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Modification of the Harris Hip Score in acetabular

fracture treatment

Stein Ovre a,*, Leiv Sandvik b, Jan Erik Madsen a, Olav Roise a

a Department of Orthopaedic Surgery, Ulleval University Hospital, Oslo, Norwayb Department of Biostatistics, University of Oslo, Oslo, Norway

Accepted 24 April 2006

Introduction

The demand for documentation of the quality andeffectiveness of treatment steadily increases. Col-lecting and evaluating results is a prerequisite forcontinuous professional improvement. The quality ofoutcome scores should satisfy different demands12

such as reliability and validity. Scores should bereproducible, consistent and responsive, and should

accurately evaluate the focused clinical area.Outcome scores are based on elements of specific

measures and generic questionnaires. The self-administered generic questionnaire, the MedicalOutcomes Study 36-item Short Form Health Survey(SF-36)9,14, is one of the most frequently used health

status measures. The disease-specific Harris HipScore is an outcome measure of hip arthroplasty,and was introduced in 1969.6 It is an extensivelyused hip questionnaire and has shown high validityand reliability in a study comparing SF-36 withWOMAC.13 Thus, the Harris Hip Score should be asuitable instrument for documentation of qualityand effectiveness of treatment.

In a previous study, however, we demonstrated

that the Harris Hip Score has a skewed distribution,with a considerable ceiling effect, which limited itsclinical use in acetabular fracture treatment. The50th percentile showed 95% of maximum score anddid not capture differences in the upper end of thescale.10 We therefore question the discriminativequalities of the score as an outcome measure inacetabular fracture treatment. Does it adequatelyrecognise minor differences in patient outcome of

Injury, Int. J. Care Injured (2007) 38, 344349

www.elsevier.com/locate/injury

KEYWORDS

Modified Harris HipScore;Harris Hip Score;Ulleval Hip Score;Acetabulum;Fracture

Summary The aim of this study was to adjust the Harris Hip Score for evaluation ofacetabular fracture treatment. The discriminating quality of the score was assessed.As there was low discriminating capacity at the upper end of the scale, with a highceiling effect and the 60th percentile showing top points, the score was modified andre-evaluated. The discrimination of the modified score was improved, with the 90thpercentile giving top points. Differences in treatment outcome of acetabular frac-tures will be easier to detect with the modified score.# 2006 Elsevier Ltd. All rights reserved.

* Corresponding author. Tel.: +47 22119540E-mail address: stovre@broadpark.no (S. Ovre).

00201383/$ see front matter # 2006 Elsevier Ltd. All rights reserved.doi:10.1016/j.injury.2006.04.129

mailto:stovre@broadpark.nohttp://dx.doi.org/10.1016/j.injury.2006.04.129http://dx.doi.org/10.1016/j.injury.2006.04.129mailto:stovre@broadpark.no

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acetabular fractures, even though it correlates wellwith the SF-36 and WOMAC? The aim of the presentstudy was to assess the discriminative characteris-tics of the Harris Hip Score in the treatment ofacetabular fractures. If necessary, we wished toimprove these characteristics by modifying thescore and evaluating the modified version.

Methods

The study population was a 10-year cohort of 450consecutive patients with acetabular fracturesrecorded from 1993. For the whole population,the age was median 44.1 (1292) years, but 53patients died because of the initial trauma or duringfollow up. Fractures were treated operatively in 223and non-operatively in 227 cases. Of these, 23patients were excluded because of total hip repla-cement surgery; 31 observations were excludedbecause the hip score was influenced by other con-ditions (e.g., leg fractures with impaired functiondue to other illness), leaving a total of 1122 obser-vations for analysis. Outcome instruments wereadministered at 6 and 12 months and at 2, 5, 7, 8and 10 years post-fracture.

