the influence of posterior tilt of the femoral head on the failure...

The influence of posterior tilt of the femoral head on

the failure rate of femoral neck fractures. An

analysis of 164 undisplaced femoral neck fractures

treated by Gannet osteosynthesis

3th year’s research clerkship

by

J.H. Kalsbeek

S1805452

Faculty supervisor: Dr. J.M. Klaase

Second supervisor: Dr. A.D.P. van Walsum

Medisch Spectrum Twente, chirurgical department

2

Abstract

The influence of posterior tilt of the femoral head on the failure rate of femoral neck

fractures. An analysis of 164 undisplaced femoral neck fractures treated by Gannet

osteosynthesis.

Introduction: Failure rates of the so called undisplaced femoral neck fractures (FNF) vary

from 4-23%. Literature states that undisplaced FNF always should be treated by internal

fixation. The classification in undisplaced and displaced FNF is most commonly performed

by the Garden classification. This classification is solely based upon the AP radiographs.

Consequently the tilting of the femoral head in the anterior and posterior direction is not

included in this classification. Over the years there have been many studies to identify pre-

and post-operative predicators for failure. Yet posterior tilt, also known as retroversion or

anterior angulation, of the femoral head as a predictor is only described by several authors.

This study investigates two different methods to measure posterior tilt of the femoral head and

its influence on the failure rate of undisplaced FNF.

Patients and methods: The posterior tilt of 164 undisplaced FNF treated by Gannet

osteosynthesis were measured on the lateral X-ray of the hip using the Lateral Garden Angle

(LGA) and the Posterior Tilt Measurement (PTM). Correlation between posterior tilt of the

femoral head and the failure rate after Gannet osteosynthesis was assessed. Furthermore an

intra- and inter observer reliability study was done with the two different methods to assess

the validity of these measure methods.

Results: The overall failure rate was 5.5%. No correlation could be found between the

posterior tilt of the femoral head and the failure rate if it was measured according to the LGA

(P=0.366). If the posterior tilt was measured using the PTM a larger angle was associated

with a higher failure rate (P=0.030). Retroversion of ≥20° measured using PTM is associated

with a 4 times higher failure rate (OR = 4.286 (CI 95% 1.092 – 16.826) (P-value = 0.037)).

The intra and inter observer reliability of the LGA was 0.765 and 0.601(P <0.001). For the

PTM the intra and inter observer reliability was 0.790 and 0.773 (P <0.001).

Conclusion: The Lateral Garden Angle should not be used to measure posterior tilt because its

validity is inferior to the Posterior Tilt Measurement. If the posterior tilt of the femoral head is

measured using the PTM it is associated with a higher failure rate. Posterior tilt of ≥20° can

be used as a significant predictor for failure in undisplaced FNF treated by Gannet

osteosynthesis. The introduction of the PTM may lead to a paradigm shift in the operative

treatment of the undisplaced FNF because it identifies that ‘stable’ FNF with a posterior tilt

greater than 20° in fact behave like unstable fractures. Therefore the indication for internal

fixation in the elderly patients will shift to a hip replacement if the posterior tilt of the femoral

head rises above 20°.

3

Samenvatting

De invloed van posterieure kanteling van de femurkop op de uitkomst van femurhals

fracturen. Een analyse van 164 stabiele femurhals fracturen behandeld met een Gannet

osteosynthese.

Introductie: Bij niet-gedisloceerde femurhalsfracturen faalt in 4-23% de therapie. Niet-

gedisloceerde oftewel stabiele femurhalsfracturen worden volgens de richtlijn behandeld

middels interne fixatie. De verdeling van gedisloceerde en niet-gedisloceerde

femurhalsfracturen wordt gedaan op basis van de Garden classificatie. Deze classificatie is

alleen gebaseerd op de voor-achterwaartse röntgenfoto. Hierdoor wordt kanteling van de

femurkop in het transversale vlak niet meegenomen in de classificatie. Enkele studies hebben

de invloed van deze posterieure kanteling, ook wel retroversie genoemd, op het falen van

osteosynthese therapie omschreven. Deze studie onderzoekt twee verschillende methoden om

de posterieure kanteling bij stabiele femurhalsfracturen te meten en zijn invloed op het falen

van de behandeling met Gannet osteosynthese.

Methode: Posterieure kanteling bij 164 stabiele femurhalsfracturen behandeld met Gannet

osteosynthese is gemeten volgens de ‘Lateral Garden Angle’ (LGA) en de ‘Posterior Tilt

Measurement’ (PTM). De invloed van de posterieure kanteling op het falen van de therapie is

geanalyseerd. Daarnaast is de validiteit van deze meetmethoden getest middels een intra- en

inter-beoordelaarsbetrouwbaarheid studie.

Resultaten:5,5% van de behandelingen faalde. Er werd geen verband gevonden tussen

posterieure kanteling en het falen van de therapie als deze gemeten werd volgens de LGA

(P=0,366). Als de posterieure kanteling werd gemeten volgens de PTM dan was een grotere

kanteling geassocieerd met een hogere kans op falen van de therapie (P=0,030). Posterieure

kanteling van ≥20° gemeten volgens PTM geeft een 4 keer grotere kans op falen van Gannet

osteosynthese therapie (OR = 4.286 (CI 95% 1.092 – 16.826) (P = 0.037)). De intra- en inter-

beoordelaarsbetrouwbaarheid van de LGA was respectievelijk 0,765 en 0,601(P<0.001). De

intra- en inter-beoordelaarsbetrouwbaarheid van de PTM was respectievelijk 0,790 en 0,773

(P<0.001).

Conclusie: De Lateral Garden Angle zou niet meer gebruikt moeten worden om posterieure

kanteling van de femurkop te meten omdat hij minder valide is dan de Posterior Tilt

Measurement. Als de posterieure kanteling wordt gemeten volgens de PTM dan is een grotere

kanteling geassocieerd met een hogere kans op falen van de behandeling. Posterieure

kanteling van ≥20° is een significante voorspeller voor falen van de Gannet osteosynthese

therapie bij niet-gedisloceerde femurhalsfracturen. Deze voorspeller kan leiden tot een

verandering van behandel logaritme welke vandaag de dag wordt gebruikt. Het laat namelijk

zien dat zogeheten stabiele femurhalsfracturen met een posterieure kanteling van de femurkop

van ≥20° zich in werkelijkheid gedragen als gedisloceerde, onstabiele femurhalsfracturen.

Daarom komen oudere patiënten met een stabiele femurhalsfractuur met een posterieure

kanteling van de femurkop van ≥20° in aanmerking voor een heuprothese in plaats van een

kopsparende behandeling.

