using fibula as a reference can be beneficial for the tibial component alignment after total knee...

KNEE

Using fibula as a reference can be beneficial for the tibialcomponent alignment after total knee arthroplasty,a retrospective study

Mehmet Erdem • Deniz Gulabi • Gultekin Sitki Cecen •

Cem Coskun Avci • Murat Asci • Fevzi Saglam

Received: 16 November 2013 / Accepted: 13 March 2014

� Springer-Verlag Berlin Heidelberg 2014

Abstract

Purpose One of the important factors in a successful

arthroplasty is component alignment. The primary objec-

tive of this study was to determine whether the fibular shaft

reference technique is beneficial for the tibial component

position on the postoperative plain radiograph after total

knee arthroplasty.

Methods A total of 42 patients between 2009 and 2011

were analysed retrospectively. The surgeon prepared the

tibia using an extramedullary cutting guide and set the

posterior tibial slope with respect to the fibular reference

rod. In the postoperative radiographic measurements, a true

anteroposterior and lateral radiograph of the lower leg

covering the whole length of the tibia was used.

Results Five patients were excluded as they did not meet

the inclusion criteria, four patients were excluded due to

improper radiographs and the study group was reduced to

33 patients and 35 knees. The mean preoperative tibiofib-

ular angle was 2.1� ± 0.8�. The mean postoperative tibial

sagittal angle measurements were 83.3� ± 1.4� (81�–86�).

33 (94 %) Knees gained the desired tibial sagittal angle

within the desired alignment (5� ± 3�). The mean post-

operative tibial coronal angle was 89.3� ± 1.5�. The tibial

component coronal angle of two knees was more than 3

alignment from the neutral mechanical axis.

Conclusion The major clinical relevance of the technique

described in the present study is cost-effectiveness, and it

does not require any extra time or surgical equipment. This

method can be used as an alternative choice for bulky

extremities which is a cause of malalignment of the

components.

Level of evidence Retrospective case series, Level IV.

Keywords Knee � Knee prothesis � Alignment � Fibula

Introduction

The lifetime utility of a knee prosthesis depends directly on

the stabilization of soft tissue and maintenance of adequate

prosthesis alignment in the coronal, sagittal, and rotational

axis, as determined by satisfactory bone resection [14, 15,

17, 23].

Resection over a femoral intramedullary rod is now

widely accepted and is being used successfully and

uneventfully for femoral resection. However, there is no

consensus for the guidance of tibial resection. Some authors

use an extramedullary guide, while others use an intra-

medullary one, computer-assisted navigation systems, and

M. Erdem

Orthopaedic and Traumatology Department, Faculty of

Medicine, Sakarya University, Sakarya, Turkey

e-mail: [email protected]

D. Gulabi (&) � G. S. Cecen � F. Saglam

Dr. Lutfi Kırdar Kartal Training and Research Hospital,

Semsi Denizer Cad. E5. Yanyol Cevizli Kavsagı,Kartal, Istanbul 34890, Turkey


G. S. Cecen


F. Saglam


C. C. Avci

Umraniye Training and Research Hospital, Umraniye, Istanbul,

Turkey


M. Asci

Tokat State Hospital, Tokat, Turkey


123

Knee Surg Sports Traumatol Arthrosc

DOI 10.1007/s00167-014-2957-x

patient-specific cutting blocks [2, 18, 25]. All these con-

ventional procedures have some challenges as long surgical

time, high costs, intramedullary canal violation, and intra-

medullary pressure in the tibia, so we aimed to evaluate an

alternative technique for use. The technique described here

was proposed by Laskin as a choice for tibial component

alignment in total knee arthroplasty (TKA) [18].

The aim of this study was to evaluate the accuracy of

tibial component alignment in knee prosthetics using the

fibula as a reference. The hypothesis was that using the

fibula as a reference could achieve optimal accuracy in

final tibial component positioning. In this study, our aim

was to achieve 85� ± 3� tibial slope angle and 90� ± 3�coronal tibial tray alignment [1, 27] over an extramedullary

tibial guide using the fibula as a reference.

