Prosthesis-Related Risk Factors for Trunnionosis: A Comprehensive Literature Review

Abstract

Trunnionosis has emerged as an increasingly recognized cause of failure in total hip arthroplasty (THA). Although multiple prosthesis-related factors have been proposed, the relative importance of these risk factors remains uncertain. A comprehensive literature review and case-based analysis were conducted using the PubMed database (up to June 15, 2025) to identify and validate prosthesis-related risk factors for trunnionosis. Device-specific data extracted from eligible case reports were aggregated to empirically confirm previously hypothesized mechanical and material risk factors. The most consistent prosthesis-related risk factors were cobalt-chromium femoral heads, stems composed of titanium–molybdenum–zirconium–iron (TMZF) alloy, large-diameter femoral heads (≥ 36 mm), increased head–neck offset, and short trunnion length. Adverse taper geometries—such as smaller diameters, shorter lengths, and specific taper angles—were associated with greater micromotion and fretting corrosion. Grooved or threaded trunnion surfaces and dual modular stem designs further amplified the risk. High body mass index, male sex, elevated activity levels, and prolonged implantation duration were recurrent patient-related contributors, whereas surgical factors such as inadequate impaction force, malalignment, and contamination during assembly also promoted early taper corrosion. Contemporary THA designs that favor large femoral heads and high-offset stems increase mechanical loading at the taper junction, inadvertently predisposing to trunnionosis. Preventive strategies should prioritize the use of ceramic heads, avoidance of TMZF stems, and careful consideration of trunnion geometry. Standardization of taper design, adherence to meticulous assembly techniques, and long-term postoperative surveillance are essential to minimize corrosion-related failures and improve implant longevity.

The adoption of modularity is a key innovation in total hip arthroplasty (THA). Modularity enables intraoperative adjustments to neck length and horizontal offset, allowing precise restoration of leg length and joint stability.¹,²⁾ It also offers greater flexibility in selecting bearing surfaces and options for revision THA.²⁾ The Morse taper is a self-locking, tapered connection joining the femoral head to the femoral stem.

Large-head metal-on-metal (MoM) bearings were introduced early in the 21st century to address polyethylene wear. However, the MoM bearings generated metal debris, which led to adverse local tissue reactions (ALTRs).¹,³,⁴,⁵⁾ Initially, ALTRs were thought to be tissue reactions attributed exclusively to MoM articulations. However, similar patterns of tissue damage have been identified even in non-MoM constructs.⁶,⁷,⁸,⁹⁾

Corrosion and fretting wear at the modular taper junction, the interface between the femoral head bore and the stem trunnion, have been identified as the causes of such reactions.³,¹⁰⁾ This phenomenon, termed trunnionosis, refers to mechanically assisted crevice corrosion (MACC) at the femoral head-neck interface, leading to the release of metal debris and ions, particularly cobalt and chromium.²,¹¹⁾ Trunnionosis has recently been recognized as a growing cause of THA failure, with reports suggesting it accounts for up to 3% of all revisions.¹²,¹³,¹⁴⁾ The actual incidence of trunnionosis may be underestimated, because the taper damage is not often recognized on radiological evaluations, and it is often misdiagnosed as aseptic loosening or osteolysis.⁶,¹⁵,¹⁶⁾

Given the increasing recognition and clinical importance of trunnionosis, understanding its pathomechanisms is crucial. However, most previous studies were case reports, reviews, or biomechanical studies, which focused on isolated issues of implant design or material properties.¹,²,³⁾ Only a limited number of case series or cohort studies are available, and even among those, detailed information on implant design, dimensions, or taper specifications is often lacking. As a result, despite a systematic search, conducting a robust meta-analysis remains unfeasible due to the insufficient number of eligible cases and incomplete prosthesis-related information. Thus, we provide a comprehensive review on prosthesis-related risk factors of trunnionosis. In addition, we systematically searched case reports of THA complicated by trunnionosis that included sufficient prosthesis data. By extracting and aggregating these device-level details, we aimed to empirically verify previously proposed prosthesis-related risk factors, thereby complementing the limited cohort evidence and strengthening the basis for design recommendations.

