1 Introduction

Increasing age of the population and global demographic situation gradually lead to a greater demand for the treatment of diseases and injuries that are common among elderly. According to the Federal State Budgetary Institution ‘Center for Expertise and Quality Control of Medical Care’ of the Ministry of Health of the Russian Federation, 238 thousand cases of proximal femur were registered in 2018. The rate of proximal femur fractures (PFF) in the structure of musculoskeletal system injuries among all fractures of long bones ranges from 3.9 to 18%.¹ In the elderly and senile people, the incidence of proximal femur fractures is significantly increased and ranges from 15 to 44% among fractures of various locations.² American authors report approximately 250,000 proximal femur fractures in the United States annually, and this rate will double by 2050.³ Annual incidence of femoral shaft fractures, according to various authors, is 15–21 cases per 100,000 population.⁴ According to Russian Ministry of Health 2020 data, the incidence of femoral fractures in Russia was up to 61 cases per 100,000 population (90,000 per year); and femoral neck fractures incidence was 4 times higher among people over 75 years of age.

Due to comorbidities often present in these patients this type of injury can be considered a life-threatening, since the injury is almost always results in immobility of the patient, leading in elderly to life-threatening hypostatic complications. Furthermore, the biomechanical features of hip joint injuries, along with the complexity of patient management, explain the high percentage of unsatisfactory treatment results and mortality.⁵ It is worth emphasizing that in displaced fractures of the femoral neck, the incidence of pseudarthrosis reaches 42%.⁶ There are different mechanisms of proximal femur fractures, and most often orthopedic traumatologists choose surgical treatment methods. The choice of surgical technique and the fixator used depend on many factors, such as fracture location and its nature, the age of the patient, comorbidities, and the quality of bone tissue. Internal osteosynthesis, is the current treatment method of choice for extra-articular proximal femur fracture, but every treatment method has its limitations.⁷ Some authors report that internal osteosynthesis is associated with a significant number of complications caused by technical errors, vicious union or nonunion with the subsequent development of false joints, the development of femoral head aseptic necrosis, which leads to coxarthrosis and persistent pain syndrome.⁸ To solve the above-described problems, it is necessary to use a conversion surgery - total hip replacement.

The risks of developing possible complications after hip replacement are described in the literature. It was noted that in patients with pseudarthrosis or fracture malunion, the risk of complications is significantly higher than after primary arthroplasty performed for hip joint degenerative changes.⁷ To date, there is no unified algorithm and strategy for treating patients with proximal femur pseudarthrosis.

2 Material and methods

It was a single-center retrospective study where two operating surgeons and single team of surgical assistants performed all interventions.

Our study was focused on the most severe complication in the treatment of proximal femur fractures - failure of primary fixation or proximal femur pseudarthrosis. The study was based on clinical and laboratory data analysis and on the results of total hip arthroplasty (THA) in 45 patients aged 56–84 years (mean age 68.3), including 32 (71.1%) women and 13 (26.1%) men. 12 patients initially received conservative treatment, and 33 patients received initial surgical treatment using various metal osteosynthesis procedures. The time from osteosynthesis or from the moment of injury to admission to the hospital for hip arthroplasty ranged from 12 to 30 months. (Table 1).

Between September 2017 and August 2022, 45 patients underwent conversion hip arthroplasty due to failed primary fixation or pseudarthrosis of the proximal femur. Before hospitalization, all patients underwent plain radiographs of the pelvic bones and damaged hip joint, and CT scans of the pelvic bones. In patients with metal fixators and failed osteosynthesis, ESR and C-reactive protein were assessed to exclude the septic etiology of osteosynthesis failure. In cases with elevated values of these parameters, diagnostic aspiration of synovial fluid was performed, with its cytological and microbiological analysis. Prevention of thromboembolic complications was performed in all patients. In all cases, before arthroplasty and at discharge, Doppler examination of lower extremities venous bed was performed.

All patients, before conversion arthroplasty and after discharge, were repeatedly invited to the clinical diagnostic department for a clinical examination and for assessment using a rating scales. 3, 6 and 12 months after the surgery, pain syndrome and patient quality of life were assessed using the following questionnaire scales: Harris Hip Score, MOS SF-36, VAS. The maximum follow-up period ranged from 12 to 60 months.

