The Classic: A Clinical Staging System for Adult Osteomyelitis

INTRODUCTION Jon Terry Mader (Fig 1) was born on March 21, 1944 in Madison, WI. He earned his BA and MD degrees at Wabash College at Indiana University in 1966 and 1970, respectively. He trained in Internal Medicine at the University of Texas Medical Branch in Galveston, TX and made his career there in the Division of Infectious Disease in the Department of Internal Medicine. At the time of his death on October 25, 2002, he had risen to the positions of Professor of Medicine, Professor of Pathology, and Adjunct Professor of Orthopaedic Surgery. During his life, he published more than 145 peerreviewed papers on osteomyelitis, antibiotic therapy, hyperbaric oxygen, joint infections, the foot in patients with diabetes, and the use of the Ilizarov technique for the treatment of musculoskeletal infections. He also was the principle investigator in numerous funded research projects and the coauthor of Musculo-Skeletal Infection. He died when the book was in its final stages of production.Fig 1.: John T. Mader, MDIn addition, Dr. Mader was a gifted athlete, Eagle Scout, captain in the U.S. Naval Reserve, and regarded with respect and affection by his patients and colleagues. Henry H. Sherk, MD At the University of Texas Medical Branch (UTMB) in Galveston, Texas, the adult osteomyelitis service now treats ten new cases of osteomyelitis each month. Since January 1981, 425 patients have been evaluated and 900 procedures performed to treat 240 lesions. In our experience, the treatment of adult osteomyelitis is influenced by four factors: the condition of the host, the functional impairment caused by the disease, the site of involvement, and the extent of bony necrosis. Without reference to these factors, it is difficult to compare the results of different treatment protocols 1–5 and the effectiveness of new therapeutic modalities. 6–9 The UTMB classification of adult osteomyelitis 10 combines four anatomic types (the disease) with three physiologic classes (the host) to define 12 clinical stages (Table I). A distinction between the acute and chronic process has not been necessary. 11 The classification system incorporates the four prognostic factors, delineates treatment for progressive stages of the disease, and provides guidelines for the use of adjunctive therapies.TABLE I: The UTMB Staging System for Adult OsteomyelitisTHE UTMB TREATMENT PROTOCOL FOR ADULT OSTEOMYELITIS ( TABLE II)TABLE II: UTMB Treatment Protocol for Adult OsteomyelitisTABLE II: UTMB Treatment Protocol for Adult Osteomyelitis (Continued)The UTMB prospective study of adult osteomyelitis began in June 1981. The methods have remained unchanged except for the antibiotic recommendations for emergency coverage and for acrylic bead mixtures. The protocol itself is unique: patient selection and medical/surgical treatment are predetermined by the clinical staging system; the preoperative antibiotic program is based on outpatient biopsy data, and the patient follow-up system correlates a clinical and biologic response to therapy. Patient Evaluation Condition of the host. Host deficiencies influence treatment options, prognosis, and the interpretation of treatment results. Following debridement surgery, the host must be able to impede infection, resist contamination, heal surgical wounds, and tolerate the metabolic stress of sequential surgeries. A list of factors influencing the ability of the host to elicit an effective response to infection and treatment is found in Table III. Local factors lead to a vascular compromise of bone and soft tissue. Systemic compromise affects immune surveillance, metabolism, leukocyte function, and/or large vessel disease. Local and systemic factors may combine (e.g., diabetes mellitus).TABLE III: Systemic or Local Factors that Affect Immune Surveillance, Metabolism, and Local VascularityDisability of the patient. The functional impairment caused by the disease, the reconstruction options, and the metabolic consequences of aggressive therapy influence the selection of treatment candidates. A draining sinus with minimal pain and/or dysfunction is not, by itself, an indication for surgical treatment. At times, the procedures required to arrest or palliate the disease are of such magnitude that treatment can lead to loss of function, limb, or life. In these latter instances, quality of life is the major factor influencing the decision to pursue therapy. Physiologic Classification (Host). At UTMB, the condition of the host and the relative disability caused by the disease are combined in a physiologic classification (Table I). A patient with a normal physiologic response to infection and surgery is designated an A-Host; a compromised patient is classified a B-Host and will have either local (BL), systemic (BS) or combined (BL,S) deficiency in wound healing (Table III). When the treatment or results of treatment are more compromising to the patient than the disability caused by the disease itself, the patient is classified a C-Host. Thus, the selection of surgical candidates may vary from institution to institution until there has been a standardization of concepts, methods, and techniques. Disease Assessment Persistent osteomyelitis is a surgical disease. Since debridement is the unchallenged cornerstone of successful therapy, a classification of osteomyelitis based on the site of necrosis will have specific implications for surgical management. Using such a system, four anatomically defined types of osteomyelitis become apparent: medullary, superficial, localized, and diffuse (Fig. 1). However, the condition of the host, regional vascularity, local milieu, and extent of necrosis will influence the natural history of the disease. 