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The Zimmer® MIS™ Anterolateral Hip Procedure
A Muscle-Sparing Approach to THA
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Objectives
• Discuss the history of minimally invasive surgery in terms of
evolution, definitions, approaches, and classification schemes
• Identify the unique characteristics of the Zimmer MIS Anterolateral
THA procedure
• Discuss in detail the stages and key elements of the Zimmer MIS
Anterolateral THA surgical procedure
• Define the Five Acts of leg positioning and describe how they relate
to the various stages of the surgical procedure
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Objectives (cont.)
• Discuss clinical data obtained from procedure to date
• Define the advantages and disadvantages of the Zimmer MIS
Anterolateral THA procedure as they relate to THA in general
• Identify and discuss key concerns in the overall continuum of care
related to the Zimmer MIS Anterolateral THA procedure
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Minimally Invasive Surgery: History,
Evolution, Definitions, and Approaches
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Minimally Invasive Surgery:
Evolution in THA Procedures
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• Maximally invasive
60s/70s
• Moderately invasive
80s/90s
• Minimally invasive
Turn of the century
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Maximally Invasive Surgery
• Typically Provides:
 Wide Exposure
 Neurovascular protection
 Confident implant placement
With this incision I can do every hip:
I can expose it,
I can see it,
I can teach it
(C. S. Ranawat, CCJR 2003)
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What is the Minimally Invasive THA?
• Length of Incision?
• Length of capsule incision.
• Amount of muscle trauma!
• Amount of bone loss!
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Minimally Invasive THA Classification
Eponymous
• Modified Watson Jones
• Modified Smith Peterson
• Modified Moore
• Keggi/Mears/Röttinger
…does not connote much meaning
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Minimally Invasive THA Classification
Proposal
• Direction
• Number of incisions
• Method of deep dissection
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Minimally Invasive THA Classification
Direction is the key
• Gluteus Medius is the
signpost
• Anterior
• Anterolateral
• Lateral
• Posterior
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Minimally Invasive THA Classification
Number of incisions
• Single Incision – acetabular/femoral preparation through one
incision
• Two incisions – acetabular preparation through anterior incision
and femur preparation through posterior incision
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Minimally Invasive Surgery THA
Method of Deep Dissection is key
• Do you divide or go between the muscles and tendons?
 Traditional – Cut
 Mini Anterolateral – Cut less
 MIS Anterolateral – Spare
• Spare: to refrain from doing harm
Merriam Webster’s Dictionary
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Minimally Invasive THA Classification
Method of Deep Dissection
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•
Anterior - Muscle Sparing
•
Anterolateral - Muscle Sparing
•
Lateral - Muscle Cutting
•
Posterior - Muscle Cutting
•
Two-incision - Muscle Sparing
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Introduction to the Zimmer MIS
Anterolateral THA Procedure
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The MIS Anterolateral Approach
Gluteus Medius
• A single incision
• Muscle sparing approach to the hip
• Interval between the anterior border of the
gluteus medius and the posterior border of
tensor fascia lata.
• Minimally invasive modification conceived
by Heinz Röttinger, M.D. from the
Orthopädische Chirurgie München (O.C.M.)
Munich, Germany in 2003
Tensor Fascia Lata
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The MIS Anterolateral Approach – Overview
•
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Interval between Gluteus Medius and Tensor Fascia Lata
 No division of any muscle or tendon
•
Acetabulum and femur directly visualized
•
8-10 cm incision
•
Posterior capsule intact → lower risk of dislocation
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The MIS Anterolateral Approach –
Overview (cont.)
