What is Hip Dysplasia?

Dysplasia is a Latin word meaning altered growth. The term “Hip Dysplasia” includes a broad spectrum of abnormal shapes (morpohologies) of both sides of the ball-and-socket joint.  These abnormal morphologies can lead to in pathological mechanics of the hip joint, early breakdown of the soft tissues structures (the acetabular cartilage and labrum), and if untreated, early arthritis. In order to understand hip dysplasia, one needs to have an understanding of the normal hip anatomy and mechanical function.

What is a Normal Hip Joint?

Two parts comprise the hip joint: a ball on the upper end of the thigh bone (femur) called the femoral head, and a socket in the pelvis known as the acetabulum.

The Normal Hip: Osseous Anatomy

The normal acetabulum “covers” the upper (superior) portion of the head of the femur as well as a partial portion of the front (anterior) and back (posterior) femoral head. This relationship allows the force of weight-bearing to be distributed throughout the acetabular cartilage surface, and allows stable motion.  Insufficient coverage of the head by the acetabulum, as in hip dysplasia, can lead to instability and abnormally high stress on the soft tissues (cartilage and labrum) in the periphery of the socket.

Figure:  The Hip Joint

A normal relationship between the acetabulum (socket) and the femur (ball).  The acetabulum covers the femoral head to keep it “contained” and stable during weight bearing and motion.

The femur is oriented into the socket, and force is distributed throughout the cartilage of the acetabulum.

What is Hip Dysplasia?

The term “hip dysplasia” most commonly refers to inadequate development of an individual’s socket, or acetabulum (acetabular dysplasia).  The resulting acetabulum is shallow, and often the upper portion (roof) of the acetabulum “angled up” rather than having the normal horizontal “flat” orientation. Because of these abnormalities, the femoral head is insufficiently covered.

When the acetabulum insufficiently covers the femoral head, instability can result.  The femoral head may migrate from the center of the socket with motion.  Also, these abnormalities can result in force concentration at the periphery of the acetabulum.

Normal Hip:  Acetabulum covers the femoral head and is horizontal, “containing” the femoral head. This allows the hip center of rotation to remain stable during motion, and the ball stays centered under the roof.  Further, the force of wight-bearing is distributed throughout the acetabular cartilage.

Dysplastic Hip: The acetabulum is shallow covering less than half of the femoral head. It is also oriented vertically, or sloped upwards.  This architecture can not maintain a stable environment of motion, and the head may migrate during motion or stance.  Force is concentrated at the edge of the socket and can lead to overload on the cartilage and labrum.

The force concentration and instability often leads to tearing of the acetabular labrum and cartilage breakdown in area of stress in the socket. Left untreated, the pathomechanics of dyplasia results in irreversible damage to the articular cartilage and arthritis.

Labral Injury with Dysplasia: The acetabular labrum is a highly innervated fibrocartilage structure that lines the acetabulum, acting as a gasket between the femoral head and the acetabular rim.  Excessive force concentration and instability associated with acetabular dysplasia may cause tearing of the acetabular labrum. This can cause significant pain, and may be the first hint that an individual has a hip problem.

There is a great range of abnormalities that fall under the umbrella of “hip dysplasia”, and every individual’s anatomy is unique.  The most drastic example is a congenitally dislocated hip where the femoral head is completely uncovered by the socket.  These patients may have severe deformity, leg length inequalities, and pain/dysfunction from very young ages.  A patient may have very shallow, upsloping acetabulum without associated femoral abnoralites that only becomes painful in their early adulthood.  Others may have dysplasia but not develop pain until their later adult years when the cartilage has broken down and arthritis ensues.  The treatment of dysplasia thus depends greatly each person’s underlying anatomy and the stage at which they seek medical attention.

A. Severe dysplasia with almost no coverage of the socket by the femoral head.  The patient presented with aching hip and back pain, with significant deformity early in adolescence.

B. This 22 year old patient first developed hints of groin and lateral hip pain at 20 years of age with dancing.  Her cartilage was well maintained, and PAO surgery was indicated.

C. A 49 YO woman who had an active, pain-free life until 48.  X-rays show dysplasia with complete deterioration of the cartilage.  THA was the treatment choice with her late presentation.

How Do You Diagnose Hip Dysplasia?

