FRACTURE FIXATION IN OSTEOPOROTIC BONE

Stephen Kates, MDHansjӧrg Wyss  Professor of Orthopaedic Surgery

Department of Orthopedics and RehabilitationAssociate Director, Center for Musculoskeletal

ResearchUniversity of Rochester Medical Center

Michael BlauthNorbert SuhmJorg Goldhahn

THE AMERICAN GERIATRICS SOCIETY

Geriatrics Health Professionals.

Leading change. Improving care for older adults.

AGS

LEARNING OUTCOMES

• Understand the factors influencing fixation in cortical and trabecular bone affected with osteoporosis

• What implant characteristics help with fixation?

• What aspects of surgical fixation are important?

• Understand basic metabolic bone work-up

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DEFINITIONS

• Insufficiency fracture: bone fails with normal weight-bearing

• Fragility fracture: result of a fall from a standing height or less

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CONTENTS

• Osteoporotic cortical bone Biomechanical properties Choice of implants Surgical technique

• Trabecular bone Biomechanical properties Choice of implants Surgical technique

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CONTENTS

• Osteoporotic cortical bone Biomechanical properties Choice of implants Surgical technique

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BONE MASS CHANGESDURING LIFE

• Peak bone mass is reached at age 25

• Heredity

• Medications

• Diet, tobacco, and alcohol

• Race / weight

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CONTENTS

• Osteoporotic cortical bone Biomechanical properties Choice of implants Surgical technique

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LOCKED-PLATE PRINCIPLE

Slide 8

by bending load

PULLOUT OF REGULAR SCREWS

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SHEARING CONVENTIONAL PLATE OR SCREW DOWN

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RESISTANCE AGAINST BENDING LOAD

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RESISTANCE AGAINST BENDING LOAD IN LOCKED PLATE

Plate-screw connectionis solid

Screw-bone interfaceFails as a unit

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CONTENTS

• Osteoporotic cortical bone Biomechanical properties Choice of implants Surgical technique

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UNI- VS. BICORTICAL SCREW FIXATION

female

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Thin cortices: choose screw diameter as large as possible

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FAILURE WITH UNICORTICAL SCREWS

10 months postop.

5 days later

Slide 16

+6%

+18%

+36%

0

100

200

300

400

500

600

Load (N)

4.5 mm Cortex, bicortical

5.0 mm Locking, bicortical

4.0 mm Locking, bicortical

4.0 mm Locking, unicortical

BIOMECHANICS: NORMAL BONE

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+17%

+82% +91%

0

100

200

300

400

500

600

Load (N)

4.5 mm Cortex, bicortical

5.0 mm Locking, bicortical

4.0 mm Locking, bicortical

4.0 mm Locking, unicortical

BIOMECHANICS:OSTEOPENIC BONE

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BRIDGING WITH LOCKED IMPLANT

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CONCEPTS OF PLATE FIXATION IN OSTEOPOROTIC BONE

• ? compression technique

• Bridge plating useful

• Neutralization plates useful

• Long plate for bone protection

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CONTENTS

• Trabecular bone Biomechanical properties Choice of implants Surgical technique

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OSTEOPOROSIS

Normal bone Osteoporosis

In osteoporotic metaphyseal bone:•Fewer trabeculae for screws to engage

•Loss of critical bony interconnections

•Thinner internal support

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SIGNS YOUR PATIENT HASPOOR-QUALITY BONE

• Poor dentition: teeth are formed similarly to bone

• Multiple vertebral compression fractures• Previous hip, radius, or tibial plateau fracture• End-stage renal disease• On steroid therapy• Anticonvulsant use

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OSTEOPOROTIC TRABECULAR BONE:CLINICAL CONSEQUENCES

• Cut out• Loss of screw fixation• Spontaneous fractures

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CONTENTS

• Trabecular bone Biomechanical properties Choice of implants Surgical technique

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Lag screw Helical blade

Flat surface, increased area

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Less loss of bone with helical blade (right)

CHOICE OF IMPLANT:ONE FIXED ANGLE VS. MANY

One fixed angle with blade plate Multiple fixed angles, longer implant

Elderly woman who fell down one step

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VARUS COLLAPSEDUE TO LACK OF MEDIAL BUTTRESS

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CONTENTS

• Trabecular bone Biomechanical properties Choice of implants Surgical technique

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INTRA-OP IMPACTION

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Augmentation to Improve Screw Fixation

Enlarges the bone implant surface area

NOT FDA APPROVED!Slide 31

AUGMENTATION IN PRACTICE

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IF BONE IS VERY POOR, CONSIDER PROSTHETIC REPLACEMENT

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DON’T FORGET THE SOFT TISSUES

The wound must heal also

Skin is also 98 years old

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BASIC OSTEOPOROSIS WORK-UP: METABOLIC

• 25-OH vitamin D level

• Intact PTH level

• Calcium

• Phosphate

• TSH

• Albumin level

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RADIOLOGIC WORK-UP OF OSTEOPOROSIS: DEXA SCAN

• DEXA is gold standardT score is comparison to normal young boneZ score is comparison to peers

• Treat with fragility fracture and osteoporosis, osteopenia

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VITAMIN D REPLETION

• Vitamin D2 50,000 units POLevel 010 ng/dL: 3 times / weekLevel 1120 ng/dL: 2 times/weekLevel 2132 ng/dL: 1 time/week

• For 612 weeks, then recheck level

• Maintain with vitamin D3 1200 IU/day

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TREATMENTSAFTER VITAMIN D REPLETION

• For viable patients:BisphosphonatesSelective estrogen receptor modulators

(SERMs)Parathyroid hormone

• Don’t forget the bone itself: treat the osteoporosis or refer

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TAKE-HOME MESSAGES

• Age & bone quality affect cortical and trabecular bone in different ways

• Absolute stability often not possible

• Principles of fixation: Angular stability Fracture reduction Long bridging plates Enlarged surface area of implant / bone Augmentation Prosthetic replacement

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