Short cementless femoral stems are increasingly popular as they allow for less dissection for insertion. Use of such stems with the anterior approach (AA) may be associated with considerable per-operative fracture risk. This study's primary aim was to evaluate whether patient-specific femoral- and pelvic- morphology and surgical technique, influence per-operative fracture risk. In doing so, we aimed to describe important anatomical thresholds alerting surgeons. This is a single-center, multi-surgeon retrospective, case-control matched study. Of 1145 primary THAs with a short, cementless stem inserted via the AA, 39 periprosthetic fractures (3.4%) were identified. These were matched for factors known to increase fracture risk (age, gender, BMI, side, Dorr classification, stem offset and indication for surgery) with 78 THAs that did not sustain a fracture. Radiographic analysis was performed using validated software to measure femoral- (canal flare index [CFI], morphological cortical index [MCI], calcar-calcar ratio [CCR]) and pelvic- (Ilium-ischial ratio [IIR], ilium overhang, and ASIS to greater trochanter distance) morphologies and surgical technique (% canal fill). Multivariate and Receiver-Operator Curve (ROC) analysis was performed to identify predictors of fracture. Femoral factors that differed included CFI (3.7±0.6 vs 2.9±0.4, p3.17 and II ratio>3 (OR:29.2 95%CI: 9.5–89.9, p<0.001). Patient-specific anatomical parameters are important predictors of fracture-risk. When considering the use of short stems via the AA, careful radiographic analysis would help identify those at risk in order to consider alternative stem options

Short cementless femoral stems are increasingly popular as they allow for less dissection for insertion. Use of such stems with the anterior approach (AA) may be associated with considerable per-operative fracture risk. This study's primary aim was to evaluate whether patient-specific femoral- and pelvic- morphology and surgical technique, influence per-operative fracture risk. In doing so, we aimed to describe important anatomical thresholds alerting surgeons. This is a single-centre, multi-surgeon retrospective, case-control matched study. Of 1145 primary THAs with a short, cementless stem inserted via the AA, 39 periprosthetic fractures (3.4%) were identified. These were matched for factors known to increase fracture risk (age, gender, BMI, side, Dorr classification, stem offset and indication for surgery) with 78 THAs that did not sustain a fracture. Radiographic analysis was performed using validated software to measure femoral- (canal flare index [CFI], morphological cortical index [MCI], calcar-calcar ratio [CCR]) and pelvic- (Ilium-ischial ratio [IIR], ilium overhang, and ASIS to greater trochanter distance) morphologies and surgical technique (% canal fill). Multivariate and Receiver-Operator Curve (ROC) analysis was performed to identify predictors of fracture. Femoral factors that differed included CFI (3.7±0.6 vs 2.9±0.4, p<0.001) and CCR (0.5±0.1 vs 0.4±0.1, p=0.006). The mean IIR was higher in fracture cases (3.3±0.6 vs 3.0±0.5, p<0.001). % Canal fill was reduced in fracture cases (82.8±7.6 vs 86.7±6.8, p=0.007). Multivariate analysis and ROC analyses revealed a threshold CFI of 3.17 was predictive of fracture (sensitivity:84.6% / specificity:75.6%). Fracture risk was 29 times higher when patients had CFI>3.17 and II ratio>3 (OR:29.2 95%CI: 9.5–89.9, p<0.001). Patient-specific anatomical parameters are important predictors of fracture-risk. When considering the use of short stems via the AA, careful radiographic analysis would help identify those at risk in order to consider alternative stem options

