The treatment of chronic osteomyelitis is a difficult clinical problem in orthopedics. The long-term recurrent inflammation of chronic osteomyelitis can cause skeletal deformation, joint stiffness, chronic sinus tracts, bone and soft tissue defects, and shortening, resulting in severe disability of the affected limb. Due to years or decades of untreated disease, patients are extremely mentally devastated and often choose to amputate their limbs in severe cases [1]. Local infection creates a local environment that inhibits blood circulation and bone regeneration, inhibiting or delaying bone healing [2]. The traditional treatment method is to first thoroughly remove the dead bone and inflammatory granulation tissue, eliminate the dead cavity and sinus tract, adequately and thoroughly drain the bone, control the infection, and then choose a suitable external fixation method to fix the bone after the local skin condition turns better. The treatment period is long, traumatic, and the number of surgeries is high, which is prone to complications such as severe bone defects, bone non-union, and deformed healing [3]. In recent years, with the gradual promotion of the Ilizarov distraction osteogenesis technique in China, many scholars have applied the distraction osteogenesis technique in the treatment of chronic osteomyelitis, especially those with bone and soft tissue defects or combined skeletal deformities, and achieved surprising results [4-7]. In this paper, we review the mechanism and technical points of clinical application of the distraction osteogenesis technique in the treatment of chronic osteomyelitis as follows.
I. Origin and development of the distraction osteogenesis (DO) technique for the treatment of chronic osteomyelitis
In the 1950s, Dr. Ilizarov in the former Soviet Union, faced with many disabled patients with chronic osteomyelitis complicated by bone defect, bone discontinuity and bone joint deformity left behind by the former Soviet Union after World War II, creatively designed and applied the annular external fixator and minimally invasive technique (Ilizarov technique) for the treatment of orthopedic and trauma, and obtained good clinical therapeutic effect, and after years of animal experiments and The Law of tension-stress (LTS), also known as the Law of tension-stress, was discovered after years of animal experiments and clinical observations, and the biological and mechanical principles of bone lengthening technology were proposed, which made bone lengthening technology widely used in the former Soviet Union. The Law of tension-stress assumes that a certain tension generated by slow and continuous stretching of living tissues is able to secondary and maintain the regeneration and active growth of certain tissue structures in the same way as fetal tissues, both of which are identical in terms of cellular mitosis.
The distraction osteogenesis (DO) technique was developed from the clinical practice of Ilizarov external fixation technique combined with the continuous summary of LTS biological theory [9-12], i.e., controlling the tensile stress of distraction to achieve bone and soft tissue regeneration, or distraction tissue regeneration technique. The core theory is that traction osteogenesis, i.e., continuous tension stimulates bone growth and causes proliferative compensatory adaptation of muscles, fascia, nerves, and skin, and after the end of tension, the new bone tissue is mineralized by the original intramembranous osteogenesis process and can be transformed into normal bone structure under physiological stress stimulation. DO techniques, Bone Transport techniques, and bone reconstruction techniques, all of which originate from the basic principles of traction osteogenesis [13]. Currently, traction osteogenesis is mostly performed through epiphyseal osteotomy (due to good collateral circulation in the epiphysis and large trabecular surface area, traction osteogenesis is faster than stem osteotomy), and external fixation devices are applied to gradually tractionally separate the severed ends and eventually produce new bone between the bone surfaces [14].
II. Mechanism of DO technique for chronic osteomyelitis
Dead bone formation, extensive local scar tissue and sinus tract formation, and poor circulation are the main reasons for the persistent chronic osteomyelitis. Then, complete removal of dead bone and other necrotic foci, repair of bone defects, reconstruction of local blood flow and promotion of bone healing are the keys to successful treatment. In contrast, DO technology can be applied to the treatment of chronic osteomyelitis to achieve simultaneous removal of dead bone, removal of lesions, bone lengthening and reconstruction of blood flow without the need for extensive bone grafting and additional trauma.
