MIS FOR THA
Selections from Harvard Medical School’s Advances in Arthroplasty
| MINI-SMITH-PETERSON APPROACH FOR MINIMALLY INVASIVE SURGERY (MIS) FOR TOTAL HIP ARTHROPLASTY
(THA)—B. Sonny Bal, MD, MBA, Associate Professor of Orthopaedic Surgery, University of Missouri
School of Medicine, Columbia
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| Setup: place patient in supine position on fracture table; leg lengths easily checked; arrange fracture drape and general
surgery abdominal drape; metal bar attached to elevated motor to raise and lower femur
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| Incision: directly anterior on thigh; dissect between tensor and sartorius muscles, and between rectus and gluteus;
typical length 4 in
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| Intraoperative steps: dislocate head anteriorly; drill hole and lift head with T-handle; visualize lesser trochanter;
mark cuts; socket easily exposed with circumferential visualization (standard reamers used); release and cut superior
capsule
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| Results: first 100 consecutive cases; mean duration 53 min when first tried, now ≈30 min; intraoperative x-rays
(none; may mislead); transient thigh numbness in 4%; wound drainage in 1 case, followed by nonfatal pulmonary
embolism; 1 case of proximal femur fracture as broach driven down; postoperatively—full weight-bearing; walker,
cane, or crutch for first month; mean follow-up 10 mo; mean hospital stay 2.1 days (range 1-5 days)
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| Conclusions: advantages—quicker and easier than 2-incision approach; thigh numbness rare; avoids blind femur access;
trial broaches for leg length; true intramuscular interval; resurfacing possible; disadvantages—learning requirements;
possible damage to abductors; possible risk to femoral and lateral cutaneous nerves; need for fracture table
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| POSTERIOR APPROACH FOR MIS—Lawrence D. Dorr, MD, Director, Arthritis Institute, Good Samaritan Hospital,
Los Angeles, CA
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| Initial experience: speaker has performed operation for 7 yr; safety in ability to extend incision if necessary; able
to do comfortably after 50 procedures; full confidence requires ≈100 operations
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| Benefit to patients: improvements in pain and function; satisfaction comes when patients achieve their expectations,
including body image and relieving concerns about hip; at 6 mo to 1 yr, 40% of patients with long-incision
procedure regret not having small incision
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| Safety: while challenged initially, safety confirmed by subsequent evidence
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| Physical benefits: purpose not to increase longevity of results; reduces early morbidity; improves patient confidence;
enhances ability to perform physical rehabilitation
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| Improvements in gait: analysis of different incisions showed minor differences; at 6 wk—posterior approach provides
better single-limb stance and stronger leg; anterior approach has problems with extension; by 3 mo—both approaches
essentially equal
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| Benefit for surgeons: accelerated recovery program; most gains from better pain management combined with active
physical therapy program; biggest advance of this decade
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| Conclusion: surgeons can pick approach based on their comfort level; MIS will become more prevalent with the
adoption of “smart tools,” including computer navigation
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| WHY WOULD I USE AN MIS APPROACH? —Charles L. Nelson, MD, Associate Professor of Orthopaedic Surgery,
University of Pennsylvania School of Medicine, Philadelphia
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| For optimal result: marry MIS with good pain management, rehabilitation, and education
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| Comprehensive approach: MIS minimizes tissue trauma; requires less perioperative medication (fewer side effects,
eg, nausea, vomiting, hypotension); enables fewer restrictions of patient activity; less difficulty with rehabilitation;
quicker recovery
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| 2-incision technique: employed by speaker for acetabular component preparation; 1 incision for femoral component
preparation; after learning curve, 70% of patients went home day of surgery; moving to more regional
anesthesia further reduced side effects and improved ability to go home; preemptive anesthesia enabled even
more patients to go home sooner; included patient education; implementing approach on 400 consecutive cases
allowed 396 patients to go home day of surgery; results in first 500 cases—2 hospital readmissions and 3 emergency
department visits; 1 stem revision; later complications “reasonable”
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 | Difficult to learn: accurate
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| High complication rate: based on experience of first 4 surgeons to complete 100 cases; first 25 to 100 cases had
higher complication rates; comparison to 100 standard 2-incision cases showed no statistical difference; next 800
cases had even lower complication rates; subsequent early adopters learned from experience; high complication
rates reported in some series
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| Cannot be done without muscle damage: while muscle damage reported in all cases, subsequent evidence showed
absence of damage
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| Recovery no faster: 4 surgeons and 4 hospitals reported stays of <1 day
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| PITFALLS OF MIS—Louis M. Kwong, MD, Associate Professor of Orthopaedic Surgery, the David Geffen School
of Medicine at the University of California, Los Angeles, and Chief, Orthopaedic Arthritis Service, and Vice Chair,
Department of Orthopaedic Surgery, Harbor-UCLA, Medical Center, Torrance, CA
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| Driving forces: decreased postoperative pain; faster rehabilitation; optimized clinical outcome; enhanced cost-effectiveness
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| Clinical milestones: reduced operative time; decreased blood loss; enhanced pain control; optimized recovery, eg,
length of hospital stay