Aims. Femoral bone preparation using compaction technique has been shown to preserve bone and improve implant fixation in animal models. No long-term clinical outcomes are available. There are no significant long-term differences between compaction and broaching techniques for primary total hip arthroplasty (THA) in terms of migration, clinical, and radiological outcomes. Methods. A total of 28 patients received one-stage bilateral primary THA with cementless femoral stems (56 hips). They were randomized to compaction on one femur and broaching on the contralateral femur. Overall, 13 patients were lost to the ten-year follow-up leaving 30 hips to be evaluated in terms of stem migration (using radiostereometry), radiological changes, Harris Hip Score, Oxford Hip Score, and complications. Results. Over a mean follow-up period of 10.6 years, the mean stem subsidence was similar between groups, with a mean of -1.20 mm (95% confidence interval (CI) -2.28 to -0.12) in the broaching group and a mean of -0.73 mm (95% CI -1.65 to 0.20) in the compaction group (p = 0.07). The long-term migration patterns of all stems were similar. The clinical and radiological outcomes were similar between groups. There were two intraoperative fractures in the compaction group that were fixed with cable wire and healed without complications. No stems were revised. Conclusion. Similar stem subsidence and radiological and clinical outcomes were identified after the use of compaction and broaching techniques of the femur at long-term follow-up. Only the compaction group had intraoperative periprosthetic femur fractures, but there were no long-term consequences of these. Cite this article: Bone Jt Open 2021;2(12):1035–1042

Purpose. The purpose of this study is to evaluate the midterm results of cementless revision total hip arthroplasty (THA) using Wagner Cone Prosthesis. Material and Methods. Between 1996 and 2007, 36 hips in 36 consecutive patients underwent femoral revision THA using Wagner Cone Prosthesis. Among them 28 hips were followed for more than 5 years. The mean age at revision surgery was 57 years and a mean follow-up was 7.6 years. The Paprosky classification system was used for preoperative bone loss evaluation. Clinical results were evaluated using Harris hip scores. For evaluation of the femoral component, radiolucent lines at bone-implant interfaces were evaluated and femoral component vertical subsidence was measured. Heterotopic bone formation and complications were also evaluated. Results. The mean period from 1. st. operation to revision THA was 8.0 years. For the femoral bone loss, in eleven hips bone grafting was done. For the prevention of femoral stem fracture, femoral wiring was done in 12 hips. In eighteen hips acetabular cup revision was done simultaneously and in 5 hips isolated stem revision was done. The mean Harris hip score improved from 52 to 83 at final follow-up. With respect to radiological results all femoral stems showed bone ingrowths, 3 out of 28 (10.7%) femoral stems showed subsidence more than 5 mm. Two patients needed acetabular revision for acetabular loosening during follow up period. There was one patient who complained of anterior thigh pain. One patient had recurrent dislocation and required revision surgery for soft tissue augmentation. Conclusions. We achieved favorable midterm clinical and radiological results for femoral stem revisions using Wagner cone prosthesis. This cementless femoral stem can be a good option for femoral stem revision

A customised, uncemented femoral stem was introduced clinically in 1995 after several years of development and pre-clinical testing. All the patients operated in our hospital have entered a prospective clinical study. The aim of this study is to present the short-term clinical data. Furthermore, the measurement of implant migration and the periprosthetic bone remodelling at two years is also reported. Materials and methods: The femoral stem is designed from preoperative CT-scans, machined in Ti-alloy and circumferentially coated with a 50μm hydroxyapatite (HA) layer in the proximal 50-70%. Fifty-one patients (median age 52 years) have been followed clinically for a minimum of 3 years using the Merle-d’Aubignè score. Migration of the femoral stem has been measured with radiostereometry (RSA), the precision of the measurements is better than 0.080 mm for translations and 0.30° for rotations. Periprosthetic bone remodelling is expressed as the change in bone mineral density (BMD) in seven zones (Gruen) relative to the postoperative values. RSA- and DEXA measurements have been performed postoperatively and then after 3, 6, 12 and 24 months. Results: One stem had to be revised after 3 months due to a periprosthetic fracture. The clinical scores were as follows (preop/3 years): Pain 2.6/5.5, ROM 3.7/5.7, function 2.7/5.9, total score 9.1/17.1. Six patients complained of thigh pain during the first two years, however, this complication resolved spontaneously in five patients within the three years follow-up. The mean subsidence after two years was 0.055 mm (SE ±0.045 mm) and the mean axial rotation was 0.29° (SE ± 0.12°). The mean bone loss in zone 7 was 34%; in the other zones the bone loss was less than 14%. The mean overall bone loss was 8%. Discussion: The short-term clinical experiences with this patient-specific, cementless femoral stem are encouraging. The stem seems to be very stable during the first two postoperative years indicating that biological fixation of the femoral stems has been achieved. The change in the BMD was less than 14% in all Gruen zones, except for the proximal medial area where the bone loss was 34%

