Early migration pattern of the uncemented CLS stem in total hip arthroplasties

Does Lack of Initial Collar-Calcar Contact Influence Performance of Collared Cementless Femoral Stems?

Background

Initial stability of cementless stems is important to minimize the risk of subsidence, pain, and periprosthetic fracture after total hip arthroplasty (THA). Collared stems improve initial component stability when contacting the femoral calcar. Direct contact is not always achieved, and collared stem performance has not been studied in this context. We hypothesized that collared stems achieving direct contact would demonstrate reduced subsidence.

Methods

A single-surgeon retrospective study of 482 consecutive primary THAs implanted between February 2020 and May 2023 using collared cementless stems was performed. The 2 cohorts included stems with initial collar-calcar contact vs stems without. Subsidence was evaluated by comparing intraoperative fluoroscopy to postoperative 8-week radiographs. Binary logistic regression identified independent risk factors for subsidence. Chi-square tests were used for categorical variables and t-tests for continuous variables.

Results

Of stems, 63.9% achieved initial collar-calcar contact, while 36.1% did not. The rate (1.3% vs 19.0%; P < .001) and magnitude (0.02 mm, range 0-3 mm vs 0.35 mm, range 0-3 mm; P < .001) of subsidence were significantly higher among stems without initial contact. Stems without initial collar-calcar contact (P < .001) and male gender (P = .007) were independent risk factors for subsidence. Two patients with initial contact had nondisplaced calcar cracks and <3 mm of subsidence at 4 weeks, which healed with protected weight-bearing. Stem survivorship was 100% in both groups, with all achieving osteointegration and none needing revision.

Conclusions

Excellent performance of collared cementless stems was observed at 8 weeks after primary THA. Initial collar-calcar contact lowered the risk and magnitude of minor subsidence but did not affect survivorship or fracture risk.

Level of Evidence

Level III.

Influence of bone mineral density on femoral stem subsidence after cementless THA

INTRODUCTION

Femoral stem subsidence can lead to aseptic loosening after total hip arthroplasty (THA). Low bone mineral density (BMD) is a risk factor for stem subsidence as it can affect the initial stability and osteointegration. We evaluated whether reduced bone mineral density is related to higher subsidence of the femoral stem after primary cementless THA with enhanced recovery rehabilitation.

METHODS

79 patients who had undergone primary cementless THA with enhanced recovery rehabilitation were analyzed retrospectively. Subsidence of the femoral stem was measured on standing pelvic anterior-posterior radiographs after 4-6 weeks and one year. Patient individual risk factors for stem subsidence (stem size, canal flare index, canal fill ratio, body mass index (BMI), demographic data) were correlated. Dual X-ray absorptiometry (DXA) scans were performed of the formal neck and the lumbar spine including the calculation of T-score and Z-score. Patient-reported outcome measures were evaluated 12 months postoperatively.

RESULTS

Stem subsidence appeared regardless of BMD (overall collective 2.3 ± 1.64 mm). Measure of subsidence was even higher in patients with normal BMD (2.8 ± 1.7 mm vs. 2.0 ± 1.5 mm, p = 0.05). High BMI was correlated with increased stem subsidence (p = 0.015). Subsidence had no impact on improvement of patient-related outcome measures (WOMAC, EQ-5D-5L and EQ-VAS) after THA. Patients with low BMD reported lower quality of life 12 month postoperatively compared to patients with normal BMD (EQ-5D-5L 0.82 vs. 0.91, p = 0.03).

CONCLUSION

Stable fixation of a cementless stem succeeds also in patients with reduced BMD. Regarding stem subsidence, enhanced recovery rehabilitation can be safely applied in patients with low BMD.

Primary Cementless Femoral Stems in Conversion Hip Arthroplasty After Failed Fixation of Intertrochanteric Fractures

Salvage conversion hip arthroplasty is a viable solution to restore function and reduce pain after failed intertrochanteric hip fracture fixation. Our primary objective was to assess early outcomes achieved with primary cementless metaphyseal-engaging femoral stems for conversion hip arthroplasty compared with revision diaphyseal-engaging stems. This was a retrospective review of 70 patients with failed intertrochanteric hip fractures subsequently managed with conversion total hip arthroplasty or hemiarthroplasty. Thirty-five patients who underwent conversion using a primary cementless stem were compared with 35 patients who underwent conversion using a revision stem. The groups were similar regarding sex, body mass index, American Society of Anesthesiologists classification, preoperative diagnosis, and implants removed. Clinical and radiographic outcomes and complications were compared over a mean follow-up of 6 years. The primary stem cohort had a shorter mean hospital stay (3.03 vs 4.34 days, P=.028). There were no significant differences between the primary and revision cohorts regarding mean time to conversion (2.26 vs 1.75 years, P=.671), operative time (127 vs 131 minutes, P=.611), incidence of discharge to home (54.3% vs 37.1%, P=.23), postoperative complications (5.71% vs 5.71%, P=1.0), reoperations (5.71% vs 11.4%, P=.669), leg length discrepancy (5.33 vs 7.38 mm, P=.210), subsidence (20.0% vs 23.3%, P=.981), and Hip dysfunction and Osteoarthritis Outcome Score for Joint Replacement (78.6 vs 81.9, P=.723). We report comparable outcomes of conversion hip arthroplasty with the use of primary cementless and revision stems. Current primary cementless femoral stems may be considered for conversion hip arthroplasty for failed intertrochanteric fracture fixation. [Orthopedics. 2024;47(1):e6-e12.].

Early unrestricted vs. partial weight bearing after uncemented total hip arthroplasty: a systematic review and meta-analysis

Background

The choice of postoperative weight bearing protocol after uncemented total hip arthroplasty (THA) remains controversial. The aim of this study was to assess the efficacy and safety of immediate unrestricted weight bearing (UWB) compared with partial weight bearing (PWB) in patients undergoing uncemented THA.

Methods

Relevant articles were retrieved from electronic databases. Both randomized controlled trials (RCTs) and non-RCTs were included but analyzed separately. All functional and clinical outcomes with at least 2 independent study outcomes were meta-analyzed.

Results

A total of 17 studies were investigated. No adverse effect was found regarding micromotion of the femoral stem with immediate UWB following uncemented THA. There was also no correlation between immediate UWB and failure of ingrowth fixation and higher risks of femoral stem subsidence and surgical revision in RCTs. Harris hip score was better in patients with immediate UWB than those with PWB at 1 year post surgery, but the difference was not statistically significant.

Conclusions

Immediate UWB did not have extra harm compared with PWB in patients undergoing uncemented THA. UWB was not superior to PWB. Considering the improvement of Harris score and the compliance of patients, UWB can be encouraged in THA rehabilitation.

High grade femoral stem subsidence in uncemented hip hemiarthroplasty - A radiographic analysis and an early prediction while treating femoral neck fractures

PURPOSE

Femoral component subsidence is a known risk factor affecting almost all hip replacements using a collarless, cement-less stems. High grade subsidence >5mm is functionally limiting to the patient. Early analysis and prediction of this complication on the immediate post-operative radiographs will help surgeons to opt for alternative solutions to mitigate this complication.

METHODS

A retrospective study including 116 patients, who underwent cement-less bipolar hemi-arthroplasties treated from 2020-2022 were included in the study. Body Mass Index (BMI) and pre-operative American Society Anesthesiologist (ASA) score was retrieved from the medical records. Post operative radiographs on postoperative day two, at four weeks and at eight weeks were evaluated. Dorr's score, initial subsidence ratio (ISR) , stem angulation, proximal stem-canal fit (PSCF) ratio, distal stem-canal fit (DSCF) ratio, medial flare modifier (MFM) were recorded.

RESULTS

A total of 18 patients showed subsidence over 5mm on radiographs evaluated at four weeks. The mean high-grade stem subsidence was 13.5mm +/- 2.67. Evaluating their respective postoperative day two radiographs- ISR was >1 in 16 out of 18 patients (89%), PSCF ratio <0.75 in 83% and DSCF ratio <0.5 in 78% patients. All these patients had a neutral/negative MFM. BMI >25 (p<0.05) and ASA >3 (p<0.001) correlated with a higher degree of stem subsidence.

CONCLUSION

A lower BMI and ASA score accompanied by a positive MFM were protective factors against femoral stem subsidence. A higher ISR along with a PSCF ratio <0.75 and DSCF ratio <0.5, were highly predictive of stem subsidence over 5 mm.

