INTRODUCTION. Wedge femoral stems used in total hip arthroplasty (THA) have evolved with modifications including shorter lengths, reduced distal geometries, and modular necks. Unlike fit and fill stems which contact most of the metaphysis, tapered wedge femoral stems are designed to achieve proximal medial/lateral fixation. These single taper, wedge stems have demonstrated positive clinical outcomes. The tapered wedge stem evaluated in this study has further reduced distal geometry to provide a wedge-fit within the metaphysis of the proximal femoral canal for all femur types (Dorr A, B, C). The objective of this study was to evaluate the early clinical outcomes, including femoral stem subsidence, of a tapered wedge femoral stem. METHODS. Fifty subjects (28 males, 22 females; mean age: 64.7±9.7 years; mean BMI: 29.6±4.6) underwent primary THA with a tapered wedge femoral stem. IRB approval was received prior to conducting the study and all participants signed the informed consent. Clinical data outcomes for this study included the Harris Hip Score (HHS), the Oxford Hip Score (OHS), revisions, and subsidence at the 6-week, 3-month, 1-year, and 2-year post-operative time points. Femoral stem subsidence was measured by an independent third party. Student t-tests were used to identify significant mean differences between genders (p<0.05). RESULTS. For patients returning for their 2-year post- operative visit (n=42), the HHS improved by 40.7 points to 91.9 from 51.2 and the OHS improved by 23.5 points to 44.6 from 21.1. There was no significant difference between genders with regard to age, BMI, or HHS scores. However, the males had significantly higher pre-operative OHS scores (23.4 vs. 18.2) and 3-month post-operative OHS scores (43.7 vs. 40.3). There were no revisions. There were no observations of femoral stem subsidence at 1 year (n=45) or 2 years (n=40). DISCUSSION. The tapered wedge femoral stem exhibited positive early clinical results as demonstrated by the significant improvement in functional outcome scores from the pre-operative visit to 2-years post-operative. These 2-year improvements are better than moderate clinically important improvements reported in the literature (40.1 points for HHS). Functional outcomes scores continued to improve at the 6-week, 3-month, and 1-year post-operative visits. The 1-year and 2-year outcomes were not significantly different. Additionally, the implant was well fixated as there were no reports of femoral stem subsidence 2 years post-operative. SIGNIFICANCE. The tapered wedge femoral stem evaluated in this study demonstrated positive early clinical performance with no reports of femoral stem subsidence or revisions. This tapered wedge stem design is a promising alternative to conventional femoral stems

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

Introduction. Cementless tapered wedge stems have shown excellent results over the last decade. Distal potting with inadequate proximal fit, as well as failure to achieve biologic fixation has led to thigh pain, loosening and implant failure. To support a variety of patient morphologies a novel tapered wedge stem was designed with reduced distal morphology, maximizing the proximal contact of the grit blasted surface. The objective of the study was to analyze the clinical outcomes of this stem design. Methods. Three hundred and nineteen patients enrolled into prospective, post-market multicenter studies received a novel tapered wedge stem. Clinical and patient-reported outcomes including the Harris Hip Score (HHS), Lower Extremity Activity Scale (LEAS), Short Form 12 (SF12), and Euroqol 5D Score (EQ-5D) were evaluated preoperative through two years postoperative. Results. Demographics of the study population include 53.3% male patients with a mean age of 62.4 ± 9.3 years and BMI of 29.8 ± 4.5. To date, there has been one incidence of thigh pain (0.3%) and a 0.63% aseptic revision rate. Kaplan-Meier survivorship analysis for the population at two years postoperative estimated 97.87% with 95% CI (93.98% – 99.25%) survivorship to all cause revision (Figure 1). Statistically significant improvements in pain, function, and quality of life were seen initially at six weeks postoperative and continued through one year in all of the clinical and patient reported outcome measures (Figure 2). Conclusion. A novel tapered wedge stem was designed to maximize proximal fit medially and laterally across a variety of patient morphologies. Radiographic studies have shown the stem design has significantly better canal fit compared to older tapered wedge designs. The current study exhibits low incidence of thigh pain and revisions, with improvements in function, pain and quality of life after hip arthroplasty with this tapered wedge stem

