Local factors
Host factors
Infection
Tobacco use
Insufficient fixation
Vitamin D deficiency/insufficiency
Poor reduction/gapping
Thyroid dysfunction
Malalignment
Parathyroid dysfunction
Poor site preparation/debridement
Diabetes mellitus
Thermal necrosis
Premature weight bearing
Soft tissue interposition
Malnutrition
Soft tissue/periosteal stripping
Arterial insufficiency
Pharmaceuticals (NSAIDs, steroids)
While not solely a technical error, surgical site infection can be a local factor that also contributes to nonunion. Infection of the local soft tissues can lead to necrosis and a dysvascular environment. Overt bacterial infection of the bone weakens its structural integrity and can cause failure of the fixation construct that leads to instability of the surgical site. Diseased fibrous tissue and interposed necrotic bone segments can be barriers to the ingrowth of healthy vascular channels and can inhibit the delivery of growth factors.
There are numerous preexisting medical conditions that are capable of contributing to the incidence of surgical nonunion. While not directly affecting the surgical site in the same manner as the previously described local factors, certain medical conditions can have adverse effects on the bone healing cascade. For the purpose of this discussion, the authors refer to these patient conditions as host factors. One host factor that is often cited as a cause of nonunion is tobacco use [15, 41–44]. Nicotine has been shown to uncouple the tightly regulated angiogenesis and osteogenesis pathways that are formed during normal bone healing [45]. Prolonged use of tobacco leads to a reduced oxygen-carrying capacity and results in generalized tissue hypoxia. The proliferation and activity of bone-forming osteoblasts are significantly diminished in subjects exposed to nicotine [46–48]. Moreover, the overall bone mineral density of smokers can be significantly less than that of individuals who do not use tobacco products, and this difference is further exacerbated in elderly and postmenopausal patients [49–52]. These combined effects lead to an increase risk of nonunion in smokers that has been reported to be 2–16-fold higher in hindfoot arthrodesis and to a significant increase in overall complications such as wound dehiscence and infection [43, 44, 52].
Endocrine and metabolic irregularities have also been shown to contribute to nonunion. Specifically, vitamin D deficiency, diabetes mellitus, parathyroid disease, thyroid dysfunction, hypogonadism, and malnutrition can have significant implications in the bone healing cascade [53–55]. One specific report of nonunion patients by Brinker and colleagues showed that 31 of 37 (84%) individuals who met their screening criteria suffered underlying metabolic or endocrine abnormalities [55].
The prolonged use of pharmaceuticals, such as nonsteroidal anti-inflammatory drugs (NSAIDs) , chemotherapy agents, anticoagulants, antibiotics, and advanced biologic antirheumatic drugs, has been hypothesized to contribute to nonunion [24, 56–70]. Although no absolute agreement exists regarding the roles of medications in elective foot and ankle surgical nonunion, causal links between diminished bone healing and certain pharmacological regimens have been reported in both clinical and laboratory models [24, 56–70]. For example, Jeffcoach and colleagues found a significant increase in complications in patients receiving NSAIDs after suffering traumatic long bone fracture [63]. Various animal model studies have shown significant implications of NSAID use on bone healing due to abnormalities in prostaglandin production at the fracture site [24, 64–67]. The long-term use of corticosteroids can predispose patients to osteopenia by inhibiting osteoblastogenesis and has been cited as one of the most common causes of secondary osteoporosis [24, 61, 62]. The cytotoxic and antiproliferative properties of chemotherapeutic drugs have been shown to inhibit healing in arthrodesis subjects [59, 60]. Furthermore, antibiotics, specifically fluoroquinolones , have been alleged to adversely affect bone healing by altering endochondral ossification and inducing chondrocyte death [68–70].
Patient Evaluation
To formulate a comprehensive treatment plan for a nonunion patient, one must begin by obtaining a thorough history and physical examination. Details of the initial surgery, including time lines before and after the intervention, the pathology that leads to the original operation, previous treatments, and other complications throughout the treatment course, should be reviewed. A complete analysis of the patient’s past medical and social histories is essential. Particular emphasis should be placed on comorbidities that are known to adversely affect bone healing, such as diabetes mellitus, peripheral vascular disease, vitamin D deficiency, thyroid dysfunction, malabsorption syndromes, autoimmune disease, and tobacco use. Pharmaceuticals linked to aberrations in bone metabolism , such as immunosuppressive agents, NSAIDs, and high-potency steroids, should also be noted.
