The seminar presentation on hip arthroplasty covers the history, evolution, and biomechanics of total hip replacement components, highlighting significant advancements and materials used over the years. Key topics include the design and selection of femoral and acetabular components, considerations for cemented versus cementless fixation, and the importance of achieving a biomechanically stable joint. Additionally, it addresses the implications of wear, stress transfer, and the impact of various design features on the performance and longevity of hip implants.

1. SEMINAR PRESENTATION ON: ARTHROPLASTY OF THE
HIP: APPLIED BIOMECHANICS, DESIGN AND SELECTION
OF TOTAL HIP COMPONENTS, ALTERNATE BARRINGS
INDICATIONS, CONTRAINDICATIONS OF THR &
TEMPLETING AND PRE-OP EVALUATION.
Chairperson: Prof. & HOD: Dr. Kiran Kalaiah
Moderator: Prof. Dr. Veeranna H D
Presenter : Dr. Yashavardhan .T.M

2. HISTORY AND EVOLUTION OF THR
• In 1912, Sir Robert Jones used Gold Foil as an
inter positional layer, other materials used were
muscle, fascia, skin, oil, rubber, celluloid, pig
bladder.
• In 1923, SMITH-PETERSON introduced the
concept of mould arthroplasty
• In 1933, PYREX GLASS was chosen as the
material for the first mould..
• In 1937, Venable and Stuck developed
VITTALIUM (an alloy of Cobalt 65%, Chromium
30%, Molybdnium 5%).

3. In 1950, JUDET and BROTHERS used acrylic
femoral head prosthesis made of methyl
methacrylate..
• In 1952 AUSTIN MOORE and FRED
THOMPSON independently conceived the idea
of fixing endoprosthesis.
• The 1950, WRIST, RING, Mc. KEE-FARRER and
others designed the metal on metal total hip
arthroplasty but did not prove satisfactory
because friction and metal wear

4. In 1960, Late Sir John Charnley(29 aug 1911 to 5 aug 1982)
has done pioneer work in all aspect of THA, including the
concept of low frictional torque arthroplasty, surgical
alteration of hip biomechanics, lubrication, materials, design
and clear air operating room environment

5. Between 1966-1988,Maurice Muller from
Switzerland developed a plastic acetabular
cup with a 32 mm diameter
chromiumcobaltmolybdenum femoral head.
• In 1964,Peter Ring began using metal-to-
metal components without cement,
• concept of modular prosthesis developed
during 1970
• cementless prostheses came in to picture by
mid 1980

16. Forces acting on hip
To describe the forces acting on the hip joint, the body weight
may be depicted as a load applied to a lever arm extending
from the body’s center of gravity to the center of the femoral
head.
• The abductor musculature, acting on lever arm extending
from the lateral aspect of the greater trochanter to the center
of the femoral head.

17. Force on hip act in coronal and saggital direction
• Coronal- tend to deflect stem medially , saggital (esp in
flexed hip) tend to deflect stem posteriorly
• Hence Implanted femoral components must withstand
substantial torsional forces even in the early postoperative
period.

18. CHARNLEY’S LOW FRICTION ARTHROPLASTY
Charnley advocated the shortening of the body weight lever
arm by
• Deepening the acetabulum and by using small head.
Lengthen the abductor lever arm by
• Reattaching the osteotomised greater trochanter laterally or
• By increasing offset between the head and stem of the
femoral component.

19. Centralisation of head and lengthening of abductor lever arm
• Whenever abductor lever arm is increased, it reduces forces
on the hip joint. This lowers the friction and frictional torque
and hence lessens the chance of wear and loosening of
implants

20. Valgus and Varus position
• A valgus of the head and neck of the femoral component relative to the
femoral shaft more than 140 degree decrease the movement of bending
and increase proportionally the axial loading of the stem
• A mild degree of valgus is usually desirable, but it does shorten the
abductor lever arm mechanism and also tend to lengthen the limb, may
result in the valgus strain on the knee.
• varus position of the head and neck segment of the femoral component
must be avoided because it increases risk of loosening, wearing and stem
failure.

