Introduction

Modern advancements in oncological therapy have led to a rise in the incidence of pathologic fractures [1, 2]. Management of these often-challenging fractures leads to increased healthcare resource utilization and a substantial socioeconomic burden [3, 4]. While the life expectancy and survival rate at 1 year in patients with metastatic bone disease have been reported to be low [5,6,7,8], the overall survivorship of patients after their first pathological fracture has more than tripled in the past 25 years [6, 7, 9].

Due to its exposition to high load transfer [10], the proximal femur is the most common location for pathologic fractures in the appendicular skeleton [11, 12]. Given that implant failure is an inherent risk with any fracture in this region, it is imperative that implants and operative techniques used in management of these pathologic fractures provide long-term stability due to the increased risk of non-union [9, 12]. The aim of treatment is to allow for anatomic stability to rapidly restore patient’s mobility and quality of life [9, 12,13,14].

Numerous treatment options have been described for impending and pathological fractures of the proximal femur. These include intramedullary nailing (IMN) [15], endoprosthetic reconstruction [16] or plating with and without augmentation of bone cement [12]. An almost forgotten technique, known as the compound osteosynthesis, has been specifically developed for surgical treatment of these pathological fractures [17, 18]. This technique comprises the reconstruction of the proximal femur using a condylar blade plate together with an intramedullary placed narrow small fragment plate in conjunction with bone cement [18]. This construct has been shown to reach the same weight-bearing stability as an intact femur [17, 18], and is up to three times more stable compared to intramedullary nailing even when augmented with cement [19, 20]. Since muscle insertions are typically preserved with this technique, functional results are superior compared to primary endoprosthetic replacement with regards to range of motion and postoperative limp [21]. In addition, this technique eliminates the risk of post-operative joint instability [2, 22] and has a lower infection rate [23]. Intramedullary nailing is a viable alternative for patients with a life expectancy of less than 6 months [15]. However, IMN offers fewer options for cement augmentation to enhance stability contributing to the elevated risk of implant failure after 6 months [15, 24].

We have been consistently using the original technique of compound osteosynthesis for more than 3 decades. The purpose of this study was to assess the mid- and long-term performance of compound double-plate osteosynthesis for proximal femoral pathological fractures. To our knowledge, this study represents the largest series to date of compound double-plate osteosynthesis with the longest follow-up.

We specifically evaluated (1) the survivorship of the construct, (2) the complications, (3) functional and clinical outcome and (4) predictors for failure.

Materials and methods

This is an IRB approved retrospective review of all patients undergoing management for a pathologic fracture between January 1990 and April 2016.

Using our institutional digital database, we identified 122 patients (148 procedures) undergoing a compound osteosynthesis for any type of pathological fracture of the extremity. The upper extremity was involved in 32 patients (36 procedures), the distal femur in 29 patients (29 procedures), the tibia in 10 patients (10 procedures) and the proximal femur in 64 patients (73 procedures). Of those with proximal femur lesions and fractures, four patients (four procedures) underwent single plating, four patients (five procedures) anterograde femoral nailing, and three patients (three procedures) total or partial hip arthroplasty. This left 61 double-plate compound osteosynthesis in 53 patients for final inclusion in the analysis (Fig. 1). The demographic characteristics of the patients included in the study are shown in Table 1.

Fig. 1
figure 1

This figure shows the exclusion and inclusion criteria. Numbers are given as flowchart. [n number of surgical procedures (number of patients)]

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Table 1 Demography and perioperative data of the study population (61 compound osteosynthesis in 53 patients)
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The indication for a compound osteosynthesis was consistently a pathological fracture of the proximal femur with an extended osteolysis to the intertrochanteric (27 hips in 23 patients) and subtrochanteric area (26 hips in 23 patients) with or without extension into the femoral neck (4 hips in 4 patients) and proximal femoral diaphysis (4 hips in 3 patients). At our institution, intramedullary nailing is indicated in pre-terminal patients, primary total hip arthroplasty in those with isolated medial femoral neck fractures, and single plating in patients with osteolysis less than 1 cm.

