|SYMPOSIUM: FRACTURE NECK OF FEMUR
|Year : 2018 | Volume
| Issue : 1 | Page : 23-28
Osteonecrosis and nonunion as complication of fracture neck femur
Rudra P. S. Thakur, Alok C Agrawal, Bikas K Sahoo, Vishal K Kujur
Department of Orthopaedics, All India Institute of Medical Sciences (AIIMS), Raipur, Chhattisgarh, India
|Date of Web Publication||28-Dec-2018|
Dr. Alok C Agrawal
Department of Orthopaedics, All India Institute of Medical Sciences (AIIMS), Raipur, Chhattisgarh
Source of Support: None, Conflict of Interest: None
Nonunion and osteonecrosis are two major problems that lead to revision surgery after treatment of intracapsular femoral neck fractures. Fixation failure and nonunion are the main modes of failure following fixation of displaced or undisplaced femoral neck fractures. The two problems are difficult to distinguish as most displaced fractures take a long time to heal after fixation, which increases the risk of fixation failure. Avascular necrosis of the femoral head occurs in 9%–18% of patients, between 2 and 8 years postfracture. Risk factors include the degree of fracture displacement, patient age, and delay in surgical treatment.
Keywords: Femoral neck fractures, nonunion, osteonecrosis
|How to cite this article:|
Thakur RP, Agrawal AC, Sahoo BK, Kujur VK. Osteonecrosis and nonunion as complication of fracture neck femur. J Orthop Dis Traumatol 2018;1:23-8
|How to cite this URL:|
Thakur RP, Agrawal AC, Sahoo BK, Kujur VK. Osteonecrosis and nonunion as complication of fracture neck femur. J Orthop Dis Traumatol [serial online] 2018 [cited 2022 Jan 24];1:23-8. Available from: https://www.jodt.org/text.asp?2018/1/1/23/248900
| Introduction|| |
Nonunion and osteonecrosis are two major problems that lead to revision surgery after treatment of intracapsular femoral neck fractures. In a meta-analysis of 18 studies involving younger patients (aged 15–50 years) with femoral neck fractures, the overall incidence of osteonecrosis was 23% and the incidence of nonunion was 9%. The 564 patients in these studies included those with both displaced and nondisplaced intracapsular femoral neck fractures. In another series including 62 Pauwels type III femoral neck fractures, osteonecrosis developed in 11% and nonunion in 16%. The average age of patients in this series was 42 years (range, 19–64 years). The higher nonunion rate in this study was likely as a result of the difficulty of treating higher Pauwels angle femoral neck fractures.
Avascular necrosis of the femoral head occurs in 9%–18% of patients, between 2 and 8 years postfracture. Risk factors include the degree of fracture displacement, patient age, and delay in surgical treatment.,, In view of the high complication rates recorded among patients undergoing osteosynthesis, often leading to repeat surgery, several works have compared arthroplasty with osteosynthesis to treat intracapsular fractures. The results indicate significantly (P < 0.001) lower complication and reoperation rates in patients undergoing arthroplasty.,A number of authors therefore recommend arthroplasty for the treatment of all intra-articular fractures in elderly patients. However, arthroplasty to treat the femoral neck fracture is associated with a number of complications. Dislocation is most commonly seen in total hip arthroplasty. Acetabular erosion often occurs in active patients undergoing hemiarthroplasty. To avoid this complication, many experts recommend total arthroplasty in these patients. Thigh pain is more frequently reported in uncemented arthroplasty. Moreover, though uncemented arthroplasty may result in higher hip scores, it appears to carry an unacceptably high risk of later femoral fractures.
Early anatomical reduction and surgical fixation remained the best bet to reduce the risk of complications such as nonunion and avascular necrosis in treating fracture neck of femur. Nonunion and early fixation failure are frequently observed in elderly as a result of osteoporosis and other factors, which include age, degree of displacement, fracture line, degree of comminution, and quality of reduction.
