Femoral stem fixation. An engineering interpretation of the long-term outcome of Charnley and Exeter stems

Multi-center study of use of the Exeter stem in Japan: a 10-year follow-up report

PURPOSE

Since the introduction of the Exeter stem for clinical use in Japan in 1996, the number of stems used has continued to rise owing to its favorable results. We investigated the outcomes of patients who had previously undergone total hip arthroplasty with the Exeter stem in Japan with a 10-year + follow-up period.

METHODS

This retrospective cohort study used clinical and radiographic data of 682 cases of primary total hip arthroplasty performed using the Exeter stem.

RESULTS

The mean postoperative follow-up period was 13.3 years. Femoral-side revision was required in 14 hips, with no cases of aseptic stem loosening-associated revision observed. Kaplan-Meier survival analysis predicted 97.3% 15-year survival when revision for any reason was used as the endpoint.

CONCLUSION

The obtained findings suggested the excellent long-term stability of the Exeter stem for primary total hip arthroplasty in Japan.

Experimental periprosthetic fractures with collarless polished tapered cemented stems

PURPOSE

After cemented total hip arthroplasty, the risk of periprosthetic fracture (PPF) of taper-slip stems is higher than that of composite-beam stems. We aimed to assess the conditions resulting in PPFs of taper-slip stems using a falling weight.

METHODS

Taper-slip stems were fixed to five types of simulated bone models using bone cement, and the fractures were evaluated by dropping stainless-steel weights from a predetermined height onto the heads. The periprosthetic fracture height in 50% of the bone models (PPFH50) was calculated using the staircase method.

RESULTS

For the fixation with 0° of flexion, the values for PPFH50 were 61 ± 11, 60 ± 13, above 110, 108 ± 49, and 78 ± 12 cm for the cobalt-chromium-molybdenum alloy, stainless steel alloy (SUS), titanium alloy (Ti), smooth surface, and thick cement mantle models, respectively; for the fixation with 10° of flexion (considering flexure), the PPFH50 values were 77 ± 5, 85 ± 9, 90 ± 2, 89 ± 5, and 81 ± 11 cm, respectively. The fracture rates of the polished-surface stems were 78.6 and 35.7% at the proximal and distal sites, respectively (p < 0.05); the fracture rates of the smooth-surface stems were 14.2 and 100%, respectively (p < 0.05).

CONCLUSION

The impact tests demonstrated that the conditions that were less likely to cause PPFs were use of Ti, a smooth surface, a thick cement mantle, and probably, use of SUS.

A 2-year prospective clinical and bone density evaluation, with a subset undergoing radiostereometric analysis, using the Absolut cemented stem

Background

Total hip arthroplasty (THA) is common though the investigation of new prostheses requires a practical, step‐wise introduction. This study reports the 2‐year clinical results and periprosthetic bone mineral density (BMD) changes, along with a subset undergoing Radiostereometric analysis (RSA), in patients undergoing primary cemented THA using a new highly polished, double tapered, collarless femoral stem (Absolut).

Methods

Between August 2013 and December 2016, 47 patients with a mean age of 74.2 years (range 36–89) underwent 51 THAs with the Absolut. All patients underwent clinical assessment pre‐surgery and at 6 weeks, 3, 12 and 24 months using the Oxford and Harris Hip Scores, as well as Dual Energy X‐ray Absorptiometry (DEXA) to assess BMD within 2–4 weeks post‐surgery, 12 and 24 months. RSA was undertaken in a patient subset (the first n = 30) early post‐surgery (1–2 days) and 3, 12 and 24 months.

Results

All clinical scores significantly improved (p < 0.05). RSA revealed a mean subsidence of 0.78 mm at 3 months, 1.23 mm at 12 months and 1.51 mm at 24 months. Anterior–posterior and medial‐lateral translation was negligible. A significant increase (p = 0.020) in BMD was observed in Gruen zone 1, though no significant changes were observed for any other zone up until 2 years. Two patients acquired an early post‐operative deep vein thrombosis that were treated accordingly and resolved, with no further complications or re‐operations.

Conclusion

The Absolut cemented femoral stem demonstrated good outcomes, BMD changes consistent with sound prosthesis integration and patterns of post‐operative micromotion observed in other successful cemented stems.

Relationship between the Surface Roughness of Material and Bone Cement: An Increased "Polished" Stem May Result in the Excessive Taper-Slip

Although some reports suggest that taper-slip cemented stems may be associated with a higher periprosthetic femoral fractures rate than composite-beam cemented stems, few studies have focused on the biomaterial effect of the polished material on the stem–cement interface. The purpose of this study was to investigate the relationship between surface roughness of materials and bone cement. Four types of metal discs—cobalt-chromium-molybdenum alloy (CoCr), stainless steel alloy 316 (SUS), and two titanium alloys (Ti-6Al-4V and Ti-15Mo-5Zr-3Al)—were prepared. Five discs of each material were produced with varying degrees of surface roughness. In order to evaluate surface wettability, the contact angle was measured using the sessile drop method. A pin was made using two bone cements and the frictional coefficient was assessed with a pin-on-disc test. The contact angle of each metal increased with decreasing surface roughness and the surface wettability of metal decreased with higher degrees of polishing. With a surface roughness of Ra = 0.06 μm and moderate viscosity bone cement, the frictional coefficient was significantly lower in CoCr than in SUS (p = 0.0073). In CoCr, the low adhesion effect with low frictional coefficient may result in excessive taper-slip, especially with the use of moderate viscosity bone cement.

Risk factors influencing fracture characteristics in postoperative periprosthetic femoral fractures around cemented stems in total hip arthroplasty : a multicentre observational cohort study on 584 fractures

Aims

This study evaluates risk factors influencing fracture characteristics for postoperative periprosthetic femoral fractures (PFFs) around cemented stems in total hip arthroplasty.

Methods

Data were collected for PFF patients admitted to eight UK centres between 25 May 2006 and 1 March 2020. Radiographs were assessed for Unified Classification System (UCS) grade and AO/OTA type. Statistical comparisons investigated relationships by age, gender, and stem fixation philosophy (polished taper-slip (PTS) vs composite beam (CB)). The effect of multiple variables was estimated using multinomial logistic regression to estimate odds ratios (ORs) with 95% confidence intervals (CIs). Surgical treatment (revision vs fixation) was compared by UCS grade and AO/OTA type.

Results

A total of 584 cases were included. Median age was 79.1 years (interquartile range 72.0 to 86.0), 312 (53.6%) patients were female, and 495 (85.1%) stems were PTS. The commonest UCS grade was type B1 (278, 47.6%). The most common AO/OTA type was spiral (352, 60.3%). Metaphyseal split fractures occurred only with PTS stems with an incidence of 10.1%. Male sex was associated with a five-fold reduction in odds of a type C fracture (OR 0.22 (95% CI 0.12 to 0.41); p < 0.001) compared to a type B fracture. CB stems were associated with significantly increased odds of transverse fracture (OR 9.51 (95% CI 3.72 to 24.34); p < 0.001) and wedge fracture (OR 3.72 (95% CI 1.16 to 11.95); p = 0.027) compared to PTS stems. Both UCS grade and AO/OTA type differed significantly (p < 0.001 and p = 0.001, respectively) between the revision and fixation groups but a similar proportion of B1 fractures underwent revision compared to fixation (45.3% vs 50.6%).

