Application of Piezosurgery in Revision Surgery through Posterior Approach for Infection after Percutaneous Vertebral Augmentation: Technique Note with Case Series

Abstract

Objectives

Pyogenic spondylitis after vertebral augmentation (PSVA) is a severe complication and even threatens the life of patients. How to deal with infectious bone cement is a big problem for surgeons. The application of piezosurgery has advantages in removal the infectious bone cement in limb bone and spinal laminectomy, but it is rarely used in PSVA. So, the present study aimed to introduce the application of piezosurgery in revision surgery for PSVA and report the preliminary radiological and clinical results.

Methods

The data of nine patients with PSVA who had undergone revision surgery were retrospectively reviewed between May 2017 and January 2023 in our hospital. The technique of removal of infectious bone cement and lesion by piezosurgery and the reconstruction of the spinal stability were described, and the operation time and intraoperative blood loss were recorded. Postoperatively, radiographs and computed tomography scans were reviewed to evaluate the condition of bone cement removal, control of infection, and bone fusion. Oswestry disability index (ODI) and visual analog scale (VAS) were assessed pre‐ and postoperatively, and clinical outcomes were assessed using Odom's criteria.

Results

All patients achieved satisfactory tainted bone cement cleaning and restoration of spinal alignment. The surgical time was 258.8 ± 63.2 (160–360) min, and the intraoperative blood loss was 613.3 ± 223.8 (300–900) mL. The VAS score decreased from 7.0 (6–8) points preoperatively to 2.4 (1–4) points postoperatively. The ODI index decreased from 71% (65%–80%) preoperatively to 20% (10%–30%) postoperatively. The patient's VAS and NDI scores after operation were significantly improved compared with those before surgery (p ≤ 0.05). Odom's outcomes were good for all patients in the last follow‐up, and all patients reported satisfactory results.

Conclusions

Piezosurgery can effectively remove large blocks of infectious bone cement through a posterior approach while avoiding nerve and spinal cord damage. We cautiously suggest that a one‐stage posterior approach using piezosurgery is an alternative option for surgical treatment of PSVA.

We first introduce the application of piezosurgery in revision surgery for pyogenic spondylitis after vertebral augmentation (PSVA). The preliminary results are satisfactory without catastrophic complications, proving its feasibility and safety. Piezosurgery can effectively remove the large block of infectious bone cement through posterior approach and avoid nerve and spinal cord damage.

Introduction

Percutaneous vertebral augmentation (VA) has gradually become primary treatment for patients with symptomatic osteoporotic vertebral fractures (OVFs). ¹ , ² Although VA is a minimally invasive surgery, there are still potential serious complications, such as neurological complications caused by cement leakage, cement embolism, and infection. ³ Infection is one of the complications of particular concern, with pyogenic spondylitis after vertebral augmentation (PSVA) as the most common, which can cause unbearable pain and even threaten life. ⁴ Revision surgery should be considered in case of significant neurological deficit, severe instability, and failure after strict conservative treatment. ⁵ , ⁶ , ⁷ Commonly used revision surgeries include the simple posterior approach and the combined anterior and posterior approach. ⁴ , ⁵ , ⁸ Different surgical approaches have their advantages. The combined anterior and posterior surgery is widely used because it can remove the lesion and PMMA more thoroughly. ⁸ However, the anterior approach to the spine is more traumatic to the abdominal and thoracic cavities than posterior surgery. ⁹ Considering that patients with PSVA are of older ages and have multiple underlying diseases, they could hardly tolerate long surgery and massive surgical trauma like combined anterior and posterior approach. One‐stage posterior debridement and internal fixation have advantages in terms of the operation time, intraoperative blood loss, and surgical trauma compared with the combined anterior and posterior approach, which provides a safe corridor to access the anterior thoracolumbar column and can be a relatively “ideal” approach. ⁴ , ⁹

Piezosurgery cuts the mineralized tissue by the high‐energy shock waves. It can selectively cut hard tissues through different ultrasonic frequencies while leaving soft‐tissue structures such as the dura mater and nerves intact. ¹⁰ The technical advantages of a piezosurgery device—such as a self‐irrigating cooling mechanism, no rolling motion, and less tip bone contact force—have made it an effective instrument for performing procedures near the dura mater and other neural tissues without excessive mechanical and thermal injury. ¹⁰ , ¹¹ , ¹² Some researchers reported the application of piezosurgery in spinal surgeries can preserve more posterior elements of the involved levels, maintaining an intact, reducing the operation time and blood loss, and avoiding injuring the dura mater and nerves. ¹² , ¹³ , ¹⁴ However, few studies have focused on the use of piezosurgery for cement removal in PSVA, and the safety and feasibility of this technique have not yet been systematically evaluated. The present study aimed: (i) to introduce the application of piezosurgery in revision surgery; (ii) to report the preliminary outcomes; and (iii) and to evaluate its feasibility and safety.

