PRE-OP DISCUSSION JSS HOSPITAL

DR ASHWANI PANCHAL JSS MEDICAL COLLEGE

MYSORE

General Anatomical OverviewThe hip is one of your body's largest weight-bearing

joints.Consists of two main parts: a ball (femoral head) that fits into a rounded socket

(acetabulum) in your pelvis.Ligaments connect the ball to the socket and

provide stability to the jointThe bone surfaces of your ball and socket have a

smooth durable cover of articular cartilage that cushions the ends of the bones and enables them to move easily.

Hip Anatomy

More…All remaining surfaces of the hip joint are covered

by a thin, smooth tissue called synovial membrane. In a healthy hip, this membrane makes a small amount of fluid that lubricates and almost eliminates friction in your hip joint.

Normally, all of these parts of your hip work in harmony, allowing you to move easily and without pain.

Total Hip ReplacementA prosthetic hip that is implanted in a similar

fashion as is done in people. It replaces the painful arthritic joint.

The modular prosthetic hip replacement system used today has three components – the femoral stem, the femoral head, and the acetabulum. Each component has multiple sizes which allow for a custom fit.

The components are made of cobalt chrome stainless steel and ultra high molecular weight polyethylene. Cementless and cemented prosthesis systems are available.

Objective AssessmentGait pattern – Adaptive walking pattern that

reduces pressure on the affected side.Muscle atrophy – Muscles in affected area are not

used as much due to pain, therefore, use-it-or-lose-it applies.

Active Range Of Motion – Limited ROM, stiffnessPassive ROM – End feels causes severe painX-ray – clear degeneration of the boneMRI – determines underlying complications

(e.g.avascular necrosis)

INDICATIONS FOR THA :The primary indication for THA is incapacitating PAIN.

Pain in the hip in the presence of destructive process as evidenced by X-ray changes is an indication.

THA is an option for nearly all patients with diseases of the hip that cause chronic discomfort and significant functional impairment.

Patients with limitation of movement, leg length inequality and limp but with little or no pain are not the candidates for THR.

Rheumatoid arthritis Osteo arthritis

Primary Secondary – Perthe’s, trauatic dislocation, Paget’s disease etc.

Ankylosing spondylitis Avascular necrosis of femoral head. Congenital subluxation or dislocation Pyogenic arthritis and TB arthritis Non union of fracture of femoral neck. Failed Hip fusion and pseudarthrosis Failed reconstruction

Osteotomy Cup arthroplasty Femoral head prosthesis Girdle stone arthroplasty Resurfacing arthroplasty

Bone tumor involving proximal femur or acetabulum Hereditary disorders viz : Achondroplasia

CONTRAINDICATIONS : Absolute a) Patient with unstable medical illness that would significantly increase the risk of morbidity and mortality. b) Active infection of the hip joint or anywhere else in the body. Relative Any process that is rapidly destroying bone eg. neuropathic joint, generalized progressive osteopenia. Insufficiency of abductor musculature. Progressive neurological disorder.

FEMORAL COMPONENTS :Neck length and offsets : The ideal femoral reconstruction reproduces the

normal center of rotation of femoral head, which can be determined by

Vertical height of the femoral head : measured from LT to center of the femoral head. Restoration of this distance is essential in correction of leg length.

Medial head stem offset : distance from the center of

the femoral head to a line through the axis of the distal part of stem. Inadequate restoration of this offset shortens the moment arm of the abductor musculature and results in increased JRF and limping, conversely excessive increase produces increased stresses within the stem that may lead to stem fracture or femoral loosening.

Version of the femoral neck : Restoration of the

femoral neck anteversion is important in achieving stability of the prosthetic joint. The normal femur has 10-15 degree of anteversion.

Femoral components are of three general types :

Cemented

Cementless with porous surface

Cementless press-fit variety

The stem fabricated of high strength super alloy (Cobalt – Chrome )has been favoured by some designers because of its higher modulus of elasticity, may decrease stresses within the proximal cement mantle.

The cross section of the stem should have broad medial and lateral border to load the proximal cement mantle in compression.

Sharp edges should be avoided. . The bond between prosthesis and the cement is

improved by surface macrotexturing . A collar aids in determining depth of insertion and

may diminish resorption of bone in the medial neck.

