A modified anatomical posterior cruciate ligament reconstruction technique using the posterior septum and posterior capsule as landmarks to position the low tibial tunnel.

BACKGROUND: Lowering the exit position of the tibial tunnel can improve the clinical efficacy of posterior cruciate ligament (PCL) reconstruction, however, there is no unified positioning standard. This study aimed to use novel soft tissue landmarks to create a low tunnel. METHODS: A total of 14 human cadaveric knees and 12 patients with PCL injury were included in this study. Firstly, we observed the anatomical position between the PCL, posterior septum, and other tissue, and evaluated the relationship between the center of the low tibial tunnel (SP tunnel) and posterior septum and distal reflection of posterior capsule, and using computed tomography (CT) to evaluate distance between the center of the SP tunnel with bony landmarks. Then, evaluated the blood vessels content in the posterior septum with HE staining. Finally, observed the posterior septum and distal reflection of the posterior capsule under arthroscopy to explore the clinical feasibility of creating a low tibial tunnel, and assessed the risk of surgery by using ultrasound to detect the distance between the popliteal artery and the posterior edge of tibial plateau bone cortex. RESULTS: In all 14 cadaveric specimens, the PCL tibial insertions were located completely within the posterior medial compartment of the knee. The distance between the center of the SP tunnel and the the articular surface of tibial plateau was 9.4 ± 0.4 mm. All SP tunnels retained an intact posterior wall, which was 1.6 ± 0.3 mm from the distal reflection of the posterior capsule. The distances between the center of the SP tunnel and the the articular surface of tibial plateau, the champagne glass drop-off were 9.2 ± 0.4 mm (ICC: 0.932, 95%CI 0.806-0.978) and 1.5 ± 0.2 mm (ICC:0.925, 95%CI 0.788-0.975) in CT image. Compared with the posterior capsule, the posterior septum contained more vascular structures. Last, all 12 patients successfully established low tibial tunnels under arthroscopy, and the distance between the posterior edge of tibial plateau bone cortex and the popliteal artery was 7.8 ± 0.3, 9.4 ± 0.4 and 7.4 ± 0.3 mm at 30°, 60° and 90° flexion angels after filling with water and supporting with shaver in posterior-medial compartment of knee joint. CONCLUSIONS: A modified low tibial tunnel could be established in the PCL anatomical footprint by using the posterior septum and posterior capsule as landmarks.

Three different patellar fixation techniques yield similar clinical and radiological outcomes in recurrent patellar dislocation undergoing medial patellofemoral ligament reconstruction.

PURPOSE: The purpose of this study was to evaluate and compare the clinical and radiological outcomes of three different patellar fixation techniques on medial patellofemoral ligament reconstruction (MPFLR) in the treatment of patellar dislocation (PD). METHODS: Between 2015 and 2020, 130 patients with recurrent PD who underwent surgical reconstruction were eligible for this retrospective study: 48 patients were treated with the semi-tunnel bone bridge fixation technique (Group A), 42 patients were treated with the suture anchor fixation technique (Group B) and 40 patients were treated with the transpatellar tunnel fixation technique (Group C). Clinical outcomes included functional outcomes (Kujala, Lysholm and International Knee Documentation Committee scores), activity levels (Tegner activity score and return to sports), physical examinations, patellar re-dislocation rate and complications. Radiological outcomes included patellar congruence angle, patellar tilt angle, lateral patellar translation and lateral patellar angle. RESULTS: All clinical and radiological outcomes improved significantly in all groups, without any significant difference among these three groups. At the final follow-up, no re-dislocation occurred, and all groups achieved a successful return to sports. However, the semi-tunnel bone bridge and suture anchor fixation techniques showed statistically higher Tegner activity scores (p = 0.004) and shorter time from surgery to return to sports (p = 0.007) than the transpatellar tunnel fixation technique. CONCLUSION: The three MPFLR patellar fixation techniques achieved favourable and comparable clinical and radiological outcomes in the treatment of PD. Compared with the transpatellar tunnel fixation technique, the semi-tunnel bone bridge and suture anchor fixation techniques may be more effective with higher activity levels. LEVEL OF EVIDENCE: Level III.

Clinical outcomes of derotational femoral osteotomy combined with medial patellofemoral ligament reconstruction in patients with patellar dislocation and increased femoral anteversion unaffected by the pattern of distribution of femoral torsion.

