Conf 4

MORTALITY
Reported mortality rates after total hip arthroplasty vary
depending on the historical time period during which the
surgeries were performed, the postoperative end point at
which the rate was determined, and the patient population
being evaluated. According to the American College of Surgeons National Surgical Quality Improvement
Program, the
30-day mortality rate is 0.35% for primary total hip arthroplasty. Mortality at 90 days postoperatively in the
United
States Medicare population is 1% for primary total hip arthroplasty and 2.6% for revision surgery. Increased
mortality rates
are associated with patients older than 70 years, male sex,
American Society of Anesthesiologists (ASA) class greater
than 2, preexisting cardiac disease, or renal insufficiency.
Although careful preoperative medical evaluation is warranted in all patients, special attention should be
directed to
patients with these risk factors.

HEMATOMA FORMATION
Careful preoperative screening should identify patients with
known risk factors for excessive hemorrhage, including antiplatelet, antiinflammatory, or anticoagulant drug
therapy;
herbal medication use; blood dyscrasias and coagulopathies;
and family or patient history of excessive bleeding with previous surgical procedures.
The most important surgical factor in preventing hematoma is careful hemostasis.

Common sources of bleeding are

(1) branches of the obturator vessels near the ligamentum
teres, transverse acetabular ligament, and inferior acetabular
osteophytes, (2) the first perforating branch of the profunda
femoris deep to the gluteus maximus insertion, (3) branches
of the femoral vessels near the anterior capsule, and (4)
branches of the inferior and superior gluteal vessels. The iliac
vessels are at risk from penetration of the medial wall of the
acetabulum and removal of a medially displaced cup. Bleeding
from a large vessel injury usually becomes apparent during
the operation (see section on vascular injuries). Late bleeding
(1 week postoperatively) may occur from a false aneurysm or
from iliopsoas impingement (Fig. 3-99). Arteriography may
be required for identification of a false aneurysm along with
possible embolization. Acetabular revision may likewise be
necessary to correct iliopsoas impingement.
We have selectively used suction drains deep to the fascia
and remove them after 24 hours. In our patients without
excessive bleeding at the time of surgery or risk factors for
hemorrhage, drainage is not required after primary total hip
arthroplasty. Drains are used routinely for revision procedures or primary surgeries with increased hemorrhage
and
in at-risk patients. The need for drainage has been questioned, however. A meta-analysis of the literature by
Parker,
Roberts, and Hay, regarding closed suction drains and total
joint replacement concluded that the use of drains led to
increased transfusion requirements but less frequent dressing
reinforcement. The benefit of closed suction drainage in
uncomplicated primary arthroplasties remains unproven.

Excessive hemorrhage leading to hematoma formation

uncommonly requires surgical intervention. Most patients

can be managed by dressing changes, discontinuation of anticoagulants, treatment of coagulopathy, and close
observation
of the wound. Indications for surgical treatment of hematoma
include wound dehiscence or marginal necrosis, associated
nerve palsy, and infected hematoma.

Evacuation of the hematoma and achievement of meticulous hemostasis should be

accomplished in the operating room. The hematoma should
be cultured to assess possible bacterial contamination, and
antibiotics should be continued until these culture results
become available. Debridement of necrotic tissue as needed
and watertight closure also are required. Closed suction
drainage seems warranted in this setting to avoid a recurrence. Patients requiring surgical evacuation of
hematomas
are more likely to experience diminished functional outcomes and lower overall satisfaction, along with higher
rates
of morbidity and mortality

HETEROTOPIC OSSIFICATION
Heterotopic ossification varies from a faint, indistinct density
seen in the region of the abductors and/or iliopsoas to complete bony ankylosis of the hip. Groups at high risk
for
heterotopic ossification include patients with a history of heterotopic ossification or hypertrophic
posttraumatic arthritis
and males with hypertrophic osteoarthritis. Moderate risk is
associated with ankylosing spondylitis, diffuse idiopathic
skeletal hyperostosis, Paget disease, and unilateral hypertrophic osteoarthritis.

Surgical technique may play a role in the development of

heterotopic ossification. Anterior and anterolateral approaches
carry a higher risk of heterotopic ossification than transtrochanteric or posterior approaches. Although
cementless fixation has been implicated as a risk factor for heterotopic
ossification in a retrospective review of cemented and cementless stems, subsequent prospective randomized
and matched
pair studies have refuted this association.

Calcification can be seen radiographically by the third or

fourth week; however, the bone does not mature fully for 1

to 2 years.

