Poor reproducibility in radiographic grading of femoral cementing technique in total hip arthroplasty

Are we getting better at cementing femoral stems in total hip arthroplasty? A 5-year institutional trend

INTRODUCTION

Femoral stem cementation provides excellent implant longevity with a low periprosthetic fracture rate among patients with compromised bone quality or abnormal anatomy. We radiologically evaluated the quality of the femoral cement mantle in patients undergoing THA to examine whether cementation quality improved with increased institutional experience.

METHODS

A retrospective study of 542 primary elective THAs performed using cemented stems from 2016 to 2021 at a high-volume orthopedic specialty center was conducted. Immediate post-operative anterior-posterior (AP) and lateral radiographs were evaluated to assess cement mantle quality based on the Barrack classification. Cement mantles were deemed satisfactory (Barrack A and B) or unsatisfactory (Barrack C and D). Regression was performed to identify predictors of unsatisfactory cementation quality.

RESULTS

The annual cemented primary THA volume increased throughout the study period from 14 cases in 2016 to 201 cases in 2021. Overall, the majority of cement mantles were deemed satisfactory; 91.7% on AP radiographs and 91.0% on lateral radiographs. Satisfactory cementation on AP radiograph achievement rates improved during the study period, which coincided with greater annual volume (p < 0.001). No association was found between posterior and direct anterior surgical approaches and satisfactory cementation quality on both AP and lateral radiographs.

CONCLUSION

Majority of femoral stems had satisfactory cementation quality. Higher institutional annual cemented THA volume was associated with improved cementation quality. Residency and fellowship training programs should place greater emphasis on the importance of femoral stem cementation for appropriately indicated patients.

LEVEL OF EVIDENCE

III, retrospective cohort study.

Cement Mantle Quality and Stem Alignment in Cemented Collarless Polished Tapered Stems Implanted via the Direct Anterior and Direct Lateral Approaches: A Single Institution Experience

BACKGROUND

The aim of this study was to compare the stem alignment and the quality of cement mantle of collarless polished tapered cemented stems inserted through the direct anterior approach (DAA) and the direct lateral approach (DLA).

METHODS

A comparative retrospective study of 232 hybrid total hip arthroplasties using a cemented collarless polished tapered stem through either the DAA (n = 147) or DLA (n = 85) was performed. Radiographic evaluation included stem alignment, cement mantle quality, and cement mantle thickness.

RESULTS

On anteroposterior radiographs, stems implanted through the DLA were more likely to be in neutral alignment, than those implanted through the DAA (83.5%[n = 71] versus 71.4% [n = 105]; P = <.001). No difference between approaches was noted for stem alignment on lateral radiographs or cement mantle quality. Multivariate analysis revealed factors associated with suboptimal cement mantle and included Dorr type B or C femur as well as male gender. A mean cement mantle thickness ≥2mm was achieved in all Gruen zones for both approaches.

CONCLUSION

In our series, the DAA was associated with a higher incidence of coronal plane stem malalignment compared to the DLA when using cemented tapered polished femoral components for total hip arthroplasty. No difference in lateral stem alignment or cement mantle quality was found.

Long-Term Outcomes of 496 Anatomical Cementless Modular Femoral Stems: Eleven to Twenty Years of Follow-Up

BACKGROUND

The aim of the study is to assess the long-term outcomes of this specific stem (anatomical cementless modular stem ESOP), to review the survivorship, complication rate, and radiographic and clinical outcomes.

METHODS

Descriptive and analytical retrospective longitudinal observational study of patients was operated on total hip arthroplasty between 1998 and 2007. Four hundred ninety-six prostheses corresponding to 447 patients were reviewed, mean age was 65.8 years (standard deviation [SD] ±11.6 years), and median follow-up time was 13.4 years (range 1-20). The most used cups were cementless (75.8%). The most frequent friction pairs were metal-polyethylene (53.1%) and ceramic-polyethylene (24.2%). Main variables analyzed were stem survival, subsidence, coronal orientation, osteolysis, reintervention, and Oxford Hip Score.

