Antibiotic-Loaded Bone Cement-Induced Membrane and Skin Grafting in Elderly Patients with Refractory Lower Limb Wounds

Summary

This protocol describes a two-stage technique using antibiotic-loaded bone cement and skin grafting for elderly patients with complex lower limb wounds.

Abstract

Refractory lower limb wounds in the elderly population represent a significant and growing clinical challenge, often complicated by factors such as chronic infection, poor tissue vascularization, and multiple comorbidities. These wounds frequently lead to prolonged healing times, increased healthcare costs, and diminished quality of life for affected patients. This protocol article describes a detailed two-stage surgical technique that utilizes antibiotic-loaded polymethyl methacrylate (PMMA) bone cement to induce a vascularized membrane, followed by secondary skin grafting. The procedure is systematically outlined, beginning with patient selection criteria and progressing through radical wound debridement, intraoperative preparation and implantation of the vancomycin-loaded cement spacer, postoperative care, and subsequent spacer removal with application of a split-thickness skin graft onto the newly formed induced membrane. We provide a direct comparative framework against the conventional vacuum sealing drainage (VSD) technique. In this retrospective cohort study, representative results demonstrate that this method contributes to local infection control, as both groups showed a reduction in culture positivity postoperatively. Furthermore, it promotes a more robust angiogenic response within the induced membrane. Although the final wound healing rate at 70 days was comparable between groups, the PMMA method demonstrated a significantly shorter time to complete healing compared to VSD. The protocol also presents potential benefits in reducing the overall economic and psychological burden on patients. This comprehensive guide enables the replication of a promising surgical strategy for managing complex lower limb wounds in elderly patients.

Introduction

The rising global elderly population has led to a significant increase in the incidence of chronic refractory lower limb wounds, posing a major clinical challenge^1,2. These wounds, characterized by their failure to heal through conventional therapies, are frequently complicated by infection, exposed deep structures like bone and tendon, and compromised perfusion due to prevalent vascular pathologies in the elderly^3,4. Effective management remains difficult.

A common standard of care involves radical debridement followed by Vacuum Sealing Drainage (VSD) for wound bed preparation⁵. While VSD promotes granulation tissue formation by removing exudate and reducing edema⁶, it possesses critical limitations. It lacks direct antimicrobial activity against the tenacious biofilms present in up to 90% of chronic wounds^7,8. Furthermore, its requirement for frequent dressing changes often prolongs hospitalization, increasing economic and psychological burdens on patients^9,10. Although flap surgery is ideal for definitive coverage, severe lower limb vascular disease in the elderly often precludes this option due to high risk^4,11.

The induced membrane technique, pioneered by Masquelet for bone defect reconstruction, offers a promising alternative principle^12,13. This two-stage method involves implanting a polymethyl methacrylate (PMMA) cement spacer, which induces a vascularized pseudo-synovial membrane. When loaded with antibiotics, the spacer also serves as a local drug delivery system^14,15. Recent applications have extended this concept to complex soft tissue wounds, such as diabetic foot ulcers^16,17. The induced membrane acts as a superior, biologically active graft bed, rich in growth factors and vasculature, while the eluting antibiotics combat local infection.

However, a standardized protocol for applying this technique specifically to the diverse etiologies of refractory lower limb wounds in the elderly, coupled with a comparative analysis against VSD, is lacking in the literature. The overall goal of this method is to provide a detailed, step-by-step protocol for using antibiotic-loaded PMMA bone cement to induce membrane formation, followed by secondary skin grafting, in this challenging patient population.

To assist researchers and clinicians in assessing the suitability of this method, we emphasize key applicability considerations early on: successful implementation requires confirming adequate distal perfusion to support the induced membrane and selecting heat-stable antibiotics capable of withstanding the exothermic polymerization of the cement. The rationale is to overcome the key limitations of VSD by providing sustained local anti-infective therapy and actively generating a highly vascularized recipient bed to enhance graft success. The principal advantages are the potential for localized antibiotic delivery and the active generation of a highly vascularized recipient bed, improved healing potential, and a reduced treatment burden. This protocol details the procedure to enable researchers and clinicians to determine its suitability for their clinical practice and to facilitate further validation.

Protocol

This study was conducted in compliance with the guidelines of the Medical Ethics Committee of Yuhuan People's Hospital (Approval No.: Yuyi Lun Shen 2024 (046)). Informed consent was obtained from all participants. The reagents and the equipment used are listed in the Table of Materials.