The following classification of Brooker et al. is

useful in describing the extent of bone formation:
Grade I: islands of bone within soft tissues
Grade II: bone spurs from the proximal femur or pelvis with
at least 1 cm between opposing bone surfaces
Grade III: bone spurs from the proximal femur or pelvis with
less than 1 cm between opposing bone surfaces
Grade IV: ankylosis

The prevalence of this complication ranges from 2% to 90%

of patients. Most who develop heterotopic ossification are
asymptomatic; however, restricted range of motion and pain
may occur in patients with more severe Brooker grade III or
IV ossification. Marked limitation of motion or bony ankylosis is uncommon, but significant loss of function
has been
reported in up to 10% of patients.

Routine prophylaxis against

heterotopic ossification is not recommended for all patients
but is warranted in high-risk groups.
Prophylactic efforts towards prevention of heterotopic
bone include low-dose radiation and nonsteroidal antiinflammatory drugs (NSAIDs). Preoperative and
postoperative
radiation regimens with doses as low as 500 cGy have been
successful. In a multicenter evaluation of radiation prophylaxis, failures occurred more commonly in patients
treated
more than 8 hours preoperatively or more than 72 hours
postoperatively. Preoperative treatment should result in less
patient discomfort than in the early postoperative period.
Radiation exposure is limited to the soft tissues immediately
around the hip joint, and ingrowth surfaces must be appropriately shielded (Fig. 3-100).
Hedley et al. reported no clinical evidence of loosening,
subsidence, or radiolucent lines around cementless prostheses after irradiation. Kennedy et al. also reported no
increase in radiolucent lines and no revisions for aseptic
loosening in a group of cementless total hip arthroplasties
treated with radiation prophylaxis. Although delayed union
or nonunion of trochanteric osteotomy is a potential
problem with radiation therapy, malignancy after prophylactic radiation has not been reported with currently
recommended dosages.
NSAIDs have been shown to reduce the formation of
heterotopic bone in many studies. Historically, nonselective

cyclooxygenase -1 (COX-1) and cyclooxygenase -2 (COX-2)

inhibitors for 6 weeks have been recommended, although
courses of administration of 7 days are successful. Compliance is limited by medical contraindications to these
drugs
and patient intolerance. Cella, Salvati, and Sculco found that
37% of patients were unable to complete a course of treatment
with indomethacin. Two meta-analyses comparing COX-1
and COX-2 inhibitors showed no difference in efficacy in
preventing heterotopic ossification. In light of a more favorable safety profile for the COX-2 inhibitors, they
were recommended for HO prophylaxis. NSAIDs have been shown to
diminish bone ingrowth into porous implants; however, no
method exists to shield the bone/implant interface from these
effects.
An operation to remove heterotopic bone is rarely indicated because associated pain usually is not severe and
excision is difficult, requiring extensile exposure. The ectopic
bone obscures normal landmarks and is not easily shelled out
of the surrounding soft tissues. Substantial blood loss can be
anticipated. Decreased technetium bone scan activity indicates that the heterotopic bone is mature, allowing
for reliable
excision. Radiation and NSAIDs have been used successfully
to prevent recurrence. Range of motion should improve, but
pain may persist.

DISLOCATION
The prevalence of dislocation after total hip arthroplasty is approximately 3%. Anatomic, surgical, and
epidemiologic factors may increase this risk.

Trochanteric nonunion, abductor muscle weakness, and increased preoperative range of motion are anatomic
features that increase the risk of instability.

Posterior approach, component malposition, uncorrected bony and/or component impingement, inadequate
soft tissue tension, and smaller head size are variables under the surgeon’s control that have also been
implicated. Previous hip surgery, including revision hip replacement, female sex, advanced age, prior hip
fracture, and preoperative diagnosis of osteonecrosis or inflammatory arthritis are epidemiologic factors that
negatively affect hip stability.

Postoperative dislocation is more common when there has been previous surgery on the hip and especially
with revision total hip replacement. Alberton, High, and Morrey reported a 7.4% dislocation rate in a group of
1548 revision total hip procedures with at least 2-year follow-up. Likely contributing factors include extensive
soft tissue release, muscular weakness, small femoral head size (22 mm), and trochanteric nonunion.

The choice of surgical approach affects the rate of postoperative dislocation. Berry et al. found the dislocation
rate to be 6.9% when a posterolateral approach was used compared with 3.1% when the anterolateral approach
was used.

