The John Charnley Award: Three-dimensional analysis of the cement mantle in total hip arthroplasty

Femoral Stem Cementation in Primary Total Hip Arthroplasty

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Femoral stem cementation has undergone considerable investigation since bone cement was first used in arthroplasty, leading to the evolution of modern femoral stem cementation techniques.

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Although there is a worldwide trend toward the use of cementless components, cemented femoral stems have shown superiority in some studies and have clear indications in specific populations.

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There is a large evidence base regarding cement properties, preparation, and application techniques that underlie current beliefs and practice, but considerable controversy still exists.

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Although the cementing process adds technical complexity to total hip arthroplasty, growing evidence supports its use in certain cohorts. As such, it is critical that orthopaedic surgeons and investigators have a thorough understanding of the fundamentals and evidence underlying modern cementation techniques.

Quality of the femoral cement mantle in total hip arthroplasty using the direct anterior hip approach

Background

Limited literature exists concerning the femoral cement mantle quality that can be achieved through an anterior approach in total hip arthroplasty (THA). We radiologically evaluated the quality and thickness of the femoral cement mantle in patients undergoing THA utilizing the direct anterior approach (DAA).

Methods

Immediate postoperative anteroposterior and lateral radiographs of 116 consecutive patients who underwent hybrid or fully cemented THA using the DAA and cemented Quadra-C stem (Medacta, International, SA, Switzerland) were assessed by 2 arthroplasty surgeons blinded to the study. Surgical indications were hip osteoarthritis or subcapital hip fracture. The cement mantle and stem alignment were evaluated using the Barrack classification and Khalily methods, respectively. After calibration of radiographs, the thinnest part of the cement mantle per Gruen zone was recorded. Parameters were compared between obese and nonobese patients.

Results

Agreement between raters was substantial for the cement quality in anteroposterior (k = 0.707, P ≤ .001) and moderate for lateral radiographs (k = 0.574, P ≤ 001). The cement mantle was graded A in 39.25%, B in 53.0%, and C in 7.75% of anteroposterior radiographs and similarly for lateral radiographs (40.1% A, 51.75% B, 9.5% C). 93% of stems had neutral alignment. The mean thinnest cement mantle (P = .237) and incidence of inadequate cement mantle (<2 mm) per zone (P = .431) were comparable between Gruen zones. The cement mantle quality (P = .174) and inadequacy (P > .05) and stem alignment (P = .652) were comparable between obese and nonobese patients.

Conclusions

DAA enables correct implantation and effective cementation of straight femoral stems. A high-quality cement mantle can be achieved using DAA even in obese patients.

Hybrid total hip arthroplasty using specifically-designed stems for patients with developmental dysplasia of the hip. A minimum five-year follow-up study

A 4-U hybrid total hip arthroplasty (THA) system was specifically designed for patients with developmental dysplasia of the hip (DDH). Straight stem with an appropriate offset and various size variations are advantages. We followed 128 hips in 124 patients, 13 men and 111 women, for a mean of 6.5 years (range, 5.0-7.5 years). Two acetabular and femoral components in two patients had been revised for infection, one acetabular component had been revised for recurrent dislocation, and one femoral component had been revised for periprosthetic femoral fracture. None of the acetabular or femoral components were revised for loosening or were found to be loose at follow-up. The Harris hip score increased from a preoperative average of 42 points to 88 points at the most recent follow-up. Primary THA using the 4-U system had a good mid-term result in patients with DDH. This system could be applied for all patients including those with the narrowest and deformed femurs.

The posterior approach reduces the risk of thin cement mantles with a straight femoral stem design

BACKGROUND AND PURPOSE

The properties of the cement mantle around a prosthesis are important. We investigated whether the surgical approach to the hip influences the quality and thickness of the cement mantle when using a straight femoral stem design.

METHODS

In a consecutive multi-surgeon series, we reviewed the radiographs of 270 patients after cemented Exeter total hip arthroplasty. 135 stems were introduced using an antero-lateral (transgluteal) approach and 135 stems were introduced using a posterior approach. Anterior-posterior and lateral radiographs were reviewed and cement mantle thickness was measured in Gruen zones 1-14. We graded cement mantle quality according to the Barrack classification.

RESULTS

Barrack grading did not reveal any difference in cement mantle quality between the two groups. AP and lateral radiographs showed no difference in stem alignment between the groups. The risk of a thin cement mantle (< 2 mm) was lower with a posterior approach (OR = 1.8, 95% CI: 1-3; p = 0.03). The greatest risk of a cement mantle thickness of < 2 mm occurred in Gruen zones 8-9 regardless of the surgical approach used.