Similar results after five years with the use of the Fitmore or the CLS femoral components

Although the Fitmore Hip Stem has been on the market for almost 15 years, it is still not well documented in randomized controlled trials. This study compares the Fitmore stem with the CementLeSs (CLS) in several different clinical and radiological aspects. The hypothesis is that there will be no difference in outcome between stems. In total, 44 patients with bilateral hip osteoarthritis were recruited from the outpatient clinic at a single tertiary orthopaedic centre. The patients were operated with bilateral one-stage total hip arthroplasty. The most painful hip was randomized to either Fitmore or CLS femoral component; the second hip was operated with the femoral component not used on the first side. Patients were evaluated at three and six months and at one, two, and five years postoperatively with patient-reported outcome measures, radiostereometric analysis, dual-energy X-ray absorptiometry, and conventional radiography. A total of 39 patients attended the follow-up visit at two years (primary outcome) and 35 patients at five years. The primary outcome was which hip the patient considered to have the best function at two years. At two and five years, more patients considered the hip with the CLS femoral component as superior but without a statistically significant difference. There were no differences in clinical outcome, magnitude of femoral component migration, or change of bone mineral density at five years. At three months, the Fitmore femoral component had subsided a median -0.71 mm (interquartile range (IQR) -1.67 to -0.20) and the CLS femoral component -0.70 mm (IQR -1.53 to -0.17; p = 0.742). In both groups the femoral head centre had migrated posteriorly (Fitmore -0.17 mm (IQR -0.98 to -0.04) and CLS -0.23 mm (IQR -0.87 to 0.07; p = 0.936)). After three months neither of the femoral components showed much further migration. During the first postoperative year, one Fitmore femoral component was revised due to aseptic loosening. Up to five years, we found no statistically significant difference in outcomes between the Fitmore and the CLS femoral components. The slightly worse outcomes, including one revised hip because of loosening, speaks against the hypothesis that the Fitmore femoral component should be advantageous compared to the CLS if more patients had been recruited to this study.

No Difference In Subsidence Between Modern Monoblock And Modular Titanium Fluted Tapered Femoral Stems

BACKGROUND

Subsidence remains a concern when utilizing tapered fluted titanium (TFT) femoral stems and may lead to leg length discrepancy, impingement, instability and failure to obtain osseointegration. This study aims to compare stem subsidence across three modern TFT stems. Our secondary aim was to investigate the influence of bicortical contact or 'scratch fit' on subsidence, as well as the role of intraoperative imaging in maximizing bicortical contact and preventing stem subsidence.

METHODS

A retrospective review of 271 hip arthroplasties utilizing modern TFT stems at a single institution was performed. Three stem designs were included in the analysis: one monoblock TFT stem (n=91) and two modular TFT stems (n=90; n=90). Patient demographics, Paprosky femoral bone loss classification, bicortical contact, utilization of intra-operative imaging, and stem subsidence (comparison of initial post-operative radiograph to the latest follow up radiograph - minimum three months) were recorded.

RESULTS

There was no statistically significant difference in overall subsidence (P=0.191) or the incidence of subsidence >5 millimeters between stems (P= 0.126). Subgroup analysis based on femoral bone loss grading showed no difference in subsidence between stems. Increased bicortical contact was associated with reduced subsidence (P=0.004). Intra-operative imaging was used in 46.5% (126 of 271) of cases; this was not correlated with bicortical contact (P=0.673) or subsidence (P=0.521).

CONCLUSION

All three modern TFT stems were highly successful and associated with low rates of subsidence, regardless of modular or monoblock design. Surgeons should select the stem that they feel is most clinically appropriate.

Results of Hip Arthroplasty Using a COREN Stem at a Minimum of Ten Years

Purpose

We report on the 10-year clinical hip function and radiologic outcomes of patients who underwent hip arthroplasty using a COREN stem.

Materials and Methods

A consecutive series of 224 primary cementless hip arthroplasty implantations were performed using a COREN stem between 2009 and 2011; among these, evaluation of 128 hips was performed during a minimum follow-up period of 10 years. The mean age of patients was 65.4 years (range, 40-82 years) and the mean duration of follow-up was 10.8 years (range, 10-12 years). Evaluation of clinical hip function and radiologic implant outcomes was performed according to clinical score, thigh pain, and radiologic analysis.

Results

Dramatic improvement of the mean Harris hip score (HHS) from 59.4 preoperatively to 93.5 was observed at the final follow-up (P≤0.01). Stable fixation was demonstrated for all implants with no change in position except for one case of Vancouver type B2 periprosthetic femur fracture. A radiolucent line (RLL) was observed in 16 hips (12.5%). Thigh pain was observed in only two hips (1.6%) at the final follow-up. There were no cases of osteolysis around the stem. The survival rate for the COREN stem was 97.7%.

Conclusion

Good long-term survival with excellent clinical and radiological outcomes can be achieved using the COREN femoral stem regardless of Dorr type.

Minimum 10-year follow-up of micro-arc oxidation coating on a cementless grit-blasted tapered-wedge stem of total hip arthroplasty: a multicentre study

BACKGROUND

Recently, a femoral stem treated with grit-blasting and micro-arc oxidation (MAO) coating has commercialised but medium-term follow-up studies are lacking. The aim of this study was to report the outcome of a grit-blasted and MAO-coated femoral component designed as a straight, double-wedged, tapered stem with a rectangular cross-section with minimum 10 years follow-up.

METHODS

Between March 2006 and December 2008, 309 primary total hip arthroplasties using a grit-blasted and MAO-coated femoral component were performed by 3 experienced hip surgeons in 3 hospitals. At minimum 10 years after index THA, 299 hips were living, 10 hips were deceased, and 65 hips were lost to follow-up or had a follow-up period <10 years. Finally, 234 hips were enrolled in this study.

RESULTS

Mean duration of clinical follow-up was 129.6 months. The mean Harris Hip Score was improved from 46.9 to 88.4 at the final follow-up. 4 hips were revised for 2 aseptic femoral loosening, 1 aseptic acetabular cup loosening and 1 late infection. 3 hips were revised for a periprosthetic femoral fracture requiring a femoral component revision. The average time to revision was 51.6 (range 0-148) months. Kaplan-Meier survivorship analysis with an end point of revision for any reason demonstrated a survival rate of 97.4% at 10 years. Survival was 98.7% with revision for aseptic loosening as the endpoint.

CONCLUSIONS

The outcomes of a cementless grit-blasted and MAO-coated tapered-wedge stem of THA were excellent to satisfactory after a follow-up of at least 10 years.

No difference in outcome or migration but greater loss of bone mineral density with the Collum Femoris Preserving stem compared with the Corail stem: a randomized controlled trial with five-year follow-up

AIMS

The aim of this study was to compare the mid-term patient-reported outcome, bone remodelling, and migration of a short stem (Collum Femoris Preserving; CFP) with a conventional uncemented stem (Corail).

METHODS

Of 81 patients who were initially enrolled, 71 were available at five years' follow-up. The outcomes at two years have previously been reported. The primary outcome measure was the clinical result assessed using the Oxford Hip Score (OHS). Secondary outcomes were the migration of the stem, measured using radiostereometric analysis (RSA), change of bone mineral density (BMD) around the stem, the development of radiolucent lines, and additional patient-reported outcome measures (PROMs).

RESULTS

There were no statistically significant differences between the groups regarding PROMs (median OHS (CFP 45 (interquartile range (IQR) 35 to 48); Corail 45 (IQR 40 to 48); p = 0.568). RSA showed stable stems in both groups, with little or no further subsidence between two and five years. Resorption of the femoral neck was evident in nine patients in the CFP group and in none of the 15 Corail stems with a collar that could be studied. Dual X-ray absorbiometry showed a significantly higher loss of BMD in the proximal Gruen zones in the CFP group (mean changes in BMD: Gruen zone 1, CFP -9.5 (95% confidence interval (CI) -14.8 to -4.2), Corail 1.0 (95% CI 3.4 to 5.4); Gruen zone 7, CFP -23.0 (95% CI -29.4 to -16.6), Corail -7.2 (95% CI -15.9 to 1.4). Two CFP stems were revised before two years' follow-up due to loosening, and one Corail stem was revised after two years due to chronic infection.

CONCLUSION

The CFP stem has a similar clinical outcome and subsidence pattern when compared with the Corail stem. More pronounced proximal stress-shielding was seen with the CFP stem, suggesting diaphyseal fixation, and questioning its femoral neck-sparing properties in the long term. Cite this article: Bone Joint J 2022;104-B(5):581-588.

Tapered wedge stems decrease early postoperative subsidence following cementless total hip arthroplasty in Dorr type C femurs compared to fit-and-fill stems

Background

To compare the degree of stem subsidence between two different femoral component designs and to determine the risk factors associated with stem subsidence after cementless total hip arthroplasty (THA) in Dorr type C femurs.

