Management of Proximal Femoral Focal Deficiency

Proximal femoral focal deficiency (PFFD) is the third most common congenital length deformity of the lower extremity. According to Applied Radiology Online, the incidence of PFFD ranges from one case per 50,000 to one case per 200,000 children. Typically, in children with PFFD, the proximal femur is partially absent resulting in varying degrees of hip deformity with shortening and altered function of the affected limb. Bilateral PFFD, as opposed to unilateral PFFD, is seen in about 15% of children.

The presentation of PFFD is the femur being shortened, flexed, abducted and externally rotated, all to varying to degrees. Management and treatment of PFFD requires a multidisciplinary and highly individualized approach.

This article discusses possible etiologies of PFFD, as well as associated anomalies, classifications and surgical and prosthetic treatments. Additionally, the differences between congenital short femur and PFFD is addressed.

Theories of etiology

Image reprinted with permission of Robin Crandall, MD. Image reprinted with permission of Matt Morel, CPO. Image reprinted with permission of Robin Crandall, MD

With the exception of thalidomide taken by an expectant mother during pregnancy as a definite cause of PFFD, the theories proposed as to the etiology of PFFD remain speculative. Agents such as viral and bacterial infections, irradiation, ischemia, hormones, chemicals and mechanical injuries have been included as possible causes. In rare cases, there may be a genetic component.

“In most patients, it is caused by a sporadic mutation that occurs probably in the sixth week of gestation during limb bud formation,” said Robin Crandall, MD, an orthopedic surgeon and director of the limb deficiency service at The Shriners Hospital for Children, Twin Cities, Minneapolis. “Almost all of the cases are sporadic. In other words, there are no other relatives who have it. It is an isolated mutation.”

At the Shriners Hospital for Children, Twin Cities, Crandall and his colleagues are treating a child with PFFD who is an identical twin. The child’s twin does not have PFFD.

“However, there are cases in the literature where there is a familial association and those have been reported in extremely rare cases,” Crandall said. “So, we tell families it is remotely possible that they could have another child with PFFD.”

Associated anomalies

There are some typical abnormalities associated with PFFD. For instance, the hips and knees often have flexion contractures and weak ligaments with instability. Due to the instability, pistoning may be present. A bulbous proximal thigh tapers to the knee resulting in difficulty examining the hip. Up to two-thirds of patients have fibular deficiency and valgus feet.

“Many patients have fibular hemimelia or longitudinal fibular deficiency,” said Matt Morel, CPO, of Shriners Hospital for Children, Twin Cities, Minneapolis. “This is a partial or complete absence of the fibula. It causes limb length inequality, so patients typically stand on their tip toes.”

Other abnormalities, although rare, have been associated with PFFD such as cleft palate, spinal anomalies, clubfoot and heart defects. According to Crandall, the majority of children with unilateral PFFD are normal in all other respects.

“Kids with bilateral PFFD, however, can present with other anomalies, usually of the upper extremities,” Crandall said.

A patient with foot ablation with uneven knee centers. A patient with a shortened femur with equinovarus foot. Both images reprinted with permission of Matt Morel, CPO.

Unilateral versus bilateral

Most patients who have bilateral PFFD require minimal or no surgery because they can walk on their natural feet.

“In many cases, bilateral patients will not undergo any surgery or the same types of surgery that a unilateral patient would,” said Robert Lipschutz, CP, codirector of the prosthetic and orthotic clinical center, Rehabilitation Institute of Chicago, Chicago. “One of the reasons is that the unilateral patient has the contralateral side that is at full length resulting in a major leg length discrepancy. Bilateral patients may only have a minimal length discrepancy of one side as compared to the other and they just may need a shoe lift.”

In bilateral patients, both femur segments are shortened and even. They can still walk around without having to wear prostheses. It can be painful and that is when the question of surgery arises, added Morel.

“The first goal is non-surgical,” Morel said. “But if there are major foot deformities, there is a possibility of surgery.”

According to Crandall, most children with bilateral PFFD are able to ambulate using their residual limbs with their feet attached. Although they are of shorter stature, there will be no need to ablate the foot or do any surgical procedures.

“Occasionally, we see one who will require surgery, but we try and retain their feet,” Crandall said. “The unilateral kids are the ones who frequently require some surgery or combination of surgeries.”

Classifications of PFFD

A PFFD prosthesis on patient. Both images reprinted with permission of Mark Devens, CO.

