Tibial Nonunions Treatment & Management


Background

Tibial fractures can now be treated successfully in the majority of patients, yet nonunions of the tibia [1are not uncommon. They may result in significant morbidity, require numerous operative procedures to treat, and leave the patient with functional deficits.

The subcutaneous position of the tibia results in a greater incidence of open fractures and provides less soft-tissue coverage, factors that produce a higher incidence of nonunion and infected nonunion. Although appropriate and prompt treatment is needed to treat tibial injuries successfully, the incidence of a nonunion is more closely related to the fracture characteristics than to subsequent treatment. [2Realistic expectations of the outcome should be established with the patient as early in the treatment course as possible, preferably before therapeutic intervention. [3]

Pathophysiology

Historically, the definitions of delayed union and nonunion have been based on time from the onset of injury. Currently, the exact time frames are considered to be less important. Fracture healing is a dynamic, progressive process, and intervention is warranted within 3-5 months after injury if monthly radiographic studies do not show progression of fracture healing. [4]

Typically, the term delayed union is used for a fracture that has not united within a period that would typically be considered adequate for bone healing. Delayed union suggests that union is slow but will eventually occur without additional surgical or nonsurgical intervention. The time frame is different for different fractures. Tibial diaphyseal fractures that do not show enough bridging callus to achieve clinical stability by 16 weeks are considered to be delayed union fractures. [4]

The term nonunion refers to a fracture that will not unite without additional surgical or nonsurgical intervention (usually by 6-9 months).

Etiology

The development of a tibial nonunion is related most often to the type and degree of injury, but several additional factors may predispose a patient to a tibial nonunion, such as the degree of fracture comminution and bone loss, whether the fracture is open, and the degree of soft-tissue injury. Subsequent complications, such as infection or compartment syndrome may play a role. [5]

In a prospective observational study of 416 patients from 41 trauma centers who underwent operative treatment of tibial shaft fractures, delayed healing or nonunion occurred in 13%. Open fractures with injuries less than 5 cm were 3.6 times as likely to have delayed healing or nonunion as closed fractures; for open fractures greater than 5 cm, the likelihood of delayed healing or nonunion was 5.7 times greater than that for closed fractures. Healing problems were twice as great for distal shaft fractures and fractures with a postoperative diastasis. [67]

In an observational study involving 200 patients who experienced tibial fractures, Fong et al found that nonunion was more likely to occur in fractures with less than 25% cortical continuity. [8The presence of a fracture gap after fixation, open fractures, and transverse fracture type were also associated with nonunion. The highest risk of nonunion occurred in cases involving an open fracture in conjunction with a fracture gap.

The patient profile also contributes to the incidence of nonunion. Cigarette smoking is well documented to place the patient at higher risk for delayed healing or nonunion. [9 It has been argued that the use of nonsteroidal anti-inflammatory drugs (NSAIDs) may inhibit bone healing, but this negative effect has not been conclusively established in human subjects. [10Impaired patient nutritional status and inadequate compliance with the postoperative regimen mal also inhibit healing.

Finally, prompt and appropriate treatment is needed because iatrogenic injury to the soft-tissue envelope (ie, excessive periosteal stripping), distraction across the fracture site, inadequate immobilization or fixation, and the splinting effect of an intact fibula may contribute to the development of a nonunion.

Epidemiology

Tibial nonunions are estimated to constitute 2-10% of all tibial fractures. An analysis of 12,808 tibial fractures by Zura et al documented an overall tibial nonunion rate of 7.37%. [11The incidence is greater with high-energy injuries and open fractures. The National Center for Health Statistics has reported that close to 500,000 tibia and fibula fractures occur each year in the United States.

Prognosis

Little documentation exists in the literature regarding the functional outcomes of patients treated for tibial nonunions. [12 Discussing the potential limitations in future functional abilities with the patient is critical. Fracture healing does not mean that full function is necessarily restored; residual weakness, pain, and limitations in function are common, even in appropriately treated patients with clinically successful outcomes.



Classification

The Weber-Cech classification is the one most widely used for tibial nonunions. [13 In this system, fractures are classified according to radiographic appearance, which correlates with the fracture biology, as follows:

  • Hypertrophic nonunions - These are tibial nonunions that show prolific callus formation; they are vascular and have excellent healing potential, given the right environment; these nonunions result from inadequate immobilization of the fracture
  • Atrophic nonunions - These are characterized by an absence of callus and atrophic bone ends, which may be tapered and osteopenic or sclerotic; bone vascularity is deficient, and the bone has poor healing potential; a special subgroup of atrophic nonunions consists of those that form a fibrous capsule around a freely mobile nonunion; this cavity is filled with a viscous fluid, creating the appearance of a joint, and is referred to as a tibial pseudarthrosis
  • Normotrophic nonunions - These are nonunions that share the characteristics of both atrophic and hypertrophic nonunions; the bone ends have moderate healing potential

Determining whether evidence of infection is present at the nonunion site is critical.

