1 Introduction

Total hip arthroplasty (THA) is the most common and effective treatment for end-stage hip osteoarthritis. According to the WHO, 1.5 million THAs, more than 500,000, and approximately 100,000 surgeries are performed annually in the world, in the USA, and in Russia, respectively.^1,2

THA has shown satisfactory clinical outcomes within a few years in 80–90% of clinical cases. However, long-term dynamic follow-up has shown a gradual decrease in the proportion of positive outcomes. The need for the replacement of an artificial joint or its components increases in proportion to the duration of time after surgery. As such, an increase in the need for primary THA causes an increase in the need for revision THA, and the number of patients with severe destruction of the acetabulum is increasing. In most clinical cases, bone mass loss or bone fragment loss is found during revision surgery.³

In the late 1960s, W. H. Harris recommended using a cobalt-chromium mash to strengthen the acetabulum in revision THA.⁴ In the 1970s and 1980s, this direction transformed into the development and use of reinforcement rings (cages), which points to intense forces on the outer acetabular edges. Thus, the application of reinforcement structures designed by Muller, Burch-Schneider, R. Ganz, Oxner, Beznosko, etc., became a worthy addition to bone grafting or cementation of the acetabulum. The effect of these innovations has exceeded the expectations and hopes of orthopaedic surgeons and widened the possibilities of their clinical range.

In 1973, Eichler first proposed the use of a metal supporting ring. In 1974, Burch reported the use of a reinforcement ring with additional fixation screws in the ilium and ischium. Today, this reinforcement device is known as the anti-protrusion or reconstructive Burch-Schneider cage. The use of Burch-Schneider cages in orthopaedic surgery has progressively increased since 1975, with more than 125,000 cages being implanted by 2006.^5,6 This design for revision surgery remains valid today. Gary Sayac et al. reported the 10-year results of the use of reinforcement cages combined with dual mobility implants; the implant survival rate was 96.1%.^7,8

The classic indications for the use of the Burch-Schneider include revision THA in patients with defects of the acetabular bottom or roof that preclude stable fixation with other implant options. Burch-Schneider cages are also indicated in cases of acetabular fractures.^9,10,11,12

Currently, there is a very small number of publications devoted to the use of anti-protrusion systems. And even fewer publications describing the long-term results of using Burch Schneider systems. We decided to analyse our long-term results of surgical treatment using Burch-Schneider systems.

The objectives of this study were to conduct a retrospective analysis of revision THA with anti-protrusion devices at our clinic and evaluate the obtained long-term functional results.

2 Materials and methods

The study was conducted in the Department of Orthopaedic Surgery at the Botkin City Hospital, an 60-bed tertiary health-care department. Fifty-eight revision surgeries were performed from 2003 to 2020 with an impaction of the anti-protrusion Burch-Schneider cages because of aseptic loosening of the acetabulum component. Patient records were retrospectively abstracted with use of a standardized data collection case report form to retrieve all data that was required according to the research plan.

The retrospective analysis included 58 patients, including 18 men and 40 women. The average age of the examined patients was 61.2 (±12.9) years. The maximum follow-up duration was 17 years. The average follow-up duration was 10.5 (±4.1) years (Table 1).

Unfortunately, it was not possible to conduct a face-to-face examination of all the included patients, both because of the natural loss of the study participants and because of the technical impossibility of patients appearing for examination. Two patients discontinued participation in the study due to death from natural causes because of comorbidities and multiple severe surgical interventions.

One patient died of a stroke over 12 years after our surgical intervention. Another patient died of cancer outcomes over 9 years after our surgical intervention. These patients completed the last follow-up, including the functional scales, two and three years before the start of the study. For the final control follow-ups, all patients were actively invoked and examined. Because of the technical impossibility of six patients appearing for the final follow-up, they were given the questionnaire over the phone (Table 2).

In this research, various data were considered, such as the number of patients, average follow-up duration, designs used, indications for use of the anti-protrusion cage, implant survival, and functional results. The patients were distributed into the following groups according to the Paprosky classification: 2C, 3A, and 3B.

The surgical approach differed according to acetabular bone scarcity.

In the 2C subgroup, we used only reinforcement rings separately in patients with intact columns and who only had bone scarcity at the acetabular floor.

Those in the 3A “up and out” subgroup exhibited dorsal column bone loss. In cases of massive bone deficiency, a reinforcement ring could become verticalized, and the cement cup position could be used to compensate for functional failure of the ring position to a certain extent.

Those in the 3B “up and in” subgroup exhibited more massive bone loss, which necessitated compensation. In cases of massive bone loss precluding stable fixation of the Burch-Schneider ring, cages from augments were used.

Functional results were evaluated using the functional Harris, WOMAC, SF-36, and FJS-12 scales.

We performed a statistical analysis of the implant survival rate according to the represented groups. A questionnaire based on the previously mentioned scales and X-ray examinations was performed to assess the stabilization of the implant components.

