Hip implants are used to replace damaged or diseased hip joints. The document discusses the history and development of hip implants from the 1950s onwards. It describes the key figures like Sir John Charnley who pioneered total hip arthroplasty. The anatomy of the hip joint and biomechanics considerations for implant design are outlined. Different types of femoral and acetabular components including cemented, cementless, and alternative bearing surfaces are explained. Indications, contraindications and risks of hip replacement surgery are also summarized.

1. Hip Implants
Dr.S.M.Muhammad Thahir MBBS., DNB(Ortho).,
M.N.A.M.S(Ortho)., M.Ch(Ortho).,

2. INTRODUCTION :
• Total hip arthroplasty is an
operative procedure in which
the diseased and destroyed
hip joint is resected and
replaced with a new bearing
surface.
• Patients with arthritis can now
look to THA with the object of
maintaining stability, while
relieving pain, increasing
mobility and correcting
deformity.
• MOST SIGNIFICANT BREAK
THROUGH OF THE 20Th
CENTURY

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 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

6. ANATOMY OF HIP JOINT

7. • The 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 joint
• The 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.

8. • Hip joint is unique in having a high degree of both
stability as well as mobility
• The stability or strength depends upon :
– The depth of acetabulum which is increased by
the acetabulur labrum.
– The strength of the ligaments and the surrounding
muscles.
– Length and obliquity of the neck of femur which
increases the range of movement

9. Neck shaft angle or angle of
inclination
• It is the angle between
the axis of the femoral
neck and the long axis
of the femoral shaft.
• On average, it is 135
degrees in the adults

10. Anteversion or angle of femoral
torsion
• Refers to the degree of
forward projection of
femoral neck from the
coronal plane of the
femoral shaft.
• In an adult, it is about
10-15 degrees

11. APPLIED BIOMECHANICS
• The total hip component must withstand many
years of cyclical loading equal to atleast 3 to 5
times the body weight and at time they may be
subjected to overloads of as much as 10 to 12
times the body weight
• So, the basic knowledge of biomechanics of the
THR and hip is necessary to properly perform the
procedure, to successfully manage the problems
that may arise during and after surgery, to select
the components.

12. Head and nec k diameters :
• The neck with the smaller
head tends to impinge on the
edge of the cup during a
shorter arc of motion which
tends to loosen the
components and dislocate the
joint.
• The deep socket and beveled
edges and the greater
diameter of the head in
comparison to the neck are
the features that allow a
greater range of motion.

13. Coefficient of friction and frictional
torque :
• CE of friction is the measure of the resistance
encountered in moving one object over the
other.
• It depends on the material used, the finish of
the surfaces ,temperature and the lubricant.
– CE for normal joint- 0.008 to 0.02.
– CF of metal on metal - 0.8
– CF of metal on HDPE (High density poly
ethylene) - 0.02

14. • A frictional torque force is
produced when the
loaded hip moves through
an arc of motion. It is
product of the frictional
force times the length of
the lever arm i.e., the
distance of given point on
the surface of the head
moves during arc of
motion.

15. • Frictional force depends
on coefficient of
friction, applied load
and also on the surface
area of contact
between the head and
socket.
• FT will increase with
large size head.
• Theoretically it causes
loosening of
components.

16. 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 :
Abrasive-THR
Adhesive -THR
Fatigue - TKR

17. 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.

18. • Wear is difficult to measures accurately, it may
be measured by depth of penetration of the
head with in the cup or the volume of debris
produced or by a change in the weight of the
polyethylene
• Newer methods- digitized x-rays and computer
assisted wear measurements
• higher in younger and more active male patients.
• Wear of more than 4 mm may result in neck
impingement on the edge of the cup and
secondary loosening of the acetabulum.

19. 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.

