Load dispersion effects of acetabular reinforcement devices used in revision total hip arthroplasty: a simulation study using finite element analysis

Computational modeling of revision total hip arthroplasty involving acetabular defects: A systematic review

Revision total hip arthroplasty (rTHA) involving acetabular defects is a complex procedure associated with lower rates of success than primary THA. Computational modeling has played a key role in surgical planning and prediction of postoperative outcomes following primary THA, but modeling applications in rTHA for acetabular defects remain poorly understood. This study aimed to systematically review the use of computational modeling in acetabular defect classification, implant selection and placement, implant design, and postoperative joint functional performance evaluation following rTHA involving acetabular defects. The databases of Web of Science, Scopus, Medline, Embase, Global Health and Central were searched. Fifty-three relevant articles met the inclusion criteria, and their quality were evaluated using a modified Downs and Black evaluation criteria framework. Manual image segmentation from computed tomography scans, which is time consuming, remains the primary method used to generate 3D models of hip bone; however, statistical shape models, once developed, can be used to estimate pre-defect anatomy rapidly. Finite element modeling, which has been used to estimate bone stresses and strains, and implant micromotion postoperatively, has played a key role in custom and off-the-shelf implant design, mitigation of stress shielding, and prediction of bone remodeling and implant stability. However, model validation is challenging and requires rigorous evaluation and comparison with respect to mid- to long-term clinical outcomes. Development of fast, accurate methods to model acetabular defects, including statistical shape models and artificial neural networks, may ultimately improve uptake of and expand applications in modeling and simulation of rTHA for the research setting and clinic.

No Differences in Major In-Hospital Outcome Metrics When Comparing the Direct Lateral Approach to the Posterior Approach for Hemiarthroplasties After Traumatic Displaced Femoral Neck Fractures

Introduction

The surgical approach of hemiarthroplasty for displaced femoral neck fractures remains debated. The study objective was to compare in-hospital outcomes for geriatric displaced femoral neck fractures treated with hemiarthroplasty based on surgical approach (direct lateral vs. posterior approach).

Materials and Methods

This retrospective cohort study included geriatric patients (≥60 y/o) admitted 7/1/2016-3/31/2020 treated with hemiarthroplasty. Outcomes included: operative time (incision to closure), length of stay (HLOS), and blood loss volume (mL). The Harding direct lateral approach was compared to the posterior approach; P < .05.

Results

There were 164 patients (59% direct lateral, 41% posterior). Patients treated with the direct lateral approach had an advanced directive (P = .03), dementia, (P = .03), or were functionally dependent (P = .03) more often than patients treated with the posterior approach. Time to surgery was comparable between groups (P = .52). The direct lateral approach was associated with a shorter operative time (2.3 vs. 2.8 h, P = .03), a longer HLOS (5.0 vs. 4.0 days, P < .01), and a lower median volume of blood loss (50 vs. 100 mL, P = .01), than the posterior approach, respectively. In a stratified analysis, for those who were not functionally dependent, did not have dementia or an advanced directive, the direct lateral approach led to a longer HLOS (P = .03) and shorter operative time (P = .04) than the posterior approach. Whereas among those who were functionally dependent, had dementia or had an advanced directive, the direct lateral approach led to less blood loss (P = .02) than the posterior approach.

Discussion

While those treated with the direct lateral approach lost significantly less blood, they had a significantly longer HLOS than those treated with the posterior approach. Comorbidities significantly modified outcomes, which may suggest their presence could assist with treatment decisions.

Conclusions

This study found neither approach, the direct lateral nor posterior, to be superior. Surgical approach could remain physician preference.

Reinforcement Ring-Augmented Hip Arthroplasty: A 35-Year Follow-up

During the late 1980s, techniques were evolving to prevent acetabular component loosening. Inadequate acetabular bone stock further complicated this concern, which was traditionally addressed with cementation and bone grafting during this time period. However, one evolving tactic to address acetabular component loosening in the setting of inadequate acetabular bone stock was to augment bone graft with an acetabular reinforcement ring. In 1963, a 26-year-old, active male sustained a right-sided femoral neck fracture following a skiing accident. He ultimately developed a collapsed femoral head and varus deformity of the femoral neck requiring a total hip arthroplasty with a cemented monoblock femoral component and a polyethylene acetabular component cemented into a reinforcement ring. The initial procedure was performed in 1988, and this prosthesis is still functioning 35 years later and represents one of the longest follow-ups of a patient with a primary total hip arthroplasty with a reinforcement ring.

Extended mechanical loads for the analysis of acetabular cages

To analyse the strength and mechanical behaviour of hip implants, it is essential to employ an appropriate loading model. Generating computational models supplemented with muscle forces is a complicated task, especially in the initial phase of implant development. This research aims to expand the possibilities of the simpler acetabular cage model based on joint loads without significantly increasing the demand for computing resources. A Python script covered and grouped the loads from daily activities. The ten calculated major loads were compared with the maximum of the walking and stair climbing loads through the finite element analyses of a custom-made acetabular cage. Sensitivity analyses were performed for the surrounding bones' elastic modulus and the pelvis boundary conditions. The major loads can geometrically cover the entire load spectrum of daily activities. The effect of many high-magnitude force vectors is uncertain in the approach that uses the most common maximum loads. Using these resultant major loads, a new stress concentration area could be detected on the acetabular cage, besides the stress concentration areas induced by the loads reported in the literature. The qualitative correctness of the results is also supported by a control computed tomography scan: a fracture occurred in an extensive, high-stress zone. The results are not sensitive to changes in the elastic modulus of the surrounding bone and the boundary conditions of the model. The presented load vectors and the algorithm make more extensive static analyses possible with little computational overhead. The proposed method can be used for checking the static strength of similar implants.