PATHOMECHANISMS

Metal debris is generated from (1) fretting corrosion due to micromotion at the interface between femoral head bore and stem trunnion, (2) galvanic corrosion: corrosion caused by an electrochemical transfer of electrons between dissimilar metals, i.e., a cobalt-chromium (CoCr) alloy femoral head on a titanium alloy stem, and (3) crevice corrosion: physicochemical interaction between a metal and its environment leading to altered mechanical properties.¹⁷⁾

The modular interface is secured by interlocking ridges on the tapered trunnion of the femoral stem and the corresponding inner bore surface of the prosthetic femoral head.¹⁸⁾ Although this taper junction is designed to self-lock and withstand substantial tensile, compressive, and rotational forces, repeated cyclic loading can lead to micromotion at the interface.⁴⁾ This micromotion disrupts the oxide layer on the surface of metal alloys, triggering oxidation-reduction cycles that generate wear particles, ultimately leading to fretting wear and corrosion (Fig. 1).¹⁹,²⁰,²¹⁾

Fig. 1. Illustration of cyclic micromotion at modular metallic interfaces disrupting the passive oxide layer and initiating fretting corrosion. Oxygen consumption during repeated re-passivation causes local oxygen depletion and acidification within the crevice, promoting crevice corrosion and accelerated metal ion release (Co²⁺, Cr³⁺, and Mo), which contribute to adverse local tissue reactions around the implant. CoCr: cobalt-chromium, Mo: molybdenum, Ti: titanium.

Often, the stem is made of titanium alloy, while the head is made of a CoCr alloy.¹⁹,²²,²³⁾ Galvanic corrosion occurs between dissimilar metallic materials. The combination of a titanium alloy stem and a CoCr alloy head can lead to galvanic corrosion.²⁴⁾ Galvanic corrosion is more pronounced under acidic conditions, such as those found in crevice microenvironments.⁹,²⁵⁾ Furthermore, micromotion at the crevice exacerbates local oxygen depletion, and thereby accelerates crevice corrosion, forming a vicious cycle.²⁶⁾ The combined effect of fretting and crevice corrosion, termed MACC, results in elevated metal ion concentrations in synovial fluid and serum, triggering ALTRs and gross trunnion failure.⁶,²⁷,²⁸⁾ A recent study suggested that fretting corrosion, rather than crevice corrosion, mainly drives the development of trunnionosis.²⁹⁾

SEARCH METHODOLOGY FOR CASE REPORTS

A literature search was conducted using the keywords listed in Supplementary Table 1 on the PubMed database up to June 15, 2025. Studies were eligible for inclusion if they were original articles, case reports, or review articles describing cases in which patients who had previously undergone THA subsequently required revision arthroplasty due to trunnionosis. Articles were excluded if they involved cases of trunnionosis following hemiarthroplasty, or if they did not provide sufficient patient demographic data (e.g., age, sex, body mass index [BMI]) and detailed information on the implant used during the index THA (e.g., articulation type, head size, manufacturer). Additionally, retrieval studies, biomechanical studies, and finite element analyses were excluded (Fig. 2). Finally, 2 original articles and 30 case reports were included for analysis, encompassing a total of 87 cases of gross trunnionosis (Supplementary Table 2).¹⁶,²⁸,³⁰,³¹,³²,³³,³⁴,³⁵,³⁶,³⁷,³⁸,³⁹,⁴⁰,⁴¹,⁴²,⁴³,⁴⁴,⁴⁵,⁴⁶,⁴⁷,⁴⁸,⁴⁹,⁵⁰,⁵¹,⁵²,⁵³,⁵⁴,⁵⁵,⁵⁶,⁵⁷,⁵⁸,⁵⁹⁾

Fig. 2. The flowchart of the study selection process.

Prosthesis-Related Risk Factors

Head compositions

To date, most trunnionosis cases involved cobalt-chromium heads and titanium alloy stems. In our case-based review, head material was predominantly cobalt alloy, used in 96.6% of cases (84 / 87)—including 78 cobalt-chrome heads and 6 cobalt-chrome-molybdenum heads. Ceramic heads were used in only 3 cases. In 2015, Banerjee et al.²⁸⁾ reported 5 patients who underwent revision due to trunnionosis. Among the 5 patients, 1 received THA with a ceramic head, 1 with use of a metal-sleeve ceramic head, and the remaining 3 with CoCr heads. Excluding the 2 patients who underwent THA with ceramic or metal-sleeved ceramic head, there have been no reports of trunnionosis after the use of ceramic heads.

Ceramic heads are less likely to deform during impaction and no cases of trunnionosis have been reported in THA cases using the combination of ceramic heads and titanium alloy stems. The use of ceramic heads on the threaded tapers decreases metal transfer to the ceramic bore surface.⁶⁰,⁶¹,⁶²⁾ Ceramic heads have a positive clearance angle with proximal contact, while metallic heads may have either positive or negative clearance angles (Fig. 1).