There is a tendency to retrovert the socket when total hip arthroplasty is done through a posterolateral
approach. This is usually caused by inadequate anterior retraction of the femur so that the acetabular
positioning device is forced posteriorly during component insertion. Division of all the short external rotators
probably is another factor, and meticulous repair of the posterior soft tissue envelope improves stability.
Various soft-tissue repair techniques are advocated for improving hip stability after the posterolateral
approach, with dislocation rates ranging from 0% to 0.85%. A meta-analysis comparing posterior approaches
with and without soft tissue repair showed an almost ten-fold reduction in dislocation rates from 4.46% to
0.4% in favor of soft-tissue repair. Our preference includes repair of the posterior capsule and short external
rotators to the greater trochanter and/or abductor tendon with nonabsorbable sutures (Fig. 3-106).

When considering total hip surgery in a patient at high risk for posterior dislocation, particularly individuals
with neuromuscular disease or marked flexion contracture, an anterior approach should be considered. In
fixing the cup in the proper position, especially with respect to anteversion, the surgeon must be able to judge
the position of the patient’s pelvis in the horizontal and vertical planes. Errors in positioning the patient on the
operating table are a common source of acetabular malposition, and

secure stabilization of the patient in the lateral position is crucial. When in the lateral position, women with
broad hips and narrow shoulders are in a relative Trendelenburg position, and the tendency is to implant the
cup more horizontally than is planned. In men with a narrow pelvis and broad shoulders, the reverse is true.
With reference to anteversion, the pelvis flexes upward by 35 degrees in the lateral position,

and with extension in the supine position it becomes relatively retroverted. Also, forceful anterior retraction of
the femur for acetabular exposure often tilts the patient forward. Placement of the acetabular component in the
usual orientation relative to the operating table produces inadvertent retroversion relative to the pelvis.
Acetabular insertion devices may provide a false sense of security, and the true position of the pelvis must
always be taken into account. Being able to palpate the anterior superior iliac spine through the drapes is
helpful in judging the position of the pelvis, and good acetabular exposure that allows observation of bony
landmarks is essential.

When an acetabular insertion device is used, the angle at which it holds the cup must be known. The trial cup
should be placed in the position in which the final cup is to be inserted, and its relationship to the periphery of
the acetabulum and the transverse acetabular ligament should be carefully noted. This orientation is precisely
reproduced on placement of the final implant.

Quantifying the degree of anteversion of the cup by plain radiographic examination is difficult. McLaren
reported a mathematic method of determining the degree of anteversion whereby the relative positions of the
anterior and posterior halves of the circumferential wire in a cemented cup are considered (Fig. 3-107).
Similarly, the anteversion of a cementless acetabular component can be estimated by comparing its anterior
and posterior margins. Superimposition of the two margins suggests little or no anteversion. If they form an
ellipse, some degree of anteversion or retroversion is present. A cross-table lateral view of the affected hip
also may be helpful in assessing acetabular anteversion, but CT can be used to assess the degree of anteversion
of the cup more accurately (Fig. 3-108). The inclination or abduction of the acetabular component can be
measured more directly from plain radiographs, although flexion or extension of the pelvis relative to the
beam may distort this relationship

Cup position correlates somewhat with dislocation risk.

Lewinnek et al. reviewed radiographs of 300 total hip replacements with direct measurement of inclination and
calculation of anteversion. The dislocation rate for cup orientation with anteversion of 15 ± 10 degrees and
inclination of 40 ± 10 degrees was 1.5%, whereas 6.1% of those outside this “safe range” dislocated.
Similarly, Biedermann, et al. studied a group of 127 hips with postoperative instability and compared them
with a control group of stable hips using computerized radiographic analysis. They found increased
anteversion and abduction for patients with anterior dislocation and decreased anteversion and abduction for
posterior dislocators. The lowest risk values for dislocation were 15 degrees of anteversion and 45 degrees of
abduction.

If the cup is excessively anteverted, anterior dislocation can occur during hip extension, adduction, and
external rotation. If the cup is retroverted, dislocation occurs posteriorly with flexion, adduction, and internal
rotation.

Excessive inclination of the cup can lead to superior dislocation with adduction, especially if there is a residual
adduction contracture, or if the femur impinges on osteophytes left along the inferior margin of the acetabulum
(Fig. 3-109). Conversely, if the cup is inclined almost horizontally, impingement occurs early in flexion and
the hip dislocates posteriorly; this is accentuated if the cup also is in less anteversion.

Femoral component anteversion is estimated intraoperatively by comparing the axis of the

prosthetic femoral neck with the shaft of the tibia when the knee is in 90 degrees of flexion. Neutral version is
defined by the prosthetic neck aligned perpendicular to the tibia. Relative anteversion occurs when this angle
is greater than 90 degrees and retroversion when it is less (Fig. 3-110). The femoral component should be
fixed with the neck in 5 to 15 degrees of anteversion.