21. Stress Transfer to Bone
• A major concern with THR is that adaptive bone remodeling arising from
stress shielding compromises implant support, produces loosening, and
predisposes to fracture of the femur or the implant itself.
• Cementless stems generally produce strains in the bone that are more
physiological than the strains caused by fully cemented stems
• Increasing the modulus of elasticity, the stem length, and the cross-
sectional area of the stem increases the stress in the stem, but decreases
the stress in the cement and proximal third of the femur

22. WEAR :
Wear can be defined as the loss of material
from the surfaces of the prosthesis as a result
of motion between those surfaces. Material is
lost in form of particulate debris. Types :
1. Abrasive-THR
2. Adhesive -THR
3. Fatigue - THR

23. The factors that determine wear are :
• CF of the substance and finishing surfaces
• Boundary lubrication
• Applied load
• The sliding distance per each cycle
• The hardness of the material
• The number of cycles of movements
The area of greater wear is in the superior aspect of the socket where the
body weight is applied to the femoral head.

24. DESIGN AND SELECTION OF TOTAL HIP COMPONENTS
1. Total hip femoral and acetabular components of various
materials and a multitude of designs are currently
available.
2. Few implant designs prove to be clearly superior or
inferior to others. Certain design features of a given
implant may provide an advantage in selected situations.
3. Properly selected and implanted total hip components of
most designs can be expected to yield satisfactory results
in a high percentage of patients.
4. No implant design or system is appropriate for every
patient, and a general knowledge of the variety of
component designs and their strengths and weaknesses is
an asset to the surgeon

25. FEMORAL COMPONENTS
• The primary function of the femoral component is the
replacement of the femoral head and neck after resection
of the arthritic or necrotic segment.
• The ultimate goal of a biomechanically sound, stable hip
joint is accomplished by careful attention to restoration of
the normal center of rotation of the femoral head.
• This location is determined by three factors:
• (1) vertical height (vertical offset),
• (2) medial offset (horizontal offset or, simply, offset), and
• (3) version of the femoral neck (anterior offset) (Fig. 3-6).

26. 1. Vertical height and offset increase as the neck is
lengthened, and proper reconstruction of both features is
the goal when selecting the length of the femoral neck. In
most modern systems, neck length is adjusted by using
modular heads with variable internal recesses that fit
onto a Morse taper on the neck of the stem
2. Neck length typically ranges from 25 to 50 mm, and
adjustment of 8 to 12 mm for a given stem size routinely
is available. When a long neck length is required for a
head diameter up to 32 mm, a skirt extending from the
lower aspect of the head may be required to fully engage
the Morse taper (Fig. 3-8). For heads larger than 32 mm a
skirt is unnecessary even for longer neck lengths.

27. 3. Vertical height (vertical offset) is determined primarily by the base
length of the prosthetic neck plus the length gained by the modular head
used. In addition, the depth the implant is inserted into the femoral canal
alters vertical height.
When cement is used, the vertical height can be adjusted further by
variation in the level of the femoral neck osteotomy.
4. This additional flexibility may be unavailable when a cementless
femoral component is used because depth of insertion is determined
more by the fit within the femoral metaphysis than by the level of the
neck osteotomy.
5. Offset (i.e., horizontal offset) is the distance from the center of the
femoral head to a line through the axis of the distal part of the stem
and is primarily a function of stem design
6. To address individual variations in femoral anatomy, many components
are now manufactured with standard and high offset versions. This is
accomplished by reducing the neck-stem angle (typically to about 127
degrees) or by attaching the neck to the stem in a more medial position

28. Version refers to the orientation of the neck in
reference to the coronal plane and is denoted as
anteversion or retroversion.
• Restoration of femoral neck version is important in
achieving stability of the prosthetic joint.
• The normal femur has 10 to 15 degrees of
anteversion of the femoral neck in relation to the
coronal plane when the foot faces straight forward,
and the prosthetic femoral neck should
approximate this.
• Proper neck version usually is accomplished by
rotating the component within the femoral canal.
This presents little problem when cement is used
for fixation

29. The size of the femoral head, the ratio of head and
neck diameters, and the shape of the neck of the
femoral component have a substantial effect on the
range of motion of the hip, the degree of
impingement between the neck and rim of the
socket, and the stability of the articulation.
This impingement can lead to dislocation,
accelerated polyethylene wear, acetabular
component loosening, and liner dislodgment or
fracture.
When this impingement does occur, the femoral head is
levered out of the socket. The “jump distance” is the distance
the head must travel to escape the rim of the socket and is
generally approximated to be half the diameter of the head.

30. Range of motion was dramatically reduced by the use of a circular neck, especially
when combined with a skirted modular head, which increases the diameter of the
femoral neck.
A trapezoidal neck yielded greater range of motion without impingement than a
circular one.