RESULTS

From 496 implants, there were 22 lost to follow-up (4.4%). Stem revision was performed in 51 patients: 26 periprosthetic joint infections (2-stage revision), 16 periprosthetic fractures, and 8 one-stage revisions (6 real aseptic loosening with negative culture after revision). The stem survivorship at more than 15 years for any reason was 89.2% and for aseptic loosening 97.97%. No specific complications were found due to modularity. The mean subsidence and orientation was 2.06 mm (SD ±5.11 mm) and 0.41° varus (SD ±2.20°) respectively. Subsidence >5 mm or varus >5° was associated with a higher revision rate. Osteolysis was found in 110 patients (zone I = 79, VII = 57), associated with zirconium-polyethylene, without relationship to the stem revision rate or Oxford Hip Score.

CONCLUSION

To our knowledge, this study represents the largest series of this stem, revealing an excellent survival rate and long-term clinical outcomes similar to the best results of classical cementless stems published in the literature.

Fourteen-year experience with short cemented stems in total hip replacement

PURPOSE

The age of the population requiring total hip replacement (THR) is increasing and this may lead to a return of cemented stems. Advantages of a short cemented femoral device include preservation of metaphyseal bone, easier insertion, and easier cement removal in case of revision. The purpose of this study is to describe the rationale and assess midterm results of unique innovative short cemented double-tapered polished stem applied with contemporary cementing techniques.

METHODS

Our experience with this short cemented stem includes two different groups of elderly patients. Group 1 (prototype version of the short stem) from January 2005 to January 2008 counts 43 THR. Group 2 (final commercial version of the short stem) from January 2013 to January 2015 counts 54 THR. The average age in groups 1 and 2 was 79 and 75 respectively. Patients underwent clinical follow-up with the Harris Hip Score (HHS) and completed radiographic evaluation.

RESULTS

Thirty-one patients of group 1 had died for reasons unrelated to their THR. The surviving 9 hips have a follow-up of 11.2 years. In group 2, eight  patients died for reasons unrelated to their THR. Follow-up for the surviving 40 patients is 4.6 years. HHS improved in both groups. In 34/43 hips of group 1 and in 41/54 of group 2 we observed a Barrack grade A cement mantle. Survival with revision of the stem for aseptic loosening as the endpoint was 100%.

CONCLUSIONS

This study confirms the effectiveness of a short, polished, collarless, tapered cemented stem implanted with contemporary cementing techniques which appears as successful as the standard sized components.

Interobserver reliability of the radiographic assessment of cement fixation in total hip arthroplasty

BACKGROUND

The objective of this work is to evaluate the performance of a modified quantitative Barrack Cement grading in primary THA. Previous studies demonstrated both poor intraobserver and interobserver reliability which may be due to the qualitative nature of the scale.

METHODS

Interobserver reliability of the Barrack Cement Grading System in its original format and then in combination with a quantitative measurement of implant/cement lengths was evaluated on 50 immediate post-operative radiographs of primary cemented arthroplasties. Intraobserver reliability was also assessed on a sub-sample of radiographs. Three evaluators with different skill levels and specialty participated: an arthroplasty surgeon, an orthopaedic resident and a radiologist. Reliability was measured using a weighted kappa coefficient for paired comparisons among the evaluators.

RESULTS

Interobserver reliability was poor (κ < 0.10) for all pairings of the Barrack System. The modified quantitative system achieved slight (κ < 0.20) to poor reliability. Intraobserver reliability was dependent on the skill and specialty of the evaluator with maximal values achieved for the experienced arthroplasty surgeon using the modified quantitative system (κ = 0.62).

CONCLUSION

Use of the modified scale may improve the reliability of ratings when used by individual experienced arthroplasty surgeons.

Radiographic grading of femoral stem cementation in hip arthroplasty

OBJECTIVE:

To determine intra and interobserver agreement of the grading system for femoral cementation in hip arthroplasty proposed by Barrack.

METHODS:

Immediate anteroposterior and lateral postoperative radiographs of 55 primary total hip arthroplasties were assessed by two observers familiar with the use of this grading system. The assessments were performed on two separate occasions by each observer and independently. The statistical analysis measured the Kappa coefficient, which determines the degree of agreement between tests with categorical variables.

RESULTS:

Intraobserver Kappa coefficient varied from 0.43 to 0.68, demonstrating moderate to substantial strength of agreement; interobserver Kappa coefficient varied from 0.19 to 0.44, demonstrating slight to moderate strength of agreement.

CONCLUSION:

Intra and particularly interobserver agreement are limited in this grading system, even when used by trained individuals. Level of Evidence III, Study of nonconsecutive patients; without consistently applied reference "gold" standard.