Conclusion

The commonest fracture types are B1 and spiral fractures. PTS stems are exclusively associated with metaphyseal split fractures, but their incidence is low. Males have lower odds of UCS grade C fractures compared to females. CB stems have higher odds of bending type fractures (transverse and wedge) compared to PTS stems. There is considerable variation in practice when treating B1 fractures around cemented stems.

Cite this article: Bone Jt Open 2021;2(7):466–475.

Temporal subsidence patterns of cemented polished taper-slip stems: a systematic review

The literature was reviewed to establish the levels of stem subsidence for both double and triple-tapered implants in order to determine whether there were any differences in subsidence levels with regard to the methods of measurement, the magnitude and rate of subsidence and clinical outcomes.

All studies reporting subsidence of polished taper-slip stems were identified. Patient demographics, implant design, radiological findings, details of surgical technique, methods of measurement and levels of subsidence were collected to investigate which factors were related to increased subsidence.

Following application of inclusion and exclusion criteria, 28 papers of relevance were identified. The studies initially recruited 3090 hips with 2099 being available for radiological analysis at final follow-up. Patient age averaged 68 years (42–70), 60.4% were female and the average body mass index (BMI) was 27.4 kg/m² (24.1–29.2).

Mean subsidence at one, two, five and 10 years was 0.97 mm, 1.07 mm, 1.47 mm and 1.61 mm respectively. Although double-tapered stems subsided more than triple-tapered stems at all time points this was not statistically significant (p > 0.05), nor was the method of measurement used (p > 0.05).

We report the levels of subsidence at which clinical outcomes and survivorship remain excellent, but based on the literature it was not possible to determine a threshold of subsidence beyond which failure was more likely.

There were relatively few studies of triple-tapered stems, but given that there were no statistically significant differences, the levels presented in this review can be applied to both double and triple-tapered designs.

Cite this article: EFORT Open Rev 2021;6:331-342. DOI: 10.1302/2058-5241.6.200086

The influence of migration of the exeter V40 stem on patient reported outcome measures: a 2-year follow-up of 112 total hip arthroplasties using radiostereometric analysis

PURPOSE

The cemented Exeter V40 stem is known to migrate distally. Several previous studies have reported on the extent of stem migration and its influence on clinical outcome. However, no studies have investigated the influence of stem migration on Patient Reported Outcome Measures (PROM).

METHODS

One hundred and twelve total hip arthroplasties (THA) were included in a 2-year follow-up using Radiostereometric Analysis (RSA). Patients were evaluated using the Oxford Hip Score (OHS) and EQ-5D-3L PROMs. The purpose of this study was to assess the influence of stem migration, measured by Maximum Total Point Motion (MTPM), on the 2-year postoperative score (OHS and EQ-5D). Furthermore, the influence of pre-operative PROM, age, gender, acetabular component and BMI was associated with the 2-year postoperative OHS and EQ-5D scores.

RESULTS

MTPM was a non-significant predictor of the 2-year postoperative OHS (regression coefficient (B) = - 2.38 (CI - 5.44; .69)) and of the 2-year postoperative EQ-5D (B = - .01 (CI - .04; .02)). The only significant predictor of the 2-year postoperative OHS and 2-year postoperative EQ-5D was gender (B = 8.71 (CI 3.52; 13.90)) and (B = .13 (CI .07; .18)), respectively.

CONCLUSION

Stem migration did not significantly influence PROMs at 2 years post-operatively. Using a patient-focused approach, our results seem to corroborate results reported by previous studies, showing that slow migration of the Exeter V40 stem does not seem to influence the clinical outcome.

Femoral Stem Cementation in Hip Arthroplasty: The Know-How of a "Lost" Art

PURPOSE OF REVIEW

To describe the (1) indications, (2) preoperative precautions, and (3) stepwise technical details of modern femoral stem cemented fixation.

RECENT FINDINGS

Femoral stem cementation provides excellent implant longevity with a low periprosthetic fracture rate among patients with compromised bone quality or aberrant anatomy. Unfamiliarity with the details of modern cementation techniques among trainees who may lack frequent exposure to cementing femoral stems may preclude them from offering this viable option to suitable patients in later stages of their careers. As such, maximizing benefit from cemented femoral stem fixation among suitable candidates is contingent upon the meticulous use of modern cementation techniques. In addition to proper patient selection, modern cementation techniques emphasize the use of (1) pulsatile lavage of the femoral canal, (2) utilization of epinephrine-soaked swabs, (3) vacuum cement mixing, (4) retrograde cement introduction, (5) cement pressurization, and (6) the use of stem centralizers. Furthermore, identifying and optimizing the preoperative status of at-risk patients with pre-existing cardiopulmonary compromise, in addition to intraoperative vigilance, are essential for mitigating the risk of developing bone cement implantation syndrome. Further research is required to assess the utility of cemented femoral stem fixation among younger patients.

Periprosthetic fractures of the proximal femur: beyond the Vancouver classification

The majority of periprosthetic femoral fractures are treated surgically.

Surgical treatment may be revision only, revision in combination with open reduction and internal fixation (ORIF), or ORIF only.

The treatment decision is dependent on whether the stem is loose or not, but loose stems are not always identified, resulting in unsatisfactory treatments.

This article presents an algorithmic approach to identifying loose stems around proximal femoral periprosthetic fractures, taking patient history, stem design, and plain radiographs into consideration. This approach may help identifying loose stems and increase the probability of effective treatments.

Cite this article: EFORT Open Rev 2020;5:449-456. DOI: 10.1302/2058-5241.5.190086

Current concepts and outcomes in cemented femoral stem design and cementation techniques: the argument for a new classification system

Cemented implant fixation design principles have evolved since the 1950s, and various femoral stem designs are currently in use to provide a stable construct between the implant-cement and cement-bone interfaces.Cemented stems have classically been classified into two broad categories: taper slip or force closed, and composite beams or shaped closed designs. While these simplifications are acceptable general categories, there are other important surgical details that need to be taken into consideration such as different broaching techniques, cementing techniques and mantle thickness.With the evolution of cemented implants, the introduction of newer implants which have hybrid properties, and the use of different broaching techniques, the classification of a very heterogenous group of implants into simple binary categories becomes increasingly difficult. A more comprehensive classification system would aid in comparison of results and better understanding of the implants' biomechanics.We review these differing stem designs, their respective cementing techniques and geometries. We then propose a simple four-part classification system and summarize the long-term outcomes and international registry data for each respective type of cemented prosthesis. Cite this article: EFORT Open Rev 2020;5:241-252. DOI: 10.1302/2058-5241.5.190034.

The effects of patient characteristics and stem alignment on distal femoral cortical hypertrophy after cemented polished tapered stem implantation

BACKGROUND

The objective of this study was to evaluate the results of over 10 years of total hip arthroplasty (THA) practice with Exeter^TM stems and the clinical relevance of distal femoral cortical hypertrophy (DFCH).

METHODS

We retrospectively reviewed 127 hips (120 patients) that had undergone THA with Exeter^TM stems between 2004 and 2007. Kaplan-Meier survival analyses for the stem of all 127 hips were performed using different endpoints. Of 127 hips, 100 (94 patients) had complete 10-year follow-up data, including the Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ) as the patient-reported outcomes, and the clinical relevance of DFCH was analyzed using multivariable logistic regression analysis.

