Aim of this work is to critically analyze the current mandatory trend to adapt femoral cementless implant shape as to allow their use through mini-invasive anterior hip approach (MIS-AA).

During decades, designers of cementless stems tried to adapt implant shapes to patient anatomy, that led to various classification systems (straight, curved, anatomic, etc …). Another way to classify cementless stems is according to their longevity, outcome quality and long-term results. This is the goal of the Orthopaedic Data Evaluation Panel (ODEP) that provided in 2017 an approved list of prostheses that meet at least the NICE 10y revision rate standard.

In the last available ODEP 2020 issue, the best rating (13y experience “13”, with strong evidence “A” and < 6.5% rev rate “∗”) was achieved by only 10 cementless implant: Mallory-Head®, Taperloc®, Bimetric®, Accolade®, SL-Alloclassic®, Corail®, CLS Spotorno®, Furlong®, Synergy® & Versys Fibermetal®. All 10 are Ti straight tapers with large metaphyseal morphology in particular in Gruen Zone I. All these 10 ODEP 13A∗ cementless stems can universally be implanted through postero-lateral (PL), MIS-PL, lateral & conventional anterior approaches, but not safely through MIS-AA. Conversely, only new short and curved stems can be inserted safely through MIS-AA. Indeed, surgeons who promote MIS-AA cannot routinely use those successful femoral implants classified ODEP 13A∗.

Obviously, surgical approach determines the choice of femoral component. Surgeons who promote MIAA can only bet/hope that these new short curved implants with currently very few clinical evidence will reach the same success and longevity that ODEP 13A∗ conventional straight tapers. Only future long-term studies will address that concern.

Since the universal failure of first generation smooth threaded cups in primary total hip arthroplasty (THA), the screw-in concept of cementless acetabular cup fixation has been largely abandoned. We hypothesised that grit-blasted titanium conical cement free threaded cup shows stable long-term fixation. 198 Alloclassic total hip arthroplasties were performed in 179 patients, mean age 66 years old (22–85). 193 hips were analyzed after a mean follow-up of 10 years (1–25 years).

Results were excellent or good in 184 hips (95%). Postel-Merle d'Aubigne score increased from 10.3 (range 1 to 15) pre-operatively to 16.7 (12 to 18) points and 151 hips (78%) were pain free at last FU. Radiographic signs indicating successful cup osseointegration were noted in 92% of hips. Polyethylene wear > 0.1mm/year was observed in 6 hips (3%). The main cause of re-operation/revision surgery was recurrent dislocation (9/17cases, 53%). 2 threaded cups were revised for any reason and the revision per cent observed acetabular component years was 0.10 at 10 years average FU. 20 year-survival of the metal back was 98.8% (77.2–99.9%) and 100% (79.6–100%) for revision for any reason and revision for aseptic loosening, respectively. Despite minimum PE thickness of 6.5mm and use of alumina ceramic 28mm heads, conventional polyethylene liner wear was the weak link of the acetabular reconstruction;

This study shows excellent long-lasting bone anchorage through bone on-grown of grit-blasted titanium threaded cup. Despite universal outstanding longevity in the worldwide literature, CSF threaded cups were retrieved from the European market in March 2017 due to insufficient sales, indicating that evidence base medicine may not be the major criteria influencing surgeons' choice.

Introduction

The causes for revision of primary total hip arthroplasty (THA) are various and quite well known. The developing use of dual-mobility THA (DM-THA) seems a relevant option to decrease the risk of instability. Due to lack of long-term follow-up, this innovative retentive concept is suspected to increase the risk of polyethylene (PE) wear. The aim of the study was to analyse the causes for DM-THA revision and assess whether or not its occurrence is different from that of fixed-standard (FS) THA, particularly for aseptic loosening or wear and/or osteolysis.

Introduction: Aim of this study was to provide survivor-ship analysis of the cementless Zweymüller, then Alloclassic flat-wedge femoral titanium alloy taper used in primary THA.

Material and Methods: Of 1128 consecutive 1ary THAs (paired with a grit-basted threaded cup in 93%) performed over the 01/1986–12/2008 period and prospectively followed-up, 31 were all-cemented (2.7%), 74 were hybrid reconstructions (6.6%) and 1023 were fully cementless (90.7%). A total of 1034 cementless tapers (72 “Hochgezogen” and 962 “Alloclassic-SL” implants) were implanted.

Results: Considering the unavoidable learning curve, first author complication rates (526 consecutive 1ary THAs) were acceptable with fracture ; femur, 0.5%: greater-trochanter, 0.8% ; subsidence > 2mm, 3.4% ; varus position 14.3% ; and osteolysis, 0.9%. Of the 1034 uncemented tapers, 19 were revised for: deep infection (7), recurrent dislocation (4), intra-operative or late fractures (4), unexplained pain (3, none loose at revision) and 1 for aseptic loosening (due to metallic head sleeve impingement). Overall femoral revision burden was 1.8% (< 0.1% per year) and survivorship with revision “for any reason” and “for aseptic loosening” was 94.2% and 99.5% % at 17 years, respectively. Currently, main reason for revision is related to osteolysis due to wear of conventional polyethylene liners.