The mechanism of DO technology in the treatment of chronic osteomyelitis is: complete removal of infected lesions, repair of tissue defects by bone retraction, and reconstruction of blood flow and function of the affected limb. Numerous basic studies and clinical observations have confirmed that biological stimulation is the most important factor in promoting tissue regeneration, and that continuous distraction stress stimulation within physiological limits activates and maintains the regenerative capacity of tissues. The human skeleton, like epithelial and connective tissues, has great regenerative potential and plasticity. According to the DO technique theory, by giving the bones a suitable draft stress, the bones and their attached muscles, fascia, blood vessels and nerves will grow in parallel [15-16], increasing the limb lengthening to some extent. Slow and continuous stretching causes cell proliferation and biosynthesis to be stimulated and tissue metabolism becomes active. Numerous histological studies of the Ilizarov method have confirmed that bone formation is intramembranous ossification within a homogeneous area [8]. A central zone of traction is formed by type I collagen tissue, bridged in the adjacent zone where the vessels grow in, along the collagen bundle where proliferating and specific osteoblasts are deposited into bone-like tissue, which then expands into a longitudinal bone column zone of uniform diameter, with the entire bone column zone parallel to the traction force given by the fixation frame and bridged over the original bone section separated by traction, and finally the bone column spans and is connected. When traction is stopped, the bone gaps begin to heal, the bone columns interconnect and collagenize, and bone reformation occurs rapidly. Histologically, it was demonstrated that there was thin capillary growth between the bone columns, and blood vessels of uniform diameter expanded from the surface of the original bone end, and microangiography confirmed that the new blood vessels were in the same longitudinal direction as the new bone [17].Yang et al [18] demonstrated in an experimental study that the osteotomy site remained elastically connected after the Ilizarov external fixator was firmly fixed, and slow distraction caused abnormal tissue metabolism to be active and stimulated cell proliferation and In the middle of the lengthening area, a growth zone can appear, in which fibroblast-like cells form collagen fibers (arranged in the same direction as the distraction direction), and osteoblasts on the collagen fibers produce bone-like tissue and gradually form bone trabeculae, which gradually ossify after fixation; active smooth muscle cells appear in the middle layer of the vascular wall, and the new capillaries have many traffic branches that anastomose with the vessels in the soft tissue around the distraction area, forming the blood circulation between the lengthening area and its surroundings. The DO technique has achieved surprising results in reconstructing the blood flow to the limb [19,20].
III. Technical features and advantages of DO technique for chronic osteomyelitis
The advantages of external fixation stent are more obvious due to its minimally invasive, easy to operate, safe, easy to promote, and wide indications, especially in some cases of chronic osteomyelitis with bone defects and soft tissue defects.Ilizarov external fixation stent is the best device applied for progressive lower limb lengthening, joint or angular deformity correction, in slow distraction of bone lengthening, treatment of various bone and joint deformities Spiegelberg et al [22] concluded that the Ilizarov external fixation technique provides a solid and adjustable fixation system for the treatment of complex fractures, deformities, osteoarthritis and other difficult orthopedic diseases, which can maximize the protection of the soft tissues around the bone and promote the bone tissue to develop its potential. The external fixation frame can be adjusted in multiple directions, with de-angling, de-rotating, de-lateralizing and biomechanical axial compression. Therefore, the DO technique uses the Ilizarov annular external fixator with more advantages than the single-arm external fixator [23,24], which is designed to be firmly fixed by multiplanar fine kerf pins running through the limb and bone tissue and connecting the annular fixator, and then assembled into a three-dimensional structure with three to four screw rods, which can eliminate both shear and rotational stresses and exert its purely distraction stress or compression effect, as well as its periodic axial micro-movement during weight-bearing walking to promote bone healing.