Depending on the radiology results, a working classification of pseudarthroses in femoral trochanteric area has been proposed (Fig. 1).

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Fig. 1 Working classification of pseudarthroses in femoral trochanteric area.

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2.3

2.3 Study exclusion criteria

•Peri-implant infection;•Pre-surgery decompensated somatic illness

Study results allowed to elucidate the criteria that are responsible for the formation of a pseudarthrosis after conservative treatment using the method of early mobilisation. Pronounced osteoporosis and somatic pathology were of certain significance, leading to disturbance of bone regeneration and bone metabolism impairment. Signs of these conditions together were a contraindication to osteosynthesis.

Causes of pseudarthrosis after surgical treatment included failure of osteosynthesis, and specifically a mechanical factor (breaking of metal structures - in 7 patients, migration of plates or rods - in 6 patients) and technical errors during osteosynthesis (in 18 patients). The breaking and the migration of metal structures were explained by the early load on the treated limb, which is often not possible to limit in elderly patients. Technical errors include incomplete reposition, incorrectly selected implant size, or its inaccurate positioning.

Before hospital admission for surgical treatment, a comprehensive examination of the patient was carried out to diagnose, treat and compensate for concomitant conditions and also to evaluate the Charlson comorbidity index (Table 2).

Table 2 Charslon comorbidity index.

Total score	Patient survival, %	Number of patients
0	99	0
1	96	0
2	90	6
3	77	19
4	53	15
5	21	5

At the time of admission to hospital all patients required additional support for ambulation using crutches or walkers. In some cases, patients were brought to the department in a wheelchair. Clinical examination found no weight bearing on the affected limb and its shortening by 3–6 cm, also there was a significantly decreases range of movements in the affected hip joint.

In previously surgically treated patients, metal structures were first removed with mandatory intraoperative microbiological culture. Due to general somatic illness of the patients, in order to reduce the aggressiveness and the extent of surgical intervention, in 13 (28.9%) cases, in the first stage of treatment, we removed the metal structure, and after stabilizing patient condition and after obtaining negative intraoperative cultures, we implanted endoprosthesis in the second stage of treatment. In 32 (71.1%) cases, simultaneous removal of fixators was performed, followed by conversion arthroplasty.

Endoprostheses of various brands were used. In 30% of cases, a cemented version of the cup and stem was used, considering patient age and present signs of osteoporosis. In other cases, cementless and hybrid structures were used in direct and reverse versions (Table 3).

Table 3 Types of endoprosthetic components fixation.

Type of endoprosthesis fixation	Cementless fixation	Cemented fixation	Hybrid fixation (cemented cup, cementless stem)
Number of patients	10 (22.2%)	13 (28.9%)	22 (48.9%)

In order to reduce the risk of potential postoperative joint instability, endoprostheses with a dual mobility acetabular component were used in 11 patients (24%). The Wagner Revision Stem femoral component was installed in 30 (66.6%) patients. It is worth emphasizing that surgical intervention was associated with major technical difficulties due to changed positional relationship of anatomically important structures, contractures with muscle retraction, severe local osteoporosis and due the requirement to excise massive scars, which was often accompanied by bleeding (Figs. 2 and 3).

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Fig. 2 Patient Х. Condition after intramedullary osteosynthesis (incorrectly installed fixator, specifically malpositioning of a dynamic screw in the distal part of the pin, which consequently led to insufficient compression in the fractured area, and therefore the development of a pseudarthrosis in the proximal femur).

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Fig. 3 Patient К. Radiographs after total left hip arthroplasty using a cemented acetabular component with dual mobility and Wagner SL type revision tapered stem.

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The following postoperative rehabilitation standard was followed: on the first day after surgical treatment, patients, under the supervision of a physical therapy instructor, were physically activated in bed, and on the second day they walked within the hospital ward with additional support using crutches or a walker with a graduated weight bearing (up to 20% of body weight) on the surgically treated limb. Full weight-bearing on the operated limb was allowed in all cases 2 months after the intervention and after X-ray control with subsequent consultation with the treating physician. Follow-up examination of patients with control radiographs was carried out at 3, 6 months and 1 year from the day of surgery.