Nonunion: Fixation failure and nonunion are the main modes of failure following fixation of displaced or undisplaced femoral neck fractures. The two problems are difficult to distinguish as most displaced fractures take a long time to heal after fixation, which increases the risk of fixation failure. In undisplaced fractures, failure of fixation is a rare complication. Infection is an occasional contributory cause and should be considered in all cases. If there is any evidence of infection, excision arthroplasty may have to be considered in the first instance with an interval arthroplasty at a later stage.
The incidence of nonunion after femoral neck fixation has been reported to be between 10% and 33%. Initial fracture displacement, quality of reduction, and increasing patient age correlate with a higher risk of nonunion. A recent study evaluating the survivorship of the hip in patients younger than 50 years after femoral neck fractures reported that 8% of patients were diagnosed with nonunion and 23% with evidence of osteonecrosis. Moreover in this series, patients with anatomic reductions had only a 4% rate of aseptic nonunion. In comparison to osteonecrosis of the femoral head, patients with nonunions present with symptoms earlier, often several months after internal fixation. Most commonly patients describe a history of persistent pain, typically localized to the groin and over the anterolateral aspect of the injured leg, aggravated by weight-bearing. Three to six months should have elapsed before a nonunion may be diagnosed but evidence of failure of fixation can allow the diagnosis to be made sooner. Plain radiographs may show a lucent fracture zone, osteopenia or bone loss, or signs of instability of the implant such as changes in screw position or backing out of the screws. When plain radiography is equivocal, computed tomography can help determine whether bony union has occurred.
Once nonunion has been diagnosed, several factors will decide whether salvage of the femoral head is a viable revision option, including the following:
- Patient’s physiological age
- Femoral head viability
- Amount of femoral neck resorption
- Duration of the nonunion
Four options are available for treatment: fixation with new hardware, angulation osteotomy, prosthetic replacement, and arthrodesis. In the physiologically young patient, salvage of the femoral head and preservation of the hip joint is preferable. This can be achieved by either improving the mechanical environment to favor healing with valgus-producing osteotomies or by improving the biologic milieu at the nonunion site with bone graft. In young patients, femoral neck nonunion is thought to be more often a result of mechanical factors over biological ones. Varus displacement of the femoral head leads impaired blood supply to the fracture and femoral head, resulting in nonunion and avascular necrosis. Two features commonly seen in young patients have been identified as predicting higher incidences of fixation failure and nonunion and posterior wall comminution and high-shear-angled fractures (Pauwels type III). With a vertical fracture line, the calcar does not offer enough support to prevent the femoral head from shearing and displacing into varus. It is unclear whether posterior comminution indicates a more extensive soft tissue and vascular injury or whether this pattern compromises stability after fixation. Valgus osteotomy reorients the fracture so that its plane is nearly perpendicular to the force across the hip joint. This converts the shearing forces parallel to the nonunion to compressive forces to stabilize the nonunion and promote healing. This procedure also restores femoral length improving the abductor mechanics by restoring the abductor moment arm. As much as 2cm of length can be gained in some instances. Rotational and angular deformities can also be corrected at the same time. The disadvantage of this osteotomy as a salvage procedure is that the valgus orientation of the proximal femur increases contact pressures on the femoral head potentially, leading to degenerative disease or progression of osteonecrosis. Although no concrete contraindications are reported for this procedure, Varghese et al. have shown that a decreased preoperative femoral neck bone stock was a risk factor for nonunion after valgus osteotomy. Several published series reporting on the outcomes of valgus-producing proximal femoral osteotomies for the treatment of femoral nonunion have shown positive results. Marti et al. reported a union rate of 86% after osteotomy in 50 patients with femoral neck nonunions with an average time to union of 4 months. The mean postoperative Harris Hip Score was 91 points in reviewed patients. Although 22 patients had radiographic evidence of osteonecrosis at the time of osteotomy, only three of these patients showed progressive collapse of the femoral head that eventually required hip replacement surgery. Four other patients required replacement surgery for persistent nonunion or hardware failure. Some authors have recently advocated sliding hip screws for the same purpose based on favorable outcomes and technical ease associated with this implant. We recommend the use of valgus intertrochanteric osteotomy for the treatment of aseptic nonunion after femoral neck fracture fixation.