The processing of the obtained data was carried out using the statistical data analysis packages Statistica 10.0 and IBM SPSS Statistics 22.0. The Kolmogorov‒Smirnov criterion was used to determine the normality of the distribution of the data. Continuous variables with a normal distribution are represented as the mean and standard deviation (SD). In the statistical analysis of small selections, Fisher's criterion (variance ratio test) and Friedman's ranked analysis of variance were used. Relative (%) and absolute frequencies are used to describe categorical data.

3 Results

Only 50 of 58 patients were available for visual examination. Two patients died before we started the research. Six patients were not able to attend the final follow-up.

In 41 (73.2%) of the patients, the implant was stable, and no clinical or X-ray evidence for implant loosening was detected; these patients continued their participation in the study. Five (8.9%) patients were diagnosed with a periprosthetic infection and underwent a two-stage treatment. Aseptic loosening of the anti-protrusion ring was detected in 7 (12.5%) patients, and periprosthetic fracture in 3 patients (5.3%).

Pre-revision functional score in group 2C, with a Harris score of 30.3 (±8.9), an FJS-12 score of 22 (±5.6), a WOMAC score of 69,2 (±11.6), and an Oxford Hip score of 15 (±6.3).

In group 3A pre-revision functional score was with a Harris score of 28.8 (±2.9), an FJS-12 score or 21 (±3.3), a WOMAC score of 67 (±18.2), and an Oxford Hip score of 18.6 (±7.7).

In group 3B pre-revision functional score was a Harris score of 27.1 (±4.9), an FJS-12 score of 20 (±5.8), a WOMAC score of 68.3 (±17.2), and an Oxford Hip score of 14.5 (±4.9).

After surgery group 2C showed good functional results, with a Harris score of 87 (±6.9), an FJS-12 score of 63.2 (±4.8), a WOMAC score of 175 (±16.7), and an Oxford Hip score of 39.06 (±9.1). However, 4 of the 18 patients examined in this group underwent implant removal. In 3 of these patients, removal of the implant was performed due to a periprosthetic infection, and a spacer implant was used. In the fourth patient, aseptic implant loosening was detected.

Group 3A also showed good functional results, with a Harris score of 78 (±7.1), an FJS-12 score or 61.2 (±5.1), a WOMAC score of 168 (±17.1), and an Oxford Hip score of 42.12 (±8.7). Four of the 24 examined patients in this group underwent implant removal. Implant removal was performed due to periprosthetic infection in 1 patient, aseptic implant loosening in 2 patients, and periprosthetic fracture in 1 patient.

Group 3B showed satisfactory functional results, with a Harris score of 70 (±5.9), an FJS-12 score of 58.9 (±4.4), a WOMAC score of 166 (±18.1), and an Oxford Hip score of 48.4 (±9.4). Seven of the 16 examined patients in this group underwent implant removal. Implant removal was performed due to aseptic implant loosening in 1 patient periprosthetic infection in 4 patients, and periprosthetic fracture in 2 patients (Table 3).

We found a significant difference in the functional results of all scales between Groups 2C and 3B (p < 0.05). A significant difference was not detected between the Groups 3A and 3B or between Groups 2C and 3A (p > 0.05). This result can probably be explained by the more severe initial orthopaedic pathology in Group 3B (Fig. 1).

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Fig. 1 Functional results by scales.

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Generally, the implant survival rate was satisfactory (73.2%); however, it should be noted that the worst results were in Group 3B due to both septic and aseptic problems, which may also be associated with the more severe orthopaedic pathology (Fig. 2, Fig. 3).

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Fig. 2 Implant survival in 10 years.

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Fig. 3 Kaplan-Meyer survival rate.

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4 Discussion

This work includes generalized clinical, X-ray, and functional data as well as data from the literature for both revision surgery of the acetabulum and complicated cases of primary THA with the use of reinforcement rings. It should be noted that the popularity of this type of construction peaked from 1995 to 2005, and at present, relevant scholarly articles are rare.

Since 2003, we have been using anti-protrusion structures such as Burch-Schneider™ reinforcement cages in cases of massive defects of the acetabular floor. We have been using Trabecular Metal™ acetabular augments in revision THA and in complicated cases of primary THA since 2010.

Despite the advent of 3D technologies and their active introduction into the treatment of complicated cases,^13,14 the Burch-Schneider system has begun to be applied again in our clinic in recent years. Revision THA remains one of the most difficult procedures in hip joint orthopaedics because of bone mass deficiency, which can be due to osteoarthrosis, posttraumatic changes, and lysis caused by micromovement of the implant components and worn particles.^15,16,17,18

The first two variants included in the study were treated via the combined use of a frame and anti-protrusion rings.

A total of 298 cases were reported in 2008; the 5-year implant survival rate was 94%, and the 8-year implant survival rate was 89%. In 2015, Alexander Ewers reported a 10-year implant survival rate of 77.7% for reinforcement cage.¹⁹ However, different data have been reported by scientists; Imran Ilyas reported a 21.2% complication rate with an average implant lifespan of 11.5 years. Generally, the analysis shows a decline in the implant survival rate.