Radiologic evaluation of the cement mantle in the femoral shaft. A comparative study using a fast-set or a standard-set cement

INTRODUCTION

At present a wide spectrum of cement types are available for cemented total hip arthroplasty (CTHA). All types have the same objective, i.e. to prolong the life of the implant for as long as possible. The purpose of this study was to compare the radiologic cement mantle of CTHA using cement with fast or standard setting characteristics.

METHOD

A prospective comparative study of patients who underwent CTHA was performed: the first group received fast setting cement (Cemex System Fast), the second group received standard setting cement (Cemex System). A radiologic evaluation of the cement mantle was done using Barrack's classification. In order to give the study clinical relevance we assembled Barrack's classification in two groups: 1) Low risk group (Types A and B); 2) High risk group (Types C and D). According to ISO 5833:2002, the international standard was used to perform physico-chemical (polymerization temperature, setting time) and mechanical testing (compression strength, bending strength and bending modulus).

RESULTS

The fast setting cement showed a shorter setting time and a higher polymerization temperature. The mechanical performances of both cements met the ISO limits. At a mean follow-up of 23 months (11-37 months) no statistically significant radiological difference was found in the radiologic cement mantle between the two groups either in the post-operative X-ray evaluation (p=0.32) or in the last follow-up (p=0.72). Statistical evaluation was done comparing the two sub-groups, i.e. low risk and high risk.

CONCLUSIONS

The use of fast or standard setting cement does not produce any difference in the quality of the radiologic cement mantle in the short-term. Both cements comply with ISO 5833 requirements.

Femoral cement pressurization in hip arthroplasty: a comparison of 3 systems

Cement pressurization is critical to achieving optimal results in cemented arthroplasty of the hip. An in vitro experiment using plastic femoral models (10 per group) was undertaken to measure the pressures developed by 3 cementing systems: the Howmedica Mark 1 (Stryker Howmedica, Limerick, Ireland) and DePuy Cemvac retrograde cementation systems (DePuy CMW, Blackpool, UK), and a novel antegrade system consisting of a 60-mL catheter-tipped syringe and a Miller proximal femoral seal (Zimmer Ltd, Swindon, UK). The mean pressure was higher for the syringe system (161.45 +/- 28.9 kPa) than the Mark 1 (103.51 +/- 22.0 kPa) or Cemvac (92.65 +/- 30.7 kPa) systems (P = .0001). In addition, fewer cement mantle defects were seen with the syringe system (1, interquartile range [IQR] 1-2) than the Mark 1 (3, IQR 2-4) or Cemvac (3, IQR 1-3) systems (P = .0256).

Prediction of Charnley femoral stem aseptic loosening by early post-operative radiological features

We describe the association between immediate post-operative radiological appearances and early aseptic failure of total hip replacement. Sixty-three hips were entered into the aseptic failure group and 138 into the control group. Alignment of the femoral stem was not associated with failure (p=0.283). Thickness of the cement mantle was associated with failure in Gruen zones 6 (p=0.040) and 7 (p=0.003). A significant association for the presence of radiolucent lines was found for Gruen zones 3 (p=0.0001) and 5 (p=0.0001). Grade of cementation was associated with failure for Barrack grades C (p=0.001) and D (p=0.001). This study has demonstrated that easily applied radiological criteria can be used to identify 'hip arthroplasties at risk' from the immediate post-operative radiograph.

Ten-year survival of the MS-30 matt-surfaced cemented stem

The Morscher-Spotorno (MS-30) femoral stem is a stainless-steel, straight, three-dimensionally tapered, collarless implant for cemented fixation in total hip replacement.

We report the results at ten years of a consecutive series of 124 total hip replacements in 121 patients with the matt-surfaced MS-30 stem and an alumina ceramic head of 28-mm diameter. All the stems were fixed with Palacos bone cement with gentamicin using a modern cementing technique. They were combined with an uncemented, press-fit cup. The mean period of observation was 10.2 years (8.3 to 12.1) and no patient was lost to follow-up. Twenty-seven patients (22%) died with the implant in situ. Nine could only be interviewed by telephone. We included 85 patients with 88 hips in the clinical and radiological follow-up examinations.

