Pelvic stabilizing osteotomy (PSO) is a surgical procedure used to treat hip instability. It involves performing a valgus osteotomy of the proximal femur and sometimes a varus osteotomy of the distal femur. This realigns the hip to improve biomechanics and stability. For patient Abonesh, who has a dislocated left hip, previous girdlestone procedure, and limb length discrepancy, a PSO may be a suitable option to reduce pain, equalize limb length, and improve hip function and gait. Careful preoperative planning including measurement of adduction contracture and overcorrection angle is required to determine the degree of valgus angulation needed at the proximal osteotomy

1. Pelvic Stabilizing Osteotomy
(PSO)
CURE Ethiopia Children's Hospital &
Soddo Christian Hospital
By: Tewodros Asegie (BLH-OSR III)
October 27, 2017
January 16, 2018

2. Introduction
• PSO: hip bypass procedure where upper femur is
bent at an angle that stabilizes the connection
between the femur and pelvis to allow walking
with less limp
• Salvage of damaged hips for whom arthrodesis or
arthroplasty not appropriate
• Successful PSO:
– Reduces limp,
– Equalizes LL and,
– Facilitates a more Energy-Efficient gait

3. Basic Principle and Goal
• Enhance femoro-pelvic stability by PF valgus
osteotomy,
– Increase weight-bearing surface between
periacetabular region and residual upper femur and
– Minimize excessive pelvic drop during single limb
stance
• Improve hip biomechanics by displacing the
center of gravity medially, which results in an
improvement in the mechanical efficiencies of
Abductor Muscles

4. History
• Bouvier in 1838 described the technique of PSO
for CDH
• Lorenz:
• Valgus osteotomy + med and prox displacement of the shaft
of femur
– Limitation of movement
• Schanz:
• Valgus, and sometimes extension, position to the distal
femoral segment
– Increased pelvic stability
• Both techniques induced limitation of movement

5. • Milch: expanded the concept and
popularized the PSO in the United
States during the mid-20th century
– (β)- postosteotomy angle
predicts abutment to pelvis
when its greater than pelvic
inclination angle (α)
– Excessive difference
restriction of movement
and secondary disability
• Recommended post-
osteotomy angle should lie
210°-240°

6. Limitations Of Traditional PSO
• Optimal extent of angulation is difficult to
achieve:
– If the angle is too large:
• Excessive genu valgum,
• Fixed pelvic obliquity, and
• Impingement pain on adduction of the lower extremity
to the neutral position may ensue
– If the angle is too small:
• Insufficient improvement in hip biomechanics, and
• Most importantly, Remaining LLD cannot be addressed

7. Ilizarov Hip Reconstruction
• Early mid 1970s
• Modified form of PSO, which combines distal
femoral osteotomy for concomitant
lengthening and varus angulation

8. • Ilizarov provided a solution through a second,
more distal osteotomy
– Enable a proximal valgus osteotomy large enough
to eradicate any degree of adduction in the hip
(and thereby eliminate the T-gait) but, through
the distal varus osteotomy, to achieve parallelism
of both legs

9. Indications
• Hip Instability: Severe Dysplastic Acetabulum
• DDH: neglected, unsuccessfully treated
• Traumatic hip dislocation with instability
• Paralytic or spastic dislocation (postpoliomyelitis, cerebral
palsy, muscular dystrophy)
• Femoral head and neck absence: partial or total
• Severe sequelae of septic arthritis (Choi type IV)
• Skeletal dysplasia (SED, Morquio, etc.)
• Severe AVN
• Post-Girdlestone resection arthroplasty

10. Relative Contraindications
• NOT performed in young children (Wolff’s law)
– Young children <12 yrs, . Rozbruch SR et al, 2005
• Rapid remodeling in 1 yr
• LLD
• Older patients when THR is better alternative
– No Specific recommendations for a cut-off age
not possible
• Chronic paralytic hip dislocations in non-
ambulating patients

11. Planning
1. Clinical
2. X-ray
3. Translating both findings

12. A. Clinical Planning
1. Adduction contracture, Arc of
abduction/adduction, Maximum adduction?
• Flexing the hip over the unaffected or Contralateral hip
abducted over the edge of the examining couch
(unilateral)- better
• Unstable hip or abductor insufficiency pelvic obliquity
is equivalent to an adduction of that hip
• Measuring maximum adduction is to provide a basis
for the size of valgus osteotomy

13. 2. Direction and degree of rotation when
maximally adducted?
• Movement of limb as it maximally adducted, foot
progression angle as pt walks
i. Normal foot progression angle but the limb externally
rotates as it is adducted-Needs to compensate during
osteotomy
ii. Abnormal foot progression angle – Calculate derotation
angle

14. 3. FFD and arc of flexion/extension?
– FFD can be addressed at proximal osteotomy site
4. Contralateral hip?

