The crescent sign: dissociation of the polyethylene liner from a modular acetabular component in total hip arthroplasty

Dissociation of Acetabular Polyethylene Liners With a Morse Taper Design

BACKGROUND

Polyethylene liner dissociation is an uncommon complication of hip replacement. Dissociation has been associated with particular acetabular component designs. This study reviewed acetabular liner dissociations in a specific modular cup with a Morse taper locking mechanism that has not been previously reported.

METHODS

The senior author performed 655 primary total hip arthroplasties with one particular design of acetabular component using Class A polyethylene liners and metal head articulation. Cases with revision surgery performed for acetabular liner dissociation were reviewed.

RESULTS

Seven of 655 patients with this cup underwent revision surgery for a dissociated liner. Liner dissociation occurred at a mean of 73 months postoperatively. Patients presented with new-onset hip pain or squeaking, 4 of which developed symptoms acutely. Two patients treated with polyethylene liner exchange into the same cup required a second revision surgery for recurrent dissociation.

CONCLUSION

Polyethylene liner dissociation is an infrequent but possible complication associated with modular acetabular components using a Morse taper locking. Providers should be vigilant with long-term follow-up of patients with this acetabular system for patient complaints of catching or squeaking. Patients treated for liner dissociation should not have a new liner placed into the same acetabular shell given the risk for further dissociation.

The Utility of a Plain Film Arthrogram to Confirm Acute Liner Dissociation in the Setting of Primary Total Hip Arthroplasty

Acute Liner dissociation is a well-documented, but uncommon complication of total hip arthroplasty, yet the journey to diagnosis remains undefined. This clinical case report outlines the use of plain film arthrogram for diagnosis in a 53-year-old female who presented to the ED following a fall, describing symptoms of increasing groin pain, reduced range of movement, difficulty weight-bearing and a grinding sensation in her left hip, all on a background of total hip replacement two years ago. Examination revealed impaired flexion, rotation and abduction while AP pelvic X-ray confirmed mild eccentric placement of the femoral head, and lateral X-ray proved joint enlocation. An arthrogram of the left hip was performed the following day with injection of 4mls of iodinated contrast injected into the joint. Inferior dissociation of the liner from the shell was evident. The femoral head and liner were replaced two days later, and the liner was found to have shearing and gross plastic deformation at the rim. The patient reported immediate relief from the groin pain and was discharged on the fourth day postoperatively. This shows how plain film imaging fails in diagnosing acute liner dissociation dynamic fluoroscopic tests, post-arthrography CT and metal artifact reduction sequence magnetic resonance imaging (MARS MRI) have previously been proposed despite their associated wait-time, radiation exposure and financial costs. This case report highlights the role of plain film arthrography as a low risk and low-cost diagnostic tool. The report also suggests the incorporation of radio-dense markers in liners to facilitate the use of arthrography when diagnosing dissociation, also raising awareness of prevention and recognition in what may be an under-reported complication of hip arthroplasty.

Imaging evaluation of polyethylene liner dissociation in total hip arthroplasty

OBJECTIVE

To describe the imaging findings of polyethylene liner dissociation in total hip arthroplasty.

MATERIALS AND METHODS

Retrospective search of our institution's radiology database identified 12 patients with polyethylene liner dissociation of a total hip arthroplasty. Clinical and operative notes were reviewed. All radiological studies were reviewed independently by two radiologists.

RESULTS

Among 12 patients (seven females/five males; mean age: 67 years; median interval after surgery at diagnosis: 8.5 months) with polyethylene liner dissociation, 11 had radiographs, six had CT, seven had MRI, and two had arthrography. "Bubble sign" and "crescent sign" on radiography were insensitive, seen only in three patients, but all showed abrupt eccentric positioning of the femoral head. CT identified the dislocated liner in five of six patients but failed to identify one liner, which was partially associated with the acetabular cup. MRI identified the dislocated liner in all seven patients, with the MAVRIC (multiacquisition variable resonance image combination) sequences either increasing the diagnostic confidence relative to the routine pulse sequences or being the sole sequences in which the liner can be identified if the liner remained partially associated with the acetabular cup. Arthrography identified the dislocated liner in one of two patients.

CONCLUSIONS

Previously described radiographic signs of polyethylene liner dissociation are insensitive, but abrupt eccentric positioning of the femoral head in the correct clinical context is highly suggestive of the diagnosis. MRI and CT can accurately localize the displaced liner. MAVRIC is particularly helpful if the dislocated liner remains partially associated with the acetabular cup.

