Aims

Several short- and mid-term studies have shown minimal liner wear of highly cross-linked polyethylene (HXLPE) in total hip arthroplasty (THA), but the safety of using thinner HXLPE liners to maximize femoral head size remains uncertain. The objective of this study was to analyze clinical survival and radiological wear rates of patients with HXLPE liners, a 36 mm femoral head, and a small acetabular component with a minimum of ten years’ follow-up.

Large ceramic femoral heads offer several advantages that are potentially advantageous to patients undergoing both primary and revision total hip replacement. Many high-quality studies have demonstrated the benefit of large femoral heads in reducing post-operative instability. Ceramic femoral heads may also offer an advantage in reducing polyethylene wear that has been reported in vitro and is starting to become clinically apparent in mid-term clinical outcome studies. Additionally, the risk of taper corrosion at a ceramic femoral head–neck junction is clearly lower than when using a metal femoral head. With improvements in the material properties of both modern ceramic femoral heads and polyethylene acetabular liners that have reduced the risk of mechanical complications, large ceramic heads have gained popularity in recent years. Cite this article: Bone Joint J 2013;95-B, Supple A:63–6

Aims

The increased in vivo resistance to wear of highly crosslinked polyethylene (HXLPE) in total hip arthroplasty (THA) has led to an increased use of larger articulations which have been shown to reduce the incidence of early dislocation. To date, there are few reports of the wear of larger articulations using second generation HXLPE liners. Our prospective cohort study measured the bedding-in and early wear of large (36 mm and 40 mm diameter) articulations involving a second generation X3 HXLPE liner and compared our findings with previous clinical and in vitro studies of the same material.

Aims

This study investigates head-neck taper corrosion with varying head size in a novel hip simulator instrumented to measure corrosion related electrical activity under torsional loads.

Dislocation remains among the most common complications of, and reasons for, revision of both primary and revision total hip replacements (THR). Hence, there is great interest in maximising stability to prevent this complication. Head size has been recognised to have a strong influence on the risk of dislocation post-operatively. As femoral head size increases, stability is augmented, secondary to an increase in impingement-free range of movement. Larger head sizes also greatly increase the ‘jump distance’ required for the head to dislocate in an appropriately positioned cup. Level-one studies support the use of larger diameter heads as they decrease the risk of dislocation following primary and revision THR. Highly cross-linked polyethylene has allowed us to increase femoral head size, without a marked increase in wear. However, the thin polyethylene liners necessary to accommodate larger heads may increase the risk of liner fracture and larger heads have also been implicated in causing soft-tissue impingement resulting in groin pain. Larger diameter heads also impart larger forces on the femoral trunnion, which may contribute to corrosion, metal release, and adverse local tissue reactions. Alternative large bearings including large ceramic heads and dual mobility bearings may mitigate some of these risks, and several of these devices have been used with clinical success.

Cite this article: Bone Joint J 2014;96-B(11 Suppl A):23–6.

Introduction. Recent studies on large diameter femoral head hip replacements have implicated the modular taper junction as one of the significant sources of wear and corrosion products and this has been attributed to increased torque and bending on the taper interface. The aim of this study was to assess the effect of frictional torque and bending moment on fretting corrosion at the taper junction and to investigate whether different material combinations also had an effect. Patients/Materials & Methods. We examined 1) Cobalt Chromium (CoCr) heads on CoCr stems 2) CoCr heads on Titanium alloy (Ti) stems and 3) Ceramic heads on CoCr stems. In test 1 increasing torque was imposed by offsetting the femoral stem in the anterior posterior plane in increments of 0 mm, 4 mm, 6 mm and 8 mm where the force generated was equivalent to 0Nm, 9Nm, 14Nm and 18Nm. In Test 2 we investigated the effect of increasing bending moment by offsetting the application of axial load from the midline in the medial-lateral (ML). Offset increments equivalent to +0, +7 and +14 heads were used. For each test we used n=3 for each different material combination. Results. Significantly higher currents and amplitudes were seen with increasing frictional torque for all material combinations, however titanium alloy stems showed the highest corrosion. Increasing bending moments associated with using larger off-set heads produced more corrosion; with titanium alloy stems generally performing worse than cobalt chrome stems. Using ceramic heads did not prevent corrosion, but this was significantly reduced in all loading configurations. Discussion & Conclusion. This is the first study to quantify corrosion associated with different material combinations and loading conditions. Increasing frictional torque and bending, together with the material combination have a significant effect on the fretting corrosion at the taper modular junction. The best performing material combination was ceramic on CoCr