Methods

We retrospectively reviewed 104 consecutive hips in 100 patients with Dorr type C proximal femoral morphology who underwent primary cementless THA using a fit-and-fill stem or a tapered wedge femoral stem at our institution between January 2012 and June 2021. A fit-and-fill stem was used in 55 hips and a tapered wedge stem was used in 49 hips. Radiologically, the distance between the apex of the major trochanter and the stem shoulder were measured at three different time points (immediately [0W], one week [1W], and six weeks [6W] after surgery) and the degrees of stem subsidence were assessed by comparing the distance between 0 and 1W, 1W and 6W, and 0W and 6W, respectively.

Results

The mean degree of stem subsidence (0W vs. 1W) was 0.24 mm (standard deviation [SD] 0.36) in the fit-and-fill stem group, and 0.23 mm (SD 0.41) in the tapered wedge stem group. There was no significant difference between the two groups (P = 0.4862). However, the mean degrees of subsidence were significantly higher in the fit-and-fill stem group (1W vs. 6W, 0.38 mm [SD 0.68]; 0W vs. 6W, 0.65 mm [SD 0.87]) than in the tapered wedge stem group (1W vs. 6W, 0.16 mm [SD 0.32]; 0W vs. 6W, 0.24 mm [SD 0.38]) (P < 0.05 for both). In addition, the rates of > 3 mm subsidence (in which instability can be observed) were 18.2% (10 of 55 hips) and 2.0% (1 of 49 hips), respectively. There was also a significant difference between the two stems (P = 0.0091). Multivariate analysis demonstrated that fit-and-fill stem was a risk factor for > 3 mm subsidence after THA in Dorr type C femurs (P = 0.0050).

Conclusion

Our findings suggest that the tapered wedge stem is more suitable for Dorr type C femurs than the fit-and-fill stem to avoid early postoperative subsidence in cementless THA.

Similar outcome with a new anteverted or a straight standard stem: a randomized study of 72 total hip arthroplasties evaluated with clinical variables, radiostereometry, and DXA up to 2 years

Background and purpose - The anatomical uncemented stem, SP-CL (Static Physiologicus - CementLess), designed to facilitate insertion and to avoid stress concentration at solitary contact points, has been on the market since 2014 but is not well documented. We studied its clinical performance, migration, and associated bone remodeling in a randomized controlled trial, with the Corail stem as control. Patients and methods - 79 patients (80 hips) were primarily recruited and 71 patients (72 hips, 36 SP-CL, 36 Corail) attended the last follow-up at 2 years. The Oxford Hip Score (OHS) was the primary outcome. In addition, we assessed stem migration, changes in bone mineral density, and development of radiolucencies by RSA, DXA, and conventional radiography. Results - At 2 years Oxford Hip Score was similar between the SP-CL and Corail stem. At 2 years the SP-CL stems showed a median distal migration of 0.23 mm (-0.1 to 5.2) and the Corail stems of 0.11 mm (-0.4 to 4.4). The SP-CL stems showed slightly more loss of bone mineral density in Gruen region 7 (p = 0.003). Interpretation - We found no difference in clinical results between the SP-CL and the well-documented Corail stem. The same stem stability was reached between 1 and 2 years postoperatively for both stems. As a next step we think that the SP-CL stem should be studied in a multi-center setting, before being accepted for general use.

Differences in femoral component subsidence rate after THA using an uncemented collarless femoral stem: full weight-bearing with an enhanced recovery rehabilitation versus partial weight-bearing

BACKGROUND

Femoral component subsidence is a known risk factor for early failure of total hip arthroplasty (THA) using cementless stems. The aim of the study was to compare an enhanced recovery concept with early full weight-bearing rehabilitation and partial weight-bearing on stem subsidence. In addition, the influence of patient-related and anatomical risk factors on subsidence shall be assessed.

METHODS

One hundred and fourteen patients underwent primary cementless THA and were retrospectively analyzed. Sixty-three patients had an enhanced recovery rehabilitation with early full weight-bearing and 51 patients had rehabilitation with partial weight-bearing (20 kg) for 6 weeks. Postoperative subsidence was analyzed on standing pelvic anterior-posterior radiographs after 4 weeks and 1 year. Subsidence was measured in mm. Anatomical and prosthetic risk factors (stem size, canal flare index, canal fill ratio as well as BMI and demographic data) were correlated.

RESULTS

Femoral stem subsidence rate was significantly higher for the group with an enhanced recovery concept compared to the group with partial weight-bearing at the first radiological follow up after 4 weeks [2.54 mm (SD ± 1.86) vs. 1.55 mm (SD ± 1.80)] and the second radiological follow up after 1 year [3.43 mm (SD ± 2.24) vs. 1.94 (SD ± 2.16)] (p < 0.001, respectively). Stem angulation > 3° had a significant influence on subsidence. Canal flare index and canal fill ratio showed no significant correlation with subsidence as well as BMI and age.

CONCLUSION

In the present study, cementless stem subsidence was significantly higher in the group with enhanced recovery rehabilitation compared to partial weight-bearing. Small absolute values and differences were demonstrated and therefore possibly below clinical relevance. Anatomical radiological parameters and anthropometric data did not appear to be risk factors for stem subsidence.

A Role for Modern Primary Cementless Femoral Stems in Revision Hip Arthroplasty

BACKGROUND

In revision total hip arthroplasty (THA) cases with preserved femoral metaphyseal bone, tapered proximally porous-coated "primary" femoral stems may be an option. The objective of this study was to compare outcomes of patients with Paprosky I or II femoral bone loss undergoing revision THA with either a primary metaphyseal-engaging cementless stem or a revision diaphyseal-engaging stem.

METHODS

This was a retrospective analysis of 70 patients with Paprosky I or II femoral bone loss who underwent femoral revision. 35 patients who were revised using a primary cementless femoral stem were compared with 35 patients who underwent femoral revision using a revision diaphyseal-engaging stem. The groups were similar regarding age, gender, body mass index, and American Society of Anesthesiologists. Clinical and radiographic outcomes and complications were compared over an average follow-up of 2.9 years (SD 1.4).

RESULTS

Revision THA was most commonly performed for periprosthetic joint infection (N = 27, 38.6%). The groups were similar with regards to Paprosky femoral classification (P = .56), length of stay (P = .68), discharge disposition (P = .461), operative time (P = .20), and complications (P = .164). There were no significant differences between primary and revision femoral stem subsidence (0.12 vs. 0.75 mm, P = .18), leg length discrepancy (2.3 vs. 4.05 mm, P = .37), and Hip Disability and Osteoarthritis Outcome Score Jr (73.1 [SD 21.1] vs. 62.8 [SD 21.7], P = .088). No patient underwent additional revision surgery involving the femoral component.

CONCLUSION

Use of modern primary cementless femoral stems is a viable option for revision hip arthroplasty in the setting of preserved proximal femoral metaphyseal bone. Outcomes are not inferior to those of revision stems and offer potential benefits.

No effect of femoral canal jet-lavage on the stability of cementless stems in primary hip arthroplasty: a randomised RSA study with 6 years follow-up

INTRODUCTION

In contrast to cemented hip prostheses, the effect of washing the bone bed with jet-lavage prior to insertion of cementless stem components in primary hip arthroplasty (THA) is unclear. Jet-lavage potentially decreases the risk of fat embolisation during rasping and stem insertion and might help in avoiding bacterial contamination. An earlier animal study has shown less debris and better-organised trabecular structure of new bone when jet-lavage was used. We hypothesised that the primary stability of cementless femoral stems implanted after jet-lavage of the femoral canal prior to stem insertion would improve with earlier stabilisation, as measured with Radiostereometry (RSA), compared with insertion without prior jet-lavage.

METHODS

40 patients with primary osteoarthritis operated on with a cementless titanium grit blasted stem are included in the study. The patients were randomised to either jet-lavage or control without any lavage of the femoral canal prior to insertion of the prosthesis. The stem migration pattern was measured with RSA at 0, 3, 12, 24 and 72 months.

RESULTS

At 6 years, 19 patients remained for analysis in the jet-lavage and 18 in the control group. We found no difference in extent or pattern of migration as measured with RSA. Both groups seemed to have stabilised within 3 months after a slight subsidence and retroversion. No stem was revised or considered loose as measured with RSA.

CONCLUSIONS

Washing the bone bed with jet-lavage prior to insertion of cementless stems does not affect the stability of cementless femoral components. No adverse effects were observed.

Subsidence Following Revision Total Hip Arthroplasty Using Modular and Monolithic Components

BACKGROUND

The ideal femoral component in revision total hip arthroplasty (rTHA) remains undetermined; however, tapered, fluted, titanium (TFT) stems are now widely used with favorable results in all types of revision scenarios. With both modular and monoblock TFT stem options, neither has been proven to be superior. Femoral stem subsidence has been linked to aseptic loosening, instability, and leg length discrepancy. This study aims to assess stem subsidence of modular and monoblock TFT stems at a single urban orthopedic specialty hospital within a tertiary academic medical center.