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| Short-term experiences: several surgical approaches yield successful clinical outcomes; advent of MIS greeted
with much fanfare by public and surgeons; initial enthusiasm dampened by technical demands and realization that
smaller not necessarily better or easier to do
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| Patient selection: essential for success; ideal candidate—thinner; better range of motion; osteoarthritis; not hampered
by musculoskeletal or cardiac function in physical rehabilitation; less-than-ideal candidate—obese; poor
range of motion or contractures; compromised bone quality; structural abnormalities; previous surgery with scarring
and obliteration of normal tissue planes
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| Clinical impact unknown: incidence of venous thromboembolism (VTE) and pulmonary embolism (PE); infection
and dislocation rate; ultimate ambulatory function; aseptic loosening rate
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| Risk for VTE: high in THA; trauma from instrumenting bone equal to standard procedure; broaching and reaming
pressures medullary contents, driving them into systemic circulation and activating coagulation cascade; shortened
hospital stay removes patients from physician surveillance for possible VTE; patients discharged on inadequate anticoagulation
therapy
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| Risk for infection: guidelines call for pre- and postoperative first-generation cephalosporin; shortened hospital stay
led to use of oral antibiotics with unproven efficacy
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| Areas of concern: improper use of retractors and soft-tissue protectors essential to reduce maceration of wound
margins; damage to abductor muscles; difficulty in correcting leg length discrepancies
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| Complications: femoral side—femoral fracture; undersizing prosthesis; peripheral nerve injury; leg-length discrepancy
(difficulty identifying lesser trochanter; uncertainty in placement of femoral neck osteotomy); acetabular
side—implant malposition; eccentric reaming (increased fracture risk); difficulty in achieving secure locking between
liner and shell
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| Dislocation: impact of MIS largely unknown; dislocation rate may be slightly higher earlier in learning curve
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| Patient positioning: secure fixation to operating table —maintaining proper pelvic orientation involves continual
manipulation of limb, sometimes to extremes of nonphysiolgic positioning; specialized tables integral to performing
operation
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| Evolutionary approach: proper surgeon education (preceptorship with experienced surgeon; instructional
courses); incremental decrease in incision size (begin with standard size; reduce wound size as experience evolves);
careful and strict patient selection (reasonable body habitus); allow extra time for surgery; exercise patience (skill
comes with experience and cannot be rushed)
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| Summary: MIS continues to evolve; less invasive techniques expected to play larger role in clinical practice; MIS
joint replacement not appropriate for all patients or all surgeons; time ultimate judge of short- and long-term
benefits of MIS
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| A SCIENTIFIC PERSPECTIVE ON MIS—Paul J. Duwelius, MD, Adjunct Associate Professor, Department of Orthopaedics
and Rehabilitation, Oregon Health and Science University School of Medicine, and Clinical Attending Orthopaedic
Surgeon, Providence St. Vincent Medical Center, Portland, OR
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| Consensus of MIS benefits: anesthesia; pain management; rapid recovery protocols; psychologic advantages for
patients; small-incision surgery safe; component position equivalent
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| Reported complications of MIS: poor cosmesis; higher periprosthetic fracture rate; sciatic nerve injury in 2 patients;
also reported—high patient satisfaction with cosmesis; no other published series with higher sciatic nerve
injury rate; periprosthetic fractures in THA relatively common (overall incidence 2%-6%)
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| Requirement for surgeons: commitment to learning; training provided by American Academy of Orthopaedic
Surgeons and industry sites
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| Technical principles: exposure with mobile windows; special retractor and instruments; trained assistants; different
intraoperative landmarks; fluoroscopy (2-incision; anterior approach); navigation helpful
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| Safety of MIS: reported by many centers and with different surgical approaches
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| Psychologic benefits: when expectations addressed and met, satisfaction high (patients more confident in outcome)
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| Muscle and tendon damage: associated with all MIS approaches
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| Functional recovery: accelerated achievement of outcomes requires adherence to recovery protocol
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| Published studies: MIS successful in many centers; randomized prospective series show no difference between
MIS THA and traditional THA (complication rates equivalent for fracture, nerve palsy, dislocation, and infection)
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| MIS protocol: preoperative protocol; regional anesthesia; postoperative protocol; switch to oral medications as
soon as possible; immediate weight-bearing, with physical therapy and occupational therapy
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| Conclusions: MIS patient-driven; safe; functional and psychologic benefits; patients satisfied; spawned successful
pathways; reproducible; prevalence increasing
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| Survey of audience: ≈50% of surgeons use MIS for >50% of primary THAs; in first 50 cases, ≈50% experienced catastrophic
complication (eg, femoral fracture, early dislocation)
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| Femoral component: Dr. Dorr—incidence of trochanteric fractures higher with Zweymuller implant; crucial to
rasp through greater trochanter on first 2 to 3 broaches to create track for component; if not done, appropriate size