Stem compositions

The choice of stem material is critical in reducing the risk of corrosion. Stems made of stiffer materials, such as CoCr alloys, tend to resist corrosion better than those made of titanium alloys. Regarding the femoral stem in our case-based review, the Accolade stem family was the most commonly used, appearing in 60 cases (70%), followed by ML taper stems in 12 cases (13.8%). The higher incidence of trunnionosis associated with the Accolade titanium–molybdenum–zirconium–iron (TMZF) alloy stem could be attributed to the relatively low modulus of TMZF (70 GPa), compared to conventional titanium alloys (110 GPa). More flexible alloys like TMZF are prone to higher rates of corrosion. Another contributing factor could be accentuated galvanic corrosion at the trunnion interface between the CoCr femoral head and the TMZF stem. While galvanic corrosion is minimal at physiological pH, the crevice microenvironment with a lower pH can accentuate galvanic corrosion.⁹,⁶³⁾

Taper geometry and surface topography

The geometry and surface characteristics of the taper are critical determinants of implant performance, as they influence micromotion, fretting, and corrosion at the modular junction. Parameters such as taper length, slope, diameter, and angle, together with the elastic modulus of the metal, play essential roles in defining the structural rigidity of the implant (Fig. 3).⁶²,⁶⁴⁾ While the impact of taper geometry on trunnionosis has been studied extensively, findings remain inconsistent and at times contradictory.²⁵,⁶⁵⁾

Fig. 3. Schematic illustration of clearance angle at the head–neck taper junction. (A) Positive clearance angle showing proximal contact and a distal gap. (B) Negative clearance angle showing distal contact and a proximal gap. Arrows indicate the contact areas corresponding to the direction of mechanical load transfer.

Modern design trends have favored smaller tapers combined with larger femoral heads to improve the range of motion and reduce dislocation risk. However, this combination may inadvertently increase mechanical loading at the trunnion and thereby accelerate fretting and corrosion.¹⁵,⁶³,⁶⁶,⁶⁷,⁶⁸⁾ In our case-based review, of the 82 cases that reported stem taper type, 60 cases (73.2%) used a 12/14 V40 taper (Accolade stem family), 18 cases used a 12/14 taper, and 3 cases used an 11/13 taper. Smaller-diameter trunnions are generally more flexible and thus more susceptible to micromotion compared with larger-diameter designs.⁶⁹⁾

Case reports have highlighted the clinical implications of unfavorable taper geometry. Botti et al.⁷⁰⁾ described a fracture within the Morse taper 15 years after implantation of an AML stem (DePuy) without antecedent trauma and attributed it to factors such as fretting corrosion from abnormal interface motion, the use of a skirted femoral neck on a thin neck diameter with reduced flexural rigidity, and surface damage during insertion. Similarly, Unnanuntana et al.⁷¹⁾ reported 2 cases of atraumatic trunnion fracture in AML prostheses with a 9/10 taper, where deep grooves and intergranular corrosion were suspected contributors.

The effect of taper length remains controversial. In vitro studies indicate that shorter tapers increase the risk of fretting. Kim et al.⁷²⁾ reported gross trunnion failure associated with the use of a 28-mm cobalt-chrome head and an ABG I stem (Stryker), linking the complication to the short 10-mm length of the 14/16 taper, which produced a larger moment per unit area and excessive fretting corrosion. On the other hand, some retrieval studies have suggested that longer taper lengths may worsen corrosion due to greater accumulation of debris.²³⁾ In a systematic review of 46 trunnionosis cases, Bansal et al. identified prosthetic design factors as risks, and although not explicitly emphasized, short taper lengths of approximately 10.5 mm were noted in several cases (Fig. 4).⁷³⁾

Fig. 4. This figure illustrates how the taper length influences the contact area and micromotion at the head–neck interface. (A) In the short taper design, the contact area between the head and the stem is limited, resulting in greater micromotion under physiological loading. This increased micromotion facilitates fluid ingress and fretting at the modular junction, making the short taper more susceptible to mechanically assisted crevice corrosion. (B) In contrast, the long taper provides a larger contact surface, offering improved mechanical stability, reduced micromotion, and consequently a lower risk of corrosion at the interface.

Surface topography is another factor with significant implications. Threaded tapers are designed to compensate for manufacturing tolerances and improve fixation, particularly with ceramic heads. Nevertheless, they can leave impressions on CoCr bores and allow fluid entrapment in thread grooves, thereby fostering crevice corrosion.⁶⁰,⁶¹,⁶²⁾ Ceramic heads, with their ability to accommodate greater taper angle mismatches, may mitigate catastrophic fracture by allowing the trunnion to sit deeper and reduce hoop stress, but the risk of corrosion remains if fluids accumulate.⁷⁴,⁷⁵⁾

Evidence from retrieval studies also highlights the influence of taper design on damage severity. Tan et al.⁶⁵⁾ analyzed 44 cobalt-chrome-on-polyethylene implants with various taper geometries and found that the 11/13 taper exhibited the highest combined fretting and corrosion scores, particularly at the trunnion base. Similarly, Esposito et al.¹⁵⁾ underscored that trunnion length, diameter, and taper angle dictate force distribution at the junction and therefore influence tribocorrosion.⁷⁶⁾ Although the nominal 12/14 taper has been widely used for the past 2 decades, the machining tolerances vary among manufacturers, and thinner, shorter trunnions may be at higher risk for edge loading at the trunnion base.²²,²³⁾ Consistent with these mechanical vulnerabilities, our case-based review revealed that the 12/14 V40 taper demonstrated the highest frequency of trunnionosis, likely reflecting both its widespread clinical use and the mechanical characteristics of its combination with TMZF stems and CoCr heads. The relatively lower flexural rigidity of this construct may predispose the taper junction to greater micromotion and fretting corrosion, reinforcing its clinical relevance as the most commonly affected design.

