C-M Type III chronic tibial osteomyelitis as a localized infection involves full-thickness cortical bone as well as the medullary tissue, which may develop to a diffused infection if not well managed. However, impaired local vascular condition on bone sclerosis and sequestrum make it difficult for parental antimicrobial therapy alone to achieve satisfying local effects, even with a prolonged course of application. Besides, Staphylococcus aureus as the most frequently detected pathogen in osteomyelitis is prone to produce biofilm, which irreversibly binds to the surface of the bone and on the internal implants, causing the infection to be stubborn and hard to eliminate . To address this embarrassing situation, surgical intervention is the cornerstone for the treatment of osteomyelitis, it not only removes the necrotic tissues but destroys the biofilms caused by pathogens. Therefore, stimulating the local blood supply and enhancing the antimicrobial effects of antibiotics.
For localized tibial osteomyelitis, surgical principles may be interpreted as the combination of “radicalization” and “limitation”. The principle of “radicalization” requires thorough removal of necrotic tissues and some adjacent healthy bone, to create a relatively clean wound for following reconstructive steps, while the principle of “limitation” requires to preserve as much healthy bone as possible (under the premise of thorough debridement, of course), to prevent the complication of postoperative fractures or deformities. Therefore, conventional aggressive debridement technique for diffused tibial osteomyelitis, segmental bone resection, is unsuitable for the treatment of localized tibial osteomyelitis. To match the demands mentioned above, local debridement (deroofing associated with the intramedullary debridement) is introduced as the treatment of localized tibial osteomyelitis, and the effects are satisfying. In a former study, Rodney K. Beals et al. reported 30 consecutive cases with tibial osteomyelitis, which included 1 case with Cierny-Mader type IIIA and the other 8 cases with type IIIB. The treatment methods of localized osteomyelitis included local debridement only in 5 cases, local debridement and muscle flaps coverage in 2 cases, and multiple debridement and posterior-lateral bone graft in 1 case. All of cases achieved good outcomes at the end of follow-up. Hakan Kinik et al. treated 26 cases with chronic localized osteomyelitis in his work. Those patients were treated with deroofing and local debridement, irrigation, vancomycin-impregnated PMMA beads implantation at first stage, followed by re-debridement, and PMMA beads removal 6 to 8 weeks later. Within a mean follow-up of 3.6 years, all patients achieved infection remission with normal clinical parameters, even though 3 patients had to receive re-debridement in the interval.
In our study, this classical local debridement technique was also employed, for effective removal of necrotic tissues. The main difference is the replacement of temporary antibiotic-impregnated PMMA beads or autologous tissues grafts by biodegradable antibiotic-impregnated calcium sulfate, which undoubtedly has its unique advantages. Primarily, the predictable high local antibiotic concentration (hundreds to thousands times higher than MIC in first 24h to 48h) and comparatively long therapeutic duration (several weeks to months) [5, 17, 18] provided by the degrading antibiotic-loaded calcium sulfate undoubtedly eliminates more residual pathogens while significantly shortens the conventional duration of systemic antibiotics administration. Moreover, similar to PMMA, the well-reported osteo-conductivity of calcium sulfate provides a crystalline structure for the osteoblasts perivascular mesenchymal tissues and osteoprogenitors, along which osteoblasts and the others crawl easily and eventually achieve the self-repair without autogenous bone grafts[19, 20]. While combined with the biodegradation characteristic of calcium sulfate, it allows orthopedists to accomplish debridement and reconstruction within one operation only, significantly avoiding the redundant reconstructive procedures.
With application of antibiotic-loaded calcium sulfate implantation, generally satisfying outcomes were achieved in our study at the end of follow-up. This was well illustrated by the fact that 88.4% of our patients achieved infection remission after first operation. Even for patients with recurrence, a chance for re-debridement could be preserved and managed accordingly. This extremely high remission rates were similar to the previous study by J. Y. Ferguson et al., who managed 144 cases with type III chronic osteomyelitis (195 cases, totally) using local debridement and implantation of tobramycin-contained calcium sulfate beads. Their records showed only 11 cases (7.6%) of type III chronic osteomyelitis recurred within a mean follow-up of 3.7 years, while most of the cases were successfully managed by re-debridement and antibiotics usage. However, although the samples of their study were relatively large, it contained a variety of infection sites (femur, tibia, humerus, radius, ulnar, pelvic and even calcaneus) and the four stage types of Cierny-Mader classification. Thus, their study ineluctably lacked an in-depth discussion on a single type and site of chronic osteomyelitis. In another comparative study, Albert Ferrandoet al. received a similar result after using topical antiobitic delivery system on chronic osteomyelits. They compared the efficacy of bioglass (BAG-S53P4) and calcium sulphate antibiotic beads in the treatment of chronic osteomyelitis. For 13 patients (7 on tibia) with antibiotic-loaded calcium sulfate implantation, 12 patients achieved infection remission during the follow-up.
While infection elimination was effective, associated complications were also of concern. Prolonged aseptic drainage was the most frequent recorded complication in our study, with a relatively high rate of 30.0%. This incidence was variant from person to person, primarily depending on the volume of implanted calcium sulfate and the abundance of soft tissues coverage. To our study, poor soft tissue coverage in the medial surface of tibia, scar formation surrounding to the focus and large volume implantation of calcium sulfate might interpret the high incidence of postoperative drainage. Kallala R et al. previously concluded a 4.2% incidence of prolonged aseptic drainage after calcium sulfate implantation, compared to the higher incidence of 15.4%, 33%, 27% respectively in other studies. If not accompanied with typical presentations, positive inflammatory markers and imaging examination, prolonged aseptic drainage alone should not be considered as a sign of infection recurrence, since it is a common presentation produced by the gradual degradation of calcium sulfate. Though the liquid is sterile, however, immediate management is of great necessity, or a soggy gauze is prone to cause wound infection. Generally, it can be well-managed with regular dressing and wound care. Other effective methods to prevent from aseptic drainage might include employing a flap or muscle flap when the soft tissue of tibia is too poor to cover, using lateral incision instead of medial incision, and implanting less antibiotic-loaded calcium sulfate if a medial incision is applied. Another complication needing attention is the, not very satisfying, self-restored shape of tibia in 17 cases during the follow-up, which was well-illustrated on X-rays. We suspect this situation might be attributed to the unconfirmed relation between degradation of calcium sulfate and growth of osteoblasts, yet there is no evidence in former studies to support our hypothesis. Although the shape of the tibia in these cases was not well-restored, however, there was no operation-related fracture or tibial bowing effect was recorded during the follow-up, which means that the tibia still has enough strength to bear the weight.
To our best knowledge, separate study for evaluating C-M type III tibial osteomyelitis is still rare. Our study might be the first to assess the outcomes of this technique for a single-stage treatment of chronic localized tibial osteomyelitis, with a larger number of patients. The drawbacks of our study were also obvious. To begin with, its retrospective characteristic means only limited information was available. Thus, it inevitably reduces the credibility of our study. In addition, outcomes of this study were not compared with those of other surgical methods, a comparative study is necessary to be carried out. Finally, we included osteomyelitis caused by fracture and related treatment, hematogenous transmission and penetration infection in our study. However, no matter whether chronic localized osteomyelitis was caused by fracture, hematogenous transmission or continuous penetration, the treatment protocols for localised osteomyelitis were similar ------ local debridement plus antibiotics-loaded calcium sulfate implantation. So, we think that including all these types in this study was rational.