A thorough appraisal of the previous clinical, surgical, and inpatient hospital records should be conducted prior to revision surgery. Obtaining a complete copy of the patient’s external records is particularly important if complications , such as surgical site infections, wound healing issues, or venous thrombotic events, transpired during the postoperative course. Patients should understand the importance of such records and be encouraged to bring reports and film copies of diagnostic imaging when available.
Furthermore, in-depth understandings of the patient’s current pain, disability status, and future treatment goals should be acquired. For example, a patient might seem to be a surgical candidate from an objective standpoint. However, certain medical or social issues might limit or preclude the option of additional surgery. A patient might be unable to proceed with further surgical intervention due to an inability to withdraw from social responsibilities or due to concurrent medical conditions. The provider might be relegated to employing nonoperative care in lieu of surgical therapy. These situations are best elucidated early in the planned treatment course.
Physical examination of the involved lower limb requires a comparison to the contralateral extremity. Disparities of temperature, edema, and erythema should be noted. Inspection of the soft tissue envelope for signs of open lesions, drainage, or skin atrophy should also be performed. Baseline neuromotor and vascular statuses as assessed by palpation of pulses, capillary refill times, and manual muscle testing should be examined and documented.
The suspected or confirmed nonunion site(s) should be palpated for tenderness, and manual stress should be applied to assess apparent gross instability. The ranges of motion of the contiguous joints of the nonunion should be evaluated for crepitation or limitation . Close attention should be given to the presence of tenderness, malalignment, diminished range of motion, and additional signs of degenerative changes at these neighboring joints. Such findings may be useful guides for future treatment. For example, when malalignment exists at a nonunion site, secondary angulation through compensation might occur at the adjacent joints. Such situations can arise when a severe varus deformity exists at a tibiotalar arthrodesis nonunion. Long-standing compensatory eversion at the subtalar joint (STJ) to achieve a plantigrade foot can result in arthrosis that might require realignment arthrodesis during the ankle revision. Revision of the tibiotalar arthrodesis without addressing the subsequent STJ deformity can create a continued source of pain even if ankle union is achieved.
Laboratory testing can be beneficial when evaluating and formulating a treatment plan for a nonunion patient. Updated chemistry and hematology (CMP, CBC) panels should be obtained and reviewed for all patients, especially when a surgical intervention is planned. When a patient’s nutritional status is in question, evaluations of the albumin, prealbumin, total lymphocyte count, and transferrin levels can be useful to ascertain the healing potential [71, 72]. Furthermore, due to the roles that vitamin D and calcium abnormalities play in nonunion, blood levels should be obtained for the majority of patients undergoing treatment. Vitamin D levels below 20 ng/mL typically warrant repletion therapy in the majority of cases [73–75].
In situations in which an underlying infectious etiology of the nonunion is suspected, acute phase reactant testing , including erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) tests, can be helpful aids for diagnosis. Acute phase reactants have high sensitivity and specificity in the diagnosis of osteomyelitis [76, 77]. A 2013 report by Stucken et al. compared the utilities of ESR and CRP in the diagnosis of infection in nonunion patients. The authors determined that the combination of ESR and CRP is a significantly accurate predictor of infection in such cases [78]. If suspicions of infection are accompanied by increases in CRP and ESR values, a biopsy of the nonunion site for gram staining, culture and sensitivity, and histologic review should be performed.
Numerous imaging modalities are available to evaluate foot and ankle nonunion including radiographs, radionucleotide scans, linear and computerized tomography (CT scanning), and magnetic resonance imaging (MRI). Depending on the specific nature of a nonunion, one or a combination of these techniques can be employed for evaluation, treatment guidance, and progress monitoring.
Plain film radiographs have become a mainstay tool in the assessment of bone healing after fracture, osteotomy, and arthrodesis. Bone union or arthrodesis is traditionally deemed to have occurred when orthogonal X-rays show trabecular bridging across three of four cortices, and patient complaints of pain and swelling have begun to subside [79, 80] (Fig. 3.1). Standard radiographs have proven to be a particularly valuable tool in the assessment of nonunion. Findings on serial radiographs frequently serve as the first indication that union is delayed or has failed to occur following surgery.
