Aims

Dual mobility implants in total hip arthroplasty are designed to increase the functional head size, thus decreasing the potential for dislocation. Modular dual mobility (MDM) implants incorporate a metal liner (e.g. cobalt-chromium alloy) in a metal shell (e.g. titanium alloy), raising concern for mechanically assisted crevice corrosion at the modular liner-shell connection. We sought to examine fretting and corrosion on MDM liners, to analyze the corrosion products, and to examine histologically the periprosthetic tissues.

Aims

There are limited published data detailing the volumetric material loss from tapers of conventional metal-on-polyethylene (MoP) total hip arthroplasties (THAs). Our aim was to address this by comparing the taper wear rates measured in an explanted cohort of the widely used Exeter THA with those measured in a group of metal-on-metal (MoM) THAs.

Aims

To present a surgically relevant update of trunnionosis.

Aims

We sought to determine whether cobalt-chromium alloy (CoCr) femoral stem tapers (trunnions) wear more than titanium (Ti) alloy stem tapers (trunnions) when used in a large diameter (LD) metal-on-metal (MoM) hip arthroplasty system.

Introduction. As the population continues to grow and age, the incidence of revision total knee replacement (RTKR) is expected to rise significantly. Modularity within revision total knee systems is common, and recognition of modular junctions as an important source adverse local tissue reaction (ALTR) has not yet been fully described in the literature. In both hips and knees, ALTR may be caused by wear debris from articulating surfaces, stress shielding, and other classic areas of focus, but now attention is shifting towards the role of corrosion products from modular junctions. In severe cases, junctions can become welded together creating significant hurdles in revisions and potentially altered biomechanics in vivo. In view of these issues, the present study was undertaken: (i) to examine the level of damage observed in modular junctions of total knee prostheses obtained at revision, (ii) to correlate the severity of surface damage to the design and composition of the mating components, and (iii) to associate patient demographics and comorbidities with the spectrum of corrosion and fretting seen in retrieved implants. Methods. 117 TKR components from 76 patients were examined after retrieval from revision procedures performed at a single institution. Patient demographics and clinical data were compiled. The retrievals consisted of 57 femoral components and 60 tibial components from a diverse range of manufacturers. The implants were disassembled manually, or in a mechanical testing machine if cold welded, and separated into groups based on mating material type. Modular junctions were then examined using stereomicroscopy (Wild) at magnifications of X6 to X31. Upon inspection, damage on the male component was graded using modified Goldberg scales for corrosion and fretting (Table 1). Factors associated with trunnions having damage scores of 3 or higher were evaluated using standard statistical procedures to determine the susceptibility for corrosion of each junction type and location. Results. Approximately two-thirds (64%) of trunnions had corrosion scores of 3 or higher. As seen in chart 1, junctions containing titanium alloys were the most susceptible to corrosion with the femoral component being the most prevalent. The most severe cases of corrosion (score of 5) were seen in mixed metal junctions in the femur (24%) and TiAlV/TiAlV junctions in the tibia (27%). Fretting was most frequently observed (73%) in tibial components with TiAlV/TiAlV junctions, over half of which were level 4. A disturbing finding was that 15% of modular junctions with a TiAlV component were cold welded and could only be disassembled using a mechanical testing machine. The femoral component tended to incur more severe levels of corrosion damage than that of the tibia for other material combinations. Conclusions. In TKR, modular junctions formed by one or more TiAlV components are the most susceptible to corrosive attack and fretting. Moreover, the most severe corrosion and fretting cases (score of 5 or 4, respectively) were only seen in the presence of a TiAlV component

Using a femoral head from one manufacturer on the stem of another manufacturer poses the risk that the taper interface between the components do not contact correctly and the performance of the joint will be impaired. The cohorts in this study are a combination of modular Birmingham Hip Resurfacing (BHR) and Adept femoral heads on CPT stems. The study reviews the geometry of the taper interfaces to establish if the taper clearance angles was outside of the normal range for other taper interfaces. In addition the rates of material loss from the bearings and taper and a ranking of the stem damage were reviewed to determine if the levels of loss were above that seen for other similar joints.

The material loss analysis demonstrated that the rates or levels of loss from the bearings, taper and stem are no different to levels published for manufacturer matched joints and in many cases are lower. The results demonstrate that the taper clearance angles for the mixed manufacturer joints (BHR-CPT: 0.067 to −0.116, Adept-CPT: 0.101 to −0.056) were within the range of other studies and manufacturer matched clearances (0.134 to −0.149).

Using components from different manufacturers has not in this instance increased the level of material loss from the joints, when compared to other similar manufacturer matched joints.

The inherent challenges of total hip replacement (THR) in children include the choice of implant for the often atypical anatomical morphology, its fixation to an immature growing skeleton and the bearing surface employed to achieve a successful long-term result. We report the medium-term results of 52 consecutive uncemented THRs undertaken in 35 paediatric patients with juvenile idiopathic arthritis. The mean age at the time of surgery was 14.4 years (10 to 16). The median follow-up was 10.5 years (6 to 15). During the study period 13 THRs underwent revision surgery. With revision as an endpoint, subgroup analysis revealed 100% survival of the 23 ceramic-on-ceramic THRs and 55% (16 of 29) of the metal- or ceramic-on-polyethylene. This resulted in 94% (95% CI 77.8 to 98.4) survivorship of the femoral component and 62% (95% CI 41.0 to 78.0) of the acetabular component. Revision of the acetabular component for wear and osteolysis were the most common reasons for failure accounting for 11 of the 13 revisions.

The success seen in patients with a ceramic-on-ceramic articulation seems to indicate that this implant strategy has the potential to make a major difference to the long-term outcome in this difficult group of patients.