Materials and methods

A total of 42 patients who had received 45 total knee pros-

theses between July 2009 and November 2011 were analysed

retrospectively. Nonoperative treatment had failed for these

patients, and they did not have any major flexion contractures

(\7�) or coronal deformity (\10� varus/valgus). The inclu-

sion criteria for the study were as follows: a diagnosis of

primary osteoarthrosis, a neutral or varus knee due to

degenerative arthrosis of the knee joint, and surgery for pain

resulting from arthrosis. Five patients were excluded from

the study; one patient with a proximal tibial osteotomy, two

patients with postinfection arthritis, and two patients with

severe instability that could not treated by a cruciate-

retaining TKA. Varus deformities of the knees were due to

intra-articular factors with loss of bone on the medial tibia

plateau. No extra-articular deformities were determined in

either the sagittal or coronal plane. Consequently, 40 knees

of 37 patients were treated with primary TKA using the fibula

as a reference. Informed consent for participation in the study

was obtained from all patients. Clinical records were

reviewed for demographic information (gender, age, side,

height, and weight) and the primary diagnosis. Body mass

index (BMI) was calculated as the weight in kilograms

divided by height in metre squared (kg/m2).

Surgical techniques

The fibula head and lateral malleolus of each patient were

marked with a sterile marking pen. All operations were

performed with a medial parapatellar approach. All patients

received a posterior cruciate-retaining prosthesis (Genesis

2, Smith-Nephew, Andover, Massachusetts, USA). Femoral

resections were made over an intramedullary guide. Before

tibial resection, the proximal head of the fibula and the

lateral malleolus were identified, and a long, 8-mm-

diameter rod was held parallel to the fibula by the assistant

surgeon. The surgeon prepared the tibia using an extra-

medullary cutting guide and set the posterior tibial slope

with respect to the fibular reference rod. The long rod of the

extramedullary guide was aligned parallel to the rod that

had been aligned with the fibula. The tibial resection block

was aligned perpendicular to a line extending from the

centre of the tibial plateau to the centre of the talus dome.

The rotation was aligned with the medial 1/3 of the tibial

tubercle. After obtaining sagittal, coronal, and rotational

alignment, the tibia cutting block was fixed with pins and

resection was made with a motorized cutter. All prostheses

were fixed with cement. The patella was not resurfaced in

any case. The objective of the tibial component implanta-

tion was to correct the tibial alignment to as close to neutral

as possible within a range of 3 varus or valgus and 5� ± 3�tibial slope. All knees were operated on by a single surgeon

(ME), so intersurgeon variation risk was minimized.

Radiographic measurements

Postoperative radiographs of each knee were measured to

determine the proximal tibial slope angle, proximal tibial

coronal angle (TCA), and mechanical axis (MA) degree.

All radiographs were reviewed with the strongest criteria

for adequacy. The fibular head and lesser trochanter were

used as landmarks to determine excessive rotation of the

limbs on the radiographs [23]. Any radiographs that

showed one of these two landmarks in excess meant the

limb was malrotated. Radiographs that revealed oblique-

ness in any plane were a cause of exclusion. Anteropos-

terior and lateral 14 9 17-in. image radiographs of the

knee were used to determine the long axis of the tibia. All

radiographic alignment measurements were taken by an

independent radiographic reviewer who was blinded to the

treatment. The independent observer assessed all radio-

graphs twice with an interval of 1 week. All measured

values were calculated to one decimal place. To eliminate

interobserver variability, a single radiographic reviewer

was used. In the measurements, a true anteroposterior and

lateral radiograph of the lower leg covering the whole

length of the tibia was used. In that method, the sagittal

MA was defined as the connecting line between the mid-

points of the tibia plateau and the tibia plafond on the

lateral X-ray. A line drawn between the centre of these two

reference points shows the tibia’s MA line. A line was then

drawn parallel to the articular surface of the proximal tibia.

