Introduction. To evaluate the effect of hydroxyapatite coating, two same shape cementless stems were compared in this randomized control trial study. Methods. Between May 2003 and February 2010, 88 patients had a primary cementless total hip arthroplasty with two different types of cementless stems. Forty-three patients had Proarc stems (P group) (Kyocera Medical, Osaka, Japan), and Forty-five patients had Proarc HA stems (HA group) (Kyocera Medical, Osaka, Japan) which was coated with thin (20 micrometer) hydroxyapatite on Proarc rough porous coating. Gender distribution, average age at surgery, average weight and average follow-up period were same in the two groups. The average follow-up period was 8.5 years (range, 5 to 13 years). The average age at the time of surgery was 63 years. Porous acetabular shells and highly crosslinked polyethylene liners made by Kyocera Medical corporation were implanted into all hips. Stems were implanted with a modified Hardinge surgical approach without trochanteric osteotomy. Harris Hip Score was used for clinical evaluation. Post-op radiographs of these patients were evaluated. Fisher's exact probability test was used for statistical analysis. P values of less than 0.05 were considered to be significant. Results. The mean preoperative score and postoperative score of P group were 39 points and 86 points, respectively. The mean preoperative score and postoperative score of HA group were 46 points and 87 points, respectively. All stems were evaluated as bone-ingrown fixation in both groups. The rate of varus inclination was not different between two groups. The rate of severe stress shielding was not different. Discussion. However hydroxyapatite coating is useful for early fixation, the adverse effect, such as delamination for long-term in vivo situation is questionable. There was no significant difference between P-group and HA group in the present study. Longer follow-up is required to evaluate hydroxyapatite coating

Clinical and radiological results of total hip arthroplasty (THA) using proximally coated single wedge (PSW) cementless stems are generally excellent. The geometry of cementless stems and the morphology of proximal femurs (Dorr types) provide optimal fit for primary stability and secondary biologic fixation. Because the geometry of PSW shape is designed to be engaged at the metaphysis, cementless PSW stem is not traditionally recommended to Dorr type C femurs with concerns of inadequate implant-host bone contact and the risk of femoral fracture. Nevertheless, previous studies on PSW cementless stems have not examined long-term survivorship according to Dorr types of femur. Paucity of a long-term comparative study makes it difficult to know whether the PSW stem plays a role in Dorr type C femurs or not. We postulated that the PSW stem could achieve stable fixation without increased risk of femoral fracture even in Dorr type C femurs, and demonstrate acceptable long-term results. The aim of this study was to investigate differences of clinical and radiological outcomes of THA using PSW stem according to proximal femoral geometry (Dorr types) in more than a 10-year follow-up. Three hundred and seven primary THA in 247 patients, which was performed with use of a single-designed PSW stem from 1997 to 2003 and was followed up for over 10 years, were included in this retrospective study. According to Dorr's criteria, 89 femora were classified as Type A, 156 as Type B, and 62 as Type C. The patients' mean age at operation was 43.2 years (range, 18.4 – 69.6 years). They were followed-up for an average of 13.2 years (the range, 10.0 – 17.3 years). All of the hips were evaluated clinically and radiologically with special attention to the occurrence of implant loosening and periprosthetic femoral fracture. The mean preoperative Harris hip score (50.4±20.6 points) improved significantly to 95.6±9.0 points at the final follow-ups. The improvements were observed regardless of Dorr types (p<0.001 in all 3 groups). The incidence of thigh pain (p=0.704) was not significantly different among groups. Implant survivorship was 100% in all 3 groups. None of the stems were loosened or revised. No significant differences were observed in osteolysis (p=0.492), pedestal formation (p=0.323), or cortical hypertrophy (p=0.169) among the groups [Fig. 1]. Radiolucent lines less than 2mm in thickness in Gruen zone 4 were observed more in Dorr type C femora than in Dorr type A or B (p=0.003) [Fig. 2]. Spot weld (p<0.001) and stress shielding (p=0.010) of proximal femur were more pronounced in Dorr C type femora than in type A or B [Fig. 3]. The prevalence of intraoperative (p=0.550) or postoperative (p=0.600) femoral fractures were not significantly different among the groups. From over a 10-year follow-up, the PSW stem provided excellent stem survivorship regardless of Dorr type with satisfactory outcomes. The remodeling process around the stem was more pronounced in Dorr type C femur. The present study shows that the PSW stem is a recommendable option for Dorr type C femur. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