The literature describes various surgical techniques for revision of the acetabular component and the correction of bone mass loss.^{20,21,22,23,24} Recently, reinforcing rings have been used for severe defects of the acetabulum. In our research, we used rings for 2C, 3A, and 3B Paprosky defects. The aim of using rings is to ensure mechanical stability of the implant in the acetabulum and protect allografts or augments by transmitting the physical stress through the ring to the bones of the pelvis.^{25,20,26,27,28}

Two main types of rings are described in the literature: anti-protrusion and supporting rings. Anti-protrusion rings are characterized by double flanges for the ilium and ischium. In our research, we used Burch-Schneider rings.^13,29

Placing the ring in the anatomically correct position is a priority for restoring the correct centre of hip rotation but is a difficult task in revision of the acetabular component in cases of significant bone mass loss. In 1994, Schutzer and Harris proposed high placement of the acetabular component to obtain sufficient contact between the implant and bone.³⁰ However, later articles reported a higher rate of instability of the acetabular component in these situations. The leading task of the supporting rings is to restore the correct rotation centre. However, the more complicated the defect is, the higher the probability of incomplete correction of the centre of rotation, which is probably one of the reasons for the poorer implant survival rate in Group 3B.^31,33,34,13

The most frequently used functional scale was the Harris scale, with an average score of 76.3 (results below 70 were considered unsatisfactory). All of the authors who used the scale for clinical evaluation of the functional results reported a significant increase in the score following revision of the acetabular component.^{13,10,23,26,31,32} In our study, we also used the FJS-12, WOMAC, and Oxford Hip score scales to obtain more objective results. The obtained results can be regarded as satisfactory and good, with observation dates up to 9.7 years. It should be noted that Group 3B showed not only lower implant survival rates but also the worst functional results. This could be explained by the cases in Group 3B being complicated in terms of not only bone loss but also muscle tissue shortage due to multiple surgeries on the joint.

The introduction of porous metallic implants has begun a new era of orthopaedic surgery. Their higher coefficients of friction, lower elastic moduli, and porous surfaces are unquestionable advantages.^20,16,32,22 The International Science Community Association concluded that these characteristics greatly increase and accelerate bone ingrowth. The trabecular hemispherical acetabular component and augments provide an alternative solution for revision of the acetabular component in cases of bone mass loss. Beckman et al. reported a lower probability of aseptic loosening of trabecular metal cups (components) compared to supporting and anti-protrusion rings. The authors strongly recommend the use of trabecular acetabular components, including for revision of the acetabular component in cases of good bone quality.³⁴

In recent years, much clinical experience has been gained in revision of the acetabular component in cases of significant acetabular bone mass loss with Burch-Schneider rings and other original devices. The efficacy of the use of anti-protrusion supportive structures has been confirmed by the published results of foreign and domestic research.^35,36

For example, in treating a pelvic ring with compromised integrity using an anti-protrusion cage, D. Berry et al. achieved satisfactory results in 11 out of 13 patients, with an average postrevision observation period of three years.⁹

Nevertheless, foreign literature contains publications in which the frequency of unsatisfactory results reached 50% after the use of synthetic acetabular bone in combination with reconstructive and anti-protrusion devices.^35,37

Based on the obtained results, anti-protrusion rings may be more appropriate in cases of type 2C and 3A defects. In cases of type 3B defects, it is probably necessary to consider more complex and expensive designs, such as individualized 3D systems, as well as combinations of cages with tantalum augments.

5 Conclusions

The use of anti-protrusion systems of the Burch-Schneider type allows surgeons to effectively manage patients with type 2C, 3A, and 3B acetabular bone mass loss and achieve good and excellent functional results. According to our data, we found a 75% implant survival rate over a 10-year period. Based on the obtained results, anti-protrusion rings may be more appropriate in cases of type 2C and 3A defects. In cases of type 3B defects, it is probably necessary to consider more complex and expensive designs, such as individualized 3D systems, as well as combinations of cages with tantalum augments.

Author contributions statement

Valery Yu. Murylev: Conceptualization, Writing - Review & Editing, Supervision. Pavel M. Elizarov: Writing - Original Draft, Visualization. Aleksei V.Muzychenkov: Methodology, Data Curation. Alexander.G. Guchkov: Investigation, Writing - Review & Editing. Grigory A. Kukovenko: Resources, Validation. Semen S. Alekseev: Resources, Validation. Nikolai E. Erohin: Investigation, Visualization.

Funding/sponsorship

This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors.

Data availability

The data that support the findings of this study are available from the corresponding author, upon reasonable request.

Institutional ethical committee approval

All studies to have been performed in accordance with the ethical standards in the 1964 Declaration of Helsinki. All studies were carried out in accordance with relevant regulations of the US Health Insurance Portability and Accountability Act (HIPAA). This study was approved by Local Ethics Committee of the Sechenov First Moscow State Medical University Ministry of Health of Russia (Sechenov University). The informed consent was obtained from all the study participants.