PURPOSE: The aim of this study was to evaluate the clinical effect of derotational femoral osteotomy combined with medial patellofemoral ligament reconstruction for patellar dislocation and the effect of the distribution of femoral torsion at different segments on postoperative function. METHODS: Forty-two patients with patellar dislocation who underwent derotational femoral osteotomy from 2017 to 2021 were retrospectively analysed. All patients received computed tomography scans from the hip to the knee to evaluate correction of the femoral anteversion (FA) angle, patellar tilt angle (PTA) and congruence angle (CA) after derotational femoral osteotomy. Subjective scores, such as the Kujala, Lysholm, International Knee Documentation Committee (IKDC), Tegner and visual analog scale (VAS) scores, were used to evaluate knee function before and after the operation. Patients with supracondylar torsion > distal torsion were categorized into the supracondylar torsion group and patients with distal torsion > supracondylar torsion were categorized into the distal torsion group. Subgroup analyses were performed. RESULTS: No presentation of redislocation occurred in these patients at the minimum 2-year follow-up visit. The mean preoperative FA angle in the supracondylar torsion group was 30.2° ± 4.2°, and the mean postoperative FA angle was 14.5° ± 2.5° (p < 0.001). The mean preoperative FA angle was 26.7° ± 1.4° and the mean postoperative FA angle was 14.1° ± 1.4° in the distal torsion group. In addition, postoperative PTA and CA were significantly corrected in both groups (p < 0.001). The postoperative Kujala, Lysholm, IKDC, Tegner and VAS scores were significantly improved in both groups (p < 0.001). Subgroup analyses showed a higher preoperative FA in the supracondylar torsion group and a higher occurrence of high-grade trochlear dysplasia in the distal torsion group. However, there was no significant difference in their postoperative clinical outcomes. CONCLUSION: Through a minimum of 2-year follow-up visits of patients with patellar dislocation and increased FA, it was found that derotational femoral osteotomy could significantly reduce FA and improve subjective knee function. The pattern of torsion distribution did not significantly affect the clinical outcomes of derotational femoral osteotomy. These findings readvised orthopaedic surgeons that derotational femoral osteotomy remains the preferred procedure for correcting rotational malalignment, but that they should be more cautious about its indications. LEVEL OF EVIDENCE: Level IV.

The tibial capsular reflection and septum in posterior compartment are safe and reliable soft-tissue landmark for tibial tunnel drilling in posterior cruciate ligament reconstruction.

PURPOSE: To investigate the validity of using tibial capsular reflection and septum in the posterior compartment as landmark during posterior cruciate ligament (PCL) reconstruction (PCLR). METHODS: Anatomic measurements were obtained for 12 fresh human cadaveric knee specimens to observe the spatial position of the tibial insertion of the PCL in relation to the posterior septum and the capsular reflection in the posterior compartment. Sixty patients who underwent reconstruction of the PCL between 2020 and 2023 were also retrospectively investigated. The tibial tunnel was replaced in all patients using the same method (with reference to the tibial capsular reflection and the posterior septum). The placement of the tibial tunnel was assessed using X-ray fluoroscopy intraoperatively and computed tomography and three-dimensional reconstruction postoperatively. RESULTS: All fibres in the tibial insertion of the PCL in the 12 cadaveric specimens were located in the posteromedial compartment, adjacent to the posterior septum. The inferior border of the PCL insertion is adjacent to the tibial capsular reflection, which is attached at the champagne glass drop-off of the posterior tibia. In our previous cases, none of the patients experienced postoperative or intraoperative complications such as neurovascular injury, and the angle between the pin and the PCL facet was 93.1 ± 3.9° as measured on intraoperative radiographs. The mean distance from the centre of the tibial tunnel outlet to the inferior border of the PCL insertion was 5.6 ± 1.1 mm, and the distance from the centre of the tibial tunnel outlet to the outer border of the PCL insertion as a percentage of the length of the inferior border of PCL insertion was 42.2 ± 6.3%. CONCLUSION: The tibial capsular reflection and septum in the posterior compartment are safe and reliable soft-tissue landmark for tibial tunnel drilling in PCLR. LEVEL OF EVIDENCE: Level Ⅳ.

Study on the correlation between the severity of patellofemoral arthritis and the morphology of the distal femur.

PURPOSE: Distal femoral torsion is a key factor for poor alignment of patellofemoral joint. This study aims to evaluate the correlation between distal femoral torsion and the severity of patellofemoral arthritis, and to analyze the correlation between distal femoral torsion and the morphology of femoral condyle. METHODS: A retrospective analysis was performed on 125 patients awaiting surgical treatment for knee osteoarthritis from January 2021 to March 2022(79 females, 46 males, average age: 65.78 years, SD 6.61). All patients underwent knee joint radiography, lower-limb digital radiography, and knee joint CT scans. The ratio of length of each distal femoral condyle, TT-TG, patellar tilt, DFL-PCL, DFL-TEA, TEA-PCL and TEA-ACL were measured. The Pearson correlation coefficient was used to evaluate the correlation between distal femoral torsion and ratio of distal femoral condyle, TT-TG and patellar tilt. Logistic regression was used to evaluate the correlation between each parameter and the severity of PFOA. RESULTS: With the increased severity of PFOA, TT-TG, patellar tilt, DFL-PCL, DFL-TEA and PCA all tended to increase. Patellar tilt was correlated with DFL-PCL (r = 0.243) and TEA-PCL(r = 0.201), but TT-TG had no evident correlation with distal femoral torsion. Compared with Grade I patients of PFOA, DFL-PCL, DFL-TEA, and TEA-PCL were risk factors for increased severity of patellofemoral arthritis in Grade III patients of PFOA, but there was no significant statistic difference in Grade II patients of PFOA. CONCLUSIONS: Distal femoral torsion correlates with the severity of patellofemoral arthritis. Variation of the femoral transepicondylar axis caused by the change of ratio of the femoral condyle is particularly important in the distal femoral torsion. In patients with severe PFOA, abnormal variation of the femoral condyle axis should be not ignored.

