Many people suffering with arthritis, hip pain, stiffness and limited hip movement can now choose minimally invasive surgery when hip replacement is the chosen treatment of the patient and their doctor.

One of the least invasive surgical options is Anterior Hip Replacement. The Anterior Approach is a proven technique that minimizes the pain and the time from surgery to recovery.

Disclaimer: The information in this web site is for informational purposes only and is not meant to replace any doctor’s advice, evaluation or diagnosis and does not suggest any form of specific medical treatment for individual cases. Consult your doctor before starting any course of treatment.

 WHAT IS ANTERIOR HIP REPLACEMENT?

The Anterior Approach to hip replacement surgery allows the surgeon to reach the hip joint from the front of the hip as opposed to the lateral (side) or the posterior (back) approach. This way, the hip can be replaced without detachment of muscle from the pelvis or femur during surgery. The surgeon can simply work through the natural interval between the muscles. The most important muscles for hip function, the gluteal muscles that attach to the pelvis and femur, are left undisturbed and, therefore, do not require a healing process to recover from surgical trauma.

The Anterior Approach to hip replacement was first performed in Europe in 1947. Since that time, the technique has been continually refined with advancing medical technology. Today, literally thousands of hip replacement patients have benefited from this minimally invasive approach in Europe and America.

In 1996, Joel M. Matta, M.D., the John C. Wilson, Jr., Chair of Orthopedic Surgery at Good Samaritan Hospital in Los Angeles brought Anterior Hip Replacement to the United States. Dr. Matta has advanced the technique even further by co-designing a special, state-of-the-art surgical table with OSI and improving many surgical protocols for the hip replacement procedure. Having performed over 1,000 Anterior Hip Replacements himself since 1996, Dr. Matta has also been instrumental in the training of many orthopedic surgeons in this important minimally invasive approach. Dr. Matta’s views on this technique can be found at: www.hipandpelvis.com.

 HOW DOES ANTERIOR HIP REPLACEMENT IMPROVE PATIENT RECOVERY?

Conventional Hip Replacement
Conventional lateral or posterior surgery typically requires strict precautions for the patient. Most patients must limit hip motion for 6 to 8 weeks after surgery. They must limit flexing of the hip to no more than 60 to 90 degrees which complicates normal activities like sitting in a chair, on a toilet seat, putting on shoes or getting into a car. Simply climbing stairs may also be more difficult during recovery.

Anterior Hip Replacement
Anterior Hip Replacement allows patients to immediately bend their hip freely and bear full weight when comfortable, resulting in a more rapid return to normal function. After surgery, patients are instructed to use their hip normally without cumbersome restrictions. In supervised therapy, patients go up and down stairs before their hospital release.

The Anterior Approach to hip replacement was first performed in Europe in 1947. Since that time, the technique has been continually refined with advancing medical technology. Today, literally thousands of hip replacement patients have benefited from this minimally invasive approach in Europe and America.

In 1996, Joel M. Matta, M.D., the John C. Wilson, Jr., Chair of Orthopedic Surgery at Good Samaritan Hospital in Los Angeles brought Anterior Hip Replacement to the United States. Dr. Matta has advanced the technique even further by co-designing a special, state-of-the-art surgical table with OSI and improving many surgical protocols for the hip replacement procedure. Having performed over 1,000 Anterior Hip Replacements himself since 1996, Dr. Matta has also been instrumental in the training of many orthopedic surgeons in this important minimally invasive approach. Dr. Matta’s views on this technique can be found at: www.hipandpelvis.com.

Since the 1960s, the typical patient who receives a total hip replacement expects near complete restoration of their quality of life and they also expect to be able to continue with physically demanding activities such as hiking, skiing, and tennis.

Many advances in the metallurgy, bearing surfaces, and bioengineering have resulted in increased longevity of the replaced joints.  Newer surgical approaches, such as the direct anterior approach, which I perform, can result in shorter hospital stays, faster recoveries, and less costs to the patient in terms of time away from work and family.