There are several classification systems for PFFD and other related congenital abnormalities of the femur and they are often debated. The debate revolves around how the hip structure is formed, whether or not certain irregularities are present or absent and how the condition should be treated. Most classification systems are based on radiographic appearances alone such at the commonly used Aitken system while others, such as the Gillespie & Torode system, also used frequently, consider both clinical and radiographic.

Aitken classification
The Aitken system classifies PFFD into four types, with each type progressively more severe:

• Type A
  Hypoplasia with presence of femoral head; risk of varus deformity
• Type B
  Femoral head present but delayed ossification; mild acetabular dysplasia; risk of varus deformities
  and pseudoarthosis
• Type C
  Femoral head absent; severe acetabular dysplasia; severe femoral shortening, unilateral
• Type D
  Bilateral femoral head absence and severe acetabular dysplasia; femur represented by the
  femoral condyles.

Gillespie & Torode
The Gillespie & Torode classification, known as the short, medium and long system, classifies patients into two groups:

• Group I – congenital short femur
  The femur is 40% to 60% shorter than normal. The hip and knee can be made functional
• Group II – true PFFD
  The femur is shorter. The hip or knee cannot be made functional.

Which one to use

According to Lipschutz, the Aitken system probably holds the most weight because it is focused on the proximal femur, as well as the integrity of the hip joint.

“This is the most important component because if you have an understanding of how the head of the femur is integrated with the pelvis, you will understand what will or will not provide structure and stability to the child’s leg during weight bearing,” he said.

Other classifications of PFFD

Some other classifications tried to incorporate a component of a leg length discrepancy and unfortunately, sometimes the leg length discrepancy will present itself similar to PFFD, Lipschutz added.

“Clinicians will surgically try to intervene as if the person has PFFD instead of performing some of the techniques they would have in the event that the deformity were only a leg length discrepancy.

“For instance, if mis-diagnosed as PFFD, surgical intervention may have included a Syme amputation and an epiphysiodesis to ablate the foot and shorten the limb as opposed to an external fixator on the involved side to lengthen the involved limb and an epiphysiodesis on the non-involved limb to slow the growth and provide equalized leg lengths at full maturity,” Lipschutz said.

The one that is being used more these days is Gillespie’s short, medium and long version, Morel said.

“This classification tells the surgeon what the options are for a particular patient,” he said. “Short, for example, might be fusing the knee and performing a Syme amputation.”

Use of radiographs

Custom shoe with crepe lift. Image reprinted with permission of Mark Devens, CO.

According to Crandall, many physicians will tend to classify based on what the radiographs show.

“The problem with this is that radiographs do not really tell you how much residual limb is left,” he said. “Often, the kids who have the worst looking hip anatomy have the best looking legs. In other words, you can have a kid with normal hip anatomy that does not have much femur at all.”

Crandall tends to classify cases clinically as short, medium or long and he also classifies them radiographically as either Aitken A, B, C or D.

“We typically use both and when we talk to physicians about PFFD, we tend to discuss both classification systems,” he said.

Congenital short femur versus PFFD

There is some controversy surrounding the issue of whether to diagnosis a child with true PFFD or congenital short femur. In the early stages, the clinical presentation is more or less similar. Others believe there are differences.

“In the beginning, kids with congenital short femur will present with abducted and externally rotated femur similar to a child with PFFD,” Lipschutz said.

One way to determine if the child has congenital short femur is to basically pull down or extend the foot as far as possible and get a sense of where the foot ends up lengthwise relative to the contralateral side, Lipschutz said. If the foot extends beyond the knee into the tibial section with respect to their other leg, then they have a decent amount of femoral length. If there is not any distal subluxation or the head of the femur is not pulling down below where the hip joint is and out of where the acetabulum is, then they are potentially a congenitally short femur versus a true PFFD.

Many times bones do not necessarily ossify or cannot be seen on a radiograph until 2 to 2½ years of age, Lipschutz said.

“In the proximal femoral location, the bone will not ossify on the x-ray early enough so the clinician may want to wait until the child is 8 to 9 months old to diagnose,” he said.

