Recommended
Recommended
More Related Content
What's hot
What's hot (20)
Similar to Trunnionosis in total hip arthroplasty
Similar to Trunnionosis in total hip arthroplasty (20)
Recently uploaded
Recently uploaded (20)
Trunnionosis in total hip arthroplasty
- 1. Trunnionosis in Total Hip Arthroplasty Mitchell C. Weiser, MD, MEng, and Carlos J. Lavernia, MD THE JOURNAL OF BONE & JOINT SURGERY, SEPTEMBER 6, 2017 Prepared by Dr.SUHAIL.A.P Junior Resident Govt Medical College Calicut
- 2. • The occurrence of wear and corrosion at the trunnion-head modular interface is commonly referred to as trunnionosis. • Clinical failures of THR ascribed to this entity have increased dramatically in the last decade, affecting an estimated 0.032% to 2% of patients with a total hip replacement
- 3. • The recent increasing prevalence of this diagnosis depends on : 1.Implant-based factors: the trend toward using larger femoral heads, mixed-metal head and stem couples, trunnion geometry, trunnion topography and decreasing flexural rigidity of the femoral neck 2. Surgeon-based factors: impaction strength and cleanliness of the trunnion 3. Patient-based factors: the time in situ, patient weight and immune response.
- 4. • ALTR through molecular mediators, leading to local tissue necrosis, osteolysis, and destruction of the abductor muscle complex. • Dissociation of the head from the stem has also been reported in patients with severe taper corrosion • Systemic toxicity manifesting as chromosomal mutations, end-organ damage and teratogenicity in pregnant females secondary to elevated serum metal ions
- 5. Corrosion • Several different mechanisms - combination of mechanical and chemical reactions • Mechanically assisted crevice corrosion (MACC) • Mechanical degradation of the passivation layer secondary to micromotion at modular junctions, leading to electrochemical corrosion and ion release
- 6. • Ceramic femoral heads less susceptible to MACC compared to cobalt-chromium (CoCr) alloy • The presence of corrosion and corrosion byproducts incites a lymphocytic T-cell-mediated tissue response resulting in tissue necrosis
- 7. Implant Design Features Implicated in Trunnionosis • Implant design features, implicated in the development of trunnion corrosion includes – taper design , – surface topography, – neck and taper flexural rigidity, – head size, and – head-trunnion material selection
- 8. Taper Geometry • Smaller-diameter and shorter trunnions are inherently more flexible • Taper contact length is also controversial, with shorter contact lengths having been shown in in vitro studies to potentiate fretting, while the opposite has been observed in retrieval studies
- 9. Taper Topography • The surface finish of the trunnion may range from macrothreads to relatively smooth, depending on the manufacturer and stem design • Threaded tapers have been observed to leave thread imprints on femoral head bores in both retrieval and in vitro studies – Crevice corrosion
- 10. • Threaded tapers are designed to accommodate ceramic femoral heads • greater taper angle mismatch than CoCr • trunnion sit deeper within the bore • Ceramic heads are less susceptible to plastic deformation during impaction, and the use of threaded tapers also improves the security of the interference fit
- 12. • The threads of the taper yield, leading to metal transfer on the surface of the ceramic bore where the contact pressures are greatest.
- 13. Head Size • Use of larger femoral heads (≥32 mm) increased in popularity. • Greater principal stresses at the head-trunnion interface as well as the medial aspect of the neck • due to an increased bending moment imparted by the longer lever arm of larger heads • 2.8-times higher revision risk for ALTR in the NJR database
- 14. Flexural Rigidity of the Trunnion
- 15. • flexural rigidity of the trunnion is partly dictated by the stem composition and the neck diameter to the fourth power. • Current trends towards smaller diameter necks • Flexible necks leads to trunnionosis secondary to increased micromotion at the head-trunnion interface
- 16. Material Properties • Stiffer alloys and larger diameter trunnions - less prone to corrosion and fretting • key material properties related to fretting and corrosion include – the ability to form a passivation layer, – the ability of the passivation layer to resist fracture, – material hardness, and material treatment
- 17. • CoCr and titanium (Ti) alloys both possess the ability to self-passivate in oxygen-rich environments - inert materials within the human body • Ti less stiff than Cocr so more susceptible to galling and fretting. • Ti alloys offer greater resistance to material dissolution at a lower pH than CoCr alloys, making them more resistant to corrosion.
- 18. Surgeon-Based Factors • Pull-off strength of the head increasing linearly with impaction force. • Greater impaction force - increase the area of contact between the bore and the trunnion
- 19. • Increasing the strength of the taper connection reduces the magnitude of micromotion at the taper interface - prevent the initiation of fretting and corrosion • The ideal impaction force varies on the basis of the head size, with a range of 4,000 to 6,000 N, with larger heads requiring greater force.
