Metal ion levels in a triathlete with a metal-on-metal resurfacing arthroplasty of the hip.

A prospective study of serum and urinary ion levels was undertaken in a triathlete who had undergone a metal-on-metal resurfacing arthroplasty of the hip four years previously. The one month study period included the final two weeks of training, the day of the triathlon, and the two weeks immediately post-race. Serum cobalt and chromium levels did not vary significantly throughout this period, including levels recorded on the day after the 11-hour triathlon. Urinary excretion of chromium increased immediately after the race and had returned to pre-race levels six days later. The clinical implications are discussed.

Focal osteolysis at the junctions of a modular stainless-steel femoral intramedullary nail.

BACKGROUND: During routine follow-up of patients treated with a three-piece stainless-steel modular femoral nail, osteolysis and periosteal reaction around the modular junctions of some of the nails were noted on radiographs. The purpose of this study was to evaluate the prevalence, etiology, and clinical relevance of these radiographic findings. METHODS: Forty-four femoral fractures or nonunions in forty-two patients were treated with a modular stainless-steel femoral intramedullary nail. Seventeen nails were excluded, leaving twenty-seven intramedullary nails in twenty-seven patients for this study. All patients had had a femoral diaphyseal fracture; nineteen had had an acute fracture and eight, a nonunion. These twenty-seven patients returned for radiographs, a physical examination, assessment of functional outcomes, assessment of thigh pain with a visual analog scale, determination of serum chromium levels, and nail removal if desired. A control group of sixteen patients treated with a one-piece stainless-steel femoral intramedullary nail was evaluated with use of the same outcome measures and was compared with the group treated with the modular femoral nail with regard to prevalence of thigh pain and serum chromium levels. Twelve modular femoral nails were removed according to the study protocol. The modular nail junctions were analyzed for corrosion products, and histopathologic analysis of tissue specimens from the femoral canal was performed. RESULTS: The twenty-seven patients were seen at a mean of twenty-one months after fracture fixation; twenty-six of the twenty-seven fractures healed. Twenty-three femora had at least one of three types of abnormalities-osteolysis, periosteal reaction, or cortical thickening--localized to one or both modular junctions. Eighteen patients had severe reactions, defined as osteolysis of > or =2 mm, cortical thickening of > or =5 mm, and/or a periosteal reaction (group 1). Nine patients had mild or no reactions (group 2). Serum chromium levels in group 1 (mean, 1.27 ng/ mL; range, 0.34 to 3.12 ng/mL) were twice as high as those in group 2 (mean, 0.53 ng/mL; range, 0.12 to 1.26 ng/mL). However, this difference did not reach significance with the numbers available. The differences in serum chromium levels between group 1 and the control group with a one-piece nail (mean, 0.26 ng/mL; range, 0.015 to 1.25 ng/mL) (p<0.01) and a control group without an implant (mean, 0.05 ng/mL; range, 0.015 to 0.25 ng/ mL) (p<0.01) were significant. The level of thigh pain recorded on the visual analog scale was also significantly different between group 1 and the control group with a one-piece implant (p = 0.03). Retrieved modular nails had signs of fretting corrosion as well as stainless-steel corrosion products adherent to the junction where the osteolysis occurred. Histologic and spectrographic analysis revealed two types of corrosion products that were consistent with stainless-steel within the peri-implant tissue and were associated with a foreign-body granulomatous response. CONCLUSIONS: The presence of corrosion products at the taper junctions suggests that particulate debris was a major factor in the etiology of the radiographic findings of osteolysis, periosteal reaction, and cortical thickening. Serum chromium levels were substantially elevated in the patients with a modular femoral nail, and such levels may serve as a marker of fretting corrosion of these devices.

Serum titanium level for diagnosis of a failed, metal-backed patellar component.

A case is presented in which an elevated serum titanium level was used to make the diagnosis of a failed metal-backed patellar component. The preoperative serum titanium level was 536.8 ppb, which was 98 times higher than the patient's previous level (taken 1 year earlier, when he was asymptomatic) and 2 orders of magnitude higher than the expected level with a well-functioning implant of this type. Revision surgery confirmed that the polyethylene portion of the patellar component had worn through, leaving the titanium portion of the patellar implant to articulate with the femoral component. Wear-through was not evident on preoperative radiographs or clinical examination. As knowledge about the expected ranges for serum metal ion levels after total joint arthroplasty continues to increase, the diagnostic utility of serum metal ion testing in the evaluation of joint arthroplasty function will continue to improve.