Comparison of re-revision rate and radiological outcomes between Kerboull-type plate and metal mesh with impaction bone grafting for revision total hip arthroplasty

BACKGROUND

This study compared the re-revision rate and radiographic outcomes of revision total hip arthroplasty (THA) using a Kerboull-type acetabular reinforcement device (KT plate) with bulk structural allograft and metal mesh with impaction bone grafting (IBG).

METHODS

Ninety-one hips of 81 patients underwent revision THA for American Academy of Orthopedic Surgeons (AAOS) classification type III defects from 2008 to 2018. Of these, seven hips of five patients and 15 hips of 13 patients were excluded due to insufficient follow-up information (< 24 months) and large bone defects with a vertical defect height ≥ 60 mm, respectively. The current study compared the survival and radiographic parameters of 45 hips of 41 patients using a KT plate (KT group) and 24 hips of 24 patients using a metal mesh with IBG (mesh group).

RESULTS

Eleven hips (24.4%) in the KT group and 1 hip (4.2%) in the mesh group exhibited radiological failure. Moreover, 8 hips in the KT group (17.0%) required a re-revision THA, while none of the patients in the mesh group required a re-revision. The survival rate with radiographic failure as the endpoint in the mesh group was significantly higher than that in the KT group (100% vs 86.7% at 1-year and 95.8% vs 80.0% at 5-years, respectively; p = 0.032). On multivariable analysis evaluating factors associated with radiographic failure, there were no significant associations with any radiographic measurement. Of the 11 hips with radiographic failure, 1 (11.1%), 3 (12.5%), and 7 (58.3%) hips were of Kawanabe classification stages 2, 3, and 4, respectively.

CONCLUSIONS

The findings of this study suggest that revision THA using KT plates with bulk structure allografts could provide poorer clinical outcomes than revision THA using a metal mesh with IBG. Although revision THA using KT plates with bulk structural allografts could set the true hip center, there is no association between a high hip center and clinical outcomes. The relationship between the position of the KT plate and the host bone might be considered more carefully.

Major acetabular defects: outcomes of first revision total hip arthroplasty using Kerboull cross-plate with allograft and cemented dual mobility cup at a maximum follow-up of fourteen years

BACKGROUND

The use of dual mobility cups (DMC) has been shown to reduce hip instability after revision surgery. For severe acetabular bone loss, reconstruction with a Kerboull cross-plate and bone allograft would contribute to restoring native hip position and bone stock. Only two papers reported on the combination of Kerboull cross-plate with bone allograft and cemented DMC in revision total hip arthroplasty (THA).

METHODS

This is a monocentric retrospective study (28 cases) of first-time revision THA using such a construct in American Association of Orthopaedic Surgeons (AAOS) grade III and IV acetabular bone defect. Detailed demographic, clinical and radiographic results were recorded and evaluated.

RESULTS

With a mean follow-up of six ± 3.63 years, no case of instability was reported. The modified Harris Hip Score (mHHS) was 88.4 ± 10.1. No hook fracture or mechanical failure was observed. Non-progressive radiolucent lines were recorded. Osteointegration of the allografts was observed in all cases with a mean Grodet score of 7.9 ± 0.97.

CONCLUSIONS

In first revision THA, the use of a Kerboull cross-plate with allograft and a cemented DMC in AAOS grade III and IV acetabular bone defects demonstrated excellent clinical and radiological outcomes with no recorded cases of dislocation or mechanical failure.

An Experimental and Virtual Approach to Hip Revision Prostheses

(1) Introduction: The changes in the joint morphology inevitably lead to prosthesis, but the hip pathology is complex. The hip arthroplasty is a therapeutic solution and can be caused, most frequently, by primary and secondary coxarthrosis due to or followed by traumatic conditions. The main aim of this study was to find the method of revision hip prosthesis that preserves as much bone material as possible and has sufficiently good mechanical strength. (2) Materials and Methods: In this study, in a first step, the two revision prostheses were performed on bone components taken from an animal (cow), and then, they were tested on a mechanical testing machine until the prostheses physically failed, and the force causing their failure was determined. (3) Results: These prostheses were then modelled in a virtual environment and tested using the finite element method (FEM) in order to determine their behaviour under loading from normal human gait. Displacement, strain, and stress maps were obtained. (4) Discussion: Discussions on hip revision prostheses, method, and theory analysis are presented at the end of the paper. (5) Conclusions: Important conclusions are drawn based on comparative analyses. The main conclusion shows that the both orthopaedic prostheses provide a very good resistance.

Primary total hip arthroplasty for acetabular fractures in elderly patients

INTRODUCTION

Life expectancy has risen, leading to an increase in acetabular fractures in fragile patients. Total hip arthroplasty with a reinforcement cage is a technically complex option, but allows fracture control and early mobilization. Our aim is to assess whether the use of Burch-Schneider cage in fragile patients with acetabular fractures allows immediate load stabilization without threatening the early survival of the arthroplasty.

MATERIAL AND METHODS

Descriptive study of a series of 14 patients with acetabular fractures treated by a reinforcement cage associated with autologous bonegraft plus a cemented acetabular cup, and mobilization and bearing. Judet Letournel fracture types, surgical delay, and complications during admission were analyzed. Following hospital discharge we recorded the incorporation of grafts according to Gie's classification, presence of calcifications according to Brooker, consolidation of the fracture, loosening of implants and functional aspects according to the HHS and Merlé D'Aubigné Postel score.