The ability to achieve equal leg lengths, reproducible implant positioning, and high levels of patient satisfaction has increased.  These two pictures are of an elderly female patient of mine, disabled by left hip pain, who underwent an anterior total hip arthroplasty, went home from the hospital on the 2nd day after surgery, and returned to hiking at 6 weeks after the operation.  An amazing result considering that this operation was not even invented 50 years ago.  Truly the operation of the century.

normal male pelvic anatomy xray female pelvis xray with osteopenia

The first Xray is of a 35 year old male with no arthritis of the hip. The second Xray is of the pelvis in a 53 year old female with osteopenia.  She is post-menopausal and has a borderline osteoporosis of the hips.  Notice that the bone in the area of the calcar is much thinner and the cortex of the femoral shaft is much thinner as well.  The third Xray is of an elderly female with severe osteoarthritis of the left hip.  The first thing to notice about this film is that in contras to the 1st two films which have equal leg lengths, this Xray demonstrates apparently unequal leg lengths.  Often the legs are in truth exactly the same length, but they appear different because the arthritic process causes a contraction of the muscles and tendons about the hip.  In my practice it is of paramount importance that the xray is taken in the standing position and the patient and I agree on what will be our criteria for deciding on equal leg lengths.

In the next Xray I illustrate how leg lengths are most commonly determined and also illustrate femoral offset — the distance between the longitudinal axis of the femur and the center of acetabulum.  This is also an important measurement because increased offset is often associated with persistent post-operative thigh pain, whereas insufficient offset is often associated with a sense that the hip is weak, or unstable.

Total hip arthoplasty is meant to relieve pain, allow the patient to walk with a more normal gait, and result in a highly satisfied patient.  One of the most troublesome problems after total hip arthoplasty for both patients and orthopedic surgeons is when the patient has unequal leg lengths after surgery, which is referred to as a “leg-length discrepancy”.  While there are a few immediate complications that can occur as the result of a leg-length discrepancy, such as a stretch injury to the sciatic nerve or peroneal nerve, back pain as the result of an uneven pelvis, or an abnormal gait, the most frequent outcome is a dissatisfied patient and an unhappy surgeon.  While careful preoperative planning and intra-operative techniques can decrease the chance of the patient noticing a leg-length discrepancy after the operation, a good course of action is to have the patient and the surgeon agree in advance on what constitutes equal leg lengths, define a standard for evaluating leg lengths, and then using a standardized X-ray technique for measuring leg lengths.  This ensures that every one is on the same page when it comes to this issue.  In our experience, the anterior approach has a few benefits over the posterior approach when it comes to making sure the leg lengths are equal after surgery.  This is primarily because the patient is flat on their back during surgery, which makes it much easier to control the alignment of the pelvis, and also because a C-arm — an intraoperative X-ray machine — is used in anterior hip surgery so that an objective measurement of leg lengths can be made before the procedure is finished.

Recent data produced by a oversight agency called the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) listed 6 major “events” that are relevant to orthopedics out of 19 frequent adverse medical events that deserve particular attention.  These “events” are occurrences that can be seen as medical errors because they may be preventable in some instances, and in this study, leg length inequality accounted for 4.7% of the total number of medical errors investigated by JCAHO.  Other events, such as patient falls while in the hospital, are relevant to orthopedic surgeons, but their prevention is a bit more complex.

The most frequent error in limb lengths after total hip replacement is that the operated hip is longer than the native hip.  Sometimes this may be necessary in order to achieve stability of the replaced joint.  When the patient is being operated on for arthritis complicated by congenital dislocation of the hip for example, it may be necessary to lengthen the leg in order to return the hip center to its normal location.  When the leg is lengthened, it may place increased stress on the sciatic nerve, stretching the nerve, and this can produce what we call a nerve palsy.  This will typically manifest as burning pain down the course of the sciatic nerve, numbness in the lower leg or foot, and sometimes muscle weakness in the foot and leg.  If patients are left with uneven leg lengths after surgery and their gait is abnormal, they can develop low back pain or other gait abnormalities that will cause them discomfort.  However, most of the time, the most common complaint from a patient with a leg length discrepancy is just that they are dissatisfied.  Indeed, dissatisfaction with unequally leg lengths after total hip arthroplasty is the SINGLE MOST COMMON reason for litigation against orthopedic surgeons.  Lets figure out a way to avoid that from happening.