OBJECTIVE OF THE STUDY. The objective of this study is to establish the medium-term clinical and radiological results with the cementless three-dimensional Vektor-Titan stem compared with conventional cementless stem, such as PerFix stem. The latter stem has a double-wedge design with a rounded distal portion for canal filling (Fig. 1). MATERIALS AND METHODS. From July, 2004, to May, 2010, fifty seven Vektor-Titan stems and 150 PerFix stems were implanted for the patients with osteoarthritis, avascular necrosis, femoral neck fracture, and rheumatoid arthritis in our hospital. The results were evaluated clinically using Japanese Orthopedic Association (JOA) scores and the Merle d’Aubigne and Postel (M&P) scores. Radiographs were analyzed retrospectively. The criteria used for determining loosening were migration or a total radiolucent zone between the prosthesis/bone cement and host bone, wherein the width increased progressively or change of position, i.e., migration or subsidence of the prosthesis. Migration of the socket seen on the radiograph was defined as either the presence of a ≥2-mm position change or rotation. Position changes of the stem seen on the radiograph were defined as the presence of a progressive subsidence of ≥2 mm or change of position, e.g., varus or valgus. The follow-up period was 9.2 ± 2.6 (range, 5.0–14.0) years. RESULTS. One patient had intraoperative femoral shaft fracture and healed by conservative treatment. The mean JOA and M&P scores improved from preoperative 39.3 and 6.8 points to postoperative 90.9 and 17.2 points, respectively. Thigh pain was less frequent for Vektor-Titan stems (Table 1). Radiolucent lines was far less likely to appear for Vektor-Titan stems evaluated by Gruen's zonal analyses (Table 2). On the other hand, there were radiolucent zones of more than 90% in zone 4 with cementless PerFix stems (Table 2). There was no cases of loosening or postoperative infection. Although signs of bone atrophy were found in the proximal femur and the trochanters in 66.7 % of all cases, bone structure was radiologically normal without stress shielding in most cases (Table 2). On the contrary, there was evidence of an even denser bone structure, such as trabeculae, at the tip of the stem and the lateral implant fixation within the greater trochanter in Vektor-Titan stem cases. These findings remained unchanged over observation periods. DISCUSSION AND CONCLUSIONS. The cementless Vektor-Titan stem is made of Ti6AI7Nb, has got the shape of a straight three-dimensional cone. It has a high proximal volume in the form of a three-dimensional taper with longitudinal ribs. This design achieves strong primary fixation in the proximal metaphysis. Radiologically, newly formed trabeculae toward to the stem were indicative of direct biological fixation at the bone-implant interface. Medium-term results with the cementless Vektor-Titan stem show no implant loosening with stable metaphyseal fixation and preservation of bone structure in the proximal femur and the absence of radiolucent zones around the stem compared with conventional cementless stem

Introduction. Fixation patterns of cementless stem were known as proximal or distal part. Distal fixation was seen in fully porous coated stem and stress shielding of the proximal femur was indicative. These phenomena did not lower the clinical results, but technical difficulties were more and more in revision surgery because of infection or dislocation. There was lot of reports that alendronate was effective for treatment of osteoporosis by induction of apoptosis in osteoclasts. We can expect alendronate to modify the bone quality around the stem after cementless THA. Objectives. We studied prospectively that quantitative computed tomography (QCT) measured bone mineral density around the stem between alendronate group and control. We tried to clarify that stress shielding after cementless THA can be prevented by use of alendronate or not. Materials and methods. From September 2011, 60 patients underwent total hip arthroplasty with cementless stems. Thirty patients took alendronate (35mg/week) after surgery (Group A) and remaining 30 patients were control (Group C). Between two groups, gender, age at surgery, diagnosis and body mass index were similar. Two types of stem were used as Zweimuller type or taperlock type. Just after THA, femoral shaft divided by Gruen zone measured bone mineral density (BMD) with QCT and forearm also measured BMD by DEXA. Following examination was performed at 6 months, 12 months and 24 months after surgery. Results. Gender of two groups was as follow: four males and twenty-six females in Group A and two males and twenty-eight females in Group C. The age at surgery was 67.6+7.9y in group A and 62.5+13.3y in group C. Zweimuller type was used for 18 patients and taperlock type was used for 12 patients in group A. Zweimuller type was used for 14 patients and taperlock type was used for 16 patients in group C. BMD of forearm were not different between two groups and it meant that bone quality and osteoporosis of groups was similar. On the other hands, femoral BMD of group A was higher than that of group C. Especially BMD of group C was relatively low in zone 1 and 7. Conclusion. Weekly use of alendronate (35mg) might be useful for preventing stress shielding after cementless THA

