Management of Intracapsular Neck of Femur Fractures

     Management of Intracapsular Neck of Femur Fractures

                                            Dr KS Dhillon

Anatomy of the proximal femur

The proximal femur consists of the head, neck, lesser trochanter and the greater trochanter. The head is approximately two-thirds of a sphere and its surface is articular except for fovea capitis femoris where ligament of head is attached. The greater trochanter is large prominence which projects upward from shaft on lateral aspect of junction of neck and the shaft of the femur and the lesser trochanter is protuberance on posteromedial side. The  intertrochanteric crest, extends between two trochanters on the posterior aspect and on the anterior aspect a wide, rough intertrochanteric line stretches from greater to lesser trochanter.

The neck extents from the head to the intertrochanteric region and it forms an angle of 125 degrees with the femoral shaft. The angle can vary between 120 to 135 degrees. The angle is less in adults, females and in short people. When the angle is more then 135 degrees, it is referred to as coxa valga and when less then 120 degrees it is referred to as coxa vara.

The head is anteverted between 5-15 degrees and when the anteversion is less then 15 degrees it is referred as increased femoral anteversion. When the the anteversion is less then 5 degrees, the condition is termed femoral retroversion.

The neck shaft angle is 140 degrees and the anteversion is 40 degrees at birth, both of which decreases as we become adults.

The blood supply to the head comes from three blood vessels. The foveal artery which is a branch of the obturator artery supplies the foveal region. The profunda femoris gives out two branches, the medial and lateral femoral circumflex. The ascending branch of the lateral femoral circumflex anteriorly and medial femoral circumflex posteriorly form an extracapsular arterial ring. This ring gives rise to ascending cervical arteries which form a subsynovial intracapsular arterial ring at the base of the head.

Classification of Intracapsular neck fractures 

Depending on the location, the fracture can be subcapital, transcervical or basicervical. Gardens classification is commonly used of intracapsular neck fractures [1].

Type                     Description                                  Undisplaced/Displaced
 I               Valgus impacted incomplete fracture                Nondisplaced
                 Lateral cortex fractured, medial intact 
II               Complete fracture                                              Nondisplaced
III              Complete fracture with partial displacement      Displaced
IV              Complete fracture with complete displacement  Displaced

Table I. Garden's classification

The Pauwel classification divides the fractures three groups based on the inclination of the fracture line relative to the horizontal. In Type I the inclination is less than 30°; in Type II, 30° to 50°; and in Type III it is greater than 50°. As the angle of inclination increases, the transition of forces from being compressive to shearing occurs [2]. The AO classification for intracapsular fractures is too complicated and its use is not recommended [3].

The  reliability of the Garden classification is poor with interobserver Kappa values of between 0.03 and 0.56 [4-7]. Despite the poor reliability of the Garden’s classification it is still the most commonly used classification.

The interobserver reliability of the Pauwels classification is also poor with overall kappa values around 0.31[8].

In order to improve reliability of the Garden classification, some have recommended simplifying the classification by having only 2 groups i.e displaced versus nondisplaced fractures [9,10]. Better Kappa values of between 0.67 and 0.77 have been reported with this simplified classification [9,11].

Treatment of intra-articular femoral neck fractures

Globally with the increasing mean age of the population, the incidence of hip fractures is bound to increase in years to come. These fractures are a common source of morbidity and mortality.

Management of these fractures depends on several factors such as preinjury ambulatory status, age of patient, cognitive function, and comorbidities as well as on fracture factors, such as age of the fracture, displacement of the fracture and the degree of osteoporosis.

The treatment options available include nonoperative and operative treatment for these fractures. Operative options include, percutaneous fixation, closed reduction with internal fixation, open reduction with internal fixation and arthroplasty. With several treatment options available, what then is the best treatment option?

Nondisplaced femoral neck fracture

The premorbid condition of the patient is important in determining whether to treat nondisplaced femoral neck fractures conservatively or surgically. Patients who are elderly and at high risk of anesthesia and surgery-related complications are ideally treated conservatively. Elderly patients who are nonambulatory and those who are severly demented can be treated conservatively. Surgical fixation for nondisplaced will prevent displacement of undisplaced fractures and allow for early mobilization of thr patient.