Challenges of Treating PFFD Treating the patient with proximal femoral focal deficiency (PFFD) can be one of the greatest challenges for the orthopedic surgeon and the prosthetist. Each patient and family has different views of treatment goals. Some prefer a one-time surgery at a young age and others want to preserve the natural limb no matter what. Still, others want to give their child a choice when they get older, but this may limit their treatment options. Our job is to give the patient and family all the information that is available along with the corresponding prosthetic device associated with their particular surgical outcome. Early challenges Challenges for the prosthetist start early on with the pediatric patient. Many times the bones must develop before deciding on definitive options. Deciding on what age to start prosthetic treatments varies from patient to patient. The treatment is dependent on how much of the femur is intact along with the femoral head and the acetabulum. At an early age, treatments vary from shoe lifts to orthoprosthesis. We often explore the orthoprosthesis when families are unsure of how the patient will function with a prosthetic device. Once the bone has developed enough, the decision is made and the prosthetic device is determined. This could include lengthening, foot ablation, knee fusion, hip reconstruction, turnaround procedure, stopping growth plates or a combination of the above. The surgeon, prosthetist, physical therapist and family create a plan of action. Surgery is performed with prostheses and physical therapy becoming the main focus. Appropriate socket choice The next challenge the prosthetist has is creating a socket for the patient with PFFD. Whether the foot is ablated with the knee fused, the foot is turned around, or there was a Symes procedure done, fitting can be difficult. Approximately 10 to 12 weeks after surgery, the patient is up on the new prosthesis, ambulating differently than he or she did in the past. We have created new weight bearing areas, a new knee axis and often, different socket designs. These are all challenging for the patient, as well as the prosthetist. Achieving goals Having a well-fitting socket with the appropriate components is a step in the right direction towards rehabilitation. At the Shriners Hospital for Children, Twin Cities, these components can include four-bar knees, outside joints, dynamic response feet and creatively designed sockets. We start slow and work toward a goal of independent walking, then running. Eventually the children are playing alongside the rest of their peers. We try to give the children what they need to achieve these goals. These children are challenging for prosthetists, but they are successful when treated appropriately. — Matt Morel, CPO

Shortened femur

According to Morel, in Aitken’s classification A PFFD, there is adequate acetabulum, the femoral head is present, and there is a shortened femur.

“Then there is Gillespie’s Group I congenital short femur, which you could essentially say should not really be a type at all; it should just be a separate diagnosis of congenital short femur,” he said. “There is this debate about which it should be called congenital short femur or PFFD. It is a gray area. In reality, both are treated the same at the beginning. It does not matter which one it is during the first 8 or 9 months. It is how you end up having to treat it later on that matters.”

In Aitken’s classification for PFFD, the treatment options are definitely delineated into B, C and D. This is where the short, medium and long conversion, such as Gillespie’s classification system, may be more useful for diagnosis, Morel said.

According to Crandall, in congenital short femur, the child is usually missing about 25% to 50% of the femur.

“The patient just does not look as much like a PFFD kid,” he said. “But they are treated the same as PFFD if the femur is shorter. In other words, they would look just like a patient with PFFD and in that respect they are indeed the same.”

Physicians may argue that a particular case may not be true PFFD, but in actuality if you truly look at the radiograph it is just Type A PFFD, Crandall said.

“Type A PFFD and congenital short femur are often grouped together and really, it does not make any difference,” he said. “They are still treated the same. There is an overlap on congenital short femur and type A PFFD. It is fundamentally a radiographic continuum. Dr. Gillespie used to say that every x-ray on a kid with PFFD is different from an x-ray of another kid with PFFD. Essentially, there are an infinite number of variations. To argue about whether it is a PFFD or congenital short femur is irrelevant because they are treated as a kid with a short femur.”

Hybrid prosthetic/orthotic device for PFFD on a 15-year-old male with unilateral PFFD. All images reprinted with permission of Mark Devens, CO.

Multiple treatment options

There are multiple options in treating a child with PFFD. The early treatment up to 8 or 9 months consists of a shoe lift. During this time, the leg length discrepancy is relatively small on a unilateral PFFD patient, usually around 1 cm to 2 cm. When the child is beginning to stand, he or she is fitted with a nonconventional or extension prosthesis.

“As little kids who are just starting to walk, oftentimes we will fit them with a nonconventional pylon incorporating their foot and they just walk around stiff-legged,” Crandall said. “When they are little, their parents are lifting them and it is not a problem.”

As the child gets older, the leg length discrepancy is about 3 cm to 4 cm. Not only does the prosthesis pose functional limitations at this point, but also the foot on the affected side is at the level of the mid-calf of the contralateral leg.