Previous reports on the outcomes of isolated head and liner exchange in revision total hip arthroplasty have found high rates of instability following these surgeries. Most reports have studied constructs using ≤28mm femoral heads. The purpose of this study was to determine if modern techniques with the use of larger head sizes can improve the rate of instability after head and liner exchange. We identified 138 hips in 132 patients who underwent isolated head and liner exchange for polyethylene wear/osteolysis (57%), acute infection (27%), metallosis (13%), or other (2%). All patients underwent revision with either 32mm (23%), 36mm (62%), or 40mm (15%) diameter heads. Crosslinked polyethylene was used in all revisions. Lipped and/or offset liners were used in 104 (75%) hips. Average follow up was 3.5 (1.0–9.1) years. Statistical analyses were performed with significance set at p<0.05. Revision-free survivorship for any cause was 94.6% and for aseptic causes was 98.2% at 5 years. 11 (8%) hips experienced a complication with 7 (5%) hips requiring additional revision surgery. Following revision, 4 (3%) hips experienced dislocation, 5 (4%) hips experienced infection, and 1 (1%) hip was revised for trunnionosis. No demographic or surgical factors significantly affected outcomes. Our study shows that isolated head and liner exchange using large femoral heads and modern liners provides for better stability than previous reports. The most common complication was infection. We did not identify specific patient, surgical or implant factors that reduced the risk of instability or other complication

The benefit of dual mobility cup (DMC) for primary total hip arthroplasties (THA) is still controversial. This study aimed to compare 1) the complications rate, 2) the revisions rate, 3) the survival rate after monobloc DMC compared to large femoral heads (LFH) in primary THA. Between 2010 and 2019, 2,075 primary THA using cementless DMC or LFH were included. Indications for DMC were patients older than 70 years old or with high risk of dislocation. Every other patient received a LFH. Exclusion criteria were cemented implants, femoral neck fracture, a follow-up of less than one year. 1,940 THA were analyzed: 1,149 DMC (59.2%), 791 LFH (40.8%). The mean age was 73 ±9.2 years old in DMC group and 57 ±12 in LFH group. The complications and the revisions have been assessed retrospectively. The mean follow-up was 41.9 months ±14 [12–134]. There were significantly fewer dislocations in DMC group (n=2; 0.17%) compared to LFH group (n=8; 1%) (p=0.019). The femoral head size had no impact on the dislocations rate in LFH group (p=0.70). The overall complication rate in DMC (n=59; 5.1%) and LFH (n=53; 6.7%) were not statistically different (p=0.21). No specific complication was attributed to the DMC. In DMC group, 18 THA (1.6%) were revised versus 15 THA in LFH group (1.9%) (p= 0.71). There was no statistical difference for any cause of revisions in both groups. The cup aseptic revision-free survival rates at 5 years were 98% in DMC group and 97.3% in LFH group (p=0.78). Monobloc DMC had a lower risk of dislocation in a high-risk population than LFH in a low-risk population at the mid-term follow-up. There was no significant risk of specific complications or revisions for DMC in a large cohort. Monobloc DMC can be safely used in a selected high-risk population

Large femoral heads have been used with increasing frequency over the last decade. The prime reason is likely the effect of large heads on stability. The larger head neck ratio, combined with the increased jump distance of larger heads result in a greater arc of impingement free motion, and greater resistance to dislocation in a provocative position. Multiple studies have demonstrated clear clinical efficacy in diminishing dislocation rates with the use of large femoral heads. With crosslinked polyethylene, wear has been shown to be equivalent between larger and smaller heads. However, the stability advantages of increasing diameter beyond 38 mm have not been clearly demonstrated. More importantly, recent data implicates large heads in the increasing prevalence of groin pain and psoas impingement. There are clear benefits with larger femoral head diameters, but the advantages of diameters beyond 38 mm have not yet been demonstrated clinically

