Introduction. Alumina ceramic-on-highly cross-linked polyethylene bearings (Al-on-X-linked PE) are attractive because of the potential for reduced wear, osteolysis and loosening of the component. The purpose of this study was to evaluate the clinical and radiographic outcomes of cementless total hip arthroplasties (THAs) using an Al-on-X-linked PE bearing and to determine the rates of osteolysis using radiographs and computer tomographic (CT) scans in young patients with osteonecrosis of femoral head. Methods. Consecutive primary cementless THAs using Al-on-X-linked PE bearing were performed in 71 patients (73 hips) who were younger than 50 years of age with osteonecrosis of the femoral head. There were 48 men (51 hips) and 23 women (23 hips). The average age at the time of the index arthroplasty was 46 years (range, 20 to 50 years). Osteolysis was evaluated using radiographs and CT scanning. The average follow-up was 11 years (range, 10 to 13 years). Results. The mean preoperative Harris hip score was 51 points (range, 27 to 55 points), which was improved to 96 points (range, 85 to 100 points) at the final follow-up. Preoperative functional activity was improved significantly (p=0.001) at the latest follow-up. All acetabular and femoral components were fixed by bone ingrown. The mean polyethylene linear penetration was 0.05 ?0.02 mm per year (range, 0.02 mm to 0.08 mm per year). Radiographic and CT scan evaluation demonstrated that no acetabular or femoral osteolysis was detected in any hip at the latest follow-up. Conclusion. The current generation of anatomic tapered cementless femoral component with Al-on-X-linked PE bearing is functioning well with no osteolysis at a 10-year minimum and average of 11-year follow-up in this series of young patients with osteonecrosis of the femoral head

Summary

The M2a-38^tm metal on metal total hip arthroplasty showed a high incidence of pseudotumors and an unexpected high revision rate in our thoroughly screened cross sectional cohort.

A large number of total hip arthroplasties (THA) are performed each year, of which 60 % use cementless femoral fixation. This means that the implant is press-fitted in the bone by hammer blows. The initial fixation is one of the most important factors for a long lasting fixation [Gheduzzi 2007]. It is not easy to obtain the point of optimal initial fixation, because excessively press-fitting the implant by the hammer blows can cause peak stresses resulting in femoral fracture. In order to reduce these peak stresses during reaming, IMT Integral Medizintechnik (Luzern, Switzerland) designed the Woodpecker, a pneumatic reaming device using a vibrating tool. This study explores the feasibility of using this Woodpecker for implant insertion and detection of optimal fixation by analyzing the vibrational response of the implant and Woodpecker. The press-fit of the implant is quantified by measuring the strain in the cortical bone surrounding the implant. An in vitro study is presented.

Two replica femur models (Sawbones Europe AB, Malmo Sweden) were used in this study. One of the femur models was instrumented with three rectangular strain gauge rosettes (Micro-Measurements, Raleigh, USA). The rosettes were placed medially, posteriorly and anteriorly on the proximal femur. Five paired implant insertions were performed on both bone models, alternating between standard hammer blow insertions and using the Woodpecker. The vibrational response was measured during the insertion process, at the implant and Woodpecker side using two shock accelerometers (PCB Piezotronics, Depew, NY, USA). The endpoint of insertion was defined as the point when the static strain stopped increasing.

Significant trends were observed in the bandpower feature that was calculated from the vibrational spectrum at the implant side during the Woodpecker insertion. The bandpower is defined as the percentage power of the spectrum in the band 0–1000 Hz. Peak stress values calculated from the strain measurement during the insertion showed to be significantly (p < 0.05) lower at two locations using the Woodpecker compared to the hammer blows at the same level of static strain. However, the final static strain at the endpoint of insertion was approximately a factor two lower using the Woodpecker compared to the hammer.

A decreasing trend was observed in the bandpower feature, followed by a stagnation. This point of stagnation was correlated with the stagnation of the periprosthetic stress in the bone measured by the strain gages. The behavior of this bandpower feature shows the possibility of using vibrational measurements during insertion to assess the endpoint of insertion. However it needs to be taken into account that it was not possible to reach the same level of static strain using the Woodpecker as with the hammer insertion. This could mean that either extra hammer blows or a more powerful pneumatic device could be needed for proper implant insertion.

Summary Statment

The dual-mobility cup seems to bring more stability without changing the gait pattern.

