Kyphoplasty for the Treatment of Very Severe Osteoporotic Vertebral Compression Fracture

Abstract

Objective:

A retrospective evaluation of the clinical outcome and technical feasibility of kyphoplasty for the treatment of very severe osteoporotic vertebral compression fracture (vsOVCF).

Methods:

Patients with vsOVCF were treated with kyphoplasty and followed-up for 1 year. Vertebral body height variation, kyphotic angle, back pain (visual analogue scale [VAS]) and Oswestry disability index (ODI) were evaluated preoperatively, postoperatively, 1 month, 3 months and 1 year after treatment.

Results:

In total, 35 patients (49 vertebrae) were treated with kyphoplasty. There were no cases of spinal or extraspinal injury, infection, bleeding, pulmonary embolism, epidural cement leakage, stroke or cardiac arrest as a result of treatment. There were significant postoperative improvements in all outcome measures (vertebral body height variation, kyphotic angle, VAS and ODI); these improvements were maintained during the follow-up period.

Conclusion:

Kyphoplasty is an effective and minimally invasive procedure for the treatment of vsOVCF.

Introduction

Osteoporosis is a growing global public health problem that causes disability and death, leading to over 700 000 vertebral compression fractures (VCFs) annually in the US alone.^1,2 Treatment of osteoporosis and associated fractures incurs costs exceeding US$17 billion each year.^{3 – 5} Vertebral compression fractures are the most common types of osteoporotic fracture, and patients may suffer from acute and chronic pain problems due to the resulting spinal deformities, as the natural history of osteoporotic vertebral fractures is often accompanied by kyphotic collapse of the affected segment. ⁶ Conservative management strategies for osteoporotic vertebral compression fracture (OVCF) include analgesics, bed rest and external bracing. However, many patients do not respond to these therapies in terms of pain relief or reduction in deformity.^{7 – 9} More invasive surgical procedures (such as internal fixation and stabilization) are not optimal treatments for the majority of patients due to their advanced age and associated comorbidities.^{10 – 12}

Vertebroplasty and kyphoplasty are minimally invasive, radiologically guided procedures, involving injection of polymethylmethacrylate (PMMA) into the fractured vertebra.^6,10 Such techniques have been reported to result in substantial pain relief and may be used in patients with OVCFs refractory to conservative therapy.^4,13 Kyphoplasty is a modified version of vertebroplasty, involving inflation of a balloon within a collapsed vertebral body to create a void prior to PMMA injection. ⁶ Kyphoplasty has gained wide clinical acceptance as an effective treatment option for OVCF, as it provides rapid pain relief and height restoration with less cement leakage than that seen following vertebroplasty.^{14 – 17} Kyphoplasty is contra indicated in fractures where the vertebral body has collapsed to < 33% of its original height (i.e., very severe osteoporotic vertebral compression fractures [vsOVCFs]) because of technical difficulties in the insertion of large-gauge trocars into a substantially compressed vertebral body and the resultant high risk of cement leakage.^{18 – 20}

Studies reporting on the outcomes of kyphoplasty in the treatment of vsOVCF are limited.^{18 – 21} The present study reports the clinical and radiological outcomes of patients with vsOVCFs of the thoracic or lumbar spine treated with kyphoplasty, in order to evaluate the feasibility, efficacy and safety of kyphoplasty in the treatment of vsOVCF.

Patients and methods

Study Population

This retrospective study included all patients with vsOVCF (vertebra[e] collapsed to < 33% of original height) who underwent kyphoplasty at the Department of Orthopaedic Surgery, the First Affiliated Hospital of Soochow University, Suzhou, China, between January 2008 and January 2011. The extent of vertebral body collapse was determined from the point of maximal collapse on lateral X-radiographs, and calculated with reference to normal vertebral body height. The diagnosis of osteoporosis was established by patient history and radiographic evaluation, and confirmed by histological examination of bone biopsy taken during kyphoplasty.

Kyphoplasty was performed in cases of osteoporosis-induced vertebral compression fracture that was causing severe pain and was nonresponsive to conservative treatments (including analgesic medication, nerve block, exercise and antiosteoporosis medication).^1,22 All patients were examined preoperatively using plain X-radiography and multislice computed tomography (CT) to evaluate the fracture configuration and vertebral wall integrity before kyphoplasty. ²³ Marrow signal changes on magnetic resonance imaging (MRI) were assessed to determine the symptomatic levels and acuity of the fracture. Bone scans were used in cases where MRI was contraindicated (e.g. presence of a pacemaker). ²⁴ Patients with systemic or local infections and those with noncorrectable coagulation disorders were excluded.

The study was approved by the Institutional Ethics Committee of Soochow University, and all patients provided written informed consent prior to participation.