Autogenous bone grafting is used in an attempt to improve the biologic milieu at the nonunion site. This can be performed using nonvascularized, free vascularized, or muscle pedicle–type grafts. Rarely are bone-grafting procedures undertaken for isolated femoral nonunions, but are indicated more so when concomitant osteonecrosis of femoral head (ONFH) is present. No clear indications are present for the use of grafting techniques for femoral neck nonunion; however, these procedures should be considered when there is considerable loss of bone stock or when nonunions are present in well-aligned fractures with low-shear angles.
Osteonecrosis: Osteonecrosis continues to be a problem after femoral neck fractures, even nondisplaced fractures. In fact, higher intracapsular pressures have been shown with nondisplaced femoral neck fractures than with displaced fractures. Routine capsulotomy is controversial. Capsulotomy probably is most effective in Garden types I and II fractures in which the capsule may not be torn or completely torn and tamponade may be a major cause in the development of osteonecrosis. Capsulotomies are usually performed in young patients with nondisplaced femoral neck fractures and only occasionally in the geriatric population. Although no conclusive study is available proving that capsulotomy decreases the frequency of osteonecrosis, it can be carried out quickly and safely and may reduce the risk of osteonecrosis.
The incidence of avascular necrosis of the femoral head to be in 9%–18% of patients, between 2 and 8 years postfracture; risk factors include the degree of fracture displacement, patient age, and delay in surgical treatment. Avascular necrosis (AVN) is a well-recognized complication of femoral neck fractures but is not frequently encountered in clinical practice. This is due to a gradual increase in the use of arthroplasty rather than fixation to treat these injuries over the past two decades.
| Blood Supplyof Femoral Head|| |
There are three sources of blood supply of femoral head as shown in [Figure 1]:
- Capsular vessels
- Intramedullary vessels
- Contribution from ligamentum teres
The medial and lateral femoral circumflex arteries arise from profunda femoris artery. The medial and lateral femoral circumflex arteries form an extracapsular circular anastomosis at the base of the femoral neck, and the ascending cervical capsular vessels arise from this, which penetrate the anterior capsule at the base of the neck at the level of the intertrochanteric line. Within the capsule, these are referred to as retinacular vessels. There are four main groups (anterior, medial, lateral, and posterior), of which the lateral group is the largest contributor to femoral head blood supply. The most important retinacular vessels arise from the deep branch of the medial femoral circumflex artery. At the junction of the articular surface of the head with the femoral neck, there is a second ring anastomosis termed the subsynovial intra-articular ring. The artery of the ligamentum teres is a branch of the obturator artery. Some additional blood supply in the adult reaches the head via the medullary bone in the neck.
| Biologyof Post-traumatic Osteonecrosisofthe Femoral Head|| |
In post-traumatic necrosis, cellular proliferation quickly invades the femoral head, inducing significant osteogenesis. The “pathologic fracture,” responsible for the collapse of the femoral head, occurs at the interface between the new and the necrotic bone. Head deformity is caused not by cell death but by the repair process. Reference studies in this regard, show the secondary nature and vascular origin of head deformity. Two stages in necrotic bone repair, forming bone tissue on the surface of dead trabeculae, are as follows:
- Cellular proliferation with invasion of the head by repair tissue
- Mesenchymatous cell differentiation into osteoblasts
In post-traumatic necrosis, once repair tissue has crossed the subcapital fracture line, it extends to form new bone. Arrest of osteoblast differentiation and of osteogenesis is related to intra-head microfractures, blocking the process by inducing mesenchymatous differentiation into fibroblasts, forming a fibrous layer similar to that found in nonunion. The development of this fibrous tissue and the mobility of the fragments leads to resorption of the necrotic trabeculae. The direct cause of the changes undergone by the femoral head is thus not cell death but rather the action of the living cells involved in the repair process, altering the mechanical properties and inducing collapse of the head. The starting point of the collapse is the area of least resistance on the lateral side of the head, created by subchondral bone resorption secondary to the repair process. Collapse shifts toward the center, at the interface between the necrotic cancellous bone and the living bone, because of differences in consistency and elasticity between the two. This two-stage theory of necrosis was confirmed by Steib et al.: intraosseous vascular assessment of necrotic hips using radioactive microspheres found no correlation between macroscopic arterial anatomy and functional vascular anatomy; they highlighted the importance of intraosseous communication and the fundamental role played by the lateral epiphyseal artery.