Aims: The aim of this study was to measure implant migration and bone remodelling of the proximal femur two years after insertion of a customized or a standard femoral stem. Materials and methods: In a prospective, randomized study 26 hips (26 patients) have been examined postoperatively and after 3, 6, 12 and 24 months using radiostereometry (RSA) and DEXA. Thirteen hips received a customized femoral stem (Unique, SCP as) and 13 hips received a standard uncemented femoral stem (ABG¨, Stryker-Howmedica). An uncemented acetabular cup (Duraloc¨, DePuy) was used in all hips. The mean age of the patients was 55 (24–67) years. Results: The median displacement of the custom/ standard femoral stems was 0.04/0.01 mm along the - medial-lateral axis, 0.08/0.02 mm along the proximal-distal axis and 0.03/0.08 mm along the anterior-posterior axis, respectively. Statistically, there was no difference between the two groups. One custom stem subsided 5.2 mm at one year, but showed no further migration at two years. The mean decrease in bone mineral density (BMD) in all Gruen zones was 6% in the Custom-group and 7% in the ABG-group. The most pronounced bone loss was seen in Zone 7 and was 21% and 25% for the two groups, respectively. Discussion: We found no statistically signiþcant difference in short-term stem migration comparing a customized and a standard, uncemented femoral stem. Furthermore, the changes in bone mineral density were almost equal in femurs with either type of prosthesis

Background: Over the past decade, several modifications have been introduced to uncemented femoral stems. The design of the stems, however, still classically fall under two categories: anatomical and straight. The purpose of this paper is to report the first clinical, radiographic and periprosthetic densitometry results of a cementless total hip arthroplasty performed with an off-the-shelf extended metaphyseal loading device. Fifty-eight consecutive patients who received aproximally loading non-cemented hip prosthesis were followed for an average of 4.4 years. Patients were clinically and radiographically followed at 3 weeks, 3 months, 6 months, 1 year and yearly thereafter. In addition, a group of 8 consecutive patients were studied with Dual X-Ray Absorptiometry Scans(DEXA) at the same intervals during the first year and at 18 months after surgery. The extended proximal geometry of the device allowed for initial and secondary stability reflected by the low subsidence values over time. The maintenance of periprosthetic bone stock over time and the absence of stress shielding can be explained by the proximal loading pattern of the stem

Purpose:. In order to acquire good stability of an arthroplasty hip, the proper placement of the implants, which prevents impingement between the stem neck and the socket, is important. In general, the anteversion of the uncemented femoral stem depends on the relationship between the three-dimensional structure of the proximal femoral canal and the proximal stem geometry. The exact degree of the anteversion will be known just after broaching during the operation. If the stem anteversion could be forecasted, preoperative planning of the socket placement would be relatively easy. Furthermore, when a high degree of anteversion is forecasted, a special femoral stem to reduce it, such as a modular stem, could be prepared. However, we experienced that the preoperatively measured anteversion of the femoral neck using computer tomography (CT) was sometimes different from that of the stem measured during the operation. The purpose of this study was to investigate whether the preoperative measurement would be helpful to predict the stem anteversion by examining the relationship between the anteversion of the femoral neck and the stem. Patients and methods:. A total of 57 primary THAs by one senior surgeon from April 2011 until March 2012 were carried out. Two THAs using a modular stem and one for the hip after previous proximal femoral osteotomy were excluded. The remaining 54 THAs were examined. The used uncemented stems were designed for proximal metaphyseal fixation. CT scans, including the distal femoral condyles as well as the hips, were carried out in all cases preoperatively. The anteversion of the femoral neck was measured as the angle of the maximum longitudinal line of the cross section of the femoral neck to the line connecting the posterior surfaces of both of the distal femoral condyles (Fig. 1). The femoral neck anteversion was measured at three levels (Fig. 1). The stem anteversion was measured just after the femoral broaching during the THA. The relationship between the anteversion angles of the femoral neck and of the stem was examined by using a regression analysis. The institutional review board approved this study. Results:. The anteversion angles of the femoral neck varied widely when they were measured at all of the levels (Table 1). The anteversion angle of the femoral neck was not always identical to that of the stem. There were 32–46% of cases in which the difference between the stem anteversion and the femoral neck anteversion was within 5 degrees. There was a significant relationship between the anteversion of the stem and that of the femoral neck measured at all three levels (Fig. 2). When it was measured just below the femoral head, it was the closest to one, and the p-value was the lowest. Discusssion and Conclusions:. The anteversion of the uncemented stem could be calculated by using the formula to show the relationship between the stem anteversion and the femoral neck antevesion measured preoperatively. The values appeared to be sufficiently correct for making clinical decisions, although a prospective study may be necessary to confirm this

