Yunsu Chen

This study aimed to compare the in-vivo kinematics and articular contact status between medial-pivot total knee arthroplasty (MP-TKA) and posterior stabilized (PS) TKA during weight-bearing single-leg lunge. 16 MP-TKA and 12 PS-TKA patients performed bilateral single-leg lunges under dual fluoroscopy surveillance to determine the in-vivo six degrees-of-freedom knee kinematics. The closest point between the surface models of the femoral condyle and the polyethylene insert was used to determine the contact position and area. The nonparametric statistics analysis was performed to test the symmetry of the kinematics between MP-TKA and PS-TKA. PS-TKA demonstrated a significantly greater range of AP translation than MP-TKA during high flexion (p = 0.0002). Both groups showed a significantly greater range of lateral compartment posterior translation with medial pivot rotation. The contact points of PS-TKA were located significantly more posterior than MP-TKA in both medial (10°–100°) and lateral (5°–40°, 55°–100°) compartments (p < 0.0500). MP-TKA had a significantly larger contact area in the medial compartment than in the lateral compartment. In contrast, no significant differences were observed in PS-TKA. The present study revealed no significant differences in clinical outcomes between the MP and PS groups. The PS-TKA demonstrated significantly more posterior translations than MP-TKA at high flexion. The contact points are located more posteriorly in PS-TKA compared with MP-TKA. A larger contact area and medial pivot pattern during high flexion in MP-TKA indicated that MP-TKA provides enhanced medial pivot rotation.

Purpose: The objectives of the present study were to investigate the length change in different bundles of the superficial medial collateral ligament (sMCL) and lateral collateral ligament (LCL) during lunge, and to evaluate their association with Knee Society Score (KSS) following medial‐pivot total knee arthroplasty (MP‐TKA).Methods: Patients with unilateral MP‐TKA knees performed a bilateral single‐leg lunge under dual fluoroscopy surveillance to determine the in‐vivo six degrees‐of‐freedom knee kinematics. The contralateral non‐operated knees were used as the control group. The attachment sites of the sMCL and LCL were marked to calculate the 3D wrapping length. The sMCL and LCL were divided into anterior, intermediate, and posterior portions (aMCL, iMCL, pMCL, aLCL, iLCL, pLCL). Correlations between lengths/elongation rate of ligament bundles from full extension to 100° flexion and the KSS were examined.Results: The sMCL and LCL demonstrated relative stability in length at low flexion, but sMCL length decreased whereas LCL increased with further flexion on operated knees. The sMCL length increased at low flexion and remained stable with further flexion, while the LCL length decreased with flexion on the contralateral non‐operated knees. The lengths of aMCL, iMCL, and pMCL showed moderate (0.5 < r < 0.7, p < 0.05) negative correlations with the KSS, and the lengths of aLCL, iLCL, and pLCL were positively correlated with the KSS at mid flexion on operated knees (p < 0.05). The elongation rates of aLCL, iLCL, and pLCL were negatively correlated with the KSS at high flexion on operated knees (p < 0.05). However, no significant correlations between the length of different bundles of sMCL or LCL with KSS were found on contralateral non‐operated knees.Conclusions: The elongation pattern of sMCL/LCL on MP‐TKA knees showed differences with contralateral non‐operated knees. The sMCL is tense at low to middle flexion and relaxed at high flexion, while LCL is relaxed at low to middle flexion and tense at high flexion following MP‐TKA. Medial stability and proper lateral flexibility during mid flexion were associated with favorable postoperative outcomes in MP‐TKA patients. In contrast, lateral relaxation at deep flexion should be avoided when applying soft‐tissue balancing in MP‐TKA.Level of evidence: Level III.

Background The medial-pivot (MP) prosthesis was developed to produce more physiological postoperative knee kinematics and better patient satisfaction than traditional prostheses, but outcomes are inconsistent in different studies of Caucasian patients. This study aimed to investigate the postoperative patient satisfaction and in vivo knee kinematics of the MP and posterior-stabilized (PS) prosthesis during gait activity in Chinese patients.Methods A retrospective analysis of 12 patients was received for this study in each MP group and PS group. Patient-reported satisfaction level and Forgotten Joint Score (FJS) were evaluated with questionnaires. A dual fluoroscopic imaging system was used to investigate in vivo knee kinematics of MP and PS total knee arthroplasty (TKA) during treadmill walking at a speed of 0.4 m/s.Results Comparable promising patient satisfaction and overall FJS (MP 60.7 ± 15.35 vs. PS 51.3 ± 17.62, p = 0.174) were found between the MP and PS groups. Peak flexion appeared at around 70% of gait cycle with values of 52.4 ± 7.4° for MP and 50.1 ± 3.6° for PS groups (no difference). Both groups maintained a stable position at the stance phase and began to translated anteriorly at toe-off with an amount of 4.5 ± 2.3 mm in the MP and 6.6 ± 2.7 mm in the PS (p = 0.08) group until late swing. The range of this external rotation motion was 5.9 ± 4.8 and 6.2 ± 4.1° (p = 0.79) for the MP and PS, respectively.Conclusion A similar knee kinematics pattern characterized by a loss of early-stance knee flexion and femoral rollback during walking was observed in the MP and PS TKAs. Our study confirmed similar effectiveness of MP TKA compared to PS TKA in Chinese patients, while the change of knee kinematics of both implants during slow walking should be noted.