Revision Total Hip Arthroplasty can be challenging in case of thin or fragile femur. Primary Bipolar Hip Prosthesis (BHP) is also difficult in severe osteoporosis case. We have used titanium alloy cementless stem with interlocking screws for revision THA since 2003, and primary BHP in senile case since 2007. Thirty four cementless THA were performed with interlocking stem (27 S-LOCK and 7 Delta-LOCK) since 2007, and 26 cases were followed for more than one year. Two for primary THA and 24 for revision THA, 3 were male and 23 were female. Seven primary Bipolar Hip Prosthesis with interlocking screw stem for femoral neck fracture were also followed more than one year. All seven BHP cases were female. Stress shielding in X-ray film were observed in 3 revision THA cases during follow up, but no pain were complained. No breakage of screws and stems were observed, and no infections and no fractures were occurred. In case of loosened stem, long interlocking stem can bypass the weak point of femur after removal of cement or metal stem tip. Patients can walk immediately after revision THA or primary BHP. Cementless interlocking stem in THA and BHP is useful for management of thin or fragile femoral cortex

Background:. Two-stage reconstruction, reimplantation after removal of an infected prosthesis, has been considered to be the gold standard for treatment of infected hip arthroplasty. However, during the removal of a well-fixed femoral stem, the proximal femur can be damaged and a sequestrum can be formed, which might lead to chronic osteomyelitis and difficulty in reimplantation. We wanted to determine whether infection after hip arthroplasty can be treated without removal of a well-fixed stem. Materials and Methods:. We treated 19 patients who had an infection after hip replacement, but a well-fixed cementless stem, with 2-stage reconstruction. At the first stage, we removed the acetabular cup, the liner and the head, but not the stem. We then implanted a cup of cement spacer. After control of infection, we reimplanted the acetabular component and head. Results:. 2 patients did not undergo second-stage reconstruction because they were satisfied with the pain relief and the activity that they had with the cement-spacer implantation. The remaining 17 patients underwent the second-stage of the reconstruction using cementless arthroplasty. At a mean follow-up time of 4 (2–8) years, 15 of the patients had no recurrence of infection, with satisfactory clinical and radiographic outcome. Discussion:. This second-stage reconstruction after retention of the stem could be an alternative treatment option for periprosthetic infection with a well-fixed stem

25 patients in age group (25–40yrs), 15 males, 10 females were implanted with a short metaphyseal cementless stem (‘Proxima’®, Depuy) and cementless acetabular cup. The average follow up was 2.3 years (1.4–2.5 yrs). Clinical evaluation using Harris Hip Score, Radiological evaluation and Bone Mineral Density were evaluated at 2weeks, 6 months, 12 months and yearly thereafter. a new zonal method suitable for short stem was used for radiological evaluation. The mean Harris Hip score improved from 44 to 95 at final follow up. There was no evidence of any radiolucent lines or osteolysis around the stems. All the stems showed evidence of osseointegration at one year follow up. There was no decrease in bone mineral density around the stems. The Short Metaphyseal cementless femoral stem is a bone conserving as well as bone preserving option for young patients especially in those in whom surface replacement is not an option

The purpose of this study was to evaluate in vivo fit and fill analysis of tapered wedge-type stem in total hip arthroplasty (THA) with computed tomography (CT)-based navigation system. 100 THAs were all performed through the posterolateral approach, with patients in the lateral decubitus position. Each cohort of 50 consecutive primary cementless THAs with was compared with and without CT-based navigation system. The post-operative antero-posterior (AP) hip radiographs were obtained two weeks after the operation. All radiographic fit and fill measurements in the proximal and distal areas were analyzed by two of the authors who were both blinded to the use of CT-based navigation system. The type of the fit in the cementless stem was divided into three types. The fit of the stem was classified as Type I, if there was both proximal and distal engagement (maximum proximal to distal engagement difference of 2 mm or greater), Type II when there was proximal engagement only, and Type III when there was distal engagement only. The fill parameters such as mean stem-to-canal ratios and mean minimum and maximum gaps between the stems to the cortical bone in proximal and distal sections were compared. There was a significantly better overall canal fit obtained by THA with CT-based navigation system compared to without the navigation system (p<0.01). With CT-based navigation system, 42 of 50 stems (84%) were categorized as Type I fit compared to 31 of 50 stems (62%) without the navigation system. As to Type II fit, There are significantly more stems without the navigation system (26%) compared to with it (12%). There were better canal fills of the stems obtained by THA with CT-based navigation system both in proximal (94%) and distal sections (88%) of the femur compared to without the navigation system (proximal 88%/distal 82%) (p<0.05). Excellent radiographic fit and fill has been previously reported to potentially correlate with improved clinical outcomes. The stems obtained by THA with CT-based navigation system had a significantly better canal fit demonstrated by higher proportion of Type I and lower proportion of Type II fits, compared to without the navigation system. The stems with the navigation system had also significantly better proximal and distal canal fill

