Pitfalls of Proximal Femoral Nailing and How to Avoid Them?
Vol 2 | Issue 1 | January-April 2025 | page: 6-17 | B. Shivashankar
Authors: B. Shivashankar [1]
[1] Iyer Orthopaedic Centre, Solapur, Maharashtra, India.
Address of Correspondence
Dr. B. Shivashankar,
Consultant Orthopaedic Surgeon and Traumatologist, Iyer Orthopaedic Centre, 103, Railway Lines, Solapur-413001, Maharashtra, India.
E-mail: drbshivashankar@gmail.com
Abstract
Intertrochanteric (IT) fractures in the elderly are a challenging surgery. The bones are osteoporotic with implants having less hold as well as the comorbidities associated in these elderly leads to almost one-third mortality by the end of 1 year, which is a major global economic burden. The hip fractures accounted for over 250,000 fractures in US itself every year. The worldwide problem at present stands at over 2 million fractures, and it is bound to triple by the next 50 years due to the elderly surviving more with better healthcare facilities. The treatment option for osteosynthesis includes open/closed reduction and fixation either with surface implants such as dynamic hip screw (DHS) or intramedullary (IM) implants such as proximal femoral nail (PFN).
Keywords: Dynamic hip screw, Proximal femoral nail, Treatment Outcome
Approximate period between 1999 and 2010, most of the studies and the Cochrane reviews were advising DHS or the sliding Hip screw for Stable IT fractures whereas for unstable fractures, the IM implants were advocated.
Now, most of the studies including the recent Cochrane data advocates the use of IM hip implants both for stable and unstable fracture. The author also prefers and advocates the same. He says that learn the technique of PFN in simple stable fractures first and then gradually master to treat complex unstable fractures. There are studies done in USA where the cost of treatment either with DHS or PFN are the same and in the early 2000 when there was not much evidence to treat stable fractures with PFN, the surgeons still preferred to treat them with PFN over the DHS/SHS. But over the years, the surgeons treating IT fractures with a DHS has become minuscule and almost all prefer to treat them now with IM Nail. The author has designed a Key Hole DHS technique with incision as small as just 2 cm but, in spite of that, he prefers to treat the IT fractures with a PFN. (Shivashankar, B., Shah, S., Kumar, G. et al. Keyhole Sliding Hip Screw Fixation for Stable Intertrochanteric Hip Fractures: A Novel Technique. JOIO 56, 1101–1107 (2022). https://doi.org/10.1007/s43465-022-00624-5).
Before discussing about some of the pitfalls, let us first know, which re the important things in a PFN which gives good fixation. Reduction is the most important aspect of any fracture. The outcome of any surgery mainly depends on the skill of the surgeon how best he can reduce the fracture in the given situation. Once a fracture is reduced well, it can be stabilized in that reduced position using any of the so many varieties of IM implants which are available in the market. The author prefers PFN and trochanteric fixation nail (TFN) with two screw system as first choice, though many surgeons prefer to use a single neck screw system like PFN A2 due to its easy in usage and surgeon friendly instrumentation set.
The most common mistake done while treating IT fractures with a nail is Varus reduction which is followed by negative cortical support, passing the nail through the fracture site, not compressing the fracture adequately, longer screws and lateralization of the shaft. There are many more reasons also. Let us discuss here in this article about most common pitfalls and how best we can avoid them by taking proper precaution.
Varus reduction: The most important cause for failure in PFN is varus reduction. This could be due to inability to access the hip from an eccentric entry due to positional problem or due to improper entry. Normally all these cephalomedullary nails became more popular due to their easy entry from the tip of the trochanter, but unfortunately as the bone is softer more on the outer aspect, the entry site automatically gets reamed more on the outer aspect and causing sift of the entry site much more lateral inadvertently, which leads to varus. This can be avoided by proper entry from medial to the base of greater trochanter or even better is taking the entry on the neck itself like piriformis fossa entry (Piriformis entry is a misnomer. It is in AP looks like piriformis fossa entry, but in lateral, it is more in the center rather posterior like piriformis fossa entry for femoral nailing). So let us discuss how we can avoid this varus by proper positioning of the patient and also by taking proper entry.
