Revision hip arthroplasty using a modular revision hip system in cases of severe bone loss

The History of Classification Systems for Periprosthetic Femoral Fractures: A Literature Review

Periprosthetic femoral fractures (PPFFs) following total hip arthroplasty (THA) present a significant clinical challenge due to their increasing incidence with an aging population and evolving surgical practices. Historically, classifications were primarily based on anatomical fracture location, the stability of the implant, and bone quality surrounding the implant. We critically analyzed 25 classification systems, highlighting the emergence and adaptations of key systems such as the Vancouver classification system (VCS) and the Unified classification system (UCS), which are lauded for their simplicity and effectiveness yet require further refinement. VCS, developed in 1995, categorizes fractures based on the site, implant stability, and bone quality, and remains widely used due to its robust applicability across different clinical settings. Introduced in 2014, UCS expands the VCS to encompass all periprosthetic fractures with additional fracture types, aiming for a universal application. Despite their widespread adoption, these systems exhibit shortcomings, including the incomplete inclusion of all PPFF types and the imprecise assessment of implant stability and surrounding bone loss. These gaps can result in misclassification and suboptimal treatment outcomes. This paper suggests the necessity for ongoing improvements in classification systems to include emerging fracture types and refined diagnostic criteria, ensuring that they remain relevant to contemporary orthopedic practices and continue to facilitate the precise tailoring of treatment to patient-specific circumstances. This comprehensive historical review serves as a foundation for future innovations in classification systems, ultimately aiming to standardize PPFF treatment and improve patient prognosis.

Long-term Outcomes of Revision Total Hip Arthroplasty Using a Modular Fluted Conical Femoral Stem

BACKGROUND

This study presents minimum 6-year follow-up data on the survival and satisfaction of an uncemented modular revision femoral system, following on from our previously published earlier results.

METHODS

We retrospectively reviewed all revision hip arthroplasties performed at our institution between January 2005 and October 2012, using a single modular femoral revision system. Patient-reported outcomes were collected (satisfaction score and Oxford Hip Score). Preoperative and postoperative radiographs were reviewed for stem subsidence, and Kaplan-Meier analysis was performed for survival. A total of 115 femoral revisions were performed in 106 patients.

RESULTS

All-cause survival was 82% (95% confidence interval 74 to 91%) at 10.8 years, and 96% (95% confidence interval 90 to 100%) excluding septic failure. Of the 19 cases requiring reoperation, 16 were for infection, 2 for aseptic loosening, and 1 for mechanical failure. At final follow-up, 88.5% of patients were "satisfied" or "very satisfied".

CONCLUSIONS

This study showed excellent clinical results of a commonly used revision hip stem with at least 10 years follow-up. Satisfaction rates were high, with few aseptic failures. Stem subsidence was more common in revisions for infection, but did not correlate with lower satisfaction scores.

Mid- to long-term results of the Cone-Conical modular system in revision hip arthroplasty

BACKGROUND

Modular design in revision hip surgery allows some flexibility intra-operatively to address leg length discrepancy, version, and offset while allowing the surgeon to bypass a deficient proximal femur and achieve axial and rotational stability distally. The purpose of this study was to analyze the mid-term to long-term survival and clinical and radiological outcomes using a conical fluted stem and a cone-shaped hydroxyapatite-coated proximal body "The Cone-Conical modular system (Stryker)" in revision hip surgery.

METHODS

We retrospectively reviewed all the patients who underwent hip revision surgery using Cone-Conical modular system between January 2006 and January 2015 at our institution. Seventy patients (72 hips) were included with a mean age of 71.3 years. We had a mean follow-up period of 8.6 years (range 5-15). All patients had a minimum follow-up of five years. A Kaplan-Meier analysis was used to determine the survival of the implant. Functional outcomes were assessed using Oxford Hip Score. Plain radiographs were performed to assess implant fixation and osseointegration.

RESULTS

The mean OHS improved significantly from 12 pre-operatively to 34 at the final follow-up (P < .001). The Cone-Conical system survivorship for aseptic loosening as an end point was 100%. The all-cause survivorship was 97.2%. Two hips had revisions for recurrence of infection.

CONCLUSIONS

The Cone-Conical femoral modular revision system has demonstrated excellent mid-term to long-term clinical and radiographic results with low failure rate and minimal complications. Longer-term follow-up would be of value to assess the ongoing survival of this implant.