31. CEMENTED FEMORAL COMPONENTS
• With the introduction of the Charnley low-friction
arthroplasty, acrylic cement became the standard for
femoral component fixation.
• Advances in stem design and in the application of cement
have dramatically improved the longterm survivorship of
cemented stems.
• Despite these advances, the use of cement for femoral
fixation has declined precipitously over the past decade and
there has been little recent innovation in implant design.
• The stem should be fabricated of highstrength superalloy.
Most designers favor cobalt-chrome alloy because its higher
modulus of elasticity may reduce stresses within the
proximal cement mantle.

32. 
Understanding what you
have in your hands, how it
behaves and how to get the
best result
Bone Cement

33. 
• Liquid
– Methyl Methacrylate
(plus optionally higher
methacrylates)
• Powder
– Polymethyl Methacrylate
(and / or copolymers of
methyl methacrylate)
COMPOSITION: MAJOR
COMPONENTS

34. • Liquid
Accelerator
-N,N’ – dimethyl – p –
toluidine
Stabiliser
-Hydroquinone
• Powder
Initiator
- Benzoyl Peroxide
Radiopaque agent
-Barium Sulphate, Zirconium
Dioxide
Antibiotic
-Gentamicin Sulphate
COMPOSITION: OTHER
COMPONENTS

35. Initial Fixation and Creation of the Cement Mantle

36. FIXATION BY BONE CEMENT
Bone cement has NO adhesive properties to bone or implants
“Cement is a GROUT not
a GLUE.”
Sir John Charnley

37. INTERDIGITATION OF
CEMENT INTO BONE
• It fixes a prosthesis
in place by
INTERDIGITATION
of cement into
porous cancellous
bone, then
hardening.
• Microinterlock
mechanism
• LIQUID ENOUGH TO FLOW INTO BONE
• STIFF ENOUGH TO STAY THERE

38. 
Cement in Load
Transfer
Strong in Compression
Weak in tension
Weak in shear

39. WHEN TO CEMENT-
ACETABULUM
 Elderly, low-demand patients without acetabular
deformity
 Tumor reconstructions
 Revision arthroplasty in which extensive acetabular
bone grafting has been necessary

40.  Osteoporosis
 Revision surgery
 Tumor reconstruction
WHEN TO CEMENT- FEMUR

42. Phases
1. Mixing
2. Waiting: Temperature dependent
3. Working: Temperature dependent
4. Hardening/Setting: Temperature dependent
Mixing Phase 2-3 minutes
1. Liquid wets the surface of the pre-polymerised
powder = homogenous dough
2. PMMA dissolves in its monomer and the pre-
polymerised beads swell and some of them
dissolve completely during mixing
3. Homogenous sticky mass

43. Waiting Phase
1. Further swelling of beads + polymerisation to proceed
increase in the viscosity of the mixture
2. Cement turns to dough
3. The end of the waiting phase is when the cement is neither
sticky nor hairy
Working phase 5-8 minutes
Low viscosity to allow application
Polymerisation continues
viscosity increases
Heat of polymerisation causes thermal expansion while
there is a volumetric shrinkage
Blood lamination of the cement causes weakness
Prosthesis must be implanted before the end of the working
phase

44. Hardening/Setting Phase 8-10 minutes
• Temperature continues to rise then slowly returns to body
temperature
• Volumetric and thermal shrinkage as it cools to body
temperature
• Ends when a hard consistency is reached
• Prolonged with environmental factors (low temp. high humidity)
• Mixing too quickly can hasten the polymerisation reaction
leading to shorter setting time
Working phase 5-8 minutes
• Low viscosity to allow application
• Polymerisation continues viscosity increases
• Heat of polymerisation causes thermal expansion while there is a
volumetric shrinkage
• Blood lamination of the cement causes weakness
• Prosthesis must be implanted before the end of the working
phase

45. Side Effects
1. Hypotension
2. Cerebrovascular insults
3. Pulmonary Embolism
4. Hypersensitivity
5. Cardiac Arrest
6. Bone cement implantation syndrome
Bone cement implantation syndrome
1. Hypoxia
2. Hypotension
3. Cardiac Arrhythmias
4. Increased Pulmonary Vascular Resistance
5. Cardiac Arrest

