A Novel Technique for Identification of Fractured Ceramic Acetabular Liner in Total Hip Arthroplasty: A Case Report

Introduction

The low wear rates associated with ceramic hip articulations have made them an increasingly popular bearing choice in total hip arthroplasty. The extremely low generation of wear debris and the excellent biologic tolerance that this material imparts should ensure a long survivorship of the implant, especially in young and active patients (1). Specific complications of ceramic bearings include fractures of the liner (2) and head (3) as well as eccentric seating of the cup liner (4). Noises from the hip joint have been reported and in particular squeaking from the hip can occur (5).

Investigation for the symptomatic total hip replacement should follow standard clinical assessment and investigation. Subtle ceramic liner fractures can be difficult to diagnose unless catastrophic failure has occurred. Plain radiographs and a high level of clinical suspicion are the usual way of detecting this complication. We report a case of ceramic liner fracture which was identified using a previously unreported technique.

Case report

An 82-year-old male was referred to our clinic with a several year history of right groin pain. After clinical and radiological assessment he was listed for a right total hip replacement for primary osteoarthritis. He underwent a routine uncemented (Corail® femoral stem, Pinnacle sector II 54 mm Acetabular cup, DePuy Orthopaedics) total hip arthroplasty. A ceramic-on-ceramic bearing was used (Biolox® Delta Articule/eze™ 36 femoral head, Biolox® Delta Ceramax™ 36 mm cup insert, DePuy Orthopaedics). Postoperatively he had an uncomplicated recovery and radiographs were satisfactory. At 6 weeks follow-up he was making good progress and was discharged to the care of the specialist joint replacement nurse for long-term follow-up.

He was referred back to the hospital by his general practitioner 6 months later. He had noticed a 1 month history of insidious discomfort in his right groin, particularly after prolonged sitting. He also complained of squeaking from the hip especially on change of direction whilst walking. On examination his right hip had a good range of movement and he walked normally without a Trendelenburg gait. There was a degree of audible squeaking from the hip but no crunching or grinding.

A plain radiograph was performed (Fig. 1). This demonstrated good alignment of all components with no evidence of liner fracture or debris in the joint. He was reassured and his symptoms treated conservatively. Three months later his symptoms had deteriorated but on further assessment there was no change in clinical findings or radiographs. At this time a differential diagnosis of liner fracture or psoas tendonitis was made.

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Fig. 1

Postoperative radiograph.

The patient subsequently had an examination under anaesthesia (EUA) of his right hip under image intensifier guidance. The hip was aspirated and the psoas tendon injected with a mixture of steroid and local anaesthetic. On EUA there was no evidence impingement of the cup nor of acetabular liner fracture with normal image penetration (Fig. 2). As a serendipitous finding over penetration of the image intensifier image revealed a subtle rim fracture of the acetabular liner was (Fig. 3).

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Fig. 2

Fluoroscopy of right hip with normal image penetration.

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Fig. 3

Fluoroscopy of right hip with over penetration of image. Arrow indicating ceramic rim fracture.

The intraoperative findings were discussed with the patient. After informed consent he underwent revision of his total hip replacement, 15 months after the primary procedure. At operation evidence of a significant fracture of the superior rim of the liner was found (Fig. 4) with progression to a complete liner fracture. The head and liner were replaced with new ceramic bearing surfaces. The patient made an excellent postoperative recovery and the symptoms from his right hip have resolved. At 40 months following revision the patient had an Oxford Hip Score of 47/48.

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Fig. 4

Ceramic liner once removed from acetabular cup (it was not damaged during its removal).

Discussion

A ceramic-on-ceramic liner for hip arthroplasty, in an octogenarian patient, may not provide an optimal cost benefit ratio compared to other bearing combinations such as metal-on-polyethylene. Certainly it is not the standard bearing combination in our institution but was used due to patient choice on this occasion.

Correctly inserting ceramic liners in acetabular cups can sometimes be difficult. Slightly malpositioned liners can be easily overlooked if the surgeon does not take the time to assess their position around the edge of the cup. Sometimes poorly seated liners can be seen on the postoperative radiographs but this is not always the case. We feel a poorly seated liner, which later became seated, may have been the cause of liner fracture in this case. There was no evidence of impingement during the EUA or revision procedure and therefore no reason to avoid a ceramic head and liner for revision.

The painful prosthetic joint in which plain radiographs are normal presents a diagnostic challenge. The literature contains little investigation regarding the early diagnosis of ceramic bearing fracture. Toni et al have suggested a set of guidelines based on a 12-year experience of ceramic liner fractures (6). Aside from clinical examination they suggest the use of plain radiography and computed tomography (CT) to assess for impingement. This was in addition to synovial fluid aspiration with further microanalysis and electron microscopy to ascertain the presence of ceramic liner fragments. The authors however did not suggest using CT for the imaging of fractured liners. We postulate metal artefact may reduce the sensitivity of CT in detecting subtle liner fractures. Arthrogram may be beneficial as an adjunct to CT but neither has been described in the literature. Investigative facilities such as synovial fluid microscopy and electron microscopy may not be available in every department. Image intensifiers however, are commonplace and EUA with live screening can be a very useful tool to help identify or rule out any abnormalities. In the case of our patient, we found that by over penetrating the image intensification film of his right hip we were able to demonstrate a subtle fracture of the ceramic liner. This fracture was not evident on postoperative plain radiographs or on the standard exposure of image intensifier film taken at EUA. To our knowledge this technique has not been previously reported in the literature and we would recommend it as a means to identify subtle rim fractures of ceramic liners in total hip arthroplasty.