Over the years, the surgeons who choose to perform total hip arthroplasty through a posterior approach have developed a number of ways to either directly or indirectly measure leg lengths before the incision is sewn up.  These include using careful pre-operative planning with overlays that anticipate what changes in leg lengths are going to occur during the course of the joint replacement, placing markers on the pelvis and the femur so that the distance between the two objects can be measured before and after the joint is replaced, taking an intra-operative X-ray to confirm the limb lengths, and feeling the length of the legs through the drapes.  In my experience with these techniques, they are not always 100% foolproof.  Pre-operative templating is certainly helpful, but minor variations in the bone and the local anatomy can result in subtle changes in the way that the implants fit into the patient.  The use of pins that are tapped into the femur and the pelvis as a standard of measurement is not 100% secure because they can move during surgery.  Taking an X-ray with a patient lying on their side (which is the standard position for posterior total hip arthroplasty) can be very difficult, especially if it is a large patient and their position has changed on the table during the operation.  This frequently happens because once a patient is covered with all of the barriers that we use to create at sterile field — the process of “prepping and draping” — it can be very difficult to make sure that the patient is correctly aligned when the X-ray is taken.  If the patient is not perfectly square with respect to the table then the X-ray technician will not be able to get an accurate picture of the pelvis, and using the the intra-operative X-ray to assess leg lengths can be problematic.  While it is desirable to aim for a “bulls-eye” and restore the legs to exactly equal lengths, this is not always perfectly possible.  There is some debate about what constitutes an acceptable leg length discrepancy after surgery, with some surgeons advocating for anything less than 1cm (less than 1/2 an inch) as a very acceptable threshold.  It is pretty difficult to identify any problems that are realistically caused by a difference in leg lengths of less than 1 centimeter, since a large proportion of the general population has a leg length discrepancy of about 1/2 of an inch by virtue of the natural underlying asymmetry of the human body — before the ever develop arthritis or have a joint replacement.

In my hands, one of the major advantages of the direct anterior total hip arthroplasty technique is what I perceive to be an increased ability to determine leg lengths accurately.  The patient is lying flat on their back, so even if they are very large, the pelvis is still perfectly square to the table, and therefore perfectly square to the X-ray beam.  Also, the intra-operative C-arm can be used to make sure that the femoral and acetabular components are in the correct place, and in general, it is much easier (and represents less of a risk to the sterility of the procedure) to take multiple X-rays with the C-arm than it is do the same thing with a portable X-ray unit, which is what is required during most conventional setups for posterior total hip arthroplasty.

Preoperative Measurement of Leg Lengths

Here is an X-ray of the pelvis of someone who is going to have their right hip replaced.  A horizontal line has been drawn across the bottom of the pelvis, just touching a part of the pelvis called the ischial tuberosities.  Notice that the pelvis is perfectly “square” with respect to the viewer, and there is a high degree of symmetry in the anatomic landmarks from one side to the other.  The distance between the horizontal line and the top of the bump of bone on the inside of the femur (the lesser trochanter) is the most commonly used method for determining leg lengths.  This is because the horizontal line is a PELVIC reference, and the top of the lesser trochanter is a FEMORAL reference.  Notice that on this X-ray, the top of the lesser trochanter on the patient’s right side (this x-ray is oriented as if the patient is looking at us) is displaced superiorly with respect to the left side.  This is because the arthritic process has thinned the cartilage inside the hip joint, and the erosion of the cartilage has resulted in a progressive shortening of the limb.  The goal of a total hip arthroplasty in this instance would be to replace the joint in such a way that the distance between the horizontal line and the top of the less trochanter is equal on both sides.

Equal Leg Lengths AP Xray

Here is an X-ray of a patient without arthritis, and the relationship between the horizontal line and the top of the lesser trochanter is equal.  I am trying to achieve the same relationship between the pelvis and the femur after a hip operation.

Intraoperative Position Direct Anterior Total Hip Approach

Here is a picture of a relatively large (but by no means very large) patient getting prepared to have a direct anterior total hip arthroplasty.  Notice how the patient is flat on their back so that the pelvis is perfectly square.  If this same patient were to lie on their side, it would be much more difficult to control the position of the pelvis because the “soft tissue envelope” around the patient makes it difficult to feel the landmarks of the pelvis and it also makes it difficult for the intra-operative positioners to hold onto the pelvis securely.  Bottom line — it is harder to orient large patients correctly 100% of the time when they are on their side, especially all throughout the procedure.