INTRODUCTION. Immediate post-operative stability of a cementless hip design is one of the key factors for osseointegration and therefore long-term success [1]. This study compared the initial stability of a novel, shortened, hip stem to a predicate standard tapered wedge stem design with good, long-term, clinical history. The novel stem is a shortened, flat tapered wedge stem design with a shape that was based on a bone morphology study of 556 CT scans to better fit a wide array of bone types [2]. METHODS. Test methods were based on a previous study [3]. Five stems of the standard tapered wedge design (Accolade, Stryker Orthopaedics, Mahwah, NJ) and the novel stem (Accolade II, Stryker Orthopaedics, Mahwah, NJ) were implanted into a homogenous set of 10 synthetic femora (Figure 1) utilizing large left fourth generation. composite femurs (Sawbones, Pacific Labs, Seattle, WA). The six degrees-of-freedom (6 DoF) motions of the implanted stems were recorded under short-cycle stair-climbing loads. Minimum head load was 0.15 kN and the maximum load varied between 3x Body Weights (BW) and 6 BW. Loading began with 100-cycles of “normal” 3 BW and was stepped up to 4 BW, 5 BW & 6 BW for 50-cycles each. Prior to each load increase, 50 cycles of 3 BW loading was applied. This strategy allowed a repeatable measure of cyclic stability after each higher load was applied. The 6 DoF micromotion data, acquired during the repeated 3 BW loading segments, were reduced to four outcome measures: two stem migrations (retroversion and subsidence at minimum load) and two cyclic motions (cyclic retroversion and cyclic subsidence). Data were analyzed using repeated measures ANOVA with a single between-subjects factor (stem type) and repeated measures defined by load-step (3 BW, 4 BW, 5 BW 6 BW). RESULTS. Both stems retroverted under increasing load (p = 0.0011, Fig 2). Retroversion of the novel stem was significantly smaller than that of the standard tapered wedge stem (p = 0.023). The rate of increase in retroversion with increasing load was significantly lower for the novel stem (p = 0.026). In addition, both stems subsided under increasing load (p = 0.0015, Fig 3). Subsidence of the novel stem was significantly smaller than that of the standard tapered wedge stem (p = 0.016). The rate of increase in subsidence with increasing load was significantly lower for the novel stem (p = 0.022). With regard to cyclic motions, both cyclic retroversion and cyclic subsidence were significantly lower for the novel stems (p = 0.0033 & p = 0.0098). In addition, the rate of increase in cyclic motion was significantly lower for the novel stems for both cyclic retroversion (p = 0.0021) and cyclic subsidence (p = 0.023). DISCUSSION. In this study, the novel tapered wedge stem demonstrated an improved stability compared to the clinically successful predicate design. It appears that through optimization of the proximal geometry, a reduction in the length of the stem can be accomplished without jeopardizing initial stability

A novel cementless tapered wedge femoral hip implant has been designed at a reduced length and with a geometry optimized to better fit a wide array of bone types (Accolade II, Stryker, Mahwah, USA). In this study, finite element analysis (FEA) is used to compare the initial stability of the new proposed hip stem to predicate tapered wedge stem designs. A fit analysis was also conducted. The novel stem was compared to a predicate standard tapered stem and a shortened version of that same predicate stem. Methods. The novel shortened tapered wedge stem geometry was designed based on a morphological study of 556 CT scans. We then selected 10 discrete femoral geometries of interest from the CT database, including champagne fluted and stove pipe femurs. The novel and the predicate stems were virtually implanted in the bones in ABAQUS CAE. A total of thirty FEA models were meshed with 4 nodes linear tetrahedral elements. Bone/implant interface properties was simulated with contact surface and a friction coefficient of 0.35. Initial stability of each stem/bone assembly was calculated using stair-climbing loading conditions. The overall initial stability of the HA coated surface was evaluated by comparing the mean rotational, vertical, gap-opening and total micromotion at the proximal bone/implant interface of the novel and predicate stem designs. To characterize the fit of the stem designs we analyzed the ratio of a distal (60 mm below lesser trochanter) and a proximal (10 mm above lesser trochanter) cross section. A constant implantation height of 20 mm above the lesser trochanter was used. The fit of the stems was classified as Type 1 (proximal and distal engagement), Type 2 (proximal engagement only) and Type 3 (distal engagement only). Results. The mean % micromotion of the HA coated surface greater than 50 mm was lowest at 40.2% (SD 11.5%) for the novel tapered wedge stem compared to the clinically successful predicate stem design (Accolade TMAZ, Stryker, Mahwah, USA) at 44.9% (SD 13.2%) and its shortened version at 48.5% (SD 9.0%) as shown in Figure 1. Improved initial stability of the new stem was also confirmed for rotational, vertical and gap-opening micromotion. However, there was no statistically significant difference. The novel tapered stem design showed a well balanced proximal to distal ratio throughout the complete size range. The novel tapered stem design showed a reduced percentage of distal engagements (2.8%) compared to the predicate standard stem (17.2%). In the 40 to 60 year old male group the distal engagement for the standard stem increases (28.2%), whereas the distal engagements for the novel stem remains unchanged (1.3%). Discussion. It appears that through optimization of the novel tapered wedge geometry, a reduced length of a tapered wedge stem can be accomplished without jeopardizing initial stability. This data also shows that simply shortening an existing tapered wedge design may reduce the initial stability, albeit not statistically significant in this model. Optimising the shape of the stem has also significantly reduced the incidence of distal only type fixation in a computer model

