CURRENT CONCEPTS IN INTRAMEDULLARY (IM) NAILING OF FEMORAL SHAFT FRACTURES
Siddhartha Sharma, Hitesh Gopalan U
Intramedullary (IM) nailing is one of the preferred methods for treatment of femoral diaphyseal fractures. Successful intramedullary nailing results in a short hospital stay, a rapid return of motion in all joints, prompt return to walking, and a relatively short total disability time.
HISTORY & EVOLUTION
1) IM nailing was first described by Gerhard Kuntscher, a German orthopaedist in the 1940s and the device came to be known by his name viz. ‘K Nail’.
2) Various ‘generations’ of nails have been described as follows:
a) First Generation Nails
i) Have a characteristic longitudinal slot along the entire length of the nail.
ii) Examples: K Nail, Grosse Kempf Nail (has a proximal portion which is tubular and allows better purchase and insertion of proximal locking screws).
b) Second Generation Nails
i) These are tubular nails without the slot and have provision for proximal and distal locking bolts.
ii) Examples: Russel Taylor Nail (has a clover leaf cross section) and Delta Nail (triangular cross section, thicker wall and thinner diameter).
c) Third Generation Nails
i) Are made from titanium alloys and may be solid or tubular.
ii) Examples: Trigen Nail, Universal Femoral Nail (Synthes)
INDICATIONS OF IM NAILING:
1) Transverse and short oblique fractures of the femoral shaft.
2) Comminuted Fractures: The nail should always be locked
3) Pathological fractures
CONTRAINDICATIONS OF IM NAILING
1. Absolute but correctable contraindications: Hypovolemia, Hypothermia and coagulopathy.
2. Relative Contraindications: presence of previously inserted devices and pre existing deformity.
3. A narrow medullary canal may rule out IM nailing as an operative option.
PRE OPERATIVE PLANNING
1. Good quality Anteroposterior and lateral radiographs of the injured extremity should be obtained to know about the fracture pattern, presence of comminution, medullary canal dimensions and the amount of femoral bow.
2. Length of IM nail: corresponds approximately to the distance between the tip of greater trochanter and the lateral epicondyle of femur. This can be measured directly on the uninjured extremity with a long ruler or on a radiograph, after correcting for magnification.
3. Pre operative skeletal traction is advisable. Many patients can have unpredictable delays in operation and traction maintains femoral length, prevents further soft tissue injury, limits the ongoing blood loss and provides patient comfort. A 2 mm pin inserted through the distal femur adequately tensioned on a traction bow and utilizing approximately 15 – 20 pounds of weight is recommended.
TECHNIQUES OF IM NAILING
1) Antegrade Nailing.
2) Retrograde Nailing.
ANTEGRADE IM NAILING
1) Most commonly used technique
2) Can be done via the Piriformis fossa or Trochanteric entry portals
3) Supine or lateral decubitus positions may be employed.
ANTEGRADE NAILING - PATIENT POSITIONING: SUPINE VS LATERAL
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Fracture table used, traction applied to affected limb
Normal limb: May be placed in hemilithotomy position, widely abducted or scissored
Lateral decubitus position
A. Ease of access for anaesthesiologist & nursing team
B. Ease of imaging the entire femur
C. Ideal for bilateral cases, cases with associated acetabular fractures, polytrauma patients and associated spine injuries (radiolucent table should be used instead of fracture table).
Improved access to Piriformis fossa (therefore better for obese patients)
A. Difficult access to entry point in case of obese patients
B. Increased compartment pressures in the normal leg, especially with hemilithotomy position
A. Difficulty in imaging the proximal fragment
B. Difficulty in assessing rotation
C. Distal fragment tends to tilt into valgus
ANTEGRADE NAILING - ENTRY PORTALS
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PIRIFORMIS FOSSA PORTAL
In the Piriformis Fossa, at the junction of anterior 2/3rd with posterior 1/3rd
From the Greater Trochanter, just lateral to the long axis of the femur
Colinear trajectory with the femoral shaft and therefore decreased risk of iatrogenic comminution & varus malalignment
A. Technically easier to obtain, especially in obese patients
B. It is more forgiving in terms of anterior translation as the bone is cancellous here.
A. Difficult to obtain in the obese patient
B. Sensitive to antero-posterior translation: anterior positioning can cause iatrogenic bursting of proximal fragment due to increased hoop stresses.