METHODS

Electronic medical records of rTHAs performed between January 2013 and March 2018 utilizing modular and monoblock TFT stems were examined. Data collected included baseline demographics, surgical indication, femoral Paprosky classification, and stem subsidence at most recent follow up (3 months to 3 years). Two-sample t-tests and chi-squared tests were used for statistical analysis.

RESULTS

A total of 186 patients (106 modular, 80 monoblock) were included in the analysis. Modular stems underwent significantly greater subsidence than monoblock stems at latest radiographic follow-up (3.9 ± 2.6 vs 2.3 ± 2.5 mm, P < .001). A significantly greater proportion of modular stems underwent >5 mm of subsidence at latest follow-up (29.2% vs 11.3%, P < .001).

CONCLUSION

Monoblock TFT stems have displayed promising clinical results in prior studies, and now have been shown to decrease the incidence of postoperative subsidence. With the potential for stem subsidence to lead to aseptic loosening, limb length discrepancy, and instability, the orthopedic surgeon should weigh the risks and benefits of utilizing modular vs monoblock TFT stems in rTHA.

New Implant Introduction in Total Hip Arthroplasty Using Radiostereometric Analysis: A Cautionary Note

BACKGROUND

It has been proposed that the introduction of new hip implant technology in orthopedic surgery be conducted in a more controlled manner in order to properly ensure patient safety and the likelihood of favorable outcomes. This stepwise introduction would first require a prospective randomized study in a small cohort of patients, using radiostereometric analysis (RSA). The aim of this study is to determine if the recent literature supports the use of RSA as an early screening tool to accurately predict the long-term outcomes of cementless femoral stems.

METHODS

A review of the recent published literature identified 11 studies that used RSA to predict the long-term stability of a cementless femoral component. These RSA predictive data were compared to the 10-year revision rate reported in the Australian Registry or in the published literature to determine its reliability.

RESULTS

RSA data did not universally predict long-term stem fixation. In 2 of the 11 cases (18%), the RSA study incorrectly predicted the ability of the cementless stem to reliably osseointegrate. Of the 9 stems considered stable in the RSA studies, the 10 year registry and literature data confirmed that 6 implants had a low revision rate and were well performing. One stem has not performed well clinically and has been listed as having a higher than anticipated rate of revision in the registry. Two stems do not have sufficient follow-up. Of the 2 stems RSA predicted to do poorly, 1 is well performing at 10 years, and 1 has a high revision rate at 8 years.

CONCLUSION

In the stepwise introduction of new hip implants, RSA should be best considered as an adjunct tool in deciding whether or not an implant should be evaluated in a larger multicenter clinical studies, rather than the sole criterion.

Long-term migration characteristics of the Corail hydroxyapatite-coated femoral stem: a 14-year radiostereometric analysis follow-up study

BACKGROUND

The magnitude and pattern of acceptable long-term migration of cementless femoral stems are not well understood. The Corail hydroxyapatite-coated cementless stem is a clinically successful and commonly used femoral stem with a long-term migration pattern not previously described in the literature. The aim of this study was to assess the long-term migration of the Corail hydroxyapatite-coated cementless stem using radiostereometric analysis (RSA) at 14-year follow-up, thereby establishing a benchmark acceptable long-term migration pattern for hydroxyapatite-coated cementless prostheses.

MATERIALS AND METHODS

A prospective cohort of 29 patients (30 hips) undergoing primary total hip arthroplasty for primary hip osteoarthritis were enrolled into a study to characterise the migration of the Corail cementless stem. A total of 13 patients (4 males, 9 females) with mean age 82 (range 68-92) underwent repeat RSA radiographs at minimum 10 years post-operation (mean 13.9 years, range 13.3-14.4). Subsidence of the stem was measured and compared to prior measurements taken at 6 months and 1, 2, and 6 years.

RESULTS

None of the 13 patients have been revised. The migration at 6 months, 1 year, 2 years, and 6 years has been previously recorded. At mean 14-year follow-up, the cohort mean subsidence of the cementless stem was 0.70 mm (range - 0.06 to 3.61 mm). For each stem followed up at 6 months and 14 years, the mean subsidence over this period was 0.05 mm (range - 0.14 to 0.57 mm). There is no significant difference in mean subsidence at 6 months and 14 years (p = 0.43).

CONCLUSIONS

The long-term pattern of the subsidence of the Corail femoral stem has not previously been described. Subsidence occurs within the first 6 months, after which there is persistent stabilisation of the implant to 14 years. This study provides a description of a long-term acceptable migration pattern to which new hydroxyapatite-coated cementless prostheses may be compared.

LEVEL OF EVIDENCE

II.

Subsidence of Hydroxyapatite-Coated Femoral Stem in Dorr Type C Proximal Femoral Morphology

BACKGROUND

Good bone quality and proper proximal femoral morphology are thought to be necessary for tapered design, cementless femoral stems to resist subsidence. Using tapered, cementless stem for patients with stovepipe morphology or Dorr type C is controversial. The purpose of this study is to analyze (1) subsidence of the fully hydroxyapatite (HA)-coated, tapered, cementless stem in different morphology according to Dorr classification, (2) subsidence of the stem related to radiographic canal-fill ratio.

METHODS

The digitized radiographs of 311 consecutive cementless primary total hip arthroplasty with fully HA-coated, tapered stem were retrospectively reviewed. Subsidence and the canal-fill ratio at 4 locations were evaluated postoperatively after a minimum of 2 years of follow-up. The threshold of subsidence >3 mm was considered as a clinically significant migration.

RESULTS

A multivariate regression analysis of subsidence across Dorr type, controlling for age, gender, and intraoperative calcar fracture, demonstrated 0.40 mm (P = .28) and 0.18 mm (P = .51) greater subsidence in Dorr type C and B when compared to Dorr type A. Age, gender, and calcar fracture had no influence on subsidence, whereas greater canal-fill ratio at 2 cm below lesser trochanter resulted in significantly less subsidence (P = .02). Additionally, all variables did not affect the risk of having subsidence >3 mm.

CONCLUSION

The proximal femoral morphology has no statistically significant effect on the subsidence of fully HA-coated stem. Therefore, this stem type might be a viable option for Dorr type C. Increasing the canal-fill ratio at metadiaphyseal junction may ensure the stability of the stem.

Effect of Denosumab on Femoral Periprosthetic BMD and Early Femoral Stem Subsidence in Postmenopausal Women Undergoing Cementless Total Hip Arthroplasty

Antiresorptive denosumab is known to improve the quality and strength of cortical bone in the proximal femurs of osteoporotic women, but its efficacy in preventing periprosthetic bone loss and reducing femoral stem migration has not been studied in women undergoing cementless total hip arthroplasty. We conducted a single-center, randomized, double-blinded, placebo-controlled trial of 65 postmenopausal women with primary hip osteoarthritis and Dorr type A or B proximal femur anatomy. The patients randomly received subcutaneous injections of denosumab 60 mg or placebo once every 6 months for 12 months, starting 1 month before surgery. The primary endpoint was the change in bone mineral density (BMD) of the proximal femur (Gruen zone 7) at week 48, and the secondary endpoint was stem subsidence measured by radiostereometric analysis (RSA) at week 48. Exploratory endpoints included changes in BMDs of the contralateral hip, lumbar spine and distal radius, serum levels of bone turnover markers, walking speed, walking activity, patient-reported outcome measures, and radiographic assessment of stem osseointegration. The participants underwent vertebral-fracture assessment in an extension safety study at 3 years. Denosumab significantly decreased bone loss in the medial femoral neck (zone 7) and increased periprosthetic BMD in the greater trochanteric region (zone 1) and lesser trochanteric region (zone 6). Denosumab did not reduce temporary femoral stem migration. The migration occurred mainly during the settling period (0 to 12 weeks) after implantation of the prosthesis. All of the stems osseointegrated, as evaluated by RSA and radiographs. There were no intergroup differences in functional recovery. Discontinuation of denosumab did not lead to any adverse events. In conclusion, denosumab increased periprosthetic BMD in the clinically relevant regions of the proximal femur, but the treatment response was not associated with any reduction of initial stem migration. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Radiostereometric migration measurement of an uncemented Cerafit® femoral stem: 26 patients followed for 10 years

Radiostereometric analysis (RSA) is the gold standard for evaluating micromotions of orthopaedic implants. The method is applied for identifying novel design weaknesses in endoprostheses. Current research frequently assesses relatively short time periods. Short-term RSA studies have been widely used for predicting the long-term stability of many hip prosthetic designs, but only a few studies have focused on uncemented hip implants, especially for extended periods. The purpose of this study was to analyse the migration pattern of the Cerafit® femoral stem within 10 years and to verify the predictive value of short-term RSA after 2 years for this uncemented femoral hip stem. Twenty-six patients were followed for 10 years. Ten years after implantation, a mean subsidence of 0.22 mm±0.56 mm, a mean internal rotation of 0.59°±1.67° and a mean maximum total point motion (MTPM) of 1.28 mm±0.54 mm were detected. The main migration took place in the first 6 weeks after surgery (subsidence of 0.36 mm±0.73 mm; internal rotation of 0.62°±1.49°, MTPM of 1.05 mm±0.68 mm). All the migration values measured were small. No late-onset migration was observed. This study suggests that the Cerafit® implants are stable after 10 years. Thus, RSA could be the best tool to assess long-term implant behaviour.