Our surgical technique has not changed since its description in 1984 [17]. The patient is placed in lateral decubitus position. A straight incision is made starting 5–7 cm proximal to the tip of the greater trochanter extending approximately 20 cm distally. A standard sub-vastus approach is used to expose the fracture. Through an additional anterior window, tumor debulking is performed using an intra-lesional technique. The calcar area is then prepared using a chisel or a high-speed burr to provide the bed for the intramedullary plate. This plate should be pre-bent and placed as close to the remaining calcar as possible to provide maximal stability. Generally, a 4.5 mm dynamic compression plate (DePuy Synthes, West Chester, PA) is used. The fracture is reduced and temporarily held with clamps and K-wires. A standard 95° condylar blade-plate (DePuy Synthes, West Chester, PA) is inserted using the standard technique [25] with the use of intraoperative fluoroscopy. Unlike a standard internal fixation, as many screws as possible should be placed through both plates to reinforce the construction. Finally, the construction is augmented with methyl-methacrylate cement (Zimmer Biomet, Warsaw, IN) and the screws tightened (Fig. 2).

Fig. 2
figure 2

The technique of augmented compound osteosynthesis of the proximal femur is shown. The metastasis is excised trough an anterior window (a). After insertion of a manually contoured 3.5 or 4.5 mm dynamic compression intramedullary plate, a 95° condylar plate is inserted using the standard technique. The fixation screws should cross both plates to reinforce the construction. Finally, the construction is augmented with insertion of bone cement and tightening of the screws (b). A pathological subtrochanteric fracture with an extended osetolysis due to a multiple myeloma in a 39-year-old active male patient is shown (c). A compound osteosynthesis was performed (d) with an excellent result 2 years postoperatively (e)

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Postoperatively, the construct stability allows for immediate full postoperative weight bearing as tolerated. Patients were followed on an interdisciplinary basis by oncologists, radio-oncologists and/or by the orthopedic department. The follow-up interval depended on the individual therapy of the primary tumor and included neo-adjuvant or postoperative chemotherapy in 19 patients and radiotherapy in 28 patients. Specifically, we reviewed data regarding patient comorbidities, timing and frequency of reoperations, indications for reoperation, number of revisions, patient survival, and the use of preoperative or postoperative radiation therapy.

We specifically assessed the mechanical integrity of the construct. Mean follow-up was 1.83 years (0.2–25.5). At the moment of the last evaluation for this study, 5 patients were still alive, 1 patient was lost of follow-up and 47 patients were dead.

All postoperative complications were recorded and graded according to Sink et al. [26]. Radiographs were analyzed to assess for implant failure. The functional clinical outcome was assessed using the Merle d’Aubigné and Postel score [27]. Since variable follow-up intervals were available, outcomes were grouped from 0–3, 3–6, 6–12 months, and yearly thereafter. The following parameters were assessed for potential confounding negative predictors for failure: age, sex, type of fracture, previous surgery, primary diagnosis, neo-adjuvant/postoperative chemo-/radiotherapy.

Two study groups were formed. The ‘primary’ group consisted of all cases in which a double-plate compound osteosynthesis was performed as initial procedure (n = 46). The ‘revision’ group consisted of all cases in which a double plate compound osteosynthesis was performed as revision procedure after failed previous attempts of internal fixation such as intramedullary nailing referred from other institutions (n = 15 hips).

We used the cumulative survivorship of the construct using the Kaplan–Meier survivorship analysis [28]. The survivorship of the two study groups was compared using the log-rank test. Failure of the implant was defined as a plate breakage or secondary displacement of the fracture. Negative predictors for failure were then identified based on a multivariate Cox-regression analysis [29]. Normal distribution for the Merle d’Aubigné score was assessed using the Kolmogorov–Smirnov test. The Merle d’Aubigné scores among all different time intervals were compared with the Kruskal–Wallis test. The values between the groups were analyzed using the Mann–Whitney U test.

Results

The cumulative Kaplan–Meier survivorship of the primary group with compound osteosynthesis was 96% at 6 months (95% confidence interval [CI] 88–100%), 90% (76–100%) at 1 year, 5 years, 10 years and thereafter, Fig. 3). The cumulative Kaplan–Meier survivorship of the revision group was 83% at 6 months (62–100%), 74% at 1 year (49–99%), 53% at 2 years (23–83%). This difference was statistically significant (p = 0.0008).