Optimal integration between the polyethylene terephthalate (PET) graft and host bone is a prerequisite to obtain a satisfactory outcome after graft implantation for ligament reconstruction. Recent studies indicate that complex biosignals including immunoregulation, cell recruitment, and osteogenic differentiation provided by the extracellular matrix (ECM) are conducive to promoting osseointegration. In the present study, a chondroitin sulfate (CS)/polydopamine-modified PET graft was developed to regulate the local immune microenvironment, guide stem cell behavior, and promote new bone formation. We found that CS-modified PET grafts significantly regulated the macrophage phenotype switching from M1 to M2 and promoted the expression of pro-repair cytokines including interleukin (IL)-4, IL-10 and transforming growth factor (TGF)-β1. Moreover, the immunoregulatory function of CS-modified PET guided stem cell behaviors, including recruitment, adhesion, and proliferation, and enhanced the osteogenic differentiation of stem cells. In vivo experiments confirmed that CS-modified PET switched the local immune microenvironment status from pro-inflammatory to anti-inflammatory, up-regulated osteogenic marker expression, and promoted the bone regeneration process, so as to achieve graft-bone osseointegration. These results indicate that an ECM-biomimetic immunoregulatory coating is an effective approach to promote graft integration. This study proposes an effective strategy for an artificial graft to achieve graft-bone osseointegration through immunoregulatory osteogenesis.

Metal wear particles play a major role in periprosthetic osteolysis and aseptic loosening in patients with total joint arthroplasty. The ability to induce osteolysis depends on the size, shape, dose, and type of the particles. However, much remains unknown regarding which type of metal particles are most reactive. We compared the inflammatory response and bone loss induced by two metal wear particles, cobalt–chromium–molybdenum (CoCrMo) and titanium (Ti), in a mouse calvaria model of osteolysis. We found that CoCrMo particles caused markedly greater bone resorption than Ti particles, according to three-dimensional images of the calvariae. CoCrMo particles activated more functional osteoclasts by significantly increasing the expression of the osteoclast-specific gene tartrate-specific acid phosphatase (Trap), calcitonin receptor (Ctr), and nuclear factor of activated T cells c1 (Nfatc1), and induced a greater increase in the ratio of receptor activator of nuclear factor kappa B ligand (RANKL)/osteoprotegerin (OPG) than Ti particles. CoCrMo particles also induced a stronger local inflammatory response, markedly increasing the expression and secretion of tumor necrosis factor-α and interleukin-1β compared with Ti particles. Therefore, CoCrMo particles induced a more severe inflammatory response and greater osteolysis than Ti particles in vivo.

Aims: There is no consensus about the best method of achieving equal leg lengths at total hip arthroplasty (THA) in patients with Crowe type-IV developmental dysplasia of the hip (DDH). We reviewed our experience of a consecutive series of patients who underwent THA for this indication.Patients and Methods: We retrospectively reviewed 78 patients (86 THAs) with Crowe type-IV DDH, including 64 women and 14 men, with a minimum follow-up of two years. The mean age at the time of surgery was 52.2 years (34 to 82). We subdivided Crowe type-IV DDH into two major types according to the number of dislocated hips, and further categorised them into three groups according to the occurrence of pelvic obliquity or spinal curvature. Leg length discrepancy (LLD) and functional scores were analysed.Results: Type-I included 53 patients with unilateral dislocation, in which 25 (category A) had no pelvic obliquity or spinal deformity, 19 (category B) had pelvic obliquity with a compensated spinal curvature and nine (category C) had pelvic obliquity and decompensated spinal degenerative changes. Type-II included 25 patients with one dislocated and one dysplastic hip, in which there were eight of category A, 15 of category B and two of category C. Pre-operatively, there were significant differences between the anatomical and functional LLD in type-IB (p = 0.005) and -IC (p < 0.001), but not in type-IA, -IIA or -IIB. Post-operatively, bony LLD increased significantly in types-IB, -IC and -IIB, whereas functional LLD decreased significantly in each type except for IIA. The mean functional LLD decreased from 30.7 mm (standard deviation (sd) 18.5) pre-operatively to 6.2 mm (sd 4.4) post-operatively and the mean anatomical LLD improved from 35.8 mm (sd 19.7) pre-operatively to 12.4 mm (sd 8.3) post-operatively.Conclusion: Pelvic and spinal changes are common in patients with Crowe type-IV DDH and need to be taken into consideration when planning THA, in order to obtain equal leg lengths post-operatively. The principal subdivisions of Crowe type-IV DDH which we describe proved effective in achieving equal leg lengths and satisfactory outcomes. Cite this article: Bone Joint J 2017;99-B:872–9.

The radiological research for pelvis asymmetry of unilateral developmental dysplasia of the hip in adult

Tissue-engineered bone grafts require an osteoblastic cellular source to be utilized in bone transplantation therapy. Human bone marrow stem cells (hBMSCs) and periosteal-derived stem cells (hPCs) are the commonly used cellular sources for bone tissue engineering and are essential in fracture healing. In the present study, hBMSCs and hPCs were co-cultured from the same donors, as the cellular source. In monolayer cultivation, co-culturing hBMSCs and hPCs demonstrated more robust mineralized nodule formation and stronger alkaline phosphatase (ALP) positive staining than hBMSCs or hPCs. Three-dimensional (3-D) culturing on porous β-tricalcium phosphate (TCP) scaffolds and co-culturing of hBMSCs and hPCs significantly promoted the osteogenic specific mRNA expression of COL1α1, BMP-2, osteopontin (OPN) and osteocalcin (OC). For in vivo bone formation and neovascularization assessment, the cellular-β-TCP scaffolds were transplanted into critical-sized femoral condyle defects in rabbits. The results confirmed that co-culturing hBMSCs and hPCs accelerated bone regeneration and enhanced mature bone formation, but also facilitated central vascularization in scaffold pores. Based on these data, we recommend co-culturing hBMSCs and hPCs as a promising cellular source for bone tissue engineering applications.