4

Index

List of abbreviations………………………………………………………………….. 5

1. Introduction………………………………………………………………………… 6

1.1 Epidemiology of the hip fracture…………………………………………… 6

1.2 Anatomy of the hip ………………………………………………………… 6

1.3 Fracture healing…………………………………………………………….. 6

1.4 Classification of intracapsular femoral fractures…………………………… 7

1.5 Garden classification……………………………………………………….. 7

1.6 Therapy of the femoral neck fracture………………………………………. 9

1.7 Retroversion of the femoral head …………………………………………... 10

2. Patient and methods ……………………………………………………………….. 12

2.1 Study population……………………………………………………………. 12

2.2 Inclusion criteria……………………………………………………………. 12

2.3 Exclusion criteria…………………………………………………………… 12

2.4 Methods……………………………………………………………………... 12

2.5 Lateral Garden Angle……………………………………………………….. 12

2.6 Posterior Tilt Measurement…………………………………………………. 13

2.7 Primary outcome ……………………………………………………………. 13

2.8 Secondary outcome………………………………………………………….. 13

2.9 Definition of failure…………………………………………………………. 13

2.10 Statistics……………………………………………………………………. 13

2.11 Ethics……………………………………………………………………….. 14

3. Results………………………………………………………………………………… 15

3.1 Population……………………………………………………………………. 15

3.2 Posterior tilt of the femoral head…………………………………………….. 15

3.3 Intra- and interoberserver reliability ………………………………………… 17

4. Discussion……………………………………………………………………………. 18

4.1 Most important findings …………………………………………………….. 18

4.2 Garden classification………………………………………………………… 18

4.3 Failure rate…………………………………………………………………… 18

4.4 Lateral X-ray…………………………………………………………………. 18

4.5 Retroversion of the femoral head and failure rate …………………………… 19

4.6 Strengths and limitations…………………………………………………….. 20

4.7 Conclusion…………………………………………………………………… 21

4.8 Clinical relevance……………………………………………………………. 21

4.9 Recommendations …………………………………………………………… 21

References………………………………………………………………………………. 22

Acknowledgements …………………………………………………………………….. 24

Appendices……………………………………………………………………………… 25

5

List of abbreviations

AP – Anterior Posterior

AVN – Avascular Necrosis

CT – Computed Tomography

DLBP – Dynamic Locking Blade Plate

FNF – Femoral Neck Fracture

GAI – Garden Alginment Index

HZ – Hazard Ratio

LGA – Lateral Garden Angle

MCL – Mid-Collum Line

OR – Odds ratio

PTM – Posterior Tilt Measurment

RCL – Radius-Collum Line

RR – Relative Risk

TAD – Tip-Apex Distance

6

1. Introduction

1.1 Epidemiology of the hip fracture

In 1990 there were an estimated 1.66 million hip fractures worldwide. This number increases

over time due to different factors and the incidence in 2050 is estimated at 6 million

worldwide.1 Half of these fractures are femoral neck fractures. Also in the Netherlands there

is an increase in proximal femur fractures. From 1991 until 2004 there is an increase of 25%

in male patients and 18% in female patients with a proximal femur fracture. In 1991 15.196

patients were treated for a proximal neck fracture. In 2025 this amount is estimated at

23.900.2 88% of these hip fractures occur in elderly above 75 years.3 This can be explained by

different contributing factors, from which osteoporosis is probably the biggest. Other

contributing factors are lack of physical exercise, tendency to fall, neurologic or psychiatric

disorders and use of psychotropic agents. With the ageing of the Dutch population the number

of patients with hip fractures will increase further in the next decades.

1.2 The anatomy of the hip

To understand the pathology and treatment of femoral neck fractures a keen knowledge is

needed about the anatomy of the hip. The proximal femur exists of the femoral head, the

femoral neck and the greater and lesser trochanters. The surface of the femoral head is coated

with cartilage, except for the fovea. The neck-shaft angle is 130°±7° which varies trough life

but not between genders. The femoral neck is also anteverted in angle of 10° ± 7° to the

shaft.4 The cancellous bone of the proximal femur has an internal trabecular system. The

trabeculae form a pattern along the lines of stress within the bone. This allows the femoral

neck resist maximal stress with a minimum of bone mass. Surrounding the neck and head of

the femur is a strong and dense capsule which is proximally attached to the rim of the

acetabulum and the transverse acetabulum ligament. Distally the capsule is attached anteriorly

to the anterior intertrochanteric line and the greater trochanter and posteriorly to the femoral

neck. The complete femoral head and ventral side of the femoral neck and the half of the

dorsal side is positioned intracapsular.5

The vascular supply of femoral head comes from 3 different sources. The main supply of

arterial blood comes from two arteries: the medial and the lateral femoral circumflex artery.

These arteries originate from the deep femoral artery. From both circumflex arteries, which lie

extracapsular, subsynovial or retinacular vessels arise and form an intracapsular ring in the

hip joint. From this ring vessels originate and penetrate into the femoral head. These vessels

called lateral epiphyseal arteries, from which the lateral epiphyseal branch is the largest. This

branch supplies most of the blood to the femoral head.6 The second source is foveal artery of

the ligamentum teres, also called medial epiphyseal artery. This artery contributes to the

vascular supply of the femoral head but this is extremely variable and it perfuses rarely a

significant area of the head. The last source is the metaphyseal vessels that extend proximally

from the nutrient artery supply. Yet the blood supply from these vessels is also limited.4

1.3 Fracture healing

Fracture healing can be divided into primary (direct) and secondary (indirect) bone healing. In

contrast to secondary bone healing, primary bone healing skips the intermediate steps of bone

healing and progresses right to the remodeling phase. To acquire sufficient secondary bone

healing a cambium layer within the periosteum is needed. The majority of the surface of

bones in the body is covered with periosteum with exception of their intra-articular surface

and the carpal and tarsal bones. The FNF is an intra-articular fracture and the larger part of the

7

femoral neck is not covered with periosteum. Without this inner layer no callus can be formed

that is needed for secondary bone healing. Primary bone healing occurs without formation of

callus. It directly progresses to remodeling of the Haversarian system. A series of concentric

circles or tubes in the cortical bone with nerves and blood vessels. Yet this kind of fracture

healing depends on stable fixation and compression.

The femoral neck fracture (FNF) is one of the toughest fractures to heal. This is due to

different factors. For one the neck of the femur lies intra-articular its surface is not covered by

periosteum. Therefore the FNF heals by direct healing and needs an almost perfect anatomical

alignment to get proper healing.7

Furthermore FNF is an intracapsular fracture. After a FNF an intracapsular hematoma can

occur, which can limit arterial inflow or venous drainage.6 The intracapsular position of the

fracture also limits the blot clot formation due to the synovial fluid inside the capsule. This

prevents a contributing factor for bone healing.5

Also a FNF is devastating for the vascular supply of the femoral head. Avascular necrosis

(AVN) of the femoral head is major consequence after a FNF and occurs in 2-4% of the

undisplaced FNF and even in 9.3-16% of the displaced fractures.8-10 The viability of the

femoral neck depends on the blood supply to the head. This can be established by

preservation of remaining vascular supply due to optimal anatomical reduction and a stable

fixation that allows revascularization of the femoral neck and head.