Methods

Patients and Data Collection

Our institutional review board approved the study protocol (KY2023109), and written informed consent was obtained from each participant. Retrospective data were obtained for a series of patients who had experienced infection after VA between May 2017 and January 2023. Postoperative infection occurred in four patients in our hospital (out of 1058 patients operated on, with an infection rate of 0.38%), and 11 were referred from other institutions.

The inclusion criteria were as follows: (1) patients with infection after VA are confirmed; (2) the revision surgical method is a simple posterior approach and a piezosurgery is used during the operation. And exclusion criteria consisted of: (1) bacterial culture after revision surgery showed nonpyogenic infection; (2) other pathological conditions such as metastasis or multiple myeloma.

Nine patients ultimately met the criteria and were included in this study. There were two men and seven women, aged between 63 and 80 years (average, 73.5 ± 5.7 years). The mean time from onset to medical consultation was 5.2 months (3–10 months). The primary reasons for revision surgery were as follows: seven patients had infection unresponsive to 2‐week antibiotic conservative treatment and two patients had severe segmental instability. Preoperatively, lesion radiographs, computed tomography (CT) scans with three‐dimensional reconstruction, and magnetic resonance imaging (MRI) scans were obtained for all patients, and routine laboratory examinations, including urine culture, sputum culture, and blood culture, confirmed the diagnosis.

Surgical Technique

Anesthesia and Position

After induction of general anesthesia, a midline incision from two to three levels above the involved vertebrae to two to three levels below was made to expose the posterior elements. The exact level was identified by intraoperative C‐arm fluoroscopy.

Approach and Exposure

The Wiltse approach was used to implant a pedicle screw into the intended fixed segment. We used shorter screws for fixation on the non‐decompressed side of the lesion segment and did not implant screws on the decompressed side. To maintain the spine stability, a temporary rod was placed on the screws of the non‐decompressed side (Figure 1). The side with more bone cement distribution in the vertebral body was selected as the channel for lesion and PMMA removal. The articular joints, lamina, pedicle, and other structures of the destroyed vertebrae were exposed through the compartment of muscles between the longissimus and multifidus muscles.

FIGURE 1.

Ultrasonic osteotome handle and various types of blades (A); Infected bone cement was cut into small pieces by ultrasonic osteotome and taken out during operation (B); Temporary rod was fixed on one side and debridement was done on the other side (C); The range of fenestration was about 2 × 2 cm (D).

Application of Piezosurgery

Piezosurgery (SMTP Technology Co., Ltd. Beijing, China) equipped with straight‐type tip was used to remove the lamina, pedicle, facet joint, and other structures on the decompressed side and fully expose the infectious lesion area. Besides, we used a nerve stripper to protect the dural sac and corresponding nerve roots, and the probe was used to carefully explore the location of the infected bone cement in the narrow and dark canal. Piezosurgery equipped with straight‐type tip was used to cut a large piece of infected bone cement slowly and repeatedly until the large pieces of bone cement were cut into smaller pieces.

Debridement and Fusion

Use the pituitary rongeur to slowly and carefully remove the small infected piece of bone cement through the narrow channel until the infected bone cement and the necrotic tissue around the destroyed vertebral body were completely removed. The tissues at the junction of necrosis and normal tissue were selected for bacterial culture and pathological examination. The infected lesion was rinsed repeatedly with copious amounts of diluted povidone‐iodine. A partial autogenous bone (referring to the uninfected bone tissue previously removed by piezosurgery) or rib was chosen to fill the bone defect depending on the lesion location, and the spinal stability was reconstructed.

Bilateral connecting rods and transverse connectors were placed. Finally, drainage tubes were placed on the two sides of the surgical area, and the surgical incision was closed. After the surgery, the patient returned to the general ward safely.

Postoperative Care

After the surgery, sterile normal saline was used to rinse the infected surgical area through the plasma drainage tube for 7–10 days. According to our experience, the irrigation volume was 6000ml per day for the first 3 days after operation and then gradually reduced to 3000 mL per day. On the fourth day after operation, the irrigation fluid was taken to culture for bacteria. If the three culture results were negative, the irrigation would be stopped. Sensitive antibiotics were selected based on the bacterial culture and pathological test after the surgery and infused intravenously for 2 weeks and orally for 8 weeks. If pathogenic microorganisms could not be cultivated, an empirical intravenous infusion of antibiotics with a higher bone tissue distribution was used.