a. Position: For doing any hip surgery, the surgeon must be comfortable and he should have good access to the hip. The author prefers eccentric placement of perineal post (Fig. 1a), so that after reduction and fixation with K wires, the limb can be adducted to get easy access of the hip to pass the nail more on the medial side of greater trochanter or from the neck itself. This eccentric placement of the perineal post helps in adducting the limb without the worry of fracture opening superiorly to cause varus which happens due to thigh touching the perineal post. To prevent the patient sliding back from eccentric position to centric position, author uses a small sand bag tied to the table as shown in Fig. 1b and c. The author also tilts the table by about 15–20° on the normal side (Fig. 1d and e). This helps in getting proper lateral view of the hip as the femoral head and neck are anteverted. This tilting prevents patient falling on the side of the surgeon too. A side support or the chest support also prevents patient sagging on operative side especially when traction is applied for the limb. Few surgeons prefer lateral decubitus position but the author prefers to operate these IT fractures on a traction table and only sub trochanteric fractures he prefers to use lateral position.
b. Entry Point: The author strongly recommends for all nailings of the femur by any implant entry in line with the medullary canal. He feels that shifting entry more laterally from the tip of trochanter is the basis of mal reduction and in turn failure due to varus. He also feels that the tip of the trochanter is more laterally placed in Asians compared to Caucasians in whom the medullary canal is almost in line with the tip of the trochanter (personal view of author, which needs to be supported by a large study). The entry point has to be done in line with the medullary canal, which is almost always either the piriformis fossa (Fig. 2a), which is a misnomer as piriformis fossa is much more posterior in the lateral view and not in the central part where the entry is taken for cephalomedullary nails, this area is medial to the tip of trochanter at its base in AP and center of neck in lateral view (Fig. 2b). One should take care to enlarge the entry site, which is on the thick cortical bone of the neck by sharp awl (Fig. 2c and d) or by a cheese cutter (Fig. 2e-g) and avoid the entry site getting lateralized. As the bone is weaker on the lateral aspect, while passing the centering awl or the entry reamer, more bone gets removed on outer aspect and the entry site will get lateralized inadvertently leading to varus happening (Fig. 2h). This in turn leads to the head and neck tilting in varus as well as screw position not proper in the head and neck, (screw in the inferior part of the neck will be central or in superior portion of the head) leading to early cut out of the improperly placed neck screw in a varus head.
2. Reduction: The second most common problem is inability to get a proper reduction. Majority of the time the beak of the proximal fragment or the neck will be lying inside the medullary canal of the shaft and the surgeon feels it as a stable reduction like a Dimon- Hughston reduction, which is a stable reduction for a surface implant like DHS. For IM implants, he beak inside the distal shaft is always a varus reduction or negative cortical support as per the newer terminology and the surgeon should first get the beak out from the medullary canal and reduce the fracture in valgus or positive cortical support. Even if one gets the reduction, but to pass a nail, limb adduction may be required and the reduction gets lost during the attempt to pass a nail. So the author strongly advices to fix all these fractures once reduced with two K wires passed at least a cm apart and then adduct the limb without the worry of fracture slipping again into varus. The author in majority of the cases uses his technique of intra focal manipulation with a Steinmann pin as discussed subsequently.
a. Reduction and Temporary K Wire fixation: The foremost important factor for successful outcome with IM nailing is reduction. Reduction has to be good both of medial as well as anterior cortex. The reduction has to be in valgus or positive cortical support, so that the neck beak can never slip into the shaft medullary canal into varus leading to failure. The reduction has to be in additional 5–10* valgus especially if there is a void medially created by avulsed lesser trochanter. The reduction can be assisted either by manipulating the fragment by closed techniques or by percutaneous mini-open techniques such as using a bone lever, bone spatula, bone hook, and collinear clamps. The author prefers to use percutaneously passed Steinmann pin (Fig. 3a) for intra focal manipulation and prefers to fix with two Kirschner’s wires of 2.5 mm thickness placed more anteriorly in the head and neck (Fig. 3b), so that they will not hinder the further steps of surgery like either passing of the nail or the neck screws. Once the fracture is fixed with 2 K wires after reduction, the limb can be adducted (Fig. 3c and d) as needed without the worry of fracture going into varus or the fracture opening superiorly especially while reaming with centering awl to lead to varus and the nail can be passed easily.