Paley and Herzenberg classified nonunions into three categories according to clinical mobility, as follows:

  • Stiff (< 5º mobility)
  • Partially mobile (5-20º mobility)
  • Flail (>20º mobility)

The Paley-Herzenberg categories are roughly correlated with the three Weber-Cech categories.

Congenital pseudarthrosis of the tibia is a unique condition observed in children. [141516 Neurofibromatosis and fibrous dysplasia are predisposing factors, though some congenital tibial pseudarthroses are idiopathic. The pathology seems to lie in the periosteum.


Approach Considerations

The most critical step in the workup is to review the patient's prior history carefully, through evaluation of previous records, imaging studies, and discussion with the patient and previous treating physicians. Most often, the nonunion has occurred despite appropriate care, and rushing into treatment without a good understanding of why the nonunion occurred and how treatment will overcome these obstacles is a mistake.

Laboratory Studies

The role of the diagnostic workup is threefold, as follows:

  • To determine whether the patient is able to undergo successful surgery
  • To evaluate the patient for any signs of infection
  • To assess the fracture deformity (see Imaging Studies)

Evaluation of suitability for surgery obviously implies a routine preoperative assessment, but more specific laboratory tests may be indicated to determine whether any systemic factors are contributing to the failure of union. Laboratory assessment to determine the patient's nutritional status may be indicated. The total lymphocyte count and Rainey-MacDonald nutritional index may be helpful in identifying patients who may (or may not) develop infections after long-bone fractures. [1718]

In looking for signs of infection, evaluation with a routine complete blood count (CBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) may be helpful. The CRP is the most accurate indicator of infection, but it is not necessarily specific for infection. [19Cultures may be helpful, but findings are often negative, especially if the patient has been treated with antibiotics.

Imaging Studies

For assessing fracture deformity, plain radiography is typically the most helpful tool. The deformity must be assessed in both anteroposterior (AP) and lateral planes, with resolution of the plane and degree of maximum deformity (see the images below).

Tibial nonunions. Anteroposterior radiograph of psTibial nonunions. Anteroposterior radiograph of pseudarthrosis with nonunion.
Tibial nonunions. Lateral radiograph of pseudarthrTibial nonunions. Lateral radiograph of pseudarthrosis with nonunion.

Any rotational component must be assessed either clinically or with computed tomography (CT). Leg-length equality should be determined clinically or, more accurately, with scanography. Finally, fracture stability must be determined. Often, the fracture nonunion is difficult to assess on plain radiography; fluoroscopy, CT, or tomography may be helpful. Assessment of the fibula is important to determine whether it is preventing tibial union.

Magnetic resonance imaging (MRI) is probably the most sensitive and specific study for osteomyelitis, with an accuracy greater than 90%. [20It also provides additional information regarding the anatomy and location of infected bone, sinus tracks, and sequestrums. Unfortunately, MRI is less effective if residual hardware is present, and other studies may be more appropriate.

Technetium-99m diphosphonate bone scanning has been used in an attempt to identify infections, but it is not specific for infection. However, combining this scan with indium-111–labeled leukocyte imaging increases the accuracy to 82%. [21]

Other Tests

Vascular studies may be indicated if prior injury is a concern or if a free soft-tissue transfer is indicated. Consultation with a plastic surgeon may be warranted. Careful assessment and documentation of skin integrity and motor and sensory function are critical for surgical planning.

Histologic Findings

A histologic assessment may be helpful and has been shown to have a high sensitivity (87%) and specificity (100%) in assessing nonunion for the possibility of infection, especially when microbiologic findings are inconclusive.


Approach Considerations

Treatment of a tibial nonunion (see the image below) depends on fracture classification, location of the nonunion, lower-extremity alignment, fracture stability, presence of infection, soft-tissue injury (including nerve deficits), and patient characteristics and possible concomitant injuries. A forthright discussion with the patient should be initiated, with the patient's wishes and the physician's experience taken into account.

Treatment algorithm for tibial nonunions. Treatment algorithm for tibial nonunions.