RESULTS

The most common fracture was both columns (6/14), with a surgical delay being of 11 days mean and 21,5 days of length of stay. One patient died after surgery. The mean follow-up was 34.4 months. All fractures healed and the bonegraft was incorporated in all cases. The mean HHS was 82 points and the Merle Score was 15/18. There were no complications related to arthroplasty.

CONCLUSIONS

Total hip arthroplasty with Burch-Schneider cage on bonegraft and no added osteosynthesis is a good option of treatment of all types of displaced acetabular fractures in a fragile patient.

Survival Analysis of Allografting and Antiprotrusio Cage in Treating Massive Acetabular Bone Defects

BACKGROUND

Massive acetabular bone defects reconstructed with allografting and antiprotrusio cage in revision hip arthroplasty is less reported in the literature. We here report a series of 84 antiprotrusio cages and analyze the risk factors associated with failure.

METHODS

All instances of use of an antiprotrusio cage for massive acetabular defect (Paprosky type IIc, III, and pelvic discontinuity) between 2002 and 2017 in the authors' institute were reviewed after institutional review board's approval. Survival analyses based on clinical data, bone defect (Paprosky system), type of allograft, size of cage, fixation quality, and position of cage were performed. Failure was defined as cage loosening or breakage, poor hip function, or cage revision for any reason.

RESULTS

A total of 84 cages in 77 patients (mean age, 62.9 years), with a mean follow-up period of 6.2 years, had a survival rate of 82.1%. Failure was noted in 15 hips, including mechanical failure in 8 hips, recurrent dislocation in 1 hip, poor hip function in 1 hip, and periprosthetic joint infection in 5 hips. Pelvic discontinuity, reconstruction with morselized allograft alone, and fewer than 4 fixation points to the host bone were associated with higher failure rates (hazard ratios, 4.02, 3.42, and 9.9, respectively).

CONCLUSION

We found that an antiprotrusio cage combined with strut allografts, fixed securely to the host bone (>4 fixation points), are beneficial for the management of massive acetabular bone defects. However, pelvic discontinuity remains a challenge that warrants the further study of technical or prosthetic innovations, such as triflange implants, cup cage, and 3D-printed implants.

Clinical and radiological survivorship of the Thackray cross plate with rim reinforcement ring for cemented acetabular revision

INTRODUCTION

Acetabular component revision surgery can be a challenging task due to the encountered bone defects. Both cemented and uncemented techniques are described. We report on the survivorship of the Thackray cross plate with rim reinforcement ring for cemented acetabular revision.

PATIENTS AND METHODS

This is a retrospective case series of all patients treated with the implant with a minimum follow-up of 2 years. Acetabular defects were characterized according to the Paprosky classification. Data on potential risk factors for failure of the construct as well as the Oxford Hip Score (OHS) were collected. Kaplan-Meier survival analysis with radiographic aseptic loosening or revision for aseptic loosening as the end point was performed.

RESULTS

From 2000 to 2017, 35 revisions in 18 male and 17 female patients with an average age of 72 years were included. Bone allograft was used in 26 cases and additional implants (medial or supero-lateral mesh) in 13. Seven patients have deceased and the fate of all revisions is known. At an average clinical follow-up of 9.7 (2.6 to 19.6) years, there were no further re-revisions for construct failure. Five hips have demonstrated radiological evidence of aseptic loosening. Radiologically loose components were associated with more severe grades of acetabular bone defects (Paprosky Type 3) (60% vs 3%, p = 0.006). Kaplan-Meier survival analysis demonstrates 79.8% overall survivorship at 7 years. Survivorship for Type 2 defects was significantly higher compared to Type 3 (90% vs 0% at 7 years, Logrank test p = 0.002, Cox proportional hazards p = 0.03). The final median OHS was 38 (12-48) and was not affected by component loosening.

CONCLUSION

This is a cost-effective device that protects the underlying bone graft (81% complete remodeling) and prevents subsidence of the cemented cup (2 mm on average). It should be used with caution in high-grade defects and perhaps not advised.

Topology optimization of 3D-printed structurally porous cage for acetabular reinforcement in total hip arthroplasty

Aseptic loosening and mechanical failure of acetabular reinforcement components are among the main causes of their reduced service life. Current acetabular implants typically feature a structural solid layer that provides load bearing capacity, coated with a foam of uniform porosity to reduce stress shielding and implant loosening. This paper presents an alternative concept for a 3D printed cage that consists of a multifunctional fully porous layer with graded attributes that integrate both structural function and bone in-growth properties. The design comprises a hemispherical cup affixed to a superior flange with architecture featuring an optimally graded porosity. The methodology here presented combines an upscaling mechanics scheme of lattice materials with density-based topology optimization, and includes additive manufacturing constraints and bone ingrowth requirements in the problem formulation. The numerical results indicate a 21.4% reduction in the maximum contact stress on the bone surface, and a 26% decrease in the bone-implant interface peak micromotion, values that are indicative of enhanced bone ingrowth and implant long-term stability.