Conclusion. In a general orthopaedic population and in a regular setting, the Alloclassic SL-stem, our everyday femoral component, was forgiving and reliable for more than 20 years. We can reasonably expect an outstanding outcome in the future due to improved surgical skill, hard bearings (Metasul, 1994), slimmer neck and “Offset” options (2004).

Introduction: Reintroduced in 1988, 28-mm metal-on-metal Metasul bearings had head sleeves and liner rim edge. It was modified in 1995 for the 2nd current design without sleeve and rim. Aim of this study was to address the fate if any of this modification.

Material and methods: 100 consecutive Alloclassic cementless titanium 1ary THA with 28mm-Metasul bearings (22 with head sleeve of the 1st design) were prospectively studied (primary arthritis in 76% of hips, mean age 59.6 years). 2 Metasul components of 1st design were exchanged for dislocation. The remaining 98 THAs were reviewed after a 6-year average follow-up (range, 17–126 months).

Results: Clinical results were graded excellent and good except for 3 patients Radiographically, wear was undetectable in the 97 bearings available for study. Post-operative cobalt level in whole blood was noted superior to the upper “normal” value (5 μg/L) for 16 THAs (3 of the 1st design, 13%). No significant relationship could be established between elevated blood Co level and any demographic or surgical data, including age (p = .61) and activity level (p = .44), except with radiographic aspect of a high anteversion of the cup, noted > 25° in 5 hips: incidentally 4 were of the 1st Metasul design (p = .0037). High dislocation rate (5%) could partly be explained by early impingement favoured by head sleeve and liner rim-edge. In 1 hip, despite excellent clinical result, posterior impingement with an extra-long sleeved head induced elevated Co level that leads to the bearing exchange. In another hip with Metasul head sleeve, the same mechanism induced femoral component aseptic loosening and osteolysis that was revised at 7.8 years. These 2 hips showed the higher Co levels of the series, up to 23.6 μg/L and 36 μg/L, respectively. The difference between revision rates of Metasul bearings of 1st (4/22, 17%) and current design (1/78, 1.3%) was significant (p =.008). At 8 year, survivorship of Metasul bearings from revision for any reason was 81.4% (95% CI, 57–93.5%) for the 1st design and 98.7% (81–99.9%) for the current design. No general toxic effect could have been detected thus far.

Conclusion: In this personal experience, impingement due to metallic head sleeve has been the main cause of osteolysis, and Co level survey has shown to be a good indicator of Metal-on-Metal bearing behaviour. Obviously, Metasul head sleeve should have been avoided.

Purpose of the study: Long-term outcome of Charnley low-friction arthroplasty in young active patients is impaired worldwide due to wear of the polyethylene (PE) component and osteolysis. In the late eighties, reports of possible low wear with some former metal on metal total hip arthroplasties led to the reintroduction of metallic bearings. The aims of this work were to examine the rationale for using metal on metal bearings in primary total hip arthroplasty (THA) and report preliminary results obtained with cementless Metasul™-Alloclassic™ hips.

Materials and methods: From January 1994 to March 1997, 64 cementless primary Alloclassic-THA (grit-blasted titanium SL stems and CSF treaded cups) with 28 mm Metasul bearings were performed. Mean age at surgery was 60 years (range, 36–73). Diagnoses were usual, mainly primary osteoarthrosis in 70 p. 100 of the hips. Two bearing surfaces were exchanged for late dislocation at 2.6 and 2.9 years. Thus, 62 hips in 58 active patients (4 bilateral) were reviewed after a minimum 2-year follow-up (mean 3.2 years, range 24–66 months).

Results: Clinical results according to the Merle d’Aubigne and Charnley rating system were graded excellent or good in all 62 hips. Radiologically, calcar, atrophy and spot welds were noted in 93 p. 100 and 82 p. 100 of hips respectively. Proximal reactive and lucent lines and mild proximal stress shielding were observed in 8 p. 100 and 4.8 p. 100 of hips respectively. No osteolysis granuloma has thus far been observed in the vicinity of any component. Cobalt blood level remained normal, except in 6 cases due to occupational exposure (n = 1), possible impingement (n = 1) or an unknown cause (n = 4). All elevated cobalt levels (range 7 to 25 mg/l) were nevertheless far below the toxic limit.

Discussion: Dislocation may be due either to the posterolateral surgical approach and/or early impingement with the first Metasul bearing design (head sleeve). Metasul acetabular component fixation is not restricted to only cementless metal-backing, unlike alumina-ceramic cups. The concern about the toxicity of metallic wear debris dissemination and the hematocarcinogenic risk must be taken into consideration as for any metallic THA. Follow-up is too short for the new polys for significant comparisons.

Conclusion: Metal on metal tribology is well known in vitro and Metasul™ bearings have functioned in vivo for 12 years (120 000 Metasul hips worldwide) as was expected from laboratory tests. Obviously, this friction couple is not the unique answer to PE-wear and THA longevity, but, in light of current data, appears as a trustworthy solution available today.