All treated patients were divided into 4 groups, according to the working classification. The first group included patients with pseudarthrosis without involvement of trochanter major, the second group included patients with transtrochanteric involvement of trochanter major, the third group included patients with intertrochanteric pseudarthrosis, and the fourth group included patients with a pseudarthrosis in the subtrochanteric area (Table 4).

Table 4 Patient group distribution.

Pseudarthrosis (localization)	Number of patients
Not involving trochanter major – Group I	7 (15.5%)
Transtrochanteric involvement of trochanter major – Group II	9 (20%)
Intertrochanteric area– Group III	20 (44.5%)
Subtrochanteric area – Group IV	9 (20%)
Total	45 (100%)

During preoperative planning, the following features were taken into account. In patients from Group I, standard endoprosthesis components were used with an increased friction pair diameter; in patients of Groups II, III, and IV, in order to fix the greater trochanter, a revision femoral component of a cylindrical shape with larger diameter friction pair was installed where it was possible. In Group II, III, and IV patients a component with double mobility was used where it was impossible to fix the greater trochanter. One of the features of THA in our patients was the need to increase the degree of endoprosthesis constraint, increase the diameter of friction pair to 40 mm and use a double mobility cup. It was due to pathological and anatomical changes in the acetabulum and proximal femur: the need to reduce the risk of dislocation caused by bone tissue deficiency (extensive defects of the proximal femur) and muscle tissue deficiency (due to the lack of an attachment point for the muscles responsible for joint stability), as well as due to massive local scarring (Table 5).

Table 5 Patient distribution according to friction pair used and the type of endoprosthesis constraint.

Friction pair diameter (mm)	Number of patients
32	7 (15.5%)
32 + constrained insert	4 (8.8%)
36	10 (22.2%)
40	4 (8.8%)
Dual mobility	20 (44.4%)

3 Statistical analysis

Statistical data analysis was performed using IBM SPSS Statistics Base 22.0 Software for Windows. Kolmogorov-Smirnov test was used to determine the distribution for normality for statistical analysis of the study results.

Considering that Kolmogorov-Smirnov D statistics for functional scale indicators (Harris hip score, WOMAC, VAS) is significant, the hypothesis that the analyzed distribution is normal should be rejected; the remaining indicators were regarded as indicators with a normal distribution. For further analysis, the following non-parametric tests were used: Wilcoxon signed rank test (examination of parameters before and after surgery) and Mann-Whitney rank test (comparative analysis of groups 1 and 2) were used for comparative analysis of quantitative parameters of the study. Relative (%) and absolute frequencies were used to describe qualitative characteristics. Pearson's chi-square test was used to compare two independent groups of qualitative characteristics. Values for continuous variables with a normal distribution are presented either as M ± SD, where M is the sample mean and SD is the standard deviation, or as the median [Q1, Q3] for non-normally distributed data in both groups. Difference with p < 0.05 was considered statistically significant.

4 Results

Aiming to improve the results of arthroplasty, we have proposed an algorithm for selecting arthroplasty strategy in patients with pseudarthrosis of the lateral area of the proximal femur guided by data from preoperative instrumental examination. A distinct feature of the algorithm is a comprehensive assessment of musculoskeletal defects of the proximal femur and acetabulum, thus allowing at the preoperative stage to evaluate the possibility of fixing the greater trochanter and to select corresponding endoprosthesis components. This algorithm is presented in Fig. 5.

We also analyzed the duration of surgical intervention depending on the presence and absence of previously installed metal fixators. The results are presented in Table 6.

We found that mean duration of intervention in patients with previously installed metal fixators among all groups was 1.34 times higher than in patients without previously installed proximal femur metal fixators. The longest duration of the operation was observed among patients in Groups 3 and 4 (Table 6).

Mean score according to Harris scale at the initial patient presentation was rated as 42 (22–69). During the entire follow-up period, this score averaged 80. The quality of life and intensity of pain in patients were also assessed using the SF-36 and VAS questionnaires. (Tables 7 and 8).

Of note that before total arthroplasty, some patients moved exclusively with additional support using crutches or walkers, and used a wheelchair to cover long distances. Based on the results obtained, patients of all 4 groups after conversion arthroplasty noted a significant quality of life improvement, a decrease in pain severity and functional results improvement. This was probably due to the presence of a severe limitation of range of movements in the joint, intense pain, absence of support ability of the extremity, as well as low operative efficacy expectations.

