ORIGINAL ARTICLE

Influence of posterior and lateral surgical approach on oxford hip score after primary hip replacement

PK Inaparthy MS*, R Chana *, PW Skinner*, G Andrew **, KW Tuson***

*Trauma & Orthopaedic Directorate
Maidstone & Tunbridge Wells NHS Trust Kent, United Kingdom.

**Department of Trauma & Orthopaedics
Hope Hospital, Salford
Manchester, United Kingdom.

***Horder Centre for Arthritis
St. John's Road, Crowbridge
East Sussex, United Kingdom.

Address for Correspondence

PK Inaparthy, MRCS
50, banks walk, bury st Edmunds, UK, IP33 2PA
Phone: 0044 7877831614
E-mail: i_praveen@yahoo.co

Abstract

INTRODUCTION

Various surgical approaches have been described for the hip joint but the optimal surgical approach for total hip replacement remains controversial as both the lateral and the posterior approaches have certain advantages.

Since its introduction in 1996, Oxford hip score (OHS) has been validated in several studies. Total hip replacement has been shown to improve the OHS in several studies but we could not find any literature on effect of the surgical approach on OHS.

AIM

To find out the affect of surgical approach on oxford hip score.

METHODS

Exeter Primary Outcomes Study was a prospective non-randomised multicentre study involving six centres across the UK. Ethical committee approval was taken and the study was conducted over a period of five years. 1610 patients were included in the study. All the patients underwent primary hip replacement with Exeter. Oxford hip score was noted at pre-operative assessment and post-operatively at three months, year one, two, three, four and five, either in the clinics or by post. All data was analysed in conjunction with a statistician using SPSS.

RESULTS

We had 1587 patients with regular follow-up. Lateral approach was the most common surgical approach (n=1143) compared to posterior approach (n=436). Sex ratio for each surgical approach was comparable. Oxford hip scores significantly improvedpostoperatively (P <0.05) up to four years, with both the surgical approaches. The posterior approach gave a better improvement in OHS compared to the lateral approach for all the four years. The absolute oxford hip scores improved significantly with the posterior approach for the first 12 months post-operatively.

CONCLUSION

Posterior approach gives greater patient perceived clinical benefit in the first year after surgery which could help in early rehabilitation compared to lateral approach. This should be considered when assessing the best approach for the patients.

J.Orthopaedics 2011;8(3)e2

Keywords:

Osteoarthritis, Total hip arthroplasty, hip surgical approach, health outcome measures, oxford hip scores.

Introduction

Various surgical approaches have been described for the hip joint but the optimal surgical approach for total hip replacement remains controversial. The lateral approach & the posterior approach are the most commonly used approaches for total hip replacement.

Each approach has got its own advantages & disadvantages as reported by different authors. Gore et al (1) reported that posterior approach led to more lateral & distal trochanteric placement, normal muscle strength and more internal rotation. In their study, Madsen et al (2) found that patients with posterior approach had normal gait at 6 months compared to the patients with lateral approach. On the other hand, Foster et al (3) reported that the dislocation rate was very low (2.5%) and re-dislocations did not occur in patients with lateral approach. Apart from these clinical outcome studies, there has not been much published on the functional outcomes with these approaches. Since its introduction in 1996, Oxford hip score (OHS) has been validated in several studies (4, 5, 6) and is being widely used. It is a patient based scoring system which is calculated from the responses to 12 questions on activities of daily living. Minimum total score of 12 indicates normal function and maximum score of 60, the most severe disability.

In our study, we examined the results for patients included in the Exeter Primary Outcomes Study (EPOS) for the effect of surgical approach on Oxford hip score.

Material & Methods

Exeter Primary Outcomes Study was a prospective non-randomised multicentre study involving six centres across the UK. Ethical committee approval was taken and the study was conducted over a period of five years.

1610 patients were included in the study. All the patients who underwent primary hip replacement with Exeter stem were followed up. Some patients underwent hip replacement with other available stems for various reasons and were excluded.
Patients were followed up in the clinics for pre-operative assessment and then at three months, year one, year two and year five post-operatively. Postal follow-up was carried out for year three & year four. Patients who had undergone revisions before the end of study were noted down as complications.

Pre-operatively, along with the oxford hip score, details of patient demographics, primary diagnosis, co-existing medical conditions, medication and range of movements were noted.
Intra-operative details included details of surgeon & assistant, surgical approach, surgical findings, implants, cement and complications.

Post-operatively, patients were followed up clinically for clinical & radiographic assessments. Data was collected on range of movement, limb length discrepancy, complications and radiographic features.
Oxford hip score was noted at pre-operative assessment and post-operatively at three months, year one, two, three, four and five, either in the clinics or by post. Physician reported scores (Merle D’Aubigne / Postel) (MDAP) were also measured pre-operatively and at first & second year clinical follow-up.