RESULTS

The survival of the stem with the endpoint of re-operation for loosening, > 5-mm subsidence, and re-operation for any reason were 100%, 99.1% (95% CI 97.5-100%), and 98.3% (95% CI 96.0-100%), respectively. Of 100 hips followed completely for 10 years, DFCH occurred in 20 hips (20%). The satisfaction and pain visual analog scale of JHEQ revealed high satisfaction and less pain in patients with DFCH. By multivariate logistic regression analysis, body weight > 55 kg (odds ratio: 2.88, p = 0.035) and varus stem alignment (odds ratio: 6.56, p = 0.003) were found to be predictors for DFCH.

CONCLUSIONS

The incidence of DFCH with the Exeter^TM stem was 20%. A body weight > 55 kg and varus stem alignment are predictors for future DFCH. DFCH with the Exeter^TM stem indicates a good outcome with less hip pain.

Prospective, comparative study of cemented, smooth-surfaced titanium stems and polish-surfaced, stainless steel stems at a minimum follow-up of 10 years

BACKGROUND

Excellent results have been reported with cemented total hip arthroplasty (THA) using both smooth-surfaced and polished-surfaced stems. However, the superiority of polished-surfaced over smooth-surfaced in cemented THA, or vice versa, is still debated.

MATERIALS AND METHODS

Forty-six smooth-surfaced, triple-tapered, titanium-alloy stem (Group C) and 46 Exeter stems (Group T) have been fixed consecutively at different periods at our institute and prospectively evaluated clinically and radiologically. The area and location demonstrating cortical hypertrophy (CH) was measured in the serial radiograph and compared.

RESULTS

The mean postoperative follow-up period was 12.4 years for group C and 10.8 years for group T. No significant difference of clinical results was found between both groups. CH was observed in 8 hips (18.6%) of group C and in 7 hips (17.1%) of group T (NS). Among the hips in which distribution of CH was observed at the medial side, a significantly low proportion belonged to group C (adjusted standardized residual = - 2.3) and a significantly high proportion belonged to group T (adjusted standardized residual = 2.3). The largest area of CH found in each group was 166.1 mm² in group C and 227.6 mm² in group T (NS). The peak location of CH was 100.4% in group C and 84.3% in group T (p = 0.02).

CONCLUSION

Medium-term results of both stems were excellent. CH was observed medially and proximally in group T and laterally and distally in group C.

Peri-prosthetic bone remodeling and change in bone mineral density in the femur after cemented polished tapered stem implantation

OBJECTIVE

We examined longitudinal changes in bone mineral density (BMD) around the femur for 5 years after total hip arthroplasty (THA) using cemented collarless polished double-tapered stem implantation and investigated the influence of BMD changes on radiological remodeling of the femur.

MATERIALS AND METHODS

Sixty hips from 56 patients who underwent cemented THA with a collarless polished double-tapered stem were included. BMD was measured 2 weeks postoperatively (baseline), 3 months, 6 months, 1 year and annually thereafter until 5 years after surgery using dual-energy X-ray absorptiometry on the lumbar spine and proximal femur of the operated side according to the Gruen's zone classification. We analyzed predictable factors for BMD preservation in the proximal femur and compared radiological remodeling of the femur and changes in BMD.

RESULTS

BMD at 5 years in zone 7 decreased less than 10%, whereas BMD in zone 1 increased to over the baseline (+ 1.9%). Multiple linear regression analyses revealed that body weight was a predictor for positive BMD change in the proximal femur. The frequency of radiolucency of the femur was significantly lower in patients who exhibited an increase in BMD at 5 years compared with BMD at 2 weeks in zone 7.

CONCLUSION

BMD preservation of the proximal femur after cemented collarless polished double-tapered stem implantation was more effective in heavier patients. Furthermore, the frequency of radiolucency around the stem was significantly lower in patients who exceeded 100% of the baseline BMD in zone 7 at 5 years.

Biomechanical behaviour of a French femoral component with thin cement mantle: The 'French paradox' may not be a paradox after all

Objective

Cement thickness of at least 2 mm is generally associated with more favorable results for the femoral component in cemented hip arthroplasty. However, French-designed stems have shown favorable outcomes even with thin cement mantle. The biomechanical behaviors of a French stem, Charnley-Marcel-Kerboull (CMK) and cement were researched in this study.

Methods

Six polished CMK stems were implanted into a composite femur, and one million times dynamic loading tests were performed. Stem subsidence and the compressive force at the bone-cement interface were measured. Tantalum ball (ball) migration in the cement was analyzed by micro CT

Results

The cement thickness of 95 % of the proximal and middle region was less than 2.5 mm. A small amount of stem subsidence was observed even with collar contact. The greatest compressive force was observed at the proximal medial region and significant positive correlation was observed between stem subsidence and compressive force. 9 of 11 balls in the medial region moved to the horizontal direction more than that of the perpendicular direction. The amount of ball movement distance in the perpendicular direction was 59 to 83% of the stem subsidence, which was thought to be slip in the cement of the stem. No cement defect and no cement breakage were seen.

Conclusion

Thin cement in CMK stems produced effective hoop stress without excessive stem and cement subsidence. Polished CMK stem may work like force-closed fixation in short-term experiment.

Cite this article: Y. Numata, A. Kaneuji, L. Kerboull, E. Takahashi, T. Ichiseki, K. Fukui, J. Tsujioka, N. Kawahara. Biomechanical behaviour of a French femoral component with thin cement mantle: The ‘French paradox’ may not be a paradox after all. Bone Joint Res 2018;7:485–493. DOI: 10.1302/2046-3758.77.BJR-2017-0288.R2.

The Exeter Trauma Stem: A radiographic follow-up at minimum of five years post implantation

INTRODUCTION

The Exeter Trauma Stem (ETS) has been recommended by National Institute of Clinical Excellence (NICE) guidelines in the United Kingdom as a proven, cemented stem. A single laboratory study in the literature has raised possible concerns about the polished finish of the ETS and subsequent potential for accelerated loosening although there is little clinical evidence to support or refute this.

METHODS

The aim of this study was to assess clinical outcomes of the ETS at a minimum of five years post implantation. Primary outcomes were radiological loosening at a minimum of five years along with survivorship of the implant. Patient demographics were prospectively collected and followed up.

RESULTS

218 ETS's (in 214 patients) were implanted from June 2002 until August 2008 in a single centre by a wide variety of surgeons of differing grades. Of these, 16 underwent revision surgery for fracture (2), dislocation (3), infection (1) and acetabular erosion (10) but there were no revisions for aseptic loosening of the implant. There were 64.0% (137/214) patients that had died by the time of this study. Of the remaining patients, 90 had radiographs of their hips at a minimum of 5 years with 36 of these at a minimum of 7 years post implantation. None of these had evidence of loosening.

CONCLUSION

The ETS is a robust and suitable stem for implantation in patients with hip fractures. There are no clinical suspicions or increased rates of loosening with the ETS in our study. The concerns about surface finish are not borne out in our clinical study which shows no evidence of loosening at a minimum of five years post operation. It confers many advantages including ease of revision and it should continue to be used as per NICE guidelines.