Fig. 3.1
AP, oblique and lateral radiographs demonstrating bridging across 3 of 4 cortices
Serial X-rays should be evaluated in a chronological manner. Multiplane projections consisting of the dorsoplantar (DP) and oblique (MO) foot and anteroposterior (AP) and mortise ankle and lateral foot and ankle should be assessed for healing, bone quality, and residual or recurrent deformity. Additional specialized alignment radiographs, such as Saltzman and Harris-Beath views, can be useful to better assess the relationship of the foot/ankle to the lower leg [81, 82] (Fig. 3.2). Disuse osteopenia, sclerosis, bone callus, and progression of radiolucent lines at the suspected nonunion site should be noted and quantified. The presence of hardware loosening, breakage, and/or migration is indicative of excessive surgical site motion and warrants further investigation. The concern about an infectious component should also be heightened when sinus tracks or radiograph signs of infection are present [83, 84].
Fig. 3.2
(a) Bilateral calcaneal axial radiographs (b) Bilateral hindfoot alignment radiographs
Despite the role of plain film X-rays, two-dimensional X-rays cannot adequately or thoroughly discern bony union in all cases. Visualizing trabeculation across an arthrodesis or osteotomy site can be difficult when internal fixation, a bone graft, or bone graft substitute has been utilized. Patients complaining of continued postoperative pain and swelling even after apparent radiographic union has occurred often warrant further investigation beyond standard X-rays. In such instances, three-dimensional imaging modalities , such as CT scanning, have proven to be exceedingly useful. Hindfoot joints exhibit a nonplanar orientation, and the significant superimposition that is present throughout the midfoot can make standard radiographs appear equivocal when evaluating nonunion. The nonplanar and compact natures of these joints can be better evaluated with helical CT scans than with standard films (Fig. 3.3). A 2006 report by Coughlin prospectively compared standard radiographs to CT scans in the evaluation of union in hindfoot arthrodesis. The study reported a significant difference in the reliabilities of the detection of true bone union between CT scans and radiographs [85]. The evaluation of CT scans allows radiologists and surgeons to quantify the percentage of fusion mass, which is difficult with plain radiographs in most instances (Fig. 3.4). It is recommended that a measurement of 50% or more bridging at an arthrodesis site be achieved before it is considered a successful union [86]. Furthermore, a thorough analysis of the adjacent joints can be performed when CT scanning is used for nonunion. When adjacent arthritis is present, the decision to incorporate these joints into the fusion mass during revision surgery might be considered.
Fig. 3.3
(a) Lateral radiograph with fractured screw (inferior-medial to superior-lateral) across talonavicular joint 6-months following selected hindfoot arthrodesis for end-stage adult acquired flatfoot. This view fails to demonstrate evidence of joint consolidation. (b) 3-months status post axial and lateral CT scans showing absence of consolidation at both the talonavicular and subtalar joints. (c) 6-months status post CT scan with continued absence of consolidation. (d) 9-months status post CT scan clearly demonstrating nonunion following an extended course of immobilization, nonweightbearing and electrical stimulation
Fig. 3.4
CT scan demonstrating near complete consolidation after subtalar joint arthrodesis
If the viability, vascularity, or suspected infection of the nonunion site or adjacent bone is in question, MRI and bone scintigraphy scans have been demonstrated to be useful [87–90]. The sensitivity of MRI in the detection of avascular necrosis (AVN) in the foot and ankle is nearly 100% [87, 91]. Adjacent articular surfaces remote to the site of nonunion can also be thoroughly assessed for degenerative changes, which can help to guide future surgical planning. However, the use of MRI after surgical reconstruction can be problematic due to artifacts and scatter if ferromagnetic implants have been utilized. In such circumstances, nuclear bone scintigraphy scans (technicium-99m MDP) have been shown to adequately detect both unifocal and multifocal AVNs at acceptable rates and are not hindered by retained hardware. Furthermore, white blood cell-labeled nuclear scans (indium-111) can be utilized in conjunction with traditional scanning techniques to detect underlying infection at the nonunion site. Combining Tc-99m MDP and indium-111 scans increases the accuracy, specificity, and sensitivity of the diagnoses of concomitant bone infections in nonunion patients to greater than 90% [87, 92].