20. • Most common reasons for total hip
replacement:
• Osteoarthritis 60 %
• Rheumatoid arthritis 7 %
• Fractures/dislocations
11 %
• Aseptic bone necrosis7 %
• Revision 6 %
• Other
9%

21. Common Causes of Hip Pain and Loss of
Hip Mobility
Osteoarthritis
•
Usually occurs after age
50 and often in an
individual with a family
history of arthritis. In this
form of the disease, the
articular cartilage
cushioning the bones of
the hip wears away. The
bones then rub against
each other, causing hip
pain and stiffness.

22. Causes (cont’d)
Rheumatoid Arthritis
• a disease in which the
synovial membrane
becomes inflamed,
produces excessive
synovial fluid, and
damages the articular
cartilage, leading to pain
and stiffness.

23. Causes (cont’d)
Traumatic Arthritis
• Can leads to a serious hip
injury or fracture. A hip
fracture can cause a
condition known as
avascular necrosis. The
articular cartilage becomes
damaged and, over time,
causes hip pain and
stiffness.

24. Osteoarthritis
Fracture

25. 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.

26. Hip Replacement Components
•
Acetabular component consists of two components
– Cup - usually made of titanium
– Liner - can be plastic, metal or
ceramic
• Femoral components
Head
Neck
stem

27. 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 (vertical offset)
-Medial head stem offset ( horizontal offset)
-Version of the femoral neck (anterior
offset)

28. • Vertical offset- 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.
• Medial offset if inadequate, shortens the
moment arm – limp, increase, bony
impingement and dislocation.
• Excessive medial offset –increase stress
on stem and cement which causes stress
fracture or loosening.
• Version of the femoral neck : important
in achieving stability of the prosthetic
joint. The normal femur has 10-15
degree of anteversion.

29. CLASSIFICATION OF TOTAL HIP FEMORAL
COMPONENTS :
• Cemented :
Charnely,Matche Brown,Muller ,alandruccio ,Aufranc – Turner
,Sarmiento,Harris
• Non cemented –
Press Fit :
Judet ,Lord ,Sivash ,
Porous Metal : Harris ,Galante,Hydroxyappatite coated
• Bipolar--Bateman ,Gilibertz ,Talwalkar
• Ceramic –Mittelmeir
• Polyacetate -Bombelli Mathes
• Custom made
• Modular System

30. FEMORAL COMPONENTS USED WITH CEMENT

31. Cemented type

32. • 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

33. CEMENTLESS STEMS WITH POROUS SURFACES

34. Basic principle
• Based on the principle-bone ingrowth from
the viable host bone into porous metal
surfaces of implant.
• Indications for cementless components
involves
1.primarily active young patients
2.and revisions of failed cemented
components.

35. • Two prerequisites for bone ingrowth
1.immediate implant stability at the time of surgery
2.and intimate contact between the porous surface
and viable host bone
• Implants must be designed to fit the endosteal
cavity of the proximal femur as closely as
possible.
• In general, the selection of implant type and size,
as well as the surgical technique and
instrumentation, must all be more precise than
with their cemented counterparts

36. Porous Coated Implants

37. Current porous stem designs
• 1.titanium alloy with a porous surface of
commercially pure titanium fiber-mesh or beads
• and (2) cobalt-chromium alloy with a sintered
beaded surface.
• 2 shapes- Cementless total hip stems are of two
basic shapes: straight and anatomical
• The aim of both types is to provide optimal fit
both proximally and distally and thereby achieve
axial and rotational stability by virtue of their
shape

38. Types of porous coated stems
• Circumferential porous coating-first
generation femoral stems
• Extensive coated stems
• Proximally coated stem – twice the incidence
of thigh pain(stem tip abutment on the
anterior cortex of femur)
• Tapered femoral stems
• Stems with hydroxyapetite coatings

39. NON POROUS CEMENTLESS FEMORAL COMPONENTS
• nonorous femoral
implants have surface
roughening that provide a
macrointerlock with bone
• No capacity for bone
ingrowth but provides
lasting implant stability
• With the concerns about
fatigue strength, ion
release and adverse
femoral remodeling, these
non porous stems came
into use over porous
stems