Femoral stem subsidence in cementless total hip arthroplasty: a retrospective single-centre study

PURPOSE AND HYPOTHESIS

Subsidence is a known reason for early failure of total hip arthroplasty (THA). In particular, cementless THA might be vulnerable to migration. The present study analysed femoral stem subsidence after primary cementless THA. Prosthetic and anatomical risk factors for early femoral stem subsidence were evaluated.

METHODS

Two hundred thirty-one consecutive patients who underwent primary cementless THA in a single centre were retrospectively analysed. Post-operative results were evaluated in consideration of prosthetic and anatomical properties in correlation with subsidence on standing pelvic anteroposterior radiographs. Stem type and design, demographic data, BMI, canal flare index (CFI) and canal fill ratio (CFR) were evaluated.

RESULTS

The subsidence rate was significantly higher in collarless femoral stems [3.1 mm (SD 2.8 mm) vs. 1.9 mm (SD 1.5 mm); p = 0.013] while the anatomical type of the proximal femur as described by the canal flare index did not influenced subsidence (p = 0.050). Also, the canal fill ratio showed no significant correlation with subsidence at any level.

CONCLUSIONS

In the present study, stem subsidence was significantly higher in the collarless group compared to collared stems. No anatomical parameter (CFI and CFR) could be identified as risk factor for subsidence. Neither age nor BMI influenced subsidence in this cohort. Still, subgroup analysis indicated a sex-dependent role of BMI. Prospective studies of large cohorts should address the problem of subsidence in the future.

LEVEL OF EVIDENCE

Retrospective therapeutic study, Level IV.

Cementless Stem for Femoral Neck Fractures in a Patient’s 10th Decade of Life: High Rate of Periprosthetic Fractures

Background:

Subsidence of cementless femoral stems in hemiarthroplasty (HA) and increased fracture rates are ongoing concerns of orthopedic surgeons when treating fractures in very old patients. Additionally, bone cement implantation syndrome may result in perioperative cardiac or pulmonary complications, especially in older patients, leading to morbidity and mortality. This study was performed to analyze possible subsidence and intraoperative fractures in a cohort of very old patients treated with cementless stems.

Methods:

We retrospectively analyzed a consecutive cohort of patients aged ≥90 years with femoral neck fractures treated by uncemented HA and an anterior minimally invasive approach. Immediate full-weight bearing was allowed postoperatively. Pelvic radiographs were examined for subsidence immediately postoperatively and 6 weeks later.

Results:

We treated 109 patients (74% women; mean age, 93 years; range, 90-102 years) by HA from January 2010 to March 2016. The 30-day mortality rate was 16%, and the morbidity rate was 47%. There were 11 (12%) intraoperative fractures: 8 (Vancouver B₂) had to be addressed immediately during the primary operation, while 3 (1 Vancouver B₁ and 2 Vancouver A_G) were treated conservatively. One periprosthetic femoral fracture (Vancouver B₁) was documented during follow-up. In 17 patients, subsidence of >2.0 mm (median, 3.9 mm; range, 2.5-9.0 mm) was documented.

Conclusion:

Early subsidence was low in this very old cohort treated with an uncemented stem and not showing a periprosthetic fracture. The risk of intraoperative periprosthetic fractures was high. The use of uncemented implants in osteoporotic bone continues to be an intervention with high risk and should only be performed by experienced surgeons.

Level of Evidence:

Level III, Therapeutic study.

Stable migration pattern of an ultra-short anatomical uncemented hip stem: a prospective study with 2 years radiostereometric analysis follow-up

INTRODUCTION

Shorter, anatomically shaped and proximally loading stems have been developed to achieve better stress distribution and be more bone preserving. The purpose of this prospective study was to evaluate the migration pattern of the Proxima™ ultra-short uncemented stem using radiostereometric analysis (RSA), and to review the literature regarding the migration of short stemmed hip arthroplasty.

METHODS

25 patients (28 hips) with hip osteoarthritis received a Proxima stem during total hip arthroplasty (THA). To measure stem migration, repeated RSA examinations were done during a 2 year follow up period. The patients were evaluated with the hip specific (HOOS) and the generic health (EQ5D) scores up to 1 year, and clinically for 6 years postoperatively.

RESULTS

Almost all migration occurred within the first 3 months, with mean subsidence of 0.22 mm and varus rotation of 1.04°, being the primary effect variables. After the third postoperative month and up to the 2 year RSA follow up no further significant migration occurred. The outcome scores showed substantial improvement after 1 year. No revisions were performed or indicated for any stem after a mean clinical follow up of 72.1 months.

CONCLUSIONS

Like many other uncemented stems, the Proxima showed early migration up to 3 months hereafter osseointegration seems to have occurred. The achieved stability and clinical outcomes indicate favorable early results for this stem in younger patients who have good bone quality and average BMI. We found, however, the surgical technique to be slightly more demanding compared to conventional stems owing to the unique implant design that necessitates specific adjusted femoral cutting and broaching procedures.

Trabecular metal tibial knee component still stable at 10 years

Background and purpose - Total knee replacement (TKR) in younger patients using cemented components has shown inferior results, mainly due to aseptic loosening. Excellent clinical results have been reported with components made of trabecular metal (TM). In a previous report, we have shown stabilization of the TM tibial implants for up to 5 years. In this study, we compared the clinical and RSA results of these uncemented implants with those of cemented implants. Patients and methods - 41 patients (47 knees) aged ≤ 60 years underwent TKR. 22 patients (26 knees) received an uncemented monoblock cruciate-retaining (CR) tibial component (TM) and 19 patients (21 knees) received a cemented NexGen Option CR tibial component. Follow-up examination was done at 10 years, and 16 patients (19 knees) with TM tibial components and 17 patients (18 knees) with cemented tibial components remained for analysis. Results - 1 of 19 TM implants was revised for infection, 2 of 18 cemented components were revised for knee instability, and no revisions were done for loosening. Both types of tibial components migrated in the first 3 months, the TM group to a greater extent than the cemented group. After 3 months, both groups were stable during the next 10 years. Interpretation - The patterns of migration for uncemented TM implants and cemented tibial implants over the first 10 years indicate that they have a good long-term prognosis regarding fixation.

New Approach and Stem Increased Femoral Revision Rate in Total Hip Arthroplasty

This study compared the femoral stem revision and loosening rates in primary total hip arthroplasty between 2 different approaches and stem designs. Recent reports comparing the direct anterior approach with either the posterior or lateral approach showed that patients undergoing the direct anterior approach have less pain and an accelerated functional recovery in the early postoperative period. After converting to an anterior approach, the authors observed an increased rate of femoral stem revision. From 2003 to 2009, a posterior or lateral approach was used to insert 514 stems of 2 designs. These cases included the use of an extensively coated cobalt-chrome stem (n=232) or a straight, dual-tapered, proximally porous-coated titanium stem (n=282). In the following years, from 2009 to 2012, 594 short, proximally coated, titanium tapered-wedge stems were inserted through a direct anterior approach. The revision rates of femoral stems inserted through a posterior approach or a lateral approach were compared with those inserted via a direct anterior approach. No stem revisions occurred in the posterior approach group or the lateral approach group, and 5 stems were revised in the anterior approach group for periprosthetic fracture or aseptic loosening (0.8%). Significantly more stem revisions occurred after the use of the new stem design and a direct anterior approach (P=.04).

Differences in subsidence rate between alternative designs of a commonly used uncemented femoral stem

INTRODUCTION

Measurement of early subsidence of uncemented femoral stems can be used to evaluate the likelihood of long term stem component loosening and therefore clinical failure. Our aim was to evaluate the factors associated with subsidence in collared and uncollared versions of the Corail femoral stem.