Ilizarov first applied an external fixation brace for bone tissue handling based on the principles of DO technique, using a progressive approach with 4 daily extensions of 0.25 mm each. with this stress stimulation, limb tissues can regain their ability to grow. the advent of DO technique has revolutionized the principles of chronic osteomyelitis treatment. With this technique, the infected bone can be completely removed and a cortical bone osteotomy performed on the normal bone proximal or distal to the infected area. One or two sets of thin steel pins are inserted in the upper and lower part of the orthopaedic limb, and a metal ring of Ilizarov external fixation frame is installed to transfer the normal bone to the defect, with different attachments to the ring depending on the treatment needs. The effect of distraction and soft tissue repair and healing is achieved by pulling the device in different directions until bone healing is achieved. Full-ring, multi-planar cross-needle compression external fixation, solid and reliable fixation, uniform stress distribution, the bending stiffness of the Kirschner pin is much lower than the compression stiffness of the bone, low stress shading rate, adjustable fixation stiffness, bioelastic external fixation, there is no stress shading effect in the lesion area, which is common in traditional internal fixation methods. The surgical operation can be performed without incision or small incision, and the needle can be inserted far from the lesion area to minimize trauma. Patients can walk and move during the treatment, early functional exercise, bone healing and joint function recovery simultaneously, and basically no incision scars after the treatment, and the functional recovery is better. The surgeon can regulate the direction of movement of the fracture block during the whole fixation period, and the incidence of serious complications is low and the cure rate is high. Bone lengthening and segmental sliding techniques can correct both bone defects and limb shortening [23,25] and are more suitable for the treatment of large segmental bone defects [26]. Therefore, it can be said that the DO technique for the treatment of chronic osteomyelitis simultaneously has the advantages of less surgical trauma, complete lesion removal, reliable fixation, and the ability to move early [27], while external fixation facilitates the observation and management of injuries and infections.
IV. Problems that should be noted in the treatment of chronic osteomyelitis by DO technique
(A) Preoperative preparation: a comprehensive physical examination of the patient to clarify the presence of combined diabetes mellitus, malnutrition and anemia and to treat them accordingly. Determine the local soft tissue blood flow, understand the size and location of local dead bone, the size of bone defect, the form of original internal fixation, and clarify the degree of osteoporosis through X-ray film. The secretion on the trauma surface was taken for bacterial culture and drug sensitivity test, and sensitive antibiotics were used for regular treatment for 1 week, and the trauma surface condition was improved in preparation for surgery. The operator reads the X-ray film carefully, designs the Ilizarov bone external fixation method and decides the osteotomy site. The Ilizarov external fixation frame and corresponding components are assembled according to the defect site, limb circumference, soft tissue condition and X-ray alteration decision.
(B) Precautions for debridement and bone segment slippage
1.Clearance: design the surgical access according to the soft tissue defect to avoid the exposure of bone and important structures (tendons, joints, ligaments, large blood vessels and nerves); the principle of surgery is to clear the trauma and to facilitate drainage. After removal of the original internal fixation, all inactivated tissues were removed, and the sclerotic bone was excised to the point of bone bleeding at the broken end. The sinus tract was marked with dilute methylene blue and completely excised to eliminate the original dead space. The two broken ends were routinely cleaned to clear the bone marrow cavity, then the wounds were flushed with volume fraction 3% hydrogen peroxide, iodophor, and plenty of saline, surgical instruments and dressings were changed, and sterile towels were re-sterilized and laid. In cases where there is much secretion trauma closure, drainage is routinely placed and must be ensured to be unobstructed. Qu Long et al [28] used the “bull’s nose” drainage method, which can guarantee continuous and adequate drainage.
2. Precautions for the installation of Ilizarov external fixator through the needle
According to the type and scope of osteomyelitis and the presence of concomitant bone defect and skin defect, design or select the matching external fixator configuration before operation according to the principle of Ilizarov technique and the theory of bone external fixation structural unit, determine the position of osteotomy at the bone end and its pin-piercing method, set the ring external fixation frame on the calf to adjust the length to the appropriate position, find the osteotomy plane, and use two 2~2.5MM Kesch pins at the proximal end. The middle sliding bone segment can be fixed with 2MM full pins or threaded half pins [29] to maintain the force line and length of the limb and prevent rotation and axial shift. Three threaded half-pins were reinforced and fixed on the ring frame, and each nut and clip were tightened and fixed firmly, and a small 1CM longitudinal incision was made, and the periosteum was cut longitudinally, paying attention to the protection of the periosteum, and the bone end that needed to be slid and extended was osteotomized with an electric drill perforated osteotome, and after testing the ability to pull the sliding bone segment, the reverse pressure was applied to the osteotomy.