The development of osteonecrosis has been correlated with multiple factors including the following:
- Age at the time of injury (older patients develop less osteonecrosis)
- Degree of displacement and presence of posterior comminution
- Verticality of the fracture line
- Quality of reduction
- Implant removal
Osteonecrosis of the femoral head can present anywhere between 6 months and many years after the initial injury; however, most cases will present within 2 years. For this reason, patients should be followed at least for 2 years postoperatively looking for signs of osteonecrosis, both clinically and radiologically. Patients will characteristically present complaining of pain localized in the groin, sometimes radiating to the anterior-medial thigh and/or ipsilateral knee. The pain is usually described as deep, throbbing and is exacerbated by weight-bearing activities or at night. There exist many different imaging modalities for diagnosing ONFH; however, plain radiographs and magnetic resonance imaging (MRI) remain the most useful.
To date, no universally accepted classification is available. Ficat and Arlet, one of the sixteen different systems existing in the literature, is the most commonly quoted, followed by those of the University of Pennsylvania, Marcus, Enneking, and Massam, the Association Research Circulation Osseous, and the Japanese Investigation Committee classification. Ficat and Arlet, perhaps the first system used for staging osteonecrosis, was described in the early 1960s by Arlet and Ficat and included three specific stages. In the 1970s, a fourth stage was added, and this form is one of the most widely used today, although a stage 0 and a transitional stage were added later [Table 1]. The patient’s symptoms and physical findings were in part correlated with the radiographic changes, and both histology and functional evaluation of bone (bone marrow pressure recordings and intramedullary venography) were required in the early stages. Bone scanning or scintigraphy was used but MRI was not included. A major disadvantage of this classification was that it did not include any measurement of lesion size or articular surface involvement. Thus, it could not differentiate between small and large lesions nor was it a sensitive indicator of progression. The classifications by Ficat and Arlet are frequently modified to include MRI, whereas bone biopsies and functional evaluation of bone are seldom used today.
The falling incidence of this complication can be seen by three studies published in separate decades. Barnes et al., in a study of over 1500 femoral neck fractures treated by internal fixation, reported an incidence of AVN in 24% of women and 15% of men. The incidence was lower in undisplaced fractures (16%) than in displaced fractures (27.6%). In the meta-analysis by Lu-Yao et al., the incidence of fixation failure and nonunion is 33% compared with a rate of AVN of 16% (95% confidence interval: 11%–19%). By the time of publication of the meta-analysis the reported rate of AVN had declined to a mean of 6.9% (range, 0%–22%). A very similar incidence of AVN of 6.6% was reported in a series of 1023 patients by Loizou and Parker. Several possible explanations are available for the decline in the incidence of this problem. There has been a gradual reduction in the widespread use of reduction and fixation for displaced fractures, the incidence of AVN is lower with undisplaced fractures, and surgeons may now be choosing patients more carefully for reduction and fixation so that only patients with a favorable prognosis are treated with this technique. In their study, Loizou and Parker identified age of less than 60 years and female sex as factors associated with a higher risk of the complication. The diagnosis can be made on the basis of typical plain radiographic appearances, but these may not be evident for a long period. Single photon-emission computed tomographic scan has been shown to be an accurate predictor of AVN if uptake is less than 90%. MRI will detect the problem before plain radiographs, but it is not an accurate predictor of AVN in the early weeks after injury. The complication tends to occur late after surgery. Fractures treated by reduction and fixation take a long time to heal, and AVN usually presents after union. Barnes et al. noted it to be the most common in the 2nd year after injury, but presentation later than this may occasionally occur. The occurrence of AVN does not always require intervention. Barnes et al. reported that of their cases, 24.3% were asymptomatic and 46.4% had an acceptable level of disability. This left 29.2% of patients with significant disability and of these 60% underwent further surgery. More recent studies have reported very similar rates of asymptomatic patients who require no surgery. Diagnosis is straightforward in patients with typical radiographic signs of increased femoral head density or collapse. In symptomatic cases, the usual treatment option is conversion to an arthroplasty. For most patients, total hip arthroplasty is the best choice as the segmental collapse of the head is often associated with degenerative changes in the acetabulum. Furthermore, many patients now treated with reduction and fixation are young, and the best long-term outcome is probably associated with a modern design of total arthroplasty. If the acetabular surface is well preserved or the patient is elderly with limited functional demands or medical comorbidities then a hemiarthroplasty is a reasonable alternative.