Background. A stem sitting proud (SP) or that above the final rasp position remains in some patients who undergo hip replacement using proximally coated tapered wedge stems. Surgeons may face challenges providing the best fit due to unpredictable stem seating. Zimmer Inc. introduced a new rasp to solve this issue but the clinical results of this rasp have not yet been published. Therefore, we aimed to address the following: 1) What is SP incidence using a proximally coated cementless tapered wedge stem? 2) Does the new rasp system improve seating height? 3) What are the risk factors of SP?. Methods. We performed a retrospective study with 338 hips, in which Tri-Lock Bone Preservation Stem (BPS) was used in 181 and M/L Taper stem was used in 157 hips (82 hips before and 75 hips after the new rasp). A positive stem SP was defined as a stem proud height of >2 mm. We analyzed and compared SP incidence in two stems and in M/L Taper stems before and after the new rasp use. Results. Statistical differences were found across mean age, sex, preoperative diagnosis, and Dorr type between the Tri-Lock BPS and M/L Taper stem groups (P < 0.05); however, no significant difference was found within the M/L Taper groups before and after the 0-mm Rasp use. The sitting proud incidence of the stem was 13% (23/181 hips) with a mean height of 3.0 mm (range: 2.1–4.3 mm) in Tri-Lock BPS and was 15% (12/82 hips) in M/L Taper stem before the 0-mm Rasp use with a mean height of 2.8 mm (range: 2.1–4.0 mm). After the 0-mm Rasp use, only 4% (3/75 hips) showed stem sitting proud with a mean height of 2.2 mm (range: 2.1–2.5 mm). There was no significant difference in the sitting proud incidence between the Tri-Lock BPS and M/L Taper stem groups; however, the sitting proud incidence with M/L Taper stem substantially decreased after the 0-mm Rasp use (P = 0.024). According to the results of the univariate analysis, stem sitting proud was significantly higher at high offset (19%) than at standard offset (8%) in the Tri-Lock BPS system (P < 0.043). In the M/L Taper stem, however, there were no significant differences across all variables, including stem offset, between the stem sitting proud and non-proud groups (Tables 3 and 4). Regarding preoperative diagnosis, the sitting proud incidence was lower in fragility fractures in patients aged ≥50 years (0/18 hips) than in other diagnoses (12/64 hips) using M/L Taper stem before the 0-mm Rasp use, but this result was not statistically significant. When multiple logistic regression analysis was performed, the significant risk factor for stem sitting proud was use of the high offset option in Tri-Lock BPS (P = 0.048; OR = 2.474; 95% CI, 1.009–6.063). There was no substantial difference in the sitting proud incidence between the case groups, each consisting of 30 cases. Regarding femoral head offset, short offset was more frequently used in the stem proud group (13% in Tri-Lock BPS and 58% in M/L Taper stem) than in the non-proud group (4% in Tri-Lock BPS and 21% in M/L Taper stem), and there was a significant difference in M/L Taper stem (P = 0.013). The mean postoperative LLD was 3.0 ± 2.9 mm in Tri-Lock BPS, 3.6 ± 3.2 mm in M/L Taper stem before the 0-mm Rasp use, and 2.7 ± 2.3 mm in M/L Taper stem after the 0-mm Rasp use. There was no significant difference in the mean postoperative LLD between the stem proud and non-proud groups regardless of stem type. At a minimum 6-month follow-up, there was no measurable stem subsidence across all cases. Conclusions. The proximally coated cementless tapered wedge stems are associated with potential problems related to stem sitting proud. The newly developed 0-mm Rasp of M/L Taper stem showed significant improvement in initial seating height compared with the conventional rasp system without postoperative stem subsidence. The use of high offset Tri-Lock BPS stem was the only risk factor for stem proud, but its clinical significance remains unknown. Therefore, large-scale multicenter studies should be conducted to determine relevant risk factors for sitting proud of these stems using a conventional rasp system. For any figures or tables, please contact the authors directly

Introduction:. Subsidence of cementless femoral stems in total hip arthroplasty (THA) has been associated with poor initial fixation and subsequent risk of aspectic loosening. There is limited literature on how subsidence of cementless, proximally porous coated, tapered wedge femoral stems impacts the patient clinically. The aim of our study was to assess whether subsidence with these stems is associated with a decline in clinical function. Method:. A review of a prospectively collected database of THAs performed by a single surgeon at one institution using two cementless, tapered wedge stem designs from January 2006 to June 2010 was performed. Radiographic analysis using Picture Archiving and Communications System (PACS) was used to identify patients with greater than 1.5 mm of subsidence, and to document osseointegration. Preoperative and postoperative pain and Harris hip scores were recorded; and analyzed to identify if the clinical recovery pattern of the subsidence versus no subsidence groups differed. Protected weight bearing was recommended to all patients with subsidence. Results:. 264 hips were reviewed clinically and radiographically at a mean follow-up of 29 months. 10 hips had subsidence greater than 1.5 mm at last follow up. There were 6 males and 3 females with a mean age of 62.1 years in the subsidence group. Subsidence was noted at the 6 week visits in all 10 patients. Mean Harris Hip scores and pain scores were significantly diminished at 6 weeks in the subsidence group (Mean 67.6) as compared to the none subsidence group (82.2) (Figure 1). The two groups had similar scores preoperatively, at 1 year and 2 years postoperatively. In the subsidence group 9 of 10 hips had no further progression of subsidence, and showed radiographic evidence of osseointegration. Persistent thigh pain was noted in 2 patients in the subsidence group. One underwent successful femoral revision for failure of osseointegration and the other continues to have pain with radiographic signs of osseointegration. All 254 hips in the control group had evidence of osseointegration. Conclusion:. Subsidence of tapered wedge stems which occurs at the 6 week mark may be associated with a transient decline in clinical function. Early modification in the rehabilitation regimen may help improve clinical outcome scores in these patients