For displaced fractures a proper reduction is of great importance. In displaced fractures

imported vessels such as the lateral epiphyseal can be kinked and give an impaired blood

flow. After a correct conducted and successful this impaired blood flow can be (partially)

restored.

1.4 Classification of intracapsular femoral neck fractures

There are several classification systems for the femoral neck fracture. Pauwels classification,

Garden classification and the AO classification are most commonly used.11 Pauwels

classification is based on the steepness of the fracture line. There are three types:

- Type 1: angle < 30°

- Type 2: angle between 30° and 50°

- Type 3: angle >50°

Pauwels suggested that an increase in vertical angle of the fracture line was related to an

increase of non-union or mal-union. Unfortunately over the years several studies showed there

is no correlation between Pauwels angle and non-union. Also there is a poor inter observer

reliability.12,13

The AO classification of femoral neck fractures is based on a combination of the level and

displacement of the fracture and the angle of the fracture:

- 31-B1 is subcapital, with slight displacement.

- 31-B2 is transcervical.

- 31-B3 is subcapital, displaced, non-impacted.

But the AO classification for intracapsular fractures has also a poor intra- and interobserver

reliability. It seems to be too complex to asses. It also has limited predictive outcome.14

1.5 Garden classification

The third and most popular classification is the Garden Classification.11 It was first described

by Garden in 1961. It is based upon the degree of displacement of the distal part of the

femoral neck. It classifies the FNF in 4 different types based solely on the Anterior-Posterior

(AP) X-ray15 :

8

Grade I is considered to be an incomplete fracture with impaction on the lateral side and

valgus angulation.

Grade II is a complete fracture without displacement in an anatomical stable position.

Grade III is seen as a complete fracture with partial displacement and varus angulation.

Grade IV is a complete fracture with full displacement. The capital fragment has returned to

its normal position in the acetabelum, and its medial trabeculae are in line with their pelvic

projections. (Figure 1)

Garden I and II fracture are considered to be undisplaced (stable) fractures and Garden III &

IV are displaced (unstable) fractures. Even though this classification is used widely there is

some controversy about the official Garden Classification. Several studies have shown there is

a rather large intra- and interobserver variability in the 4-grade Garden Classification.16-19 The

interobserver reliability improves if the classification is simplified into stable (Garden typ 1 &

2) and unstable (Garden 3&4).18-20

Furthermore is the addition of the lateral hip X-ray to the Garden Classification an ongoing

discussion. Studies showed that adding the lateral X-ray changes the management plan in

21.1-32.2%.17,21,22 This is contradictive with the results of Kumar et al. which showed 0%

change of management plan. Yet Kumar et al. only included two observers who did not

independently looked at the X-rays.23

Figure 1. Garden type I: an incomplete fracture with impaction on the lateral side and valgus angulation.(A)

Garden type II: a complete fracture without displacement in an anatomical stable position. (B)

Garden type III: a complete fracture with partial displacement and varus angulation. (C)

Garden type IV: a complete fracture with full displacement. (D) 24

The Garden Alignment Index (GAI) was introduced by Garden to objectify the position of the

femoral head after reduction. This index withholds the AP angle and the lateral angle of the

femur (AP angle/lateral angle). On the AP view the angle between the medial trabeculae of

the femoral head and the medial cortex of the femoral diaphysis is measured, which is around

160°. On the lateral view the central lines of the femoral head and neck are supposed to be in

9

a straight line, so 180°. Acceptable reduction is considered to be an angle of 155-180° on AP

and the lateral view.25,26

1.6 Therapy of the femoral neck fracture

There are several therapies used to treat a FNF, some are more used then others. Conservative

therapy does not play a big role in the treatment of FNF anymore. Several studies showed

surgical treatment is superior to conservative therapy.27-29Surgical treatment exists of two

main therapies, (hemi)arthroplasty and internal fixation of the FNF with an implant.

The choice of therapy depends on the stability of the fracture and the biological age of the

patient. The general therapy for undisplaced (stable) FNF, regardless the biological age of the

patient, is always internal fixation. Young patients (<65 years) with a displaced (unstable)

FNF are commonly treated by internal fixation as well. Elderly patients (>75 years) with

displaced FNF are treated by (hemi)arthroplasty.30,31 The treatment of young elderly (between

65 and 75 years old) is still under debate and is therefore referred as the ‘unsolved fracture’.32

Hemi arthroplasty was first used by Moore and Bohlman in 1940 for a patient with a recurrent

giant cell tumour.33After this hemi arthroplasty is also used for displaced femoral neck

fractures. Yet (hemi)arthroplasty has still a high rate of failure and complications. One year

mortality rate is 13-15%, 4-7% needs revision surgery, 3-9% of the hips experience

dislocation and patients suffer in 24-25% major complication such as deep infection,

pulmonary embolism, sepsis or a re-operation (not revision).34

Internal fixation is used in all undisplaced FNF and displaced FNF in biological young

patients. There are numerous implants available for internal fixation of the femoral neck as

seen in a Cochrane review by Parker.35 From which the Multiple parallel Screws and the

Compression Screw and Side-Plate are most popular.30 But the results of these widely used

implants are still unsatisfactory. The failure rate in undisplaced FNF is still 4-13% and AVN

of the femoral head occurs in 4% of the undisplaced FNF. In displaced FNF these numbers

are even higher. AVN occurs in 10-16% and the incidence of non-union is 30-33% in

displaced FNF.

Figure 2. AP and lateral X-ray of undisplaced femoral neck fracture of the right hip after DLBP fixation.

10

Recently a new implant is developed from which the first results were obtained. The

DLBP(dynamic locking blade plate), marked as the Gannet, is a new implant for internal

fixation for intracapsular hip fracture (Figure 2). These first results look promising with a

failure rate of 4% in undisplaced fractures and 13.5% in adequate reduced displaced

fractures.8,9

But there was something notable in the study with the undisplaced FNF(Garden type I & II).

From 6 of the failures (of the 149 patients), three of the failed fractures showed a posterior tilt

of the femoral of more than 20 degrees on the preoperative lateral X-ray as seen in Figure 3.

This is 50% of all failures. The question arises if you can call these undisplaced stable femoral

neck fractures really stable. Several studies investigated the true stability of the stable Garden

type I & II fractures.

Du et al. and Chen et al. showed with computed tomography (CT) that incomplete, impacted

Garden type 1 fractures can actually be complete fractures with a considerably large

displacement.36,37 Further Fu et al. showed that stable Garden type 2 fractures, although these

fractures supposed to be anatomical in line, all have a certain degree of spatial or 3-

dimensional displacement.38 But is a significant posterior tilt of the femoral head seen on the

lateral view also associated with a higher failure rate of the so called ‘stable’ Garden I and II

FNF after osteosynthesis?

