Hip replacement with use of small incisions has been practiced selectively
by a few practitioners for many years, but only in the last several years has
so-called minimally invasive hip replacement been widely introduced to the
majority of orthopaedic surgeons.
Minimally invasive hip replacement, in fact, is not a single type of
surgery but rather is a family of operations designed to allow total hip
replacement to be done through smaller incisions, potentially with less
soft-tissue disruption. The three main methods involve a combination of a
small incision and a posterior approach to the hip, a combination of a small
incision and an anterior approach to the hip, or two small incisions performed
with use of the Smith-Peterson interval for acetabular placement and the
approach usually used for femoral intramedullary nailing for femoral component
insertion.
Minimally invasive total hip arthroplasty has created much controversy
among orthopaedic surgeons and a great deal of publicity in the popular press.
Advocates emphasize the potential for these methods to reduce soft-tissue
trauma and thereby reduce operative blood loss, postoperative pain, and
hospitalization time; speed the postoperative recovery; and improve the
cosmetic appearance of the surgical scar. Advocates view minimally invasive
total hip arthroplasty as a logical extension of less invasive methods that
have revolutionized other fields, such as arthroscopy, laparoscopic
cholecystectomy, and cardiac surgery, just to name a few. Those with
reservations about minimally invasive total hip replacement point out that
conventional hip replacement already provides excellent pain relief,
functional improvement, and durability with a low complication rate. Skeptics
are concerned that minimally invasive procedures introduce new potential
problems related to reduced visualization at the time of the operation, such
as implant malposition, neurovascular injury, poor implant fixation, or
compromised long-term results.
Advocates of minimally invasive methods believe that minimally invasive hip
arthroplasty holds the promise of providing all of the benefits of modern
total hip arthroplasty along with shorter recovery and faster rehabilitation.
This redefinition of the goals of surgery appears to resonate with some
patients.
An unavoidable part of the discussion surrounding minimally invasive total
hip arthroplasty has been an emotional element. Advocates at times seem to
suggest that minimally invasive total hip arthroplasty is the way of the
future and that those who do not learn it will be left behind. On the other
hand, those with reservations often criticize the hype, the lack of objective
data demonstrating the benefit of the procedure, and the marketing aspects
associated with minimally invasive operations.
Beyond the emotional element of the discussion, serious and important
issues are at stake. Even those with reservations about changing an already
successful procedure cannot deny the potential advantages of reduced
soft-tissue trauma and possibly quicker recuperation with less cost. At the
same time, enthusiasts must be concerned about the new risks that these
procedures and their widespread introduction might bring to an operation that
in its present form is already remarkably successful.
Ultimately, orthopaedic surgeons need to determine whether minimally
invasive methods actually provide their touted benefits, and at what cost, in
objectively performed studies. The potential benefits of a smaller incision
and possibly somewhat quicker rehabilitation need to be balanced against the
added operative difficulty, reduced visualization, possibly increased
operating time, and the drawbacks of a new learning curve associated with
minimally invasive methods. Then, orthopaedic surgeons and their patients need
to weigh the benefits and the risks to determine whether, for an individual
patient and an individual surgeon, minimally invasive methods are worth
pursuing. This symposium brings together advocates for and those with
reservations about minimally invasive total hip arthroplasty to provide
preliminary information on the results of these procedures and also to provide
measured consideration of this topic.
Suggested Reading
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The use of a single "mini-incision" is the most common
minimally invasive surgical technique for hip replacement. Either a posterior
or an anterior approach can be used. An incision length of =10 cm has
become the usual definition of a mini-incision, but some surgeons use 12 cm.
My experience has been with a posterior approach, which I use because it
avoids any incision of the gluteus medius muscle. With this posterior
approach, an 8-cm incision is made in the gluteus maximus muscle, and the
capsule, with the external rotators, is elevated as a single tissue flap,
which is then repaired at the completion of the operation. This technique
allows patients to be fully weight-bearing immediately after surgery and
provides them with early control of the lower extremity to optimize early
function.
Several questions have arisen as a result of the performance of total hip
replacement with a single mini-incision: (1) Is this operation as safe as one
performed with a traditional incision with regard to the avoidance of
neurovascular injuries and dislocation? (2) Does the patient have more rapid
relief of pain and improvement in function because there is less muscle
injury? (3) Can the components be positioned as reliably as they are with the
larger, traditional incision? The purpose of this study was to attempt to
answer these questions with regard to a single posterior mini-incision.
Materials and Methods
Three hundred and ninety total hip replacements performed with use of
posterior incisions of =12 cm have been done since February 2001. The first
sixty operations were done with standard hip instrumentation, which usually
required a 10 to 12-cm incision. During this time, instrumentation that
allowed the operation to be performed through incisions of 5 to 10 cm was
developed (Fig. 1). These
instruments had curvatures and an increased handle length designed to minimize
skin trauma and yet provide optimal exposure for reproducible component
placement. A curved reamer for acetabular preparation was developed.