Nondisplaced fractures can be treated by percutaneous pinning or screw fixation. Zu et al [12] in 2017 carried out a systematic review of the treatment of undisplaced femoral neck fractures in the elderly. Their review included 29 studies involving 5071 patients. One thousand one hundred twenty patients were treated conservatively and 3951 had surgical treatment. The union rates were 68.8% in patients treated conservatively and 92.6% in patients treated surgically. The incidence of avascular necrosis was 10.3% in patients treated conservatively and 7.7% in those treated surgically. Fixation failure rate was low at 3.3%.

Surgical treatment is the treatment of choice for undisplaced fractures of the femoral neck in younger patients (less then 65 years). Conservative treatment is reserved for patients whose surgical risks outweigh any benefits from the surgery. Union rates are higher with operative treatment [13-15].

Oñativia et al [16] carried out a systematic review to study the outcome of treatment of undisplaced femoral neck fractures with screw fixation in the elderly (more then 60 years) patients. Three studies reported mortality rates of 18.8%; 22%, and 19% at one year follow up. One study reported mortality rate of  42% at 5 years. The overall reoperation rate ranged from 8%-19%, with conversion to hip arthroplasty in 8% and16% of the patients.

The authors concluded that internal fixation with cannulated screws for undisplaced fractures of the femoral neck in the elderly is a valuable option despite the substantial reoperation and mortality rates.

Displaced femoral neck fractures

Treatment options for displaced femoral neck fractures include closed reduction and internal fixation, open reduction and internal fixation, hemiarthroplasty and total hip replacement.

Parker and Stockton [17] carried out a Cochrane database systematic  review to determine which implant is superior for the internal fixation of intracapsular proximal femoral fractures. The review included 28 randomized or quasi randomized trials of 5,547 patients with femoral neck fractures who were treated with 19 different pin and/or screw constructs. They found that no one implant was superior to another when it came to outcomes such as fracture healing, AVN, infection, pain scores, reoperation rate, use of walking aids, periprosthetic fracture, or mortality. The sliding hip screw took longer to insert and was associated with an increased blood loss as compared to other modes of fixation.

Parker and Blundell [18] carried out a meta-analysis of 25 randomized controlled clinical trials (RCTs) involving 4,925 patients with intracapsular femoral neck fractures who were treated with various implants. They also found that no one implant was superior to another with regards to nonunion and fracture displacement rates. There was limited evidence of superiority of screw fixation over smooth pins. There was no advantage in using a side
plate for fixation.

Internal Fixation Versus Hemiarthroplasty

Masson et al [19] carried out Cochrane Database systematic review to compare internal fixation with hemiarthroplasty for treatment of displaced femoral neck fractures. The review included 13 trials involving 2091 patients. They found that with internal fixation the duration of surgery was shorter, operative blood loss was less, less blood transfusion were needed and the infection rates were lower when compared to hemiarthroplasty surgery. Arthroplasty on the other hand had a lower re-operation rate as compared to fixation (8% vs 31%). There was no difference in the length of hospital stay, mortality, degree of residual pain and postoperative mobility.

Parker et al [20] carried out a prospective randomised study to compare the outcome of internal fixation as compared to hemiarthroplasty in patients over the age of 70 years with displaced fracture of the femoral neck. The study included 455 patients. They found no differences in the outcomes for
pain, mobility, or mortality at 3-year follow-up. The revision rate was 5% for the hemiarthroplasty group and 40% in the internal fixation group.

Rödén et al [21] carried out RCT of 100 patients with displaced femoral neck fracture who were treated either with screw fixation or a bipolar prosthesis. The patients were more then 70 years old and were ambulatory before the injury. The duration of surgery was shorter and the blood loss was less in the internal fixation group. The revision rates were very high (34 of 53 patients) in the internal fixation group. Seven out of 47 patients with hemiarthroplasty had a postoperative dislocation. The mortality rates were similar at  2- or 5-year follow-up.

Rogmark et al [22]  carried out an RCT comparing internal fixation with hemiarthroplasty. At 2-year follow-up, those patients who hemiarthroplasty had improved walking and stair climbing ability, and less pain as compared to those who had internal fixation.

Lu-Yao et al [23] carried out a meta-analysis of 106 reports on the treatment of displaced fractures of the femoral neck. They found that within the first 2 years of follow up, 33% of patients who had internal fixation of a displaced fracture of the femoral neck, developed a non-union and 16% developed avascular necrosis. The reoperation rates were 20% to 30% in patients who had internal fixation as compared to 6% to 18% after hemiarthroplasty. They found that the mortality rate at thirty days was higher in patients who had a hemiarthroplasty as compared to patients who had internal fixation. The difference, however, was not significant (p = 0.22) and the difference did not persist beyond three months. The mortality rates at 2 months were lower in patients who had an anterior operative approach for the arthroplasty as compared to a posterior approach.