None of the stems or cups had been revised. The Harris hip score was excellent or good in 97% (85 hips) and moderate in 3% (three hips). Radiologically, six hips (6.8%) had osteolysis adjacent to the stem, mostly in Gruen zone 7. Twenty (22.7%) showed one or more radiolucent lines. Twenty-two stems (25%) had subsided by 2 mm to 5 mm. In these cases two showed osteolysis (9.1%) with subsidence and four without (6.1%). Radiolucent lines were seen in seven with migration (31.8%) and in 13 without (19.7%). No infections and no acetabular osteolysis were observed.

The clinical results were excellent with survivorship after ten years of 100% and only a slightly statistically non-significant higher rate of osteolysis and radiolucency in cases of subsidence.

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.

Peri-acetabular radiolucent lines: inter- and intra-observer agreement on post-operative radiographs

Peri-acetabular radiolucent lines (RLLs) seen on "early" post-operative radiographs have been identified as a potential predictor of long-term implant performance. This study examines the inter- and intra-observer variation encountered when assessing such radiographs. Four consultant orthopaedic surgeons assessed the presence, extent and width of RLLs in 220 radiographs performed on 50 patients taken one to two weeks, six weeks, six months and one year following surgery. Inter-observer agreement was fair at 7-14 days but improved to moderate to good in films at six and 12 months. Intra-observer agreement was moderate to good at 7-10 days but again improved to good at 6 and 12 months. When only the presence or absence of RLLs was considered, both inter-observer and intra-observer agreement improved for both the six-month and one-year radiographs. This experiment shows that caution must be used for the interpretation of RLLs on hip radiographs taken during the very early post-operative period. We recommend that films taken at least six weeks to six months following surgery should be used for assessment to reduce observer variation. For optimum results, a single experienced observer should do the assessment with a simple classification.

The Elite Plus total hip arthroplasty

We prospectively studied 217 patients who underwent 234 Elite Plus total hip arthroplasties. At a mean of 6.4 (SD 0.7) years post-operatively, 39 patients had died and 22 were either lost to follow-up or had no radiographs available. Clinical (Oxford hip score) and radiological assessments were performed on 156 patients (168 hip arthroplasties) who had a mean age of 67.7 (SD 9.7) years at operation.

In the assessed group, 26 of 159 (16.4%) of femoral stems which had not already been revised and 19 of 159 (11.9%) of acetabular cups were definitely loose. In total, 52 of 168 (31%) of hips had either been revised or had definite evidence of loosening of a component. We could not establish any relationship between clinical and radiological outcomes.

Despite the fact that the clinical outcome and rate of revision for the Elite Plus appeared to meet international standards, our findings give us cause for concern. We believe that joint registries should include radiological surveillance in order to provide reliable information about medium-term outcomes for hip prostheses.

A comparison of distal canal restrictors in primary cemented femoral hip arthroplasty

A retrospective study evaluated 75 total hip arthroplasties performed over a 4-year period using 4 different cement restrictors. A harvested bone restrictor, polyethylene restrictor (Smith & Nephew, Richards Inc, Memphis, Tenn), Biostop G (Depuy Orthopaedics, Warsaw, Ind), and polymethylmethacrylate (PMMA) (Wright Medical Technology, Arlington, Tex) were compared for the percentage of failures, the average length of the cement mantle, and the width of the femoral canal compared to the cement grade. Patient age, sex, and cement type were also evaluated for their influence on cement grade. The PMMA restrictor and bone performed better than the Richards plug and Biostop G restrictor.

Plug migration and cement mantle assessment in total hip replacement

We reviewed a series of consecutive total hip replacements with cemented femoral components. Modern cementing techniques were followed in all cases, but two different medullary plugs were used-one was polyethylene and the other bioabsorbable gelatin. Cement mantle quality and plug migration were assessed by three different observers (X, Y, and Z); their findings did not agree. This was particularly evident when the cement mantles were assessed. There was a better cement mantle grading and less distal migration with polyethylene plugs, although there was no significant statistical difference between the two groups.

Radiographic evaluation of Charnley cups used in first-time revision: repeated observations for 7-15 years

The radiographs of 46 consecutive polyethylene cups used in cemented first-time revision of the acetabulum were studied up to a mean of 10.7 years (range, 0.5-16.3 years). Six cups developed loosening, of which 2 were revised. New radiolucent lines appeared mainly up to the 3 years follow-up. Progression of radiolucencies to new regions was noted in 28 (61%) cups. This progression occurred as an increase in extension from the periphery to the central region of the interface, whereas the width only showed minor changes. Our findings indicate that even radiolucent lines with a width <1.0 mm should be given attention because these lines can surround the cup before significant migration (>5 mm) is established. True lateral radiographs exposed to visualize the interface add information concerning presence of loosening. According to our opinion, complete radiolucent lines on either the anterior-posterior or lateral view, with a width of 0.3 to 0.5 mm or more, should be regarded as radiographic failure.