41. Advantages of cementless femoral stem
prosthesis
• No cement required and problem related to
cement to bone and cement implant interface
reduced
• In young active patients
• Decreased incidence of asceptic loosening
• Less bone destruction
• Circumferential porous coating of proximal stem
provide effective barrier to ingress debris particle
and thus limit early development of osteolysis of
distal stem

42. 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.
• optimum position for the prosthetic socket which
should be inclined 45⁰ or less to maximize
stability of the joint.(normal 55⁰)
Types :
• Cemented acetabular components.
• Cementless acetabular components.
• Custom made acetabular components

43. CEMENTED ACETABULAR COMPONENTS
• Original sockets- thick walled polyethylene cups.
Vertical and horizontal grooves on external surface to
increase stability within the cement mantle
• 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.
• used in elderly patients, tumour reconstruction and
the circumstances with less chances of bony ingrowth
as in revision THR.

44. Cementless Acetabular Components
• Most cementless
acetabular components
are porous coated over
their entire
circumference for bone
ingrowth
• Fixation of the porous
shell with
transacetabular screws

45. • Pegs and spikes driven
into prepared recesses
in the bone provide
some rotational stability
but less than that
obtained with screws.

46. • ZTT socket
Hemispherical , porous
coated cup designed
with dome screw holes
and transacetabular
screws for stability. Six
peripheral screw holes
provide choice of screw
locations for additional
stability and also lock in
the polyethylene insert.

47. Two techniques involved
1.Initial stability of the metal shell against the
acetabular bone using screws, spikes , lugs, or fins
2. Stratch fit- underream the acetabular bone bed
by 1-2 mm and use the roughness of the outer
surface of metal shell to achieve scratch fit
• Expansion cup method-Cup diameter is reduced
with with a special instrument , cup then
implanted and then allowed to return to initial
diameter.

48. polyethylene liner
• Most modern modular acetabular components are
supplied with a variety of polyethylene liner choices
• The polyethylene liner must be fastened securely to
the metal shell.
• Current mechanisms include plastic flanges and metal
wire rings that lock behind elevations or ridges in the
metal shell, and peripherally placed screws
• in vivo dissociation of polyethylene liners from their
metal backings has been reported micromotion
between the nonarticulating side of the liner and the
interior of the shell may be a source of polyethylene
debris generation, or “backside wear.”

49. 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-highly cross linked polyethylene
-metal-on-metal
-ceramic-on-ceramic
-Ceramic on Polyethylene

50. 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

51. 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
(J Bone Joint Surg [Br] 2003;85-B:650-4)

52. 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. (J
Bone Joint Surg [Br] 2003;85-B:650-4

53. 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.

54. Operation
Removing the Femoral Head
• Once 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.

55. Reaming the Acetabulum
• After 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.

56. Inserting the Acetabular Component
• A 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.

57. Preparing the Femoral Canal
• To 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.

58. Inserting Femoral Stem
• Once the size and
shape of the canal
exactly fit the
femoral component,
the stem is inserted
into the femoral
canal.

59. Attaching the Femoral Head
• The metal ball that
replaces the femoral
head is attached to
the femoral stem.

60. 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.

61. COMPLICATIONS :
•Inherent to any major surgical
procedure in elderly patients.
•Specifically related to the procedure of
THR:
LATE
EARLY
Nerve injury
Hemarthrosis/vascular injury
Thromboembolism
Bladder injuries
INDEPENDENT OF TIME
Infection
Dislocation
Trochanteric non union
Femoral fracture
Limbs length discrepancy
-Loosening
-Component failure
-Osteolysis
-Heterotrophic
ossification

62. Dislocation or subluxation :
• Can occur in 3 %
Causes :
• Excess retroversion or
ateversion
• Small size head,
• Laxity of the soft tissue
around the joint.
• Insufficient offset.
Treatment :
Reduction by : Bigelows or
Stimsons method