Figure 3. AP X-ray of a Garden type 1 fracture. (A)Lateral X-ray of an undisplaced FNF with retroversion of

the femoral head. (B)

1.7 Posterior tilt of the femoral head

Posterior tilt, also known as retroversion or anterior angulation, of the femoral head is seen on

the lateral X-ray of the hip. If there is displacement in the transverse plane it is almost always

a posterior tilt of the femoral head due to the mechanism of the trauma and the anatomy of the

hip. Over the years several authors described the influence of posterior tilt on the outcome of

FNF if they are treated with osteosynthesis.

Alho et al. were the first to describe the correlation between retroversion and the failure rate

of FNF treated with internal fixation. They did not find a significant effect of posterior tilt on

the failure rate. Yet this study included 149 cases from only 13 were undisplaced.39

11

Conn and Parker showed in 2004 that a smaller Lateral Garden Angle (larger posterior tilt) in

undisplaced fractures is associated with non-union (mean = 162° vs mean = 172° in

uncomplicated fractures) but not associated with AVN (mean = 172° vs mean = 172° in

uncomplicated fractures).27

Clement stated in 2013 that the posterior tilt (defined as a LGA <170°) was a significant

predictor for failure of the fixation.40

In 2009 Palm et al. suggested a new method for measuring the posterior tilt because the

Lateral Garden Angle (LGA) would be too unreliable. With this new measurement for

posterior tilt (Posterior Tilt Measurement or PTM) they found that 56% of the patients with a

posterior tilt ≥20° needed reoperation (due to technical failures = fracture displacement, non

union, AVN, subsequent fractures around the implant, or cut-out of the implant) against 14%

reoperations in patients with a posterior tilt <20°. According to Palm this new measurement

method has an acceptable inter- and intra-reader reliability. The interclass coefficient (95%

CI) was 0.94 (0.91-0.97) and the intraclass coefficient varies between 0.95-0.97.41 This new

method to measure the posterior tilt has been used in several other studies. But the results are

contradictive. Riaz et al. and Bajada et al. found that posterior tilt measured using the PTM is

a significant predictor for failure in undisplaced FNF.42,43 But Lapidus was not able to

reproduce these results and concluded that posterior tilt could not be used as a discriminator

for fracture healing complications.44

The latest study regarding this topic was performed by Dolatowski and is published in March

2016. He measured the posterior tilt using Palms PTM of 322 undisplaced FNF. He divided

the fractures in 3 categories (<10°, 10-20°, >20°). The result showed that the group with a

posterior tilt >20° had a hazard ratio (HZ) of 3.4.45

Taking these previous studies into account there is no consensus about the effect of

retroversion of the femoral head on the outcome of internal fixation in FNF or which method

is valid to measure this angle. If the effect of posterior tilt is significant, the so called ‘stable’

fractures could perhaps qualify for classification and treatment as displaced (unstable) FNF.

This would change the treatment protocol for FNF we use today.

In this study an analysis was done of the correlation between the posterior tilt of the femoral

head and the failure rate in patients with a stable FNF after internal fixation using the Gannet

implant. Furthermore the conformity between the LGA described by Garden and the PTM

according to Palm is analyzed.

12

2. Patients and methods

2.1 Study population

A database was used with 468 patients with a FNF that were treated by internal fixation using

the Gannet implant. This data came from 5 different hospitals from within the Netherlands.

All patients were treated between 01-08-2010 and 01-01-2015.

The data from the patients was initially collected and assessed by their treating trauma

surgeons. These data included: sex, age, displaced/undisplaced classification, 4-grade Garden

classification, delay until operation, operation time, the Garden Alignment index (GAI) was

measured after reposition (an angle between 155-180° on the AP and lateral X-ray was

considered to be a good reduction), Tip-Apex Distance (TAD), 1 year impaction, primary

outcome(AVN, no-union, implant cut out), revision surgery, reoperation (for example due to

complaints about the implant), general operation complications, mobility patient preoperative

and 1 year postoperative (defined as: no walking aids, one crutch, two crutches, or a walker).

2.2 Inclusion criteria

Included were all patients with a FNF treated with a DLBP, irrespective of the age of the

patient.

2.3 Exclusion criteria

Patients with pathological fractures, concomitant fractures of the lower extremity,

symptomatic arthritis, local infection or inflammation, inadequate local tissue coverage,

morbid obesity and any mental or neurological disorder which would create an unacceptable

risk of fixation failure.

2.4 Methods

Classification of the FNF into displaced and undisplaced (2-grade Garden Classification) and

measurements of the preoperative LGA of the FNF has initially been conducted by 5 trauma

surgeons. All the fractures were also classified by the researcher. In case of any discrepancy

in the classification or measurement the case was reviewed and discussed with the second

supervisor.

Classification of patients according to a 2-grade Garden classification:

• Undisplaced, stable FNF – Garden type 1 & 2

• Displaced, unstable FNF – Garden type 3 & 4

A 2-grade Garden classification is used here because the inter and intra observer variability is

less in a 2-grade Garden Classification than a 4-grade Garden Classification.18-20

In all undisplaced fractures the anterior angle on the lateral view is measured according to the

Lateral Garden Angle.26

Besides LGA, the retroversion of the femoral head will also be measured using the Posterior

Tilt Measurement according to Palm et al.41

2.5 Lateral Garden Angle

This angle is measured according to Gardens description using the trabeculae on the lateral

view of the X-ray. The central axes of the femoral head and the neck normally lie in a straight

line 180°.(Figure 4)25,26

13

2.6 Posterior Tilt Measurement

The retroversion of the femoral head is determined by the angle between two lines, the mid-

collum line (MCL) and the radius collum line (RCL). The middle of the collum (femoral

neck) is determined by drawing three perpendicular lines across the narrowest part of the

collum, with 5 mm between each line. The RCL is drawn from the middle of the femoral head

to the intersection of the MCL and the caput circle. (Figure 4)41

2.7 Primary outcome

Correlation between failure and retroversion of the femoral head was assessed for both

measurements, LGA and PTM. Literature states that a posterior tilt of ≥20° is associated with

a higher failure rate. An analysis is done to estimate the influence of posterior tilt on the

failure rate.

2.8 Secondary outcome

Also an analysis will be done of the reliability of these two different measure methods by

doing an intra- and inter observer study done by 4 observers. 50 anonymized undisplaced FNF

were collected from one hospital. These fractures were randomized for 4 different CD’s. The

posterior tilt angle was assessed 4 times by 4 different observers (3 trauma surgeons and the

researcher) using the 2 different methods according to the schedule below. Al the trauma

surgeons are familiar with the LGA, still the definition according paragraph 2.5 was given.