In patients for whom a suspicion of underlying osteopenia or osteoporosis is present, bone densitometry scanning can be a valuable tool. The healthcare community recommends bone density testing (via dual-energy X-ray absorptiometry (DEXA) ) for postmenopausal women at the age of 65 and for male and female patients with risk factors such as tobacco use, alcoholism, chronic steroid use, and endocrine disorders that contribute to osteoporosis prior to age 65 [93–95]. When a bone mass deficiency is present in a nonunion patient, the patient might benefit from the utilization of additional orthobiologics or fixation methods, such as locked plating constructs and/or external fixation, which have proven successful in the osteoporotic/osteopenic bone.
Nonunion Management/Treatment Strategies
Treatment strategies should obviously be focused on healing the nonunion. However, nonunions in the foot and ankle are often associated with malunions and deformities. Additionally, the joints in close proximity might be stiff, malaligned, and painful due to compensation, particularly in cases of long-standing nonunions. Therefore, one should employ a global approach that accounts for the entire foot, ankle, and lower leg. The ultimate goal is a well-aligned, painless, and functional foot and ankle. Obtaining this goal can be challenging and is certainly not possible for every patient. Nonetheless, some degree of pain relief and improved function should be expected. The surgeon needs to develop a treatment plan and then determine a realistic prognosis, and the plan and prognosis should be thoroughly communicated to the patient. Patients should understand that the treatment process will be long and cumbersome and will often require multiple surgical sessions. While some nonunions heal rather easily, others require a long period of time to heal.
Patient goals typically include pain relief and normal function . The primary goals for the surgeon include union, normal architecture/alignment, resolution of symptoms, and functionality. The goals must be kept realistic and attainable. Obviously, these goals will vary based on the patient’s unique situation and circumstances. Factors such as medical history, prior surgery, anatomic site, compliance, etc. will directly affect the patient’s prognosis and should be the starting point of any discussion between the patient and surgeon. The surgeon should provide reasonable options and associated outcomes based on his/her experience and the current literature. Furthermore, the surgeon and patient should agree on the definition of an acceptable outcome. The patient’s motivation, disability, social problems, litigation issues, mental status, and desires should be considered before a revision is undertaken.
Revision surgery to address nonunion often requires much thought, thorough planning, patient education, patient optimization, appropriate technology and resources, extended convalescence, advanced imaging, further surgery, and long-term follow-up. Patients should have clear understandings of their problems. Surgical consultation and informed consent should provide clarity and understanding regarding each patient’s unique situation. This process might require several visits and various types of educational media for the patient to thoroughly comprehend his or her situation and develop realistic expectations. Such patients and their families should understand the uncertainties associated with nonunion healing, the extended course of treatment, and that multiple surgical interventions might be required.
Appropriate consultation with other services is important prior to surgery. Any issues that might adversely affect patient outcomes should be addressed by the appropriate specialist before surgical intervention.
If preoperative noninvasive lower limb arterial studies demonstrate poor perfusion, a vascular surgery consultation is recommended. These tests might indicate that the proposed surgery might not heal. A vascular intervention can be performed to increase arterial perfusion or might indicate that the patient is not a surgical candidate.
If incision placement is necessary in an area that is predisposed to dehiscence or if soft tissue deficits are anticipated following realignment, a plastic surgery consultation is recommended. A plastic surgeon might suggest an optimal site for incision placement or perform soft tissue reconstruction concomitantly during revision for the nonunion.
Unfortunately, patients with long-standing nonunions might be dependent on oral narcotics. Referral to pain management is helpful both during the course of treatment and ultimately for the detoxification and weaning of the patient off of all narcotic medications [96–98].
Obtaining a preoperative physical therapy consultation is particularly important in situations in which premature weight bearing was a contributing factor to nonunion. A physical therapist can provide gait training that accounts for the postoperative activity expectations and the use of assistive or adaptive devices. Furthermore, such training provides an opportunity for the patient to develop a relationship with a physical therapist who will work with him or her following surgery. Rehabilitation will be necessary following surgery for independent transfer and ambulation. Ultimately, physical therapy will be necessary to address the strengths and ranges of motion of the surrounding joints.