Purpose. While changes in lower limb alignment and pelvic inclination after total hip arthroplasty (THA) using certain surgical approaches have been studied, the effect of preserving the joint capsule is still unclear. We retrospectively investigated changes in lower limb alignment, length and pelvic inclination before and after surgery, and the risk of postoperative dislocation in patients who underwent capsule preserving THA using the anterolateral-supine (ALS) approach. Methods. Between July 2016 and March 2018, 112 hips (non-capsule preservation group: 42 hips, and capsule preservation group: 70 hips) from patients with hip osteoarthritis who underwent THA were included in this study. Patients who underwent spinal fusion and total knee arthroplasty on the same side as that of the THA were excluded. Using computed tomography, we measured lower limb elongation, external rotation of the knee, and femoral neck/stem anteversion before operation and three to five days after operation. We examined the pelvic inclination using vertical/transverse ratio of the pelvic cavity measured by X-ray of the anteroposterior pelvic region in the standing position before and six to 12 months after operation. All operations were performed using the ALS approach and taper wedge stem. Results. No dislocation was found in both groups. Lower limb elongation was 14.5±6.3 (mean±SD) mm in the non-capsule preservation group and 9.4±8.8 mm in the capsule preservation group. A significant reduction was found in the capsule preservation group (p<0.05). Changes in knee external rotation was 7.2±10.5 degrees in the non-capsule preservation group and 3.5±10.3 degrees in the capsule preservation group. A trend toward decreased knee external rotation in the capsule preservation group (p=0.07) was observed. There was no difference in femoral neck/stem anteversion and vertical/transverse ratio of the pelvic cavity between both groups. Discussion. Patients in the capsule preservation group tended to have reduced external rotation of lower limb, which might prevent postoperative anterior dislocation due to preservation of anterior structures. The capsule preservation group had significantly reduced lower limb elongation, suggesting that preservation of the hip joint capsule ligament contributes to joint stability. There was no significant difference in the pelvic inclination between both groups. Long-term changes will be assessed by regular follow up after operation

Introduction. Femoral component loosening is one of the most common failure modes in cementless total hip arthroplasty (THA). Patient age, weight, gender, osteopenia, stem design and Dorr-C bone have all been proposed as risk factors for poor fixation and subsequent stem subsidence and poor outcome. With the increased popularity of CT-based assistive technologies in THA, (Stryker MAKO and Corin OPSTM), we sought to develop a technique to predicted femoral stem fixation using pre-operative CT. Methods. Fourteen patients requiring THA were randomly selected from a previous study investigating component alignment. Mean age was 64 (53 to 76), and 57% were female. All patients received pre-operative CT for 3D dynamic templating (OPSTM), and a TriFit stem and Trinity cup (Corin, UK) implanted through a posterior approach. Post-operatively, patients received an immediate CT and AP x-ray prior to leaving the hospital, and a 1-year follow-up x-ray. On both the immediate post-op x-ray and 1-year follow-up x-ray, the known cup diameter was used to scale the image. On both images, the distance between the most superior point of the greater trochanter and the shoulder of the stem was measured. The difference was recorded as stem subsidence. Subsidence greater than 4mm was deemed clinically relevant. The post-operative CT was used to determine the precise three-dimensional placement of the stem immediately after surgery by registering the known 3D implant geometry to the CT. For each patient, the achieved stem position from post-op CT was then virtually implanted back into the pre-operative OPSTM planning software. The software provides a colour map of the bone density at the stem/bone interface using the Hounsfield Units (HU) of each pixel of the CT [Fig. 1]. Blue represents low density bone transitioning through to green and then red (most dense). Results. Mean stem subsidence was 2.1mm (0.2mm to 11.1mm). Two patients had clinically relevant subsidence. The first stem in a 68M subsided 11.1mm. The second in a 58M subsided 5.0mm. Both density colour plots had significant areas of blue (low density bone) around the proximal portion of the stem, with minimal medium/high density fixation when compared to the stems with minimal subsidence. Discussion. Using the Hounsfield units of the CT scan as an indicator for bone density, we were able to predict poor implant fixation and subsequent subsidence in a taper wedge stem. This new technology might have pre-operative value in providing a more quantitative measure of fixation and resultant stem choice. For any figures or tables, please contact the authors directly

