Combined Anterior Pelvic (CAP) approach for fracture acetabulum fixation - Functional outcome evaluation and predictors of outcome

Abstract

Objective

Ilio-inguinal approach has been considered standard anterior approach for acetabulum fracture fixation. Different modifications of this approach have been described. This study analysed the patients treated using a Combined Anterior Pelvic (CAP) approach - minimal AIP (anterior intra-pelvic) with modified ilio-femoral along with ’anterior superior iliac spine’ osteotomy. This combined approach provides wide exposure of pelvis to direct visualise the entire anterior column from sacroiliac joint to pubic symphysis, medial side of quadrilateral plate and entire iliac wing with minimal retraction of soft tissues required.

Methods

Data of patients treated from July 2014 to June 2018 for acetabulum fracture using CAP approach was retrieved from hospital record system. Inclusion criteria were - acetabulum fractures treated surgically using CAP approach. Exclusion criteria were – age less than 18 years, associated pelvis ring injury and incomplete peri-operative radiological record (pre-operative/post-operative antero-posterior, 45° obturator and 45° iliac oblique radiographs and pre-operative computed tomographic (CT) scans. 62 patients who met inclusion exclusion criteria were called in out-patient-department for final functional evaluation using Matta modified Merle d’aubigne score.

Results

Out of 62 patients 47 patients who turned up for final functional evaluation were included in study. 19 patients had excellent, 15 had good, 2 had fair and 11 had poor results. Age less than 40 years, anterior column fracture pattern, Pre-operative fracture displacement >20 mm, fracture comminution and post-operative fracture reduction within 3 mm were the predictors of the functional outcome. When analysed using logistic regression model, post-operative fracture reduction was found to be the only significant predictor of functional outcome.

Conclusion

CAP approach is useful anterior approach to acetabulum. Fracture reduction is the independent predictor of functional outcome. Comparison of this approach with other anterior approaches to acetabulum can be area of further research.

Introduction

Acetabulum fracture fixation is a technically demanding procedure. Surgical approaches to acetabulum may be anterior, posterior or combined. The choice of surgical approach depends upon the type of fracture, displacement of fracture fragments and the surgeon’s preference. Ilio-inguinal approach has been the standard approach for anterior acetabulum fractures since it was first described by Letournal et al., in 1964.¹ This approach provides access to most of the anterior acetabulum, iliac surface, pelvic brim and anterior sacroiliac joint. However meticulous dissection is required to prevent injury to major neurovascular structures like lateral femoral cutaneous nerve (LFCN) and the external iliac vessels. Also the learning curve is quite steep with this approach.² Different modifications of this approach have been described to decrease the extensive dissection and improve the exposure.^3,4

Smith-Petersen described an anterior approach to hip joint for pelvic osteotomy and arthroplasty in 1917 and 1949 respectively.^5,6 This approach was popularised as ilio-femoral approach. Superficially the internervous plane of dissection was between sartorius and tensor fascia. The deep internervous plane was between rectus femoris and gluteus medius. The muscles from the medial aspect of crest were released to expose the inner side of pelvis. This approach has extra advantage of providing exposure to hip joint which is not possible with ilio-inguinal approach. Following years different modifications of this approach were described. Kloen et al. described a combination of ilio-inguinal and modified Smith-Petersen approach.³ The proximal part of approach was similar to lateral window of ilio-inguinal approach with medial retraction of iliacus muscle to expose inner aspect of ilium. Extending distally, the approach was like Smith-Petersen approach with complete exposure to hip joint. Additionally the osteotomy of ‘anterior superior iliac spine’ (ASIS) with retraction of attached Sartorius muscle and inguinal ligament provided wide distal exposure to anterior acetabulum. Sagi et al. also described lateral window of ilio-inguinal approach along with ASIS osteotomy.⁷ Since the authors did not extend the lateral window distally, the exposure was limited distally up to pubic root.

Sen et al. described ilio-femoral approach along with ASIS osteotomy.⁸ The approach provided wide exposure to anterior acetabulum and internal pelvis. The authors combined this exposure with medial window of ilio-inguinal to access whole pelvic brim from pubic symphysis to anterior sacroiliac joint, supra-acetabular part of iliopectineal eminence, quadrilateral plate and whole ilium internally along with visualisation of hip joint. The advantages of ASIS osteotomy in these approaches were lesser dissection, wide visualisation of anterior column along with hip joint access.^3,7

Other approaches like modified Stoppa and pararectus were described with advantage of quadrilateral plate access, joint visualisation and lesser morbidity.⁹ Hirvensalo et al., in 1993 and Cole and Bolhofner in 1994 independently described modified Stoppa approach to treat fracture acetabulum.^10,11 The advantage of the approach is to access the acetabulum from within the pelvic cavity below the pelvic ring. The medial displaced fractures can be reduced and fixed along the vector of injury. Sagi et al. described modification of this approach and termed it as AIP (anterior intra-pelvic) approach.¹² Rocca et al. combined the modified Stoppa approach with lateral window of ilio-inguinal approach and termed it as ACE (anterior combined endopelvic) approach.¹³ The authors argued that extra lateral approach reduces the soft tissue tension and injury to iliac vessels particularly in obese patients.

This study aimed to analyse the functional outcome and its predictors after fixing the acetabulum fractures using a Combined Anterior Pelvic (CAP) approach - minimal AIP with modified ilio-femoral along with ASIS osteotomy. This approach provides wide exposure to direct visualise the entire anterior column from sacroiliac joint to pubic symphysis, medial side of quadrilateral plate and entire iliac wing, without much retraction of soft tissue. Both supra-pectenial as well as infra-pectenial fixation is possible with this approach.