Acetabular reconstruction for primary and revision total hip arthroplasty using Kerboull-type acetabular reinforcement devices-case-control study with factors related to poor outcomes of surgery

Kerboull-type acetabular support rings (KT) and allogenic bone graft were used for severe periacetabular bone loss with primary and revision total hip arthroplasty (THA). The purpose of this case-control study is to evaluate the risk factors related to poor outcomes of surgery.Sixty patients underwent primary THA and revision THA using allogenic bone graft with KT for large acetabular deficiency. These patients were retrospectively evaluated postoperatively and followed-up by radiograph. The minimum follow-up period was 4 years and averaged 7 years. A radiological failure was defined by the following criteria:Expected risk factors were defined as female, age >75 years, body mass index (BMI) >25%, medical history of hypertension, renal failure, liver steatosis, diabetes, hyperlipidemia, cardiac infarction, smoking, American Academy of Orthopedic Surgery (AAOS) classification III or IV, bleeding>500 mL, time of surgery >3hours, high hip center-type KT, inclination of KT >45 degrees, screw angle >25 degrees, morselized bone graft, Kawanabe's classification stage 3 or 4 and revision surgery. Nineteen hips (31.6%) revealed radiological failure according to our criteria, and revision THA was performed in 2 hips (3.3%). In the statistical analysis, morselized bone graft and high hip center-type KT were identified as factors of poor outcomes of surgery.

Acetabular reinforcement ring with additional hook improves stability in three-dimensional finite element analyses of dysplastic hip arthroplasty

Background

The stability of acetabulum reconstructions using reinforcement rings and hooks is important for successful replacement surgery. The objective of this study was to biomechanically determine the effects of the hook on stress and the related micromotions of the acetabular reinforcement ring during the immediate postoperative period.

Methods

Acetabular reinforcement ring models were developed using a nonlinear, three-dimensional, finite element method. Using a pre-prepared template, we constructed without-hook and bone graft models of varying volumes and material properties.

Results

The stress on the inferior margin of the acetabulum was higher in the with-hook model than in the without-hook model, especially with increased bone graft volumes, and the stiffness of the bone graft material was decreased. Relative micromotions in the without-hook model were higher than in the with-hook models. The highest relative micromotion was observed in the model with increased bone graft volume and lower stiffness of bone graft material.

Conclusions

In biomechanical analyses, the hook effectively dispersed stress and improved the initial fixation strength of the acetabular reinforcement ring.

Total Hip Arthroplasty for Periacetabular Metastatic Disease. An Original Technique of Reconstruction According to the Harrington Classification

BACKGROUND

Periacetabular metastatic disease requires complex acetabular reconstruction. The complication rate for these frail patients is high. Various cement-rebar reinforced techniques allowing cemented total hip arthroplasty (THA) have been described. The optimal procedure has not yet been identified.

METHODS

A continuous series of 131 THAs performed in 126 patients with periacetabular metastatic disease was prospectively included in this study. After bone metastasis curettage and cementation, an original technique of acetabular reconstruction was performed using a dual mobility cup cemented into an acetabular reinforcement device (ie, Kerboull cross-plate or Burch-Schneider antiprotrusio cage) according to the Harrington classification. Functional outcome for independent ambulation in the community, pain relief, and occurrence of dislocation or mechanical failure of the acetabular reconstruction were assessed.

RESULTS

At a mean follow-up of 33 ± 17 months, the improvement in the preoperative to postoperative functional outcome and pain relief was significant (P < .001). The dislocation rate was 2%. Two of the 3 cases of dislocation occurred in acetabular reconstructions associated with a proximal femoral arthroplasty. No mechanical failure or aseptic loosening of the acetabular reconstruction was observed.

CONCLUSION

This study emphasized that our original technique combining bone metastasis curettage and cementation, acetabular reinforcement device and cemented dual mobility cup was effective to restore a painless functional independence and ensure a durable acetabular reconstruction able to face to adjuvant radiation therapy and mechanical solicitations for long survivors. In addition, dual mobility cup limited the risk of dislocation in patients undergoing THA for periacetabular metastatic disease.

Burch-Schneider ring associated with morselized bone allografts, survival and clinical outcomes after acetabular revision surgery

INTRODUCTION AND OBJECTIVES

Acetabular revision surgery is a challenge due to the appearance of bone defects that make primary fixation of implants difficult when extracting loosened components. Reinforcement rings, such as Burch-Schneider (BS), have been shown to be allies in moderate or severe bone defects. The objective of the study is to evaluate the results and survival of these types of implants in acetabular revision surgery in the medium follow-up.

MATERIAL AND METHODS

Retrospective study on a cohort of 64 patients (67 replacements) with BS rings associated with morselized bone allografts in a 2 years minimum follow-up. Data were collected regarding clinical outcomes, graft incorporation, implant mobilization, survival and complications.

RESULTS

The mean follow-up was 5.06 years (R=2.2-12). The Merle scale improved from 8 points to 15 points at the end of follow-up (P<.0001) with 76.11% of good or excellent results. Reproduction of the anatomical centre of rotation was associated with a better result (P<.05). There was total or subtotal incorporation of the bone allograft in 97% of the patients, although this did not prevent a significant migration of the ring according to Gill criteria in 6 cases. We observed an overall survival of the implant for any cause of 93.4% at 5 years, and 84.6% at 10 years.

CONCLUSIONS

The BS reinforcement ring shows good results in the medium and long term enabling anatomical reconstruction in revision surgery as well as replacement of the bone stock. These results are also comparable and are a vast improvement on other rings.

A 2- to 16-Year Clinical Follow-Up of Revision Total Hip Arthroplasty Using a New Acetabular Implant Combined With Impacted Bone Allografts and a Cemented Cup

BACKGROUND

Treatment of acetabular bone loss with impaction bone grafting (IBG) at revision total hip arthroplasty is highly dependent on mechanical stability and graft compression for clinical success. Here, we describe a new technique to further compress and stabilize the acetabular graft bed with a thin, perforated titanium shell.