11Fig. 1: Anatomic classification of adult osteomyelitis.Anatomic classification. The medullary and superficial types of osteomyelitis share a pathophysiologic component: soft tissue compromise. In medullary osteomyelitis the primary lesion is endosteal. The etiology of the disease is variable but the nidus remains constant: ischemic scar, chronic granulations, and splinter sequestra within the medullary canal. In superficial osteomyelitis the problem is on the surface of the bone. This is a true contiguous focus lesion. A compromised soft tissue envelope either begins or perpetuates an exposure of the bone. The involved surface may be on an old saucerization, and healed Papineau graft, the prominent callus of a healed open fracture, or the metatarsal head in a neuropathic foot ulcer. The hallmark of localized osteomyelitis is full-thickness, cortical sequestration and/or cavitation. It is a discrete lesion within a stable bony segment. Although localized osteomyelitis usually follows trauma, it often has the combined features of medullary and superficial osteomyelitis and may even result as an extension of either of these two entities. Diffuse osteomyelitis is a permeative, circumferential, or through-and-through disease of hard and soft tissue. In this type, an intercalary segment of the skeletal unit must be removed in order to resect all the compromised tissue. Instability is present either before or after a thorough debridement. Stabilization is an essential factor in the treatment and separates the diffuse lesion from the other types of osteomyelitis. Infected nonunions, end-stage septic joints, and through-and-through metaphyseal/epiphyseal lesions of the proximal femur are examples of this type of osteomyelitis. Clinical staging of adult osteomyelitis. The four anatomic types of osteomyelitis are numerically ordered according to the complexity of the disease and/or its treatment: I—medullary; II—superficial; III—localized; IV—diffuse (Table I). In our classification system, the anatomic type (I-IV) is combined with the physiologic class (A-C) to designate one of 12 clinical stages of adult osteomyelitis. The clinical stage can change during the course of treatment (Table IV).TABLE IV: Clinical Stage ManipulationMicrobiology The bacteria responsible for the infection may be reliably isolated in two ways: preoperative biopsies, or from tissue sampled at the time of debridement surgery. 15 All isolated pockets of granulation tissue or necrosis must be sampled. Whenever possible, an antibiotic regime tailored to the sensitivities of all organisms isolated from biopsy material obtained in the outpatient setting is begun prior to debridement. 16 At the first and all subsequent debridements, multiple biopsies are obtained again for aerobic/anaerobic cultures and histologic evaluation. During therapy, antibiotic coverage may be changed or modified on the basis of clinical findings, serial debridement isolates and their sensitivities, inadequate serum bactericidal levels, abnormal laboratory studies, and/or patient intolerance. Antibiotics are given for six weeks after the last major debridement surgery. 16 At UTMB, all isolated organisms are placed in defibrinated sheep blood and stored at −70°C for future reference. Outpatient intravenous antibiotic therapy is utilized once serum bactericidal levels and/or surgical wounds permit. 13 Surgical Treatment Osteomyelitis surgery is disciplined and demanding. The average number of operations for a limb-salvage patient in our 1983 series as 3.8 procedures. Depending on the clinical stage of the disease and the planned reconstruction, the diagnostic biopsies, debridements, and reconstructions may be combined or performed separately. Biopsies are usually performed in the outpatient setting under local anesthesia. The organisms are thereby established, and questionable areas of involvement are assessed histologically. Debridement. As in musculoskeletal tumor surgery, careful preoperative planning is critical to achieve a high rate of success and to minimize wound complications in the patient with osteomyelitis. The debridement is direct, atraumatic, and executed with the reconstruction in mind. Whenever possible, the incisions are laced between myocutaneous territories, at times disregarding previous incisions. Soft tissue retraction is minimized by careful wound planning. Sinus tracts are excised if present for more than one year. All dead or ischemic hard and soft tissues are excised unless a palliative procedure has been chosen from the start. The extent of the debridement is predictable from the preliminary assessment. 