The PTM was explained to all the trauma surgeons individually and the observers were

allowed to practice the PTM on 10 patients before they participated in the study. Also all the

observers were obliged to read the article of Palm.41

Table 1. Design intra- and interobserver reliability study

Time Week 1 Week 2 Week 3 Week 4

Observer 1 cd 1 cd 4 cd 3 cd 2




Measure method LGA1 PTM2 LGA1 PTM2 1LGA: Lateral Garden Angle 2PTM: Posterior Tilt Measurement

2.9 Causes for revision surgery

- Non-union: displacement of fracture or visible margins of the fracture line one year

postoperative.

- Avascular necrosis: defined using the Steinberg Classification from stage 2 and

upward.

- Failure of fixation: need for revision surgery due to non-union, avascular necrosis, cut

out of the implant.

Radiographic examples of these causes for revision surgery can be seen in appendix 1.

2.10 Statistics

Statistical analysis will be performed using SPSS v. 21 ((IBM Corp., Armonk, NY, USA) for

Windows 7. Baseline characteristics are displayed as mean with SD or median range for

continuous variables. Categorical variables are displayed as number with corresponding

percentage. Differences between healed and failed fractures in baseline characteristics were

tested with independent T-test or Mann-Whitney U test dependent on distribution of

continuous data. For categorical data this was performed with Chi Square test. To test

14

association between PTM <20° and ≥20° with failure a univariate logistic regression analyze

was performed. Potential confounders from table 3 that were associated with PTM and with

failure (P-value<0.15) were taken into account in the multivariate logistic regression analyses.

For analysis of the conformity of the two measure methods the intra class coefficients is

assessed using the method of Fleiss.46 Intra class coefficient was interpreted as follows:

excellent (>0.75), fair to good (0.40-0.75) and poor (<0.40).47 P-values less than 0.05 were

considered to be statistically significant.

Figure 4. Lateral Garden Angle (LGA) according to Garden is the angle between the trabeculae of the femoral

neck and the femoral head on the lateral X-ray.25,26 (A) The Posterior Tilt Measurement (PTM) according to

Palm is the angle (α) between the Mid-Collum Line (MCL) and the Radius Collum Line (RCL).41 (B)

2.11 Ethics

During this study an observation was done on already obtained X-rays. If the X-rays were

absence or inadequate no new X-rays were obtained. There was no contact with the included

patients. The data was anonymized. The included patients did not directly benefit of this

study, but this study will contribute to already existing knowledge on femoral neck fractures.

The measurements and analysis are in line with earlier performed studies in this research line

which permission was given by METC.

15

3. Results

3.1 Population

468 patients were treated for a hip fracture by Gannet osteosynthesis between 01-08-2010 and

01-01-2015 as seen in figure 5. All the fractures were reclassified by the researcher. In 46

cases there was discrepancy between the initial classification done by the treating trauma

surgeon and the researcher. All 46 cases were reviewed by the researcher and the supervisor

and consensus was reached in all the cases.

Of these 468 patients there were 12 pertrochanteric fractures, 258 displaced FNF and 198

undisplaced FNF. Of these 198 patients 8 patients were lost since they had follow up abroad

or in hospitals not attending to this study. 20 patients died during follow up. None of these

patients died as a result of the operation or a related complication. In the group with

undisplaced fractures 6 patients were excluded because 2 patients had concomitant fractures

of the lower extremity, from 1 patient no pre-operative X-rays could be retained and 3

patients had a mental and/or neurologic disorder. The mean age of the remaining 164 patients

with an undisplaced FNF was 68.5 years old (range 35-101) and 61.6% were female. 12

patients had post-operative malreduction. In 2 of these patients treatment failed. In total 9

patients (5.5%) the treatment failed and the patients needed a reoperation. 3 patients had

avascular necrosis seen on X-rays, 1 patient had a clinical suspicion for avascular necrosis

with non-union but not seen on the X-ray, 2 patients had non-union of the fracture, 3 patients

had cut out of the implant.

Figure 5. Flowchart population

3.2 Posterior tilt of the femoral head

The posterior displacement of the femoral head was measured by two methods. The PTM was

corrected trough deducting the posterior tilt angle from 180° so the data could be compared.

The characteristics of these methods are seen in table 2. No significant differences were found

in the distribution of both measurement methods (P-value = 0.270).

Healed and failed

Follow up Reclassifcation

Patients with FNF treated by

Gannet osteosynthesis

n=468

198 non-displaced

8 lost

170 with 1 year follow up

155 healed

9 failed

6 exluded

20 dead258 displaced

12 Pertorchanteric

16

Table 2. Characteristics different measurement methods

Method N Mean Std Deviation Minimum Maximum

LGA 164 166,53 9,85 140 184

PTM corrected 164 165,77 10,56 124 180

Table 3 shows that failed fractures have a smaller mean angle (larger posterior tilt) than

healed fractures for both measure methods. For the LGA this was not significant (P-value =

0.366) but the PTM method showed a significant correlation between a smaller angle and the

percentages of failures (P-value =0.030). Failure of treatment was associated with a higher

age and Tip Apex Distance (TAD), yet not statistical proven. There were no statistical

differences between healed and failed FNF in terms of gender and time until operation

(delay).

Table 3. Variable characteristics divided in healed and failed fractures

Healed Failed P-value

Mean LGA (SD) 166.7(9.9) 164.4(9.3) 0.366

Mean PTM corrected (SD) 166.2(10.4) 158.6(11.1) 0.030

Female, N(%) 94(60.6) 7(77.8) 0.484

Mean age in years (SD) 68.3(14.2) 73.7(9.3) 0.129

Mean TAD in centimeters (SD) 21.0(6.4) 24.2(7.7) 0.152

Mean delay in days <1 <1

Equal to today’s literature the data was dichotomized into posterior tilt ≥20° and <20°. There

were no statistical differences found in the failed group and healed group if we divide them

into posterior tilt ≥20° and posterior tilt <20° if the angle is measured according to the LGA

(Table 4) (P-value = 0.69). Yet if we measure the posterior tilt according to PTM and the

angles are dichotomized in ≥20° and <20° we find statistical difference between these groups

as seen in table 5 (P-value = 0.04).

Table 4. Crosstab of dichotomized LGA into <20° and ≥20° related to healed and failed fractures

Failed Healed Total

LGA ≥20° 3(7.5%) 37(92.5%) 40

LGA <20° 6(4.8%) 118(95.2%) 124

Total 9(5.5%) 155(94.5%) 164

Table 5. Crosstab of dichotomized PTM into <20° en ≥20° related to healed and failed fractures

Failed Healed Total

PTM ≥20° 5 (12.5%) 35 (87.5%) 40

PTM <20° 4 (3.2%) 120 (96.8%) 124

Total 9 (5.5%) 155 (94.5%) 164

A posterior tilt of ≥ 20° measured by PTM was associated with an increased risk of almost 4

times (OR = 4.286 (CI 95% 1.092 – 16.826) (P-value = 0.037)). No differences in the groups

with a posterior tilt ≥20° and <20° measured by PTM in terms of gender (P-value = 0.194),

time until surgery (P-value = 0.865) and TAD (P-value = 0.365) were found. Yet patients with

a posterior tilt ≥20° are on average 5.41 years (mean <20° = 69.9, mean ≥20° = 64.5) younger

17

than patients with a posterior tilt <20° (P-value = 0,033). If we correct the odds ratio (OR) of

an angle ≥20° for age, the odds ratio increases to 5.36 (CI 95% 1.302 – 22.114) (P-value =

0.020).