Good medial reduction (positive cortical reduction) or the valgoid reduction of at least 5° more in valgus compared to the normal side is also very important. While reducing make sure that neck beak is outside the distal fragment (positive cortical reduction) and should not enter into the shaft (negative cortical support) (Fig. 3e-g). One should aim at neutral with valgus or Positive cortical reduction. This can be done by intrafocal Steinmann pin pushing the beak out medially and reducing the foot traction minimally so that beak will overlap medially on the beak of the shaft and it can never slip back inside the distal canal due to this few mm overlap (Fig. 3n).
If there is a large medial fragment of lesser trochanter extending into the subtrochanteric area, the author prefers to fix them with encirclage wiring. In just avulsion of lesser trochanter, even if you do not open or reduce it into its bed, a good valgus compensates for the medial void very well (Fig. 3l and m).
If there is a large medial fragment, fixing them with a encirclage wiring (Fig. 3o and p) as the first step as this gives stability to the fracture and helps in early union. Minor fragments can be left alone if fracture is treated by closed methods, but if large fragments are left alone, it takes more time for the fragment to get incorporated and heal and hence the author advocates anatomical reduction and wiring whenever possible.
3. Passing Nail through fracture site: This is another major common mistake which is noticed by the author. Many a times surgeons feels that, as the fracture is due to severe osteoporosis and the bone is soft and comminuted, he shovels the nail through the fracture without making any space for the nail or by not using the proximal reamer or the centering reamer (Fig. 3a and b). Sometimes it is due to not using the proximal reamer or the centering awl properly to ream the canal. The reamer is inserted at the fracture site and reaming is done, unfortunately sometimes if the bone is strong, this reamer doesn’t ream the proximal canal well and the fractured bone surfaces just gets separated from one another while the reaming is being carried out. Once the nail is passed after this improper proximal canal preparation, the nail distracts the fracture surfaces and acts as a spacer (Fig. 3c and d).Thus reducing the contact of fractures ends as well as lateralising the femoral shaft. Which in turn leads to longer neck screws to be used. The longer neck screws will have more stress at the nail screw junction leading to improper sliding and failure in due course of time which is mainly varus collapse of the head and cut out of the jammed screws superiorly.
This can be avoided by placing the patient eccentrically and also fixing the fracture with two K wires as described earlier. Regarding the eccentric placement of the patient which has been already described earlier, it needs little more detailed understanding. Hence, in the next few lines, the author is explaining in detail to drive home the point.
a. Eccentric Placement of Patient on the table: Normally, the perineal post will be in the center, but on adduction, the thigh touches the perineal post and on further adduction, the perineal post becomes the fulcrum against which the thigh will be adducted and the fracture opens up superiorly leading to varus. Many a times even an undisplaced fracture on adduction and trying to ream with centering awl, fracture opens up superiorly leading to varus. Sometimes, the surgeon notices the varus happening at the fracture and he tries to abduct the limb after passing the nail, during this procedure the fracture opens up inferiorly also leading to lateralization of the shaft. The nail will be acting as a spacer and distracting the fracture site and also the length of the neck screws required will be much longer than expected. Here is few diagrammatic representation of the distraction and lateralization cause due to shovelling of the nail through the fracture site without preparing the canal properly.
Lateralization of the shaft due to insertion of nail through fracture site without proper reaming. Normally the line dropped from outermost part of pelvis (White dotted line) just grazes the trochanter or passes tangentially. On the operated side due to shaft lateralization, note that it passes more medially. Though the fracture has united here, the biomechanics of the hip will be altered and the patient will limp due to the lateralization of shaft and will have Trendlenberg gait.
b. Fixing the Fracture with K wires: As described earlier in detail, fixing the fracture after reduction with K wires helps in adducting the limb as much as required without the worry of fracture going into varus. These K wires also helps in proper reaming with the entry reamer without causing separation of the fracture surfaces, as shown in Fig. 3e and f.