Medium Term Radiographic and Clinical Outcomes Using a Modular Tapered Hip Revision Implant

Background

The rate of revision hip arthroplasty surgery is rising. Surgeons must use implants with proven outcomes to help overcome the technical challenges faced during revision surgery. However, outcome studies using these implants are limited. The aim of this study is to investigate the radiographic and clinical outcomes of the Stryker Restoration stem, the most commonly used hip revision stem in the United Kingdom (UK).

Methods

A retrospective review of a single surgeon case series was performed. Immediate postoperative radiographs were analyzed for offset and leg length discrepancy. Radiographic evidence of subsidence was assessed using follow-up radiographs. Kaplan-Meier survival analysis was applied using explantation and reoperation as endpoints. Patient-reported outcomes were measured using the Oxford Hip Score and EQ-5D-5L.

Results

One hundred ninety-eight cases were identified. Mean follow-up duration was 51.8 months (range: 24-121). Stem survival during this period was 98%. Reoperation for any reason was 13%. Mean subsidence was 4.18 mm. Analysis of variance testing showed no difference in mean subsidence between revision indications. Mean offset and leg length discrepancies were measured at 4.5 mm and 4.3 mm, respectively. The mean Oxford Hip Score for participants was 27.6.

Conclusions

This series demonstrates excellent implant survival, with radiographic parameters for reconstruction and subsidence levels comparable to those in the existing literature. The tapered modular hip revision stem provides surgeons with the intraoperative flexibility to overcome some of the anatomical difficulties encountered during revision surgery; this is reflected in the radiographic and clinical outcomes of the cohort in this study.

Clinical, radiographic, and survivorship analysis of a modular fluted tapered stem in revision hip arthroplasty

PURPOSE

Modular fluted tapered stems are one of the most commonly used implants in femoral revision surgery. Due to the relative lack of studies on the Restoration modular fluted tapered stem, we conducted a study to evaluate its short- to mid-term clinical, radiographic, and survival outcomes.

METHODS

We identified all 45 patients treated with this revision stem at our institution. Five patients did not complete the minimum 2-year follow-up, leaving 40 patients (41 hips) for assessment. Mean follow-up was 5.1 years (range 2-11 years). Clinical outcomes were assessed using the Harris hip score (HHS). Radiographs were evaluated for subsidence and loosening. Kaplan-Meier survival analysis was performed using revision of the stem for any reason as end point.

RESULTS

The mean HHS improved from 44.6 points preoperatively to 78.4 points at the most recent follow-up (p < 0.0001). Nonprogressive subsidence occurred in 83% of the hips (mean 2.8 mm; range 1-7 mm). One stem (2.4%) showed progressive subsidence (20 mm) and was considered loose. The most common cause for reoperation was dislocation (three hips, 7.3%). The 10-year survivorship with revision of the stem for any reason as the end point was 93.5% (95% CI, 84.9-100%).

CONCLUSION

There was a significant improvement in the HHS and a low likelihood of revision at short- to mid-term follow-up, adding to the current evidence base for use of this implant in revision surgery. A longer follow-up and a larger number of cases are necessary to fully evaluate its role and performance.

Promising results of revision total hip arthroplasty using a hexagonal, modular, tapered stem in cases of aseptic loosening

Background

Modular stems are widely used in revision total hip arthroplasty (THA) with aseptic loosening being a common reason for revision. Despite the good results reported on the use of modular stem designs, there are only few studies focusing on aseptic revisions and few studies on a hexagonal stem design. The goal of this study is to determine stem survival, clinical and functional outcome along with possible risk factors for implant failure in aseptic revision THA.

Methods

We retrospectively identified 53 patients with aseptic THA revision using a modular hexagonal stem with a minimum follow-up of two years. Femoral bone loss, radiographic and clinical outcomes as well as function measured using the Harris Hip Score (HHS) was assessed. Patients’ previous medical history was analyzed for comorbidities and the body mass index. Stem survival was calculated using the Kaplan-Meier method. Possible risk factors for implant failure were analyzed using the log-rank test. The median age at revision was 69 (IQR 62–73) with a median follow up of 74 months.

Results

Implant survival rates amounted to 90.4% at 3 and 5 years. The median HHS improved by 47 points (34 (IQR 22–47) vs 81 (IQR 59–90) p<0.001). There was a reduced implant survival after 5 years when the revision stem was used following a previous cemented stem (83.4% vs 100%, p = 0.04).

Conclusion

A modular, hexagonal stem can be successfully used in aseptic revision THA with remarkable functional results and excellent survivorship. Revision of a cemented stem using this implant might result in reduced survival which must be considered when planning treatment.