Asnis and Wanek-Sgaglione retrospectively reviewed the results of stabilization of femoral neck fractures with cannulated screws in 141 elderly patients. Thirteen patients (9.2%) developed osteonecrosis within 24 months. Osteonecrosis developed in 13 additional patients during 8 years of follow-up, of which 8 patients had displaced fractures. Osteonecrosis occurred in 19.5% patients who had Garden type 2 fracture, in 20% of Garden type 3, and in 30% of Garden type 4 fractures.
Surgical management of osteonecrosis of the femoral head: Treatment of post-traumatic osteonecrosis depends on multiple factors including patient age, stage of disease, level of activity, and symptoms. In majority of cases, once osteonecrosis develops and particularly if it is symptomatic, it will eventually progress to subchondral collapse and secondary osteoarthritis. Once this occurs, the only definitive option remaining is total hip arthroplasty. However, questions remain surrounding the young patient with pre-collapse and early post-collapse ONFH. Multiple joint salvaging techniques have been proposed for patients in whom revision arthroplasty within the patient’s lifetime is a foreseeable concern. Core decompression has been almost exclusively studied in the treatment of idiopathic ONFH. It is the most common method of treatment for pre-collapsed stages of ONFH. It is theorized to work by reducing elevated intraosseous pressure, improving venous outflow, and thereby restoring vascular inflow. Despite early studies showing improvement for all stages of disease, a recent review of four prospective studies with validated outcome scores and a minimum 2-year follow-up showed only minimally improved outcomes. In all four studies, better results were found in pre-collapse and smaller femoral head lesions. Overall, core decompression is a cost-effective choice over observation and its use is recommended as a first-line treatment for pre-collapse disease. Various methods of nonvascularized bone grafting have also been used in the treatment of ONFH. Bone grafting has been recommended when there is less than 2mm of subchondral bone depression, when under 30% of the femoral head is involved, and when core decompression fails. It has also been used in conjunction with other methods, such as core decompression. Post-traumatic osteonecrosis tends to create large lesions, and decompression alone is thought to be insufficient to completely prevent collapse. Without good reproducible evidence, evaluation of these techniques in long-term prospective studies is necessary before they can be recommended for routine use. Vascularized bone grafting using either a local muscle pedicle iliac crest graft or a free vascularized fibular graft has been described for young patients with femoral neck nonunion or ONFH. Commonly cited indications from the studies of nontraumatic ONFH include no evidence of bony collapse or articular collapse of less than 3mm in lesions involving less than 50% of the femoral head. The main pitfalls of vascular grafting are donor-site morbidity and advanced microvascular surgical techniques. Although less predictable for larger lesions typical of post-traumatic ONFH, when following indications, vascularized bone grafting can be effective if used early and should be considered for improving hip function and delaying disease progression. For patients with more advanced ONFH, usually with post-collapse disease, proximal femoral osteotomies have been proposed with the premise of moving the lesion away from the weight-bearing zone. Currently no general consensus is present on indications for proximal femoral osteotomies with some authors obtaining good results, whereas others observed high failure rates. Other concerns surrounding these procedures are poorer outcomes with more challenging subsequent total hip arthroplasty, with increased rates of blood loss, operative time, femoral shaft fracture, and component loosening. We believe that in the right hands, osteotomies can lead to reproducible results, however without generalizable results, one should proceed cautiously when considering proximal femoral osteotomies for the treatment of ONFH.
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