Clinical and Radiological Assessment

Radiographs and CT scans were reviewed to evaluate the condition of bone cement removal, infection control, and bone fusion. The operation time and intraoperative blood loss were recorded. Clinical outcomes were evaluated using the preoperative and postoperative Oswestry disability index (ODI) and visual analog scale (VAS). Clinical outcomes were also assessed using Odom's criteria. Demographic and clinical symptoms of the patients are demonstrated in Table 1.

TABLE 1.

Summary of demographic characteristics of the patients treated with PSVA.

Case No.	Sex	Age	Diagnosis (PSVA)	Comorbidities	Clinical symptoms	WBC (10^9/L)	ESR (mm/h)	CRP (mg/L)	SDP (months)
1	F	79	T7, T8	Pneumonia	Chest and back pain	8.71	22	1.52	6
2	M	71	T12	Emphysema; Pulmonary Bullae.	Chest and back pain	6.02	34	0.5	3
3	M	78	L1	Parkinson disease; Hypertension	Chest and back pain	5.12	6	0.52	7
4	F	67	L1	None	Low back pain with lower extremity pain	9.15	120	36.78	5
5	F	75	L1	Pneumonia; Bronchiectasi; Hypertension	Paraparesis	11.4	41	81.07	3
6	F	76	T12, L1	Hyperlipidemia; Hypertension	Chest and back pain	8.88	89	29.7	10
7	F	63	L4	Hypertension	Low back pain	8.96	64	15.49	4
8	F	80	L1	Diabetes; Hypertension	Low back pain	7.04	91	33.75	4
9	F	73	T12	None	Radiculopathy	6	61	7.6	5

Abbreviations: CRP, C‐reactive protein; ESR, erythrocyte sedimentation rate; F, female; M, male; PSVA, pyogenic spondylitis after vertebral augmentation; SDP, symptom duration period; WBC, white blood count.

Results

Surgical results are summarized in Tables 2 and 3. All patients successfully underwent simple posterior debridement with piezosurgery, bone graft fusion, and fixation. None of the patients experienced neurological deterioration and pain aggravation after surgery. The surgical time was 258.8 ± 63.2 (160–360) min, and the intraoperative blood loss was 613.3 ± 223.8 (300–900) mL.

TABLE 2.

Surgical technique of the patients treated with infection after VA.

Case No	Reason for revision surgery	Surgical approach	Operation time (minutes)	Blood loss (mL)	Causative organism	Follow‐up (months)
1	A	P	300	800	No	9
2	B	P	290	500	Staphylococcus epidermidis	N
3	A	P	360	560	No	6
4	A	P	260	860	No	6
5	A	P	265	800	No	N
6	B	P	300	900	No	N
7	A	P	200	300	Staphylococcus aureus	N
8	A	P	195	300	No	N
9	A	P	160	500	No	3

Abbreviations: A, infection unresponsive to antibiotics through 2‐week conservation treatment; B, severe instability; P, posterior debridement with piezosurgery; VA, vertebral augmentation.

TABLE 3.

Clinical outcomes of patients before operation and a week after operation.

	Pre‐operation	Post‐operation	p‐value
VAS	7.0 ± 0.7	2.4 ± 1.1	0.007
NDI (%)	71.0 ± 5.2	20.0 ± 6.0	0.008

Abbreviations: ODI, Oswestry disability index; VAS, visual analog scale.

The VAS score decreased from 7.0 (6–8) points preoperatively to 2.4 (1–4) points postoperatively. The ODI index decreased from 71% (65%–80%) preoperatively to 20% (10%–30%) postoperatively. The patient's VAS and NDI scores after operation were significantly improved compared with those before surgery (p ≤ 0.05). Satisfactory tainted bone cement cleaning and the sequence recovery of the spine were achieved in all patients (Figures 2 and 3). No severe complications, such as infection worsening, neurological deficit, or failure of the screws, occurred in any of the patients. Two patients complained of bloating but recovered after 7 days with conservative treatment. One patient complained of rib pain but recovered after 2 months. Odom's outcomes were good for all patients at the last follow‐up, and all patients reported satisfactory results. Bacteria were cultured in only two patients after the operation.

FIGURE 2.