16 If complete excision will threaten stability, external fixation and/or a bypass graft may be necessary prior to or during debridement surgery. At UTMB, the instruments used in the debridement procedures include scalpels, curettes, straight stem and angled dental mirrors, and a pneumatic bone scalpel. Because of the speed and gentle efficiency of this pneumatic system, osteotomes are rarely used. Tetracycline labeling, fluorescein, and other dyes have not been useful. The debridement process begins in a centrifugal fashion. This technique retains an outer ring of bone that shares its circulation with the attached soft tissues. This shell of bleeding bone is dressed with either bone grafts, antibiotic beads, or soft tissue at the time on reconstruction. The residual cortical and cancellous bone must bleed uniformly (Fig. 6). Definitive wound management usually takes place five to seven days after the last debridement. In the interim, the wound usually is left open.Fig. 6: Tangential excision with the bone scalpel is carried down to uniform haversian or cancellous bleeding (the paprika sign 17).Dead space management. The techniques of managing the dead space created by debridement surgery are illustrated in Fig. 7. Secondary intention healing is discouraged; the scar tissue that fills the defect later becomes avascular and may lead to recurrent drainage. Similarly, suction/drainage systems are rarely used. The goal of surgery is to replace dead bone and scar with durable, vascularized tissue.Fig. 7: Methods of dead space management.A complete wound closure is secured whenever possible. Cancellous bone grafts are placed beneath local or transferred tissues when structural augmentation is necessary or a significant dead space will otherwise persist in the bone. Bypass grafts are performed when an in situ reconstruction will prove inadequate or is not feasible (Fig. 8). Open cancellous grafts 14 are used sparingly as the epithelial coverage is not durable and may lead to superficial ulceration following minor trauma or persistent venous stasis. 18 They are, however, simple to do, effective, and particularly useful when a free or local tissue transfer is not an option.Fig. 8: Bone graft techniques.Antibiotic-impregnated acrylic beads 6 have been used to sterilize and/or temporarily maintain a dead space created by debridement surgery. In our experience, any patient-compatible, powdered antibiotic may be safely delivered in this manner; it must first be adequately pulverized and then thoroughly mixed with the powdered cement prior to adding the monomer. 10 Thermal stability of the antibiotic(s) is not necessary when the beads are fashioned in the dough phase. 19 Two or three antibiotics may be combined in a single mix. Before using this technique, the debridement must first be thorough and the wound flora ideally sensitive to the antibiotic mixed with the cement. The beads usually are removed within two to four weeks and replaced with cancellous bone grafts. If strung on a line, 6,20 the beads are removed in ten to 12 days. The five antibiotics most commonly used in beads and their mixing ratios are listed in Table V. If the volumetric ratio of the powders exceeds 24cc/120cc (antibiotic/40gm cement), the cement will not harden reliably.TABLE V: Antibiotic Bead Cocktails June 1984Application Stage IA,B,C: Medullary Osteomyelitis ( Fig. 9A, 9B)Fig. 9A: Stage I classification of osteomyelitis.Fig. 9B: Treatment algorithm for Stages IA and IB.Once the medullary process extends into the soft tissues, the usefulness of medical management alone will depend on the site and extent of the process, the physiologic class of the patient, and the functional disability expected from disease and treatment. The majority of the patients with Stage I osteomyelitis are systemically compromised hosts and suffer stage progression to Stage IIIB or IVB. When extension occurs, the process usually becomes intraarticular and the subchondral bone and articular cartilages sequester. or usually is necessary until and/or bone grafts This stage often is and on the first the dead space can be with simple of the soft tissues. The is obtained and wound closure is by antibiotic the of the medullary a of the is This minimal to the is for an and/or medullary When using the latter technique, the disease must be within an or to the of an otherwise a of and will be necessary. The bony be placed of the soft tissue closure to of the wound and persistent drainage. The operations for Stage I lesions whenever medullary involvement is present (Fig. techniques are to each stage but combine as the complexity of the disease Osteomyelitis ( Fig. Stage classification of osteomyelitis.Fig. Treatment algorithm for Stages and management of superficial osteomyelitis with soft tissue soft tissues are excised and the bony surface is removed until the paprika sign is A or free tissue transfer is performed at the or as a The to the success of this is a and prior to soft tissue If the Stage lesion is in the acute or treatment with and/or local wound may be The wounds heal unless tissue local factors, or patient are not At UTMB, the septic joint is classified as a superficial osteomyelitis The soft tissue of the process is the compromised The disease and to treatment as the other Stage with host and to and sequestration if The operations for Stage lesions whenever superficial involvement is present Stage Osteomyelitis ( Fig. Stage classification of osteomyelitis.Fig. Treatment algorithm for Stages and hallmark of this process is cortical sequestration and cavitation. surgery usually saucerization, medullary scar and superficial The reconstruction will depend on the dead space the of the residual and the site of The procedures include hard and soft tissue cancellous bone grafts, bypass and simple wound is when the extent of the debridement the bone at for Stage lesions are and or of infection may be present within the treatment to prior or external The preliminary usually these lesions and an staging and treatment. 