15. B. X-ray Planning
• Three radiographs:
• Standing AP view of both lower limbs (preferably a
parallel beam scanogram),
• Pelvis AP view with
– Maximum abduction affected hip and
– Fully adducted affected pelvis

16. • Document:
• Presence of any deformities of
femur and tibia
• Hip pathology
• Estimate of LLD

17. Abduction X-Ray
• Reveals adduction contracture

18. Max Addn X-ray

19. • Position of the pelvis and
of the weight-bearing
limb in single stance that
serves as a reference in
planning for a pelvic
support osteotomy
• Horizontal line to the
pelvis with the knee and
ankle joint inclinations
parallel to it and to the
ground are the reference
positions

21. C. Translating Findings
1. Proximal femoral osteotomy:
• Level,
• Degree and
• Direction of osteotomy
2. Distal femoral osteotomy:
• Level,
• Degree and
• Direction of osteotomy

22. Level of PFO
• Fully adduct femur
• Level situated between the
infracotyloid recess and the
ischial tuberosity
• Level can vary:
– Undiagnosed hip dislocations:
may be at a level coincident
with the superior border of
obturator foramen;
– Other scenarios: Lies with
projection of the ischial
tuberosity
• Long prox segment
advantage:abductor
mechanical benefits

23. Amount of Valgus
• Highly controversial
• Milch: Traditonal PSO recommends
• Postosteotomy angle 210-230 degree
• Mean PFO angle in different literature 35-60
degree
• IHR: irrespective of PF valgus overcorrection,
abduction deformity can be compensated by
DF osteotomy if it restores knee joint
inclination parallel to horizontal

24. • Paley: recommends
overcorrection 15-
25 degree in
addition to pelvic
drop angle
– Overcorrection
offsets the loss of
the valgus from
remodelling at the
osteotomy site

25. • Pafilas and Nayagam:
• Valgus Adduction = Max
Addn + Addn Contract + +
9 degree + Overcorrection
(30-40deg or 21-31
extravalgus)
• Choi et al:
• Recommend at least 25
degrees
overcorrection, and
>30 degrees in
preadolescents

26. • Overcorrection is entirely empirical in
anticipation of remodeling at the valgus
osteotomy and some atrophy of the soft
tissue interposed between the femur and
lateral pelvic wall

27. Amount of Extension
• Extension should be adjusted to correct hip
flexion contracture and pelvic tilt, and the
sacrofemoral angle
• FFC can be compensated for in the osteotomy
and this usually amounts to 20 degree

28. Amount of Derotation
• Clinicaly assessed
• Foot progression angle when walking and the
amount and direction of rotation when the
femur was fully adducted
• The sum of the two will be incorporated as a
derotation osteotomy either at the PF or DF

29. DFO Level
• Addresses:
– Excessive valgus of PFO
– Allows for derotation, and
– Lengthening as well

30. • Paley: CORA method which
utilizes an imaginary
proximal mechanical axis line
• proximal MAL corresponds
to a line perpendicular to the
horizontal pelvic line, passing
through the point of 1/3 to
1/2 the distance lateral to
the medial edge of the
proximal fragment
• Too proximally it can
medialise the entire limb
and vice versa

31. • IHR: presented a
formula that took into
consideration the
amount of PF valgus
and DF varus
angulation

32. • This level can be determined using image
manipulation software or using simple trigonometry

33. Amount of Varus
• Serves to bring the inclination of the knee
joint parallel with that of the horizontal line of
the pelvis
• Mean DF varus angulations varied: 10 and 22
degrees
• To maintain some overcorrection, we suggest
that the distal osteotomy is undercorrected
(the knee joint line left in some valgus created
by the proximal osteotomy);

34. Amount of Derotation
• Performed at the distal osteotomy instead of
the proximal

35. Amount of Lengthening
• Most reliable measurement is after PSO
• Woodblock or scanogram to obtain a level
pelvis
• Overlengthening is poorly tolerated

36. Where Is the Weight-bearing Fulcrum?
• Not absolute, nor a true joint or false
articulation
• The center of rotation seems to vary with the
position direction of motion of the lower
limbs and depends on the soft-tissue
interpositional weight-bearing surface
between the PF osteotomy and the pelvis

37. • When determining the
center of rotation during
adduction/ abduction
motion, the main fulcrum
is seemingly located
around the lesser
trochanter and not
around the apex of the
valgus angulation
adjacent to the ischial
tuberosity during passive
abduction and adduction

38. T-Gait after PSO
• 30.3% (0-62.5%)
– Abductor Insufficiency (preop atrophy or loss of
fulcrum during follow up)
• Inan et al.: correction of Trendelenburg sign
depended on the age at the time of operation
and the volume of the gluteus medius muscle

39. PSO to THR
• Still possible, although it is
a technically demanding
procedure due to the PF
deformity
• More complications are
present for patients with
hip instability due to septic
reasons
– Chen et al. : 14% rate of
infection after hip
arthroplasty in patients with
coxarthrosis due to previous
septic arthritis, and a 36%
rate of total complications