The discriminative characteristics were assessedfor the first 100 consecutive follow-up observationswith the Harris Hip Score as the outcome instrument.Thisis a staff-administered evaluation score compris-ing the domains of Pain, Function, Absence of Defor-mity, and Range of Movement (ROM).6 It is a disease-

specific instrument assessing hip disabilities, origin-ally worked out as an outcome score after mouldarthroplasties. The maximum score is 100 points, ofwhich the Pain domain contributes 44, Function 47,ROM 5 and Absence of Deformity 4 points. Function issubdivided intoGait and Activities of Daily Living. Thedesign of the score makes it possible to compare and

analyse the total score as well as the domains andsplit elements within the domains.Because of the high ceiling effect and low dis-

criminating capacity, the Harris Hip Score was mod-ified and assessed for the next 100 consecutivefollow-up observations. One of our concerns wasthe discrepancy between self-reported pain in theoutpatient clinic and the score recorded in the Paindomain. The Pain domain was then modified toinclude a visual analogue scale (VAS) of pain atnight, at rest and walking. No pain at night yielded20 points, intolerable pain 0 points, pain at restduring the day 17 points and pain at gait 13 points.

Additionally, the Pain domain was supplementedwith the use of analgesics (Table 1).

The elements describing Activities of Daily Livingwere not changed except for entering public trans-portation and use of shoes and socks, which wereerased. Gait Support was reduced from seven to fourgrades.

The domain Absence of Deformity was erased andreplaced by Relative Strength, as hip muscle strengthis related to functional outcome.4,5 In both hips thestrength of hip flexion, extension and abduction wasscaled and allottedthe following points: 5, normal;4,

Modification of the Harris Hip Score in acetabular fracture treatment 345

Table 1 The Pain domain in the modified Harris Hip Score (a)

(a)No analgesic use,additional 10 points; infrequentuse,5 points; daily use,0 points; (b)no pain at rest is weighted 85% of no pain atnight. Pain at gait is weighted 65%.

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moving against resistance; 3, moving against gravity;2, moving, but not against gravity; 1, trace of con-traction; and 0, paralysed limb.1 The index pointswere then added and relative strength of theaffected hip was calculated. Relative strength ofmore than 95% of the strength of the normal hipyielded 10 points; 8695%, 7 points; 6685%, 4points; 5165%, 2 points; and less than 51%, 0 points.

The ROM domain was altered to Relative ROM.Flexion, extension, abduction, adduction and inter-nal and external rotation in flexion were measuredin both hips. Total ROM of more than 95% of thecontralateral normal hip attracted 8 points; 8695%, 5 points; 6685%, 2 points; 5165%, 1 point;and less than 51%, 0 points. Synopses of the mod-ifications are shown in Table 2.

Both the original and modified Harris Hip Scoreswere evaluated for the following 922 observations.The outcome instruments were compared usingNCSS Statistical Software for Windows (version2004). Descriptive statistical analyses were per-formed on the outcome for the original and modified

Harris Hip Scores as well as the domains. The dis-tribution was described with skewness and percen-tiles. Because of proven skewness, Spearmans rhowas used as correlation coefficient. The coefficientswere interpreted as follows: poor correlation(r< 0.3); moderate correlation (0.3< r< 0.6);good correlation (0.6 < r< 0.8); and excellent cor-

relation (r> 0.8).3

A linear relationship betweenoutcomes in the original and modified Harris HipScores was expected. Kappa agreement analysis wasevaluated as follows: poor agreement (kappa value

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The domain of Relative ROM showed a mean 6.0points (18; S.D. 2.3) and the 25th, 50th and 60thpercentiles were at 5, 7 and 8 points, respectively.

In the 922 observations where the original and themodified hip scores were compared (Fig. 1), theoverall correlation between the total Harris HipScore and the modified score was r= 0.74. Thekappa agreement was 0.55 (kappa S.E. 0.04). Thedifference in agreement was due to redistribution of52 observations in the 4th quartile in the originalHarris Hip Score to the 3rd quartile in the modifiedscore, and of 16 observations from the 3rd quartilein the original to the 2nd in the modified score.Finally, 2 observations were redistributed from the2nd to the 1st quartile.

