Internal fixation of intracapsular fractures
M J Parker and CE Tagg
Orthopaedic Department, Peterborough District Hospital, Thorpe Road, Peterborough, PE3 6DA, UK
J.R.Coll.Surg.Edinb., 47, June 2002, 541-547        

The main indications for internal fixation of intracapsular fractures are undisplaced and minimally displaced fractures and displaced intracapsular fractures in those aged less than about 70 years. For displaced fractures, closed reduction is to be preferred to open reduction. Numerous different implants may have to be used; with current practice favouring two or three parallel cannulated cancellous screws. These may be inserted either percutaneously or with minimal surgical exposure. Attention to surgical details of fracture reduction and implant positioning will minimise the risk of fracture healing complications. Postoperative care should generally be unrestricted mobilization with weight bearing as tolerated.

Keywords: hip fracture, intracapsular, internal fixation

INTRODUCTION

A proximal femoral fracture or ‘hip fracture’ is the commonest reason for an elderly person to be admitted to an acute orthopaedic ward. The average age of such patients is about 80 years and approximately three quarters are female. As to be expected in this elderly population, other medical conditions, many of which are chronic, are invariably present. Patients with intracapsular fractures tend to be about two years younger, more mobile and less likely to live in institutional care than those with an extracapsular fracture. (1)

CLASSIFICATION OF INTRACAPSULAR FRACTURES

Intracapsular fractures are also termed subcapital, cervical, transcervical and medial femoral neck fractures. Some of these terms reflect the level of the fracture. Clinical studies, however, indicate that the difference in fracture healing complications between the more distal versus proximal intracapsular fractures is inconsequential.(2) Numerous classification systems exist for intracapsular fractures but the only one of proven clinical value is the simple division into displaced and undisplaced fractures.(3-5) Both the AO and Garden classification have no value other that the divisions into displaced and UN-displaced fractures. (3-6)

INDICATIONS OF SURGICAL TREATMENT

The treatment options for an intracapsular fracture can be either operative or conservative. Conservative treatment has been used in the following situations:

• Immobilisation of the hip in traction or a hip spica was used prior to the development of surgical implants and is now only used occasionally for hip fractures in children.
• Undisplaced and impacted intracapsular fractures may be treated by bed rest followed by gentle mobilisation. This is associated with a markedly increased risk of fracture displacement (up to 50-60%), compared with that after internal fixation (5-15%). This method of treatment, therefore, is only occasionally used nowadays.
• Occasionally, for those patients where life expectancy is assessed to be less than a few days, those individuals who are completely immobile prior to the fracture, or where the patient is at high anaesthetic risk ‘skillful neglect’ of the fracture may be appropriate. This entails good analgesia and expert nursing care. However, even for the immobile patients operative treatment has value in relieving pain and making nursing care easier for transfers.

Operative treatment of an intracapsular fracture may be either replacement arthroplasty or internal fixation of the fracture. Arthroplasty is not dealt with in this article. The indications for internal fixation are outlined in Table 1.

Table 1: Indications for internal fixation of intracapsular fractures

Partially displaced fractures, refers to those cases when the fracture appears to be undisplaced on one view of the radiograph but is slightly displaced on the other view. Normally, it is the lateral radiograph, which reveals the fracture line to be opening as the femoral head tilts into retroversion. Such fractures are better considered as an undisplaced intracapsular fracture and reduction, if necessary, is easily achieved using the fracture table.

When discussing intracapsular fractures a ‘young’ patient is one aged less than 70 years. In practice, a ‘young’ patient is one who is independently mobile and able to get out of the house. Patients considered to be ‘young’ are generally best treated by internal fixation, because if an arthroplasty is used there is a risk that the increased functional demands and life expectancy will lead to a revision arthroplasty in the future. In addition, the younger the patient, the lower the risk of non-union. (3,7) For displaced intracapsular fractures in the elderly, debate exists about whether internal fixation or arthroplasty should be used. In practice, given appropriate surgical facilities and expertise, either treatment may be used to good effect. (8)