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•
Extensile - bail out is full Watson Jones exposure
•
Acceptable learning curve
•
Familiar lateral positioning
•
Clear of neurovascular hazards
•
Compatible with most contemporary Zimmer implants
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The MIS Anterolateral Key Principles
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•
Identification of interval
•
Anatomical referencing
•
Retraction and mobile window
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Femoral exposure/Extensibility of capsular incision
•
Leg positioning
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MIS Anterolateral Procedure
The Five Leg Positions
1. Skin and Capsular Incisions/Closure
2. Transcapital Neck Cut
3. Definitive Neck Cut
4. Acetabulum
5. Femur
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Leg Positioning
Incisions
Femoral Side
Acetabular Side
1st Femoral Cut
Definitive Osteotomy
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Surgical Technique for the Zimmer
MIS Anterolateral THA Procedure
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The MIS Anterolateral Surgical Considerations
•
Pre-op Templating
•
•
Table
•
•
Positioning
•
•
•
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Draping
Incision
Dissection
Capsule
Referencing (intra-operative
measurements)
•
Neck Osteotomies
•
Acetabulum
•
Femur
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Templating
• Measure down from the “Saddle”
• Other anatomical references
• Lesser trochanter can usually be palpated for cross reference
“Saddle”
Greater Trochanter
Lesser Trochanter
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Surgical Technique
•
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Table set up
 Trumpf Jupiter table or Maquet
 Skytron table attachments
 Local custom modification
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Patient and Table Preparation
• Patient in direct lateral position
• Securely held on table
• Leg support modified to allow posterior leg
•
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positioning
Surgeon works on anterior side
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Draping
• Drape can become unstable
• Sterile bag
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Team Positioning
• Surgeon Anterior
• 1st Assistant Distal/Posterior
• 2nd Assistant Posterior
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Skin Incision and Intermuscular Interval
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Skin Incision
• Identify greater trochanter and anterior superior iliac crest
 Extend incision from anterosuperior aspect of greater
trochanter about 8cm to a point 2-4cm posterior to the ASIS
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The Interval
Gluteus Medius
Approximate incision
location
Tensor Fascia
Lata
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The Interval
Gluteus Medius
Head
Greater
Trochanter
ASIS
Tensor Fascia
Lata
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Capsular Exposure
•
The Instruments
 Retractors numbered for ease of use
 Optimized radius to be gentle to muscle
Retractor 1
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Retractor 2
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The Interval
Capsule
Tensor Fascia Lata
Gluteus Medius
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Capsulotomy
•
A “Z” shaped capsular incision with
two flaps is created
 Slight internal hip rotation
 Neutral to slight hip abduction
 Ability to extend lateral capsular
incision can be critical to obtaining
adequate femoral exposure
 T or H shaped capsular incisions
are certainly viable options
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Femoral Neck Exposure
• Retractors are replaced inside
the capsule
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Referencing
• The “Saddle”
• Other anatomical references
• Lesser trochanter can usually be
palpated for cross reference
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“Saddle”
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First Neck Osteotomy
• Femoral head and neck are
taken out in two pieces
• First “neck” cut is in articular
portion of femoral head
• Direct blade inferior
• Externally rotate maximally to
approximately 60 or to
allowable range of motion
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Neck-Head Disassociation
• Place Cobb elevator in the
first neck cut
• Move leg into extension and
external rotation and lever
with Cobb elevator to
disassociate femoral neck
from residual head and deliver
neck into incision
• Neck will now be parallel to
the floor
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Definitive Femoral Neck Cut(s)
• Hip and leg are rotated 90
externally with thigh parallel to the
floor
• Slight hip flexion may help and saw
must be adjusted accordingly
• Retractors placed more distal on
neck
• Osteotomy - Identify references
 Oblique portion based on
preoperative plan for angle and
position
 Horizontal portion medial to
trochanter
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Femoral Head Removal
• Proximal positioned first osteotomy facilitates
easier removal
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Acetabular Exposure
•
The Instruments
 Retractors
Retractor 1
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Retractor 3
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Acetabular Exposure
•
Retractor Placement
 4 o’clock and 8 o’clock positions
Retractor 3
Retractor 1
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Acetabular Preparation
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The Instruments
 Offset reamer handle, low profile reamers and offset cup positioner
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Acetabular Preparation
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Reaming
 Position handle superiorly with flat portion of low
profile reamer resting on superior rim of
acetabulum
 Rotate reamer handle distally and position
reamer
 Hip flexion and abduction can facilitate insertion
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Acetabular Preparation
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Acetabular implant
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Femoral Exposure - Leg Position
• Foot and leg in a bag on the
posterior table
• Deliver the proximal femur into