The larger patellar tilt angle and lower intercondylar notch angle might increase posterior cruciate ligament injury risk: a retrospective comparative study.

BACKGROUND: Posterior cruciate ligament (PCL) injuries are common ligament injuries of the knee, and previous studies often focused on the associations between the morphology of the knee and PCL injuries. Studies on the correlation between PCL injuries and patellofemoral alignment are limited. METHODS: This retrospective study included 92 patients with PCL injured and 92 patients with PCL intact. Measurement parameters were compared between the two groups, including patellar tilt angle, congruence angle, patellar height, hip-knee-ankle angle, lateral trochlear inclination, femoral condyle ratio, bicondylar width, intercondylar notch width and index, notch angle, trochlear facet asymmetry, and trochlear sulcus depth and angle. Independent risk factors associated with PCL injuries were identified by logistic regression analyses. RESULTS: In the PCL injured group, the patellar tilt angle was significantly larger (13.19 ± 5.90° vs. 10.02 ± 4.95°, P = 0.04); the intercondylar notch angle was significantly lower (60.97 ± 7.83° vs. 67.01 ± 6.00°, P = 0.004); the medial and lateral femoral condyle ratio were significantly larger (0.63 ± 0.64 vs. 0.60 ± 0.56, P = 0.031; 0.65 ± 0.60 vs. 0.58 ± 0.53, P = 0.005) than in the PCL intact group. There were 11 patients with patellar dislocation in the PCL injured group, accounting for 12%. In these patients, the patellar height was higher (1.39 ± 0.17 vs. 1.09 ± 0.25, P = 0.009); the trochlear sulcus angle was larger (157.70 ± 8.7° vs. 141.80 ± 8.78°, P < 0.001); and the trochlear sulcus depth was shallower (3.10 ± 1.20mm vs. 5.11 ± 1.48mm, P = 0.003) than those in the patients without patellar dislocation. Multivariate analyses showed that patellar tilt angle (each increase 1 degree, OR = 1.14) and intercondylar notch angle (each increase 1 degree, OR = 0.90) were independent risk factors for PCL injuries. CONCLUSION: The patients with PCL injuries had larger patellar tilt angles, lower intercondylar notch angles, and longer posterior femoral condyles than patients with PCL intact. The larger patellar tilt angle and lower intercondylar notch angle might be risk factors for PCL injuries.

Residual varus alignment after posterior-stabilized total knee arthroplasty limits medial soft tissue remodeling.

BACKGROUND: Proper lower limb alignment and soft tissue balance are significant indicators to measure the success of total knee arthroplasty (TKA). Previous studies have confirmed that soft tissue relaxation around the knee after TKA will change over time; however, the relationship between lower limb alignment and soft tissue balance after TKA remains unclear. We studied (1) whether the change of soft tissue balance around the knee with time after posterior-stabilized (PS) TKA would affect the alignment of the lower limbs; (2) Whether the accuracy of lower limb alignment during PS TKA affects postoperative soft tissue remodeling. METHODS: In this study, 100 patients were recruited after PS TKA. Among them, 50 patients with a hip knee ankle (HKA) angle of ≤ ± 3° were set as the neutral group, and 50 patients with an HKA angle of > ± 3° were set as the deviation group. The imaging results measured the HKA angle before the operation as well as the HKA, varus, and valgus angles at 1, 3, 6, 12, and 24 months after TKA. Clinical assessment included range of motion (ROM), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Knee Society Score (KSS). RESULTS: Eight people were excluded from the study. After the exclusion, the study enrolled 47 patients in the neutral group and 45 patients in the deviant group and were followed for up to 2 years. There was no statistical significance in mean varus angles as well as HKA angle changes during the follow-up phase of each groups (P > 0.05). The mean valgus angles of the patients in the neutral group group were 2.47°, 3.45°, 3.63°, 3.60° and 3.63°, and in the deviation group were 2.45° (P = 0.841), 2.88° (P < 0.001), 3.07° (P < 0.001), 3.06° (P < 0.001), and 3.10° (P < 0.001). ROM, WOMAC and KSS of the two groups were significantly improved after operation, with no difference between the two groups. CONCLUSION: This study shows that whether the alignment is accurate or not in the early stage after TKA, the relaxation of the medial and lateral soft tissues of the knee joint change; however, this change will not significantly affect the alignment of the lower limbs. Postoperative residual varus deformity limits medial soft tissue remodeling. LEVEL OF EVIDENCE: III.