For the patient who is considered to be at high risk from anaesthesia (spinal or general), rather than accepting conservative treatment, fixation of the fracture under local nerve blocks should be considered. Other factors that favour internal fixation are those patients taking anticoagulation treatment. In this latter situation, closed reduction and percutaneous internal fixation without discontinuation of anticoagulation treatment may be used. Sources of infection, such as a chronic leg ulcer or indwelling urinary catheter, may increased the risk of sepsis after an arthroplasty and tip the balance in favour of internal fixation. Patients with particular types of intracapsular fractures (Table 1) are generally not suitable for internal fixation. These include pathological fractures secondary to malignant disease or Paget’s disease and patients with metabolic bone disorders secondary to hyperparathyroidism or chronic renal failure. In these situations there is an increased risk of fracture nonunion This also applies to a lesser extent for patients with rheumatoid arthritis. Displaced intracapsular fractures, in which there is a delay of more than a week from injury to surgery, cannot generally be reduced by closed means. Such fractures will either require an open reduction or replacement arthroplasty.

PREOPERATIVE PREPARATION OF PATIENTS

The different aspects of preoperative care to be considered in patients listed for surgery is given in Table 2.

Table 2: Preoperative care

Preoperative traction has no value in relieving pain. (9) It has been claimed to reduce the risk of further fracture displacement occurring, but this remains unproven. The injured leg should always be treated with care as further movements of the joint may jeopardise the precarious blood supply to the femoral head.

For an undisplaced intracapsular fracture, delay from fracture to surgery will not influence the risk of fracture healing complications, other than for the risk of the fracture becoming displaced. Surgery, therefore, is recommended as soon as the patient is appropriately prepared, but need not be out of hours. For displaced intracapsular fractures there is contradictory evidence regarding the timing of surgery. Limited evidence suggests that surgery must be performed as soon as possible after injury to reduce the risk of fracture healing complications.(10) Other studies indicate that a delay of up to a week have no effect on fracture healing but after that time the risk of nonunion is markedly increased.(11,12)

Choice of Implant for Fracture Fixation

Numerous different implants are available for the internal fixation of intracapsular fractures.(13) Comparison between implants can only be made within randomised trials. This is because of the differences in patient selection and variable reporting of results between different case series of patients. A summary of all previously undertaken randomised trials indicates that smooth pins tend to produce inferior results to that of screws.(14,15)

The sliding hip screw has an equal risk of fracture healing complications to that of a multiple parallel screw technique. However, a sliding hip screw fixation is associated with a more prolonged operation, increased operative blood loss and increased risk of wound healing complications. Based on the studies, to date, it is not possible to determine the optimum number (two, three or more), or the type of screws to be used. In summary, at present, a multiple parallel screw method should be used for the internal fixation of intracapsular fractures.

OPERATIVE TECHNIQUE

Fracture table

The first stage of the operation involves transferring the patient on to the fracture table and appropriate positioning. It is the responsibility of the surgeon to supervise this to ensure the patient is secure on the narrow fracture table. The legs are positioned within the traction boots, which need to be correctly fastened, such that the leg cannot fall out. In addition, to enable good quality radiographs in both the anterioposterior (AP) and lateral views to be achieved, the following points should be noted:

• A restraining support should be used at the level of the chest for the injured side.
  
  
• The patient is positioned such that the injured hip can be screened on the AP view without having the fracture table directly beneath the hip.
  
  
• The uninjured leg is flexed and abducted out of the way to allow good access for the image intensifier (Figure 1)
  
  

  Figure 1 Correct positioning of the patient on the fracture table

  
  
• To get the clearest picture on the AP radiograph the screen for the image intensifier should be close to the patient. (Figure 2)
  
  

  Figure 2 Optimum positioning of image intensifier, AP view

  
  
• On the lateral view the optimum position for the image intensifier is again with the screen as close to the patient as possible. (Figure 3)
  
  

  Figure 3 Optimum positioning of image intensifier, lateral view

  
  
• A post in the groin may be omitted if longitudinal traction is not used to give maximum clarity of picture on the lateral view.
  
  
• Excessive movements of the injured limb should be avoided at all times as this may damage the precarious blood supply to the femoral head.