Four-angle radiographic assessment of cement mantle thickness in cemented total hip arthroplasty

In this study, the cement mantle thickness of 57 hips undergoing primary cemented total hip arthroplasty (THA) were investigated with 4 angle radiographs. All surgeries were performed with a standardized posterolateral surgical approach. In addition to conventional anteroposterior and lateral radiographs, obturator oblique and iliac oblique radiographs were taken. In the evaluation of the cementing grade on the anteroposterior radiograph, the incidence of hips with thin cement mantles was 25%. In evaluating the cementing grade on the anteroposterior and lateral radiographs, we found an incidence of hips with thin cement mantles of 37%. From the evaluations with 4 angle radiographs, 10 hips were additionally assigned as being of a poor cementing grade (Mulroy's grade C-2). Thin cement mantles were mainly seen on the iliac oblique radiographs.

Femoral impaction grafting in revision hip arthroplasty with irradiated bone

We evaluated the results of femoral impaction grafting with the Exeter stem (Stryker Howmedica Osteonics, Newbury, UK) and irradiated bone-graft. We followed 57 hips for an average of 27 months. Endo-Klinik grading showed 8 grade 1, 22 grade 2, and 27 grade 3 hips. Radiographic analysis revealed cortical repair in 34% and graft incorporation in 39% but no evidence of trabecular remodeling. Moderate subsidence (5-10 mm) occurred in 7 patients (12.5%), and massive subsidence (>10 mm) occurred in 4 patients (7%). Complications included 6 dislocations, 3 periprosthetic fractures, and 2 stem revisions. Impaction grafting with the Exeter system produces satisfactory results for most patients, but a few hips perform poorly, and the reasons for this are unclear. We have concerns about irradiated bone-graft because the characteristic changes of graft remodeling are not seen.

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

Cemented fixation of the femoral stem is the gold standard for patients older than 60 years. The importance of reliably achieving an adequate cement mantle has been shown in many studies. Currently, inspection and grading of plain radiographs is the accepted method for study of the cement mantle. However, the reliability of plain radiographs for this purpose has been questioned. In addition, the interobserver agreement of current grading systems has been shown to be limited. A new in vitro method of cement mantle analysis is described. Plastic replicas of six contemporary stems were implanted into femurs from cadavers. The specimens were imaged with a computed tomography scanner. Detailed, computer-assisted analysis of mantle thickness was done. Comparisons were made between designs. A subset was compared with standard radiographs. Plain radiographs overestimated thickness and underestimated the deficiencies. There was significant variability in the mantle produced by the different designs. Commonly used designs had deficiencies in their mantles by standard criteria despite proper surgical technique. The importance of being fully acquainted with the particular implant one uses is emphasized by these results. This is a valuable technique for investigation of the effects on the cement mantle of implant design, surgical technique, and patient anatomy.

Dependency of cement mantle thickness on femoral stem design and centralizer

Deficient cement mantles may be detrimental with regard to long-term outcome of cemented femoral stems. We performed a cadaver study on 48 left femora with 4 different stem designs (1 anatomic, 3 straight) to study the influence of stem design, centralizer, and femur type on cement mantle thickness. A radiographic and microradiograhic analysis was done. Overall, 88% of stems were aligned within 1 degrees of neutral in the frontal plane. In Gruen zones 1 through 7, we measured 24 thin cement mantles (<2 mm) in 19 specimens with no correlation to stem design or zone. In the sagittal plane, typical areas of thin cement mantles were identified in Gruen zones 8 and 9 (n = 39) and 12 (n = 21). The anatomic stem design carried the lowest risk (54%) of producing a thin cement mantle proximally in Gruen zones 8 and 9. The risk for straight stem designs was >90%. Straight stems without centralizer showed the highest risk of thin cement mantles in Gruen zone 12 (93%). Centralizers were efficient to prevent thin cement mantles in zone 12 but had no effect proximally. Lateral radiographs are essential to allow for adequate radiographic assessment of the cement mantle and stem alignment. There is a high risk of producing thin cement mantles in Gruen zones 8 and 9, in particular when straight stems are used. Posterior canal entry and low neck osteotomies are essential. Anatomic stems respect the anatomy, allow for more even cement mantles, minimize the risk of thin cement mantles without the use of centralizers, and may be considered in the femur with marked proximal bow.