The best mean results on the HHS scale were obtained among Group I and Group II patients. This can be explained by less pronounced soft tissue defects and bone deficiency in the proximal femur in these Groups. Also patients in Group 1 and 2 showed better muscle condition both at pre- and postoperative stage, which contributed to better functional results and earlier rehabilitation. When analyzing the results obtained using a visual analogue scale (VAS) among patients of all 4 groups, the least intense pain syndrome in the postoperative period was observed in patients of Groups 3 and 4 (Table 8).

Intraoperative blood loss considering all four comparison groups was higher in patients without previously installed metal fixators compared to patients who underwent conversion arthroplasty with removal of previously installed implants. Thus, in Group 1 patients the average intraoperative blood loss was 370 ml versus 450 ml, respectively. In Group 2 it was 350 ml versus 550 ml, in Group 3: 360 ml versus 470 ml, and in Group 4 it was 450 ml versus 600 ml, respectively. Volumes of intraoperative and drainage blood loss in these groups are presented in Table 9. According to data obtained, it can be noted that the greatest intraoperative blood loss was observed in Group 4 patients. These results, apparently, may be due to severe post-traumatic tissue changes, a massive scar process (the presence of well-supplied scar tissue that must be excised during surgery) in the subtrochanteric area.

Volumes of intraoperative and drainage blood loss for patients in all 4 groups are presented in Table 9.

Long-term results over a period of 1–5 years were received for 45 patients. During a period of 28–46 months from the day of conversion surgery, 7 (15%) patients died for reasons not related to surgical intervention (stroke - 2 patients, AMI - 4 patients, accident (road accident) - 1 patient).

In 1 (2%) patient, acute PJI was diagnosed in the early postoperative period, followed by sepsis and death.

37 of patients (82%) had no complaints and were ambulant, using a cane only when walking long distances. Hip function was rated at an average of 84 points according to Harris scale. The results obtained were considered good.

Complaints of moderate pain in the operated hip joint, residual shortening of the operated limb and some range of motion limitation were noted in 4 patients (9%). These data correspond to a satisfactory treatment result.

In 4 patients (9%) the result was considered unsatisfactory. At 1 year of follow-up after surgery, they complained of pain and claudication in the operated joint. X-ray examination showed signs of acetabular component loosening.

The following complications in the immediate postoperative period were registered: hematoma in 9 (20%) patients, requiring in 6 of them aspiration of accumulated fluid; dislocation of the femoral component due to violation of the regime in 3 (6%) patients, with the diameter of the friction pair 32 mm (2 patients) and 40 mm (1 patient). These 3 patients underwent reduction of dislocation. Periprosthetic infection was diagnosed in 3 (6%) patients. These patients underwent surgical debridement, after which relief of the infectious process was noted. During follow-up, severe sepsis developed in 1 case, resulting in death.

All complications registered are presented in the table (Table 10).

5 Discussion

There are literature reports that after unsuccessful osteosynthesis of the proximal femur with the development of a pseudarthrosis, the only treatment option for this group of patients expecting good functional result is total hip arthroplasty.⁹

Results of our study showed that preoperative survey of patients using HHS, SF-36, and VAS questionnaires before conversion arthroplasty, demonstrated an unsatisfactory functional state and high intensity of pain in the hip joint among all groups of patients (Table 8). Analyzing preoperative survey results of patients during follow-up period of 12 months from the day of surgery, a significant improvement in joint function and a decrease in the severity of pain was noted, especially in Group 1 and 2 patients.

Despite its high efficacy and good long term results, hip arthroplasty in patients who have undergone femur osteosynthesis is associated with numerous technical difficulties, including increased blood loss and intervention duration, difficulties associated with replacing bone defects and changes in proximal femur anatomy due to injury and the formation of a false joint.¹⁰