46. Grading of BCIS
1. Moderate Hypoxia (94%) OR Hypotension (20% fall in SBP)
2. Severe Hypoxia (88%) OR Hypotension (40% fall in SBP) OR
Unexpected loss of consciousness
3. Cardiovascular collapse requiring CPR

47. • Higher rates of loosening and bone resorption were found
with the use of an Exeter stem with a matte surface than
with an identical stem with a polished surface.
• Ling recommended a design that is collarless, polished, and
tapered in two planes to allow a small amount of
subsidence and to maintain compressive stresses within the
cement mantle.
• Stems should be available in a variety of sizes (typically
• four to six) to allow the stem to occupy approximately 80%
of the cross section of the medullary canal with an optimal
cement mantle of approximately 4 mm proximally and 2
mm distally. Neutral stem placement within the canal
lessens the chance of localized areas of thin cement
mantle.
• The centralizers bond to the new cement and are
incorporated into the cement mantle.

48. 
MODERN CEMENTING
TECHNIQUE
Vacuum mixing of bone cement
Pulsatile lavage cleaning
Medullary canal restrictor
Cement Gun & Proximal femoral pressurisation
Acetabular cement pressurisation
Use of proximal and distal stem centralizers.

49. 
MODERN CEMENTING
TECHNIQUE
Vacuum Mixing - The Vital Step to stronger bone
cement and long term cemented fixation
- Smeds, Goetzen ‘97
Vacu-Mix Plus

50. CEMENTLESS FEMORAL COMPONENTS
In the mid-1970s, problems related to the fixation of
femoral components with acrylic cement began to
emerge.
The two prerequisites for biologic fixation are
• immediate mechanical stability at the time of
surgery and
• intimate contact between the implant surface and
viable host bone.

51. • Titanium alloy has been recommended as the material of
choice because its modulus of elasticity is approximately
half that of cobalt-chromium alloy and therefore less likely
to be associated with thigh pain.
• A variety of surface modifications including porous coat-
ings, grit blasting, plasma spraying, and hydroxyapatite
coating have been used to enhance implant fixation.
• Schmalzried et al. referred to these extensions of joint fluid
as the “effective joint space.”
• This design feature has been associated with early
development of osteolysis around the tip of the stem
despite bone ingrowth proximally.

52. Porous metals have higher porosity than traditional porous
coatings, and their high coefficient of friction against
cancellous bone may improve their initial stability. Porous
tantalum closely resembles the structure of cancellous bone.
Rapid and extensive bone ingrowth into this implant surface
has been reported.
Khanuja, Vakil, Goddard, and Mont proposed a
classification system for cementless stems based on shape.
Types 1 through 5 are straight stems, and fixation area
increases with type. Type 6 is an anatomic shape.

53. Type 1 stems are so called single-wedge stems.
They are flat in the anteroposterior plane and tapered in the mediolateral plane.
Consequently, it is important to ensure that the stem is wedged proximally.

54. Type 2 stems engage the proximal femoral cortex in both mediolateral
and anteroposterior planes.
So-called dualwedge designs fill the proximal femoral metaphysis more
completely than type 1 stems

55. type 3 represents a more disparate group of implants.
These stems are tapered in two planes, but fixation is achieved more at the
metaphyseal-diaphyseal junction than proximally as with types 1 and 2.
• Type 3A stems are tapered with a round conical distal geometry.
• Longitudinal cutting flutes are added to type 3B stems these implants have
recently gained popularity in complex revision cases.
• Type 3C implants are rectangular and thus provide four-point rotational support

56. Type 4 are extensively coated implants with fixation along the entire length of the
stem.
Canal preparation requires distal cylindrical reaming and proximal broaching

57. Type 5 or modular stems have separate metaphyseal sleeves and diaphyseal
segments that are independently sized and instrumented.
Such implants often are recommended for patients with altered femoral anatomy,
particularly those with rotational malalignment such as developmental dysplasia.
This feature makes modular stems an attractive option when femoral osteotomy is
required

58. Type 6 or anatomic femoral components incorporate a posterior bow in the
metaphyseal portion and variably an anterior bow in the diaphyseal portion,
corresponding to the geometry of the femoral canal.