Introduction. Resorptive bone remodeling secondary to stress shielding has been a concern associated with cementless total hip arthroplasty (THA). At present, various types of cementless implants are commercially available. The difference in femoral stem design may affect the degree of postoperative stress shielding. In the present study, we aimed to compare the difference in bone mineral density (BMD) change postoperatively in femurs after the use of 1 of the 3 types of cementless stems. Methods. Ninety hips of 90 patients who underwent primary cementless THA for the treatment of osteoarthritis were included in this study. A fit-and-fill type stem was used for 28 hips, a tapered-rectangular Zweymüller type stem was used for 32 hips, and a tapered-wedge type stem was used for 30 hips. The male/female ratio of the patients was 7/21 in the fit-and-fill type stem group, 6/26 in the tapered-rectangular Zweymüller type stem group, and 6/24 in the tapered-wedge type stem group. The mean age at surgery was 59.9 (39–80) in the fit-and-fill type stem group, 61.7 (48–84) in the tapered-rectangular Zweymüller type stem group and 59.6 (33–89) in the tapered-wedge type stem group. To assess BMD change after THA, we obtained dual-energy X-ray absorptiometry scans preoperatively and at 6, 12, 24, and 36 months postoperatively. Results. There were no differences in demographic data, such as gender, age at surgery, and body mass index, among the 3 groups (Table1). In terms of BMD change after THA, no differences were observed in Gruen zones 1–5 among the 3 groups during the 3-year follow-up. The BMD in Gruen zone 6 was maintained in the tapered-wedge type stem group, but decreased by 5% in the fit-and-fill type stem group and by 20% in the tapered-rectangular Zweymüller type stem group (p < 0.01). The BMD loss in Gruen zone 7 was observed in all stem types; however, the BMD loss at 36 months in the tapered-wedge type stem group (−15%) was significantly less than that of the other 2 groups (the fit-and-fill type stem group: −29%; the tapered-rectangular Zweymüller type stem group: −30%; p < 0.001 for both groups) (Figure). Discussion and Conclusion. A difference in postoperative BMD loss was observed among the 3 stem designs. This may be a result of the different fixation concept associated with each stem design. In the present study, we compared the postoperative BMD change after THA among a fit-and-fill type stem, a tapered-rectangular Zweymüller type stem, and a tapered-wedge type stem. BMD in the medial-proximal femur was maintained 3 years after THA in the group with the tapered-wedge type stem, which is fixed in a more proximal part of the femur compared to the other stems

Total hip arthroplasty has become one of the most successful orthopaedic procedures with long-term survival rate. An ever-increasing acceptance of the potential longevity of THA systems has contributed to an increasing incidence of THA in younger and more active patients. Nowadays, especially in younger patients, cementless THA is the favored method worldwide. Since the first cementless THA in late 1970s, many implant designs and modifications have been made. Despite excellent long-term results for traditional straight cementless stems, periprosthetic fractures or gluteal insufficiency are still a concern. For instance, as reported in a meta-analysis by Masonis and Bourne, the incidence of gluteal insufficiency after THA varies between 4% and 22%. In contrast, the flattened lateral profile of the SP-CL. ®. anatomical cementless stem can protect the greater trochanter during the use of cancellous bone compressors and can avoid gluteal insufficiency after THA. Another benefit of this stem design is the rotational stability and the natural load transfer due to the anatomical concept. In this context, we report our experiences using the SP-CL. ®. anatomical cementless stem. The study group consists of 1452 THA cases (850 male, 602 female) with an average age of 62 years (range 25–76 years). After a mean follow-up of 20 months, in seven cases (0.5%) a stem exchange was necessitated. The reason for stem revision was periprosthetic fracture in 4 cases (0.3%) and periprosthetic joint infection in three cases (0.2%). In five patients, hip dislocation and in four patients migration of the stem occurred. However, stem exchange was not required in those cases. In conclusion, the SP-CL. ®. anatomical cementless stem has excellent short-term results