Case 1. 79‐year‐old woman. Preoperative plain radiograph in sagittal plane showing T6–8 subjected to percutaneous kyphoplasty surgery (A). Preoperative sagittal computed tomography (CT) (B) and sagittal magnetic resonance imaging (MRI) (C) showing T8 vertebral bone cement collapse and displacement forward (B) and T7–8 bone cement and T9 vertebral body infection (C). Postoperative plain radiograph in the sagittal plane showed that T7–8 bone cement was removed entirely, and there was no bone cement residue (D). Partial bony fusion was seen, and the screws were not loosened or broken on sagittal CT scans at 3 months postoperatively (E). Solid bone fusion was observed on sagittal CT scans at 9 months postoperatively (F).

FIGURE 3.

Case 2. 71‐year‐old man. Preoperative plain radiograph in sagittal plane showing T12 subjected to percutaneous kyphoplasty surgery (A). Preoperative sagittal computed tomography (CT) (B) and sagittal magnetic resonance imaging (MRI) (C) showing T12 vertebral bone cement collapse and T11–L1 kyphosis (B) and T12 bone cement and T11 vertebral body infection (C). Postoperative plain radiographs in coronal (D) and sagittal (E) planes showed that the lesion was completely removed, no bone cement residue was found, and the spinal sequence was well restored. CT scans in the coronal plane showed a satisfactory amount of bone grafting in the T12 vertebral body and recovery of spinal sequence (F).

Discussion

Main Finding

In this study, we reviewed the clinical and radiological outcomes of patients with postoperative infection who underwent one‐stage posterior debridement using piezosurgery. The surgical time was 258.8 ± 63.2 min, and the intraoperative blood loss was 613.3 ± 223.8 mL. Satisfactory tainted bone cement cleaning and the sequence recovery of the spine were achieved in all patients. Satisfactory results were achieved without severe complications associated with instrumentation, and no implant failure occurred during the follow‐up.

Advantages of Piezosurgery

Park et al. ⁵ reported 11 cases of infection after VA who received revision surgery via the combined anterior and posterior approach, and showed that the mean operative time was 299 min and the average blood loss was 1375 mL. Hu et al. ⁶ reported seven patients with infection who underwent anterior and posterior debridement and fixation and showed that the revision operation time was 239 ± 81.2 min and the intraoperative blood loss was 812.2 ± 243.5 mL. Moreover, complications of the combined anterior and posterior surgery, including pulmonary infection, poor wound healing, asymptomatic hardware loosening, and even death due to septic shock and incomplete clearance of the infected lesions, had also been reported. ⁵ , ⁶ , ⁷ , ⁸ , ¹⁵ In our study, we used a simple posterior method and piezosurgery for patients with PSVA in revision surgery and the intraoperative blood loss was 613.3 ± 223.8 mL, and there was significantly less bleeding than in other studies. The surgical time was 258.8 ± 63.2 min. Unskilled use of piezosurgery during operation may lead to prolongation of operation time. However, the operative time, intraoperative blood loss, drainage time, and hospital stay improved as the experience increased. ¹⁶ With the familiar use of piezosurgery, the operative time and blood loss will be further reduced in the future. Piezosurgery is a new technology in orthopaedic surgery that exploits high‐frequency ultrasonic drilling to destroy bone tissues and cuts through osseous structures. ¹⁷ The advantage of this technique is having a hemostatic effect in time on the surface where the bone has been cut and reducing the intraoperative bleed. ¹⁸ Besides, direct damage to the blood vessels and nerve tissue is avoided to the greatest extent in piezosurgery, which significantly improves the accuracy and safety of orthopaedic surgery. ¹⁷ , ¹⁹ So far, the application of piezosurgery in spinal laminectomy has been reported to provide good surgical outcomes. ²⁰ In addition to the reduced bleeding and less damage to bony structures in the resection of articular processes, lamina, and other corresponding structures, piezosurgery can better clear the infected bone cement tissue. According to Roitzsch et al., ²¹ piezosurgery is a highly effective technique and removes more than 99% of the PMMA. It has been confirmed in bone revision surgery of extremities and has achieved satisfactory clinical results. In our study, none of our patients had bone cement residues on postoperative X‐ray or CT. All the patients were discharged safely and received satisfactory treatment. The application of piezosurgery in revision surgery can also clean the infectious bone cement completely and safely.