Fracture reduction

Fracture reduction is only necessary for displaced fractures. For those fracture that are partially displaced, gentle reduction may be undertaken whilst screening the fracture. This normally entails internal rotation of the foot whilst screening the fracture on the lateral view. For displaced fractures all reduction maneuvers are achieved using the fracture table and should be undertaken whilst screening the fracture in the appropriate view. (16)

The first part of the procedure is reduction of the fracture in the AP view. This is achieved using longitudinal traction whilst screening. The foot at this stage is in neutral or slight external rotation. In general, only light traction is necessary to bring the leg out to length (Figure 4).

Figure 4 Reduction of the fracture on the AP radiograph using longitudinal traction whilst screening in the AP view to correct limb shortening

Over distraction of the fracture must be avoided as this may damage the femoral head vascularity. Reduction of the fracture on the AP radiograph can be assessed by measurement of the Garden alignment index.(17) The optimum reduction angle is a slight valgus angle of 165-170º, but between 160 to 180º is acceptable (Figure 5). A varus position of less than 160º is unacceptable as it is associated with an increase risk of fracture nonunion

Figure 5 Correct alignment on the AP view of 165-170º

Next the image intensifier is turned to the lateral position and the fracture reduced, whilst screening in the lateral view by internal rotation of the foot. This is likened to placing a scoop of ice cream back on it cone, or closing an open book. The aim is to restore the normal curves around the femoral neck (Figure 6).

Figure 6 Reduction of the fracture on the lateral view to restore the normal curve around the femoral neck

It may be necessary to fully internally rotate the foot; failure to apply full internal rotation is the commonest reason for an inadequate reduction. Over reduction of the fracture is usually impossible due to the intact soft tissue hinge of the posterior femoral neck (retinaculum of Weitbrecht). The reduction alignment angles can be measured and should be 180º, with the femoral head, neck, trochanteric region and shaft in a straight line (Figure 7).

Figure 7 Correct alignment of 180º on the lateral view, with the femoral head, trochanteric region and shaft in a straight line

Open reduction

Failure to achieve a satisfactory reduction by closed means should be rare in an acute intracapsular fracture. In some cases the surgeon has to accept the best reduction possible and this, generally, is preferable to changing the surgical procedure to an arthroplasty. In a young patient, where preservation of the femoral head is preferred, an open reduction may be necessary. Normally, an open reduction procedure should be planned having ascertained the history of a delayed presentation of a displaced intracapsular fracture in a young patient.

The full description of the surgical technique of open reduction is beyond the scope of this article. Essentially, the procedure involves an anterior approach to the hip, incising the anterior hip joint capsule and reducing the fracture under direct vision. (3) Routine open reduction of displaced intracapsular fractures is unjustified as it increases the risk of fracture healing complications. (18)

Aspiration of the hip

Following an intracapsular hip fracture, bleeding from the fracture site may result in an increase in the intracapsular joint pressure, which could impair the femoral head blood supply, by a tamponade effect. Aspiration of the hip by either a capsulotomy or needle aspiration has been recommended to reduce this haematoma. Clinical studies have demonstrated the presence of a haemathrosis with raised pressures within the joint, which are reduced after needle aspiration. However, to date, it is unknown if aspiration of the haematoma leads to reduced fracture healing complications.

As present, it may be prudent to aspirate the hip using a needle, inserted under radiographic control, at the time of surgery. This is more likely to be beneficial for undisplaced fractures in which the intact hip joint capsule leads to higher intracapsular pressures. Open capsulotomy undertaken solely to decompress the joint is inappropriate.

Implant insertion and positioning

The correct positioning of the implant is a matter of debate and much dogma, which is based on little sound evidence. Many of the studies on implant positioning are either theoretical or laboratory-based studies; there are few clinical trials. This is because numerous other factors will influence fracture healing beside the position of the implant. In addition, variations in the radiographic projection of the hip will lead to apparent changes in the screw positions.

There does appear to be consensus, however, that if technically possible, a three-point screw fixation should be achieved. Namely, there should be one screw placed inferiorly (confirmed on the AP radiograph), to achieve three-point fixation at the lateral femoral cortex, calcar and subchondral bone. On the lateral view this screw is centrally placed. A second screw should be superior to this on the AP view but posterior on the lateral view, to again get three point contact with the lateral cortex, calcar and subchondral bone. If a third screw is used, this should be placed separate to the other two screws to achieve fixation of a different segment of the femoral head; such a central placement being seen on both the AP and lateral radiographic views (Figures 8,9).

