Pulsed Lavage in Cementless Total Hip Arthroplasty Reduces the Incidence ofBrooker Grade 3 and 4 Heterotopic Ossifications

doi:10.4236/ojo.2011.12003

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Open Journal of Orthopedics, 2011, 1, 9-13

doi:10.4236/ojo.2011.12003 Published Online December 2011 (http://www.SciRP.org/journal/ojo)

Pulsed Lavage in Cementless Total Hip

Arthroplasty Reduces the Incidence of

Brooker Grade 3 and 4 Heterotopic Ossifications*

Joris Mellema1, Wierd Zijlstra2, Tom van Raaij2, Basten Have2, Jos van Raay2

1Department of Surgery, Isala klinics, Zwolle, The Netherlands; 2Department of Orthopaedic Surgery, Martini Hospital, Groningen,

The Netherlands.

E-mail: [email protected]

Received October 9th, 2011; revised November 16th, 2011; accepted November 24th, 2011.

ABSTRACT

Heterotopic ossification (HO) may cause pain, and can lead to loss of hip motion after total hip arthroplasty (THA).

There is evidence that pulsed lavage may lower the incidence of HO formation. We assessed the effect of pulsed lavage

on the incidence of HO in 87 male patients after THA. All patients received an uncemented THA through a poster-

olateral approach. 39 patients were treated with pulsed lavage (index group) and 48 males were treated without pulsed

lavage (historical control group, matched on aetiology, gender, surgical approach and type of prosthesis). Both groups

followed the same postoperative treatment regimen. HO severity was scored in both groups according to the Brooker

classification by three blinded orthopaedic surgeons one year postoperatively. Good inter-observer agreement (Kappa

0.7) for scoring HO was found. The incidence of HO (51%) in the index group did not differ significantly (p = 0.53)

from the control group (58%). However, the incidence of clinically relevant HO (Brooker grades 3 and 4) was signifi-

cantly lower (p = 0.04) in the index group (3%) as compared to the control group (17%). These results suggest a bene-

ficial effect of pulsed lavage on the incidence of severe heterotopic ossification after cementless THA in male patients.

Keywords: Heterotopic Ossification, Pulsed Lavage, Total Hip Arthroplasty, Uncemented

1. Introduction

Heterotopic ossification (HO) is a well-known co mplica-

tion after total hip arthroplasty (THA). The incidence of

HO varies from 8% to 90% depending on risk factors and

the criteria used [1,2]. A large meta-analysis of 13 ran-

domized trials, involving 4129 individuals treated with

Non Steroid Anti Inflammatory Drugs (NSA IDs) after

major hip surgery, reported an overall HO incidence of

37% [3]. Especially advanced stages of HO, Brooker

grades 3 and 4, are clinically relevant because of pain

and hip function impairment [4-6].

The exact aetiology of HO remains unclear. Some

have suggested that surgical trauma may stimulate pri-

mitive mesenchymal cells to differentiate into osteoblastic

cells, which form bone [7,8]. Earlier, Lo and Healy [9]

found that non-circulating connective tissue cells with

fibroblastic features may cause HO. It seems likely that

HO is the result of inappropriate differentiation of pluri-

potential mesenchymal cells into osteoblastic stem cells.

Some risk factors for HO around the hip have been

identified; male gender, a lateral surgical approach, un-

cemented arthroplasty, HO after contralateral hip arthro-

plasty and revision surgery [10,11]. Several studies re-

ported beneficial effects of post-operative NSA IDs us-

age [12] and local radiation therapy [13] in preventing

HO formation. However, NSAIDs often cause gastroin-

testinal side effects, and local radiation may generate

higher costs, logistic problems, wound healing disorders

and introduces the risk of secondary malignnancies.

Pulsed lavage around the hip jo int and gluteal muscles

may prevent HO formation by washing out the primitive

mesenchymal cells. It is inexpensive and has no known

side effects. Only one study on the effect of pulsed lav-

age has been published and suggested no protective ef-

fect on HO formation [1]. In this study, however, all pa-

tients received lavage; pulsed or manual with a syringe.

Aim of the current study was to determine whether pul sed

lavage compared to no lavage resulted in less clinically

relevant HO formation after cementless THA in male

patients.

*Conflict of Interests: None declared

Pulsed Lavage in Cementless Total Hip Arthroplasty Reduces the Incidence of Brooker

10 Grade 3 and 4 Heterotopic Ossifications

2. Materials and Methods

Between May 2003 and February 2006, 41 consecutive

male patients scheduled for cementless THA were in-

cluded prospectively. All patients underwent cementless

THA through a posterolateral approach because of pri-

mary hypertrophic coxarthrosis, and received pulsed

lavage during the procedure. Two patients were lost to

follow-up. The index group of 39 patients was matched

(on aetiology, gender, surgical approach, type of prosthe-

sis and time of follow-up) to a historical control group of

48 patients who received a cementless THA without any

form of lavage between March 1993 and December 2001.