Ninety patients (105 hips) had a single incision that averaged 8.2 cm
(range, 6 to 10 cm). During this same time period, sixteen hips (15%) required
an incision of >10 cm. The average age of the ninety patients was
sixty-four years (range, thirty-seven to eighty-five years), and there were
forty-five women and forty-five men. The average body-mass index for these
patients was 26.2 (range, 19 to 37). The duration of the operation from the
time of the incision to closure of the wound averaged sixty-four minutes
(range, fifty to seventy-three minutes). All patients received an uncemented
cup (Anatomic Porous Replacement; Centerpulse, Austin, Texas) and a proximally
porous-coated anatomic uncemented stem (Anatomic Porous Replacement). The
hospital stay averaged 4.1 days (range, three to nine days), with only two of
the ninety patients attending a rehabilitation facility. During
hospitalization, the daily pain score for these patients averaged 3 on a scale
of 10 (with 10 indicating maximum pain). Thirty-six patients (40%) went home
walking with a cane. At six weeks, sixty of the ninety patients were able to
walk without an assistive device and one-third was able to walk with use of
one cane. The complications in this group included an infection in one patient
and a transient sciatic nerve palsy that lasted one month in another
patient.
These patients were treated with an anesthesia and postoperative pain
management protocol that evolved during the study. The purpose of the
protocol, which we now use, is to increase the functional recovery of the
patient by minimizing postoperative nausea and emesis and by increasing
alertness for physical therapy. The basic tenet of this program is to avoid
epidural or intravenous narcotics. One hour before surgery, 40 mg of Bextra
(valdecoxib; Pfizer, New York, New York) and 20 mg of OxyContin (oxycodone;
Purdue Pharmaceuticals, Stamford, Connecticut) are adminstered orally.
Intraoperatively, anesthesia is performed with an epidural catheter with use
of 8 to 10 mL of 1% ropivacaine (Naropin; AstraZeneca, Wilmington, Delaware).
The patient is kept unconscious during the operation with use of intravenous
propofol (Diprivan; AstraZeneca) with initial infusion of 200 µg/kg/min.
This dose is then titrated to a maintenance level of 100 µg/kg/min. No
general anesthetic agents are used. Following the operation, in the recovery
room, four hours after the initial dose of OxyContin, 20 mg of oral OxyContin
is again given. On return to the floor, the patient is given 10 mg of Norco
(hydrocodone; Watson Laboratories, Corona, California), one to two tablets
every three hours, according to the age of the patient. The pain medicine is
given preemptively throughout the first forty-eight hours. Ten to 20 mg of
OxyContin is also given every twelve hours, if needed, to supplement the
Norco. OxyContin has the tendency to make patients lethargic so it is avoided
in favor of Norco whenever possible. Twenty milligrams of Bextra is also given
every morning. Toradol (ketorolac; Roche Pharmaceuticals, Nutley, New Jersey)
also can be used for "break-through pain." The patient is
discharged home with 5 mg of hydrocodone, either Norco or Vicodin (Knoll
Laboratories, Mount Olive, New Jersey), according to the individual's
needs.
Results
The radiographic results for these 105 hips showed that the average
inclination angle (and standard deviation) was 38.4° ± 6.3° and
the average anteversion was 20.1° ± 5.7°. The goal at the
operation was an inclination of 25° to 45° and anteversion of 15°
to 30°. Eleven percent of the hips were outliers (those outside the
desired range) with regard to inclination and 8% were outliners for
anteversion. The femoral component alignment was within 3° of neutral in
the coronal plane in ninety-five hips, 4° to 5° of varus alignment in
nine hips, and 6° of varus in one hip in which a lateral femoral fracture
(which subsequently healed without treatment) had occurred. The average limb
length was increased 4.5 ± 4.8 mm compared with the preoperative
length, and the average femoral displacement was increased 3.0 ± 6.2
mm. At two years after the operation, all femoral components were
radiographically stable.
Gait analysis was performed for ten of the patients to gain an objective
measurement of the functional recovery. Testing was done preoperatively and
postoperatively. By ten weeks, the average gait velocity was 80% to 85% of
normal, the average single-limb stance time was 90% of normal, the average
cadence was 82% to 90% of normal, and the average stride length was 62% to 74%
of normal (with the greatest deficit associated with hip extension). This
level of function was reached sooner for the patients who had a mini-incision
than it was for the patients who had traditional incisions, although the
postoperative protocols were not identical.
Discussion
With our method and strict definitions of satisfactory component position,
11% of the sockets fell outside the desired range of cup abduction and 8% fell
outside the desired range of cup anteversion. Wenz et al. reported that, with
their mini-incision, 7% of the cups were outliers, but they also accepted
inclination of up to 55°, which is 10° above our accepted limit of
45°. We currently perform our minimally invasive operations with computer
assistance in the hope that these outliers can be eliminated.
It is not possible to compare minimally invasive hip surgery with a single
incision and that performed with two incisions because of the paucity of
published data. Our experience with patients who are discharged home within
twenty-four hours would suggest that the most important factors allowing early
discharge include patient selection, patient motivation, anesthesia and pain
management techniques, and the postoperative protocol rather than the use of
one or two incisions. Even though we offer discharge home within twenty-four
hours, few patients choose it. One of the greatest associated benefits of
minimally invasive hip surgery for our patients has been the modification of
anesthesia and pain management techniques to avoid epidural and intravenous
narcotics because doing so nearly eliminates postoperative emesis and vertigo,
which can interfere with in-hospital functional recovery.