METHODS

We retrospectively analyzed 170 cases of acetabular revision arthroplasty 7 years (standard deviation 2.8) after IBG combined with a graft-compressing titanium shell implant. The patients were reviewed by clinical score and radiography. Three patients were lost to follow-up. The medical journals of the 33 deceased cases were reviewed for any reoperation. Of the 170 cases, 74 had a cavitary acetabular bone defect, 93 had combined segmental and cavitary bone defects, and 3 had a pelvic dissociation. Bone graft incorporation was assessed and correction of the hip center of rotation was calculated.

RESULTS

Five cases (3%) were reoperated for mechanical loosening. One more was assessed as loose but asymptomatic and was not planned for revision. There were 3 reoperations for recurrent dislocation, 2 for deep infection and 1 for technical error. Reoperation for any reason, as the end point of survivorship, showed a survival rate of 92% after 10 years. Hip score according to Merle, d'Aubigne, and Postel increased from 10.8 (preoperatively) to 16.4 at follow-up. The clinical and radiological results were excellent.

CONCLUSION

IBG combined with the compressing shell results in excellent results for this challenging condition.

Revision Total Hip Arthroplasty Using the Kerboull Acetabular Reinforcement Device and Structural Allograft for Severe Defects of the Acetabulum

BACKGROUND

The purpose of this study is to review our experience with Kerboull reinforcement device combined with bulk allograft for management of severe acetabular defects.

METHODS

We investigated the results of revision total hip arthroplasty (THA) in 65 hips of 59 patients (10 male, 49 female) with Paprosky type 3A or 3B acetabular bone defects. Functional outcome was assessed using the Merle d'Aubigne hip score. Post-operative radiographs were examined for evidence of cup loosening. The mean age at revision THA was 59.1 years (23-85) and mean follow-up duration was 11.2 years (2-15).

RESULTS

The Merle d'Aubigne hip score improved from 10.6 points (5-15) before surgery to 17.1 points (15-18) (P < .05) at the time of last investigation. In this series, mean coverage of the bone graft was 83.0% (34.6-100) of the loading portion in the horizontal plane on radiography immediately after revision. However, consolidation of the bone graft was completed within 12 months for all cases. There were 4 radiological failures due to acetabular aseptic loosening at a mean of 10.8 years (8-13) after index surgery; all 4 cases demonstrated massive bone loss that no part of the rounded plate could be placed on the host bone. Kaplan-Meier analysis showed that the 15.2-year survival rate was 85.1% (95% confidence interval 71-99) with re-revision surgery for any reason as the end point.

CONCLUSION

Despite massive bone defects, we achieved favorable results for revision THA using bulk allograft and the Kerboull reinforcement device.

Risk factors for failure of revision total hip arthroplasty using a Kerboull-type acetabular reinforcement device

Background

The present study aimed to identify the risk factors associated with revision total hip arthroplasty (THA) failure using a Kerboull-type (KT) plate.

Methods

We analyzed 77 revision THAs using cemented acetabular components with a KT plate for aseptic loosening between May 2000 and March 2012. We examined the association of bone graft type, acetabular bone defects, age at the time of surgery, preoperative Japanese Orthopaedic Association (JOA) score, postoperative JOA hip score, and body mass index, with radiographic failure as the outcome.

Results

The 7.4-year radiographic failure survival rate was 81.6%. The survival rate was significantly different between the beta-tricalcium phosphate (β-TCP) group and the bulk allograft group (p = 0.019). The survival curves were also significantly different between the β-TCP group and bulk allograft group (p = 0.036). American Academy of Orthopaedic Surgeons type IV was significantly associated with radiographic failure (odds ratio [OR]: 15.5, 95% confidence interval [CI]: 1.4–175.4; p = 0.032).

Conclusions

The midterm outcomes of revision THA indicate that type of bone graft and bone defect size may affect radiographic survival rate when using a KT plate.

Total hip arthroplasty revision by dual-mobility acetabular cup cemented in a metal reinforcement: A 62 case series at a minimum 5 years' follow-up

INTRODUCTION

Total hip arthroplasty (THA) requires bone reconstruction in case of severe acetabular injury, with risk of dislocation, especially postoperatively. Dual-mobility cups have proved effective in preventing dislocation in THA revision for instability, but their behavior when cemented in a metal reinforcement has been little studied.

OBJECTIVES

The present study assessed results for a dual-mobility cup cemented in a metal reinforcement, in terms of aseptic loosening and postoperative instability.

MATERIAL AND METHODS

A single-center continuous series of 62 patients receiving such an assembly in THA revision was assessed retrospectively at a minimum 5 years' follow-up. Failure due to aseptic loosening or instability and implant survival at last follow-up were analyzed.

RESULTS

Radiological and clinical analysis was performed at a mean 77 months' follow-up. Mean Merle-d'Aubigné-Postel score was 14, Harris score 73 and Oxford-12 score 23.9 at last follow-up. Complications comprised 5 cases of loosening and 2 of dislocation. Loosening risk was significantly greater in case of<2mm cement thickness between cup and reinforcement. Eight-year infection-free survival was 91.9%.

DISCUSSION

The present clinical results were comparable to those in series using the same kind of assembly; the dislocation rate was low, but the rate of aseptic loosening was higher than reported elsewhere. Cement thickness between cup and reinforcement was a determining factor for stability. Cup design may also be relevant to loosening. This technique seemed to be a good option in THA revision with severe bone loss.

LEVEL OF EVIDENCE

IV, retrospective study.