4. Improper Neck Screw Placement: Many a complications are due to improper placement of the neck screws. The Cervical screw which is inferior in the neck will be either in the center or superior portion of the head. They are also many a times short and not sub Chondrally placed leading to having less purchase in osteoporotic bone and walking off in due course or using a longer derotation screw causing the derotation screw taking the brunt of weight transmission leading to failure like breakage at the junction of shaft with threaded portion or Z effect due to jamming of the superior bolt in the nail.
a. Proper placement of Neck Screws: Neck screws should be placed parallel to the calcar, in the centre or inferior third of the neck in AP view so that the tip of the screw should also be in the inferior part of the head and not at the centre or superior portion of the head (Fig. 4a). This will allow easy sliding of the neck screw within the nail and causes less jamming. Similarly in the lateral view, it should be in the center or slightly posterior to the center so that it has the best purchase in the strongest part of the bone. For passing these screws properly over guide wire, one should use the trocar first to make the starting hole in the lateral cortex of the bone. The long guide wires of 1.8–2mm are not made for drilling the thick lateral cortex like the drill bits and they may slip over the bone especially due to longer lever arm from the other end where drill machine is attached (Fig. 4c). Author prefers to use the two screw system and if, two screw system are used, both the neck screw should preferably end at a same horizontal plane, the derotation screw being little smaller and shorter. This helps in easy sliding of both the screws, while if superior derotational screw is longer, the load is taken predominantly by this screw leading to breakage or the sliding mechanism getting jammed due to stress in the screw nail junction leading to Z effect. b. TAD of neck screw: TAD more leading to neck screw not having good purchase leading to screws backing out is another common pitfall noticed. The best purchase any neck screw will have is in the sub chondral bone and hence, the neck screw should be placed as sub chondral as possible, so that TAD is very less. As the author prefers neck screw placement in the inferior part of the head and neck, if TAD is measured from fovea centralis, even though the screw is sub chondral, the TAD measured will be more in spite of screw being in a very good and strong bone position. Hence one should measure not TAD but, The Calcar TAD (Cal TAD), which is measured by extrapolating the screw line to the subchondral bone and where that line meets the articular surface, the TAD is measured from that point instead of measuring from more centrally and superiorly placed fovea Centralis (Fig. 4g). Hence, we should aim to keep the Cal TAD definitely below 25 mm considering both AP and Lateral picture measurements together.
Fracture not compressed: Many a times, we all feel that the sliding mechanism in the nail will allow gradual collapse and compression to happen. We all are so much brain washed by the sliding of DHS/SHS, we all feel that sliding and collapse is required in all the implants for the IT fractures to unite. Unfortunately, this sliding is uncontrolled and in some cases, too much of sliding will cause more problems. We all have seen failures in intracapsular fractures when partly threaded CC screws are used and hence nowadays, we all prefer to prevent this unwanted collapse either using fully threaded screws or using a Pauwel’s screw which is more horizontal and prevents sliding and collapse. The author feels that he failure with PFN is also due to uncontrolled collapse in a improperly compressed fracture. Hence he advocates to compress the fracture to satisfaction on table (after releasing the foot traction). This is possible with neck screws having head like PFN or TFN and not available in newer single screw systems such as PFN A2, TFN A, ZNN, and Halifax Nail. Even though these newer headless screw systems have set screw to compress fracture ad fix in that position by set screw, the lateral wall will be still mobile and the desired compression will not be retained (though can be achieved on table) till the time fracture requires to unite.
a. Well compressed fracture: The author feels that the fracture needs to be well compressed on table itself and one should not rely on the uncontrolled inbuilt collapse which can happen by gradual sliding of the neck screws within the nail. Author feels that failures in PFN is mainly due to not adequately compressing fracture which mainly happens due to not releasing the traction before final neck screw tightening or by using a little shorter screw or due to using little longer screw and leaving it out slightly. Using little shorter screw the surgeon tries to reach the subchondral bone and by these extra tightening the shorter screw the threads of the screw looses its purchase and becomes loose in the osteoporotic head. The author further says that the failure are mainly due to head of the neck screw not having the support of the lateral wall which leads to toggling of the screw and to loose purchase in the bone.