[Introduction]. Short tapered wedge-shaped cementless (TW) stems have been widely used for several years. The concept of fixation of TW stem is wedge-fit fixation in the proximal metaphysis. Developmental dysplasia of the hip (DDH) has anatomical abnormality, such as excessive femoral anteversion, short femoral neck length, narrow femoral cavity, or proximal-distal mismatching of the femoral canal. Therefore, Mismatching between stem and bone might be occurred in DDH. We evaluated intramedullary matching of short TW stem for DDH by three dimensional (3D) digital template in order to clarify whether mismatching between stem and bone is seen in DDH implanted short TW stem. [Materials and Methods]. One hundred hips (92 patients) with DDH were performed preoperative simulation for total hip arthroplasty by 3D digital template system (ZedHip: Lexi, Tokyo, Japan). The average age was 63.5 years old. There were 12 males and 80 females. The average bone mass index was 21.5 kg/m. 2. Femoral canal shape was normal in 71, champagne-flute in 16 and stovepipe in 13 hips. Bone quality was classified into type A in 23, type B in 74 and type C in 3 hips. Preoperative computed tomography data were used for 3D digital template and reconstructed to 3D femoral model. Short TW stem (Taperloc Complete Microplasty: Biomet, Warsaw, IN) model constructed from computer-assisted design was matched to the reconstructed femoral model. Short TW stem model was in principle implanted according to the femoral neck anteversion with neutral alignment (varus and valgus < 2 degrees, flexion and extension < 2 degrees) at the coronal and sagittal plane of the femur. Stem size was determined in order to obtain the largest intramedullary matching at the coronal plane. Area of stem fitting with the cortical bone was investigated at 10 mm intervals above and below of mid minor trochanter. Intramedullary matching pattern was classified into proximal mediolateral metaphyseal fit, proximal flare fit and diaphyseal fit at multiple reconstructed planes of the 3D femoral model according to stem fitting area. [Results]. Ninety-three percent of stem could be implanted with neutral alignment at the coronal plane, and 86 percent at the sagittal plane. The average stem anteversion was 31.4 degrees. Over 70 percent of stem could be fit with the medial and lateral cortical bone at 10 mm above and below of mid minor trochanter. Intramedullary matching pattern was proximal mediolateral metaphyseal fit in 49%, proximal flare fit in 44% and diaphyseal fit in 7%. [Discussion and Conclusion]. Early migration or failure of osteointegration of TW stem was recently published. Diaphyseal fixation or mismatching between stem and bone is considered as risk factors of early failure of TW stem. In this study, proximal metaphyseal fit, such as mediolateral metaphyseal fit or flare fit, could be achieved in 93% of DDH patients. Mismatching between stem and bone, such as diaphyseal fit, was observed only in 7% of DDH. Short TW stem is good choice for DDH in order to avoid of diaphyseal fixation followed by early migration of stem and decreased osteointegration

Purpose. The purpose of this study was to evaluate the results of modular revision stems, uncemented fluted, tapered to treat periprosthetic femoral (PFF) fracture; we specifically evaluated fracture union, implant stability, patient outcomes, and complications to compare the differences between cemented and cementless primary stem. Materials and Methods. We retrospectively reviewed 56 cases of unstable periporsthetic femoral fracture (forty B2 and sixteen B3) treated with the uncemented fluted and tapered modular distal fixation stem with or with or without autogenous bone graft. Clinical outcomes were assessed with Harris Hip Score and WOMAC score. Radiologic evaluations were conducted using Beals and Tower's criteria. Any complication during the follow-up period was recorded. Results. The average follow-up period was 52.1±32.7 months. The average Harris Hip Score was 72.4±19.1. All fractures were united, and a good consolidation was achieved in 47 cases. There was femoral stem subsidence in 3 cases less than 10 mm without an evidence of loosening both radiologically and clinically. The radiologic results using Beals and Towers’ criteria were excellent in 36 hips, good in 10 hips and poor in 10 hips. Radiologic bone union took longer time and statistically significant stem subsidence was observed in cemented primary stem compared to cementless primary stem (Fig1,2). At each follow-up examination the clinical score was significantly higher in patients with cementless primary stem. Conclusion. Our results support the view that cement primary stem has less favorable result in terms of revision arthroplasty for periprosthetic femoral fractures