(C) postoperative treatment: postoperative application of antibiotics for about 1 week, postoperative to local swelling, pain slightly reduced after the start of functional exercise. In the early postoperative period, the isometric contraction of muscle groups and functional activities of adjacent joints should be started; in the prolongation period and the early stage of mineralization, part of the weight-bearing functional exercises should be carried out; in the late stage of mineralization, the weight-bearing should be gradually increased to the point of abandoning the abduction. In all cases of transarticular fixation, the nut of the external fixator should be loosened periodically and the joint should be moved appropriately to reduce the occurrence of severe joint stiffness. Postoperatively, iodophor is used daily to clean the pinhole, check the pin channel and pay attention to any infection and exudation. Rotate the nut 7~10 days after surgery to make the bone slowly slide to the distal end, and carry out bone transfer at the speed of 0.75MM-1MM/d (the nut has six sides, rotate one plane in 3 hours on average, rotate six sides in one day, one circle in total), the rotation speed can be changed appropriately according to the age, and the speed of bone transfer can be slowed down appropriately in older age, and the length of bone transfer can be decided according to the length of the diseased bone amputation. The length of bone removal is decided according to the length of the osteotomy of the diseased bone, and the length of bone removal and the osteogenesis in the periosteum are observed by regular film. When the bone is lengthened to the expected position, the soft tissue at the joint of the bone segment is cleaned to promote the healing of the bone segment. The local blood circulation and inflammation can be checked regularly, and for serious and complicated patients, secondary debridement and drainage of the trauma can be carried out, and X-ray films can be taken every 4 weeks for review, and the lengthening and orthopedic plan can be revised in time according to the X-ray performance. In order to facilitate the stress stimulation of the osteotomy to promote bone healing, we use the method of gradually reducing the fixation stiffness to remove the external fixator in phases after the orthopedic goal is achieved.
The criteria for complete removal of the external fixator are: healing of osteomyelitis, no recurrence is expected, repair of bone discontinuity, bone defects and skin defects, stabilization of soft tissue distraction for at least 1.5 months after deformity correction contracture, satisfactory bone healing with bone shaping and molding completed by bony surgery, and full weight-bearing walking of the affected limb for a few days after release of the fixator to observe the strength of the healing end of the bone. After removal of the external fixator, according to the bone quality of the soft tissue and the backbone, the corresponding orthopedic brace was worn reasonably for 2~3 months for walking. Due to the factor of elastic memory, patients with osteomyelitis combined with flexion knee contracture or clubfoot, postoperative attention was paid to prevent the recurrence of soft tissue deformity [20].
(iv) Efficacy assessment: clinical fracture healing time was determined based on fracture healing and radiographic review in follow-up patients; postoperative complications such as deep infection, skin necrosis, and fracture deformity healing were recorded in patients. The Paley et al. infected fracture (osteomyelitis) healing scale [30] can be selected for evaluation, excellent: healing of osteomyelitis and osteonecrosis, no recurrent infection, local deformity <7°, and limb inequality <2.5 cm; good: fracture healing, plus any two of the last three above; acceptable: fracture healing, plus any one of the last three above; poor: fracture not healed or re-fractured, or any of the last None of the above three is satisfied.
V. Summary
Compared with the traditional method of treating chronic osteomyelitis, DO technology has breakthrough advantages, mainly in: 1) the ability to remove the infected bone and inflammatory tissue more thoroughly; 2) the formation of bone defects through osteotomy slip lengthening, in the same period of curing osteomyelitis to repair bone and soft tissue defects; 3) the ability to correct different kinds of bone and joint deformities that accompany the reconstruction of the length of the limb and the mechanical axis of the lower limb 4. it can save lower limb stumps that are on the verge of amputation [20]; 5. it does not restrict the weight-bearing exercise of the limb during the treatment period and ensures good joint function; 6. it rarely recurs after the osteomyelitis is cured.