The author feels that the sliding mechanism of the neck screws in the nail is not at all required in all cases and only in few cases where there will be extra resorption at the fracture site only the implants sliding neck screw mechanism should be relied. Yes in the eighties and nineties when the IM implants were not available, the DHS with its sliding mechanism was the gold standard and we all relied upon the fracture collapse for union. That does not mean that we should allow uncontrolled collapse to happen even now when better fixation systems like the IM nails are available.
b. Tips for headless neck screws: The author personally prefers IM Nail for the hip like PFN and TFN which have heads for the neck screw and the fracture can be adequately compressed as required by tightening these neck screws having head against the lateral wall or even against the nail in osteoporotic bones or in cases having deficit lateral wall. There are many newer single neck screw system which are more surgeon friendly due to its ease of usage and passing just a single neck screw, and hence, they are more popular with the surgeons such as PFN A2, ZNN, and TFN A. All these newer systems do not have head for the neck screw. Hence, if these screws are passed inside beyond the lateral cortex hole created, many a times during the course of fracture healing and a bit collapse, these helicle blades cannot slide out of the lateral cortex hole due to mismatch and they cannot slide out leading to these helicle blades penetrating into the joint. Hence, the author advises, if at all these types of implants with neck screw having no heads are used, then it is better to keep the back end of these neck screws or the blades 3–5 mm out so that they can slide out easily rather than penetrating into the joint during the course of fracture collapse and healing.
6. Static Locking/Delayed Dynamisation: Although there are many literatures showing good outcome both with static locking as well as dynamic locking, the author feels that in few cases where fracture resorption is a bit more than normally expected, either they require dynamization in time at 6–8 weeks or it can be dynamically locked from day 1 itself. To be on the safer side, as few patients especially, the socioeconomically poor class patients the author treats may try to avoid the ‘second surgery’ of dynamization leading to complications and failures in due course. Hence, the author does only dynamic locking from day 1 itself and with the experience of treating large number of cases over three decades, he strongly advocates only dynamic locking. The dynamic locking allows axial micromotion like an Ilizarov fixator while walking with walker in the initial few weeks and helps in throwing secondary callus and early consolidation. His views are also same as that of Mr. Subhash Halder, Halifax, UK (Originator of Gamma Nail and Halifax Nails) who also does no distal locking in short Gamma Nails or just does Dynamic Locking with long Gamma Nails (Personal Communication as well as through his presentations widely at many places in India). But, the author prefers Dynamic locking from day 1 and he is not having any experience of not at all locking distally in short nails.
7. Choice of implant: Good implant from a good manufacturer with laser marking to trace back if complication arises and not a poor copy from a fly by night lesser-known company, costing a bit less should be used to avoid complications related to metal quality and strength of the implant. Many of these nails from lesser known companies are having thinner nail causing breakage at the screw hole or they are not tapered or crimped for easy insertion as well as to increase strength of the nail. Many have distal locking very nearer to the tips also causing peri-implant fracture due to stress concentration.
8. Weight Bearing: Finally, after a very robust and stable fixation, the patient should be mobilized as pain tolerated weight bearing with a walker to enhance early fracture union and to minimize complications of prolonged immobilization. Once the patient is made to walk, his/her morale will be boosted and will cooperate for proper physiotherapy also.
These are some of the pitfalls which are commonly noted which are the main causes for failure of the PFN.
References
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| How to Cite this article: Shivashankar B. Pitfalls of Proximal Femoral Nailing and How to Avoid Them?. Journal of Orthopaedic Complications | January-April 2025;2(1):06-17. |