METHODS

121 hips in 113 consecutive patients were studied, operated on by two surgeons in our hospital differing in their choice of Corail stem. This gave two groups of patients with 66 hips having collared stems and 55 hips having uncollared. We recorded patients' age, sex, ASA grade and BMI. Radiographs post-operatively at day 1, 6 weeks and 1 year were evaluated measuring subsidence, angulation, signs of stability and fixation, and canal fill ratio at the metaphysis and diaphysisafter correcting for magnification errors by calibration using femoral head size.

RESULTS

Clinically significant subsidence (>3 mm) occurred in 7.6% of collared and 10.9% of uncollared stems, all within 6-8 weeks, but did not reach statistical significance (p = 0.345). Revision for symptomatic loosening was required in 1 patient in each group (1.5% collared versus 1.8% uncollared).

DISCUSSION

Early subsidence of Corail femoral stem should alert surgeons to closer patient follow-up as the rate of early revision is 18% in stems with >3 mm of subsidence. However, the presence of a collar does not seem to be protective.

Early Migration Predicts Aseptic Loosening of Cementless Femoral Stems: A Long-term Study

BACKGROUND

Excessive early migration of cemented stems and cups after THA has been associated with poor long-term survival and allows predictable evaluation of implant performance. However, there are few data regarding the relationship between early migration and aseptic loosening of cementless femoral components, and whether early migration might predict late failure has not been evaluated, to our knowledge. Einzel-Bild-Röntgen-Analyse-femoral component analysis (EBRA-FCA) is a validated technique to accurately measure axial femoral stem migration without the need for tantalum markers, can be performed retrospectively, and may be a suitable tool to identify poor performing implants before their widespread use.

QUESTIONS/PURPOSES

We asked: (1) Is axial migration within the first 24 months as assessed by EBRA-FCA greater among cementless stems that develop aseptic loosening than those that remain well fixed through the second decade; (2) what is the diagnostic performance of implant migration at 24 months postoperatively to predict later aseptic loosening of these components; and (3) how does long-term stem survivorship compare between groups with high and low early migration?

METHODS

We evaluated early axial stem migration in 158 cementless THAs using EBRA-FCA. The EBRA-FCA measurements were performed during the first week postoperatively (baseline measurement) and at regular followups of 3, 6, and 12 months postoperatively and annually thereafter. The mean duration of followup was 21 years (range, 18-24 years). The stems studied represented 45% (158 of 354) of the cementless THAs performed during that time, and cementless THAs represented 34% (354 of 1038) of the THA practice during that period. No patient enrolled in this study was lost to followup. Multivariate survivorship analysis using Cox's regression model was performed with an endpoint of aseptic loosening of the femoral component. Loosening was defined according to the criteria described by Engh et al. and assessed by two independent observers. Patients with a diagnosis of prosthetic joint infection were excluded. Receiver operating characteristic (ROC) curve analysis was used to evaluate diagnostic performance of axial stem migration 1, 2, 3, and 4 years postoperatively as a predictor of aseptic loosening. Survivorship of hips with high (≥ 2.7 mm) and low (< 2.7 mm) migration was compared using a competing-events analysis.

RESULTS

Femoral components that had aseptic loosening develop showed greater mean distal migration at 24 months postoperatively than did components that remained well fixed throughout the surveillance period (4.2 mm ± 3.1 mm vs 0.8 mm ± 0.9 mm; mean difference, 3.4 mm, 95% CI, 2.5-4.4; p ≤ 0.001). Distal migration at 24 months postoperatively was a strong risk factor for aseptic loosening (hazard ratio, 1.98; 95% CI, 1.51-2.57; p < 0.001). The associated overall diagnostic performance of 2-year distal migration for predicting aseptic loosening was good (area under the ROC curve, 0.86; 95% CI, 0.72-1.00; p < 0.001). Sensitivity of early migration measurement was high for the prediction of aseptic loosening during the first decade after surgery but decreased markedly thereafter. Stems with large amounts of early migration (≥ 2.7 mm) had lower 18-year survivorship than did stems with little early migration (29% [95% CI, 0%-62%] versus 95% [95% CI, 90%-100%] p < 0.001).

CONCLUSIONS

Early migration, as measured by EBRA-FCA at 2 years postoperatively, has good diagnostic capabilities for detection of uncemented femoral components at risk for aseptic loosening during the first and early second decades after surgery. However, there was no relationship between early migration patterns and aseptic loosening during the late second and third decades. EBRA-FCA can be used as a research tool to evaluate new cementless stems or in clinical practice to evaluate migration patterns in patients with painful femoral components.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Radiostereometric migration analysis of the Cerafit femoral stem: 28 patients followed for 2 years

Radiostereometric analysis (RSA) is the gold standard evaluating micromovements after total hip arthroplasty. The aim of this study was to investigate the migratory pattern of an uncemented femoral stem during the first 2 years after surgery. We followed 28 patients with a mean age of 57 (SD 13) years for the first two postoperative years. Radiostereometric analysis was used to measure the translation and rotation of the femoral component. The Harris hip score (HHS) was determined to evaluate the clinical outcome. No stem had to be revised. The mean HHS advanced from 35 (SD 11) preoperative to 89 (SD 10) 1 year after surgery. At the end of the observation period, mean subsidence of the stem was 0.26 mm (SD 0.82). Maximum total point motion (MTPM) was 1.23 mm (SD 1.22). The main distal migration took place up to 6 weeks after surgery with nearly no further subsidence up to 2 years postoperatively. All the measured migrations of the hip stem were very small. Results of the HHS demonstrate good clinical outcome. Long-term RSA is necessary to assess possible late migration of the Cerafit standard femoral stem.

Subsidence in Collarless Corail Hip Replacement

The purpose of this study was to assess whether subsidence occurs in collarless Corail hip replacement (CCHR) and to ascertain the extent and timing of subsidence if present. Retrospective case notes analysis was performed. Sixty eight patients who had CCHR were identified from our database. Male to female ratio was 32:36. Their mean age was 74.2 years (range 37-95 years). Indications for surgery were osteoarthritis in 64 (94%) patients, rheumatoid arthritis in two (3%) patients and avascular necrosis in two (3%) patients. Subsidence was measured at 6 weeks, 6 months and 1 year post-op compared to initial post-op x-rays. At 6 weeks x-ray 21 patients did not have any subsidence, 18 patients had 1 millimeter (mm) subsidence, 10 patients had 2mms subsidence, 4 patients had 3mms subsidence, 5 patients had 4mms subsidence, 1 patient had 5mms subsidence, 4 patients had 6 mms subsidence and 1 patient each had subsidence of 7mms, 9mms, 11mms, 13mms and 26 mms respectively. When compared with 6 months x-rays only 2 patients had a further subsidence of 2mms while another patient had 3mms subsidence. No further subsidence occurred at 1 year follow up x-rays. One patient had revision surgery due to symptomatic subsidence (29mms) at 6 months follow up. Subsidence does occur in the first 6 weeks in collarless Corail hip replacement, and to a lesser extent until 6 months postoperatively, but does not progress further.

A randomised trial comparing a short and a standard-length metaphyseal engaging cementless femoral stem using radiostereometric analysis

This was a randomised controlled trial studying the safety of a new short metaphyseal fixation (SMF) stem. We hypothesised that it would have similar early clinical results and micromovement to those of a standard-length tapered Synergy metaphyseal fixation stem. Using radiostereometric analysis (RSA) we compared the two stems in 43 patients. A short metaphyseal fixation stem was used in 22 patients and a Synergy stem in 21 patients. No difference was found in the clinical outcomes pre- or post-operatively between groups. RSA showed no significant differences two years post-operatively in mean micromovement between the two stems (except for varus/valgus tilt at p = 0.05) (subsidence 0.94 mm (sd 1.71) vs 0.32 mm (sd 0.45), p = 0.66; rotation 0.96° (sd 1.49) vs 1.41° (sd 2.95), p = 0.88; and total migration 1.09 mm (sd 1.74) vs 0.73 mm (sd 0.72), p = 0.51). A few stems (four SMF and three Synergy) had initial migration > 1.0 mm but stabilised by three to six months, with the exception of one SMF stem which required revision three years post-operatively. For most stems, total micromovement was very low at two years (subsidence < 0.5 mm, rotation < 1.0°, total migration < 0.5 mm), which was consistent with osseous ingrowth. The small sample makes it difficult to confirm the universal applicability of or elucidate the potential contraindications to the use of this particular new design of stem.

Cite this article: Bone Joint J 2015; 97-B:595–602.