Fracture of the neck are common in the elderly and hence most of these studies were carried out in elderly patients. There is a paucity of literature on the outcome of treatment in the younger population.Though the outcome in patients with hip arthroplasty appear to be better then internal fixation in most of the studies, the goal of treatment in the younger population would be preservation of the hip by internal fixation of the fracture and dealing with complications as they arise.

Cemented or Cementless Hemiarthroplasty

The earlier hemiarthroplasty prosthesis known as the Austin Moore prosthesis were uncemented prosthesis. Then came the Thomson prosthesis which were cemented. These are still in use today. The outcome with cemented prosthesis is better then non-cemented prosthesis.

Parker et al [24] carried out a Cochrane systematic review to assess the outcome of cemented and uncemented hip arthroplasties for the treatment of femoral neck fractures. They found that there is good evidence which shows that cementing the prosthesis in place reduces postoperative pain and leads to better mobility.

Emery et al [25] carried out RCT of 53 hemiarthroplasties. Twenty seven patients had a cemented hemiarthroplasty, and 26 patients had a cementless hemiarthroplasty. At 17 month follow up they found no statistically significant difference between the groups as far as  postoperative complications such as surgical time, estimated blood loss, or mortality, were concerned. Patients with cementless stems, however,  experienced a much higher level of hip pain and were more dependent on walking aids.

Lo et al [26] also found less thigh pain in patients with cemented stem and their Harris Hip Score was higher then those with uncemented stems. There was no significant difference in complication and mortality rates.

Foster et al [27] found that 7% of the patients with cementless prosthesis had periprosthetic fracture while none of the patients cemented hemiarthroplasty had periprosthetic fracture. This study involved 244 patients, Austin Moore prosthesis were used in 70 patients and cemented Thompson prosthesis was used in 174 patients.

There is overwhelming evidence in the literature to support the use of a cemented prosthesis in the treatment of displaced femoral neck fractures in the elderly.

Unipolar or Bipolar Hemiarthroplasty

The bipolar prosthesis was introduced to reduce acetabular wear and revisions after a hemiarthroplasty by having prosthesis to prosthesis interface in a bipolar prosthesis. Many studies have tried to document superior results with a bipolar prosthesis.

A Cochrane systematic review by Parker et al [24], involving 7 trials with 857 participants and 863 fractures of the neck of the femur, comparing  unipolar hemiarthroplasty with bipolar  hemiarthroplasty showed no significant differences between the two types of implants.

There is level II evidence in the SIGN database which compares unipolar with bipolar prostheses. One of the studies by Eiskjaer et al [28] showed that there was radiological evidence that majority of motion in bipolar prosthesis occurred at the outer articulation (acetabulum-prosthesis interface). There was little or no motion at the motion at the bipolar interface. Hence the bipolar prosthesis are no different from unipolar prosthesis. The SIGN recommendations state that bipolar hemiarthroplasty should not be used in preference to unipolar hemiarthroplasty since there is limited evidence of clinical benefit of bipolar prosthesis.

Kanto et al [29] carried out a prospective, randomized controlled trial of 175 displaced intracapsular femoral neck fractures in patients over 65 years. Eighty eight had patients were treated with unipolar and 87 with bipolar prosthesis. They found no difference in revision rates between the two groups at 8 years follow up.

Ng and Lee [30] carried out a study involving 193 patients who had displaced femoral neck fractures. One hundred and eighteen of the patients were treated with unipolar prosthesis and 75 were treated with a bipolar prosthesis. At an average follow up of 4 years there was no difference between the two groups with regard to hip pain, functional hip scores, rates of acetabular erosion, component migration, revision surgery and complications rates. The authors concluded that the use of more expensive bipolar prosthesis in elderly patients is not justified.

Calder et al [31] performed a randomised prospective trial to compare a unipolar prosthesis with a bipolar prosthesis in the treatment of hip fractures in patients over the age of 80 years. At 2 years follow up they found no statistical difference between the rate of complications in the two groups. The degree of return to the preinjury state was significantly greater (p = 0.04) in patients with unipolar prosthesis. The cost of a unipolar prosthesis, according to the authors, is one quarter that of a bipolar.  The authors concluded that there can be no justification for the use of an expensive bipolar prosthesis in patients over 80 years of age.