FEMORAL COMPONENTS USED WITH CEMENT FEMORAL COMPONENTS USED WITH CEMENT

Non circular shapes, longitudinal grooves give rotational stability.

Stems should occupy 80% of the cross section of the medullary canal with cement mantle of 4 mm proximally,2mm distally.

Proximal and distal PMMA centralizers to give uniform cement mantle around the stem and neutral placement of stem.

Range of head sizes – 22, 26, 28 & 32 mm. Incidence of dislocation is higher for smaller head. Neck diameter : Original charnleys was 12.5 mm but

has been reduced to 10.5 mm – reduced neck diameter avoids impingement during flexion and abduction.

Range of stem lengths -120 mm to 170 mm. The main problem is mechanical loosening and

extensive bone loss associated with fragmented cement

CEMENTLESS STEMS WITH POROUS SURFACES Currently available porous coated stress designs are

made up of : Titanium – vanadium-aluminum alloy with porous surfaces of

pure titanium fibre mesh or beads. Cobalt – chromium alloy with sintered beaded surface. The advantages of cementless femoral stem prosthesis : No cement is required and problems related to cement are

eliminated. Applicability in young and active patients and in revision THR. Circumferential porous coating of proximal stem provides more

effective barrier to ingress of particle and thus limits early development of osteolysis in distal stem

Decreased incidence of aseptic loosening. Less bone destruction.

Two pre-requisites for bone in growth in porous coated stem are

Immediate implant stability. Intimate contact between implant and bone in

endosteal cavity of the proximal femur.

NON POROUS CEMENTLESS FEMORAL COMPONENTS

With the concerns about fatigue strength, ion release and adverse femoral remodeling, these non porous stems came into use over porous stems.

These devices have groove and other surface modifications that provide a macro interlock with bone, but have no other capacity for biologic fixation.

ACETABULAR COMPONENTS :

The articulating surface of all acetabular components is made of UHMWPE. Most systems feature a metal shell with an outside diameter of 40 to 75 mm which is mated to a polythene liner..

The normal acetabulum is inclined from the transverse plane at an angle of about 55 degrees. This is somewhat more vertical than the optimum position for the prosthetic socket which should be inclined 45 degrees or less to maximize stability of the joint.

Types : Cemented acetabular components. Cementless acetabular components. Custom made acetabular components.

CEMENTED ACETABULAR COMPONENTS

Original sockets for cemented use were thick walled polyethylene cusp. Vertical and horizontal grooves often were added to external surface to increase stability within the cement mantle and wire markers were embedded in plastic to allow better assessment of position on postoperative roentgenograms.

More recent designs have a textured metal back which improves adhesion at the prosthesis cemented interface. A flange at the rim improves pressurization of the cement.

They are commonly used in elderly patients, tumour reconstruction and the circumstances with less chances of bony ingrowth as in revision THR.

CEMENT LESS ACETABULAR COMPONENTS :

Most cementless acetabular components are porous coated over entire surface for bone in growth with different methods of initial stabilization. Viz: transacetabulum screws, pegs and spikes.

Most systems have outer diameter of metal shell of 40-75 mm with polythene inner liner.

The thickness of the metal backing must be sufficient to avoid fatigue failure and also good amount of polythene liner thickness (> 5mm) should be there.

- Custom made acetabular cups

BONE CEMENT :

Also known as PMMA (poly methyl methacrylate) acrylic cement, is not a glue, it has no adhesive qualities, it is a space filing, load transferring material

In palcos cement the powder is added to liquid for mixing, in simplex cement the liquid is added to the powder.

Regular PMMA cement is supplied as 2 sterile components, a packet of powder containing particles of PMMA and about 10% opaque barium sulphate and a polymerization initiator, the other component is a vial containing methyl methacrylate monomer and a activator that promote the curing process.

ROENTEGENOGRAPHIC EVALUATION :

AP view of pelvis with both hips with upper third femur with limbs in 15degrees internal rotation.

Spine, knee x-ray taken Note the following : Acetabulum : Bone stock, floor, migration,

protrusio, osteophytes and cup size. Femur : Medullary cavity (size & shape). Limb length discrepancy Neck.

TEMPLATING :

Draw two horizontal lines : One joining both ischial tuberosites and the other joining lesser trochanter. Measure limb length discrepancy as the difference in lengths of lesser trochanters.