63. Heterotopic ossification :
• Most commonly develops
in male patients who have
been operated for
anklyosing spondylitis
• Cause is unknown
• Loss of motion is the
predominant functional
limitation
Management :
• Prophylaxis: Diphosphates
• Low dose NSAIDs,
indomethacin 75mg/day x
6 weeks
• Radiotherapy

64. 9. Loosening :
• Femoral and acetabular loosening are the most serious
femoral and acetabular long-term complications.
• Most common indications for revision arthroplasty.
Cemented femoral loosening :
• Loosening of a femoral stem as defined as radiographically
demonstrable change in the mechanical integrity of the
load carrying cemented femoral component.
• Loosening is present if a radiolucent zone more than 2 mm
wide is seen. Especially if noted about the entire cement
mass and if it is increased progressively in width.

65. BIOMECHANICAL CONSIDERATIONS IN THR :
• Lengths of the lever arm can are surgically
changed to approach r ratio of 1:1 (which reduces
the hip total load by 30 % ).
• Abductor lever arm can be increased either by
increasing the medial offset of the femoral
component or lateral / distal reattachment of
greater trochanter.
• Joint reaction forces are minimal if hip center is
placed in anatomical position.
• Adjustment of neck length is important as it has
effect on both medial offset and vertical offset.
Neck length typically ranges from 25 to 50 mm.

66. • Femoral components must be produced with a
fixed neck shaft angle typically about 1350.
• Restoration of the neck in coronal plane
Increased anteversion – anterior dislocation
Increased Retroversion – posterior dislocation
• Socket depth and beveled edges and greater
diameter of head in comparison of neck allow
greater range of motion.

67. •Neck diameter should approach that to make
neck stronger especially with small femoral heads.
•Frictional torque of small head will be less
compared to larger head.
•Increasing stem length and cross sectional area
increases the stress in the stem.
•Any loading of proximal medial neck likely to
decrease bony resorption and reduces stresses on
cement.
•Loose fitted stem – increase stresses in proximal
femur.

68. Cementless femoral stem :
• Fixation by bone ingrowth is defined as an implant
with minimal or no opaque line formation around
the stem.
• An implant is considered to have a stable fibrous
ingrowth when no progressive migration occurs
but an extensive radio-opaque line forms around
the stem. These lines surround the stem in parallel
fashion and are separated from the stem by a
radiolucent space upto 1 mm wide.
• An unstable implant is defined as one with
definitive evidence of either progressive migration
within the canal and is atleast partially surrounded
by divergent radio-opaque lines that are more
widely separated from the stem at its extremities.

69. Acetabular loosening :
• In general it is agreed that the acetabular cup is
loose if a radiolucency of 2 mm or more in
width is present in all three zones.
• “The diagnosis of loosening is accepted in most
instances if the radiolucent zone about one or
both components is 2mm or more in width and
the patient has symptoms on weight bearing
and motion that are relieved by rest”.
• Solution is the revision THR

72. Depuy Pinnacle

73. ZIMMER DUROM

75. Resurfacing Arthroplasty
• Surface hip replacement consists of
resurfacing the acetabulum with a thin layer
of bearing surface, and replacement of only
the femoral head (not neck) with a metal ball.
• The ideal candidate for a resurfacing hip
arthroplasty is a young (<60 years old), active
individual, with normal proximal femoral
anatomy and bone density who might be
anticipated to outlive a conventional hip
arthroplasty.

76. • The procedure is more technically demanding
than conventional hip arthroplasty, particularly
with reference to exposure of the acetabulum
because the femoral head is not resected.
• Although the procedure is conservative of bone,
a more extensile soft-tissue dissection is required
for adequate exposure. Resurfacing of the
femoral head alone as a hemiarthroplasty may
be valuable in young patients with osteonecrosis.

78. Thank You