Introduction. Proper initial fixation of the stem in the femoral canal is important to achieve successful long-term clinical results in total hip arthroplasty (THA) and bipolar hemiarthroplasty (BHA). However, this factor fully relies on surgeon's experience and skill during the hammering process. The goal of this study is to evaluate the frequency of the stem hammering sound which enables the achievement of proper stem fixation and avoiding femoral bone fracture. Materials and methods. 57 patients who received BHA as a result of femoral neck fracture were evaluated. Intraoperative images of stem hammering were recorded using a digital video camera (Everio GZ-MG275, Victor, Japan). The frequency of the hammering sound was analyzed using a digital audio editor, GoldWave (GoldWave Inc.) (Figure 1). The frequency change during hammering was categorized into two groups, convergent and non-convergent, according to the frequency change pattern (Figure 2). The definition of “convergent group” is as follows: in the last five hammering sounds to finish the stem insertion, 1) Three consecutive hammering frequency shape and distribution 2) Formant peak frequency within the range of 3,000 Hz. Two types of cementless stems, SYNERGY SELECT II (tapered) and ECHELON TITANIUM (cylindrical, both from Smith & Nephew, Inc.) were used. Stem hammering was conducted using the same stem inserter. Canal Flare Index (CFI), Cortical Index (CI), Singh Index (SI), canal filling ratio, and the total number of stem-cortex contact zones were evaluated on x-ray images. The Mann-Whitney U-test was used for statistical analysis. Results. The number of contact zones was significantly different between convergent and non-convergent groups in both SYNERGY and ECHELON stems. However, no significant difference was found in CFI, CI, SI, and canal filling ratio. With the SYNERGY stem 24 cases showed convergence in hammering frequency and non-convergence in 16 cases. The mean total contact zones were 6.08±1.18 (convergent group) and 4.44±1.71 (non-convergent group). In the ECHELON group 9 cases showed convergence in hammering frequency and non-convergence in 8 cases. The total contact zones were 6.78±1.09 (convergent group) and 4.88±1.55 (non-convergent group) (Table 1). Discussion. Regardless of femoral geometry and stem design, hammering sound frequency was convergent when the stem-bone contact area increased. Change in the hammering sound frequency can provide reliable information during the stem insertion in terms of stem-bone contact to prevent bone fracture

OBJECTIVE OF THE STUDY. The objective of this study is to establish the short-term and medium-term clinical and radiological results with the cementless three-dimensional Vektor-Titan stem (Figure 1). This three-dimensional tapered stem has been given to evaluate the extent to which the implant design achieves an optimal proximal anchoring property, thus reducing bone atrophy and avoiding stress shielding in the proximal femur. MATERIAL AND METHODS. From July, 2004, to May, 2010, 80 Vektor-Titan stems were implanted in 75 patients in the Shinonoi General Hospital. Forty two patients (42 hips) with femoral neck fracture (FNF) and one patients (2 hips) with aseptic necrosis of the femoral head (ANF) were died or impossible to come outpatient clinic for postoperative follow-up due to serious illness not related to the surgery. Of 32 patients (36 hips) with a minimum two-year follow-up, 23 patients (23 hips) with FNF and 9 patients (13 hips) with ANF were analyzed in the study. Demographics and clinical outcomes of the patients were shown in Table 1. The results were evaluated clinically using Japanese Orthopedic Association (JOA) Scores and radiologically within the scope of a retrospective cohort study. RESULTS. One patient had intraoperative femoral shaft fracture and healed by conservative treatment. There was no radiolucent zones around stems evaluated by Gruen's zonal analyses. There was no cases of loosening or postoperative infection. Although signs of bone atrophy were found in the proximal femur and the trochanters in 13 hips (FNF group) and 11 hips (ANF group) (66.7âζŠ% of all cases), bone structure was radiologically normal without stress shielding. On the contrary, there was evidence of an even denser bone structure, such as trabeculae, at the tip of the stem and the lateral implant fixation within the greater trochanter. These findings remained unchanged over observation periods. Clinically, JOA Scores were improved significantly in the ANF group (Table 1). DISCUSSION AND CONCLUSIONS. The cementless Vektor-Titan stem is made of Ti6AI7Nb, has got the shape of a straight three-dimensional cone. It has a high proximal volume in the form of a three-dimensional taper with longitudinal ribs. This design achieves strong primary fixation in the proximal metaphysis. Radiologically, newly formed trabeculae toward to the stem were indicative of direct biological fixation at the bone-implant interface. Short-term and medium-term results with the cementless Vektor-Titan stem show no implant loosening with stable metaphyseal fixation and preservation of bone structure in the proximal femur and the absence of radiolucent zones around the stem