Quantitating the effect of prosthesis design on femoral remodeling using high-resolution region-free densitometric analysis (DXA-RFA)

Dual energy X-ray absorptiometry (DXA) is the reference standard method used to study bone mineral density (BMD) after total hip arthroplasty (THA). However, the subtle, spatially complex changes in bone mass due to strain-adaptive bone remodeling relevant to different prosthesis designs are not readily resolved using conventional DXA analysis. DXA region free analysis (DXA RFA) is a novel computational image analysis technique that provides a high-resolution quantitation of periprosthetic BMD. Here, we applied the technique to quantitate the magnitude and areal size of periprosthetic BMD changes using scans acquired during two previous randomized clinical trials (2004 to 2009); one comparing three cemented prosthesis design geometries, and the other comparing a hip resurfacing versus a conventional cementless prosthesis. DXA RFA resolved subtle differences in magnitude and area of bone remodeling between prosthesis designs not previously identified in conventional DXA analyses. A mean bone loss of 10.3%, 12.1%, and 11.1% occurred for the three cemented prostheses within a bone area fraction of 14.8%, 14.4%, and 6.2%, mostly within the lesser trochanter (p < 0.001). For the cementless prosthesis, a diffuse pattern of bone loss (-14.3%) was observed at the shaft of femur in a small area fraction of 0.6% versus no significant bone loss for the hip resurfacing prosthesis (p < 0.001). BMD increases were observed consistently at the greater trochanter for all prostheses except the hip-resurfacing prosthesis, where BMD increase was widespread across the metaphysis (p < 0.001). DXA RFA provides high-resolution insights into the effect of prosthesis design on the local strain environment in bone. © 2017 The Authors Journal of Orthopaedic Research published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 35:2203-2210, 2017.

Excellent mid-term results of a new polished tapered modular cemented stem: a study of 113 hip replacements with minimum 5-year follow-up

BACKGROUND

This prospective cohort study reports the medium-term clinical and radiographic results of 113 hips treated with a hybrid total hip replacement (THR) with a new cemented tapered cobalt-chrome (Co-Cr) stem with a titanium (Ti) modular neck (ProfemurXm®).

METHOD

Between October 2008 and December 2010 we performed 115 consecutive hybrid THR with the ProfemurXm® in 105 patients.

RESULTS

Survivorship of the implant (stem and modular neck) at a mean of 6.5 years (min 5-max 8) was 100% with the endpoint revision for any reason. No implant was at risk for revision or showed signs of loosening. The mean Harris Hip Score was 89/100, mean Oxford Hip Score was 43/48, mean WOMAC was 91/100. No patient had thigh pain, no patient reported squeaking. There were no dislocations in this cohort. No implant showed development of radiolucent lines (RLL), either at the stem-cement or cement-bone interface. No hip showed osteolysis or calcar resorption. The mean femoral subsidence of the stem within the cement mantel was 0.31 mm (range 0-0.6 mm) after 6.5 years. With the use of this modular stem, 93% of hips showed no measurable leg length difference after THR, and leg length could be restored within a 5-mm limit in 99% of hips.

CONCLUSIONS

The mid-term results of this new polished stem were excellent, without adverse effects from the use of modularity.

Intraoperative blood pressure changes during cemented versus uncemented bipolar hemiarthroplasty for displaced femoral neck fracture: a multi-center cohort study : The effect of bone cement for bipolar hemiarthroplasty in elderly patients

INTRODUCTION

The purpose of this study was to compare the cemented bipolar hemiarthroplasty with uncemented about the change of intraoperative blood pressure and the incidence of major complications in elderly patients with femoral neck fracture.

MATERIALS AND METHODS

This multiple center prospective cohort study included only patients with acute displaced femoral neck fracture (Garden stage III or IV). All patients were treated with cemented or uncemented bipolar hemiarthroplasty using modified Hardinge or Watson-Jones approach in the lateral decubitus position. Baseline data, medical history, type of anesthesia, FiO₂ value, the number of vasopressor using during operation, femoral component, intraoperative blood pressure, SaO₂, and major complications were evaluated.

RESULTS

Of 164 patients (45 males and 119 females), 86 underwent cemented and 78 underwent uncemented bipolar hemiarthroplasty. Baseline medical histories were similar in both groups. In both the cemented and uncemented groups, intraoperative systolic blood pressure significantly decreased during cementing or rasping (106.3 and 103.6 mmHg) and after femoral component insertion (103.3 and 99.1 mmHg) compared to before rasping (120.7 and 116.4 mmHg) (p < 0.0001, respectively). Donaldson's grade seemed more favorable in uncemented group than in cemented group during cementing or rasping, during stem insertion; however, no patients experienced the lethal complication in both groups.

CONCLUSIONS

Intraoperative blood pressure did not change during cemented and uncemented bipolar hemiarthrplasty for displaced femoral neck fracture. If the standard modern cement technique was performed during operation, bone cement is a safe and acceptable for elderly patients who have a lot of medical histories.

Principles of managing Vancouver type B periprosthetic fractures around cemented polished tapered femoral stems

The management of periprosthetic fractures around total hip replacements is a complex and challenging problem. Getting it right first time is an important factor in reducing the morbidity, mortality and financial burden associated with these injuries. Understanding and applying the basic principles of fracture management helps increase the chance of successful treatment. Based on these principles, we suggest a treatment algorithm for managing periprosthetic fractures around polished tapered femoral stems.

The effect of isotonic saline on the strength of bone cement during the polymerisation period

It is common practice to irrigate the wound in hip and knee replacement surgery during the working and setting phases of cement polymerisation. We sought to establish whether the addition of normal saline during the various stages of polymerisation would affect bone cement strength. Cement specimens were moulded to the dimensions defined in ISO 5833: 2002 and tested in an electro-mechanical test machine with a calibrated 50 kN load cell at a compression rate of 24 mm/min. The results suggest that the compressive strength of bone cement is not affected by the presence of saline following the initiation of polymerisation. However, saline added to the mix prior to the initiation of polymerisation increased its porosity and significantly decreased its strength. This may explain why vacuum mixing is important as it removes water vapour.

Effect of removal and reinsertion of force-closed stems on deformation of total hip arthroplasty

Objectives

This study investigated removal of a force-closed stem, done in order to improve acetabular exposure during revision, with reinsertion afterwards. It is unknown how much this procedure modifies the stem/cement interface.

Methods

Three tapered stem models were implanted into composite femurs. Strain gauges were embedded in the medial aspect of the cement mantle and in several positions on the outer surface of the femurs. The deformation was measured during static loading, which was applied at two different times: after implantation and after one million loading cycles, followed by stem removal and reinsertion. The t test was performed. The differences in deformation were compared (at p ≤ 0.05) between the two static loading times and among the three stem designs.

Results

No significant differences in deformation were found after the two loading times for the three models. No significant differences in the initial deformations of the three models were found for most of the gauges attached to the femurs.

Conclusions

Reinsertion of the force-closed stem does not alter the load transmission from the stem to the cement and to the surface of the femur, even after one million loading cycles.

A Cannulated Tri-Tapered Femoral Stem for Total Hip Arthroplasty: Clinical and Radiological Results at Ten Years

We report the ten-year clinical and radiological outcomes of a novel cannulated, tri-tapered femoral stem, used in primary total hip arthroplasty (110 stems in 98 patients). At ten years, two Tri-taper stems had been revised for infection and dislocation. The mean Oxford Hip Score improved from 13.46 pre-operatively, to 37.04. Radiological analysis revealed radiolucent lines in 57 cases, but none exceeded 2 mm thickness. Stem subsidence was identified in 63 cases, with mean distal tip migration of 3.8 mm. Survivorship with revision for aseptic loosening as the end point was 100% at 10 years. Stem survival with revision for any cause was 98.2% (95% CI, 92.9% to 99.5%). The ten-year results of the Tri-taper stem are comparable to other polished, tapered femoral stems.