In general, hypertrophic nonunions are treated with rigid stabilization with or without compression; additional biologic stimulation in the form of bone grafting is not required. Atrophic nonunions require augmentation to stimulate bone formation. This may require bone grafting, soft-tissue coverage, or other forms of biologic stimulation, such as bone morphogenetic proteins (BMPs) [23 or autologous mesenchymal stem cells. [24Infected nonunions should be treated in an attempt to sterilize the nonunion site, but stability of the fracture site should not be sacrificed. [25]

Contraindications for operative management depend on a number of factors, all of which must be weighed carefully in the decision-making process.

The overall health of the patient is critical to the decision-making process. If the patient is critically ill or has undergone multiple previous procedures without success, further treatment may not be possible or may be ill advised. Active infection modifies how and even whether the nonunion is treated. An injury to the neurovascular structures such that the foot is insensate may discourage heroic attempts for treatment of the nonunion. Amputation usually results in a quick return to activities, but it may result in overgrowth at the amputation site in children.

The use of adjunctive treatment modalities continues to be the most controversial aspect of therapy, including the need and indication for electrical stimulation, ultrasound, various synthetic bone osteoconductive carriers, and osteoinductive bone growth factors (such as BMPs [23).

Nonoperative Therapy

Nonoperative treatment methods should always be considered. Although they are rarely considered definitive therapy, they may be helpful as adjunctive therapy or as a temporizing option.

Functional cast bracing may be considered for selected cases. In a study by Sarmiento, this treatment was unsuccessful in fewer than 10% of patients, though the majority of patients also had fibular osteotomies and/or bone grafting. [26This is especially common in patients at the extremes of age. Geriatric patients, especially those who are unfit for major surgery, can be treated successfully with a cast brace. Meticulous attention is required for the condition of the skin.

Pediatric nonunions (not congenital pseudarthrosis) generally result from open fractures with soft-tissue stripping and bone devascularization. Functional cast bracing is an effective method for achieving union.

Pulsed electromagnetic stimulation has been shown to be an effective modality, especially for hypertrophic nonunions, but it does not address issues of instability, deformity, or leg-length inequality. [272829]

Low-frequency ultrasound has been shown to decrease fracture healing time. [30A meta-analysis that reviewed 138 articles (of which only six met the authors' rigorous inclusion criteria) reported that fracture healing occurred about 2 months sooner with the use of ultrasound therapy. [31]

Surgical Therapy

Treatment principles and rationale

Hypertrophic nonunion

Hypertrophic nonunions display extensive callus formation. These vascular nonunions have excellent healing potential. They are best treated with rigid stabilization with or without compression. Additional biologic stimulation in the form of bone grafting is not required.

Atrophic nonunion

Atrophic nonunions are characterized by an absence of callus, deficient bone vascularity, and poor healing potential. Debridement of all necrotic tissue is necessary, with opposition of viable and vascular bone fragments. In addition, biologic stimulation is required.

Historically, biologic stimulation has taken the form of bone grafting, preferably autograft, which is osteogenic, osteoconductive, and osteoinductive. The posterolateral approach usually is preferred to the anterolateral approach because greater space is available for bone grafting and an additional incision through the previous scar is avoided. The posterolateral approach should not be used in proximal-third tibial fractures because of the high risk of injury to the neurovascular structures.

Bone marrow injection has been shown to be an easy and effective treatment. This should be accomplished with the aid of fluoroscopy. Marrow is harvested from the iliac crest and injected directly into the posterior fracture site. In one study, nine of 11 nonunions healed within 4-23 weeks, without further surgery. [32]

Sugaya et al evaluated the efficacy of percutaneous autologous concentrated bone marrow grafting in 17 cases of fracture nonunion (femur, 10 cases; tibia, five cases; humerus, one case; ulna, one case). [33By 6 months after grafting, healing of the nonunion had occurred in 11 of the 17 patients; by 12 months, healing had occurred in 13 of the patients.

The use of BMPs and other osteoinductive agents has gained increased support experimentally and clinically. [233435With high costs and limited clinical applications, indications are still being determined. [36]

Surgical approaches

Surgical treatment typically incorporates the following:

  • Fibular osteotomy
  • Removal of ineffective, broken, or infected hardware
  • Use of biologic bone enhancement
  • Bone stabilization
  • Eradication of infection

A fibular osteotomy should be used if the fibula is felt to be inhibiting compression across the tibial nonunion site. This is usually performed in combination with other procedures and is used as an isolated procedure only if a stable noninfected hypertrophic nonunion with little or no deformity is present. Usually, a small segment of bone is removed (1-2 cm).

Removal of necrotic or infected bone must be performed for a union to occur. This may involve the need for significant bone graft, shortening, or bone transport.