Bone Remodeling in Acetabular Reconstruction Using a Kerboull-Type Reinforcement Device and Structural Bone-Grafting in Total Hip Arthroplasty

BACKGROUND

The purpose of this study was to identify the long-term durability of the Kerboull-type reinforcement device (KT plate) in acetabular reconstruction for massive bone defects, assessing the remodeling of structural bone grafts.

METHODS

This study retrospectively evaluated 106 hips that underwent acetabular reconstruction using a KT plate between November 2000 and December 2010. Thirty-eight primary total hip arthoplasties (THAs) and 68 revised THAs were performed, and the mean duration of clinical follow-up was 8 years (5-14 years). Regarding reconstructing the acetabular bone defects, autografts were used in 37 hips, allografts in 68 hips, and A-W glass ceramics in 2 hips.

RESULTS

One hip exhibited radiological migration and no revision for aseptic loosening. The mean Merle d'Aubigné Clinical Score improved from 7.5 points (4-12 points) preoperatively to 10.9 points (9-18 points) at the last follow-up. The Kaplan-Meier survival rate for radiological migration of primary and revised THAs at 10 years was 100% and 97% (95% confidence interval: 96%-100%), respectively. Bone remodeling was evaluated using the radiological demarcation at the bone-to-bone interface, and an improvement of 100% in primary THAs and 94% in revised THAs was observed.

CONCLUSION

For massive bone defects, acetabular reconstruction using the KT plate with a structural bone grafting can yield successful results.

Role of Cages in Revision Arthroplasty of the Acetabulum

➤ The outcome of acetabular revision is heavily influenced by the degree of associated bone loss.➤ Uncemented hemispherical acetabular components can be used in the majority of acetabular revisions, although occasionally the degree of bone loss precludes the stability of the hemispherical component at the correct anatomic level or there is minimal bleeding host bone left for biologic fixation.➤ Massive acetabular bone loss resulting in the need for bone grafts or highly porous augments involving more than half of the acetabulum is one of the main indications for the use of cages.➤ The cup-cage reconstruction is based on bone-grafting the deficient acetabulum and securing a hemispherical, highly porous metal component with multiple screws to bridge the discontinuity and off-loading the hemispherical component with a titanium cage spanning from ischium to ilium.➤ In addition to managing pelvic discontinuities, the cup-cage construct can also be used in hips without discontinuity as the hemispherical, highly porous metal component is used to restore bone stock.➤ In situations in which there is not enough bleeding host bone to secure a hemispherical component, a highly porous metal augment can be used to address the osseous deficiency. The augment is also protected with a cage to assist bone ingrowth.

The role of cages in the management of severe acetabular bone defects at revision arthroplasty

An uncemented hemispherical acetabular component is the mainstay of acetabular revision and gives excellent long-term results.

Occasionally, the degree of acetabular bone loss means that a hemispherical component will be unstable when sited in the correct anatomical location or there is minimal bleeding host bone left for biological fixation. On these occasions an alternative method of reconstruction has to be used.

A major column structural allograft has been shown to restore the deficient bone stock to some degree, but it needs to be off-loaded with a reconstruction cage to prevent collapse of the graft. The use of porous metal augments is a promising method of overcoming some of the problems associated with structural allograft. If the defect is large, the augment needs to be protected by a cage to allow ingrowth to occur. Cup-cage reconstruction is an effective method of treating chronic pelvic discontinuity and large contained or uncontained bone defects.

This paper presents the indications, surgical techniques and outcomes of various methods which use acetabular reconstruction cages for revision total hip arthroplasty.

Cite this article: Bone Joint J 2016;98-B(1 Suppl A):73–7.

Importance of maintaining the basic stress pathway above the acetabular dome during acetabular reconstruction

The basic stress pathway above the acetabular dome is important for the maintenance of implant stability in press-fit acetabular reconstruction of total hip arthroplasty. However, information on the basic stress pathway and its impact factors remains unclear. The objective of this study was to investigate the effects of the orientations and positions of the acetabular component on the basic stress pathway. The basic stress pathway above the acetabular dome was defined as two parts: 3D basic trabecular bone stress distribution and quantified basic cortical bone stress level, using two subject-specific finite element normal hip models. The effects were then analysed by generating 32 reconstructed acetabular cases with different cup abduction and anteversion angles within a range of 35-50° and 10-25°, respectively, and 12 cases with different hip centre heights within a range of 0-15 mm above the acetabular dome. The 3D trabecular stress distribution decreased remarkably in all cases, while the 80% of the basic cortical bone stress level was maintained in cases when the acetabular component was positioned at 10° or 15° anteversion and 40° or 45° abduction angles. The basic stress pathway above the acetabular dome was disturbed when the superior displacement of the hip centre exceeded 5 mm above the anatomical hip centre. Positioning the acetabular component correctly contributes to maintain the stress balance between the acetabular cup and the bone during acetabular reconstruction, thus helping restore the normal hip biomechanics and preserve the stability of the implants.

Long-Term Outcome of Acetabular Reconstruction Using a Kerboull-Type Acetabular Reinforcement Device with Hydroxyapetite Granule and Structural Autograft for AAOS type II and III Acetabular Defects

We evaluated the clinical results of the reconstruction of acetabular bone deficiency using hydroxyapatite (HA) granules and structural autografts supported by a Kerboull-type acetabular reinforcement device at a minimum of 10 years follow-up. Between 1993 and 2003, 40 consecutive THA revisions were performed in 37 patients with a mean age of 66.4 years. The mean follow-up period was 12.8 years. Radiologically, 5 hips failed, of which 2 were revised. The survival rate of the acetabular component at 10 years was 100% in type II defects and 94.9% in the type III defects, using acetabular revision for loosening as the end point. Acetabular reconstruction with HA granules, structural autografts and a Kerboull-type acetabular reinforcement device provided satisfactory clinical and radiological results at 12.8 years postoperatively.