The angle between the MA line and the articular surface

line was designated as the tibial slope (TSA) (Fig. 1a). The

TCA was determined by the intersection of a line drawn

from the centre of the knee to the centre of the talus with a

line drawn across the tibial component (Fig. 1b). The MA

was determined by the angle of the line drawn from the


123

centre of the femoral head to the centre of the knee to the

line drawn from the centre of the knee to the centre of the

talus. The fibular shaft axis (FSA) was defined as the line

connecting the midpoints of the outer cortical diameter of

the proximal and distal ends of the fibular diaphysis [33].

The angle between the FSA and the sagittal MA line of the

tibia is the tibiofibular angle (TFA) (Fig. 2).

Postoperative radiographic measurements were taken at

mean postoperative 5th month. The radiographic assessments

were performed according to the Knee Society Roentgeno-

graphic Evaluation System [9]. Radiological measurements

were taken, using a ruler. The accuracy of the measurements

cannot be more than 0.1 mm when a ruler is used.

Statistical analysis

All measurements were taken twice at a week apart by one

independent reviewer for all patients, and the average of

these two measurements was used as the data. The statis-

tical analysis was carried out using Number Cruncher

Statistical System (NCSS) 2007 and Power Analysis and

Sample Size (PASS) 2008 statistical software (NCSS Sta-

tistical Software, Utah, USA). The paired sample t test was

used to test the differences between mean measurements.

Descriptive statistical methods (mean, standard deviation,

median, percentage, ratio) were used in the evaluation of

data, and for the analysis of the relationship beween

parameters, Pearson’s correlation coefficient was used.

Results with p values \0.05 were considered significant.

Test–retest was performed for intraobserver reliability with

the observer taking the measurements again after 1 week in

all cases.

The number of outliers in this study, defined as tibial

component alignment outside of 90� ± 3� in the coronal

plane, a tibial posterior slope outside of 85� ± 3� in the

sagittal plane, and lower extremity mechanical alignment

outside of 3� of the neutral MA, were determined. Positions

of the femoral and tibial components that fell within the

above parameters were considered to be in the optimal

position.

Results

The median age of the patients was 67 years (range 63–75).

Five patients were excluded as they did not meet the

inclusion criteria, 4 patients were excluded due to improper

radiographs, and the study group was reduced to 33

patients and 35 knees. The male to female ratio was 2:1 (22

female, 11 male). Twenty-five knees had Kellgren–Law-

rence [5] grade 3 knee arthrosis, and 10 had grade 4. The

knees operations were 25 right side and 10 left side.

Osteoarthritis was the primary diagnosis in all knees

(Table 1).

Fig. 1 Sixty-eight-year-old

female patient. a Postoperative

lateral radiographs of the left

knee showing a tibial slope of

84. b Postoperative AP

radiograph of the left knee

showing tibial coronal angle of

91�

Fig. 2 Preoperative tibiofibular angle of the right lower extremity of 2.0�


123

The mean BMI was 32.4 kg/m2 (range 22.9–45 kg/m2).

Six (18 %) patients were normal weight (18.5–24.9 kg/

m2), 13 (40 %) patients were overweight (BMI

25–29.9 kg/m2), and 14 (42 %) patients were obese (BMI

[30). There was no statistically significant difference

between radiographic values in respect of BMI (p [ 0.05).

The mean preoperative TFA was 2.1� ± 0.8� (range

1.3�–3.1�). The mean postoperative tibial sagittal angle

measurements were 83.3� ± 1. 4� (range 81�–86�). Thirty-

three (94 %) knees gained the desired tibial sagittal angle

within the desired alignment (5� ± 3�). The tibial slope

angle of 2 (6 %) knees was out of the target range. The

mean postoperative TCA was 89.3� ± 1.5� (range 84�–

92�). The intraclass correlation coefficient was 0.88 for

TFA, 0.92 for TSA, 0.93 for TCA, and 0.90 for MAA. The

tibial component coronal angle of two knees was more than

3� alignment from the neutral MA. One of these knees had

grade 3 gonarthrosis and BMI of obesity, and the other

knee had grade 4 gonarthrosis and normal BMI. The mean

MA angle was 179.4 (range 174�–183�) as measured on

the postoperative standing orthorontgeonagraphic images

(Table 2).