Introduction and Objective. A proper restoration of hip biomechanics is fundamental to achieve satisfactory outcomes after total hip arthroplasty (THA). A global hip offset (GO) postoperatively reduction of more than 5 mm was known to impair hip functionality after THA. This study aimed to verify the restoration of the GO radiographic parameter after primary THA by the use of a cementless femoral stem available in three different offset options without length changing. Materials and Methods. From a consecutive series of 201 patients (201 hips) underwent primary cementless THA in our centre with a minimum 3-year follow up, 80 patients (80 hips) were available for complete radiographic evaluation for GO and limb length (LL) and clinical evaluation with Harris hip score (HHS). All patients received the same femoral stem with three different offset options (option A with – 5 mm offset, option B and option C with + 5 mm offset, constant for each sizes) without changing stem length. Results. Mean GO significantly increased by + 3 mm (P < 0.05) and mean LL significantly decreased by + 5 mm (P < 0.05) after surgery, meaning that postoperatively the limb length of the operated side increased by + 5 mm. HHS significantly improved from 56.3 points preoperatively to 95.8 postoperatively (P < 0.001). Offset option A was used in 1 hip (1%), B in 59 hips (74%) and C in 20 hips (25%). Conclusions. The femur is lateralized with a mean of + 5mm after surgery than, the native anatomy, whatever type of stem was used. Thus, the use of this 3-offset options femoral stem is effective in restoring the native biomechanical hip parameters as GO, even if 2 offset options were considered sufficient to restore GO

Uncemented total hip arthroplasty (THA) implants have become the standard for younger patients on account of increased implant survivorship and multiple other advantages. Nevertheless, uncemented THA remains controversial in elderly patients. The evidence base for this is limited, as previous studies have compared octogenarians to a younger control group. The aim of this prospective cohort study is to evaluate the outcome of octogenarian patients undergoing uncemented THA with a control group of similarly aged patients undergoing hybrid THA with a minimum 5 years follow up. Clinical outcomes including intra and postoperative complications, blood transfusion, revision rate and mortality were recorded. Radiological analysis of pre and postoperative radiograph assessed bone quality, implant fixation and any subsequent loosening. 143 patients, (mean age 86.2 yrs.) were enrolled in the study. 76 patients underwent uncemented THA and 67 underwent hybrid THA. The uncemented cohort had fewer intraoperative and postoperative complications. The uncemented cohort also had a lower transfusion rate (p=0.002). Mean hospital stay (p=0.27) was comparable between the 2 groups. Two patients underwent revision surgery in either cohort. Our study demonstrates uncemented THA is safe for the octogenarian patient and we recommend that age should be not be a barrier of choice of implant. However intraoperative assessment of bone quality should guide surgeon to the optimum decision regarding uncemented and hybrid implant

SL-PLUS MIA stem (Smith & Nephew Orthopaedics AG) is a modified implant of Zweymuller type SL-PLUS standard stem (Smith & Nephew Orthopaedics AG). We constructed finite element (FE) models and analysed equivalent stresses in the femur. In addition, we measured bone mineral density (BMD) in the femur by dual-energy X-ray absorptiometry (DEXA) after THA. The purpose of this study was to investigate the equivalent stress and to compare the results of the FE analyses with changes in BMD after THA. Twenty-one patients (18 women and 3 men) who underwent primary cementless THA with SL-PLUS MIA or SL-PLUS formed the basis of this study. Eleven patients received SL-PLUS MIA and ten patients received SL-PLUS. Zones were defined according to Gruen's system (zones 1∼7). Computed-tomography (CT) images of the femur were taken before and at 1 week after THA. FE models of the femur and prosthesis were obtained from CT data by Mechanical Finder (Research Center of Computational Mechanics Inc., Tokyo, Japan), software that creates FE models showing individual bone shape and density distribution. Equivalent stresses were analysed in zones 1 to 7 and compared to the DEXA data. FE studies revealed that there was no significant difference in equivalent stress between SL-PLUS MIA and SL-PLUS. BMD was maintained after THA in zones 3, 4, and 5, whereas BMD decreased in zones 2, 6, and 7. In zone 1, BMD decreased in SL-PLUS MIA stem group by 14%, while BMD was maintained in SL-PLUS standard stem

