Cement-Augmented Pedicle Screw Fixation in Medically Unfit Patients Under Local Anesthesia Using the Minimally Invasive Surgery Technique

Kunal Singh; Varun Kumar Agarwal; Rahul Jain

doi:10.21182/jmisst.2025.02271

Abstract

Objective

A high rate of implant failure is frequently observed in osteoporotic spines. The majority of patients with osteoporosis are relatively old and are often unfit for general anesthesia due to various systemic comorbidities. Cement-augmented pedicle screw fixation is designed to improve stability and fixation strength in patients with compromised bone quality.

Methods

A total of 45 patients (23 women and 22 men), with a mean age of 71.37 years (range, 53–94 years), diagnosed with osteoporosis (T score > -2.5) and deemed unfit for general anesthesia, underwent instrumentation with polymethylmethacrylate augmentation of cannulated pedicle screws. In total, 214 pedicle screws were inserted: 28 patients received 4 screws and 17 patients received 6 screws, all with cement augmentation. Preoperative and postoperative visual analogue scale (VAS) scores for pain, as well as Oswestry Disability Index (ODI) questionnaire data, were analyzed. Screw migration, defined as the distance from the screw tip to the anterior cortex and the upper endplate of the vertebra, was also evaluated immediately after surgery. The mean follow-up period was 15.3 months.

Results

The mean preoperative VAS was 8.76 (range, 7–10). As intractable pain was the most common complaint, significant improvement was observed postoperatively: the mean postoperative VAS decreased to 2.24 (range, 0–5) (p<0.001). ODI scores also showed significant improvement in quality of life as measured by the ODI (p<0.001).

Conclusion

Our results support the use of cement-augmented pedicle screw fixation in medically unfit patients with osteoporosis. This technique appears effective in increasing stabilization of fixation and preventing screw loosening in this patient population. The main complication observed was cement leakage.

Key Words: Pedicle screw fixation, Polymethylmethacrylate, Cement augmentation, Osteoporosis, Unfit patient, Local anesthesia

INTRODUCTION

Cemented pedicle screw fixation is a widely used technique in spinal surgery, particularly for providing stability in cases of osteoporosis, vertebral fractures, deformities, or degenerative conditions [1]. Traditionally, this procedure has been performed under general anesthesia due to the complexity of the surgical approach and the need for precise placement of screws and cement. However, recent advancements in anesthesia techniques and surgical methods have opened the possibility of performing this procedure under local anesthesia by minimally invasive surgery technique [2].

Performing cemented pedicle screw fixation in local anesthesia offers several potential benefits, including reduced risks associated with general anesthesia, faster recovery times, and decreased hospital stay durations. This is especially advantageous for elderly or high-risk patients who may not tolerate and who are unfit for general anesthesia. Despite these advantages, the application of local anesthesia in such a demanding procedure raises concerns about patient comfort, procedural accuracy, and overall outcomes.

This study aims to explore the feasibility, safety, and efficacy of cemented pedicle screw fixation under local anesthesia. By analyzing clinical outcomes and reviewing current techniques, we seek to evaluate the potential for this approach to become a viable alternative to the traditional use of general anesthesia in spinal fixation surgeries [3].

MATERIALS AND METHODS

Forty-five patients (23 women, 22 men), mean age of 71.37 (range, 53–94) years, with osteoporosis (T score>2.5) who had osteoporotic compression fracture with kyphosis with intact neurology and who were not fit for general anesthesia but needed spine instrumentation to correct the kyphosis with polymethylmethacrylate (PMMA) augmentation of cannulated pedicle screws (Figure 1).

Total of 214 pedicle screw were inserted 28 individuals had 4 and 17 individuals had 6 pedicle screw insertion with cement augmentation. Ten individuals had fracture at lumbar region 18 at thoracic and 17 individuals had thoracolumbar junction.

Preoperative and postoperative visual analogue scale scores for pain and the Oswestry Disability Index (ODI) questionnaire data were analyzed [4]. Screw migration, which is the distance from the screw tip to the anterior cortex and the upper endplate of the vertebra, was also evaluated immediately after surgery. Mean follow-up was upto 15.3 months [5].

The study was conducted after taking approval from Institutional Review Board and written and informed consent was taken from each patient for participation in the study

1. Inclusion Criteria

(1) All the patient with osteoporosis (T score >-2.5) with type 2 kummells fracture; (2) All the patient requiring spine fixation but are not medically fit for general anesthesia; (3) Patients with Kummell type 2 osteoporotic fracture (nontraumatic).