Severe anteversion of the anatomic femoral neck is seen in developmental dysplasia or juvenile rheumatoid
arthritis, whereas retroversion may be encountered with previous slipped capital femoral epiphysis, proximal
femoral malunion, or low levels of neck resection. If the neck of the component is in more than 15 degrees of
anteversion,

anterior dislocation is more likely (Fig. 3-111). Conversely, retroversion of the femoral component tends to
make the hip dislocate posteriorly, especially during flexion and internal rotation.

Amuwa and Dorr described combined anteversion, a method in which the anteversion of the femoral
component is determined by femoral preparation first. The acetabular component is then placed and the sum of
the anteversion of the cup and stem is determined, with the goal of 35 degrees total and an acceptable range of
25 to 50. Computer navigation is required to precisely determine these values.

Impingement may occur because of prominences on the femoral, acetabular, or both sides of the joint. Bone
or cement protruding beyond the flat surface of the cup must be removed

after the cup has been fixed in place; otherwise, it serves as a fulcrum to dislocate the hip in the direction
opposite its location. Residual osteophytes, especially located anteriorly, cannot be seen well on standard
radiographs but are easily shown by CT scan (Fig. 3-112). After a shallow acetabulum is deepened to provide
coverage of the superior part of the cup, excess bone often must be removed anteriorly, posteriorly, and
inferiorly. This is difficult if the cup has been placed with a high hip center. If the greater trochanter is
enlarged or distorted because of previous surgery or as a result of the underlying disease process, some bone
often must be removed from its anterior or posterior margin to prevent impingement. Finally, bony
impingement is much more likely if femoral offset has not been adequately restored. The use of a femoral
component with enhanced offset can be very beneficial in this situation (see Fig. 3-9).
The ratio of the head diameter to that of the neck of the prosthesis is important, as smaller heads have a lower
“jumping distance” required for dislocation (see Fig. 3-12). Larger head size is a stabilizing factor reported in
some series of primary and revision total hip arthroplasties. Modular femoral head components that have an
extension, or “skirt,” to provide additional neck length reduce the head-to-neck diameter ratio because the
neck of the component is fitted over a tapered trunnion that must be of sufficient diameter (see Fig. 3-8).

The range of motion to impingement is decreased compared with a shorter neck that does not use a skirt.
Although lengthening the prosthetic neck may improve soft-tissue tension and increase offset, the range of
prosthetic motion and ultimate stability of the hip may be diminished if the longer neck requires the addition
of a skirted head. Many current acetabular components have modular liners with elevations that can be rotated
into a variety of positions to reorient the face of the acetabulum to a slight degree to provide greater coverage
of the prosthetic head (see Fig. 3-33).

Such components may improve stability, but they

may have the opposite effect if an excessively large elevation is used, or if it is rotated into an inappropriate
orientation. Careful assessment of impingement of the prosthetic neck on the liner elevation during trial
reduction is mandatory. The adequacy of soft-tissue tension across the hip joint often is suggested as a cause
of postoperative dislocation as well. In a series of 34 dislocated total hips reported by Fackler and Poss, the leg
on the operated side was 1.5 mm longer than the opposite normal leg; however, there was a tendency toward
decreased femoral offset (average 5 mm decrease) in the dislocation group. Trochanteric nonunion, with
resultant diminished abductor tension, also is associated with an increased incidence of dislocation. Woo and
Morrey found a dislocation rate of 17.6% in patients with displaced trochanteric nonunions compared with
2.8% when the trochanter healed by osseous or fibrous union without displacement. Physical therapists,
nurses, and other attendants who care for the patient and assist in postoperative mobilization should be aware
of the positions likely to cause dislocation. These positions may differ from patient to patient, depending on
the surgical approach and other factors. Above all, the patient should be able to voice the appropriate
precautions before discharge, and instructions should be reiterated at follow-up office visits. Specialized
devices for reaching the floor and dressing the feet are immensely helpful for maintaining independence while
avoiding extremes of positioning in the early postoperative period. Noncompliance with hip precautions,
whether because of alcohol abuse, medication, or unrecognized dementia with short-term memory loss, can
increase the risk of dislocation.