16 The operations for Stage lesions whenever and often include procedures from Stage I and treatment protocols (Fig. Stage Diffuse Osteomyelitis ( Fig. Stage classification of osteomyelitis.Fig. Treatment algorithm for Stage and are in this stage and the for a wound healing bone graft infections, and stress The techniques used in managing Stage osteomyelitis are and executed with a procedure in mind. The preoperative planning must be and to tissue in the and in use of cancellous bone fixation medullary and cortical are used and are listed according to our and of In our experience, external fixation is the and most of When the host is to or tissues, the infection becomes The nidus will persist until the of the process is by therapy. Although debridement surgery usually is the treatment of lesions to of therapy. The in these wounds is scar not bone This is minimal necrosis osteomyelitis. of host is the treatment of than debridement surgery. osteomyelitis. osteomyelitis of the is an of osteomyelitis with minimal necrosis. When the Stage I lesion to Stage in the the process usually becomes intraarticular and the within the septic The blood and high cancellous to cortical bone ratio a of subchondral bone and medullary The disease will arrest if is and the host with antibiotic therapy. The is a osteomyelitis. is a Stage lesion with minimal necrosis. these lesions are in management of Stages or treatment involved a system or intention In the preliminary dead bone can be to for a chronic the ischemic soft tissue to bony is the nidus that to persistent disease. include and soft tissue hyperbaric therapy, or Infected with minimal bony necrosis. In this the problem again is scar tissue. and are by and the local compromise. and/or bypass surgery will the soft tissue and If the necrosis is more than superficial in septic often bony UTMB June to patients with adult osteomyelitis evaluated and on our 10 Definitive treatment was given to patients with and surgical procedures performed (Table a first five a limb-salvage the primary in Stage Stage Two of the patients with at and 12 but two patients a with and a with an During the first six of therapy there three one to trauma at four one from at three and the from an bleeding at three Classification of of Adult Osteomyelitis at UTMB the patients The of the patients not by our service either the or lesions for or osteomyelitis with minimal necrosis patients our limb-salvage protocol and for a of two (Table these limb-salvage and at Two patients had more than one the number of to Treatment to an arrest in of the Two and at treatment (Table one and four defined by recurrent with minimal necrosis tumor and The for inadequate debridement fixation and stress the treatment with of the four treatment in the an was until the and two compromised patients stage progression and a after a limb-salvage The other had an at 12 disease arrest Two Treatment lesions prior to treatment. Since there four for of these lesions had a normal rate and an abnormal at 18 three and two of these six patients with normal at and the two palliative procedure was performed in the of patients this rate and are abnormal at The organisms isolated in patients are listed in Table was the most commonly isolated than two organisms present in of our The number and type of organisms had on the of an debridement was In all antibiotic coverage was and for the of the treatment in rate for Stage and are in The Stage I is a of A and hosts to the problem that in using a rate to compromised hosts are by minor and that this In Stage the rate not before three a to soft tissue infections. The for Stages and the wound healing with bone grafts, infections, and rate for Stage and I lesions are in rate is an inadequate follow-up in these to The response of the in the a patient with a The clinical stages of adult osteomyelitis may during their natural history and their response to therapy (Fig. anatomic or physiologic stage progression the of treatment. The for disease arrest is when a of the process can be by and to Stage or will whenever Stages I and with Stage lesions suffer the number of complications and the majority of treatment The Stage rate (Fig. a of with type lesions deficiencies with successful host (Table The and arrest rate in these patients have the Stage results have our to the and treatment of host The the of and the for effective adjunctive to the The rate of three with lesions to A by host our experience, has been in persistent osteomyelitis in The of this technique have not been anatomic of after have in tissues with and as as with This is not to acute and and to have a for bone. The methods used in the management of wounds have influenced our results. All of the to normal by 12 Similarly, of the wounds with primary closure (Fig. in Stages and normal at one year. The of wound healing in reconstructions to the in the in the follow-up of the Stage and lesions at 12 if dead space management cancellous bone grafts and/or an However, this to and at 18 and respectively. Two of our treatment had at one normal rate prior to a of disease at seven and 12 patient with a has prospective study define the of sequential in following cases of adult osteomyelitis. The treatment and of adult osteomyelitis with the clinical stage of the disease. The UTMB staging system provides guidelines for the use of adjunctive and a basis for treatment protocols from institution to may prove a sensitive for following patients with osteomyelitis.