Finally, dual modular stem systems add complexity, as the additional stem–neck junction introduces another site of micromotion. Titanium neck adapters, in particular, have been shown to generate higher interface micromotion than CoCr adapters, and the presence of this extra junction has been linked to increased damage at the head–stem interface.⁷⁷,⁷⁸⁾ Overall, the evidence suggests that unfavorable taper geometries—shorter length, smaller diameter, and certain taper angles—as well as adverse surface features such as grooves or threads, significantly increase the risk of fretting and corrosion. These design issues, coupled with contemporary trends toward smaller tapers and larger heads, underscore the importance of careful taper selection to minimize the risk of trunnionosis.

Femoral head diameter

Large-diameter femoral heads and trunnion geometry were common features identified in the studies that associated elements of implant design with tribocorrosion in taper junctions.⁷⁹,⁸⁰⁾ Large-diameter femoral heads, while reducing the risk of dislocation, increase torsional forces at the head-neck junction, because they generate a larger friction torque force on the surface through longer length of friction torque lever arm (that is, head diameter) (Fig. 5).⁸¹⁾ Finite element analyses have demonstrated that stress at this interface rises with larger head diameters.⁸²,⁸³⁾ Clinical studies have also shown that femoral heads of 36 mm or larger are associated with increased corrosion at the trunnion junction.²⁰,⁸⁴⁾ A large-scale registry-based study demonstrated that patients with femoral heads measuring 36 mm or more had a higher likelihood of revision surgery due to adverse reactions to metal debris compared to those with smaller heads.⁸⁵⁾ In our case-based review, head size was reported in 81 cases, with 36-mm heads being the most common (n = 50), followed by 32 mm (n = 17), 40 mm (n = 7), 28 mm (n = 3), 44 mm (n = 1), and 52 mm (n = 1).

Fig. 5. For smaller femoral heads (A), frictional torque generated at the bearing surface (a–b) is limited and largely dissipated at the articulation, resulting in minimal torque transmission to the head–taper junction. In contrast, for larger femoral heads (B), the increased radius amplifies frictional torque, leading to greater transmission to the head–taper junction (e–f), such that frictional torque at e–f exceeds that at a–b. Frictional torque acting on the head surface is equivalent in both models (c–d = g–h).

Head length and femoral neck offset

Increased head–neck offset has been associated with elevated micromechanical stress at the modular interface.⁷⁹,⁸⁰⁾ This increased offset functions as an extended lever arm, magnifying micromotion and exacerbating the risk of MACC at the head–neck interface. Additionally, patients requiring high femoral neck offset typically receive longer femoral heads to restore appropriate joint mechanics (Fig. 6).¹⁰,²⁴⁾ In our case-based review, among the 50 cases that provided information on stem offset, 90% (45 / 50) involved high offset stems or stems with a 127° neck-shaft angle. Among the 64 cases reporting head offset, the average head offset was 4.3 ± 3.7 mm, with 11 cases having 0 mm offset, 4 cases having negative offset, and 49 cases having positive offset.

Fig. 6. This figure compares a standard offset stem and a high offset stem in total hip arthroplasty. The high offset stem positions the femoral head medially to restore hip biomechanics and abductor tension; however, the increased lever arm can lead to greater bending moments at the head–neck junction under physiological loading. As a result, the high offset design may generate more micromotion and mechanical stress at the modular taper interface compared with the standard offset stem, potentially increasing the risk of fretting and corrosion.

Patient-Related Factors

Body mass index

A higher BMI leads to greater mechanical stress on the hip implant, which in turn increases micromotion at the head-neck junction. This increased movement exacerbates wear and corrosion. Studies have shown that for every 10 kg increase in body weight, there is a 1-µm increase in micromotion at this critical junction, which accelerates the progression of trunnionosis due to the added mechanical load.⁸⁰⁾ In our case-based review, the mean BMI reported in 65 cases was 34.8 ± 6.7 kg/m², with 87.7% of patients (57 / 65) having a BMI of 25 kg/m² or greater.