INTERPRETATION

With a straight femoral stem design, the posterior approach to the hip joint appears to give a lower risk of a thin cement mantle. Irrespective of the approach, there was a risk of thin cement mantles in Gruen zones 8 and 9, which highlights the importance of lateral radiographs in the postoperative radiographic assessment of total hip replacements.

Anatomic stem design reduces risk of thin cement mantles in primary hip replacement

PURPOSE

To analyse the influence of femoral stem design in the lateral plane (anatomic vs. straight) on the cement mantle quality.

METHOD

In this consecutive multi-surgeon radiographic study we determined, Dorr grading, cement mantle quality (Barrack) and mantle thickness using Gruen zones 1–14 in 280 primary cemented total hip replacements, divided into two groups (140 anatomic Biomet Olympia, 140 straight Exeter Universal Series).

RESULTS

Twenty-three per cent of the straight Exeter Universal stems had a cement mantle of <2 mm thickness in Gruen zone 8 and 25% in Gruen zone 9, compared to 0.7% of the anatomical Olympia stems in Gruen zone 8 and 1.4% in Gruen zone 9. The difference between the two groups was statistically significant (P < 0.001). In all other zones no significant differences were found.

CONCLUSION

This radiological study confirms that femoral stems with an anatomical curve in the lateral plane carry a lower risk of thin cement mantles (especially in Gruen zones 8 and 9) than straight stems. Cement mantle analysis in one radiographic plane only is insufficient.

The cement mantle of femoral hip implants is more influenced by stem-broach sizing than by shape: an in vitro CT analysis of straight Charnley-Kerboul and anatomic Lubinus SPII stems

INTRODUCTION

Both, the stem shape and the implantation technique could influence the quality of the cement mantle surrounding femoral hip implants. We investigated which of these two factors is most important for the stem-cement-bone construct.

METHODS

We compared morphological data of 22 straight Charnley-Kerboul and 18 anatomic Lubinus SPII plastic replicas implanted line-to-line with the broach or one size undersized in paired cadaver femora. Specimens were CT scanned and assessed with validated segmentation software.

RESULTS

According to a general linear model, the canal-filling capacity of the stem, the cement thickness, the amount of thin and deficient cement and cortical support to areas of weak cement, were exclusively related to the implantation technique. The anatomic shape of Lubinus stems did not improve centralization or alignment.

CONCLUSION

Stem shape was the most obvious difference between Lubinus SPII and Chanrley-Kerboul implants. However, comparing both, stem-broach sizing was the most important determining factor for the cemented stem construct.

Fixation of the cemented stem: clinical relevance of the porosity and thickness of the cement mantle

The aim of this review paper is to define the fixation of the cemented stem. Polymethyl methacrylate, otherwise known as “bone cement”, has been used in the fixation of hip implants since the early 1960s. Sir John Charnley, the pioneer of modern hip replacement, incorporated the use of cement in the development of low frictional torque hip arthroplasty. In this paper, the concepts of femoral stem design and fixation, clinical results, and advances in understanding of the optimal use of cement are reviewed. The purpose of this paper is to help understanding and discussions on the thickness and the porosity of the cement mantle in total hip arthroplasty. Cement does not act as an adhesive, as sometimes thought, but relies on an interlocking fit to provide mechanical stability at the cement–bone interface, while at the prosthesis– cement interface it achieves stability by optimizing the fit of the implant in the cement mantle, such as in a tapered femoral stem.

2008 Otto Aufranc Award: component design and technique affect cement penetration in hip resurfacing

Either excessive or insufficient cement penetration within the femoral head after hip resurfacing influences the risk of femoral failures. However, the factors controlling cement penetration are not yet fully understood. We determined the effect of femoral component design and cementation technique on cement penetration. Six retrieved femoral heads were resurfaced for each implant (BHR, ASR, Conserve Plus, DuROM, ReCAP) using the manufacturers' recommendations for implantation. In addition, the BHR was implanted using the Conserve Plus high-viscosity cementation technique, "BHR/hvt," and vice versa for the Conserve, "Conserve/lvt." The average cement penetration was highest with BHR (65.62% +/- 15.16%) compared with ASR (12.25% +/- 5.12%), Conserve Plus(R) (19.43% +/- 5.28%), DuROM (17.73% +/- 3.96%), and ReCAP (26.09% +/- 5.20%). Cement penetration in BHR/hvt remained higher than all other implants equaling 36.7% +/- 6.6%. Greater femoral component design clearance correlated with cement mantle thickness. Femoral component design in hip resurfacing plays a major role in cement penetration.