Medial patellofemoral ligament reconstruction combined with derotational distal femoral osteotomy yields better outcomes than isolated procedures in patellar dislocation with increased femoral anteversion.

PURPOSE: The purpose of this study was to evaluate and compare clinical and radiological outcomes between isolated medial patellofemoral ligament reconstruction (MPFLR) and MPFLR combined with derotational distal femoral osteotomy (DDFO) for patellar dislocation with increased femoral anteversion (FA). METHODS: Between 2014 and 2019, 36 patients who underwent isolated MPFLR and 31 patients who underwent MPFLR combined with DDFO were retrospectively included. Clinical outcomes included physical examinations, functional outcomes (Kujala, Lysholm, International Knee Documentation Committee (IKDC), and Banff Patella Instability Instrument (BPII) scores), activity level (Tegner activity score and return to sports), complications, and patellar re-dislocation rate. Radiological outcomes included patella tilt angle, patellar congruence angle, and patella-trochlear groove distance. RESULTS: All clinical outcomes improved significantly in both groups, but the DDFO group had significantly better postoperative scores than the MPFLR group (Kujala: 85.1 ± 7.7 vs. 80.5 ± 8.4, P = 0.023; Lysholm: 86.8 ± 8.2 vs. 81.9 ± 9.1, P = 0.026; IKDC: 86.2 ± 10.0 vs. 81.7 ± 8.1, P = 0.045; and BPII: 68.0 ± 12.5 vs. 62.3 ± 10.0, P = 0.039). Both groups achieved successful return to sports (90.3% vs. 91.7%). No re-dislocation or major complications occurred. Radiological outcomes improved significantly in both groups, but the DDFO group had better outcomes (P < 0.05). The tibial tubercle-trochlear groove distance was only improved after DDFO from 17.0 ± 2.3 mm to 15.1 ± 2.0 mm (P = 0.001). CONCLUSION: Both isolated MPFLR and MPFLR combined with DDFO yielded satisfactory clinical and radiological outcomes in the treatment of patellar dislocation with increased FA. However, combined DDFO had better outcomes and should be considered a priority. LEVEL OF EVIDENCE: Level III.

Distal femoral torsion is correlated with higher-grade trochlear dysplasia and shorter anterior condyles in patients with patellar dislocation and increased femoral torsion.

PURPOSE: To describe the characteristics of femoral torsion in patients with different segmental torsion types and to evaluate the correlations between segmental torsion and the morphology of the femoral condyles and trochlea in patients with patellar dislocation and increased femoral torsion. METHODS: Between January 2021 and March 2023, 69 patients were included and classified into two groups according to the femoral segment contributing the most to total torsion: 32 patients in Group A (femoral neck and shaft torsion) and 37 patients in Group B (distal torsion). Trochlear dysplasia was evaluated using Dejour's classification and sulcus angle. The morphology of the femoral condyles was evaluated using the lengths and ratios of the medial and lateral condyles. Correlations between femoral torsion and morphology were evaluated. RESULTS: Total torsion was significantly correlated with femoral neck and shaft torsion (r = 0.882, P < 0.001) and distal torsion (r = 0.262, P = 0.030). Femoral neck and shaft torsion was significantly increased with increasing total torsion. The trochlear sulcus was flatter and more dysplastic, and the anterior condyles were shorter in Group B. Distal torsion was significantly correlated with the lengths of the medial and lateral anterior condyles (r = - 0.567, P < 0.001; r = -0.701, P < 0.001), sulcus angle (r = 0.611, P < 0.001) and Dejour trochlea type (r = 0.512, P = 0.001), while femoral neck and shaft torsion showed no correlations. CONCLUSION: Femoral torsion is a complex of femoral neck and shaft torsion and distal torsion, especially femoral neck and shaft torsion. Distal torsion was significantly correlated with a flatter trochlear sulcus, higher-grade trochlear dysplasia, and shorter anterior condyles. The new findings highlighted the importance of the segmental evaluation of femoral torsion, which would facilitate understanding of the anatomical characteristics of femoral torsion in patients with patellar dislocation and increased femoral torsion and may lead to improvement in the surgical options regarding femoral torsion. LEVEL OF EVIDENCE: Level III.

Patients with trochlear dysplasia have dysplastic medial femoral epiphyseal plates.