Aims. The purpose of this study was to compare two different types of metal-on-metal (MoM) bearing for total hip arthroplasty (THA): one with a large femoral head (38 mm to 52 mm) and the other with a conventional femoral head (28 mm or 32 mm). We compared clinical outcome, blood metal ion levels, and the incidence of pseudotumour in the two groups. Patients and Methods. Between December 2009 and December 2011, 62 patients underwent MoM THA with a large femoral head (Magnum group) and 57 patients an MoM THA with a conventional femoral head (conventional group). Clinical outcome was assessed using the Harris Hip score, University of California, Los Angeles (UCLA) activity score and EuroQol-5D (EQ-5D). Blood metal ion levels were measured and MRI scans were analyzed at a minimum of five years postoperatively. Results. No acetabular component was implanted with more than 50° of inclination in either group. The Harris Hip Score, UCLA activity score, and EQ-5D improved postoperatively in both groups; no significant clinical differences were noted between the groups. The blood cobalt ion levels in the conventional group continued to rise postoperatively to five years while reaching a plateau at two years postoperatively in the Magnum group. At five years, the mean cobalt ion level of 1.16 μg/l (. sd. 1.32) in the Magnum group was significantly lower than the 3.77 μg/l (. sd. 9.80) seen in the conventional group (p = 0.0015). The incidence of moderate to severe pseudotumour was 4.7% in the Magnum group and 20.6% in the conventional group. There were no dislocations in the Magnum group and two in the conventional group. One patient in the Magnum group underwent revision for pseudotumour at 4.7 years postoperatively. Conclusion. At five years, a well-positioned large head MoM THA has a significantly lower level of metal ion release and a lower incidence of moderate to severe pseudotumour than a MoM bearing of conventional size. Cite this article: Bone Joint J 2018;100-B:1018–24

Aims. The aim of this study was to evaluate blood metal ion levels, leucocyte profiles, and serum cytokines in patients with a total hip arthroplasty (THA) involving modular dual-mobility components. Patients and Methods. A total of 39 patients were recruited, with clinical follow-up of up to two years. Outcome was assessed using the Harris Hip Score (HHS, the 12-Item Short-Form Health Survey (SF-12), the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and a visual analogue scale (VAS) for pain. Blood concentrations of cobalt (Co), chromium (Cr), and serum cytokines were measured. Subpopulations of leucocytes were analyzed by flow cytometry. Results. The clinical performance was good. Blood Co levels (ref 1.0 µg/l) were mildly elevated in seven patients at three months, and two patients at two years’ follow-up. The preoperative Cr levels were normal except for one patient with a detectable Cr (1.2 µg/l). Cr levels were detectable in three patients at three months, two patients at one year, and three patients at two years’ follow-up. No patients had symptoms suggestive of failure. Although flow cytometry showed constant circulating leucocyte profiles, there was a significant reduction of serum interleukin (IL)-4, IL-5, and interferon gamma (IFNγ) postoperatively compared with the preoperative levels (p < 0.05). Conclusion. These results suggest that THA using modular dual-mobility components is safe. This allows an opportunity to use a large femoral head and a thick polyethylene bearing surface, which is especially useful in revision procedures or high-risk situations when added stability is required. Cite this article: Bone Joint J 2019;101-B:1035–1041

Introduction. Porous coated cups have a low modulus of elasticity that enhances press-fit and a surface that promotes osseointegration as well as permitting modularity. Monoblock ceramic acetabular cups represent a subtype of uncemented cup permitting the use of large femoral heads. The aim of this study was to compare the short-term clinical and radiographic performances of both cups. Methods. This was a prospective RCT of 86 unilateral THA patients (M: 40, F: 48; mean age: 59.5 ± 10.6) randomized to either a porous-coated, modular metal-on-polyethylene (MoP) acetabular component (pore size 250µm, 45% mean volume porosity)(n=46) or a hydroxyapatite (HA) and titanium-coated monoblock shell with ceramic-on-ceramic(CoC) bearing (pore size 300µm, 48% mean volume porosity & 80nm HA coating thickness)(n=42). All sockets were under-reamed by 1 mm. Two-year radiographs and patient-reported outcomes (PROMs) were available. Results. Thirty-two (69%) and 28 (6%) gaps were found in modular cup and monoblock groups, respectively (p=0.001). For the modular, 17 filled the gaps, whereas 15 turned into radiolucency; for the monoblock, 1 of the gaps turned into radiolucency at final follow-up (p<0.001). Complete shell-to-bone contact without radiolucent lines was seen in 30 (65%) porous-coated cups and in 41 (98%) HA shells (p<0.001). There were no associations between presence of lucent lines and PROMs (mHHS, WOMAC and UCLA) (p>0.05) in both groups. Modular cup group was an independent predictor of developing lucent lines (OR: 19.1, p= 0.007). No case underwent revision surgery due to acetabular loosening. There were 2 cases of squeaking in CoC monoblock shell with no functional limitations. Conclusion. Both cups showed successful clinical results at short-term follow-up; however, the porous-coated modular evidenced a significantly higher rate of radiolucent line occurrence, without any association with PROMs. Since these lines indicate the possibility of future cup loosening, longer follow-up is necessary. For any tables or figures, please contact the authors directly