INTRODUCTION:. Good survival rates of cementless hip stems serve as motivation for further development, just like modular implant systems or short stems. New aims are worth striving for, e.g. soft tissue or bone sparing options with similar survival rates in case of short stems. Even minimal design modifications might result in complications, e.g. missing osseointegration, loosening of the implant or painful stem, as shown in the past. One of these developments is the Biomet – GTS™ stem [Fig. 1], a hybrid between conventional cementless straight stem and potentially sparing short stem. Aim of this biomechanical study was to analyze, if the biomechanical behavior of the stem is comparable to a clinically proofed design with respect to the stem fixation in the bone and to the mechanical behavior of the stem itself. That's why the primary stability of the GTS™ stem has been determined and subsequently was compared to the Zimmer – CLS® stem. MATERIAL & METHODS. Four GTS™ stems and four CLS® stems were implanted standardized in eight synthetic femurs. Micromotions of the stem and the bone were measured at different sites. A high precision measuring device was used to apply two different cyclic load situations: 1. Axial torque of +/−7 Nm around the longitudinal stem axis to determine the rotational implant stability. 2. Varus-valgus-torque of +/−3, 5 Nm to determine the bending behavior of the stem. Comparing the motions of the stem and femur at different sites allowed the calculation of relative micromotions at the bone-implant-interface. RESULTS:. Lowest relative micromotions were detected near the lesser trochanter within the proximal part of both stems. Maximum relative micromotions were measured near the proximal end of the stem for both designs, indicating a proximal fixation of both stems [Fig. 2]. Concerning varus-valgus-torque, a similar flexibility between proximal stem shoulder and distal tip of stem was shown for both stems. DISCUSSION & CONCLUSION:. The relative micromotions of both groups seem to indicate an adequate primary stability of the stems. Obviously, the shortened design might have no fundamental influence on the biomechanical rotational stability in the bone. Compared to the CLS® stem, the GTS™ seemed to act similar flexibel during varus-valgus-torque application. Both stems might follow the bending of the bone instead of ‘tilting’ within the femur. This study showed, that the CLS® stem and the GTS™ stem biomechanically behave similar. However, a clinical confirmation of these experimental results remains to be

Background. The clinical results of total hip arthroplasty (THA) with a cementless prosthesis have been constantly improving due to progress in the area of stem design and surface finish. However, majority of stems are well-fixed with canal filling or diaphyseal fit, and cortical hypertrophy or metaphyseal bone atrophy has been often observed. Cementless Spotorno stem (CLS stem; Zimmer, Warsaw, USA) is a double-tapered rectangular straight stem. The purpose of this study is to investigate the mean 13 years' results of CLS stem and to evaluate the press-fit stability of CLS stem. Methods. Between 1999 and 2004, we treated 134 patients (142 hips) with CLS stem. Of those patients, 86 females (92 hips) and 13 males (14 hips), in total 99 patients (106 hips) were available at minimum of 11 years after surgery. At the time of follow-up, six females and five males were dead. The follow-up rate was 82% and the mean follow-up period was 13 years (SD; 20, range; 11–16). The mean age at the time of surgery was 65 years (SD; 10, range; 38–86). The mean body mass index was 24 (SD; 1.8, range; 19 to 28). Preoperative diagnoses were osteoarthritis in 92 patients, osteonecrosis in five patients, and rheumatoid arthritis in two patients. Majority of the patients were female because 84 patients of osteoarthritis suffered from hip dysplasia. For cementless acetabular reconstruction, APR cups (Zimmer, Warsaw, USA) were implanted in 10 hips, IOP cups (Zimmer, Warsaw, USA) in 22 hips, and Converge cups (Zimmer, Warsaw, USA) in 74 hips. As the liner of acetabular component, conventional UHMWPE (Sulene: Zimmer, Warsaw, USA) was used in APR cup and highly crosslinked UHMWPE (Durasul: Zimmer, Warsaw, USA) in IOP and Converge cups. The lipped liner was chosen in all cases, and lipped lesion was placed posteriorly. The radiographic stability of the femoral stem was determined by Engh's criteria. The ascertained period of spot welds was noted by Gruen zones on the femoral side. The presence of stress shielding, and subsidence was also evaluated. Results. A stable stem with bony on-growth was identified in all cases. The mean period of expression of spot welds was 11 months in zone 2, 10 months in zone 3, 9 months in zone 5, and 9 months in zone 6. Stress shielding of more than grade 2 was observed in only 8 hips, which was non-progressive at 1 year after surgery. Subsidence of more than 2mm was not observed in any of the hips. The cortical hypertrophy at the tip of stem was not observed. The postoperative dislocation occurred in six hips (6%) and periprosthetic femoral fracture occurred in two hips (2%). Revised surgery was performed in three hips for a recurrent dislocation and two periprosthetic femoral fracture. Conclusions. Excellent stability of CLS stem has been maintained without abnormal bone reaction at proximal femur. CLS stem is considered to achieve not only press-fit stability at trochanteric and subtrochanteric level, but bony fixation by osseointegration within 1 year after THA