The Taperloc Microplasty stem design was based on that of the Taperloc stem with flat tapered wedge and the distal portion of the Taperloc stem was shortened by 35mm. We report the minimum two-year follow up (mean, 26 months) of 68 primary total hip arthroplasty using the Taperloc Microplasty stem. 39 Magnum acetabular cups and 29 M2a Taper acetabular cups were inserted with metal on metal articulation. The series comprised 67 patients (20 men, 47 women) with a mean age at operation of 65 years (31 to 85). The principal diagnosis was osteosrthritis. Their mean JOA Hip Score improved significantly from 36 points preoperatively to 96 points at two-year follow up. Radiological asseement showed good bony stability in all implants. There was one case of post operative anterior dislocation. We did not see intra-operative fracture previously reported for this implant. There were no clinical and radiological complications related to MOM articulation. This short-term follow up study demonstrates that the clinical outcome of the Tapeloc Microplasty stem is comparable with that of standard Taperloc stem and other flat taper wedge stems

Intra-operative fractures of the femur are on the rise mainly due to the increased use of cementless implants and the desire to get a tight press fit. The prevalence has been reported to be between 1–5% in cementless THAs. The key to preventing these fractures is to identify patients at high risk and careful surgical technique. Surgical risk factors include the use of cementless devices, revision hip surgery, the use of flat tapered wedges and MIS surgery. Patient factors that increased risk include increasing age, female gender, osteopenia and rheumatoid arthritis. These risk factors tend to be additive and certainly when more than one is present extra caution needs to be taken. Surgical technique is critical to avoid these intra-operative fractures. Fractures can occur during exposure and dislocation, during implant removal (in revision THA), during canal preparation and most commonly during stem insertion. In both primary, and especially in revision, THA be wary of the stiff hip in association with osteopenia or osteolysis. These patients require a very gentle dislocation. If this cannot be achieved, then alteration of the standard approach and dislocation may be needed. Examples of these include protrusion with an osteopenic femur and revision THA with a very stiff hip with lysis in the femur. Lastly, in cases with retained hardware, dislocate prior to removing plates and screws. After dislocation, the next challenge is gentle preparation of the femoral canal. A reasonable exposure is required to access the femoral canal safely. MIS procedures do not offer good access to femoral canal and this probably results in increased risk of fracture during broaching or implant insertion. When broaching, stop when broach will not advance further. When inserting a tapered wedge stem, be worried if stem goes further in than broach. In revision surgery, when taking the stem out from above, make sure the area of the greater trochanter does not overhang the canal. A high speed burr can clear the shoulder for easier access for removal. In revision THA with an ETO, place a cerclage wire prior to reaming and retighten prior to stem insertion. Even with careful surgical technique intra-operative femoral fractures will still occur. When inserting the stem, a sudden change in resistance is highly suggestive of fracture. Wide exposure of the entire proximal femur is necessary to confirm the diagnosis. The distal extent of the fracture must be seen. Only on occasion is an intra-operative radiograph needed. Management is directed to ensuring component stability and good fracture fixation. In primary total hip arthroplasty, calcar fractures are by far the most common. If using proximal fixation and you are certain the stem is stable, then all that is needed is cerclage wiring. As already mentioned, you must follow the fracture line distally so you are aware of how far down it goes. Often what appears to be a calcar split actually propagates distal to the lesser trochanter. In these cases, one would probably go for distal fixation plus wiring. In conclusion, intra-operative femoral fractures are on the rise. Prevention is the key