The aim of this study is the presentation of the results in 48 cases of revision THA with excessive proximal bone loss with the use of the Wagner cementless femoral stem. The bone loss classified with the AAOS system for proximal femoral bone deficiency in type I (17 patients), II (27 patients), and III (4 patients). We used the titanium alloy Wagner stem trying to achieve primary distal stabilisation because of its conical shape and its longitudinal ridges while we expected secondary proximal stabilization due to the osseointegration properties of the material. We didn’t use grafts. The mean follow- up is 9, 6 years. The results are very satisfactory to excellent with marked pain relief, improvement of the walking ability and excessive bone restoration in the proximal part of the femur. 7 of the patients had a symptomless stem subsidence up to 16mm the first year with subsequent stabilization thereafter. One of the patients required a new revision the 7th postoperative year due to stem’s fracture in its distal part. We conclude that the Wagner stem in these difficult THA revisions offers firm primary distal fixation, impressive proximal bone regeneration and satisfactory clinical outcomes without using grafts

Background

Uncemented dual-tapered stems are a popular choice for primary total hip arthroplasty (THA). The purpose of this study was to examine long-term outcomes after primary THA utilizing a single dual-tapered stem.

Introduction and Aims: With interest in minimally invasive surgery, and smaller incisions for total hip arthroplasty (THA), ways to ensure appropriate alignment are critical. Femoral stem varus has been associated with poorer results. We report the incidence of varus placement of a tapered, proximally plasma-sprayed, titanium femoral component and describe the outcomes of varus at minimum five-year follow-up.

Method: Between 1986 and 1997, 1080 tapered, proximally plasma-sprayed femoral components were implanted in primary cementless THA at one institution. Twenty-six components in 25 patients were placed in five degrees or more of varus. Two patients were lost to follow-up. The need for further surgery was assessed and Harris hip scores evaluated.

Results: Harris hip scores improved an average of 44 points. All femoral components were judged to be osteo-integrated. There was no displacement or progression into further varus, or impending failures. One well-fixed stem was revised at an outside institution for unexplained pain at 2.5 years. Survival with aseptic loosening as an end-point is 100 percent. Overall survival of the femoral component is 96 percent at 10 years average follow-up.

Conclusion: As visualisation decreases with decreasing incision length, a component that is reliably placed into appropriate position is required. Implant position with this component is forgiving. It may be an excellent choice for less-invasive techniques with compromised visualisation. In varus, the stem performs well, with no revisions for aseptic loosening and a 96 percent survival at up to 16 years.

A clinical and radiographic study was conducted on 97 total hip arthroplasties (79 patients) performed for congenital hip dislocation using three-dimensional custom cementless stem. The mean age was 48 years (17 to 72). The mean follow up was 123 months (83 to 182).