59. SPECIALIZED AND CUSTOM-MADE FEMORAL COMPONENTS
• The adoption of minimally invasive surgical techniques has
generated interest in shorter bone-sparing femoral
implants. Some are novel implants designed to fit within the
intact ring of bone of the femoral neck.
• Modular segmental replacement stems also are used in
patients with extensive femoral bone loss from multiple
failed arthroplasty procedures and periprosthetic fractures.
• ustomized, cementless, CT-generated computer-assisted
design/computer-assisted manufacturing (CAD/CAM)
prostheses have been recommended when preoperative
planning indicates that an off-the-shelf prosthesis cannot
provide optimal fit or when excessive bone removal would
be required.
• Such implants require a carefully made preoperative CT scan
of the acetabulum, hip joint, and femur.

60. CEMENTED ACETABULAR COMPONENTS
• The original sockets for cemented use were thick-walled
polyethylene cups.
• Vertical and horizontal grooves often were added to the
external surface to increase stability within the cement
mantle, and wire markers were embedded in the plastic to
allow better assessment of position on postoperative radiographs.

61. • Many of these designs are still in regular use. More recent designs have
modifications that ensure a more uniform cement mantle. PMMA spacers,
typically 3 mm in height, ensure a uniform cement mantle and avoid the
phenomenon of “bottoming out,” which results in a thin or discontinuous
cement mantle.
• Cemented acetabular fixation also is used in some tumor reconstructions and
when operative circumstances indicate that bone ingrowth into a porous
surface is unlikely, as in revision arthroplasty in which extensive acetabular
bone grafting has been necessary. In these instances, a cemented acetabular
component often is used with an acetabular reconstruction ring

62. CEMENTLESS ACETABULAR COMPONENTS
1. Most cementless acetabular components are porous coated over their
entire circumference for bone ingrowth. Instrumentation typically
provides for oversizing of the implant 1 to 2 mm larger than the
reamed acetabulum as the primary method of press-fit fixation.
2. Pegs, fins, and spikes driven into prepared recesses in the bone
provide some rotational stability, but less than that obtained with
screws. The use of these other types of supplemental fixation devices
has declined as manufacturers have incorporated highly porous metal
coatings with improved initial press-fixation
3. Most modern modular acetabular components are A supplied with a
variety of polyethylene liner choices. Some designs incorporate an
elevation over a portion of the circumference of the rim, whereas
others completely reorient the opening face of the socket up to 20
degrees. Still other designs simply lateralize the hip center without
reorienting its opening face

63. • A locking ring is applied to the rim to prevent escape of the head.
• Indications for constrained liners include
1. insufficient soft tissues,
2. deficient hip abductors,
3. neuromuscular disease, and
4. hips with recurrent dislocation despite well-positioned implants.
• Constrained acetabular liners have reduced range of motion compared with
conventional inserts.
• Consequently, they are more prone to failure because of prosthetic
impingement.

64. Historically, metal rings, wire mesh, and other materials have been used to improve
acetabular fixation.
These devices were intended to reinforce cement, and generally their longterm
performance was poor.
The reconstruction ring provides immediate support for the acetabular component
and protects bone grafts from excessive early stresses while union occurs. These
devices are commonly referred to as antiprotrusio rings and cages.

65. Alternative Bearings
• Osteolysis secondary to polyethylene particulate
debris has emerged as the most notable factor
endangering the long-term survivorship of total hip
replacements.
• alternative bearings have been advocated to
diminish this problem
• These are-
1. highly cross linked polyethylene –
2. metal-on-metal –
3. ceramic-on-ceramic –
4. Ceramic on Polyethylene

66. Highly Cross-Linked Polyethylene
• Higher doses of radiation(gamma or
electron,10mrad) can produce polyethylene with a
more highly cross-linked molecular structure.
• This material has shown remarkable wear
resistance.
• Only short-term data on the performance of highly
cross-linked polyethylenes are presently available
• Diadvantage -lower fracture toughness and tensile
strength

67. Metal-on-Metal Bearings
• Metal-on-metal implants seem to be tolerant of high impact
loading, and mechanical failure has not been reported.
• wear rates less than 10 mm/y for modern metalon-metal
articulations
• But there remains major concern regarding the production of
cobalt and chromium metallic debris, and its elimination from
the body.
• metal-on-metal (MOM) bearings have a ‘suctionfit’ less
chance of dislocation.
Diametral clearance refers to the gap between the two
implants at the equator of the articulation and may be the
most important variable affecting wear of the couple. Smaller
clearances tend to produce fluid film lubrication and reduced
wear