INTRODUCTION. Femoral stem impingement can damage an acetabular liner, create polyethylene wear, and potentially lead to dislocation. To avoid component-to-component impingement, many surgeons aim to align acetabular cups based on the “Safe Zone” proposed by Lewinnek. However, a recent study indicates that the historical target values for cup inclination and anteversion defined by Lewinnek et al. may be useful but should not be considered a safe zone. The purpose of this study was to determine the effect of altering femoral head size on hip range-of-motion (ROM) to impingement. METHODS. Ten healthy subjects were instrumented and asked to perform six motions commonly associated with hip dislocation, including picking up an object, squatting, and low-chair rising. Femur-to-pelvis relative motions were recorded throughout for flexion/extension, abduction/adduction, and internal/external rotation. A previously reported custom, validated hip ROM three-dimensional simulator was utilized. The user imports implant models, and sets parameters for pelvic tilt, stem version, and specific motions as defined by the subjects. Acetabular cup orientations for abduction and anteversion combinations were chosen. The software was then used to compute minimum clearances or impingement between the components for any hip position. Graphs for acetabular cup abduction vs. anteversion were generated using a tapered wedge stem with a 132º neck angle, a stem version of 15°, and a pelvic tilt of 0°. The only variable changed was femoral head size. Head sizes reviewed were 32mm, 36mm, and a Dual-Mobility liner with an effective head size of 42mm. All femoral head sizes can be used with a 50mm acetabular cup. RESULTS. We found that the “Safe Zone” varies considerably depending on the size of the femoral head used for all subjects. A typical plot illustrating the ROM to impingement is presented in Figures 1a-1c. The area to the left of each curve represents an impingement zone for that motion, and to the right, a non-impingement zone. In all cases the non-impingement area is smaller than the Lewinnek safe zone. Motions like picking up an object and squatting had the greatest influence on impingement. CONCLUSIONS. The true acetabular target for impingement-avoidance motion is much smaller than previously believed and identifies the need to take into account the size of the femoral head to be used. This may explain why approximately 70% of dislocations have been reported to be found even when cups were placed within the Lewinnek safe zone. Certain activities, such as picking up an object and squatting reduce the size of the safe zone. This study supports the need for better patient planning and intraoperative execution for placement of the acetabular component

The aim was to study the evolution of radiographic patterns of osteointegration of tapered wedge stems and determine if there is correlation with bony morphology and initial stem fit. We reviewed primary total hip replacements performed by two surgeons using a single cementless tapered wedge design and that had a complete series of radiographs (defined as preoperative, 6 weeks, 1 year and 5 or more years). Signs of bony remodeling were recorded at each Gruen zone. Calcar remodeling, changes in cortical thickness, evidence of subsidence and pedestal formation were recorded (Figure 1). 57 hips (50 patients) were available for analysis with a mean follow up of 5.03 years. Mean changes in cortical thickness were positive in zones 2(7.51) and 6(5.36) and negative in zones 1(−7.53) and 7(−13.51). Radiolucent lines were found in gruen zones 3,4(39%), and 5. Femoral neck cancellization was seen in zone 7 in 8 patients (14%) in year 1 and 36 (63%) by year 5. Correlations were seen with proximal canal fill and radiolucent lines at zones 3 (0.278; p0.36) and 5 (0.258; p 0.05) and with distal canal fill and hypertrophy of the cortex in zone 3 (0.429; p0.001) and 5. Cortical hypertrophy around the midstem, lack of radiolucent lines around the proximal stem and cancellization of the calcar are all radiographic patterns which occur routinely. A positive correlation with distal canal fill and hypertrophy of zones 3 and 5 was noted. There was no significant correlation with preoperative boney morphology or initial stem fit proximally

Cementless femoral components have an excellent track record that includes efficient implantation and long-term survival, thus are the predominant stem utilised in North America. Femoral component stability and resistance to subsidence are critical for osseointegration and clinical success. Implant design, surgical technique, anatomic fit, and patient characteristics, such as bone quality, can all effect initial implant stability and resistance to subsidence. Variability in stem shape and in the anatomy of the proximal femoral metaphysis has been implicated in the failure of some stem designs. Biologic fixation obtained with osseointegration of cementless implants may improve implant longevity in young, active, and obese patients. Lack of intimate fit can lead to clinical complications such as subsidence, aseptic loosening, and peri-prosthetic fracture. Currently, there are several stem designs, all of which aim to achieve maximal femoral stability and minimal subsidence and include: Fit and Fill / Double Taper Proximally Porous Coated Stems; Parallel Sided Taper Wedge or “Blade” Stems; Wagner Style Conical Shape Splined Titanium Stems; Tapered Rectangular Cross-Section Zweymuller Stem; Fully-Porous Coated Stems; Modular Proximal Sleeve Fluted Stem; Anatomic Proximally Porous Coated Stems. The majority of patients with relatively straightforward anatomy can be treated with any of the aforementioned femoral implant types. However, more complicated femoral anatomy frequently requires a particular implant type to maximise stability and promote osseointegration. Stems with femoral deformity in the meta-diaphyseal region may require a shorter stem in order to avoid an osteotomy. Distorted femoral anatomy typically seen in childhood diseases, such as dysplasia, may require a modular proximal sleeve tapered fluted stem or Wagner style cone stem to impart optimal stem anteversion separate from the native femoral neck version. The most severe forms of dysplasia may require a shortening osteotomy and subsequent distal fixation and neck version flexibility, which can be addressed with a modular proximal sleeve fluted or fully porous coated stem. A stovepipe or osteoporotic femur may require a stem that engages more distally such as a conical splined tapered stem, a fully porous coated stem or even a cemented stem to achieve adequate stability. Finally, obese patients are a particular challenge and emerging data suggests that a morphologically based parallel-sided taper wedge stems may confer greater stability and resistance to subsidence in these patients. Ultimately, an appropriate selection algorithm will facilitate an appropriate match of the patient morphology with femoral implant geometry that facilitates stable fixation and osseointegration