Kyphoplasty

Kyphoplasty was performed under general anaesthesia, with the patient in a prone position on a carbon fibre radiolucent C-arm table, with the spine extended by chest and pelvic cushions. The fractured vertebra was localized using fluoroscopy, and the skin was disinfected and covered with sterile drapes. The pedicles of the fractured vertebra were displayed under fluoroscopy using the C-arm and kyphoplasty was performed as described.^24,25 Guide wires were inserted in order to obtain bilateral transpedicular access to the fractured vertebral body. In cases where pedicles were not visualized on fluoroscopy, the extra- or unipedicular approach was performed.^22,25 The opening was gradually enlarged using successively larger trochars. Kyphon^® balloon tamps (Medtronic, Sunnyvale, CA, USA) were inserted through the cannula and placed in the anterior portion of the vertebral body on the lateral view, covering both sides to the midline on the anteroposterior view. The balloons were then inflated slowly to reduce the fracture and to create a void for the injection of cement. Inflation was continued until the vertebral body height was restored, the balloon touched a vertebral body cortical wall, balloon pressure reached 300 psi or maximal balloon volume was reached. The balloon was then deflated and removed, and PMMA cement was slowly injected to fill the cavity. The bone cement introducer was then retracted slightly but left in place until the cement hardened. Cement leakage was examined by fluoroscopy during surgery and by postoperative CT scan.^23,26 The position of any cement leakage was noted and was correlated with any symptoms reported during the follow-up period.

Study Definitions

Vertebral body height variation and degree of kyphosis were determined using lateral X-radiography. Anterior and midvertebral heights were defined as the distance between the upper and lower endplates at the anterior vertebral body wall and in the centre of the vertebral body, respectively. Normal heights for the anterior and midvertebral wall were defined as the mean of the equivalent values for the adjacent superior and inferior nonfractured vertebrae. Vertebral body height variation was calculated as: (fractured vertebral body height/normal vertebral body height) × 100%. ²³ The degree of kyphosis was assessed by measuring the kyphotic angle from the superior endplate of the vertebral body one level above the injury, to the inferior endplate of the vertebral body one level below. ²³ All radiological assessments were conducted by a radiologist who was unaware of the clinical presentation and outcome of the patient.

Follow-up

Patients were followed-up postoperatively, and at 1 and 3 months and 1 year after surgery. Lateral X-radiographs were performed to determine vertebral body height variation and degree of kyphosis. Back pain was assessed using a visual analogue scale (VAS; 0, no pain; 10, very severe pain). Functional status was assessed using the Oswestry Disability Index (ODI) questionnaire. ²³

Statistical Analyses

Data were presented as mean ± SD. Between-timepoint comparisons were made using the paired Student's t-test. Statistical analyses were performed with SPSS^® version 13.0 (SPSS, Inc., Chicago, IL, USA) for Windows^®. A P-value < 0.05 was considered statistically significant.

Results

The study included 35 patients with a total of 49 fractures (21 women/14 men; mean age 72.5 years; age range 62.0 – 83.0 years). All patients had ≥ 1 vsOVCF (mean 1.4; range 1 – 2). The time since fracture was extremely variable, ranging from several weeks to > 1 year. The mean vertebral body height was 22.0% (range, 18.5 – 25.0%) of the original height. Fractures were located between T5 and L5 (T5, 1; T6, 2; T7, 2; T8, 5; T9, 2; T10, 3; T11, 2; T12, 9; L1, 10; L2, 7; L3, 2; L4, 3; L5, 1).

The mean duration of kyphoplasty was 32.5 ± 5.2 min/vertebra, the mean duration of fluoroscopy was 6.53 ± 2.13 min/vertebra and the mean cement volume was 4.6 ± 1.6 ml/vertebra. Bilateral access was possible in 29 cases (41 vertebrae), four cases (six vertebrae) required extrapedicular access and two cases (two vertebrae) required unipedicular access. Kyphoplasty was well tolerated by all patients: there were no cases of spinal or extraspinal injury, infection, bleeding, pulmonary embolism, stroke, cardiac arrest, or local or systemic reactions to PMMA. Pre- and postoperative images of a typical case are shown in Fig. 1.

Figure 1:

The spine of a 78-year-old woman with a very severe osteoporotic compression fracture. (A) Preoperative X-radiographs and (B) computed tomography images indicating the presence of a compression fracture at L1; the vertebral body is collapsed to 22% of its original height. (C) Magnetic resonance images showing signal changes at L1 in T2-weighted (centre panel) and short TI inversion recovery imaging (right panel). (D) Postoperative X-radiographs indicating homogeneous cement distribution and an absence of cement leakage

Cement leakage occurred in 12/49 vertebrae (24.5%). Leaks were located in the venous plexus (five leaks), paravertebral soft tissues (four leaks) and adjacent discs (three leaks). There were no cases of pulmonary embolism or epidural leakage.