The patients had good pain scores and functional recovery, but it has not
been determined how much of the pain relief and functional recovery is
attributable to new anesthesia and pain management techniques and to altered
patient expectations and perceptions rather than to the operation itself. We
have not yet answered the questions concerning the complication rate, pain
level, or functional recovery associated with the mini-incision procedure
compared with those associated with the traditional incision.
Note: The author thanks Robin Chorn, MD, who helped to develop
the anesthesia protocol described in this section.
Early development of total hip arthroplasty and subsequent research efforts
have focused on the identification of superior biomaterials that display
better wear characteristics, strength, and fixation to bone to improve the
implant durability. Although multiple surgical exposures were devised, each
with an incision length of 6 to 12 in (15 to 30 cm) or more, they shared
potential problems, all related to a prolonged weakness of the hip muscles,
which manifest in a minority of patients as a limp or secondary instability of
the hip joint. Innovations in other surgical specialties, such as endoscopic
cholecystectomy, were shown to reduce postoperative pain, shorten
hospitalization, and accelerate clinical recovery. On the basis of these
experiences, some surgeons began exploring the feasibility of performing total
hip arthroplasty with smaller incisions and potentially less soft-tissue
trauma. Different methods have been developed, and some of them use
conventional operative approaches with progressively shorter incisions. My
colleagues and I developed an approach using two small incisions to expose the
acetabulum and the femur, respectively.
Development of a Two-Incision Surgical Approach
Our goal, as we worked in an anatomy laboratory, was to develop surgical
routes to the hip without violating adjacent muscles or neighboring vessels
and nerves. A 2-in (5-cm) anterior incision was used to prepare the acetabulum
and insert the cup. A second 1-in (2.5-cm) posterior incision was used to
prepare the femur and insert the femoral component
(Fig. 2). Special illuminated
retractors and novel smaller handles for the bone-shaping tools were designed.
Standard cementless total hip components of known efficacy were selected.
Supplementary image intensification was used to provide intraoperative
radiographic guidance (Fig. 3).
After a three-year developmental period, we filed a patent application for the
method.
In January 2000, a multicenter clinical trial of the two-incision minimally
invasive total hip replacement was initiated after receiving institutional
review board approval. The study evaluated operative factors related to the
procedure, such as operative time, blood loss, technical difficulty, and
potential problems and complications. In addition, postoperative events in the
hospital, as well as events after discharge, were examined.
Complications observed in the initial study included proximal femoral
fractures, which occurred in 2.8% of the patients. This rate was about three
times greater than that associated with conventional procedures. Other
complications included partial, temporary injuries to the lateral femoral
cutaneous nerve. Most of the femoral fractures occurred in a surgeon's first
case and all occurred in the surgeons' first ten cases, as part of a so-called
learning curve. In an effort to diminish the prevalence and clinical
significance of the fractures, a proximally porous-coated device was replaced
with a fully porous-coated femoral implant. As further clinical experience has
been gained, we also have modified the orientation of the skin incision to
allow a better view of the femur during preparation and have learned that
extending the hip during femoral preparation is helpful. These changes have
made femoral preparation easier, may allow a wide selection of femoral
implants to be used, and may reduce the risk of intraoperative femoral
fracture.
Intraoperative Anesthetic Regimen and Postoperative Pain
Management
Historically, after a total hip replacement, a patient started physical
therapy on the following day. Earlier initiation of therapy was hampered by
the side effects of anesthetic agents and medications used for postoperative
pain control. Problems with traditional perioperative regimens have included
persistent pain, postoperative nausea, vomiting, urinary retention,
drowsiness, confusion, muscle weakness, and numbness in the lower extremities.
To optimize the potential of minimally invasive total hip replacement to allow
rapid initiation of therapy and a corresponding acceleration in hospital
discharge, we worked with Dr. Jacques Chelly to develop a regimen that reduced
these undesirable features. The perioperative management regimen that we now
use emphasizes regional anesthetics, use of non-narcotic pain medication, and
portable local anesthetic infusion pumps to reduce pain.
We also developed an accelerated physical therapy program and clinical
pathway that emphasizes immediate weight-bearing to tolerance and multiple
physical therapy sessions for gait training and for teaching the activities of
daily living in the first twenty-four hours after the operation. Recently, for
patients with minimal comorbidities, this regimen has allowed over 90% of our
patients to be discharged within twenty-four hours after surgery. Many
patients have been able to shed all assistive devices within two to three
weeks after hospital discharge.
Teaching Minimally Invasive Total Hip Replacement
If future documentation of the clinical outcomes after minimally invasive
total hip replacement proves to be favorable, a major challenge will be to
train orthopaedic surgeons to perform the surgical technique. During the past
few years, industry-sponsored cadaveric courses have been established.
Supplementary audiovisual presentations, visits to surgical procedures, and,
potentially, a mentoring surgeon to assist in the first clinical procedure are
available.
Whereas endoscopic training relied upon the availability of a highly
comparable pig model, there is no such animal model for total hip replacement.
To date, attempts to develop accurate plastic replicas have been
disappointing. At present, few orthopaedic residencies possess a trained
surgeon to educate their residents in the technique. I believe that surgeons
need to gain specialized hands-on training in cadavera and by visiting
experienced mentoring surgeons before undertaking these procedures
independently.