In general, the term “Hip Dysplasia” encompasses many specific abnormalities. During your evaluation at Nashville Hip Institute, your specific anatomy and the mechanics of YOUR hip will be studied.  This involves a detailed evaluation by the nursing team and the physicians, advanced imaging of the hip and pelvis, and may involve the input of our masterful physical therapists.

Physical examination is key and involves complete gait evaluation.  The physical therapists will often contribute advanced information regarding the muscles around the hip and the functional limitations weakness of these muscles might be contributing to a patient’s overall clinical problem.

The radiographic interpretation of the underlying deformity is essential to understanding the mechanical pathology of the hip. Multiple specialized x-rays, CT scans and high quality MRIs are essential to this evaluation.

Very often ultrasonography is utilized to better understand the contributions of the intra-articular environment to the hip’s pain, and may be useful in dynamically assessing instability.  Therapeutic injections may be recommended to give the hip pain-free interval to achieve pre-surgical goals with physical therapy.

Physical Therapy with PAO: The NHI physical therapy team will often perform a “functional” assessment of the hip and pelvis musculature, and determine if any specific weakness in the abductors, the iliopsoas may benefit from “Pre-hab”. These sam therapists will individualize your rehabilitation program and communicate with your local therapist if you do not live in Nashville.

Sonographic evaluation and guided injections are often part of the evaluation and treatment at Nashville Hip Institute. The injections may be used diagnostically to help identify contributions of various structures to each individual’s hip pain. Additionally, therapeutic injections may be used to temporarily alleviate pain in order to allow pre-operative rehabilitation programs to be successful.

A surgical tactic is then individually tailored to each individual’s hip. The ultimate surgical plan is always unique to each person’s specific portfolio of osseous abnormalities and soft tissue structural injuries

What is the treatment for Hip Dysplasia?

The severity of the dysplasia and the state of the intra-articular soft tissues define the treatment plan for hip dysplasia.

  1. Periacetabular Osteotomy (PAO): When identified before the acetabular cartilage has been irreversibly damaged, PAO surgery is the preferred treatment for acetabular dysplasia. Surgery is aimed at preserving the patient’s native hip joint. This is an operation aimed at repositioning the hip socket to better cover the femoral head, optimizing the intra-articular mechanics to protect the soft tissues, and thus preserving the patient’s native hip joint.
  1. Hip Arthroscopy: In rare circumstances, there may be a role for an arthroscopic-only interventions to address the pain of a labral tear associated with mild dysplasia (see HIP ARTHROSCOPY FOR DYSPLASIA below).
  2. Total Hip Replacement: Unfortunately, many patients present with hip dysplasia late after the cartilage has degenerated beyond repair and progressed to arthritis. In these cases, THA is indicated (See THA FOR DYSPLASIA BELOW)

What is Periacetabular Osteotomy (PAO) Surgery?

Periacetabular Osteotomy (PAO) is a surgical treatment for hip dysplasia that involves repositioning the acetabulum (socket) into a location that best covers the femoral head. “Periacetabular” means around the acetabulum. “Osteotomy” means to cut bone. Simply put, the PAO cuts the bone around the acetabulum that joins the acetabulum to the pelvis. Once the acetabulum is detached from the rest of the pelvis by a series of carefully controlled cuts, it is rotated (or “reoriented”) to a position that provides better coverage of the femoral head, thereby improving the stability of the hip joint and unloading the peripheral soft tissues. The socket fragment is then secured with screws.

This “reorientation” unloads the peripheral articular cartilage and acetabular labrum such that they are no longer subject to the force concentration associated with the shallow socket.  The shallow, upsloping roof that incompletely covered the femoral head is brought over the head to provide normal coverage and also brings the roof to a horizontal position. This improves the coverage of the femoral head, decreases the instability associated with dysplasia, and unloads the peripheral labrum and articular cartilage.  These changes optimize the mechanics of the hip such that the soft tissues no longer are subject to damaging forces.

Periacetabular Osteotomy.  Pre-operatively (left) the socket is shallow, covering only part of the femoral head.  It is upward sloping, and the force of weightbearing concentrated to the periphery rather than distributed throughout the acetabulum.

After PAO surgery, the socket has been repositioned to optimize coverage of the head, and the peripheral labrum and articular cartilage no longer experience the loaded stress.