Effects of micro-arc oxidation coating on outcomes of a cementless grit-blasted tapered-wedge stem in total hip arthroplasty

To evaluate the effects of micro-arc oxidation (MAO) coating on the outcomes of a grit-blasted tapered-wedge stem in total hip arthroplasty (THA), we performed a retrospective review of 141 THAs using MAO coated stem for a minimum of 5years and compared them to 219 THAs using the same geometry stem without MAO coating. Harris hip score improved from 43.7 points preoperatively to 93.9 points postoperatively. No hips were revised for aseptic loosening. Complications included one squeaking hip, one iliopsoas tendonitis, and one deep vein thrombosis. Postoperative Harris hip scores, WOMAC scores, UCLA activity scores, stem stabilities, and complication rates did not differ between the groups. After medium-term follow-up, our findings did not support the use of MAO coating on grit-blasted tapered-wedge stem to improve clinical outcomes.

Adherence of hip and knee arthroplasty studies to RSA standardization guidelines. A systematic review

BACKGROUND AND PURPOSE

Guidelines for standardization of radiostereometry (RSA) of implants were published in 2005 to facilitate comparison of outcomes between various research groups. In this systematic review, we determined how well studies have adhered to these guidelines.

METHODS

We carried out a literature search to identify all articles published between January 2000 and December 2011 that used RSA in the evaluation of hip or knee prosthesis migration. 2 investigators independently evaluated each of the studies for adherence to the 13 individual guideline items. Since some of the 13 points included more than 1 criterion, studies were assessed on whether each point was fully met, partially met, or not met.

RESULTS

153 studies that met our inclusion criteria were identified. 61 of these were published before the guidelines were introduced (2000-2005) and 92 after the guidelines were introduced (2006-2011). The methodological quality of RSA studies clearly improved from 2000 to 2011. None of the studies fully met all 13 guidelines. Nearly half (43) of the studies published after the guidelines demonstrated a high methodological quality and adhered at least partially to 10 of the 13 guidelines, whereas less than one-fifth (11) of the studies published before the guidelines had the same methodological quality. Commonly unaddressed guideline items were related to imaging methodology, determination of precision from double examinations, and also mean error of rigid-body fitting and condition number cutoff levels.

INTERPRETATION

The guidelines have improved methodological reporting in RSA studies, but adherence to these guidelines is still relatively low. There is a need to update and clarify the guidelines for clinical hip and knee arthroplasty RSA studies.

No association between serum metal ions and implant fixation in large-head metal-on-metal total hip arthroplasty

BACKGROUND

The mechanism of failure of metal-on-metal (MoM) total hip arthroplasty (THA) has been related to a high rate of metal wear debris, which is partly generated from the head-trunnion interface. However, it is not known whether implant fixation is affected by metal wear debris.

PATIENTS AND METHODS

49 cases of MoM THA in 41 patients (10 women) with a mean age of 52 (28-68) years were followed with stereoradiographs after surgery and at 1, 2, and 5 years to analyze implant migration by radiostereometric analysis (RSA). Patients also participated in a 5- to 7-year follow-up with measurement of serum metal ions, questionnaires (Oxford hip score (OHS) and Harris hip score (HHS)), and measurement of cup and stem positions and systemic bone mineral density.

RESULTS

At 1-2 years, mean total translation (TT) was 0.04 mm (95% CI: -0.07 to 0.14; p = 0.5) for the stems; at 2-5 years, mean TT was 0.13 mm (95% CI: -0.25 to -0.01; p = 0.03), but within the precision limit of the method. For the cups, there was no statistically significant TT or total rotation (TR) at 1-2 and 2-5 years. At 2-5 years, we found 4 cups and 5 stems with TT migrations exceeding the precision limit of the method. There was an association between cup migration and total OHS < 40 (4 patients, 4 hips; p = 0.04), but there were no statistically significant associations between cup or stem migration and T-scores < -1 (n = 10), cup and stem positions, or elevated serum metal ion levels (> 7µg/L (4 patients, 6 hips)).

INTERPRETATION

Most cups and stems were well-fixed at 1-5 years. However, at 2-5 years, 4 cups and 5 stems had TT migrations above the precision limits, but these patients had serum metal ion levels similar to those of patients without measurable migrations, and they were pain-free. Patients with serum metal ion levels > 7 µg/L had migrations similar to those in patients with serum metal ion levels < 7 µg/L. Metal wear debris does not appear to influence the fixation of hip components in large-head MoM articulations at medium-term follow-up.

Prospective randomised clinical trial assessing subsidence and rotation, using radiostereometric analysis, of two modular cementless femoral stems (Global K2 and Apex)

AIMS

To accurately assess subsidence, rotation and clinical scores in two cementless femoral stems.

METHODS

260 patients received either K2 or Apex femoral stems and were studied over 2y, with RSA and clinical scores.

RESULTS

Mean Oxford Hip score for both stems was excellent (45.78 and 46.76). Very little subsidence or rotation were noted on RSA in either stem. There were no statistically significant differences in clinical scores, or radiological motion between stems. Revision rate was 0.8% over the study period.

CONCLUSION

Excellent clinical and RSA scores over the 2y study period predict good long term outcomes for these stems.

Radiographic Subsidence in Asymptomatic Patients After THR Using the Furlong Active HAP Stem

BACKGROUND

The short, tapered, collarless Furlong Active stem has been recently associated in the published literature with significant subsidence using Roentgen stereophotogrammetric analysis.

QUESTIONS/PURPOSES

The purpose of this study was to analyze the short-term radiographic subsidence in Furlong Active HAP stems and correlate the results with the age, gender, bone morphology, and bone quality of the proximal femur, stem diameter, and medullary canal filling.

METHODS

Sixty-five consecutive patients (70 hips) receiving the Furlong Active HAP stems were enrolled in this prospective series. The average follow-up was 2.99 ± 1.38 years. All patients were evaluated clinically using the Harris Hip Score (HHS) and radiographically for femoral stem subsidence. In addition, proximal femoral osteopenia, proximal femur morphology, and medullary canal filling were also evaluated.

RESULTS

The average subsidence was 2.4 mm (from 0 to 13 mm) at the end of the follow-up period. The average HHS score at the end of follow-up was 90 (range, 81-98). There was one intraoperative fracture.

CONCLUSIONS

Of the Furlong Active stems 61% subsided with initial weight bearing. Subsidence is higher in males, but no correlation has been found with age, stem diameter, morphology, osteopenia, or canal filling.

Effect of immediate full weight bearing on abductor repair and clinical function after THA through a modified Hardinge approach

This study evaluated the effect of immediate full weight bearing on abductor repair and clinical function after total hip arthroplasty (THA) using a direct lateral (modified Hardinge) approach. The surgical approach detached a bone flake with the abductors, providing a radiographic marker for abductor displacement and healing. Patients in whom weight bearing was restricted for 6 weeks (partial-weight bearing group) were compared with patients who were immediately weight bearing (full-weight bearing group). A total of 307 patients (309 hips) were followed for a mean of 14 months (range, 12-36 months). The partial-weight bearing group (163 patients) underwent 6 weeks of partial weight bearing, and the full-weight bearing group (146 patients) underwent immediate full weight bearing. The abductor repair was assessed radiographically via the bone flake harvested with abductor muscles. Nonunion of the abductor bone was observed in 12 (7%) patients in the partial-weight bearing group and 9 (6%) patients in the full-weight bearing group (P=.55). Patients in the full-weight bearing group had significantly earlier discharge from hospital than the partial-weight bearing group (2.6 vs 3.5 months, respectively; P=.0021). Patients in the full-weight bearing group had a higher mean Engh score (6.58) radiographically than did patients in the partial-weight bearing group (4.92) (P=.0005). No difference was observed in Harris Hip Score, limp, thigh pain, high-grade heterotopic bone, trochanteric bursitis, or stem subsidence between groups. Restricting weight bearing postoperatively to protect the Hardinge abductor repair appears unnecessary, and recovery of activity is improved with immediate weight bearing.

Early micromovement of the Articular Surface Replacement (ASR) femoral component: two-year radiostereometry results

Radiostereometric analysis (RSA) can detect early micromovement in unstable implant designs which are likely subsequently to have a high failure rate. In 2010, the Articular Surface Replacement (ASR) was withdrawn because of a high failure rate. In 19 ASR femoral components, the mean micromovement over the first two years after implantation was 0.107 mm (SD 0.513) laterally, 0.055 mm (SD 0.204) distally and 0.150 mm (SD 0.413) anteriorly. The mean backward tilt around the x-axis was -0.08° (SD 1.088), mean internal rotation was 0.165° (SD 0.924) and mean varus tilt 0.238° (SD 0.420). The baseline to two-year varus tilt was statistically significant from zero movement, but there was no significant movement from one year onwards. We conclude that the ASR femoral component achieves initial stability and that early migration is not the mode of failure for this resurfacing arthroplasty.