2. Exclusion Criteria

Patient who is allergic to local anesthetic agents. Sequential radiological and clinical evaluation was done at immediate postoperative, 6 weeks, 12 weeks, 6 months, and 1 year.

3. Screw Design

Fenestrated screws have gained popularity in recent years due to their ability to streamline the cementation process and provide a more consistent distribution of cement within the vertebral body to coat the bone-implant interface. They have a cannulated core and various windows along the length of the screw that allows the cement to flow from the screw head to the tip. It is a self-tapping screw (Figure 2).

4. Surgical Technique

1) Percutaneous screw fixation under local anesthesia

Patient is positioned supine on allen table and is held in comfortable position with the help of belts (Figure 3B). Firstly, squaring of vertebrae is done by making the end plates parallel to each other in anterior-posterior (AP) view on C-arm and position of pedicle are confirmed by help of 2 artery forceps under C-arm in AP view on either side. Using marker, marking is done lateral to the lateral pedicle border at the sites marked by artery forceps (Figure 4). A 1 mL local anesthetic mixture (50% lidocaine with adrenaline and 50% bupivacaine) was injected at each incision site (Figure 5). Lignocaine with adrenaline plus bupivacaine 50/50 each is given through the path and entry point in to the PERIOSTEUM (0.5 mL at each entry point). Then travelled laterally over the transverse process and 1st dip felt there 5 mL is given which mimics like erector spinal block [6]. Through paraspinal approach, the skin incision is made to be large enough to accommodate the towers of the screws. The entry is made with a Jamshidi needle usually in the upper outer quadrant of pedicle under C-arm guidance on AP view like Figure 6. A mallet is used to gently tap and advance the Jamshidi in the transpedicular channel approximately 30 mm. Tip of Jamshidi should not be crossing the medial pedicle border in AP and should be at the posterior vertebral line in lateral view as in Figure 7. The guide wire is inserted through the needles under C-arm guidance. Jamshidi needle is removed and followed by placement of serial dilators and cannulated screw with towers over the guide wire: Cement is prepared and inserted in the tower funnel using special cement injectors that allow cement to be injected through the MIS Screws (Figures 8 and 9); Cement pedicle screw funnel is inserted through the tower; Cement is pushed with the help of cement pusher and checked under C-arm in AP and lateral views (Figure 10A and B).

A rod measuring device is used to measure the appropriate rod length with the extenders assembled. French bender is used to contour the rods before insertion. Entry of rod is marked, and local anesthesia is given. The rods are placed percutaneously from a small separate proximal incision. Using the checker, placement of rod inside screws is confirmed clinically and final confirmed under C-arm. The rods are checked under AP view and lateral view. Set screw is used to tighten the rods to the screws. Final tightening done and towers are removed along with the cement cannula. Wound irrigated and closure done in layers.

5. Postoperative Protocol

1) Immediate postoperative care (first 24 hours)

(1) Observation and monitoring

Vital signs (blood pressure, heart rate, oxygen levels) were monitored and assessment for complications such as bleeding, hematoma, or neurological deficits was done. Neurological status was assessed intraoperatively as patient was in local anesthesia and immediate postoperatively after shifting the patient to recovery room. Continuous pain assessment and management using nonopioid medications like acetaminophen and nonsteroidal anti-inflammatory drugs was done.

(2) Mobilization

Early mobilization was done with lumbo-sacral corset or Taylor brace and walker depending upon the level of fracture, starting at postoperative day (POD) 0 with sitting up and standing bedside POD1 walking with assistance, depending on the patient's pain.

(3) Wound care

Dressing was done on POD2, 5, 8, 11.

2) Early mobilization (first week)

(1) Physical activity

All patients were encouraged to do light activity such as walking as tolerated. Avoid bending, twisting, or lifting heavy objects to protect the spinal fixation. Gradual increase in activity levels was done as tolerated by the patient.

(2) Pain control

All Patients were educated on the use of pain medication and nonpharmacological measures such as cold compresses to reduce pain and inflammation. A follow-up appointment for suture removal at POD14 was done.

3) Weeks 2–6 postoperative

(1) Physical therapy

After the first week, supervised physical therapy were initiated, focusing on gentle stretches, core strengthening, and improving mobility.

(2) Activity progression

All patients gradually resumed to their normal daily activities by around 3–4 weeks.

(3) Follow-up imaging

X-rays were taken at follow-up visits to ensure proper screw placement and check for early signs of hardware failure (6 weeks, 3 months, 6 months, and 1 year).

4) Long-term follow-up (6 weeks–3 months)

(1) Physical therapy

Continued structured rehabilitation focusing on muscle strengthening, posture improvement was done.

