Runx2 and Polycystins in Bone Mechanotransduction: Challenges for Therapeutic Opportunities.

Bone mechanotransduction is a critical process during skeletal development in embryogenesis and organogenesis. At the same time, the type and level of mechanical loading regulates bone remodeling throughout the adult life. The aberrant mechanosensing of bone cells has been implicated in the development and progression of bone loss disorders, but also in the bone-specific aspect of other clinical entities, such as the tumorigenesis of solid organs. Novel treatment options have come into sight that exploit the mechanosensitivity of osteoblasts, osteocytes, and chondrocytes to achieve efficient bone regeneration. In this regard, runt-related transcription factor 2 (Runx2) has emerged as a chief skeletal-specific molecule of differentiation, which is prominent to induction by mechanical stimuli. Polycystins represent a family of mechanosensitive proteins that interact with Runx2 in mechano-induced signaling cascades and foster the regulation of alternative effectors of mechanotransuction. In the present narrative review, we employed a PubMed search to extract the literature concerning Runx2, polycystins, and their association from 2000 to March 2024. The keywords stated below were used for the article search. We discuss recent advances regarding the implication of Runx2 and polycystins in bone remodeling and regeneration and elaborate on the targeting strategies that may potentially be applied for the treatment of patients with bone loss diseases.

Total Talectomy and Reconstruction Using a 3-dimensional Printed Talus Prosthesis for Ewing's Sarcoma: A 3.5-Year Follow-up.

Ewing's sarcoma is extremely rare in the foot. Below the knee amputation is indicated for most primary malignant bone tumors of the hindfoot, with few cases of successful limb salvage surgery having been reported. The use of 3-dimensional printed implants may successfully address reconstruction challenges after tumor resection. The authors present a case of a 30-year-old woman with a Ewing's sarcoma of the talus who underwent total talectomy and replacement of the entire talus with a custom-made 3-dimensional printed talar prosthesis. [Orthopedics. 2019; 42(4):e405-e409.].

Total Calcaneus Resection and Reconstruction Using a 3-dimensional Printed Implant.

Considering the specific anatomic features of the foot, below-knee amputation is the treatment of choice for foot malignancies. However, advances in imaging modalities, adjuvant therapies, and improved surgical techniques have made foot salvage surgery increasingly possible. The calcaneus is an unusual location for malignant tumors, and there is limited information about foot salvage. Currently, 3-dimensional printed implants may successfully address reconstruction challenges after tumor resection. The authors present 2 patients with Ewing's sarcoma of the calcaneus who underwent total calcaneus resection and reconstruction using a custom-made 3-dimensional printed implant. [Orthopedics. 2019; 42(2):e282-e287.].

Similar function and complications for patients with short versus long hip nailing for unstable pertrochanteric fractures.

PURPOSE: To compare short with long intramedullary hip nailing for elderly patients with unstable pertrochanteric fractures. METHODS: We prospectively studied 50 patients (33 women, 17 men; mean age, 80 years; range, 74-93 years) with unstable pertrochanteric fractures admitted and treated with a short (group A) or a long (group B) intramedullary hip nail from January 2013 to 2017. The patients were randomly allocated into each group according to their order of admission. The mean follow-up was 2 years (range, 1-5 years). We evaluated operative time, function, fracture healing, varus/valgus loss of reduction, and distance between the distal line of the fracture and the distal locking screw of the nail. RESULTS: Operative time was significantly shorter in group A. Function, fracture healing and varus/valgus loss of reduction was similar between the two groups. The mean distance between the distal fracture line and distal locking screw was 7.2 cm (range, 3-10 cm) in patients of group A; in all patients of group B, an appropriate nail length was chosen so that the distal locking screw was inserted at least 3 times the diameter of the bone at the distal fracture line. Complications included periprosthetic fracture (one patient of group A), and z-effect phenomenon (one patient of group B); complications rate was similar between the two groups. CONCLUSION: Short intramedullary hip nailing is associated with similar function and complications, but shorter operative time compared to long intramedullary hip nails for patients with unstable pertrochanteric fractures.

Complications After Hip Nailing for Fractures.

Pertrochanteric fractures in elderly patients represent a major health issue. The available surgical options are fixation with extramedullary devices, intramedullary nailing, and arthroplasty. Intramedullary nailing for hip fractures has become more popular in recent years. Advantages of intramedullary nailing for hip fracture fixation include a more efficient load transfer due to the proximity of the implant to the medial calcar, less implant strain and shorter lever arm because of its closer positioning to the mechanical axis of the femur, significantly less soft tissue disruption and periosteal stripping of the femoral cortex, shorter operative time and hospital stay, fewer blood transfusions, better postoperative walking ability, and lower rates of leg-length discrepancy. Compromise of the posteromedial cortex and/or the lateral cortex, a subtrochanteric extension of the fracture, and a reversed obliquity fracture pattern represent signs of fracture instability, warranting the use of intramedullary nailing. However, the use of intramedullary nailing, with its unique set of clinical implications, has introduced a new set of complications. The reported complications include malalignment, cutout, infection, false drilling, wrong lag screw length and drill bit breakage during the interlocking procedure, external or internal malrotation (≥20°) of the femoral diaphysis, elongation of the femur (2 cm), impaired bone healing, periprosthetic fracture distal to the tip of the nail, fracture collapse, implant failure, lag screw intrapelvic migration, neurovascular injury, secondary varus deviation, complications after implant removal, trochanteric pain, and refracture. Many of these complications are related to technical mistakes. This article reviews intramedullary nailing for the treatment of pertrochanteric femoral fractures, with an emphasis on complications.