To find a cut-off point with the highest clinical relevance the data was also dichotomized in

groups ≥ and < than 10°, 15° and 25°. No differences were found in these groups for PTM (P-

value = 0.083 – 0.092) and LGA (P-value = 0.491 – 1.000).

3.3 Intra- and inter rater reliability

A intra- and inter rater reliability study was performed for both the LGA and the PTM. The

results show there is excellent intra rater reliability for the LGA as well for the PTM. Yet the

inter rater reliability for the PTM is considerably better with an intra class coefficient of 0.773

compared to 0.601 of the LGA. All the data of the observers is written in appendix 2. The

measurements of the observer were also divided into 2 categories (<20° and ≥20°). Cohen’s

kappa for 2 categories was calculated to evaluate intra and inter reliability of the observers.

This data is presented in appendix 3. Due to technical problems the second measurement of

observer 2 and the third measurement of observer 2, 3 and 4 could not be performed and

therefore not be included in the analyses.

Table 6. Intra- and interrater reliability of the Lateral Garden Angle and the Posterior Tilt Measurement.

Intra rater reliability Intra class coefficient 95% CI P-value

Cicchetti 1994

Lower bound Upper bound

Lateral Garden Angle 0.765 0.616 0.861 <0.001 Excellent

Posterior Tilt Measurement 0.790 0.654 0.877 <0.001 Excellent

Inter rater reliability

Lateral Garden Angle 0.601 0.467 0.726 <0.001 Fair to Good

Posterior Tilt Measurement 0.773 0.664 0.856 <0.001 Excellent

18

4. Discussion

In 2012 almost 19.000 patients with a hip fracture were treated in the Netherlands.48 Optimal

treatment outcome starts with the right indication. The right indication is based upon evidence

based predictors to strive for the best possible outcome. This study aimed to identify a

predictor for failure in undisplaced FNF treated by Gannet osteosynthesis.

4.1 Most important findings

9 of the 164 patients (5.5%) with an undisplaced FNF failed and had revision surgery. No

correlation could be found between the posterior tilt of the femoral head and the failure rate if

it was measured according to the LGA. If the retroversion was measured using the PTM a

larger angle was associated with a higher failure rate. Posterior tilt of ≥20° using PTM is

associated with a 4 times higher failure rate. The intra observer reliability of the LGA was

excellent and the inter observer reliability was fair to good. For the PTM the intra- and inter

observer reliability were excellent.

4.2 Garden classification

To divide all the undisplaced FNF from the displaced FNF all the fractures were reclassified

into a 2-grade Garden classification. Garden type I and II were classified as undisplaced and

Garden type III and IV as displaced. This reclassification was strictly based upon the AP X-

ray like Garden originally described. Initially the classification was performed by the treating

trauma surgeons. A reclassification was done because in everyday practice clinicians tend to

get biased by the lateral X-ray. In this way none of the fractures that showed only

displacement on the lateral X-ray were excluded from the study. To avoid a single observer

bias any discrepancy between the treating surgeons (original classification) and the researcher

was reviewed by the supervisor.

4.3 Failure rate

The percentage of patients that needed revision surgery in this study was 5.5%. This is a little

higher than the previous results regarding the failure rate in patients with undisplaced FNF

treated by Gannet osteosynthesis (4.0%).8 But the failure rate in patients treated by internal

fixation with other implants is reported higher. It varies between 9.6%, and 23%.27,39-41,44,45

This difference can be explained by different factors. First is the fact we used a different

implant. The Gannet has less implant volume and better rotational stability in comparison to

the present devices used.8,9 This could contribute to a lower failure rate. Also the definition of

failure rate varies among studies. For example, Clement included every reoperation, this

included also the healed fractures and the implant was removed in case of discomfort.40 We

defined these fractures as healed. Dolatwoski grouped fixation failure and AVN differently. 45

Furthermore the follow up period vary widely from 3 months until 5 years.27,39-41,44,45 This

could influence the failure rate because AVN can be seen after a year follow up.45,49 Therefore

this study also could have missed some failures. The different implants, definitions of failure

rate and follow up periods used by different authors make it difficult to compare the failure

rates.

4.4 Lateral X-ray

Last decennium different authors advised against routinely obtaining the lateral hip X-ray.22,23

It would be too discomforting for the patient, the quality is poor and it has no clinical

relevance. But none of these authors looked at the influence of the posterior tilt seen on the

lateral view. We agree the quality of the lateral films is often poor. Trabeculae cannot be seen

as good in comparison to the AP view. Furthermore the FNF is an injury of the elderly, which

19

have often osteopenia or osteoporosis which lead to relative less trabeculae. Also a lot of

lateral images are more oblique views. This influences the way the trabeculae are projected

and therefore influence the LGA. These reasons complicate the measurement of the LGA

which, officially, is measured using the trabeculae. But in today’s literature is as far as we

know no evidence provided regarding the reliability of the LGA.

Palm described a new method to measure the posterior tilt.41 But he did not compare this new

method with the old method, which was used by several authors.27,39,40 Palm only validated

his new PTM. The intra rater reliability lies between 0.95-0.97 and the inter rater reliability

varies between 0.90-0.97.41,45

We could not reproduce these results. Our intra rater reliability was 0.790 and inter rater

reliability was 0.773. The differences could be explained by the use of different radiograph

software. Also 3 of the observers participating in the study had no experience with the PTM.

They had only one explanation and they never used the PTM clinically. A learning curve must

be taken into account and a better reliability of the PTM is to be expected if it is used for a

longer period of time. Yet the LGA was clinically used by all the observers. Still the inter

observer reliability of the PTM is superior to the old LGA, 0.773 vs. 0.601.

Despite a better reliability of the Palms method to measure the posterior tilt the lateral view

often still lacks quality. Frequently 3 perpendicular lines cannot be drawn due to the oblique

view and the trochanter major blocks the view of the narrowest part of the collum. Yet in our

opinion, if the PTM is used, the poor quality of the X-rays has less effect on measurement of

the posterior tilt.

The measured angles were also divided into 2 categories (<20° and ≥20°) to evaluate clinical

validity for both measurement methods as seen in appendix 3. Yet no stable analyzes could be

achieved due to too few fractures with an angle of ≥20° within the 50 fractures measured by

the observers. So no conclusion could be drawn from this data.

4.5 Posterior tilt of the femoral head and failure rate

In today’s literature there is no consensus on the influence of posterior tilt on undisplaced

FNF treated by osteosynthesis. Several authors published results about this topic.