Femoral alignment of the Charnley stem: a randomized trial comparing the original with the new instrumentation in 123 hips

Deficient cement mantles are associated with aseptic loosening of the stem component of total hip replacement. In a former study of 206 Charnley stems, we found high frequencies of stem malalignment, especially on the lateral view, consequently resulting in a high percentage of low cement mantle grading. If the "true" lateral radiographic projection is not used, there is a risk that the frequency of mantle defects is underestimated. A logistic regression analysis showed a high correlation between low cement mantle grading and stem loosening after a mean follow-up of 10 years. The new Charnley instrumentation was introduced in 1994 and we started a randomized trial including 123 prostheses to determine whether the new instrumentation improved the position of the stem in both the AP and lateral planes. Postoperative radiographs revealed a significant change in AP positioning-i.e., from a high percentage of varus with the original method to valgus with the new instrumentation. However, there was no difference on the lateral view, with a persisting high frequency of stems with implant-inner cortex contact resulting in high percentages of low cement-mantle grading in both systems. If this deficiency, in a long-term perspective, is associated with aseptic loosening, as many authors have claimed, the manufacturers should address the problem.

Effect of stem stiffness and bone stiffness on bone remodeling in cemented total hip replacement

The hypothesis in this study is that the stem stiffness-to-bone stiffness ratio influences the incidence and type of bone remodeling and fixation with cemented total hip arthroplasty. Ninety-one patients with 99 hips had cemented stems using 3 different anatomic porous replacement designs. The APR I and APR II titanium stems with proximal porous coating on the proximal one fourth of the stem were cemented into 49 and 35 patients. The APR II-C stem, which is a cobalt-chrome stem only for cemented fixation, was cemented into 15 patients. These 3 different stem designs were used to study different metals as well as different stem shapes. The average follow-up was 4.3 years (range, 2-10 years) with all hips having 2 years' follow-up and 42 hips at least 5 years' follow-up. Bone remodeling was measured as stress shielding, calcar resorption, and distal hypertrophy on anteroposterior and lateral radiographs of the hip. Stress shielding was measured by the 4 grades described by Engh. A stem stiffness-to-femoral bone stiffness ratio was calculated from the plain radiographs with the stem stiffness known from the manufacturer and the bone stiffness calculated using measurements of the outer and inner diameters of the femur. There was no statistical difference for bone remodeling and fixation between the 3 stem shapes or 2 metal types used in these hips. No stem was loose, and only 10 had radiolucent lines. Stress shielding was statistically related to stem stiffness but was more strongly related to the axial stiffness ratio, mediolateral bending stiffness ratio, anteroposterior stiffness ratio, and torsional stiffness ratio. Stress shielding grade 3 and 4 was present in 20% of hips with a torsional stiffness ratio < 0.33, in 38% of hips with a torsional stiffness ratio of 0.34 to 0.5, and in 70% of hips with a torsional stiffness ratio > 0.5. Five-year results showed no statistical change in stress shielding, calcar resorption, and distal hypertrophy from the 2-year observations. The stem stiffness-to-bone stiffness ratio influenced bone remodeling but not fixation of these cemented stems.

Femoral cement grading in total hip arthroplasty

The current gold standard for primary total hip arthroplasty is a cemented femoral component combined with a porous-coated acetabular component. Barrack and colleagues described a femoral cement mantle grading system which is increasingly being used to evaluate surgical technique and to compare arthroplasty results. The immediate postoperative radiographs of 100 primary total hip arthroplasty cases from five community surgeons were assessed by three observers to evaluate the overall quality of cement technique, the interobserver variability in cement mantle grading, and specific characteristics of the grading system. All three observers agreed on the grading in only 73% of the x-rays (anteroposterior view, 69%; lateral view, 77%). Compared with reports in the literature from specialized hip arthroplasty centers, a very high proportion of the cases had grade C mantles. To gain a balanced perspective of the global effectiveness and longevity of cemented total hip arthroplasty it is important that follow-up studies be reported upon from representative cross sections of the orthopaedic community.