Activity level

The loads placed on hip prostheses during everyday activities can be significantly higher than a patient’s body weight. Bergmann et al.⁸⁶⁾ revealed that activities such as jogging and brisk walking increase the load by 3.9 times the patient’s body weight, while even a stumble can elevate the load to 11 times the body weight. These increased forces contribute to higher micromotion at the taper interface, accelerating the onset of fretting and corrosion.

Implantation duration

The longer the implant remains in place, the greater the likelihood of corrosion at the taper junction. Prolonged implantation has been closely linked to increased corrosion at the interface, which is a contributing factor to implant failure over time.⁷,⁹,²⁵,⁸⁴,⁸⁷⁾ In our case-based review, the average time from primary THA to revision surgery due to trunnionosis in 86 cases was 7.7 ± 3.2 years.

Immune response to corrosion products

The patient’s immune response to the metal ions released from the implant may influence the development of ALTRs. Hallab et al.⁸⁸⁾ demonstrated that lymphocytes from patients with hip implants exhibited heightened sensitivity to metal ions compared to those from healthy individuals. A subgroup analysis further revealed that patients with osteolysis showed significantly stronger lymphocyte reactivity to metal ions, suggesting a potential link between these immune responses and implant complications.

Emerging evidence also indicates that inter-subject variability in biological responses to wear particles may play a role in accelerating corrosion progression. Activated macrophages, in response to CoCr alloy particles, can exacerbate cell-induced corrosion. Moreover, improperly seated heads may allow for micromotions under physiological loads, facilitating macrophage infiltration at the taper interface, which can ultimately accelerate corrosion and contribute to implant failure.⁸⁹,⁹⁰,⁹¹⁾

Sex

Male patients have been identified as being at a higher risk for increased wear and corrosion in THA, possibly due to greater activity levels or anatomical differences that place more stress on the implant interface.⁷³⁾ In our case-based review, the mean age of the patients was 69.1 ± 10.2 years, with a striking predominance of males (80.5%, 70 / 87) compared to females (19.5%, 17 / 87).

Surgical Factors

Impaction force

Ensuring optimal seating of the prosthesis during surgery requires a significant impaction force. Studies have determined that a force of at least 4,000 N is necessary for proper seating. This level of force can be achieved using a hammer weighing approximately 500 g. The force from the most impactful blow determines the seating, not the number of blows, as the effect is not cumulative. To ensure proper fixation, 2 blows are typically recommended: the first for alignment and the second to secure the prosthesis properly.⁴,⁹²,⁹³,⁹⁴⁾

Alignment of impact

The alignment of the impactor with the neck of the femoral stem plays a crucial role in achieving maximum stability. Any misalignment, even by 10°, can reduce the stability of the neck-stem interface. Proper alignment ensures that the force is transmitted efficiently, preventing instability at the taper junction.⁹⁵⁾

Impactor characteristics

The material of the impactor significantly influences the final fixation force. For example, plastic impactors, while gentle on the prosthesis, may not apply sufficient force compared to metallic ones. Ceramic heads, which are increasingly used, should never be struck directly to prevent damage. Rubber-tipped impactors should also be avoided due to their lack of stiffness, which impedes effective force transmission.⁹⁶⁾

Contamination effects

Any fat or fluid left on the trunnion during the assembly process can reduce the fixation strength. It is essential to clean and dry both the taper and bore thoroughly before assembly. Contaminants can cause micromotion at the taper junction, leading to corrosion, which in turn increases the risk of fractures, particularly for ceramic heads.⁵,⁹³,⁹⁷,⁹⁸,⁹⁹⁾

Head size and impaction force

Larger femoral heads necessitate stronger impaction forces to achieve the same pull-off strength as smaller heads. The recommended range for impaction force is between 4,000 N and 6,000 N, with larger heads requiring higher forces. Failure to apply adequate force can result in improper seating and increased risk of loosening.¹⁰⁰⁾ Therefore, head size directly impacts the necessary force for secure fixation. The causative factors of trunnionosis are summarized in Table 1.

Table 1. Causative Factors of Trunnionosis Following Total Hip Arthroplasty.

Category		Factor
Prosthesis-related factors
	Head composition	· Cobalt-chromium heads
	Stem composition	· Cobalt-chromium alloys
	Taper geometry and surface topography	· 12/14 V40 taper– skirted femoral neck on a thin neck diameter– thinner, shorter taper length–threaded tapers– crevice corrosion
	Femoral head diameter	· Large-diameter femoral heads
	Head length and femoral neck offset	· Increased head–neck offset
Patient-related factors
	Body mass index	· Higher body mass index
	Activity level	· High activity level
	Implantation duration	· Prolonged implantation period
	Immune response to metal ions	· Lymphocyte/macrophage response
	Sex	· Male
Surgical factors
	Impaction force	· Low impaction force
	Alignment of impact	· Misaligned impaction
	Impactor characteristics	· Plastic or rubber-tipped impactors
	Contamination effects	· Contamination during assembly (fat or fluid)
	Head size and impaction force	· Larger heads requiring stronger impaction force