The above studies provided level I evidence in support of unipolar prosthesis. There are several studies which favour the use of bipolar prosthesis and these include studies by Eiskjaer and Ostgård [32] (level II evidence), Yamagata et al [33] (level III evidence) and Haidukewych et al [34] (level IV evidence).

Internal Fixation or Total Hip Arthroplasty (THA)

There are several studies which provide level I and II evidence that THA
leads to better outcomes than internal fixation in patients with displaced femoral neck fractures. The function scores are higher and revision surgery rates are lower in patients treated with THA, as compared to those treated with internal fixation [35-42]. This can be an option in patients who are elderly, healthy and cognitively intact.

Complications of fracture neck femur

High mortality rates in patients with femoral neck are seen in the elderly population and not in the younger population. The young patients, however, suffer great morbidity due to high rates of osteonecrosis and non-unions.

Femoral head osteonecrosis 

The overall incidence of AVN of the femoral head in patients with femoral neck fractures has been reported to be as high as 25%. In young patients the average incidence AVN after femoral neck fractures is about 45% [43].

Several factors influence the development of osteonecrosis including age at the time of injury (AVN is less in older patients) the degree of displacement, posterior comminution, fracture line verticality and the quality of fracture reduction [44]. Most cases of AVN present within 2 years but it can manifest anytime between 6 months and 6 years [43].

Patients usually complain of groin, gluteal, or proximal thigh and or ipsilateral knee pain.The pain is usually deep seated, throbbing in nature and weight-bearing activities aggravate the pain. The pain can also be present at night.

In the early stages an MRI is the most useful imaging tool and in the later stages, x rays can demonstrate the presence of AVN. The Ficat and Arlet classification is commonly used for classifying the stages of AVN. They use a combination of plain x rays, MRI, and clinical features to stage avascular necrosis of the femoral head.

Ficat and Arlet Classification [45]

Stage 0

• Plain x rays: normal
• MRI: normal
• Clinical symptoms: nil

Stage I

• Plain x rays: normal or minor osteopenia
• MRI: edema
• Bone scan: increased uptake
• Clinical symptoms: pain usually in the groin

Stage II

• Plain x rays: mixed osteopenia and/or sclerosis and/or subchondral cysts, without subchondral lucency 
• MRI: geographic defect
• Bone scan: increased uptake
• Clinical symptoms: pain and stiffness

Stage III

• Plain x rays: crescent sign with/without cortical collapse
• MRI: same as plain radiograph
• Clinical symptoms: pain and stiffness hip with pain radiating to knee and limp
• Stage IV
• Plain x rays: end-stage with evidence of secondary osteoarthritis 
• MRI: same as plain radiograph
• Clinical symptoms: pain and limp

Haidukewych et al [46]  reported an overall AVN rate of 23% in 82 patients aged between 15 and 50 years, with 83 femoral neck fractures. Sixty five percent of the patients with AVN required total hip arthroplasty. Twenty nine percent of the patients with AVN did not have significant symptoms and did not require additional surgery. Jain et al [47] in a retrospective review of 38 patients with subcapital fractures of the femoral neck treated with internal fixation reported that the occurrence of AVN did not significantly affect patient functioning at the 2.5-year follow-up. Overall the rate of femoral head retention at 6 years is about 82% which would mean that about 18% of patients younger than age 50 years would require a total hip replacement [43].

Management of osteonecrosis of the femoral head

The definitive treatment of symptomatic AVN is total hip arthroplasty. However in young active patients this is not a suitable option. Several joint preservation options are available such as core decompression, bone grafting and femoral osteotomy.

Core decompression

Core decompression has been used in the treatment of idiopathic AVN. The procedure involves drilling a 10mm channel from the lateral femoral cortex to the center of the necrosis area to improve venous flow and improve perfusion of the femoral head. Its efficacy in post traumatic AVN has not been tested. This technique can only be used for Ficat grades I and II for pain relief. It however cannot prevent progression of the lesion [48]. Buckley et al [49] achieved a 90% success rate with core decompression combined with curettage of the necrotic area and insertion of autograft, in the treatment of atraumatic AVN. This technique will be more useful than core decompression alone in the treatment of traumatic AVN.

