The Zimmer MIS Anterolateral Hip Procedure A MuscleSparing Approach to THA

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The Zimmer MIS Anterolateral Hip ProcedureA
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 SurgeryEvolution in THA
Procedures

• 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 Websters Dictionary

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Minimally Invasive THA Classification

• Method of Deep Dissection
• 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

• 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.)

• 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

• Identification of interval
• Anatomical referencing
• Retraction and mobile window
• Femoral exposure/Extensibility of capsular
  incision
• Leg positioning

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MIS Anterolateral Procedure

• The Five Leg Positions
• Skin and Capsular Incisions/Closure
• Transcapital Neck Cut
• Definitive Neck Cut
• Acetabulum
• 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
• 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

• 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
  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
Approximate incision location
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The Interval
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Capsular Exposure

• The Instruments
• Retractors numbered for ease of use
• Optimized radius to be gentle to muscle

Retractor 1
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

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
Retractor 3
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Acetabular Exposure

• Retractor Placement
• 4 oclock and 8 oclock positions

Retractor 3
Retractor 1
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Acetabular Preparation

• The Instruments
• Offset reamer handle, low profile reamers and
  offset cup positioner

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Acetabular Preparation

• 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

• 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
300 Rasp Handle
CLS 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

• Remove any residual anterior and lateral capsule
  at top of neck to deliver femur

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Wound closure

• 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
• Skin and Capsular Incisions/Closure
• Transcapital Neck Cut
• Definitive Neck Cut
• Acetabulum
• 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

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

Position 3
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Acetabulum
Position 4

• 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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Femur
Position 5

• Assistant moves leg into
• 90? External Rotation
• 20? Extension
• 40 ? Adduction
• Foot in bag
• Tibia perpendicular to floor
• Elevates femur

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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

• 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
2 days Post-op

• 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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Clinical ExperienceComplications

• 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
• 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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