1. Patient selection and preoperative preparation

1. Screen potential candidates using the inclusion and exclusion criteria detailed in Table 1.
   1. Ensure the patient is 60 years or older.
   2. Document a wound history of one month or longer.
   3. Verify the presence of lower limb vascular pathology via imaging (e.g., CTA or Doppler) that precludes complex flap surgery. Exclude patients with critical limb ischemia (e.g., ABI < 0.5).
2. Obtain informed consent from the patient after thoroughly explaining the two-stage nature of the procedure, potential risks, and benefits.
3. Perform a preoperative workup.
   1. Collect a deep tissue or swab sample from the wound for microbiological culture and sensitivity testing.
   2. Conduct routine blood tests and imaging studies to assess the patient's overall fitness for anesthesia and surgery.

2. First-stage surgery: Radical debridement and cement spacer implantation

1. Administer appropriate anesthesia, such as spinal anesthesia or lower limb nerve block (following institutionally approved protocols).
2. Prepare the surgical site using standard aseptic techniques.
3. Perform a radical debridement of the wound.
   1. Excise all non-viable, necrotic, and infected tissue until a viable wound bed with punctuate bleeding is achieved (the "Paprika sign").
   2. Irrigate the wound cavity copiously with 500 mL of 3% hydrogen peroxide, followed by 500 mL of 0.5% iodophor (povidone-iodine) solution, and finally with 1 L of sterile normal saline.
   3. Obtain a second swab sample from the wound bed for culture post-debridement.
4. Prepare the antibiotic-loaded bone cement at room temperature (22-25 °C).
   NOTE: Ensure the chosen antibiotic is heat-stable (e.g., Vancomycin, Gentamicin). Adjust antibiotic selection to include coverage for Gram-negative bacteria if indicated by local antibiograms.
   ​CAUTION: PMMA monomer is volatile and toxic. Ensure adequate operating room ventilation and wear appropriate PPE during mixing.
   1. Measure vancomycin powder and PMMA bone cement powder at a mass ratio of 1:20.
   2. Mix the powders thoroughly in a dry bowl.
   3. Add the liquid monomer to the powder mixture and stir until a homogeneous, dough-like consistency is achieved.
5. Implant the cement spacer.
   1. Mold the cement dough to fit the contour of the debrided wound cavity.
   2. Place the cement spacer into the wound. Ensure it does not exert excessive pressure on the wound edges.
   3. CRITICAL STEP: During the polymerization phase, continuously irrigate the cement and surrounding soft tissues with ice-cold sterile saline. This prevents thermal injury to the wound bed caused by the exothermic reaction of the PMMA (which can reach >70 °C).
   4. Create several small perforations in the spacer surface to facilitate drainage.
   5. Use pre-placed sutures to loosely secure the spacer if necessary to prevent displacement.
   6. Allow the cement to polymerize and harden completely (approximately 10-15 min).
6. Cover the wound with a non-adherent sterile dressing.

3. Postoperative management after first-stage surgery

1. Monitor the patient for any signs of systemic infection or local complications.
2. Administer systemic antibiotics based on culture sensitivity results for 2 weeks (or as clinically indicated).
3. Collect wound drainage or swab samples for culture on postoperative days 3 and 7.
4. Discharge the patient when the wound condition is stable, typically around 1 week postoperatively, with instructions for simple outpatient wound care.
5. Schedule the patient for readmission and the second-stage procedure 3-6 weeks after the initial surgery.
   NOTE: The optimal timing for the second stage may vary based on the patient's general condition and the appearance of the induced membrane, but it should generally not exceed 6 weeks.

4. Second-stage surgery: Cement removal and skin grafting

1. Administer anesthesia as required.
2. Carefully remove the PMMA cement spacer.
3. Inspect the wound bed for the presence of a well-formed, pink, and vascularized induced membrane.
4. Gently debride the surface of the membrane if necessary, taking care not to damage its integrity.
5. Harvest a split-thickness skin graft from a suitable donor site, such as the thigh.
6. Mesh the skin graft according to standard surgical practice.
7. Apply and secure the skin graft onto the prepared wound bed covered by the induced membrane.
8. Apply a non-adherent dressing and connect a Vacuum Sealing Drainage (VSD) system over the graft to ensure good contact and stability.
   1. Set the VSD negative pressure to -125 mmHg in continuous mode.