The 6-year migration characteristics of a hydroxyapatite-coated femoral stem: a radiostereometric analysis study

A prospective cohort of 30 patients undergoing primary total hip arthroplasty for treatment of osteoarthritis was enrolled in a study to characterize the migration behavior of a clinically successful cementless stem. At 6 years, the mean subsidence of the stem was 0.63 mm (range, -0.33 to 3.68 mm); the mean rotation into retroversion was 1.41° (range, -1.33° to 7.48°). No stems had additional subsidence of more than 0.25 mm between 6 months and 6 years. The resultant mean subsidence between 2 and 6 years was 0.03 mm, which is below the limit measurable by radiostereometric analysis. The data demonstrate that subsidence of this cementless stem occurs within the first 6 months, after which there is persistent stabilization.

Migration analysis of a metaphyseal anchored short-stem hip prosthesis

BACKGROUND AND PURPOSE

Metaphyseal anchored short-stem hip implants were designed to improve load transmission and preserve femoral bone stock. Until now, only few outcome data have been available and migration studies are one of the few ways of obtaining data that are predictive of implant survival. We therefore evaluated a metaphyseal anchored short-stem hip implant by Ein Bild Roentgen Analyse femoral component analysis (EBRA-FCA).

PATIENTS AND METHODS

First, the EBRA-FCA method was validated for the short-stem hip implant. Then 80 of the first 100 consecutive implants were evaluated after at least 2 years. Clinical assessment was performed using the WOMAC and the UCLA score.

RESULTS

After 2.7 (2.0-4.2), years none of the implants had been revised and by that time the stems had subsided by a mean of 0.7 mm (SD 1.8) (95% CI: 0.3-1.1). Of the 80 implants, 78 were stable after 2 years, with 74 being primary stable and 4 showing secondary stabilization after initial subsidence. Continuous migration was seen in only 2 patients. The clinical outcome showed good results with a mean WOMAC of 11 (SD 13) and a mean UCLA score of 7.3 (SD 2.0).

INTERPRETATION

The metaphyseal anchored short-stem hip implant showed good functional results and a high degree of stability after 2 years. The outcome is comparable to that of clinically proven conventional hip implants and if the results are confirmed by long-term studies, short-stem hip arthroplasty might be an alternative for young patients requiring hip replacement.

The optimal timing of baseline radiostereometric analysis of uncemented press fit cups

BACKGROUND AND AIMS

The baseline radiostereometric analysis (RSA) is usually performed during the first postoperative week. We investigated the micromotion of two uncemented press fit acetabular cups during the first week after total hip arthroplasty.

MATERIAL AND METHODS

All study patients had unilateral osteoarthritis of the hip and received an uncemented THA combination consisting of a CLS stem and either an Allofit or an Interop acetabular cup. The study group consisted of 24 patients who underwent RSA within 1 hour after skin closure, and at 1 and 7 days after surgery.

RESULTS

The upper limit of the 95% confidence interval for micromotion was less than or close to the precision of the method for all studied directions during the first week after surgery. Mean values indicate proximal and medial translation of the uncemented cup at one week.

CONCLUSIONS

We found only minimal micromotion, barely above the precision limit, measured as medial and proximal translations of these uncemented cups. This indicates that the first postoperative RSA measurement following a primary THA with an uncemented press fit ace-tabular cup should be made as early as possible after the first postoperative day.

Periprosthetic bone mineral density and fixation of the uncemented CLS stem related to different weight bearing regimes: A randomized study using DXA and RSA in 38 patients followed for 5 years

BACKGROUND AND PURPOSE

There is no consensus on the best rehabilitation regime after uncemented total hip arthroplasty. Theoretically, bone ingrowth into the implant should benefit from initial partial weight bearing. We investigated whether the degree of postoperative weight bearing influences the periprosthetic bone mineral density (BMD) and/or the stability of the CLS stem.

PATIENTS AND METHODS

38 patients received an uncemented CLS stem and were randomized to either unrestricted postoperative weight bearing or to partial weight bearing for 3 months. Periprosthetic BMD was measured in the 7 Gruen zones with DXA and the stability of the femoral stem was assessed by radiostereometric analysis (RSA) after surgery and at 3, 12, 24, and 60 months.

RESULTS

Periprosthetic BMD was not influenced by the type of postoperative weight bearing. BMD was reduced by 8-15% in all Gruen zones at 3 months. Restoration toward initial BMD was observed in all zones except in zone 7 (calcar region), where BMD was reduced by 22% at 5 years. Immediate weight bearing after surgery had no influence on the stability of the CLS stem, as assessed by RSA.

INTERPRETATION

Immediate full weight bearing after uncemented total hip arthroplasty is safe. There is no difference in the periprosthetic BMD or in stability of the stem as measured by RSA compared to partial weight bearing for 3 months. BMD is reduced by more than 20% in the calcar region around a CLS stem after 5 years.

Partial versus unrestricted weight bearing after an uncemented femoral stem in total hip arthroplasty: recommendation of a concise rehabilitation protocol from a systematic review of the literature

The aim of this systematic review was to find evidence-based support in the literature to allow immediate unrestricted weight bearing after primary uncemented total hip arthroplasty (THA). Accelerated rehabilitation programs for THA are becoming increasingly popular to shorten hospital stay and to facilitate rapid restoration of function. The goals of these rehabilitation programs could be more easily achieved if immediate unrestricted weight bearing (UWB) could be allowed after a THA. So far, however, immediate weight bearing is frequently contraindicated in widely accepted protocols for uncemented THA due to fear for subsidence and absence of osseous integration of the femoral stem. Thus, frequently protected weight bearing and restricted activities are still advocated for at least 6 weeks after surgery. In addition, we analyzed the literature to come to a recommendation on gait pattern and walking aid. From a systematic search in several electronic databases 13 studies met the inclusion criteria. These studies were reviewed according to the Cochrane methodology. We found moderate to strong evidence that no adverse effects on subsidence and osseous integration of the femoral stem after uncemented THA occur after immediate UWB. Based on this literature review, we recommend early rehabilitation after uncemented THA with a reciprocally gait pattern using crutches, one cane for independency in ADL in case patients walk limp-free and walking without crutches as soon as possible. During the first weeks after surgery only stair climbing should be performed with protected weight bearing because of high torsion loads on the hip.

Case report: Cementless stem stabilization after intraoperative fracture: a radiostereometric analysis

We present the case of a patient with intraoperative femoral fracture during THA, which was repaired using cerclage fixation and insertion of an hydroxyapatite-coated cementless stem. The patient was evaluated postoperatively using radiostereometry during a 2-year course, and despite a large amount of subsidence and rotation, stabilization occurred and was maintained by 6 months. By evaluating the pattern of stem migration after intraoperative fracture, this case shows, even in the presence of instability, a successful clinical outcome can be achieved using an hydroxyapatite-coated cementless stem.

Early migration characteristics of a hydroxyapatite-coated femoral stem: an RSA study

Measurement of early stem subsidence can be used to predict the likelihood of long-term femoral component loosening and clinical failure. Data that examines the early migration pattern of clinically proven stems will provide clinicians with useful baseline data with which to compare new stem designs. This study was performed to evaluate the early migration pattern of a hydroxyapatite-coated press-fit femoral component that has been in use for over ten years. We enrolled 30 patients who underwent THA for osteoarthritis. The median age was 70 years (range, 55-80 years). Patients were clinically assessed using the Harris hip score. Radiostereometric analysis was used to evaluate stem migration at three to four days, six months, one year and two years. We observed a mean subsidence of 0.73 mm at six months, 0.62 mm at one year and 0.58 mm at two years and a mean retroversion of 1.82° at six months, 1.90° at one year and 1.59° at two years. This data suggests that subsidence is confined to the first six months after which there was no further subsidence. The results from this study can be compared with those from novel cementless stem designs to help predict the long-term outcome one may expect from new cementless stem designs.

Results with the cementless Spotorno stem in total hip arthroplasty

Increasingly young and active patients are undergoing total hip arthroplasty, making hip prosthesis survival rates an important issue. Cementless total hip arthroplasty provides better prosthesis longevity than does cemented hip arthroplasty, especially in younger patients. Because there is growing support in the literature for tapered geometry in cementless femoral components, we evaluated short-term results for total hip arthroplasty using Cementless Spotorno (CLS) titanium stems. We performed 100 consecutive primary cementless total hip arthroplasties in 87 patients during a 9-year period using CLS stems. Outcome was assessed in terms of survival rate and Harris Hip Score. The stem survival rate was 99%, and the average Harris Hip Score improved from 41 before surgery to 92 at a mean point of 5 years after surgery. Only 1 hip underwent stem revision for a periprosthetic shaft femur fracture caused by high-velocity trauma from a vehicle accident that occurred 6 months after the original surgery. The CLS stems have an excellent survival rate in the short term, especially in younger patients, but long-term studies are required to provide a fuller picture.