Scott J. Douglas et al. in their study compared the rate of possible complications in patients after conversion and primary (total) hip arthroplasty. The authors report a higher probability of intra- and postoperative complications in patients who have undergone conversion arthroplasty. In particular, the rate of periprosthetic infection compared to primary arthroplasty was 7.7% versus 1.4%, and during 2-years follow-up it was 12.2% versus 2.4%; endoprosthesis dislocation: 4.5% versus 2%, mechanical complications (periprosthetic fractures, wear of the insert, aseptic loosening of endoprosthetic components, etc.): 5.5% versus 1%, deep vein thrombosis – 3.5% versus 2.6%, blood components transfusion requirement: 2% versus 1%. Of note, the average cost of treatment for patients with conversion arthroplasty during 90 days follow-up was significantly higher than for patients after primary hip arthroplasty - 18,800 versus 13,611 thousand US dollars.¹¹

A systematic review of Stibolt RD Jr reported a mean total blood loss of 898 ml and 1000 ml, and also reported that the average duration of total arthroplasty surgery in patients with hip joint post-traumatic changes was 97–240 min.¹²

In our study, intraoperative blood loss in patients with installed metal fixators was greater than in interventions voiding the need for concurrent removal of metal fixators and averaged of all 4 groups 517.5 ml and 382.5 ml, respectively.

Analysing the postoperative (drainage) blood loss, it was also higher in subgroups of patients with previously installed metal fixators (Table 9). Considering patients of all 4 groups mean values of drainage blood loss in the subgroup with installed metal fixators was 562.5 ml and in the subgroup of patients voiding concurrent removal of previously installed metal fixators was 437.5 ml.

In addition, there are difficulties associated with the removal of metal fixators and subsequent use of cement fixation of components. One should consider that difficulties performing conversion interventions (removal of an existing internal fixation implant and installation of an endoprosthesis) are faced already at the stage of access to the metal fixator. Extensive cicatrical adhesions already at this stage cause increased blood loss and increase the duration of the intervention. Broken locking screws or the rod itself (elements of metal fixators of the proximal femur) during attempts to remove, lead to increased tissue trauma and significant bone defects.

Faced with the need for one-step concurrent removal of previously installed metal fixators in the area of the proximal femur, we observed an increase of intervention duration (Table 6). In all 4 groups the average duration of surgery for patients with previously established metal fixators was 135.5 min and in patients without previously installed fixators it was 101 min.

Yuan B.J. et al., in their study focused on conversion arthroplasty after surgical treatment of intertrochanteric femur fractures, also reported the high duration of surgical intervention. Depending on the type of previously installed fixator, mean surgery duration ranged from 190 to 252 min.¹³

Controversial results were obtained by various authors when using standard femoral components for hip arthroplasty after unsuccessful proximal femur fractures osteosynthesis attempts.^14–20

Data analysis showed that the use of standard femoral components for hip replacement, is often unacceptable for various reasons. In turn, cementless modular components can provide a number of advantages. In most cases, we currently use Wagner Revision Stem endoprosthesis with conical stems (manufactured by Zimmer) of various lengths. The length of the stem is selected at the preoperative step, depending on the absence of proximal femur bone tissue. Previously, modular femoral components were also used, allowing to achieve optimal fixation at the area distal to the fracture site, to adjust individual limb length, and to achieve the required offset and the desired anteversion angle.²¹ Given the modular, split design, it is possible to separately prepare the proximal and distal parts of the femur for installation of the endoprosthesis, which in turn ensures stable fixation. According to the literature reports and our own observations, femoral modular components are also optimally suited for cases with bone tissue deficiency in the proximal femur, achieving stable fixation in the distal femur.²¹

However, there were reports on specific limitations associated with the use of modular femoral components, including the appearance of massive metal debris (in cases of micromobility of the modular components), dislocations of the modular neck and even fractures of the modular neck due to fretting corrosion.^22–24 Also, an additional factor that increases the probability of fracture of modular-type femoral components is the deposition of metal ions and abrasive particles in case of wear in the additional friction unit.²³ (Fig. 4). These factors reduce the strength of metal components, increasing the risk of fracture.²⁵

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Fig. 4 Fracture of modular endoprosthesis stem.

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Fig. 5 Algorithm for choosing arthroplasty strategy.