The value of bulk femoral head allograft in acetabular reconstruction using Kerboull-type plate

PURPOSE

This study investigated the mid- and long-term results of acetabular reconstruction using a KT plate with an allograft and showed the utility of filling the bony defect with bulk femoral head allograft rather than morselised allograft.

METHODS

We retrospectively investigated a consecutive series of 31 hips in 30 patients who underwent primary THA or revision THA between March 2002 and March 2012. Bulk grafts from femoral head allografts were used in 16 hips and morselised grafts were used in 15 hips. The mean follow-up period was 7.2 years (3-13 years). The acetabular bone defects were classified according to the American Academy of Orthopedic Surgeons grading system. Type II defects were present in five hips; 26 hips were type III.

RESULTS

Radiological failure, defined as absolute error of the inclination of the KT plate >3°, breakage of the KT plate or screw, and/or absolute error of the vertical or horizontal migration of the femoral head >3 mm was found in 12 cases. All these complications appeared in the morselized group; there were no complications in the bulk group. The eight-year survival rate of morselised grafts was 52.5% and that of bulk grafts was 100%, using radiological loosening as an end point.

CONCLUSIONS

We conclude that using bulk graft from femoral head allografts is necessary to achieve mechanically stable reconstruction for large acetabular bone defects.

Preliminary biomechanical study of different acetabular reinforcement devices for acetabular reconstruction

Background

Acetabular reinforcement devices (ARDs) are frequently used as load-sharing devices to allow allograft incorporation in revision hip arthroplasty with massive acetabular bone loss. The key to a successful reconstruction is robust fixation of the device to the host acetabulum. Interlocking fixation is expected to improve the initial stability of the postoperative construct. However, all commercially available ARDs are designed with non-locking fixation. This study investigates the efficacy of standard ARDs modified with locking screw mechanisms for improving stability in acetabular reconstruction.

Methods

Three types of ARDs were examined to evaluate the postoperative compression and angular stability: i) standard commercial ARDs, ii) standard ARDs modified with monoaxial and iii) standard ARDs modified with polyaxial locking screw mechanisms. All ARDs were implanted into osteomized synthetic pelvis with pelvic discontinuity. Axial compression and torsion tests were then performed using a servohydraulic material testing machine that measured load (angle) versus displacement (torque). Initial stability was compared among the groups.

Results

Equipping ARDs with interlocking mechanisms effectively improved the initial stability at the device/bone interface compared to standard non-locked ARDs. In both compression and torsion experiments, the monoaxial interlocking construct demonstrated the highest construct stiffness (672.6 ± 84.1 N/mm in compression and 13.3 ± 1.0 N·m/degree in torsion), whereas the non-locked construct had the lowest construct stiffness (381.4 ± 117.2 N/mm in compression and 6.9 ± 2.1 N·m/degree in torsion) (P < 0.05).

Conclusions

Our study demonstrates the potential benefit of adding a locking mechanism to an ARD. Polyaxial ARDs provide the surgeon with more flexibility in placing the screws at the cost of reduced mechanical performance. This in vitro study provides a preliminary evaluation of biomechanical performance for ARDs with or without interlocking mechanisms, actual clinical trial deserves to be further investigated in future studies.

Contact between the acetabulum and dome of a Kerboull-type plate influences the stress on the plate and screw

We used a three-dimensional finite element method to investigate the conditions behind the Kerboull-type (KT) dome. The KT plate dome was divided into five areas, and 14 models were created to examine different conditions of dome contact with the acetabulum. The maximum stress on the KT plate and screws was estimated for each model. Furthermore, to investigate the impact of the contact area with the acetabulum on the KT plate, a multiple regression analysis was conducted using the analysis results. The dome-acetabulum contact area affected the maximum equivalent stress on the KT plate; good contact with two specific areas of the vertical and horizontal beams (Areas 3 and 5) reduced the maximum equivalent stress. The maximum equivalent stress on the hook increased when the hardness of the bone representing the acetabulum varied. Thus, we confirmed the technical importance of providing a plate with a broad area of appropriate support from the bone and cement in the posterior portion of the dome and also proved the importance of supporting the area of the plate in the direction of the load at the center of the cross-plate and near the hook.

Finite element modelling for assessing effect of acetabular component orientation on the basic stress path above acetabular dome

OBJECTIVE

To investigate the effect of acetabular component orientation on the basic stress path above the acetabular dome in the recommended safe zone.

METHODS

A subject-specific normal hip finite element model was generated and a convergence study carried out to determine the number of material properties for trabecular bone using a normal hip model. Four abduction angles (35°, 40°, 45° and 50°) and four anteversion angles (10°, 15°, 20° and 25°) from the recommended safe zone of acetabular cup orientation were chosen to simulate acetabular reconstruction. The distribution and level of periacetabular stress was assessed using a normal hip model as a control and 16 reconstructed acetabula in simulated single-legged stances.

RESULTS

The error of the average stress between plans four and five (50 and 100 materials for trabecular bone respectively) was 4.8%, which is less than the previously defined 5% error. The effect of acetabular component orientation on stress distribution in trabecular bone was not pronounced. When the acetabular component was at 15° anteversion and the abduction angle was 40° or 45°, the stress level on posterolateral cortical bone above the acetabular dome was as stable as that in the normal hip model.

CONCLUSIONS

Acetabular component orientation affects the basic stress path above the acetabular dome. Thus, orientation should be considered when attempting to restore normal biomechanics in the main load-bearing area.