Limitations of Traditional Instruments

Bone cement is a commonly used material in VA. Methyl methacrylate (MMA) is the main component of bone cement. MMA molecules bind to long chains by radical polymerization to PMMA. ²² PMMA cement must provide adequate strength against bending, impact, tension, torsion, and shear forces. ²³ Meanwhile, PMMA cements do not have a blood supply, and it is difficult for antibiotics to reach a high level of distribution within the infectious PMMA. As a result, conservative treatment may fail in patients with severe infections. Because of these characteristics of bone cement, cement removal can be technically challenging and time‐consuming and is associated with increased complications, such as bleeding, bone damage, fractures, or perforations. ²⁴ , ²⁵ Additionally, it is difficult for traditional instruments to cut bone cement into small blocks. Some patients with PSVA have large blocks of bone cement, so removing it through a small hole in the window is difficult. Direct removal may scratch the dura mater and lead to cerebrospinal fluid leakage, nerve damage, and even paralysis. PMMA bone cement in limb bones is commonly removed using a combination of chisels, burrs, reverse cutting hooks, drills, and long‐distance windowing. ²⁶ However, if traditional instruments such as bone knives are used to chisel bone cement into small pieces in spine surgery, large vibrations, and unstable handling may cause spinal nerve injury.

Status of Current Treatment

Considering the aforementioned risks associated with the removal of infected bone cement, some studies recommend using anterior debridement combined with posterior internal fixation can effectively remove the lesions, pus, and PMMA in patients of PSVA. ⁵ , ⁷ , ⁸ , ²⁷ The advantage of this approach is that it can remove the lesion and PMMA more thoroughly and safely. However, the anterior approach to the spine is more traumatic to the abdominal and thoracic cavities than posterior surgery. ⁹ Long surgery time and massive surgical trauma for patients with PSVA are big challenges. There is also a certain mortality rate in the combined anterior and posterior approach. ⁸ , ¹⁵ One‐stage posterior debridement, fusion, and fixation have been proven to be feasible, which provides a safe corridor to access the anterior thoracolumbar column, shorter surgery time, and less blood loss. ⁴ , ⁹ However, it is more difficult to remove larger blocks of infection bone cement directly through the narrow channel. So, the application of piezosurgery is essential, which can cut these large pieces of bone cement into small pieces and smoothly remove them. Debridement and bone cement removal can be achieved piece by piece using clamps or rongeurs, through the route between the nerve roots to preserve the nerve roots. ⁹ Moreover, the space is also adequate for partial autogenous bone implantation. So, a one‐stage posterior approach using piezosurgery is a feasible and effective method, which is more conducive to the recovery of patients.

Experience of Piezosurgery

Furthermore, based on our experience, the authors believe that the following points should be paid attention to when using piezosurgery: (1) because the bone cement is hard, we usually shake the piezosurgery from side to side gently and not press down hard when we cut the bone cement; (2) (3) although piezosurgery can only destroy bone tissue with a certain hardness and does not damage blood vessels, nerves, and other tissues, there were still case reports of nerve damage. ²⁸ Thus, particular care is mandatory when manipulating, especially in narrow passages surrounded by the dura mater and nerves in revision surgery.

Strengths and Limitations of this Study

This study is first reporting the application of piezosurgery in PSVA and we discovered this technique could bring many advantages, including less bleeding and infectious bone cement cleaned completely. However, there are some limitations to this study. First, this study was a preliminary technique report with a limited number of cases; further large clinical studies are needed to validate the outcomes. Second, the follow‐up was not long enough, so we were not able to assess the long‐term curative effect. In addition, the type of ultrasonic knife head used during the procedure is a cause of concern since it was relatively fixed, and the head of the piezosurgery was not compared and analyzed according to the specific shape of the bone cement block. As such, which type of piezosurgery is better still needs further clinical research.

Conclusions

In this study, it was found that in patients with PSVA, a one‐stage posterior approach combined with piezosurgery for debridement of abscess and removal of infected bone cement, bone grafting, fusion, and internal fixation was practical, and the preliminary results were satisfactory without catastrophic complications, thus demonstrating its feasibility and safety. Therefore, we cautiously suggest that a one‐stage posterior approach using piezosurgery is an alternative option for surgical treatment of PSVA.

Author Contributions

HZ participated in data collection and analysis, and HZ also contributed to drafting the manuscript. QW, GL, and GW performed the surgery and contributed to the study design and conception, interpretation of data, and revision of the manuscript. All authors reviewed and approved the final manuscript.

Conflict of Interest Statement

The authors declare no conflict of interest. No benefits in any form have been, or will be, received from a commercial party related directly or indirectly to the subject of this manuscript.

Ethics Statement

All procedures performed in studies involving human participants were in accordance with the ethical standards of the Clinical Trial Ethics Committee of the Affiliated Hospital of Southwest Medical University and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards (KY2023109). Informed consent was obtained from the participant included in the study. And all methods were carried out in accordance with relevant guidelines and regulations (Declaration of Helsinki).