Dieter Cadosch

Metal implants are essential therapeutic tools for the treatment of bone fractures and joint replacements. The metals and metal alloys used in contemporary orthopedic and trauma surgery are well tolerated by the majority of patients. However, complications resulting from inflammatory and immune reactions to metal implants have been well documented. This review briefly discusses the different mechanisms of metal implant corrosion in the human body, which lead to the release of significant levels of metal ions into the peri-implant tissues and the systemic blood circulation. Additionally, this article reviews the effects of the released ions on bone metabolism and the immune system and discusses their involvement in the pathophysiological mechanisms of aseptic loosening and metal hypersensitivity in patients with metal implants.

OBJECTIVE: This study was designed to investigate the specific type and incidence of implant failure in patients with a proximal femur fracture treated with a proximal femoral nail antirotation. This device has a helical-shaped blade as a neck-head holding device, instead of the lag screw used in other intramedullary nails. The advantage of the blade is believed to originate from bone impaction and a larger bone-implant interface in comparison with the lag screw design, with consequential greater mechanical resistance to torsion in the cancellous bone. PATIENTS AND METHODS: This is a retrospective cohort study conducted at the state hospital of Winterthur, Switzerland. From December 2006 until November 2008, 210 consecutive patients were treated with a pertrochanteric femur fracture (OTA type 31-A1, 31-A2, and 31-A3) using a proximal femoral nail antirotation. One hundred and twelve patients were followed up clinically for a minimum of 12 months after discharge. Clinical and radiologic assessment of fracture healing and/or implant failure was investigated. RESULTS: We report 7 cases of implant failure with a "Cut Through," defined as a postoperative central perforation of the spiral blade into the hip joint, without any displacement of the neck-head fragment. CONCLUSIONS: Cut through needs to be distinguished from the well-known anterocranial perforation combined with a varus displacement of the neck-head fragment, known as "Cut Out," seen with intramedullary nails utilizing lag screws. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

All metals in contact with a biological system undergo corrosion through an electrochemical redox reaction. This study investigated whether human osteoclasts (OC) are able to grow on titanium and aluminum, and directly corrode the metals leading to the release of corresponding metal ions, which are believed to cause inflammatory reactions and activate osteoclastic differentiation. Scanning electron microscopy analysis demonstrated long-term viable OC cultures on the surface of titanium and aluminum foils. Atomic emission spectrometry investigations showed significantly increased levels of aluminum in the supernatant of OC cultured on aluminum; however, all measurements in the supernatants of cell cultures on titanium were below detection limits. Despite this, confocal microscopy analysis with Newport Green DCF diacetate ester staining depicted intense fluorescence throughout the cytoplasm and nucleolus of OC cultured on titanium foils. Comparable fluorescence intensities were not observed in monocytes and control cells cultured on glass. The present study demonstrated that human osteoclast precursors are able to grow and differentiate toward mature OC on titanium and aluminum. Furthermore, it established that the mature cells are able to directly corrode the metal surface and take up corresponding metal ions, which subsequently may be released and thereby induce the formation of osteolytic lesions in the periprosthetic bone, contributing to the loosening of the implant.

BACKGROUND: Scientific evidence is mounting for an association between traumatic brain injury and enhanced osteogenesis. The aim of this study was to correlate the in vitro osteoinductive potential of serum with the features of fracture-healing and the extent of brain damage in patients with severe traumatic brain injury and bone fracture. METHODS: Patients with a long-bone fracture and a traumatic brain injury (seventeen patients) or without a brain injury (twenty-four patients) were recruited. The Glasgow Coma Scale score was determined on admission. Radiographs of the fracture were made before surgery, at six weeks, and at three, six, and twelve months after surgery. The time to union was estimated clinically and radiographically, and the callus ratio to shaft diameter was calculated. Serum samples were collected at six, twenty-four, seventy-two, and 168 hours after injury, and their osteogenic potential was determined by measurement of the in vitro proliferation rate of the human fetal osteoblastic cell line hFOB1.19. RESULTS: Patients with a traumatic brain injury had a twofold shorter time to union (p = 0.01), a 37% to 50% increased callus ratio (p < 0.01), and their sera induced a higher proliferation rate in hFOB cells (p < 0.05). A linear relationship was revealed between hFOB cell proliferation rates and the amount of callus formed (p < 0.05). The Glasgow Coma Scale score was correlated with the callus ratio on both radiographic projections (p < 0.05), time to union (p = 0.04), and the proliferation rate of hFOB cells at six hours after injury (p = 0.03). CONCLUSIONS: Patients with a severe brain injury release unknown humoral factors into the blood circulation that enhance and accelerate fracture-healing.

Most metals in contact with biological systems undergo corrosion by an electrochemical process. This study investigated whether human osteoclasts (OC) are able to grow on stainless steel (SS) and directly corrode the metal alloy leading to the formation of corresponding metal ions, which may cause inflammatory reactions and activate the immune system. Scanning electron microscopy analysis demonstrated long-term viable OC cultures and evident resorption features on the surface of SS discs on which OC were cultured for 21 days. The findings were confirmed by atomic emission spectrometry investigations showing significantly increased levels of chromium, nickel, and manganese in the supernatant of OC cultures. Furthermore, significant levels of pro-inflammatory cytokines IL-1beta, IL-6, and TNF-alpha, which are considered to be major mediators of osteolysis, were revealed in the same cultures by cytometric bead array analysis. Within the present study, it was shown that human osteoclast precursors are able to grow and differentiate towards mature OC on SS. The mature cells are able to directly corrode the metal surface and release corresponding metal ions, which induce the secretion of pro-inflammatory cytokines that are known to enhance osteoclast differentiation, activation, and survival. Enhanced corrosion and the subsequently released metal ions may therefore result in enhanced osteolytic lesions in the peri-prosthetic bone, contributing to the aseptic loosening of the implant.