Tight fit technique in primary hybrid total hip arthroplasty for patients with hip dysplasia

This article presents the midterm results of hybrid total hip arthroplasty for patients with hip dysplasia by use of a tight fit technique for the femoral component. We followed up 113 hips in 99 patients for a mean of 11 years. All final femoral rasps used in this study overrasped by 0.5 to 1.0 mm for stem insertion, resulting in relatively thin cement mantles. Both components of one hip were removed because of infection. The other 5 acetabular components were revised for osteolysis, recurrent dislocation, or dislodgement of the polyethylene liner. No femoral component was revised for aseptic loosening. We conclude that the tight fit technique using a canal-filling stem may produce good long-term results for patients with hip dysplasia.

Uncompromised quality of the cement mantle in Exeter femoral components implanted through a minimally-invasive direct anterior approach

A complete cement mantle is important for the longevity of a total hip replacement. In the minimally-invasive direct anterior approach used at the Innsbruck University hospital, the femoral component has to be inserted into the femoral canal by an angulated movement. In a cadaver study, the quality and the extent of the cement mantle surrounding 13 Exeter femoral components implanted straight through a standard anterolateral transgluteal approach were compared with those of 13 similar femoral components implanted in an angulated fashion through a direct anterior approach. A third-generation cementing technique was used. The inner and outer contours of the cement mantles was traced from CT scans and the thickness and cross-sectional area determined.

In no case was the cement mantle incomplete. The total mean thickness of the cement mantle was 3.62 mm (95% confidence interval 3.59 to 3.65). The mean thickness in the group using the minimally-invasive approach was 0.16 mm less than that in the anterolateral group. The distribution of the thickness was similar in the two groups. The mean thickness was less on the anteromedial and anterolateral aspect than on the posterior aspect of the femur.

There is no evidence that the angulated introduction of Exeter femoral components in the direct anterior approach in cadavers compromises the quality, extent or thickness of the cement mantle.

CT analysis of defects of the cement mantle and alignment of the stem

Using a modern cementing technique, we implanted 22 stereolithographic polymeric replicas of the Charnley-Kerboul stem in 11 pairs of human cadaver femora. On one side, the replicas were cemented line-to-line with the largest broach. On the other, one-size undersized replicas were used (radial difference, 0.89 mm sd 0.13).

CT analysis showed that the line-to-line stems without distal centralisers were at least as well aligned and centered as undersized stems with a centraliser, but were surrounded by less cement and presented more areas of thin (< 2 mm) or deficient (< 1 mm) cement. These areas were located predominantly at the corners and in the middle and distal thirds of the stem. Nevertheless, in line-to-line stems, penetration of cement into cancellous bone resulted in a mean thickness of cement of 3.1 mm (sd 0.6) and only 6.2% of deficient and 26.4% of thin cement. In over 90% of these areas, the cement was directly supported by cortical bone or cortical bone with less than 1 mm of cancellous bone interposed.

When Charnley-Kerboul stems are cemented line-to-line, good clinical results are observed because cement-deficient areas are limited and are frequently supported by cortical bone.

In vitro analysis of the cement mantle of femoral hip implants: development and validation of a CT-scan based measurement tool

We developed, validated and assessed inter- and intraobserver reliability of a CT-scan based measurement tool to evaluate morphological characteristics of the bone-cement-stem complex of hip implants in cadaver femurs. Two different models were investigated: the stem-cavity model using a double tapered polished femoral-stem that is removed after cement curing and the plastic-replica model using a stereolithographic stem replica that is left in place during CT-scanning. Software was developed to segment and analyze connective CT-images and identify the contours of bone, cement, and stem based on their respective gray values. Volume parameters (whole specimen, cement, stem, air contents of bone and cement), concentricity parameters (distances between centroids of stem and cement, cement and bone, stem and bone), contact surfaces (bone/air and cement/bone) and bone cement mantle thickness parameters were calculated. A three-dimensional protocol was developed to evaluate the minimal mantle thickness out of the CT-plane. The average accuracy for surfaces within CT-images was 7.47 mm2 (1.80%), for bone and cement mantle thickness it was 0.51 mm (9.39%), for distances between centroids it was 0.38 mm (18.5%) and contours: 0.27 mm (2.57%). The intra- and interobserver reliability of air content in bone and cement was sub-optimal (intraclass-correlation coefficient (ICC) as low as 0.54 with an average ICC of 0.85). All other variables were reliable (ICC>0.81, average ICC: 0.96). This in vitro technique can assess characteristics of cement mantles produced by different cementing techniques, stem types or centralizers.