Femoral stem modularity

Femoral stem modularity in hip replacement was first developed to connect a ceramic head to the stem, then extended to metal heads using the Morse taper principle. Is it a good thing, or a necessary evil? It contributes to improving lower limb length and lateralization setting, at the cost of fairly rare complications such as dissociation and fretting corrosion, which can exceptionally lead to ARMD (Adverse Reaction to Metal Debris). Modular necks were later recommended, with a double Morse taper: cylindrical for the head junction, and more or less flattened for the stem. Is this one modularity too far? Dual modularity in theory perfectly reproduces the biomechanical parameters of the hip, but is unfortunately associated with fractures and severe corrosion, leading to ARMD and pseudotumor, especially in Cr-Co necks. Moreover, it provides no functional advantage, and no longer has a role outside dysplasia and other femoral deformities. Metaphyseal-diaphyseal modularity is not widespread in primary implants, and is it really necessary? Only one model has been widely studied: S-Rom™ (Depuy®). It features a metaphyseal sleeve adapting to the anatomy of the proximal femur, with a stem fitted via an inverse Morse taper. Its only interest is in case of congenital dislocation; like all metal connections, it incurs a risk of fracture and corrosion. On the other hand, modularity is widely employed in revision implants. Does it really help these procedures? The connection between a proximal femoral component of variable geometry and a diaphyseal stem with press-fit distal fixation provides a real solution to problems of length, lateralization and anteversion. Early models encountered high rates of fracture, but current implants and rigorous surgical technique have reduced this risk. Corrosion is a less serious problem, as the Morse taper undergoes only axial stress, without the friction undergone by other models subject to varus stress.

Use of the Corail stem for revision total hip arthroplasty: evaluation of clinical outcomes and cost

Background

With the growing number of total hip arthroplasty (THA) procedures performed, revision surgery is also proportionately increasing, resulting in greater health care expenditures. The purpose of this study was to assess clinical outcomes and cost when using a collared, fully hydroxyapatite-coated primary femoral stem for revision THA compared to commonly used revision femoral stems.

Methods

We retrospectively identified patients who underwent revision THA with a primary stem between 2011 and 2016 and matched them on demographic variables and reason for revision to a similar cohort who underwent revision THA. We extracted operative data and information on in-hospital resource use from the patients’ charts to calculate average cost per procedure. Patient-reported outcomes were recorded preoperatively and 1 year postoperatively.

Results

We included 20 patients in our analysis, of whom 10 received a primary stem and 10, a typical revision stem. There were no significant between-group differences in mean Western Ontario and McMaster Universities Osteoarthritis Index score, Harris Hip Score, 12-Item Short Form Health Survey (SF-12) Mental Composite Scale score or Physical Composite Scale score at 1 year. Operative time was significantly shorter and total cost was significantly lower (mean difference –3707.64, 95% confidence interval –5532.85 to –1882.43) with a primary stem than with other revision femoral stems.

Conclusion

We found similar clinical outcomes and significant institutional cost savings with a primary femoral stem in revision THA. This suggests a role for a primary femoral stem such as a collared, fully hydroxyapatite-coated stem for revision THA.

Total Hip Arthroplasty Performed for Coxarthrosis Preserves Long-Term Physical Function: A 40-Year Experience

BACKGROUND

Measures of long-term success of total hip arthroplasty (THA) over the past 50 years have focused primarily on implant survival, with less evidence on long-term functional outcomes.

QUESTIONS/PURPOSES

We aimed to study 20-to-40-year functional outcomes after primary THA. We investigated the extent to which (1) functional outcomes after THA are maintained long term; (2) patient characteristics such as age, hip disease diagnosis, and comorbidities affect recovery of function and survivorship after THA; and (3) patients' overall function after THA is affected by the need for revision, the aging process, and associated comorbidities.

METHODS

We retrospectively reviewed outcomes of the senior author's patients between 1968 and 1993. Of 1207 patients, we identified 167 patients (99 female, 68 male; 276 primary THAs) who were at least 65 years old at follow-up and had at least 20 years of follow-up. Mean age at surgery was 55 years; mean follow-up time was 27 years. Bilateral THAs were performed in 109 patients (65%), and revisions in 81 patients (48.5%). Clinical outcomes including pain level, walking ability, range of motion, and overall function were determined by the Hospital for Special Surgery (HSS) hip scoring system. Contralateral and revision surgery, as well as patient age, sex, and body mass index, were included as covariates. To account for unequally spaced follow-up time points and competing causes of functional decline (e.g., age, contralateral hip disease, and need for revision THA), a latent class mixed model approach was used to identify unobserved classes of patients who had similar outcomes. Linear, quadratic, and piecewise-polynomial growth models were considered for class identification. The best fitting model was determined based on Bayesian information criterion.