Alho was first to describe this correlation in 1992. Yet his study only included 13 undisplaced

FNF so no hard conclusions could be drawn from his study.39 Conn and Parker showed in a

study with 375 undisplaced FNF an association between a larger posterior tilt and non-union,

but no association between posterior tilt and AVN. He measured the posterior tilt using the

LGA. We could not reproduce these results due to too few non-unions (N=2 (1.2%)) and

AVNs (N=4(2.4%)). No comparison could be drawn with our results regarding the general

failure rate. Because only separate fixation related failures were given in the study of Conn. 27

In 2013 Clement published the last study which used the LGA to measure posterior tilt. He

concluded that a LGA <170° is a significant predicator for fixation failure.40 In our opinion it

is hard to make this statement because the LGA was never validated before. This also applies

to the studies done by Conn and Alho. In the study of Clement the LGA was measured by a

single observer. Our result show the LGA has excellent intra observer reliability. However

these results cannot be reproduced properly since the LGA has only fair to good inter observer

reliability. Also Clement defined posterior tilt as a LGA <170°. No foundation was given for

this amount of degrees. We could not find a significant correlation between posterior tilt and

failure if we dichotomized our data in posterior tilt ≥10° and <10°.

Palm was first to use a different method to measure posterior tilt.41 His results show a 56%

failure rate for FNF with a posterior tilt ≥20° compared to 12.5% in our study. His overall re

operation rate was 23% against 5.5% in this study. Outcome parameter and follow up period

were in both studies the same. The patients in Palms study were slightly older. Besides age,

the used implant was the only discrepancy that could be identified. Other factors could be the

20

number of FNF treated by trauma surgeons or (junior/senior) registrars, ASA classification or

postoperative reduction however this could not be objectified. Yet we found a OR of 4.3 for

patients with posterior tilt ≥20° using PTM. If we calculate the OR for Palms if we

dichotomize his population we find a similar OR of 4.1. (Appendix 4) Obviously no hard

conclusion can be drawn from this fact due to the heterogeneity of both populations. However

we can see a positive trend of the influence of posterior tilt on the failure rate.

Dolatowski also finds an increased risk of fixation failure for posterior tilt ≥20° if the angle is

dichotomized with a hazard ratio of 2.4.45 Yet the definition of fixation failure was revision if

indicated due to persistent pain and when radiographs showed loss of screw purchase or non-

union. AVN was grouped separately. These are an additional 13 cases to the 31 failure of

fixation. Yet no statistical correlation was found between larger posterior tilt and AVN due to

the small number of AVN. If AVN and fixation of failure are combined, maybe a statistical

stable higher HR will be found. Dolatowski hypothesized a simple morphological

classification would be as reliable as measuring posterior tilt. The inter-rater agreement was

good for all classification systems yet the intraclass coefficient for inter rater reliability was

excellent for angular measurements. No statistical increased risk was seen if posterior tilt was

assessed using this morphological classification. We did not analyze a morphological

classification system but we feel the posterior tilt should be measured. No evidence based

founding can be given due to lack of data yet we think the intra-observer reliability is also

better if the posterior tilt is measured and not clinically assessed.

The only large study contradicting the influence of posterior tilt on failure in undisplaced FNF

was done by Lapidus in 2013.44 He measured the posterior tilt in 382 undisplaced FNF using

Palms PTM. In his study overall healing complications was 12%. This is twice as high as

ours. Possible reasons explaining the higher failure rate could be a higher mean age, longer

follow up (5 years versus 1 year) and other implants. If his data is dichotomized in <20° or ≥

20° posterior tilt we find a lower percentage of failure in the group with a posterior tilt ≥20°,

9.6% versus 12.3% (appendix 5). These results contradict the present literature and the results

in our study. An explanation could be the operation indication. This is also mentioned by

Palm in his invited commentary on this study.44 If patients with a large posterior tilt were

identified as displaced FNF it would be possible that they were treated with

(hemi)arthroplasty. This way not all the true undisplaced FNF (Garden I and II, only assessed

on the AP X-ray) would be included. Yet this could be said for all the studies regarding this

topic including our study. As mentioned earlier the heterogeneity of the different study

population could also lead to contradicting results. These factors make it hard to compare the

results of different studies surrounding posterior tilt.

4.6 Strengths and limitations

The strengths of this study are its design and the fact no patients were missed in this cohort.

We scooped the different methods of measuring the posterior tilt and validated both which has

not been done before. Also there was no missing data of patients treated by Gannet

osteosynthesis due to the prospective design of this study. The limitations of our study are low

failure rate and follow up of 1 year. Therefore we could not perform a stable multivariate

analysis. Also we could have missed some failures because AVN also occurs more than 1

year post-operative which can influence our outcome.

21

4.7 Conclusion

Several conclusions can be drawn based upon this study and studies done in the past. First the

Lateral Garden Angle should not be used to measure the posterior tilt of the femoral head

because it is inferior to the new measurement method. Second the Posterior Tilt Measurement

is the most reliable method of measuring posterior tilt on the lateral X-ray. If this method is

used, posterior tilt predicts a higher failure rate in undisplaced FNF treated by Gannet

osteosynthesis. Posterior tilt ≥20° of the femoral head should be considered as a significant

predictor for failure of treatment in FNF treated by Gannet osteosynthesis.

4.8 Clinical relevance

The treatment algorithm for FNF in our hospital is based upon age and displacement of the

FNF. All undisplaced FNF, regardless the biological age of the patient, is internal fixation.

Young patients (<65 years) with a displaced (unstable) FNF are commonly treated with

internal fixation as well. Elderly patients (>75 years) with displaced FNF are treated with

(hemi)arthroplasty. The treatment of young elderly (between 65 and 75 years old) is still

under debate. Displacement of the fracture is assessed on the AP X-ray. Our study showed a

failure rate of 12.5% if posterior tilt is ≥20°. These numbers are similar with the failure rate of

displaced FNF treated by Gannet osteosynthesis.9 It seems that ‘stable’ displaced FNF with

significant posterior tilt (≥20°) in fact behave like unstable fractures. Therefore the indication

for internal fixation in the elderly patients will shift to a hip replacement when the PTM rises

above 20° of posterior tilt of the femoral head.

But not only posterior tilt influences the outcome of undisplaced FNF. Literature suggests

other patient related characteristics which influence the treatment such as age, ASA

classification, intraoperative fracture reduction.27,40 Therefore more evidence should be

obtained before changing the algorithm we use today.

4.9 Recommendations

As mentioned our study result show a low failure rate. To identify more patient related

characteristics which influence the treatment outcome of undisplaced FNF treated by Gannet

osteosynthesis a larger cohort should be obtained. Using a larger cohort, a stable multivariate

analysis can be performed to identify significant independent predictors that influence the

treatment.

22

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fractures: posterior tilt did not influence the reoperation rate in 382 consecutive hips followed for a minimum of

5 years. J Orthop Trauma 2013 Jul;27(7):386-90; discussion 390-1.

