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 vessels 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 frequent detected pathogen of osteomyelitis prone to produce a biofilm, which irreversibly binds to the surface of the bone and the internal plant, causing the infection stubborn and hard to be eliminated [14]. To address this embarrassing situation, surgical intervention is the cornerstone for the treatment of osteomyelitis, since 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 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 is 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 cases achieved good outcomes at the end of follow-up[16]. 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 received infection remission with normal clinical parameters, even though 3 patients suffered from re-debridement in the interval.
In our study, this classical local debridement technique was also introduced for the removal of necrotic tissues. The main difference lies in the replacement of temporary antibiotic-impregnated PMMA beads or autologous tissues grafts with biodegradable antibiotic-impregnated calcium sulfate, which undoubtedly owns its unique advantages. Primarily, the predictable high local antibiotic concentration (hundreds to thousands times higher than MIC in first 24 h to 48 h) and comparatively long therapeutic duration (several weeks to months) [5, 17, 18] produced 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 osteoprogenitor, 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 previous study of 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 cases were successfully managed by re-debridement and antibiotics usuage[21]. 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 four types of Cierny-Mader classification. Thus, their study ineluctably lacked of the in-depth discussion on a single type and site of chronic osteomyelitis.
While infection elimination was effective, associated complications were also of concern. Prolonged drainage was the most frequent recorded complication in our study, with a relatively high rate of 30.0%. This incidence was various 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 tissues coverage in the medial surface of tibia 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 drainage after calcium sulfate implantation[9], compared to higher incidence of 15.4%[21], 33%[22], 27%[23] respectively in other studies. Though the liquid is sterile, immediate management of this postoperative drainage is of great necessity, or a soggy gauze is prone to cause wound infection. Generally, its methods included good suture and placement of drainage tubes during operation, frequent dressing change or even the assistance of VAC device. For cases with continuous draining, we deemed that a re-debridement to remove the lump was available, as long as the ease of presentations of inflammation had been achieved for weeks. Another complication needing attention is the, not very satisfying, self-restored shape of tibia during the follow-up, which was 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 are no evidence in former studies was detected to support our hypothesis. Fortunately, no case of operation-related fracture was recorded.
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 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, 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.