Acetabular liner dissociation: A case report and review of the literature

Dissociation of the polyethylene liner from the acetabular shell is a rare but catastrophic complication of total hip arthroplasty (THA). There have been reports of polyethylene liner dissociation (PLD) as well as ceramic liner dissociation (CLD) in the literature. Amongst the commonly used implants, liner dissociation has been reported with the Pinnacle (DePuy), Harris–Galante (Zimmer) and Trident (Stryker) acetabular components.

To the best of our knowledge, this is the first case report of PLD in an R3 (Smith & Nephew) acetabular component. This case report highlights the implant choice for treatment of the liner dissociation and the role of constrained implants in such cases.

Using Double-Contrast CT Arthrography to Confirm Suspected Dissociation of a Cemented Polyethylene Liner in the Setting of Revision Total Hip Arthroplasty: A Case Report

CASE

A 67-year-old woman who underwent a re-revision of a total hip arthroplasty with a cemented polyethylene liner fell 14 months after surgery. The patient had symptoms of pain and weakness; however, clinical, laboratory, and radiographic evaluation did not disclose fracture, infection, osteolysis, or component migration. Liner dissociation was suspected, and a double-contrast computed tomography (CT) arthrogram confirmed failure at the cement-liner interface. She underwent additional revision surgery and was doing well at the 3-year follow-up.

CONCLUSION

Double-contrast CT arthrography confirmed failure at the cement-liner interface and is an effective diagnostic tool in identifying suspected dissociations of cemented polyethylene liners.

A review of outcomes and modes of presentation following liner dissociation from Harris-Galante uncemented acetabular components

PURPOSE

Dissociation of the polyethylene liner is a known failure mechanism of the Harris Galante I and II uncemented acetabular components. The outcomes of revision surgery for this indication and the influence of time to diagnosis are not well described.

METHODS

We report a series of 29 cases revised due to this failure mechanism. The median time from primary to revision surgery was 13 years.

RESULTS

At a median of 4 years follow-up, the mean OHS was 34 (range 6-48) but results were poorer (mean 29; range 6-45) when the diagnosis and revision was delayed compared to when it was not (mean 39; range 20-48). A large proportion of our patients (n = 14) presented with sudden onset of symptoms with or without trauma. Osteolysis was common in this series but the cup was well fixed in 20/29 cases. There was macroscopic damage to the shell in all cases.

CONCLUSIONS

In our experience, prompt revision of liner dissociation optimises outcomes in this group of patients and radiology reporting alone is not sufficient to identify these cases.

The tram track sign: a characteristic sonographic feature of polyethylene liner dissociation after total-hip arthroplasty

OBJECTIVES

Polyethylene liner dissociation from an acetabular component is a complication of total-hip arthroplasty (THA) caused by slippage of the liner, which causes pain and requires a revision. The aim of this study was to evaluate sonographic features of liner dissociation and detect useful sonographic findings compared to conventional radiography and computed tomography (CT).

METHODS

Among a total of 226 patients who underwent revision THA at our institution between September 2008 and June 2012, 10 patients (6 male and 4 female; mean age, 56.2 years) who showed severe narrowing of the superior joint space on the THA side and underwent sonography were retrospectively reviewed by evaluating radiographic, CT, and sonographic findings. In evaluation of the images, we put more emphasis on the "radiographic crescent sign," "CT crescent sign," and "sonographic tram track sign."

RESULTS

At surgery, 7 patients showed liner dissociation, and 3 showed severe liner wear. On radiography, 8 of 10 patients (80%) had a correct diagnosis of the presence or absence of liner dissociation; on sonography, all 10 patients (100%) had a correct diagnosis. The sensitivity, specificity, and accuracy for diagnosis of liner dissociation by pelvic radiography and sonography were 100% (7 of 7), 33% (1 of 3), and 80% (8 of 10) and 100% (7 of 7), 100% (3 of 3), and 100% (10 of 10), respectively.

CONCLUSIONS

Liner dissociation can be easily and well visualized by sonography, especially compared to pelvic radiography and CT. The sonographic tram track sign should be a very useful feature in the early diagnosis of liner dissociation.

Development of ceramic-on-ceramic implants for total hip arthroplasty

Over the past three decades, alumina ceramic, now in its third/fourth generation, has been markedly improved in terms of its mechanical properties, including purity, grain microstructure, and burst strength. In the clinic, it is particularly suitable for young and for very active patients. This paper discusses the development and characteristics of different kinds of ceramics. In addition, ceramics in the third/fourth generation which are used in total hip arthroplasty clinically are reviewed in detail.

