## 6 The Contributions in This Special Issue  
The current special issue includes six contributions [88; 89; 90; 91; 92; 93], which cover a variety of topics ranging from modelling of load transfer in artificial joints and orthopaedic implants to recent advances in EMG analysis techniques, highlighting recent research and technology developments in the field of Orthopaedic and Rehabilitation Engineering. The first contribution [88] presents a finite element analysis of lumbar spine hybrid fixation verteba-plasty combined with Cement-Augmented Screw Fixation. The study shows that the hybrid fixation method presented can lead to better stabilization of the spine and reduce the risk of implant failure, through slowing the progression of screw loosening by decreasing the range of motion. Whereas the findings appear tentatively promising, the model also contained some practical limitations and weaknesses that needed solving. For example, the model didnot include the mechanical effects of muscle contraction. Therefore, it was not possible to determine an accurate representation of true physiological loading conditions in the model. The second contribution [89] deals with the implementation of a single actuated pneumatic artificial muscle (single-PAM) combined with a torsion spring for a one degree-of-freedom (1-DOF) robotic lower-limb wearable accessory. The authors demonstrated that using a fuzzy sliding mode controller (FSMC) to control the path tracking could control the tracking angle error within 0.5 degrees. The system showed better robustness against changes in the external environment as compared to the proportional integral derivative (PID) controller, which had a larger overshoot and slower response. Based on this finding, it was concluded that single-PAM with a torsion spring can be considered as an alternative actuating system for a robotic lower-limb system in rehabilitation settings. The authors proposed that this novel design would reduce the size, complexity and production cost of the wearable accessory and improve its portability and convenience as compared to the more frequently used wearable accessories driven by dual-actuated pneumatic artificial muscles (dual-PAMs). The third contribution [90] deals with the evaluation of the wear-simulation response of custom-fabricated parts for artificial temporo-mandibular-joint (TMJ), including the electron beam melted titanium (EBM-Ti), zirconia and acrylic. The findings from this study demonstrated that the use of custom fabricated zirconia condyle and glenoid fossa resulted in greater wear (in terms of mean reduction in weight of the prosthetic TM) parts) on the other biomaterials. Specifically, acrylic and EBM-Ti condyle and fossa parts exhibited greater wear in comparison to the zirconia fossa or condyle parts against which they were tested. Based on the findings, it was concluded that custom fabrication of alloplastic TMJ condyle and glenoid fossa parts can make a viable alternative to stock and custom fitted TMJ replacements. Furthermore, the authors proposed that EBM-Ti and acrylic had good biomechanical stability during simulation testing and that accurate custom-fabrication of the TMJ parts is possible. The use of zirconia as a biomaterial for customized alloplastic TMJ replacement requires further examination. The fourth paper [91] evaluated the diagnostic accuracy of physical examination and magnetic resonance imaging (MRI) in knee injuries. The study included 96 participants, of whom 32 were diagnosed with total anterior cruciate ligament (ACL) ruptures, 45 with medial meniscus lesions, and 17 with lateral meniscus lesions. Physical examination and MRI scans were compared with knee arthroscopy findings as a golden standard for meniscal and ligamentous lesions.