The medians in the original and transformedmodified Harris Hip Scores (transformed into a cor-responding 0100 scale) were 94 and 85 points,

respectively, and means were 85.5 points (32100; S.D. 12.7) and 81.9 points (16.7100; S.D.15.3), respectively. In the Pain domain, the meanand transformed mean were 39.9 (1044; S.D. 5.9)and 35.0 (044; S.D. 8.8), respectively. The meanand transformed mean of the Function domainswere in the original score 40.8 (947; S.D. 8.4),and in the modified score 40.3 (10.147; S.D. 8.5).ROM showed a mean 4.9 points (25; S.D. 0.4) in theoriginal score and 3.6 points (05; S.D. 1.5) in thetransformed modified score. In the original HarrisHip Score, Absence of Deformity showed a mean 3.9points (04; S.D. 0.5). In the modified score, meanRelative Strength was 5.7 (08; S.D. 2.4). The dis-tributions are shown by the skewness in Table 3 andthe percentiles in Table 4.

Intheoperatedgroup,thecorrelationbetweentheoriginal and modified score was r= 0.74, compared

Modification of the Harris Hip Score in acetabular fracture treatment 347

Table 2 The modified Harris Hip Score has four domains adding to a total numeric score, as the original

I Pain A Pain at night 200B Pain at rest by day 170C Pain at gait 130D Analgesics:

no use 10 points;infrequently 5;daily use 0 points

100

II FunctionA Gait 1 Limp a None 11 c Moderate 5

b Slight 8 d Severe 0

2 Support a None 11 c One crutch 2b One cane 6 d One/two

canes/crutches0

B Activities 1 Stairs a Normally withoutusing any railing

4

b Normally using a railing 2c In any manner 1d Unable to manage stairs 0

2 Sitting a Sitting comfortablyin ordinary chair 1 h 5

b On a high chair for 30 min 3c Unable to sit comfortably

in any chair0

3 Distance a Unlimited 11 d Indoors only 2b 1 km 8 e Not able to walk 0c 500 m 5

III Relative strengtha >95% of normal side 10 d >50 and 85 and 65 and 95% of normal side 8 d >50 and 85 and 51% 0c >65 and

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with r= 0.72 in the conservatively treated group. Thekappa agreements were 0.56 (kappa S.E. 0.05) in theoperatively treated group and 0.56 (kappa S.E. 0.06)in the conservatively treated group. The percentilesof the original and modified Harris Hip Scores for theoperatedand conservatively treated groups are givenin Table 5.

Discussion

The reliability and validity of the Harris Hip Scorehave been tested in previous studies.13,7,8 When thescore wasintroduced, it wascompared with the olderLarson and Sheperd systems6, and it was pointed outthat thenewscorepresenteda widerspread ofrating,making recognition of differences in hips easier.

Today the same argument is still valid; an outcomescore should be as discriminative as possible. Discre-pancies between patients complaints after acetab-ular fracture treatment and a fair or high Harris HipScore in the outpatient clinic are not unusual. Whendifferent outcomes of acetabular fracture treatmentrepresent almostthe same score, it is very difficult torecognise differences in treatment.

Our modification of the Harris Hip Score wasbased on an acetabular fracture patient series,

limiting conclusions regarding other patient cate-gories such as total hip replacements. Furthermore,patients with hip arthrosis tend to be older than

acetabular fracture patients. There may also be alearning curve in using scores, which may affect theresults. Our study design was, however, consecu-tive, and a large number of observations made thestudy reliable. Almost identical Spearman correla-tions and kappa agreements within the modifiedconservative and operative groups argue for therobustness of the method.

In the first 100 observations in the originalHarris Hip Score, the Pain domain showed skewed

348 S. Ovre et al.

Table 3 Skewness in the scores and domains in 461pairs of observations in the original and modified HarrisHip Scoresa, reflecting both the ceiling effect in theupper end of the score and the length of the tails

Original HarrisHip Score

Modified HarrisHip Score

Total score 1.73 Total score 1.37

Pain

2.26 Pain

1.33Function 1.77 Function 1.76Absence of

deformity7.53 Relative

strength1.81

ROM 3.45 Relative ROM 0.58

ROM, range of movement.a Minuses are due to left tails in the distributions.