implant will break base of trochanter; lateral proximal flare at shoulder different from other flat tapered stems; stem
modification needed (small short stem available in Europe; less invasive to bone; modified stems expected in
United States); implant cementless femoral component first (determine anteversion; only 40% of cementless stems
have 10°-20° of anteversion)
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| Proximal femoral fracture: Dr. Bal—able to visualize proximal femur; if fracture present, drill hole and place
cable through lesser trochanter; important for patients to restrict activities until ingrowth evaluated at first postoperative
visit; Dr. Kwong—ability to visualize proximal femur reduced with smaller incisions; patients often encouraged
to increase activity prematurely; Dr. Nelson—uses tapered stem that lodges more distally and can be seen with
fluoroscopy; rapid rehabilitation may increase undetected stress fracture; Dr. Duwelius—problem results from
learning curve (decreases over time); Dr. Dorr—problem actually due to new tapered stems used in cementless
THA; fractures often result from attempt to pound in broach at 10° to 15° of anteversion
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| Approach and risk for fracture: Dr. Dorr—with anterior approach, fracture rate 6%; with posterior approach,
2%; in cementless THA, amount of diaphyseal bulge controls placement of tip of stem (risk for fracture with high
diaphyseal bulge, forcing implant into more retroversion)
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| MANAGEMENT OF PERIPROSTHETIC FRACTURES —Dr. Duwelius
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| Introduction: fractures more prevalent, due to increase in primary and revision surgery
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| Mechanical problem: stress risers; limited options for fixation; poor bone quality
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| Biologic problem: osteolysis; cytokine abnormalities; impaired cell function
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| Prevention: careful preoperative planning; avoid eccentric reaming; avoid varus positioning; careful surgical technique;
prophylactic distal cerclage wiring helpful
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| Recommended treatment: determine if implant stable or unstable; basis for all classification systems
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| Unstable implant: loose interface (cemented or uncemented); stabilize fracture; revision; noncemented long-stem
prosthesis preferred
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| Stable implant: open reduction; standard or locking compression plates; cable plates; 90°/90° strut; retrograde femoral
nailing (for supracondylar fractures above total knee arthroplasty; between implants)
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| Concluding advice: regular follow-up important; treat impending fracture; look for osteolysis; avoid intraoperative
stress fracture; do not miss unstable implant
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Suggested Reading
Bal BS et al: Early complications of primary total hip replacement performed with a two-incision minimally invasive
technique. J Bone Joint Surg Am 87:2432, 2005; Berger RA et al: The two-incision minimally invasive total hip
arthroplasty: technique and results. Orthop Clin North Am 35:163, 2004; Berry DJ et al: Minimally invasive total
hip arthroplasty. Development, early results, and a critical analysis. Presented at the Annual Meeting of the American
Orthopaedic Association, Charleston, South Carolina, USA, June 14, 2003. J Bone Joint Surg Am 85-A:2235, 2003;
Berry DJ: Management of periprosthetic fractures: the hip. J Arthroplasty 17:11, 2002; Dorr LD et al: Early pain
relief and function after posterior minimally invasive and conventional total hip arthroplasty. A prospective, randomized,
blinded study. J Bone Joint Surg Am 89:1153, 2007; Dorr LD et al: Psychologic reasons for patients preferring
minimally invasive total hip arthroplasty. Clin Orthop Relat Res 458:94, 2007; Duwelius PJ et al: A prospective,
modernized treatment protocol for periprosthetic femur fractures. Orthop Clin North Am 35:485, 2004; Inaba Y et
al: Operative and patient care techniques for posterior mini-incision total hip arthroplasty. Clin Orthop Relat Res
441:104, 2005; Malik A et al: The science of minimally invasive total hip arthroplasty. Clin Orthop Relat Res
463:74, 2007; Springer BD et al: Treatment of periprosthetic femoral fractures following total hip arthroplasty
with femoral component revision. J Bone Joint Surg Am 85-A:2156, 2003.
Educational Objectives
| The goal of this program is to equip orthopaedists with current clinical recommendations on minimally invasive surgery
(MIS) for total hip arthroplasty (THA). After hearing and assimilating this program, the surgeon will be better
able to:
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| 1. Employ the mini-Smith-Peterson approach for MIS.
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| 2. Adopt the posterior approach for MIS.
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| 3. Recognize pitfalls of MIS.
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| 4. Evaluate scientific perspectives on MIS.
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| 5. Manage periprosthetic fractures.
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Faculty Disclosure
In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty and members of the
planning committee to disclose relevant financial relationships within the past 12 months that might create any personal
conflicts of interest. Any identified conflicts were resolved to ensure that this educational activity promotes
quality in health care and not a proprietary business or commercial interest. For this program, the following has been
disclosed: Dr. Dorr—Zimmer; Dr. Nelson—Zimmer (consultant); ExacTech (royalties); Dr. Kwong—Zimmer
(consultant); Bayer; GlaxoSmithKline; Pfizer; Astellas; Bristol-Myers Squibb (research grant); Dr. Duwelius—
Zimmer (design surgeon for total hip replacement and fracture systems). Dr. Bal and the planning committee reported
nothing to disclose.
Acknowledgments
The speakers were recorded at Advances in Arthroplasty, sponsored by the Harvard Medical School, September 26-29,
2007, in Cambridge, MA. The Audio-Digest Foundation thanks the speakers and the sponsor for their cooperation in
the production of this program.
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