Aims. We have previously demonstrated raised cobalt and chromium levels in patients with larger diameter femoral heads, following metal-on-polyethylene uncemented total hip arthroplasty. Further data have been collected, to see whether these associations have altered with time and to determine the long-term implications for these patients and our practice. Methods. Patients from our previous study who underwent Trident-Accolade primary total hip arthroplasties using a metal-on-polyethylene bearing in 2009 were reviewed. Patients were invited to have their cobalt and chromium levels retested, and were provided an Oxford Hip Score. Serum ion levels were then compared between groups (28 mm, 36 mm, and 40 mm heads) and over time. Results. Metal ion levels were repeated in 33 patients. When comparing the results of serum metal ion levels over time, regardless of head size, there was a significant increase in both cobalt and chromium levels (p < 0.001). Two patients with larger head sizes had undergone revision arthroplasty with evidence of trunnion damage at surgery. Two patients within the 40 mm subgroup had metal ion levels above the MHRA (Medicines and Healthcare Products Regulatory Agency) threshold for detailed investigation. The increase in cobalt and chromium, when comparing the 36 mm and 40 mm groups with those of the 28 mm group, was not significant (36 mm vs 28 mm; p = 0.092/p = 0.191; 40 mm vs 28 mm; p = 0.200/p = 0.091, respectively). There was no difference, between femoral head sizes, when comparing outcome as measured by the Oxford Hip Score. Conclusion. This study shows an increase in cobalt and chromium levels over time for all modular femoral head sizes in patients with metal-on-polyethylene bearings, with two patients demonstrating ion levels above the MHRA threshold for failure, and a further two patients requiring revision surgery. These results may have clinical implications regarding longer term follow-up of patients and future implant choice, particularly among younger patients. Cite this article: Bone Joint J 2020;102-B(7):832–837

Introduction. Prior to the introduction of alternative bearing surfaces, patients were typically counseled to expect that their total hip arthroplasty (THA) using conventional polyethylene would last for 10 years. With the introduction of crosslinked polyethylene and hard-on-hard bearing surfaces, revisions related to bearing surface wear were expected to decrease. We examined six different bearing surfaces used at our institution over three decades to evaluate how the overall survivorship, reasons for revision and Harris Hip Scores have changed with time. Methods. We identified six cohorts of patients with 754 primary hips done between 1983 and 2007. With the exception of 81 Birmingham hip resurfacings (BHR), all femoral components were straight, extensively porous-coated cylindrical (EPC) stems (AML and Prodigy). All cups were porous coated. In addition to the BHRs, the bearing surfaces included 223 conventional polyethylene (CPE) in a non-modular shell, 114 CPE in a modular shell, 116 crosslinked polyethylene (XLPE), 130 metal-on-metal (MOM), and 90 ceramic-on-ceramic (COC). The mean follow-up for all hip replacements is 13.0±6.0 years. Kaplan-Meier survivorship using revision for any reason as an endpoint with log rank testing was used to evaluate differences among groups. Results. Although there were no differences in survivorship at 10-year follow-up among the groups (p=0.53), the XLPE liners demonstrated improved survivorship at 15-years compared to both CPE groups owing to the absence of wear-related revisions (97% versus 83% for non-modular and 85% for modular cups respectively, p=0.001 and p=0.008). Revisions for femoral loosening have only occurred among 0.6% (4/673) of EPC stems. Revisions for cup loosening have occurred among 4% (10/223) of the non-modular cups but there are none among the other groups. The incidence of dislocation was reduced with the MOM, BHR and COC bearings that used 36-mm or larger femoral heads compared to the THAs that used 28-mm or 32-mm heads [1.1 % (3/261) versus 5.1% (25/493), p<0.01]. Infection has led to revision among 2 THAs with CPE in non-modular cups (0.9%), 2 MOM (1.5%), and 2 COC (2.2%). At 10-year follow-up, Harris Hip Scores tended to be higher among the BHRs compared to the other groups (92.1 versus 82.9, p<0.01). Discussion. The introduction of XLPE has eliminated wear-related revisions through 15-year follow-up. Hard-on-hard bearing surfaces are performing relatively well but differences are not yet discernable compared to CPE. Dislocation incidence has been reduced with the introduction of larger diameter heads but remains a persistent concern. Infection continues to occur although the incidence remains low. For any tables or figures, please contact the authors directly