Metal release in patients who have had a primary total hip arthroplasty. A prospective, controlled, longitudinal study.

UNLABELLED: There is an increasing recognition that, in the long term, total joint replacement may be associated with adverse local and remote tissue responses that are mediated by the degradation products of prosthetic materials. Particular interest has centered on the metal-degradation products of total joint replacements because of the known toxicities of the metal elements that make up the alloys used in the implants. We measured the concentrations of titanium, aluminum, cobalt, and chromium in the serum and the concentration of chromium in the urine of seventy-five patients during a three-year prospective, longitudinal study. Twenty patients had had a so-called hybrid total hip replacement (insertion of a modular cobalt-alloy femoral stem and head with cement and a titanium acetabular cup without cement), fifteen had had insertion of an extensively porous-coated cobalt-alloy stem with a cobalt-alloy head and a titanium-alloy socket without cement, and twenty had had insertion of a proximally porous-coated titanium-alloy stem with a cobalt-alloy head and a titanium socket without cement. The remaining twenty patients did not have an implant and served as controls. The results of our study showed that, thirty-six months postoperatively, patients who have a well functioning prosthesis with components containing titanium have as much as a threefold increase in the concentration of titanium in the serum and those who have a well functioning prosthesis with cobalt-alloy components have as much as a fivefold and an eightfold increase in the concentrations of chromium in the serum and urine, respectively. The predominant source of the disseminated chromium-degradation products is probably the modular head-neck junction and may be a function of the geometry of the coupling. Passive dissolution of extensively porous-coated cobalt-alloy stems was not found to be a dominant mode of metal release. CLINICAL RELEVANCE: Increased concentrations of circulating metal-degradation products derived from orthopaedic implants may have deleterious biological effects over the long term that warrant investigation. This is a particularly timely concern because of recent clinical trends, including the reintroduction of metal-on-metal bearing surfaces and the increasing popularity of extensively porous-coated devices with large surface areas of exposed metal. Accurate monitoring of the concentrations of metal in the serum and urine after total hip replacement also can provide insights into the mechanisms of metal release. Our findings suggest that fretting corrosion at the head-neck coupling is an important source of metal release that can lead to increased concentrations of chromium in the serum. Determinations of the concentrations of metal in the serum and urine may be useful in the diagnosis of patients who are symptomatic after a total joint replacement as increased levels are indicative of at least one mode of mechanical dysfunction (for example, fretting corrosion) of the device.

Release and excretion of metal in patients who have a total hip-replacement component made of titanium-base alloy.

Serum concentration and urinary excretion of titanium, aluminum, and vanadium were measured for patients who had a well functioning cementless primary total hip replacement of one of two different designs, for patients who had a loose total hip replacement that was to be revised, and for control subjects who had no implant. Serum concentrations of titanium were elevated approximately twofold in the patients who had a loose implant, compared with the values for the control subjects. No major differences in terms of urine concentration of titanium, serum concentration of aluminum, or urine concentration of aluminum were observed among any of the groups that were studied. Concentrations of vanadium were uniformly low in all groups.

Bone ingrowth into the tibial component of a canine total condylar knee replacement prosthesis.

The purpose of this study was to evaluate the occurrence of bone ingrowth in a porous coated tibial component of a canine total condylar design knee replacement model. The entire undersurface of the tibial prosthesis was covered by a titanium fiber metal porous composite pad. Projecting from this surface were three short, cylindrical, fiber metal coated pegs that along with a posterior screw provided initial stabilization of the device. Left total knee replacements were performed on six dogs using alignment and cutting jigs to prepare the bony surfaces. The dogs were killed 6 months following surgery. Extensive bone ingrowth was present in all pegs of every tibial component. Bone ingrowth was present in 12% of the pad area of one component, 22.7 to 41.6% in four components, and 81.1% in another. The void spaces in other areas were filled with fibrous tissue or in the periphery of the device with fibrocartilage. Bone ingrowth in the pad was consistent in the vicinity of the pegs and was variable in regions not adjacent to the pegs, suggesting that the pegs exerted a strong influence on the pattern of bone ingrowth into the pad.