Periprosthetic fractures around polished collarless cemented stems: the effect of stem design on fracture pattern

BACKGROUND

Predictable patterns of periprosthetic fracture have been observed around polished double tapered stems. Finite element studies have suggested that triple-tapered stems cause less cement strain in torsion compared to double-tapered stems. Hence, we hypothesised that the in vitro behaviour of implanted double- and triple-tapered polished stems, like the CPT (Zimmer, Warsaw, USA) or C-Stem (DePuy, Leeds, U.K.) when subjected to pathological torsional loads may cause different patterns of periprosthetic fractures.

METHODS

Ten double-tapered stems (CPT) and ten triple-tapered stems (C-Stem) were cemented into synthetic femur bones. A constant axial compression load of 100 N and a torsional pre-load of 0.1 N.m were applied using a biaxial testing machine. The distal femur was then loaded in external rotation at 45 degrees until failure.

RESULTS

Seven of the 10 CPT stems fractured at the level of the stem body while fracturing the cement mantle at the same level. In three of ten of the CPT stems and all ten C-Stems, the synthetic bone fractured at the tip of the prosthesis while the cement mantle remained intact. This was significant for the resulting fracture pattern (P=0.001). There was no significant difference between the groups for either torque (P=0.13) or angle at failure (P=0.49).

INTERPRETATION

This biomechanical study indicates that the CPT and C-Stem create a different fracture pattern under the same loading condition. The C-Stem (a triple tapered stem) may produce lower strain in torsion to the cement mantle of a cemented THA. However, fractures that do occur may be more difficult to treat than those produced around a stem like the CPT subjected to comparable loading.

Cement in cement revision of the femoral component using a collarless triple taper: a midterm clinical and radiographic assessment

This study describes the midterm clinical and radiological results of the cement in cement technique for the femur using a collarless triple taper. Radiographic assessment was made retrospectively from 44 patients at two time points. Clinical outcomes included the Oxford Hip Score, EQ5D and Self Reported Patient Satisfaction Scale. Implant and patient survival were also recorded. The mean clinical follow up period was 5years 3months and the radiological follow up 2years 10months. The mean OHS was 34, the mean EQ5D 0.814 and the mean SAPS 94. Kaplan-Meier survival with revision, as the end point was 95.2% at 11years with a survivorship of 76.5% with death as the end point. Cement in cement revision using a collarless triple tapered stem demonstrates promising results both clinically and radiologically at midterm follow up.

A 5-8 year retrospective follow-up of the C-stem AMT femoral component: patient reported outcomes and survivorship analysis

We report midterm functional, radiographic and survivorship data for the cemented, triple taper C-stem AMT femoral component from a consecutive cohort of 415 hip arthroplasties in 386 patients at a non-developer centre. Follow-up ranges were from 60 to 99 months, with a mean of 76 months. 32 hips were lost to follow-up. The median OHS was 40, median SF-12 mental component score (MCS) was 50, and median SF-12 physical component score (PCS) was 39. At 99 months follow up, stem survivorship is 96.9% (95% confidence interval (CI) 82.5-99.5), and construct survivorship is 96.0% (95% CI 84.2-99.0). Adverse events such as calcar fracture, greater trochanter fracture and dislocation were rare at <1%. There have been no revisions for aseptic loosening.

The effect of a collar and surface finish on cemented femoral stems: a prospective randomised trial of four stem designs

PURPOSE

The optimal design for a cemented femoral stem remains a matter of debate. Over time, the shape, surface finish and collar have all been modified in various ways. A clear consensus has not yet emerged regarding the relative merits of even the most basic design features of the stem. We undertook a prospective randomised trial comparing surface finish and the effect of a collar on cemented femoral component subsidence, survivorship and clinical function.

METHODS

One hundred and sixty three primary total hip replacement patients were recruited prospectively and randomised to one of four groups to receive a cemented femoral stem with either a matt or polished finish, and with or without a collar.

RESULTS

At two years, although there was a trend for increased subsidence in the matt collarless group, this was not statistically significant (p = 0.18). At a mean of 10.1 years follow-up, WOMAC scores for the surviving implants were good, (Range of means 89-93) without significant differences. Using revision or radiographic loosening as the endpoint, survivorship of the entire cohort was 93 % at 11 yrs, (CI 87-97 %). There were no significant differences in survivorship between the two groups with polished stems or the two groups with matt stems. A comparison of the two collarless stems demonstrated a statistically significant difference in survivorship between polished (100 %) and matt (88 %) finishes (p = 0.02).

CONCLUSIONS

In the presence of a collar, surface finish did not significantly affect survivorship or function. Between the two collarless groups a polished surface conferred an improved survivorship.

Coordinating retrieval and register studies improves postmarket surveillance

BACKGROUND

The relative risk of revision of the Titan(®) femoral stem due to aseptic loosening increased after 2000; however, the reasons for this have not been established. A retrieval analysis was initiated with the aim of delineating the failure mechanism.

QUESTIONS/PURPOSES

We asked whether aseptic loosening in stems after 2000 was associated with (1) appearance of osteolytic lesions, (2) wear particle exposure, (3) stem damage, or (4) changes to the implant or surgical instrumentation.

METHODS

Femoral stems, cement, tissue, and radiographs were collected from 28 patients. We assessed the development of osteolytic lesions in 17 patients. Exposure to wear particles was quantified in 18 patients. Stem damage was assessed in 15 patients. We observed differences in the implants by examination of 24 retrieved stems. Information concerning changes to instrumentation was requested from the manufacturer.

RESULTS

We found osteolysis in all patients receiving implants after 2000, which was associated with a median dose of cement and stem particles of 14,726/mm(2). Abrasion covered 59% of the surface of stems implanted from 1999. We identified geometric changes to the stem, the percent weight of aluminum in the stem's oxide layer decreased from 25% to 14% after 1997 and the rasp used to prepare the femoral cavity changed to a broach in 1999.

CONCLUSIONS

Stems implanted from 2000 failed through osteolysis induced by particles released from the cement and implant. Changes to implant geometry, surface oxide layer, and surgical tools occurred in the same time frame as the reduction in survivorship.

Multi-center study of use of the Exeter stem in Japan: evaluation of 1000 primary THA

BACKGROUND

The Exeter stem was introduced to the Japanese market in 1996. Since then, owing to excellent clinical results, the number of stems used has increased year by year and more than 2000 stems were implanted in 2009. The objective of this study was to prove the efficacy of the Exeter stem for Japanese patients by evaluating the short-term results of four major dedicated hip centers.

METHODS

We performed a retrospective study of clinical and radiographic results of 1000 primary total hip arthroplasties (THA) performed using the Exeter stem on 881 patients who were followed-up for at least 2 years after surgery. The average age of the patients at operation was 62.3 years (range 23-89 years). Mean postoperative follow-up period was 4.0 (range 2-9) years.

RESULTS

Thirty postoperative complications were observed, including 9 infections, 14 dislocations, 5 cases of deep vein thrombosis, and 2 cases of sciatic nerve palsy. No symptomatic pulmonary embolization or femoral fractures were observed. Re-operations for infection and dislocation were performed in 8 and 6 hips, respectively. According to Barrack's classification, the postoperative cementing grade was judged as A for 735 hips, B for 246 hips, and C for 4 hips. At final follow-up, no radiolucent line was observed at the bone-cement interface. Cortical hypertrophy was observed in 9.5 % of cases in Gruen zones 2-6. Kaplan-Meier survival analysis predicted 100 % survival at 5 years when a radiolucent line at the bone-cement interface of the femur was used as the endpoint, 98.8 % when re-operation was required for any reason.