Fig. 3
figure 3

Survivorship curves of the two study groups including the 95% confidence interval of the compound osteosynthesis with implant breakage or secondary dislocation as endpoints. Circles indicated censored data. The primary compound osteosynthesis group consisted of cases where the procedure was done without previous surgeries. The revision group was defined as having previous attempts of internal fixation

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According to the classification of Sink et al. [26], there were 14 events in 12 patients with a Grade II complication (8 presenting anemia, 3 urinary tract infections, 1 a thromboembolic disease, 1 prolonged wound secretion not requiring revision, and 1 neuropraxia); 16 events in 14 patients with grade III complications (1 hematoma, 1 deep infection, 1 vascular complication, 1 tumor progression, 6 compound osteosynthesis failures and 4 peri-implant failures), 2 events in 2 patients with grade IV (1 metastases progression with secondary hip exarticulation and one cerebral vascular insult). Regarding grade V complications (within 30 days after surgery), there were no deaths directly related to the orthopaedic intervention (Table 2). The rate of grade III and IV complications was significantly lower in the primary group (4/46 cases [9%]) compared to the revision group [13/15 cases [87%], p < 0.0001).

Table 2 Complications of the double-plate compound osteosynthesis for pathological fractures of the proximal femur according to Sink [26] specified for the two study groups
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The mean Merle d’Aubigné score was 14 ± 7 (range 3–17), at 0–3 months, 13 ± 3 (7–18), at 3–6 months, 15 ± 3 (9–18), at 6–12 months and 15 ± 4 (8–18) thereafter (Fig. 4). There were no differences among all groups (p = 0.54) or between the different time intervals (p values in Fig. 4).

Fig. 4
figure 4

This figure shows the postoperative course of the Merle d’Aubigné score for different time intervals

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The only multivariate negative predictor was previous surgery with a hazard ratio of 9.2 (p < 0.006, Table 3). We did not find any association with age, sex, type of primary carcinoma, the use of neo-adjuvant chemo- or radiotherapy and type and localization of the fracture.

Table 3 Cox-regression analysis showing the factors associated with failure defined as revision surgery of the compound osteosynthesis
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Discussion

Bony metastases cause considerable morbidity, including pain and impaired mobility. Appropriate management of pathological fractures, especially in the proximal femur is of paramount importance as advances in oncologic management have substantially improved survivorship [7]. Achieving construct stability with a low complication rate is the most challenging factor, as the pathological bone often fails to consolidate leading to incomplete healing and increased rates of nonunion [6, 7, 21]. Thus, as life expectancy increases, cost-effective techniques that provide long-term stability are required [10]. The goals of surgical intervention are to provide pain relief, allow rapid return to full weight bearing, and to decrease hospital stays to improve quality of life in patients with metastatic bone disease [7]. Compound osteosynthesis, even if technically demanding, seems to be a valuable treatment in impending and pathological fractures of the proximal femur [9, 21]. To our knowledge, this study represents largest series to date of double-plate compound osteosynthesis with the longest follow-up.

Survivorship of compound osteosynthesis

We found construct survival rates of 96% at 6 months, and 90% thereafter for primary reconstructions. These results are comparable to the early, previously published reports for this technique [12, 18, 30]. In contrast to the present study, none of these investigations presented a similar follow-up of 2 decades. Comparing our calculated survivorship with the literature, it is evident that double-plate compound osteosynthesis is superior to simple open reduction and internal fixation (Fig. 5a) with or without cement augmentation, intramedullary nailing (Fig. 5b), and comparable if not higher than endoprosthetic replacement (Fig. 5c, Table 4). In revision cases with previous attempts of internal fixation using intramedullary nails, we have observed a lower survivorship of a double-plate compound osteosynthesis construct. In these cases, the mechanical resistance of the proximal femur is weakened by the intramedullary reaming leading to subsequent failure at the shoulder of the blade plate (Fig. 6).