PURPOSE: To investigate the growth of the epiphyseal plate in patients with trochlea dysplasia using a 3D computed tomography (CT)-based reconstruction of the bony structure of the distal femur. The epiphysis plate was divided into a medial part and a lateral part to compare their differences in patients with trochlear dysplasia. METHODS: This retrospective study included 50 patients with trochlea dysplasia in the study group and 50 age- and sex-matched patients in the control group. Based on the CT images, MIMICS was used to reconstruct the bony structure of the distal femur. Measurements included the surface area and volume of the growth plate (both medial and lateral), the surface area and capacity of the proximal trochlea, trochlea-physis distance (TPD) (both medial and lateral), and height of the medial and lateral condyle. RESULTS: The surface area of the medial epiphyseal plate (1339.8 ± 202.4 mm2 vs. 1596.6 ± 171.8 mm2), medial TPD (4.9 ± 2.8 mm vs. 10.6 ± 3.0 mm), height of the medial condyle (1.1 ± 2.5 mm vs. 4.9 ± 1.3 mm), and capacity of the proximal trochlear groove (821.7 ± 230.9 mm3 vs. 1520.0 ± 498.0 mm3) was significantly smaller in the study group than in the control group. A significant positive correlation was found among the area of the medial epiphyseal plate, the medial TPD, the height of the medial condyle and the capacity of the proximal trochlear groove (r = 0.502-0.638). CONCLUSION: The medial epiphyseal plate was dysplastic in patients with trochlea dysplasia. There is a significant positive correlation between the surface area of the medial epiphyseal plate, medial TPD, height of the medial condyle and capacity of the proximal trochlear groove, which can be used to evaluate the developmental stage of the trochlea in clinical practice and to guide targeted treatment of trochlear dysplasia. LEVEL OF EVIDENCE: III.

Two-type classification system for femoral trochlear dysplasia in recurrent patellar instability based on three-dimensional morphology.

PURPOSE: Radiographic and two-dimensional (2D) CT/MRI analysis of femoral trochlear dysplasia play a significant role in surgical decision-making for recurrent patellar instability. However, the three-dimensional morphology of dysplastic trochlea is rarely studied due to the limitations of conventional imaging modalities. This study aimed to (1) develop a 3D morphological classification for trochlear dysplasia based on the concavity of the trochlear groove and (2) analyze the interrater reliability of the classification system. METHODS: The 3D trochleae of 132 knees with trochlear dysplasia and recurrent patellar instability were reconstructed using CT scan data and classified using the innovative classification criteria between January 2016 and June 2020. A concave trochlear sulcus with sloped medial and lateral trochlear facets was classified as Type I trochlea. The trochlear groove with no concavity is classified as Type II. Furthermore, in Type II, the trochlea with the elevated trochlear floor at the proximal part was identified as IIa and the trochlea with the hypoplastic trochlear facets as IIb. The intra- and inter-rater reliability was examined using kappa (κ) statistics. RESULTS: The 3D classification system showed substantial intra-rater agreement and moderate interrater agreement (0.581 ~ 0.772). The intra- and interrater agreement of Dejour's four-grade classification was fair-to-moderate (0.332 ~ 0.633). Eighty-one trochleae with concave trochlear sulcus were classified as Type I, and fifty-one without concavity as Type II. Twenty-five non-concave trochleae were classified as type IIa due to the elevated trochlear floor and 26 trochleae into IIb with the hypoplasia of trochlear facets. CONCLUSION: This study developed a 3D classification system to classify trochlear dysplasia according to trochlear concavity and morphology of the trochlear facets. On CT/MRI scans or 3D reconstructions, the interpretation of features of dysplastic trochleae may vary, especially for the flat and convex trochleae. The novel system provides morphological evidence for when to consider trochleoplasty according to the different types of trochlear sulcus.

Derotational distal femur osteotomy combined with medial patellofemoral ligament reconstruction yields satisfactory results in recurrent patellar dislocation with excessive femoral anteversion angle and trochlear dysplasia.

PURPOSE: The purpose of this study was to evaluate the clinical outcomes of medial patellofemoral ligament (MPFL) reconstruction combined with derotational distal femur osteotomy in patients with recurrent patellar dislocation who had excessive femoral anteversion angle and trochlear dysplasia. METHODS: Between 2015 and 2020, 64 patients (64 knees) with recurrent patellar dislocation, who had excessive femoral anteversion angle (≥ 25°) and trochlear dysplasia and were surgically treated using derotational distal femur osteotomy and MPFL reconstruction, were eligible for this retrospective study. These patients were assigned to two groups according to the grade of trochlear dysplasia. Group A (type A trochlear dysplasia, n = 33) and Group B (type B, C, D trochlear dysplasia, n = 31). Preoperative and postoperative patellar tilt angle (PTA), Caton-Deschamps index (CD-I), tibial tubercle-trochlear groove (TT-TG) distance and femoral anteversion angle were evaluated. Patient outcomes were assessed using the preoperative and postoperative International Knee Documentation Committee (IKDC) score, Kujala score, Lysholm score, Tegner score, and visual analog scale (VAS) score. RESULTS: A total of 64 patients (64 knees) were evaluated in this study, with a mean follow-up period of 28.4 ± 3.6 months. There were no cases of wound infection, osteotomy site fractures, deep venous thrombosis of the lower extremities, or re-dislocation in the two groups during the postoperative follow-up period. All patients returned to full extension and flexion. The postoperative Tegner score, Lysholm score, Kujala score, IKDC score, VAS score, PTA, CD-I, TT-TG distance, and femoral anteversion angle were significantly improved compared with the preoperative status (P < 0.05). There was no significant difference between the two groups (n.s.). CONCLUSION: MPFL reconstruction combined with derotational distal femur osteotomy showed satisfactory clinical outcomes during follow-up in patients with recurrent patellar dislocation who had excessive femoral anteversion angle and trochlear dysplasia. Even patients with high-grade trochlear dysplasia showed satisfactory results. For those patients, additional surgery is not necessary. LEVEL OF EVIDENCE: Level III.