Technique
One minimally invasive two-incision total hip arthroplasty approach
involves the placement of an anterior incision that is 4 to 6 cm in length
directly over the femoral neck. The skin incision is oblique from the
intertrochanteric line to the center of the femoral head. The landmarks for
the skin incision are verified with fluoroscopy. The interval between the
sartorius and the tensor fasciae latae is exposed superficially. The deeper
interval utilizes the plane between the rectus femoris and the tensor fasciae
latae. The anterior circumflex femoral vessels, which serve as a landmark for
the anterior approach just superficial to the hip capsule, are ligated. The
hip capsule is divided longitudinally from the center of the femoral head to
the trochanteric ridge. The capsule is retracted with lighted retractors to
allow for osteotomy of the femoral neck. The neck is osteotomized, and the
femoral head and neck are removed in situ. Next, the lighted retractors are
repositioned to retract the capsule. An additional retractor may be placed to
retract the rectus femoris and allow for acetabular preparation. The
acetabular labrum is removed with sharp dissection. The acetabulum is prepared
by reaming with specialized beveled reamers, and the cup is inserted with
20° of anteversion and 45° of abduction. A specialized dog-leg cup
inserter allows for proper acetabular cup position and avoids impingement on
the femur. Screws may be inserted through the cup in the superolateral
weight-bearing dome. The liner is then inserted. The cup position is verified
with fluoroscopy.
A second, posterior, incision that is 3 to 4 cm in length is made in line
with the femoral canal. The gluteus fascia is split superficially, allowing
placement of reamers to prepare the femoral canal. A direct pathway to the
femoral canal is found with blunt dissection posterior to the abductor
tendons, anterior to the piriformis tendon. Specially designed reamers are
utilized to prepare the proximal part of the canal and to clean out the medial
greater trochanteric region to allow for proper stem insertion. Anteversion is
determined under direct vision by viewing the rasp through the anterior
incision or by sighting the broach handle off the center of the patellae as an
indirect landmark. Once the canal is reamed with straight reamers and the
broaching is completed, the stem is inserted through the posterior incision.
Either a proximally coated or a fully porous-coated stem can be used. Final
seating of the stem can be seen under direct vision through the anterior
incision. Fluoroscopy to confirm instrument position can be used at any time
during the canal preparation.
Once the femoral stem is inserted, a trial reduction is performed. Because
the patient is supine, the limb length can be determined by comparison with
the contralateral lower limb. Hip stability is assessed by placing the
involved limb through a full range of motion. After final prosthetic head
placement, both wounds are closed. The anterior wound is closed over a
drain.
Postoperatively, patients are managed with an accelerated critical pathway
for total hip arthroplasty, in which they are seen by a physical therapist
immediately upon return from the recovery room. Patients are allowed to bear
weight as tolerated with crutches. Patients are discharged when they have met
the critical pathway objectives.
Results
At one center (St. Vincent Hospital and Medical Center, Portland, Oregon),
100 patients under the care of Dr. Paul Duwelius were selected for the
two-incision approach. Informed patient consent was obtained with
institutional review board protocol. During this same time-period, this
surgeon treated 183 other patients with primary total hip arthroplasty. The
patients who were chosen for a two-incision procedure weighed less than 220 lb
(100 kg), they were less muscularly developed than patients who had one
incision, and they were less than seventy-five years old. They also had no
major comorbidities, osteoporosis, or cognitive impairment, and they had had
no prior operations on the ipsilateral hip. The first twenty-five patients who
had a two-incision procedure were managed with a proximally porous-coated
uncemented stem (Fiber Metal MidCoat; Zimmer, Warsaw, Indiana). The remaining
seventy-five patients were managed with an uncemented Beaded FullCoat
prosthesis (Zimmer). All had an uncemented socket (Trilogy; Zimmer). The
primary diagnosis was osteoarthritis for ninety-four patients, osteonecrosis
for four patients, and rheumatoid arthritis for two patients. The average age
was fifty-seven years for the men and sixty years for the women. The average
weight was 184 lb for the men and 141 lb for the women. The average operating
time was ninety minutes (range, eighty to 120 minutes). Ninety patients were
discharged home within twenty-four hours, and ten were discharged on the
second postoperative day.
Complications included two posterior hip dislocations, both of which were
treated with closed reduction and use of a brace for six weeks. Neither
patient has had a redislocation. One femoral component subsided and required
revision because of loosening. One patient had a calcar fracture, which was
treated with a cerclage wire and advancement of the fully coated stem. The
fracture healed without incident. There were no readmissions for medical
complications. At nine months postoperatively, one patient who had a primary
diagnosis of rheumatoid arthritis had an infection develop around the
prosthesis, which was probably due to hematogenous infection from a lung
abscess. The average Harris hip score improved from 52 points preoperatively
to 90 points at one year postoperatively.
At another center (Hackensack University Medical Center, Hackensack, New
Jersey), 100 patients under the care of Dr. Mark Hartzband were selected for
treatment with a two-incision protocol. (During this same time-period, this
surgeon performed 337 other primary hip arthroplasties with different
operative approaches.) Fifty-six patients were men, and forty-four were women.
