9- to 11-year results of cemented titanium mueller straight stem in total hip arthroplasty

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

Better early functional outcome after short stem total hip arthroplasty? A prospective blinded randomised controlled multicentre trial comparing the Collum Femoris Preserving stem with a Zweymuller straight cementless stem total hip replacement for the treatment of primary osteoarthritis of the hip

OBJECTIVES

Primary aim was to compare the functional results at 3 months and 2 years between short and conventional cementless stem total hip arthroplasty (THA). Secondary aim was to determine the feasibility of a double-blind implant-related trial.

DESIGN

A prospective blinded randomised controlled multicentre trial in patients with osteoarthritis of the hip. All patients, research assistants, clinical assessors, investigators and data analysts were blinded to the type of prosthesis.

POPULATION

150 patients between 18 and 70 years with osteoarthritis of the hip, 75 in the short stem and 75 in the conventional stem group. Mean age: 60 years (SD 7).

INTERVENTIONS

the Collum Femoris Preserving short stem versus the Zweymuller Alloclassic conventional stem.

MAIN OUTCOME MEASURES

The Dutch version of the Hip Disability and Osteoarthritis Outcome Score (HOOS). Secondary outcomes measures: Harris Hip Score, the Physical Component Scale of the SF12, the Timed Up and Go test, Pain and the EQ-5D. Feasibility outcomes: continued blinding, protocol adherence and follow-up success rate.

RESULTS

No significant difference between the two groups. Mean HOOS total score in the short stem group increased 32.7 points from 36.6 (95% CI 32.9 to 40.2) preoperatively to 69.3 (95% CI 66.4 to 72.1) at 3 months follow-up. Mean HOOS total score in the conventional straight stem group increased 36.3 points from 37.1 (95% CI 33.9 to 40.3) preoperatively to 73.4 (95% CI 70.3 to 76.4) at 3 months follow-up. 91.2% of patients remained blinded at 2 years follow-up. Both protocol adherence and follow-up success rate were 98%.

CONCLUSIONS

Functional result at 3 months and 2 years after short stem THA is not superior to conventional cementless THA. There were more perioperative and postoperative complications in the short stem group. Direct comparison of two hip implants in a double-blinded randomised controlled trial is feasible.

TRIAL REGISTRATION NUMBER

NTR1560.

Curved versus Straight Stem Uncemented Total Hip Arthroplasty Osteoarthritis Multicenter trial (CUSTOM): design of a prospective blinded randomised controlled multicentre trial

INTRODUCTION

Answering the demands of an increasingly young and active patient population, recent developments in total hip arthroplasty (THA) have shifted towards minimising tissue damage. The Collum Femoris Preserving (CFP) stem was developed to preserve the trochanteric region of the femur, which potentially preserves the insertion of the gluteus musculature. This might accelerate early postoperative rehabilitation and improve functional outcome. Currently the functional results of the CFP stem have not been compared with conventional straight stems in a randomised controlled trial (RCT). The primary purpose of this trial is to compare the functional result of CFP stem THA with conventional uncemented straight stem THA, measured by the Dutch Hip disability and Osteoarthritis Outcome Score (HOOS) at 3-month follow-up.

METHODS

A prospective blinded multicentre RCT will be performed. We aim to recruit 150 patients. The patients will be randomly allocated to a THA with a straight or a curved stem. All patients, research assistants, clinical assessors and investigators will be blinded for the type of prosthesis for 5 years. Clinical assessments and roentgenograms will be taken preoperative, at 6 weeks after surgery, at 1, 2, 3, 4 and 5 years after surgery. Patient reported outcome measures (PROMs) will be obtained at the same follow-up moments. In addition, the PROMs will also be sent to the patients at 3 and 6 months after surgery. The HOOS at 3-month follow-up will be our primary outcome.

ETHICS AND DISSEMINATION

This trial will be performed in accordance with the Declaration of Helsinki. A local ethics committee has approved this trial. Written informed consent will be obtained from all participating patients. All serious adverse events will be reported to the ethics committee.

RESULTS

Results will be submitted for publication to an orthopaedics related journal.

TRIAL REGISTRATION NUMBER

NTR1560.