Coronal Laxity at Flexion is Larger After Posterior-Stabilized Total Knee Arthroplasty Than With Cruciate-Retaining Procedures.

BACKGROUND: It is unclear whether coronal stability differs between cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasty (TKA). The purpose of this study was to compare coronal laxity, radiological, and clinical outcomes between CR-TKA and PS-TKA. METHODS: Seventy five CR-TKAs and 72 PS-TKAs with a minimum 2-year follow-up were retrospectively evaluated. Coronal laxity was assessed at knee extension and 80° of flexion on varus and valgus stress radiographs. Radiological evaluation included femoral-tibial angle, hip-knee-ankle angle, and positions of femoral and tibial components. Clinical evaluation included the modified Hospital for Special Surgery score, the Western Ontario and McMaster Universities Osteoarthritis index, and range of motion. RESULTS: PS-TKA resulted in significantly larger varus, valgus, and total laxities at 80° flexion (P = .034, .031, and 0.001, respectively) compared with CR-TKA, while no significant difference was found at extension (P = .513, .964, and .658, respectively). No statistical difference was found in radiological and clinical outcomes between CR-TKA and PS-TKA, but the functional scores were slightly better in CR-TKA. There were adverse correlations between varus laxity at flexion and the Western Ontario and McMaster Universities Osteoarthritis index, the modified Hospital for Special Surgery score, and range of motion (r = 0.933, -0.229, -0.472, respectively). CONCLUSION: Coronal laxity at 80° of flexion was larger after PS-TKA than CR-TKA. In addition, clinical outcomes were adversely affected by the larger varus laxity at flexion. Care should be taken to maintain the coronal stability, especially at flexion, during surgery to obtain better patient-reported outcomes. LEVEL OF EVIDENCE: Level III.

Distalization of tibial tubercle osteotomy is not necessary for patients with recurrent patellar dislocation accompanied by patella alta and increased TT-TG distance.

BACKGROUND: The aim of this study is to determine whether distalization of the tibial tubercle is necessary for patients with recurrent patellar dislocation accompanied by patella alta and increased TT-TG. METHODS: In this retrospective study, all 70 patients (70 knees) with recurrent patellar dislocation accompanied by TT-TG distance ≥20 mm and patella alta (CD-I ≥ 1.4) were surgically treated using MPFLR combined with medialization of the tibial tubercle or medialization and distalization of the tibial tubercle in the Third Hospital of Hebei Medical University between 2017 and 2019. 33 patients(33 knees) received MPFLR combined with medialization of the tibial tubercle (MPFLR + TTm group), 37 patients(37 knees) received MPFLR combined with medialization and distalization of the tibial tubercle (MPFLR + TTm-d group). Evaluation indicators included knee injury and osteoarthritis prognostic score (KOOS) and Kujala score evaluation, congruence angle (CA), patellar tilt angle (PTA), TT-TG distance, Blackburne-Peel index (BP-I), Caton-Deschamps index (CD-I). RESULTS: A total of 70 knees (70 patients) with a mean follow-up time of 32 ± 6 months were evaluated in the present study. The postoperative, the PTA, CA, CD-I, BP-I, and TT-TG distance significantly improved in the two groups (P < 0.05), and there was no statistical difference between the two groups (>0.05). The KOOS and Kujala scores of the two groups at the last follow-up were significantly higher than the preoperative scores (P < 0.05), and there was no statistical difference between the two groups (P>0.05). No complications were noted in either group. CONCLUSION: For patients with recurrent patellar dislocation accompanied by increased TT-TG distance and patella alta, distalization is not needed and medialization is sufficient even in the presence of patella alta.

The tibial tubercle-posterior cruciate ligament (TT-PCL) distance does not truly reflect the lateralization of the tibial tubercle.