(45) Dolatowski FC, Adampour M, Frihagen F, Stavem K, Erik Utvag S, Hoelsbrekken SE. Preoperative

posterior tilt of at least 20 degrees increased the risk of fixation failure in Garden-I and -II femoral neck

fractures. Acta Orthop 2016 Mar 3:1-5.

(46) Fleiss J. Statistical methods for rates and proportions. 2nd ed. New York: John Wiley and Sons; 1981.

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instruments in psychology. Psychological Assessment Dec 1994;6(4):284-290.

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costs of treating femoral neck fracture patients with hemi- or total hip arthroplasty: a cost analysis of a

multicenter prospective study. Osteoporos Int 2016 Jun;27(6):1999-2008.

(49) Bachiller FG, Caballer AP, Portal LF. Avascular necrosis of the femoral head after femoral neck fracture.

Clin Orthop Relat Res 2002 Jun;(399)(399):87-109.

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1977;33(1):159-174.

24

Acknowledgements

I wish to express my gratitude to some persons that have contributed to this thesis. First I

want to thank my faculty supervisor dr. J.M. Klaase for reviewing my final paper. Prof. dr.

Job van der Palen and dr. Marjolein Brusse-Keizer, thank you for guiding me through the

maze that is called statistics. Also I am thankful for the trauma surgeons, prof. dr. A.B. van

Vugt and dr. E. van de Krol, for participating in the validity study. Next I want to thank my

fellow students in de medical library for the long lunches and superb cakes and pies every

Friday. Inge, thank you for listening to all my unorganized thoughts and giving them some

structure.

At last I want to thank my direct supervisor, dr. A.D.P. van Walsum, for his enthusiasm,

supervision and everyday feedback. You taught me already a lot and got me truly interested to

do more research in the future.

25

Appendices

Appendix 1 – Radiographs of cut out of the implant, avascular necrosis of the femoral head

and non-union of the fracture line.

Appendix 2 – Results from the validity study of the Lateral Garden Angle and the Posterior

Tilt Measurement.

Appendix 3- Results from the validity study of the Lateral Garden Angle and the Posterior

Tilt Measurement with dichotomized data.

Appendix 4- Crosstab of data from the study published by Palm dichotomized into <20° and

>20° of posterior tilt.

Appendix 5 - Crosstab of data from the study published by Lapidus dichotomized into <20° or

≥20° of posterior tilt.

26

Appendix 1

Appendix 1.1 AP and lateral radiograph of a cut out of DLBP in an undisplaced FNF in a 78 year old patient.

Appendix 1.2 AP and lateral radiograph of avascular necrosis of the femoral head after a displaced FNF

treated by DLBP. Collaps of the femoral head is seen. Also no consolidation of the fracture line is noticed.

27

Appendix 1.3 AP and lateral radiograph of displaced FNF treated by DLBP with non-union of the fracture line

after 6 months.

28

Appendix 2

Appendix 2.1. Intra- and inter rate reliability of the Lateral Garden Angle (LGA).

Intra rater reliability

LGA

Intra class

coefficient 95% CI P-value

Cicchetti

1994

Lower

bound Upper bound

Observer 1 0.765 0.616 0.861 <0.001 Excellent


Observer 3 0.712 0.538 0.827 <0.001 Fair to good



LGA

Observer 1/Observer 2 0.736 0.574 0.843 <0.001 Fair to good






Observer 1/2/3/4 0.601 0.467 0.726 <0.001 Fair to good Intra class coefficient was interpreted as follows: excellent (>0.75), fair to good (0.40-0.75) and poor (<0.40).47

Appendix 2.2. Intra- and inter rate reliability of the Posterior Tilt Measurement (PTM).

Intra rater reliability

PTM

Intra class

coefficient 95% CI P-value

Cicchetti

1994

Lower bound Upper bound



PTM

Observer 1/Observer 2 -0.450 -0.323 0.239 0.621

Observer 1/Observer 3 0.757 0.604 0.856 <0.001 Excellent





Observer 1/3/4 0.773 0.664 0.856 <0.001 Excellent Intra class coefficient was interpreted as follows: excellent (>0.75), fair to good (0.40-0.75) and poor (<0.40).47

Only intra rater reliability of observer 1 could be evaluated due to missing data of the other observers.

29

Appendix 3

Appendix 3.1. Intra- and inter rater reliability of the Lateral Garden Angle (LGA) if angles are dichotomized

into <20° and ≥20°. Intra rater reliability LGA Kappa P-value Landis and Koch (1977)

Observer 1 0.733 <0.001 Good


Observer 3 0.556 <0.001 Moderate

Observer 4 0.357 0.013 Weak

Inter rater reliability LGA

Observer 1/Observer 2 0.289 0.004 Weak

Observer 1/Observer 3 0.515 <0.001 Moderate

Observer 1/Observer 4 0.667 <0.001 Good



Observer 3/Observer 4 0.654 <0.001 Good Kappa was interpreted as follows: poor (0.00-0.20), weak (0.21-0.40), moderate (0.41-0.60, good (0.61-0.80)

and very good (0.81-1.0).50

Appendix 3.2. Intra- and inter rater reliability of the Posterior Tilt Measurement (PTM) if angles are

dichotomized into <20° and ≥20°. Intra rater reliability PTM Kappa P-value Landis and Koch (1977)


Inter rater reliability PTM

Observer 1/Observer 2 -0.015 0.904 Observer 1/Observer 3 0.934 <0.001 Very good

Observer 1/Observer 4 0.647 <0.001 Good

Observer 2/Observer 3 -0.07 0.574 Observer 2/Observer 4 0 1 Observer 3/Observer 4 0.697 <0.001 Good

Kappa was interpreted as follows: poor (0.00-0.20), weak (0.21-0.40), moderate (0.41-0.60, good (0.61-0.80)

and very good (0.81-1.0).50 Only intra rater reliability of observer 1 could be evaluated due to missing data of

the other observers.

30

Appendix 4

Appendix 4. Crosstab of data from the study published by Palm dichotomized into <20° and >20° of posterior

tilt. 41 1 Relative risk: 4.1.

Failed Healed Total

PTM ≥20°1 N=14 (56.0%) N=11 (44.0%) N = 25

PTM <20° N=12 (13.6%) N=76 (86.4%) N=88

Total N = 26 (23.0%) N = 87 (77.0%) N = 113

31

Appendix 5

Appendix 5. Crosstab of data from the study published by Lapidus dichotomized into <20° or ≥20° of

posterior tilt.44

Failed Healed Total

PTM ≥20° N=7 (9.6%) N=66 (90.4%) N = 73

PTM <20° N=38 (12.3%) N= 271 (87.7%) N=309

Total N = 45 (11.8%) N = 337 (88.2%) N = 382

the influence of posterior tilt of the femoral head on the failure...

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