DIAGNOSIS

Symptoms

Although trunnionosis is generally described as presenting with non-specific symptoms such as groin, thigh, or buttock pain accompanied by limping and muscular weakness, our case-based review found that pain was the most commonly reported symptom (81.6%, 71 / 87), followed by difficulties with walking or ambulation (71.9%, 43 / 87). The average time from implantation to symptom onset is between 3.7 and 4.3 years.⁶,¹⁰¹,¹⁰²⁾ In some cases, limping and Trendelenburg gait patterns may also be observed.⁸²⁾

A comprehensive medical history and physical examination are critical to rule out other potential causes of hip and groin pain. In particular, palpation of soft-tissue swelling is important. Unexplained pain after THA should raise suspicion for trunnionosis, especially when other common causes such as infection, aseptic loosening, or iliopsoas tendonitis have been excluded.⁸²⁾ It is also worth noting that some patients may present with a rash, which is presumed to be a hypersensitivity reaction to elevated metal ions, potentially without any accompanying pain.⁴,¹⁰³,¹⁰⁴,¹⁰⁵⁾ Furthermore, certain presentations may mimic conditions like iliopsoas tendinitis or trochanteric bursitis, which necessitate a more thorough diagnostic approach.

In cases of ALTR due to metal debris, patients may develop a lump or abductor lurch, caused by necrosis induced by the local tissue reaction.¹⁰³⁾ Although pain is not universally present, some patients may experience instability or swelling, with rare cases presenting a palpable fluid collection in the peritrochanteric region.⁶,¹⁰²⁾ Notably, more than 40% of patients report audible sounds such as clicks or pops before experiencing dislocation.⁴²⁾

Systemic Toxicity

While systemic toxicity related to elevated metal ion levels is most frequently observed in MoM bearings, its potential association with trunnionosis in metal-on-polyethylene (MoP) bearings remains theoretical. Symptoms of systemic toxicity include fatigue, shortness of breath, palpitations, cognitive impairments, and disturbances in vision or hearing. Although these symptoms are primarily linked to MoM bearings, it is crucial for clinicians to be aware of the possibility of systemic toxicity in trunnionosis cases and conduct thorough assessments of the patient’s symptoms.¹⁰⁶⁾ Early detection is essential, as delayed diagnosis may lead to more severe soft-tissue damage.⁶⁹⁾

Radiographic Evaluation

Radiographi c evaluation, including plain x-rays, is crucial for assessing implant loosening, osteolysis, or malalignment. However, in many cases, plain radiographs may not conclusively indicate trunnionosis. Cross-sectional imaging techniques such as computed tomography or magnetic resonance imaging (MRI) may provide more detailed insights, with metal artifact reduction sequence (MARS)-MRI scans helping detect synovitis or pseudotumors around the hip.⁸⁰,⁸⁸,¹⁰³⁾ Radiographs primarily serve to rule out major implant failures, including osteolysis and malalignment.¹⁰⁷⁾ In severe cases, radiographic findings may reveal osteolysis at the calcar or greater trochanter, or even head-neck dissociation, indicating advanced ALTR.⁴²,⁴⁴,¹⁰¹,¹⁰²⁾

Ultrasonography

Ultrasonography (US) serves as a helpful supplementary diagnostic tool for trunnionosis, particularly in the evaluation of pseudotumors and soft-tissue alterations. It is especially beneficial for patients who cannot undergo MRI due to limitations such as the presence of a cardiac pacemaker, as US does not face issues related to metal artifacts. Research by Nishii et al.¹⁰⁸⁾ showed that US demonstrated a sensitivity of 74%, specificity of 92%, and accuracy of 84% in patients with MoM THA, while these figures were 90%, 83%, and 85%, respectively, for MoP THA patients. This suggests that US is a valuable screening tool, particularly for those unable to receive MRI scans.

Magnetic Resonance Imaging

MRI, particularly with MARS-MRI, is often regarded as the most reliable imaging technique for identifying trunnionosis. MARS-MRI mitigates the metal artifacts from CoCr alloys, allowing for enhanced visualization of periprosthetic soft tissues and a detailed assessment of the extent of ALTR and pseudotumors. MRI plays an important role not only in diagnosing complications such as trunnionosis but also in preoperative assessment, helping to exclude other possible sources of hip pain, such as issues with the lumbosacral spine. Moreover, MRI allows for accurate evaluation of the abductor musculature and the degree of soft-tissue damage.⁵,¹⁸,⁷⁵,¹⁰⁹⁾