CONCLUSIONS

This study revealed that excellent short-term results were achieved by fixing the Exeter stem with modern cementing techniques for primary THA in Japanese patients.

Shortening cemented femoral implants: an in vitro investigation to quantify exeter femoral implant rotational stability vs simulated implant length

The Exeter stems vary in length from 90 to 150 mm. The shorter stems generally have lower offsets. The purpose of this study was to determine if length of stem, with fixed offset, affected rotational stability. Mechanical testing was carried out on 10 implant-cement constructs with 2 loading profiles, rising from chair and stair climbing, at different simulated implant lengths using purpose-built apparatus. This paper presents a mechanism for clinically observed rotational stability and explains the mechanical characteristics required for rotational stability in Exeter femoral stems.

The migration pattern of the Charnley femoral stem: a five-year follow-up RSA study in a well-functioning patient group

BACKGROUND

Implant stability is considered vital to long-time implant survival in total hip arthroplasty (THA), since loose implants are reported to be a major cause of hip revision. There is an association between early implant micromotion and increased risk of revision. More implant-specific data are needed to establish acceptable levels of early implant movement.

MATERIALS AND METHODS

Thirty-five patients (36 hips) undergoing Charnley THA were followed with repeated clinical, radiographic, and radiostereometric analysis (RSA) over 5 years. Twenty-three patients attended 5 years postoperatively.

RESULTS

The patient group was well functioning based on the radiological and clinical evaluations. The stems constantly moved up to 5 years postoperatively, with subsidence, retroversion, and varus tilt, based on the RSA.

CONCLUSION

Continuous movement of the Charnley stem was observed up to 5 years postoperatively in a well-functioning patient group. The migration data presented herein could be useful when defining acceptable migration limits for certain types of cemented femoral stems.

The Exeter femoral stem continues to migrate during its first decade after implantation: 10-12 years of follow-up with radiostereometric analysis (RSA)

BACKGROUND

Due to its collarless, double-tapered polished design, the Exeter femoral stem is known to migrate distally in the first 5 years after implantation. However, its long-term migration pattern has not been investigated.

PATIENTS AND METHODS

39 consecutive patients (41 total hip arthroplasties) received a cemented Exeter stem and had prospective clinical and RSA follow-up. Patients were evaluated postoperatively at 6, 12, 26, and 52 weeks, and annually thereafter. Short-term results have been reported. In this study, the mean length of follow-up was 9.4 years (SD 3.2 years). No patients were lost to follow-up. 15 patients died during follow-up.

RESULTS

No stems were revised. In 4 stems, fractures of the cement mantle were noted within the first 3 postoperative years. In 3 stems, this resulted in a complete circumferential cement mantle discontinuity. For the 37 well-performing stems, continuous but small migration was measured between 2 and 12 years of follow-up. Continued subsidence of 0.08 mm/year (95% CI: 0.05-0.12, p < 0.001) was seen in combination with continued rotation in retroversion of 0.07°/year (95% CI: 0.02-0.12, p = 0.01). At 10 years of follow-up, mean subsidence was 2.1 (SD 1.2) mm and mean retroversion was 1.8° (SD 2.0). Two-thirds of this occurred during the first 2 postoperative years. In the 3 stems with a complete circumferential cement fracture, a sudden and disproportionately high increase in subsidence was measured in the time period of occurrence.

INTERPRETATION

The Exeter femoral stem continues to migrate during the first decade after implantation. Absolute stability is not required for good long-term survival if this is compatible with the design of the implant.

Femoral stem dislodgement during bipolar hemiarthroplasty dislocation

Bipolar hemiarthroplasty remains a treatment option for displaced femoral neck fractures in elderly patients without pre-existing hip disease. Implant-related complications associated with this procedure include acetabular erosion, dislocation, disassembly of the modular components, polyethylene debris-induced osteolysis, metallosis from outer cup impingement, and femoral component loosening. This article presents a case of a patient in whom the polished collarless tapered femoral stem dislodged out of the cement mantle during traumatic bipolar hemiarthroplasty dislocation, 28 days after the index procedure. This complication, associated with bipolar hemiarthroplasty dislocation, was adequately managed by driving the stem back to the original cement mantle, followed by reduction of bipolar component dislocation and placing bone cement over the shoulder of the femoral stem to prevent a new dislodgement episode. Although rare, dislodgement of cemented polished collarless tapered stems from the cement mantle has been recently reported either during dislocation or, more frequently, as a complication of reduction of a dislocated total hip arthroplasty. However, its occurrence in association with bipolar hemiarthroplasty dislocation was not found to have been reported in the literature. The occurrence of femoral stem dislodgement during bipolar hemiarthroplasty dislocation should be considered as a possible complication of such a procedure and may be prevented by routinely placing bone cement over the shoulder of the femoral implant.

Cemented versus cementless total hip replacements in patients fifty-five years of age or older with rheumatoid arthritis

BACKGROUND

results obtained from single-center studies indicate that a cemented total hip replacement is the treatment of choice for the management of patients over fifty-five years of age with rheumatoid arthritis. The aim of this study was to analyze population-based survival rates for cemented and cementless total hip replacements in patients aged fifty-five years or over with rheumatoid arthritis in Finland.

METHODS

between 1980 and 2006, a total of 6000 primary total hip replacements performed for the management of rheumatoid arthritis in patients who were fifty-five years of age or older were entered in the Finnish Arthroplasty Registry. 4019 of them fulfilled our inclusion criteria and were subjected to analysis. The implants were classified into one of three possible groups: (1) a cementless group (a noncemented proximally porous-coated stem and a noncemented porous-coated press-fit cup), (2) a cemented group 1 (a cemented, loaded-taper stem combined with a cemented, all-polyethylene cup), or (3) a cemented group 2 (a cemented, composite-beam stem with a cemented, all-polyethylene cup).

RESULTS

cementless stems and cups, analyzed separately, had a significantly lower risk of revision for aseptic loosening than cemented implants in patients who were fifty-five years of age or older with rheumatoid arthritis. The fifteen-year survival rate of cementless total hip replacements (80%) was comparable with the rates of the cemented groups (86% in cemented group 1 and 79% in cemented group 2) when revisions for any reason were used as the end point.

CONCLUSIONS

cementless and cemented total hip replacements produced comparable long-term results in patients who were fifty-five years of age or older with rheumatoid arthritis.

LEVEL OF EVIDENCE

therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.

A comparison of subsidence of Exeter standard and long stems

The survivorship of the polished, double taper Exeter stem is related to subsidence within the cement mantle. Long Exeter stems have altered geometry which may influence subsidence characteristics. Using digitised x-rays and appropriate computer software we measured the subsidence of 35 standard and 40 long stem Exeter implants. Measurements were taken from initial postoperative radiographs and repeated at intervals up to 5 years. Long stem implants were used in cemented revisions without the use of impaction bone grafting. Subsidence rates of the standard length stems in our study were comparable to that in published literature. Long stems did not replicate this subsidence pattern and had subsided less at 6, 12 and 24 months. However, the 205mm long stem, which has a fully tapered design, did follow the subsidence characteristics of the standard stem. Subsidence of long stem Exeter implants does not mirror that of the standard length stem. Loss of the fully tapered geometry of the longer stem implants may account for this finding. We suggest that whenever possible, the 205mm long stem should be used if the biomechanical principles of the standard Exeter stem are to be utilised.