The men and the women both had an average age of fifty-six years. The average
weight was 194 lb for the men and 148 lb for the women. The preoperative
diagnosis was osteoarthritis for eighty patients, developmental hip dysplasia
for nine, osteonecrosis for eight, and trauma for three. An uncemented socket
(Trilogy) and an uncemented femoral component (Beaded FullCoat Plus; Zimmer)
were used in each patient. The mean duration of follow-up was twelve months
(range, three to eighteen months). Complications included two femoral
fractures, one deep venous thrombosis, and one bowel obstruction. There were
no revisions or hospital readmissions. The average duration of the operation
in this series was sixty-two minutes (range, thirty-eight to 140 minutes).
Seventy-seven patients were discharged within twenty-four hours after
surgery.
Dr. Richard Berger reported that, at his center (Rush-Presbyterian-St.
Luke's Medical Center, Chicago, Illinois), 100 patients were selected for
treatment with a two-incision protocol. During the same time-period, this
surgeon performed 534 other total hip arthroplasties. The two-incision
procedures were performed only as the first operative procedure of the day,
which limited the number of patients. During the first part of the study, only
the patients with straightforward anatomy were chosen; during the middle part
of the study, more difficult cases including obese patients and patients with
dysplasia were chosen; and, for the remainder of the study, patients who were
representative of the surgeon's practice were chosen. There were seventy-five
men and twenty-five women. The average age was fifty-five years (range, thirty
to seventy-six years). The diagnosis was osteoarthritis in eighty-seven
patients, developmental dysplasia of the hip in eight patients, and
osteonecrosis in five. The average weight was 176 lb (range, 102 to 265 lb).
All patients were treated with an uncemented socket (Trilogy) and an
uncemented fully porous-coated stem (Beaded FullCoat). Complications included
one calcar fracture, which was treated with a cerclage wire and advancement of
the fully coated, beaded stem. There were no other complications or
readmissions. The duration of the operation was between eighty and 120 minutes
(average, 101 minutes). Of the last eighty-eight patients, seventy-five (85%)
were managed in an outpatient setting with discharge on the same day as the
total hip replacement. The patients followed a rigorous critical pathway that
included use of a regional anesthetic, immediate weight-bearing, and physical
therapy on the day of surgery. There were no readmissions for any reason. No
patient had his or her procedure aborted or converted to a different
procedure.
As reported by Dr. Dana Mears, seventy-five consecutive patients at his
hospital (University of Pittsburgh Medical Center—Shadyside Hospital,
Pittsburgh, Pennsylvania) had a total hip arthroplasty performed with the
two-incision approach and with use of a modified anterior incision that was
superficial to the intertrochanteric ridge. Informed consent was obtained with
institutional review board protocol. Three patients underwent a bilateral
procedure, and two others had sequential arthroplasties. This consecutive
series of patients represents all primary hip arthroplasties performed by this
surgeon during this time-period. Following this series, he excluded from the
two-incision protocol patients with retained obstructive femoral or acetabular
hardware, bone deformity, or marked osteoporosis suitable for a cemented stem.
A proximally coated femoral stem (Fiber Metal Taper; Zimmer) was used with a
multiholed cup (Harris-Galante-2; Zimmer). The primary diagnosis was
osteoarthritis for sixty-three patients, posttraumatic arthritis for five,
developmental hip dysplasia for four, and rheumatoid arthritis for three. The
men were an average of fifty-eight years old (range, thirty-two to eighty-four
years), and the women were an average of sixty-two years old (range,
forty-three to eighty-two years). The men weighed an average of 229 lb (range,
155 to 315 lb), and the women weighed an average of 184 lb (range, 112 to 270
lb). All patients but one were discharged directly to their homes. Seven
patients were discharged on the day of surgery, and fifty-eight were
discharged within a day after surgery. Seven patients, including the three
with a bilateral procedure, were discharged on the second postoperative day.
Two patients, one of whom was transferred to a rehabilitation center, were
discharged on the fourth day.
There were no readmissions for medical complications. Two hips had an
undisplaced calcar fracture that was recognized after insertion of a tapered
stem and was treated with a cerclage wire. The fractures healed uneventfully,
without stem subsidence or loosening. One stem subsided 5 mm but was
asymptomatic. Two hips had Grade-I heterotopic bone, according to the
classification of Brooker et al. Two patients had partial femoral nerve
palsies, which fully resolved within eight weeks after the procedures. Sixteen
patients complained of hypoesthesia of the anterior part of the thigh,
consistent with a partial injury to the lateral femoral cutaneous nerve of the
thigh. Nine of them had a full recovery, and the seven others had partial
resolution. The average operating time was eighty-five minutes (range,
fifty-five to 125 minutes).
The authors (P.J.D., R.A.B., M.A.H., and D.C.M.) believe that the benefit
of a two-incision minimally invasive approach for total hip arthroplasty is
not the size of the incision but is, instead, the limited surgical dissection
that is required. This procedure is dependent on the technique and the
instruments, and both continue to evolve. This procedure is clearly more
difficult than either the mini-anterior or mini-posterior incisions. In our
limited experience to date, the early perioperative complication rate has been
acceptable. Additional experience and longer-term evaluation will be needed to
rigorously compare the results of this procedure with those of total hip
replacement performed with conventional approaches.
