INTRODUCTION

Without a doubt, vertebral fracture (VF) is the most prevalent type of bone rupture in patients with low bone mass¹. The most recent epidemiological data in the Spanish population indicate about 35% VF prevalence in women over 45 years of age². In men, the prevalence at 50 years is estimated 5 times lower than that of the female population, although this increases beyond 70 years of age³.

Osteoporotic VFs (OVF) are conservatively treated, usually including rest, analgesia (in combination with muscle relaxants), orthotics and rehabilitation. This treatment is crucial in the first weeks post-fracture, so that proper follow-up usually resolves OVFs effectively. However, in 10-35% of patients, complications may arise from the fracture itself, such as delayed bone union, increased kyphosis, appearance of neurological disorders or the appearance of pseudo-arthrosis (Kümmell's disease). In these cases, patients frequently do not respond well to conservative treatment, complicating the management of their symptoms. This tends to worsen over time⁴.

Regarding these patients' failure to respond to conservative treatment, the appearance in recent decades of minimally invasive techniques, such as vertebroplasty (VP) and percutaneous kyphoplasty, has provided a good therapeutic alternative both for managing symptoms and avoiding serious long-term complications.

VP consists of injecting polymethylmethacrylate (PMMA) bone cement into the fractured vertebral body, with the immediate objective of curbing the vertebra's collapse, increasing its resistance and alleviating pain⁵.

The new cements available for use in cementoplasty require preparation in a highly specific monomer/polymer ratio that prevents alterations in the viscosity of the final mixture. This factor is crucial both for a correct polymerization and for the application of the cement itself, since it is during this phase when the mixture is injected into the affected vertebrae of the patient. Thanks to the improvement of its properties in recent years, the new cement mixtures minimize material leaks from the bodies and reduce the thermal effect on the healthy bone surrounding the fracture. Thus, the PMMA is more effective in repairing the OVF as well as making it more secure⁶,⁷. Although several studies demonstrate VP's short-term efficacy and safety^{8 9 10 11}-¹², its long-term stability has not yet been fully established.

This paper is the first to evaluate the bone status of fractured osteoporotic vertebrae that were cemented by PVP and that have a follow-up of µ15 years. Our main objective is to assess the long-term bone integrity of the intervened vertebrae, to thus clarify the safety and efficacy of the technique over time.

MATERIAL AND METHODS

RESULTS

After reviewing the SPU-FJD database, we obtained a total of 69 records corresponding to patients operated by PVP in our hospital 15 years or older. From this total of cases, we observed 26 follow-up losses (38% with respect to the total number of records) as we were unable to contact these patients or know their current status. However, we contacted a total of 43 patients or their relatives, which allowed us to know a total of 30 cases of exitus (70%) and 13 cases of patients still alive (30%) (Figure 1). Among the living patients, 7 of them agreed to undergo a new radiography, these images being the most recent radiological studies and corresponding to the follow-up PO≥15a after the VP. Thus, we obtained a series of 7 cases of patients having undergone VP surgery with a radiological follow-up of 15 years or more.

Figure 1. Summary graph of the study population. From a total of 69 patients operated by VP 15 or more years ago in our hospital, a total of 43 patients/relatives (62% of the total) were contacted. After confirming 70% of cases of death, the remaining 30% (13 patients) are invited to go to the hospital for a new radiological study (PO≥15 years). Finally, 7 patients accept and form the case series on which the study is based 

This case series consisted of 6 Caucasian women and 1 male whose median age at the time of surgery was 67 years (min=62; max=87, interquartile range=18). The pre-operative BMI had a median of 26.67 (min=18.36; max=31.96, interquartile range=5.21) (Table 1). All patients in this series presented T-score values compatible with osteoporosis or osteopenia before surgery.

Table 1. Demographic data of the series of 7 patients operated 15 or more years ago by VP in the SPU-FJD 

Age Qx: age at surgery; M: male; F: female; BMI: body mass index; DXA: dual energy x-ray absorptiometry.

In addition, in all cases the OVF intervened was single level (total number of intervened levels within the case series=7), the conservative treatment prior to surgery having been ineffective (Table 1).

SPU-FJD surgeons of the carried out the corresponding surgical interventions, with a uni-portal approach in 5 cases and bi-portal in 2 cases. The intervened vertebrae were in 4 thoracic cases: T7, T11 and T12 (2 cases of the latter) and in 3 lumbar cases: L3, L4 and L5.

The measurements taken by the FJD team of neuroradiologists allowed us to establish that there were no clinically significant differences in the height of the vertebral bodies (anterior, middle or posterior wall) of the patients comparing the PO and PO≥15a times (Table 2).

Table 2. PVP characterization, vertebral PO and PO measures ≥15a and data related to the presence of osteolysis/fragmentation foci of the PMMA of the series of 7 operated patients 

T: thoracic vertebra; L: lumbar vertebra; QX approach: surgical approach; U: uniportal; B: biportal; PO: immediate post-operative; PO≥15a: post-operative at 15 or more years of follow-up; Fx: fracture.

Similarly, except for case 5, in which the corresponding measurements could not be made, the remaining cases did not show differences in the angulation of the intervened vertebrae by comparing their PO and PO values ≥15a (Table 2).