PURPOSE: The role of the tibial tubercle-posterior cruciate ligament (TT-PCL) and tibial tubercle-trochlear groove (TT-TG) in recurrent patellar instability (RPI) remains unclear. This study aims to confirm the validity of the TT-TG and TT-PCL in predicting RPI and to verify whether the TT-PCL can truly reflect the lateralization of the tibial tubercle. METHODS: A total of 50 patients with RPI and 50 controls were recruited and underwent magnetic resonance imaging examinations. The TT-TG, TT-PCL, and tibial tubercle lateralization (TTL) were measured independently by two authors in a blinded and randomized fashion. T-test was used for parametric variances and the Mann-Whitney U and Chi-square tests were used for non-parametric variances. Pearson's product moment correlation coefficients were calculated to determine correlations between the defined measurements. The intraclass correlation coefficient was used to assess the reliability of the measurements. RESULTS: All defined measurements showed excellent intra- and inter-observer reliability. The TT-TG distance, TT-PCL distance, and TTL were significantly greater in the PI group than in the control group. The AUC was highest for the TT-TG distance compared with that for the TT-PCL distance, and TTL were 0.798, 0.764, and 0.769, with the calculated cut-off value of 12.5 mm, 16.5 mm, and 66.1 percentages. There was a moderate correlation (r = 0.595) between the TT-TG distance and TTL, and a weak correlation (r = 0.430) between the TT-PCL distance and TTL. CONCLUSION: Both the TT-TG distance and TT-PCL distance can be measured with excellent reliability on magnetic resonance imaging. The TT-TG distance, rather than the TT-PCL distance, has a better performance in predicting RPI. Most interestingly, the TT-PCL distance cannot reflect the real lateralization of TT. This study provides new information to evaluate TTL in patients with RPI. LEVEL OF EVIDENCE: III.

Early patellofemoral articular cartilage degeneration in a rat model of patellar instability is associated with activation of the NF-κB signaling pathway.

BACKGROUND: Patellar instability (PI) often increases the possibility of lateral patellar dislocation and early osteoarthritis. The molecular mechanism of early articular cartilage degeneration during patellofemoral osteoarthritis (PFOA) still requires further investigation. However, it is known that the NF-κB signaling pathway plays an important role in articular cartilage degeneration. The aim of this study was to investigate the relationship between the NF-κB signaling pathway and patellofemoral joint cartilage degeneration. METHODS: We established a rat model of PI-induced PFOA. Female 4-week-old Sprague-Dawley rats (n = 120) were randomly divided into two groups: the PI (n = 60) and control group (n = 60). The distal femurs of the PI and control group were isolated and compared 4, 8, and 12 weeks after surgery. The morphological structure of the trochlear cartilage and subchondral bone were evaluated by micro-computed tomography and histology. The expression of NF-κB, matrix metalloproteinase (MMP)-13, collagen X, and TNF-ɑ were evaluated by immunohistochemistry and quantitative polymerase chain reaction. RESULTS: In the PI group, subchondral bone loss and cartilage degeneration were found 4 weeks after surgery. Compared with the control group, the protein and mRNA expression of NF-κB and TNF-ɑ were significantly increased 4, 8, and 12 weeks after surgery in the PI group. In addition, the markers of cartilage degeneration MMP-13 and collagen X were more highly expressed in the PI group compared with the control group at different time points after surgery. CONCLUSIONS: This study has demonstrated that early patellofemoral joint cartilage degeneration can be caused by PI in growing rats, accompanied by significant subchondral bone loss and cartilage degeneration. In addition, the degeneration of articular cartilage may be associated with the activation of the NF-κB signaling pathway and can deteriorate with time as a result of PI.

Disruption of the Gut Microbiome Increases the Risk of Periprosthetic Joint Infection in Mice.

BACKGROUND: Periprosthetic joint infection (PJI) is one of the most devastating complications of total joint arthroplasty. Given the mortality and morbidity associated with PJI and the challenges in treating it, there has been increased interest in risk factors that can be modified before surgery. In this study, we used a novel mouse model to consider the role of the gut microbiome as a risk factor for PJI. QUESTIONS/PURPOSES: (1) Does the state of the gut microbiota before surgery influence the likelihood of developing an established infection in a mouse model of PJI? (2) How does the state of the gut microbiota before surgery influence the local and systemic response to the presence of an established infection in a mouse model of PJI? METHODS: Male C57Bl/6 mice were divided into two groups: those with modified microbiome [INCREMENT]microbiome (n = 40) and untreated mice (n = 42). In [INCREMENT]microbiome mice, the gut flora were modified using oral neomycin and ampicillin from 4 weeks to 16 weeks of age. Mice received a titanium tibial implant to mimic a joint implant and a local inoculation of Staphylococcus aureus in the synovial space (10 colony forming units [CFUs]). The proportion of animals developing an established infection in each group was determined by CFU count. The local and systemic response to established infection was determined using CFU counts in surrounding joint tissues, analysis of gait, radiographs, body weight, serum markers of inflammation, and immune cell profiles and was compared with animals that received the inoculation but resisted infection. RESULTS: A greater proportion of animals with disrupted gut microbiota had infection (29 of 40 [73%]) than did untreated animals (21 of 42 [50%]; odds ratio, 2.63, 95% CI, 1.04-6.61; p = 0.035). The immune response to established infection in mice with altered microbiota was muted; serum amyloid A, a marker of systemic infection in mice, was greater than in mice with disrupted gut microbiota with infection (689 µg/dL; range, 68-2437 µg/dL, p < 0.05); infection associated increases in monocytes and neutrophils in the spleen and local lymph node in untreated mice but not were not observed in mice with disrupted gut microbiota. CONCLUSIONS: The findings from this in vivo mouse model suggest that the gut microbiota may influence susceptibility to PJI. CLINICAL RELEVANCE: These preclinical findings support the idea that the state of the gut microbiome before surgery may influence the development of PJI and justify further preclinical and clinical studies to develop appropriate microbiome-based interventions.