Intraoperative Imaging During Total Hip Arthroplasty

Here is a picture of the same patient during the middle of the procedure.  In this instance, the C-arm has been prepped and draped so that in can easily be pulled in and out of the surgical field whenever we need to verify the position of the components.  For example, in the next picture, a spot view has been taken of the acetabular reamer after preparation of the socket side of the hip replacement.  This will verify that the socket has been appropriately reamed to accept the new component.

Acetabular Reaming Total Hip Arthroplasty C Arm Femoral Stem Insertion

In the second picture, the femoral stem has been inserted, and the C-arm is being used to verify that all of the components are in the correct position and that the relationship between the anatomic landmarks on the acetabular side and the femoral side of the joint replacement are all correct.

There are five main causes for hip pain. Osteoarthritis, the main reason for painful hips causes degeneration or wearing down of the articular cartilage. The end result is progressive erosion of the joint surface making the movements and weight bearing painful. This pain of the hip joint is usually localized in the groin, thighs and the knees. There even may be low back pain. The joint is not able to move in al planes of movement. It becomes disabling to the extent that a person has difficulty even in tying shoelaces.

Rheumatoid arthritis causes degeneration of the joint as well, resulting in pain and disability of the joint. Avascular necrosis, as the name suggests is caused by decreased blood supply to the joint, specifically head of the femur. The absence of blood supply causes death of the affected bone tissue leading to collapse of the femoral head. Researchers have enumerated many causes for reduction in blood supply to the hip joint. Some of these are use of corticosteroids, alcohol dependence, certain disorders of fat metabolism, nitrogen embolism, etc. in cases where the condition does not heal spontaneously or has not been treated, may lead to wearing down of the joint.

Other Causes Of Hip Pain & Degeneration

Dislocation and fracture around the joint, as a result of trauma to the joint may be a contributing factor in degeneration of joint. This is most common in elderly group having weak bones that gets easily fractured. Other hip pain causes include developmental dysplasia of the hip. It is a congenital deformity and may range from a minor dislodgment of the ball out of the socket to a complete dislocation of the ball out of the socket which may be severe. Developmental dysplasias should be treated early in life in order to prevent subsequent degeneration.

anatomy of the hip joint and location of the blood supply

In the anatomic illustration above, we see that the hip joint is surrounded by a thick white capsule of tissue that encases the femoral head and the acetabulum.  The blood supply to the femoral head comes from the femoral artery, specifically a branch called the medial femoral circumflex artery, which is an important land mark during surgical treatment of hip disease.  Below, we have two thumbnail images of X-rays of a normal pelvis and a pelvis with osteoarthritis of the hip joint.  If you click on the images, a large version of the picture will launch which makes it much easier to see the annotation describing the various anatomic landmarks.

AP pelvis xray anatomy osteoarthritisIn this xray of an elderly female with osteoarthritis, the joint space of the left hip has been obliterated as the cartilage has deteriorated.  This hip has progressed to the point where there is bone on bone contact.  In addition, the soft tissues (the muscles and the ligaments) about the hip have started to stiffen and contract which is why she stands with an unequal pelvis, giving the left leg an appearance that it is longer than the right.  By convention, X-rays are usually displayed as if the patient were facing the viewer, but most X-rays have a marker on the film itself indicating which is the right or the left side of the patient.

There have been two types of FAI described, [Cam] and [Pincer] types.  Although they are described as separate entities, most patients have components of both types of impingement.  Cam type femoroacetabular impingement occurs when a femur with an abnormal head neck junction and insufficient head-neck offset creates shear forces on the acetabular cartilage and labrum.  This kind of impingement often occurs in patients with post-traumatic deformities, slipped capital femoral epiphysis (SCFE), coxa vara, and avascular necrosis (AVN).  Many patients are males who are physically active or heavy laborers.

History, Past Medical History, and Physical Exam

This part of the consultation is used to determine if the pain is due to trauma, arthritis, or some other entity.  The past medical history can give clues to possible causes, such as AVN due to glucocorticoid use, and the physical exam is extremely important to identify the possible causes of hip pain and exclude other conditions such as low back pain or other causes of pelvic pain.  There are a number of physical examination tests that can be use to reproduce the patients pain and verify that the hip is the source of the discomfort, such as the FADDIR, FABER, and scour tests.