Currently, the DO technique is internationally recognized as the gold standard for the treatment of chronic osteomyelitis with bone defects [7]. Its shortcomings are mainly the long time to achieve a strong bony connection, the relatively cumbersome instrumentation, the long postoperative physician management process, the long learning curve for the physician, and the efficacy related to the physician’s proficiency and clinical experience with this technique. Exploring lighter and simpler fixation devices and operating procedures, as well as integrating DO techniques with microsurgery, VSD techniques, and techniques to improve local immunity, could shorten treatment cycles and improve outcomes.
References
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Typical case presentation.
Patient Female, 22 years old. She was admitted to the hospital with functional limitation of bone shortening deformity in the left lower leg after infection for 19 years. The patient developed a persistent generalized hyperthermia 19 years ago with no obvious cause, which did not improve after treatment in the local hospital. After the anti-infection treatment failed, “left calf abscess incision and drainage” as well as anti-infection and blood transfusion were performed, and the body temperature returned to normal and the wound healed and was discharged. Thereafter, the left lower extremity was gradually left with abnormal shortening and limited movement of the left ankle joint (Figure 1-2), and he was admitted with “left tibial bone defect and left calf flexion shortening deformity” for further treatment.
Physical examination: physiological curvature of the spine existed, with mild bending deformity to the right side, the pelvis was tilted to the left, and the appearance of both upper limbs and the right lower limb was not abnormal. The left calf was short and small, and the mid calf was retroflexed with no localized pressure pain, and the left ankle joint was limited. The muscle tone of the left lower limb was not high and the muscle strength was normal. The skin sensation of the left lower limb was basically normal, the left patellar ligament and Achilles tendon reflexes were present, and Babinski’s sign was not elicited. Auxiliary examination: preoperative radiographs of both lower extremities revealed a bone defect in the middle part of the left tibia, inversion and retroflexion of the fibula, fusion of the distal left tibia and fibula, and shortening of the left lower extremity by about 9 cm compared with the right lower extremity (Figure 2).
The upper fibula was osteotomized, the proximal tibial stump was osteotomized and slid distally, the supra-ankle osteotomy was lengthened, and the Ilizarov external fixator was fixed under continuous epidural anesthesia (Figure 3). Postoperative infection prevention treatment was given for 3 days, with attention to pinhole care. On the 9th postoperative day, orthopedic and functional exercises were performed at the same time as planned, and appropriate activities were performed with the aid of a walker.
Postoperative X-ray and physical and functional review: 20 days postoperative showed that the lengthened end was distracted, 3 months postoperative showed that the tibial stump was in contact and the supra-ankle lengthening was 5 cm. 7 months postoperative showed that the tibial stump had slipped 11 cm distally and the two stumps had overlapped, the bone scab at the supra-ankle lengthening end was growing well, and the appearance showed that the deformity was mostly corrected. At 10 months postoperatively, the bone scabs of the upper and lower extremities were growing well, and the deformity was corrected. At 15 months postoperatively, the overlap of the two stumps had healed well. At 17 months postoperatively, both external fixations were removed, and the full-length lower limb standing film showed that both lower limbs were basically equal in length and the force line was restored. The appearance showed that the force lines of both lower limbs were restored (Figure 3-15).
Discussion Septic osteomyelitis occurs in the hip and knee joints of children, who have poor body resistance. Delayed treatment or misdiagnosis during the acute phase often leads to chronic osteomyelitis, with common complications such as joint ankylosis, joint deformity, growth or shortening of the affected limb, pathological fracture and even cancer [1]. Developmental deformities of the affected limb are due to inflammatory stimulation of the epiphysis and destruction of the epiphyseal plate leading to overgrowth or growth disorders, which eventually seriously affects limb function. Ilizarov technique is an effective treatment for severe rigid limb deformity and large bone defects [3-5]. The deformity was characterized by a large tibial bone defect, inversion of the fibula, retroflexion deformity and fusion of the distal left tibia and fibula, which seriously affected the left knee and left ankle movement and weight-bearing function of the lower limb. For such a complex and severe bony deformity, we tried to apply Ilizarov technique combined with limited orthopedic phase I to correct the compound deformity and achieved satisfactory results.