Cemented polished tapered stems in patients less than 50 years of age: a minimum 10-year follow-up

We report the outcome of 58 consecutive polished tapered stems in 47 patients younger than 50 years, with a minimum of 10 years of follow-up. No stems were revised for aseptic loosening or osteolysis. The Harris hip scores were good or excellent in 76% of the patients. There was excellent preservation of proximal bone. Despite higher patient weight and frequent previous surgery, the outcome of polished tapered stems in patients younger than 50 years is comparable to the general population undergoing total hip arthroplasty and superior to other non-polished tapered stem designs in young patients. Cup wear and cup failure were significantly worse in this group, with a higher incidence of periarticular osteolysis. Polished tapered stem designs are the benchmark for comparison to other arthroplasty options in young patients.

Basic science considerations in primary total hip replacement arthroplasty

Total Hip Replacement is one of the most common operations performed in the developed world today. An increasingly ageing population means that the numbers of people undergoing this operation is set to rise. There are a numerous number of prosthesis on the market and it is often difficult to choose between them. It is therefore necessary to have a good understanding of the basic scientific principles in Total Hip Replacement and the evidence base underpinning them. This paper reviews the relevant anatomical and biomechanical principles in THA. It goes on to elaborate on the structural properties of materials used in modern implants and looks at the evidence base for different types of fixation including cemented and uncemented components. Modern bearing surfaces are discussed in addition to the scientific basis of various surface engineering modifications in THA prostheses. The basic science considerations in component alignment and abductor tension are also discussed. A brief discussion on modular and custom designs of THR is also included. This article reviews basic science concepts and the rationale underpinning the use of the femoral and acetabular component in total hip replacement.

Cemented total hip stem design influence on adaptative cortical thickness and femoral morphology

INTRODUCTION

Five-year following total hip implantation femur adaptive morphology was compared between two groups differing only in their femoral stem design.

MATERIAL AND METHODS

Group 1, recruited prospectively, included 51 Dédicace stems(Stryker-Howmedica) and group 2, retrospectively matched to group 1, comprised 51 Kerboull MK3 stems (Stryker-Howmedica). While MK3 prosthetic system increases in size homogeneously (widening along the whole length as the implant dimension increases), the Dédicace prosthetic system provides various metaphyseal widths for a given diaphyseal size. We opted for primary fixation (press fit according to the "French paradox") prior to cementing in both cases, despite the risk of discontinuity in the cement mantle. The homogeneous dimensioning of the MK3 stem enables distal primary fixation, whereas the Dédicace range allows differentiated adaptation to diaphyseal length and metaphyseal caliber. The following parameters were measured and calculated: Noble index, femoral cortical thickness score of Barnett and Nordindiaphyseal filling and stress-shielding at three levels around the stem.

RESULTS

Bone-remodeling, assessed on X-ray, was without clinical impact, whether it took the form of spongialization or stress-shielding. The sole factor tending to induce stress-shielding was a high degree of canal filling by the distal third of the stem, more frequently encountered with the MK3 model. Metaphyseal filling was equivalent with all stems. In the matched series on the contralateral healthy side, femoral spongialization was comparable.

LEVEL OF PROOF

Level III; case/control study.

Initial evaluation on subsidence of cemented collarless polished tapered stem applied to the patients with narrow femoral medullar canal

Purpose:

The geometry of the proximal femur is one of the important factors for choosing the suitable stem. We have been applied cemented collarless polished tapered (CPT) stem to the patients with small femur. Radiographic evaluation was performed to access the clinical feature of the stem in early stage of the follow-up.

Methods:

One hundred total hip arthroplasties with CPT system were performed between October 2004 to February 2006. This study focused on the 53 cases to whom size 1 or smaller sized stem were implanted, and its post-operative period was 41 months (30-46 months). Morphologic classification of preoperative proximal femur, stem alignment, thickness of the cement mantle, cementing technique, subsidence of the stem, improvement in the bone-cement interface, and stress shielding were assessed.

Results:

The size of the inserted stem was X-SMALL in one case, SMALL in two cases, SIZE 0 in 12 cases, and SIZE 1 in 38 cases. Canal shape of proximal femur was stovepipe type in five cases, normal type in 43 cases, and champagne-flute type in five cases. There was no subsidence in eight cases. 44 stems subsided within 1 mm, one stem subsided 1 to 2 mm, and no stem subsided over 2 mm. In 39 of 45 cases, subsidence was appeared within six months after operation. Marked progressive and excessive subsidence was not seen after the two years of follow-up.

Conclusions:

Short term radiographic results of THA with CPT stem to small femur were satisfactory with less unfavorable radiographic findings, which imply contribution to longer survivorship of the stem.

Impaction bone grafting in revision hip surgery: past, present and future

Joint replacement surgery can have excellent clinical results. However, as the number of patients undergoing surgery increases, the number of failed joint replacements is set to rise. One of the greatest challenges for the revision surgeon is the restoration of bone stock. This article focuses upon revision hip surgery, with particular reference to the scope of the problem; historical and current solutions to bone loss in the femur and acetabulum; the clinical results following revision surgery; and the basic science behind impaction bone grafting, before ending with possible future directions for improving the restoration of bone stock.

The long-term results of the original Exeter polished cemented femoral component: a follow-up report

We present a long-term follow-up report of the results of the original Exeter polished cemented stems inserted between November 1970 and the end of 1975 at our institution by surgeons of widely differing experience using crude cementing techniques. The results of this series were reported in 1988 (Fowler et al. Orthopaedic Clinics of North America. 1988;19:477) and again in 1993 (Timperley et al. Journal of Bone and Joint Surgery. 1993;75-B:33). There have been no failures from aseptic femoral component loosening since the 1993 report. From the original series of 433 hips, there were, at the end of 2003, 26 living patients with 33 hips. Of the latter, there were 25 hips in 20 patients with their original femoral components still in situ. Twenty-eight (6.46%) hips from the original series have been lost to follow-up, although none since 1992. With the end point reoperation for aseptic stem loosening, the survivorship is 93.5% (95% confidence interval, 90.0%-97.0%). The reoperation rate for aseptic femoral component loosening is 3.23% into the 33rd year of follow-up.

Total hip arthroplasty for primary osteoarthritis in patients fifty-five years of age or older. An analysis of the Finnish arthroplasty registry

BACKGROUND

According to the long-term results obtained from the Scandinavian arthroplasty registries, cemented total hip replacement has been the treatment of choice for osteoarthritis of the hip in elderly patients. The aim of the present study was to analyze population-based survival rates of the cemented and cementless total hip replacements performed for primary osteoarthritis in patients fifty-five years of age or older in Finland.

METHODS

From 1980 to 2004, a total of 50,968 primary total hip replacements that met our criteria were entered in the Finnish Arthroplasty Registry. The success rate of different implant groups was analyzed. The implants included were classified in one of the following four groups: implants with a cementless, straight, proximally circumferentially porous-coated stem and a modular, porous-coated press-fit cup (cementless group 1); implants with a cementless, anatomic, proximally circumferentially porous-coated and/or hydroxyapatite-coated stem with a modular, porous-coated and/or hydroxyapatite-coated press-fit cup (cementless group 2); a hybrid total hip replacement consisting of a cemented stem combined with a modular, press-fit cup (the hybrid group); and a cemented loaded-taper or composite-beam stem combined with an all-polyethylene cup (the cemented group).