5. Postoperative care and follow-up after second-stage surgery

1. Monitor the skin graft for take and any signs of infection or hematoma.
2. Perform the first dressing change approximately 5 to 7 days post-grafting.
3. Schedule regular follow-up visits to assess wound healing at 21, 35, and 70 days postoperatively.
4. Document healing rates, complications, and patient-reported outcomes.

Results

The following results demonstrate the typical outcomes observed when applying the described protocol for antibiotic-loaded bone cement-induced membrane formation in elderly patients with refractory lower limb wounds, compared to conventional VSD treatment.

A key objective of the protocol is effective infection control at the wound site. Representative microbiological data from a cohort of patients showed that while both the PMMA and VSD groups had high and comparable positive secretion culture...

Discussion

This protocol details a structured approach for managing refractory lower limb wounds in elderly patients by adapting the induced membrane technique, traditionally used in orthopedics, for complex soft tissue reconstruction. The success of this method hinges on several critical steps. First, a radical and thorough initial debridement is paramount, as it establishes the foundation for a viable wound bed and is crucial for managing any chronic wound¹⁸. Second, the antibiotic-to-cement ratio must be ...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Antibodies & Assays
Anti-CD31 Primary Antibody	Abcam (Cambridge, UK)	ab28364	Rabbit polyclonal; Dilution 1:50
Anti-CD34 Primary Antibody	Abcam (Cambridge, UK)	ab81289	Rabbit monoclonal [EP373Y]; Dilution 1:100
Anti-ERG Primary Antibody	Abcam (Cambridge, UK)	ab92513	Rabbit monoclonal [EPR3864]; Dilution 1:250
Anti-VEGF Primary Antibody	Abcam (Cambridge, UK)	ab46154	Rabbit polyclonal; Dilution 1:100
Digital Slide Scanner	Leica Biosystems (Nussloch, Germany)	Aperio AT2	For whole-slide imaging (Optional)
Electric Dermatome	Zimmer Biomet (Indiana, USA)	Jan-01	For harvesting split-thickness skin grafts
Equipment & Instruments
Formalin Solution (10%)	Generic Medical Supplier	Hospital Pharmacy Supply	Neutral buffered formalin for tissue fixation
Hydrogen Peroxide (3%)	Generic Medical Supplier	Hospital Pharmacy Supply	For wound irrigation during debridement
IHC Detection Kit	Agilent Dako (California, USA)	K5007	EnVision+ System-HRP (DAB)
Iodophor Solution (0.5%)	Generic Medical Supplier	Hospital Pharmacy Supply	Povidone-iodine antiseptic for irrigation
Light Microscope	Olympus Corporation (Tokyo, Japan)	BX43	Equipped with DP73 camera for image capture
Microbiological Culture Swabs	BD (Becton, Dickinson and Co.)	BBL CultureSwab	For aerobic/anaerobic bacterial collection
Microscopy & Software
Negative Pressure Therapy Unit	Guangzhou Runhong Medical Technology Co., Ltd. (Guangzhou, China)	Welsuc NPWT Unit	Portable unit providing -125 mmHg continuous pressure
Non-Adherent Dressing	Smith & Nephew (London, UK)	Jelonet	Paraffin gauze dressing to protect graft/spacer
PMMA Bone Cement	Heraeus Medical GmbH (Wehrheim, Germany)	PALACOS R	High-viscosity bone cement; 40g/pack
Reagents & Drugs
Sterile Normal Saline (0.9%)	Generic Medical Supplier	Hospital Pharmacy Supply	For irrigation and cooling during polymerization
Surgical Sutures	Ethicon, Johnson & Johnson (NJ, USA)	Ethilon 3-0	Nylon sutures for spacer fixation/wound closure
Tissue Forceps and Scissors	Generic Surgical Supplier	Standard Surgical Set	For debridement and graft preparation
Vancomycin Hydrochloride	Zhejiang Medicine Co., Ltd. (Zhejiang, China)	0.5 g / Vial	Powder for solution; mixed with PMMA at 1:20 ratio
VSD Foam Dressing Kit	Guangzhou Runhong Medical Technology Co., Ltd. (Guangzhou, China)	Welsuc VSD Kit	Polyvinyl alcohol foam with drainage tubing
Wound Care Supplies
Statistical Software	IBM Corp. (Armonk, NY, USA)	SPSS v26.0	For all statistical analyses