All data was analysed in conjunction with a statistician using SPSS.

Results

We had 1587 patients with regular follow-up. 23 patients were lost for follow-up. There were 587 males & 971 females (male: female ratio of 1: 1.65). Average age at the time of surgery was 68.2 years.

All operations were carried out using either the lateral approach (Hardinge or modification) or posterior approach. Lateral approach was the most common surgical approach (n=1143) compared to posterior approach (n=436). Sex ratio for each surgical approach was comparable.

1354 patients (84.1%) underwent hip replacement for primary osteoarthritis and the remaining 233 patients (25.9%) for various reasons including secondary osteoarthritis, osteonecrosis, inflammatory arthritis, acute fractures of femoral head and metabolic bone disease.

Table 1 – primary reason for hip replacement

 
Consultants were more commonly the lead surgeons compared to other junior staff. 667 out of 1143 (58.4%) surgeries with lateral approach and 333 out of 426 (78.2%) with posterior approach were performed by the consultants. This was found to be statistically significant (P = 0.0001). There was no significant difference in duration of surgery with both the approaches.
 
Oxford hip scores significantly improved postoperatively (P <0.05) up to four years, with both the surgical approaches, as demonstrated in the following table. The posterior approach gave a better improvement in OHS compared to the lateral approach for all the four years.

Table – 2 Improvement in OHS (Preop OHS vs postop OHS)

The absolute oxford hip scores improved significantly with the posterior approach for the first 12 months post-operatively, as demonstrated in the following table.

Table – 3 Absolute Oxford Hip Scores

Difference in the MDAP score between the groups was not statistically significant
We also assessed whether surgical approach influenced the positioning of implant & limb length discrepancy. Data was available on 1305 patients, of whom 972 underwent surgery through lateral approach & 333 through posterior approach.

86 out of 333 patients (25.8%) with posterior approach had varus positioning of the stem compared to 118 out of 972 patients (12%) with lateral approach. This was not statistically significant (P > 0.05).

Limb length discrepancy was more or less similar in both the groups.

Complications - various complications namely dislocations, infections, re-operation rate and medical complications were found to be similar in both the groups except heterotrophic ossification which was found to be higher in the lateral approach group (P < 0.05).

Discussion

Osteoarthritis affects 10% of the population and mainly the weight bearing joints such as hips (5%) (8). The usual clinical course is deteriorating gait, increasing pain and stiffness that will ultimately require a total hip arthroplasty (THA) (9). Of the two principal surgical approaches for THA, there is not enough evidence to show which one is best suited for THA. In fact, a few studies claimed similar clinical results with both the approaches (10, 11). In our study, we included the oxford hip score (OHS) along with the clinical parameters to assess both these approaches.

Most of the patients in our study (>90%) underwent THA for osteoarthritis with lateral approach being the most commonly used surgical approach. Patients undergoing surgery through posterior approach were more likely to be operated upon by the consultants.
The mean pre-operative OHS in our study (44.1) was similar to that reported by Dawson et al (44) and Fitzpatrick et al (44.5) (12, 13). Our study showed that the improvement in OHS post-operatively is statistically significant for four years which is in agreement to the findings of Field et al (7).
Our study shows that the absolute OHS improvement is statistically significant for the first one year with posterior approach compared to the lateral approach. This result demonstrates that the patients perceive greater clinical benefit after THA through posterior approach than with a lateral approach, though only for the first one year. This could help them to rehabilitate & get back to normal life quicker, improving the quality of life.

Merle D’Aubigne / Poster (MDAP) score which is a physician based scoring system did not detect any difference between the two groups in our study, which further proves that patient based scoring systems are superior to physician based scoring systems.

Of all the complications, only heterotrophic ossification rate was found to be higher in the lateral approach group which was statistically significant. The possible explanation is the damage to the abductors of the hip in this approach. Varus positioning of the implant was higher in posterior approach group but there was no statistical significance.

Conclusion

Posterior approach gives greater patient perceived clinical benefit in the first year after surgery which could help in early rehabilitation compared to lateral approach. This should be considered when assessing the best approach for the patients.

Acknowledgements: This study was supported by Stryker. We acknowledge the major contribution of the research nurses at each site.

Reference

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This is a peer reviewed paper 

Please cite as : PK Inaparthy MS,Influence of posterior and lateral surgical approach on oxford hip score after primary hip replacement

J.Orthopaedics 2011;8(3)e2

URL: http://www.jortho.org/2011/8/3/e2