Since it is ‘offset’, there are higher chances of iatrogenic comminution and varus malalignment.
RETROGRADE IM NAILING
1. Difficult access to proximal femur: Obese patients, Pregnant patients
2. Ipsilateral Pelvic fractures, femoral neck fractures, Patellar fractures, or Tibial fractures (floating knee).
3. Associated vascular injury, spinal injury or polytrauma patients: rapid stabilization of the femoral fracture can be achieved with the patient placed in the supine position on a radiolucent fracture table.
4. Distal metaphyseal fractures.
1. Limited knee range of motion
2. Patella baja: inadequate room for the nail between the patella and the tibial condyle with the knee in flexion.
3. Open fractures: risk of septic arthritis of the knee
At the Blumensaat line, 1 cm anterior to the origin of Posterior Cruciate Ligament (PCL).
RETROGRADE NAILING - PEARLS & PITFALLS
1. Use of reamed and snug fit locked nails is essential to avoid delayed union and non union.
2. The distal tip of the nail must be countersunk into the subchondral bone of the distal femur. This will prevent it’s impingement on the patella in knee flexion.
3. The nailed should be locked doubly distally. This prevents telescoping of the nail distally into the knee joint which can occur in cases of comminuted fractures.
REAMED Vs UNREAMED NAILING
ADVANTAGES OF REAMED NAILING
Reamed nailing remains the gold standard for IM nails. Prospective randomized controlled trials have shown reamed IM nailing to have union rates approaching 99% with low complication rates. The overall better healing rates can be attributed to:
1. Increased cortical contact area of the nail & thereby better stability.
2. Beneficial inflammatory response to reaming.
3. Deposition of local bone graft at the fracture site.
DISADVANTAGES OF REAMED NAILING
These are mainly theoretical and include:
1) Increased marrow pressures, pulmonary artery pressures and higher rates of fat embolism.
a) These phenomenon have been demonstrated only in animal studies.
b) The phenomenon of embolism is limited & transient.
c) The rates of fat embolism in reamed and unreamed nails are similar.
d) Fat extravasation is greatest during insertion of nail in the medullary cavity and is not dependent upon increased intra medullary pressure.
2) Endosteal thermal damage & endosteal cortical blood supply disruption.
a) The disrupted endosteal blood supply regenerates rapidly and this accounts for high healing rates with reamed nails.
b) However, thermal damage should be minimized by using sharp reamers with deep cutting flutes. The process of reaming should be slow and smooth.
1. OPEN FRACTURES
a. These are much less common than in the tibia, and a good soft tissue cover around the femur accounts for the fact that extensive soft tissue injury must occur before the compounding takes place. Small skin wounds may disguise severe underlying muscle and periosteal injury.
b. The most important risk factor in the development of infection is the severity of initial trauma rather than the timing of initial debridement. It is therefore prudent to wait for the medical condition of the patient to stabilize before proceeding onto management of the open fracture.
c. The principles of treatment are the same as for other open fractures. All non viable tissues should be debrided and thorough lavage done. Debridement should be repeated at 24 – 48 hours in case of highly contaminated fractures.
d. The only contraindication to immediate IM nailing in an open fracture is a case with grossly contaminated medullary canal and severe soft tissue damage. In such cases, provisional external fixation is done to permit serial debridement and thorough lavage. Once the canal has been thoroughly cleansed, conversion to intra medullary nailing may be done.
e. Most gunshot injuries need debridement of the entry and exit wounds only. The deeper tissues may be left as such. Exceptions to this rule include close range shotgun injuries and high velocity gunshot injuries, which are managed as other open femoral fractures.
a. The timing of IM nailing in polytrauma patients should be optimized to prevent further deterioration of the patient’s medical status.
b. IM nailing is associated with release of inflammatory mediators, surgical blood loss and hypothermia, which may jeopardise borderline polytrauma patients, especially those with pulmonary compromise.
c. It is therefore prudent to follow the principle of damage control orthopaedics. Fracture stabilization can be achieved in a quick and effective manner by using monolateral external fixators. This can be converted to IM nailing once the patient’s medical condition improves and there are no signs of pin track infection.
d. Recently,Unreamed retrograde nailing with or without proximal locking has been advocated as an alternative to external fixation in such cases.