According to Crowe, there were 37 class 1, 28 class 2, 13 class 3 and 19 class 4. The average lengthening was 25 mm (5 to 58 mm), the mean femoral anteversion 38.6° (2° to 86°) and the correction in the prosthetic neck −23.6° (71° to 13°). The average Harris hip score improved from 58 to 93 points. Six hips (6.2%) required a revision. The survival rate was 97.7% ± 0.3% at 13 years.

Custom cementless stem allows anatomical reconstruction and good functional results in a young and active population with disturbed anatomy, while avoiding a femoral osteotomy.

We report the results of cementless total hip arthroplasty using the Bi-metric titanium femoral stem at a minimum follow up of 10 years and a mean of 12.2 years (range 10–17).

64 hips (43 male/21 female) were implanted consecutively into 54 patients between 1988 and 1995. The mean age at operation was 54.3 years (range 42–65). All patients had a Bi-metric uncemented stem (Biomet UK). The first 13 patients received a metal backed screw in acetabular cup (TTAP-ST, Biomet UK) with the remainder receiving metal backed pressfit cups (Universal, Biomet UK).

All patients were followed up annually and assessed using the Hip Society Score (HSS; max 40 points) to record pain, function and mobility. Survivorship was calculated using the Kaplan-Meier method.

57 hips were followed up for a minimum of ten years. There were 4 deaths (6 hips) before completion of follow up and 1 patient was lost to follow up.

Using revision for any reason as the end point of the study; survivorship for the total hips at 10 years was 89.5% (95% confidence interval: 78.1–96.1%) with a mean Hip Society Score of 34.9 (range 20–40) compared to 14.5 (range 8–24) pre-operatively (p< 0.01 student t test).

Survivorship for the femoral stem in isolation was 100% at 10 years (95% CI 93.7–100%) and there continues to be no revisions to date at a mean follow up of 12.2 years.

The screw fix cup performed poorly with 3 acetabular revisions (including 1 liner change) before the 10 year follow up, a failure rate of 23.1%. There has sub-sequently been a further 4 acetabular revisions.

Ten year survivorship for the pressfit cup is 93.5% (95% CI 82.0–98.8%) with 3 revisions (including 2 liner changes) at ten years. There has subsequently been one further acetabular revision and 9 further liner changes (29.5% failure rate).

There have been no recorded infections and no instances of thigh pain.

Radiographs at ten years showed all the femoral stems were stable with no evidence of migration. Two stems had small radiolucent lines at the bone-implant interface but no signs of loosening. One stem had an area of osteolysis in Gruen zone 7 but didn’t require revision. Rates of osteolysis were extremely low given the large amounts of particulate debris in the hip from the worn acetabular liners.

In conclusion, although neither cup has proved to be particularly successful the Bi-metric stem has performed well at 10 year follow up and continues to do so. This is inspite of the fact they were implanted into a young and active group of patients.

Femoral stem design affects periprosthetic bone mineral density (BMD), which may impact long term survival of cementless implants in total hip arthroplasty (THA). The aim of this study was to examine proximal femoral BMD in three morphologically different uncemented femoral stems designs to investigate whether one particular design resulted in improved preservation of BMDMethods: 119 patients were randomised to receive either a proximally coated dual taper wedge stem, a proximally coated anatomic stem or a fully coated collarless triple tapered stem. All surgeries were performed via the posterior approach with mobilization on the day of surgery. Dual energy x-ray absorptiometry scans (Lunar iDXA, GE Healthcare, Madison, WI) assessed BMD across the seven Gruen zones pre-operatively, and post-operatively at 6-weeks, 1-year, and 2-years and compared to the unoperated contralateral femur as a control. Patient reported outcome measures of pain, function and health were also included at these corresponding follow-ups. BMD increased in zones one (2.5%), two (17.1%), three (13.0%), five (10%) and six (17.9%) for all stems. Greater preservation of BMD was measured on the lateral cortex (zone 2) for both the dual taper wedge and anatomic stems (p = 0.019). The dual taper wedge stem also demonstrated preservation of BMD in the medial calcar (zone 7) whilst the anatomic and triple taper stem declined in this region, however this was not statistically significant (p = 0.059). BMD decreased on average by 2.1% inthe mid-diaphysis region, distal to the stem tip (zone 4) for all implants. All stems performed equivalently at final follow-up in all patient reported outcome measures. This study demonstrated maintenance of femoral BMD in three different cementless femoral stem designs, with all achieving excellent improvements in patient reported outcomes. There was no significant stress shielding observed, however longer follow-up is required to elucidate the impact of this finding on implant survivorship