Fig. 5
figure 5

Comparison of different survivorship curves for available surgical techniques for the treatment of pathological proximal femoral fracture: a osteosynthesis and compound osteosynthesis; b intramedullary nailing; and c endoprosthetic reconstruction

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Table 4 Literature overview of various surgical treatments for pathological fractures of the proximal femur
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Fig. 6
figure 6

A pathological intertrochanteric fracture of a 79-year-old male patient with prostate cancer is shown (a, b). Intramedullary nailing was planned at an external institution but had to be abandoned due to the sclerotic bone (c). After reconstruction with a double-plate compound osteosynthesis (d), the construct failed at the shoulder of the blade plate (e). The revision consisted of a tumor endoprosthesis (f)

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Complications

Comparing our complication rate with the literature is difficult due to a lack of consistency of reporting in literature. However, a comparison of grade III and IV complications according to Sink (Table 4, Fig. 7) is possible since these more severe complications are mentioned in most of the relevant literature. It seems obvious that the rate of complications is highest for open reduction and internal fixation, followed by prosthetic replacement and intramedullary nailing (Fig. 7). The complication rate of primary double-plate compound osteosynthesis in primary cases is low (4%). The majority of postoperative complications were nonspecific regarding to the surgery, as hematoma, anemia or urinary tract infections (Table 2). In revision cases, the complication rate rises to 26% and is mainly related to loss of integrity of the construct as mentioned before. Compared to intramedullary nailing, the double-plate compound osteosynthesis is biomechanically more stable with a very low rate of implant failures or refractures. Compared to prosthetic replacement, the double-plate compound osteosynthesis bears little risk for infection and no risk for dislocation due to the preserved muscle attachments.

Fig. 7
figure 7

Comparison of the rate of complications for Grade III and IV according to Sink [26]

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Functional outcome

The functional outcome of each patient was evaluated from present data of postoperative controls. We used the Merlé d’Aubigné score [27], as it is a simple score regarding the ability to bear weight, pain and range of motion of the hip, parameters that are usually recorded data in patients history. Even if the majority of patients were dead at the moment of our study, we, therefore, could calculate the score.

Mean score was 13 in the first year after surgery and 15 afterwards. Literature supports better functional outcome for double-plate osteosynthesis compared to tumor prosthesis [7, 12]. As we did not compare other surgical techniques, we cannot confirm those results, but the mean functional outcome in our patients was very satisfactory, as most of the patients were pain free and able to bear weight. An important factor for the good functional result of double-plate compound osteosynthesis is the preservation of the insertion of the abductor musculature. With endoprosthetic treatment, the abductor mechanism can be difficult to reattach leading to potential abductor deficiency.

Risk factors for failure of compound osteosynthesis

Interestingly, our analysis of negative predictors leading to implant failure did not reveal any correlation between implant failure or age of patient, sex, primary cancer, localization of the fracture, adjuvant or neo-adjuvant chemotherapy or pre-/postoperative radiotherapy. The only significant multivariate negative predictor for failure of compound osteosynthesis was a history of any previous surgery that has failed (IMN, DHS, ORIF or previous compound osteosynthesis). In our study, of the six patients that suffered failure of their compound osteosynthesis, four had previous surgery with another implant (IMN or single plate osteosynthesis). We recorded a total of seven patients in whom secondary compound osteosynthesis was done after failing of another technique as an intramedullary nailing, dynamic hip screw or single-plate osteosynthesis for a pathological fracture of the proximal femur. Of them, two patients died 4 and 6 months after the procedure and showed no failure until then and one patient had no failure until his death 3 years later.

Limitations

Our study has limitations. We do not have a control group so that only literature comparisons to other surgical techniques could be performed. In addition, most of our patients were deceased at the moment the study was made. Therefore, we could only calculate the Merlé d’Aubigné score as a clinical outcome score by reading the medical records to evaluate the functional outcome of this technique. The Merlé d’Aubigné score is easy to reproduce but this score has not been validated with previous studies.

Conclusion

Double-plate osteosynthesis is a cost-effective valuable treatment option for pathological fractures in proximal femur. It provides sufficient stability to allow immediate post-operative weight bearing and range of motion with a good functional result. The complication rate is low compared to all other surgical treatments and the survivorship of the osteosynthesis is higher than with an intramedullary implant. In revision cases with previous attempts of internal fixation, double-plate osteosynthesis has a significantly higher failure rate. In these cases, endoprosthetic reconstruction has become the treatment of choice in our institution.