- 20. • Fluid or fat left on the trunnion at the time of head assembly negatively affects pull-off strength, increases micromotion of the head, and potentiates fretting
- 21. Patient-Based Factors • length of implantation time • Patient weight, femoral architecture,and activity level • patient-specific immune response to corrosion products may also play a role in the development of ALTR.
- 22. Diagnosis • Delayed onset of groin, thigh, or buttock pain with or without muscular weakness and a limp • mean time from implantation to presentation of 3.7 to 4.3 years • Painless instability • Unilateral leg swelling, or rarely with a palpable fluid collection in the peritrochanteric region
- 23. • 1% to 2% of patients with a total hip replacement • Underestimated • Osteolysis and a loose implant are often the given diagnoses, even with the surgeon finding “black debris” on the taper head junction. • C/f of systemic cobalt toxicity - fatigue, dyspnea, palpitations, change in vision or hearing, or unexplained mood change
- 24. Laboratory Studies • ESR, CRP • Joint Aspiration – Cell count and culture • patients with ALTR – False positive • If ALTR is suspected, serum Co and Cr levels • Serum CoCr levels should be <1 ppb in well- functioning MoP total hip replacements.
- 25. • serum Co level of >1.6 ng/mL - threshold for MACC • differential elevation of the serum Co to Cr ratio, on the order of approximately 5:1 • Preferential deposition of chromium at the head-neck junction in the form of Cr orthophosphate
- 26. Imaging • Plain radiographs -AP pelvic and crosstable lateral hip views • Osteolysis at the base of the calcar and greater trochanter • Patients with suspected ALTR - Metal artifact reduction sequence magnetic resonance imaging (MARS MRI) is currently considered the gold standard
- 27. Treatment • Revision surgery - preoperative planning • The implants are usually well-fixed, and revision may often be accomplished with isolated head-and-liner exchange • severe trunnion damage or cold-welding of the head-neck junction - removal of the stem
- 28. • All necrotic and nonviable tissue should be excised • After removal of the head, the trunnion should be cleaned of corrosion debris and inspected for damage
- 29. • Trunnion crushed – remove the stem • Minimally damaged - a ceramic head with a manufacturer-specific titanium sleeve adaptor • The acetabular liner should also be exchanged • Acetabular component not explanted • Complications - Recurrent instability and an increased risk of periprosthetic joint infection
- 30. Take Home Message • Causes of trunnionosis are multifactorial • the risk of trunnionosis may be minimized by Avoiding mixed-metal bearing couples, utilizing more rigid stems and trunnions, utilizing the minimal necessary head sizes and offset to restore leg length and stability, and paying meticulous attention to the intraoperative assembly of the head on the trunnion, through the cleaning, drying, and firm impaction of the head on the trunnion
- 31. use of ceramic heads in primary total hip arthroplasty Understanding the presentation, workup, diagnosis, and treatment of trunnionosis- induced ALTR and having the full revision surgical armamentarium available
Editor's Notes
- -The occurrence of wear and corrosion at the trunnion-head modular interface is commonly referred to as trunnionosis -Shortly after the introduction of femoral stem modularity in the 1980s, wear and corrosion at modular interfaces in total hip replacements became recognized entities with the first report of osteolysis secondary to the deposition of chromium orthophosphate at modular junctions in 1994. -Clinical failures of THR ascribed to this entity have increased dramatically in the last decade, affecting an estimated 0.032% to 2% of patients with a total hip replacement
- -Several theories that have been postulated for the recent increasing prevalence of this diagnosis include the following: Implant-based factors: the trend toward using larger femoral heads, mixed-metal head and stem couples, trunnion geometry, trunnion topography and decreasing flexural rigidity of the femoral neck 2. Surgeon-based factors: impaction strength and cleanliness of the trunnion 3. Patient-based factors: the time in situ, Patient weight and immune response. There is no single identifiable cause of trunnionosis, but rather a synergistic combination of factors
- -Wear and corrosion at the head-neck interface can induce an ALTR through molecular mediators, leading to local tissue necrosis, osteolysis, and destruction of the abductor muscle complex. -Dissociation of the head from the stem has also been reported in patients with severe taper corrosion. -Rare instances of systemic toxicity manifesting as chromosomal mutations, end-organ damage, and teratogenicity in pregnant females secondary to elevated serum metal ions in MoM bearings have also been described -Trunnion corrosion has also resulted in device recalls and legal action against device manufacturers.
