Treating Avascular Necrosis

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Most cases of AVN require either joint replacement or arthrodesis.

Preoperative view of patient suffering from avascular necrosis of the

right hip.

Postoperative view of patient who underwent total hip replacement

using lateral flare internal collar prosthesis.

Avascular necrosis (AVN) is not an uncommon affliction. It occurs as

a direct consequence of an obstruction of arterial blood flow in

tissues with inadequate or no collateral circulation (ie,

endarterioles). This obstruction of blood flow can arise from an

intravascular, vascular, or extravascular event (ie, thrombus,

vasculitis, trauma).

In the proximal femur, the femoral head is nourished by such an

endarteriole arrangement of intraosseous vessels (the pattern of

these vessels resembles the branches of a tree). As such, if an

obstructive event does occur, the resultant " downstream " area of

tissue damage will have a wedge shape.

This acute ischemic event may be associated with a brief but

exquisitely painful episode. In and of itself, it is of no other

immediate consequence to the patient. Paradoxically, the most serious

functional incapacitations result not from the direct insult to the

bone tissue, but are due to the body's attempt to repair the damage

done by the ischemic event. The death of the bone initiates a

sequence of events that will isolate, repair, and replace the damaged

tissue. During this process, the newly formed bone must pass through

a nonossified stage of healing. This nonossified bone does not

possess the structural integrity to withstand the normal compressive

loads that occur across a hip joint. As a result, the spherocity of

the femoral head is compromised. The congruity of the articular

surfaces is lost, and the articular cartilage delaminates from the

underlying subchondral bone due to its collapse.

The extent of femoral head involvement will be reflected in a

proportionate degree of compromise of hip range of motion (ROM) and

function. AVN is associated with a significant degree of inflammatory

synovitis. This synovitis is the direct result of the body's response

to a necrotic event and the body's attempt to repair the damage it

caused. This synovitis is most significant because of the amount of

pain associated with it and the resultant restrictions of hip ROM and

function it causes.

Successful treatment of AVN (and its analogous condition in children,

termed Legg-Calve-Perthes disease) requires early diagnosis,

prevention of articular deformity, and control of pain secondary to

the associated inflammatory reaction present. However, since the

patients usually do not present until after collapse of femoral bone

has occurred and articular destruction has taken place, most cases of

AVN in adults come to either joint replacement or arthrodesis as the

favored means for achieving pain reduction and restoration of hip

function.

A Case History

The following case report concerns a 33-year-old white male who

presented with an acute complaint of right groin pain. This pain had

an insidious onset with no identifiable antecedent trauma. He stated

that the pain presented originally 1 year earlier as lower back

discomfort with simultaneous nonradiating pain appearing in the groin

and testicle. The pain increased over the ensuing months so as to

interfere with his ability to function as a house painter.

Eventually, the increasing pain incapacitated him in the performance

of ADL (activities of daily living). He became dependent upon a cane

for ambulation, even within the home, and found little benefit from

nonsteroidal anti-inflammatory drugs. His only relief came from

narcotic analgesics. He reported no changes in bowel or bladder

function. Work-up originally performed at his local hospital had

identified his " only pathology " as a Grade II L5-S spondylolisthesis

with an associated " partial " sacroiliac radiculopathy, documented by

an electromyogram. Due to his lack of response to conservative

treatment, the patient underwent an L5-SI instrumented fusion for

stabilization of this condition, but achieved no relief from his

preoperative complaints.

The patient's past medical history was significant for a long-

standing diagnosis of ulcerative colitis, for which he had been

treated with sulfasalazine, folic acid, and episodic courses of oral

corticosteroids.

At the time of his presentation, the patient was a slender male who

ambulated with an antalgic limp, dependent on a wheelchair and

crutches for mobility. He had no leg length discrepancy. Examination

showed a well-healed lumbar surgical wound. There was minimal low

back discomfort and no obvious neurovascular deficits in his lower

extremities. His right lower extremity examination was extremely

limited due to exquisite groin pain caused by passive or active

attempts at hip ROM. Results of laboratory tests, including the

erythrocyte sedimentation rate, were unremarkable. Radiographs

demonstrated the aforementioned instrumented L5-S1 fusion;

deformation with irregular radiodensity in the right femoral head;

the contralateral left femoral head was rotated medially and

posteriorly upon the femoral neck. The presumptive diagnoses at that

time were: AVN of the right hip; mild osteoarthritis of the left hip

secondary to old slipped femoral epiphysis (SCFE) of the left hip,

and status-post SA L5-S1 fusion for a spondylolisthesis.

Fusion versus total hip replacement (THR) were considered as

procedural options, once it was determined that the hip was the cause

of the patient's symptoms. Then, etiology was established, ie,

infection vs AVN. Additional considerations were how to maximize the

use of available bone stock, and minimize the amount of bone to

remove.

Preoperative planning included an MRI of bilateral hips, followed by

an evaluation of the lumbosacral spine and lower extremities. After a

discussion with the patient of treatment options available, their

attendant risks and benefits, and potential limitations and

complications, autologous blood banking was performed.

The Procedure

A preoperative work-up demonstrated AVN of the right femoral head.

The left proximal femur deformity was consistent with an old SCFE and

secondary mild degenerative changes, but showed no evidence of AVN

within the left femoral head. There were no significant neurological

deficits identified.

Because of his desire to retain hip mobility, the patient declined an

arthrodesis of the hip. He underwent a right THR using a LFIC

(lateral flare internal collar) prosthesis created off standard

anteroposterior and lateral radiographs. He had an uneventful peri-

operative recovery, being out of bed and full weight-bearing on the

first postoperative day. He was discharged to go home on the fourth

postoperative day. He underwent an individualized program of physical

therapy and returned to his profession as a painter by 4 months

postsurgery. At 12 months postsurgery, the patient reported that he

had subjectively achieved a fully functional return to normal

activities with no lower extremity discomfort.