Minimally invasive posterior locked compression plate osteosynthesis shows excellent results in elderly patients with fragility fractures of the pelvis

Osteoporosis related fractures are common in older patients and its prevalence is rising with advancing age [1, 2]. Even though a high number of fractures involve the wrist, hip and spine the number of osteoporotic pelvic fractures including sacral and pubic rami fractures is likewise increasing rapidly [3, 4]. The incidence of pelvic fractures in the German population aged 60 years or older was 22.4 per 10,000 person years. A significant age and sex effect on first fracture risk was confirmed [3].

The number of people affected by osteoporotic fractures is increasing worldwide just as the older population [5]. However, the social and economic burden will unavoidably become more and more relevant. In the United States 7% of all osteoporosis related fractures in people over 50 years of age are pelvic fractures which accounts for 5% of the total economic costs [1].

Studies revealed a substantial one-year mortality of about 8–27% in pelvic fractures with excess mortality being highest in the first four weeks after the occurrence of the fracture [6]. There was also a high number of patients moving from an independent to a dependent living situation, which was similar to data reported for elderly patients with a hip fracture [7].

However it is still not thoroughly investigated which portion of the excess mortality is caused by the fracture itself or caused by associated prior existing comorbidities and poor health status [8].

Low energy trauma such as sliding of a chair or even lack of trauma, may result in an unstable pelvic fracture which can lead to immobilizing pain. The loss of elasticity and strength, hence a reduced bone quality results in so called fragility fractures of the pelvis.

Recent studies on osteoporosis related pelvic fractures demonstrated an increase of incident rates over the last decade [3, 9, 10]. Part of the increase may be due to improved diagnostic methods (CT, MRI) and greater awareness of the fracture pattern, as well as to an increase of life expectancy. Still, the overall impact of pelvic fractures is immense.

The World Health Organization (WHO) defines a fragility fracture as one caused by a trauma that would be insufficient to injure bone if the bone substance were normal.

In some cases particular isolated fractures of the sacrum cannot immediately be detected, but are only seen in the magnetic resonance imaging (MRI scan) [11]. Patients suffer from severe lower back pain and loss of mobility.

In 2013, the Fragility Fractures of the Pelvis classification was introduced for this fracture entity [12]. The classification is based on instability signs and includes treatment recommendations. Nevertheless, there are still controversies regarding when and how these fractures should be treated. In recent years it has become more and more obvious that fragility fractures of the pelvis are a different entity in comparison to traumatic pelvic fractures due to different fracture mechanism, bone quality and degree of instability [13, 14].

In patients with anterior fractures only, conservative treatment with early mobilization and pain relief medication is highly recommended [14, 15]. However, patients with combined posterior and anterior pelvic fractures suffer from severe pain when being mobilized; surgical treatment should be considered to avoid institutionalization. There are a number of operative procedures available, such as percutaneous iliosacral screw fixation, sacroplasty, lumbo-pelvic stabilization, sacral bar fixation with or without additional ventral fixation, transiliac internal fixator and minimally invasive posterior locked compression plate (MIPLCP) [16‐29].

In this paper, outcomes of the MIPLCP osteosynthesis as a standalone treatment option in pelvic fractures, which was first applied for polytraumatized patients [26], was applied to elderly patients with osteoporotic bone stock.

The purpose of our study was to determine whether the MIPLCP osteosynthesis shows equal results regarding complication rate and outcome as ilio-sacral-screw osteosynthesis and whether operation time and radiation time is lower.

Until now there is no golden standard surgical procedure for osteoporotic pelvis fractures and appropriate studies are rare or pending. The aim of our study was to investigate whether MIPLCP shows sufficient results compared to other methods.

The most commonly used method is the ilio-sacral screw fixation (with or without cement augmentation), sometimes with additional ventral plating, retrograde transpubic screw fixation or external fixation. Thus we compared our data to studies regarding percutaneous ilio-sacral screw fixation in patients with fragility fractures of the pelvis.

Similar to other studies we found a mean age of about 79 (60–99) years with a predominance of women, which constituted 90% of our collective [16, 30‐36].

In our data the mean hospital stay until surgery was 6.7 days (SD 5.1) and the mean hospital stay overall was 21.2 days (SD 7.7), which goes in line with other studies, where the mean hospital stay varies from 13 to 23.7 days [16, 31, 33, 34, 36].

Hopf et al. [16] describe in their collective a mean hospital stay until surgery of 9.2 (1–24) days, which is similar to our findings.

In the after-care patients were mobilized according to their capacity with full weight bearing to avoid additional risk factors and further decrease of bone quality and muscle mass.

In our collective mean time from symptom onset until surgery was 55.5 days (3–720). This is in accordance with the data by Eckardt et al. and Sanders et al. which detected a mean time from first symptom to operation of 33.1 (7–103) to 68 days, with mentionable 10% of the patients suffering more than 104 days [30, 35].

Analysing the FFP classifications that led to the surgical procedure we found data similar to Noser et al., whereas the patient collective of Eckhardt et al. consisted more from FFP 4 than FFP 3 fractures [30, 31].

In our own proceed patients were operated whenever mobilization with full weight bearing was not possible or when patients presented with increase of pain and dismobility after initial conservative treatment. Whenever suitable (no soft tissue problems, no immobility prior to the acute trauma), we used the MIPLCP as surgical procedure. In cases of vertical instability or severe dislocation of the ventral pelvic ring we performed a combination of ventral and dorsal fixation techniques, such as additional ventral plating or retrograde transpubic screw osteosynthesis. Additional ventral fixation let to exclusion of the study.

