Trunnionosis in total hip arthroplasty

Trunnionosis in THR

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. T he recent increasing prevalence of this diagnosis depends on : 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. D issociation of the head from the stem has also been reported in patients with severe taper corrosion S ystemic toxicity manifesting as chromosomal mutations, end-organ damage and teratogenicity in pregnant females secondary to elevated serum metal ions

5. C orrosion S everal 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. C eramic 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 I mplant 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 S maller-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

11. The threads of the taper yield , leading to metal transfer on the surface of the ceramic bore where the contact pressures are greatest.

12. 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

13. Flexural Rigidity of the Trunnion

14. 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

15. 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

16. 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.

17. Surgeon-Based Factors P ull-off strength of the head increasing linearly with impaction force. Greater impaction force - increase the area of contact between the bore and the trunnion

18. 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.

19. 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

20. 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.

21. 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

22. 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

23. Laboratory Studies ESR, CRP Joint Aspiration – Cell count and culture patients with ALTR – False positive If ALTR is suspected, serum Co and Cr levels S erum CoCr levels should be <1 ppb in well-functioning MoP total hip replacements.

24. 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

25. 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

26. Treatment R evision surgery - preoperative planning The implants are usually well-fixed, and revision may often be accomplished with isolated head-and-liner exchange s evere trunnion damage or cold-welding of the head-neck junction - removal of the stem

27. 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

28. 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

29. 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

30. 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