Aetabulum : Place acetabular templates on the film and select a

size that closely matches the contour of patients acetabulum. The medial surface of the cup is at the teardrop and the inferior limit is at the level of obturator foramen.

Femur : Select a size that most precisely matches the contour of

proximal canal with 2-3 mm of cement mantle. Select a neck length so that the difference in the height of femoral and acetabular center is equal to the limb length discrepancy.

Mark the level of anticipated neck cut and measure its distance

from the lesser trochanter.

PREPARATION :

Take an informed consent. Bath the entire extremity and hip with germicidal

solution twice daily after patients is admitted to the hospital.

Shave the extremity, perineal area, hemipelvis to at least 10 cm proximal to the iliac crest and wash with soap as soon before surgery as possible and cover with sterile towels.

Prophylactic antibiotics.

OPERATION THEATRE : Laminar flow room with body exhaust system

SURGICAL APPROACHES AND TECHNIQUES :

Each approach has relative advantages and drawbacks. Choice of specific approach for THR is largely a matter of personnel preference.

Posterolateral approach with patient in lateral position without greater trochanter osteotomy and dislocating the hip posteriorly is commonly done.

EVALUATION BEFORE SURGERY Evaluate whether pain is sufficient to justify surgery.Asess patient’s general condition (thorough medical examination

with laboratory test is must)Investigate for any ongoing infection Physical examination of spine, both lower limbs, soft tissue

around the hip. Asess the strength of abductor mechanism Any fixed flexion deformity assessed. Limb length Neurological status When both the hip and knee are arthritic usually hip should be

operated first because THR alters the knee mechanics. If bilateral involvement present operate on most painful hip first

and after 3 months operate on the other side.

OperationRemoving the Femoral HeadOnce the hip joint is

entered, the femoral head is dislocated from the acetabulum.

Then the femoral head is removed by cutting through the femoral neck with a power saw.

Reaming the AcetabulumAfter the femoral head

is removed, the cartilage is removed from the acetabulum using a power drill and a special reamer.

The reamer forms the bone in a hemispherical shape to exactly fit the metal shell of the acetabular component.

Inserting the Acetabular ComponentA trial component, which is

an exact duplicate of your hip prosthesis, is used to ensure that the joint will be the right size and fit for the client.

Once the right size and shape is determined for the acetabulum, the acetabular component is inserted into place.

Preparing the Femoral CanalTo begin replacing the

femoral head, special rasps are used to shape and scrape out femur to the exact shape of the metal stem of the femoral component.

Once again, a trial component is used to ensure the correct size and shape. The surgeon will also test the movement of the hip joint.

Inserting Femoral StemOnce the size and shape

of the canal exactly fit the femoral component, the stem is inserted into the femoral canal.

Attaching the Femoral HeadThe metal ball that

replaces the femoral head is attached to the femoral stem.

The Completed Hip Replacement• Client now has a new

weight bearing surface to replace the affected hip.

• Before the incision is closed, an x-ray is made to ensure new prosthesis is in the correct position.

Treatment by Kinesiologist-Early Postoperative Exercises-

Regular exercises to restore your normal hip motion and strength and a gradual return to everyday activties.

Exercise 20 to 30 minutes a day divided into 3 sections.

Increase circulation to the legs and feet to prevent blood clots

Strengthen musclesImprove hip movement

Exercise PrescriptionEarly Stage

Kinesiologist’s Role (cont)The patient is released few days after the surgeryA list of Do’s and Don’tsHip is sore and weak Start with light exercisesErgonomics: Rearrange furniture in the house to

make using crutches easier. Setup a ‘recovery centre’, a table where u put phone, remote control, radio, medication and other essential things that you need. It makes it more accessible.

- Do’s and Don’ts -To avoid hip dislocation:Using 2-3 pillows between your legs when sleeping

(roll onto your ‘good side’Not crossing your legs Use chairs with armrest Not bending forward past 90 degrees Using a high-rise toilet seat if necessary Avoid pronation the legsTo avoid stairs, sleep in the living room

Exercise Prescription- Later Stages -

Post-Surgery ComplicationsThrombophlebitis

the blood in the large veins of the leg forms blood clots within the veins.

If the blood clots in the veins break apart they can travel to the lung.

Infection in the joint Dislocation of the jointLoosening of the joint