Total hip replacement has been performed in the United States for over
three decades and in Europe for more than four decades. It is one of the most,
if not the most, studied surgical procedure ever in medicine. Its efficacy in
relieving the pain and functional limitations from end-stage arthritis of the
hip has been documented. During this thirty to forty-year experience,
investigators and surgeons have documented some of the complications and
shortcomings of the procedure as well as some of the potential innovations,
which through the test of time have ended up being "steps
backwards." The potential benefits of the minimally invasive approach
(i.e., the cosmetic appearance, quicker functional return, short length of
stay, and fewer transfusions) have been outlined. If these goals can be
accomplished while still addressing the major issues that confront orthopaedic
surgeons who perform total hip replacement today, there may be a place for
this enthusiasm. However, as described below, there are several reasons for
skepticism as well as for concern about the approaches that have been
implemented to encourage the widespread use of the minimally invasive
approach.
What is the major problem with total hip arthroplasty today? From both an
economic perspective, as well as from the perspective of the patient requiring
a total hip arthroplasty, the need for additional surgery following the index
procedure is of paramount concern. The revision rate in the United States is
18% to 20%, and unfortunately it is twice that of some other countries such as
Sweden, where the rate is 8%. More data are arising to suggest that the volume
of surgery performed at an institution, as well as the volume of surgery
performed by an individual surgeon, is a major factor contributing to the
revision rate. However, the practical reality is that more, not less, total
hip replacements will be indicated in the aging and active population, as data
have suggested that people will be living longer (and hence have an increased
risk for the development of disabling hip arthritis) and the so-called
baby-boomer generation is reaching the peak age for the onset of disabling hip
arthritis. These replacements cannot all be done at centers that do over 500
to 1000 hip replacements a year. There will still be a huge need for surgeons
who perform less than fifty hip replacements a year. Arthroplasties need to be
performed with the fewest complications and with the least possible need for
revision, as both are costly to the patient and to society. In addition, the
increase in the rate of obesity in this country may prohibit more and more
patients with disabling hip arthritis from being optimal candidates for a
so-called minimally invasive procedure. Some proponents of the procedure
recommend that minimally invasive techniques be performed in patients with a
body-mass index of less than 30.
What are the major complications following total hip replacement that
require revision? Failure of fixation, instability, and infection have been
documented as the major causes of reoperation following total hip replacement.
To minimize failure of fixation, implantbone interfaces must be optimally
prepared. To minimize dislocation, components need to be positioned optimally,
osseous impingement (including osteophytes) should be eliminated, and
stability needs to be assessed. To minimize infection, tissue trauma needs to
be minimized, as does the duration of the operation. Small incisions do not
address these problems, and they could potentially increase each of them,
especially in the hands of a surgeon who is less skilled or who is doing fewer
procedures. Some enthusiasts of the minimally invasive procedure assert that
combining minimally invasive procedures with computer-assisted surgery will
allow the computer images to overcome the lack of visualization allowed by the
incision to optimize the position of the components. This presents a
tremendous risk for very little, if any, proven benefit.
Is the comparison of minimally invasive hip surgery with the conversion
from knee arthrotomy to knee arthroscopy accurate? There are reasons why this
argument may not hold. The short and long-term results of knee arthrotomy,
unlike those of total hip replacement, were not optimal. In addition, it has
been documented that visualization is actually better with arthroscopy. This
claim has not and cannot be made for minimally invasive hip surgery. Minimally
invasive hip surgery may turn out to be more akin to the endoscopic carpal
tunnel release than to knee arthroscopy. Endoscopic carpal tunnel release was
touted for its ability to provide a smaller scar and early return to work. The
subsequent peer-reviewed publications demonstrated no long-term benefit.
Today, questions have arisen as to whether the potential early return to work
after the procedure was mostly perceptual (the surgeons' enthusiasm for the
procedure and the patients' desire to please the surgeon). The major
complications of carpal tunnel release, including nerve laceration and tendon
injury, still occurred after experience was gained with the procedure. For
these reasons, endoscopic carpal tunnel release, which initially gained
enthusiasm and popularity, has been abandoned by the majority of hand
surgeons. This skeptic questions whether the results achieved by a traditional
joint replacement surgeon who selects the most motivated and fit patients,
convinces those patients of the possibility of early discharge, and performs
the standard incision with optimal preoperative, intraoperative, and
postoperative anesthesia, pain management, and rehabilitation would not match
the early results or exceed the long-term results achieved by the surgeon who
uses the minimally invasive approach.
Are there medical-legal liability issues associated with implementing the
minimally invasive hip replacement approach? The argument has been stated
that, since the patient has come to the surgeon desiring the technique, then
he or she must understand that there is a learning curve that could involve
the potential for complications, such as nerve palsy and component
malposition. Legally, the surgeon should recognize that he or she probably
will be judged by the same standards as the surgeon who uses conventional
incisions. In addition, complications may not be as well understood by
patients with extremely high expectations of the surgery.
Has the minimally invasive hip surgery movement been appropriately
implemented? The Internet and advertisements have encouraged patients to seek
new treatments before traditional peer review can be completed. This creates
potential problems for both the surgeon and the patient. There are many
examples of self-aggrandizing promotions of unique treatments outside the
peer-reviewed system that have not held up in the scientific review process or
have not withstood the test of time. Our medical profession has been designed
for us to self-regulate. We have an obligation to educate the public and help
them to interpret nonscientific premises and promotions. Developers of
groundbreaking treatments for patient care are obligated to promote their
ideas through the scientific peer review of their data, which can substantiate
their enthusiasm. In the case of the minimally invasive approach to hip
surgery, the promoters have rarely recognized the work of Keggi, as reported
by Light in 1980, who described a similar minimally invasive approach for
performing total hip replacement. Finally, if a treatment does prove to be an
improvement, it should not be limited to a select group of surgeons. These
premises are the basis for the respect that the public holds for the medical
profession today.