68. Complication of metal on metal:
1. Metal ions are excreted in the urine. Impaired renal function can result
in large increases in serum levels of cobalt and chromium.
2. Willert described a delayed-type hypersensitivity reaction in
approximately 0.3% of patients with metal-on-metal hip arthroplasties.
3. Local tissues are characterized by a perivascular lymphocytic infiltrate
on biopsy, and the histologic presentation has been termed aseptic
lymphocytic vasculitisassociated lesion (ALVAL).
4. More recently, various adverse local tissue reactions have been
reported in association with metal-on-metal bearings.
Patients present with a spectrum of findings,
• including pain,
• periarticular fluid accumulation,
• solid mass formation (or so-called pseudotumor), and,
• rarely, extensive tissue necrosis,
• including the hip abductors.
• The phenomenon appears related to wear debris and corrosion
products.

69. Ceramic-on-Ceramic Bearings
• Alumina ceramic has many properties that make it
desirable as a bearing surface in hip arthroplasty
• high density- surface finish smoother than metal
implants
• The hydrophilic nature- ceramic promotes
lubrication • Ceramic is harder than metal and more
resistant to scratching from third-body wear particles.
• The linear wear rate of alumina-on-alumina has
been shown to be 4000 times less than cobalt-
chrome alloy– on–polyethylene.
• Ceramic-on-ceramic arthroplasties may be more
sensitive to implant malposition than other bearings.

70. Complication of ceramic on ceramic :
1. Impingment between femoral neck and rim of
acetabulam
• Causes: dislocation,
• accelerated polyethylene wear,
• acetabular component loosening, and
• liner dislodgment or fracture.
2. Malposition
3. Microseparation in swing phase produces
squaking noise.
4. Notching b/t metal femoral head by hard
ceramic

71. Oxidized zirconium (OXINIUM, Smith & Nephew, Memphis, TN)
is a zirconium metal alloy that is placed through an oxidation
process to yield an implant with a zirconia ceramic surface.
The enhanced surface is integral to the metal substrate and
not a surface coating.
So-called ceramicized metals are not susceptible to chipping,
flaking, or fracture as are other ceramics.
Ongoing investigation with composites of alumina and
zirconia ceramic (BIOLOX delta, CeramTec GmbH, Plochingen,
Germany) holds promise for further improvement in the
material properties of these implants.

73. CONTRAINDICATIONS TO TOTAL HIP ARTHROPLASTY
1. Absolute contraindications for total hip arthroplasty include
active infection of the hip joint or any other region and any
unstable medical illnesses that would significantly increase the
risk of morbidity or mortality.
2. Other relative contraindications include morbid obesity,
severe dementia, tobacco use, severe osteoporosis, untreated
skin conditions such as psoriasis, and absence or relative
insufficiency of the abductor musculature.
3. Asymptomatic bacteriuria has not been associated with
postoperative surgical site infections and should not be
considered a contraindication.
4. Although perioperative glycemic control seems important,
hemoglobin A1c levels are also not reliable for predicting
postoperative infection.
5. According to Charnley, total hip arthroplasty can be done in
the presence of a chronic, low-grade infection in the opposite
hip

74. EVALATION BEFORE SURGERY
1. Evaluate whether pain is sufficient to justify surgery.
2. Assess patient’s general condition (thorough medical
examination with laboratory test is must)
3. Investigate for any ongoing infection
4. Physical examination of spine, both lower limbs, soft tissue
around the hip.
5. Assess the strength of abductor mechanism
6. Any fixed flexion deformity assessed.
7. Limb length
8. Neurological status
9. When both the hip and knee are arthritic usually hip
should be operated first because THR alters the knee
mechanics.
10. If bilateral involvement present operate on most painful
hip first and after 3 months operate on the other side.

75. ROENTEGENOGRAPHIC EVAL U ATION
• 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.

76. Templating
1. • Draw horizontal lines: one joining both IT and other
joining both lesser trochanters. Measure the limb length
discrepancy as the difference in the length of lesser
trochanter .
2. Acetabulum :place acetabular template on the film and
select a size that closely matches the contour of the pts
acetabulam
3. Medial surface of the cup is at tear drop and inferior limit is
at the level of obturator foramen
4. Femur : select a size that most precisely matches the
contour of proximal canal with 23mm of cement
mantle.select a neck length so that the diff in the height of
femoral and acetabular centre is equal to LLD
5. Mark the level of anticipated neck cut and measure its
distance from lesser trochanter. template the femur
similarly in lateral view

77. THANK YOU 