The local medical ethical committee approved the study

design. Informed consent was obtained in all patients.

The trial was performed in compliance with the Helsinki

Declaration. There were no competing interests.

2.1. Surgical Procedure

All patients received a unilateral plasma sprayed porous

coated titanium alloy ce mentless total hip pros thesis with

a polyethylene liner (Mallory Head®, Biomet, Warsaw,

Indiana, USA) through a standard posterolateral ap-

proach. No lavage or irrigation was used in the control

group. The index group received pulsed lavage with a

total of 1 litre saline at 2 time points; 1:50 0 mL after im-

plantation of cup and stem with the hip in dislocated po-

sition and 2:500 mL after reposition. Pulsed lavage was

performed with the OptiLavage system® (Biomet, War-

saw, Indiana, USA) in and around the joint and gluteal

muscles. After surgery a suction drain was used in all

patients routinely. According to protocol no NSAIDs

were given postoperatively in both groups. The rehabili-

tation programme was similar for both groups, and con-

sisted of full weight bearing from the first day after sur-

gery.

2.2. Scoring Procedure

HO formation was scored using the Brooker classifica-

tion on standardized supine anteroposterior pelvic radio-

graphs at time of follow-up [14]. Three blinded orthopae-

dic surgeons scor ed all radiographs to assess inter-obser-

ver variability [5]. Th e mode of the 3 observers was used

as definitive Brooker score when disagreement in HO

rating oc curred.

2.3. Statistical Analysis

Baseline characteristics of both groups are displayed us-

ing descriptive statistics. Differences between groups

were tested with Student’s T-test or Mann-Whitney U-

test in case of non-normal distribution of a parametric

variable or non-p arametric var iable. In ter-observ er agree-

ment between the 3 observers in scoring of HO formation

using the Brooker classification was determined with the

kappa statistics. Numbers and percentages of the amount

of HO formation in both grou ps we re calculated. Brooker

scores were divided into 2 groups; grades 1 and 2 (clini-

cally irrelevant) and grades 3 and 4 (clinically relevant)

[4-6]. Differences between both groups in Brooker gr ades

were tested with the Fischer’s Exact test. All analyses

were performed with SPSS version 16.0 for Windows

(SPSS inc., Chicago, Illinois). A p value < 0.05 was con-

sidered statistically significant.

3. Results

Both groups were equal regarding aetiology, gender, sur-

gical approach, type of prosthesis, and time of follow-up.

The index group was significantly (p = 0.002) older with

a mean age of 62 years as compared to the control group

mean age of 55 years (Table 1).

Good inter-observer agreement (K = 0.7) for scoring

HO formation according to the Brooker classification

was found (Table 2).

Figure 1 shows the distribution of Brooker grades in

the index and control group. HO formation was found in

20 out of 39 patients in th e index group, and in 28 out of

48 patients in the control group. Total HO incidence

percentage (51% and 58%, respectively) did not differ

significantly (p = 0.53) between both groups. However,

the index group (1 of 39 patients) had significantly (p =

0.04) less Brooker grades 3 and 4 HO compared to the

control group (8 of 48 patients); 3% versus 17%, respec-

tively.

Table 1. Baseline characteristics for the index and control

group.

Group Index(N = 39) Control (N = 48)

Follow up, months (mean, SD)12 (7) 15 (8)

Age, years (mean, SD) 62 (9)ª 55 (10)ª

ap = 0.002.

Table 2. Inter-observer variability for scoring HO forma-

tion (Brooker classification).

Observer combination ĸ coefficient

O1-O2 0.779

O1-O3 0.654

O2-O3 0.734

Average 0.722

Pulsed Lavage in Cementless Total Hip Arthroplasty Reduces the Incidence of Brooker 11

Grade 3 and 4 Heterotopic Ossifications

Figure 1. Distribution of the Brooker grades between the

index and control groups.

4. Discussion

Our results demonstrated significantly less severe HO

formation (Brooker grades 3 and 4) with the use of puls ed

lavage in male patients treated for symptomatic primary

hypertrophic coxarthrosis with uncemented THA. Given

the large variation in HO incidence from 8% - 90%

across different trials [1,2], and the use of a historical

control group, rather than a randomised study, we con-

sider that the low numbers compared at Brooker grade 3

& 4 could lead to misleading conclusions. The present

study was limited that patients were not randomized,

which may prevent correction for unknown confounding

factors that may affect formation of heterotopic bone.