Diagnostic Imaging

Xrays, MRI scans, and CT scans are extremely useful in understanding the causes of hip pain and possible treatment options.  In our office, we will obtain the appropriate xrays and if we need advanced imaging, such as an MRI scan or a CT scan, we will make arrangements to have these tests performed.  Some of the measurements that we use in evaluating patients for hip pain include the following:

Joint space: measures the amount of cartilage between the femoral head and acetabulum.

Tonnis Angle: measures the degree of acetabular overcoverage or undercoverage.

The Crossover sign: measures acetabular retroversion or anteversion.

The Alpha angle: measures cam impingement and lack of roundness of the femoral head.

Coxa Profunda: measures how deep the femoral head sits inside the acetabulum.

The following xrays show some examples of the xrays of patients with femoral acetabular impingement and demonstrate the use of these measurements.

xray of bilateral cam impingement of the hip joint

This is the AP weight bearing xray of a 40 year old male with bilateral hip pain, good preservation on the joint space and cam impingement with a relatively large alpha angle.  The alpha angle is considered to be normal when it is less than 40 to 50 degrees, and abnormal when it is more than 60 degrees.  In this case it measures approximately 75 degrees.  This patient has sharp catching pain in his groin, is still very active — playing pickup basketball — and is an excellent candidate for hip arthroscopy and femoral head debridement / osteoplasty.

This xray is of a 40 year old female with mixed cam and pincer impingement and with joint space narrowing.

She has acetabular overcoverage as measured by a low Tonnis angle, calcification of the acetabular labrum, and a large alpha angle.  Unfortunately, she also has loss of joint space and so she is not a candidate for a joint preserving procedure but instead will require a joint replacement procedure to alleviate her hip pain.

Non-operative Treatment

A course of non-operative treatment for most hip pathology is usually the first line of treatment. Patients presenting with femoroacetabular impingement or labral disease may try modification of activity, avoiding excessive hip movement and regular non-steroidal anti-inflammatory medication such as Advil, Tylenol, or Ibuprofen.

Selective injections and a pain journal

Injections inside the hip joint can be used help diagnose and manage the symptoms of patients with hip pain, especially if there is any question as to whether or not the patient could have disease in other areas, such as the back.  During this procedure, an intra-operative xray machine called a fluoroscope to accurately identify the correct area to inject medicine.  Typically, two different types of medications are injected.  One is an anesthetic agent that results in immediate pain relief lasting for 2 to 3 hours.  The other medication is an anti-inflammatory medicine that takes 2 to 3 days to work and then lasts for a much longer time.  These injections have two purposes: they are DIAGNOSTIC and they are THERAPEUTIC.

The diagnostic component of the injection helps us to confirm that we are working towards a correct diagnosis.  For example, if the patient’s hip is injected and all of the patient’s pain goes away, we know that we have identified the source of the pain.  If the injection results in no pain relief or only partial pain relief, then we suspect that another anatomic area may be contributing to the patient’s pain.

The therapeutic component of the injection helps the patient to manage their pain and possibly avoid having surgery.

A pain journal is often used to help document the effects of selective injections and demonstrate to the patient and the doctor that the correct source of the pain has been identified.  This journal begins on the day of the injection and then covers the next 7 days.  It is important that you fill this document out on a daily basis for the 1st week after then injection and then bring it to your follow-up visit when in order to discuss the results of the injection and what it means in terms of future treatment decisions.   You can download a copy of a sample pain journal by clicking here:

Download | Free Pain Journal

Arthroscopy — Joint Preservation

Arthroscopic surgery for femoral acetabular impingement is an emerging treatment for hip disease.  With arthroscopic surgery, we can repair tears in the labrum around the edge of the acetabulum, remove delaminated cartilage, and remove the abnormal bone spur that causes cam impingement.  This type of surgery is typically performed as an outpatient at a surgery center with an overnight stay.

Here are a series of xrays and intra-operative arthroscopic pictures of a 50 year old woman with classic findings of cartilaginous delamination caused by femoral acetabular impingement.  The first row of pictures includes her pre-operative xray of the hip, the fluoroscopic picture taken by the radiologist after injection of the contrast material for the MRI arthrogram, and the last two pictures demonstrate the MRI findings of femoral acetabular impingement.

Here we have the intra-operative pictures at the time of hip arthroscopy.  In the first image the torn and degenerative part of the acetabular labrum is being removed.  In the second image the bent probe is indicating the area of delaminated cartilage, and in the third picture the femoral head osteoplasty is being performed.