Individual cases of dysplasia however present with their own unique morphologies, and the osteotomies must be tailored to solve these unique problems.  The femur may  be abnormally shaped and benefit from a combined femoral osteotomy, for example.  Commonly, the femoral neck is excessively long and straight (Coxa Valga).  Alternatively, the femoral neck may be too short (Coxa Breva) or the femoral head insufficiently round (CAM deformity).

A. Coxa Vara, Coxa Breva. The femoral neck is short and the angle low. An osteotomy to lengthen the neck and open the angle would be indicated at PAO.

Normal proximal femur, requiring no additional surgery at the time of the PAO performed to address the acetabular dysplasia.

C. Coxa Valga. The femoral neck angle is too high, contributing to the force concentration on the shallow socket. Surgery to decrease the neck angle is indicated.

If there is an abnormality of the proximal femur that threatens the intra-articular tissues after the socket has been reoriented, a combined Proximal Femoral Osteotomy may be required.   Below is an example of a patient with a dysplastic acetabulum, but also a femoral deformity common to Legg–Calvé–Perthes Disease.  A combined Periacetabular Osteotomy and Proximal Femoral Osteotomy was performed to optimize the hip mechanics.

Often, the abnormal mechanics associated with hip dysplasia have cause labral injury and cartilage damage.  In the majority of cases, the labrum will be evaluated and treated at the time of the surgery (either by open means or with a combined arthroscopic surgery.  The articular cartilage may be injured and require treatment as well.

Hip Arthroscopy for Hip Dysplasia

As described above, the labrum and articular surfaces may have degenerated or become injured by the time a patient seeks medical attention for hip dysplasia.  In rare circumstances, there may be a role for an arthroscopic-only intervention to address the pain of a labral tear associated with mild dysplasia.

A. The acetabular labrum is often detached and injured at the time of reorientation osteotomy.

B. This MRI of a patient with acetabular dysplasia is compelling for injury to the acetabular labrum.

C. Injury was identified at the chondrolabral junction in this patient with a hpertropic acetabular labrum arthroscopically during this combined procedure.

This is a considerable option in patients without an upsloping socket and mild coverage insufficiencies, particularly if the patient is older and there is some evidence of early cartilage deterioration. An arthroscopic procedure in the properly selected individual may provide sufficient relief to delay hip replacement. Arthroscopy does not improve the acetabular coverage and does not substantially alter stability in patients with acetabular dysplasia. Thus, if applied to a patient with significant instability and stress concentration associated with dysplasia, arthroscopic treatment alone may lead to predictable recurrence of the soft tissue injuries and labral tearing. Great care must be taken when selecting this option, and Dr. Byrd will guide patients in choosing the best preservation treatment option for each individual patient.

Total Hip Replacement for Hip Dysplasia

Unfortunately, many patients present with hip dysplasia late, and have started down the path towards arthritis. In these cases, when the joint is not likely to be preserved with an osteotomy surgery, the best option may be total hip replacement.

Why is Osteotomy Preferable to Total Hip Replacement?

Over the past 5 years, there has been a renewed and growing interest in adult hip osteotomy. Osteotomy was used more frequently as a treatment for adult hip problems before the advent of Charnley’s low friction arthroplasty (the first successful artificial hip joint) in the 1960’s. The encouraging early good results regarding function and pain relief after Charnley total hip replacement in young patients led many surgeons to abandon osteotomy.

However, despite good initial results of total hip replacement, the long-term follow up of these patients has shown increased problems, especially in the young active population. Osteolysis (bone loss) can cause loosening of the hip prosthesis (artificial hip) when patients outlive the longevity of their artificial hip. This is particularly important in young patients, who are active and will cycle their hips move over many years. Hip replacement revision surgery for failed THA presents significant problems, particular for the patients with osteolsis. Failure of THA requiring revision surgeries in active young to middle aged adults have underscored the importance of preserving the hip rather than replacing it.

Osteotomy should not be thought of as an inferior second choice to total hip replacement that the young patient with early arthritis must undergo because he or she is too young for total hip replacement. The results after PAO, which preserves the patient’s own hip, justify its use, and the long-term results can be better than what the patient could have obtained from a hip replacement. The patient’s own hip is a living tissue with self-maintenance capabilities, whereas deterioration with time is inevitable for an artificial part. The sensory capabilities of the joint are preserved, and the patient can continue to remain as active as symptoms or lack thereof permits. The patient with a total hip replacement, however, must always be cautioned regarding possible hip dislocation and the substantial complication portfolio associated with implant based replacement surgeries.