Introduction. The purpose of this study was to evaluate the functional and radiographical mid-term follow-up results of a second generation metal-on-metal cementless total hip arthroplasty for the treatment of osteonecrosis of the femoral head in patients younger than 50 years. Methods. Twenty eight patients (35 hips) who underwent total hip arthroplasty with second generation metal-on-metal bearings for osteonecrosis of the femoral head at a minimum 5-year follow-up were included in this study. There were 5 women (6 hips) and 23 men (29 hips) who had a mean age of 40 years (range, 23 to 49 years) and a mean follow-up of 7 years. We used a Fitmore (Zimmer) cup and a 28mm Metasul femoral head in all cases. A CLS (Protek AG/Zimmer) femoral stem was used in 30 hips and a Cone prosthesis¯ (Protek AG) was used in 5 hips. Functional results were measured by Harris hip (HHS) and WOMAC scores. Radiographic evaluations were used to assess loosening and osteolysis according to Gruen and Delee and Charnley criteria. Results. The mean Harris hip score improved from 58 points (range, 35 to 67 points) pre-operatively to 92 points (range, 84 to 99 points) post-operatively, and the mean WOMAC score improved from 73 points (range, 63 to 89 points) to 30 points (range, 24 to 41 points). On radiological evaluation, all femoral and acetabular components were well-fixed without loosening or subsidence. Osteolysis was observed in 5 hips (14%) (acetabular osteolysis in 2 cases-Zone 2; 1, Zone 3; 1, femoral osteolysis in 3 cases- Zone 1; 2, Zone 7; 1). There were no complications including immediate post-operative deep infection, delayed infection, or recurrent dislocation. There was no case of revision for aseptic loosening. Conclusion. Second generation metal-on-metal cementless total hip arthroplasty for the treatment of osteonecrosis of the femoral head in patients younger than 50 years showed favorable functional and radiographic results

Ceramic-on-ceramic (CoC) total hip arthroplasty (THA) can produce articular noise during the normal activities, generating discomfort to the patient. THA noise has to be investigated also as a potential predictor and a clinical sign of prosthetic failure. An observational study has been carried out to characterize the noise in CoC cementless THA, and to analyze the related factors. A total of 46 patients with noisy hip have been enrolled in 38 months, within the follow-up protocol normally applied for the early diagnosis of ceramic liner fracture [1]. Noise recording was based on a high-quality audible recorder (mod. LS 3, Olympus, Japan) and a portable ultrasonic transducer (mod USB AE 1ch, PAC, USA). The sensors for noise recording were applied to the hip of the patient during a sequence of repeatable motorial activities (forward and backward walking, squat, sit in a chair, flexion and extension of the leg). Sessions were also video-recorded to associate the noise emission to the specific movements. Each noise event was initially identified by the operator and therefore classified by comparison to the spectral characteristics (duration, intensity and frequency) of the main noise types. Number and spectral characteristics of noise events were obtained and correlated to the factors describing the clinical status of the patient, the surgical approach, the prosthetic device implanted. The study investigated also the noise as a sign of implant failure, by comparison with the total number of implants failed in the cohort during the study. We observed three types of noise with the main spectral characteristics in agreement to the literature: clicking, squeaking and popping. Among the identified types of noise, squeaking showed the longest duration and the highest amplitude. The 63% of hip presented the emission of just one type of noise, while the remaining a mix of types. The movement with the highest presence of noise was walking, followed by squat. Correlation was found between the noise type and the dimension of the ceramic head (p<0.001), with the sizes of 32 mm more affected by squeaking that the smaller one. Squeaking appeared before during the follow-up than the other types of noise. The 35% (16/46) of the noisy hips were revised during the study. Among the revised hips, the 81% (13/16) were affected by impingement and/or severe damage of the prosthetic components. The antiversion of the cup (p=0.008), the presence of debris in the synovial fluid (p=0.021) and the average frequency of squeaking (p=0.006) were significant predictors for the revision, but it has to be mentioned that the squeaking data was obtained on a small subset of revised patients. Ultrasonic analysis did not show significant correlations. The study presented and validated an experimental procedure to analyze noisy hips in clinical trials. Noise is confirmed to be a significant parameter in the follow-up evaluation of ceramic THA