Abstract. Extended Trochanteric Osteotomy (ETO) improves surgical exposure and aids femoral stem and bone cement removal in Revision Total Hip Replacement (RTHR) surgery. The aim of this study was to identify healing rates and complications of ETO in RTHR. Methods. From 2012 to 2019 we identified patients who underwent ETO for RTHR. Data collected demographics, BMI, diabetes, anticoagulants, indication for ETO, surgical approach, length of ETO and complications. Descriptive analysis of patient demographics, multiple linear regression analysis was performed to assess ETO complications. Results. There were 63 patients with an average age of 69 years. Indications for ETO were aseptic loosening (30), infection (15), periprosthetic fracture (9), recurrent dislocation (5), broken implant (4). There were 44 cemented and 19 uncemented femoral stem that underwent ETO. Average time from index surgery was 12 years (less than a year to 38 years). All procedures were through posterolateral approach and all ETO were stabilised with cables. Average length of ETO was 12.5cm. BMI varied from 18 to 37. There were 5 diabetics and 16 on anticoagulants. All but one ETO went on to unite. Other complications included infection, dislocations, lateral thigh pain and significant limp. Discussion. Fixation of ETO can be with either wires or cables or plate with cables/screws. Advantages of cables are no irritation over greater trochanter, no disruption of gluteus medius/vastus lateralis continuity, reproducible tension in cables and use of torque limiter minimises loss of tension in cables

Abstract. Objective. To estimate the effect of calcar collar contact on periprosthetic fracture mechanics using a collared fully coated cementless femoral stem. Methods. Three groups of six composite femurs were implanted with a fully coated collared cementless femoral stem. Neck resection was increased between groups (group 1 = normal, group 2 = 3mm additional, group 3 = 6mm additional), to simulate failure to obtain calcar collar contact. Periprosthetic fractures of the femur were simulated using a previously published technique. Fracture torque and rotational displacement were measured and torsional stiffness and rotational work prior to fracture were estimated. High speed video recording identified if collar to calcar contact (CCC) occurred. Results between trials where calcar contact did and did not occur where compared using Mann-Whitney U tests. Results. Where CCC occurred versus where no CCC occurred, fracture torque was greater (47.33 [41.03 to 50.45] Nm versus 38.26 [33.70 to 43.60] Nm, p= 0.05), Rotational displacement was less (0.29 [0.27 to 0.39] rad versus 0.37 [0.33 to 0.49] rad, p= 0.07), torsional stiffness was greater (151.38 [123.04 to 160.42] rad. Nm-1 versus 96.86 [84.65 to 112.98] rad.Nm-1, p <0.01) and rotational work was similar (5.88 [4.67, 6.90] J versus 5.31 [4.40, 6.56] J, p= 0.6). Conclusions. Resistance to fracture and construct stiffness increased when a collared cementless stem made contact with the femoral calcar prior to fracture. These results demonstrate that calcar-collar contact and not a calcar collar per se, is crucial to maximising the protective effect of a medial calcar collar on the risk of post-operative periprosthetic fractures of the femur. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Femoral stem design affects periprosthetic bone mineral density (BMD), which may impact long term survival of cementless implants in total hip arthroplasty (THA). The aim of this study was to examine proximal femoral BMD in three morphologically different uncemented femoral stems designs to investigate whether one particular design resulted in improved preservation of BMD. 119 patients were randomized to receive either a proximally coated dual taper wedge stem, a proximally coated anatomic stem or a fully coated collarless triple tapered stem. Dual energy x-ray absorptiometry scans (Lunar iDXA, GE Healthcare, Madison, WI) assessed BMD across the seven Gruen zones pre-operatively, and post-operatively at 6-weeks, 1-year, and 2-years comparing the unoperated contralateral femur as a control. BMD increased in zones one (2.5%), two (17.1%), three (13.0%), five (10%) and six (17.9%) for all stems. Greater preservation of BMD was measured on the lateral cortex (zone 2) for both the dual taper wedge and anatomic stems (p = 0.019). The dual taper wedge stem also demonstrated preservation of BMD in the medial calcar (zone 7) whilst the anatomic and triple taper stem declined in this region, however this was not statistically significant (p = 0.059). BMD decreased on average by 2.1% in the mid-diaphysis region, distal to the stem tip (zone 4) for all implants. All stems performed equivalently at final follow-up in all patient reported outcome measures. Implant design was shown to impact BMD changes. All stems preserved bone at the metaphyseal level in early follow-up, which theoretically indicates favorable implant fixation. There was no significant stress shielding observed, however longer follow-up is required to elucidate the impact of this finding on implant survivorship

