A Case of Infrapatellar Fat Pad Ganglion of the Knee.

INTRODUCTION: A ganglion cyst can induce symptoms around the knee and should be considered as an intra-articular mass in differential diagnosis. CASE PRESENTATION: A 22-year-old female presented with a persistent medial knee joint pain in her left knee for 2 years. There was soft tissue swelling on the anteromedial aspect of the infrapatellar region on her left knee. Lachman and McMurray tests were negative. MRI showed a multilobular cyst in the infrapatellar fat pad with T1 low intensity and T2 STIR high intensity. The cyst was not attached to either meniscus. ACL and PCL looked normal.During surgery, the cyst was found to arise from the intra-patellar fat pad and was not attached to the menisci or synovium. The cyst was completely resected.Histological findings showed a multilobular cyst with a glassy fibrous tissue wall and clear jelly-like consistency, confirming the diagnosis of a ganglion. The patient recovered asymptomatically and has been without recurrence 7 years postoperatively. CONCLUSION: Differential diagnoses of an infrapatellar swelling are a meniscal cyst, synovial cyst, or ganglion. Most cases of cysts around the knee generate from fluid collection through meniscal tears. A ganglion cyst is a synovium-lined structure and is common around the wrist joint, but rare in the knee joint. A ganglion cyst in the knee joint often arises from ACL or PCL, but rarely arises from the infrapatellar fat pad. A ganglion cyst is one of the differential diagnoses of parameniscal cysts around the knee. We recommended an open resection with arthroscopic examination.