Intra-operative fractures of the femur are on the rise mainly due to the increased use of cementless implants and the desire to get a tight pressfit. The prevalence has been reported to be between 1–5% in cementless total hip arthroplasties (THAs). The key to preventing these fractures is to identify patients at high risk and careful surgical technique. Surgical risk factors include the use of cementless devices, revision hip surgery, the use of flat tapered wedges and MIS surgery. Patient factors that increased risk include increasing age, female gender, osteopenia and rheumatoid arthritis. These risk factors tend to be additive and certainly when more than one is present extra caution needs to be taken. Surgical technique is critical to avoid these intra-operative fractures. Fractures can occur during exposure and dislocation, during implant removal (in revision THA), during canal preparation and most commonly during stem insertion. In both primary and especially in revision THA, be wary of the stiff hip in association with osteopenia or osteolysis. These patients require a very gentle dislocation. If this cannot be achieved, then alteration of the standard approach and dislocation may be needed. Examples of these include protrusion with an osteopenic femur and revision THA with a very stiff hip with lysis in the femur. Lastly, in cases with retained hardware, dislocate prior to removing plates and screws. After dislocation, the next challenge is gentle preparation of the femoral canal. A reasonable exposure is required to access the femoral canal safely. MIS procedures do not offer as good access to femoral canal and this probably results in increased risk of fracture during broaching or implant insertion. When broaching, stop when broach will not advance further. When inserting a tapered wedge stem, be worried if stem goes further in than broach. In revision surgery when taking the stem out from above, make sure the greater trochanter does not overhang the canal. A high speed burr can clear the shoulder for easier access for removal. In revision THA with an ETO place a cerclage wire prior to reaming and retighten prior to stem insertion. Even with careful surgical technique intra-operative femoral fractures will still occur. When inserting the stem a sudden change in resistance is highly suggestive of fracture. Wide exposure of the entire proximal femur is necessary to confirm the diagnosis. The distal extent of the fracture must be seen. Only on occasion is an intra-operative radiograph needed. Management is directed to ensuring component stability and good fracture fixation. In primary total hip arthroplasty calcar fractures are by far the most common. If using proximal fixation and you are certain the stem is stable, then all that is needed is cerclage wiring. As already mentioned, you must follow the fracture line distally so you are aware of how far down it goes. Often what appears to be a calcar split actually propagates distal to the lesser trochanter. In these cases, one would probably go for distal fixation plus wiring. In conclusion intra-operative femoral fractures are on the rise. Prevention is the key. If a fracture, exposure is the key to deciding on a treatment plan

INTRODUCTION:. Short femoral stems are receiving increasing attention for less invasive total hip replacement (THR). The purpose of this study is to report our initial experience with a short modular femoral (SMF) stem at a minimum two-year follow up. METHODS:. Twenty-six primary total hip arthroplasties (THAs) using the SMF stem were performed between August 2009 and January 2010. Patients were evaluated clinically with Harris Hip Score (HHS) and radiographically up to two years. Radiographs were analyzed to determine the degree of stem migration from its initial postoperative position. These parameters were compared to those of a cohort of 54 patients implanted with a monolithic tapered wedge stem from the same manufacturer over the same time period. RESULTS:. There were three early revisions of the femoral component for thigh pain in the SMF group, and one revision for CoCr allergy, with improvement in HHS from 60 to 89. Radiographically, 20 of 26 stems (76%) migrated into varus in the first six weeks. Of these, eight patients (29.6%) reported moderate to severe thigh pain. Radiographic evidence of isolated lateral cortical hypertrophy at the stem tip was seen in 46% of study patients, and evidence of osteointegration was seen in all cases by one year. Between one and two years post op the pain had resolved in four patients not revised. It was persistent in one patient. Comparative analysis with the control group demonstrated no significant difference in stem subsidence, but a significantly greater varus shift in coronal-plane angulation (Mean 4.3°, SD 3.8° vs. Mean 1.0°, SD 1.1°; p < 0.0001). Mean HHS was lower in the SMF group (85.2 vs. 91.4; p < 0.01) at last follow up. DISCUSSION AND CONCLUSION:. The SMF stem demonstrated a tendency towards migration into a varus position where the lateral stem touches the lateral cortex of the femur, with resulting relatively higher incidence of thigh pain and early aseptic revision