The mean preoperative HSS knee score [11] was

64.7 ± 10.3. The mean final follow-up HSS knee score

was 95.1 ± 4.2. No intraoperative complications were

noted in this study group. Superficial infection was

observed in two cases in the early postoperative period, and

these were resolved with wound care.

There was no statistically significant correlation

between the final follow-up HSS knee scores and age, BMI,

and radiological TSA, TCA, MA, and FSA (p [ 0.05)

(Table 3).

Discussion

To the best of our knowledge, this is first study to have

examined the postoperative tibial component accuracy

using the fibula as a reference. The most important of the

findings of the present study were that coronal and sagittal

alignment of the tibial component could be achieved with

the present technique, which was first proposed by Laskin

[18], and has been described above. Previous studies have

reported success rates of 65–95.8 % for tibial component

coronal alignment within the target alignment [16, 19, 20,

24, 26, 27, 31]. In the current study, coronal tibial com-

ponent alignment of 90� ± 3� was achieved in 94 % of the

knees. There were two outliers. One of these knees had

grade 3 gonarthrosis and BMI of obesity, and the other

knee had grade 4 gonarthrosis and normal BMI. That, there

were no severe extra-articular deformities in the operated

knees and all the operations were performed by a single

experienced surgeon can be said to have contributed to our

success. However, intramedullary instrumentation has a

deleterious effect as it can increase the intramedullary

pressure in the tibia, which can lead to the risk of embo-

lization [6, 28]. Moreover, in elderly and osteoporotic

patients, the proximal metaphysis of the tibia is wide and

the cortex is thin so there is a high risk of malalignment. To

avoid these risks, the intramedullary technique was not

used in the current study.

The posterior tibial slope after knee prosthesis opera-

tions has a direct effect on anteroposterior stability, knee

Table 1 Demographic data

N %

Gender

Male 22 66.7

Female 11 33.3

Side

Right 24 68.6

Left 11 31.4

Grade

3 25 71.4

4 10 28.6

BMI

\25 6 18.2

25–30 13 39.4

[30 14 42.4

Table 2 Radiographic measurements and HSS results

Min–Max Mean ± SD

Age 63–75 67.5 ± 3.23

BMI 22.9–45 32.4 ± 6.41

Preop TFA 1.3–3.1 2.1 ± 0.83

Postop tibial sagittal angle 81–86 83.32 ± 1.39

Postop coronal tibial angle 84–92 89.32 ± 1.47

Postop mechanical axis 174–183 179.4 ± 2.26

Preop HSS 54–76 64.7 ± 10.3

Postop HSS 88–100 95.1 ± 4.2

Table 3 Relationship of HSS scores with Age, BMI, and tibial

component angles

Postop HSS

R

Age 0.145

BMI (kg/m2) 0.002

Postop tibial sagittal angle 0.249

Postop coronal tibial angle 0.305

Postop mechanical axis 0.343

R Pearson’s correlation cofficient


123

joint range of motion, and contact pressure inside the joint

[3, 12, 13, 32]. Previous studies have reported success rates

of 72.1–94 % for tibial component sagittal alignment

within the target alignment [24, 27, 31]. In the current

study, we achieved 94 % of the tibial slope of the tibial

component within the target degrees (85� ± 3�). There

were two outliers. One of these knees had grade 4 gon-

arthrosis and BMI of obesity, and the other had grade 3

gonarthrosis and normal BMI. Berend et al. [4] and Seo

et al. [29] demonstrated that patients with BMI greater than

33.7 kg/m2 were at risk of postoperative malalignment.