Systemic IFNγ predicts local implant macrophage response

Implantation of biomaterials can cause complications often associated with inflammatory reactions. However, repeated evaluation of the implant site would be burdening for patients. Alternatively, blood examinations with analysis of inflammatory serum markers could potentially be useful to reflect the local cellular response for detection and/or prediction of inflammation-related complications. Therefore, following intramuscular implantation of surface-modified Ti implants in rats, this study aimed at examining possible associations between the post-implantation time course of pro-inflammatory (INFγ, IL-2) and anti-inflammatory (IL-4, IL-10) cytokine serum concentrations and the local peri-implant tissue response after 56 days (pro-inflammatory CD68-positive monocytes/macrophages, anti-inflammatory CD163-positive macrophages, MHC class II-positive cells, activated natural killer cells and mast cells). Multivariate correlation analysis revealed a significant interaction between serum IFNγ and peri-implant tissue CD68-positive monocytes/macrophages (p = 0.001) while no interactions were found for other cytokines and cell types. Additional Pearson correlation analysis of IFNγ serum concentrations on each experimental day vs. the CD68-positive monocytes/macrophages response on day 56 demonstrated a consistently positive correlation that was strongest during the first three weeks. Thus, high early pro-inflammatory IFNγ serum concentration was associated with high late number of pro-inflammatory CD68-positive monocyte/macrophages and low early serum IFNγ with low late CD68-positive monocyte/macrophage numbers. Further studies aimed at examination of patient samples could establish the relevance of this association to predict clinical complications. After implantation of titanium samples, high early IFNγ serum concentrations were associated with a pronounced late pro-inflammatory CD68-positive monocyte/ macrophage (red circle) response, while no correlation was found for other investigated cytokines and inflammatory cells (green circle). In contrast, low early IFNγ serum concentrations were correlated with low late monocyte/ macrophage numbers.

Which implant should we use for primary total hip replacement? A systematic review and meta-analysis

BACKGROUND

Many total hip implants are currently available on the market worldwide. We aimed to estimate the probability of revision surgery at ten years for each individual total hip implant and to compare these estimates with the National Institute for Health and Care Excellence (NICE) benchmark.

METHODS

We performed a meta-analysis of cohort studies. The methodological quality was assessed with use of the Assessment of Quality in Lower Limb Arthroplasty (AQUILA) checklist. We searched PubMed, Embase, Web of Science, and the Cochrane Library. Additionally, national joint registries that were full members of the International Society of Arthroplasty Registers (ISAR) were hand searched. Studies in which the authors reported the survival probability for either the acetabular or the femoral component of primary total hip replacements with use of revision for any reason or for aseptic loosening at ten years as the end point, with at least 100 implants at baseline, and in which at least 60% of the patients had primary osteoarthritis were eligible for inclusion.

RESULTS

The search strategy revealed 5513 papers describing survival probabilities for thirty-four types of acetabular components and thirty-two types of femoral components. Eight types of acetabular cups and fifteen types of femoral stems performed better than the NICE benchmark.

CONCLUSIONS

We recommend that surgeons performing a primary total hip replacement use an implant that outperforms the NICE benchmarks.

Characteristic loosening of the distally straight cylindrical femoral stem

BACKGROUND

The cemented femoral stem with a distally straight cylindrical shape was designed to fill the distal femoral canal to facilitate higher cement pressurization and stability. We examined the mid-term outcomes of a stem made of titanium alloy and the efficacy of this shape.

METHODS

Four hundred and twenty-nine consecutive patients (505 hips), who underwent a total hip arthroplasty with the distally straight cylindrical stem made of titanium alloy as their primary hip arthroplasty at two institutes, were followed for a minimum 2 years. Loosening was defined as subsidence of over 3 mm, tilting of the femoral component, or fracture of the cement or the stem. A continuous radiolucent line along the entire interface was considered to indicate loosening, too. We examined the interface stresses on the distally straight cylindrical stem compared with a newly manufactured femoral prosthesis with a double-taper design using a finite element model study.

RESULTS

The mean follow-up was 101.3 months after surgery. Thirty patients (30 hips) had aseptic loosening of the stems. Of these 30 hips, 18 had osteolysis, 17 showed subsidence, and 11 had cement fractures at the tip of the stem. These 11 hips had osteolysis and ectasia in the same place: the stem tip. The stem survival rate with stem loosening as the end-point was 94.4 % at 10 years and 66.9 % at 15 years. A finite element model study revealed higher stress around the tip of the cylindrical stem compared with that in the double-taper stem.

CONCLUSIONS

The straight cylindrical stem is potentially subject to early failure because of high stress around the tip of the stem, and showed a characteristic loosening with osteolysis and ectasia at the tip of the stem.

Implants in bone: part II. Research on implant osseointegration: material testing, mechanical testing, imaging and histoanalytical methods

PURPOSE

In order to determine whether a newly developed implant material conforms to the requirements of biocompatibility, it must undergo rigorous testing. To correctly interpret the results of studies on implant material osseointegration, it is necessary to have a sound understanding of all the testing methods. The aim of this overview is to elucidate the methods that are used for the experimental evaluation of the osseointegration of implant materials.