I use an uncemented femoral stem which means that the stem has to have a solid press-fit into the femoral canal and no bone cement is used.  The femoral stem is coated with a special metal layer that mimics the micro-architecture of bone.  As the bone remodels around the stem, it locks onto the minute variations in the surface of the metal and essentially makes it a permanent part of the femur.  This process is called osteointegration, and it is absolutely a requirement for a successful long term implant.  Because patients are allowed to weight bear immediately after surgery they will put a lot of stress and strain on the hip prosthesis before the bone has solidly grown into the micro-architecture of the femoral stem.

taperloc total hip stems

The biology of osteointegration is not completely understood and all of the major manufacturers of orthopedic implants have their own proprietary metal surfaces and coating that are designed to facilitate osteointegration.  We speculate that some stress is essential for osteointegration to occur, but too much stress occurring before the femoral stem has completely bonded to the bone may cause micromotion at interface between the bone and metal which may inhibit the process of osteointegration.  If this occurs, a layer of fibrous tissue may stabilize the stem, but in the worse case scenario, the stem is loose inside the femoral canal and becomes a source of pain for the patient.  Therefore, we try to balance early activity with the benefits of decreased blood clots, faster rehabilitation, higher patient satisfaction, and possibly even enhanced ingrowth if the stresses are appropriate, with the theoretical concerns of too much stress early on may be detrimental to the biology of integration.

Choosing the correct stem for the correct patient is a little bit art and a little bit science, and it is also influenced heavily by the maxim that if you do the same thing over and over again, you tend to get better at it.  Most surgeons in the US try to limit themselves to one or two stems for most of their index procedures.  Currently, the design that I am using is the Biomet Taperloc stem.  I believe that this stem does a good job of meeting the needs of a proximal fit and fill stem with good initial stability, ease of insertion for the direct anterior approach, has a good track record, and is manufactured by a solid company with a long history in orthopedics in the United States.  Biomet orthopedics (www.biomet.com) is on record as saying that they have over 22 years of experience with this stem design, that it has been successfully implanted in a very large group of patients, and that it has functioned well in the young and the elderly.  In my mind, the greatest advantage of this stem is the reduced diameter of the distal portion of the stem which allows for solid contact between the proximal metaphyseal area of the femur and the porous coating and decreases the incidence of post-operative thigh pain.

When I first began to use the direct anterior total hip approach in 2005, I exclusively used an implant on the femoral side that is classified as a non-cemented, proximally porous coated, tapered wedge design.  There are several features that make this an ideal stem for the anterior approach.  It has a cut out at the shoulder on the lateral side of the prosthesis which makes it easier to insert if there is any residual femoral neck bone stock remaining — since this area can sometimes be a difficult to visualize during the anterior approach.  It is designed to be inserted with a hand broaching technique (which avoids the need to ream the femur with a power reamer), and the double offset broaches that were developed for the insertion of this stem are well suited to the anterior approach.  Most importantly, the tapered wedge design had proven itself to be a successful design, with very high (>98%) success rates in a large number of patients in published clinical reports in the united states.  It is worth noting that most of these patients were treated with a posterior approach to the hip, and there may be a few subtle differences between the anterior and posterior approach that makes this stem less likely to be successful if it is put in anteriorly.

This stem is meant to sit in the femoral canal in a fashion where there is direct contact between the porous surfaces of the proximal portion of the stem and the femoral bone.  If the bone is able to attach to this part of the femoral stem, it is said to have achieved osteointegration, and that is widely seen as a prerequisite for a long term successful outcome following total joint replacement.

In a very small minority of my patients, these stems appeared to fail to osteointegrate — the bone failed to solidly attach to the femoral stem.  The number of patients was very small, but it was significant, since many of these patients had specifically sought out an anterior approach because their independent research had led them to believe that their ability to return to physical activity, hiking, cycling, and other sports would be improved if they had an anterior approach.  Indeed, most of the patients who failed to achieve solid osteointegration on the femoral side were those who had exceptionally fast recoveries.  They went home from the hospital earlier, they completed their goals in rehabilitation faster, and they returned to a normal gait faster.  However, by six months, they started to complain of thigh pain.  The thigh pain appears to be due to the fact that if the stem is loose, the micromotion between the stem and the bone is a source of discomfort.  Often this discomfort is very similar to osteoarthritic pain — it is worse when the patient first starts moving and then tends to improve once they have taken a few steps.  The degree of pain was highly variable, but the radiographic findings were relatively constant.  The stems appeared to fit tightly in the femoral canal on the AP X-ray, but the lateral view would demonstrate a radiolucency around the stem that to my eye, suggested that the stem was primarily loose about the longitudinal axis of the femur.