Hip arthroplasty. Part 2: normal and abnormal radiographic findings

This review addresses the normal and abnormal radiographic findings that can be encountered during the follow-up of patients with total hip arthroplasty (THA). The relative significance of different patterns of radiolucency, bone sclerosis, and component position is discussed. The normal or pathological significance of these findings is correlated with design, surface, and fixation of the prosthetic components. It is essential to have a good knowledge of expected and unexpected radiological evolution according to the different types of prostheses. This paper emphasizes the importance of serial studies compared with early postoperative radiographs during follow-up in order to report accurately any sign of prosthetic failure and trigger prompt specialist referral. Basic technical guidelines and schedule recommendations for radiological follow-up are summarized.

Ten-year results of a bone-preserving low-modulus composite total hip replacement stem

A cementless composite femoral stem was developed with the aim of reducing bone loss secondary to stress shielding. Thirty-one stems were implanted in 27 patients, combined with a cementless acetabular component with polyethylene bearing surface in 30 cases and a bipolar head in 1 case. Patients were followed-up annually with clinical and radiographic evaluation. Fourteen hips underwent dual X-ray absorptiometry (DEXA) scans to monitor postoperative bone mineral density around the stem. The mean follow-up was 10.1 years. The mean Harris hip score improved from 57 to 92. To date, no stem has required revision. All stems are radiographically stable. Acetabular component revision has been required in 8 cases; 3 for liner dissociation and 5 for polyethylene wear. Radiographs and DEXA scans have shown some improvement in bone mineral density (BMD) between the 2 and 5-year follow-up. A cohort of patients displayed improvement in radiographic appearance and BMD in Gruen zone 7. This stem shows evidence of proximal bone preservation and has excellent results at medium to long-term follow-up. The limiting factor in our cohort of patients has been the polyethylene bearing surface.

The Harris-Galante porous-coated, hemispherical, polyethylene-lined acetabular component in patients under 50 years of age

We have reviewed 70 Harris-Galante uncemented acetabular components implanted as hybrid hip replacements with cemented stems between 1991 and 1995 in 53 patients whose mean age was 40 years (19 to 49). The mean follow-up was for 13.6 years (12 to 16) with no loss to follow-up. We assessed the patients both clinically and radiologically.

The mean Oxford hip score was 20 (12 to 46) and the mean Harris hip score 81 (37 to 100) at the final review. Radiologically, 27 hips (39%) had femoral osteolysis, 13 (19%) acetabular osteolysis, and 31 (44%) radiolucent lines around the acetabular component. Kaplan-Meier survival curves were constructed for the outcomes of revision of the acetabular component, revision of the component and polyethylene liner, and impending revision for progressive osteolysis.

The cumulative survival for revision of the acetabular component was 94% (95% confidence interval 88.4 to 99.7), for the component and liner 84% (95% confidence interval 74.5 to 93.5) and for impending revision 55.3% (95% confidence interval 40.6 to 70) at 16 years.

Uncemented acetabular components with polyethylene liners undergo silent lysis and merit regular long-term radiological review.

High incidence of squeaking in THAs with alumina ceramic-on-ceramic bearings

Ceramic-on-ceramic bearings in THA are a popular alternative to overcome wear concerns in traditional metal-polyethylene bearings. However, squeaking is a potentially worrisome phenomenon in ceramic-on-ceramic THAs which we observed in some of our patients. We reviewed all 42 patients who underwent 43 ceramic-on-ceramic noncemented THAs during the time of the study. Squeaking, defined as a reproducible sound of squeaking, clicking, or grating, occurred in nine of 43 implants (20.9%). Standard radiographs were normal. We used CT imaging to determine cup anteversion and inclination angles, comparing the squeaking hips with those of a randomly selected control group, but found no differences. We then hypothesized specific design features (stem size, cup size, head size, and neck length of the head) would be risk factors for squeaking. We found a difference in neck length between squeaking and nonsqueaking implants. A neck length of -4 mm or shorter resulted in a relative risk of 5.56 (95% confidence interval, 1.14-27.01) for squeaking. We found a high incidence of squeaking in our population, and we believe this phenomenon is an underreported side effect of these types of bearings. A short neck length of the femoral implant was a risk factor for squeaking in ceramic-on-ceramic THA.

LEVEL OF EVIDENCE

Level III, therapeutic study.