DISCUSSION

In recent decades, there has been a constant proliferation of new materials and surface modifications in the field of dental implants. This continuous development of innovative biomaterials requires a precise and detailed evaluation in terms of biocompatibility and implant healing before clinical use. The current gold standard is in vivo animal testing on well validated animal models. However, long-term outcome studies on patients have to follow to finally validate and show patient benefit.

CONCLUSION

No experimental set-up can provide answers for all possible research questions. However, a certain transferability of the results to humans might be possible if the experimental set-up is carefully chosen for the aspects and questions being investigated. To enhance the implant survival rate in the rising number of patients with chronic diseases which compromise wound healing and osseointegration, dental implant research on compromised animal models will further gain importance in future.

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.

Is there still a place for the cemented titanium femoral stem? 10,108 cases from the Norwegian Arthroplasty Register

BACKGROUND AND PURPOSE

Despite the fact that there have been some reports on poor performance, titanium femoral stems intended for cemented fixation are still used at some centers in Europe. In this population-based registry study, we examined the results of the most frequently used cemented titanium stem in Norway.

PATIENTS AND METHODS

11,876 cases implanted with the cemented Titan stem were identified for the period 1987-2008. Hybrid arthroplasties were excluded, leaving 10,108 cases for this study. Stem survival and the influence of age, sex, stem offset and size, and femoral head size were evaluated using Cox regression analyses. Questionnaires were sent to the hospitals to determine the surgical technique used.

RESULTS

Male sex, high stem offset, and small stem size were found to be risk factors for stem revision, (adjusted RR = 2.5 (1.9-3.4), 3.3 (2.3-4.8), and 2.2 (1.4-3.5), respectively). Patients operated in the period 2001-2008 had an adjusted relative risk (RR) of 4.7 (95% CI: 3.0-7.4) for stem revision due to aseptic stem loosening compared to the period 1996-2000. Changes in broaching technique and cementing technique coincided with deterioration of the results in some hospitals.

INTERPRETATION

The increased use of small stem sizes and high-offset stems could only explain the deterioration of results to a certain degree since the year 2000. The influence of discrete changes in surgical technique over time could not be fully evaluated in this registry study. We suggest that this cemented titanium stem should be abandoned. The results of similar implants should be carefully evaluated.

Radiographic preoperative templating of extra-offset cemented THA implants: how reliable is it and how does it affect survival?

INTRODUCTION

Securing femoral offset should in theory improve hip stability and abductor muscles moment arms. As problems arise mainly in case of originally increased offset (>40 mm), a range of extra-offset stems is available; the exact impact in terms of fixation, however, is not known.

HYPOTHESIS

Extra-offset stems should more reliably reestablish original femoral offsets exceeding 40 mm than standard femoral components, limiting instability risk without possible adverse effect on fixation.

OBJECTIVE

To compare the ability of five commonly available femoral stem designs to restitute offset exceeding 40 mm, and to assess function and cement fixation at a minimum 6 years' follow-up in a stem conceived to reproduce such offset.

PATIENTS AND METHODS

A continuous series of 74 total hip replacements (THR) in hips with increased (>40 mm) femoral offset was studied. All underwent preoperative X-ray templating on Imagika™ software to assess offset reproduction by five models of stem: four standard, and one Lubinus SP2™ extra-offset stem. A retrospective clinical and X-ray study was conducted with a minimum 6 years' follow-up on the Lubinus SP2™ 117° stems used to try to reproduce offset in the 74 THRs.

RESULTS

Apart from the increased (>40 mm) offset, the cervicodiaphyseal angle was consistently <135°, <130° in 60 femurs (81%) and <125° in 45 (60%). Planning showed the four standard stems to induce (>5mm femoral offset reduction in 50-83% of cases, versus only 25% with the Lubinus SP2™ 117°). All 74 hips received Lubinus SP2™ 117° stems: at a mean 78 months FU (range, 70-94 mo), their mean Postel-Merle d'Aubigné score was 17±1.8 (range, 13-18). Five of the 74 THRs underwent surgical revision: three cases of loosening, in which the stem was replaced, and two of instability, without change of stem. Loosening was not related to offset reproduction quality; two of the three cases were due to initial cementing defect, and the third occurred in a femur with previous history of two osteotomies. There were four cases of dislocation (5.4%: two primary, which were not operated on, and two recurrent, managed by acetabular revision), despite good reproduction of the preoperative offset in three of the four cases. Mean 7-year implant survivorship was 95.1% (±4.8).

DISCUSSION AND CONCLUSION

The anatomic form of the Lubinus™ SP2 117° should in theory provide a uniform cement mantle. Survivorship, however, is less good than for regular offset versions (126° or 135°). On the other hand, it does reproduce anatomy in case of >40mm offset, providing extra offset of more than 51mm. The slightly shorter survivorship requires more long-term surveillance.

LEVEL OF EVIDENCE

Level IV, retrospective study.