3. VASCULAR & NEUROLOGICAL INJURY
a. These are rare injuries and are associated with penetrating trauma.
b. Traditionally, treatment protocols center on skeletal stabilization followed by vascular repair. The monolateral external fixator can be applied rapidly and the fixation can be converted to IM nailing within two weeks, having ensured that there are no pin site infections.
c. However, recent clinical evidence has shown that vascular repair can be done immediately and definitive skeletal stabilization can be safely accomplished subsequently. Reversing the traditional sequence has the advantage of reducing the ischemia time and avoiding the need for a fasciotomy. Definitive fracture fixation can be performed afterwards without the danger of disrupting the vascular repair.
4. IPSILATERAL FEMORAL SHAFT AND PROXIMAL FEMORAL FRACTURES
a. Up to 9% of all femoral shaft fractures are associated with ipsilateral femoral neck or intertrochanteric fractures.
b. 25 – 60% of these fractures are minimally displaced and are therefore easily missed. The diagnostic yield of such injuries can be improved by using dedicated internal rotation radiographs of the pelvis or Computed Tomographic Scans with fine cuts.
c. The treatment plan is dictated by the femoral neck fracture. Optimal treatment is a must for the femoral neck fracture, though it may not necessarily be dealt with initially.
d. Some occult non displaced fractures of the femoral neck can get displaced during IM nailing. Therefore, it is prudent to rule out such fractures in every case of IM nailing on the image intensifier preoperatively and after the nailing procedure. This practice helps in avoiding the delay in diagnosis of such injuries and prevents the devastating complication of avascular necrosis of the femoral head.
e. The different treatment strategies include:
i. A retrograde nail or plating for the femoral shaft fracture along with cannulated screws or sliding hip screw for femoral neck fracture.
ii. A reconstruction IM nail to address both the fractures simultaneously.
iii. In cases of high energy trauma, the femoral neck fractures are vertically oriented midcervial fractures that are inherently unstable. In such cases, a sliding hip screw combined with an antirotation screw is biomechanically better than multiple cannulated screws.
5. OBESE PATIENTS
a. The difficulty in obese patients lies in obtaining a proper entry portal through the piriformis fossa.
b. IM nailing through the trochanteric entry portal using a nail with a proximal lateral bend can be useful in such cases. Another option is to perform retrograde nailing.
COMPLICATIONS OF INTRAMEDULLARY NAILING
1. INTRAOPERATIVE COMPLICATIONS
a. Complications related to positioning:
i. Compartment Syndrome: occurs in the normal limb when it is placed in the hemilithotomy position for the supine approach.
ii. Pudendal Nerve Palsy: can occur due to hip adduction and excessive traction. Most of the cases are transient and show full recovery.
b. Complications related to entry portal:
i. With piriformis fossa entry portal: A portal that is too medial or too lateral may cause fracture of the femoral neck or the greater trochanter respectively. A portal that is too anterior will result in excessive hoop stresses and lead to bursting of the proximal fragment.
ii. With the trochanteric entry portal: There are chances of iatrogenic comminution and varus malalignment. This can be minimized by using nails with a proximal lateral bend.
c. Complications related to reaming & nail insertion:
i. Thermal necrosis and fat embolism: Though the risk is theoretical, it can be prevented by using sharp reamers with deep flutes that are passed down the canal in a slow and gradual fashion.
ii. Iatrogenic comminution: This can be prevented by choosing a proper sized nail i.e. 1 -1.5 mm less than the largest reamer used. The fracture should be kept well reduced during nail insertion.
iii. Malalignment: This can be prevented by ensuring central placement of the guide wire in the distal fragment.
d. Complications related to locking:
i. Overzealous drilling can lead to vascular injury and pseudoaneurysm formation.
ii. Proximal locking screws of the retrograde IM nail can injure branches of the femoral nerve. This complication can be minimized by inserting these screws above the level of the lesser trochanter.