Fluoroscopy-Based 3-D Reconstruction of Femoral Bone Cement: A New Approach for Revision Total Hip Replacement

In revision total hip replacement the removal of the distal femoral bone cement can be a time consuming and risky operation due to the difficulty in determining the three-dimensional (3-D) boundary of the cement. We present a new approach to reconstruct the bone cement volume by using just a small number of calibrated multiplanar X-ray images. The modular system design allows the surgeon to react intraoperatively to problems arising during the individual situation. When encountering problems during conventional cement removal, the system can be used on demand to acquire a few calibrated X-ray images. After a semi-automatic segmentation and 3-D reconstruction of the cement with a deformable model, the system guides the surgeon through a free-hand navigated or robot-assisted cement removal. The experimental evaluation using plastic test implants cemented into anatomic specimen of human femoral bone has shown the potential of this method with a maximal error of 1.2 mm (0.5 mm RMS) for the distal cement based on just 4-5 multiplanar X-ray images. A first test of the complete system, comparing the 3-D-reconstruction with a computed tompgraphy data set, confirmed these results with a mean error about 1 mm.

Cement microcracks in thin-mantle regions after in vitro fatigue loading

An in vitro study of cemented femoral hip components was conducted to determine if microcracks in the cement mantle would preferentially form in thin-mantle regions as a result of cyclic fatigue loading via stair-climbing. Overall, there was not an increased amount of microcracks in thin-mantle (<2 mm) regions (number found/number expected = 0.59, P<.03). However, through cracks that extended between the stem to the bone were more prevalent in thin-mantle regions (number found/number expected = 2.93, P<.03). Although cracks form throughout the cement mantle and appear to grow at the same rate, thin-mantle regions are most likely to have through cracks after fatigue loading. This is consistent with results from at-autopsy studies of well-fixed femoral components and supports the general guideline that thin-mantle regions should be avoided in the cementing of the femoral stem.

The Effect of Stem Length on Femoral Component Positioning in Canine Total Hip Arthroplasty

OBJECTIVE

To determine the effects of femoral prosthesis stem length on positioning of the femoral component within the canine femur.

STUDY DESIGN

An in vitro experimental study.

SAMPLE POPULATION

Eleven adult, mixed breed, canine cadaver femurs.

METHODS

Polymethylmethacrylate centralized Biomedtrix size 5, 6, and 7 standard and 1cm shortened implants were placed in specimens, manipulated to achieve maximal displacements of the implant tip in each plane, and radiographed. Measurements of the implant angle, tip offset, and minimal tip to endosteal surface distance were obtained with image processing software. The effects of implant length and size on implant positioning were evaluated with the use of Student's t, chi(2) exact, and 2-way ANOVA testing.

RESULTS

Statistically significant increases were noted in tip to caudal cortex distance in the sagittal plane, and available angle variability and tip offset variability in the transverse plane for shortened size 6 and 7 stems relative to the standard stems. No significant differences were noted in size 5 stems. Statistically significant increases in tip to caudal cortex distance and transverse plane available angle variability for standard 6 compared to standard 7 stems were noted.

CONCLUSIONS

Shortened stems result in statistical improvement of several variables of femoral component positioning. However, the improvement appears to be clinically negligible.

CLINICAL RELEVANCE

Alteration of current stem lengths is not recommended. The use of undersized standard implants may improve femoral component positioning in total hip arthroplasty.

A quantitative analysis of bone support comparing cementless tapered and distal fixation total hip replacements

The purpose of this study was to develop a technique to accurately assess cementless femoral stem-bone contact. Using this technique, differences in contact patterns between tapered (Synergy) and cylindrical distal fixation (Prodigy) cementless stems were explored. Femurs were prepared and the 2 types of femoral stems were implanted. After implantation, the femurs were imaged in a spiral computed tomography scanner and analyzed using novel custom-developed imaging software. This analysis used a geometric deformable-model UNIX-based software that determined bone-prosthesis contact area. The tapered stem features proximal, cancellous bone contact and a 3-point fixation pattern. The cylindrical distal fixation stem demonstrates cortical support in the distal aspect of the stem.