What Should You Expect After Surgery?

Dr. Byrd operates these cases at the St. Thomas Midtown Center in Nashville, Tennessee. You will be evaluated by our Medical Hospitalist or Pediatric Hospitalist partners before surgery, and these physicians will see you each day and contribute to your non-orthopaedic care while you are in the hospital. ­­

The usual hospital stay is five to seven days and depends on how rapidly pain subsides and physical therapy progresses. You will have a Foley catheter in your bladder for at least one night, have compressive devices on your legs to prevent blood clots, and be treated with a multi-modal analgesic program to address post-surgical pain.

St. Thomas Midtown Nursing team.  These nurses truly enjoy caring for patients after complex hip and pelvis surgery.  They are specialized in orthopaedic patient care, and the floor only has patients that have had orthopaedic surgery.Our patients after PAO surgery commonly visit the team at the time of their return clinical visits.

Your incision will most likely be closed without sutures nor staples requiring removal, and will be sealed with a glue.  Surgical drains will be removed 1-2 days after surgery.  Occassionaly patients require a blood transfusion.  If you have chosen to obtain a “Game Ready” device, it will be applied at the time of surgery, and you will be trained to apply it and adjust it while in the hospital.

You will work with Physical therapy 2x a day and be encouraged to ambulate (with restrictions) as much as possible, starting the day after the surgery. Weightbearing is restricted to 30lbs on the operative side for 8 weeks after surgery to allow the osteotomy sites to begin healing.  Most commonly patients utilize a walker for 3 weeks, and then transition to crutches.  There are some restrictions on the range of motion after the surgery, including limitations to active flexion and flexion beyond 90 degrees.  If labral surgery is performed, there may be rotational restrictions also.  A continuous passive motion machine is utilized, allowing safe and controlled motion starting the day after the surgery.

*Each surgery is individualized, and therefore the specific restrictions and precautions for each patient will be different for each patient.  We will spend a lot of time with you after surgery ensuring that you understand your unique protocols before you leave the hospital.

When Will I Be Discharged?

Patients are discharged once pain is controlled with oral medications and physical therapy goals are met.  In general, this takes 5-7 nights of stay in the hospital.

At discharge, pain medication is prescribed as well as an anticoagulant to prevent blood clots. Some degree of pain after discharge is natural, which may increase or decrease on different days, but the general trend should be toward decreasing pain. Some patients may sense an occasional “click” or “pop” in or around the hip. Numbness and a tingling sensation is common around the incision area. Patients experiencing new, severe pain or having ANY wound drainage, redness or seperation should call NHI (615-284-5800) regardless of the time or day to discuss with the oncall practitioner.  *Concerns should NOT be sent by email.

When Do I Return to Nashville Hip Institute?

Follow-up outpatient visits are necessary to monitor progress by X-ray and physical examination, and to graduate patients to the next phases of rehabilitation. The first follow-up visit is usually scheduled about 6 weeks after surgery with Morgan Schlundt, the Physician Assistant. The second visit is at 3 months.

At 8 weeks after the surgery, the patient is allowed to be full weight bearing and work toward discontinuing use of the crutches (which usually takes 2-4 weeks).

Ultimately, your postoperative course depends on return of muscle strength. Working with one of our trained physical therapist adept in treating hip dysplasia is critical.  You will develop a relationship with a therapist before surgery, and many patients benefit from working with therapists as part of the “pre-hab” strengthening program.  These therapists will be critical in your post-surgical rehabilitation, particularly once weight-bearing is allowed after 8 weeks.

You will be asked to visit us 6 weeks after surgery (or see your local surgeon who might be coordinating your care locally), again at 3 months, at 6 months, and at 1 year and 2 years for routine follow-up.  After the second year, we schedule appointments at 2 year intervals.

A minority of patients request removal of one or more screws that were used to fix the PAO, and this can be performed as an outpatient procedure that does not interrupt a patient’s continued full function.  Patients who have undergone some femoral osteotomies at the time of PAO often require secondary metal removal for symptomatic implants.

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