It is the job of a skeptic to ask tough questions. This skeptic hopes that
minimally invasive hip surgery enthusiasts prove him wrong for this skeptical
stance. [boxshadowdwn]
There is a general consensus that new technology and innovative surgical
techniques can enhance patient outcomes. Minimally invasive hip surgery has
sparked substantial interest in the orthopaedic community because patient
outcomes may be improved in both the short and the long term and because
patients believe that smaller incisions will lead to improved results.
Although orthopaedic surgeons are ready to embrace new technological advances,
four major questions need to be answered in order to enhance the development
of a new technology or new surgical procedures and still protect patient
safety: (1) Is the development of a new surgical procedure an experiment or an
innovation? (2) What is the role of industry in establishing widespread use of
new procedures? (3) How do we provide our patients with true informed consent?
(4) Why are failed procedures rarely reported to the orthopaedic
community?
Innovation Compared with Experimentation
Surgical innovation is essential to improve the care of patients over time.
The question is whether the safeguards associated with the regulatory
ethics paradigm are necessary in every case? According to the regulatory
ethics paradigm, any innovative surgical treatment needs to be placed into a
protocol that has institutional review board approval in order to protect
patient welfare. Proponents of this philosophy believe that any surgical
innovation is really human experimentation and must be evaluated with use of
rigorous scientific experimental protocols. Therefore, if there is no protocol
approved by the institutional review board, then the application of a surgical
innovation would not meet ethical standards.
However, in a provocative essay, Agich pointed out that the regulatory
ethics paradigm may not be appropriate for the development of new surgical
procedures. A potential problem with the regulatory ethics paradigm is that it
may not be applicable in situations where present treatments either are not
optimal or are ineffective. The development of surgical techniques requires
fine-tuning, which makes use of institutional review board protocols difficult
during the developmental phase. The development of a new surgical technique
may require frequent adjustments related to the surgical approach, the design
of new surgical instruments, and the identification of the appropriate patient
population. It could be argued that the development of a new surgical approach
for total hip arthroplasty (i.e., a mini-incision or two small incisions) is
just a modification of a well-established procedure and therefore does not
require institutional review board approval. Although protocols approved by
the institutional review board may not be necessary during the initial
development of some surgical procedures, informed consent and protection of
the patient's welfare are still absolutely necessary.
The surgical innovator must also realize that he or she may have a
potential conflict of interest with the patient. The new technique may not be
better than the standard procedure. Therefore, true informed consent is
essential.
The failure to perform a clinical trial to determine whether a new
procedure actually provides benefits to patients is the strongest argument for
applying the regulatory ethics paradigm in all cases. In general, once the
surgical technique has been refined, a randomized trial should be performed,
otherwise the efficacy of the new procedure will not be established. The
widespread use of a new technique should be delayed until the indications,
pitfalls, and potential complications have been identified. Numerous surgical
techniques have been adapted by the orthopaedic community before the outcomes
have been established in either clinical trials or a prospective analysis.
Some examples include the use of the microfracture technique and autologous
chondrocyte transplantation to treat cartilage defects and the use of
nonvascularized or vascularized bone grafts to treat osteonecrosis of the hip.
The development of an institutional review board protocol to compare a
minimally invasive hip arthroplasty with a standard approach or different
types of minimally invasive approaches should not be avoided because it is
inconvenient.
Industry and Innovation
When a new technology or even a new surgical procedure is being developed,
industry can play an important role. Industry has the infrastructure to
support the development of a new technology. In addition, companies have the
resources to make a new technology available to a wider group of
orthopaedists. Many advances made in orthopaedic surgery over the past five
decades have occurred as a result of excellent collaborations between
orthopaedic surgeons and industrial partners. However, there are a number of
concerns that must be considered or else surgeons risk providing inadequate
protection for their patients. First, financial gain could be placed ahead of
patient interest. A company may push for rapid entry into the marketplace with
a new technology or technique in order to obtain a return on an investment.
Companies may wish to avoid clinical trials to save resources, especially if
the results are uncertain or if a trial is not required by the Food and Drug
Administration. Second, manufacturers have started to market directly to the
consumer to move the marketplace in a specific direction. This may lead to an
inadvertent conflict of interest with patient interests. Advertisements may
urge patients to seek physicians who use new devices or new surgical
procedures even though better outcomes have not been established. Finally, a
manufacturer may discourage the free flow of information between surgeons,
especially to individuals who do not have a defined relationship with the
company. This type of communication has been a critical element in fostering
clinical advances in the past. Therefore, orthopaedic surgeons who are working
as partners with industry to develop new surgical techniques or other new
technology must be aware of the potential conflicts of interest related to
financial gain and must provide appropriate informed consent for their
patients in order to protect patient welfare.