“The shortening gets worse because they have essentially lost part of a growth plate,” Morel said. “Basically, the femur is not growing or it is growing at a slow rate. When they first start walking the discrepancy is only maybe a centimeter or two. But projected out over their lifetime, it will likely reach 20 centimeters.”

Imagination and Creativity Essential in the Treatment of PFFD Years ago, when I first started to treat patients with proximal femoral focal deficiency (PFFD), my naiveté and inexperience actually helped. I was not channeled into a set way of treatment or a mind set that “this is what we give PFFD patient.” I also had the good fortune of having Norris Carroll, MD, as a mentor. He was a leading pediatric orthopedist who had become chief of orthopedic surgery at the Children’s Memorial Hospital in Chicago, during the 1980s. When a patient presented, he would ask, “What can you come up with for this patient?” I was allowed to fail and succeed encumbered only by the pressure I put on myself to come up with a device that was innovative and benefited the patient. Trying something new Because these children were otherwise active and healthy, the limiting factor was providing something that allowed them to gain equality with their peers during various activities. When we treated a patient who did not have a Van Nes procedure, we were faced with a short limb, and to widely varying degrees with stable and unstable parts such as the knee hip and ankle. I quickly learned that PFFD patients and parents were as willing to try something new as I was. Their patience for our various beta models gave me encouragement and reinforcement to continue coming up with new ways to bring the floor to the foot. As time passed, I was able to follow some of these patients as they grew and saw what did and did not work. Cosmesis Usually, the rule of thumb in orthotics and prosthetics is “cosmesis always trumps function.” You can have both, but many times, practitioners have had to struggle with a patient who does not want to use the optimal device because of its appearance. Shoe lifts were always the bane of any orthotist’s existence. This simple, helpful device seemed always to be met with such negative reaction, even after the terrible limp went away. In the case of PFFD, the lifts were reaching Mt. Everest heights. Three inches, 4″, 7″ and more. The weight, or bulk, even with urethane foams, made any patient and parent cringe at the thought of their child having to wear it, least of all, in public. No matter that it at least made them able to stand normally. Activity level was only moderately enhanced when lifts exceeded 4″ or more. The lift would be so stiff and tall that the shoe tended to actually inhibit walking and running. Keeping the shoe on was a problem. The child’s ankles and muscles could not control the large crepe or foam block under their shortened limb. Bringing the floor up to the foot The 1980s also saw the surge in endoskeletal component prosthetics. No longer was every device laminated and laboriously altered every time growth occurred. This allowed easier changes in height, angles and components as the patients’ needs changed. Cosmetically, I wanted to achieve something presentable, and this meant dealing with the involved foot. It was obvious the most expedient solution was to plantarflex it into alignment with the shaft of the leg. While this achieved better cosmesis, biomechanically it eliminated one of the involved limbs best levers – the foot. So, instead of eliminating it, we incorporated it into a solid ankle AFO and then worked on solving how to bring the floor and foot together. Experimenting For the young patient, I experimented with PVC pipe and attachments, as well as nylon blocks that could be machined and vacuum formed into the AFO; a pylon and foot that was light, and inexpensive and disposable. I found that you could pull loose pants or sweat pants over the upper foot and cover the device, but this was rarely necessary. Once the parent saw the increased activity of the child, suddenly the cosmesis did not matter as much. For larger patients and longer length discrepancies, true prosthetic components were used that allowed adjustability and true dynamic alignment, allowing changes in gait based on how they progressed with the device. Depending on how stable the hip was, determined the amount of coverage or socket that was needed. Sometimes, a pelvic belt or band was used. Other times a KAFO design was used if the knee was unstable; the knee being maintained in a neutral position. Follow-up visits Some patients returned faithfully to have their devices adjusted, repaired or replaced. I could see which materials held up and which did not. I also could start to see how they reacted over time to a device that was not always the most cosmetically pleasing; they accepted it as long as it allowed them equality with their peers. Surprisingly, many of the hardware store items lasted quite well and we used plastics with little failure. As some patients became teenagers, this tradeoff was not as clear, yet they continued to use their devices. The 1990s saw the advent of baggy pants, so this alleviated some of the problem. I also began to acquiesce to more plantar flexion in the devices to allow more cosmesis. Some patients did not come in for long periods of time, yet had continued to use devices made for them years ago. Remarkably, they persevered with a less than optimal device. That gave rise to my frequently used phrase “You can tie a broom stick to most kids and they will do fine, so long as you let them be kids.” Kids will always make you look good if you can just get them going. No one prosthesis Treating the patient with PFFD is truly one of our last challenges, but rewarding in so many ways because of the opportunity to challenge your skills, innovate and go beyond the routine. There is no one “PFFD prosthesis,” nor has there ever been. Now there are thousands of components and just as many ways to attach and align them that allow your patient to meet their peers on a level playing field. What limits you is your courage to take a chance. — Mark Devens, CO