2. POST OPERATIVE COMPLICATIONS
i. ANGULAR MALUNION:
· This is most commonly seen in proximal (30%) and distal (10%) femoral fractures. This is because the interference fit of the nail is not good enough in these situations to ensure adequate alignment.
· It can be prevented by using blocking screws and choosing a nail that is 1 mm smaller than the largest reamer used so as to ensure a snug fit.
ii. ROTATIONAL MALUNION:
· Proper limb rotation can be ascertained by observing the alignment of the anterior superior iliac spine, the patella and the second toe. A comparison with the normal side should also be made.
· If rotational malalignment is identified per operatively, it can be corrected by removing the distal locking screws, correcting the rotation and reinserting the screws.
· CT Scan can help in better evaluation of rotational malunions.
· Symptomatic rotational malunions can be treated by an osteotomy, either open or with an IM saw.
i. The rates of non union with IM nailing are low (<10%), regardless of technique chosen.
ii. Deep seated infection should always be ruled out as a cause of non-union and adequately treated prior to surgical treatment for non union.
iii. The different treatment modalities include:
· Dynamization: This is a useful technique for fractures with distraction. Dynamization allows compression at the fracture site. Success rates vary from 54% - 92.3%.
· Exchange Nailing: This may be used for cases of failed dynamization, atrophic changes or bony defects. Success rates vary from 53% - 96%.
· Plating and bone grafting: This is especially useful for recalcitrant non unions. However, a thorough search must be undertaken to identify and correct any metabolic disturbances prior to such a procedure.
i. The overall infection rates with IM nailing are low (1% - 3.8%).
ii. Infections may be categorised as:
· Early Infection (< 3 months): Such cases are treated by nail retention, serial debridement and organism specific intravenous antibiotics. Nail removal is indicated only if the infection cannot be controlled. In such cases, external fixation or antibiotic coated cement nails may be used. Antibiotic coated cement nails can be created over guide wires or other suitable substrates. Although the fixation is not as good as an external fixator, the dead space in the medullary cavity is filled up and high concentrations of antibiotic are delivered.
· Chronic Infection: Is treated along the lines of chronic osteomyelitis. The aim is to eradicate infection prior to definitive fixation. The IM nail is removed and the medullary canal reamed to allow debridement. Organism specific intravenous antibiotics along with local antibiotic therapy, in the form of antibiotic beads or cement spacers are used for 6 weeks. Host factors, such as smoking, malnutrition and any metabolic disorder are addressed. Regular monitoring is done which includes both clinical and laboratory examinations (Complete Blood Count, Erythrocyte Sedimentation Rates, C Reactive Protein). If there is still any doubt, fresh frozen tissue sections can be obtained intra operatively at the time of definitive reconstruction.
d. Leg Length Discrepancy:
i. This complication occurs in up to 43% of comminuted femoral shaft fractures.
ii. Peroperatively, limb length should be ascertained using a radio opaque ruler and compared with the normal side. In the immediate postoperative period, clinical examination, scanogram or CT Scan can be used to identify leg length discrepancy.
iii. If identified per operatively or in the immediate post operative period, the nail should be relocked at the correct length.
e. Heterotopic ossification:
i. This may occur at the site of nail insertion and is usually of no significance.
ii. Large masses can be excised if they are painful and limit motion.
f. Hardware Prominence:
i. Most commonly seen in case of distal locking screws of the retrograde IM nail.
ii. Knee pain may occur with retrograde nails if the nail is not countersunk properly and impinges against the patella in knee flexion. This may warrant removal if the fracture has united or revision if the fracture has not united, to prevent damage to the articular surface of patella.
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