Table 4 Percentiles of the original and modified Har-ris Hip Scores in 461 pairs of observations

Percentile Original HarrisHip Score

Modified HarrisHip Score

Exactvalue

Relativevaluea

Exactvalue

99 100.0 100.0 120.0

95 100.0 100.0 120.090 100.0 97.5 117.085 100.0 95.6 114.780 100.0 94.7 113.675 99.0 93.3 112.070 98.0 91.7 110.065 97.0 90.0 108.060 96.0 89.2 107.055 95.0 86.7 104.050 94.0 85.8 103.045 93.0 83.3 100.040 92.0 81.7 98.035 90.0 80.0 96.0

30 89.0 77.5 93.025 86.0 75.0 90.020 82.0 72.5 87.015 77.0 68.3 82.010 71.0 60.8 73.0

5 59.4 48.4 58.11 47.1 35.5 42.6a Relative value of the modified Harris Hip Score is compar-

able to the exact value of the original score.

Table 5 Percentiles of the original and modified Harris Hip Scores in 247 observations of operated and 214

conservatively treated acetabular fractures

Percentile Original Harris Hip Score Modified Harris Hip Score

Exact value Operated Conservative

Operated Conservative Exact value Relative valuea Exact value Relative valuea

95 100.0 100.0 118.0 98.3 120.0 100.075 97.0 100.0 111.0 92.5 113.0 94.250 93.0 96.0 100.0 83.3 104.0 86.725 82.0 89.5 87.0 72.5 93.0 77.5

5 54.4 69.0 50.8 42.3 70.0 58.3a The relative value of the modified score is comparable to the original Harris Hip Score.

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distribution with a ceiling value for the 60th per-centile. The patients had to characterise their painin exact terms that sometimes did not express theirexperience. Further, the clinician was in the posi-tion of interpreting the pain experience and couldthus influence the score. In the modified score, painwas expressed on a VAS during the night, at rest and

walking. VAS is a validated tool both for chronic andexperimental pain.11 If pain at night was the mostdevastating, pain at rest was set to contribute only85% of the night pain and pain at gait only 65%.Comparing the two scores, the introduction of theVAS clearly implied a less skewed distribution andbetter discrimination.

The ROM domain in the Harris Hip Score waschanged to Relative ROM in the modified score.The reason for this was the very low discriminatoryability in the Flexion element. In the modified HarrisHip Score, ROM of the affected hip was comparedwith that of the normal hip, and the maximum

numeric score in the domain was shifted from the15th to 60th percentile. The sub-element Shoes andSocks in the original score informed on function aswell as hip motion, and the impact on the total scorewas limited (4 of 100 points), and with low discri-mination. In the modified score, the information onhip motion was given in the Relative ROM domain.

The domain Absence of Deformity showed anextreme skewness, with the 10th percentile pre-senting maximum numeric score, and was changedto Relative Strength. Hip muscle strength has beenshown to relate to functional outcome.4,5

There was good correlation between the originaland modified Harris Hip Scores, and the kappaagreement showed moderate association2 betweenthe scores. The reason for this moderate associationwas particularly the redistribution of observationsfrom the 4th and 3rd quartiles in the original scoreto the 3rd and 2nd quartiles in the modified score.Dividing into operatively and conservatively treatedgroups showed almost identical Spearman correla-tions and kappa agreements in both groups. Themodification of the score had the same effect onmeasured outcome, irrespective of treatment.

Conclusions

To improve acetabular fracture treatment, we needmeasures which discriminate well anddo notdisguisedifferences in outcome. The discriminative qualitiesof the modified score were better, with lower ceiling

effects, than those of the original Harris Hip Score.Differences in the outcomes of treatment of acet-abular fractures will be more obvious with the mod-ified score, which may therefore improve evaluationof differenttreatments.Furtherstudies should assessthe validity, repeatability and sensitivity to change ofthe modified Harris Hip Score.

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