Bony alignment and stability are essential for satisfactory treatment of a tibial nonunion (see the images below). The use of a reamed intramedullary (IM) nail is an excellent method of treating noninfected nonunions, especially in the middle three fifths of the tibia. [37Conversion from a nonreamed nail or plate in closed and grade I or II open fractures with no evidence of infection is the primary indication. This technique allows early rehabilitation and maintenance of the alignment, and the reaming may act as a bone graft at the fracture site.

Tibial nonunions. Anteroposterior radiograph of tiTibial nonunions. Anteroposterior radiograph of tibial fracture after provisional fixation.
Tibial nonunions. Oblique view of tibial fracture Tibial nonunions. Oblique view of tibial fracture after provisional fixation (note the fracture gap is not visible on the anteroposterior and lateral radiographs).
Tibial nonunions. Lateral radiograph of tibial fraTibial nonunions. Lateral radiograph of tibial fracture after provisional fixation.

For patients with a history of infection, previous external fixation, very proximal or distal fractures, or significant malalignment, reamed IM nailing is less effective. This technique can also be difficult, and the surgeon must be experienced with IM nailing techniques. The use of end reaming (cutting) bits, fluoroscopy, and a femoral IM distracter may be helpful.

In a multicenter, blinded, randomized trial of 1226 patients with tibial shaft fractures who underwent reamed nailing (622 patients) and unreamed nailing (604 patients), study investigators found that there may be a possible benefit for the use of reamed IM nailing in patients with closed-end fractures. The authors found no difference for open fractures. They suggested that delaying reoperation for nonunion for at least 6 months may reduce the number of reoperations. [38]

Compression plating has also been shown to be effective for treating tibial nonunions. Wiss treated 49 patients with a tibial nonunion after initial external fixation. [39The patients demonstrated a 92% healing rate in a mean of 7 months with no further treatment.

Compression plating has the advantage of being applicable anywhere along the tibia, and casting is usually unnecessary. However, it may contribute to difficulties with wound healing and can potentially devascularize a segment of bone. The soft tissues must be handled in an atraumatic manner, and dissection and periosteal stripping must be kept to a minimum. Additionally, in patients with poor bone quality, the fixation is less secure. The use of a locking custom blade plate for periarticular nonunions has been described. [40]

External fixation, especially small-wire and hybrid external fixation, is an excellent option for treatment of tibial nonunions, especially if the fracture is very proximal or distal (periarticular), if bone loss is significant, if deformity (including shortening) is significant, or if ongoing infection is present. External fixation allows concurrent treatment of multiple issues. It can provide stability to the fracture site, even in very proximal or distal fractures, with the use of fine-wire fixation. Large infected bone segments can be removed and grafted, or a shortening can be performed. [41]

Limb-length equalization can be performed with bone transport or as an isolated procedure after union has occurred. Adjunctive therapy, such as the use of antibiotic bone cement or bone substitute beads (see the image below), can easily be incorporated, and stabilization with external fixation usually provides for access if soft-tissue grafts are needed.

Tibial nonunions. Close-up view of antibiotic boneTibial nonunions. Close-up view of antibiotic bone cement beads.

The use of external fixation is probably the best technique for patients with complex and significant angular deformities that require correction and are too great for acute correction. Although highly versatile, pin-site infections occur routinely, making subsequent conversion to an IM nail difficult. Specialized training or experience in these techniques is important.

In a 3-year prospective study, Tall et al surgically treated 50 patients for neglected diaphyseal nonunion (femur, 14 cases; tibia, 22 cases; humerus, eight cases; forearm bones, six cases) an average of 11 months after the fracture event. [42The procedure consisted of osteoperiosteal decortication followed by repermeabilization of the medullary canal and then internal fixation. Nonunion of the middle third of the femur and tibia was treated with IM nailing.

In this study, patients were reviewed clinically and radiographically on postoperative days 21, 45, 90 and 120. [42Bone union was obtained in less than 120 days for the lower-limb fractures. No additional grafting was needed. There were two cases of leg-length differences. The investigators concluded that osteoperiosteal decortication is a reliable technique that leads to predictable, satisfactory results.

Complications

Most complications that occur in the treatment of nonunions are an extension of the existing condition, but all tibial nonunions should nevertheless be approached with great care to avoid making a bad situation worse.

Possibly the greatest concern is creating an infected nonunion from an aseptic nonunion. [43In a 1994 study by Wu, a 13% rate of infection occurred, regardless of treatment technique (ie, compression plating vs IM nailing). [44Conversion from external fixation to IM nailing should be avoided if possible. [45Malalignment, shortening, and continued nonunion may also occur, as well as graft-site morbidity (if autograft is used).

Other complications, such as neurovascular injury, compartment syndrome, persistent nonunion, and ultimately amputation, may also result.



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