Bone grafting

Vascularised and non vascularised bone grafting has been used in the treatment of AVN. Various methods of bone grafting have also been used. Bone grafting is usually recommended in patients who have less than 2 mm of subchondral bone depression and when the femoral head involvement is less than 30% and also in patients when core decompression has failed [50].
Both vascularised and non vascularised fibular grafts have been used to treat non traumatic AVN.

Plakseychuk et al [51] compared the outcome of vascularized and nonvascularized fibular grafts for Ficat stages I to III AVN. At 7 years follow-up, the authors reported an 80% femoral head survival for stage I and II hips in the vascularized fibula group compared with 30% in the nonvascularized group. The results for stage III hips were poor in both  groups.

Rotational Osteotomy

The anterior-superior part of the femoral head is typically involved in  advanced osteonecrosis (stages III and IV). In such patients a rotational proximal femoral osteotomy can be carried out to shift the collapsed portion away from the weight bearing zone of the femoral head. This operation can only be carried out when at least 66% of the femoral head cartilage is intact [52]. Sugioka et al [53] have reported excellent results with rotational osteotomies of the proximal femur in patients with stage III and IV.  They reported a 73% success rate in stage III and a 70% success rate in stage IV disease at 3-year to 6-year follow-up. Gallinaro and Masse [54] obtained satisfactory outcome in 62.5% of their patients with stage II and stage III disease with a flexion osteotomy of the proximal femur.

Mont et al [54] were able to obtain good or excellent results in 76% of their patients who had osteotomies for stage II and stage III disease. Twenty four percent of their patients had a fair or poor result.

Total Hip Arthroplasty

The last option for the treatment of AVN is a total hip replacement. The earlier reports of total hip arthroplasty (THA) in patients with AVN showed poor survivorship and outcomes [56-60]. More recent reports, however, suggests that the survivorship or outcomes of THA for AVN are improving [61-64]. With better outcome of THA in patients with AVN, more patients are now offered a THA instead of joint salvage procedure.

Non-union

The incidence of non-union after femoral neck fractures varies between 10% to 33% [65]. The degree of initial fracture displacement, the quality of reduction and increasing age of the patient correlates with a higher risk of a non-union[66-69].

The patient typically presents with pain in the groin. X rays will show the presence of nonunion. When any doubt exists then a CT scan will help confirm the diagnosis.
The options available for treatment of a nonunion include, fixation with new implant, valgus osteotomy, prosthetic replacement and arthrodesis. In  young patients, salvage of the femoral head with preservation of the hip joint is desirable. This can be achieved by a valgus osteotomy or bone grafting [70].

A valgus osteotomy converts a vertical fracture line into a horizontal fracture line thereby converting the shearing forces parallel to the nonunion to compressive forces which promote healing.
Marti et al [71] published a large series of 50 patients with femoral neck nonunion who were treated with a Pauwel abduction osteotomy. The average age of the patients was 53 years and the average follow-up was  7.1 years. Forty-three of the 50 femoral neck nonunions healed (86% union rate). The seven femoral neck nonunions which did not heal were treated with prosthetic replacement. Other authors have reported union rates of between 85% to 100% [72].

Bone grafting is rarely used for treatment of femoral neck nonunions. Bone grafting is usually carried out when there is considerable loss of bone stock and in non-unions with well-aligned fractures where the shear angles are low [44].

Conclusion

Nearly half of the hip fractures involve the femoral neck and these fractures are seen in the elderly who sustain these fractures from simple falls. Femoral neck fractures are rare in young adults. Displaced femoral neck fractures in the elderly patients are treated with a hemiarthroplasty or a hip replacement. Non-displaced and valgus impacted femoral neck fractures are treated with internal fixation. Nonelderly patients are not suitable for hip arthroplasty and they are treated by hip preservation surgical procedures such as close or open reduction with internal fixation of the fracture.
Non surgical treatment is reserved for patients who are not fit to undergo a surgical procedure.
The outcome of surgical fixation of nondisplaced fracture is good but the treatment of displaced fractures is fraught with major complications such as nonunions and or AVN. Nonunions of femoral neck fractures can be treated with valgus osteotomy with very high success rate. Treatment of AVN can be a problem in young active patients. The treatment options for AVN are not so reliable and often a total hip arthroplasty is required which has a limited lifespan and is not suitable for young patients.

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