Laboratory Tests

Blood tests are vital for evaluating metal-related complications such as periprosthetic joint infection (PJI). Key tests include the erythrocyte sedimentation rate (ESR) and C-reactive protein, which help detect inflammation. CoCr ion levels should also be measured, as abnormal levels are indicative of potential issues. Specifically, elevated cobalt levels greater than 1 ng/mL or chromium levels exceeding 0.35 ng/mL are considered abnormal and suggest complications, regardless of the follow-up duration.¹¹⁰⁾ Additionally, an increased cobalt-to-chromium ratio, with cobalt levels surpassing chromium, is commonly observed in trunnionosis. A ratio above 1.4 has been associated with a sensitivity of 93% and specificity of 70% for diagnosing trunnion corrosion.¹¹¹⁾

Due to symptom overlap, distinguishing trunnionosis from a PJI can be challenging. Joint aspiration and synovial fluid analysis are critical for differentiating between the 2 conditions. Corrosion products can skew automated white blood cell (WBC) counts, making manual WBC counts essential for accurate diagnosis.⁴²⁾ Additionally, elevated ESR or C-reactive protein levels may indicate infection, prompting further diagnostic workup, including aspiration for culture and cell count analysis.¹⁵⁾

A study of 150 patients with trunnionosis found that a manual WBC count threshold of 4,350 WBC/mL, with more than 85% polymorphonuclear leukocytes, is a highly sensitive and specific diagnostic criterion for infection.¹¹²⁾ Other biomarkers, such as leukocyte esterase andα-defensin, have also been explored to help differentiate infection from corrosion reactions. While α-defensin has shown high sensitivity and specificity for PJI in some studies, its accuracy is debated, with some studies reporting lower sensitivity.¹¹³,¹¹⁴,¹¹⁵⁾

Histopathological Findings

Histopathological examinations of tissue affected by ALTR often show a chronic inflammatory response, including the presence of fibrous tissue and chronic inflammatory cells such as macrophages, histiocytes, granulomas, and giant cells, all of which are indicative of metal debris. These findings suggest that the process of corrosion and ALTR unfolds over an extended period. Such insights reinforce the significant role of corrosion and ALTR in causing progressive tissue damage.⁴⁴⁾

Intra-articular Metal Ions

McGrory et al.¹¹⁶⁾ conducted a study investigating intra-articular metal ion levels in patients with symptomatic taper corrosion. They found that cobalt and chromium concentrations within the joint were significantly higher than in the serum—137 times higher for cobalt and 320 times higher for chromium. These differences were statistically significant. The findings highlight the potential importance of measuring intra-articular metal ion levels in diagnosing trunnionosis, although further research is needed to clarify the clinical implications.

TREATMENTS

Nonsurgical management plays no significant role in treating trunnionosis.¹⁷⁾ Once revision surgery is determined, thorough preoperative planning is crucial to achieve optimal surgical outcomes.¹⁵⁾ Revision surgery for trunnionosis typically involves debridement of synovial tissue, removal of pseudotumors, and excision of the affected femoral head, particularly when CoCr materials are involved. If any components show signs of loosening, they should be revised accordingly.¹¹⁷⁾ However, when the femoral stem is well-fixed and corrosion is minimal, it may be retained, as removing a stable stem can increase the risk of complications.⁶⁵,⁸⁷⁾ A ceramic femoral head with a titanium sleeve is commonly used for replacement, along with concurrent exchange of the acetabular liner. In cases involving rare or proprietary taper geometries, custom titanium adapters may be required.¹¹⁸⁾ For patients with well-fixed implants, isolated head-and-liner exchange is often sufficient for revision surgery.⁶,¹⁰¹,¹⁰²,¹¹⁹,¹²⁰⁾ However, in cases of severe trunnion damage, removal of the stem may be necessary.⁴²,⁴⁴,¹²¹⁾ The degree of trunnion damage can be classified according to the Goldberg Fretting and Corrosion Score⁹⁾ (Table 2). The decision to revise the femoral stem is based on the extent of corrosion, while the acetabular liner is routinely replaced.⁴⁸⁾

Table 2. Goldberg Fretting and Corrosion Score: Grading System for Damage at the Modular Taper Junction between the Femoral Head and Stem.