Most dislocations occur within the first 3 months after surgery. The dislocation often is precipitated by
malpositioning of the hip at a time when the patient has not yet recovered muscle control and strength. Late
dislocations can be caused by progressive improvement in motion after surgery. Impingement caused by
component malposition or retained osteophytes may not become manifest until extremes of motion are
possible. Late dislocations are more likely to become recurrent and require surgical intervention. Von Knoch
et al. reported that 55% of late dislocations were recurrent, with 61% of the recurrent dislocators requiring
surgery.

All attending personnel, including nurses and physical therapists, should be aware that excessive pain, limited
range of motion, rotational deformity, or shortening of the limb is suggestive of dislocation. If these symptoms
are noted, radiographs of the hip should be obtained.

Reduction usually is not difficult if dislocation occurs during the early postoperative period and a timely
diagnosis is made. If the dislocation is not discovered for more than a few hours, reduction may be more
difficult because of additional swelling and muscle spasm. Intravenous sedation and analgesia often are
sufficient, but sometimes a general anesthetic is required to assist with reduction of the hip.

Reduction techniques should always be gentle to minimize damage to the articulating surfaces. The use of
image intensification sometimes is valuable in reducing the hip. Reduction is accomplished by longitudinal
traction and slight abduction when the head is at the level of the acetabulum. The Allis or Stimson maneuver
(see Chapter 55) also can be used. Radiographs should be repeated to confirm the adequacy of reduction.
Modular polyethylene liners may dissociate from their metal backings when dislocation occurs, or when
reduction is affected. Incongruous

placement of the femoral head within the metal backing indicates such an occurrence.

Open reduction with replacement of the liner or revision of the acetabular component is required (Fig. 3-113).
If the components are in satisfactory position, closed reduction is followed by a period of bed rest.
Mobilization is accomplished in a prefabricated abduction orthosis that maintains the hip in 20 degrees of
abduction and prevents flexion past 60 degrees, although removable devices are not practical in noncompliant
patients. Immobilization for 6 weeks to 3 months is recommended. The efficacy of abduction bracing was
challenged in a retrospective review by DeWal et al., who found no difference in the risk of subsequent
dislocation between groups of patients treated with or without an abduction brace. Wera et al. published a
series of 75 revision total hip arthroplasties performed for recurrent dislocation according to a proposed
algorithmic classification. The six etiologies were: Type I: acetabular component malposition Type II: femoral
component malposition Type III: abductor deficiency Type IV: impingement Type V: late wear Type VI:
unresolved

Types I and II are treated by revision of the malpositioned component(s). Abductor deficiency and those
without known etiology for dislocation (types III and VI) are revised to constrained acetabular liners. When
impingement is the causative factor (type IV), sources of impingement are removed, offset is restored, and
head size is increased. Late wear (type V) associated with instability requires modular head and liner
exchange, including a larger femoral head. In their series, repeat dislocation occurred in 14.6% of patients,
with the highest risk of recurrence in those with abductor deficiency.

If no component malposition or source of impingement is identifiable, distal advancement of the greater

trochanter was recommended by Kaplan, Thomas, and Poss to improve soft-tissue tension. In their series, 17
of 21 patients had no additional dislocations. Ekelund reported similar results. Constrained liner designs offer
higher resistance to dislocation than do unconstrained components because the femoral head is mechanically
captured into the socket. Callaghan et al. reported the best results with constrained acetabular components.
They used a tripolar liner in combination with a new uncemented acetabular component (6% failure rate) or
cemented into a well-fixed existing shell (7% failure rate). They did not report increased wear or osteolysis
with this device. In a literature review of constrained components, Williams, Ragland, and Clarke found an
average recurrent dislocation rate of 10% and an average reoperation rate for reasons other than instability of
4%.

If a constrained component is used, the range of motion of the hip is reduced, and correct positioning of the
component is crucial to minimize impingement of the neck on the rim of the liner. Excessive prosthetic
impingement with constrained components can disrupt the liner locking mechanism or lever the entire
component out of the acetabulum if fixation is not rigid. Guyen, Lewallen, and Cabanela described and
categorized the various modes of failure of a tripolar constrained liner in 43 patients. Failures occurred at the
bone/implant interface (type I), at the liner/shell interface (type II), at the locking mechanism (type III), by
dislocation of the inner bearing from the bipolar femoral head (type IV), and as a result of infection (type V).
They recommended the use of these devices only as a last resort because of their complexity and multiple
modes of mechanical failure. Finally, some patients are not candidates for reconstruction. Noncompliant
individuals; alcohol and drug abusers; elderly, debilitated patients; and patients with several previous failed
attempts to stop recurrent dislocation are best treated by removal of the components without further
reconstruction.