Limb Salvage After Osteomyelitis Using an Absorbable Antibiotic Cement Spacer

It is well established in the literature that systemic antibiotics have limitations in treating diabetic foot infections. Seabrook studied the antibiotic level in a diabetic foot at the time of sepsis during surgical debridement.¹ The sample was taken at the time of surgical debridement with antibiotic application 1 hour prior. The author found that only 12/26 patients showed the presence of antibiotics in the surrounding muscle tissue of a septic patient with diabetes when administering the antibiotic an hour before surgery. Only 6 of the 26 patients had therapeutic antibiotic levels within the foot.¹ Due to the low level of systemic antibiotics found within the pedal bone and soft tissue, local antibiotics can become a valuable addition to treating pedal osteomyelitis.

Polymethyl methacrylate (PMMA) antibiotic beads and cement are widely used and accepted as part of treatment plans for osteomyelitis. Klemm first published on the results of using PMMA beads in 1979 with a 91.4% cure rate for chronic osteomyelitis when used concurrently with surgical debridement.² However, there are a few risks with using nonabsorbable antibiotic cement, including inconsistent drug elution rates, the need for secondary operation for antibiotic bead/spacer removal, nidus for bacteria to adhere, tissue necrosis, vasodilation and high inflammatory reaction.^3,4    

Absorbable antibiotic cement may expand the usage of, and minimize the issues related to, nonabsorbable antibiotic beads. There are 2 primary substances in absorbable beads: calcium sulfate and calcium phosphate. Calcium sulfate is an absorbable synthetic material that can release antibiotics at a more constant rate after implantation. The advantages of absorbable beads include biofilm resistance,⁵ absorbability,⁶ low inflammatory response, minimal drainage, and a minimal nidus for infection.^6,7 Moreover, research shows that the concentration of antibiotics released from calcium sulfate beads has been as high as 3 times that of antibiotics released from PMMA beads in vitro.⁸ Absorbable antibiotic beads can slowly release high concentrations of antibiotics locally for up to 6–10 weeks and are known to dissolve into the surrounding tissue from that point onward.⁹ In my experience, relative contraindications to the use of antibiotic beads include patient hypersensitivity to particular antibiotics or cement material, wounds that are not large enough to hold antibiotic materials, open wounds without a soft tissue envelope, and unsalvageable limbs.

The standard indications of antibiotic beads and cement today are to prevent infections (open fractures, bone infections, soft tissue infections), infected total joint replacements, or as a bone void filler for dead space management. Patients unable to tolerate systemic antibiotics or patients with kidney or hepatic disease can safely tolerate the local implantation of antibiotic beads/cement.

Case Report: Osteomyelitis Following Arthrodesis

Below is a case report on a non-diabetic male with osteomyelitis after an arthrodesis procedure. With an absorbable antibiotic cement spacer, we salvaged the first ray, which is crucial in preventing subsequent foot and ankle issues and further amputations.

The patient is a 67-year-old male with a past medical history significant for hypertension, arthritis, and gout. The patient had undergone a first metatarsophalangeal joint (MTPJ) fusion performed by another surgeon on 11/5/2020 with ensuing surgical dehiscence. The patient was immediately referred to infectious disease and placed on oral antibiotics. Despite conservative care and treating the soft tissue infection, the patient failed to improve and underwent removal of hardware and debridement of bone with bone biopsy on 12/23/2020. Bone biopsy at the level of the MTPJ was positive for acute osteomyelitis, resulting in bone excision at the level of the MTPJ and application of antibiotic cement spacer.

At his initial presentation to our clinic, he had developed a second surgical dehiscence after his last surgery (Figure 1). Upon obtaining radiographs (Figures 2 and 3), the antibiotic spacer appeared more prominent than the void created from the debridement of the MTPJ area, which presumably led to wound healing issues.

The patient had failed multiple efforts at conservative wound care management. The patient was taken back to the operating room on 02/26/2021 for an exchange of antibiotic cement spacer, bone biopsies, and the application of a mini-rail external fixator (Figures 4 and 5). Bone biopsies were obtained both at the metatarsal and at the proximal phalanx. Bone biopsy resulted in chronic focal osteomyelitis. The patient was treated locally with vancomycin-infused absorbable calcium phosphate antibiotic cement spacer and systemically with 6–8 weeks of IV antibiotic therapy. The patient was allowed to ambulate in a surgical shoe with a cutout for the external mini-rail.

The patient returned to the operating room for bone biopsies on 4/2/21 at the level of the metatarsal and base of the proximal phalanx. Biopsies at this time were negative for acute or chronic osteomyelitis.

The patient was planned to have a staged procedure with the removal of an antibiotic cement spacer and application of a bone graft to fuse the MTPJ. However, the patient wanted to wait until retirement before the final reconstruction. We discussed the risks, benefits, and alternatives of leaving the antibiotic cement spacer, and the patient understood and wanted to proceed with a later operation date.   

At the patient’s final follow-up six weeks after mini-rail removal, the patient ambulates in custom orthotics and has been wound- and pain-free to date (Figures 6 and 7). The patient is happy with his recovery as he has returned to his prior activity level, including playing sports such as golf.

Chandana Halaharvi, DPM, AACFAS, is in private practice in Houston.

References
1.    Seabrook G, Edmiston C, Schmitt D, Krepel C, Bandyk D, Towne J. Comparison of serum and tissue antibiotic levels in diabetes-related foot infections. Surgery. 1991; 110(4):671–677.
2.    Klemm K. Gentamicin-PMMA-beads in treating bone and soft tissue infections. Zentralbl Chir. 1979;104(14):934–42.
3.    Samelis PV, Papagrigorakis E, Sameli E, Mavrogenis A, Savvidou O, Koulouvaris P. Current concepts on the application, pharmacokinetics and complications of antibiotic-loaded cement spacers in the treatment of prosthetic joint infections. Cureus. 2022 Jan 5;14(1):e20968. doi: 10.7759/cureus.20968. PMID: 35154947; PMCID: PMC8815820.
4.    Shridhar P, Chen Y, Khalil R, Plakseychuk A, Cho SK, Tillman B, et al. A review of PMMA bone cement and intra-cardiac embolism. Materials (Basel). 2016; 9(10):821.     
5.    Delury C, et al. Determining the efficacy of antibiotic-loaded calcium sulfate beads against pre-formed biofilms: an in vitro study, in ASM Microbe. 2019: San Francisco, USA.
6.    Lazarou SA, Contodimos GB, Gkegkes ID. Correction of alveolar cleft with calcium-based bone substitutes. J Craniofac Surg. 2011; 22(3):854–7.
7.    Lei D, Zhanzhong M, Huaikuo Y, Lei X, Gongbo Y. Treatment of distal radius bone defects with injectable calcium sulphate cement. In (Zorzi A, ed.) Bone Grafting. 2012, InTech. pp. 125–134
8.    Udomkusonsri P, Kaewmokul S, Arthitvong S, et al. Elution profiles of cefazolin from PMMA and calcium sulfate beads prepared from commercial cefazolin formulations. J Vet Med Sci. 2012;74:301–305
9.    Ferguson JY, Dudareva M, Riley ND, et al. The use of a biodegradable antibiotic-loaded calcium sulphate carrier containing tobramycin for the treatment of chronic osteomyelitis: a series of 195 cases. Bone Joint J. 2014;96-B:829–836
10.    Somasundaram K, Huber CP, Babu V, Zadeh H. Proximal humeral fractures: the role of calcium sulphate augmentation and extended deltoid splitting approach in internal fixation using locking plates. Injury. 2013; 44(4):481–7.