Secondly, although our population was homogeneous

with respect to gender, aetiolo gy, type of prosthesis, sur-

gical approach, and rehabilitation protocol, the index

group was significan tly older . Adva nced age at surg ery is

a risk factor for HO after THA [15]. This would suggest

that the effect of pulsed lavage is even greater than our

results have shown. Thirdly, we only used a radiological

outcome at one-year follow-up and no clinical scores

were assessed. However, several studies have shown that

radiological Brooker grades 3 and 4 correlate positively

with clinically relevant HO formation [4-6]. Also a fol-

low-up of one year seems appropriate because HO will

be evident and stable in size at 6 weeks postoperatively,

while maturation of formed HO takes place up to 6

months after surgery [16].

A wide range (8% - 90%) in HO incidence after THA

has been described.[1,11,15] These differences may de-

pend on the reliability of the HO classification system

used. Different systems have been suggested for assess-

ing HO formation. Toom et al. [17] reported high in-

ter-observer reliability for three methods assessing HO

formation (Arcq (k = 0.9) [18] DeLee (k = 0.9) [19] and

Della Valla (k = 0.9) [5]). We used the widely accepted

and most frequently used Brooker's classification [20]. A

recent study showed good inter-observer agreement (k =

0.8) for assessing HO formation with the Brooker’s clas-

sification [17]. We also found good inter-observer agree-

ment (k = 0.7) between three experienced blinded ortho-

paedic surgeons for scoring HO on standard anteroposte-

rior pelvic radiographs. More likely, heterogeneity a-

mong studies contributes to the various incidences of HO

reported. A recent report on 134 patients who had a ce-

mentless hydroxyapatite-coated THA without pharma-

cologic or radiotherapeutic prophylaxis, showed 67% HO

formation [21]. While another randomized study reported

31% HO formation in 97 patients treated with unce-

mented total hip arthroplasty [22]. A systematic over-

view of 201 studies showed the incidence of any het-

erotopic bone formation to be 43% after total hip re-

placement, the incidence of severe HO was 9%. Informa-

tion about patient characteristics, use of heterotopic bone

formation prophylaxis, other NSAID use and details of

surgery and follow up were very incompletely reported

and generally available for less than one-quarter of the

included studies [20]. Risk factors for HO have been re-

cognized and include male sex, posterolateral approach

and hypertrophic osteoarthritis [10,11]. Our study popu-

lation was selected for these known risk factors, and HO

formation was found in 51% of the cases in the index

group versus 58% in the control group.

The incidence of clin ically relevant HO was 3% in the

index group versus 17% in the control group, which was

significantly (p = 0.04) different. This suggests a benefi-

cial effect on severe HO formation by using pulsed lav-

age. The exact aetiology of HO formation is still un-

known. Some have suggested that mesenchymal pluripo-

tential stem cell release from bone during surgery may

act as a stimulus [23,24]. McCarthy proposed a chain of

events in which four factors are important: surgical

trauma that leads to haematoma; protein messengers re-

lease from traumatized cells or inflammatory cells that

arrive at the location of trauma; protein messengers acti-

vation of mesenchymal cells to transform into osteob lasts

or chondroblasts, and a proper environmental condition

that enables HO formation [8]. Pulsed lavage may have

the potential to washout mesenchymal pluripotential stem

cells and messenger proteins, or to distort the proper en-

vironmental condition needed for HO formation. Clinical

studies on the effect of pulsed lavage in THA treatment

are rare, and only one study reported on pulsed lavage

and HO formation [1]. This small and heterogeneous

study found no positive effect for pulsed over syringe

lavage, but lacked a true control group which had no

lavage at all. A recent Japanese trial on 1000 uncemented

THA’s through a postero lateral approach reported severe

Pulsed Lavage in Cementless Total Hip Arthroplasty Reduces the Incidence of Brooker

12 Grade 3 and 4 Heterotopic Ossifications

HO formation in only 1% of the cases. A large portion of

patients (40%) received NSAIDs postoperatively, and all

wounds were irrigated with 1000 mL of saline [25]. Al-

though no pulsatile lavage was used wound lavage may

have had an additional beneficial effect, causing the low

incidence of HO.

5. Conclusions

In conclusion our study showed significantly less Brooker

grades 3 and 4 heterotopic ossifications after cementless

THA in male patients treated with pulsed lavage. This

suggests a positive effect of pulsed lavage on preventing

clinically relevant HO formation. Other studies suggested

that lavage in general reduces the incidence of HO after

THA. Future prospective randomized trials should eluci-

date whether pulsed lavage, in addition to syringe lavage

and no lavage at all, is superior.

6. Acknowledgements

We thank I. van de Akker-Scheek, PhD, for her contribu-

tion to the manuscript.

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