A nutritionist consultation should be considered for patients who are malnourished or obese. It has been clearly established that poor dietary intakes of proteins, particularly albumin, and vitamins can contribute to delayed union or nonunion. Furthermore, a nutritionist can help a severely obese patient reduce his or her weight. Obesity obviously makes the offloading of the surgical site technically very difficult [53, 99–101].
Endocrinology consultations are beneficial for patients with diabetes, particularly those patients with elevated HgA1c levels. Hoogwerf et al. have demonstrated a linear relationship between the incidence of complications and elevated HgA1c levels in patients with diabetes mellitus [102].
Therefore, tight glucose control should be a part of patient optimization when diabetes mellitus is present. Furthermore, in a 2007 report by Brinker et al., the investigators strongly recommended endocrinology referrals for patients with nonunion when technical errors have been excluded [55], i.e., the patient’s failure to heal was not caused by underutilization of fixation, fixation failure, or infection. Endocrinology can isolate the metabolic deficiency that contributed to the nonunion and treat the abnormality to optimize the patient throughout their treatment course. These treatments can include the repletion of low vitamin D levels, thyroid hormone, and the optimization of blood glucose.
Depression is not uncommon in patients with chronic medical conditions; thus, patients with nonunions often exhibit signs of clinical depression. Referral to their primary care physician or psychiatrist might be beneficial [103–106].
Although the majority of revision procedures to address nonunion can be performed in one surgical setting, there are situations in which multiple surgeries are required. Factors that influence this decision include prior operative procedures, fixation that necessitates removal, the fixation that will be utilized for the revision, the necessity of harvesting an autogenous bone graft , and the times anticipated for the various parts of the surgery. It is important to anticipate technical difficulties and unforeseen challenges that might develop during surgery. Unfortunately, technical difficulties occur even under ideal circumstances and with the best of plans. Maintaining a surgical schedule that provides a margin to accommodate these unanticipated problems is recommended.
Procedures as simple as removing hardware can be rather difficult even when the appropriate instrumentation and image intensification are available. Such procedures can require a significant amount of time and effort that might be better utilized to address other, more important aspects of the procedure. Therefore, it might be better to stage the surgery so that the fixation can be removed during the initial surgical session and debridement, realignment, fixation, etc. can be performed in the next surgical session. Additionally, if intramedullary nails, large diameter screws, or other types of devices with large diameters are removed, the patient can be permitted a period of time to allow these bony deficits to fill in or consolidate. These processes can be expedited via the use of adjuvant nonsurgical therapies , such as pulsed electromagnetic field and ultrasonic therapies. The goal is to improve bone quality, which might enhance the effectiveness of the fixation that will be used in subsequent procedures.
In situations in which osteomyelitis is suspected, staged procedures are recommended. Although preoperative advanced imaging is helpful in the diagnosis of osteomyelitis, a definitive diagnosis can only be made with bone cultures and biopsy. Because infection will adversely affect bony union, it is imperative that the organisms are identified and appropriate antibiotics are administered if osteomyelitis is present. The primary surgical session can be used to obtain a bone biopsy and cultures to rule out or treat osteomyelitis. Additionally, hardware can also be removed during this initial surgical session.
Staging provides time for the patients to contemplate their upcoming procedures and develop a thorough understanding of their situation. Staging also provides an opportunity to address metabolic deficiencies or issues such as elevated HgA1c or hypovitaminosis D. Additionally, staging can provide time for a patient to implement smoking cessation program if necessary.
Lastly, the staging of procedures gives the surgeon an opportunity to ascertain the patient’s ability to comply and to determine whether there are socioeconomic, psychological, family, or other factors that require attention.
Deformity Assessment
Deformity is invariably associated with nonunion in the foot and ankle. In addition to addressing nonunion, surgeries must also address any existing deformity (Fig. 3.5). Deformity, whether secondary to inadequate reduction during the index procedure or due to gradual development following a failed union, must be completely reduced. One of the major surgical goals is to obtain complete realignment. Any residual deformity will result in stress or an unevenly distributed axial load on the nonunion site and increase the risk of failure following revision. Residual deformities can further result in compensatory gaits that predispose surrounding joints to degenerative processes. Thus, deformity assessments must be thorough and comprehensive. Evaluations should include clinical examination, radiographs, and advanced imaging.