A cemented acetabular component with a reinforcement cross provides excellent medium-term fixation in total hip arthroplasty after pelvic irradiation

Conventional cemented acetabular components are reported to have a high rate of failure when implanted into previously irradiated bone. We recommend the use of a cemented reconstruction with the addition of an acetabular reinforcement cross to improve fixation.

We reviewed a cohort of 45 patients (49 hips) who had undergone irradiation of the pelvis and a cemented total hip arthroplasty (THA) with an acetabular reinforcement cross. All hips had received a minimum dose of 30 Gray (Gy) to treat a primary nearby tumour or metastasis. The median dose of radiation was 50 Gy (Q1 to Q3: 45 to 60; mean: 49.57, 32 to 72).

The mean follow-up after THA was 51 months (17 to 137). The cumulative probability of revision of the acetabular component for a mechanical reason was 0% (0 to 0%) at 24 months, 2.9% (0.2 to 13.3%) at 60 months and 2.9% (0.2% to 13.3%) at 120 months, respectively. One hip was revised for mechanical failure and three for infection.

Cemented acetabular components with a reinforcement cross provide good medium-term fixation after pelvic irradiation. These patients are at a higher risk of developing infection of their THA.

Cite this article: Bone Joint J 2015;97-B:177–84.

Effect of high hip center on stress for dysplastic hip

High hip center reconstruction has been advocated in treating deficient acetabulum. However, there is no consensus on the clinical outcome of this technique. In addition, it remains unclear to what extend this technique restores the normal hip biomechanics. The goal of this study was to investigate stress above the acetabular dome in response to a range of high hip center positioning for Crowe type I and II hip dysplasia. This study consisted of 2 main parts, radiologic and biomechanical. Pelvic radiographs of 18 patients were studied to determine the amount of displacement of the hip center in the superior direction compared with the normal side. Second, qualitative and quantitative changes in stress on cortical and trabecular bone in the region of the acetabular dome as a result of superior displacement of the hip center were analyzed with subject-specific finite element models. The results showed that the range of the hip center position in the superior direction for Crowe type I and II hip dysplasia was 0 to 15 mm above the contralateral femoral head center. When superior displacement of the hip center exceeded 5 mm above the anatomic hip center, cortical bone mass on the 2 thickest cross-sections above the acetabular dome decreased quickly and the stress value on posterolateral cortical bone was obviously lower than the normal level. This study showed that to restore the normal load above the acetabular dome, there is a limit of 5 mm above the anatomic hip center for high hip center acetabular reconstruction for Crowe type I and II hip dysplasia.

Acetabular reconstruction with the Burch-Schneider antiprotrusio cage and bulk allografts: minimum 10-year follow-up results

Reconstruction of severe pelvic bone loss is a challenging problem in hip revision surgery. Between January 1992 and December 2000, 97 hips with periprosthetic osteolysis underwent acetabular revision using bulk allografts and the Burch-Schneider antiprotrusio cage (APC). Twenty-nine patients (32 implants) died for unrelated causes without additional surgery. Sixty-five hips were available for clinical and radiographic assessment at an average follow-up of 14.6 years (range, 10.0 to 18.9 years). There were 16 male and 49 female patients, aged from 29 to 83 (median, 60 years), with Paprosky IIIA (27 cases) and IIIB (38 cases) acetabular bone defects. Nine cages required rerevision because of infection (3), aseptic loosening (5), and flange breakage (1). The average Harris hip score improved from 33.1 points preoperatively to 75.6 points at follow-up (P < 0.001). Radiographically, graft incorporation and cage stability were detected in 48 and 52 hips, respectively. The cumulative survival rates at 18.9 years with removal for any reason or X-ray migration of the cage and aseptic or radiographic loosening as the end points were 80.0% and 84.6%, respectively. The use of the Burch-Schneider APC and massive allografts is an effective technique for the reconstructive treatment of extensive acetabular bone loss with long-lasting survival.

Acetabular reconstruction using a Kerboull cross-plate, structural allograft and cemented dual-mobility cup in revision THA at a minimum 5-year follow-up

The current study aimed to evaluate the outcome of a continuous and prospective series of 61 revision THAs with AAOS grade III and IV acetabular bone defect reconstruction using a Kerboull cross-plate, structural allograft and cemented dual mobility cup (Saturne, Amplitude, Valence, France). At a 7.5-year mean follow-up, no instability was reported after revision. In addition, no failure of the acetabular reconstruction was observed in 98% of the patients with complete allograft osseointegration and no evidence of mechanical rupture of the Kerboull cross-plate and/or loosening of the cemented dual mobility cup. In conclusion, such reconstruction technique demonstrated excellent results at mid-term follow-up in terms of prevention of instability after revision, restoration of the acetabular bone stock, and stable cemented fixation of the dual mobility cup.

Effect of acetabular reinforcement ring with hook for acetabular dysplasia clarified by three-dimensional finite element analysis

The objective of this study was to biomechanically determine the effect of the severity of acetabular dysplasia, number and positions of screws and type of bone graft material used on the initial fixation strength of the acetabular reinforcement ring with hook (Ganz ring) using the finite element method. Relative micromotion increased as the severity of acetabular dysplasia increased and tended to decrease as the number of screws increased, but varied according to screw placement position. Increased strength of the bone graft material led to decreased relative micromotion. Biomechanically, the Ganz ring can be placed securely using 3 screws in patients with Crowe 1 dysplasia. However, in patients with Crowe 2 or higher dysplasia, it is necessary to spread at least 4 screws across an area of good host bone.