Dual mobility (DM) bearing implants reduce the incidence of dislocation following total hip arthroplasty (THA) and as such they are used for the treatment of hip instability in both primary and revision cases. The aim of this study was to compare lower limb muscle activity of patients who underwent a total hip arthroplasty (THA) with a dual mobility (DM) or a common cup (CC) bearing compared to healthy controls (CON) during a sit to stand task. A total of 21 patients (12 DM, 9 CC) and 12 CON were recruited from the local Hospital. The patients who volunteered for the study were randomly assigned to either a DM or a CC cementless THA after receiving informed consent. All surgeries were performed by the same surgeon using the direct anterior approach. Participants underwent electromyography (EMG) and motion analysis while completing a sit-to-stand task. Portable wireless surface EMG probes were placed on the vastus lateralis, rectus femoris, biceps femoris, semitendinosus (ST), gluteus medius and tensor fasciae latae muscles of the affected limb in the surgical groups and the dominant limb in the CON group. Motion capture was used to record lower limb kinematics and kinetics. Muscle strength was recorded using a hand-held dynamometer during maximal voluntary isometric contraction (MVIC) testing. Peak linear envelope (peakLE) and total muscle activity (iEMG) were extrapolated and normalized to the MVIC and time cycle for the sit to stand task. Using iEMG, quadriceps-hamstrings muscle co-activation index was calculated for the task. Nonparametric Kruskal Wallace ANOVA tests and Wilcoxon rank sum tests were used to identify where significant (p < 0.05) differences occurred. The DM group had greater iEMG of the ST muscle compared to the CC (p=0.045) and the CON (p=0.015) groups. The CC group had lower iEMG for hamstring muscles compared to the DM (p=0.041) group. The DM group showed lower quadriceps-hamstrings co-activation index compared to the CON group and it approached significance (p=0.054). The CC group had greater anterior pelvis tilt compared to both DM (p=0.043) and the CON (p=0.047) groups. The DM also had larger knee varus angles and less knee internal rotation compared to both groups, however this never reached significance. No significant differences in muscle strength existed between the groups. Higher ST muscle activity in the DM group is explained by the reduction in internal rotation at the knee joint as the ST muscle was more active to resist the varus forces during the sit-to-stand task. Reduced quadriceps activity in the CC group is explained by increased pelvic anterior tilt as this would shorten the moment arm and muscle length in the quadriceps, ultimately reducing quadriceps muscle activity. The reduced co-activation between quadriceps and hamstrings activity in the DM group compared to the CC and CON groups is related to better hip function and stability. Combining lower co-activation and larger range of motion for the DM group without impingement, this implant seems to offer better prevention against THA subluxation and less wear of the implant

Introduction. Ceramic-on-ceramic couplings are an attractive alternative bearing surface to eliminate or reduce problems related to polyethylene wear debris. Past disappointing experiences with alumina-ceramic bearings have led to many improvements in the manufacture and the design of ceramic implants. The purpose of this study was to report the results of contemporary alumina-on-alumina total hip arthroplasties (THAs) with regard to wear, osteolysis, and fracture of the ceramic in patients with osteonecrosis of the femoral head. Methods. Between February 1998 and October 2003, 365 patients (432 hips) with osteonecrosis of the femoral head underwent cementless total hip arthroplasty using contemporary alumina bearings. There were 243 men and 122 women who had a mean age at the time of index operation of 43 years (range, 18 to 65 years). They were evaluated clinically and radiographically at 5 to 10 years (average, 7 years). During the follow-up, special regards were addressed to wear, periprosthetic osteolysis and ceramic failure. Results. The mean Harris hip score was 94 points at the latest follow-up evaluation. All of the prostheses had radiographic evidence of a bone ingrowth. No implant was loosened radiographically and no implant was revised. Ceramic wear was not detectable in 83 hips where differentiation of the femoral head from the cup was possible on radiographs. Periprosthetic osteolysis was observed in no hips. Fracture of the alumina femoral head occurred in 5 hips, and fracture of the alumina liner occurred in 5 hips using sandwich-type ceramic liners. Conclusion. The results of contemporary alumina-on-alumina THAs with a metal-backed socket and a cementless stem were encouraging in young, active patients. We believe that these improved alumina-on-alumina bearing implants offer a promising option for younger active patients

Currently, there are no generally accepted treatments for the prevention of osteonecrosis. To compound this further, despite considerable research efforts, the natural history of this disease remains poorly understood. The disease process appears to be initially asymptomatic, but after symptoms appear, the course becomes rapidly progressive. Clinical studies have shown that, if left untreated, collapse of the femoral head will occur in 80 per cent of the cases or greater within four years. As our knowledge of the etiology and pathogenesis of osteonecrosis improves, new treatments to halt, or at least impede, the progression of the disease may be possible. Achieving the best outcomes in the treatment of osteonecrosis depends on early, accurate diagnosis, and prompt treatment appropriate for the stage of the disease. In many cases, if treated early, long-term preservation of the native joint is possible. Magnetic resonance imaging allows accurate diagnosis in even the earliest asymptomatic stages of the disease. Non-surgical treatments such as pharmacological agents have shown promise in experimental studies, although further work remains before they are appropriate for widespread use. Various hip salvaging procedures such as core decompression, percutaneous drilling, non-vascularized and vascularized bone grafting, and various osteotomies have been successful in the majority of properly selected patients over follow-up times of a decade or more. Advances in arthroplasty technologies and techniques, including hip resurfacing and modern cementless total hip arthroplasty have allowed patients to return to pain-free, active lifestyles with excellent long-term prosthesis survival. Current treatments for osteonecrosis, while generally successful, focus on halting or delaying the progression of symptomatic disease. Recent discoveries concerning the relationship between genetic factors and the development of osteonecrosis, as well as the pathophysiologic effects of various indirect and direct risk factors such as corticosteroid use and sickle cell disease, continue to improve our understanding of the underlying disease process. While these discoveries are promising, we must continue to work towards the goal of being able to identify and treat the precursors of osteonecrosis before it progresses to symptomatic disease and threatens the survival of native joints