In our collective we recorded a mean x-ray time of 9.42 s (SD 9.66), a mean dose-length-product of 70.125 mGycm (SD 57.9) and an operation time of 52.3 (34–117) minutes (SD 13.9). The notable outlier of 117 min of surgical time for the MIPLCP is caused by an additional total hip replacement due to a severe arthrosis of the hip, which was performed at the same time. We found five studies regarding fragility fractures of the pelvis which assessed operation times. Sanders et al. recorded operation times of 26.6 min, Höch et al. of 27 min per screw with 33 of the 34 patients needing additional ventral fixation, the total operation time was not assessed. Eckhardt et al. recorded operation times of 79 min, König et al. of 45.25 min, Wong et al. described mean operation times of 93.7 min (SD 32.4) and 133 min (SD 38.3), depending on whether the procedure was planned in advance or intra-operatively [30, 32, 34, 35, 37]. Percutaneous screw insertion is typically associated with considerable fluoroscopy use, although there have only been a few studies that fully assessed radiation doses in FFP. Eckhardt et al. recorded an mean dose-length-product of 449.6 mGycm, Sanders et al. assessed a radiation time of 2 min (range 101–143 s) [30, 35].

Far more data is available concerning ilio-sacral screw osteosynthesis in polytraumatized patients. Radiation doses up to two minutes and a dose-length-product (DLP) of up to 952.4 mGycm are described in studies that examined polytraumatized patients treated with ilio-sacral screw osteosynthesis [38‐41]. Fischer et al. registered operation times with an average of 84 min (SD 35.2) and a mean radiation dose of 336.7 mGycm (53–2238 mGycm) [38, 42, 43]. Osterhoff et al. registered operation times of 16 min (SD 7) per screw, radiation doses or times have not been assessed. Time to full weight bearing was 9 weeks (SD 4) in their collective [23]. Compared to these studies, our collective had low radiation doses and a moderate operation time. An analysis from the Tennessee Surgical Quality Collaborative suggests that duration of operation correlates with complications and higher risks, thus a fast and effective surgical procedure could add to the safety of this rather frail patient cohort [44]. Our data show, that the MIPLCP is a suitable technique even in patients with FFP TYP IV b fractures [42, 44, 45]. The technique of the dorsal plating is simple whereas the iliosacral screw osteosynthesis can sometimes be silent, especially if it is difficult to reach a good view with the c-arm. Our locking plate has a high stability, as it provides threedimensional fixation with four angularstable screws that are placed through a 4.5 Locking Plate into the massa lateralis of the sacrum via the ilium.

Especially in cases of dysmorphic sacra where screw placement can be demanding and in bilateral injuries the MIPLCP might prove to be an excellent treatment option, due to relatively easy placement and high stability [42, 45, 46]. Biomechanical studies have shown that even non-locking plates show equal stablility to iliosacral screws. A biomechanical study by Albert et al. demonstrated a strong fixation of the pelvis by using a 4.5 recontruction plate, which was comparable to the fixation with a transsacral bar [47, 48]. Our technique provides even greater stability, as the fixation is angularstable and an arthrodesis of the iliosacral joint is performed using 45–55 mm 4.5 locking screws.

The positive effect of percutaneous approaches on perioperative complications has been described previously, therefore we are using a minimally invasive approach [41, 49, 50]. Similar to the therapy of osteoporotic fractures in other regions of the body, the use of angular stable implants has significant potential to result in higher stability and pull-out forces than conventional implants [51‐54]. In our data, we did not see any complication regarding implant failure, even though we only managed to get hold of follow-up X-ray examinations in 32 out of 53 patients. Our results are promising, but further prospective, comparative studies with defined follow-up are necessary.

In our collective we registered 13% surgery related complications. As non-surgery-related complications, urinal tract infections occurred in 15%. We had one case of pneumonia (1.8%) in a 99 year old patient, who died during the hospital stay. Hopf et al. found a complication rate of 20% which is equal to the findings in our population [16]. In other studies complication rates from zero to 41% are described [16, 30, 32‐36, 42, 55, 56] (Table 1).

In the Hopf data pain level at discharge was 1.8 on average, with a significant reduction compared to pain level at admission. In our study we found similar pain levels at discharge of 1.9 in the whole study cohort and 2.1 in the sub-group (n = 34), that was followed-up, resulting in a significant reduction of pain level from 4.8 at admission. In the follow-up examination we found a pain level of 2.35. Other studies reported VAS at follow-up varying from 0.36 to 3.4 [16, 32‐36, 56]. Comparison of pain level at discharge (1.98) and in the follow up (2.4) in our collective to the findings in the Hopf paper (1.73 at discharge) shows no statistically relevant differences. In both findings a relevant reduction of the pain level at admission to the pain level at discharge could be noted [16] (Tables 2, 3).

All patients in our collective were immediately mobilized with full weight bearing, resulting in an excellent mobility at discharge and at follow-up examination.

The follow-up of our collective showed a low number of patients who had to be institutionalized after trauma and a large number (74%) which returned to their former homes and living conditions. Noser et al. describe institutionalization rates of up to 75% [31].

For follow-up score we decided to apply the Iowa Pelvic Score (IPS). Until now there is no consistently validated outcome scoring system for pelvic fracture outcomes. In our collective the IPS at follow-up examination was 85.6 (SD 11.1) on a range from zero to 100 with 100 being the best possible result.

Limitations of the study are: retrospective analysis with small sample size, only a subgroup that has been followed up with pain and activity level. No comparison group. Follow-up range between 6 month and 7.5 years due to retrospective study design over a period of 8 years (5/2007-6/2015).

The data of our retrospective clinical study demonstrates that using the minimally invasive posterior locked compression plate is a simple, safe, quick and reliable stabilization technique for patients with fragility fractures of the pelvis with lower radiation times and equal complication rates as ilio-sacral screw fixation.