Surgical options

An orthoprosthesis for a PFFD patient. Image reprinted with permission of Matt Morel, CPO.

Around 3 or 4 years of age, decisions about surgery need to be made. If certain criteria are met, limb lengthening may be an option. If the patient is not a candidate, the appropriate surgery will be done with the goal of fitting the child with the most functional prosthesis. Surgeries include knee arthrodeses, limb rotationplasty, foot amputation, hip reconstruction or a combination of two or more surgeries.

Knee arthrodesis (knee fusion) is a common surgical procedure for children with PFFD. Among several advantages, it enables a longer and more efficient lever arm and a residual limb that fits better within the prosthesis.

Often performed at the time of knee fusion, amputation shortens the new lever arm. Syme amputation is commonly performed which allows for an immediate postoperative prosthetic fitting. The Boyd amputation, which preserves the entire calcaneus is another alternative.

Rotationplasty

The Van Nes rotationplasty may be another option. It involves a partial transfemoral amputation. The lower leg and foot are then rotated 180·, the length is adjusted and the tibia is fused to the remaining proximal femur. The foot is positioned where the knee was with the heel in front and the toes in the back. The ankle functions as the knee joint. This procedure has both advantages and disadvantages. Psychologically and cosmetically it may pose problems for some patients and their families. Yet functionally, it is superior to a transfemoral prosthesis.

“If someone is thinking of a Van Nes procedure, it is important to present it to the patient and the family in a positive way,” Crandall said. “They should understand that a Van Nes procedure would essentially make them a transtibial rather than a transfemoral amputee.”

The prosthetic fitting of a Van Nes rotationplasty is challenging, added Lipschutz.

“We are trying to fit a foot that is on backward,” he said. “So we must try to find weight bearing surfaces on the foot, which can be difficult.”

The key part of a successful fitting for a Van Nes patient is maintaining good range of motion at their ankle, Lipschutz said.

“The ankle is acting like a knee in reverse and if they do not have good range of motion, then all they have done is taken a foot and put it on backward,” he said.

Based on metabolic studies and gait efficiencies, the procedure results in a more efficient gait than someone with a Syme amputation.

Goals of treatment

The ultimate goal of treating children with PFFD is clear.

“We want to make the child as functional and as good an ambulator as we can with the least amount of oxygen consumed per meter traveled,” Crandall said. “We want to make the kid the best he or she can be. So we do these operations to provide them with a streamlined way of walking using a nice prosthesis that makes them look as normal as possible.”

PFFD prosthesis lateral view. PFFD prosthesis, laminated, endoskeletal attachment with four-bar knee. Both images reprinted with permission of Mark Devens, CO.

For more information:

• Abdel-Mota’al M, Jayakumar S. Proximal femoral focal deficiency. Clinical case presentation, orthopaedic department, The Alfred I. Dupont Institute, Wilmington, Del. Available at: http://gait.aidi.udel.edu/educate/pffd.htm. Accessed February 25, 2007.
• Applied Radiology Online. Limb discrepancies at birth. Available at: www.medscape.com/viewarticle/503800_2. Accessed February 25, 2007.
• Carroll K. Radical innovation in above-knee amputation. Orthopedic Technology Review. Available at: www.orthopedictechreview.com/issues/articles/2006-03_06.asp. Accessed February 25, 2007.
• emedicine. Proximal femoral focal deficiency. Available at: www.emedicine.com/orthoped/topic547.htm. Accessed February 25, 2007.
• Pediatric Orthopaedic Society of North America. Proximal focal femoral deficiency. Available at: http://www.posna.org/index?service=page/coreCurriculum&article=proximalFocalFemoralDeficiency.html. Accessed February 25, 2007.

Rachel Kelley is a staff writer for O&P Business News.