Severity of corrosion and fretting	Score	Criteria
None	1	No visible corrosion observed No visible signs of fretting observed
Mild	2	< 30% of taper surface discolored or dull Single band or bands of fretting scars involving 3 or fewer machine lines on taper surface
Moderate	3	> 30% of taper surface discolored or dull, or < 10% of taper surface containing black debris, pits, or etch marks Several bands of fretting scars or single band involving more than 3 machine lines
Severe	4	> 10% of taper surface containing black debris, pits, or etch marks Several bands of fretting scars involving several adjacent machine lines, or flattened areas with nearby fretting scars

The surgeon should also assess the integrity of the soft-tissue envelope, particularly the abductor mechanism, and evaluate implant stability. In the presence of instability, constrained liners, face-changing or lipped liners, or dual-mobility acetabular components may be required to enhance joint stability.¹⁵⁾ After removal of the femoral head, the trunnion must be carefully cleaned of corrosion debris using sponges or abrasive pads and inspected thoroughly for damage.⁶,¹⁰²,¹²²⁾ If only minimal damage is present, a ceramic head paired with a compatible titanium sleeve adapter should be used. Reimplantation of a CoCr femoral head is discouraged, as it may lead to recurrence of ALTR.¹⁰²⁾

POSTOPERATIVE COMPLICATIONS

Recurrent instability is the most common complication following revision surgery for trunnion corrosion.⁶,¹⁰²⁾ In a study by Cooper et al.,⁶⁾ 2 of 13 patients required further revision due to recurrent instability; 1 patient developed sciatic nerve palsy, and another experienced a deep infection. Similarly, Plummer et al. reported that among 27 patients who underwent revision for ALTRs, 2 with ceramic heads experienced recurrent instability, 1 developed a deep infection, and another had peroneal nerve palsy. Among 4 patients with CoCr heads, 1 experienced a recurrence of ALTRs and was subsequently revised with a ceramic head and titanium sleeve.¹⁰²⁾

In cases of severe hip destruction caused by corrosion, the use of a constrained liner or dual-mobility cup can help prevent recurrent instability.¹¹⁷⁾ Lash et al.⁴⁰⁾ reported major complications in 6 of 10 patients with ALTRs, including recurrent dislocations. McGrory and Jorgensen¹²³⁾ also documented complications in 7 of 27 revisions for MACC following MoP THA, with 6 cases involving recurrent dislocations—highlighting the importance of using constrained liners or dual-mobility components in such cases.

A retrospective study of 65 hips revised for MACC-induced trunnionosis reported a major complication rate of 11.6% and a reoperation rate of 5.8% at a mean follow-up of 3.2 years after revision.¹²⁴⁾ Although long-term data on isolated head-liner exchange for MACC are limited, Goyal et al.¹²⁰⁾ found that this approach did not increase the rate of revision surgery due to MACC recurrence, with an average follow-up of 3.3 years. Recurrent instability and an elevated risk of PJI—primarily due to soft-tissue necrosis and destruction—are the most common complications following revision surgery for ALTR. These complications occur at higher rates than those seen in revisions for other conditions.¹⁰¹,¹⁰²,¹¹⁹⁾

LEGAL IMPLICATIONS

Managing patients with trunnionosis and ALTR can be further complicated by ongoing legal issues.⁶⁹⁾ Surgeons should ask whether patients are involved in litigation, as this may necessitate returning explanted components for third-party analysis following revision surgery. Legal involvement can also influence how patients report their symptoms. In 2016, Stryker Orthopaedics voluntarily recalled several LFIT-V40 femoral head models manufactured before 2011 due to failures related to trunnionosis.⁶⁹⁾ This recall led the Australian Department of Health to issue a hazard warning, and lawsuits concerning these implants have since increased across multiple states in the United States.⁶⁹⁾

CONCLUSION

Trunnionosis is a significant complication of THA that arises from MACC at the head–neck junction, leading to ALTRs, pseudotumor formation, and eventual implant failure. Our review highlights prosthesis-related factors—most notably CoCr heads, flexible stem alloys, large femoral heads, increased offset, and short trunnion length—as consistent risks. Patient characteristics such as male sex, elevated BMI, and prolonged implantation further compound these risks, while surgical factors such as inadequate impaction force, misalignment, or contamination can precipitate early failure.

Given current implant design trends that favor larger heads and greater offsets, surgeons have limited ability to avoid all prosthesis-related risks. Nonetheless, certain modifiable strategies remain crucial: selecting ceramic heads when feasible, avoiding TMZF stems, and exercising caution with shorter or thinner trunnions. In revision settings, ceramic heads with titanium sleeves, dual mobility constructs, or constrained liners may help mitigate recurrent instability.

Ultimately, a multidisciplinary approach involving careful implant selection, meticulous surgical assembly, vigilant postoperative monitoring, and standardized manufacturing practices will be necessary to minimize the incidence of trunnionosis. Greater awareness of this complication, combined with ongoing refinement of implant design and surgical techniques, is essential for improving long-term THA outcomes.

SUPPLEMENTARY MATERIAL

Supplementary material is available in the electronic version of this paper at the CiOS website, www.ecios.org.

Supplementary Table 1

List of Keywords and the Number of Results for Each from a PubMed search (Jun 15, 2025)

Supplementary Table 2

A Systematic Review of 87 Reported Cases of Trunnionosis