The dysplastic trochlear sulcus due to the insufficient patellar stress in growing rats.

BACKGROUND: Developmental factors were assumed to be the key factors that influenced the morphology of femoral trochlea. This study investigated the effects of insufficient patellar stress after birth on the morphological development of the femoral trochlea. Effects of insufficient patellar stress on femoral trochlea were investigated using surgical induced patellectomy and patellar dislocation in growing rat model. METHODS: In this study, two experimental groups and one sham group (SG) were established. Thirty-six Wistar rats (female, 28 days of age) were randomly assigned to three groups. The patellectomy group (PG), rats underwent the patellectomy in this group. The dislocation group (DG), rats underwent the surgery-induced patellar dislocation. Histological staining (Safranin-O and fast green), Micro-computed tomographic (Micro-CT) analysis in two experimental endpoints (3, 12 weeks postoperatively) were selected to evaluate morphological changes of the femoral trochlea. RESULTS: Articular cartilage on the trochlear sulcus was remodeled at 3 weeks after the surgery, and degenerated at 12 weeks through the histological staining. The femoral trochlear angle (FTA) did not show a significant difference at 3 week between the experimental groups and the sham group (PG vs SG P = 0.38, DG vs SG p = 0.05), but the FTA was significantly increased in experimental groups at 12 weeks(PG vs SG P = 0.001, DG vs SG p = 0.005). The Bone volume density (BV/TV), Trabecular number (Tb.N) under the trochlea groove were significantly reduced at 3 weeks postoperatively in the experimental groups (PG vs SG p = 0.001, DG vs SG p = 0.002). No significant difference was found in BV/TV and Tb. N among the three groups at 12 weeks postoperatively. CONCLUSION: Surgical induced patellectomy and patellar dislocation leads to the dysplastic trochlear sulcus in growing rats. Besides the bone morphology of trochlear sulcus, the articular cartilage and subchondral trabecula under the trochlear sulcus were remodeled early stage after the surgery.

Anterior-medial collateral ligament portal : easy access to the torn posteromedial horn of the medial meniscus.

The posteromedial horn of the medial meniscus is prone to injury, and repair of a tear in this portion of the medial meniscus is especially challenging for the arthroscopist. We present a novel technique that allows good management of the posterior horn of the medial meniscus, even in patients with tight medial compartments. This technique uses two standard portals (the anterolateral portal and the anteromedial portal) to conduct arthroscopic examination, and uses a third portal as the workhorse portal to manage the posterior region so that the posterior horn tear can be easily removed. This new third portal is named the anterior-medial collateral ligament portal, and is positioned anterior to the anterior rim of the medial collateral ligament. This three-portal technique decreases the difficulty associated with management of the posteromedial region in knees with tight medial compartments.

Evaluation of Trochlear Dysplasia Severity Using Trochlear Angle: A Retrospective Study Based on Computed Tomography (CT) Scans.

BACKGROUND Trochlear dysplasia is an important pathological factor in patellofemoral instability. Quantitative evaluation of the severity of trochlear dysplasia is rare and remains unclear. MATERIAL AND METHODS Computed tomography (CT) data on 136 knees (95 patients) with trochlear dysplasia in the case group and an age- and sex-matched cohort of 120 knees (70 patients) in the control group were collected for this retrospective study. All participants had undergone CT scans in the supine position. The trochlear angles (TA) formed by the posterior condylar line and the trochlear line were calculated and compared. The threshold for statistical significance was set at p<0.05. RESULTS The mean TA values were significantly greater in the case group compared to the control group independent of sex (p<0.01). The distribution of trochlear dysplasia of Dejour grades was type A n=34, type B n=31, type C n=40, and type D n=31. Except for types A and B, differences in the trochlear dysplasia grade between any 2 other types were statistically significant (p<0.01). CONCLUSIONS The technique of measuring TA is reproducible and accurate in patients with patellar instability and normal controls. The TA positively correlates with higher levels of trochlear dysplasia. This technique can help to evaluate and treat trochlear dysplasia in research as well as in clinical practice.