- Corrosion of metal implants occurs via several different mechanisms and often occurs as a combination of mechanical and chemical reactions -The most clinically relevant mechanism of corrosion in the development of trunnionosis is believed to be the process of mechanically assisted crevice corrosion (MACC) -This process results in the mechanical degradation of the passivation layer secondary to micromotion at modular junctions, leading to electrochemical corrosion and ion release. -Micromotion fractures the oxide layer of both the stem and the head, producing crevices and exposing the underlying substrate metal alloy to oxygen-rich fluid. The repassivation of the substrate metal results in consumption of oxygen from the local environment. The repetition of this process leads to the acidification of the trapped fluid as the oxygen is consumed, ultimately resulting in ion release from the substrate metal and the local deposition of corrosion products. This causes material loss from both the trunnion and the femoral head bore, with preferential loss from the bore
- Ceramic femoral heads appear to be much less susceptible to the process of MACC than those composed of cobalt-chromium (CoCr) alloy. The presence of corrosion and corrosion byproducts incites a lymphocytic T-cell-mediated tissue response resulting in tissue necrosis and has been shown to potentiate the wear rate of the polyethylene liner
- -Taper geometry and flexural rigidity of the trunnion are closely linked, as smaller-diameter and shorter trunnions are more flexible than those of a larger diameter for a given metal alloy. -Taper contact length is also controversial, with shorter contact lengths having been shown in in vitro studies to potentiate fretting while the opposite has been observed in retrieval studies.
- -The surface finish of the trunnion may range from macrothreads to relatively smooth, depending on the manufacturer and stem design. -Among stems with threaded tapers, the thread height, pattern, and thread pitch are manufacturer dependent variables. -Threaded tapers have been observed to leave thread imprints on femoral head bores in both retrieval and in vitro studies. -These observations have led to the theory that threaded tapers might contribute to the process of crevice corrosion, as fluid may become trapped in the troughs between thread peaks when the femoral head is engaged on the taper.
- -Threaded tapers are designed to accommodate ceramic femoral heads, which themselves are designed with a greater taper angle mismatch than CoCr heads in order to prevent fracture during impaction. This allows the trunnion to sit deeper within the bore, applying contact pressure where the cross-sectional area of the ceramic head is greatest to resist hoop stresses. Ceramic heads are less susceptible to plastic deformation during impaction, and the use of threaded tapers also improves the security of the interference fit, while avoiding unwanted local stress concentrations.
- The threads of the taper yield, thus accommodating for manufacturing intolerances, ultimately leading to metal transfer on the surface of the ceramic bore where the contact pressures are greatest.
- -The use of larger femoral heads (‡32 mm) in total hip arthroplasty has increased in popularity throughout the last decade, encompassing approximately 90% of total hip arthroplasties performed in 2015. -The use of larger heads imparts greater principal stresses at the head-trunnion interface as well as the medial aspect of the neck. - this is due to an increased bending moment imparted by the longer lever arm of larger heads. -larger heads (36 versus 28 or 32 mm) has been associated with a 2.8-times higher revision risk for ALTR in the NJR database.
- The flexural rigidity of the trunnion is determined by the following Equation:
- -Based on this equation, the flexural rigidity of the trunnion is partly dictated by the stem composition and the neck diameter to the fourth power. -Current trends are towards stems with smaller-diameter necks in order to maximize the range of motion prior to the impingement of the femoral implant. -These smaller, more flexible necks have been implicated as a cause of trunnionosis secondary to increased micromotion at the head-trunnion interface
- -Stems made of stiffer alloys and those with larger diameter trunnions are less prone to corrosion and fretting. -Other key material properties related to fretting and corrosion include the ability to form a passivation layer, the ability of the passivation layer to resist fracture, material hardness, and material treatment.
- -CoCr and titanium (Ti) alloys both possess the ability to self-passivate in oxygen-rich environments. This passivation layer allows these alloys to be relatively inert materials within the human body. -Ti alloys are not as hard as CoCr alloys, making them more susceptible to galling and fretting. However, Ti alloys offer greater resistance to material dissolution at a lower pH than CoCr alloys, making them more resistant to corrosion.
- The impaction force at the assembly of the head on the trunnion have a direct effect on the amount of force necessary to pull the head off the trunnion, with pull-off strength of the head increasing linearly with impaction force. - Greater impaction force at the head-trunnion assembly has also been shown to increase the area of contact between the bore and the trunnion -If multiple mallet blows are used to impact the head on the trunnion, the mallet blow with the largest magnitude of force accounts for 90% of the strength at the head-trunnion interface
- -Increasing the strength of the taper connection reduces the magnitude of micromotion at the taper interface, and may prevent the initiation of fretting and corrosion -The ideal impaction force varies on the basis of the head size, with a range of 4,000 to 6,000 N, with larger heads requiring greater impaction forces to impart an equivalent pull-off strength to those of smaller heads -ideal impaction forces may be difficult to achieve in vivo, as a surgeon may only deliver approximately 2,000 N with a typical mallet blow during head Impaction.