40. Implant Options
• Plate (locking)
• Monolateral
External
Fixator

41. • Retrospective, 21 hips of 20 pts, 13 neglected hip dislocation, 7
septic, 1 failed THR, age 12- 34(22.6), follow up 33.45months(16-45)
• Result:
• Harris score 48.3 t0 80.1
• Preop LLD 53.3 mm and mean proximal migration was 42.9 mm, reduced to 16
mm after an average lengthening of 63.3mm
• Trendelenburg gait disappeared completely in 13 of 21 hips and was improved
in 8 hips
• Conclusion: Pelvic support osteotomy is a good treatment option to
overcome hip instability asit improves pain and equalizes limb length

42. Literature Review

43. HBS: harris score before, HAS: after surgery

47. Abonesh Lemi, 17 F, ET34277
• Subj:
– Left hip deformity since 10 yrs old
– Severe pain in the right hip, lay in bed for the last 3 yrs
– Had no hx of previous treatment
• Obj:
– Hip;
• Gait: Severely antalgic,
• LLD = 4 cm,
• FFD of hip = 10 degree,
• Flexion = 90 degree,
• Minimal rotation,
• Fixed adduction = 15-20 degree,
– Knee: fine
• Ass: Lt degenerate/dislocated hip

48. X-Ray

49. 18/09/2017
• Done: Lt 1st stage hip Girdle Stone
– Approach: Anterior
– Rectus left intact
– Neck cut above LT

50. Post Girdlestone

51. 12/10/2017
• In the wards put on traction
• Wound healed without complication
• Done:
– Lt Schanz Osteotomy
– Approach: Lateral vastus elevating
– Prebent plate with 60 degrees applied
– Predrilled with 3 proximal screws
– Osteotomy at the level of ischium with 60 degree abduction of
hip
– Wedge excised and plated distally
– Anterior 4 hole recon plate applied
– Hip stable
– Wound closed in layers

52. Inraop: Max adduction

54. • Proximal screws
• Remove plate
• Osteotomy

59. Options of treatment for Abonesh in
Our Setup
• Treatment of hip instability in adolescents and
young adults:
– Greater trochanteric arthroplasty,
– THR
– Hip arthrodesis,
– Femoral osteotomy, and
– Girdlestone operation---unstable hip, crutches
for life
– PSO

60. Summary
• The aim in the treatment of patients with hip
instability is overcoming:
– hip pain,
– equalizing limb length deficiency,
– preventing limping,
– improving range of motion of the hip and thus
restoring hip stability whilst preserving the
biomechanical alignment of the extremity
• Milch: femoral head resection is an improvement
of PSO
• PSO is a possible option in Ethiopian set up too

61. References
• In Ho Choi, Tae-Joon Cho, etal, Recurrent
dislocations and complete necrosis: the role
of pelvic support osteotomy. J Pediatr
Orthop july/august,2013
• Dimitros Pafilas, Selvadurai Nayagam, The
pelvic support osteotomy: Indications and
preoperative planning. Strat Traum Limb
Recon, August 2008

62. • Thankyou

65. • Loss of parallelism was in effect an ‘abduction
contracture’
– Compensate with eversion of the foot and with
tilting of the pelvis (relative adduction of
contralateral hip)

66. Valgus Osteotomy
= Max Addn + Addn Contracture
• Brings shaft to vertical with 9 deg
overcorrection(a)
– Does not lateralise shaft or knee joint
sufficiently
• Overcorrection in the region of 30
deg is preferable to allow a shift of
the limb from the midline
– Produces an ‘abduction contracture’,
i.e. in order to stand with both legs
parallel, the patient has to tilt the
pelvis

67. • If a varus correction is produced at the distal
osteotomy, then the effect of this ‘abduction
contracture’ is lost (and so will any
overcorrection at the proximal osteotomy)
• overcorrection factor should be added to the
valgus correction at the proximal osteotomy
because a failure to do so will leave the entire
limb medialised and much closer to the
midline than the contralateral side

68. • overcorrection of 9 deg will leave the shaft of the
femur parallel to the vertical axis of the pelvis
• In view of this, we suggest that the
overcorrection performed at the proximal
osteotomy level should be greater than the 25
suggested by Choi et al to enable an abduction of
the shaft of the femur away from the midline
• An overcorrection of 30–40 brings the
postosteotomy angle of Milch close to the
recommended 240 deg

69. • X-ray parameters:
1. Distance of the centre of the contralateral knee to the
midline axis of the body (from the standing AP film of
both lower limbs)
2. Distance of the proposed proximal osteotomy site from
the midline axis of the body (from the AP film of the
pelvis with hip in maximum adduction
3. Proposed overcorrection—we recommend adding 30 of
extra valgus to the sum of the adduction range and
measured adduction contracture
• Nine degrees of this overcorrection will bring the femur parallel
to the vertical axis, and the remaining 21 will take the femur
away from the midline