Abstract. Objective. To compare the periprosthetic fracture mechanics between a collared and collarless fully coated cementless femoral stem in a composite femur. Methods. Two groups of six composite femurs (‘Osteoporotic femur’, SawBones, WA USA) were implanted with either a collared (collared group) or collarless (collarless group) cementless femoral stem which was otherwise identical by a single experienced surgeon. Periprosthetic fractures of the femur were simulated using a previously published technique. High speed video recording was used to identify fracture mechanism. Fracture torque and angular displacement were measured and rotational work and system stiffness were estimated for each trial. Results were compared between collared and collarless group and the comparison was evaluated against previously published work using fresh frozen femurs and the same protocol. Results. In composite femur testing median fracture torque (IQR) was greater with a collared versus collarless implant (48.41 [42.60 to 50.27] Nm versus 45.12 [39.13 to 48.09] Nm, p= 0.4). Median rotational displacement (IQR) was less with a collared versus collarless implant (0.29 [0.27 to 0.31] radians versus 0.33 [0.32 to 0.34] radians, p= 0.07). Estimated rotary work was similar between groups (5.76 [4.92 to 6.64] J versus 5.21 [4.25 to 6.04] J, p= 0.4). Torsional stiffness was greater with a collared versus collarless implant (158.36 [152.61, 163.54] Nm per radian versus 138.79 [122.53, 140.59] Nm per radian, p= 0.5). Collarless stems were seen to move independently of the femur and fracture patterns originated at the calcar. Conclusions. Testing with composite femurs using an established protocol produced similar results to previously published studies using human femurs, but the difference between collared and collarless stems was smaller. The internal homogenous foam material in composite femurs does not accurately represent the heterogeneous cancellous bone which supports a femoral stem in vivo and may lead to overestimation of implant stability. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Introduction. Trunnion wear has been reported as a cause for failure of modern total hip replacement implants. While there are several reports on the prevalence of trunnion corrosion with specific stem designs, little is known about the prevalence of this problem across other femoral stem designs. The purpose of this study is to review three commonly used uncemented femoral stems and to correlate any established risk factors with rates of revision. Methods. We reviewed all patients followed prospectively over a 15-year period (March 2000 to September 2015) who underwent total hip arthroplasty with one of three modern uncemented femoral stem designs. All of the stems were made of titanium (Ti. 6. Al. 4. V alloy) with a 12/14 taper design. We included only metal (cobalt chromium) on highly cross-linked polyethylene articulations. We evaluated age, gender, body mass index (BMI), femoral head size, head length, neck angle and offset as potential risk factors for all cause revision and revision excluding infection by univariate analysis. We performed a logistic regression analysis with odds ratios (OR) for each parameter for both all cause revision as well as with infection excluded. We used a p value of <0.05 as a level of significance. Results. A total of 2095 patients were included during the study period and had a minimum three-year follow-up. There were no differences in age, gender, or BMI across the three femoral component groups. There were no cases of trunnion wear or corrosion (with or without an associated adverse local tissue reaction) requiring revision identified across all three stem groups. Univariate logistic regression analysis demonstrated that head size was associated with increased risk of both all cause revision and revision excluding infection. Age, BMI, gender, offset and neck angle did not have significant association to all cause revision or to revisions excluding infection (p>0.05). Multivariate logistic regression controlling for age and BMI demonstrated that a femoral head size less than 32mm was associated with increased likelihood of all cause revision rates (OR 4.60 (95%CI 1.8, 11.8)) and revision excluding infection (OR 4.94 (95%CI 1.7, 14.41). Conclusions. None of the patients who received one of the three modern uncemented femoral stem designs in this cohort demonstrated trunnion wear or corrosion requiring revision for adverse local soft tissue reactions. We recognize that low-levels of corrosion might exist in this cohort and therefore continued follow-up of these patients is required. For any tables or figures, please contact the authors directly