Introduction. The use of larger femoral heads in Total Hip Arthroplasty has increased in order to reduce the risk of dislocation and to improve the range of motion of the joint. In 2003, within the UK, the “standard” head size of 28mm was used in 73% of all hip procedures, whereas by 2012, this figure dropped to 36%. Concerns regarding the impact of this increment in head size on the cement and bone stresses have arisen; however, this has yet to be clearly determined. Methods. To understand the relationship between femoral head size and cement mantle and bone stress in cemented hip arthroplasty, 3D-Finite-Element models of a hemipelvis with cemented cup[tb6] (50mm outer-diameter) were developed. Loading conditions of single-leg-stance (average and overweight) were simulated for three head sizes (28, 32 and 36mm). The models were validated with an in-vitro experiment using the average loading condition. Results. Stresses were evaluated at the periacetabular bone and cement mantle. In the pelvic bone the peak von Mises stress value presented no change in magnitude due to change in head size for the average patient; for the overweight patient, there was a small increment. In the cement mantle, there was a noticeable difference in the pattern distribution and magnitude of the stresses for the two loading conditions[tb7]. For the average patient, average stresses in the cement were 1.7MPa, 1.8MPa and 1.9MPa for 28, 32 and 36mm heads, respectively; whereas for the overweight patient the stresses were 3.4MPa, 3.6MPa and 3.8MPa. Conclusions. Pelvic bone remained largely unaffected by the changes in femoral head size. The major effect of femoral head size occurs in the stress level and stress distribution pattern in the cement mantle. The current predicted cement stresses are below the cement endurance limit, this indicates that the cement fatigue life is not affected by the increasing head size

Aims

This study aims to assess the relationship between history of pseudotumour formation secondary to metal-on-metal (MoM) implants and periprosthetic joint infection (PJI) rate, as well as establish ESR and CRP thresholds that are suggestive of infection in these patients. We hypothesized that patients with a pseudotumour were at increased risk of infection.

Aims

Iliopsoas impingement occurs in 4% to 30% of patients after undergoing total hip arthroplasty (THA). Despite a relatively high incidence, there are few attempts at modelling impingement between the iliopsoas and acetabular component, and no attempts at modelling this in a representative cohort of subjects. The purpose of this study was to develop a novel computational model for quantifying the impingement between the iliopsoas and acetabular component and validate its utility in a case-controlled investigation.

This study aimed to examine the changing trends in the causes for early revision of total hip replacements (THR) in one country over fifteen years to assess whether changes in arthroplasty practices have changed revision patterns. The cause for revision within one year was extracted from the New Zealand Joint Registry for the period of January 1999 to December 2013. The results were grouped into three periods of 5 years (Period 1=1999–2003, Period 2=2004–2008 and Period 3 = 2009–2013). The causes were compared across the three periods and were adjusted for age, gender and ASA grade. The rate of early revisions (within one year) rose from 0.86% to 1.30% per year. There was significant rise in revision for deep infection (14% increased to 21% of all causes, p<0.001) and femoral fracture (5% increased to20%, p<0.001), whereas revision for dislocation decreased (55% decreased to 35%, p<0.001). Adjusting for age and gender femoral fracture and deep infection rates remained significant for both (p<0.05). Adjusting for age, gender as well as ASA only remained significant for infection (P<0.05). The reduction in revision for dislocation followed the registry trend for the use of larger femoral heads and cross linked polyethylene. The rise in early periprosthetic femoral fracture rates was directly associated (p<0.001) with the increased use of uncemented femoral prostheses. The worrying increase in infection rate was unexplained on the basis of registry data alone. It was related to ASA grade but the overall ratios of ASA grades remained consistent over the 15 years

Aims

Radiostereometric analysis (RSA) is the most accurate radiological method to measure in vivo wear of highly cross-linked polyethylene (XLPE) acetabular components. We have previously reported very low wear rates for a sequentially irradiated and annealed X3 XLPE liner (Stryker Orthopaedics, USA) when used in conjunction with a 32 mm femoral heads at ten-year follow-up. Only two studies have reported the long-term wear rate of X3 liners used in conjunction with larger heads using plain radiographs which have poor sensitivity. The aim of this study was to measure the ten-year wear of thin X3 XLPE liners against larger 36 or 40 mm articulations with RSA.

Aims

Dislocation remains a leading cause of failure following revision total hip arthroplasty (THA). While dual-mobility (DM) bearings have been shown to mitigate this risk, options are limited when retaining or implanting an uncemented shell without modular DM options. In these circumstances, a monoblock DM cup, designed for cementing, can be cemented into an uncemented acetabular shell. The goal of this study was to describe the implant survival, complications, and radiological outcomes of this construct.