Figure 8 Suggested positioning of three screws on the AP radiograph

Figure 9 Suggested positioning of three screws on the lateral radiograph

Other technical aspects of screw placement that need to be considered are outlined below:

• The tips of the screws in the subchondral bone should be less than 5mm from the joint line, as this give the best hold on the femoral head.
  
  
• If a screw is being placed off centre on both the AP and lateral views, it should be kept away from the joint line. This is because a screw may appear to be in the bone on the radiographs, but in fact may have penetrated the femoral head (Figure 10).
  
  

  Figure 10 A peripherally placed screw may appear to be within the femoral head on both radiographic views, but in fact it has penetrated the joint

  
  
• The superior/anterior part of the femoral head should be avoided, as the bone here is weak and does not provide such good purchase for the screw. In addition, the screw may damage the blood vessels in this area.
  
  
• Over tightening of the screws or compression of the fracture should be avoided, as this may cause a fracture of the lateral femoral cortex or impair circulation to the femoral head. 18 Washers on the screws are not-necessary.
  
  
• The entry point of the lower screw should not be lower than the lower border of the lesser trochanter (Figure 11). Low angle insertion of screws may lead to a stress point resulting in a femoral fracture at this level.
  
  

  Figure 11: The lower screw should not be inserted below the lower border of the lesser trochanter. An angle of about 130° between implant and the femoral shaft as is suggested

  
  
• Ideally, the screws should be placed parallel to each other to reduce the risk of the screws penetrating into the hip joint as the fracture collapses. However, the dictum of parallel screw placement is not proven. In clinical practice it may be better to achieve some spread of the screws within the femoral head, rather than perfectly parallel screws.

COMPLICATIONS FOLLOWING SURGERY

Apart from the usual complications that may occur in elderly patients after hip fracture surgery, there are specific problems relating to the fracture and its repair.

The main fracture healing complications are that of failure of the fixation to hold, and nonunion of the fracture. This complication may also be termed ‘early re-displacement’and ‘pseudo-arthrosis’. Collectively, this complication is termed ‘nonunion’.An incidence of nonunion of about 5% is to be expected for undisplaced fractures and for displaced fractures it is about 21-33%. (3, 20) Treatment of nonunion may be conservative, but this generally leads to a painful functionless hip. Operative treatment usually entails a replacement arthroplasty. In a young patient in which femoral head preservation is preferred, however, a proximal femoral osteotomy may be indicated. (3) A possible alternative to an osteotomy is refixation with a bone pedicle graft, such as that described by Meyers et al. (21)

The other main fracture healing complication is that of avascular necrosis. This complication is more common in the younger patient, and when it does occur in the elderly it tends to cause less symptoms and may not require surgery. The incidence of avascular necrosis has been reported as about 10% for undisplaced fractures and 12-16% for displaced fractures. (3,20) Treatment is generally with a replacement arthroplasty, although in the younger patient an osteotomy or re-vascularisation procedure may be considered.

POSTOPERATIVE CARE

There need be no restriction of hip movement post-operatively, but the main decision is whether to allow weight bearing. Clinical studies on this topic are few and the limited studies published, suggest that weight-bearing should be allowed. (19) For a young patient who has had internal fixation of a displaced intracapsular fracture, the cautious physician may prefer a period of partial weight-bearing, till radiographic evidence of fracture healing is seen. If non-weight-bearing is the policy, this may actually increase the forces on the hip and its fixation, due to the strength of the muscles around the hip used to keep the limb off the ground.

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2. Rajan DT, Parker MJ. Does the level of an intracapsular femoral fracture influence fracture healing after internal fixation? A study of 411 patients. Injury 2001; 32:53-6
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21. Meyers MH, Moore TM, Harvey JP Jr. Displaced fracture of the femoral neck treated with a muscle-pedicle graft. With emphasis on the treatment of these fractures in young adults. J Bone Joint Surg Am 1975; 57: 718-720