- -The condition of the trunnion at the time of head assembly has also been shown to affect the interface security. -Several in vitro studies have demonstrated that fluid or fat left on the trunnion at the time of head assembly negatively affects pull-off strength, increases micromotion of the head, and potentiates fretting.
- Several studies have noted that the length of implantation time is associated with the development of corrosion at the headneck junction. -Patient weight, femoral architecture, and activity level may also play a role in the development of trunnionosis. -a patient-specific immune response to corrosion products may also play a role in the development of ALTR. -Hallab et al. demonstrated that lymphocytes collected from patients with a total hip replacement were more sensitive to stimulation from metal ions than those collected from control subjects.
- variable presentation, but most commonly presents as a delayed onset of groin, thigh, or buttock pain with or without muscular weakness and a limp, with a mean time from implantation to presentation of 3.7 to 4.3 year. -Pain is not universally present, and some patients with ALTR may present with painless instability. -Patients may also present with unilateral leg swelling, or rarely with a palpable fluid collection in the peritrochanteric region.
- only 1% to 2% of patients with a total hip replacement will experience trunnionosis resulting in ALTR this is likely an Underestimation. -Osteolysis and a loose implant are often the given diagnoses, even with the surgeon finding “black debris” on the taper head junction. -The surgeon must be alert to the remote possibility of systemic cobalt toxicity and perform clinical examination noting any fatigue, dyspnea, palpitations, change in vision or hearing, or unexplained mood change. -The timeliness of the diagnosis of ALTR is key, as a delay may lead to an increase in the severity of soft-tissue damage.
- Symptoms of periprosthetic joint infection and those of ALTR are quite similar. Blood work, including erythrocyte sedimentation rate and C-reactive protein level, should be obtained. -If either is elevated, the joint should be aspirated and the fluid should be sent for cell count and culture -patients with ALTR may have corrosion products and a cellular conglomeration that interfere with automated cell counts, leading to a false-positive result. -Yi et al. suggested performing a manual white blood-cell count (WBC) with an optimal cutoff of >4,350 WBC/mL and a differential of >85% polymorphonuclear leukocytes for diagnosing periprosthetic joint infection in a patient who has either a corroded MoP total hip replacement or an MoM bearing. -If ALTR is suspected, serum Co and Cr levels should be obtained. -Levine et al. suggested that serum CoCr levels should be <1 ppb in well-functioning MoP total hip replacements
- -serum Co level of >1.6 ng/mL has been suggested as a threshold for MACC. -Patients with clinically important trunnion corrosion often demonstrate a differential elevation of the serum Co to Cr ratio, on the order of approximately 5:1. -This differential elevation occurs secondary to the preferential deposition of chromium at the head-neck junction in the form of Cr orthophosphate, while the released Co ions are systemically absorbed.
- Plain radiographs including anteroposterior pelvic and crosstable lateral hip views should be routinely made during the clinical examination. Findings of osteolysis at the base of the calcar and greater trochanter can be suggestive of ALTR. -Patients with suspected ALTR should undergo crosssectional imaging to evaluate the soft-tissue envelope surrounding the hip. Metal artifact reduction sequence magnetic resonance imaging (MARS MRI) is currently considered the gold standard modality for its ability to visualize fluid collections as well as cystic and solid masses, its ability to evaluate gluteal musculature and soft tissue, and its high degree of concordance of soft-tissue destruction with intraoperative findings.
- Once the decision to proceed with revision surgery is made, careful preoperative planning is essential. The soft-tissue envelope should be assessed for abductor deficiency and implant stability, and the surgeon should be prepared for the potential intraoperative need for constrained liners, face-changing or lipped liners, or dual-mobility acetabular construct -The implants are usually well-fixed, and revision may often be accomplished with isolated head-and-liner exchange -removal of the stem may be necessary in cases of severe trunnion damage or cold-welding of the head-neck junction.
- -all necrotic and nonviable tissue should be excised and the implant position should be assessed, with a low threshold to revise malpositioned components -After removal of the head, the trunnion should be cleaned of corrosion debris with a sponge or scratch pad and inspected for damage
- -trunnion crushed – remove the stem. -If the trunnion is minimally damaged, a ceramic head with a manufacturer-specific titanium sleeve adaptor is recommended, as exchange of the CoCr femoral head to another CoCr femoral head may result in recurrence of ALTR The acetabular liner should also be exchanged because of the possibility of embedded metal debris -Consideration should be given to using a facechanging, lipped, or constrained liner to guard against postoperative instability -The acetabular component usually does not need to be explanted, unless it is malpositioned or is unable to accept either a standard or cemented liner -Recurrent instability and an increased risk of periprosthetic joint infection, because of necrosis and destruction of the soft-tissue envelope, are the most common complications following revision surgery for ALTR