However, in the current study, only two knees had varus

alignment, one of which was obese. Although the fibula

was marked under fluoroscopy, in obese patients, bulky

extremities will be a cause of malalignment of the extra-

medullary guides. Therefore, the fluoroscopy control of the

fibula in obese patients requires particular attention.

For the management of limb alignment, standing lower

extremity orthorontgenographs are the gold standard. More

reliable measurements can be obtained from full lower

extremity CT scans [17] although that entails radiation

exposure and high costs. It was critical to take scans, so we

used 14 9 17 in. images and standing lower extremity

orthorontgenography for the measurement, as recom-

mended by Skytta et al. [30] stated. In previous studies,

Mason et al. [20] demonstrated 68.2 %, Nam et al. [24]

74.5 %, and Roh et al. [27] 90 % of total knee arthropla-

sties performed using conventional techniques to be within

3 of neutral alignment. In the present study, 94 % of total

knee arthroplasties were aligned within 3 of neutral

mechanical alignment. We concluded this to be due to

careful planning on the orthoroentography AP/LAT

radiographs which were taken in a standing position and no

femoral and tibial deformities which may cause

malalignment.

Computer-assisted navigation systems have been used to

achieve accuracy of component alignment in TKA, but

conflicting results have been reported [2, 8, 25]. In a

multicentre, prospective randomized study, Barrett et al.

[2] reported that there was a statistically significant dif-

ference between a conventional extramedullary guide sys-

tem and a computer-assisted navigation system only in

tibial component coronal alignment, with no statistically

significant improvement in the MA, femoral coronal, sag-

ittal, and tibial sagittal alignment.

However, clinical outcomes and postoperative ROM are

influenced by various factors, such as the severity of the

preoperative deformity, alteration of posterior femoral

offset, flexion angle of the femoral component, and the

tension of the soft tissues (PCL). In the current study, an

improvement was seen in the HSS knee score [11]. We

believe that this improvement is due to the postoperative

component alignment obtained at the desired values, and

none of the patients had major flexion contracture or

coronal deformities. There was no statistically significant

correlation between the postoperative tibial sagittal angle,

TCA, or mechanical angle with the final follow-up HSS

scores (p [ 0.05).

The major clinical relevance of the technique described

in the present study was cost-effectiveness when compared

with computer-assisted TKA and patient-specific guides,

which are time-consuming to prepare. Avoidance of

intramedullary canal violation and intramedullary pressure

in the tibia, which can cause a risk of embolization, are the

other advantages of this technique. Bulky extremities are a

cause of malalignment in TKA using extramedullary

guides. Matziolis et al. [22] stated that tibial component

alignment according to the ankle joint or second metatarsal

is problematic. The references of the bone prominence are

not palpable, but in the present study, the reference rod of

the fibula was managed under fluoroscopy. Therefore, this

technique could be used as an alternative choice for bulky

extremities.

This study has some limitations. First, anatomical fea-

tures of the tibia and fibula can vary with the ethnic origin

of the study group [7, 10, 21]. All the patients in the current

study were ethnically from the north of Turkey, and it

might be wrong to reflect our findings of TFA to a popu-

lation of different ethnic origin. Second, this study did not

have a comparison group to examine the accuracy of the

technique used. Third, this was a radiographic study of

component alignment so an improper radiographic tech-

nique may lead to measurement errors. Finally, all mea-

surements were taken by an independent reviewer with a

ruler, so there might have been some measurement bias.

The retrospective nature of the study and low number of

the sample group were other limitations.

Conclusion

This study demonstrates that a fibula reference-assisted

technique reduces the number of outliers for tibial com-

ponent alignment and MA alignment. This technique can

be preferable as costs are low, and it does not require any

extra time or surgical equipment.

Conflict of interest No benefits in any form have been or will be

received from a commercial party related directly or indirectly to the

subject of this manuscript.

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