In addition, in no case were fractures and/or height losses in segments adjacent to the original fracture (a single case recorded a new non-adjacent fracture). There was no osteolytic phenomena around the injected PMMA or fragmentation in the images analyzed corresponding to PO≥15a (Table 2, Figure 2).

Figure 2. Stability and absence of PMMA fragmentation 15 years post-PVP. Radiological images of the immediate PO (A) and PO≥15a (B) after the VP of one of the patients included in the case series (Case 1) 

DISCUSSION

OVFs constitute the most common simple fracture worldwide. In fact, in our country, the Spanish Society of Geriatrics and Gerontology (SEGG) provided data in 2017 that documents a 3-fold higher incidence of this type of fracture compared to hip fractures¹⁵.

Recent research lines have shown that, in addition to osteoporosis, factors such as advanced age, high BMI and/or fractures in thoracic levels (especially in the thoracolumbar junction) are significantly related to the failure of conservative treatment¹⁶,¹⁷. According to the clinical practice carried out in our center, we can establish a failure rate of conservative treatment in the management of acute OVFs of around 15%. These data are similar to those reported by some authors who place it close to 20% according to the specific type of VF¹⁸. In the series of 7 patients that we presented, all women were operated on in an advanced postmenopausal age, while the male patient underwent surgery was octogenarian. In addition, 3 patients presented BMI values compatible with overweight and 1 with obesity. As for the intervened vertebral level, 4 patients presented fractures in the thoracic vertebrae, of which in 2 cases the T12 (thoracolumbar junction) coincided. These data seem to support the relationship between the aforementioned risk factors and the failure of conservative treatment in their fractures.

Beyond 65 years of age, especially in women, the maximum level of prevalence of OVFs in the Spanish population is reached. Thus, our study accurately represents this situation with the case series analyzed. The profile of the recruited patients would be within a population group that, due to their demographic and physiological characteristics, is at risk of suffering an OVF.

Faced with an OVF with symptoms that cannot be managed by conservative treatment, PVP presents an effective option in the improvement of the patient's pain, functional status and quality of life, even in elderly cases^{19 21 22}-²².

The safety and immediate effects of PVP are well documented in the literature^{23 24 25 26}-²⁷. However, so far, there are very few data that continue to demonstrate the effectiveness and safety of this technique in the long term²⁸,²⁹. In fact, the post-op follow-up periods published do not generally exceed 2 years^{9 10 11}-¹².

According to the latest data from the National Statistics Institute (NSI) updated in 2018, the life expectancy of the Spanish population stands at 83 years, taking into account both sexes³⁰. This increase in the aging of the population provides new information that allows us to show PVP as a safe technique in the longer term.

In addition, there is some controversy among authors regarding a possible relationship between the realization of PVP and the appearance over time of new FV^{31 32}-³³. This reason justifies the analysis, such as the one we present here, where post-surgery follow-ups are recorded much longer over time.

In the 7 cases presented, the patients presented stability in the intervened vertebral bodies at the level of the anterior, middle and posterior walls with 15 or more years elapsed from the time of surgery. There are some published data that associate changes in the angulation of the lamellar plate after VF as a risk factor in the appearance of new VF³¹,³⁴. In our series of patients analyzed, there were no clinically significant differences in this angulation after 15 or more years post-op which could justify, together with other factors such as maintenance of osteoporotic treatment, that these patients have not suffered new VF in adjacent segments.

The local response of the host to PMMA has been studied as a long-term phenomenon mainly in cases of implantation of total hip prostheses (THPs). In this type of prosthesis with peri-prosthetic cementation, the development of an inflammatory response by the surrounding bone to the implant cement is common. This reaction would derive, among other causes, as a consequence of the exothermic process during setting and the release of PMMA particles that appear due to wear and tear due to the compression exerted by the movement itself³⁵.

Unlike the PMMA of the THPs, in the PVP the cement is interdigitated in the trabecular bone and is not subject to direct compression. This may explain why, as we present in our case series, no PMMA fragmentation or osteolytic phenomena is observed in PO≥15a.

In recent years, new PMMA formulations have been developed, for example, without setting temperature or coated with osteoblasts^{36 37}-³⁸. According to published data, these new cements do not seem to offer much more beneficial effects or greater efficacy than conventional PMMA compared to an OVF. Given current concerns regarding health costs, it would seem illogical to increase this expense in other PMMAs or in more expensive techniques such as balloon kyphoplasty without clinical data that clearly endorse it³⁹. In addition, as we present, in our center we observe that 70% of the patients operated 15 or more years ago were exitus due to causes unrelated to their OVF. Meanwhile, those who were still alive presented stability of the injected PMMA after this time.

The present study describes the experience of a small group of patients (n=7 of 13 available) with a similar diagnosis. Due to the limitation in their number of cases there is no way to carry out statistics of inferential type, although descriptive study is possible.

CONCLUSION

This work constitutes the first evidence of PVP as a safe and effective technique in patients with a follow-up of 15 or more years after their surgery. PMMA kept both heights (anterior, middle and posterior) and vertebral angulation stable, in addition to not causing osteolytic phenomena or observing long-term material fragmentation.