the incision for instrumentation
• 20 Extension
• 40 Adduction
• 90 External Rotation
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Femoral Preparation
•
The Instruments: Angled/offset rasp handles
400 Rasp Handle
CLS® Rasp Handle
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300 Rasp Handle
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Femoral Preparation
• Retractor placement
 Retractor 3 inferior and
medial to cut femoral neck
― Elevates femur
― Retracts tensor &
capsule
 Retractor 1 lateral to
posterior, superior tip of
greater trochanter
― Retracts abductors
Retractor 1
• Remove any residual anterior
and lateral capsule at top of
neck to deliver femur
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Retractor 3
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Wound closure
•
•
•
•
•
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Adapting capsule suture
Deep drain 6 – 24 hours
Closure of fascia
Subcutaneous suture
Intracutaneous suture
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Surgical Recap:
The Five Acts of Leg Positioning
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MIS Anterolateral Procedure
The Five Leg Positions
1. Skin and Capsular Incisions/Closure
2. Transcapital Neck Cut
3. Definitive Neck Cut
4. Acetabulum
5. Femur
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Leg Positioning
Incisions
Femoral Side
Acetabular Side
1st Femoral Cut
Definitive Osteotomy
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Skin and Capsular Incision
Position 1
• Assistant holds leg in neutral to
slight hip abduction
• Relaxes abductors to achieve
maximum exposure
• Mayo Stand
• Arm Elevator
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Transcapital Neck Cut
• Assistant holds leg in
 neutral ab/adduction
 slight hip flexion
 external rotation that
anatomy allows
• Foot in bag
• Relaxes iliopsoas
• Provides improved
visualization of femoral neck
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Position 2
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Definitive Neck Cut
• Assistant moves leg into
 90 External Rotation
• Foot in bag
• Femur parallel to floor
• Tibia perpendicular to floor
• Positions femoral neck
parallel to floor to visualize cut
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Position 3
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Acetabulum
• Assistant moves leg into
 Full knee extension
 Slight external hip rotation
• Slight hip abduction and hip
flexion can help insertion
and extraction of reamers
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Position 4
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Femur
• Assistant moves leg into
 90 External Rotation
 20 Extension
 40  Adduction
• Foot in bag
• Tibia perpendicular to floor
• Elevates femur
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Position 5
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Closure
• Assistant moves leg back to
initial position
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Clinical Data Associated With the Zimmer
MIS Anterolateral THA Procedure
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Clinical data
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2 surgeons (03/03 – 2/05)
•
>700 THA
•
Bodyweight 74.5 kg (min. 43 kg, max. 134 kg)
•
BMI 26 (maximum 42)
•
Surgery time 46 minutes
•
Retransfusion volume 302 ml (intraoperative to 6 hrs.
postop.)
Röttinger, 2005
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Clinical Experience – Early Results
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>700 patients
 Excellent early mobilization
 Decreased pain
 Excellent abductor function
 Excellent standard approach
(also for revisions)
 Acceptable learning curve
Röttinger, 2005
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2 days Post-op
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Clinical Experience—Complications
•
>700 patients
 5 postop. periprothetic fractures
― Caused by a particular femoral component
 6 greater trochanter fractures
― Asymptomatic
 2 dislocations of the acetabular
component
 3 anterior dislocations
― Increased anteversion of acetabular
component (2 revisions)
Röttinger, 2005
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Greater Trochanteric Fractures
•
No dislocation
•
No muscle insufficiency
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Likely related to insufficient lateral superior
capsular release
Röttinger, 2005
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Discussion: Advantages, Disadvantages,
and the Continuum of Care With the
Zimmer MIS Anterolateral THA Procedure
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Where does this new approach fit?
Great alternative for surgeons who prefer anterior approaches
• Advantages
 Theoretically better early abductor muscle function
 Lateral femoral cutaneous nerve and lateral femoral
circumflex vessel not in operative field
 Acceptable surgical time
 No intraoperative x-ray necessary
 Acetabulum and femur directly visualized
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Where does this new approach fit?
• More Advantages
 Familiar lateral positioning
 Compatible with many Zimmer implants
 Performed through small incision (patient preference)
 Viable bail out
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Where does this new approach fit?
• For surgeons who prefer posterior approach
 Many of the aforementioned features
with
 New view of hip
 Low dislocation rate
 Time, experience and well designed studies will tell
Röttinger, 2005
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Where does this new approach fit?
• Potential Challenges
 New surgeon positioning
 May require two surgical assistants
 Expect a variable learning curve
 Initial risk of complications
― Excessively anteverted cup
― Insufficient capsular release
– Varus stem
– Greater trochanteric fracture
 Obese and very muscular patients still difficult
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Discussion
• Post-Op Care
• Anesthesia
• Challenges
 Leg Position
 Interval
 Capsular Incision
 Acetabulum
 Femur
• Patient Outcomes
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Conclusions
• This MIS anterolateral approach is intermuscular
 Potentially little to no delay in rehab
 Potentially little to no abductor weakness
• Clinical results are encouraging
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