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In 1988, Widmer et al. proposed the theory of combined anteversion, according to which it is necessary to correctly select the proper combined orientation of both components in order to avoid joint instability. Therefore, it is important to implant the femoral component with an optimal anteversion angle.²⁶

T. Tetsunaga in 2017 et al., comparing the use of different types of femoral components (cement fixation, metaphyseal and modular type stems) in patients after treatment of trochanteric fractures, came to the conclusion that with correctly installed anteversion of the stem there is no significant difference in the development of instability in the joint.²⁷

In the setting of excessive cervical anteversion, proximal femoral bone deficiency, or narrow medullary canal, the use of a long, tapered Wagner Cone stem is considered the optimal option.²⁸ Distal fixation ensures the stability of the femoral component via the distribution of the load onto the proximal one in conditions of proximal femur bone deficiency. A distinctive feature of conical stems is the ability to set the proper degree of anteversion. This is achieved due to special design that allows the component to be implanted according to the required anteversion angle. The main disadvantages of these stems remain limited offset capabilities and the risk of femur cortical bone fracture during aggressive implantation, as well as the need to create a “bed” under the neck of the endoprosthesis.²⁹

Considering the above, as well as the fact that the presence of metallosis contributes to possible infection, as well as the high cost of the design, our clinic decided not to use this type of femoral components.

In our study, in cases where dual mobility components, a constrained insert or friction pairs with a large diameter of 36–40 mm were used, there were no cases of joint instability. All 3 cases of endoprosthesis head dislocation in the postoperative period were registered in patients with a 32 mm friction pair (without the use of a ‘constraint’ type insert).

Of note, nonunion of the greater trochanter leads to weakness of the abductor muscles, resulting in joint instability.²⁹ These complications are best to be avoided by achieving better secondary fixation of the greater trochanter, improving stability.³⁰

Foreign colleagues, reported the following complications: hematomas, thromboembolism of the veins of the lower extremities or pulmonary artery, dislocation or periprosthetic fracture, as well as infections. They were using similar to our management and prevention strategies for these complications: compression stockings, anticoagulants, rehabilitation, antibiotics. Particular attention was paid to patients with coagulopathies, patients receiving anticoagulant or antiplatelet therapy before surgery, and patients with major bleeding during previous interventions.³¹

Also there are scientific reports on the following complications after total arthroplasty in patients with post-traumatic changes in the hip joint: iatrogenic damage to the sciatic nerve (2.7%), heterotopic ossification (38.2%), head of the endoprosthesis dislocations (6.2%), periprosthetic infection (10.2%), and loosening of endoprosthetic components (20.32%).¹²

According to our results we found a total of 33.3% of complications, including endoprosthesis head dislocation (6.6%), periprosthetic infection (6.6%) and the formation of hematomas in the area of surgical intervention (20%) (Table 10).

To date, there is no common strategy for the selection and treatment of patients with proximal femur pseudarthroses. The algorithm we have developed will likely allow to optimize treatment, making possible to standardize each individual case and determine a common treatment strategy with the choice of the appropriate type of implant and the volume of preoperative examinations.

6 Conclusions

Strict adherence to the recommended treatment algorithm for patients with proximal femur pseudarthrosis made it possible to achieve good treatment results in 90% of surgically treated patients.

Considering the severe local changes including extensive scarring and osteoporosis with topographic changes in hip joint anatomy, we recommend the use of endoprostheses with an increased friction pair diameter.

According to the developed treatment strategy, in patients with deficient greater trochanter bone tissue, and in patients with pseudarthrosis of the inter- and subtrochanteric areas it is recommended to increase the degree of endoprosthesis constrain (the use of ‘constrain’ type inserts, and use of dual mobility components).

Of note, an important step in the treatment of this group of patients is a careful preoperative planning with thorough assessment of bone tissue quality and muscles condition in the proximal femur area, allowing to choose the optimal endoprosthesis components.

Data availability

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

Ethics approval

Not applicable to this kind of study.

Funding/sponsorship

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

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CRediT authorship contribution statement

Valery Yu Murylev: Conceptualization, Writing – review & editing, Supervision. Gennady G. Rubin: Writing – original draft, Visualization. Grigory A. Kukovenko: Resources, Validation. Pavel M. Elizarov: Investigation, Writing – review & editing. Aleksei V. Muzychenkov: Methodology, Data curation. Semyon S. Alekseev: Resources, Validation. Nikolay E. Erokhin: Investigation, Visualization. Evgeniya Yu Tselishcheva: Investigation, Writing – review & editing. Alexander G. Zhuchkov: Investigation, Visualization. Alexander I. Rudnev: Investigation, Writing – review & editing.