Here are two radiographs (click on the thumbnails to enlarge them) of a stem that has not properly integrated with the bone.

In this picture, I’ve put dots around the radiolucent lines in the femur that indicate that the stem is rotating on its longitudinal axis.

Just recently, a report was published out of the department of orthopedic surgery at Lennox Hill hospital in New York City, reporting similar findings.  In this report, the senior author found that this same type of stem failed to achieve osteointegration in 4.7% of a series of nearly 300 patients.  This surgeon reported that he switched from the posterior approach to the anterior approach towards the end of the study period but the number of anterior approach patients was too small (16 patients) to draw any conclusions about whether this mode of failure was more or less likely with the anterior or the posterior approach.  The orthopedic surgeon who published this report concluded that the cause of failure was due to the geometry of the proximal portion of the femur, which in some cases, resulted in a tight fit between the distal, smooth, and non-porous coated portion of the stem, leaving the proximal portion of the stem without the contact and stresses required to achieve osteointegration.  In his study, larger male patients were more likely to fail to achieve osteointegration, and he concluded that this was because their proximal femoral geometry was ill-suited to the tapered design of the Accolade stem.  Interesting, the author also concluded that this may be an “underreported” phenomenon, since he was not aware of any other papers specifically documenting this type of failure of osteointegration.

For a complete PDF of this article click here: Distal Fixation of Proximally Coated Tapered Stems May Predispose to a Failure of Osteointegration.

It is difficult to know for certain, but I hypothesize that another potential reason why this stem may fail to integrate in a minority of my patients after an anterior approach is because their speedy recovery and fast rehabilitation puts too great of a stress about the “rolling axis” (to use a term borrowed from aviation) of the component before the stem can be adequately stabilized by ingrowing bone.  In my cases, the stems never moved on the AP view but they definitely were unstable on the lateral view, and the radiolucent lines that are present seem to suggest that the stem rocks back and forth when downward pressure is put on the femoral head.  This is the type of load that would be encountered when the patient goes up stairs, leading with the operated leg — a movement that we call single leg stair climbing.  I believe, but I do not know for certain, that some patients with a less favorable geometry of the proximal femoral canal, coupled with a very fast recovery and a quick return to normal activities that are the hallmarks of the anterior approach, are more likely than others to develop this complication.

The degree of disability created by this micromotion is very variable.  Some patients are barely bothered at all, and in a couple of cases, I have had to revise the femoral components of patients with thigh pain and place a different implant on the femoral side.  The revisions have resulted in a dramatic improvement in the presenting complaint of thigh pain after a total hip arthroplasty, and in each case, the femoral component that was removed was indeed loose with no evidence of solid ingrowth.

This year, at the annual meeting of the American Academy of Orthopedic Surgeons, there was a series of presentations on “high performance total hip arthroplasty”, which was variably defined by the presenters but essentially seemed to mean a total hip in a patient that returned to playing singles tennis, running, active combat military service, or surfing, for example.  In those cases, the femoral components were said to be in a very “high torque environment” and it was noted that a key feature of total joint replacement in a very active person was some degree of thigh pain.  I believe that this condition may be more likely following an anterior approach to the hip since there is less surgical disruption of the short external rotators of the hip, a faster return to normal hip function, and possibly an increased ability to perform athletic activities.

As a result of these cases where the stem did not osteointegrate completely, I have switched to a “fit and fill” design or a “reduced distal diameter design”  that is intended to occupy more of the space in the proximal portion of the femoral canal.  In my mind, increased filling of the femoral canal and a larger area of contact between the ingrowth medium and bone provides increased resistance to movement of the stem about the longitudinal, or axis of roll, of the component.  Time will tell.

This series of pictures illustrates the use of a “fit and fill” femoral stem design on an elderly female patient with osteoarthritis of the left hip.  Click on the thumbnails to enlarge.