Learning New Procedures and Obtaining Informed Consent
What is the best way for the surgeons to learn new procedures? What
training is necessary to learn new procedures? The answers to these questions
obviously depend on the type of procedure and the surgeon's previous surgical
experience. However, it is important that the surgeon have a frank discussion
with the patient about the potential benefits and risks of a new procedure and
the surgeon's experience with that procedure. Patients often assume that a new
procedure will have a better outcome than an old procedure. A patient may also
underestimate the risks associated with the new procedure, particularly if it
is called a minimally invasive operation. Patients may not grasp that,
although a "minimally invasive operation" has a smaller skin
incision, the complications associated with that procedure may be equal to or
even greater than the complication rate associated with a standard surgical
procedure. In addition, the patients need to understand that they may not
experience all of the benefits of a new procedure during the learning curve
for a new surgical technique. Finally, surgeons must be sensitive to
overmarketing a new procedure to try to enhance their practice. There is a
natural tendency to oversell new technology, which can have a negative impact
on the doctor-patient relationship and can erode the public's trust in
physicians.
Innovative Failures
A major problem within the orthopaedic community has been a failure to
publish negative results that are associated with any new technology. There
are many potential reasons why this has occurred on a chronic basis. First,
surgeon innovators often move on to the next innovation once it is clear that
a new technique or technology does not work. Second, there is potential damage
to a surgeon's reputation and financial interests for reporting negative
results. Third, surgeons may want to avoid conflicts with industrial partners
who may be reluctant to publish negative outcomes, particularly if the new
technology is still being sold. Fourth, it is often quite difficult to publish
negative data. However, the release of both positive and negative outcomes
related to the use of a new technology or techniques is critical in order to
establish the appropriate indications for a new procedure and for future
surgeon innovators to learn from these experiences.
An enhanced understanding of the biology of musculoskeletal disease and
advances in computerized technology, materials science, and human genetics
will promote technological developments that will improve outcomes for our
patients. As revolutionary changes occur in orthopaedics, surgeons must ensure
that the protection of patient safety remains the highest priority. New
technology should be incorporated into our practices only when it can be shown
to enhance outcomes and to be cost-effective, or we will lose the public's
trust.
Conclusions
Minimally invasive total hip arthroplasty provides a potentially valuable
new variation on a well-established and widely used technology. It is hard not
to see the potential value—and potential risk—of quicker
rehabilitation and shorter hospital stays. The possible future marriage of
minimally invasive operative methods with image-guided surgery and computer
navigation methods also is intuitively appealing. However, many questions
remain about the short-term results of these operations and whether they can
be performed with the same level of safety and efficacy as a conventional
total hip arthroplasty. There are no long-term data comparing the durability
of reconstructions performed through these approaches with conventional total
hip arthroplasty. Practitioners must decide what level of evidence
demonstrating safety and efficacy will be needed before they consider using
socalled minimally invasive methods. Surgeons who are advocates will need to
explore and refine indications and contraindications, define optimal patient
populations, and understand the limitations of minimally invasive methods. If
these methods prove to be valuable, the best methods to teach the techniques
to surgeons in practice, and during training, will need to be considered.
Often overlooked in the discussion on minimally invasive total hip
arthroplasty is the role that an integrated program of anesthesia and
accelerated rehabilitation that is instituted with minimally invasive methods
may play in facilitating shorter hospital stays. Also, an objective evaluation
of the degree to which patient selection and changes in patient expectations
may contribute to perceived improvements in pain relief and shortened hospital
stays needs to be considered. Unless carefully designed and executed studies
are performed in the future, it will be difficult to disentangle the effects
of patient selection, altered patient expectations, and radically changed
perioperative management from those of the changed surgical approach itself.
It is of note that, for all of the series reported in this symposium, the
surgeons not only made changes in the operative approach for total hip
arthroplasty but also made changes in the anesthetic protocol, perioperative
pain management protocols, and rehabilitation protocols.
No one can foresee with certainty whether the current methods of minimally
invasive total hip arthroplasty will be widely adapted, used on a selective
basis, or used very little in the future. Almost without doubt, however,
efforts to develop minimally invasive total hip arthroplasty will have an
effect on how conventional total hip arthroplasty is performed. For instance,
optimal placement and use of incisions can reduce the length of the incision
in some patients, and better retractors, bone preparation instruments, and
implant insertion instruments will allow surgeons to use conventional methods
with less soft-tissue dissection. The success of accelerated rehabilitation
protocols with minimally invasive methods may demonstrate that rehabilitation
after most conventional total hip arthroplasties can be accelerated. Better
anesthetic techniques pioneered for minimally invasive surgery may also
benefit many patients who are treated with conventional total hip
arthroplasty.
New procedures often are greeted with great enthusiasm, particularly as
early positive results are reported by the developers, who are also experts in
applying the technology. Subsequently, as the technology is disseminated more
widely, problems related to the procedure often are identified and a
retrenchment in enthusiasm may follow. Technologies are adapted as an enduring
part of practice only if a sufficient number of surgeons become experts in the
technology, the operative indications and methods allow the procedure to be
performed at least as safely and reliably as previously available procedures,
and the long-term results match or exceed those of conventional, established
methods. Greater experience and longer detailed follow-up with careful
comparison with conventional hip arthroplasty will direct the future course of
minimally invasive total hip arthroplasty.