RESULTS

A four-class model of this patient population was identified: (1) the Elderly Class, who had a mean age of 62 years at the time of primary THA; (2) the Bilateral Class, who underwent simultaneous or staged bilateral THA; (3) the Revision Class, who required at least one revision; and (4) the Youngest Class, who had a mean age of 49 years. After an initial period of improvement in all groups, the functional trajectory diverged according to classifications. Age was the strongest determinant of long-term outcome, with HSS hip scores in the Elderly Class declining after about 20 years. The Youngest Class maintained good-to-excellent hip function for over 30 years. Revision THA and contralateral THA accounted for a temporary decline in function, after which overall good function was regained for the long term.

CONCLUSIONS

All classes in the study population enjoyed good-to-excellent outcomes after THA for about 20 years. Thereafter, functional decline was attributed more to aging than to the need for revision. One or more revision THA did not negatively influence long-term clinical outcomes, suggesting that, even for younger patients, symptoms, rather than the avoidance of possible revision, should be the primary determining factor when indicating THA.

Factors influencing taper failure of modular revision hip stems

Stem modularity of revision hip implant systems offers the advantage of the restoration of individual patient geometry but introduces additional interfaces, which are subjected to repetitive bending loading and have a propensity for fretting corrosion. The male stem taper is the weakest part of the modular junction due to its reduced cross section compared to the outside diameter of the stem. Taper fractures can be the consequence of overloading in combination with corrosion. The purpose of this study was to assess the influence of implant design factors, patient factors, and surgical factors on the risk of taper failure of the modular junction of revision stems. An analytical bending model was used to estimate the strength of the taper connection for pristine, fatigued and corroded conditions. Additionally, a finite element contact model of the taper connection was developed to assess the relative motion and potential for surface damage at the taper interface under physiological loading for varyied assembly and design parameters. Increasing the male taper diameter was shown to be the most effective means for increasing taper strength but would require a concurrent increase in the outer implant diameter to limit a greater risk of total surface damage for a thinner female taper wall. Increasing the assembly force decreases the total surface damage but not local magnitudes, which are probably responsible for crack initiation. It is suggested that in unfavourable loading conditions a monobloc implant system will reduce the risk of failure.

Management of femoral bone loss in revision total hip arthroplasty

Femoral bone loss is frequently encountered during revision total hip arthroplasty. The quality and quantity of remaining bone helps determine the best method for reconstruction. Extensively porous-coated cylindrical stems or titanium fluted tapered devices that achieve fixation in the diaphysis have both demonstrated excellent long-term survivorship. Titanium fluted tapered stems with a modular proximal body allow for more accurate leg length, offset, and version adjustments independent of the distal stem which may optimise hip biomechanics. Intraoperative fractures are more common with cylindrical stems and subsidence with tapered stems, particularly monoblock designs and in both dislocation continues to be one of the most common postoperative complications. In salvage situations in which an ectatic femoral canal is unable to support an uncemented device, impaction bone grafting, allograft-prosthetic composite, or a segmental proximal femoral replacement may be required.

Implant-delivered Alendronate Causes a Dose-dependent Response on Net Bone Formation Around Porous Titanium Implants in Canines

BACKGROUND

Bony fixation of cementless orthopaedic implants is not always achieved, particularly in challenging scenarios such as revision surgery, trauma, and tumor reconstruction. An adjunct therapy for improving porous implant fixation could improve the reliability and durability of these reconstructive procedures.

QUESTIONS/PURPOSES

In this study, we asked whether there is a positive and dose-dependent effect of the local release of the bisphosphonate alendronate from (1) alendronate/hydroxyapatite (HA) porous-coated titanium implants compared with bare metal porous controls; and (2) alendronate/HA on porous-coated titanium implants compared with HA-coated porous controls with respect to extent of bone ingrowth, bone apposition, and periimplant bone formation in a canine model?

METHODS

Three-dimensional printed porous-coated cylindrical implants coated with three different doses (0.02, 0.06, and 0.18 mg/cm(2)) of alendronate were inserted bilaterally in the intramedullary canal of the proximal femora of 15 adult mongrel dogs (age range, 3-9 years; mean, 5 years) weighing between 36 kg and 60 kg (mean, 43 kg). In each dog, an implant coated with HA and one of three different doses of alendronate was inserted on one side while the contralateral femur had a bare metal porous control implant and an identical control implant with a coating of HA. The dose effect of locally released alendronate on the extent of bone ingrowth, bone apposition, and periimplant bone was assessed by backscattered electron microscopy of three pairs of cross-sections taken from each implant at 12 weeks after surgery. A linear mixed model was used to perform the statistical analyses to account for the correlation in the data resulting from the multiple measures performed on each dog.