RESULTS

Cementless total hip replacements, as well as cementless stems and cups analyzed separately, had a significantly reduced risk of revision for aseptic loosening compared with cemented hip replacements (p < 0.001). When revision for any reason was the end point in survival analyses, however, there were no significant differences among the groups. In patients between the ages of fifty-five and sixty-four years, the fifteen-year survival rates of the two cementless groups (78% and 80%) were higher than that of the cemented group (71%) with revision for aseptic loosening as the end point. In patients who were sixty-five to seventy-four years old, the fifteen-year survival rate of the implants in cementless group 1 was 94%, while cemented total hip replacements had an 85% survival rate. In patients who were seventy-five years old or more, no significant differences were detected among the total hip replacement groups; all of them had survivorship of >90% at ten years.

CONCLUSIONS

In patients who were fifty-five years of age or older, the long-term survival of cementless total hip replacements was comparable with that of cemented replacements. In patients who were fifty-five to seventy-four years old, straight porous-coated cementless stems had better long-term survival than the cemented stems. In patients who were seventy-five years of age and older, there were no significant differences in the results. Multiple wear-related revisions of the cementless cups in the present study indicate that excessive polyethylene wear was a major clinical problem with modular cementless cups in all age groups.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.

The relationship between stem subsidence and improvement in the radiolucency in polished tapered stems

We studied the relationship between stem subsidence and improvement in the initial radiolucency at the bone-cement interface in polished- and rough-surface stems. Stem subsidence was seen in 34 of 42 hips (81.0%), and improvement in the initial radiolucency was seen in 15 hips (35.7%) in collarless polished tapered stems at 1 year after operation. In polished stems, stem subsidence in cases with improvement in the initial radiolucency was significantly greater than in those with no change (average 1.12 mm and 0.48 mm, P<0.005). In rough-surface stems partially coated with polymethylmethacrylate (VerSys Cemented Plus), no stem subsidence and no improvement in the initial radiolucency was seen. In polished stems, stem subsidence leads to cement creep and compressive force on the bone-cement interface and can improve the initial radiolucency.

Comparison between triple-tapered and double-tapered cemented femoral stems in total hip arthroplasty: a prospective study comparing the C-Stem versus the Exeter Universal early results after 5 years of clinical experience

A prospective study was conducted comparing the early clinical and radiological results between the triple-tapered C-Stem (DePuy International, Leeds, UK) and the double-tapered Exeter Universal (Stryker Howmedica Osteonics, Mahwah, NJ) in cemented total hip arthroplasty. A total of 192 patients (200 hips) received the C-Stem and 189 patients (205 hips) received the Exeter Universal. Average follow-up was 29 and 31 months in the C-Stem and Exeter groups, respectively. From the short-term results, we found similar mean improvements in clinical scores and no difference was noted in the incidence of complications. Average subsidence was comparable (C-Stem, 0.77 mm +/- 0.56; Exeter, 0.82 +/- 0.63). Radiolucencies in the cement-stem and cement-bone interfaces were seen primarily in the proximal zones in both groups. No stems were considered at risk of aseptic loosening and the extent of proximal femoral resorption was comparable.

Removal of solidly fixed implants during revision hip and knee arthroplasty

The removal of solidly fixed implants during revision hip and knee arthroplasty is a technically challenging procedure with the potential for a large amount of bone loss during component removal. This bone loss may compromise the subsequent reconstruction. Careful preoperative planning is essential before undertaking removal of solidly fixed implants. The surgeon should determine the type and size of the implants and be familiar with any specialized removal equipment that may be available. For both the hip and knee, extensive exposure is often necessary. Removal of a well-fixed femoral component often requires an extended trochanteric osteotomy. The most difficult component to remove from the knee is a well-fixed cementless patellar component. The primary goal in removing well-fixed components is to minimize loss of surrounding bone, which requires effective planning and often access to specialized tools and techniques.

Validation d’une méthode de mesure de l’enfoncement d’un implant fémoral cimenté de type Exeter

PURPOSE OF THE STUDY

Total hip arthroplasty has become one of the most common procedures in orthopedic surgery. These patients must nevertheless be followed with care due to the risk of instability. Knowledge of early migration behavior can provide an indirect assessment of implant fixation. The purpose of this work was to develop a new measurement tool for early assessment of the femoral component.

MATERIAL AND METHODS

We analyzed the x-rays of ten Exeter stems (Stryker-Howmedica) implanted between 1996 and 2001 using a simple software designed to calculate the vertical subsidence of each implant. The technical precision and inter-observer reproducibility were checked.

RESULTS

The software provided a precision of 0.14-0.3 millimeters. The overall precision of the technique was 1.2 millimeters. There was no statistically significant inter-observer variability. We observed a mean subsidence of 1.3+/-0.7 millimeters at six Months, followed by no further migration.

DISCUSSION AND CONCLUSION

This new method was found to be reliable. It is useful for identifying implant migration at different bone-cement-implant interfaces. The time course of subsidence appears to be important to determine threshold values for failure. This tool provides an easy-to-use method for both retrospective and prospective analysis. With minor modifications of the software program, this tool can be used for other types of implants.

Interface biomechanics of the Anca Dual fit hip stem: an in vitro experimental study

The Anca Dual Fit hip stem (Cremascoli Wright, Milan, Italy) is a partially cemented stem developed to overcome the drawbacks of both cemented and uncemented fixations. Its design was based on the hypothesis that partial cementing would ensure the primary stability necessary to allow bone ingrowth on the cement-free stem surfaces. At the same time, the limitation of the cement to the proximal regions would prevent stress-shielding by increasing proximal load transfer. After finite element (FE) simulations and in vitro primary stability assessment, an analysis of the long-term stability of the Anca Dual Fit stem was necessary to conclude the preclinical testing. Three stems were implanted in composite femurs and subjected to testing for 1 x 10(6) cycles, each cycle reproducing the activity of stair climbing. The simulation was designed so as to replicate the physiological loading in a simplified, yet relevant way for this test. Various measurements were collected before, during and after the test in order to give exhaustive information on the response of the implant to long-term, cyclic loading. The present study confirmed the positive results of previous investigations, and proved that the Anca Dual Fit stem has excellent long-term stability; therefore successful clinical outcomes are predicted.

Collarless polished tapered stem: clinical and radiological follow-up over 5 years

The clinical and radiologic outcome of a cemented, polished, tapered stem (CPT), implanted using contemporary cementing techniques in 108 consecutive operated hips in 100 patients (68 women and 32 men, aged 19 to 83 years at the time of surgery [mean, 65 years]) was assessed after >5 years. The Harris hip scores were good or excellent in 96% of the patients. Stem subsidence measured by the computer-assisted method described by Braud and Freeman was at a mean rate of 0.44 mm/y, 1.08 mm during the first year, and stabilizing to a mean total of 2.18 mm at >5 years. Subsidence was related inversely to the completeness of the cement mantle but did not correlate with the clinical or radiologic outcome. This study confirms that collarless, polished, tapered stems subside within the cement mantle but without loosening and that the CPT performs at least as well as the Exeter stem.