All patients completed follow-up. All patients subjectively reported immediate postoperative pain relief, and none complained of worsening pain at any timepoint. There were significant postoperative improvements in all outcome measures (vertebral body height variation, kyphotic angle, VAS and ODI), and these improvements were maintained during the follow-up period (P < 0.05 for all comparisons; Table 1).

Table 1:

Clinical and functional characteristics of patients with very severe osteoporotic vertebral compression fractures before and after kyphoplasty (n = 35)

Parameter	Preoperative	Follow-up
		Postoperative	1 month	3 months	1 year
Vertebral body height variation, % a
Anterior	21.6 ± 3.8	65.2 ± 11.6*	65.0 ± 6.7*	64.8 ± 7.9*	63.5 ± 10.6*
Midbody	23.4 ± 2.9	67.4 ± 17.3*	67.1 ± 10.3*	66.7 ± 8.3*	66.2 ± 16.2*
Kyphotic angle (°)	24.5 ± 5.4	10.2 ± 2.8*	10.6 ± 2.1*	11.2 ± 1.9*	11.4 ± 1.3*
Back pain b	8.5 ± 1.3	3.4 ± 1.2*	3.3 ± 1.4*	3.3 ± 1.5*	3.2 ± 1.4*
ODI	79.2 ± 13.8	34.1 ± 8.8*	32.4 ± 5.9*	31.2 ± 6.2*	29.5 ± 11.7*

a

Fractured vertebral body height/normal vertebral body height) × 100%.

b

Assessed using a visual analogue scale (0, no pain; 10, very severe pain).

ODI, Oswestry disability index. ²³

*

P < 0.05 versus preoperative value; paired Student's t-test.

Discussion

Kyphoplasty is a minimally invasive, radiologically guided procedure, involving inflation of a balloon within the collapsed vertebra to create a void prior to injection of PMMA.^27,28 It provides rapid pain relief and vertebral height restoration, with minimal cement leakage. ⁶ The reduction in pain results in improved health-related quality of life and the ability to move independently. In the present study of patients with vsOVCFs, kyphoplasty resulted in significant, long-lasting improvements in deformity, pain and function, with no major complications.

Osteoporotic vertebral compression fracture diagnosis is made by examination of preoperative standing anteroposterior and lateral X-radiographs, and MR images.^18,20 Fractures are graded on the basis of the extent of vertebral body collapse: mild (20 – 25% collapse); moderate (26 – 40%); severe (> 40%); very severe (> 67%). ²⁰ Studies assessing vertebroplasty and kyphoplasty in vsOVCFs are scarce, and are mainly limited to case reports or small patient cohorts.^20,21 Vertebroplasty has been shown to result in significant pain relief in patients with vsOVCF.^18,19

The findings of the present study suggest that kyphoplasty is an effective and feasible treatment for vsOVCF. Needle placement is technically difficult, because of the extreme kyphotic angle and the severe loss of vertebral height.^{18– 20,29} The present study adopted a modified technique, involving a low lateral transpedicular approach in combination with a small gauge trochar, allowing a needle to be advanced into the vertebral body while remaining lateral to the dominant portion of the vertebral body.

Very severe vertebral compression fractures often have some cleft in the vertebral wall, which increases the risk of cement leakage. The majority of leakages are cortical, with venous leakages occurring infrequently.^18,19 Asymptomatic cement leakage was seen in 24.5% of vertebrae in the current study, which is a notably lower frequency than the 91.9% that has previously been documented for vsOVCF.^{1,18 – 20,29 – 31} Good technique can minimize leakage through vertebral clefts.^23,26,32 In the present study, small amounts of almost-hardened bone cement were used to block anterior wall defects, followed by filling of the cavity with liquid cement. In cases where the posterior or side wall was damaged, continuous fluoroscopic monitoring was carried out during the filling process. Filling was stopped as soon as the bone cement reached the lateral margin, or when ∼25% of the distance to the posterior wall of the vertebral body remained. Cement was injected slowly and carefully, and the surgeon adjusted the needle direction (or terminated the injection) as soon as cement leakage was detected. In addition, balloon expansion was moderated in order to prevent excessive fracture reduction that may cause the cleft to enlarge.

The present study was limited by its retrospective design, and a large-scale prospective evaluation of kyphoplasty in vsOVCF is required.

In conclusion, patients with painful vsOVCF can be successfully treated with kyphoplasty. Although technically demanding, kyphoplasty is a feasible and effective minimally invasive procedure for the treatment of vsOVCF.