We determined serum cobalt levels in 55 patients by atomic absorption spectrophotometry before and after implantation of uncemented total hip arthroplasties. In a randomised, prospective trial 27 wrought Co-28Cr-6Mo-0.2C metal-on-metal articulations were compared with 28 ceramic-on-polyethylene hips which did not contain cobalt. Other sources of iatrogenic cobalt loading were excluded. The metal-on-metal group produced detectable serum cobalt levels (median 1.1 μg/l after one year) which were significantly different (p < 0.0001) from those of the ceramic-on-polyethylene control group (median below detection limit of 0.3 μg/l after one year). Our findings indicate that metal-on-metal bearings generate some systemic release of cobalt

In uncemented total hip arthroplasty (THA), the optimal femoral component should allow both maximum cortical contact with proximal load transfer and accurate restoration of individual joint biomechanics. This is often compromised due to a high variability in proximal femoral anatomy. The aim of this on-going study is to assess the variation in proximal femoral canal shape and its association with geometric and anthropometric parameters in primary hip OA. In a retrospective cohort study, AP-pelvis radiographs of 98 consecutive patients (42 males, 56 females, mean age 61 (range:45-74) years, BMI 27.4 (range:20.3-44.6) kg/m2) who underwent THA for primary hip OA were reviewed. All radiographs were calibrated and femoral offset (FO) and neck-shaft-angle (NSA) were measured using a validated custom programme. Point-based active shape modelling (ASM) was performed to assess the shape of the inner cortex of the proximal femoral meta- and diaphysis. Independent shape modes were identified using principal component analysis (PCA). Hierarchical cluster analysis of the shape modes was performed to identify natural groupings of patients. Differences in geometric measures of the proximal femur (FO, NSA) and demographic parameters (age, height, weight, BMI) between the clusters were evaluated using Kruskal-Wallis one-way-ANOVA or Chi-square tests, as appropriate. In the entire cohort, mean FO was 39.0 mm, mean NSA was 131 degrees. PCA identified 10 independent shape modes accounting for over 90% of variation in proximal femoral canal shape within the dataset. Cluster Analysis revealed 6 shape clusters for which all 10 shape modes demonstrated a significantly different distribution (p-range:0.000-0.015). We observed significant differences in age (p=0.032), FO (p<0.001) and NSA (p<0.001) between the clusters. No significant differences with regard to gender or BMI were seen. Our preliminary analysis has identified 6 different patterns of proximal femoral canal shape which are associated with significant differences in femoral offset, neck-shaft-angle and age at time of surgery. We are currently evaluating the entire dataset of 345 patients which will allow a comprehensive classification of variation in proximal femoral shape and joint geometry. The present data may optimise preoperative planning and improve future implant design in THA

The reduced stability of hydroxyapatite (HA)-coated implants in osteopenic conditions is considered to be a major problem. We therefore developed a model of a boosted cementless implantation in osteopenic rats.

Twelve-week-old rats were either ovariectomised (OVX) or sham-operated (SO), and after 24 weeks plain or HA-coated implants were inserted. They were treated with either a prostaglandin EP4 receptor agonist (ONO-4819) or saline for one month.

The EP4 agonist considerably improved the osteoporosis in the OVX group. Ultrastructural analysis and mechanical testing showed an improvement in the implant-bone attachment in the HA-coated implants, which was further enhanced by the EP4 agonist. Although the stability of the HA-coated implants in the saline-treated OVX rats was less than in the SO normal rats, the administration of the EP4 agonist significantly compensated for this shortage. Our results showed that the osteogenic effect of the EP4 agonist augmented the osteoconductivity of HA and significantly improved the stability of the implant-bone attachment in the osteoporotic rat model.