Iliopsoas tendonitis after total hip arthroplasty (THA) can be a considerable cause of pain and patient dissatisfaction. The optimal cup position to avoid iliopsoas tendonitis has not been clearly established. Implant designs have also been developed with an anterior recess to avoid iliopsoas impingement. The purpose of this cadaveric study was to determine the effect of cup position and implant design on iliopsoas impingement. Bilateral THA was performed on three fresh frozen cadavers using oversized (jumbo) offset head center revision acetabular cups with an anterior recess (60, 62 and 66 mm diameter) and tapered wedge primary stems through a posterior approach. A 2mm diameter flexible stainless steel cable was inserted into the psoas tendon sheath between the muscle and the surrounding membrane to identify the location of the psoas muscle radiographically. CT scans of each cadaver were imported in an imaging software. The acetabular shells, cables as well as pelvis were segmented to create separate solid models of each. The offset head center shell was virtually replaced with an equivalent diameter hemispherical shell by overlaying the outer shell surfaces of both designs and keeping the faces of shells parallel. The shortest distance between each shell and cable was measured. To determine the influence of cup inclination and anteversion on psoas impingement, we virtually varied the inclination (30°/40°/50°) and anteversion (10°/20°/30°) angles for both shell designs. The CT analysis revealed that the original orientation (inclination/anteversion) of the shells implanted in 3 cadavers were as follows: Left1: 44.7°/23.3°, Right1: 41.7°/33.8°, Left2: 40/17, Right2: 31.7/23.5, Left3: 33/2908, Right3: 46.7/6.3. For the offset center shells, the shell to cable distance in all the above cases were positive indicating that there was clearance between the shells and psoas. For the hemispherical shells, in 3 out of 6 cases, the distance was negative indicating impingement of psoas. With the virtual implantation of both shell designs at orientations 40°/10°, 40°/20°, 40°/30° we found that greater anteversion helped decrease psoas impingement in both shell designs. When we analyzed the influence of inclination angle on psoas impingement by comparing wire distances for three orientations (30°/20°, 40°/20°, 50°/20°), we found that the effect was less pronounced. Further analysis comparing the offset head center shell to the conventional hemispherical shell revealed that the offset design was favored (greater clearance between the shell and the wire) in 17 out of 18 cases when the effect of anteversion was considered and in 15 out of 18 cases when the effect of inclinations was considered. Our results indicate that psoas impingement is related to both cup position and implant geometry. For an oversized jumbo cup, psoas impingement is reduced by greater anteversion while cup inclination has little effect. An offset head center cup with an anterior recess was effective in reducing psoas impingement in comparison to a conventional hemispherical geometry. In conclusion, adequate anteversion is important to avoid psoas impingement with jumbo acetabular shells and an implant with an anterior recess may further mitigate the risk of psoas impingement

While short stem designs are not a new concept, interest has surged with increasing popularity of less invasive techniques. If the goal of the tapered stem is to load preferentially proximally, why do we need a stem at all? Perhaps the only reason to use a tapered, long stem is to prevent varus; however, studies have shown that varus malalignment of a tapered stem does not affect results. Short stems are easier to insert, especially when using an anterior approach such as the anterior supine intermuscular in which the proximal femur is elevated anteriorly from the wound during stem insertion. Femoral preparation can be accomplished with straightforward broaching of the canal, without use of reamers. Short stems are bone conserving. They violate less femoral bone stock, providing more favorable conditions should a revision be required. However, ease of insertion and bone conservation matter little if not supported by clinical results. Thus, we reviewed our early experience with 2094 patients undergoing 2457 primary THA using short, tapered titanium, porous plasma spray-coated femoral components since January 2006 at our center. The TaperLoc Microplasty stem (Biomet, Warsaw, IN) has been used in 1881 THA, and the TaperLoc Complete Microplasty stem (Biomet) in 576. Patient age averaged 63.6 years. Increased offset was used in 1990 hips (81%). The surgical approach was less invasive direct lateral (LIDL) in 1194 THA (49%), anterior supine intermuscular (ASI) in 1117 (46%), and standard direct lateral (Std) in 146 (6%). Follow-up averaged 20 months. Thirty-five stems (1.4%) have been revised: 15 for infection (12 LIDL, 3 ASI), 1 same day revision for intraoperative femoral shaft perforation (Std), 1 at 3 days for patellar dislocation (LIDL), 2 for early subsidence (1 LIDL, 1 ASI), 13 for periprosthetic femoral fracture (1 Std, 12 ASI), 2 for aseptic loosening (1 LIDL, 1 ASI), and 1 stem well fixed (ASI) removed for loose cup and unable to disarticulate trunnion. What lessons have we learned? First, we usually require one or two diameter sizes larger with short porous tapered stem versus the standard length version of the same design. The surgeon should be aggressive with sizing, pushing to the largest size possible. Use the broach like a rasp. Drive the component in valgus during insertion. Upon seating the component, do a trial reduction using the shortest available neck length. The component will generally sit slightly prouder than the broach and may require additional effort to seat completely. Conservation of existing bone stock, compatibility with soft-tissue sparing surgery, more physiologic loading of the proximal femur, and versatility with varying femoral anatomy make the short taper an attractive implant option. The tapered wedge short stem represents the natural evolution of joint arthroplasty to a smaller, less-invasive, and more efficient implant