While Oxidized Zirconium (OxZr) femoral heads matched with highly cross-linked polyethylene (XLPE) have demonstrated the lowest rate of revision compared to other bearing couples in the Australian National Joint Registry, it has been postulated that these results may, in part, be due to the fact that a single company offers this bearing option with a limited combination of femoral and acetabular prostheses. The purpose of this study was to assess clinical and radiographic outcomes in a matched cohort of total hip replacements (THR) utilizing an identical cementless femoral stem and acetabular component with either an Oxidized Zirconium (OxZr) or Cobalt-Chrome (CoCr) femoral heads at a minimum of 10 years follow-up. We reviewed our institutional database to identify all patients whom underwent a THR with a single cementless femoral stem, acetabular component, XLPE liner and OxZr femoral head with a minimum of 10 years of follow-up. These were then matched to patients who underwent a THR with identical prosthesis combinations with CoCr femoral head by gender, age and BMI. All patients were prospectively evaluated with WOMAC, SF-12 and Harris Hip Score (HHS) preoperatively and postoperatively at 6 weeks, 3 months, 1 and 2 years and every 2 years thereafter. Charts and radiographs were reviewed to determine the revision rates and survivorship (both all cause and aseptic) at 10 years for both cohorts. Paired analysis was performed to determine if differences exist in patient reported outcomes. There were 208 OxZr THRs identified which were matched with 208 CoCr THRs. There was no difference in average age (OxZr, 54.58 years, CoCr, 54.75 years), gender (OxZr 47.6% female, CoCr 47.6% female), and average body max index (OxZr, 31.36 kg/m2, CoCr, 31.12 kg/m2) between the two cohorts. There were no significant differences preoperatively in any of the outcome scores between the two groups (WOMAC (p=0.449), SF-12 (p=0.379), HHS(p=0.3718)). Both the SF12 (p=0.446) and the WOMAC (p=0.278) were similar between the two groups, however the OxZr THR cohort had slightly better HHS compared to the CoCr THR cohort (92.6 vs. 89.7, p=0.039). With revision for any reason as the end point, there was no significant difference in 10 years survivorship between groups (OxZr 98.5%, CoCr 96.6%, p=0.08). Similarly, aseptic revisions demonstrated comparable survivorship rates at 10 year between the OxZr (99.5%) and CoCr groups (97.6%)(p=0.15). Both THR cohorts demonstrated outstanding survivorship and improvement in patient reported outcomes. The only difference was a slightly better HHS score for the OxZr cohort which may represent selection bias, where OxZr implants were perhaps implanted in more active patients. Implant survivorship was excellent and not dissimilar for both the OxZr and CoCr groups at 10 years. Therefore, with respect to implant longevity at the end of the first decade, there appears to be no clear advantage of OxZr heads compared to CoCr heads when paired with XLPE for patients with similar demographics. Further follow-up into the second and third decade may be required to demonstrate if a difference does exist