RESULTS

Compared with paired bare metal controls, periimplant bone increased by 92% (p = 0.007), and 114% (p < 0.001) in the femora with the alendronate implants with a dose of 0.06 mg/cm(2), or 0.18 mg/cm(2), respectively. At a dose of 0.02 mg/cm(2), there was no difference (46% change; p = 0.184, with the numbers available). The comparison of the alendronate-dosed implants with their HA-coated controls showed that the intermediate dose of 0.06 mg/cm(2) alendronate had the greatest effect on net bone formation. Bone apposition was enhanced with the 0.06-mg/cm(2) alendronate femoral implants (82%; p = 0.008), although there was no change in bone ingrowth (37% change; p = 0.902, with the numbers available). When compared with the HA-coated control implants, the greatest effect of the alendronate-dosed implants was the increased amount of periimplant bone at the intermediate dose of 0.06-mg/cm(2) (108%, p = 0.009). There was no effect of the low (0.02-mg/cm(2)) and high (0.18-mg/cm(2)) alendronate-dosed implants (4%, and 6%, respectively; p = 0.321, p = 0.502). Overall, all three alendronate-dosed implants revealed little to no effect on bone ingrowth compared with the HA-coated control implants.

CONCLUSIONS

The local release of alendronate from a three-dimensional printed porous-coated implant from the three doses studied showed an overall improvement in bone apposition and periimplant bone at the intermediate dose compared with bare metal or with HA-coated controls, although the effect was more pronounced compared with bare metal. Long-term studies to show the effects of localized alendronate delivery and mechanical fixation would be the next step for future studies.

CLINICAL RELEVANCE

Local release of alendronate from a three-dimensional printed porous-coated implant may improve the reliability of cementless fixation of currently available porous-coated bare metal implants.

An In Vitro Comparison of the Primary Stability of 2 Tapered Fluted Femoral Stem Designs

BACKGROUND

Proximal bony deficiencies present a biomechanical challenge to achieving primary stability in revision hip arthroplasty. Long tapered fluted stems have been engineered to span these defects but concerns of early subsidence are well documented. This work aimed primarily to investigate the issue of subsidence with this design using a cadaveric model. A secondary aim was to compare the stability of 2 versions of this design.

METHODS

Seven pairs of cadaveric femora were obtained, dual emission x-ray absorpitometry scanned, with calibration radiographs taken for digital templating. Each bone was potted according to the ISO standard for fatigue testing and a Paprosky type 3 defect was simulated. The established cone-conical Restoration Modular (Stryker) system and a novel design with a chamfered tip and flute configuration (Redapt, Smith & Nephew) were examined. Movement at the stem-bone interface was measured using radiostereometric analysis and micromotion transducers.

RESULTS

All restoration stems and 85% of the Redapt stems achieved stability by recognized criteria, micromotion < 150 μm and migration less than 2 mm. A Fisher exact test comparing the proportion of stems which were stable or unstable was not significant, P = .055. Mean axial subsidence (SD) was 0.17 mm (0.32) and 0.1 mm (0.131) for the Restoration and Redapt stems respectively.

CONCLUSION

This study has demonstrated minimal subsidence in the immediate post-operative period using tapered fluted stems. Both designs achieved excellent stability despite simulation of Paprosky type 3 bony defects in the cadaveric model. This geometry appears satisfactory for use in revision surgery in the presence of significant proximal bony deficiencies.

New fracture pattern focusing on implant fracture for periprosthetic femoral fractures

PURPOSE

The Vancouver Classification System (VCS) for assessing periprosthetic femoral fractures has become universally accepted. The Unified Classification System (UCS) has expanded upon and updated the VCS and applied treatment principles to all periprosthetic fractures. However, periprosthetic femoral fractures accompanied by stem fracture after hip arthroplasty were not classifiable under the original VCS or the UCS.

RESULTS

Our new fracture pattern is based on the periprosthetic femoral fracture as well as stem fracture after hip arthroplasty, and its treatment is dependent upon the stability of the proximal portion of the fractured femoral prosthesis.

CONCLUSION

We believe that our new fracture pattern, a supplement to the VCS and UCS, is useful in the establishment of a therapeutic strategy for periprosthetic femoral fractures.