(2) Return to work

Patients were seen usually returning to desk jobs or light physical work within 3 weeks, but heavy lifting jobs took up to 3 months or more [7].

RESULTS

The mean preoperative VAS was 8.76 (range, 7–10). Being the most common complaint, pain showed significant improvement, and the mean postoperative VAS became 2.24 (range, 0–5) recorded during the last clinical control (p<0.001). Intractable pain was the main indications for surgery in 9 patients. Patients showed significant improvement in the quality of life as measured using the ODI (p<0.001) [8]. All the patients tolerated the surgery well under local anesthesia (Figure 11).

DISCUSSION

With the increasing aging population, osteoporosis has become a prevalent condition, contributing to a rise in spinal surgeries involving transpedicular screw fixation. This trend is driven by efforts to enhance the quality of life in patients with degenerative spinal diseases or osteoporotic vertebral fractures, particularly those characterized by poor bone quality. For spine surgeons, performing transpedicular screw fixation in osteoporotic spines presents a significant challenge, as osteoporosis is a leading cause of screw loosening and pullout. In osteoporotic bone, the reduced fixation strength heightens the risk of screw displacement or subsidence. To mitigate these risks, multilevel screw fixation is often recommended [9].

To address these limitations, various strategies and adjunct procedures have been introduced to increase pedicle screw pullout strength, notably through the use of bone cement augmentation. Several experimental studies have demonstrated the efficacy of different types of bone cements, such as PMMA, hydroxyapatite, and calcium sulfate, in enhancing screw fixation. Among these, PMMA has gained popularity due to its simplicity, availability, and cost-effectiveness. Studies have shown that PMMA can significantly increase the pullout strength and stiffness of pedicle screws, with reports of strength improvements ranging from 96% to 262% [10].

Despite its advantages, the use of bone cement in spinal surgery is not without risks. The primary concern is cement leakage into the epidural space, which can lead to complications such as myelopathy or radiculopathy. Proper surgical technique is crucial to minimize the risk of leakage. Techniques such as ensuring an appropriate screw diameter, injecting cement at a low pressure, and maintaining optimal cement viscosity are essential for safe and effective application. Systemic complications, including hypoxia, fever, infection, and pulmonary embolism, have also been reported with the use of PMMA, requiring careful monitoring [11].

Cement is injected after insertion of screws and distributed according to the fenestration pattern. Fenestrated screws have been shown to reduce cement injection pressure, which may help prevent cement leakage. The distance between fenestrations, as well as their location and number, varies greatly between screw types and can affect cement distribution as well as the biomechanics of the fixation. The injection pressures resulted in variable cement distribution patterns with the various techniques.

While bone cement augmentation increases the physical stability of spinal implants.

Local anesthesia in pedicle screw fixation is increasingly used, especially for patients who are at higher risk of complications from general anesthesia, such as the elderly or those with comorbidities. This technique involves numbing the specific area where screws are inserted into the vertebrae, allowing patients to remain awake during the procedure.

Advantages include reduced recovery time, less postoperative nausea, and lower overall risk since the patient avoids the systemic effects of general anesthesia. Additionally, patients can provide immediate feedback during surgery, which can help prevent nerve damage.

However, this approach requires precise anesthesia administration and good patient cooperation, as there may be some discomfort during the procedure. While local anesthesia is effective for less complex cases, it might not be suitable for more extensive or multilevel spinal surgeries. Overall, local anesthesia for pedicle screw fixation offers a viable option in carefully selected patients, promoting faster recovery and fewer anesthesia-related complications [12]. Risks of local anesthesia for spinal surgery previously, focus was placed on the risks of utilizing local anesthesia for spinal surgery, including toxicity associated with high local anesthetic doses, and venous air embolism. None of our patients suffered from any local anesthesia-related toxicity; this is consistent with other reports in the literature [13,14]. Furthermore, the risk of air embolism is virtually nonexistent unless the patient is in a unique head up position.

CONCLUSION

There was no significant screw migration when the screws’ distances were compared just after the operation and at the final follow-up (1 year) (p>0.01). There was no major neurovascular injury, except in 1 patient, who had persistent left thigh pain due to cement leakage at the L1 level, and the symptom was controlled with analgesics.

Based on our results, we think that the use of this technique in patients with osteoporotic fracture is recommended. This is due to being helpful for increasing the stabilization of fixation and preventing screw loosening and reduced surgical time eventually leading to reduced blood loss in medically unfit patients. Also, reduced risks associated with general anesthesia, Faster recovery time decreased hospital stay duration as done as day care procedure. The main complication is cement leakage.