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Wheeless' Textbook of Orthopaedics

Cannulated Screws for Femoral Neck Fracture


- Indications for Closed Reduction and Fixation:
    - indications for closed reduction and fixation:
          - physiologically young patient: age < 65, working patient, good bone stock;
          - demented elderly patient that requires total care;
    - adequate closed reduction w/ no frx comminution or femoral neck defects;
          - patient should be aware that with an inadequate closed reduction, then an open reduction or hemiarthroplasty will be required;

- Radiographs:  - accetable reduction parameters

- Screw Insertion Technique:
    - technique of closed reduction 
    - positioning:
          - supine position on the fracture table:
                  - this is the optimal position for fracture fixation, assuming that a satisfactory reduction is obtained;
                  - advantage is that it is easy to directed the guide pins into the femoral neck and head, since an AP and surgical lateral flourscopic
                           view can be obtained w/o having to move the patient's hip;
                  - disadvantage is that if reduction slips, it can be difficult to re-reduce the hip while the hip is in extended position on fracture table;
          - lateral position:
                  - main advantage is that the fracture table is not required and that hip can be re-reduced if the initial reduction is lost;
                  - main disadvantage is that the frx reduction may slip as the hip is flexed and externally rotated (for the frog leg lateral view); 
    - configuration and number of screws 
    - guide pin insertion point and angle of insertion 
          - ref: Using a cannulated screw as a drill guide and sleeve: a simple technique for multiple-screw fixation for intracapsular femoral neck fracture. 
    - depth of guide pin placement:
          - under flouroscopy, guide-pin is drilled into place along medial cortex of femoral neck & into head to within 5 mm of subchondral bone; 
          - cannulated drill is then placed over each pin and drilling carried out to depth of 5 to 10 mm short of the tip of the pin to keep guide
                 wire from coming out;
          - length of screws to be implanted is determined by direct measurement of guide pins, which have been inserted just shy of subchondral bone; 
          - cautions: if screw and guide pins need to be repositioned due to mismeasurement, replace the guide pin using the blunt end so as
                 to avoid joint penetration;
          - references:
                 - Articular penetration is more likely in Garden-I fractures of the hip
                 - Subchondral screw fixation for femoral neck fractures. 
                 - Prevention of unrecognized joint penetration during internal fixation of hip fractures: a geometric model based on Steinmetz Solid.
                 - [Femoral neck fractures: position of the implant, unrecognized articular penetration and its consequences
                 - [Predictive criterions of unrecognized articular effraction after internal fixation of femoral neck fractures].

- screw selection and insertion: (see insertion of pins for hip frx)
          - in very dense bone, a tap should be utilized into femoral head, but generally is only necessary in lateral cortex;
          - in most systems there are two screw-thread lengths available: short and medium;
          - essential that all screw threads are past frx site (inorder to achieve compression), and therefore short threaded screws will often be required;
          - screws are then inserted and retightened after any traction that has been placed on the limb has been released;
                 - inferior screw is placed first, followed by the superior screws;
                 - guide wire should be removed after screw has passed across fracture to prevent advancing the guide wire into the hip joint;
          - screws are tightened simultaneously, to apply uniform compression across frx & to avoid tipping of femoral head into varus angulation; 
          - reference:
                 - Short versus long thread cannulated cancellous screws for intracapsular hip fractures: a randomised trial of 432 patients.
    - washers: role in maximizing compresssion;
          - The value of washers in internal fixation of femoral neck fractures with cancellous screws: A biomechanical evaluation.
    - impaction of frx:
          - when bone is dense, impaction of frx can be performed after traction is released by applying mallet blows to a broad bone tamp
                     placed on lateral surface of the proximal femur adjacent to screws;
          - following such impaction, the screws should be retightened in hopes of maintaining interfragmentary compression;
    - anterior capsulotomy 
          - some surgeons feel that these patients require emergent reduction and pinning along with capsulotomy (to avoid hematoma and
                   increase in intra-articular pressure); 
          - Intraosseous pO2 in femoral neck fracture. Restoration of blood flow after aspiration of hemarthrosis in undisplaced fractures.






- Post Operative Care:
    - forces acting on the hip joint 
    - as noted by Koval KJ, et al (1998), elderly patients who are allowed to bear wt as tolerated, will voluntarily limit loading of the injured limb;
    - references:
          - Postoperative weight bearing after a fracture of the femoral neck or an intertrochanteric fracture



- Complications:
    - avascular necrosis:
          - Asnis SE and Wanek-Sgaglione L (1994), patients who develop AVN following hip frxs may continue to maintain high level of function;
    - non-union:
    - subtrochanteric fracture:
          - if guide pins are inserted into the lateral cortex at a point below the lesser trochanter a stress riser will be created, risking frx;
                 - holes at this location have been associated with 20 % prevalence of subtrochanteric frx; 
          - references: 
                    Intracapsular Fractures of the Femoral Neck. Results of Cannulated Screw Fixation.
                    Subtrochanteric fracture after cannulated screw fixation of femoral neck fractures: a report of four cases. 

                   
                     


Internal fixation of femoral neck fractures. A comparative biomechanical study of Knowles pins and 6.5-mm cancellous screws

A comparison of femoral neck fixation with the reconstruction nail versus cancellous screws in anatomic specimens.

Fixation of displaced femoral neck fractures. A comparison between sliding screw plate and four cancellous bone screws.

Subcapital fractures of the femur. A prospective review.

Intracapsular fractures of the femoral neck. Results of cannulated screw fixation.

Femoral neck fractures in skeletally mature patients, fifty years old or less

Internal Fixation Compared with Arthroplasty for Displaced Fractures of the Femoral Neck. A Meta-Analysis.

Comparison of internal fixation with total hip replacement for displaced femoral neck fractures. Randomized, controlled trial performed at four years.

Bone grafting in femoral neck fractures: results in 28 cases operated on with multiple pinning and cancellous bone grafting.



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Monday, September 29, 2014 8:30 pm