Fig. 3.5
(a) AP radiograph showing nonunion following a first metatarsal base osteotomy for hallux valgus reconstruction resulting in severe shortening. (b) Lateral radiograph demonstrating significant first ray elevation. (c) Skeletal deficit following resection of the nonunion. (d) Defect filled with a structural autogenous bone graft and secured with plate fixation. (e, f) AP and lateral radiographs demonstrating restoration of length and sagittal plane realignment
Clinical examination should include both static and dynamic assessments. Frontal, transverse, and sagittal plane deformities should be evaluated in both open and closed kinetic chains. Open kinetic chain evaluations of both the nonunion site and the surrounding joints are important. Compensatory deformities can often develop in adjacent joints. A long-standing nonunion of the subtalar joint (STJ) following arthrodesis for stage III adult-acquired flatfoot with residual valgus deformity might develop ankle valgus (Fig. 3.6). Revision surgery of the STJ nonunion should also address the ankle valgus to obtain complete realignment. Furthermore, one must ascertain whether the ankle valgus is fixed or reducible. An attempt should be made to passively manipulate the deformity into realignment. This determination can be made during open kinetic chain assessment. Closed kinetic chain or weight-bearing assessment is also very important. The level of deformity and the areas of compensation can be determined. The patient should be able to place the foot and ankle into a corrected position during weight bearing. If this cannot be accomplished, then the deformity is fixed. If the patient cannot place the ankle joint into a position that parallels the subtalar deformity at the nonunion site, the joint deformity is fixed and requires correction. If the patient can achieve the corrected position, the joint deformity might resolve with realignment of the nonunion. Reducible valgus deformities of the ankle can be managed with joint-sparing procedures, such as deltoid ligament repair and periarticular osteotomies. However, a fixed deformity might require ankle arthrodesis or total ankle replacement to obtain complete realignment. Another example is the compensatory forefoot supinatus/varus that develops due to an ankle or hindfoot nonunion in valgus deformity. The supinatus/varus might require correction during surgical management of the nonunion. Such deformities will be exposed and magnified following ankle or hindfoot realignment. A fixed supinatus/varus requires surgery. However, a reducible deformity might resolve without intervention following ankle or hindfoot realignment [107].
Fig. 3.6
(a) Lateral radiograph of late-stage adult-acquired flat foot with significant angular deformity. (b) Preoperative and postoperative radiograph following triple arthrodesis. Note the undercorrection of transverse plane deformity with inadequate talar head coverage by the navicular. (c) 6-months status post lateral and axial radiographs demonstrating nonunion. (d) AP radiograph of the ankle showing valgus deformity
Plain radiographs are an important part of deformity assessment because they can fully characterize all other deformities associated with the nonunion. Radiographs can be used to evaluate length, angulation, rotation, and translation. It is occasionally important to obtain weight-bearing radiographs of the contralateral extremity as well as the involved extremity. Stress radiology can be helpful in the evaluation of the competence of the collateral ligaments of the ankle.
Shortening is not uncommon with nonunion. One must ascertain the degree of shortening that is acceptable from a functional standpoint. It is important to anticipate the quantity of bony resection that will be necessary to develop a healthy cancellous substrate at the nonunion site. This quantity will have implications in terms of the type and size of bone graft that will be required. Furthermore, this quantity will also influence the type of fixation that is necessary and whether adjacent joints will need to be included in the arthrodesis.
Angular deformities , particularly in the frontal and sagittal planes, can be thoroughly reviewed with plain radiographs. Nonunion following STJ or ankle joint arthrodesis can often be associated with a severe frontal plane deformity. Plain radiographs will demonstrate the extent of the deformity so that plans can be made for realignment during revision surgery of the nonunion. Templates can be helpful when planning realignments for frontal plane deformities. One can determine whether complete realignment is possible based on the extent of the deformity. There are situations in which a complete reduction of a severe deformity can place a compromised soft tissue envelope at risk for wound problems. In such situations, one must accept incomplete realignment or consider shortening the bony segment. Otherwise, one should prepare for possible soft tissue reconstruction.
Nonunions following arthrodeses of the tarsometatarsal, midfoot, and midtarsal articulations are often associated with sagittal plane deformities. Axial loads will invariably result in dorsiflexion deformities. Plain radiographs will demonstrate the degree of deformity so that the surgeon can plan accordingly.
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