Background. Tapered cementless femoral components have been used in total hip arthroplasty (THA) constructs for more than 20 years. The Synergy femoral component was introduced in 1996 as a second generation titanium proximally porous-coated tapered stem with dual offsets to better restore femoral offset at THA (Figure 1). The purpose of this study was to evaluate the outcome of the authors' experience using the Synergy stem at minimum 15 years of follow-up. Material and methods. We retrospectively reviewed a consecutive series of 102 patients (112 hips) who underwent surgery between November 1996 and October 1998 for primary THA using cementless Synergy stem with a minimum 15-years follow-up. The mean age at the time of surgery was 61 years, and the mean duration of follow-up was 16.3 years. Seventeen patients were lost at FU (8 died before the 15 years mark, 8 changed residency, 1 not willing to be seen) with no problems related to the replaced hip. Ninety-four hips in 85 patients were available for clinical and radiologic analysis. Clinical results of the 94 THAs with more than 15 years of follow-up were assessed preoperatively and postoperatively at 5, 10 and 15 years by means of standard evaluation tools: SF12, WOMAC and Harris Hip Score. Thigh pain frequency and intensity were also recorded. Radiographic analysis (Figure 2) was focused on stem alignment, bone ingrowth, radiolucent lines presence, width and progression, stress-shielding and heterotopic ossification (HTO). Student paired test and Kaplan-Meier survival analysis were used for statistical analysis. Results. All clinical evaluation tools showed at 5-year FU, 10-year FU and at latest FU (15–17 years) a statistically significant improvement compared to the preoperative scores. We observed a not constant thigh pain in 5 hips (4.75%). Nine stems were revised due to polyethylene wear (3 cases), late periprosthetic fracture (2 cases), infection (2 cases), subsidence (1 case) and instability (1 case). Stem related revision was a case of subsidence, related to occult intraoperative calcar crack and early revised (within 1 year); cumulative stem-related survival rate at 15 years was 99%. Alignment was varus in 5 cases and valgus in 1. Bone in-growth was observed in 93 hips (98%). Radiolucent lines were uncommon, non progressive, less than 2 mm, in Gruen zones 2 and 6. Stress-shielding was present as cortical reaction in 5 femurs in Gruen zones 3 and 5. Fifteen cases of HTO (grade I and II in 12 case and grade III in 3 cases) were observed. Conclusions. The Synergy stem demonstrated excellent clinical and radiographic results at 15–17 years FU in 85 patients. Survivorship (with stem revision as end point) was 99% at 15 years. Thigh pain was uncommon and the level of activity and autonomy is excellent. Radiographically bone ingrowth is evident in all stems and radiolucent lines are “benign” with no aseptic loosening

Introduction

Finite element (FE) models are commonly used to analyse the mechanical behaviour of the bone under different conditions. They provide detail information but they can be numerically expensive and this limits their use in cases where large or numerous simulations are required. On the other hand, 2D models show less computational cost but the precision of results depends on the approach used for the simplification. Three 2D approaches are commonly used: models without side-plate (WOSP)[1]; models with variable thickness side-plate and constant cortical thickness (SPCT)[2]; models with side-plate and variable cortical thickness (SPVT)[3]. The aim of this study is to determine which 2D approach reproduces best the FE results obtained with a 3D model involving hip stems.

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.

Introduction

Cementless femoral hip stems crucially depend on the initial stability to ensure a long survival of the prosthesis. There is only a small margin between obtaining the optimal press fit and a femoral fracture. The incidence of an intraoperative fracture is reported to be as high as 30% for revision surgery. The aim of this study is to assess what information is contained in the acoustic sound produced by the insertion hammer blows and explore whether this information can be used to assess optimal seating and warn for impeding fractures.